Adding upstream version 115.8.0esr.upstream/115.8.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

59 files changed, 12202 insertions, 0 deletions

diff --git a/caps/BasePrincipal.cpp b/caps/BasePrincipal.cpp
new file mode 100644
index 0000000000..97924b23c5
--- /dev/null
+++ b/caps/BasePrincipal.cpp
@@ -0,0 +1,1625 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/BasePrincipal.h"
+
+#include "nsDocShell.h"
+
+#include "ExpandedPrincipal.h"
+#include "nsNetUtil.h"
+#include "nsContentUtils.h"
+#include "nsIOService.h"
+#include "nsIURIWithSpecialOrigin.h"
+#include "nsScriptSecurityManager.h"
+#include "nsServiceManagerUtils.h"
+#include "nsAboutProtocolUtils.h"
+#include "ThirdPartyUtil.h"
+#include "mozilla/ContentPrincipal.h"
+#include "mozilla/ExtensionPolicyService.h"
+#include "mozilla/NullPrincipal.h"
+#include "mozilla/dom/BlobURLProtocolHandler.h"
+#include "mozilla/dom/ChromeUtils.h"
+#include "mozilla/dom/ReferrerInfo.h"
+#include "mozilla/dom/ToJSValue.h"
+#include "mozilla/dom/nsMixedContentBlocker.h"
+#include "mozilla/Components.h"
+#include "mozilla/dom/StorageUtils.h"
+#include "mozilla/dom/StorageUtils.h"
+#include "nsIURL.h"
+#include "nsEffectiveTLDService.h"
+#include "nsIURIMutator.h"
+#include "mozilla/StaticPrefs_permissions.h"
+#include "nsIURIMutator.h"
+#include "nsMixedContentBlocker.h"
+#include "prnetdb.h"
+#include "nsIURIFixup.h"
+#include "mozilla/dom/StorageUtils.h"
+#include "mozilla/StorageAccess.h"
+#include "nsPIDOMWindow.h"
+#include "nsIURIMutator.h"
+#include "mozilla/PermissionManager.h"
+
+#include "json/json.h"
+#include "nsSerializationHelper.h"
+
+namespace mozilla {
+
+const char* BasePrincipal::JSONEnumKeyStrings[4] = {
+    "0",
+    "1",
+    "2",
+    "3",
+};
+
+BasePrincipal::BasePrincipal(PrincipalKind aKind,
+                             const nsACString& aOriginNoSuffix,
+                             const OriginAttributes& aOriginAttributes)
+    : mOriginNoSuffix(NS_Atomize(aOriginNoSuffix)),
+      mOriginSuffix(aOriginAttributes.CreateSuffixAtom()),
+      mOriginAttributes(aOriginAttributes),
+      mKind(aKind),
+      mHasExplicitDomain(false) {}
+
+BasePrincipal::BasePrincipal(BasePrincipal* aOther,
+                             const OriginAttributes& aOriginAttributes)
+    : mOriginNoSuffix(aOther->mOriginNoSuffix),
+      mOriginSuffix(aOriginAttributes.CreateSuffixAtom()),
+      mOriginAttributes(aOriginAttributes),
+      mKind(aOther->mKind),
+      mHasExplicitDomain(aOther->mHasExplicitDomain.load()) {}
+
+BasePrincipal::~BasePrincipal() = default;
+
+NS_IMETHODIMP
+BasePrincipal::GetOrigin(nsACString& aOrigin) {
+  nsresult rv = GetOriginNoSuffix(aOrigin);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsAutoCString suffix;
+  rv = GetOriginSuffix(suffix);
+  NS_ENSURE_SUCCESS(rv, rv);
+  aOrigin.Append(suffix);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetAsciiOrigin(nsACString& aOrigin) {
+  aOrigin.Truncate();
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+  return nsContentUtils::GetASCIIOrigin(prinURI, aOrigin);
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetHostPort(nsACString& aRes) {
+  aRes.Truncate();
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+  return prinURI->GetHostPort(aRes);
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetHost(nsACString& aRes) {
+  aRes.Truncate();
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+  return prinURI->GetHost(aRes);
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetOriginNoSuffix(nsACString& aOrigin) {
+  mOriginNoSuffix->ToUTF8String(aOrigin);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetSiteOrigin(nsACString& aSiteOrigin) {
+  nsresult rv = GetSiteOriginNoSuffix(aSiteOrigin);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsAutoCString suffix;
+  rv = GetOriginSuffix(suffix);
+  NS_ENSURE_SUCCESS(rv, rv);
+  aSiteOrigin.Append(suffix);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetSiteOriginNoSuffix(nsACString& aSiteOrigin) {
+  return GetOriginNoSuffix(aSiteOrigin);
+}
+
+// Returns the inner Json::value of the serialized principal
+// Example input and return values:
+// Null principal:
+// {"0":{"0":"moz-nullprincipal:{56cac540-864d-47e7-8e25-1614eab5155e}"}} ->
+// {"0":"moz-nullprincipal:{56cac540-864d-47e7-8e25-1614eab5155e}"}
+//
+// Content principal:
+// {"1":{"0":"https://mozilla.com"}} -> {"0":"https://mozilla.com"}
+//
+// Expanded principal:
+// {"2":{"0":"<base64principal1>,<base64principal2>"}} ->
+// {"0":"<base64principal1>,<base64principal2>"}
+//
+// System principal:
+// {"3":{}} -> {}
+// The aKey passed in also returns the corresponding PrincipalKind enum
+//
+// Warning: The Json::Value* pointer is into the aRoot object
+static const Json::Value* GetPrincipalObject(const Json::Value& aRoot,
+                                             int& aOutPrincipalKind) {
+  const Json::Value::Members members = aRoot.getMemberNames();
+  // We only support one top level key in the object
+  if (members.size() != 1) {
+    return nullptr;
+  }
+  // members[0] here is the "0", "1", "2", "3" principalKind
+  // that is the top level of the serialized JSON principal
+  const std::string stringPrincipalKind = members[0];
+
+  // Next we take the string value from the JSON
+  // and convert it into the int for the BasePrincipal::PrincipalKind enum
+
+  // Verify that the key is within the valid range
+  int principalKind = std::stoi(stringPrincipalKind);
+  MOZ_ASSERT(BasePrincipal::eNullPrincipal == 0,
+             "We need to rely on 0 being a bounds check for the first "
+             "principal kind.");
+  if (principalKind < 0 || principalKind > BasePrincipal::eKindMax) {
+    return nullptr;
+  }
+  MOZ_ASSERT(principalKind == BasePrincipal::eNullPrincipal ||
+             principalKind == BasePrincipal::eContentPrincipal ||
+             principalKind == BasePrincipal::eExpandedPrincipal ||
+             principalKind == BasePrincipal::eSystemPrincipal);
+  aOutPrincipalKind = principalKind;
+
+  if (!aRoot[stringPrincipalKind].isObject()) {
+    return nullptr;
+  }
+
+  // Return the inner value of the principal object
+  return &aRoot[stringPrincipalKind];
+}
+
+// Accepts the JSON inner object without the wrapping principalKind
+// (See GetPrincipalObject for the inner object response examples)
+// Creates an array of KeyVal objects that are all defined on the principal
+// Each principal type (null, content, expanded) has a KeyVal that stores the
+// fields of the JSON
+//
+// This simplifies deserializing elsewhere as we do the checking for presence
+// and string values here for the complete set of serializable keys that the
+// corresponding principal supports.
+//
+// The KeyVal object has the following fields:
+// - valueWasSerialized: is true if the deserialized JSON contained a string
+// value
+// - value: The string that was serialized for this key
+// - key: an SerializableKeys enum value specific to the principal.
+//        For example content principal is an enum of: eURI, eDomain,
+//        eSuffix, eCSP
+//
+//
+//  Given an inner content principal:
+//  {"0": "https://mozilla.com", "2": "^privateBrowsingId=1"}
+//    |                |          |         |
+//    -----------------------------         |
+//         |           |                    |
+//        Key          ----------------------
+//                                |
+//                              Value
+//
+// They Key "0" corresponds to ContentPrincipal::eURI
+// They Key "1" corresponds to ContentPrincipal::eSuffix
+template <typename T>
+static nsTArray<typename T::KeyVal> GetJSONKeys(const Json::Value* aInput) {
+  int size = T::eMax + 1;
+  nsTArray<typename T::KeyVal> fields;
+  for (int i = 0; i != size; i++) {
+    typename T::KeyVal* field = fields.AppendElement();
+    // field->valueWasSerialized returns if the field was found in the
+    // deserialized code. This simplifies the consumers from having to check
+    // length.
+    field->valueWasSerialized = false;
+    field->key = static_cast<typename T::SerializableKeys>(i);
+    const std::string key = std::to_string(field->key);
+    if (aInput->isMember(key)) {
+      const Json::Value& val = (*aInput)[key];
+      if (val.isString()) {
+        field->value.Append(nsDependentCString(val.asCString()));
+        field->valueWasSerialized = true;
+      }
+    }
+  }
+  return fields;
+}
+
+// Takes a JSON string and parses it turning it into a principal of the
+// corresponding type
+//
+// Given a content principal:
+//
+//                               inner JSON object
+//                                      |
+//       ---------------------------------------------------------
+//       |                                                       |
+// {"1": {"0": "https://mozilla.com", "2": "^privateBrowsingId=1"}}
+//   |     |             |             |            |
+//   |     -----------------------------            |
+//   |              |    |                          |
+// PrincipalKind    |    |                          |
+//                  |    ----------------------------
+//           SerializableKeys           |
+//                                    Value
+//
+// The string is first deserialized with jsoncpp to get the Json::Value of the
+// object. The inner JSON object is parsed with GetPrincipalObject which returns
+// a KeyVal array of the inner object's fields. PrincipalKind is returned by
+// GetPrincipalObject which is then used to decide which principal
+// implementation of FromProperties to call. The corresponding FromProperties
+// call takes the KeyVal fields and turns it into a principal.
+already_AddRefed<BasePrincipal> BasePrincipal::FromJSON(
+    const nsACString& aJSON) {
+  Json::Value root;
+  Json::CharReaderBuilder builder;
+  std::unique_ptr<Json::CharReader> const reader(builder.newCharReader());
+  bool parseSuccess =
+      reader->parse(aJSON.BeginReading(), aJSON.EndReading(), &root, nullptr);
+  if (!parseSuccess) {
+    MOZ_ASSERT(false,
+               "Unable to parse string as JSON to deserialize as a principal");
+    return nullptr;
+  }
+
+  return FromJSON(root);
+}
+
+// Checks if an ExpandedPrincipal is using the legacy format, where
+// sub-principals are Base64 encoded.
+//
+// Given a legacy expanded principal:
+//
+//         *
+// {"2": {"0": "eyIxIjp7IjAiOiJodHRwczovL2EuY29tLyJ9fQ=="}}
+//   |     |                      |
+//   |     ----------           Value
+//   |              |
+// PrincipalKind    |
+//                  |
+//           SerializableKeys
+//
+// The value is a CSV list of Base64 encoded prinipcals. The new format for this
+// principal is:
+//
+//                       Subsumed principals
+//                               |
+//             ------------------------------------
+//         *   |                                  |
+// {"2": {"0": [{"1": {"0": https://mozilla.com"}}]}}
+//   |            |                  |
+//   --------------                Value
+//         |
+//   PrincipalKind
+//
+// It is possible to tell these apart by checking the type of the property noted
+// in both diagrams with an asterisk. In the legacy format the type will be a
+// string and in the new format it will be an array.
+static bool IsLegacyFormat(const Json::Value& aValue) {
+  const auto& specs = std::to_string(ExpandedPrincipal::eSpecs);
+  return aValue.isMember(specs) && aValue[specs].isString();
+}
+
+/* static */
+already_AddRefed<BasePrincipal> BasePrincipal::FromJSON(
+    const Json::Value& aJSON) {
+  int principalKind = -1;
+  const Json::Value* value = GetPrincipalObject(aJSON, principalKind);
+  if (!value) {
+#ifdef DEBUG
+    fprintf(stderr, "Unexpected JSON principal %s\n",
+            aJSON.toStyledString().c_str());
+#endif
+    MOZ_ASSERT(false, "Unexpected JSON to deserialize as a principal");
+
+    return nullptr;
+  }
+  MOZ_ASSERT(principalKind != -1,
+             "PrincipalKind should always be >=0 by this point");
+
+  if (principalKind == eSystemPrincipal) {
+    RefPtr<BasePrincipal> principal =
+        BasePrincipal::Cast(nsContentUtils::GetSystemPrincipal());
+    return principal.forget();
+  }
+
+  if (principalKind == eNullPrincipal) {
+    nsTArray<NullPrincipal::KeyVal> res = GetJSONKeys<NullPrincipal>(value);
+    return NullPrincipal::FromProperties(res);
+  }
+
+  if (principalKind == eContentPrincipal) {
+    nsTArray<ContentPrincipal::KeyVal> res =
+        GetJSONKeys<ContentPrincipal>(value);
+    return ContentPrincipal::FromProperties(res);
+  }
+
+  if (principalKind == eExpandedPrincipal) {
+    // Check if expanded principals is stored in the new or the old format. See
+    // comment for `IsLegacyFormat`.
+    if (IsLegacyFormat(*value)) {
+      nsTArray<ExpandedPrincipal::KeyVal> res =
+          GetJSONKeys<ExpandedPrincipal>(value);
+      return ExpandedPrincipal::FromProperties(res);
+    }
+
+    return ExpandedPrincipal::FromProperties(*value);
+  }
+
+  MOZ_RELEASE_ASSERT(false, "Unexpected enum to deserialize as a principal");
+}
+
+nsresult BasePrincipal::PopulateJSONObject(Json::Value& aObject) {
+  return NS_OK;
+}
+
+// Returns a JSON representation of the principal.
+// Calling BasePrincipal::FromJSON will deserialize the JSON into
+// the corresponding principal type.
+nsresult BasePrincipal::ToJSON(nsACString& aJSON) {
+  MOZ_ASSERT(aJSON.IsEmpty(), "ToJSON only supports an empty result input");
+  aJSON.Truncate();
+
+  Json::Value root = Json::objectValue;
+  nsresult rv = ToJSON(root);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  static StaticAutoPtr<Json::StreamWriterBuilder> sJSONBuilderForPrincipals;
+  if (!sJSONBuilderForPrincipals) {
+    sJSONBuilderForPrincipals = new Json::StreamWriterBuilder();
+    (*sJSONBuilderForPrincipals)["indentation"] = "";
+    (*sJSONBuilderForPrincipals)["emitUTF8"] = true;
+    ClearOnShutdown(&sJSONBuilderForPrincipals);
+  }
+  std::string result = Json::writeString(*sJSONBuilderForPrincipals, root);
+  aJSON.Append(result);
+  if (aJSON.Length() == 0) {
+    MOZ_ASSERT(false, "JSON writer failed to output a principal serialization");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  return NS_OK;
+}
+
+nsresult BasePrincipal::ToJSON(Json::Value& aObject) {
+  static_assert(eKindMax < ArrayLength(JSONEnumKeyStrings));
+  nsresult rv = PopulateJSONObject(
+      (aObject[Json::StaticString(JSONEnumKeyStrings[Kind()])] =
+           Json::objectValue));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return NS_OK;
+}
+
+bool BasePrincipal::FastSubsumesIgnoringFPD(
+    nsIPrincipal* aOther, DocumentDomainConsideration aConsideration) {
+  MOZ_ASSERT(aOther);
+
+  if (Kind() == eContentPrincipal &&
+      !dom::ChromeUtils::IsOriginAttributesEqualIgnoringFPD(
+          mOriginAttributes, Cast(aOther)->mOriginAttributes)) {
+    return false;
+  }
+
+  return SubsumesInternal(aOther, aConsideration);
+}
+
+bool BasePrincipal::Subsumes(nsIPrincipal* aOther,
+                             DocumentDomainConsideration aConsideration) {
+  MOZ_ASSERT(aOther);
+  MOZ_ASSERT_IF(Kind() == eContentPrincipal, mOriginSuffix);
+
+  // Expanded principals handle origin attributes for each of their
+  // sub-principals individually, null principals do only simple checks for
+  // pointer equality, and system principals are immune to origin attributes
+  // checks, so only do this check for content principals.
+  if (Kind() == eContentPrincipal &&
+      mOriginSuffix != Cast(aOther)->mOriginSuffix) {
+    return false;
+  }
+
+  return SubsumesInternal(aOther, aConsideration);
+}
+
+NS_IMETHODIMP
+BasePrincipal::Equals(nsIPrincipal* aOther, bool* aResult) {
+  NS_ENSURE_ARG_POINTER(aOther);
+
+  *aResult = FastEquals(aOther);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::EqualsForPermission(nsIPrincipal* aOther, bool aExactHost,
+                                   bool* aResult) {
+  *aResult = false;
+  NS_ENSURE_ARG_POINTER(aOther);
+  NS_ENSURE_ARG_POINTER(aResult);
+
+  auto* other = Cast(aOther);
+  if (Kind() != other->Kind()) {
+    // Principals of different kinds can't be equal.
+    return NS_OK;
+  }
+
+  if (Kind() == eSystemPrincipal) {
+    *aResult = this == other;
+    return NS_OK;
+  }
+
+  if (Kind() == eNullPrincipal) {
+    // We don't store permissions for NullPrincipals.
+    return NS_OK;
+  }
+
+  MOZ_ASSERT(Kind() == eExpandedPrincipal || Kind() == eContentPrincipal);
+
+  // Certain origin attributes should not be used to isolate permissions.
+  // Create a stripped copy of both OA sets to compare.
+  mozilla::OriginAttributes ourAttrs = mOriginAttributes;
+  PermissionManager::MaybeStripOriginAttributes(false, ourAttrs);
+  mozilla::OriginAttributes theirAttrs = aOther->OriginAttributesRef();
+  PermissionManager::MaybeStripOriginAttributes(false, theirAttrs);
+
+  if (ourAttrs != theirAttrs) {
+    return NS_OK;
+  }
+
+  if (mOriginNoSuffix == other->mOriginNoSuffix) {
+    *aResult = true;
+    return NS_OK;
+  }
+
+  // If we are matching with an exact host, we're done now - the permissions
+  // don't match otherwise, we need to start comparing subdomains!
+  if (aExactHost) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIURI> ourURI;
+  nsresult rv = GetURI(getter_AddRefs(ourURI));
+  NS_ENSURE_SUCCESS(rv, rv);
+  // Some principal types may indicate success, but still return nullptr for
+  // URI.
+  NS_ENSURE_TRUE(ourURI, NS_ERROR_FAILURE);
+
+  nsCOMPtr<nsIURI> otherURI;
+  rv = other->GetURI(getter_AddRefs(otherURI));
+  NS_ENSURE_SUCCESS(rv, rv);
+  NS_ENSURE_TRUE(otherURI, NS_ERROR_FAILURE);
+
+  // Compare schemes
+  nsAutoCString otherScheme;
+  rv = otherURI->GetScheme(otherScheme);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsAutoCString ourScheme;
+  rv = ourURI->GetScheme(ourScheme);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (otherScheme != ourScheme) {
+    return NS_OK;
+  }
+
+  // Compare ports
+  int32_t otherPort;
+  rv = otherURI->GetPort(&otherPort);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  int32_t ourPort;
+  rv = ourURI->GetPort(&ourPort);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (otherPort != ourPort) {
+    return NS_OK;
+  }
+
+  // Check if the host or any subdomain of their host matches.
+  nsAutoCString otherHost;
+  rv = otherURI->GetHost(otherHost);
+  if (NS_FAILED(rv) || otherHost.IsEmpty()) {
+    return NS_OK;
+  }
+
+  nsAutoCString ourHost;
+  rv = ourURI->GetHost(ourHost);
+  if (NS_FAILED(rv) || ourHost.IsEmpty()) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIEffectiveTLDService> tldService =
+      do_GetService(NS_EFFECTIVETLDSERVICE_CONTRACTID);
+  if (!tldService) {
+    NS_ERROR("Should have a tld service!");
+    return NS_ERROR_FAILURE;
+  }
+
+  // This loop will not loop forever, as GetNextSubDomain will eventually fail
+  // with NS_ERROR_INSUFFICIENT_DOMAIN_LEVELS.
+  while (otherHost != ourHost) {
+    rv = tldService->GetNextSubDomain(otherHost, otherHost);
+    if (NS_FAILED(rv)) {
+      if (rv == NS_ERROR_INSUFFICIENT_DOMAIN_LEVELS) {
+        return NS_OK;
+      }
+      return rv;
+    }
+  }
+
+  *aResult = true;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::EqualsConsideringDomain(nsIPrincipal* aOther, bool* aResult) {
+  NS_ENSURE_ARG_POINTER(aOther);
+
+  *aResult = FastEqualsConsideringDomain(aOther);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::EqualsURI(nsIURI* aOtherURI, bool* aResult) {
+  *aResult = false;
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+  return prinURI->EqualsExceptRef(aOtherURI, aResult);
+}
+
+NS_IMETHODIMP
+BasePrincipal::Subsumes(nsIPrincipal* aOther, bool* aResult) {
+  NS_ENSURE_ARG_POINTER(aOther);
+
+  *aResult = FastSubsumes(aOther);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::SubsumesConsideringDomain(nsIPrincipal* aOther, bool* aResult) {
+  NS_ENSURE_ARG_POINTER(aOther);
+
+  *aResult = FastSubsumesConsideringDomain(aOther);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::SubsumesConsideringDomainIgnoringFPD(nsIPrincipal* aOther,
+                                                    bool* aResult) {
+  NS_ENSURE_ARG_POINTER(aOther);
+
+  *aResult = FastSubsumesConsideringDomainIgnoringFPD(aOther);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::CheckMayLoad(nsIURI* aURI, bool aAllowIfInheritsPrincipal) {
+  AssertIsOnMainThread();
+  return CheckMayLoadHelper(aURI, aAllowIfInheritsPrincipal, false, 0);
+}
+
+NS_IMETHODIMP
+BasePrincipal::CheckMayLoadWithReporting(nsIURI* aURI,
+                                         bool aAllowIfInheritsPrincipal,
+                                         uint64_t aInnerWindowID) {
+  AssertIsOnMainThread();
+  return CheckMayLoadHelper(aURI, aAllowIfInheritsPrincipal, true,
+                            aInnerWindowID);
+}
+
+nsresult BasePrincipal::CheckMayLoadHelper(nsIURI* aURI,
+                                           bool aAllowIfInheritsPrincipal,
+                                           bool aReport,
+                                           uint64_t aInnerWindowID) {
+  AssertIsOnMainThread();  // Accesses non-threadsafe URI flags and the
+                           // non-threadsafe ExtensionPolicyService
+  NS_ENSURE_ARG_POINTER(aURI);
+  MOZ_ASSERT(
+      aReport || aInnerWindowID == 0,
+      "Why do we have an inner window id if we're not supposed to report?");
+
+  // Check the internal method first, which allows us to quickly approve loads
+  // for the System Principal.
+  if (MayLoadInternal(aURI)) {
+    return NS_OK;
+  }
+
+  nsresult rv;
+  if (aAllowIfInheritsPrincipal) {
+    // If the caller specified to allow loads of URIs that inherit
+    // our principal, allow the load if this URI inherits its principal.
+    bool doesInheritSecurityContext;
+    rv = NS_URIChainHasFlags(aURI,
+                             nsIProtocolHandler::URI_INHERITS_SECURITY_CONTEXT,
+                             &doesInheritSecurityContext);
+    if (NS_SUCCEEDED(rv) && doesInheritSecurityContext) {
+      return NS_OK;
+    }
+  }
+
+  // Web Accessible Resources in MV2 Extensions are marked with
+  // URI_FETCHABLE_BY_ANYONE
+  bool fetchableByAnyone;
+  rv = NS_URIChainHasFlags(aURI, nsIProtocolHandler::URI_FETCHABLE_BY_ANYONE,
+                           &fetchableByAnyone);
+  if (NS_SUCCEEDED(rv) && fetchableByAnyone) {
+    return NS_OK;
+  }
+
+  // Get the principal uri for the last flag check or error.
+  nsCOMPtr<nsIURI> prinURI;
+  rv = GetURI(getter_AddRefs(prinURI));
+  if (!(NS_SUCCEEDED(rv) && prinURI)) {
+    return NS_ERROR_DOM_BAD_URI;
+  }
+
+  // If MV3 Extension uris are web accessible by this principal it is allowed to
+  // load.
+  bool maybeWebAccessible = false;
+  NS_URIChainHasFlags(aURI, nsIProtocolHandler::WEBEXT_URI_WEB_ACCESSIBLE,
+                      &maybeWebAccessible);
+  NS_ENSURE_SUCCESS(rv, rv);
+  if (maybeWebAccessible) {
+    bool isWebAccessible = false;
+    rv = ExtensionPolicyService::GetSingleton().SourceMayLoadExtensionURI(
+        prinURI, aURI, &isWebAccessible);
+    if (NS_SUCCEEDED(rv) && isWebAccessible) {
+      return NS_OK;
+    }
+  }
+
+  if (aReport) {
+    nsScriptSecurityManager::ReportError(
+        "CheckSameOriginError", prinURI, aURI,
+        mOriginAttributes.mPrivateBrowsingId > 0, aInnerWindowID);
+  }
+
+  return NS_ERROR_DOM_BAD_URI;
+}
+
+NS_IMETHODIMP
+BasePrincipal::IsThirdPartyURI(nsIURI* aURI, bool* aRes) {
+  if (IsSystemPrincipal() || (AddonPolicyCore() && AddonAllowsLoad(aURI))) {
+    *aRes = false;
+    return NS_OK;
+  }
+
+  *aRes = true;
+  // If we do not have a URI its always 3rd party.
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+  ThirdPartyUtil* thirdPartyUtil = ThirdPartyUtil::GetInstance();
+  return thirdPartyUtil->IsThirdPartyURI(prinURI, aURI, aRes);
+}
+
+NS_IMETHODIMP
+BasePrincipal::IsThirdPartyPrincipal(nsIPrincipal* aPrin, bool* aRes) {
+  *aRes = true;
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+  return aPrin->IsThirdPartyURI(prinURI, aRes);
+}
+
+NS_IMETHODIMP
+BasePrincipal::IsThirdPartyChannel(nsIChannel* aChan, bool* aRes) {
+  AssertIsOnMainThread();
+  if (IsSystemPrincipal()) {
+    // Nothing is 3rd party to the system principal.
+    *aRes = false;
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIURI> prinURI;
+  GetURI(getter_AddRefs(prinURI));
+  ThirdPartyUtil* thirdPartyUtil = ThirdPartyUtil::GetInstance();
+  return thirdPartyUtil->IsThirdPartyChannel(aChan, prinURI, aRes);
+}
+
+NS_IMETHODIMP
+BasePrincipal::IsSameOrigin(nsIURI* aURI, bool* aRes) {
+  *aRes = false;
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    // Note that expanded and system principals return here, because they have
+    // no URI.
+    return NS_OK;
+  }
+  *aRes = nsScriptSecurityManager::SecurityCompareURIs(prinURI, aURI);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::IsL10nAllowed(nsIURI* aURI, bool* aRes) {
+  AssertIsOnMainThread();  // URI_DANGEROUS_TO_LOAD is not threadsafe to query.
+  *aRes = false;
+
+  if (nsContentUtils::IsErrorPage(aURI)) {
+    *aRes = true;
+    return NS_OK;
+  }
+
+  // The system principal is always allowed.
+  if (IsSystemPrincipal()) {
+    *aRes = true;
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIURI> uri;
+  nsresult rv = GetURI(getter_AddRefs(uri));
+  NS_ENSURE_SUCCESS(rv, NS_OK);
+
+  bool hasFlags;
+
+  // Allow access to uris that cannot be loaded by web content.
+  rv = NS_URIChainHasFlags(uri, nsIProtocolHandler::URI_DANGEROUS_TO_LOAD,
+                           &hasFlags);
+  NS_ENSURE_SUCCESS(rv, NS_OK);
+  if (hasFlags) {
+    *aRes = true;
+    return NS_OK;
+  }
+
+  // UI resources also get access.
+  rv = NS_URIChainHasFlags(uri, nsIProtocolHandler::URI_IS_UI_RESOURCE,
+                           &hasFlags);
+  NS_ENSURE_SUCCESS(rv, NS_OK);
+  if (hasFlags) {
+    *aRes = true;
+    return NS_OK;
+  }
+
+  auto policy = AddonPolicyCore();
+  *aRes = (policy && policy->IsPrivileged());
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::AllowsRelaxStrictFileOriginPolicy(nsIURI* aURI, bool* aRes) {
+  *aRes = false;
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+  *aRes = NS_RelaxStrictFileOriginPolicy(aURI, prinURI);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetPrefLightCacheKey(nsIURI* aURI, bool aWithCredentials,
+                                    const OriginAttributes& aOriginAttributes,
+                                    nsACString& _retval) {
+  _retval.Truncate();
+  constexpr auto space = " "_ns;
+
+  nsCOMPtr<nsIURI> uri;
+  nsresult rv = GetURI(getter_AddRefs(uri));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsAutoCString scheme, host, port;
+  if (uri) {
+    uri->GetScheme(scheme);
+    uri->GetHost(host);
+    port.AppendInt(NS_GetRealPort(uri));
+  }
+
+  if (aWithCredentials) {
+    _retval.AssignLiteral("cred");
+  } else {
+    _retval.AssignLiteral("nocred");
+  }
+
+  nsAutoCString spec;
+  rv = aURI->GetSpec(spec);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsAutoCString originAttributesSuffix;
+  aOriginAttributes.CreateSuffix(originAttributesSuffix);
+
+  _retval.Append(space + scheme + space + host + space + port + space + spec +
+                 space + originAttributesSuffix);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::HasFirstpartyStorageAccess(mozIDOMWindow* aCheckWindow,
+                                          uint32_t* aRejectedReason,
+                                          bool* aOutAllowed) {
+  AssertIsOnMainThread();
+  *aRejectedReason = 0;
+  *aOutAllowed = false;
+
+  nsPIDOMWindowInner* win = nsPIDOMWindowInner::From(aCheckWindow);
+  nsCOMPtr<nsIURI> uri;
+  nsresult rv = GetURI(getter_AddRefs(uri));
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+  *aOutAllowed = ShouldAllowAccessFor(win, uri, aRejectedReason);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetIsNullPrincipal(bool* aResult) {
+  *aResult = Kind() == eNullPrincipal;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetIsContentPrincipal(bool* aResult) {
+  *aResult = Kind() == eContentPrincipal;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetIsExpandedPrincipal(bool* aResult) {
+  *aResult = Kind() == eExpandedPrincipal;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetAsciiSpec(nsACString& aSpec) {
+  aSpec.Truncate();
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+  return prinURI->GetAsciiSpec(aSpec);
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetSpec(nsACString& aSpec) {
+  aSpec.Truncate();
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+  return prinURI->GetSpec(aSpec);
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetAsciiHost(nsACString& aHost) {
+  aHost.Truncate();
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+  return prinURI->GetAsciiHost(aHost);
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetExposablePrePath(nsACString& aPrepath) {
+  aPrepath.Truncate();
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIURI> exposableURI = net::nsIOService::CreateExposableURI(prinURI);
+  return exposableURI->GetDisplayPrePath(aPrepath);
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetExposableSpec(nsACString& aSpec) {
+  aSpec.Truncate();
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+  nsCOMPtr<nsIURI> clone;
+  rv = NS_MutateURI(prinURI)
+           .SetQuery(""_ns)
+           .SetRef(""_ns)
+           .SetUserPass(""_ns)
+           .Finalize(clone);
+  NS_ENSURE_SUCCESS(rv, rv);
+  return clone->GetAsciiSpec(aSpec);
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetPrePath(nsACString& aPath) {
+  aPath.Truncate();
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+  return prinURI->GetPrePath(aPath);
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetFilePath(nsACString& aPath) {
+  aPath.Truncate();
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+  return prinURI->GetFilePath(aPath);
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetIsSystemPrincipal(bool* aResult) {
+  *aResult = IsSystemPrincipal();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetIsAddonOrExpandedAddonPrincipal(bool* aResult) {
+  *aResult = AddonPolicyCore() || ContentScriptAddonPolicyCore();
+  return NS_OK;
+}
+
+NS_IMETHODIMP BasePrincipal::GetIsOnion(bool* aIsOnion) {
+  *aIsOnion = false;
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+
+  nsAutoCString host;
+  rv = prinURI->GetHost(host);
+  if (NS_FAILED(rv)) {
+    return NS_OK;
+  }
+  *aIsOnion = StringEndsWith(host, ".onion"_ns);
+  return NS_OK;
+}
+
+NS_IMETHODIMP BasePrincipal::GetIsIpAddress(bool* aIsIpAddress) {
+  *aIsIpAddress = false;
+
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+
+  nsAutoCString host;
+  rv = prinURI->GetHost(host);
+  if (NS_FAILED(rv)) {
+    return NS_OK;
+  }
+
+  PRNetAddr prAddr;
+  memset(&prAddr, 0, sizeof(prAddr));
+
+  if (PR_StringToNetAddr(host.get(), &prAddr) == PR_SUCCESS) {
+    *aIsIpAddress = true;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP BasePrincipal::GetIsLocalIpAddress(bool* aIsIpAddress) {
+  *aIsIpAddress = false;
+
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIIOService> ioService = do_GetIOService(&rv);
+  if (NS_FAILED(rv) || !ioService) {
+    return NS_OK;
+  }
+  rv = ioService->HostnameIsLocalIPAddress(prinURI, aIsIpAddress);
+  if (NS_FAILED(rv)) {
+    *aIsIpAddress = false;
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetScheme(nsACString& aScheme) {
+  aScheme.Truncate();
+
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+
+  return prinURI->GetScheme(aScheme);
+}
+
+NS_IMETHODIMP
+BasePrincipal::SchemeIs(const char* aScheme, bool* aResult) {
+  *aResult = false;
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_WARN_IF(NS_FAILED(rv)) || !prinURI) {
+    return NS_OK;
+  }
+  *aResult = prinURI->SchemeIs(aScheme);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::IsURIInPrefList(const char* aPref, bool* aResult) {
+  AssertIsOnMainThread();
+  *aResult = false;
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+  *aResult = nsContentUtils::IsURIInPrefList(prinURI, aPref);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::IsURIInList(const nsACString& aList, bool* aResult) {
+  *aResult = false;
+  nsCOMPtr<nsIURI> prinURI;
+
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+
+  *aResult = nsContentUtils::IsURIInList(prinURI, nsCString(aList));
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::IsContentAccessibleAboutURI(bool* aResult) {
+  *aResult = false;
+
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+
+  if (!prinURI->SchemeIs("about")) {
+    return NS_OK;
+  }
+
+  *aResult = NS_IsContentAccessibleAboutURI(prinURI);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetIsOriginPotentiallyTrustworthy(bool* aResult) {
+  AssertIsOnMainThread();
+  *aResult = false;
+
+  nsCOMPtr<nsIURI> uri;
+  nsresult rv = GetURI(getter_AddRefs(uri));
+  if (NS_FAILED(rv) || !uri) {
+    return NS_OK;
+  }
+
+  *aResult = nsMixedContentBlocker::IsPotentiallyTrustworthyOrigin(uri);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetIsLoopbackHost(bool* aRes) {
+  AssertIsOnMainThread();
+  *aRes = false;
+  nsAutoCString host;
+  nsresult rv = GetHost(host);
+  // Swallow potential failure as this method is infallible.
+  NS_ENSURE_SUCCESS(rv, NS_OK);
+
+  *aRes = nsMixedContentBlocker::IsPotentiallyTrustworthyLoopbackHost(host);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetAboutModuleFlags(uint32_t* flags) {
+  AssertIsOnMainThread();
+  *flags = 0;
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+  if (!prinURI->SchemeIs("about")) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIAboutModule> aboutModule;
+  rv = NS_GetAboutModule(prinURI, getter_AddRefs(aboutModule));
+  if (NS_FAILED(rv) || !aboutModule) {
+    return rv;
+  }
+  return aboutModule->GetURIFlags(prinURI, flags);
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetOriginAttributes(JSContext* aCx,
+                                   JS::MutableHandle<JS::Value> aVal) {
+  if (NS_WARN_IF(!ToJSValue(aCx, mOriginAttributes, aVal))) {
+    return NS_ERROR_FAILURE;
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetOriginSuffix(nsACString& aOriginAttributes) {
+  MOZ_ASSERT(mOriginSuffix);
+  mOriginSuffix->ToUTF8String(aOriginAttributes);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetUserContextId(uint32_t* aUserContextId) {
+  *aUserContextId = UserContextId();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetPrivateBrowsingId(uint32_t* aPrivateBrowsingId) {
+  *aPrivateBrowsingId = PrivateBrowsingId();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetIsInIsolatedMozBrowserElement(
+    bool* aIsInIsolatedMozBrowserElement) {
+  *aIsInIsolatedMozBrowserElement = IsInIsolatedMozBrowserElement();
+  return NS_OK;
+}
+
+nsresult BasePrincipal::GetAddonPolicy(
+    extensions::WebExtensionPolicy** aResult) {
+  AssertIsOnMainThread();
+  RefPtr<extensions::WebExtensionPolicy> policy(AddonPolicy());
+  policy.forget(aResult);
+  return NS_OK;
+}
+
+nsresult BasePrincipal::GetContentScriptAddonPolicy(
+    extensions::WebExtensionPolicy** aResult) {
+  RefPtr<extensions::WebExtensionPolicy> policy(ContentScriptAddonPolicy());
+  policy.forget(aResult);
+  return NS_OK;
+}
+
+extensions::WebExtensionPolicy* BasePrincipal::AddonPolicy() {
+  AssertIsOnMainThread();
+  RefPtr<extensions::WebExtensionPolicyCore> core = AddonPolicyCore();
+  return core ? core->GetMainThreadPolicy() : nullptr;
+}
+
+RefPtr<extensions::WebExtensionPolicyCore> BasePrincipal::AddonPolicyCore() {
+  if (Is<ContentPrincipal>()) {
+    return As<ContentPrincipal>()->AddonPolicyCore();
+  }
+  return nullptr;
+}
+
+bool BasePrincipal::AddonHasPermission(const nsAtom* aPerm) {
+  if (auto policy = AddonPolicyCore()) {
+    return policy->HasPermission(aPerm);
+  }
+  return false;
+}
+
+nsIPrincipal* BasePrincipal::PrincipalToInherit(nsIURI* aRequestedURI) {
+  if (Is<ExpandedPrincipal>()) {
+    return As<ExpandedPrincipal>()->PrincipalToInherit(aRequestedURI);
+  }
+  return this;
+}
+
+bool BasePrincipal::OverridesCSP(nsIPrincipal* aDocumentPrincipal) {
+  MOZ_ASSERT(aDocumentPrincipal);
+
+  // Expanded principals override CSP if and only if they subsume the document
+  // principal.
+  if (mKind == eExpandedPrincipal) {
+    return FastSubsumes(aDocumentPrincipal);
+  }
+  // Extension principals always override the CSP of non-extension principals.
+  // This is primarily for the sake of their stylesheets, which are usually
+  // loaded from channels and cannot have expanded principals.
+  return (AddonPolicyCore() &&
+          !BasePrincipal::Cast(aDocumentPrincipal)->AddonPolicyCore());
+}
+
+already_AddRefed<BasePrincipal> BasePrincipal::CreateContentPrincipal(
+    nsIURI* aURI, const OriginAttributes& aAttrs, nsIURI* aInitialDomain) {
+  MOZ_ASSERT(aURI);
+
+  nsAutoCString originNoSuffix;
+  nsresult rv =
+      ContentPrincipal::GenerateOriginNoSuffixFromURI(aURI, originNoSuffix);
+  if (NS_FAILED(rv)) {
+    // If the generation of the origin fails, we still want to have a valid
+    // principal. Better to return a null principal here.
+    return NullPrincipal::Create(aAttrs);
+  }
+
+  return CreateContentPrincipal(aURI, aAttrs, originNoSuffix, aInitialDomain);
+}
+
+already_AddRefed<BasePrincipal> BasePrincipal::CreateContentPrincipal(
+    nsIURI* aURI, const OriginAttributes& aAttrs,
+    const nsACString& aOriginNoSuffix, nsIURI* aInitialDomain) {
+  MOZ_ASSERT(aURI);
+  MOZ_ASSERT(!aOriginNoSuffix.IsEmpty());
+
+  // If the URI is supposed to inherit the security context of whoever loads it,
+  // we shouldn't make a content principal for it.
+  bool inheritsPrincipal;
+  nsresult rv = NS_URIChainHasFlags(
+      aURI, nsIProtocolHandler::URI_INHERITS_SECURITY_CONTEXT,
+      &inheritsPrincipal);
+  if (NS_FAILED(rv) || inheritsPrincipal) {
+    return NullPrincipal::Create(aAttrs);
+  }
+
+  // Check whether the URI knows what its principal is supposed to be.
+#if defined(MOZ_THUNDERBIRD) || defined(MOZ_SUITE)
+  nsCOMPtr<nsIURIWithSpecialOrigin> uriWithSpecialOrigin =
+      do_QueryInterface(aURI);
+  if (uriWithSpecialOrigin) {
+    nsCOMPtr<nsIURI> origin;
+    rv = uriWithSpecialOrigin->GetOrigin(getter_AddRefs(origin));
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return nullptr;
+    }
+    MOZ_ASSERT(origin);
+    OriginAttributes attrs;
+    RefPtr<BasePrincipal> principal =
+        CreateContentPrincipal(origin, attrs, aInitialDomain);
+    return principal.forget();
+  }
+#endif
+
+  nsCOMPtr<nsIPrincipal> blobPrincipal;
+  if (dom::BlobURLProtocolHandler::GetBlobURLPrincipal(
+          aURI, getter_AddRefs(blobPrincipal))) {
+    MOZ_ASSERT(blobPrincipal);
+    MOZ_ASSERT(!aInitialDomain,
+               "an initial domain for a blob URI makes no sense");
+    RefPtr<BasePrincipal> principal = Cast(blobPrincipal);
+    return principal.forget();
+  }
+
+  // Mint a content principal.
+  RefPtr<ContentPrincipal> principal =
+      new ContentPrincipal(aURI, aAttrs, aOriginNoSuffix, aInitialDomain);
+  return principal.forget();
+}
+
+already_AddRefed<BasePrincipal> BasePrincipal::CreateContentPrincipal(
+    const nsACString& aOrigin) {
+  MOZ_ASSERT(!StringBeginsWith(aOrigin, "["_ns),
+             "CreateContentPrincipal does not support System and Expanded "
+             "principals");
+
+  MOZ_ASSERT(
+      !StringBeginsWith(aOrigin, nsLiteralCString(NS_NULLPRINCIPAL_SCHEME ":")),
+      "CreateContentPrincipal does not support NullPrincipal");
+
+  nsAutoCString originNoSuffix;
+  OriginAttributes attrs;
+  if (!attrs.PopulateFromOrigin(aOrigin, originNoSuffix)) {
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIURI> uri;
+  nsresult rv = NS_NewURI(getter_AddRefs(uri), originNoSuffix);
+  NS_ENSURE_SUCCESS(rv, nullptr);
+
+  return BasePrincipal::CreateContentPrincipal(uri, attrs);
+}
+
+already_AddRefed<BasePrincipal> BasePrincipal::CloneForcingOriginAttributes(
+    const OriginAttributes& aOriginAttributes) {
+  if (NS_WARN_IF(!IsContentPrincipal())) {
+    return nullptr;
+  }
+
+  nsAutoCString originNoSuffix;
+  nsresult rv = GetOriginNoSuffix(originNoSuffix);
+  NS_ENSURE_SUCCESS(rv, nullptr);
+
+  nsCOMPtr<nsIURI> uri;
+  MOZ_ALWAYS_SUCCEEDS(GetURI(getter_AddRefs(uri)));
+
+  // XXX: This does not copy over the domain. Should it?
+  RefPtr<ContentPrincipal> copy =
+      new ContentPrincipal(uri, aOriginAttributes, originNoSuffix, nullptr);
+  return copy.forget();
+}
+
+extensions::WebExtensionPolicy* BasePrincipal::ContentScriptAddonPolicy() {
+  AssertIsOnMainThread();
+  RefPtr<extensions::WebExtensionPolicyCore> core =
+      ContentScriptAddonPolicyCore();
+  return core ? core->GetMainThreadPolicy() : nullptr;
+}
+
+RefPtr<extensions::WebExtensionPolicyCore>
+BasePrincipal::ContentScriptAddonPolicyCore() {
+  if (!Is<ExpandedPrincipal>()) {
+    return nullptr;
+  }
+
+  auto* expanded = As<ExpandedPrincipal>();
+  for (const auto& prin : expanded->AllowList()) {
+    if (RefPtr<extensions::WebExtensionPolicyCore> policy =
+            BasePrincipal::Cast(prin)->AddonPolicyCore()) {
+      return policy;
+    }
+  }
+
+  return nullptr;
+}
+
+bool BasePrincipal::AddonAllowsLoad(nsIURI* aURI,
+                                    bool aExplicit /* = false */) {
+  if (Is<ExpandedPrincipal>()) {
+    return As<ExpandedPrincipal>()->AddonAllowsLoad(aURI, aExplicit);
+  }
+  if (auto policy = AddonPolicyCore()) {
+    return policy->CanAccessURI(aURI, aExplicit);
+  }
+  return false;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetLocalStorageQuotaKey(nsACString& aKey) {
+  aKey.Truncate();
+
+  nsCOMPtr<nsIURI> uri;
+  nsresult rv = GetURI(getter_AddRefs(uri));
+  NS_ENSURE_SUCCESS(rv, rv);
+  NS_ENSURE_TRUE(uri, NS_ERROR_UNEXPECTED);
+
+  // The special handling of the file scheme should be consistent with
+  // GetStorageOriginKey.
+
+  nsAutoCString baseDomain;
+  rv = uri->GetAsciiHost(baseDomain);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (baseDomain.IsEmpty() && uri->SchemeIs("file")) {
+    nsCOMPtr<nsIURL> url = do_QueryInterface(uri, &rv);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    rv = url->GetDirectory(baseDomain);
+    NS_ENSURE_SUCCESS(rv, rv);
+  } else {
+    nsCOMPtr<nsIEffectiveTLDService> eTLDService(
+        do_GetService(NS_EFFECTIVETLDSERVICE_CONTRACTID, &rv));
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    nsAutoCString eTLDplusOne;
+    rv = eTLDService->GetBaseDomain(uri, 0, eTLDplusOne);
+    if (NS_SUCCEEDED(rv)) {
+      baseDomain = eTLDplusOne;
+    } else if (rv == NS_ERROR_HOST_IS_IP_ADDRESS ||
+               rv == NS_ERROR_INSUFFICIENT_DOMAIN_LEVELS) {
+      rv = NS_OK;
+    }
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  OriginAttributesRef().CreateSuffix(aKey);
+
+  nsAutoCString subdomainsDBKey;
+  rv = dom::StorageUtils::CreateReversedDomain(baseDomain, subdomainsDBKey);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  aKey.Append(':');
+  aKey.Append(subdomainsDBKey);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetNextSubDomainPrincipal(
+    nsIPrincipal** aNextSubDomainPrincipal) {
+  nsCOMPtr<nsIURI> uri;
+  nsresult rv = GetURI(getter_AddRefs(uri));
+  if (NS_FAILED(rv) || !uri) {
+    return NS_OK;
+  }
+
+  nsAutoCString host;
+  rv = uri->GetHost(host);
+  if (NS_FAILED(rv) || host.IsEmpty()) {
+    return NS_OK;
+  }
+
+  nsCString subDomain;
+  rv = nsEffectiveTLDService::GetInstance()->GetNextSubDomain(host, subDomain);
+
+  if (NS_FAILED(rv) || subDomain.IsEmpty()) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIURI> subDomainURI;
+  rv = NS_MutateURI(uri).SetHost(subDomain).Finalize(subDomainURI);
+  if (NS_FAILED(rv) || !subDomainURI) {
+    return NS_OK;
+  }
+  // Copy the attributes over
+  mozilla::OriginAttributes attrs = OriginAttributesRef();
+
+  if (!StaticPrefs::permissions_isolateBy_userContext()) {
+    // Disable userContext for permissions.
+    attrs.StripAttributes(mozilla::OriginAttributes::STRIP_USER_CONTEXT_ID);
+  }
+  RefPtr<nsIPrincipal> principal =
+      mozilla::BasePrincipal::CreateContentPrincipal(subDomainURI, attrs);
+
+  if (!principal) {
+    return NS_OK;
+  }
+  principal.forget(aNextSubDomainPrincipal);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetStorageOriginKey(nsACString& aOriginKey) {
+  aOriginKey.Truncate();
+
+  nsCOMPtr<nsIURI> uri;
+  nsresult rv = GetURI(getter_AddRefs(uri));
+  NS_ENSURE_SUCCESS(rv, rv);
+  NS_ENSURE_TRUE(uri, NS_ERROR_UNEXPECTED);
+
+  // The special handling of the file scheme should be consistent with
+  // GetLocalStorageQuotaKey.
+
+  nsAutoCString domainOrigin;
+  rv = uri->GetAsciiHost(domainOrigin);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (domainOrigin.IsEmpty()) {
+    // For the file:/// protocol use the exact directory as domain.
+    if (uri->SchemeIs("file")) {
+      nsCOMPtr<nsIURL> url = do_QueryInterface(uri, &rv);
+      NS_ENSURE_SUCCESS(rv, rv);
+      rv = url->GetDirectory(domainOrigin);
+      NS_ENSURE_SUCCESS(rv, rv);
+    }
+  }
+
+  // Append reversed domain
+  nsAutoCString reverseDomain;
+  rv = dom::StorageUtils::CreateReversedDomain(domainOrigin, reverseDomain);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  aOriginKey.Append(reverseDomain);
+
+  // Append scheme
+  nsAutoCString scheme;
+  rv = uri->GetScheme(scheme);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  aOriginKey.Append(':');
+  aOriginKey.Append(scheme);
+
+  // Append port if any
+  int32_t port = NS_GetRealPort(uri);
+  if (port != -1) {
+    aOriginKey.Append(nsPrintfCString(":%d", port));
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetIsScriptAllowedByPolicy(bool* aIsScriptAllowedByPolicy) {
+  AssertIsOnMainThread();
+  *aIsScriptAllowedByPolicy = false;
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+  nsIScriptSecurityManager* ssm = nsContentUtils::GetSecurityManager();
+  if (!ssm) {
+    return NS_ERROR_UNEXPECTED;
+  }
+  return ssm->PolicyAllowsScript(prinURI, aIsScriptAllowedByPolicy);
+}
+
+bool SiteIdentifier::Equals(const SiteIdentifier& aOther) const {
+  MOZ_ASSERT(IsInitialized());
+  MOZ_ASSERT(aOther.IsInitialized());
+  return mPrincipal->FastEquals(aOther.mPrincipal);
+}
+
+NS_IMETHODIMP
+BasePrincipal::CreateReferrerInfo(mozilla::dom::ReferrerPolicy aReferrerPolicy,
+                                  nsIReferrerInfo** _retval) {
+  nsCOMPtr<nsIURI> prinURI;
+  RefPtr<dom::ReferrerInfo> info;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    info = new dom::ReferrerInfo(nullptr);
+    info.forget(_retval);
+    return NS_OK;
+  }
+  info = new dom::ReferrerInfo(prinURI, aReferrerPolicy);
+  info.forget(_retval);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BasePrincipal::GetPrecursorPrincipal(nsIPrincipal** aPrecursor) {
+  *aPrecursor = nullptr;
+  return NS_OK;
+}
+
+NS_IMPL_ADDREF(BasePrincipal::Deserializer)
+NS_IMPL_RELEASE(BasePrincipal::Deserializer)
+
+NS_INTERFACE_MAP_BEGIN(BasePrincipal::Deserializer)
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+  NS_INTERFACE_MAP_ENTRY(nsISerializable)
+  if (mPrincipal) {
+    return mPrincipal->QueryInterface(aIID, aInstancePtr);
+  } else
+NS_INTERFACE_MAP_END
+
+NS_IMETHODIMP
+BasePrincipal::Deserializer::Write(nsIObjectOutputStream* aStream) {
+  // Read is used still for legacy principals
+  MOZ_RELEASE_ASSERT(false, "Old style serialization is removed");
+  return NS_OK;
+}
+
+/* static */
+void BasePrincipal::SetJSONValue(Json::Value& aObject, const char* aKey,
+                                 const nsCString& aValue) {
+  aObject[Json::StaticString(aKey)] =
+      Json::Value(aValue.BeginReading(), aValue.EndReading());
+}
+
+}  // namespace mozilla
diff --git a/caps/BasePrincipal.h b/caps/BasePrincipal.h
new file mode 100644
index 0000000000..8b4a9ffee0
--- /dev/null
+++ b/caps/BasePrincipal.h
@@ -0,0 +1,472 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_BasePrincipal_h
+#define mozilla_BasePrincipal_h
+
+#include <stdint.h>
+#include "ErrorList.h"
+#include "js/TypeDecls.h"
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/OriginAttributes.h"
+#include "mozilla/RefPtr.h"
+#include "nsAtom.h"
+#include "nsIObjectOutputStream.h"
+#include "nsIPrincipal.h"
+#include "nsJSPrincipals.h"
+#include "nsStringFwd.h"
+#include "nscore.h"
+
+class ExpandedPrincipal;
+class mozIDOMWindow;
+class nsIChannel;
+class nsIReferrerInfo;
+class nsISupports;
+class nsIURI;
+namespace Json {
+class Value;
+}
+
+namespace mozilla {
+
+namespace dom {
+enum class ReferrerPolicy : uint8_t;
+}
+
+namespace extensions {
+class WebExtensionPolicy;
+class WebExtensionPolicyCore;
+}  // namespace extensions
+
+class BasePrincipal;
+
+// Content principals (and content principals embedded within expanded
+// principals) stored in SiteIdentifier are guaranteed to contain only the
+// eTLD+1 part of the original domain. This is used to determine whether two
+// origins are same-site: if it's possible for two origins to access each other
+// (maybe after mutating document.domain), then they must have the same site
+// identifier.
+class SiteIdentifier {
+ public:
+  void Init(BasePrincipal* aPrincipal) {
+    MOZ_ASSERT(aPrincipal);
+    mPrincipal = aPrincipal;
+  }
+
+  bool IsInitialized() const { return !!mPrincipal; }
+
+  bool Equals(const SiteIdentifier& aOther) const;
+
+ private:
+  friend class ::ExpandedPrincipal;
+
+  BasePrincipal* GetPrincipal() const {
+    MOZ_ASSERT(IsInitialized());
+    return mPrincipal;
+  }
+
+  RefPtr<BasePrincipal> mPrincipal;
+};
+
+/*
+ * Base class from which all nsIPrincipal implementations inherit. Use this for
+ * default implementations and other commonalities between principal
+ * implementations.
+ *
+ * We should merge nsJSPrincipals into this class at some point.
+ */
+class BasePrincipal : public nsJSPrincipals {
+ public:
+  // Warning: this enum impacts Principal serialization into JSON format.
+  // Only update if you know exactly what you are doing
+  enum PrincipalKind {
+    eNullPrincipal = 0,
+    eContentPrincipal,
+    eExpandedPrincipal,
+    eSystemPrincipal,
+    eKindMax = eSystemPrincipal
+  };
+
+  template <typename T>
+  bool Is() const {
+    return mKind == T::Kind();
+  }
+
+  template <typename T>
+  T* As() {
+    MOZ_ASSERT(Is<T>());
+    return static_cast<T*>(this);
+  }
+
+  enum DocumentDomainConsideration {
+    DontConsiderDocumentDomain,
+    ConsiderDocumentDomain
+  };
+  bool Subsumes(nsIPrincipal* aOther,
+                DocumentDomainConsideration aConsideration);
+
+  NS_IMETHOD GetOrigin(nsACString& aOrigin) final;
+  NS_IMETHOD GetAsciiOrigin(nsACString& aOrigin) override;
+  NS_IMETHOD GetOriginNoSuffix(nsACString& aOrigin) final;
+  NS_IMETHOD Equals(nsIPrincipal* other, bool* _retval) final;
+  NS_IMETHOD EqualsConsideringDomain(nsIPrincipal* other, bool* _retval) final;
+  NS_IMETHOD EqualsURI(nsIURI* aOtherURI, bool* _retval) override;
+  NS_IMETHOD EqualsForPermission(nsIPrincipal* other, bool aExactHost,
+                                 bool* _retval) final;
+  NS_IMETHOD Subsumes(nsIPrincipal* other, bool* _retval) final;
+  NS_IMETHOD SubsumesConsideringDomain(nsIPrincipal* other,
+                                       bool* _retval) final;
+  NS_IMETHOD SubsumesConsideringDomainIgnoringFPD(nsIPrincipal* other,
+                                                  bool* _retval) final;
+  NS_IMETHOD CheckMayLoad(nsIURI* uri, bool allowIfInheritsPrincipal) final;
+  NS_IMETHOD CheckMayLoadWithReporting(nsIURI* uri,
+                                       bool allowIfInheritsPrincipal,
+                                       uint64_t innerWindowID) final;
+  NS_IMETHOD GetAddonPolicy(extensions::WebExtensionPolicy** aResult) final;
+  NS_IMETHOD GetContentScriptAddonPolicy(
+      extensions::WebExtensionPolicy** aResult) final;
+  NS_IMETHOD GetIsNullPrincipal(bool* aResult) override;
+  NS_IMETHOD GetIsContentPrincipal(bool* aResult) override;
+  NS_IMETHOD GetIsExpandedPrincipal(bool* aResult) override;
+  NS_IMETHOD GetIsSystemPrincipal(bool* aResult) override;
+  NS_IMETHOD GetScheme(nsACString& aScheme) override;
+  NS_IMETHOD SchemeIs(const char* aScheme, bool* aResult) override;
+  NS_IMETHOD IsURIInPrefList(const char* aPref, bool* aResult) override;
+  NS_IMETHOD IsURIInList(const nsACString& aList, bool* aResult) override;
+  NS_IMETHOD IsContentAccessibleAboutURI(bool* aResult) override;
+  NS_IMETHOD IsL10nAllowed(nsIURI* aURI, bool* aResult) override;
+  NS_IMETHOD GetAboutModuleFlags(uint32_t* flags) override;
+  NS_IMETHOD GetIsAddonOrExpandedAddonPrincipal(bool* aResult) override;
+  NS_IMETHOD GetOriginAttributes(JSContext* aCx,
+                                 JS::MutableHandle<JS::Value> aVal) final;
+  NS_IMETHOD GetAsciiSpec(nsACString& aSpec) override;
+  NS_IMETHOD GetSpec(nsACString& aSpec) override;
+  NS_IMETHOD GetExposablePrePath(nsACString& aResult) override;
+  NS_IMETHOD GetExposableSpec(nsACString& aSpec) override;
+  NS_IMETHOD GetHostPort(nsACString& aRes) override;
+  NS_IMETHOD GetHost(nsACString& aRes) override;
+  NS_IMETHOD GetPrePath(nsACString& aResult) override;
+  NS_IMETHOD GetFilePath(nsACString& aResult) override;
+  NS_IMETHOD GetOriginSuffix(nsACString& aOriginSuffix) final;
+  NS_IMETHOD GetIsIpAddress(bool* aIsIpAddress) override;
+  NS_IMETHOD GetIsLocalIpAddress(bool* aIsIpAddress) override;
+  NS_IMETHOD GetIsOnion(bool* aIsOnion) override;
+  NS_IMETHOD GetIsInIsolatedMozBrowserElement(
+      bool* aIsInIsolatedMozBrowserElement) final;
+  NS_IMETHOD GetUserContextId(uint32_t* aUserContextId) final;
+  NS_IMETHOD GetPrivateBrowsingId(uint32_t* aPrivateBrowsingId) final;
+  NS_IMETHOD GetSiteOrigin(nsACString& aSiteOrigin) final;
+  NS_IMETHOD GetSiteOriginNoSuffix(nsACString& aSiteOrigin) override;
+  NS_IMETHOD IsThirdPartyURI(nsIURI* uri, bool* aRes) override;
+  NS_IMETHOD IsThirdPartyPrincipal(nsIPrincipal* uri, bool* aRes) override;
+  NS_IMETHOD IsThirdPartyChannel(nsIChannel* aChannel, bool* aRes) override;
+  NS_IMETHOD GetIsOriginPotentiallyTrustworthy(bool* aResult) override;
+  NS_IMETHOD GetIsLoopbackHost(bool* aResult) override;
+  NS_IMETHOD IsSameOrigin(nsIURI* aURI, bool* aRes) override;
+  NS_IMETHOD GetPrefLightCacheKey(nsIURI* aURI, bool aWithCredentials,
+                                  const OriginAttributes& aOriginAttributes,
+                                  nsACString& _retval) override;
+  NS_IMETHOD HasFirstpartyStorageAccess(mozIDOMWindow* aCheckWindow,
+                                        uint32_t* aRejectedReason,
+                                        bool* aOutAllowed) override;
+  NS_IMETHOD GetAsciiHost(nsACString& aAsciiHost) override;
+  NS_IMETHOD GetLocalStorageQuotaKey(nsACString& aRes) override;
+  NS_IMETHOD AllowsRelaxStrictFileOriginPolicy(nsIURI* aURI,
+                                               bool* aRes) override;
+  NS_IMETHOD CreateReferrerInfo(mozilla::dom::ReferrerPolicy aReferrerPolicy,
+                                nsIReferrerInfo** _retval) override;
+  NS_IMETHOD GetIsScriptAllowedByPolicy(
+      bool* aIsScriptAllowedByPolicy) override;
+  NS_IMETHOD GetStorageOriginKey(nsACString& aOriginKey) override;
+
+  NS_IMETHOD GetNextSubDomainPrincipal(
+      nsIPrincipal** aNextSubDomainPrincipal) override;
+
+  NS_IMETHOD GetPrecursorPrincipal(nsIPrincipal** aPrecursor) override;
+
+  nsresult ToJSON(nsACString& aJSON);
+  nsresult ToJSON(Json::Value& aObject);
+
+  static already_AddRefed<BasePrincipal> FromJSON(const nsACString& aJSON);
+  static already_AddRefed<BasePrincipal> FromJSON(const Json::Value& aJSON);
+  // Method populates a passed Json::Value with serializable fields
+  // which represent all of the fields to deserialize the principal
+  virtual nsresult PopulateJSONObject(Json::Value& aObject);
+
+  virtual bool AddonHasPermission(const nsAtom* aPerm);
+
+  virtual bool IsContentPrincipal() const { return false; };
+
+  static BasePrincipal* Cast(nsIPrincipal* aPrin) {
+    return static_cast<BasePrincipal*>(aPrin);
+  }
+
+  static BasePrincipal& Cast(nsIPrincipal& aPrin) {
+    return *static_cast<BasePrincipal*>(&aPrin);
+  }
+
+  static const BasePrincipal* Cast(const nsIPrincipal* aPrin) {
+    return static_cast<const BasePrincipal*>(aPrin);
+  }
+
+  static const BasePrincipal& Cast(const nsIPrincipal& aPrin) {
+    return *static_cast<const BasePrincipal*>(&aPrin);
+  }
+
+  static already_AddRefed<BasePrincipal> CreateContentPrincipal(
+      const nsACString& aOrigin);
+
+  // This method may not create a content principal in case it's not possible to
+  // generate a correct origin from the passed URI. If this happens, a
+  // NullPrincipal is returned.
+  //
+  // If `aInitialDomain` is specified, and a ContentPrincipal is set, it will
+  // initially have its domain set to the given value, without re-computing js
+  // wrappers. Unlike `SetDomain()` this is safe to do off-main-thread.
+
+  static already_AddRefed<BasePrincipal> CreateContentPrincipal(
+      nsIURI* aURI, const OriginAttributes& aAttrs,
+      nsIURI* aInitialDomain = nullptr);
+
+  const OriginAttributes& OriginAttributesRef() final {
+    return mOriginAttributes;
+  }
+  extensions::WebExtensionPolicy* AddonPolicy();
+  RefPtr<extensions::WebExtensionPolicyCore> AddonPolicyCore();
+  uint32_t UserContextId() const { return mOriginAttributes.mUserContextId; }
+  uint32_t PrivateBrowsingId() const {
+    return mOriginAttributes.mPrivateBrowsingId;
+  }
+  bool IsInIsolatedMozBrowserElement() const {
+    return mOriginAttributes.mInIsolatedMozBrowser;
+  }
+
+  PrincipalKind Kind() const { return mKind; }
+
+  already_AddRefed<BasePrincipal> CloneForcingOriginAttributes(
+      const OriginAttributes& aOriginAttributes);
+
+  // If this is an add-on content script principal, returns its AddonPolicy.
+  // Otherwise returns null.
+  extensions::WebExtensionPolicy* ContentScriptAddonPolicy();
+  RefPtr<extensions::WebExtensionPolicyCore> ContentScriptAddonPolicyCore();
+
+  // Helper to check whether this principal is associated with an addon that
+  // allows unprivileged code to load aURI.  aExplicit == true will prevent
+  // use of all_urls permission, requiring the domain in its permissions.
+  bool AddonAllowsLoad(nsIURI* aURI, bool aExplicit = false);
+
+  // Call these to avoid the cost of virtual dispatch.
+  inline bool FastEquals(nsIPrincipal* aOther);
+  inline bool FastEqualsConsideringDomain(nsIPrincipal* aOther);
+  inline bool FastSubsumes(nsIPrincipal* aOther);
+  inline bool FastSubsumesConsideringDomain(nsIPrincipal* aOther);
+  inline bool FastSubsumesIgnoringFPD(nsIPrincipal* aOther);
+  inline bool FastSubsumesConsideringDomainIgnoringFPD(nsIPrincipal* aOther);
+
+  // Fast way to check whether we have a system principal.
+  inline bool IsSystemPrincipal() const;
+
+  // Returns the principal to inherit when a caller with this principal loads
+  // the given URI.
+  //
+  // For most principal types, this returns the principal itself. For expanded
+  // principals, it returns the first sub-principal which subsumes the given URI
+  // (or, if no URI is given, the last allowlist principal).
+  nsIPrincipal* PrincipalToInherit(nsIURI* aRequestedURI = nullptr);
+
+  /* Returns true if this principal's CSP should override a document's CSP for
+   * loads that it triggers. Currently true for expanded principals which
+   * subsume the document principal, and add-on content principals regardless
+   * of whether they subsume the document principal.
+   */
+  bool OverridesCSP(nsIPrincipal* aDocumentPrincipal);
+
+  uint32_t GetOriginNoSuffixHash() const { return mOriginNoSuffix->hash(); }
+  uint32_t GetOriginSuffixHash() const { return mOriginSuffix->hash(); }
+
+  virtual nsresult GetSiteIdentifier(SiteIdentifier& aSite) = 0;
+
+ protected:
+  BasePrincipal(PrincipalKind aKind, const nsACString& aOriginNoSuffix,
+                const OriginAttributes& aOriginAttributes);
+  BasePrincipal(BasePrincipal* aOther,
+                const OriginAttributes& aOriginAttributes);
+
+  virtual ~BasePrincipal();
+
+  // Note that this does not check OriginAttributes. Callers that depend on
+  // those must call Subsumes instead.
+  virtual bool SubsumesInternal(nsIPrincipal* aOther,
+                                DocumentDomainConsideration aConsider) = 0;
+
+  // Internal, side-effect-free check to determine whether the concrete
+  // principal would allow the load ignoring any common behavior implemented in
+  // BasePrincipal::CheckMayLoad.
+  //
+  // Safe to call from any thread, unlike CheckMayLoad.
+  virtual bool MayLoadInternal(nsIURI* aURI) = 0;
+  friend class ::ExpandedPrincipal;
+
+  // Helper for implementing CheckMayLoad and CheckMayLoadWithReporting.
+  nsresult CheckMayLoadHelper(nsIURI* aURI, bool aAllowIfInheritsPrincipal,
+                              bool aReport, uint64_t aInnerWindowID);
+
+  void SetHasExplicitDomain() { mHasExplicitDomain = true; }
+  bool GetHasExplicitDomain() { return mHasExplicitDomain; }
+
+  // KeyValT holds a principal subtype-specific key value and the associated
+  // parsed value after JSON parsing.
+  template <typename SerializedKey>
+  struct KeyValT {
+    static_assert(sizeof(SerializedKey) == 1,
+                  "SerializedKey should be a uint8_t");
+    SerializedKey key;
+    bool valueWasSerialized;
+    nsCString value;
+  };
+
+  // Common base class for all Deserializer implementations in concrete
+  // subclasses. Subclasses will initialize `mPrincipal` in `Read`, and then
+  // calls to `QueryInterface` will QI on the target object.
+  class Deserializer : public nsISerializable {
+   public:
+    NS_DECL_ISUPPORTS
+    NS_IMETHOD Write(nsIObjectOutputStream* aStream) override;
+
+   protected:
+    virtual ~Deserializer() = default;
+    RefPtr<BasePrincipal> mPrincipal;
+  };
+
+ private:
+  static const char* JSONEnumKeyStrings[4];
+
+  static void SetJSONValue(Json::Value& aObject, const char* aKey,
+                           const nsCString& aValue);
+
+ protected:
+  template <size_t EnumValue>
+  static inline constexpr const char* JSONEnumKeyString() {
+    static_assert(EnumValue < ArrayLength(JSONEnumKeyStrings));
+    return JSONEnumKeyStrings[EnumValue];
+  }
+  template <size_t EnumValue>
+  static void SetJSONValue(Json::Value& aObject, const nsCString& aValue) {
+    SetJSONValue(aObject, JSONEnumKeyString<EnumValue>(), aValue);
+  }
+
+ private:
+  static already_AddRefed<BasePrincipal> CreateContentPrincipal(
+      nsIURI* aURI, const OriginAttributes& aAttrs,
+      const nsACString& aOriginNoSuffix, nsIURI* aInitialDomain);
+
+  bool FastSubsumesIgnoringFPD(nsIPrincipal* aOther,
+                               DocumentDomainConsideration aConsideration);
+
+  const RefPtr<nsAtom> mOriginNoSuffix;
+  const RefPtr<nsAtom> mOriginSuffix;
+
+  const OriginAttributes mOriginAttributes;
+  const PrincipalKind mKind;
+  std::atomic<bool> mHasExplicitDomain;
+};
+
+inline bool BasePrincipal::FastEquals(nsIPrincipal* aOther) {
+  MOZ_ASSERT(aOther);
+
+  auto other = Cast(aOther);
+  if (Kind() != other->Kind()) {
+    // Principals of different kinds can't be equal.
+    return false;
+  }
+
+  // Two principals are considered to be equal if their origins are the same.
+  // If the two principals are content principals, their origin attributes
+  // (aka the origin suffix) must also match.
+  if (Kind() == eSystemPrincipal) {
+    return this == other;
+  }
+
+  if (Kind() == eContentPrincipal || Kind() == eNullPrincipal) {
+    return mOriginNoSuffix == other->mOriginNoSuffix &&
+           mOriginSuffix == other->mOriginSuffix;
+  }
+
+  MOZ_ASSERT(Kind() == eExpandedPrincipal);
+  return mOriginNoSuffix == other->mOriginNoSuffix;
+}
+
+inline bool BasePrincipal::FastEqualsConsideringDomain(nsIPrincipal* aOther) {
+  MOZ_ASSERT(aOther);
+
+  // If neither of the principals have document.domain set, we use the fast path
+  // in Equals().  Otherwise, we fall back to the slow path below.
+  auto other = Cast(aOther);
+  if (!mHasExplicitDomain && !other->mHasExplicitDomain) {
+    return FastEquals(aOther);
+  }
+
+  // Principals of different kinds can't be equal.
+  if (Kind() != other->Kind()) {
+    return false;
+  }
+
+  // Only ContentPrincipals should have mHasExplicitDomain set to true, so test
+  // that we haven't ended up here instead of FastEquals by mistake.
+  MOZ_ASSERT(IsContentPrincipal(),
+             "Only content principals can set mHasExplicitDomain");
+
+  return Subsumes(aOther, ConsiderDocumentDomain) &&
+         other->Subsumes(this, ConsiderDocumentDomain);
+}
+
+inline bool BasePrincipal::FastSubsumes(nsIPrincipal* aOther) {
+  MOZ_ASSERT(aOther);
+
+  // If two principals are equal, then they both subsume each other.
+  if (FastEquals(aOther)) {
+    return true;
+  }
+
+  // Otherwise, fall back to the slow path.
+  return Subsumes(aOther, DontConsiderDocumentDomain);
+}
+
+inline bool BasePrincipal::FastSubsumesConsideringDomain(nsIPrincipal* aOther) {
+  MOZ_ASSERT(aOther);
+
+  // If neither of the principals have document.domain set, we hand off to
+  // FastSubsumes() which has fast paths for some special cases. Otherwise, we
+  // fall back to the slow path below.
+  if (!mHasExplicitDomain && !Cast(aOther)->mHasExplicitDomain) {
+    return FastSubsumes(aOther);
+  }
+
+  return Subsumes(aOther, ConsiderDocumentDomain);
+}
+
+inline bool BasePrincipal::FastSubsumesIgnoringFPD(nsIPrincipal* aOther) {
+  return FastSubsumesIgnoringFPD(aOther, DontConsiderDocumentDomain);
+}
+
+inline bool BasePrincipal::FastSubsumesConsideringDomainIgnoringFPD(
+    nsIPrincipal* aOther) {
+  return FastSubsumesIgnoringFPD(aOther, ConsiderDocumentDomain);
+}
+
+inline bool BasePrincipal::IsSystemPrincipal() const {
+  return Kind() == eSystemPrincipal;
+}
+
+}  // namespace mozilla
+
+inline bool nsIPrincipal::IsSystemPrincipal() const {
+  return mozilla::BasePrincipal::Cast(this)->IsSystemPrincipal();
+}
+
+#endif /* mozilla_BasePrincipal_h */
diff --git a/caps/ContentPrincipal.cpp b/caps/ContentPrincipal.cpp
new file mode 100644
index 0000000000..5aeecaf2bd
--- /dev/null
+++ b/caps/ContentPrincipal.cpp
@@ -0,0 +1,709 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "ContentPrincipal.h"
+
+#include "mozIThirdPartyUtil.h"
+#include "nsContentUtils.h"
+#include "nscore.h"
+#include "nsScriptSecurityManager.h"
+#include "nsString.h"
+#include "nsReadableUtils.h"
+#include "pratom.h"
+#include "nsIURI.h"
+#include "nsIURL.h"
+#include "nsIStandardURL.h"
+#include "nsIURIWithSpecialOrigin.h"
+#include "nsIURIMutator.h"
+#include "nsJSPrincipals.h"
+#include "nsIEffectiveTLDService.h"
+#include "nsIClassInfoImpl.h"
+#include "nsIObjectInputStream.h"
+#include "nsIObjectOutputStream.h"
+#include "nsIProtocolHandler.h"
+#include "nsError.h"
+#include "nsIContentSecurityPolicy.h"
+#include "nsNetCID.h"
+#include "js/RealmIterators.h"
+#include "js/Wrapper.h"
+
+#include "mozilla/dom/BlobURLProtocolHandler.h"
+#include "mozilla/dom/ScriptSettings.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/ExtensionPolicyService.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/HashFunctions.h"
+
+#include "nsSerializationHelper.h"
+#include "json/json.h"
+
+using namespace mozilla;
+
+NS_IMPL_CLASSINFO(ContentPrincipal, nullptr, 0, NS_PRINCIPAL_CID)
+NS_IMPL_QUERY_INTERFACE_CI(ContentPrincipal, nsIPrincipal)
+NS_IMPL_CI_INTERFACE_GETTER(ContentPrincipal, nsIPrincipal)
+
+ContentPrincipal::ContentPrincipal(nsIURI* aURI,
+                                   const OriginAttributes& aOriginAttributes,
+                                   const nsACString& aOriginNoSuffix,
+                                   nsIURI* aInitialDomain)
+    : BasePrincipal(eContentPrincipal, aOriginNoSuffix, aOriginAttributes),
+      mURI(aURI),
+      mDomain(aInitialDomain) {
+  if (mDomain) {
+    // We're just creating the principal, so no need to re-compute wrappers.
+    SetHasExplicitDomain();
+  }
+
+#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+  // Assert that the URI we get here isn't any of the schemes that we know we
+  // should not get here.  These schemes always either inherit their principal
+  // or fall back to a null principal.  These are schemes which return
+  // URI_INHERITS_SECURITY_CONTEXT from their protocol handler's
+  // GetProtocolFlags function.
+  bool hasFlag = false;
+  MOZ_DIAGNOSTIC_ASSERT(
+      NS_SUCCEEDED(NS_URIChainHasFlags(
+          aURI, nsIProtocolHandler::URI_INHERITS_SECURITY_CONTEXT, &hasFlag)) &&
+      !hasFlag);
+#endif
+}
+
+ContentPrincipal::ContentPrincipal(ContentPrincipal* aOther,
+                                   const OriginAttributes& aOriginAttributes)
+    : BasePrincipal(aOther, aOriginAttributes),
+      mURI(aOther->mURI),
+      mDomain(aOther->mDomain),
+      mAddon(aOther->mAddon) {}
+
+ContentPrincipal::~ContentPrincipal() = default;
+
+nsresult ContentPrincipal::GetScriptLocation(nsACString& aStr) {
+  return mURI->GetSpec(aStr);
+}
+
+/* static */
+nsresult ContentPrincipal::GenerateOriginNoSuffixFromURI(
+    nsIURI* aURI, nsACString& aOriginNoSuffix) {
+  if (!aURI) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsCOMPtr<nsIURI> origin = NS_GetInnermostURI(aURI);
+  if (!origin) {
+    return NS_ERROR_FAILURE;
+  }
+
+  MOZ_ASSERT(!NS_IsAboutBlank(origin),
+             "The inner URI for about:blank must be moz-safe-about:blank");
+
+  // Handle non-strict file:// uris.
+  if (!nsScriptSecurityManager::GetStrictFileOriginPolicy() &&
+      NS_URIIsLocalFile(origin)) {
+    // If strict file origin policy is not in effect, all local files are
+    // considered to be same-origin, so return a known dummy origin here.
+    aOriginNoSuffix.AssignLiteral("file://UNIVERSAL_FILE_URI_ORIGIN");
+    return NS_OK;
+  }
+
+  nsresult rv;
+// NB: This is only compiled for Thunderbird/Suite.
+#if IS_ORIGIN_IS_FULL_SPEC_DEFINED
+  bool fullSpec = false;
+  rv = NS_URIChainHasFlags(origin, nsIProtocolHandler::ORIGIN_IS_FULL_SPEC,
+                           &fullSpec);
+  NS_ENSURE_SUCCESS(rv, rv);
+  if (fullSpec) {
+    return origin->GetAsciiSpec(aOriginNoSuffix);
+  }
+#endif
+
+  // We want the invariant that prinA.origin == prinB.origin i.f.f.
+  // prinA.equals(prinB). However, this requires that we impose certain
+  // constraints on the behavior and origin semantics of principals, and in
+  // particular, forbid creating origin strings for principals whose equality
+  // constraints are not expressible as strings (i.e. object equality).
+  // Moreover, we want to forbid URIs containing the magic "^" we use as a
+  // separating character for origin attributes.
+  //
+  // These constraints can generally be achieved by restricting .origin to
+  // nsIStandardURL-based URIs, but there are a few other URI schemes that we
+  // need to handle.
+  if (origin->SchemeIs("about") ||
+      (origin->SchemeIs("moz-safe-about") &&
+       // We generally consider two about:foo origins to be same-origin, but
+       // about:blank is special since it can be generated from different
+       // sources. We check for moz-safe-about:blank since origin is an
+       // innermost URI.
+       !StringBeginsWith(origin->GetSpecOrDefault(),
+                         "moz-safe-about:blank"_ns))) {
+    rv = origin->GetAsciiSpec(aOriginNoSuffix);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    int32_t pos = aOriginNoSuffix.FindChar('?');
+    int32_t hashPos = aOriginNoSuffix.FindChar('#');
+
+    if (hashPos != kNotFound && (pos == kNotFound || hashPos < pos)) {
+      pos = hashPos;
+    }
+
+    if (pos != kNotFound) {
+      aOriginNoSuffix.Truncate(pos);
+    }
+
+    // These URIs could technically contain a '^', but they never should.
+    if (NS_WARN_IF(aOriginNoSuffix.FindChar('^', 0) != -1)) {
+      aOriginNoSuffix.Truncate();
+      return NS_ERROR_FAILURE;
+    }
+    return NS_OK;
+  }
+
+  // This URL can be a blobURL. In this case, we should use the 'parent'
+  // principal instead.
+  nsCOMPtr<nsIPrincipal> blobPrincipal;
+  if (dom::BlobURLProtocolHandler::GetBlobURLPrincipal(
+          origin, getter_AddRefs(blobPrincipal))) {
+    MOZ_ASSERT(blobPrincipal);
+    return blobPrincipal->GetOriginNoSuffix(aOriginNoSuffix);
+  }
+
+  // If we reached this branch, we can only create an origin if we have a
+  // nsIStandardURL.  So, we query to a nsIStandardURL, and fail if we aren't
+  // an instance of an nsIStandardURL nsIStandardURLs have the good property
+  // of escaping the '^' character in their specs, which means that we can be
+  // sure that the caret character (which is reserved for delimiting the end
+  // of the spec, and the beginning of the origin attributes) is not present
+  // in the origin string
+  nsCOMPtr<nsIStandardURL> standardURL = do_QueryInterface(origin);
+  if (!standardURL) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // See whether we have a useful hostPort. If we do, use that.
+  nsAutoCString hostPort;
+  if (!origin->SchemeIs("chrome")) {
+    rv = origin->GetAsciiHostPort(hostPort);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+  if (!hostPort.IsEmpty()) {
+    rv = origin->GetScheme(aOriginNoSuffix);
+    NS_ENSURE_SUCCESS(rv, rv);
+    aOriginNoSuffix.AppendLiteral("://");
+    aOriginNoSuffix.Append(hostPort);
+    return NS_OK;
+  }
+
+  rv = aURI->GetAsciiSpec(aOriginNoSuffix);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // The origin, when taken from the spec, should not contain the ref part of
+  // the URL.
+
+  int32_t pos = aOriginNoSuffix.FindChar('?');
+  int32_t hashPos = aOriginNoSuffix.FindChar('#');
+
+  if (hashPos != kNotFound && (pos == kNotFound || hashPos < pos)) {
+    pos = hashPos;
+  }
+
+  if (pos != kNotFound) {
+    aOriginNoSuffix.Truncate(pos);
+  }
+
+  return NS_OK;
+}
+
+bool ContentPrincipal::SubsumesInternal(
+    nsIPrincipal* aOther,
+    BasePrincipal::DocumentDomainConsideration aConsideration) {
+  MOZ_ASSERT(aOther);
+
+  // For ContentPrincipal, Subsumes is equivalent to Equals.
+  if (aOther == this) {
+    return true;
+  }
+
+  // If either the subject or the object has changed its principal by
+  // explicitly setting document.domain then the other must also have
+  // done so in order to be considered the same origin. This prevents
+  // DNS spoofing based on document.domain (154930)
+  if (aConsideration == ConsiderDocumentDomain) {
+    // Get .domain on each principal.
+    nsCOMPtr<nsIURI> thisDomain, otherDomain;
+    GetDomain(getter_AddRefs(thisDomain));
+    aOther->GetDomain(getter_AddRefs(otherDomain));
+
+    // If either has .domain set, we have equality i.f.f. the domains match.
+    // Otherwise, we fall through to the non-document-domain-considering case.
+    if (thisDomain || otherDomain) {
+      bool isMatch =
+          nsScriptSecurityManager::SecurityCompareURIs(thisDomain, otherDomain);
+#ifdef DEBUG
+      if (isMatch) {
+        nsAutoCString thisSiteOrigin, otherSiteOrigin;
+        MOZ_ALWAYS_SUCCEEDS(GetSiteOrigin(thisSiteOrigin));
+        MOZ_ALWAYS_SUCCEEDS(aOther->GetSiteOrigin(otherSiteOrigin));
+        MOZ_ASSERT(
+            thisSiteOrigin == otherSiteOrigin,
+            "SubsumesConsideringDomain passed with mismatched siteOrigin!");
+      }
+#endif
+      return isMatch;
+    }
+  }
+
+  // Do a fast check (including origin attributes) or a slow uri comparison.
+  return FastEquals(aOther) || aOther->IsSameOrigin(mURI);
+}
+
+NS_IMETHODIMP
+ContentPrincipal::GetURI(nsIURI** aURI) {
+  *aURI = do_AddRef(mURI).take();
+  return NS_OK;
+}
+
+bool ContentPrincipal::MayLoadInternal(nsIURI* aURI) {
+  MOZ_ASSERT(aURI);
+
+#if defined(MOZ_THUNDERBIRD) || defined(MOZ_SUITE)
+  nsCOMPtr<nsIURIWithSpecialOrigin> uriWithSpecialOrigin =
+      do_QueryInterface(aURI);
+  if (uriWithSpecialOrigin) {
+    nsCOMPtr<nsIURI> origin;
+    nsresult rv = uriWithSpecialOrigin->GetOrigin(getter_AddRefs(origin));
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return false;
+    }
+    MOZ_ASSERT(origin);
+    OriginAttributes attrs;
+    RefPtr<BasePrincipal> principal =
+        BasePrincipal::CreateContentPrincipal(origin, attrs);
+    return nsIPrincipal::Subsumes(principal);
+  }
+#endif
+
+  nsCOMPtr<nsIPrincipal> blobPrincipal;
+  if (dom::BlobURLProtocolHandler::GetBlobURLPrincipal(
+          aURI, getter_AddRefs(blobPrincipal))) {
+    MOZ_ASSERT(blobPrincipal);
+    return nsIPrincipal::Subsumes(blobPrincipal);
+  }
+
+  // If this principal is associated with an addon, check whether that addon
+  // has been given permission to load from this domain.
+  if (AddonAllowsLoad(aURI)) {
+    return true;
+  }
+
+  if (nsScriptSecurityManager::SecurityCompareURIs(mURI, aURI)) {
+    return true;
+  }
+
+  // If strict file origin policy is in effect, local files will always fail
+  // SecurityCompareURIs unless they are identical. Explicitly check file origin
+  // policy, in that case.
+  if (nsScriptSecurityManager::GetStrictFileOriginPolicy() &&
+      NS_URIIsLocalFile(aURI) && NS_RelaxStrictFileOriginPolicy(aURI, mURI)) {
+    return true;
+  }
+
+  return false;
+}
+
+uint32_t ContentPrincipal::GetHashValue() {
+  MOZ_ASSERT(mURI, "Need a principal URI");
+
+  nsCOMPtr<nsIURI> uri;
+  GetDomain(getter_AddRefs(uri));
+  if (!uri) {
+    GetURI(getter_AddRefs(uri));
+  };
+  return NS_SecurityHashURI(uri);
+}
+
+NS_IMETHODIMP
+ContentPrincipal::GetDomain(nsIURI** aDomain) {
+  if (!GetHasExplicitDomain()) {
+    *aDomain = nullptr;
+    return NS_OK;
+  }
+
+  mozilla::MutexAutoLock lock(mMutex);
+  NS_ADDREF(*aDomain = mDomain);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+ContentPrincipal::SetDomain(nsIURI* aDomain) {
+  AssertIsOnMainThread();
+  MOZ_ASSERT(aDomain);
+
+  {
+    mozilla::MutexAutoLock lock(mMutex);
+    mDomain = aDomain;
+    SetHasExplicitDomain();
+  }
+
+  // Set the changed-document-domain flag on compartments containing realms
+  // using this principal.
+  auto cb = [](JSContext*, void*, JS::Realm* aRealm,
+               const JS::AutoRequireNoGC& nogc) {
+    JS::Compartment* comp = JS::GetCompartmentForRealm(aRealm);
+    xpc::SetCompartmentChangedDocumentDomain(comp);
+  };
+  JSPrincipals* principals =
+      nsJSPrincipals::get(static_cast<nsIPrincipal*>(this));
+
+  dom::AutoJSAPI jsapi;
+  jsapi.Init();
+  JS::IterateRealmsWithPrincipals(jsapi.cx(), principals, nullptr, cb);
+
+  return NS_OK;
+}
+
+static nsresult GetSpecialBaseDomain(const nsCOMPtr<nsIURI>& aURI,
+                                     bool* aHandled, nsACString& aBaseDomain) {
+  *aHandled = false;
+
+  // Special handling for a file URI.
+  if (NS_URIIsLocalFile(aURI)) {
+    // If strict file origin policy is not in effect, all local files are
+    // considered to be same-origin, so return a known dummy domain here.
+    if (!nsScriptSecurityManager::GetStrictFileOriginPolicy()) {
+      *aHandled = true;
+      aBaseDomain.AssignLiteral("UNIVERSAL_FILE_URI_ORIGIN");
+      return NS_OK;
+    }
+
+    // Otherwise, we return the file path.
+    nsCOMPtr<nsIURL> url = do_QueryInterface(aURI);
+
+    if (url) {
+      *aHandled = true;
+      return url->GetFilePath(aBaseDomain);
+    }
+  }
+
+  bool hasNoRelativeFlag;
+  nsresult rv = NS_URIChainHasFlags(aURI, nsIProtocolHandler::URI_NORELATIVE,
+                                    &hasNoRelativeFlag);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  // In case of FTP we want to get base domain via TLD service even if FTP
+  // protocol handler is disabled and the scheme is handled by external protocol
+  // handler which returns URI_NORELATIVE flag.
+  if (hasNoRelativeFlag && !aURI->SchemeIs("ftp")) {
+    *aHandled = true;
+    return aURI->GetSpec(aBaseDomain);
+  }
+
+  if (aURI->SchemeIs("indexeddb")) {
+    *aHandled = true;
+    return aURI->GetSpec(aBaseDomain);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+ContentPrincipal::GetBaseDomain(nsACString& aBaseDomain) {
+  // Handle some special URIs first.
+  bool handled;
+  nsresult rv = GetSpecialBaseDomain(mURI, &handled, aBaseDomain);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (handled) {
+    return NS_OK;
+  }
+
+  // For everything else, we ask the TLD service via the ThirdPartyUtil.
+  nsCOMPtr<mozIThirdPartyUtil> thirdPartyUtil =
+      do_GetService(THIRDPARTYUTIL_CONTRACTID);
+  if (!thirdPartyUtil) {
+    return NS_ERROR_FAILURE;
+  }
+
+  return thirdPartyUtil->GetBaseDomain(mURI, aBaseDomain);
+}
+
+NS_IMETHODIMP
+ContentPrincipal::GetSiteOriginNoSuffix(nsACString& aSiteOrigin) {
+  nsresult rv = GetOriginNoSuffix(aSiteOrigin);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // It is possible for two principals with the same origin to have different
+  // mURI values. In order to ensure that two principals with matching origins
+  // also have matching siteOrigins, we derive the siteOrigin entirely from the
+  // origin string and do not rely on mURI at all here.
+  nsCOMPtr<nsIURI> origin;
+  rv = NS_NewURI(getter_AddRefs(origin), aSiteOrigin);
+  if (NS_FAILED(rv)) {
+    // We got an error parsing the origin as a URI? siteOrigin == origin
+    // aSiteOrigin was already filled with `OriginNoSuffix`
+    return rv;
+  }
+
+  // Handle some special URIs first.
+  nsAutoCString baseDomain;
+  bool handled;
+  rv = GetSpecialBaseDomain(origin, &handled, baseDomain);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (handled) {
+    // This is a special URI ("file:", "about:", "view-source:", etc). Just
+    // return the origin.
+    return NS_OK;
+  }
+
+  // For everything else, we ask the TLD service. Note that, unlike in
+  // GetBaseDomain, we don't use ThirdPartyUtil.getBaseDomain because if the
+  // host is an IP address that returns the raw address and we can't use it with
+  // SetHost below because SetHost expects '[' and ']' around IPv6 addresses.
+  // See bug 1491728.
+  nsCOMPtr<nsIEffectiveTLDService> tldService =
+      do_GetService(NS_EFFECTIVETLDSERVICE_CONTRACTID);
+  if (!tldService) {
+    return NS_ERROR_FAILURE;
+  }
+
+  bool gotBaseDomain = false;
+  rv = tldService->GetBaseDomain(origin, 0, baseDomain);
+  if (NS_SUCCEEDED(rv)) {
+    gotBaseDomain = true;
+  } else {
+    // If this is an IP address or something like "localhost", we just continue
+    // with gotBaseDomain = false.
+    if (rv != NS_ERROR_HOST_IS_IP_ADDRESS &&
+        rv != NS_ERROR_INSUFFICIENT_DOMAIN_LEVELS &&
+        rv != NS_ERROR_INVALID_ARG) {
+      return rv;
+    }
+  }
+
+  // NOTE: Calling `SetHostPort` with a portless domain is insufficient to clear
+  // the port, so an extra `SetPort` call has to be made.
+  nsCOMPtr<nsIURI> siteUri;
+  NS_MutateURI mutator(origin);
+  mutator.SetUserPass(""_ns).SetPort(-1);
+  if (gotBaseDomain) {
+    mutator.SetHost(baseDomain);
+  }
+  rv = mutator.Finalize(siteUri);
+  MOZ_ASSERT(NS_SUCCEEDED(rv), "failed to create siteUri");
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  aSiteOrigin.Truncate();
+  rv = GenerateOriginNoSuffixFromURI(siteUri, aSiteOrigin);
+  MOZ_ASSERT(NS_SUCCEEDED(rv), "failed to create siteOriginNoSuffix");
+  return rv;
+}
+
+nsresult ContentPrincipal::GetSiteIdentifier(SiteIdentifier& aSite) {
+  nsCString siteOrigin;
+  nsresult rv = GetSiteOrigin(siteOrigin);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  RefPtr<BasePrincipal> principal = CreateContentPrincipal(siteOrigin);
+  if (!principal) {
+    NS_WARNING("could not instantiate content principal");
+    return NS_ERROR_FAILURE;
+  }
+
+  aSite.Init(principal);
+  return NS_OK;
+}
+
+RefPtr<extensions::WebExtensionPolicyCore> ContentPrincipal::AddonPolicyCore() {
+  mozilla::MutexAutoLock lock(mMutex);
+  if (!mAddon.isSome()) {
+    NS_ENSURE_TRUE(mURI, nullptr);
+
+    RefPtr<extensions::WebExtensionPolicyCore> core;
+    if (mURI->SchemeIs("moz-extension")) {
+      nsCString host;
+      NS_ENSURE_SUCCESS(mURI->GetHost(host), nullptr);
+      core = ExtensionPolicyService::GetCoreByHost(host);
+    }
+
+    mAddon.emplace(core);
+  }
+  return *mAddon;
+}
+
+NS_IMETHODIMP
+ContentPrincipal::GetAddonId(nsAString& aAddonId) {
+  if (RefPtr<extensions::WebExtensionPolicyCore> policy = AddonPolicyCore()) {
+    policy->Id()->ToString(aAddonId);
+  } else {
+    aAddonId.Truncate();
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+ContentPrincipal::Deserializer::Read(nsIObjectInputStream* aStream) {
+  MOZ_ASSERT(!mPrincipal);
+
+  nsCOMPtr<nsISupports> supports;
+  nsCOMPtr<nsIURI> principalURI;
+  nsresult rv = NS_ReadOptionalObject(aStream, true, getter_AddRefs(supports));
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  principalURI = do_QueryInterface(supports);
+  // Enforce re-parsing about: URIs so that if they change, we continue to use
+  // their new principals correctly.
+  if (principalURI->SchemeIs("about")) {
+    nsAutoCString spec;
+    principalURI->GetSpec(spec);
+    NS_ENSURE_SUCCESS(NS_NewURI(getter_AddRefs(principalURI), spec),
+                      NS_ERROR_FAILURE);
+  }
+
+  nsCOMPtr<nsIURI> domain;
+  rv = NS_ReadOptionalObject(aStream, true, getter_AddRefs(supports));
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  domain = do_QueryInterface(supports);
+
+  nsAutoCString suffix;
+  rv = aStream->ReadCString(suffix);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  OriginAttributes attrs;
+  bool ok = attrs.PopulateFromSuffix(suffix);
+  NS_ENSURE_TRUE(ok, NS_ERROR_FAILURE);
+
+  // Since Bug 965637 we do not serialize the CSP within the
+  // Principal anymore. Nevertheless there might still be
+  // serialized Principals that do have a serialized CSP.
+  // For now, we just read the CSP here but do not actually
+  // consume it. Please note that we deliberately ignore
+  // the return value to avoid CSP deserialization problems.
+  // After Bug 1508939 we will have a new serialization for
+  // Principals which allows us to update the code here.
+  // Additionally, the format for serialized CSPs changed
+  // within Bug 965637 which also can cause failures within
+  // the CSP deserialization code.
+  Unused << NS_ReadOptionalObject(aStream, true, getter_AddRefs(supports));
+
+  nsAutoCString originNoSuffix;
+  rv = GenerateOriginNoSuffixFromURI(principalURI, originNoSuffix);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mPrincipal =
+      new ContentPrincipal(principalURI, attrs, originNoSuffix, domain);
+  return NS_OK;
+}
+
+nsresult ContentPrincipal::PopulateJSONObject(Json::Value& aObject) {
+  nsAutoCString principalURI;
+  nsresult rv = mURI->GetSpec(principalURI);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // We turn each int enum field into a JSON string key of the object
+  // aObject is the inner JSON object that has stringified enum keys
+  // An example aObject might be:
+  //
+  // eURI                   eSuffix
+  //    |                           |
+  //  {"0": "https://mozilla.com", "2": "^privateBrowsingId=1"}
+  //    |                |          |         |
+  //    -----------------------------         |
+  //         |           |                    |
+  //        Key          ----------------------
+  //                                |
+  //                              Value
+  SetJSONValue<eURI>(aObject, principalURI);
+
+  if (GetHasExplicitDomain()) {
+    nsAutoCString domainStr;
+    {
+      MutexAutoLock lock(mMutex);
+      rv = mDomain->GetSpec(domainStr);
+      NS_ENSURE_SUCCESS(rv, rv);
+    }
+    SetJSONValue<eDomain>(aObject, domainStr);
+  }
+
+  nsAutoCString suffix;
+  OriginAttributesRef().CreateSuffix(suffix);
+  if (suffix.Length() > 0) {
+    SetJSONValue<eSuffix>(aObject, suffix);
+  }
+
+  return NS_OK;
+}
+
+already_AddRefed<BasePrincipal> ContentPrincipal::FromProperties(
+    nsTArray<ContentPrincipal::KeyVal>& aFields) {
+  MOZ_ASSERT(aFields.Length() == eMax + 1, "Must have all the keys");
+  nsresult rv;
+  nsCOMPtr<nsIURI> principalURI;
+  nsCOMPtr<nsIURI> domain;
+  nsCOMPtr<nsIContentSecurityPolicy> csp;
+  OriginAttributes attrs;
+
+  // The odd structure here is to make the code to not compile
+  // if all the switch enum cases haven't been codified
+  for (const auto& field : aFields) {
+    switch (field.key) {
+      case ContentPrincipal::eURI:
+        if (!field.valueWasSerialized) {
+          MOZ_ASSERT(
+              false,
+              "Content principals require a principal URI in serialized JSON");
+          return nullptr;
+        }
+        rv = NS_NewURI(getter_AddRefs(principalURI), field.value.get());
+        NS_ENSURE_SUCCESS(rv, nullptr);
+
+        {
+          // Enforce re-parsing about: URIs so that if they change, we
+          // continue to use their new principals correctly.
+          if (principalURI->SchemeIs("about")) {
+            nsAutoCString spec;
+            principalURI->GetSpec(spec);
+            if (NS_FAILED(NS_NewURI(getter_AddRefs(principalURI), spec))) {
+              return nullptr;
+            }
+          }
+        }
+        break;
+      case ContentPrincipal::eDomain:
+        if (field.valueWasSerialized) {
+          rv = NS_NewURI(getter_AddRefs(domain), field.value.get());
+          NS_ENSURE_SUCCESS(rv, nullptr);
+        }
+        break;
+      case ContentPrincipal::eSuffix:
+        if (field.valueWasSerialized) {
+          bool ok = attrs.PopulateFromSuffix(field.value);
+          if (!ok) {
+            return nullptr;
+          }
+        }
+        break;
+    }
+  }
+  nsAutoCString originNoSuffix;
+  rv = ContentPrincipal::GenerateOriginNoSuffixFromURI(principalURI,
+                                                       originNoSuffix);
+  if (NS_FAILED(rv)) {
+    return nullptr;
+  }
+
+  RefPtr<ContentPrincipal> principal =
+      new ContentPrincipal(principalURI, attrs, originNoSuffix, domain);
+
+  return principal.forget();
+}
diff --git a/caps/ContentPrincipal.h b/caps/ContentPrincipal.h
new file mode 100644
index 0000000000..d2f9d7ed83
--- /dev/null
+++ b/caps/ContentPrincipal.h
@@ -0,0 +1,94 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ContentPrincipal_h
+#define mozilla_ContentPrincipal_h
+
+#include "nsCOMPtr.h"
+#include "nsJSPrincipals.h"
+#include "nsTArray.h"
+#include "nsNetUtil.h"
+#include "nsScriptSecurityManager.h"
+#include "mozilla/BasePrincipal.h"
+#include "mozilla/Mutex.h"
+#include "mozilla/extensions/WebExtensionPolicy.h"
+
+namespace Json {
+class Value;
+}
+
+namespace mozilla {
+
+class ContentPrincipal final : public BasePrincipal {
+ public:
+  NS_IMETHOD QueryInterface(REFNSIID aIID, void** aInstancePtr) override;
+  uint32_t GetHashValue() override;
+  NS_IMETHOD GetURI(nsIURI** aURI) override;
+  NS_IMETHOD GetDomain(nsIURI** aDomain) override;
+  NS_IMETHOD SetDomain(nsIURI* aDomain) override;
+  NS_IMETHOD GetBaseDomain(nsACString& aBaseDomain) override;
+  NS_IMETHOD GetAddonId(nsAString& aAddonId) override;
+  NS_IMETHOD GetSiteOriginNoSuffix(nsACString& aSiteOrigin) override;
+  bool IsContentPrincipal() const override { return true; }
+
+  ContentPrincipal(nsIURI* aURI, const OriginAttributes& aOriginAttributes,
+                   const nsACString& aOriginNoSuffix, nsIURI* aInitialDomain);
+  ContentPrincipal(ContentPrincipal* aOther,
+                   const OriginAttributes& aOriginAttributes);
+
+  static PrincipalKind Kind() { return eContentPrincipal; }
+
+  virtual nsresult GetScriptLocation(nsACString& aStr) override;
+
+  nsresult GetSiteIdentifier(SiteIdentifier& aSite) override;
+
+  static nsresult GenerateOriginNoSuffixFromURI(nsIURI* aURI,
+                                                nsACString& aOrigin);
+
+  RefPtr<extensions::WebExtensionPolicyCore> AddonPolicyCore();
+
+  virtual nsresult PopulateJSONObject(Json::Value& aObject) override;
+  // Serializable keys are the valid enum fields the serialization supports
+  enum SerializableKeys : uint8_t {
+    eURI = 0,
+    eDomain,
+    eSuffix,
+    eMax = eSuffix
+  };
+  typedef mozilla::BasePrincipal::KeyValT<SerializableKeys> KeyVal;
+
+  static already_AddRefed<BasePrincipal> FromProperties(
+      nsTArray<ContentPrincipal::KeyVal>& aFields);
+
+  class Deserializer : public BasePrincipal::Deserializer {
+   public:
+    NS_IMETHOD Read(nsIObjectInputStream* aStream) override;
+  };
+
+ protected:
+  virtual ~ContentPrincipal();
+
+  bool SubsumesInternal(nsIPrincipal* aOther,
+                        DocumentDomainConsideration aConsideration) override;
+  bool MayLoadInternal(nsIURI* aURI) override;
+
+ private:
+  const nsCOMPtr<nsIURI> mURI;
+  mozilla::Mutex mMutex{"ContentPrincipal::mMutex"};
+  nsCOMPtr<nsIURI> mDomain MOZ_GUARDED_BY(mMutex);
+  Maybe<RefPtr<extensions::WebExtensionPolicyCore>> mAddon
+      MOZ_GUARDED_BY(mMutex);
+};
+
+}  // namespace mozilla
+
+#define NS_PRINCIPAL_CID                             \
+  {                                                  \
+    0x653e0e4d, 0x3ee4, 0x45fa, {                    \
+      0xb2, 0x72, 0x97, 0xc2, 0x0b, 0xc0, 0x1e, 0xb8 \
+    }                                                \
+  }
+
+#endif  // mozilla_ContentPrincipal_h
diff --git a/caps/ContentPrincipalInfoHashKey.h b/caps/ContentPrincipalInfoHashKey.h
new file mode 100644
index 0000000000..ed1f79852f
--- /dev/null
+++ b/caps/ContentPrincipalInfoHashKey.h
@@ -0,0 +1,56 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef CAPS_PRINCIPALHASHKEY_H_
+#define CAPS_PRINCIPALHASHKEY_H_
+
+#include "mozilla/ipc/PBackgroundSharedTypes.h"
+#include "PLDHashTable.h"
+#include "nsHashKeys.h"
+#include "nsUnicharUtils.h"
+
+namespace mozilla {
+
+class ContentPrincipalInfoHashKey : public PLDHashEntryHdr {
+ public:
+  using KeyType = const ipc::ContentPrincipalInfo&;
+  using KeyTypePointer = const ipc::ContentPrincipalInfo*;
+
+  explicit ContentPrincipalInfoHashKey(KeyTypePointer aKey)
+      : mPrincipalInfo(*aKey) {
+    MOZ_COUNT_CTOR(ContentPrincipalInfoHashKey);
+  }
+  ContentPrincipalInfoHashKey(ContentPrincipalInfoHashKey&& aOther) noexcept
+      : mPrincipalInfo(aOther.mPrincipalInfo) {
+    MOZ_COUNT_CTOR(ContentPrincipalInfoHashKey);
+  }
+
+  MOZ_COUNTED_DTOR(ContentPrincipalInfoHashKey)
+
+  KeyType GetKey() const { return mPrincipalInfo; }
+
+  bool KeyEquals(KeyTypePointer aKey) const {
+    // Mocks BasePrincipal::FastEquals()
+    return mPrincipalInfo.originNoSuffix() == aKey->originNoSuffix() &&
+           mPrincipalInfo.attrs() == aKey->attrs();
+  }
+
+  static KeyTypePointer KeyToPointer(KeyType aKey) { return &aKey; }
+  static PLDHashNumber HashKey(KeyTypePointer aKey) {
+    nsAutoCString suffix;
+    aKey->attrs().CreateSuffix(suffix);
+    return HashGeneric(HashString(aKey->originNoSuffix()), HashString(suffix));
+  }
+
+  enum { ALLOW_MEMMOVE = true };
+
+ protected:
+  const ipc::ContentPrincipalInfo mPrincipalInfo;
+};
+
+}  // namespace mozilla
+
+#endif  // CAPS_PRINCIPALHASHKEY_H_
diff --git a/caps/DomainPolicy.cpp b/caps/DomainPolicy.cpp
new file mode 100644
index 0000000000..65ad3d8df4
--- /dev/null
+++ b/caps/DomainPolicy.cpp
@@ -0,0 +1,222 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=4 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "DomainPolicy.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/ipc/URIUtils.h"
+#include "mozilla/Unused.h"
+#include "nsIURIMutator.h"
+#include "nsScriptSecurityManager.h"
+
+namespace mozilla {
+
+using namespace ipc;
+using namespace dom;
+
+NS_IMPL_ISUPPORTS(DomainPolicy, nsIDomainPolicy)
+
+static nsresult BroadcastDomainSetChange(DomainSetType aSetType,
+                                         DomainSetChangeType aChangeType,
+                                         nsIURI* aDomain = nullptr) {
+  MOZ_ASSERT(XRE_IsParentProcess(),
+             "DomainPolicy should only be exposed to the chrome process.");
+
+  nsTArray<ContentParent*> parents;
+  ContentParent::GetAll(parents);
+  if (!parents.Length()) {
+    return NS_OK;
+  }
+
+  for (uint32_t i = 0; i < parents.Length(); i++) {
+    Unused << parents[i]->SendDomainSetChanged(aSetType, aChangeType, aDomain);
+  }
+  return NS_OK;
+}
+
+DomainPolicy::DomainPolicy()
+    : mBlocklist(new DomainSet(BLOCKLIST)),
+      mSuperBlocklist(new DomainSet(SUPER_BLOCKLIST)),
+      mAllowlist(new DomainSet(ALLOWLIST)),
+      mSuperAllowlist(new DomainSet(SUPER_ALLOWLIST)) {
+  if (XRE_IsParentProcess()) {
+    BroadcastDomainSetChange(NO_TYPE, ACTIVATE_POLICY);
+  }
+}
+
+DomainPolicy::~DomainPolicy() {
+  // The SSM holds a strong ref to the DomainPolicy until Deactivate() is
+  // invoked, so we should never hit the destructor until that happens.
+  MOZ_ASSERT(!mBlocklist && !mSuperBlocklist && !mAllowlist &&
+             !mSuperAllowlist);
+}
+
+NS_IMETHODIMP
+DomainPolicy::GetBlocklist(nsIDomainSet** aSet) {
+  nsCOMPtr<nsIDomainSet> set = mBlocklist.get();
+  set.forget(aSet);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DomainPolicy::GetSuperBlocklist(nsIDomainSet** aSet) {
+  nsCOMPtr<nsIDomainSet> set = mSuperBlocklist.get();
+  set.forget(aSet);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DomainPolicy::GetAllowlist(nsIDomainSet** aSet) {
+  nsCOMPtr<nsIDomainSet> set = mAllowlist.get();
+  set.forget(aSet);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DomainPolicy::GetSuperAllowlist(nsIDomainSet** aSet) {
+  nsCOMPtr<nsIDomainSet> set = mSuperAllowlist.get();
+  set.forget(aSet);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DomainPolicy::Deactivate() {
+  // Clear the hashtables first to free up memory, since script might
+  // hold the doomed sets alive indefinitely.
+  mBlocklist->Clear();
+  mSuperBlocklist->Clear();
+  mAllowlist->Clear();
+  mSuperAllowlist->Clear();
+
+  // Null them out.
+  mBlocklist = nullptr;
+  mSuperBlocklist = nullptr;
+  mAllowlist = nullptr;
+  mSuperAllowlist = nullptr;
+
+  // Inform the SSM.
+  nsScriptSecurityManager* ssm =
+      nsScriptSecurityManager::GetScriptSecurityManager();
+  if (ssm) {
+    ssm->DeactivateDomainPolicy();
+  }
+  if (XRE_IsParentProcess()) {
+    BroadcastDomainSetChange(NO_TYPE, DEACTIVATE_POLICY);
+  }
+  return NS_OK;
+}
+
+void DomainPolicy::CloneDomainPolicy(DomainPolicyClone* aClone) {
+  aClone->active() = true;
+  mBlocklist->CloneSet(&aClone->blocklist());
+  mSuperBlocklist->CloneSet(&aClone->superBlocklist());
+  mAllowlist->CloneSet(&aClone->allowlist());
+  mSuperAllowlist->CloneSet(&aClone->superAllowlist());
+}
+
+static void CopyURIs(const nsTArray<RefPtr<nsIURI>>& aDomains,
+                     nsIDomainSet* aSet) {
+  for (uint32_t i = 0; i < aDomains.Length(); i++) {
+    if (NS_WARN_IF(!aDomains[i])) {
+      continue;
+    }
+    aSet->Add(aDomains[i]);
+  }
+}
+
+void DomainPolicy::ApplyClone(const DomainPolicyClone* aClone) {
+  CopyURIs(aClone->blocklist(), mBlocklist);
+  CopyURIs(aClone->allowlist(), mAllowlist);
+  CopyURIs(aClone->superBlocklist(), mSuperBlocklist);
+  CopyURIs(aClone->superAllowlist(), mSuperAllowlist);
+}
+
+static already_AddRefed<nsIURI> GetCanonicalClone(nsIURI* aURI) {
+  nsCOMPtr<nsIURI> clone;
+  nsresult rv =
+      NS_MutateURI(aURI).SetUserPass(""_ns).SetPathQueryRef(""_ns).Finalize(
+          clone);
+  NS_ENSURE_SUCCESS(rv, nullptr);
+  return clone.forget();
+}
+
+NS_IMPL_ISUPPORTS(DomainSet, nsIDomainSet)
+
+NS_IMETHODIMP
+DomainSet::Add(nsIURI* aDomain) {
+  nsCOMPtr<nsIURI> clone = GetCanonicalClone(aDomain);
+  NS_ENSURE_TRUE(clone, NS_ERROR_FAILURE);
+  mHashTable.Insert(clone);
+  if (XRE_IsParentProcess()) {
+    return BroadcastDomainSetChange(mType, ADD_DOMAIN, aDomain);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DomainSet::Remove(nsIURI* aDomain) {
+  nsCOMPtr<nsIURI> clone = GetCanonicalClone(aDomain);
+  NS_ENSURE_TRUE(clone, NS_ERROR_FAILURE);
+  mHashTable.Remove(clone);
+  if (XRE_IsParentProcess()) {
+    return BroadcastDomainSetChange(mType, REMOVE_DOMAIN, aDomain);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DomainSet::Clear() {
+  mHashTable.Clear();
+  if (XRE_IsParentProcess()) {
+    return BroadcastDomainSetChange(mType, CLEAR_DOMAINS);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DomainSet::Contains(nsIURI* aDomain, bool* aContains) {
+  *aContains = false;
+  nsCOMPtr<nsIURI> clone = GetCanonicalClone(aDomain);
+  NS_ENSURE_TRUE(clone, NS_ERROR_FAILURE);
+  *aContains = mHashTable.Contains(clone);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DomainSet::ContainsSuperDomain(nsIURI* aDomain, bool* aContains) {
+  *aContains = false;
+  nsCOMPtr<nsIURI> clone = GetCanonicalClone(aDomain);
+  NS_ENSURE_TRUE(clone, NS_ERROR_FAILURE);
+  nsAutoCString domain;
+  nsresult rv = clone->GetHost(domain);
+  NS_ENSURE_SUCCESS(rv, rv);
+  while (true) {
+    // Check the current domain.
+    if (mHashTable.Contains(clone)) {
+      *aContains = true;
+      return NS_OK;
+    }
+
+    // Chop off everything before the first dot, or break if there are no
+    // dots left.
+    int32_t index = domain.Find(".");
+    if (index == kNotFound) break;
+    domain.Assign(Substring(domain, index + 1));
+    rv = NS_MutateURI(clone).SetHost(domain).Finalize(clone);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  // No match.
+  return NS_OK;
+}
+
+void DomainSet::CloneSet(nsTArray<RefPtr<nsIURI>>* aDomains) {
+  AppendToArray(*aDomains, mHashTable);
+}
+
+} /* namespace mozilla */
diff --git a/caps/DomainPolicy.h b/caps/DomainPolicy.h
new file mode 100644
index 0000000000..24fe3b9395
--- /dev/null
+++ b/caps/DomainPolicy.h
@@ -0,0 +1,64 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DomainPolicy_h__
+#define DomainPolicy_h__
+
+#include "nsIDomainPolicy.h"
+#include "nsTHashSet.h"
+#include "nsURIHashKey.h"
+
+namespace mozilla {
+
+enum DomainSetChangeType {
+  ACTIVATE_POLICY,
+  DEACTIVATE_POLICY,
+  ADD_DOMAIN,
+  REMOVE_DOMAIN,
+  CLEAR_DOMAINS
+};
+
+enum DomainSetType {
+  NO_TYPE,
+  BLOCKLIST,
+  SUPER_BLOCKLIST,
+  ALLOWLIST,
+  SUPER_ALLOWLIST
+};
+
+class DomainSet final : public nsIDomainSet {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIDOMAINSET
+
+  explicit DomainSet(DomainSetType aType) : mType(aType) {}
+
+  void CloneSet(nsTArray<RefPtr<nsIURI>>* aDomains);
+
+ protected:
+  virtual ~DomainSet() {}
+  nsTHashSet<nsURIHashKey> mHashTable;
+  DomainSetType mType;
+};
+
+class DomainPolicy final : public nsIDomainPolicy {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIDOMAINPOLICY
+  DomainPolicy();
+
+ private:
+  virtual ~DomainPolicy();
+
+  RefPtr<DomainSet> mBlocklist;
+  RefPtr<DomainSet> mSuperBlocklist;
+  RefPtr<DomainSet> mAllowlist;
+  RefPtr<DomainSet> mSuperAllowlist;
+};
+
+} /* namespace mozilla */
+
+#endif /* DomainPolicy_h__ */
diff --git a/caps/ExpandedPrincipal.cpp b/caps/ExpandedPrincipal.cpp
new file mode 100644
index 0000000000..ce8ccd8b82
--- /dev/null
+++ b/caps/ExpandedPrincipal.cpp
@@ -0,0 +1,401 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "ExpandedPrincipal.h"
+#include "nsIClassInfoImpl.h"
+#include "nsIObjectInputStream.h"
+#include "nsReadableUtils.h"
+#include "mozilla/Base64.h"
+#include "mozilla/extensions/WebExtensionPolicy.h"
+#include "json/json.h"
+
+using namespace mozilla;
+
+NS_IMPL_CLASSINFO(ExpandedPrincipal, nullptr, 0, NS_EXPANDEDPRINCIPAL_CID)
+NS_IMPL_QUERY_INTERFACE_CI(ExpandedPrincipal, nsIPrincipal,
+                           nsIExpandedPrincipal)
+NS_IMPL_CI_INTERFACE_GETTER(ExpandedPrincipal, nsIPrincipal,
+                            nsIExpandedPrincipal)
+
+ExpandedPrincipal::ExpandedPrincipal(
+    nsTArray<nsCOMPtr<nsIPrincipal>>&& aPrincipals,
+    const nsACString& aOriginNoSuffix, const OriginAttributes& aAttrs)
+    : BasePrincipal(eExpandedPrincipal, aOriginNoSuffix, aAttrs),
+      mPrincipals(std::move(aPrincipals)) {}
+
+ExpandedPrincipal::~ExpandedPrincipal() = default;
+
+already_AddRefed<ExpandedPrincipal> ExpandedPrincipal::Create(
+    const nsTArray<nsCOMPtr<nsIPrincipal>>& aAllowList,
+    const OriginAttributes& aAttrs) {
+  nsTArray<nsCOMPtr<nsIPrincipal>> principals;
+  for (size_t i = 0; i < aAllowList.Length(); ++i) {
+    principals.AppendElement(aAllowList[i]);
+  }
+
+  nsAutoCString origin;
+  origin.AssignLiteral("[Expanded Principal [");
+  StringJoinAppend(
+      origin, ", "_ns, principals,
+      [](nsACString& dest, const nsCOMPtr<nsIPrincipal>& principal) {
+        nsAutoCString subOrigin;
+        DebugOnly<nsresult> rv = principal->GetOrigin(subOrigin);
+        MOZ_ASSERT(NS_SUCCEEDED(rv));
+        dest.Append(subOrigin);
+      });
+  origin.AppendLiteral("]]");
+
+  RefPtr<ExpandedPrincipal> ep =
+      new ExpandedPrincipal(std::move(principals), origin, aAttrs);
+  return ep.forget();
+}
+
+NS_IMETHODIMP
+ExpandedPrincipal::GetDomain(nsIURI** aDomain) {
+  *aDomain = nullptr;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+ExpandedPrincipal::SetDomain(nsIURI* aDomain) { return NS_OK; }
+
+bool ExpandedPrincipal::SubsumesInternal(
+    nsIPrincipal* aOther,
+    BasePrincipal::DocumentDomainConsideration aConsideration) {
+  // If aOther is an ExpandedPrincipal too, we break it down into its component
+  // nsIPrincipals, and check subsumes on each one.
+  if (Cast(aOther)->Is<ExpandedPrincipal>()) {
+    auto* expanded = Cast(aOther)->As<ExpandedPrincipal>();
+
+    for (auto& other : expanded->AllowList()) {
+      // Use SubsumesInternal rather than Subsumes here, since OriginAttribute
+      // checks are only done between non-expanded sub-principals, and we don't
+      // need to incur the extra virtual call overhead.
+      if (!SubsumesInternal(other, aConsideration)) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  // We're dealing with a regular principal. One of our principals must subsume
+  // it.
+  for (uint32_t i = 0; i < mPrincipals.Length(); ++i) {
+    if (Cast(mPrincipals[i])->Subsumes(aOther, aConsideration)) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+bool ExpandedPrincipal::MayLoadInternal(nsIURI* uri) {
+  for (uint32_t i = 0; i < mPrincipals.Length(); ++i) {
+    if (BasePrincipal::Cast(mPrincipals[i])->MayLoadInternal(uri)) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+uint32_t ExpandedPrincipal::GetHashValue() {
+  MOZ_CRASH("extended principal should never be used as key in a hash map");
+}
+
+NS_IMETHODIMP
+ExpandedPrincipal::GetURI(nsIURI** aURI) {
+  *aURI = nullptr;
+  return NS_OK;
+}
+
+const nsTArray<nsCOMPtr<nsIPrincipal>>& ExpandedPrincipal::AllowList() {
+  return mPrincipals;
+}
+
+NS_IMETHODIMP
+ExpandedPrincipal::GetBaseDomain(nsACString& aBaseDomain) {
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+NS_IMETHODIMP
+ExpandedPrincipal::GetAddonId(nsAString& aAddonId) {
+  aAddonId.Truncate();
+  return NS_OK;
+};
+
+bool ExpandedPrincipal::AddonHasPermission(const nsAtom* aPerm) {
+  for (size_t i = 0; i < mPrincipals.Length(); ++i) {
+    if (BasePrincipal::Cast(mPrincipals[i])->AddonHasPermission(aPerm)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+bool ExpandedPrincipal::AddonAllowsLoad(nsIURI* aURI,
+                                        bool aExplicit /* = false */) {
+  for (const auto& principal : mPrincipals) {
+    if (Cast(principal)->AddonAllowsLoad(aURI, aExplicit)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+void ExpandedPrincipal::SetCsp(nsIContentSecurityPolicy* aCSP) {
+  AssertIsOnMainThread();
+  mCSP = new nsMainThreadPtrHolder<nsIContentSecurityPolicy>(
+      "ExpandedPrincipal::mCSP", aCSP);
+}
+
+NS_IMETHODIMP
+ExpandedPrincipal::GetCsp(nsIContentSecurityPolicy** aCsp) {
+  AssertIsOnMainThread();
+  NS_IF_ADDREF(*aCsp = mCSP);
+  return NS_OK;
+}
+
+nsIPrincipal* ExpandedPrincipal::PrincipalToInherit(nsIURI* aRequestedURI) {
+  if (aRequestedURI) {
+    // If a given sub-principal subsumes the given URI, use that principal for
+    // inheritance. In general, this only happens with certain CORS modes, loads
+    // with forced principal inheritance, and creation of XML documents from
+    // XMLHttpRequests or fetch requests. For URIs that normally inherit a
+    // principal (such as data: URIs), we fall back to the last principal in the
+    // allowlist.
+    for (const auto& principal : mPrincipals) {
+      if (Cast(principal)->MayLoadInternal(aRequestedURI)) {
+        return principal;
+      }
+    }
+  }
+  return mPrincipals.LastElement();
+}
+
+nsresult ExpandedPrincipal::GetScriptLocation(nsACString& aStr) {
+  aStr.AssignLiteral("[Expanded Principal [");
+  for (size_t i = 0; i < mPrincipals.Length(); ++i) {
+    if (i != 0) {
+      aStr.AppendLiteral(", ");
+    }
+
+    nsAutoCString spec;
+    nsresult rv =
+        nsJSPrincipals::get(mPrincipals.ElementAt(i))->GetScriptLocation(spec);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    aStr.Append(spec);
+  }
+  aStr.AppendLiteral("]]");
+  return NS_OK;
+}
+
+//////////////////////////////////////////
+// Methods implementing nsISerializable //
+//////////////////////////////////////////
+
+// We've had way too many issues with unversioned serializations, so
+// explicitly version this one.
+static const uint32_t kSerializationVersion = 1;
+
+NS_IMETHODIMP
+ExpandedPrincipal::Deserializer::Read(nsIObjectInputStream* aStream) {
+  uint32_t version;
+  nsresult rv = aStream->Read32(&version);
+  if (version != kSerializationVersion) {
+    MOZ_ASSERT(false,
+               "We really need to add handling of the old(?) version here");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  uint32_t count;
+  rv = aStream->Read32(&count);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  nsTArray<nsCOMPtr<nsIPrincipal>> principals;
+  if (!principals.SetCapacity(count, fallible)) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+
+  for (uint32_t i = 0; i < count; ++i) {
+    nsCOMPtr<nsISupports> read;
+    rv = aStream->ReadObject(true, getter_AddRefs(read));
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+
+    nsCOMPtr<nsIPrincipal> principal = do_QueryInterface(read);
+    if (!principal) {
+      return NS_ERROR_UNEXPECTED;
+    }
+
+    principals.AppendElement(std::move(principal));
+  }
+
+  mPrincipal = ExpandedPrincipal::Create(principals, OriginAttributes());
+  return NS_OK;
+}
+
+nsresult ExpandedPrincipal::GetSiteIdentifier(SiteIdentifier& aSite) {
+  // Call GetSiteIdentifier on each of our principals and return a new
+  // ExpandedPrincipal.
+
+  nsTArray<nsCOMPtr<nsIPrincipal>> allowlist;
+  for (const auto& principal : mPrincipals) {
+    SiteIdentifier site;
+    nsresult rv = Cast(principal)->GetSiteIdentifier(site);
+    NS_ENSURE_SUCCESS(rv, rv);
+    allowlist.AppendElement(site.GetPrincipal());
+  }
+
+  RefPtr<ExpandedPrincipal> expandedPrincipal =
+      ExpandedPrincipal::Create(allowlist, OriginAttributesRef());
+  MOZ_ASSERT(expandedPrincipal, "ExpandedPrincipal::Create returned nullptr?");
+
+  aSite.Init(expandedPrincipal);
+  return NS_OK;
+}
+
+nsresult ExpandedPrincipal::PopulateJSONObject(Json::Value& aObject) {
+  Json::Value& principalList =
+      aObject[Json::StaticString(JSONEnumKeyString<eSpecs>())] =
+          Json::arrayValue;
+  for (const auto& principal : mPrincipals) {
+    Json::Value object = Json::objectValue;
+    nsresult rv = BasePrincipal::Cast(principal)->ToJSON(object);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    principalList.append(std::move(object));
+  }
+
+  nsAutoCString suffix;
+  OriginAttributesRef().CreateSuffix(suffix);
+  if (suffix.Length() > 0) {
+    SetJSONValue<eSuffix>(aObject, suffix);
+  }
+
+  return NS_OK;
+}
+
+already_AddRefed<BasePrincipal> ExpandedPrincipal::FromProperties(
+    nsTArray<ExpandedPrincipal::KeyVal>& aFields) {
+  MOZ_ASSERT(aFields.Length() == eMax + 1, "Must have all the keys");
+  nsTArray<nsCOMPtr<nsIPrincipal>> allowList;
+  OriginAttributes attrs;
+  // The odd structure here is to make the code to not compile
+  // if all the switch enum cases haven't been codified
+
+  for (const auto& field : aFields) {
+    switch (field.key) {
+      case ExpandedPrincipal::eSpecs:
+        if (!field.valueWasSerialized) {
+          MOZ_ASSERT(false,
+                     "Expanded principals require specs in serialized JSON");
+          return nullptr;
+        }
+        for (const nsACString& each : field.value.Split(',')) {
+          nsAutoCString result;
+          nsresult rv;
+          rv = Base64Decode(each, result);
+          MOZ_ASSERT(NS_SUCCEEDED(rv), "failed to decode");
+
+          NS_ENSURE_SUCCESS(rv, nullptr);
+          nsCOMPtr<nsIPrincipal> principal = BasePrincipal::FromJSON(result);
+          allowList.AppendElement(principal);
+        }
+        break;
+      case ExpandedPrincipal::eSuffix:
+        if (field.valueWasSerialized) {
+          bool ok = attrs.PopulateFromSuffix(field.value);
+          if (!ok) {
+            return nullptr;
+          }
+        }
+        break;
+    }
+  }
+
+  if (allowList.Length() == 0) {
+    return nullptr;
+  }
+
+  RefPtr<ExpandedPrincipal> expandedPrincipal =
+      ExpandedPrincipal::Create(allowList, attrs);
+
+  return expandedPrincipal.forget();
+}
+
+/* static */
+already_AddRefed<BasePrincipal> ExpandedPrincipal::FromProperties(
+    const Json::Value& aJSON) {
+  MOZ_ASSERT(aJSON.size() <= eMax + 1, "Must have at most, all the properties");
+  const std::string specs = std::to_string(eSpecs);
+  const std::string suffix = std::to_string(eSuffix);
+  MOZ_ASSERT(aJSON.isMember(specs), "The eSpecs member is required");
+  MOZ_ASSERT(aJSON.size() == 1 || aJSON.isMember(suffix),
+             "eSuffix is optional");
+
+  const auto* specsValue =
+      aJSON.find(specs.c_str(), specs.c_str() + specs.length());
+  if (!specsValue) {
+    MOZ_ASSERT(false, "Expanded principals require specs in serialized JSON");
+    return nullptr;
+  }
+
+  nsTArray<nsCOMPtr<nsIPrincipal>> allowList;
+  for (const auto& principalJSON : *specsValue) {
+    if (nsCOMPtr<nsIPrincipal> principal =
+            BasePrincipal::FromJSON(principalJSON)) {
+      allowList.AppendElement(principal);
+    }
+  }
+
+  if (allowList.Length() == 0) {
+    return nullptr;
+  }
+
+  OriginAttributes attrs;
+  if (aJSON.isMember(suffix)) {
+    const auto& value = aJSON[suffix];
+    if (!value.isString()) {
+      return nullptr;
+    }
+
+    bool ok = attrs.PopulateFromSuffix(nsDependentCString(value.asCString()));
+    if (!ok) {
+      return nullptr;
+    }
+  }
+
+  RefPtr<ExpandedPrincipal> expandedPrincipal =
+      ExpandedPrincipal::Create(allowList, attrs);
+
+  return expandedPrincipal.forget();
+}
+
+NS_IMETHODIMP
+ExpandedPrincipal::IsThirdPartyURI(nsIURI* aURI, bool* aRes) {
+  // ExpandedPrincipal for extension content scripts consist of two principals,
+  // the document's principal and the extension's principal.
+  // To make sure that the third-party check behaves like the web page on which
+  // the content script is running, ignore the extension's principal.
+
+  for (const auto& principal : mPrincipals) {
+    if (!Cast(principal)->AddonPolicyCore()) {
+      return Cast(principal)->IsThirdPartyURI(aURI, aRes);
+    }
+  }
+
+  if (mPrincipals.IsEmpty()) {
+    *aRes = true;
+    return NS_OK;
+  }
+
+  return Cast(mPrincipals[0])->IsThirdPartyURI(aURI, aRes);
+}
diff --git a/caps/ExpandedPrincipal.h b/caps/ExpandedPrincipal.h
new file mode 100644
index 0000000000..748a0c4138
--- /dev/null
+++ b/caps/ExpandedPrincipal.h
@@ -0,0 +1,105 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef ExpandedPrincipal_h
+#define ExpandedPrincipal_h
+
+#include "nsCOMPtr.h"
+#include "nsJSPrincipals.h"
+#include "nsProxyRelease.h"
+#include "nsTArray.h"
+#include "nsNetUtil.h"
+#include "mozilla/BasePrincipal.h"
+
+class nsIContentSecurityPolicy;
+
+namespace Json {
+class Value;
+}
+
+class ExpandedPrincipal : public nsIExpandedPrincipal,
+                          public mozilla::BasePrincipal {
+ public:
+  static already_AddRefed<ExpandedPrincipal> Create(
+      const nsTArray<nsCOMPtr<nsIPrincipal>>& aAllowList,
+      const mozilla::OriginAttributes& aAttrs);
+
+  static PrincipalKind Kind() { return eExpandedPrincipal; }
+
+  NS_DECL_NSIEXPANDEDPRINCIPAL
+
+  NS_IMETHOD_(MozExternalRefCountType) AddRef() override {
+    return nsJSPrincipals::AddRef();
+  };
+  NS_IMETHOD_(MozExternalRefCountType) Release() override {
+    return nsJSPrincipals::Release();
+  };
+  NS_IMETHOD QueryInterface(REFNSIID aIID, void** aInstancePtr) override;
+  uint32_t GetHashValue() override;
+  NS_IMETHOD GetURI(nsIURI** aURI) override;
+  NS_IMETHOD GetDomain(nsIURI** aDomain) override;
+  NS_IMETHOD SetDomain(nsIURI* aDomain) override;
+  NS_IMETHOD GetBaseDomain(nsACString& aBaseDomain) override;
+  NS_IMETHOD GetAddonId(nsAString& aAddonId) override;
+  NS_IMETHOD IsThirdPartyURI(nsIURI* uri, bool* aRes) override;
+  virtual bool AddonHasPermission(const nsAtom* aPerm) override;
+  virtual nsresult GetScriptLocation(nsACString& aStr) override;
+
+  bool AddonAllowsLoad(nsIURI* aURI, bool aExplicit = false);
+
+  void SetCsp(nsIContentSecurityPolicy* aCSP);
+
+  // Returns the principal to inherit when this principal requests the given
+  // URL. See BasePrincipal::PrincipalToInherit.
+  nsIPrincipal* PrincipalToInherit(nsIURI* aRequestedURI = nullptr);
+
+  nsresult GetSiteIdentifier(mozilla::SiteIdentifier& aSite) override;
+
+  virtual nsresult PopulateJSONObject(Json::Value& aObject) override;
+  // Serializable keys are the valid enum fields the serialization supports
+  enum SerializableKeys : uint8_t { eSpecs = 0, eSuffix, eMax = eSuffix };
+  typedef mozilla::BasePrincipal::KeyValT<SerializableKeys> KeyVal;
+
+  // This is the legacy serializer for expanded principals. See note for
+  // `IsLegacyFormat` in BasePrincipal.cpp.
+  static already_AddRefed<BasePrincipal> FromProperties(
+      nsTArray<ExpandedPrincipal::KeyVal>& aFields);
+
+  // This is the new serializer for expanded principals. See note for
+  // `IsLegacyFormat` in BasePrincipal.cpp.
+  static already_AddRefed<BasePrincipal> FromProperties(
+      const Json::Value& aJSON);
+
+  class Deserializer : public BasePrincipal::Deserializer {
+   public:
+    NS_IMETHOD Read(nsIObjectInputStream* aStream) override;
+  };
+
+ protected:
+  explicit ExpandedPrincipal(nsTArray<nsCOMPtr<nsIPrincipal>>&& aPrincipals,
+                             const nsACString& aOriginNoSuffix,
+                             const mozilla::OriginAttributes& aAttrs);
+
+  virtual ~ExpandedPrincipal();
+
+  bool SubsumesInternal(nsIPrincipal* aOther,
+                        DocumentDomainConsideration aConsideration) override;
+
+  bool MayLoadInternal(nsIURI* aURI) override;
+
+ private:
+  const nsTArray<nsCOMPtr<nsIPrincipal>> mPrincipals;
+  nsMainThreadPtrHandle<nsIContentSecurityPolicy> mCSP
+      MOZ_GUARDED_BY(mozilla::sMainThreadCapability);
+};
+
+#define NS_EXPANDEDPRINCIPAL_CID                     \
+  {                                                  \
+    0xe8ee88b0, 0x5571, 0x4086, {                    \
+      0xa4, 0x5b, 0x39, 0xa7, 0x16, 0x90, 0x6b, 0xdb \
+    }                                                \
+  }
+
+#endif  // ExpandedPrincipal_h
diff --git a/caps/NullPrincipal.cpp b/caps/NullPrincipal.cpp
new file mode 100644
index 0000000000..f0a0ad4708
--- /dev/null
+++ b/caps/NullPrincipal.cpp
@@ -0,0 +1,333 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set sw=2 sts=2 ts=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * This is the principal that has no rights and can't be accessed by
+ * anything other than itself and chrome; null principals are not
+ * same-origin with anything but themselves.
+ */
+
+#include "mozilla/ArrayUtils.h"
+
+#include "mozilla/dom/BlobURLProtocolHandler.h"
+#include "mozilla/StaticPrefs_network.h"
+#include "nsDocShell.h"
+#include "NullPrincipal.h"
+#include "DefaultURI.h"
+#include "nsSimpleURI.h"
+#include "nsIClassInfoImpl.h"
+#include "nsNetCID.h"
+#include "nsError.h"
+#include "nsEscape.h"
+#include "ContentPrincipal.h"
+#include "nsScriptSecurityManager.h"
+#include "pratom.h"
+#include "nsIObjectInputStream.h"
+
+#include "json/json.h"
+
+using namespace mozilla;
+
+NS_IMPL_CLASSINFO(NullPrincipal, nullptr, 0, NS_NULLPRINCIPAL_CID)
+NS_IMPL_QUERY_INTERFACE_CI(NullPrincipal, nsIPrincipal)
+NS_IMPL_CI_INTERFACE_GETTER(NullPrincipal, nsIPrincipal)
+
+NullPrincipal::NullPrincipal(nsIURI* aURI, const nsACString& aOriginNoSuffix,
+                             const OriginAttributes& aOriginAttributes)
+    : BasePrincipal(eNullPrincipal, aOriginNoSuffix, aOriginAttributes),
+      mURI(aURI) {}
+
+/* static */
+already_AddRefed<NullPrincipal> NullPrincipal::CreateWithInheritedAttributes(
+    nsIPrincipal* aInheritFrom) {
+  MOZ_ASSERT(aInheritFrom);
+  nsCOMPtr<nsIURI> uri = CreateURI(aInheritFrom);
+  return Create(Cast(aInheritFrom)->OriginAttributesRef(), uri);
+}
+
+/* static */
+already_AddRefed<NullPrincipal> NullPrincipal::Create(
+    const OriginAttributes& aOriginAttributes, nsIURI* aNullPrincipalURI) {
+  nsCOMPtr<nsIURI> uri = aNullPrincipalURI;
+  if (!uri) {
+    uri = NullPrincipal::CreateURI(nullptr);
+  }
+
+  MOZ_RELEASE_ASSERT(uri->SchemeIs(NS_NULLPRINCIPAL_SCHEME));
+
+  nsAutoCString originNoSuffix;
+  DebugOnly<nsresult> rv = uri->GetSpec(originNoSuffix);
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
+
+  RefPtr<NullPrincipal> nullPrin =
+      new NullPrincipal(uri, originNoSuffix, aOriginAttributes);
+  return nullPrin.forget();
+}
+
+/* static */
+already_AddRefed<NullPrincipal> NullPrincipal::CreateWithoutOriginAttributes() {
+  return NullPrincipal::Create(OriginAttributes(), nullptr);
+}
+
+void NullPrincipal::EscapePrecursorQuery(nsACString& aPrecursorQuery) {
+  // origins should not contain existing escape sequences, so set `esc_Forced`
+  // to force any `%` in the input to be escaped in addition to non-ascii,
+  // control characters and DEL.
+  nsCString modified;
+  if (NS_EscapeURLSpan(aPrecursorQuery, esc_Query | esc_Forced, modified)) {
+    aPrecursorQuery.Assign(std::move(modified));
+  }
+}
+
+void NullPrincipal::UnescapePrecursorQuery(nsACString& aPrecursorQuery) {
+  nsCString modified;
+  if (NS_UnescapeURL(aPrecursorQuery.BeginReading(), aPrecursorQuery.Length(),
+                     /* aFlags */ 0, modified)) {
+    aPrecursorQuery.Assign(std::move(modified));
+  }
+}
+
+already_AddRefed<nsIURI> NullPrincipal::CreateURI(
+    nsIPrincipal* aPrecursor, const nsID* aNullPrincipalID) {
+  nsCOMPtr<nsIURIMutator> iMutator;
+  if (StaticPrefs::network_url_useDefaultURI()) {
+    iMutator = new mozilla::net::DefaultURI::Mutator();
+  } else {
+    iMutator = new mozilla::net::nsSimpleURI::Mutator();
+  }
+
+  nsID uuid = aNullPrincipalID ? *aNullPrincipalID : nsID::GenerateUUID();
+
+  NS_MutateURI mutator(iMutator);
+  mutator.SetSpec(NS_NULLPRINCIPAL_SCHEME ":"_ns +
+                  nsDependentCString(nsIDToCString(uuid).get()));
+
+  // If there's a precursor URI, encode it in the null principal URI's query.
+  if (aPrecursor) {
+    nsAutoCString precursorOrigin;
+    switch (BasePrincipal::Cast(aPrecursor)->Kind()) {
+      case eNullPrincipal: {
+        // If the precursor null principal has a precursor, inherit it.
+        if (nsCOMPtr<nsIURI> nullPrecursorURI = aPrecursor->GetURI()) {
+          MOZ_ALWAYS_SUCCEEDS(nullPrecursorURI->GetQuery(precursorOrigin));
+        }
+        break;
+      }
+      case eContentPrincipal: {
+        MOZ_ALWAYS_SUCCEEDS(aPrecursor->GetOriginNoSuffix(precursorOrigin));
+#ifdef DEBUG
+        nsAutoCString original(precursorOrigin);
+#endif
+        EscapePrecursorQuery(precursorOrigin);
+#ifdef DEBUG
+        nsAutoCString unescaped(precursorOrigin);
+        UnescapePrecursorQuery(unescaped);
+        MOZ_ASSERT(unescaped == original,
+                   "cannot recover original precursor origin after escape");
+#endif
+        break;
+      }
+
+      // For now, we won't track expanded or system principal precursors. We may
+      // want to track expanded principal precursors in the future, but it's
+      // unlikely we'll want to track system principal precursors.
+      case eExpandedPrincipal:
+      case eSystemPrincipal:
+        break;
+    }
+    if (!precursorOrigin.IsEmpty()) {
+      mutator.SetQuery(precursorOrigin);
+    }
+  }
+
+  nsCOMPtr<nsIURI> uri;
+  MOZ_ALWAYS_SUCCEEDS(mutator.Finalize(getter_AddRefs(uri)));
+  return uri.forget();
+}
+
+nsresult NullPrincipal::GetScriptLocation(nsACString& aStr) {
+  return mURI->GetSpec(aStr);
+}
+
+/**
+ * nsIPrincipal implementation
+ */
+
+uint32_t NullPrincipal::GetHashValue() { return (NS_PTR_TO_INT32(this) >> 2); }
+
+NS_IMETHODIMP
+NullPrincipal::GetURI(nsIURI** aURI) {
+  nsCOMPtr<nsIURI> uri = mURI;
+  uri.forget(aURI);
+  return NS_OK;
+}
+NS_IMETHODIMP
+NullPrincipal::GetIsOriginPotentiallyTrustworthy(bool* aResult) {
+  *aResult = false;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+NullPrincipal::GetDomain(nsIURI** aDomain) {
+  nsCOMPtr<nsIURI> uri = mURI;
+  uri.forget(aDomain);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+NullPrincipal::SetDomain(nsIURI* aDomain) {
+  // I think the right thing to do here is to just throw...  Silently failing
+  // seems counterproductive.
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+bool NullPrincipal::MayLoadInternal(nsIURI* aURI) {
+  // Also allow the load if we are the principal of the URI being checked.
+  nsCOMPtr<nsIPrincipal> blobPrincipal;
+  if (dom::BlobURLProtocolHandler::GetBlobURLPrincipal(
+          aURI, getter_AddRefs(blobPrincipal))) {
+    MOZ_ASSERT(blobPrincipal);
+    return SubsumesInternal(blobPrincipal,
+                            BasePrincipal::ConsiderDocumentDomain);
+  }
+
+  return false;
+}
+
+NS_IMETHODIMP
+NullPrincipal::GetBaseDomain(nsACString& aBaseDomain) {
+  // For a null principal, we use our unique uuid as the base domain.
+  return mURI->GetPathQueryRef(aBaseDomain);
+}
+
+NS_IMETHODIMP
+NullPrincipal::GetAddonId(nsAString& aAddonId) {
+  aAddonId.Truncate();
+  return NS_OK;
+};
+
+/**
+ * nsISerializable implementation
+ */
+NS_IMETHODIMP
+NullPrincipal::Deserializer::Read(nsIObjectInputStream* aStream) {
+  nsAutoCString spec;
+  nsresult rv = aStream->ReadCString(spec);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIURI> uri;
+  rv = NS_NewURI(getter_AddRefs(uri), spec);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsAutoCString suffix;
+  rv = aStream->ReadCString(suffix);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  OriginAttributes attrs;
+  bool ok = attrs.PopulateFromSuffix(suffix);
+  NS_ENSURE_TRUE(ok, NS_ERROR_FAILURE);
+
+  mPrincipal = NullPrincipal::Create(attrs, uri);
+  NS_ENSURE_TRUE(mPrincipal, NS_ERROR_FAILURE);
+
+  return NS_OK;
+}
+
+nsresult NullPrincipal::PopulateJSONObject(Json::Value& aObject) {
+  nsAutoCString principalURI;
+  nsresult rv = mURI->GetSpec(principalURI);
+  NS_ENSURE_SUCCESS(rv, rv);
+  SetJSONValue<eSpec>(aObject, principalURI);
+
+  nsAutoCString suffix;
+  OriginAttributesRef().CreateSuffix(suffix);
+  if (suffix.Length() > 0) {
+    SetJSONValue<eSuffix>(aObject, suffix);
+  }
+
+  return NS_OK;
+}
+
+already_AddRefed<BasePrincipal> NullPrincipal::FromProperties(
+    nsTArray<NullPrincipal::KeyVal>& aFields) {
+  MOZ_ASSERT(aFields.Length() == eMax + 1, "Must have all the keys");
+  nsresult rv;
+  nsCOMPtr<nsIURI> uri;
+  OriginAttributes attrs;
+
+  // The odd structure here is to make the code to not compile
+  // if all the switch enum cases haven't been codified
+  for (const auto& field : aFields) {
+    switch (field.key) {
+      case NullPrincipal::eSpec:
+        if (!field.valueWasSerialized) {
+          MOZ_ASSERT(false,
+                     "Null principals require a spec URI in serialized JSON");
+          return nullptr;
+        }
+        rv = NS_NewURI(getter_AddRefs(uri), field.value);
+        NS_ENSURE_SUCCESS(rv, nullptr);
+        break;
+      case NullPrincipal::eSuffix:
+        bool ok = attrs.PopulateFromSuffix(field.value);
+        if (!ok) {
+          return nullptr;
+        }
+        break;
+    }
+  }
+
+  if (!uri) {
+    MOZ_ASSERT(false, "No URI deserialized");
+    return nullptr;
+  }
+
+  return NullPrincipal::Create(attrs, uri);
+}
+
+NS_IMETHODIMP
+NullPrincipal::GetPrecursorPrincipal(nsIPrincipal** aPrincipal) {
+  *aPrincipal = nullptr;
+
+  nsAutoCString query;
+  if (NS_FAILED(mURI->GetQuery(query)) || query.IsEmpty()) {
+    return NS_OK;
+  }
+  UnescapePrecursorQuery(query);
+
+  nsCOMPtr<nsIURI> precursorURI;
+  if (NS_FAILED(NS_NewURI(getter_AddRefs(precursorURI), query))) {
+    MOZ_ASSERT_UNREACHABLE(
+        "Failed to parse precursor from nullprincipal query");
+    return NS_OK;
+  }
+
+  // If our precursor is another null principal, re-construct it. This can
+  // happen if a null principal without a precursor causes another principal to
+  // be created.
+  if (precursorURI->SchemeIs(NS_NULLPRINCIPAL_SCHEME)) {
+#ifdef DEBUG
+    nsAutoCString precursorQuery;
+    precursorURI->GetQuery(precursorQuery);
+    MOZ_ASSERT(precursorQuery.IsEmpty(),
+               "Null principal with nested precursors?");
+#endif
+    *aPrincipal =
+        NullPrincipal::Create(OriginAttributesRef(), precursorURI).take();
+    return NS_OK;
+  }
+
+  RefPtr<BasePrincipal> contentPrincipal =
+      BasePrincipal::CreateContentPrincipal(precursorURI,
+                                            OriginAttributesRef());
+  // If `CreateContentPrincipal` failed, it will create a new NullPrincipal and
+  // return that instead. We only want to return real content principals here.
+  if (!contentPrincipal || !contentPrincipal->Is<ContentPrincipal>()) {
+    return NS_OK;
+  }
+  contentPrincipal.forget(aPrincipal);
+  return NS_OK;
+}
diff --git a/caps/NullPrincipal.h b/caps/NullPrincipal.h
new file mode 100644
index 0000000000..cbce27c700
--- /dev/null
+++ b/caps/NullPrincipal.h
@@ -0,0 +1,127 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * This is the principal that has no rights and can't be accessed by
+ * anything other than itself and chrome; null principals are not
+ * same-origin with anything but themselves.
+ */
+
+#ifndef mozilla_NullPrincipal_h
+#define mozilla_NullPrincipal_h
+
+#include "nsIPrincipal.h"
+#include "nsJSPrincipals.h"
+#include "nsCOMPtr.h"
+
+#include "mozilla/BasePrincipal.h"
+#include "gtest/MozGtestFriend.h"
+
+class nsIDocShell;
+class nsIURI;
+namespace Json {
+class Value;
+}
+
+#define NS_NULLPRINCIPAL_CID                         \
+  {                                                  \
+    0xbd066e5f, 0x146f, 0x4472, {                    \
+      0x83, 0x31, 0x7b, 0xfd, 0x05, 0xb1, 0xed, 0x90 \
+    }                                                \
+  }
+
+#define NS_NULLPRINCIPAL_SCHEME "moz-nullprincipal"
+
+namespace mozilla {
+
+class NullPrincipal final : public BasePrincipal {
+ public:
+  static PrincipalKind Kind() { return eNullPrincipal; }
+
+  NS_IMETHOD QueryInterface(REFNSIID aIID, void** aInstancePtr) override;
+  uint32_t GetHashValue() override;
+  NS_IMETHOD GetURI(nsIURI** aURI) override;
+  NS_IMETHOD GetIsOriginPotentiallyTrustworthy(bool* aResult) override;
+  NS_IMETHOD GetDomain(nsIURI** aDomain) override;
+  NS_IMETHOD SetDomain(nsIURI* aDomain) override;
+  NS_IMETHOD GetBaseDomain(nsACString& aBaseDomain) override;
+  NS_IMETHOD GetAddonId(nsAString& aAddonId) override;
+  NS_IMETHOD GetPrecursorPrincipal(nsIPrincipal** aPrecursor) override;
+
+  // Create a NullPrincipal, inheriting origin attributes from the given
+  // principal.
+  // If aInheritFrom is a content principal, or has a content principal
+  // precursor, it will be used as the precursor for this principal.
+  static already_AddRefed<NullPrincipal> CreateWithInheritedAttributes(
+      nsIPrincipal* aInheritFrom);
+
+  // Create a new NullPrincipal with the specified OriginAttributes.
+  //
+  // If `aNullPrincipalURI` is specified, it must be a NS_NULLPRINCIPAL_SCHEME
+  // URI previously created using `NullPrincipal::CreateURI`, and will be used
+  // as the origin URI for this principal.
+  static already_AddRefed<NullPrincipal> Create(
+      const OriginAttributes& aOriginAttributes,
+      nsIURI* aNullPrincipalURI = nullptr);
+
+  static already_AddRefed<NullPrincipal> CreateWithoutOriginAttributes();
+
+  // Generates a new unique `moz-nullprincipal:` URI. If `aPrecursor` is
+  // specified, it will be included in the generated URI as the null principal's
+  // precursor.
+  //
+  // The `aPrincipalID` attribute is used to force the creation of a
+  // deterministic NullPrincipal in situations where that is required. Avoid
+  // using this parameter unless absolutely necessary.
+  static already_AddRefed<nsIURI> CreateURI(nsIPrincipal* aPrecursor = nullptr,
+                                            const nsID* aPrincipalID = nullptr);
+
+  virtual nsresult GetScriptLocation(nsACString& aStr) override;
+
+  nsresult GetSiteIdentifier(SiteIdentifier& aSite) override {
+    aSite.Init(this);
+    return NS_OK;
+  }
+
+  virtual nsresult PopulateJSONObject(Json::Value& aObject) override;
+
+  // Serializable keys are the valid enum fields the serialization supports
+  enum SerializableKeys : uint8_t { eSpec = 0, eSuffix, eMax = eSuffix };
+  typedef mozilla::BasePrincipal::KeyValT<SerializableKeys> KeyVal;
+
+  static already_AddRefed<BasePrincipal> FromProperties(
+      nsTArray<NullPrincipal::KeyVal>& aFields);
+
+  class Deserializer : public BasePrincipal::Deserializer {
+   public:
+    NS_IMETHOD Read(nsIObjectInputStream* aStream) override;
+  };
+
+ protected:
+  NullPrincipal(nsIURI* aURI, const nsACString& aOriginNoSuffix,
+                const OriginAttributes& aOriginAttributes);
+
+  virtual ~NullPrincipal() = default;
+
+  bool SubsumesInternal(nsIPrincipal* aOther,
+                        DocumentDomainConsideration aConsideration) override {
+    MOZ_ASSERT(aOther);
+    return FastEquals(aOther);
+  }
+
+  bool MayLoadInternal(nsIURI* aURI) override;
+
+  const nsCOMPtr<nsIURI> mURI;
+
+ private:
+  FRIEND_TEST(NullPrincipalPrecursor, EscapingRoundTrips);
+
+  static void EscapePrecursorQuery(nsACString& aPrecursorQuery);
+  static void UnescapePrecursorQuery(nsACString& aPrecursorQuery);
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_NullPrincipal_h
diff --git a/caps/OriginAttributes.cpp b/caps/OriginAttributes.cpp
new file mode 100644
index 0000000000..734a230495
--- /dev/null
+++ b/caps/OriginAttributes.cpp
@@ -0,0 +1,494 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/OriginAttributes.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/dom/BlobURLProtocolHandler.h"
+#include "mozilla/dom/quota/QuotaManager.h"
+#include "nsIEffectiveTLDService.h"
+#include "nsIURI.h"
+#include "nsNetCID.h"
+#include "nsNetUtil.h"
+#include "nsString.h"
+#include "nsURLHelper.h"
+
+static const char kSourceChar = ':';
+static const char kSanitizedChar = '+';
+
+namespace mozilla {
+
+static void MakeTopLevelInfo(const nsACString& aScheme, const nsACString& aHost,
+                             int32_t aPort, bool aUseSite,
+                             nsAString& aTopLevelInfo) {
+  if (!aUseSite) {
+    aTopLevelInfo.Assign(NS_ConvertUTF8toUTF16(aHost));
+    return;
+  }
+
+  // Note: If you change the serialization of the partition-key, please update
+  // StoragePrincipalHelper.cpp too.
+
+  nsAutoCString site;
+  site.AssignLiteral("(");
+  site.Append(aScheme);
+  site.Append(",");
+  site.Append(aHost);
+  if (aPort != -1) {
+    site.Append(",");
+    site.AppendInt(aPort);
+  }
+  site.AppendLiteral(")");
+
+  aTopLevelInfo.Assign(NS_ConvertUTF8toUTF16(site));
+}
+
+static void MakeTopLevelInfo(const nsACString& aScheme, const nsACString& aHost,
+                             bool aUseSite, nsAString& aTopLevelInfo) {
+  MakeTopLevelInfo(aScheme, aHost, -1, aUseSite, aTopLevelInfo);
+}
+
+static void PopulateTopLevelInfoFromURI(const bool aIsTopLevelDocument,
+                                        nsIURI* aURI, bool aIsFirstPartyEnabled,
+                                        bool aForced, bool aUseSite,
+                                        nsString OriginAttributes::*aTarget,
+                                        OriginAttributes& aOriginAttributes) {
+  nsresult rv;
+
+  if (!aURI) {
+    return;
+  }
+
+  // If the prefs are off or this is not a top level load, bail out.
+  if ((!aIsFirstPartyEnabled || !aIsTopLevelDocument) && !aForced) {
+    return;
+  }
+
+  nsAString& topLevelInfo = aOriginAttributes.*aTarget;
+
+  nsAutoCString scheme;
+  nsCOMPtr<nsIURI> uri = aURI;
+  // The URI could be nested (for example view-source:http://example.com), in
+  // that case we want to get the innermost URI (http://example.com).
+  nsCOMPtr<nsINestedURI> nestedURI;
+  do {
+    NS_ENSURE_SUCCESS_VOID(uri->GetScheme(scheme));
+    nestedURI = do_QueryInterface(uri);
+    // We can't just use GetInnermostURI on the nested URI, since that would
+    // also unwrap some about: URIs to hidden moz-safe-about: URIs, which we do
+    // not want. Thus we loop through with GetInnerURI until the URI isn't
+    // nested anymore or we encounter a about: scheme.
+  } while (nestedURI && !scheme.EqualsLiteral("about") &&
+           NS_SUCCEEDED(nestedURI->GetInnerURI(getter_AddRefs(uri))));
+
+  if (scheme.EqualsLiteral("about")) {
+    MakeTopLevelInfo(scheme, nsLiteralCString(ABOUT_URI_FIRST_PARTY_DOMAIN),
+                     aUseSite, topLevelInfo);
+    return;
+  }
+
+  // If a null principal URI was provided, extract the UUID portion of the URI
+  // to use for the first-party domain.
+  if (scheme.EqualsLiteral("moz-nullprincipal")) {
+    // Get the UUID portion of the URI, ignoring the precursor principal.
+    nsAutoCString filePath;
+    rv = uri->GetFilePath(filePath);
+    MOZ_ASSERT(NS_SUCCEEDED(rv));
+    // Remove the `{}` characters from both ends.
+    filePath.Mid(filePath, 1, filePath.Length() - 2);
+    filePath.AppendLiteral(".mozilla");
+    // Store the generated file path.
+    topLevelInfo = NS_ConvertUTF8toUTF16(filePath);
+    return;
+  }
+
+  // Add-on principals should never get any first-party domain
+  // attributes in order to guarantee their storage integrity when switching
+  // FPI on and off.
+  if (scheme.EqualsLiteral("moz-extension")) {
+    return;
+  }
+
+  nsCOMPtr<nsIPrincipal> blobPrincipal;
+  if (dom::BlobURLProtocolHandler::GetBlobURLPrincipal(
+          uri, getter_AddRefs(blobPrincipal))) {
+    MOZ_ASSERT(blobPrincipal);
+    topLevelInfo = blobPrincipal->OriginAttributesRef().*aTarget;
+    return;
+  }
+
+  nsCOMPtr<nsIEffectiveTLDService> tldService =
+      do_GetService(NS_EFFECTIVETLDSERVICE_CONTRACTID);
+  MOZ_ASSERT(tldService);
+  NS_ENSURE_TRUE_VOID(tldService);
+
+  nsAutoCString baseDomain;
+  rv = tldService->GetBaseDomain(uri, 0, baseDomain);
+  if (NS_SUCCEEDED(rv)) {
+    MakeTopLevelInfo(scheme, baseDomain, aUseSite, topLevelInfo);
+    return;
+  }
+
+  // Saving before rv is overwritten.
+  bool isIpAddress = (rv == NS_ERROR_HOST_IS_IP_ADDRESS);
+  bool isInsufficientDomainLevels = (rv == NS_ERROR_INSUFFICIENT_DOMAIN_LEVELS);
+
+  int32_t port;
+  rv = uri->GetPort(&port);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  nsAutoCString host;
+  rv = uri->GetHost(host);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  if (isIpAddress) {
+    // If the host is an IPv4/IPv6 address, we still accept it as a
+    // valid topLevelInfo.
+    nsAutoCString ipAddr;
+
+    if (net_IsValidIPv6Addr(host)) {
+      // According to RFC2732, the host of an IPv6 address should be an
+      // IPv6reference. The GetHost() of nsIURI will only return the IPv6
+      // address. So, we need to convert it back to IPv6reference here.
+      ipAddr.AssignLiteral("[");
+      ipAddr.Append(host);
+      ipAddr.AppendLiteral("]");
+    } else {
+      ipAddr = host;
+    }
+
+    MakeTopLevelInfo(scheme, ipAddr, port, aUseSite, topLevelInfo);
+    return;
+  }
+
+  if (aUseSite) {
+    MakeTopLevelInfo(scheme, host, port, aUseSite, topLevelInfo);
+    return;
+  }
+
+  if (isInsufficientDomainLevels) {
+    nsAutoCString publicSuffix;
+    rv = tldService->GetPublicSuffix(uri, publicSuffix);
+    if (NS_SUCCEEDED(rv)) {
+      MakeTopLevelInfo(scheme, publicSuffix, port, aUseSite, topLevelInfo);
+      return;
+    }
+  }
+}
+
+void OriginAttributes::SetFirstPartyDomain(const bool aIsTopLevelDocument,
+                                           nsIURI* aURI, bool aForced) {
+  PopulateTopLevelInfoFromURI(
+      aIsTopLevelDocument, aURI, IsFirstPartyEnabled(), aForced,
+      StaticPrefs::privacy_firstparty_isolate_use_site(),
+      &OriginAttributes::mFirstPartyDomain, *this);
+}
+
+void OriginAttributes::SetFirstPartyDomain(const bool aIsTopLevelDocument,
+                                           const nsACString& aDomain) {
+  SetFirstPartyDomain(aIsTopLevelDocument, NS_ConvertUTF8toUTF16(aDomain));
+}
+
+void OriginAttributes::SetFirstPartyDomain(const bool aIsTopLevelDocument,
+                                           const nsAString& aDomain,
+                                           bool aForced) {
+  // If the pref is off or this is not a top level load, bail out.
+  if ((!IsFirstPartyEnabled() || !aIsTopLevelDocument) && !aForced) {
+    return;
+  }
+
+  mFirstPartyDomain = aDomain;
+}
+
+void OriginAttributes::SetPartitionKey(nsIURI* aURI) {
+  PopulateTopLevelInfoFromURI(
+      false /* aIsTopLevelDocument */, aURI, IsFirstPartyEnabled(),
+      true /* aForced */, StaticPrefs::privacy_dynamic_firstparty_use_site(),
+      &OriginAttributes::mPartitionKey, *this);
+}
+
+void OriginAttributes::SetPartitionKey(const nsACString& aDomain) {
+  SetPartitionKey(NS_ConvertUTF8toUTF16(aDomain));
+}
+
+void OriginAttributes::SetPartitionKey(const nsAString& aDomain) {
+  mPartitionKey = aDomain;
+}
+
+void OriginAttributes::CreateSuffix(nsACString& aStr) const {
+  URLParams params;
+  nsAutoString value;
+
+  //
+  // Important: While serializing any string-valued attributes, perform a
+  // release-mode assertion to make sure that they don't contain characters that
+  // will break the quota manager when it uses the serialization for file
+  // naming.
+  //
+
+  if (mInIsolatedMozBrowser) {
+    params.Set(u"inBrowser"_ns, u"1"_ns);
+  }
+
+  if (mUserContextId != nsIScriptSecurityManager::DEFAULT_USER_CONTEXT_ID) {
+    value.Truncate();
+    value.AppendInt(mUserContextId);
+    params.Set(u"userContextId"_ns, value);
+  }
+
+  if (mPrivateBrowsingId) {
+    value.Truncate();
+    value.AppendInt(mPrivateBrowsingId);
+    params.Set(u"privateBrowsingId"_ns, value);
+  }
+
+  if (!mFirstPartyDomain.IsEmpty()) {
+    nsAutoString sanitizedFirstPartyDomain(mFirstPartyDomain);
+    sanitizedFirstPartyDomain.ReplaceChar(kSourceChar, kSanitizedChar);
+
+    params.Set(u"firstPartyDomain"_ns, sanitizedFirstPartyDomain);
+  }
+
+  if (!mGeckoViewSessionContextId.IsEmpty()) {
+    nsAutoString sanitizedGeckoViewUserContextId(mGeckoViewSessionContextId);
+    sanitizedGeckoViewUserContextId.ReplaceChar(
+        dom::quota::QuotaManager::kReplaceChars16, kSanitizedChar);
+
+    params.Set(u"geckoViewUserContextId"_ns, sanitizedGeckoViewUserContextId);
+  }
+
+  if (!mPartitionKey.IsEmpty()) {
+    nsAutoString sanitizedPartitionKey(mPartitionKey);
+    sanitizedPartitionKey.ReplaceChar(kSourceChar, kSanitizedChar);
+
+    params.Set(u"partitionKey"_ns, sanitizedPartitionKey);
+  }
+
+  aStr.Truncate();
+
+  params.Serialize(value, true);
+  if (!value.IsEmpty()) {
+    aStr.AppendLiteral("^");
+    aStr.Append(NS_ConvertUTF16toUTF8(value));
+  }
+
+// In debug builds, check the whole string for illegal characters too (just in
+// case).
+#ifdef DEBUG
+  nsAutoCString str;
+  str.Assign(aStr);
+  MOZ_ASSERT(str.FindCharInSet(dom::quota::QuotaManager::kReplaceChars) ==
+             kNotFound);
+#endif
+}
+
+already_AddRefed<nsAtom> OriginAttributes::CreateSuffixAtom() const {
+  nsAutoCString suffix;
+  CreateSuffix(suffix);
+  return NS_Atomize(suffix);
+}
+
+void OriginAttributes::CreateAnonymizedSuffix(nsACString& aStr) const {
+  OriginAttributes attrs = *this;
+
+  if (!attrs.mFirstPartyDomain.IsEmpty()) {
+    attrs.mFirstPartyDomain.AssignLiteral("_anonymizedFirstPartyDomain_");
+  }
+
+  if (!attrs.mPartitionKey.IsEmpty()) {
+    attrs.mPartitionKey.AssignLiteral("_anonymizedPartitionKey_");
+  }
+
+  attrs.CreateSuffix(aStr);
+}
+
+bool OriginAttributes::PopulateFromSuffix(const nsACString& aStr) {
+  if (aStr.IsEmpty()) {
+    return true;
+  }
+
+  if (aStr[0] != '^') {
+    return false;
+  }
+
+  // If a non-default mPrivateBrowsingId is passed and is not present in the
+  // suffix, then it will retain the id when it should be default according
+  // to the suffix. Set to default before iterating to fix this.
+  mPrivateBrowsingId = nsIScriptSecurityManager::DEFAULT_PRIVATE_BROWSING_ID;
+
+  // Checking that we are in a pristine state
+
+  MOZ_RELEASE_ASSERT(mUserContextId == 0);
+  MOZ_RELEASE_ASSERT(mPrivateBrowsingId == 0);
+  MOZ_RELEASE_ASSERT(mFirstPartyDomain.IsEmpty());
+  MOZ_RELEASE_ASSERT(mGeckoViewSessionContextId.IsEmpty());
+  MOZ_RELEASE_ASSERT(mPartitionKey.IsEmpty());
+
+  return URLParams::Parse(
+      Substring(aStr, 1, aStr.Length() - 1),
+      [this](const nsAString& aName, const nsAString& aValue) {
+        if (aName.EqualsLiteral("inBrowser")) {
+          if (!aValue.EqualsLiteral("1")) {
+            return false;
+          }
+
+          mInIsolatedMozBrowser = true;
+          return true;
+        }
+
+        if (aName.EqualsLiteral("addonId") || aName.EqualsLiteral("appId")) {
+          // No longer supported. Silently ignore so that legacy origin strings
+          // don't cause failures.
+          return true;
+        }
+
+        if (aName.EqualsLiteral("userContextId")) {
+          nsresult rv;
+          int64_t val = aValue.ToInteger64(&rv);
+          NS_ENSURE_SUCCESS(rv, false);
+          NS_ENSURE_TRUE(val <= UINT32_MAX, false);
+          mUserContextId = static_cast<uint32_t>(val);
+
+          return true;
+        }
+
+        if (aName.EqualsLiteral("privateBrowsingId")) {
+          nsresult rv;
+          int64_t val = aValue.ToInteger64(&rv);
+          NS_ENSURE_SUCCESS(rv, false);
+          NS_ENSURE_TRUE(val >= 0 && val <= UINT32_MAX, false);
+          mPrivateBrowsingId = static_cast<uint32_t>(val);
+
+          return true;
+        }
+
+        if (aName.EqualsLiteral("firstPartyDomain")) {
+          nsAutoString firstPartyDomain(aValue);
+          firstPartyDomain.ReplaceChar(kSanitizedChar, kSourceChar);
+          mFirstPartyDomain.Assign(firstPartyDomain);
+          return true;
+        }
+
+        if (aName.EqualsLiteral("geckoViewUserContextId")) {
+          mGeckoViewSessionContextId.Assign(aValue);
+          return true;
+        }
+
+        if (aName.EqualsLiteral("partitionKey")) {
+          nsAutoString partitionKey(aValue);
+          partitionKey.ReplaceChar(kSanitizedChar, kSourceChar);
+          mPartitionKey.Assign(partitionKey);
+          return true;
+        }
+
+        // No other attributes are supported.
+        return false;
+      });
+}
+
+bool OriginAttributes::PopulateFromOrigin(const nsACString& aOrigin,
+                                          nsACString& aOriginNoSuffix) {
+  // RFindChar is only available on nsCString.
+  nsCString origin(aOrigin);
+  int32_t pos = origin.RFindChar('^');
+
+  if (pos == kNotFound) {
+    aOriginNoSuffix = origin;
+    return true;
+  }
+
+  aOriginNoSuffix = Substring(origin, 0, pos);
+  return PopulateFromSuffix(Substring(origin, pos));
+}
+
+void OriginAttributes::SyncAttributesWithPrivateBrowsing(
+    bool aInPrivateBrowsing) {
+  mPrivateBrowsingId = aInPrivateBrowsing ? 1 : 0;
+}
+
+/* static */
+bool OriginAttributes::IsPrivateBrowsing(const nsACString& aOrigin) {
+  nsAutoCString dummy;
+  OriginAttributes attrs;
+  if (NS_WARN_IF(!attrs.PopulateFromOrigin(aOrigin, dummy))) {
+    return false;
+  }
+
+  return !!attrs.mPrivateBrowsingId;
+}
+
+/* static */
+bool OriginAttributes::ParsePartitionKey(const nsAString& aPartitionKey,
+                                         nsAString& outScheme,
+                                         nsAString& outBaseDomain,
+                                         int32_t& outPort) {
+  outScheme.Truncate();
+  outBaseDomain.Truncate();
+  outPort = -1;
+
+  // Partition keys have the format "(<scheme>,<baseDomain>,[port])". The port
+  // is optional. For example: "(https,example.com,8443)" or
+  // "(http,example.org)".
+  // When privacy.dynamic_firstparty.use_site = false, the partitionKey contains
+  // only the host, e.g. "example.com".
+  // See MakeTopLevelInfo for the partitionKey serialization code.
+
+  if (aPartitionKey.IsEmpty()) {
+    return true;
+  }
+
+  // PartitionKey contains only the host.
+  if (!StaticPrefs::privacy_dynamic_firstparty_use_site()) {
+    outBaseDomain = aPartitionKey;
+    return true;
+  }
+
+  // Smallest possible partitionKey is "(x,x)". Scheme and base domain are
+  // mandatory.
+  if (NS_WARN_IF(aPartitionKey.Length() < 5)) {
+    return false;
+  }
+
+  if (NS_WARN_IF(aPartitionKey.First() != '(' || aPartitionKey.Last() != ')')) {
+    return false;
+  }
+
+  // Remove outer brackets so we can string split.
+  nsAutoString str(Substring(aPartitionKey, 1, aPartitionKey.Length() - 2));
+
+  uint32_t fieldIndex = 0;
+  for (const nsAString& field : str.Split(',')) {
+    if (NS_WARN_IF(field.IsEmpty())) {
+      // There cannot be empty fields.
+      return false;
+    }
+
+    if (fieldIndex == 0) {
+      outScheme.Assign(field);
+    } else if (fieldIndex == 1) {
+      outBaseDomain.Assign(field);
+    } else if (fieldIndex == 2) {
+      // Parse the port which is represented in the partitionKey string as a
+      // decimal (base 10) number.
+      long port = strtol(NS_ConvertUTF16toUTF8(field).get(), nullptr, 10);
+      // Invalid port.
+      if (NS_WARN_IF(port == 0)) {
+        return false;
+      }
+      outPort = static_cast<int32_t>(port);
+    } else {
+      NS_WARNING("Invalid partitionKey. Too many tokens");
+      return false;
+    }
+
+    fieldIndex++;
+  }
+
+  // scheme and base domain are required.
+  return fieldIndex > 1;
+}
+
+}  // namespace mozilla
diff --git a/caps/OriginAttributes.h b/caps/OriginAttributes.h
new file mode 100644
index 0000000000..02e52f0799
--- /dev/null
+++ b/caps/OriginAttributes.h
@@ -0,0 +1,289 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_OriginAttributes_h
+#define mozilla_OriginAttributes_h
+
+#include "mozilla/dom/ChromeUtilsBinding.h"
+#include "mozilla/StaticPrefs_privacy.h"
+#include "nsIScriptSecurityManager.h"
+
+namespace mozilla {
+
+class OriginAttributes : public dom::OriginAttributesDictionary {
+ public:
+  OriginAttributes() = default;
+
+  explicit OriginAttributes(bool aInIsolatedMozBrowser) {
+    mInIsolatedMozBrowser = aInIsolatedMozBrowser;
+  }
+
+  explicit OriginAttributes(const OriginAttributesDictionary& aOther)
+      : OriginAttributesDictionary(aOther) {}
+
+  void SetFirstPartyDomain(const bool aIsTopLevelDocument, nsIURI* aURI,
+                           bool aForced = false);
+  void SetFirstPartyDomain(const bool aIsTopLevelDocument,
+                           const nsACString& aDomain);
+  void SetFirstPartyDomain(const bool aIsTopLevelDocument,
+                           const nsAString& aDomain, bool aForced = false);
+
+  void SetPartitionKey(nsIURI* aURI);
+  void SetPartitionKey(const nsACString& aDomain);
+  void SetPartitionKey(const nsAString& aDomain);
+
+  enum {
+    STRIP_FIRST_PARTY_DOMAIN = 0x01,
+    STRIP_USER_CONTEXT_ID = 0x02,
+    STRIP_PRIVATE_BROWSING_ID = 0x04,
+    STRIP_PARITION_KEY = 0x08,
+  };
+
+  inline void StripAttributes(uint32_t aFlags) {
+    if (aFlags & STRIP_FIRST_PARTY_DOMAIN) {
+      mFirstPartyDomain.Truncate();
+    }
+
+    if (aFlags & STRIP_USER_CONTEXT_ID) {
+      mUserContextId = nsIScriptSecurityManager::DEFAULT_USER_CONTEXT_ID;
+    }
+
+    if (aFlags & STRIP_PRIVATE_BROWSING_ID) {
+      mPrivateBrowsingId =
+          nsIScriptSecurityManager::DEFAULT_PRIVATE_BROWSING_ID;
+    }
+
+    if (aFlags & STRIP_PARITION_KEY) {
+      mPartitionKey.Truncate();
+    }
+  }
+
+  bool operator==(const OriginAttributes& aOther) const {
+    return EqualsIgnoringFPD(aOther) &&
+           mFirstPartyDomain == aOther.mFirstPartyDomain &&
+           // FIXME(emilio, bug 1667440): Should this be part of
+           // EqualsIgnoringFPD instead?
+           mPartitionKey == aOther.mPartitionKey;
+  }
+
+  bool operator!=(const OriginAttributes& aOther) const {
+    return !(*this == aOther);
+  }
+
+  [[nodiscard]] bool EqualsIgnoringFPD(const OriginAttributes& aOther) const {
+    return mInIsolatedMozBrowser == aOther.mInIsolatedMozBrowser &&
+           mUserContextId == aOther.mUserContextId &&
+           mPrivateBrowsingId == aOther.mPrivateBrowsingId &&
+           mGeckoViewSessionContextId == aOther.mGeckoViewSessionContextId;
+  }
+
+  [[nodiscard]] bool EqualsIgnoringPartitionKey(
+      const OriginAttributes& aOther) const {
+    return EqualsIgnoringFPD(aOther) &&
+           mFirstPartyDomain == aOther.mFirstPartyDomain;
+  }
+
+  // Serializes/Deserializes non-default values into the suffix format, i.e.
+  // |^key1=value1&key2=value2|. If there are no non-default attributes, this
+  // returns an empty string.
+  void CreateSuffix(nsACString& aStr) const;
+
+  // Like CreateSuffix, but returns an atom instead of producing a string.
+  already_AddRefed<nsAtom> CreateSuffixAtom() const;
+
+  // Don't use this method for anything else than debugging!
+  void CreateAnonymizedSuffix(nsACString& aStr) const;
+
+  [[nodiscard]] bool PopulateFromSuffix(const nsACString& aStr);
+
+  // Populates the attributes from a string like
+  // |uri^key1=value1&key2=value2| and returns the uri without the suffix.
+  [[nodiscard]] bool PopulateFromOrigin(const nsACString& aOrigin,
+                                        nsACString& aOriginNoSuffix);
+
+  // Helper function to match mIsPrivateBrowsing to existing private browsing
+  // flags. Once all other flags are removed, this can be removed too.
+  void SyncAttributesWithPrivateBrowsing(bool aInPrivateBrowsing);
+
+  // check if "privacy.firstparty.isolate" is enabled.
+  static inline bool IsFirstPartyEnabled() {
+    return StaticPrefs::privacy_firstparty_isolate();
+  }
+
+  // check if the access of window.opener across different FPDs is restricted.
+  // We only restrict the access of window.opener when first party isolation
+  // is enabled and "privacy.firstparty.isolate.restrict_opener_access" is on.
+  static inline bool IsRestrictOpenerAccessForFPI() {
+    // We always want to restrict window.opener if first party isolation is
+    // disabled.
+    return !StaticPrefs::privacy_firstparty_isolate() ||
+           StaticPrefs::privacy_firstparty_isolate_restrict_opener_access();
+  }
+
+  // Check whether we block the postMessage across different FPDs when the
+  // targetOrigin is '*'.
+  [[nodiscard]] static inline bool IsBlockPostMessageForFPI() {
+    return StaticPrefs::privacy_firstparty_isolate() &&
+           StaticPrefs::privacy_firstparty_isolate_block_post_message();
+  }
+
+  // returns true if the originAttributes suffix has mPrivateBrowsingId value
+  // different than 0.
+  static bool IsPrivateBrowsing(const nsACString& aOrigin);
+
+  // Parse a partitionKey of the format "(<scheme>,<baseDomain>,[port])" into
+  // its components.
+  // Returns false if the partitionKey cannot be parsed because the format is
+  // invalid.
+  static bool ParsePartitionKey(const nsAString& aPartitionKey,
+                                nsAString& outScheme, nsAString& outBaseDomain,
+                                int32_t& outPort);
+};
+
+class OriginAttributesPattern : public dom::OriginAttributesPatternDictionary {
+ public:
+  // To convert a JSON string to an OriginAttributesPattern, do the following:
+  //
+  // OriginAttributesPattern pattern;
+  // if (!pattern.Init(aJSONString)) {
+  //   ... // handle failure.
+  // }
+  OriginAttributesPattern() = default;
+
+  explicit OriginAttributesPattern(
+      const OriginAttributesPatternDictionary& aOther)
+      : OriginAttributesPatternDictionary(aOther) {}
+
+  // Performs a match of |aAttrs| against this pattern.
+  bool Matches(const OriginAttributes& aAttrs) const {
+    if (mInIsolatedMozBrowser.WasPassed() &&
+        mInIsolatedMozBrowser.Value() != aAttrs.mInIsolatedMozBrowser) {
+      return false;
+    }
+
+    if (mUserContextId.WasPassed() &&
+        mUserContextId.Value() != aAttrs.mUserContextId) {
+      return false;
+    }
+
+    if (mPrivateBrowsingId.WasPassed() &&
+        mPrivateBrowsingId.Value() != aAttrs.mPrivateBrowsingId) {
+      return false;
+    }
+
+    if (mFirstPartyDomain.WasPassed() &&
+        mFirstPartyDomain.Value() != aAttrs.mFirstPartyDomain) {
+      return false;
+    }
+
+    if (mGeckoViewSessionContextId.WasPassed() &&
+        mGeckoViewSessionContextId.Value() !=
+            aAttrs.mGeckoViewSessionContextId) {
+      return false;
+    }
+
+    // If both mPartitionKey and mPartitionKeyPattern are passed, mPartitionKey
+    // takes precedence.
+    if (mPartitionKey.WasPassed()) {
+      if (mPartitionKey.Value() != aAttrs.mPartitionKey) {
+        return false;
+      }
+    } else if (mPartitionKeyPattern.WasPassed()) {
+      auto& pkPattern = mPartitionKeyPattern.Value();
+
+      if (pkPattern.mScheme.WasPassed() || pkPattern.mBaseDomain.WasPassed() ||
+          pkPattern.mPort.WasPassed()) {
+        if (aAttrs.mPartitionKey.IsEmpty()) {
+          return false;
+        }
+
+        nsString scheme;
+        nsString baseDomain;
+        int32_t port;
+        bool success = OriginAttributes::ParsePartitionKey(
+            aAttrs.mPartitionKey, scheme, baseDomain, port);
+        if (!success) {
+          return false;
+        }
+
+        if (pkPattern.mScheme.WasPassed() &&
+            pkPattern.mScheme.Value() != scheme) {
+          return false;
+        }
+        if (pkPattern.mBaseDomain.WasPassed() &&
+            pkPattern.mBaseDomain.Value() != baseDomain) {
+          return false;
+        }
+        if (pkPattern.mPort.WasPassed() && pkPattern.mPort.Value() != port) {
+          return false;
+        }
+      }
+    }
+
+    return true;
+  }
+
+  bool Overlaps(const OriginAttributesPattern& aOther) const {
+    if (mInIsolatedMozBrowser.WasPassed() &&
+        aOther.mInIsolatedMozBrowser.WasPassed() &&
+        mInIsolatedMozBrowser.Value() != aOther.mInIsolatedMozBrowser.Value()) {
+      return false;
+    }
+
+    if (mUserContextId.WasPassed() && aOther.mUserContextId.WasPassed() &&
+        mUserContextId.Value() != aOther.mUserContextId.Value()) {
+      return false;
+    }
+
+    if (mPrivateBrowsingId.WasPassed() &&
+        aOther.mPrivateBrowsingId.WasPassed() &&
+        mPrivateBrowsingId.Value() != aOther.mPrivateBrowsingId.Value()) {
+      return false;
+    }
+
+    if (mFirstPartyDomain.WasPassed() && aOther.mFirstPartyDomain.WasPassed() &&
+        mFirstPartyDomain.Value() != aOther.mFirstPartyDomain.Value()) {
+      return false;
+    }
+
+    if (mGeckoViewSessionContextId.WasPassed() &&
+        aOther.mGeckoViewSessionContextId.WasPassed() &&
+        mGeckoViewSessionContextId.Value() !=
+            aOther.mGeckoViewSessionContextId.Value()) {
+      return false;
+    }
+
+    if (mPartitionKey.WasPassed() && aOther.mPartitionKey.WasPassed() &&
+        mPartitionKey.Value() != aOther.mPartitionKey.Value()) {
+      return false;
+    }
+
+    if (mPartitionKeyPattern.WasPassed() &&
+        aOther.mPartitionKeyPattern.WasPassed()) {
+      auto& self = mPartitionKeyPattern.Value();
+      auto& other = aOther.mPartitionKeyPattern.Value();
+
+      if (self.mScheme.WasPassed() && other.mScheme.WasPassed() &&
+          self.mScheme.Value() != other.mScheme.Value()) {
+        return false;
+      }
+      if (self.mBaseDomain.WasPassed() && other.mBaseDomain.WasPassed() &&
+          self.mBaseDomain.Value() != other.mBaseDomain.Value()) {
+        return false;
+      }
+      if (self.mPort.WasPassed() && other.mPort.WasPassed() &&
+          self.mPort.Value() != other.mPort.Value()) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+};
+
+}  // namespace mozilla
+
+#endif /* mozilla_OriginAttributes_h */
diff --git a/caps/PrincipalHashKey.h b/caps/PrincipalHashKey.h
new file mode 100644
index 0000000000..1c245532a6
--- /dev/null
+++ b/caps/PrincipalHashKey.h
@@ -0,0 +1,58 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_PrincipalHashKey_h
+#define mozilla_PrincipalHashKey_h
+
+#include "BasePrincipal.h"
+#include "PLDHashTable.h"
+#include "mozilla/Unused.h"
+#include "nsCOMPtr.h"
+#include "nsHashKeys.h"
+
+namespace mozilla {
+
+class PrincipalHashKey : public PLDHashEntryHdr {
+ public:
+  using KeyType = nsIPrincipal*;
+  using KeyTypePointer = const nsIPrincipal*;
+
+  explicit PrincipalHashKey(const nsIPrincipal* aKey)
+      : mPrincipal(const_cast<nsIPrincipal*>(aKey)) {
+    MOZ_ASSERT(aKey);
+    MOZ_COUNT_CTOR(PrincipalHashKey);
+  }
+  PrincipalHashKey(PrincipalHashKey&& aKey)
+      : mPrincipal(std::move(aKey.mPrincipal)) {
+    MOZ_COUNT_CTOR(PrincipalHashKey);
+  }
+
+  MOZ_COUNTED_DTOR(PrincipalHashKey)
+
+  nsIPrincipal* GetKey() const { return mPrincipal; }
+
+  bool KeyEquals(const nsIPrincipal* aKey) const {
+    return BasePrincipal::Cast(mPrincipal)
+        ->FastEquals(const_cast<nsIPrincipal*>(aKey));
+  }
+
+  static const nsIPrincipal* KeyToPointer(const nsIPrincipal* aKey) {
+    return aKey;
+  }
+  static PLDHashNumber HashKey(const nsIPrincipal* aKey) {
+    auto* bp = BasePrincipal::Cast(aKey);
+    return HashGeneric(bp->GetOriginNoSuffixHash(), bp->GetOriginSuffixHash());
+  }
+
+  enum { ALLOW_MEMMOVE = true };
+
+ protected:
+  nsCOMPtr<nsIPrincipal> mPrincipal;
+};
+
+}  // namespace mozilla
+
+#endif
diff --git a/caps/SystemPrincipal.cpp b/caps/SystemPrincipal.cpp
new file mode 100644
index 0000000000..5c2ed63a9a
--- /dev/null
+++ b/caps/SystemPrincipal.cpp
@@ -0,0 +1,118 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* The privileged system principal. */
+
+#include "nscore.h"
+#include "SystemPrincipal.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "nsCOMPtr.h"
+#include "nsReadableUtils.h"
+#include "nsCRT.h"
+#include "nsString.h"
+#include "nsIClassInfoImpl.h"
+#include "pratom.h"
+
+using namespace mozilla;
+
+NS_IMPL_CLASSINFO(SystemPrincipal, nullptr, nsIClassInfo::SINGLETON,
+                  NS_SYSTEMPRINCIPAL_CID)
+NS_IMPL_QUERY_INTERFACE_CI(SystemPrincipal, nsIPrincipal, nsISerializable)
+NS_IMPL_CI_INTERFACE_GETTER(SystemPrincipal, nsIPrincipal, nsISerializable)
+
+static constexpr nsLiteralCString kSystemPrincipalSpec =
+    "[System Principal]"_ns;
+
+SystemPrincipal::SystemPrincipal()
+    : BasePrincipal(eSystemPrincipal, kSystemPrincipalSpec,
+                    OriginAttributes()) {}
+
+static StaticMutex sSystemPrincipalMutex;
+static StaticRefPtr<SystemPrincipal> sSystemPrincipal
+    MOZ_GUARDED_BY(sSystemPrincipalMutex);
+
+already_AddRefed<SystemPrincipal> SystemPrincipal::Get() {
+  StaticMutexAutoLock lock(sSystemPrincipalMutex);
+  return do_AddRef(sSystemPrincipal);
+}
+
+already_AddRefed<SystemPrincipal> SystemPrincipal::Init() {
+  AssertIsOnMainThread();
+  StaticMutexAutoLock lock(sSystemPrincipalMutex);
+  if (MOZ_UNLIKELY(sSystemPrincipal)) {
+    MOZ_ASSERT_UNREACHABLE("SystemPrincipal::Init() may only be called once");
+  } else {
+    sSystemPrincipal = new SystemPrincipal();
+  }
+  return do_AddRef(sSystemPrincipal);
+}
+
+void SystemPrincipal::Shutdown() {
+  AssertIsOnMainThread();
+  StaticMutexAutoLock lock(sSystemPrincipalMutex);
+  MOZ_ASSERT(sSystemPrincipal);
+  sSystemPrincipal = nullptr;
+}
+
+nsresult SystemPrincipal::GetScriptLocation(nsACString& aStr) {
+  aStr.Assign(kSystemPrincipalSpec);
+  return NS_OK;
+}
+
+///////////////////////////////////////
+// Methods implementing nsIPrincipal //
+///////////////////////////////////////
+
+uint32_t SystemPrincipal::GetHashValue() { return NS_PTR_TO_INT32(this); }
+
+NS_IMETHODIMP
+SystemPrincipal::GetURI(nsIURI** aURI) {
+  *aURI = nullptr;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SystemPrincipal::GetIsOriginPotentiallyTrustworthy(bool* aResult) {
+  *aResult = true;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SystemPrincipal::GetDomain(nsIURI** aDomain) {
+  *aDomain = nullptr;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SystemPrincipal::SetDomain(nsIURI* aDomain) { return NS_OK; }
+
+NS_IMETHODIMP
+SystemPrincipal::GetBaseDomain(nsACString& aBaseDomain) {
+  // No base domain for chrome.
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SystemPrincipal::GetAddonId(nsAString& aAddonId) {
+  aAddonId.Truncate();
+  return NS_OK;
+};
+
+//////////////////////////////////////////
+// Methods implementing nsISerializable //
+//////////////////////////////////////////
+
+NS_IMETHODIMP
+SystemPrincipal::Read(nsIObjectInputStream* aStream) {
+  // no-op: CID is sufficient to identify the mSystemPrincipal singleton
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SystemPrincipal::Write(nsIObjectOutputStream* aStream) {
+  // Read is used still for legacy principals
+  MOZ_RELEASE_ASSERT(false, "Old style serialization is removed");
+  return NS_OK;
+}
diff --git a/caps/SystemPrincipal.h b/caps/SystemPrincipal.h
new file mode 100644
index 0000000000..7b89d7ddff
--- /dev/null
+++ b/caps/SystemPrincipal.h
@@ -0,0 +1,83 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* The privileged system principal. */
+
+#ifndef mozilla_SystemPrincipal_h
+#define mozilla_SystemPrincipal_h
+
+#include "nsIPrincipal.h"
+#include "nsJSPrincipals.h"
+
+#include "mozilla/BasePrincipal.h"
+
+#define NS_SYSTEMPRINCIPAL_CID                      \
+  {                                                 \
+    0x4a6212db, 0xaccb, 0x11d3, {                   \
+      0xb7, 0x65, 0x0, 0x60, 0xb0, 0xb6, 0xce, 0xcb \
+    }                                               \
+  }
+#define NS_SYSTEMPRINCIPAL_CONTRACTID "@mozilla.org/systemprincipal;1"
+
+class nsScriptSecurityManager;
+
+namespace Json {
+class Value;
+}
+
+namespace mozilla {
+
+class SystemPrincipal final : public BasePrincipal, public nsISerializable {
+  SystemPrincipal();
+
+ public:
+  static already_AddRefed<SystemPrincipal> Get();
+
+  static PrincipalKind Kind() { return eSystemPrincipal; }
+
+  NS_IMETHOD_(MozExternalRefCountType) AddRef() override {
+    return nsJSPrincipals::AddRef();
+  };
+  NS_IMETHOD_(MozExternalRefCountType) Release() override {
+    return nsJSPrincipals::Release();
+  };
+
+  NS_DECL_NSISERIALIZABLE
+  NS_IMETHOD QueryInterface(REFNSIID aIID, void** aInstancePtr) override;
+  uint32_t GetHashValue() override;
+  NS_IMETHOD GetURI(nsIURI** aURI) override;
+  NS_IMETHOD GetDomain(nsIURI** aDomain) override;
+  NS_IMETHOD SetDomain(nsIURI* aDomain) override;
+  NS_IMETHOD GetBaseDomain(nsACString& aBaseDomain) override;
+  NS_IMETHOD GetAddonId(nsAString& aAddonId) override;
+  NS_IMETHOD GetIsOriginPotentiallyTrustworthy(bool* aResult) override;
+
+  virtual nsresult GetScriptLocation(nsACString& aStr) override;
+
+  nsresult GetSiteIdentifier(SiteIdentifier& aSite) override {
+    aSite.Init(this);
+    return NS_OK;
+  }
+
+ protected:
+  friend class ::nsScriptSecurityManager;
+
+  virtual ~SystemPrincipal() = default;
+
+  static already_AddRefed<SystemPrincipal> Init();
+  static void Shutdown();
+
+  bool SubsumesInternal(nsIPrincipal* aOther,
+                        DocumentDomainConsideration aConsideration) override {
+    return true;
+  }
+
+  bool MayLoadInternal(nsIURI* aURI) override { return true; }
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_SystemPrincipal_h
diff --git a/caps/moz.build b/caps/moz.build
new file mode 100644
index 0000000000..6d5d95f934
--- /dev/null
+++ b/caps/moz.build
@@ -0,0 +1,80 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+MOCHITEST_MANIFESTS += ["tests/mochitest/mochitest.ini"]
+MOCHITEST_CHROME_MANIFESTS += ["tests/mochitest/chrome.ini"]
+BROWSER_CHROME_MANIFESTS += ["tests/mochitest/browser.ini"]
+XPCSHELL_TESTS_MANIFESTS += ["tests/unit/xpcshell.ini"]
+
+# Hack to make this file available as a resource:// URI.
+TESTING_JS_MODULES += [
+    "tests/mochitest/resource_test_file.html",
+]
+
+XPIDL_SOURCES += [
+    "nsIAddonPolicyService.idl",
+    "nsIDomainPolicy.idl",
+    "nsIPrincipal.idl",
+    "nsIScriptSecurityManager.idl",
+]
+
+XPIDL_MODULE = "caps"
+
+EXPORTS += [
+    "nsJSPrincipals.h",
+    "nsScriptSecurityManager.h",
+]
+
+EXPORTS.mozilla = [
+    "BasePrincipal.h",
+    "ContentPrincipal.h",
+    "ContentPrincipalInfoHashKey.h",
+    "ExpandedPrincipal.h",
+    "NullPrincipal.h",
+    "OriginAttributes.h",
+    "PrincipalHashKey.h",
+    "SystemPrincipal.h",
+]
+
+SOURCES += [
+    # Compile this separately since nsExceptionHandler.h conflicts
+    # with something from NullPrincipal.cpp.
+    "BasePrincipal.cpp",
+]
+
+UNIFIED_SOURCES += [
+    "ContentPrincipal.cpp",
+    "DomainPolicy.cpp",
+    "ExpandedPrincipal.cpp",
+    "nsJSPrincipals.cpp",
+    "nsScriptSecurityManager.cpp",
+    "NullPrincipal.cpp",
+    "OriginAttributes.cpp",
+    "SystemPrincipal.cpp",
+]
+
+USE_LIBS += [
+    "jsoncpp",
+]
+
+LOCAL_INCLUDES += [
+    "/docshell/base",
+    "/dom/base",
+    "/js/xpconnect/src",
+    "/netwerk/base",
+    "/netwerk/cookie",
+    "/toolkit/components/jsoncpp/include",
+]
+
+if CONFIG["ENABLE_TESTS"]:
+    DIRS += ["tests/gtest"]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul"
+
+with Files("**"):
+    BUG_COMPONENT = ("Core", "Security: CAPS")
diff --git a/caps/nsIAddonPolicyService.idl b/caps/nsIAddonPolicyService.idl
new file mode 100644
index 0000000000..de218ff70c
--- /dev/null
+++ b/caps/nsIAddonPolicyService.idl
@@ -0,0 +1,102 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+#include "nsIURI.idl"
+
+/**
+ * This interface allows the security manager to query custom per-addon security
+ * policy.
+ */
+[scriptable, uuid(8a034ef9-9d14-4c5d-8319-06c1ab574baa)]
+interface nsIAddonPolicyService : nsISupports
+{
+  /**
+   * Returns the default content security policy which applies to extension
+   * documents which do not specify any custom policies.
+   */
+  readonly attribute AString defaultCSP;
+
+  /**
+   * Same as above, but used for extensions using manifest v3.
+   */
+  readonly attribute AString defaultCSPV3;
+
+  /**
+   * Returns the base content security policy which applies to all extension resources.
+   */
+  AString getBaseCSP(in AString aAddonId);
+
+  /**
+   * Returns the content security policy which applies to documents belonging
+   * to the extension with the given ID. This may be either a custom policy,
+   * if one was supplied, or the default policy if one was not.
+   */
+  AString getExtensionPageCSP(in AString aAddonId);
+
+  /**
+   * Returns the generated background page as a data-URI, if any. If the addon
+   * does not have an auto-generated background page, an empty string is
+   * returned.
+   */
+  ACString getGeneratedBackgroundPageUrl(in ACString aAddonId);
+
+  /**
+   * Returns true if the addon was granted the |aPerm| API permission.
+   */
+  boolean addonHasPermission(in AString aAddonId, in AString aPerm);
+
+  /**
+   * Returns true if unprivileged code associated with the given addon may load
+   * data from |aURI|.  If |aExplicit| is true, the <all_urls> permission and
+   * permissive host globs are ignored when checking for a match.
+   */
+  boolean addonMayLoadURI(in AString aAddonId, in nsIURI aURI, [optional] in boolean aExplicit);
+
+  /**
+   * Returns the name of the WebExtension with the given ID, or the ID string
+   * if no matching add-on can be found.
+   */
+  AString getExtensionName(in AString aAddonId);
+
+  /**
+   * Returns true if a given extension:// URI is web-accessible and loadable by the source.
+   * This should be called if the protocol flags for the extension URI has URI_WEB_ACCESSIBLE.
+   */
+  boolean sourceMayLoadExtensionURI(in nsIURI aSourceURI, in nsIURI aExtensionURI);
+
+  /**
+   * Maps an extension URI to the ID of the addon it belongs to.
+   */
+  AString extensionURIToAddonId(in nsIURI aURI);
+};
+
+/**
+ * This interface exposes functionality related to add-on content policy
+ * enforcement.
+ */
+[scriptable, uuid(7a4fe60b-9131-45f5-83f3-dc63b5d71a5d)]
+interface nsIAddonContentPolicy : nsISupports
+{
+  /* options to pass to validateAddonCSP
+   *
+   * Manifest V2 uses CSP_ALLOW_ANY.
+   * In Manifest V3, extension_pages would use CSP_ALLOW_WASM
+   * and sandbox would use CSP_ALLOW_EVAL.
+   */
+  const unsigned long CSP_ALLOW_ANY = 0xFFFF;
+  const unsigned long CSP_ALLOW_LOCALHOST = (1<<0);
+  const unsigned long CSP_ALLOW_EVAL = (1<<1);
+  const unsigned long CSP_ALLOW_REMOTE = (1<<2);
+  const unsigned long CSP_ALLOW_WASM = (1<<3);
+
+  /**
+   * Checks a custom content security policy string, to ensure that it meets
+   * minimum security requirements. Returns null for valid policies, or a
+   * string describing the error for invalid policies.
+   */
+  AString validateAddonCSP(in AString aPolicyString, in unsigned long aPermittedPolicy);
+};
diff --git a/caps/nsIDomainPolicy.idl b/caps/nsIDomainPolicy.idl
new file mode 100644
index 0000000000..74d7f3b656
--- /dev/null
+++ b/caps/nsIDomainPolicy.idl
@@ -0,0 +1,76 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+interface nsIURI;
+interface nsIDomainSet;
+
+%{ C++
+namespace mozilla {
+namespace dom {
+class DomainPolicyClone;
+}
+}
+%}
+
+[ptr] native DomainPolicyClonePtr(mozilla::dom::DomainPolicyClone);
+[ptr] native DomainPolicyCloneConstPtr(const mozilla::dom::DomainPolicyClone);
+
+/*
+ * When a domain policy is instantiated by invoking activateDomainPolicy() on
+ * nsIScriptSecurityManager, these domain sets are consulted when each new
+ * global is created (they have no effect on already-created globals).
+ * If javascript is globally enabled with |javascript.enabled|, the blocklists
+ * are consulted. If globally disabled, the allowlists are consulted. Lookups
+ * on blocklist and allowlist happen with contains(), and lookups on
+ * superBlocklist and superAllowlist happen with containsSuperDomain().
+ *
+ * When deactivate() is invoked, the domain sets are emptied, and the
+ * nsIDomainPolicy ceases to have any effect on the system.
+ */
+[scriptable, builtinclass, uuid(82b24a20-6701-4d40-a0f9-f5dc7321b555)]
+interface nsIDomainPolicy : nsISupports
+{
+    readonly attribute nsIDomainSet blocklist;
+    readonly attribute nsIDomainSet superBlocklist;
+    readonly attribute nsIDomainSet allowlist;
+    readonly attribute nsIDomainSet superAllowlist;
+
+    void deactivate();
+
+    [noscript, notxpcom] void cloneDomainPolicy(in DomainPolicyClonePtr aClone);
+    [noscript, notxpcom] void applyClone(in DomainPolicyCloneConstPtr aClone);
+};
+
+[scriptable, builtinclass, uuid(665c981b-0a0f-4229-ac06-a826e02d4f69)]
+interface nsIDomainSet : nsISupports
+{
+    /*
+     * Add a domain to the set. No-op if it already exists.
+     */
+    void add(in nsIURI aDomain);
+
+    /*
+     * Remove a domain from the set. No-op if it doesn't exist.
+     */
+    void remove(in nsIURI aDomain);
+
+    /*
+     * Remove all entries from the set.
+     */
+    void clear();
+
+    /*
+     * Returns true if a given domain is in the set.
+     */
+    bool contains(in nsIURI aDomain);
+
+    /*
+     * Returns true if a given domain is a subdomain of one of the entries in
+     * the set.
+     */
+    bool containsSuperDomain(in nsIURI aDomain);
+};
diff --git a/caps/nsIPrincipal.idl b/caps/nsIPrincipal.idl
new file mode 100644
index 0000000000..09d16e1bad
--- /dev/null
+++ b/caps/nsIPrincipal.idl
@@ -0,0 +1,767 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* Defines the abstract interface for a principal. */
+
+#include "nsIContentSecurityPolicy.idl"
+#include "nsISerializable.idl"
+#include "nsIAboutModule.idl"
+#include "nsIReferrerInfo.idl"
+interface nsIChannel;
+#include "mozIDOMWindow.idl"
+
+%{C++
+struct JSPrincipals;
+#include "nsCOMPtr.h"
+#include "nsTArray.h"
+#include "nsString.h"
+#include "mozilla/DebugOnly.h"
+namespace mozilla {
+class OriginAttributes;
+}
+
+/**
+ * Some methods have a fast path for the case when we're comparing a principal
+ * to itself. The situation may happen for example with about:blank documents.
+ */
+
+#define DECL_FAST_INLINE_HELPER(method_)                       \
+  inline bool method_(nsIPrincipal* aOther)                    \
+  {                                                            \
+    mozilla::DebugOnly<bool> val = false;                      \
+    MOZ_ASSERT_IF(this == aOther,                              \
+                  NS_SUCCEEDED(method_(aOther, &val)) && val); \
+                                                               \
+    bool retVal = false;                                       \
+    return                                                     \
+      this == aOther ||                                        \
+      (NS_SUCCEEDED(method_(aOther, &retVal)) && retVal);      \
+  }
+
+%}
+
+interface nsIURI;
+
+webidl WebExtensionPolicy;
+
+[ptr] native JSContext(JSContext);
+[ptr] native JSPrincipals(JSPrincipals);
+[ref] native PrincipalArray(const nsTArray<nsCOMPtr<nsIPrincipal>>);
+[ref] native const_OriginAttributes(const mozilla::OriginAttributes);
+native ReferrerPolicy(mozilla::dom::ReferrerPolicy);
+
+[scriptable, builtinclass, uuid(f75f502d-79fd-48be-a079-e5a7b8f80c8b)]
+interface nsIPrincipal : nsISupports
+{
+    /**
+     * Returns whether the other principal is equivalent to this principal.
+     * Principals are considered equal if they are the same principal, or
+     * they have the same origin.
+     *
+     * May be called from any thread.
+     */
+    boolean equals(in nsIPrincipal other);
+
+    /**
+     * Returns whether the other principal is equivalent to this principal
+     * for permission purposes
+     * Matches {originAttributes ,equalsURIForPermission}
+     *
+     * May be called from any thread.
+     */
+
+    boolean equalsForPermission(in nsIPrincipal other, in bool aExactHost);
+
+    /**
+     * Like equals, but takes document.domain changes into account.
+     *
+     * May be called from any thread, though document.domain may racily change
+     * during the comparison when called from off-main-thread.
+     */
+    boolean equalsConsideringDomain(in nsIPrincipal other);
+
+    %{C++
+      DECL_FAST_INLINE_HELPER(Equals)
+      DECL_FAST_INLINE_HELPER(EqualsConsideringDomain)
+    %}
+
+    /*
+     * Returns whether the Principals URI is equal to the other URI
+     *
+     * May be called from any thread.
+     */
+    boolean equalsURI(in nsIURI aOtherURI);
+
+    /**
+     * Returns a hash value for the principal.
+     *
+     * May be called from any thread.
+     */
+    [notxpcom, nostdcall] readonly attribute unsigned long hashValue;
+
+    /**
+     * The principal URI to which this principal pertains.  This is
+     * generally the document URI.
+     *
+     * May be called from any thread.
+     */
+    [infallible] readonly attribute nsIURI URI;
+
+    /**
+     * The domain URI to which this principal pertains.
+     * This is null unless script successfully sets document.domain to our URI
+     * or a superdomain of our URI.
+     * Setting this has no effect on the URI.
+     * See https://developer.mozilla.org/en-US/docs/Web/Security/Same-origin_policy#Changing_origin
+     *
+     * The getter may be called from any thread, but may only be set on the main thread.
+     */
+    [noscript] attribute nsIURI domain;
+
+    /**
+     * Returns whether the other principal is equal to or weaker than this
+     * principal. Principals are equal if they are the same object or they
+     * have the same origin.
+     *
+     * Thus a principal always subsumes itself.
+     *
+     * The system principal subsumes itself and all other principals.
+     *
+     * A null principal (corresponding to an unknown, hence assumed minimally
+     * privileged, security context) is not equal to any other principal
+     * (including other null principals), and therefore does not subsume
+     * anything but itself.
+     *
+     * May be called from any thread.
+     */
+    boolean subsumes(in nsIPrincipal other);
+
+    /**
+     * Same as the previous method, subsumes(), but takes document.domain into
+     * account.
+     *
+     * May be called from any thread, though document.domain may racily change
+     * during the comparison when called from off-main-thread.
+     */
+    boolean subsumesConsideringDomain(in nsIPrincipal other);
+
+    /**
+     * Same as the subsumesConsideringDomain(), but ignores the first party
+     * domain in its originAttributes.
+     *
+     * May be called from any thread, though document.domain may racily change
+     * during the comparison when called from off-main-thread.
+     */
+    boolean subsumesConsideringDomainIgnoringFPD(in nsIPrincipal other);
+
+    %{C++
+      DECL_FAST_INLINE_HELPER(Subsumes)
+      DECL_FAST_INLINE_HELPER(SubsumesConsideringDomain)
+      DECL_FAST_INLINE_HELPER(SubsumesConsideringDomainIgnoringFPD)
+#undef DECL_FAST_INLINE_HELPER
+    %}
+
+    /**
+     * Checks whether this principal is allowed to load the network resource
+     * located at the given URI under the same-origin policy. This means that
+     * content principals are only allowed to load resources from the same
+     * domain, the system principal is allowed to load anything, and null
+     * principals can only load URIs where they are the principal. This is
+     * changed by the optional flag allowIfInheritsPrincipal (which defaults to
+     * false) which allows URIs that inherit their loader's principal.
+     *
+     * If the load is allowed this function does nothing. If the load is not
+     * allowed the function throws NS_ERROR_DOM_BAD_URI.
+     *
+     * NOTE: Other policies might override this, such as the Access-Control
+     *       specification.
+     * NOTE: The 'domain' attribute has no effect on the behaviour of this
+     *       function.
+     * NOTE: Main-Thread Only.
+     *
+     *
+     * @param uri    The URI about to be loaded.
+     * @param allowIfInheritsPrincipal   If true, the load is allowed if the
+     *                                   loadee inherits the principal of the
+     *                                   loader.
+     * @throws NS_ERROR_DOM_BAD_URI if the load is not allowed.
+     */
+    void checkMayLoad(in nsIURI uri,
+                      in boolean allowIfInheritsPrincipal);
+
+    /**
+     * Like checkMayLoad, but if returning an error will also report that error
+     * to the console, using the provided window id.  The window id may be 0 to
+     * report to just the browser console, not web consoles.
+     *
+     * NOTE: Main-Thread Only.
+     */
+    void checkMayLoadWithReporting(in nsIURI uri,
+                                   in boolean allowIfInheritsPrincipal,
+                                   in unsigned long long innerWindowID);
+
+    /**
+     * Checks if the provided URI is considered third-party to the
+     * URI of the principal.
+     * Returns true if the URI is third-party.
+     *
+     * May be called from any thread.
+     *
+     * @param uri - The URI to check
+     */
+    boolean isThirdPartyURI(in nsIURI uri);
+
+    /**
+     * Checks if the provided principal is considered third-party to the
+     * URI of the Principal.
+     * Returns true if the principal is third-party.
+     *
+     * May be called from any thread.
+     *
+     * @param principal - The principal to check
+     */
+    boolean isThirdPartyPrincipal(in nsIPrincipal principal);
+
+    /**
+     * Checks if the provided channel is considered third-party to the
+     * URI of the principal.
+     * Returns true if the channel is third-party.
+     * Returns false if the Principal is a System Principal
+     *
+     * NOTE: Main-Thread Only.
+     *
+     * @param channel - The Channel to check
+     */
+    boolean isThirdPartyChannel(in nsIChannel channel);
+
+    /**
+     * A dictionary of the non-default origin attributes associated with this
+     * nsIPrincipal.
+     *
+     * Attributes are tokens that are taken into account when determining whether
+     * two principals are same-origin - if any attributes differ, the principals
+     * are cross-origin, even if the scheme, host, and port are the same.
+     * Attributes should also be considered for all security and bucketing decisions,
+     * even those which make non-standard comparisons (like cookies, which ignore
+     * scheme, or quotas, which ignore subdomains).
+     *
+     * If you're looking for an easy-to-use canonical stringification of the origin
+     * attributes, see |originSuffix| below.
+     */
+    [implicit_jscontext]
+    readonly attribute jsval originAttributes;
+
+    // May be called from any thread.
+    [noscript, notxpcom, nostdcall, binaryname(OriginAttributesRef)]
+    const_OriginAttributes OriginAttributesRef();
+
+    /**
+     * A canonical representation of the origin for this principal. This
+     * consists of a base string (which, for content principals, is of the
+     * format scheme://host:port), concatenated with |originAttributes| (see
+     * below).
+     *
+     * We maintain the invariant that principalA.equals(principalB) if and only
+     * if principalA.origin == principalB.origin.
+     *
+     * May be called from any thread.
+     */
+    readonly attribute ACString origin;
+
+    /**
+     * Returns an ASCII compatible representation
+     * of the principals Origin
+     *
+     * May be called from any thread.
+     */
+    [noscript] readonly attribute ACString asciiOrigin;
+
+    /**
+     * Returns the "host:port" portion of the
+     * Principals URI, if any.
+     *
+     * May be called from any thread.
+     */
+    readonly attribute ACString hostPort;
+
+    /**
+     * Returns the "host:port" portion of the
+     * Principals URI, if any.
+     *
+     * May be called from any thread.
+     */
+    readonly attribute ACString asciiHost;
+
+    /**
+     * Returns the "host" portion of the
+     * Principals URI, if any.
+     *
+     * May be called from any thread.
+     */
+    readonly attribute ACString host;
+
+    /**
+     * Returns the prePath of the principals uri
+     * follows the format scheme:
+     * "scheme://username:password@hostname:portnumber/"
+     *
+     * May be called from any thread.
+     */
+    readonly attribute ACString prePath;
+
+    /**
+     * Returns the filePath of the principals uri. See nsIURI.
+     *
+     * May be called from any thread.
+     */
+    readonly attribute ACString filePath;
+
+    /**
+     * Returns the ASCII Spec from the Principals URI.
+     * Might return the empty string, e.g. for the case of
+     * a SystemPrincipal or an EpxandedPrincipal.
+     *
+     * May be called from any thread.
+     *
+     * WARNING: DO NOT USE FOR SECURITY CHECKS.
+     * just for logging purposes!
+     */
+    readonly attribute ACString asciiSpec;
+
+    /**
+     * Returns the Spec from the Principals URI.
+     * Might return the empty string, e.g. for the case of
+     * a SystemPrincipal or an EpxandedPrincipal.
+     *
+     * May be called from any thread.
+     *
+     * WARNING: Do not land new Code using, as this will be removed soon
+     */
+    readonly attribute ACString spec;
+
+    /**
+     * Returns the Pre Path of the Principals URI with
+     * user:pass stripped for privacy and spoof prevention
+     *
+     * May be called from any thread.
+     */
+    readonly attribute ACString exposablePrePath;
+
+    /**
+     * Returns the Spec of the Principals URI with
+     * user/pass/ref/query stripped for privacy and spoof prevention
+     *
+     * May be called from any thread.
+     */
+    readonly attribute ACString exposableSpec;
+
+    /**
+     * Return the scheme of the principals URI
+     *
+     * May be called from any thread.
+     */
+    readonly attribute ACString scheme;
+
+    /**
+     * Checks if the Principal's URI Scheme matches with the parameter
+     *
+     * May be called from any thread.
+     *
+     * @param scheme    The scheme to be checked
+     */
+    [infallible]
+    boolean schemeIs(in string scheme);
+
+    /*
+     * Checks if the Principal's URI is contained in the given Pref
+     *
+     * NOTE: Main-Thread Only.
+     *
+     * @param pref    The pref to be checked
+     */
+    [infallible]
+    boolean isURIInPrefList(in string pref);
+
+    /**
+     * Check if the Principal's URI is contained in the given list
+     *
+     * May be called from any thread.
+     *
+     * @param list The list to be checked
+     */
+    [infallible]
+    boolean isURIInList(in ACString list);
+
+    /**
+     * Check if the Principal's URI is a content-accessible about: page
+     *
+     * May be called from any thread.
+     */
+    [infallible]
+    boolean isContentAccessibleAboutURI();
+
+    /**
+     * Uses NS_Security Compare to determine if the
+     * other URI is same-origin as the uri of the Principal
+     *
+     * May be called from any thread.
+     */
+    [infallible]
+    boolean isSameOrigin(in nsIURI otherURI);
+
+    /*
+     * Checks if the Principal is allowed to load the Provided file:// URI
+     * using NS_RelaxStrictFileOriginPolicy
+     *
+     * May be called from any thread.
+     */
+    bool allowsRelaxStrictFileOriginPolicy(in nsIURI aURI);
+
+
+    /*
+     * Generates a Cache-Key for the Cors-Preflight Cache
+     *
+     * May be called from any thread.
+     */
+    [noscript]
+    ACString getPrefLightCacheKey(in nsIURI aURI ,in bool aWithCredentials,
+                                  in const_OriginAttributes aOriginAttributes);
+
+
+    /*
+     * Checks if the Principals URI has first party storage access
+     * when loaded inside the provided 3rd party resource window.
+     * See also: ContentBlocking::ShouldAllowAccessFor
+     *
+     * NOTE: Main-Thread Only.
+     */
+    bool hasFirstpartyStorageAccess(in mozIDOMWindow aWindow, out uint32_t rejectedReason);
+
+
+    /*
+     * Returns a Key for the LocalStorage Manager, used to
+     * check the Principals Origin Storage usage.
+     *
+     * May be called from any thread.
+     */
+    readonly attribute ACString localStorageQuotaKey;
+
+    /**
+     * Implementation of
+     * https://w3c.github.io/webappsec-secure-contexts/#is-origin-trustworthy
+     *
+     * The value returned by this method feeds into the the Secure Context
+     * algorithm that determins the value of Window.isSecureContext and
+     * WorkerGlobalScope.isSecureContext.
+     *
+     * This method returns false instead of throwing upon errors.
+     *
+     * NOTE: Main-Thread Only.
+     */
+    [infallible]
+    readonly attribute boolean isOriginPotentiallyTrustworthy;
+
+    /**
+     * NOTE: Main-Thread Only.
+     */
+    [infallible]
+    readonly attribute boolean isLoopbackHost;
+
+    /**
+     * Returns the Flags of the Principals
+     * associated AboutModule, in case there is one.
+     *
+     * NOTE: Main-Thread Only.
+     */
+    uint32_t getAboutModuleFlags();
+
+    /**
+     * Returns the Key to access the Principals
+     * Origin Local/Session Storage
+     *
+     * May be called from any thread.
+     */
+    readonly attribute ACString storageOriginKey;
+
+    /**
+     * Creates and Returns a new ReferrerInfo with the
+     * Principals URI
+     *
+     * May be called from any thread.
+     */
+    nsIReferrerInfo createReferrerInfo(in ReferrerPolicy aReferrerPolicy);
+
+    /**
+     * The base part of |origin| without the concatenation with |originSuffix|.
+     * This doesn't have the important invariants described above with |origin|,
+     * and as such should only be used for legacy situations.
+     *
+     * May be called from any thread.
+     */
+    readonly attribute ACString originNoSuffix;
+
+    /**
+     * A string of the form ^key1=value1&key2=value2, where each pair represents
+     * an attribute with a non-default value. If all attributes have default
+     * values, this is the empty string.
+     *
+     * The value of .originSuffix is automatically serialized into .origin, so any
+     * consumers using that are automatically origin-attribute-aware. Consumers with
+     * special requirements must inspect and compare .originSuffix manually.
+     *
+     * May be called from any thread.
+     */
+    readonly attribute AUTF8String originSuffix;
+
+    /**
+     * A canonical representation of the site-origin for this principal.
+     * This string has the same format as |origin| (see above). Two principals
+     * with differing |siteOrigin| values will never compare equal, even when
+     * considering domain mutations.
+     *
+     * For most principals, |siteOrigin| matches |origin| precisely. Only
+     * principals which allow mutating |domain|, such as ContentPrincipal,
+     * override the default implementation in BasePrincipal.
+     *
+     * May be called from any thread.
+     */
+    readonly attribute ACString siteOrigin;
+
+    /**
+     * The base part of |siteOrigin| without the concatenation with
+     * |originSuffix|.
+     *
+     * May be called from any thread.
+     */
+    readonly attribute ACString siteOriginNoSuffix;
+
+    /**
+     * The base domain of the principal URI to which this principal pertains
+     * (generally the document URI), handling null principals and
+     * non-hierarchical schemes correctly.
+     *
+     * May be called from any thread.
+     */
+    readonly attribute ACString baseDomain;
+
+    /**
+     * Gets the ID of the add-on this principal belongs to.
+     *
+     * May be called from any thread.
+     */
+    readonly attribute AString addonId;
+
+    /**
+     * Gets the WebExtensionPolicy of the add-on this principal belongs to.
+     *
+     * NOTE: Main-Thread Only.
+     */
+    readonly attribute WebExtensionPolicy addonPolicy;
+    readonly attribute WebExtensionPolicy contentScriptAddonPolicy;
+
+    /**
+     * Gets the id of the user context this principal is inside.  If this
+     * principal is inside the default userContext, this returns
+     * nsIScriptSecurityManager::DEFAULT_USER_CONTEXT_ID.
+     *
+     * May be called from any thread.
+     */
+    [infallible] readonly attribute unsigned long userContextId;
+
+    /**
+     * Gets the id of the private browsing state of the context containing
+     * this principal. If the principal has a private browsing value of 0, it
+     * is not in private browsing.
+     *
+     * May be called from any thread.
+     */
+    [infallible] readonly attribute unsigned long privateBrowsingId;
+
+    /**
+     * Returns true iff the principal is inside an isolated mozbrowser element.
+     * <xul:browser> is not considered to be a mozbrowser element.
+     * <iframe mozbrowser noisolation> does not count as isolated since
+     * isolation is disabled.  Isolation can only be disabled if the
+     * containing document is chrome.
+     *
+     * May be called from any thread.
+     */
+    [infallible] readonly attribute boolean isInIsolatedMozBrowserElement;
+
+    /**
+     * Returns true iff this is a null principal (corresponding to an
+     * unknown, hence assumed minimally privileged, security context).
+     *
+     * May be called from any thread.
+     */
+    [infallible] readonly attribute boolean isNullPrincipal;
+
+    /**
+     * Returns true iff this principal corresponds to a principal origin.
+     *
+     * May be called from any thread.
+     */
+    [infallible] readonly attribute boolean isContentPrincipal;
+
+    /**
+     * Returns true iff this is an expanded principal.
+     *
+     * May be called from any thread.
+     */
+    [infallible] readonly attribute boolean isExpandedPrincipal;
+
+    /**
+     * Returns true iff this is the system principal.  C++ callers should use
+     * IsSystemPrincipal() instead of this scriptable accessor.
+     *
+     * May be called from any thread.
+     */
+    readonly attribute boolean isSystemPrincipal;
+
+    /**
+     * Faster and nicer version callable from C++.  Callers must include
+     * BasePrincipal.h, where it's implemented.
+     *
+     * May be called from any thread.
+     */
+    %{C++
+      inline bool IsSystemPrincipal() const;
+    %}
+
+    /**
+     * Returns true iff the principal is either an addon principal or
+     * an expanded principal, which contains at least one addon principal.
+     *
+     * May be called from any thread.
+     */
+    [infallible] readonly attribute boolean isAddonOrExpandedAddonPrincipal;
+
+    %{C++
+    // MOZ_DBG support (threadsafe)
+    friend std::ostream& operator<<(std::ostream& aOut, const nsIPrincipal& aPrincipal) {
+      nsIPrincipal* principal = const_cast<nsIPrincipal*>(&aPrincipal);
+      nsAutoCString origin;
+      mozilla::DebugOnly<nsresult> rv = principal->GetOrigin(origin);
+      MOZ_ASSERT(NS_SUCCEEDED(rv));
+      return aOut << "nsIPrincipal { " << origin << " }";
+    }
+    %}
+
+    /**
+     * Returns true if the URI is an Onion URI.
+     *
+     * May be called from any thread.
+     */
+    [infallible] readonly attribute boolean isOnion;
+
+    /**
+     * Returns true if the Domain Policy allows js execution
+     * for the Principal's URI
+     *
+     * NOTE: Main-Thread Only.
+     */
+    readonly attribute boolean isScriptAllowedByPolicy;
+
+
+    /**
+     * Returns true if the Principal can acess l10n
+     * features for the Provided DocumentURI
+     *
+     * NOTE: Main-Thread Only.
+     */
+    boolean isL10nAllowed(in nsIURI aDocumentURI);
+
+    /**
+     * Returns a nsIPrincipal, with one less Subdomain Segment
+     * Returns `nullptr` if there are no more segments to remove.
+     *
+     * May be called from any thread.
+     */
+    [infallible] readonly attribute nsIPrincipal nextSubDomainPrincipal;
+
+    /**
+     * Returns if the principal is for an IP address.
+     *
+     * May be called from any thread.
+     */
+    [infallible] readonly attribute boolean isIpAddress;
+
+    /**
+     * Returns if the principal is for a local IP address.
+     *
+     * May be called from any thread.
+     */
+    [infallible] readonly attribute boolean isLocalIpAddress;
+
+    /**
+     * If this principal is a null principal, reconstruct the precursor
+     * principal which this null principal was derived from. This may be null,
+     * in which case this is not a null principal, there is no known precursor
+     * to this null principal, it was created by a privileged context, or there
+     * was a bugged origin in the precursor string.
+     *
+     * May be called from any thread.
+     *
+     * WARNING: Be careful when using this principal, as it is not part of the
+     * security properties of the null principal, and should NOT be used to
+     * grant a resource with a null principal access to resources from its
+     * precursor origin. This is only to be used for places where tracking how
+     * null principals were created is necessary.
+     */
+    [infallible] readonly attribute nsIPrincipal precursorPrincipal;
+};
+
+/**
+ * If SystemPrincipal is too risky to use, but we want a principal to access
+ * more than one origin, ExpandedPrincipals letting us define an array of
+ * principals it subsumes. So script with an ExpandedPrincipals will gain
+ * same origin access when at least one of its principals it contains gained
+ * sameorigin acccess. An ExpandedPrincipal will be subsumed by the system
+ * principal, and by another ExpandedPrincipal that has all its principals.
+ * It is added for jetpack content-scripts to let them interact with the
+ * content and a well defined set of other domains, without the risk of
+ * leaking out a system principal to the content. See: Bug 734891
+ */
+[uuid(f3e177Df-6a5e-489f-80a7-2dd1481471d8)]
+interface nsIExpandedPrincipal : nsISupports
+{
+  /**
+   * An array of principals that the expanded principal subsumes.
+   *
+   * When an expanded principal is used as a triggering principal for a
+   * request that inherits a security context, one of its constitutent
+   * principals is inherited rather than the expanded principal itself. The
+   * last principal in the allowlist is the default principal to inherit.
+   *
+   * Note: this list is not reference counted, it is shared, so
+   * should not be changed and should only be used ephemerally.
+   *
+   * May be called from any thread.
+   */
+  [noscript, notxpcom, nostdcall]
+  PrincipalArray AllowList();
+
+
+  /**
+   * Bug 1548468: Move CSP off ExpandedPrincipal.
+   *
+   * A Content Security Policy associated with this principal. Use this function
+   * to query the associated CSP with this principal.
+   *
+   * NOTE: Main-Thread Only.
+   */
+  readonly attribute nsIContentSecurityPolicy csp;
+
+%{ C++
+  inline already_AddRefed<nsIContentSecurityPolicy> GetCsp()
+  {
+    nsCOMPtr<nsIContentSecurityPolicy> result;
+    mozilla::DebugOnly<nsresult> rv = GetCsp(getter_AddRefs(result));
+    MOZ_ASSERT(NS_SUCCEEDED(rv));
+    return result.forget();
+  }
+%}
+
+};
diff --git a/caps/nsIScriptSecurityManager.idl b/caps/nsIScriptSecurityManager.idl
new file mode 100644
index 0000000000..e0497db336
--- /dev/null
+++ b/caps/nsIScriptSecurityManager.idl
@@ -0,0 +1,335 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+#include "nsIPrincipal.idl"
+interface nsIURI;
+interface nsIChannel;
+interface nsIClassInfo;
+interface nsIDocShell;
+interface nsIDomainPolicy;
+interface nsILoadContext;
+
+%{ C++
+#include "jspubtd.h"
+
+namespace mozilla {
+namespace dom {
+class DomainPolicyClone;
+}
+}
+%}
+
+[ptr] native JSContextPtr(JSContext);
+[ptr] native JSObjectPtr(JSObject);
+[ptr] native DomainPolicyClonePtr(mozilla::dom::DomainPolicyClone);
+
+[scriptable, builtinclass, uuid(51daad87-3a0c-44cc-b620-7356801c9022)]
+interface nsIScriptSecurityManager : nsISupports
+{
+    /**
+     * For each of these hooks returning NS_OK means 'let the action continue'.
+     * Returning an error code means 'veto the action'. XPConnect will return
+     * false to the js engine if the action is vetoed. The implementor of this
+     * interface is responsible for setting a JS exception into the JSContext
+     * if that is appropriate.
+     */
+    [noscript] void canCreateWrapper(in JSContextPtr aJSContext,
+                                     in nsIIDRef aIID,
+                                     in nsISupports aObj,
+                                     in nsIClassInfo aClassInfo);
+
+    [noscript] void canCreateInstance(in JSContextPtr aJSContext,
+                                      in nsCIDRef aCID);
+
+    [noscript] void canGetService(in JSContextPtr aJSContext,
+                                  in nsCIDRef aCID);
+
+    /**
+     * Check that the script currently running in context "cx" can load "uri".
+     *
+     * Will return error code NS_ERROR_DOM_BAD_URI if the load request
+     * should be denied.
+     *
+     * @param cx the JSContext of the script causing the load
+     * @param uri the URI that is being loaded
+     */
+    [noscript] void checkLoadURIFromScript(in JSContextPtr cx, in nsIURI uri);
+
+    /**
+     * Default CheckLoadURI permissions
+     */
+    // Default permissions
+    const unsigned long STANDARD = 0;
+
+    // Indicate that the load is a load of a new document that is not
+    // user-triggered.  Here "user-triggered" could be broadly interpreted --
+    // for example, scripted sets of window.location.href might be treated as
+    // "user-triggered" in some circumstances.  A typical example of a load
+    // that is not user-triggered is a <meta> refresh load.  If this flag is
+    // set, the load will be denied if the originating principal's URI has the
+    // nsIProtocolHandler::URI_FORBIDS_AUTOMATIC_DOCUMENT_REPLACEMENT flag set.
+    const unsigned long LOAD_IS_AUTOMATIC_DOCUMENT_REPLACEMENT = 1 << 0;
+
+    // Allow the loading of chrome URLs by non-chrome URLs.  Use with great
+    // care!  This will actually allow the loading of any URI which has the
+    // nsIProtocolHandler::URI_IS_UI_RESOURCE protocol handler flag set.  Ths
+    // probably means at least chrome: and resource:.
+    const unsigned long ALLOW_CHROME = 1 << 1;
+
+    // Don't allow URLs which would inherit the caller's principal (such as
+    // javascript: or data:) to load.  See
+    // nsIProtocolHandler::URI_INHERITS_SECURITY_CONTEXT.
+    const unsigned long DISALLOW_INHERIT_PRINCIPAL = 1 << 2;
+
+    // Alias for DISALLOW_INHERIT_PRINCIPAL for backwards compat with
+    // JS-implemented extensions.
+    const unsigned long DISALLOW_SCRIPT_OR_DATA = DISALLOW_INHERIT_PRINCIPAL;
+
+    // Don't allow javascript: URLs to load
+    //   WARNING: Support for this value was added in Mozilla 1.7.8 and
+    //   Firefox 1.0.4.  Use in prior versions WILL BE IGNORED.
+    // When using this, make sure that you actually want DISALLOW_SCRIPT, not
+    // DISALLOW_INHERIT_PRINCIPAL
+    const unsigned long DISALLOW_SCRIPT = 1 << 3;
+
+    // Do not report errors if we just want to check if a principal can load
+    // a URI to not unnecessarily spam the error console.
+    const unsigned long DONT_REPORT_ERRORS = 1 << 4;
+
+    /**
+     * Check that content with principal aPrincipal can load "uri".
+     *
+     * Will return error code NS_ERROR_DOM_BAD_URI if the load request
+     * should be denied.
+     *
+     * @param aPrincipal the principal identifying the actor causing the load
+     * @param uri the URI that is being loaded
+     * @param flags the permission set, see above
+     * @param innerWindowID the window ID for error reporting.  If this is 0
+     *        (which happens automatically if it's not passed from JS), errors
+     *        will only appear in the browser console, not window-associated
+     *        consoles like the web console.
+     */
+    [binaryname(CheckLoadURIWithPrincipal)]
+    void checkLoadURIWithPrincipalXPCOM(in nsIPrincipal aPrincipal,
+                                        in nsIURI uri,
+                                        in unsigned long flags,
+                                        [optional] in unsigned long long innerWindowID);
+
+    /**
+     * Same as the above, but when called from JS, raises exceptions with more
+     * useful messages, including both the tested URI and the principal string.
+     */
+    [implicit_jscontext, binaryname(CheckLoadURIWithPrincipalFromJS)]
+    void checkLoadURIWithPrincipal(in nsIPrincipal aPrincipal,
+                                   in nsIURI uri,
+                                   [optional] in unsigned long flags,
+                                   [optional] in unsigned long long innerWindowID);
+
+    /**
+     * Similar to checkLoadURIWithPrincipal but there are two differences:
+     *
+     * 1) The URI is a string, not a URI object.
+     * 2) This function assumes that the URI may still be subject to fixup (and
+     * hence will check whether fixed-up versions of the URI are allowed to
+     * load as well); if any of the versions of this URI is not allowed, this
+     * function will return error code NS_ERROR_DOM_BAD_URI.
+     */
+    [binaryname(CheckLoadURIStrWithPrincipal)]
+    void checkLoadURIStrWithPrincipalXPCOM(in nsIPrincipal aPrincipal,
+                                           in AUTF8String uri,
+                                           in unsigned long flags);
+
+    /**
+     * Same as the above, but when called from JS, raises exceptions with more
+     * useful messages, including both the tested URI and the principal string.
+     */
+    [implicit_jscontext, binaryname(CheckLoadURIStrWithPrincipalFromJS)]
+    void checkLoadURIStrWithPrincipal(in nsIPrincipal aPrincipal,
+                                      in AUTF8String uri,
+                                      [optional] in unsigned long flags);
+
+    /**
+     * Returns true if the URI is from a domain that is allow-listed through
+     * prefs to be allowed to use file:// URIs.
+     * @param aUri the URI to be tested
+     */
+    bool inFileURIAllowlist(in nsIURI aUri);
+
+    ///////////////// Principals ///////////////////////
+
+    /**
+     * Return the all-powerful system principal.
+     */
+    nsIPrincipal getSystemPrincipal();
+
+    /**
+     * Returns a principal that has the OriginAttributes of the load context.
+     * @param loadContext to get the OriginAttributes from.
+     */
+    nsIPrincipal getLoadContextContentPrincipal(in nsIURI uri,
+                                                 in nsILoadContext loadContext);
+
+    /**
+     * Returns a principal that has the OriginAttributes of the docshell.
+     * @param docShell to get the OriginAttributes from.
+     */
+    nsIPrincipal getDocShellContentPrincipal(in nsIURI uri,
+                                              in nsIDocShell docShell);
+
+    /**
+     * If this is a content principal, return a copy with different
+     * origin attributes.
+     */
+    [implicit_jscontext]
+    nsIPrincipal principalWithOA(in nsIPrincipal principal,
+                                 in jsval originAttributes);
+
+    /**
+     * Returns a principal whose origin is composed of |uri| and |originAttributes|.
+     * See nsIPrincipal.idl for a description of origin attributes, and
+     * ChromeUtils.webidl for a list of origin attributes and their defaults.
+     */
+    [implicit_jscontext]
+    nsIPrincipal createContentPrincipal(in nsIURI uri, in jsval originAttributes);
+
+    /**
+     * Returns a principal whose origin is the one we pass in.
+     * See nsIPrincipal.idl for a description of origin attributes, and
+     * ChromeUtils.webidl for a list of origin attributes and their defaults.
+     */
+    nsIPrincipal createContentPrincipalFromOrigin(in ACString origin);
+
+    /**
+     * Takes a principal and returns a string representation of it or a nullptr if it can't be serialized.
+     * Example output: `{"1": {"0": "https://mozilla.com", "2": "^privateBrowsingId=1"}}`
+     */
+    ACString principalToJSON(in nsIPrincipal principal);
+
+    /**
+     * Takes a string of the following format:
+     * `{"1": {"0": "https://mozilla.com", "2": "^privateBrowsingId=1"}}`
+     * and turns it into a principal or a nullptr on error.
+     */
+    nsIPrincipal JSONToPrincipal(in ACString json);
+
+    /**
+     * Returns a unique nonce principal with |originAttributes|.
+     * See nsIPrincipal.idl for a description of origin attributes, and
+     * ChromeUtils.webidl for a list of origin attributes and their defaults.
+     */
+    [implicit_jscontext]
+    nsIPrincipal createNullPrincipal(in jsval originAttributes);
+
+    /**
+     * Returns OK if aSourceURI and target have the same "origin"
+     * (scheme, host, and port).
+     * ReportError flag suppresses error reports for functions that
+     * don't need reporting.
+     * FromPrivateWindow indicates whether the error occurs in a private
+     * window or not.
+     */
+    void checkSameOriginURI(in nsIURI aSourceURI,
+                            in nsIURI aTargetURI,
+                            in boolean reportError,
+                            in boolean fromPrivateWindow);
+
+    /**
+     * Get the principal for the given channel.  This will typically be the
+     * channel owner if there is one, and the content principal for the
+     * channel's URI otherwise.  aChannel must not be null.
+     */
+    nsIPrincipal getChannelResultPrincipal(in nsIChannel aChannel);
+
+    /**
+     * Get the storage principal for the given channel.  This is basically the
+     * same of getChannelResultPrincipal() execept for trackers, where we
+     * return a principal with a different OriginAttributes.
+     */
+    nsIPrincipal getChannelResultStoragePrincipal(in nsIChannel aChannel);
+
+    /**
+     * This method returns 2 principals from a nsIChannel:
+     * - aPrincipal is the regular principal.
+     * - aPartitionedPrincipal is aPrincipal plus an isolation key in its
+     *   originAttributes.
+     * See more in StoragePrincipalHelper.h
+     */
+    void getChannelResultPrincipals(in nsIChannel aChannel,
+                                    out nsIPrincipal aPrincipal,
+                                    out nsIPrincipal aPartitionedPrincipal);
+
+    /**
+     * Temporary API until bug 1220687 is fixed.
+     *
+     * Returns the same value as getChannelResultPrincipal, but ignoring
+     * sandboxing.  Specifically, if sandboxing would have prevented the
+     * channel's triggering principal from being returned by
+     * getChannelResultPrincipal, the triggering principal will be returned
+     * by this method.
+     *
+     * Note that this method only ignores sandboxing of the channel in
+     * question, it does not ignore sandboxing of any channels further up a
+     * document chain.  The triggering principal itself may still be the null
+     * principal due to sandboxing further up a document chain.  In that regard
+     * the ignoring of sandboxing is limited.
+     */
+    [noscript, nostdcall]
+    nsIPrincipal getChannelResultPrincipalIfNotSandboxed(in nsIChannel aChannel);
+
+    /**
+     * Get the content principal for the channel's URI.
+     * aChannel must not be null.
+     */
+    nsIPrincipal getChannelURIPrincipal(in nsIChannel aChannel);
+
+    const unsigned long DEFAULT_USER_CONTEXT_ID = 0;
+
+    const unsigned long DEFAULT_PRIVATE_BROWSING_ID = 0;
+
+    /**
+     * Per-domain controls to enable and disable script. This system is designed
+     * to be used by at most one consumer, and enforces this with its semantics.
+     *
+     * Initially, domainPolicyActive is false. When activateDomainPolicy() is
+     * invoked, domainPolicyActive becomes true, and subsequent calls to
+     * activateDomainPolicy() will fail until deactivate() is invoked on the
+     * nsIDomainPolicy returned from activateDomainPolicy(). At this point,
+     * domainPolicyActive becomes false again, and a new consumer may acquire
+     * control of the system by invoking activateDomainPolicy().
+     */
+    nsIDomainPolicy activateDomainPolicy();
+    readonly attribute boolean domainPolicyActive;
+
+    /**
+     * Only the parent process can directly access domain policies, child
+     * processes only have a read-only mirror to the one in the parent.
+     * For child processes the mirror is updated via messages
+     * and ContentChild will hold the DomainPolicy by calling
+     * ActivateDomainPolicyInternal directly. New consumer to this
+     * function should not be addded.
+     */
+    [noscript] nsIDomainPolicy activateDomainPolicyInternal();
+
+    /**
+     * This function is for internal use only. Every time a child process is spawned, we
+     * must clone any active domain policies in the parent to the new child.
+     */
+    [noscript, notxpcom] void cloneDomainPolicy(in DomainPolicyClonePtr aClone);
+
+    /**
+     * Query mechanism for the above policy.
+     *
+     * If domainPolicyEnabled is false, this simply returns the current value
+     * of javascript.enabled. Otherwise, it returns the same value, but taking
+     * the various blocklist/allowlist exceptions into account.
+     */
+    bool policyAllowsScript(in nsIURI aDomain);
+};
+
+%{C++
+#define NS_SCRIPTSECURITYMANAGER_CONTRACTID "@mozilla.org/scriptsecuritymanager;1"
+%}
diff --git a/caps/nsJSPrincipals.cpp b/caps/nsJSPrincipals.cpp
new file mode 100644
index 0000000000..d089bffdf5
--- /dev/null
+++ b/caps/nsJSPrincipals.cpp
@@ -0,0 +1,369 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsIPrincipal.h"
+#include "xpcpublic.h"
+#include "nsString.h"
+#include "nsJSPrincipals.h"
+#include "nsCOMPtr.h"
+#include "nsStringBuffer.h"
+#include "mozilla/BasePrincipal.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/dom/StructuredCloneTags.h"
+#include "mozilla/ipc/BackgroundUtils.h"
+#include "mozilla/ipc/PBackgroundSharedTypes.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+using namespace mozilla::ipc;
+
+NS_IMETHODIMP_(MozExternalRefCountType)
+nsJSPrincipals::AddRef() {
+  MOZ_ASSERT(int32_t(refcount) >= 0, "illegal refcnt");
+  nsrefcnt count = ++refcount;
+  NS_LOG_ADDREF(this, count, "nsJSPrincipals", sizeof(*this));
+  return count;
+}
+
+NS_IMETHODIMP_(MozExternalRefCountType)
+nsJSPrincipals::Release() {
+  MOZ_ASSERT(0 != refcount, "dup release");
+  nsrefcnt count = --refcount;
+  NS_LOG_RELEASE(this, count, "nsJSPrincipals");
+  if (count == 0) {
+    delete this;
+  }
+
+  return count;
+}
+
+/* static */
+bool nsJSPrincipals::Subsume(JSPrincipals* jsprin, JSPrincipals* other) {
+  bool result;
+  nsresult rv = nsJSPrincipals::get(jsprin)->Subsumes(
+      nsJSPrincipals::get(other), &result);
+  return NS_SUCCEEDED(rv) && result;
+}
+
+/* static */
+void nsJSPrincipals::Destroy(JSPrincipals* jsprin) {
+  // The JS runtime can call this method during the last GC when
+  // nsScriptSecurityManager is destroyed. So we must not assume here that
+  // the security manager still exists.
+
+  nsJSPrincipals* nsjsprin = nsJSPrincipals::get(jsprin);
+
+  // We need to destroy the nsIPrincipal. We'll do this by adding
+  // to the refcount and calling release
+
+#ifdef NS_BUILD_REFCNT_LOGGING
+  // The refcount logging considers AddRef-to-1 to indicate creation,
+  // so trick it into thinking it's otherwise, but balance the
+  // Release() we do below.
+  nsjsprin->refcount++;
+  nsjsprin->AddRef();
+  nsjsprin->refcount--;
+#else
+  nsjsprin->refcount++;
+#endif
+  nsjsprin->Release();
+}
+
+#ifdef DEBUG
+
+// Defined here so one can do principals->dump() in the debugger
+JS_PUBLIC_API void JSPrincipals::dump() {
+  if (debugToken == nsJSPrincipals::DEBUG_TOKEN) {
+    nsAutoCString str;
+    nsresult rv = static_cast<nsJSPrincipals*>(this)->GetScriptLocation(str);
+    fprintf(stderr, "nsIPrincipal (%p) = %s\n", static_cast<void*>(this),
+            NS_SUCCEEDED(rv) ? str.get() : "(unknown)");
+  } else {
+    fprintf(stderr,
+            "!!! JSPrincipals (%p) is not nsJSPrincipals instance - bad token: "
+            "actual=0x%x expected=0x%x\n",
+            this, unsigned(debugToken), unsigned(nsJSPrincipals::DEBUG_TOKEN));
+  }
+}
+
+#endif
+
+/* static */
+bool nsJSPrincipals::ReadPrincipals(JSContext* aCx,
+                                    JSStructuredCloneReader* aReader,
+                                    JSPrincipals** aOutPrincipals) {
+  uint32_t tag;
+  uint32_t unused;
+  if (!JS_ReadUint32Pair(aReader, &tag, &unused)) {
+    return false;
+  }
+
+  if (tag != SCTAG_DOM_NULL_PRINCIPAL && tag != SCTAG_DOM_SYSTEM_PRINCIPAL &&
+      tag != SCTAG_DOM_CONTENT_PRINCIPAL &&
+      tag != SCTAG_DOM_EXPANDED_PRINCIPAL) {
+    xpc::Throw(aCx, NS_ERROR_DOM_DATA_CLONE_ERR);
+    return false;
+  }
+
+  return ReadKnownPrincipalType(aCx, aReader, tag, aOutPrincipals);
+}
+
+static bool ReadPrincipalInfo(JSStructuredCloneReader* aReader,
+                              OriginAttributes& aAttrs, nsACString& aSpec,
+                              nsACString& aOriginNoSuffix,
+                              nsACString& aBaseDomain) {
+  uint32_t suffixLength, specLength;
+  if (!JS_ReadUint32Pair(aReader, &suffixLength, &specLength)) {
+    return false;
+  }
+
+  nsAutoCString suffix;
+  if (!suffix.SetLength(suffixLength, fallible)) {
+    return false;
+  }
+
+  if (!JS_ReadBytes(aReader, suffix.BeginWriting(), suffixLength)) {
+    return false;
+  }
+
+  if (!aAttrs.PopulateFromSuffix(suffix)) {
+    return false;
+  }
+
+  if (!aSpec.SetLength(specLength, fallible)) {
+    return false;
+  }
+
+  if (!JS_ReadBytes(aReader, aSpec.BeginWriting(), specLength)) {
+    return false;
+  }
+
+  uint32_t originNoSuffixLength, dummy;
+  if (!JS_ReadUint32Pair(aReader, &originNoSuffixLength, &dummy)) {
+    return false;
+  }
+
+  MOZ_ASSERT(dummy == 0);
+  if (dummy != 0) {
+    return false;
+  }
+
+  if (!aOriginNoSuffix.SetLength(originNoSuffixLength, fallible)) {
+    return false;
+  }
+
+  if (!JS_ReadBytes(aReader, aOriginNoSuffix.BeginWriting(),
+                    originNoSuffixLength)) {
+    return false;
+  }
+
+  uint32_t baseDomainIsVoid, baseDomainLength;
+  if (!JS_ReadUint32Pair(aReader, &baseDomainIsVoid, &baseDomainLength)) {
+    return false;
+  }
+
+  if (baseDomainIsVoid != 0 && baseDomainIsVoid != 1) {
+    return false;
+  }
+
+  if (baseDomainIsVoid) {
+    if (baseDomainLength != 0) {
+      return false;
+    }
+
+    aBaseDomain.SetIsVoid(true);
+    return true;
+  }
+
+  if (!aBaseDomain.SetLength(baseDomainLength, fallible)) {
+    return false;
+  }
+
+  if (!JS_ReadBytes(aReader, aBaseDomain.BeginWriting(), baseDomainLength)) {
+    return false;
+  }
+
+  return true;
+}
+
+static bool ReadPrincipalInfo(JSStructuredCloneReader* aReader, uint32_t aTag,
+                              PrincipalInfo& aInfo) {
+  if (aTag == SCTAG_DOM_SYSTEM_PRINCIPAL) {
+    aInfo = SystemPrincipalInfo();
+  } else if (aTag == SCTAG_DOM_NULL_PRINCIPAL) {
+    OriginAttributes attrs;
+    nsAutoCString spec;
+    nsAutoCString originNoSuffix;
+    nsAutoCString baseDomain;
+    if (!::ReadPrincipalInfo(aReader, attrs, spec, originNoSuffix,
+                             baseDomain)) {
+      return false;
+    }
+    aInfo = NullPrincipalInfo(attrs, spec);
+  } else if (aTag == SCTAG_DOM_EXPANDED_PRINCIPAL) {
+    uint32_t length, unused;
+    if (!JS_ReadUint32Pair(aReader, &length, &unused)) {
+      return false;
+    }
+
+    ExpandedPrincipalInfo expanded;
+
+    for (uint32_t i = 0; i < length; i++) {
+      uint32_t tag;
+      if (!JS_ReadUint32Pair(aReader, &tag, &unused)) {
+        return false;
+      }
+
+      PrincipalInfo sub;
+      if (!ReadPrincipalInfo(aReader, tag, sub)) {
+        return false;
+      }
+      expanded.allowlist().AppendElement(sub);
+    }
+
+    aInfo = expanded;
+  } else if (aTag == SCTAG_DOM_CONTENT_PRINCIPAL) {
+    OriginAttributes attrs;
+    nsAutoCString spec;
+    nsAutoCString originNoSuffix;
+    nsAutoCString baseDomain;
+    if (!::ReadPrincipalInfo(aReader, attrs, spec, originNoSuffix,
+                             baseDomain)) {
+      return false;
+    }
+
+#ifdef FUZZING
+    if (originNoSuffix.IsEmpty()) {
+      return false;
+    }
+#endif
+
+    MOZ_DIAGNOSTIC_ASSERT(!originNoSuffix.IsEmpty());
+
+    // XXX: Do we care about mDomain for structured clone?
+    aInfo = ContentPrincipalInfo(attrs, originNoSuffix, spec, Nothing(),
+                                 baseDomain);
+  } else {
+#ifdef FUZZING
+    return false;
+#else
+    MOZ_CRASH("unexpected principal structured clone tag");
+#endif
+  }
+
+  return true;
+}
+
+/* static */
+bool nsJSPrincipals::ReadPrincipalInfo(JSStructuredCloneReader* aReader,
+                                       PrincipalInfo& aInfo) {
+  uint32_t tag, unused;
+  if (!JS_ReadUint32Pair(aReader, &tag, &unused)) {
+    return false;
+  }
+  return ::ReadPrincipalInfo(aReader, tag, aInfo);
+}
+
+/* static */
+bool nsJSPrincipals::ReadKnownPrincipalType(JSContext* aCx,
+                                            JSStructuredCloneReader* aReader,
+                                            uint32_t aTag,
+                                            JSPrincipals** aOutPrincipals) {
+  MOZ_ASSERT(aTag == SCTAG_DOM_NULL_PRINCIPAL ||
+             aTag == SCTAG_DOM_SYSTEM_PRINCIPAL ||
+             aTag == SCTAG_DOM_CONTENT_PRINCIPAL ||
+             aTag == SCTAG_DOM_EXPANDED_PRINCIPAL);
+
+  PrincipalInfo info;
+  if (!::ReadPrincipalInfo(aReader, aTag, info)) {
+    return false;
+  }
+
+  auto principalOrErr = PrincipalInfoToPrincipal(info);
+  if (NS_WARN_IF(principalOrErr.isErr())) {
+    xpc::Throw(aCx, NS_ERROR_DOM_DATA_CLONE_ERR);
+    return false;
+  }
+
+  nsCOMPtr<nsIPrincipal> principal = principalOrErr.unwrap();
+
+  *aOutPrincipals = get(principal.forget().take());
+  return true;
+}
+
+static bool WritePrincipalInfo(JSStructuredCloneWriter* aWriter,
+                               const OriginAttributes& aAttrs,
+                               const nsCString& aSpec,
+                               const nsCString& aOriginNoSuffix,
+                               const nsCString& aBaseDomain) {
+  nsAutoCString suffix;
+  aAttrs.CreateSuffix(suffix);
+
+  if (!(JS_WriteUint32Pair(aWriter, suffix.Length(), aSpec.Length()) &&
+        JS_WriteBytes(aWriter, suffix.get(), suffix.Length()) &&
+        JS_WriteBytes(aWriter, aSpec.get(), aSpec.Length()) &&
+        JS_WriteUint32Pair(aWriter, aOriginNoSuffix.Length(), 0) &&
+        JS_WriteBytes(aWriter, aOriginNoSuffix.get(),
+                      aOriginNoSuffix.Length()))) {
+    return false;
+  }
+
+  if (aBaseDomain.IsVoid()) {
+    return JS_WriteUint32Pair(aWriter, 1, 0);
+  }
+
+  return JS_WriteUint32Pair(aWriter, 0, aBaseDomain.Length()) &&
+         JS_WriteBytes(aWriter, aBaseDomain.get(), aBaseDomain.Length());
+}
+
+/* static */
+bool nsJSPrincipals::WritePrincipalInfo(JSStructuredCloneWriter* aWriter,
+                                        const PrincipalInfo& aInfo) {
+  if (aInfo.type() == PrincipalInfo::TNullPrincipalInfo) {
+    const NullPrincipalInfo& nullInfo = aInfo;
+    return JS_WriteUint32Pair(aWriter, SCTAG_DOM_NULL_PRINCIPAL, 0) &&
+           ::WritePrincipalInfo(aWriter, nullInfo.attrs(), nullInfo.spec(),
+                                ""_ns, ""_ns);
+  }
+  if (aInfo.type() == PrincipalInfo::TSystemPrincipalInfo) {
+    return JS_WriteUint32Pair(aWriter, SCTAG_DOM_SYSTEM_PRINCIPAL, 0);
+  }
+  if (aInfo.type() == PrincipalInfo::TExpandedPrincipalInfo) {
+    const ExpandedPrincipalInfo& expanded = aInfo;
+    if (!JS_WriteUint32Pair(aWriter, SCTAG_DOM_EXPANDED_PRINCIPAL, 0) ||
+        !JS_WriteUint32Pair(aWriter, expanded.allowlist().Length(), 0)) {
+      return false;
+    }
+
+    for (uint32_t i = 0; i < expanded.allowlist().Length(); i++) {
+      if (!WritePrincipalInfo(aWriter, expanded.allowlist()[i])) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  MOZ_ASSERT(aInfo.type() == PrincipalInfo::TContentPrincipalInfo);
+  const ContentPrincipalInfo& cInfo = aInfo;
+  return JS_WriteUint32Pair(aWriter, SCTAG_DOM_CONTENT_PRINCIPAL, 0) &&
+         ::WritePrincipalInfo(aWriter, cInfo.attrs(), cInfo.spec(),
+                              cInfo.originNoSuffix(), cInfo.baseDomain());
+}
+
+bool nsJSPrincipals::write(JSContext* aCx, JSStructuredCloneWriter* aWriter) {
+  PrincipalInfo info;
+  if (NS_WARN_IF(NS_FAILED(PrincipalToPrincipalInfo(this, &info)))) {
+    xpc::Throw(aCx, NS_ERROR_DOM_DATA_CLONE_ERR);
+    return false;
+  }
+
+  return WritePrincipalInfo(aWriter, info);
+}
+
+bool nsJSPrincipals::isSystemOrAddonPrincipal() {
+  JS::AutoSuppressGCAnalysis suppress;
+  return this->IsSystemPrincipal() ||
+         this->GetIsAddonOrExpandedAddonPrincipal();
+}
diff --git a/caps/nsJSPrincipals.h b/caps/nsJSPrincipals.h
new file mode 100644
index 0000000000..54cf5f44c0
--- /dev/null
+++ b/caps/nsJSPrincipals.h
@@ -0,0 +1,82 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+/* describes principals by their orginating uris*/
+
+#ifndef nsJSPrincipals_h__
+#define nsJSPrincipals_h__
+
+#include "js/Principals.h"
+#include "nsIPrincipal.h"
+
+struct JSContext;
+struct JSStructuredCloneReader;
+struct JSStructuredCloneWriter;
+
+namespace mozilla {
+namespace ipc {
+class PrincipalInfo;
+}  // namespace ipc
+}  // namespace mozilla
+
+class nsJSPrincipals : public nsIPrincipal, public JSPrincipals {
+ public:
+  /* SpiderMonkey security callbacks. */
+  static bool Subsume(JSPrincipals* jsprin, JSPrincipals* other);
+  static void Destroy(JSPrincipals* jsprin);
+
+  /* JSReadPrincipalsOp for nsJSPrincipals */
+  static bool ReadPrincipals(JSContext* aCx, JSStructuredCloneReader* aReader,
+                             JSPrincipals** aOutPrincipals);
+
+  static bool ReadKnownPrincipalType(JSContext* aCx,
+                                     JSStructuredCloneReader* aReader,
+                                     uint32_t aTag,
+                                     JSPrincipals** aOutPrincipals);
+
+  static bool ReadPrincipalInfo(JSStructuredCloneReader* aReader,
+                                mozilla::ipc::PrincipalInfo& aInfo);
+
+  /* For write() implementations of off-main-thread JSPrincipals. */
+  static bool WritePrincipalInfo(JSStructuredCloneWriter* aWriter,
+                                 const mozilla::ipc::PrincipalInfo& aInfo);
+
+  bool write(JSContext* aCx, JSStructuredCloneWriter* aWriter) final;
+
+  bool isSystemOrAddonPrincipal() final;
+
+  /*
+   * Get a weak reference to nsIPrincipal associated with the given JS
+   * principal, and vice-versa.
+   */
+  static nsJSPrincipals* get(JSPrincipals* principals) {
+    nsJSPrincipals* self = static_cast<nsJSPrincipals*>(principals);
+    MOZ_ASSERT_IF(self, self->debugToken == DEBUG_TOKEN);
+    return self;
+  }
+  static nsJSPrincipals* get(nsIPrincipal* principal) {
+    nsJSPrincipals* self = static_cast<nsJSPrincipals*>(principal);
+    MOZ_ASSERT_IF(self, self->debugToken == DEBUG_TOKEN);
+    return self;
+  }
+
+  NS_IMETHOD_(MozExternalRefCountType) AddRef(void) override;
+  NS_IMETHOD_(MozExternalRefCountType) Release(void) override;
+
+  nsJSPrincipals() {
+    refcount = 0;
+    setDebugToken(DEBUG_TOKEN);
+  }
+
+  /**
+   * Return a string that can be used as JS script filename in error reports.
+   */
+  virtual nsresult GetScriptLocation(nsACString& aStr) = 0;
+  static const uint32_t DEBUG_TOKEN = 0x0bf41760;
+
+ protected:
+  virtual ~nsJSPrincipals() { setDebugToken(0); }
+};
+
+#endif /* nsJSPrincipals_h__ */
diff --git a/caps/nsScriptSecurityManager.cpp b/caps/nsScriptSecurityManager.cpp
new file mode 100644
index 0000000000..532412b198
--- /dev/null
+++ b/caps/nsScriptSecurityManager.cpp
@@ -0,0 +1,1852 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsScriptSecurityManager.h"
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/StaticPrefs_extensions.h"
+#include "mozilla/StaticPrefs_security.h"
+#include "mozilla/StoragePrincipalHelper.h"
+
+#include "xpcpublic.h"
+#include "XPCWrapper.h"
+#include "nsILoadContext.h"
+#include "nsIScriptObjectPrincipal.h"
+#include "nsIScriptContext.h"
+#include "nsIScriptError.h"
+#include "nsINestedURI.h"
+#include "nspr.h"
+#include "nsJSPrincipals.h"
+#include "mozilla/BasePrincipal.h"
+#include "mozilla/ContentPrincipal.h"
+#include "ExpandedPrincipal.h"
+#include "SystemPrincipal.h"
+#include "DomainPolicy.h"
+#include "nsString.h"
+#include "nsCRT.h"
+#include "nsCRTGlue.h"
+#include "nsContentSecurityUtils.h"
+#include "nsDocShell.h"
+#include "nsError.h"
+#include "nsGlobalWindowInner.h"
+#include "nsDOMCID.h"
+#include "nsTextFormatter.h"
+#include "nsIStringBundle.h"
+#include "nsNetUtil.h"
+#include "nsIEffectiveTLDService.h"
+#include "nsDirectoryServiceDefs.h"
+#include "nsIScriptGlobalObject.h"
+#include "nsPIDOMWindow.h"
+#include "nsIDocShell.h"
+#include "nsIConsoleService.h"
+#include "nsIOService.h"
+#include "nsIContent.h"
+#include "nsDOMJSUtils.h"
+#include "nsAboutProtocolUtils.h"
+#include "nsIClassInfo.h"
+#include "nsIURIFixup.h"
+#include "nsIURIMutator.h"
+#include "nsIChromeRegistry.h"
+#include "nsIResProtocolHandler.h"
+#include "nsIContentSecurityPolicy.h"
+#include "mozilla/Components.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/dom/BindingUtils.h"
+#include "mozilla/NullPrincipal.h"
+#include <stdint.h>
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/Exceptions.h"
+#include "mozilla/dom/nsCSPContext.h"
+#include "mozilla/dom/ScriptSettings.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/ExtensionPolicyService.h"
+#include "mozilla/ResultExtensions.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/dom/WorkerCommon.h"
+#include "mozilla/dom/WorkerPrivate.h"
+#include "nsContentUtils.h"
+#include "nsJSUtils.h"
+#include "nsILoadInfo.h"
+
+// This should be probably defined on some other place... but I couldn't find it
+#define WEBAPPS_PERM_NAME "webapps-manage"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+StaticRefPtr<nsIIOService> nsScriptSecurityManager::sIOService;
+std::atomic<bool> nsScriptSecurityManager::sStrictFileOriginPolicy = true;
+
+namespace {
+
+class BundleHelper {
+ public:
+  NS_INLINE_DECL_REFCOUNTING(BundleHelper)
+
+  static nsIStringBundle* GetOrCreate() {
+    MOZ_ASSERT(!sShutdown);
+
+    // Already shutting down. Nothing should require the use of the string
+    // bundle when shutting down.
+    if (sShutdown) {
+      return nullptr;
+    }
+
+    if (!sSelf) {
+      sSelf = new BundleHelper();
+    }
+
+    return sSelf->GetOrCreateInternal();
+  }
+
+  static void Shutdown() {
+    sSelf = nullptr;
+    sShutdown = true;
+  }
+
+ private:
+  ~BundleHelper() = default;
+
+  nsIStringBundle* GetOrCreateInternal() {
+    if (!mBundle) {
+      nsCOMPtr<nsIStringBundleService> bundleService =
+          mozilla::components::StringBundle::Service();
+      if (NS_WARN_IF(!bundleService)) {
+        return nullptr;
+      }
+
+      nsresult rv = bundleService->CreateBundle(
+          "chrome://global/locale/security/caps.properties",
+          getter_AddRefs(mBundle));
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return nullptr;
+      }
+    }
+
+    return mBundle;
+  }
+
+  nsCOMPtr<nsIStringBundle> mBundle;
+
+  static StaticRefPtr<BundleHelper> sSelf;
+  static bool sShutdown;
+};
+
+StaticRefPtr<BundleHelper> BundleHelper::sSelf;
+bool BundleHelper::sShutdown = false;
+
+}  // namespace
+
+///////////////////////////
+// Convenience Functions //
+///////////////////////////
+
+class nsAutoInPrincipalDomainOriginSetter {
+ public:
+  nsAutoInPrincipalDomainOriginSetter() { ++sInPrincipalDomainOrigin; }
+  ~nsAutoInPrincipalDomainOriginSetter() { --sInPrincipalDomainOrigin; }
+  static uint32_t sInPrincipalDomainOrigin;
+};
+uint32_t nsAutoInPrincipalDomainOriginSetter::sInPrincipalDomainOrigin;
+
+static nsresult GetOriginFromURI(nsIURI* aURI, nsACString& aOrigin) {
+  if (!aURI) {
+    return NS_ERROR_NULL_POINTER;
+  }
+  if (nsAutoInPrincipalDomainOriginSetter::sInPrincipalDomainOrigin > 1) {
+    // Allow a single recursive call to GetPrincipalDomainOrigin, since that
+    // might be happening on a different principal from the first call.  But
+    // after that, cut off the recursion; it just indicates that something
+    // we're doing in this method causes us to reenter a security check here.
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  nsAutoInPrincipalDomainOriginSetter autoSetter;
+
+  nsCOMPtr<nsIURI> uri = NS_GetInnermostURI(aURI);
+  NS_ENSURE_TRUE(uri, NS_ERROR_UNEXPECTED);
+
+  nsAutoCString hostPort;
+
+  nsresult rv = uri->GetHostPort(hostPort);
+  if (NS_SUCCEEDED(rv)) {
+    nsAutoCString scheme;
+    rv = uri->GetScheme(scheme);
+    NS_ENSURE_SUCCESS(rv, rv);
+    aOrigin = scheme + "://"_ns + hostPort;
+  } else {
+    // Some URIs (e.g., nsSimpleURI) don't support host. Just
+    // get the full spec.
+    rv = uri->GetSpec(aOrigin);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  return NS_OK;
+}
+
+static nsresult GetPrincipalDomainOrigin(nsIPrincipal* aPrincipal,
+                                         nsACString& aOrigin) {
+  aOrigin.Truncate();
+  nsCOMPtr<nsIURI> uri;
+  aPrincipal->GetDomain(getter_AddRefs(uri));
+  nsresult rv = GetOriginFromURI(uri, aOrigin);
+  if (NS_SUCCEEDED(rv)) {
+    return rv;
+  }
+  // If there is no Domain fallback to the Principals Origin
+  return aPrincipal->GetOriginNoSuffix(aOrigin);
+}
+
+inline void SetPendingExceptionASCII(JSContext* cx, const char* aMsg) {
+  JS_ReportErrorASCII(cx, "%s", aMsg);
+}
+
+inline void SetPendingException(JSContext* cx, const char16_t* aMsg) {
+  NS_ConvertUTF16toUTF8 msg(aMsg);
+  JS_ReportErrorUTF8(cx, "%s", msg.get());
+}
+
+/* static */
+bool nsScriptSecurityManager::SecurityCompareURIs(nsIURI* aSourceURI,
+                                                  nsIURI* aTargetURI) {
+  return NS_SecurityCompareURIs(aSourceURI, aTargetURI,
+                                sStrictFileOriginPolicy);
+}
+
+// SecurityHashURI is consistent with SecurityCompareURIs because
+// NS_SecurityHashURI is consistent with NS_SecurityCompareURIs.  See
+// nsNetUtil.h.
+uint32_t nsScriptSecurityManager::SecurityHashURI(nsIURI* aURI) {
+  return NS_SecurityHashURI(aURI);
+}
+
+/*
+ * GetChannelResultPrincipal will return the principal that the resource
+ * returned by this channel will use.  For example, if the resource is in
+ * a sandbox, it will return the nullprincipal.  If the resource is forced
+ * to inherit principal, it will return the principal of its parent.  If
+ * the load doesn't require sandboxing or inheriting, it will return the same
+ * principal as GetChannelURIPrincipal. Namely the principal of the URI
+ * that is being loaded.
+ */
+NS_IMETHODIMP
+nsScriptSecurityManager::GetChannelResultPrincipal(nsIChannel* aChannel,
+                                                   nsIPrincipal** aPrincipal) {
+  return GetChannelResultPrincipal(aChannel, aPrincipal,
+                                   /*aIgnoreSandboxing*/ false);
+}
+
+nsresult nsScriptSecurityManager::GetChannelResultPrincipalIfNotSandboxed(
+    nsIChannel* aChannel, nsIPrincipal** aPrincipal) {
+  return GetChannelResultPrincipal(aChannel, aPrincipal,
+                                   /*aIgnoreSandboxing*/ true);
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::GetChannelResultStoragePrincipal(
+    nsIChannel* aChannel, nsIPrincipal** aPrincipal) {
+  nsCOMPtr<nsIPrincipal> principal;
+  nsresult rv = GetChannelResultPrincipal(aChannel, getter_AddRefs(principal),
+                                          /*aIgnoreSandboxing*/ false);
+  if (NS_WARN_IF(NS_FAILED(rv) || !principal)) {
+    return rv;
+  }
+
+  if (!(principal->GetIsContentPrincipal())) {
+    // If for some reason we don't have a content principal here, just reuse our
+    // principal for the storage principal too, since attempting to create a
+    // storage principal would fail anyway.
+    principal.forget(aPrincipal);
+    return NS_OK;
+  }
+
+  return StoragePrincipalHelper::Create(
+      aChannel, principal, /* aForceIsolation */ false, aPrincipal);
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::GetChannelResultPrincipals(
+    nsIChannel* aChannel, nsIPrincipal** aPrincipal,
+    nsIPrincipal** aPartitionedPrincipal) {
+  nsresult rv = GetChannelResultPrincipal(aChannel, aPrincipal,
+                                          /*aIgnoreSandboxing*/ false);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  if (!(*aPrincipal)->GetIsContentPrincipal()) {
+    // If for some reason we don't have a content principal here, just reuse our
+    // principal for the storage principal too, since attempting to create a
+    // storage principal would fail anyway.
+    nsCOMPtr<nsIPrincipal> copy = *aPrincipal;
+    copy.forget(aPartitionedPrincipal);
+    return NS_OK;
+  }
+
+  return StoragePrincipalHelper::Create(
+      aChannel, *aPrincipal, /* aForceIsolation */ true, aPartitionedPrincipal);
+}
+
+nsresult nsScriptSecurityManager::GetChannelResultPrincipal(
+    nsIChannel* aChannel, nsIPrincipal** aPrincipal, bool aIgnoreSandboxing) {
+  MOZ_ASSERT(aChannel, "Must have channel!");
+
+  // Check whether we have an nsILoadInfo that says what we should do.
+  nsCOMPtr<nsILoadInfo> loadInfo = aChannel->LoadInfo();
+  if (loadInfo->GetForceInheritPrincipalOverruleOwner()) {
+    nsCOMPtr<nsIPrincipal> principalToInherit =
+        loadInfo->FindPrincipalToInherit(aChannel);
+    principalToInherit.forget(aPrincipal);
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsISupports> owner;
+  aChannel->GetOwner(getter_AddRefs(owner));
+  if (owner) {
+    CallQueryInterface(owner, aPrincipal);
+    if (*aPrincipal) {
+      return NS_OK;
+    }
+  }
+
+  if (!aIgnoreSandboxing && loadInfo->GetLoadingSandboxed()) {
+    // Determine the unsandboxed result principal to use as this null
+    // principal's precursor. Ignore errors here, as the precursor isn't
+    // required.
+    nsCOMPtr<nsIPrincipal> precursor;
+    GetChannelResultPrincipal(aChannel, getter_AddRefs(precursor),
+                              /*aIgnoreSandboxing*/ true);
+
+    // Construct a deterministic null principal URI from the precursor and the
+    // loadinfo's nullPrincipalID.
+    nsCOMPtr<nsIURI> nullPrincipalURI = NullPrincipal::CreateURI(
+        precursor, &loadInfo->GetSandboxedNullPrincipalID());
+
+    // Use the URI to construct the sandboxed result principal.
+    OriginAttributes attrs;
+    loadInfo->GetOriginAttributes(&attrs);
+    nsCOMPtr<nsIPrincipal> sandboxedPrincipal =
+        NullPrincipal::Create(attrs, nullPrincipalURI);
+    sandboxedPrincipal.forget(aPrincipal);
+    return NS_OK;
+  }
+
+  bool forceInherit = loadInfo->GetForceInheritPrincipal();
+  if (aIgnoreSandboxing && !forceInherit) {
+    // Check if SEC_FORCE_INHERIT_PRINCIPAL was dropped because of
+    // sandboxing:
+    if (loadInfo->GetLoadingSandboxed() &&
+        loadInfo->GetForceInheritPrincipalDropped()) {
+      forceInherit = true;
+    }
+  }
+  if (forceInherit) {
+    nsCOMPtr<nsIPrincipal> principalToInherit =
+        loadInfo->FindPrincipalToInherit(aChannel);
+    principalToInherit.forget(aPrincipal);
+    return NS_OK;
+  }
+
+  auto securityMode = loadInfo->GetSecurityMode();
+  // The data: inheritance flags should only apply to the initial load,
+  // not to loads that it might have redirected to.
+  if (loadInfo->RedirectChain().IsEmpty() &&
+      (securityMode ==
+           nsILoadInfo::SEC_REQUIRE_SAME_ORIGIN_INHERITS_SEC_CONTEXT ||
+       securityMode ==
+           nsILoadInfo::SEC_ALLOW_CROSS_ORIGIN_INHERITS_SEC_CONTEXT ||
+       securityMode == nsILoadInfo::SEC_REQUIRE_CORS_INHERITS_SEC_CONTEXT)) {
+    nsCOMPtr<nsIURI> uri;
+    nsresult rv = NS_GetFinalChannelURI(aChannel, getter_AddRefs(uri));
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    nsCOMPtr<nsIPrincipal> principalToInherit =
+        loadInfo->FindPrincipalToInherit(aChannel);
+    bool inheritForAboutBlank = loadInfo->GetAboutBlankInherits();
+
+    if (nsContentUtils::ChannelShouldInheritPrincipal(
+            principalToInherit, uri, inheritForAboutBlank, false)) {
+      principalToInherit.forget(aPrincipal);
+      return NS_OK;
+    }
+  }
+  return GetChannelURIPrincipal(aChannel, aPrincipal);
+}
+
+/* The principal of the URI that this channel is loading. This is never
+ * affected by things like sandboxed loads, or loads where we forcefully
+ * inherit the principal.  Think of this as the principal of the server
+ * which this channel is loading from.  Most callers should use
+ * GetChannelResultPrincipal instead of GetChannelURIPrincipal.  Only
+ * call GetChannelURIPrincipal if you are sure that you want the
+ * principal that matches the uri, even in cases when the load is
+ * sandboxed or when the load could be a blob or data uri (i.e even when
+ * you encounter loads that may or may not be sandboxed and loads
+ * that may or may not inherit)."
+ */
+NS_IMETHODIMP
+nsScriptSecurityManager::GetChannelURIPrincipal(nsIChannel* aChannel,
+                                                nsIPrincipal** aPrincipal) {
+  MOZ_ASSERT(aChannel, "Must have channel!");
+
+  // Get the principal from the URI.  Make sure this does the same thing
+  // as Document::Reset and PrototypeDocumentContentSink::Init.
+  nsCOMPtr<nsIURI> uri;
+  nsresult rv = NS_GetFinalChannelURI(aChannel, getter_AddRefs(uri));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsILoadInfo> loadInfo = aChannel->LoadInfo();
+
+  // Inherit the origin attributes from loadInfo.
+  // If this is a top-level document load, the origin attributes of the
+  // loadInfo will be set from nsDocShell::DoURILoad.
+  // For subresource loading, the origin attributes of the loadInfo is from
+  // its loadingPrincipal.
+  OriginAttributes attrs = loadInfo->GetOriginAttributes();
+
+  // If the URI is supposed to inherit the security context of whoever loads it,
+  // we shouldn't make a content principal for it, so instead return a null
+  // principal.
+  bool inheritsPrincipal = false;
+  rv = NS_URIChainHasFlags(uri,
+                           nsIProtocolHandler::URI_INHERITS_SECURITY_CONTEXT,
+                           &inheritsPrincipal);
+  if (NS_FAILED(rv) || inheritsPrincipal) {
+    // Find a precursor principal to credit for the load. This won't impact
+    // security checks, but makes tracking the source of related loads easier.
+    nsCOMPtr<nsIPrincipal> precursorPrincipal =
+        loadInfo->FindPrincipalToInherit(aChannel);
+    nsCOMPtr<nsIURI> nullPrincipalURI =
+        NullPrincipal::CreateURI(precursorPrincipal);
+    *aPrincipal = NullPrincipal::Create(attrs, nullPrincipalURI).take();
+    return *aPrincipal ? NS_OK : NS_ERROR_FAILURE;
+  }
+
+  nsCOMPtr<nsIPrincipal> prin =
+      BasePrincipal::CreateContentPrincipal(uri, attrs);
+  prin.forget(aPrincipal);
+  return *aPrincipal ? NS_OK : NS_ERROR_FAILURE;
+}
+
+/////////////////////////////
+// nsScriptSecurityManager //
+/////////////////////////////
+
+////////////////////////////////////
+// Methods implementing ISupports //
+////////////////////////////////////
+NS_IMPL_ISUPPORTS(nsScriptSecurityManager, nsIScriptSecurityManager)
+
+///////////////////////////////////////////////////
+// Methods implementing nsIScriptSecurityManager //
+///////////////////////////////////////////////////
+
+///////////////// Security Checks /////////////////
+
+bool nsScriptSecurityManager::ContentSecurityPolicyPermitsJSAction(
+    JSContext* cx, JS::RuntimeCode aKind, JS::Handle<JSString*> aCode) {
+  MOZ_ASSERT(cx == nsContentUtils::GetCurrentJSContext());
+
+  nsCOMPtr<nsIPrincipal> subjectPrincipal = nsContentUtils::SubjectPrincipal();
+
+  // Check if Eval is allowed per firefox hardening policy
+  bool contextForbidsEval =
+      (subjectPrincipal->IsSystemPrincipal() || XRE_IsE10sParentProcess());
+#if defined(ANDROID)
+  contextForbidsEval = false;
+#endif
+
+  if (contextForbidsEval) {
+    nsAutoJSString scriptSample;
+    if (aKind == JS::RuntimeCode::JS &&
+        NS_WARN_IF(!scriptSample.init(cx, aCode))) {
+      return false;
+    }
+
+    if (!nsContentSecurityUtils::IsEvalAllowed(
+            cx, subjectPrincipal->IsSystemPrincipal(), scriptSample)) {
+      return false;
+    }
+  }
+
+  // Get the window, if any, corresponding to the current global
+  nsCOMPtr<nsIContentSecurityPolicy> csp;
+  if (nsGlobalWindowInner* win = xpc::CurrentWindowOrNull(cx)) {
+    csp = win->GetCsp();
+  }
+
+  if (!csp) {
+    // Get the CSP for addon sandboxes.  If the principal is expanded and has a
+    // csp, we're probably in luck.
+    auto* basePrin = BasePrincipal::Cast(subjectPrincipal);
+    // ContentScriptAddonPolicy means it is also an expanded principal, thus
+    // this is in a sandbox used as a content script.
+    if (basePrin->ContentScriptAddonPolicy()) {
+      basePrin->As<ExpandedPrincipal>()->GetCsp(getter_AddRefs(csp));
+    }
+    // don't do anything unless there's a CSP
+    if (!csp) {
+      return true;
+    }
+  }
+
+  nsCOMPtr<nsICSPEventListener> cspEventListener;
+  if (!NS_IsMainThread()) {
+    WorkerPrivate* workerPrivate =
+        mozilla::dom::GetWorkerPrivateFromContext(cx);
+    if (workerPrivate) {
+      cspEventListener = workerPrivate->CSPEventListener();
+    }
+  }
+
+  bool evalOK = true;
+  bool reportViolation = false;
+  if (aKind == JS::RuntimeCode::JS) {
+    nsresult rv = csp->GetAllowsEval(&reportViolation, &evalOK);
+    if (NS_FAILED(rv)) {
+      NS_WARNING("CSP: failed to get allowsEval");
+      return true;  // fail open to not break sites.
+    }
+  } else {
+    if (NS_FAILED(csp->GetAllowsWasmEval(&reportViolation, &evalOK))) {
+      return false;
+    }
+    if (!evalOK) {
+      // Historically, CSP did not block WebAssembly in Firefox, and some
+      // add-ons use wasm and a stricter CSP. To avoid breaking them, ignore
+      // 'wasm-unsafe-eval' violations for MV2 extensions.
+      // TODO bug 1770909: remove this exception.
+      auto* addonPolicy = BasePrincipal::Cast(subjectPrincipal)->AddonPolicy();
+      if (addonPolicy && addonPolicy->ManifestVersion() == 2) {
+        reportViolation = true;
+        evalOK = true;
+      }
+    }
+  }
+
+  if (reportViolation) {
+    JS::AutoFilename scriptFilename;
+    nsAutoString fileName;
+    unsigned lineNum = 0;
+    unsigned columnNum = 0;
+    if (JS::DescribeScriptedCaller(cx, &scriptFilename, &lineNum, &columnNum)) {
+      if (const char* file = scriptFilename.get()) {
+        CopyUTF8toUTF16(nsDependentCString(file), fileName);
+      }
+    } else {
+      MOZ_ASSERT(!JS_IsExceptionPending(cx));
+    }
+
+    nsAutoJSString scriptSample;
+    if (aKind == JS::RuntimeCode::JS &&
+        NS_WARN_IF(!scriptSample.init(cx, aCode))) {
+      JS_ClearPendingException(cx);
+      return false;
+    }
+    uint16_t violationType =
+        aKind == JS::RuntimeCode::JS
+            ? nsIContentSecurityPolicy::VIOLATION_TYPE_EVAL
+            : nsIContentSecurityPolicy::VIOLATION_TYPE_WASM_EVAL;
+    csp->LogViolationDetails(violationType,
+                             nullptr,  // triggering element
+                             cspEventListener, fileName, scriptSample, lineNum,
+                             columnNum, u""_ns, u""_ns);
+  }
+
+  return evalOK;
+}
+
+// static
+bool nsScriptSecurityManager::JSPrincipalsSubsume(JSPrincipals* first,
+                                                  JSPrincipals* second) {
+  return nsJSPrincipals::get(first)->Subsumes(nsJSPrincipals::get(second));
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::CheckSameOriginURI(nsIURI* aSourceURI,
+                                            nsIURI* aTargetURI,
+                                            bool reportError,
+                                            bool aFromPrivateWindow) {
+  // Please note that aFromPrivateWindow is only 100% accurate if
+  // reportError is true.
+  if (!SecurityCompareURIs(aSourceURI, aTargetURI)) {
+    if (reportError) {
+      ReportError("CheckSameOriginError", aSourceURI, aTargetURI,
+                  aFromPrivateWindow);
+    }
+    return NS_ERROR_DOM_BAD_URI;
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::CheckLoadURIFromScript(JSContext* cx, nsIURI* aURI) {
+  // Get principal of currently executing script.
+  MOZ_ASSERT(cx == nsContentUtils::GetCurrentJSContext());
+  nsIPrincipal* principal = nsContentUtils::SubjectPrincipal();
+  nsresult rv = CheckLoadURIWithPrincipal(
+      // Passing 0 for the window ID here is OK, because we will report a
+      // script-visible exception anyway.
+      principal, aURI, nsIScriptSecurityManager::STANDARD, 0);
+  if (NS_SUCCEEDED(rv)) {
+    // OK to load
+    return NS_OK;
+  }
+
+  // Report error.
+  nsAutoCString spec;
+  if (NS_FAILED(aURI->GetAsciiSpec(spec))) return NS_ERROR_FAILURE;
+  nsAutoCString msg("Access to '");
+  msg.Append(spec);
+  msg.AppendLiteral("' from script denied");
+  SetPendingExceptionASCII(cx, msg.get());
+  return NS_ERROR_DOM_BAD_URI;
+}
+
+/**
+ * Helper method to handle cases where a flag passed to
+ * CheckLoadURIWithPrincipal means denying loading if the given URI has certain
+ * nsIProtocolHandler flags set.
+ * @return if success, access is allowed. Otherwise, deny access
+ */
+static nsresult DenyAccessIfURIHasFlags(nsIURI* aURI, uint32_t aURIFlags) {
+  MOZ_ASSERT(aURI, "Must have URI!");
+
+  bool uriHasFlags;
+  nsresult rv = NS_URIChainHasFlags(aURI, aURIFlags, &uriHasFlags);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (uriHasFlags) {
+    return NS_ERROR_DOM_BAD_URI;
+  }
+
+  return NS_OK;
+}
+
+static bool EqualOrSubdomain(nsIURI* aProbeArg, nsIURI* aBase) {
+  nsresult rv;
+  nsCOMPtr<nsIURI> probe = aProbeArg;
+
+  nsCOMPtr<nsIEffectiveTLDService> tldService =
+      do_GetService(NS_EFFECTIVETLDSERVICE_CONTRACTID);
+  NS_ENSURE_TRUE(tldService, false);
+  while (true) {
+    if (nsScriptSecurityManager::SecurityCompareURIs(probe, aBase)) {
+      return true;
+    }
+
+    nsAutoCString host, newHost;
+    rv = probe->GetHost(host);
+    NS_ENSURE_SUCCESS(rv, false);
+
+    rv = tldService->GetNextSubDomain(host, newHost);
+    if (rv == NS_ERROR_INSUFFICIENT_DOMAIN_LEVELS) {
+      return false;
+    }
+    NS_ENSURE_SUCCESS(rv, false);
+    rv = NS_MutateURI(probe).SetHost(newHost).Finalize(probe);
+    NS_ENSURE_SUCCESS(rv, false);
+  }
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::CheckLoadURIWithPrincipal(nsIPrincipal* aPrincipal,
+                                                   nsIURI* aTargetURI,
+                                                   uint32_t aFlags,
+                                                   uint64_t aInnerWindowID) {
+  MOZ_ASSERT(aPrincipal, "CheckLoadURIWithPrincipal must have a principal");
+
+  // If someone passes a flag that we don't understand, we should
+  // fail, because they may need a security check that we don't
+  // provide.
+  NS_ENSURE_FALSE(
+      aFlags &
+          ~(nsIScriptSecurityManager::LOAD_IS_AUTOMATIC_DOCUMENT_REPLACEMENT |
+            nsIScriptSecurityManager::ALLOW_CHROME |
+            nsIScriptSecurityManager::DISALLOW_SCRIPT |
+            nsIScriptSecurityManager::DISALLOW_INHERIT_PRINCIPAL |
+            nsIScriptSecurityManager::DONT_REPORT_ERRORS),
+      NS_ERROR_UNEXPECTED);
+  NS_ENSURE_ARG_POINTER(aPrincipal);
+  NS_ENSURE_ARG_POINTER(aTargetURI);
+
+  // If DISALLOW_INHERIT_PRINCIPAL is set, we prevent loading of URIs which
+  // would do such inheriting. That would be URIs that do not have their own
+  // security context. We do this even for the system principal.
+  if (aFlags & nsIScriptSecurityManager::DISALLOW_INHERIT_PRINCIPAL) {
+    nsresult rv = DenyAccessIfURIHasFlags(
+        aTargetURI, nsIProtocolHandler::URI_INHERITS_SECURITY_CONTEXT);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  if (aPrincipal == mSystemPrincipal) {
+    // Allow access
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIURI> sourceURI;
+  auto* basePrin = BasePrincipal::Cast(aPrincipal);
+  basePrin->GetURI(getter_AddRefs(sourceURI));
+  if (!sourceURI) {
+    if (basePrin->Is<ExpandedPrincipal>()) {
+      // If the target addon is MV3 or the pref is on we require extension
+      // resources loaded from content to be listed in web_accessible_resources.
+      auto* targetPolicy =
+          ExtensionPolicyService::GetSingleton().GetByURL(aTargetURI);
+      bool contentAccessRequired =
+          targetPolicy &&
+          (targetPolicy->ManifestVersion() > 2 ||
+           StaticPrefs::extensions_content_web_accessible_enabled());
+      auto expanded = basePrin->As<ExpandedPrincipal>();
+      const auto& allowList = expanded->AllowList();
+      // Only report errors when all principals fail.
+      // With expanded principals, which are used by extension content scripts,
+      // we check only against non-extension principals for access to extension
+      // resource to enforce making those resources explicitly web accessible.
+      uint32_t flags = aFlags | nsIScriptSecurityManager::DONT_REPORT_ERRORS;
+      for (size_t i = 0; i < allowList.Length() - 1; i++) {
+        if (contentAccessRequired &&
+            BasePrincipal::Cast(allowList[i])->AddonPolicy()) {
+          continue;
+        }
+        nsresult rv = CheckLoadURIWithPrincipal(allowList[i], aTargetURI, flags,
+                                                aInnerWindowID);
+        if (NS_SUCCEEDED(rv)) {
+          // Allow access if it succeeded with one of the allowlisted principals
+          return NS_OK;
+        }
+      }
+
+      if (contentAccessRequired &&
+          BasePrincipal::Cast(allowList.LastElement())->AddonPolicy()) {
+        bool reportErrors =
+            !(aFlags & nsIScriptSecurityManager::DONT_REPORT_ERRORS);
+        if (reportErrors) {
+          ReportError("CheckLoadURI", sourceURI, aTargetURI,
+                      allowList.LastElement()
+                              ->OriginAttributesRef()
+                              .mPrivateBrowsingId > 0,
+                      aInnerWindowID);
+        }
+        return NS_ERROR_DOM_BAD_URI;
+      }
+      // Report errors (if requested) for the last principal.
+      return CheckLoadURIWithPrincipal(allowList.LastElement(), aTargetURI,
+                                       aFlags, aInnerWindowID);
+    }
+    NS_ERROR(
+        "Non-system principals or expanded principal passed to "
+        "CheckLoadURIWithPrincipal "
+        "must have a URI!");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  // Automatic loads are not allowed from certain protocols.
+  if (aFlags &
+      nsIScriptSecurityManager::LOAD_IS_AUTOMATIC_DOCUMENT_REPLACEMENT) {
+    nsresult rv = DenyAccessIfURIHasFlags(
+        sourceURI,
+        nsIProtocolHandler::URI_FORBIDS_AUTOMATIC_DOCUMENT_REPLACEMENT);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  // If either URI is a nested URI, get the base URI
+  nsCOMPtr<nsIURI> sourceBaseURI = NS_GetInnermostURI(sourceURI);
+  nsCOMPtr<nsIURI> targetBaseURI = NS_GetInnermostURI(aTargetURI);
+
+  //-- get the target scheme
+  nsAutoCString targetScheme;
+  nsresult rv = targetBaseURI->GetScheme(targetScheme);
+  if (NS_FAILED(rv)) return rv;
+
+  //-- Some callers do not allow loading javascript:
+  if ((aFlags & nsIScriptSecurityManager::DISALLOW_SCRIPT) &&
+      targetScheme.EqualsLiteral("javascript")) {
+    return NS_ERROR_DOM_BAD_URI;
+  }
+
+  // Check for uris that are only loadable by principals that subsume them
+  bool targetURIIsLoadableBySubsumers = false;
+  rv = NS_URIChainHasFlags(targetBaseURI,
+                           nsIProtocolHandler::URI_LOADABLE_BY_SUBSUMERS,
+                           &targetURIIsLoadableBySubsumers);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (targetURIIsLoadableBySubsumers) {
+    // check nothing else in the URI chain has flags that prevent
+    // access:
+    rv = CheckLoadURIFlags(
+        sourceURI, aTargetURI, sourceBaseURI, targetBaseURI, aFlags,
+        aPrincipal->OriginAttributesRef().mPrivateBrowsingId > 0,
+        aInnerWindowID);
+    NS_ENSURE_SUCCESS(rv, rv);
+    // Check the principal is allowed to load the target.
+    if (aFlags & nsIScriptSecurityManager::DONT_REPORT_ERRORS) {
+      return aPrincipal->CheckMayLoad(targetBaseURI, false);
+    }
+    return aPrincipal->CheckMayLoadWithReporting(targetBaseURI, false,
+                                                 aInnerWindowID);
+  }
+
+  //-- get the source scheme
+  nsAutoCString sourceScheme;
+  rv = sourceBaseURI->GetScheme(sourceScheme);
+  if (NS_FAILED(rv)) return rv;
+
+  if (sourceScheme.LowerCaseEqualsLiteral(NS_NULLPRINCIPAL_SCHEME)) {
+    // A null principal can target its own URI.
+    if (sourceURI == aTargetURI) {
+      return NS_OK;
+    }
+  } else if (sourceScheme.EqualsIgnoreCase("file") &&
+             targetScheme.EqualsIgnoreCase("moz-icon")) {
+    // exception for file: linking to moz-icon://.ext?size=...
+    // Note that because targetScheme is the base (innermost) URI scheme,
+    // this does NOT allow file -> moz-icon:file:///... links.
+    // This is intentional.
+    return NS_OK;
+  }
+
+  // Check for webextension
+  bool targetURIIsLoadableByExtensions = false;
+  rv = NS_URIChainHasFlags(aTargetURI,
+                           nsIProtocolHandler::URI_LOADABLE_BY_EXTENSIONS,
+                           &targetURIIsLoadableByExtensions);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (targetURIIsLoadableByExtensions &&
+      BasePrincipal::Cast(aPrincipal)->AddonPolicy()) {
+    return NS_OK;
+  }
+
+  // If we get here, check all the schemes can link to each other, from the top
+  // down:
+  nsCOMPtr<nsIURI> currentURI = sourceURI;
+  nsCOMPtr<nsIURI> currentOtherURI = aTargetURI;
+
+  bool denySameSchemeLinks = false;
+  rv = NS_URIChainHasFlags(aTargetURI,
+                           nsIProtocolHandler::URI_SCHEME_NOT_SELF_LINKABLE,
+                           &denySameSchemeLinks);
+  if (NS_FAILED(rv)) return rv;
+
+  while (currentURI && currentOtherURI) {
+    nsAutoCString scheme, otherScheme;
+    currentURI->GetScheme(scheme);
+    currentOtherURI->GetScheme(otherScheme);
+
+    bool schemesMatch =
+        scheme.Equals(otherScheme, nsCaseInsensitiveCStringComparator);
+    bool isSamePage = false;
+    bool isExtensionMismatch = false;
+    // about: URIs are special snowflakes.
+    if (scheme.EqualsLiteral("about") && schemesMatch) {
+      nsAutoCString moduleName, otherModuleName;
+      // about: pages can always link to themselves:
+      isSamePage =
+          NS_SUCCEEDED(NS_GetAboutModuleName(currentURI, moduleName)) &&
+          NS_SUCCEEDED(
+              NS_GetAboutModuleName(currentOtherURI, otherModuleName)) &&
+          moduleName.Equals(otherModuleName);
+      if (!isSamePage) {
+        // We will have allowed the load earlier if the source page has
+        // system principal. So we know the source has a content
+        // principal, and it's trying to link to something else.
+        // Linkable about: pages are always reachable, even if we hit
+        // the CheckLoadURIFlags call below.
+        // We punch only 1 other hole: iff the source is unlinkable,
+        // we let them link to other pages explicitly marked SAFE
+        // for content. This avoids world-linkable about: pages linking
+        // to non-world-linkable about: pages.
+        nsCOMPtr<nsIAboutModule> module, otherModule;
+        bool knowBothModules =
+            NS_SUCCEEDED(
+                NS_GetAboutModule(currentURI, getter_AddRefs(module))) &&
+            NS_SUCCEEDED(NS_GetAboutModule(currentOtherURI,
+                                           getter_AddRefs(otherModule)));
+        uint32_t aboutModuleFlags = 0;
+        uint32_t otherAboutModuleFlags = 0;
+        knowBothModules =
+            knowBothModules &&
+            NS_SUCCEEDED(module->GetURIFlags(currentURI, &aboutModuleFlags)) &&
+            NS_SUCCEEDED(otherModule->GetURIFlags(currentOtherURI,
+                                                  &otherAboutModuleFlags));
+        if (knowBothModules) {
+          isSamePage = !(aboutModuleFlags & nsIAboutModule::MAKE_LINKABLE) &&
+                       (otherAboutModuleFlags &
+                        nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT);
+          if (isSamePage &&
+              otherAboutModuleFlags & nsIAboutModule::MAKE_LINKABLE) {
+            // XXXgijs: this is a hack. The target will be nested
+            // (with innerURI of moz-safe-about:whatever), and
+            // the source isn't, so we won't pass if we finish
+            // the loop. We *should* pass, though, so return here.
+            // This hack can go away when bug 1228118 is fixed.
+            return NS_OK;
+          }
+        }
+      }
+    } else if (schemesMatch && scheme.EqualsLiteral("moz-extension")) {
+      // If it is not the same exension, we want to ensure we end up
+      // calling CheckLoadURIFlags
+      nsAutoCString host, otherHost;
+      currentURI->GetHost(host);
+      currentOtherURI->GetHost(otherHost);
+      isExtensionMismatch = !host.Equals(otherHost);
+    } else {
+      bool equalExceptRef = false;
+      rv = currentURI->EqualsExceptRef(currentOtherURI, &equalExceptRef);
+      isSamePage = NS_SUCCEEDED(rv) && equalExceptRef;
+    }
+
+    // If schemes are not equal, or they're equal but the target URI
+    // is different from the source URI and doesn't always allow linking
+    // from the same scheme, or this is two different extensions, check
+    // if the URI flags of the current target URI allow the current
+    // source URI to link to it.
+    // The policy is specified by the protocol flags on both URIs.
+    if (!schemesMatch || (denySameSchemeLinks && !isSamePage) ||
+        isExtensionMismatch) {
+      return CheckLoadURIFlags(
+          currentURI, currentOtherURI, sourceBaseURI, targetBaseURI, aFlags,
+          aPrincipal->OriginAttributesRef().mPrivateBrowsingId > 0,
+          aInnerWindowID);
+    }
+    // Otherwise... check if we can nest another level:
+    nsCOMPtr<nsINestedURI> nestedURI = do_QueryInterface(currentURI);
+    nsCOMPtr<nsINestedURI> nestedOtherURI = do_QueryInterface(currentOtherURI);
+
+    // If schemes match and neither URI is nested further, we're OK.
+    if (!nestedURI && !nestedOtherURI) {
+      return NS_OK;
+    }
+    // If one is nested and the other isn't, something is wrong.
+    if (!nestedURI != !nestedOtherURI) {
+      return NS_ERROR_DOM_BAD_URI;
+    }
+    // Otherwise, both should be nested and we'll go through the loop again.
+    nestedURI->GetInnerURI(getter_AddRefs(currentURI));
+    nestedOtherURI->GetInnerURI(getter_AddRefs(currentOtherURI));
+  }
+
+  // We should never get here. We should always return from inside the loop.
+  return NS_ERROR_DOM_BAD_URI;
+}
+
+/**
+ * Helper method to check whether the target URI and its innermost ("base") URI
+ * has protocol flags that should stop it from being loaded by the source URI
+ * (and/or the source URI's innermost ("base") URI), taking into account any
+ * nsIScriptSecurityManager flags originally passed to
+ * CheckLoadURIWithPrincipal and friends.
+ *
+ * @return if success, access is allowed. Otherwise, deny access
+ */
+nsresult nsScriptSecurityManager::CheckLoadURIFlags(
+    nsIURI* aSourceURI, nsIURI* aTargetURI, nsIURI* aSourceBaseURI,
+    nsIURI* aTargetBaseURI, uint32_t aFlags, bool aFromPrivateWindow,
+    uint64_t aInnerWindowID) {
+  // Note that the order of policy checks here is very important!
+  // We start from most restrictive and work our way down.
+  bool reportErrors = !(aFlags & nsIScriptSecurityManager::DONT_REPORT_ERRORS);
+  const char* errorTag = "CheckLoadURIError";
+
+  nsAutoCString targetScheme;
+  nsresult rv = aTargetBaseURI->GetScheme(targetScheme);
+  if (NS_FAILED(rv)) return rv;
+
+  // Check for system target URI.  Regular (non web accessible) extension
+  // URIs will also have URI_DANGEROUS_TO_LOAD.
+  rv = DenyAccessIfURIHasFlags(aTargetURI,
+                               nsIProtocolHandler::URI_DANGEROUS_TO_LOAD);
+  if (NS_FAILED(rv)) {
+    // Deny access, since the origin principal is not system
+    if (reportErrors) {
+      ReportError(errorTag, aSourceURI, aTargetURI, aFromPrivateWindow,
+                  aInnerWindowID);
+    }
+    return rv;
+  }
+
+  // Used by ExtensionProtocolHandler to prevent loading extension resources
+  // in private contexts if the extension does not have permission.
+  if (aFromPrivateWindow) {
+    rv = DenyAccessIfURIHasFlags(
+        aTargetURI, nsIProtocolHandler::URI_DISALLOW_IN_PRIVATE_CONTEXT);
+    if (NS_FAILED(rv)) {
+      if (reportErrors) {
+        ReportError(errorTag, aSourceURI, aTargetURI, aFromPrivateWindow,
+                    aInnerWindowID);
+      }
+      return rv;
+    }
+  }
+
+  // If MV3 Extension uris are web accessible they have
+  // WEBEXT_URI_WEB_ACCESSIBLE.
+  bool maybeWebAccessible = false;
+  NS_URIChainHasFlags(aTargetURI, nsIProtocolHandler::WEBEXT_URI_WEB_ACCESSIBLE,
+                      &maybeWebAccessible);
+  NS_ENSURE_SUCCESS(rv, rv);
+  if (maybeWebAccessible) {
+    bool isWebAccessible = false;
+    rv = ExtensionPolicyService::GetSingleton().SourceMayLoadExtensionURI(
+        aSourceURI, aTargetURI, &isWebAccessible);
+    if (NS_SUCCEEDED(rv) && isWebAccessible) {
+      return NS_OK;
+    }
+    if (reportErrors) {
+      ReportError(errorTag, aSourceURI, aTargetURI, aFromPrivateWindow,
+                  aInnerWindowID);
+    }
+    return NS_ERROR_DOM_BAD_URI;
+  }
+
+  // Check for chrome target URI
+  bool targetURIIsUIResource = false;
+  rv = NS_URIChainHasFlags(aTargetURI, nsIProtocolHandler::URI_IS_UI_RESOURCE,
+                           &targetURIIsUIResource);
+  NS_ENSURE_SUCCESS(rv, rv);
+  if (targetURIIsUIResource) {
+    // ALLOW_CHROME is a flag that we pass on all loads _except_ docshell
+    // loads (since docshell loads run the loaded content with its origin
+    // principal). We are effectively allowing resource:// and chrome://
+    // URIs to load as long as they are content accessible and as long
+    // they're not loading it as a document.
+    if (aFlags & nsIScriptSecurityManager::ALLOW_CHROME) {
+      bool sourceIsUIResource = false;
+      rv = NS_URIChainHasFlags(aSourceBaseURI,
+                               nsIProtocolHandler::URI_IS_UI_RESOURCE,
+                               &sourceIsUIResource);
+      NS_ENSURE_SUCCESS(rv, rv);
+      if (sourceIsUIResource) {
+        // Special case for moz-icon URIs loaded by a local resources like
+        // e.g. chrome: or resource:
+        if (targetScheme.EqualsLiteral("moz-icon")) {
+          return NS_OK;
+        }
+      }
+
+      if (targetScheme.EqualsLiteral("resource")) {
+        if (StaticPrefs::security_all_resource_uri_content_accessible()) {
+          return NS_OK;
+        }
+
+        nsCOMPtr<nsIProtocolHandler> ph;
+        rv = sIOService->GetProtocolHandler("resource", getter_AddRefs(ph));
+        NS_ENSURE_SUCCESS(rv, rv);
+        if (!ph) {
+          return NS_ERROR_DOM_BAD_URI;
+        }
+
+        nsCOMPtr<nsIResProtocolHandler> rph = do_QueryInterface(ph);
+        if (!rph) {
+          return NS_ERROR_DOM_BAD_URI;
+        }
+
+        bool accessAllowed = false;
+        rph->AllowContentToAccess(aTargetBaseURI, &accessAllowed);
+        if (accessAllowed) {
+          return NS_OK;
+        }
+      } else if (targetScheme.EqualsLiteral("chrome")) {
+        // Allow the load only if the chrome package is allowlisted.
+        nsCOMPtr<nsIXULChromeRegistry> reg(
+            do_GetService(NS_CHROMEREGISTRY_CONTRACTID));
+        if (reg) {
+          bool accessAllowed = false;
+          reg->AllowContentToAccess(aTargetBaseURI, &accessAllowed);
+          if (accessAllowed) {
+            return NS_OK;
+          }
+        }
+      } else if (targetScheme.EqualsLiteral("moz-page-thumb") ||
+                 targetScheme.EqualsLiteral("page-icon")) {
+        if (XRE_IsParentProcess()) {
+          return NS_OK;
+        }
+
+        auto& remoteType = dom::ContentChild::GetSingleton()->GetRemoteType();
+        if (remoteType == PRIVILEGEDABOUT_REMOTE_TYPE) {
+          return NS_OK;
+        }
+      }
+    }
+
+    if (reportErrors) {
+      ReportError(errorTag, aSourceURI, aTargetURI, aFromPrivateWindow,
+                  aInnerWindowID);
+    }
+    return NS_ERROR_DOM_BAD_URI;
+  }
+
+  // Check for target URI pointing to a file
+  bool targetURIIsLocalFile = false;
+  rv = NS_URIChainHasFlags(aTargetURI, nsIProtocolHandler::URI_IS_LOCAL_FILE,
+                           &targetURIIsLocalFile);
+  NS_ENSURE_SUCCESS(rv, rv);
+  if (targetURIIsLocalFile) {
+    // Allow domains that were allowlisted in the prefs. In 99.9% of cases,
+    // this array is empty.
+    bool isAllowlisted;
+    MOZ_ALWAYS_SUCCEEDS(InFileURIAllowlist(aSourceURI, &isAllowlisted));
+    if (isAllowlisted) {
+      return NS_OK;
+    }
+
+    // Allow chrome://
+    if (aSourceBaseURI->SchemeIs("chrome")) {
+      return NS_OK;
+    }
+
+    // Nothing else.
+    if (reportErrors) {
+      ReportError(errorTag, aSourceURI, aTargetURI, aFromPrivateWindow,
+                  aInnerWindowID);
+    }
+    return NS_ERROR_DOM_BAD_URI;
+  }
+
+#ifdef DEBUG
+  {
+    // Everyone is allowed to load this. The case URI_LOADABLE_BY_SUBSUMERS
+    // is handled by the caller which is just delegating to us as a helper.
+    bool hasSubsumersFlag = false;
+    NS_URIChainHasFlags(aTargetBaseURI,
+                        nsIProtocolHandler::URI_LOADABLE_BY_SUBSUMERS,
+                        &hasSubsumersFlag);
+    bool hasLoadableByAnyone = false;
+    NS_URIChainHasFlags(aTargetBaseURI,
+                        nsIProtocolHandler::URI_LOADABLE_BY_ANYONE,
+                        &hasLoadableByAnyone);
+    MOZ_ASSERT(hasLoadableByAnyone || hasSubsumersFlag,
+               "why do we get here and do not have any of the two flags set?");
+  }
+#endif
+
+  return NS_OK;
+}
+
+nsresult nsScriptSecurityManager::ReportError(const char* aMessageTag,
+                                              const nsACString& aSourceSpec,
+                                              const nsACString& aTargetSpec,
+                                              bool aFromPrivateWindow,
+                                              uint64_t aInnerWindowID) {
+  if (aSourceSpec.IsEmpty() || aTargetSpec.IsEmpty()) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIStringBundle> bundle = BundleHelper::GetOrCreate();
+  if (NS_WARN_IF(!bundle)) {
+    return NS_OK;
+  }
+
+  // Localize the error message
+  nsAutoString message;
+  AutoTArray<nsString, 2> formatStrings;
+  CopyASCIItoUTF16(aSourceSpec, *formatStrings.AppendElement());
+  CopyASCIItoUTF16(aTargetSpec, *formatStrings.AppendElement());
+  nsresult rv =
+      bundle->FormatStringFromName(aMessageTag, formatStrings, message);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIConsoleService> console(
+      do_GetService(NS_CONSOLESERVICE_CONTRACTID));
+  NS_ENSURE_TRUE(console, NS_ERROR_FAILURE);
+  nsCOMPtr<nsIScriptError> error(do_CreateInstance(NS_SCRIPTERROR_CONTRACTID));
+  NS_ENSURE_TRUE(error, NS_ERROR_FAILURE);
+
+  // using category of "SOP" so we can link to MDN
+  if (aInnerWindowID != 0) {
+    rv = error->InitWithWindowID(
+        message, u""_ns, u""_ns, 0, 0, nsIScriptError::errorFlag, "SOP"_ns,
+        aInnerWindowID, true /* From chrome context */);
+  } else {
+    rv = error->Init(message, u""_ns, u""_ns, 0, 0, nsIScriptError::errorFlag,
+                     "SOP"_ns, aFromPrivateWindow,
+                     true /* From chrome context */);
+  }
+  NS_ENSURE_SUCCESS(rv, rv);
+  console->LogMessage(error);
+  return NS_OK;
+}
+
+nsresult nsScriptSecurityManager::ReportError(const char* aMessageTag,
+                                              nsIURI* aSource, nsIURI* aTarget,
+                                              bool aFromPrivateWindow,
+                                              uint64_t aInnerWindowID) {
+  NS_ENSURE_TRUE(aSource && aTarget, NS_ERROR_NULL_POINTER);
+
+  // Get the source URL spec
+  nsAutoCString sourceSpec;
+  nsresult rv = aSource->GetAsciiSpec(sourceSpec);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Get the target URL spec
+  nsAutoCString targetSpec;
+  rv = aTarget->GetAsciiSpec(targetSpec);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return ReportError(aMessageTag, sourceSpec, targetSpec, aFromPrivateWindow,
+                     aInnerWindowID);
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::CheckLoadURIStrWithPrincipal(
+    nsIPrincipal* aPrincipal, const nsACString& aTargetURIStr,
+    uint32_t aFlags) {
+  nsresult rv;
+  nsCOMPtr<nsIURI> target;
+  rv = NS_NewURI(getter_AddRefs(target), aTargetURIStr);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = CheckLoadURIWithPrincipal(aPrincipal, target, aFlags, 0);
+  if (rv == NS_ERROR_DOM_BAD_URI) {
+    // Don't warn because NS_ERROR_DOM_BAD_URI is one of the expected
+    // return values.
+    return rv;
+  }
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Now start testing fixup -- since aTargetURIStr is a string, not
+  // an nsIURI, we may well end up fixing it up before loading.
+  // Note: This needs to stay in sync with the nsIURIFixup api.
+  nsCOMPtr<nsIURIFixup> fixup = components::URIFixup::Service();
+  if (!fixup) {
+    return rv;
+  }
+
+  // URIFixup's keyword and alternate flags can only fixup to http/https, so we
+  // can skip testing them. This simplifies our life because this code can be
+  // invoked from the content process where the search service would not be
+  // available.
+  uint32_t flags[] = {nsIURIFixup::FIXUP_FLAG_NONE,
+                      nsIURIFixup::FIXUP_FLAG_FIX_SCHEME_TYPOS};
+  for (uint32_t i = 0; i < ArrayLength(flags); ++i) {
+    uint32_t fixupFlags = flags[i];
+    if (aPrincipal->OriginAttributesRef().mPrivateBrowsingId > 0) {
+      fixupFlags |= nsIURIFixup::FIXUP_FLAG_PRIVATE_CONTEXT;
+    }
+    nsCOMPtr<nsIURIFixupInfo> fixupInfo;
+    rv = fixup->GetFixupURIInfo(aTargetURIStr, fixupFlags,
+                                getter_AddRefs(fixupInfo));
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = fixupInfo->GetPreferredURI(getter_AddRefs(target));
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    rv = CheckLoadURIWithPrincipal(aPrincipal, target, aFlags, 0);
+    if (rv == NS_ERROR_DOM_BAD_URI) {
+      // Don't warn because NS_ERROR_DOM_BAD_URI is one of the expected
+      // return values.
+      return rv;
+    }
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  return rv;
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::CheckLoadURIWithPrincipalFromJS(
+    nsIPrincipal* aPrincipal, nsIURI* aTargetURI, uint32_t aFlags,
+    uint64_t aInnerWindowID, JSContext* aCx) {
+  MOZ_ASSERT(aPrincipal,
+             "CheckLoadURIWithPrincipalFromJS must have a principal");
+  NS_ENSURE_ARG_POINTER(aPrincipal);
+  NS_ENSURE_ARG_POINTER(aTargetURI);
+
+  nsresult rv =
+      CheckLoadURIWithPrincipal(aPrincipal, aTargetURI, aFlags, aInnerWindowID);
+  if (NS_FAILED(rv)) {
+    nsAutoCString uriStr;
+    Unused << aTargetURI->GetSpec(uriStr);
+
+    nsAutoCString message("Load of ");
+    message.Append(uriStr);
+
+    nsAutoCString principalStr;
+    Unused << aPrincipal->GetSpec(principalStr);
+    if (!principalStr.IsEmpty()) {
+      message.AppendPrintf(" from %s", principalStr.get());
+    }
+
+    message.Append(" denied");
+
+    dom::Throw(aCx, rv, message);
+  }
+
+  return rv;
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::CheckLoadURIStrWithPrincipalFromJS(
+    nsIPrincipal* aPrincipal, const nsACString& aTargetURIStr, uint32_t aFlags,
+    JSContext* aCx) {
+  nsCOMPtr<nsIURI> targetURI;
+  MOZ_TRY(NS_NewURI(getter_AddRefs(targetURI), aTargetURIStr));
+
+  return CheckLoadURIWithPrincipalFromJS(aPrincipal, targetURI, aFlags, 0, aCx);
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::InFileURIAllowlist(nsIURI* aUri, bool* aResult) {
+  MOZ_ASSERT(aUri);
+  MOZ_ASSERT(aResult);
+
+  *aResult = false;
+  for (nsIURI* uri : EnsureFileURIAllowlist()) {
+    if (EqualOrSubdomain(aUri, uri)) {
+      *aResult = true;
+      return NS_OK;
+    }
+  }
+
+  return NS_OK;
+}
+
+///////////////// Principals ///////////////////////
+
+NS_IMETHODIMP
+nsScriptSecurityManager::GetSystemPrincipal(nsIPrincipal** result) {
+  NS_ADDREF(*result = mSystemPrincipal);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::CreateContentPrincipal(
+    nsIURI* aURI, JS::Handle<JS::Value> aOriginAttributes, JSContext* aCx,
+    nsIPrincipal** aPrincipal) {
+  OriginAttributes attrs;
+  if (!aOriginAttributes.isObject() || !attrs.Init(aCx, aOriginAttributes)) {
+    return NS_ERROR_INVALID_ARG;
+  }
+  nsCOMPtr<nsIPrincipal> prin =
+      BasePrincipal::CreateContentPrincipal(aURI, attrs);
+  prin.forget(aPrincipal);
+  return *aPrincipal ? NS_OK : NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::CreateContentPrincipalFromOrigin(
+    const nsACString& aOrigin, nsIPrincipal** aPrincipal) {
+  if (StringBeginsWith(aOrigin, "["_ns)) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  if (StringBeginsWith(aOrigin,
+                       nsLiteralCString(NS_NULLPRINCIPAL_SCHEME ":"))) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  nsCOMPtr<nsIPrincipal> prin = BasePrincipal::CreateContentPrincipal(aOrigin);
+  prin.forget(aPrincipal);
+  return *aPrincipal ? NS_OK : NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::PrincipalToJSON(nsIPrincipal* aPrincipal,
+                                         nsACString& aJSON) {
+  aJSON.Truncate();
+  if (!aPrincipal) {
+    return NS_ERROR_FAILURE;
+  }
+
+  BasePrincipal::Cast(aPrincipal)->ToJSON(aJSON);
+
+  if (aJSON.IsEmpty()) {
+    return NS_ERROR_FAILURE;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::JSONToPrincipal(const nsACString& aJSON,
+                                         nsIPrincipal** aPrincipal) {
+  if (aJSON.IsEmpty()) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsCOMPtr<nsIPrincipal> principal = BasePrincipal::FromJSON(aJSON);
+
+  if (!principal) {
+    return NS_ERROR_FAILURE;
+  }
+
+  principal.forget(aPrincipal);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::CreateNullPrincipal(
+    JS::Handle<JS::Value> aOriginAttributes, JSContext* aCx,
+    nsIPrincipal** aPrincipal) {
+  OriginAttributes attrs;
+  if (!aOriginAttributes.isObject() || !attrs.Init(aCx, aOriginAttributes)) {
+    return NS_ERROR_INVALID_ARG;
+  }
+  nsCOMPtr<nsIPrincipal> prin = NullPrincipal::Create(attrs);
+  prin.forget(aPrincipal);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::GetLoadContextContentPrincipal(
+    nsIURI* aURI, nsILoadContext* aLoadContext, nsIPrincipal** aPrincipal) {
+  NS_ENSURE_STATE(aLoadContext);
+  OriginAttributes docShellAttrs;
+  aLoadContext->GetOriginAttributes(docShellAttrs);
+
+  nsCOMPtr<nsIPrincipal> prin =
+      BasePrincipal::CreateContentPrincipal(aURI, docShellAttrs);
+  prin.forget(aPrincipal);
+  return *aPrincipal ? NS_OK : NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::GetDocShellContentPrincipal(
+    nsIURI* aURI, nsIDocShell* aDocShell, nsIPrincipal** aPrincipal) {
+  nsCOMPtr<nsIPrincipal> prin = BasePrincipal::CreateContentPrincipal(
+      aURI, nsDocShell::Cast(aDocShell)->GetOriginAttributes());
+  prin.forget(aPrincipal);
+  return *aPrincipal ? NS_OK : NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::PrincipalWithOA(
+    nsIPrincipal* aPrincipal, JS::Handle<JS::Value> aOriginAttributes,
+    JSContext* aCx, nsIPrincipal** aReturnPrincipal) {
+  if (!aPrincipal) {
+    return NS_OK;
+  }
+  if (aPrincipal->GetIsContentPrincipal()) {
+    OriginAttributes attrs;
+    if (!aOriginAttributes.isObject() || !attrs.Init(aCx, aOriginAttributes)) {
+      return NS_ERROR_INVALID_ARG;
+    }
+    auto* contentPrincipal = static_cast<ContentPrincipal*>(aPrincipal);
+    RefPtr<ContentPrincipal> copy =
+        new ContentPrincipal(contentPrincipal, attrs);
+    NS_ENSURE_TRUE(copy, NS_ERROR_FAILURE);
+    copy.forget(aReturnPrincipal);
+  } else {
+    // We do this for null principals, system principals (both fine)
+    // ... and expanded principals, where we should probably do something
+    // cleverer, but I also don't think we care too much.
+    nsCOMPtr<nsIPrincipal> prin = aPrincipal;
+    prin.forget(aReturnPrincipal);
+  }
+
+  return *aReturnPrincipal ? NS_OK : NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::CanCreateWrapper(JSContext* cx, const nsIID& aIID,
+                                          nsISupports* aObj,
+                                          nsIClassInfo* aClassInfo) {
+  // XXX Special case for Exception ?
+
+  // We give remote-XUL allowlisted domains a free pass here. See bug 932906.
+  JS::Rooted<JS::Realm*> contextRealm(cx, JS::GetCurrentRealmOrNull(cx));
+  MOZ_RELEASE_ASSERT(contextRealm);
+  if (!xpc::AllowContentXBLScope(contextRealm)) {
+    return NS_OK;
+  }
+
+  if (nsContentUtils::IsCallerChrome()) {
+    return NS_OK;
+  }
+
+  //-- Access denied, report an error
+  nsAutoCString originUTF8;
+  nsIPrincipal* subjectPrincipal = nsContentUtils::SubjectPrincipal();
+  GetPrincipalDomainOrigin(subjectPrincipal, originUTF8);
+  NS_ConvertUTF8toUTF16 originUTF16(originUTF8);
+  nsAutoCString classInfoNameUTF8;
+  if (aClassInfo) {
+    aClassInfo->GetClassDescription(classInfoNameUTF8);
+  }
+  if (classInfoNameUTF8.IsEmpty()) {
+    classInfoNameUTF8.AssignLiteral("UnnamedClass");
+  }
+
+  nsCOMPtr<nsIStringBundle> bundle = BundleHelper::GetOrCreate();
+  if (NS_WARN_IF(!bundle)) {
+    return NS_OK;
+  }
+
+  NS_ConvertUTF8toUTF16 classInfoUTF16(classInfoNameUTF8);
+  nsresult rv;
+  nsAutoString errorMsg;
+  if (originUTF16.IsEmpty()) {
+    AutoTArray<nsString, 1> formatStrings = {classInfoUTF16};
+    rv = bundle->FormatStringFromName("CreateWrapperDenied", formatStrings,
+                                      errorMsg);
+  } else {
+    AutoTArray<nsString, 2> formatStrings = {classInfoUTF16, originUTF16};
+    rv = bundle->FormatStringFromName("CreateWrapperDeniedForOrigin",
+                                      formatStrings, errorMsg);
+  }
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  SetPendingException(cx, errorMsg.get());
+  return NS_ERROR_DOM_XPCONNECT_ACCESS_DENIED;
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::CanCreateInstance(JSContext* cx, const nsCID& aCID) {
+  if (nsContentUtils::IsCallerChrome()) {
+    return NS_OK;
+  }
+
+  //-- Access denied, report an error
+  nsAutoCString errorMsg("Permission denied to create instance of class. CID=");
+  char cidStr[NSID_LENGTH];
+  aCID.ToProvidedString(cidStr);
+  errorMsg.Append(cidStr);
+  SetPendingExceptionASCII(cx, errorMsg.get());
+  return NS_ERROR_DOM_XPCONNECT_ACCESS_DENIED;
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::CanGetService(JSContext* cx, const nsCID& aCID) {
+  if (nsContentUtils::IsCallerChrome()) {
+    return NS_OK;
+  }
+
+  //-- Access denied, report an error
+  nsAutoCString errorMsg("Permission denied to get service. CID=");
+  char cidStr[NSID_LENGTH];
+  aCID.ToProvidedString(cidStr);
+  errorMsg.Append(cidStr);
+  SetPendingExceptionASCII(cx, errorMsg.get());
+  return NS_ERROR_DOM_XPCONNECT_ACCESS_DENIED;
+}
+
+const char sJSEnabledPrefName[] = "javascript.enabled";
+const char sFileOriginPolicyPrefName[] =
+    "security.fileuri.strict_origin_policy";
+
+static const char* kObservedPrefs[] = {sJSEnabledPrefName,
+                                       sFileOriginPolicyPrefName,
+                                       "capability.policy.", nullptr};
+
+/////////////////////////////////////////////
+// Constructor, Destructor, Initialization //
+/////////////////////////////////////////////
+nsScriptSecurityManager::nsScriptSecurityManager(void)
+    : mPrefInitialized(false), mIsJavaScriptEnabled(false) {
+  static_assert(
+      sizeof(intptr_t) == sizeof(void*),
+      "intptr_t and void* have different lengths on this platform. "
+      "This may cause a security failure with the SecurityLevel union.");
+}
+
+nsresult nsScriptSecurityManager::Init() {
+  nsresult rv;
+  RefPtr<nsIIOService> io = mozilla::components::IO::Service(&rv);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+  sIOService = std::move(io);
+  InitPrefs();
+
+  // Create our system principal singleton
+  mSystemPrincipal = SystemPrincipal::Init();
+
+  return NS_OK;
+}
+
+void nsScriptSecurityManager::InitJSCallbacks(JSContext* aCx) {
+  //-- Register security check callback in the JS engine
+  //   Currently this is used to control access to function.caller
+
+  static const JSSecurityCallbacks securityCallbacks = {
+      ContentSecurityPolicyPermitsJSAction,
+      JSPrincipalsSubsume,
+  };
+
+  MOZ_ASSERT(!JS_GetSecurityCallbacks(aCx));
+  JS_SetSecurityCallbacks(aCx, &securityCallbacks);
+  JS_InitDestroyPrincipalsCallback(aCx, nsJSPrincipals::Destroy);
+
+  JS_SetTrustedPrincipals(aCx, BasePrincipal::Cast(mSystemPrincipal));
+}
+
+/* static */
+void nsScriptSecurityManager::ClearJSCallbacks(JSContext* aCx) {
+  JS_SetSecurityCallbacks(aCx, nullptr);
+  JS_SetTrustedPrincipals(aCx, nullptr);
+}
+
+static StaticRefPtr<nsScriptSecurityManager> gScriptSecMan;
+
+nsScriptSecurityManager::~nsScriptSecurityManager(void) {
+  Preferences::UnregisterPrefixCallbacks(
+      nsScriptSecurityManager::ScriptSecurityPrefChanged, kObservedPrefs, this);
+  if (mDomainPolicy) {
+    mDomainPolicy->Deactivate();
+  }
+  // ContentChild might hold a reference to the domain policy,
+  // and it might release it only after the security manager is
+  // gone. But we can still assert this for the main process.
+  MOZ_ASSERT_IF(XRE_IsParentProcess(), !mDomainPolicy);
+}
+
+void nsScriptSecurityManager::Shutdown() {
+  sIOService = nullptr;
+  BundleHelper::Shutdown();
+  SystemPrincipal::Shutdown();
+}
+
+nsScriptSecurityManager* nsScriptSecurityManager::GetScriptSecurityManager() {
+  return gScriptSecMan;
+}
+
+/* static */
+void nsScriptSecurityManager::InitStatics() {
+  RefPtr<nsScriptSecurityManager> ssManager = new nsScriptSecurityManager();
+  nsresult rv = ssManager->Init();
+  if (NS_FAILED(rv)) {
+    MOZ_CRASH("ssManager->Init() failed");
+  }
+
+  ClearOnShutdown(&gScriptSecMan);
+  gScriptSecMan = ssManager;
+}
+
+// Currently this nsGenericFactory constructor is used only from FastLoad
+// (XPCOM object deserialization) code, when "creating" the system principal
+// singleton.
+already_AddRefed<SystemPrincipal>
+nsScriptSecurityManager::SystemPrincipalSingletonConstructor() {
+  if (gScriptSecMan)
+    return do_AddRef(gScriptSecMan->mSystemPrincipal)
+        .downcast<SystemPrincipal>();
+  return nullptr;
+}
+
+struct IsWhitespace {
+  static bool Test(char aChar) { return NS_IsAsciiWhitespace(aChar); };
+};
+struct IsWhitespaceOrComma {
+  static bool Test(char aChar) {
+    return aChar == ',' || NS_IsAsciiWhitespace(aChar);
+  };
+};
+
+template <typename Predicate>
+uint32_t SkipPast(const nsCString& str, uint32_t base) {
+  while (base < str.Length() && Predicate::Test(str[base])) {
+    ++base;
+  }
+  return base;
+}
+
+template <typename Predicate>
+uint32_t SkipUntil(const nsCString& str, uint32_t base) {
+  while (base < str.Length() && !Predicate::Test(str[base])) {
+    ++base;
+  }
+  return base;
+}
+
+// static
+void nsScriptSecurityManager::ScriptSecurityPrefChanged(const char* aPref,
+                                                        void* aSelf) {
+  static_cast<nsScriptSecurityManager*>(aSelf)->ScriptSecurityPrefChanged(
+      aPref);
+}
+
+inline void nsScriptSecurityManager::ScriptSecurityPrefChanged(
+    const char* aPref) {
+  MOZ_ASSERT(mPrefInitialized);
+  mIsJavaScriptEnabled =
+      Preferences::GetBool(sJSEnabledPrefName, mIsJavaScriptEnabled);
+  sStrictFileOriginPolicy =
+      Preferences::GetBool(sFileOriginPolicyPrefName, false);
+  mFileURIAllowlist.reset();
+}
+
+void nsScriptSecurityManager::AddSitesToFileURIAllowlist(
+    const nsCString& aSiteList) {
+  for (uint32_t base = SkipPast<IsWhitespace>(aSiteList, 0), bound = 0;
+       base < aSiteList.Length();
+       base = SkipPast<IsWhitespace>(aSiteList, bound)) {
+    // Grab the current site.
+    bound = SkipUntil<IsWhitespace>(aSiteList, base);
+    nsAutoCString site(Substring(aSiteList, base, bound - base));
+
+    // Check if the URI is schemeless. If so, add both http and https.
+    nsAutoCString unused;
+    if (NS_FAILED(sIOService->ExtractScheme(site, unused))) {
+      AddSitesToFileURIAllowlist("http://"_ns + site);
+      AddSitesToFileURIAllowlist("https://"_ns + site);
+      continue;
+    }
+
+    // Convert it to a URI and add it to our list.
+    nsCOMPtr<nsIURI> uri;
+    nsresult rv = NS_NewURI(getter_AddRefs(uri), site);
+    if (NS_SUCCEEDED(rv)) {
+      mFileURIAllowlist.ref().AppendElement(uri);
+    } else {
+      nsCOMPtr<nsIConsoleService> console(
+          do_GetService("@mozilla.org/consoleservice;1"));
+      if (console) {
+        nsAutoString msg =
+            u"Unable to to add site to file:// URI allowlist: "_ns +
+            NS_ConvertASCIItoUTF16(site);
+        console->LogStringMessage(msg.get());
+      }
+    }
+  }
+}
+
+nsresult nsScriptSecurityManager::InitPrefs() {
+  nsIPrefBranch* branch = Preferences::GetRootBranch();
+  NS_ENSURE_TRUE(branch, NS_ERROR_FAILURE);
+
+  mPrefInitialized = true;
+
+  // Set the initial value of the "javascript.enabled" prefs
+  ScriptSecurityPrefChanged();
+
+  // set observer callbacks in case the value of the prefs change
+  Preferences::RegisterPrefixCallbacks(
+      nsScriptSecurityManager::ScriptSecurityPrefChanged, kObservedPrefs, this);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::GetDomainPolicyActive(bool* aRv) {
+  *aRv = !!mDomainPolicy;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::ActivateDomainPolicy(nsIDomainPolicy** aRv) {
+  if (!XRE_IsParentProcess()) {
+    return NS_ERROR_SERVICE_NOT_AVAILABLE;
+  }
+
+  return ActivateDomainPolicyInternal(aRv);
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::ActivateDomainPolicyInternal(nsIDomainPolicy** aRv) {
+  // We only allow one domain policy at a time. The holder of the previous
+  // policy must explicitly deactivate it first.
+  if (mDomainPolicy) {
+    return NS_ERROR_SERVICE_NOT_AVAILABLE;
+  }
+
+  mDomainPolicy = new DomainPolicy();
+  nsCOMPtr<nsIDomainPolicy> ptr = mDomainPolicy;
+  ptr.forget(aRv);
+  return NS_OK;
+}
+
+// Intentionally non-scriptable. Script must have a reference to the
+// nsIDomainPolicy to deactivate it.
+void nsScriptSecurityManager::DeactivateDomainPolicy() {
+  mDomainPolicy = nullptr;
+}
+
+void nsScriptSecurityManager::CloneDomainPolicy(DomainPolicyClone* aClone) {
+  MOZ_ASSERT(aClone);
+  if (mDomainPolicy) {
+    mDomainPolicy->CloneDomainPolicy(aClone);
+  } else {
+    aClone->active() = false;
+  }
+}
+
+NS_IMETHODIMP
+nsScriptSecurityManager::PolicyAllowsScript(nsIURI* aURI, bool* aRv) {
+  nsresult rv;
+
+  // Compute our rule. If we don't have any domain policy set up that might
+  // provide exceptions to this rule, we're done.
+  *aRv = mIsJavaScriptEnabled;
+  if (!mDomainPolicy) {
+    return NS_OK;
+  }
+
+  // We have a domain policy. Grab the appropriate set of exceptions to the
+  // rule (either the blocklist or the allowlist, depending on whether script
+  // is enabled or disabled by default).
+  nsCOMPtr<nsIDomainSet> exceptions;
+  nsCOMPtr<nsIDomainSet> superExceptions;
+  if (*aRv) {
+    mDomainPolicy->GetBlocklist(getter_AddRefs(exceptions));
+    mDomainPolicy->GetSuperBlocklist(getter_AddRefs(superExceptions));
+  } else {
+    mDomainPolicy->GetAllowlist(getter_AddRefs(exceptions));
+    mDomainPolicy->GetSuperAllowlist(getter_AddRefs(superExceptions));
+  }
+
+  bool contains;
+  rv = exceptions->Contains(aURI, &contains);
+  NS_ENSURE_SUCCESS(rv, rv);
+  if (contains) {
+    *aRv = !*aRv;
+    return NS_OK;
+  }
+  rv = superExceptions->ContainsSuperDomain(aURI, &contains);
+  NS_ENSURE_SUCCESS(rv, rv);
+  if (contains) {
+    *aRv = !*aRv;
+  }
+
+  return NS_OK;
+}
+
+const nsTArray<nsCOMPtr<nsIURI>>&
+nsScriptSecurityManager::EnsureFileURIAllowlist() {
+  if (mFileURIAllowlist.isSome()) {
+    return mFileURIAllowlist.ref();
+  }
+
+  //
+  // Rebuild the set of principals for which we allow file:// URI loads. This
+  // implements a small subset of an old pref-based CAPS people that people
+  // have come to depend on. See bug 995943.
+  //
+
+  mFileURIAllowlist.emplace();
+  nsAutoCString policies;
+  mozilla::Preferences::GetCString("capability.policy.policynames", policies);
+  for (uint32_t base = SkipPast<IsWhitespaceOrComma>(policies, 0), bound = 0;
+       base < policies.Length();
+       base = SkipPast<IsWhitespaceOrComma>(policies, bound)) {
+    // Grab the current policy name.
+    bound = SkipUntil<IsWhitespaceOrComma>(policies, base);
+    auto policyName = Substring(policies, base, bound - base);
+
+    // Figure out if this policy allows loading file:// URIs. If not, we can
+    // skip it.
+    nsCString checkLoadURIPrefName =
+        "capability.policy."_ns + policyName + ".checkloaduri.enabled"_ns;
+    nsAutoString value;
+    nsresult rv = Preferences::GetString(checkLoadURIPrefName.get(), value);
+    if (NS_FAILED(rv) || !value.LowerCaseEqualsLiteral("allaccess")) {
+      continue;
+    }
+
+    // Grab the list of domains associated with this policy.
+    nsCString domainPrefName =
+        "capability.policy."_ns + policyName + ".sites"_ns;
+    nsAutoCString siteList;
+    Preferences::GetCString(domainPrefName.get(), siteList);
+    AddSitesToFileURIAllowlist(siteList);
+  }
+
+  return mFileURIAllowlist.ref();
+}
diff --git a/caps/nsScriptSecurityManager.h b/caps/nsScriptSecurityManager.h
new file mode 100644
index 0000000000..bc55a70ad6
--- /dev/null
+++ b/caps/nsScriptSecurityManager.h
@@ -0,0 +1,142 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=4 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsScriptSecurityManager_h__
+#define nsScriptSecurityManager_h__
+
+#include "nsIScriptSecurityManager.h"
+
+#include "mozilla/Maybe.h"
+#include "nsIPrincipal.h"
+#include "nsCOMPtr.h"
+#include "nsServiceManagerUtils.h"
+#include "nsStringFwd.h"
+#include "js/TypeDecls.h"
+
+#include <stdint.h>
+
+class nsIIOService;
+class nsIStringBundle;
+
+namespace mozilla {
+class OriginAttributes;
+class SystemPrincipal;
+}  // namespace mozilla
+
+namespace JS {
+enum class RuntimeCode;
+}  // namespace JS
+
+/////////////////////////////
+// nsScriptSecurityManager //
+/////////////////////////////
+#define NS_SCRIPTSECURITYMANAGER_CID                 \
+  {                                                  \
+    0x7ee2a4c0, 0x4b93, 0x17d3, {                    \
+      0xba, 0x18, 0x00, 0x60, 0xb0, 0xf1, 0x99, 0xa2 \
+    }                                                \
+  }
+
+class nsScriptSecurityManager final : public nsIScriptSecurityManager {
+ public:
+  static void Shutdown();
+
+  NS_DEFINE_STATIC_CID_ACCESSOR(NS_SCRIPTSECURITYMANAGER_CID)
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSISCRIPTSECURITYMANAGER
+
+  static nsScriptSecurityManager* GetScriptSecurityManager();
+
+  // Invoked exactly once, by XPConnect.
+  static void InitStatics();
+
+  void InitJSCallbacks(JSContext* aCx);
+
+  // This has to be static because it is called after gScriptSecMan is cleared.
+  static void ClearJSCallbacks(JSContext* aCx);
+
+  static already_AddRefed<mozilla::SystemPrincipal>
+  SystemPrincipalSingletonConstructor();
+
+  /**
+   * Utility method for comparing two URIs.  For security purposes, two URIs
+   * are equivalent if their schemes, hosts, and ports (if any) match.  This
+   * method returns true if aSubjectURI and aObjectURI have the same origin,
+   * false otherwise.
+   */
+  static bool SecurityCompareURIs(nsIURI* aSourceURI, nsIURI* aTargetURI);
+  static uint32_t SecurityHashURI(nsIURI* aURI);
+
+  static nsresult ReportError(const char* aMessageTag, nsIURI* aSource,
+                              nsIURI* aTarget, bool aFromPrivateWindow,
+                              uint64_t aInnerWindowID = 0);
+  static nsresult ReportError(const char* aMessageTag,
+                              const nsACString& sourceSpec,
+                              const nsACString& targetSpec,
+                              bool aFromPrivateWindow,
+                              uint64_t aInnerWindowID = 0);
+
+  static uint32_t HashPrincipalByOrigin(nsIPrincipal* aPrincipal);
+
+  static bool GetStrictFileOriginPolicy() { return sStrictFileOriginPolicy; }
+
+  void DeactivateDomainPolicy();
+
+ private:
+  // GetScriptSecurityManager is the only call that can make one
+  nsScriptSecurityManager();
+  virtual ~nsScriptSecurityManager();
+
+  // Decides, based on CSP, whether or not eval() and stuff can be executed.
+  static bool ContentSecurityPolicyPermitsJSAction(JSContext* cx,
+                                                   JS::RuntimeCode kind,
+                                                   JS::Handle<JSString*> aCode);
+
+  static bool JSPrincipalsSubsume(JSPrincipals* first, JSPrincipals* second);
+
+  nsresult Init();
+
+  nsresult InitPrefs();
+
+  static void ScriptSecurityPrefChanged(const char* aPref, void* aSelf);
+  void ScriptSecurityPrefChanged(const char* aPref = nullptr);
+
+  inline void AddSitesToFileURIAllowlist(const nsCString& aSiteList);
+
+  nsresult GetChannelResultPrincipal(nsIChannel* aChannel,
+                                     nsIPrincipal** aPrincipal,
+                                     bool aIgnoreSandboxing);
+
+  nsresult CheckLoadURIFlags(nsIURI* aSourceURI, nsIURI* aTargetURI,
+                             nsIURI* aSourceBaseURI, nsIURI* aTargetBaseURI,
+                             uint32_t aFlags, bool aFromPrivateWindow,
+                             uint64_t aInnerWindowID);
+
+  // Returns the file URI allowlist, initializing it if it has not been
+  // initialized.
+  const nsTArray<nsCOMPtr<nsIURI>>& EnsureFileURIAllowlist();
+
+  nsCOMPtr<nsIPrincipal> mSystemPrincipal;
+  bool mPrefInitialized;
+  bool mIsJavaScriptEnabled;
+
+  // List of URIs whose domains and sub-domains are allowlisted to allow
+  // access to file: URIs.  Lazily initialized; isNothing() when not yet
+  // initialized.
+  mozilla::Maybe<nsTArray<nsCOMPtr<nsIURI>>> mFileURIAllowlist;
+
+  // This machinery controls new-style domain policies. The old-style
+  // policy machinery will be removed soon.
+  nsCOMPtr<nsIDomainPolicy> mDomainPolicy;
+
+  static std::atomic<bool> sStrictFileOriginPolicy;
+
+  static mozilla::StaticRefPtr<nsIIOService> sIOService;
+  static nsIStringBundle* sStrBundle;
+};
+
+#endif  // nsScriptSecurityManager_h__
diff --git a/caps/tests/gtest/TestBackgroundThreadPrincipal.cpp b/caps/tests/gtest/TestBackgroundThreadPrincipal.cpp
new file mode 100644
index 0000000000..82c7b15757
--- /dev/null
+++ b/caps/tests/gtest/TestBackgroundThreadPrincipal.cpp
@@ -0,0 +1,94 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#include "gtest/gtest.h"
+#include "mozilla/gtest/MozAssertions.h"
+#include "mozilla/BasePrincipal.h"
+#include "mozilla/ContentPrincipal.h"
+#include "mozilla/NullPrincipal.h"
+#include "mozilla/ipc/BackgroundUtils.h"
+#include "mozilla/ipc/PBackgroundSharedTypes.h"
+#include "nsIEventTarget.h"
+#include "nsISerialEventTarget.h"
+#include "nsIURIMutator.h"
+#include "nsNetUtil.h"
+#include "nsPrintfCString.h"
+#include "nsThreadUtils.h"
+
+namespace mozilla {
+
+template <typename F>
+void RunOnBackgroundThread(F&& aFunction) {
+  nsCOMPtr<nsISerialEventTarget> backgroundQueue;
+  ASSERT_NS_SUCCEEDED(NS_CreateBackgroundTaskQueue(
+      "RunOnBackgroundThread", getter_AddRefs(backgroundQueue)));
+  ASSERT_NS_SUCCEEDED(NS_DispatchAndSpinEventLoopUntilComplete(
+      "RunOnBackgroundThread"_ns, backgroundQueue,
+      NS_NewRunnableFunction("RunOnBackgroundThread",
+                             std::forward<F>(aFunction))));
+}
+
+TEST(BackgroundThreadPrincipal, CreateContent)
+{
+  RunOnBackgroundThread([] {
+    nsCOMPtr<nsIURI> contentURI;
+    ASSERT_NS_SUCCEEDED(NS_NewURI(getter_AddRefs(contentURI),
+                                  "http://subdomain.example.com:8000"_ns));
+    RefPtr<BasePrincipal> contentPrincipal =
+        BasePrincipal::CreateContentPrincipal(contentURI, OriginAttributes());
+    EXPECT_TRUE(contentPrincipal->Is<ContentPrincipal>());
+
+    nsCString origin;
+    ASSERT_NS_SUCCEEDED(contentPrincipal->GetOrigin(origin));
+    EXPECT_EQ(origin, "http://subdomain.example.com:8000"_ns);
+
+    nsCString siteOrigin;
+    ASSERT_NS_SUCCEEDED(contentPrincipal->GetSiteOrigin(siteOrigin));
+    EXPECT_EQ(siteOrigin, "http://example.com"_ns);
+  });
+}
+
+TEST(BackgroundThreadPrincipal, CreateNull)
+{
+  RunOnBackgroundThread([] {
+    nsCOMPtr<nsIURI> contentURI;
+    ASSERT_NS_SUCCEEDED(NS_NewURI(getter_AddRefs(contentURI),
+                                  "data:text/plain,hello world"_ns));
+    RefPtr<BasePrincipal> principal =
+        BasePrincipal::CreateContentPrincipal(contentURI, OriginAttributes());
+    EXPECT_TRUE(principal->Is<NullPrincipal>());
+
+    nsCString origin;
+    ASSERT_NS_SUCCEEDED(principal->GetOrigin(origin));
+    EXPECT_TRUE(StringBeginsWith(origin, "moz-nullprincipal:"_ns));
+  });
+}
+
+TEST(BackgroundThreadPrincipal, PrincipalInfoConversions)
+{
+  RunOnBackgroundThread([] {
+    nsCOMPtr<nsIURI> contentURI;
+    ASSERT_NS_SUCCEEDED(NS_NewURI(getter_AddRefs(contentURI),
+                                  "http://subdomain.example.com:8000"_ns));
+    RefPtr<BasePrincipal> contentPrincipal =
+        BasePrincipal::CreateContentPrincipal(contentURI, OriginAttributes());
+    EXPECT_TRUE(contentPrincipal->Is<ContentPrincipal>());
+
+    ipc::PrincipalInfo info;
+    ASSERT_NS_SUCCEEDED(ipc::PrincipalToPrincipalInfo(contentPrincipal, &info));
+
+    EXPECT_TRUE(info.type() == ipc::PrincipalInfo::TContentPrincipalInfo);
+    EXPECT_EQ(info.get_ContentPrincipalInfo().spec(),
+              "http://subdomain.example.com:8000/"_ns);
+    EXPECT_EQ(info.get_ContentPrincipalInfo().baseDomain(), "example.com"_ns);
+
+    auto result = PrincipalInfoToPrincipal(info);
+    ASSERT_TRUE(result.isOk());
+    nsCOMPtr<nsIPrincipal> deserialized = result.unwrap();
+    EXPECT_TRUE(deserialized->GetIsContentPrincipal());
+
+    EXPECT_TRUE(deserialized->Equals(contentPrincipal));
+  });
+}
+
+}  // namespace mozilla
diff --git a/caps/tests/gtest/TestNullPrincipalPrecursor.cpp b/caps/tests/gtest/TestNullPrincipalPrecursor.cpp
new file mode 100644
index 0000000000..96db5aeffd
--- /dev/null
+++ b/caps/tests/gtest/TestNullPrincipalPrecursor.cpp
@@ -0,0 +1,56 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#include "gtest/gtest.h"
+#include "mozilla/gtest/MozAssertions.h"
+#include "mozilla/NullPrincipal.h"
+#include "nsIURIMutator.h"
+#include "nsPrintfCString.h"
+
+namespace mozilla {
+
+TEST(NullPrincipalPrecursor, EscapingRoundTrips)
+{
+  nsTArray<nsCString> inputs;
+
+  inputs.AppendElements(mozilla::Span(std::array{
+      "mailbox:///dev/shm/tmp5wkt9ff_.mozrunner/Mail/Local%20Folders/secure-mail?number=5"_ns,
+  }));
+
+  // Add a string for every ASCII byte both escaped and unescaped.
+  for (uint8_t c = 0; c < 128; ++c) {
+    inputs.AppendElement(nsPrintfCString("%02X: %c", c, (char)c));
+    inputs.AppendElement(nsPrintfCString("%02X: %%%02X", c, c));
+  }
+
+  nsID dummyID{0xddf15eaf,
+               0x3837,
+               0x4678,
+               {0x80, 0x3b, 0x86, 0x86, 0xe8, 0x17, 0x66, 0x71}};
+  nsCOMPtr<nsIURI> baseURI = NullPrincipal::CreateURI(nullptr, &dummyID);
+  ASSERT_TRUE(baseURI);
+
+  for (auto& input : inputs) {
+    // First build an escaped version of the input string using
+    // `EscapePrecursorQuery`.
+    nsCString escaped(input);
+    NullPrincipal::EscapePrecursorQuery(escaped);
+
+    // Make sure that this escaped URI round-trips through a `moz-nullprincipal`
+    // URI's query without any additional escapes.
+    nsCOMPtr<nsIURI> clone;
+    EXPECT_NS_SUCCEEDED(
+        NS_MutateURI(baseURI).SetQuery(escaped).Finalize(clone));
+    nsCString query;
+    EXPECT_NS_SUCCEEDED(clone->GetQuery(query));
+    EXPECT_EQ(escaped, query);
+
+    // Try to unescape our escaped URI and make sure we recover the input
+    // string.
+    nsCString unescaped(escaped);
+    NullPrincipal::UnescapePrecursorQuery(unescaped);
+    EXPECT_EQ(input, unescaped);
+  }
+}
+
+}  // namespace mozilla
diff --git a/caps/tests/gtest/TestOriginAttributes.cpp b/caps/tests/gtest/TestOriginAttributes.cpp
new file mode 100644
index 0000000000..fa759f80d5
--- /dev/null
+++ b/caps/tests/gtest/TestOriginAttributes.cpp
@@ -0,0 +1,118 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#include "gtest/gtest.h"
+#include "mozilla/BasePrincipal.h"
+#include "mozilla/NullPrincipal.h"
+#include "mozilla/Preferences.h"
+#include "nsNetUtil.h"
+
+using mozilla::OriginAttributes;
+using mozilla::Preferences;
+
+#define FPI_PREF "privacy.firstparty.isolate"
+#define SITE_PREF "privacy.firstparty.isolate.use_site"
+
+#define TEST_FPD(_spec, _expected) \
+  TestFPD(nsLiteralString(_spec), nsLiteralString(_expected))
+
+namespace mozilla {
+
+static void TestSuffix(const OriginAttributes& attrs) {
+  nsAutoCString suffix;
+  attrs.CreateSuffix(suffix);
+
+  OriginAttributes attrsFromSuffix;
+  bool success = attrsFromSuffix.PopulateFromSuffix(suffix);
+  EXPECT_TRUE(success);
+
+  EXPECT_EQ(attrs, attrsFromSuffix);
+}
+
+static void TestFPD(const nsAString& spec, const nsAString& expected) {
+  OriginAttributes attrs;
+  nsCOMPtr<nsIURI> url;
+  ASSERT_EQ(NS_NewURI(getter_AddRefs(url), spec), NS_OK);
+  attrs.SetFirstPartyDomain(true, url);
+  EXPECT_TRUE(attrs.mFirstPartyDomain.Equals(expected));
+
+  TestSuffix(attrs);
+}
+
+TEST(OriginAttributes, Suffix_default)
+{
+  OriginAttributes attrs;
+  TestSuffix(attrs);
+}
+
+TEST(OriginAttributes, Suffix_inIsolatedMozBrowser)
+{
+  OriginAttributes attrs(true);
+  TestSuffix(attrs);
+}
+
+TEST(OriginAttributes, FirstPartyDomain_default)
+{
+  bool oldFpiPref = Preferences::GetBool(FPI_PREF);
+  Preferences::SetBool(FPI_PREF, true);
+  bool oldSitePref = Preferences::GetBool(SITE_PREF);
+  Preferences::SetBool(SITE_PREF, false);
+
+  TEST_FPD(u"http://www.example.com", u"example.com");
+  TEST_FPD(u"http://www.example.com:80", u"example.com");
+  TEST_FPD(u"http://www.example.com:8080", u"example.com");
+  TEST_FPD(u"http://s3.amazonaws.com", u"s3.amazonaws.com");
+  TEST_FPD(u"http://com", u"com");
+  TEST_FPD(u"http://com.", u"com.");
+  TEST_FPD(u"http://com:8080", u"com");
+  TEST_FPD(u"http://.com", u"");
+  TEST_FPD(u"http://..com", u"");
+  TEST_FPD(u"http://127.0.0.1", u"127.0.0.1");
+  TEST_FPD(u"http://[::1]", u"[::1]");
+  TEST_FPD(u"about:config",
+           u"about.ef2a7dd5-93bc-417f-a698-142c3116864f.mozilla");
+  TEST_FPD(u"moz-extension://f5b6ca10-5bd4-4ed6-9baf-820dc5152bc1", u"");
+  TEST_FPD(u"moz-nullprincipal:{9bebdabb-828a-4284-8b00-432a968c6e42}",
+           u"9bebdabb-828a-4284-8b00-432a968c6e42.mozilla");
+  TEST_FPD(
+      u"moz-nullprincipal:{9bebdabb-828a-4284-8b00-432a968c6e42}"
+      u"?https://www.example.com",
+      u"9bebdabb-828a-4284-8b00-432a968c6e42.mozilla");
+
+  Preferences::SetBool(FPI_PREF, oldFpiPref);
+  Preferences::SetBool(SITE_PREF, oldSitePref);
+}
+
+TEST(OriginAttributes, FirstPartyDomain_site)
+{
+  bool oldFpiPref = Preferences::GetBool(FPI_PREF);
+  Preferences::SetBool(FPI_PREF, true);
+  bool oldSitePref = Preferences::GetBool(SITE_PREF);
+  Preferences::SetBool(SITE_PREF, true);
+
+  TEST_FPD(u"http://www.example.com", u"(http,example.com)");
+  TEST_FPD(u"http://www.example.com:80", u"(http,example.com)");
+  TEST_FPD(u"http://www.example.com:8080", u"(http,example.com)");
+  TEST_FPD(u"http://s3.amazonaws.com", u"(http,s3.amazonaws.com)");
+  TEST_FPD(u"http://com", u"(http,com)");
+  TEST_FPD(u"http://com.", u"(http,com.)");
+  TEST_FPD(u"http://com:8080", u"(http,com,8080)");
+  TEST_FPD(u"http://.com", u"(http,.com)");
+  TEST_FPD(u"http://..com", u"(http,..com)");
+  TEST_FPD(u"http://127.0.0.1", u"(http,127.0.0.1)");
+  TEST_FPD(u"http://[::1]", u"(http,[::1])");
+  TEST_FPD(u"about:config",
+           u"(about,about.ef2a7dd5-93bc-417f-a698-142c3116864f.mozilla)");
+  TEST_FPD(u"moz-extension://f5b6ca10-5bd4-4ed6-9baf-820dc5152bc1", u"");
+  TEST_FPD(u"moz-nullprincipal:{9bebdabb-828a-4284-8b00-432a968c6e42}",
+           u"9bebdabb-828a-4284-8b00-432a968c6e42.mozilla");
+  TEST_FPD(
+      u"moz-nullprincipal:{9bebdabb-828a-4284-8b00-432a968c6e42}"
+      u"?https://www.example.com",
+      u"9bebdabb-828a-4284-8b00-432a968c6e42.mozilla");
+
+  Preferences::SetBool(FPI_PREF, oldFpiPref);
+  Preferences::SetBool(SITE_PREF, oldSitePref);
+}
+
+}  // namespace mozilla
diff --git a/caps/tests/gtest/TestPrincipalAttributes.cpp b/caps/tests/gtest/TestPrincipalAttributes.cpp
new file mode 100644
index 0000000000..bc0bff90f6
--- /dev/null
+++ b/caps/tests/gtest/TestPrincipalAttributes.cpp
@@ -0,0 +1,39 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#include "gtest/gtest.h"
+#include "mozilla/BasePrincipal.h"
+#include "nsScriptSecurityManager.h"
+
+using namespace mozilla;
+
+class PrincipalAttributesParam {
+ public:
+  nsAutoCString spec;
+  bool expectIsIpAddress;
+};
+
+class PrincipalAttributesTest
+    : public ::testing::TestWithParam<PrincipalAttributesParam> {};
+
+TEST_P(PrincipalAttributesTest, PrincipalAttributesTest) {
+  nsCOMPtr<nsIScriptSecurityManager> ssm =
+      nsScriptSecurityManager::GetScriptSecurityManager();
+
+  nsAutoCString spec(GetParam().spec);
+  nsCOMPtr<nsIPrincipal> principal;
+  nsresult rv =
+      ssm->CreateContentPrincipalFromOrigin(spec, getter_AddRefs(principal));
+  ASSERT_EQ(rv, NS_OK);
+
+  ASSERT_EQ(principal->GetIsIpAddress(), GetParam().expectIsIpAddress);
+}
+
+static const PrincipalAttributesParam kAttributes[] = {
+    {nsAutoCString("https://mozilla.com"), false},
+    {nsAutoCString("https://127.0.0.1"), true},
+    {nsAutoCString("https://[::1]"), true},
+};
+
+INSTANTIATE_TEST_SUITE_P(TestPrincipalAttributes, PrincipalAttributesTest,
+                         ::testing::ValuesIn(kAttributes));
diff --git a/caps/tests/gtest/TestPrincipalSerialization.cpp b/caps/tests/gtest/TestPrincipalSerialization.cpp
new file mode 100644
index 0000000000..159cf1c269
--- /dev/null
+++ b/caps/tests/gtest/TestPrincipalSerialization.cpp
@@ -0,0 +1,214 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#include "gtest/gtest.h"
+#include "mozilla/Base64.h"
+#include "mozilla/BasePrincipal.h"
+#include "mozilla/ContentPrincipal.h"
+#include "mozilla/NullPrincipal.h"
+#include "mozilla/SystemPrincipal.h"
+#include "mozilla/ExpandedPrincipal.h"
+
+using mozilla::BasePrincipal;
+using mozilla::ContentPrincipal;
+using mozilla::NullPrincipal;
+using mozilla::SystemPrincipal;
+
+// None of these tests work in debug due to assert guards
+#ifndef MOZ_DEBUG
+
+// calling toJson() twice with the same string arg
+// (ensure that we truncate correctly where needed)
+TEST(PrincipalSerialization, ReusedJSONArgument)
+{
+  nsCOMPtr<nsIScriptSecurityManager> ssm =
+      nsScriptSecurityManager::GetScriptSecurityManager();
+
+  nsAutoCString spec("https://mozilla.com");
+  nsCOMPtr<nsIPrincipal> principal;
+  nsresult rv =
+      ssm->CreateContentPrincipalFromOrigin(spec, getter_AddRefs(principal));
+  ASSERT_EQ(rv, NS_OK);
+
+  nsAutoCString JSON;
+  rv = BasePrincipal::Cast(principal)->ToJSON(JSON);
+  ASSERT_EQ(rv, NS_OK);
+  ASSERT_TRUE(JSON.EqualsLiteral("{\"1\":{\"0\":\"https://mozilla.com/\"}}"));
+
+  nsAutoCString spec2("https://example.com");
+  nsCOMPtr<nsIPrincipal> principal2;
+  rv = ssm->CreateContentPrincipalFromOrigin(spec2, getter_AddRefs(principal2));
+  ASSERT_EQ(rv, NS_OK);
+
+  // Reuse JSON without truncation to check the code is doing this
+  rv = BasePrincipal::Cast(principal2)->ToJSON(JSON);
+  ASSERT_EQ(rv, NS_OK);
+  ASSERT_TRUE(JSON.EqualsLiteral("{\"1\":{\"0\":\"https://example.com/\"}}"));
+}
+
+// Assure that calling FromProperties() with an empty array list always returns
+// a nullptr The exception here is SystemPrincipal which doesn't have fields but
+// it also doesn't implement FromProperties These are overly cautious checks
+// that we don't try to create a principal in reality FromProperties is only
+// called with a populated array.
+TEST(PrincipalSerialization, FromPropertiesEmpty)
+{
+  nsTArray<ContentPrincipal::KeyVal> resContent;
+  nsCOMPtr<nsIPrincipal> contentPrincipal =
+      ContentPrincipal::FromProperties(resContent);
+  ASSERT_EQ(nullptr, contentPrincipal);
+
+  nsTArray<ExpandedPrincipal::KeyVal> resExpanded;
+  nsCOMPtr<nsIPrincipal> expandedPrincipal =
+      ExpandedPrincipal::FromProperties(resExpanded);
+  ASSERT_EQ(nullptr, expandedPrincipal);
+
+  nsTArray<NullPrincipal::KeyVal> resNull;
+  nsCOMPtr<nsIPrincipal> nullprincipal = NullPrincipal::FromProperties(resNull);
+  ASSERT_EQ(nullptr, nullprincipal);
+}
+
+// Double check that if we have two valid principals in a serialized JSON that
+// nullptr is returned
+TEST(PrincipalSerialization, TwoKeys)
+{
+  // Sanity check that this returns a system principal
+  nsCOMPtr<nsIPrincipal> systemPrincipal =
+      BasePrincipal::FromJSON("{\"3\":{}}"_ns);
+  ASSERT_EQ(BasePrincipal::Cast(systemPrincipal)->Kind(),
+            BasePrincipal::eSystemPrincipal);
+
+  // Sanity check that this returns a content principal
+  nsCOMPtr<nsIPrincipal> contentPrincipal =
+      BasePrincipal::FromJSON("{\"1\":{\"0\":\"https://mozilla.com\"}}"_ns);
+  ASSERT_EQ(BasePrincipal::Cast(contentPrincipal)->Kind(),
+            BasePrincipal::eContentPrincipal);
+
+  // Check both combined don't return a principal
+  nsCOMPtr<nsIPrincipal> combinedPrincipal = BasePrincipal::FromJSON(
+      "{\"1\":{\"0\":\"https://mozilla.com\"},\"3\":{}}"_ns);
+  ASSERT_EQ(nullptr, combinedPrincipal);
+}
+
+#endif  // ifndef MOZ_DEBUG
+
+TEST(PrincipalSerialization, ExpandedPrincipal)
+{
+  // Check basic Expandedprincipal works without OA
+  nsCOMPtr<nsIScriptSecurityManager> ssm =
+      nsScriptSecurityManager::GetScriptSecurityManager();
+
+  uint32_t length = 2;
+  nsTArray<nsCOMPtr<nsIPrincipal> > allowedDomains(length);
+  allowedDomains.SetLength(length);
+
+  nsAutoCString spec("https://mozilla.com");
+  nsCOMPtr<nsIPrincipal> principal;
+  nsresult rv =
+      ssm->CreateContentPrincipalFromOrigin(spec, getter_AddRefs(principal));
+  ASSERT_EQ(rv, NS_OK);
+  ASSERT_EQ(BasePrincipal::Cast(principal)->Kind(),
+            BasePrincipal::eContentPrincipal);
+  allowedDomains[0] = principal;
+
+  nsAutoCString spec2("https://mozilla.org");
+  nsCOMPtr<nsIPrincipal> principal2;
+  rv = ssm->CreateContentPrincipalFromOrigin(spec2, getter_AddRefs(principal2));
+  ASSERT_EQ(rv, NS_OK);
+  ASSERT_EQ(BasePrincipal::Cast(principal2)->Kind(),
+            BasePrincipal::eContentPrincipal);
+  allowedDomains[1] = principal2;
+
+  mozilla::OriginAttributes attrs;
+  RefPtr<ExpandedPrincipal> result =
+      ExpandedPrincipal::Create(allowedDomains, attrs);
+  ASSERT_EQ(BasePrincipal::Cast(result)->Kind(),
+            BasePrincipal::eExpandedPrincipal);
+
+  nsAutoCString JSON;
+  rv = BasePrincipal::Cast(result)->ToJSON(JSON);
+  ASSERT_EQ(rv, NS_OK);
+  ASSERT_STREQ(JSON.get(),
+               "{\"2\":{\"0\":[{\"1\":{\"0\":\"https://mozilla.com/"
+               "\"}},{\"1\":{\"0\":\"https://mozilla.org/\"}}]}}");
+
+  nsCOMPtr<nsIPrincipal> returnedPrincipal = BasePrincipal::FromJSON(JSON);
+  auto outPrincipal = BasePrincipal::Cast(returnedPrincipal);
+  ASSERT_EQ(outPrincipal->Kind(), BasePrincipal::eExpandedPrincipal);
+
+  ASSERT_TRUE(outPrincipal->FastSubsumesIgnoringFPD(principal));
+  ASSERT_TRUE(outPrincipal->FastSubsumesIgnoringFPD(principal2));
+
+  nsAutoCString specDev("https://mozilla.dev");
+  nsCOMPtr<nsIPrincipal> principalDev;
+  rv = ssm->CreateContentPrincipalFromOrigin(specDev,
+                                             getter_AddRefs(principalDev));
+  ASSERT_EQ(rv, NS_OK);
+  ASSERT_EQ(BasePrincipal::Cast(principalDev)->Kind(),
+            BasePrincipal::eContentPrincipal);
+
+  ASSERT_FALSE(outPrincipal->FastSubsumesIgnoringFPD(principalDev));
+}
+
+TEST(PrincipalSerialization, ExpandedPrincipalOA)
+{
+  // Check Expandedprincipal works with top level OA
+  nsCOMPtr<nsIScriptSecurityManager> ssm =
+      nsScriptSecurityManager::GetScriptSecurityManager();
+
+  uint32_t length = 2;
+  nsTArray<nsCOMPtr<nsIPrincipal> > allowedDomains(length);
+  allowedDomains.SetLength(length);
+
+  nsAutoCString spec("https://mozilla.com");
+  nsCOMPtr<nsIPrincipal> principal;
+  nsresult rv =
+      ssm->CreateContentPrincipalFromOrigin(spec, getter_AddRefs(principal));
+  ASSERT_EQ(rv, NS_OK);
+  ASSERT_EQ(BasePrincipal::Cast(principal)->Kind(),
+            BasePrincipal::eContentPrincipal);
+  allowedDomains[0] = principal;
+
+  nsAutoCString spec2("https://mozilla.org");
+  nsCOMPtr<nsIPrincipal> principal2;
+  rv = ssm->CreateContentPrincipalFromOrigin(spec2, getter_AddRefs(principal2));
+  ASSERT_EQ(rv, NS_OK);
+  ASSERT_EQ(BasePrincipal::Cast(principal2)->Kind(),
+            BasePrincipal::eContentPrincipal);
+  allowedDomains[1] = principal2;
+
+  mozilla::OriginAttributes attrs;
+  nsAutoCString suffix("^userContextId=1");
+  bool ok = attrs.PopulateFromSuffix(suffix);
+  ASSERT_TRUE(ok);
+
+  RefPtr<ExpandedPrincipal> result =
+      ExpandedPrincipal::Create(allowedDomains, attrs);
+  ASSERT_EQ(BasePrincipal::Cast(result)->Kind(),
+            BasePrincipal::eExpandedPrincipal);
+
+  nsAutoCString JSON;
+  rv = BasePrincipal::Cast(result)->ToJSON(JSON);
+  ASSERT_EQ(rv, NS_OK);
+  ASSERT_STREQ(JSON.get(),
+               "{\"2\":{\"0\":[{\"1\":{\"0\":\"https://mozilla.com/"
+               "\"}},{\"1\":{\"0\":\"https://mozilla.org/"
+               "\"}}],\"1\":\"^userContextId=1\"}}");
+
+  nsCOMPtr<nsIPrincipal> returnedPrincipal = BasePrincipal::FromJSON(JSON);
+  auto outPrincipal = BasePrincipal::Cast(returnedPrincipal);
+  ASSERT_EQ(outPrincipal->Kind(), BasePrincipal::eExpandedPrincipal);
+
+  ASSERT_TRUE(outPrincipal->FastSubsumesIgnoringFPD(principal));
+  ASSERT_TRUE(outPrincipal->FastSubsumesIgnoringFPD(principal2));
+
+  nsAutoCString specDev("https://mozilla.dev");
+  nsCOMPtr<nsIPrincipal> principalDev;
+  rv = ssm->CreateContentPrincipalFromOrigin(specDev,
+                                             getter_AddRefs(principalDev));
+  ASSERT_EQ(rv, NS_OK);
+  ASSERT_EQ(BasePrincipal::Cast(principalDev)->Kind(),
+            BasePrincipal::eContentPrincipal);
+
+  ASSERT_FALSE(outPrincipal->FastSubsumesIgnoringFPD(principalDev));
+}
diff --git a/caps/tests/gtest/TestRedirectChainURITruncation.cpp b/caps/tests/gtest/TestRedirectChainURITruncation.cpp
new file mode 100644
index 0000000000..34c633499c
--- /dev/null
+++ b/caps/tests/gtest/TestRedirectChainURITruncation.cpp
@@ -0,0 +1,231 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#include "gtest/gtest.h"
+#include "mozilla/BasePrincipal.h"
+#include "mozilla/ContentPrincipal.h"
+#include "mozilla/NullPrincipal.h"
+#include "mozilla/SystemPrincipal.h"
+#include "mozilla/ExpandedPrincipal.h"
+#include "nsContentUtils.h"
+#include "mozilla/LoadInfo.h"
+
+namespace mozilla {
+
+void checkPrincipalTruncation(nsIPrincipal* aPrincipal,
+                              const nsACString& aExpectedSpec = ""_ns,
+                              const nsTArray<nsCString>& aExpectedSpecs = {}) {
+  nsCOMPtr<nsIPrincipal> truncatedPrincipal =
+      net::CreateTruncatedPrincipal(aPrincipal);
+  ASSERT_TRUE(truncatedPrincipal);
+
+  if (aPrincipal->IsSystemPrincipal()) {
+    ASSERT_TRUE(truncatedPrincipal->IsSystemPrincipal());
+    return;
+  }
+
+  if (aPrincipal->GetIsNullPrincipal()) {
+    nsCOMPtr<nsIPrincipal> precursorPrincipal =
+        aPrincipal->GetPrecursorPrincipal();
+
+    nsAutoCString principalSpecEnding("}");
+    nsAutoCString expectedTestSpec(aExpectedSpec);
+    if (!aExpectedSpec.IsEmpty()) {
+      principalSpecEnding += "?"_ns;
+      expectedTestSpec += "/"_ns;
+    }
+
+    if (precursorPrincipal) {
+      nsAutoCString precursorSpec;
+      precursorPrincipal->GetAsciiSpec(precursorSpec);
+      ASSERT_TRUE(precursorSpec.Equals(expectedTestSpec));
+    }
+
+    // NullPrincipals have UUIDs as part of their scheme i.e.
+    // moz-nullprincipal:{9bebdabb-828a-4284-8b00-432a968c6e42}
+    // To avoid having to know the UUID beforehand we check the principal's spec
+    // before and after the UUID
+    nsAutoCString principalSpec;
+    truncatedPrincipal->GetAsciiSpec(principalSpec);
+    ASSERT_TRUE(StringBeginsWith(principalSpec, "moz-nullprincipal:{"_ns));
+    ASSERT_TRUE(
+        StringEndsWith(principalSpec, principalSpecEnding + aExpectedSpec));
+    return;
+  }
+
+  if (aPrincipal->GetIsExpandedPrincipal()) {
+    const nsTArray<nsCOMPtr<nsIPrincipal>>& truncatedAllowList =
+        BasePrincipal::Cast(truncatedPrincipal)
+            ->As<ExpandedPrincipal>()
+            ->AllowList();
+
+    for (size_t i = 0; i < aExpectedSpecs.Length(); ++i) {
+      nsAutoCString principalSpec;
+      truncatedAllowList[i]->GetAsciiSpec(principalSpec);
+      ASSERT_TRUE(principalSpec.Equals(aExpectedSpecs[i]));
+    }
+    return;
+  }
+
+  if (aPrincipal->GetIsContentPrincipal()) {
+    nsAutoCString principalSpec;
+    truncatedPrincipal->GetAsciiSpec(principalSpec);
+    ASSERT_TRUE(principalSpec.Equals(aExpectedSpec));
+    return;
+  }
+
+  // Tests should not reach this point
+  ADD_FAILURE();
+}
+
+void checkPrincipalTruncation(nsIPrincipal* aPrincipal,
+                              const nsTArray<nsCString>& aExpectedSpecs = {}) {
+  checkPrincipalTruncation(aPrincipal, ""_ns, aExpectedSpecs);
+}
+
+TEST(RedirectChainURITruncation, ContentPrincipal)
+{
+  // ======================= HTTP Scheme =======================
+  nsAutoCString httpSpec(
+      "http://root:toor@www.example.com:200/foo/bar/baz.html?qux#thud");
+  nsCOMPtr<nsIURI> uri;
+  nsresult rv = NS_NewURI(getter_AddRefs(uri), httpSpec);
+  ASSERT_EQ(rv, NS_OK);
+
+  nsCOMPtr<nsIPrincipal> principal;
+  OriginAttributes attrs;
+  principal = BasePrincipal::CreateContentPrincipal(uri, attrs);
+  ASSERT_TRUE(principal);
+
+  checkPrincipalTruncation(principal,
+                           "http://www.example.com:200/foo/bar/baz.html"_ns);
+
+  // ======================= HTTPS Scheme =======================
+  nsAutoCString httpsSpec(
+      "https://root:toor@www.example.com:200/foo/bar/baz.html?qux#thud");
+  rv = NS_NewURI(getter_AddRefs(uri), httpsSpec);
+  ASSERT_EQ(rv, NS_OK);
+
+  principal = BasePrincipal::CreateContentPrincipal(uri, attrs);
+  ASSERT_TRUE(principal);
+
+  checkPrincipalTruncation(principal,
+                           "https://www.example.com:200/foo/bar/baz.html"_ns);
+
+  // ======================= View Source Scheme =======================
+  nsAutoCString viewSourceSpec(
+      "view-source:https://root:toor@www.example.com:200/foo/bar/"
+      "baz.html?qux#thud");
+  rv = NS_NewURI(getter_AddRefs(uri), viewSourceSpec);
+  ASSERT_EQ(rv, NS_OK);
+
+  principal = BasePrincipal::CreateContentPrincipal(uri, attrs);
+  ASSERT_TRUE(principal);
+
+  checkPrincipalTruncation(
+      principal, "view-source:https://www.example.com:200/foo/bar/baz.html"_ns);
+
+  // ======================= About Scheme =======================
+  nsAutoCString aboutSpec("about:config");
+  rv = NS_NewURI(getter_AddRefs(uri), aboutSpec);
+  ASSERT_EQ(rv, NS_OK);
+
+  principal = BasePrincipal::CreateContentPrincipal(uri, attrs);
+  ASSERT_TRUE(principal);
+
+  checkPrincipalTruncation(principal, "about:config"_ns);
+
+  // ======================= Resource Scheme =======================
+  nsAutoCString resourceSpec("resource://testing/");
+  rv = NS_NewURI(getter_AddRefs(uri), resourceSpec);
+  ASSERT_EQ(rv, NS_OK);
+
+  principal = BasePrincipal::CreateContentPrincipal(uri, attrs);
+  ASSERT_TRUE(principal);
+
+  checkPrincipalTruncation(principal, "resource://testing/"_ns);
+
+  // ======================= Chrome Scheme =======================
+  nsAutoCString chromeSpec("chrome://foo/content/bar.xul");
+  rv = NS_NewURI(getter_AddRefs(uri), chromeSpec);
+  ASSERT_EQ(rv, NS_OK);
+
+  principal = BasePrincipal::CreateContentPrincipal(uri, attrs);
+  ASSERT_TRUE(principal);
+
+  checkPrincipalTruncation(principal, "chrome://foo/content/bar.xul"_ns);
+}
+
+TEST(RedirectChainURITruncation, NullPrincipal)
+{
+  // ======================= NullPrincipal =======================
+  nsCOMPtr<nsIPrincipal> principal =
+      NullPrincipal::CreateWithoutOriginAttributes();
+  ASSERT_TRUE(principal);
+
+  checkPrincipalTruncation(principal, ""_ns);
+
+  // ======================= NullPrincipal & Precursor =======================
+  nsAutoCString precursorSpec(
+      "https://root:toor@www.example.com:200/foo/bar/baz.html?qux#thud");
+
+  nsCOMPtr<nsIURI> precursorURI;
+  nsresult rv = NS_NewURI(getter_AddRefs(precursorURI), precursorSpec);
+  ASSERT_EQ(rv, NS_OK);
+
+  OriginAttributes attrs;
+  nsCOMPtr<nsIPrincipal> precursorPrincipal =
+      BasePrincipal::CreateContentPrincipal(precursorURI, attrs);
+  principal = NullPrincipal::CreateWithInheritedAttributes(precursorPrincipal);
+  ASSERT_TRUE(principal);
+
+  checkPrincipalTruncation(principal, "https://www.example.com:200"_ns);
+}
+
+TEST(RedirectChainURITruncation, SystemPrincipal)
+{
+  nsCOMPtr<nsIPrincipal> principal = nsContentUtils::GetSystemPrincipal();
+  ASSERT_TRUE(principal);
+
+  checkPrincipalTruncation(principal, ""_ns);
+}
+
+TEST(RedirectChainURITruncation, ExtendedPrincipal)
+{
+  // ======================= HTTP Scheme =======================
+  nsAutoCString httpSpec(
+      "http://root:toor@www.example.com:200/foo/bar/baz.html?qux#thud");
+  nsCOMPtr<nsIURI> uri;
+  nsresult rv = NS_NewURI(getter_AddRefs(uri), httpSpec);
+  ASSERT_EQ(rv, NS_OK);
+
+  nsCOMPtr<nsIPrincipal> firstContentPrincipal;
+  OriginAttributes attrs;
+  firstContentPrincipal = BasePrincipal::CreateContentPrincipal(uri, attrs);
+  ASSERT_TRUE(firstContentPrincipal);
+
+  // ======================= HTTPS Scheme =======================
+  nsCOMPtr<nsIPrincipal> secondContentPrincipal;
+  nsAutoCString httpsSpec(
+      "https://root:toor@www.example.com:200/foo/bar/baz.html?qux#thud");
+  rv = NS_NewURI(getter_AddRefs(uri), httpsSpec);
+  ASSERT_EQ(rv, NS_OK);
+
+  secondContentPrincipal = BasePrincipal::CreateContentPrincipal(uri, attrs);
+  ASSERT_TRUE(secondContentPrincipal);
+
+  // ======================= ExpandedPrincipal =======================
+  const nsTArray<nsCString>& expectedSpecs = {
+      "http://www.example.com:200/foo/bar/baz.html"_ns,
+      "https://www.example.com:200/foo/bar/baz.html"_ns,
+  };
+  nsTArray<nsCOMPtr<nsIPrincipal>> allowList = {firstContentPrincipal,
+                                                secondContentPrincipal};
+  nsCOMPtr<nsIPrincipal> principal =
+      ExpandedPrincipal::Create(allowList, attrs);
+  ASSERT_TRUE(principal);
+
+  checkPrincipalTruncation(principal, expectedSpecs);
+}
+
+}  // namespace mozilla
diff --git a/caps/tests/gtest/moz.build b/caps/tests/gtest/moz.build
new file mode 100644
index 0000000000..10b1a66f3b
--- /dev/null
+++ b/caps/tests/gtest/moz.build
@@ -0,0 +1,18 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+UNIFIED_SOURCES += [
+    "TestBackgroundThreadPrincipal.cpp",
+    "TestNullPrincipalPrecursor.cpp",
+    "TestOriginAttributes.cpp",
+    "TestPrincipalAttributes.cpp",
+    "TestPrincipalSerialization.cpp",
+    "TestRedirectChainURITruncation.cpp",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul-gtest"
diff --git a/caps/tests/mochitest/browser.ini b/caps/tests/mochitest/browser.ini
new file mode 100644
index 0000000000..a1c76eb57b
--- /dev/null
+++ b/caps/tests/mochitest/browser.ini
@@ -0,0 +1,2 @@
+[browser_checkloaduri.js]
+[browser_aboutOrigin.js]
diff --git a/caps/tests/mochitest/browser_aboutOrigin.js b/caps/tests/mochitest/browser_aboutOrigin.js
new file mode 100644
index 0000000000..fc2e2d8f53
--- /dev/null
+++ b/caps/tests/mochitest/browser_aboutOrigin.js
@@ -0,0 +1,12 @@
+"use strict";
+
+let tests = ["about:robots?foo", "about:robots#foo", "about:robots?foo#bar"];
+tests.forEach(async test => {
+  add_task(async () => {
+    await BrowserTestUtils.withNewTab(test, async browser => {
+      await SpecialPowers.spawn(browser, [], () => {
+        is(content.document.nodePrincipal.origin, "about:robots");
+      });
+    });
+  });
+});
diff --git a/caps/tests/mochitest/browser_checkloaduri.js b/caps/tests/mochitest/browser_checkloaduri.js
new file mode 100644
index 0000000000..11ff2d1a08
--- /dev/null
+++ b/caps/tests/mochitest/browser_checkloaduri.js
@@ -0,0 +1,393 @@
+"use strict";
+
+let ssm = Services.scriptSecurityManager;
+// This will show a directory listing, but we never actually load these so that's OK.
+const kDummyPage = getRootDirectory(gTestPath);
+
+const kAboutPagesRegistered = Promise.all([
+  BrowserTestUtils.registerAboutPage(
+    registerCleanupFunction,
+    "test-chrome-privs",
+    kDummyPage,
+    Ci.nsIAboutModule.ALLOW_SCRIPT
+  ),
+  BrowserTestUtils.registerAboutPage(
+    registerCleanupFunction,
+    "test-chrome-privs2",
+    kDummyPage,
+    Ci.nsIAboutModule.ALLOW_SCRIPT
+  ),
+  BrowserTestUtils.registerAboutPage(
+    registerCleanupFunction,
+    "test-unknown-linkable",
+    kDummyPage,
+    Ci.nsIAboutModule.MAKE_LINKABLE | Ci.nsIAboutModule.ALLOW_SCRIPT
+  ),
+  BrowserTestUtils.registerAboutPage(
+    registerCleanupFunction,
+    "test-unknown-linkable2",
+    kDummyPage,
+    Ci.nsIAboutModule.MAKE_LINKABLE | Ci.nsIAboutModule.ALLOW_SCRIPT
+  ),
+  BrowserTestUtils.registerAboutPage(
+    registerCleanupFunction,
+    "test-unknown-unlinkable",
+    kDummyPage,
+    Ci.nsIAboutModule.ALLOW_SCRIPT
+  ),
+  BrowserTestUtils.registerAboutPage(
+    registerCleanupFunction,
+    "test-unknown-unlinkable2",
+    kDummyPage,
+    Ci.nsIAboutModule.ALLOW_SCRIPT
+  ),
+  BrowserTestUtils.registerAboutPage(
+    registerCleanupFunction,
+    "test-content-unlinkable",
+    kDummyPage,
+    Ci.nsIAboutModule.URI_SAFE_FOR_UNTRUSTED_CONTENT |
+      Ci.nsIAboutModule.ALLOW_SCRIPT
+  ),
+  BrowserTestUtils.registerAboutPage(
+    registerCleanupFunction,
+    "test-content-unlinkable2",
+    kDummyPage,
+    Ci.nsIAboutModule.URI_SAFE_FOR_UNTRUSTED_CONTENT |
+      Ci.nsIAboutModule.ALLOW_SCRIPT
+  ),
+  BrowserTestUtils.registerAboutPage(
+    registerCleanupFunction,
+    "test-content-linkable",
+    kDummyPage,
+    Ci.nsIAboutModule.URI_SAFE_FOR_UNTRUSTED_CONTENT |
+      Ci.nsIAboutModule.MAKE_LINKABLE |
+      Ci.nsIAboutModule.ALLOW_SCRIPT
+  ),
+  BrowserTestUtils.registerAboutPage(
+    registerCleanupFunction,
+    "test-content-linkable2",
+    kDummyPage,
+    Ci.nsIAboutModule.URI_SAFE_FOR_UNTRUSTED_CONTENT |
+      Ci.nsIAboutModule.MAKE_LINKABLE |
+      Ci.nsIAboutModule.ALLOW_SCRIPT
+  ),
+]);
+
+const URLs = new Map([
+  [
+    "http://www.example.com",
+    [
+      // For each of these entries, the booleans represent whether the parent URI can:
+      // - load them
+      // - load them without principal inheritance
+      // - whether the URI can be created at all (some protocol handlers will
+      //   refuse to create certain variants)
+      ["http://www.example2.com", true, true, true],
+      ["https://www.example2.com", true, true, true],
+      ["moz-icon:file:///foo/bar/baz.exe", false, false, true],
+      ["moz-icon://.exe", false, false, true],
+      ["chrome://foo/content/bar.xul", false, false, true],
+      ["view-source:http://www.example2.com", false, false, true],
+      ["view-source:https://www.example2.com", false, false, true],
+      ["data:text/html,Hi", true, false, true],
+      ["view-source:data:text/html,Hi", false, false, true],
+      ["javascript:alert('hi')", true, false, true],
+      ["moz://a", false, false, true],
+      ["about:test-chrome-privs", false, false, true],
+      ["about:test-unknown-unlinkable", false, false, true],
+      ["about:test-content-unlinkable", false, false, true],
+      ["about:test-content-linkable", true, true, true],
+      // Because this page doesn't have SAFE_FOR_UNTRUSTED, the web can't link to it:
+      ["about:test-unknown-linkable", false, false, true],
+    ],
+  ],
+  [
+    "view-source:http://www.example.com",
+    [
+      ["http://www.example2.com", true, true, true],
+      ["https://www.example2.com", true, true, true],
+      ["moz-icon:file:///foo/bar/baz.exe", false, false, true],
+      ["moz-icon://.exe", false, false, true],
+      ["chrome://foo/content/bar.xul", false, false, true],
+      ["view-source:http://www.example2.com", true, true, true],
+      ["view-source:https://www.example2.com", true, true, true],
+      ["data:text/html,Hi", true, false, true],
+      ["view-source:data:text/html,Hi", true, false, true],
+      ["javascript:alert('hi')", true, false, true],
+      ["moz://a", false, false, true],
+      ["about:test-chrome-privs", false, false, true],
+      ["about:test-unknown-unlinkable", false, false, true],
+      ["about:test-content-unlinkable", false, false, true],
+      ["about:test-content-linkable", true, true, true],
+      // Because this page doesn't have SAFE_FOR_UNTRUSTED, the web can't link to it:
+      ["about:test-unknown-linkable", false, false, true],
+    ],
+  ],
+  // about: related tests.
+  [
+    "about:test-chrome-privs",
+    [
+      ["about:test-chrome-privs", true, true, true],
+      ["about:test-chrome-privs2", true, true, true],
+      ["about:test-chrome-privs2?foo#bar", true, true, true],
+      ["about:test-chrome-privs2?foo", true, true, true],
+      ["about:test-chrome-privs2#bar", true, true, true],
+
+      ["about:test-unknown-unlinkable", true, true, true],
+
+      ["about:test-content-unlinkable", true, true, true],
+      ["about:test-content-unlinkable?foo", true, true, true],
+      ["about:test-content-unlinkable?foo#bar", true, true, true],
+      ["about:test-content-unlinkable#bar", true, true, true],
+
+      ["about:test-content-linkable", true, true, true],
+
+      ["about:test-unknown-linkable", true, true, true],
+      ["moz-icon:file:///foo/bar/baz.exe", true, true, true],
+      ["moz-icon://.exe", true, true, true],
+    ],
+  ],
+  [
+    "about:test-unknown-unlinkable",
+    [
+      ["about:test-chrome-privs", false, false, true],
+
+      // Can link to ourselves:
+      ["about:test-unknown-unlinkable", true, true, true],
+      // Can't link to unlinkable content if we're not sure it's privileged:
+      ["about:test-unknown-unlinkable2", false, false, true],
+
+      ["about:test-content-unlinkable", true, true, true],
+      ["about:test-content-unlinkable2", true, true, true],
+      ["about:test-content-unlinkable2?foo", true, true, true],
+      ["about:test-content-unlinkable2?foo#bar", true, true, true],
+      ["about:test-content-unlinkable2#bar", true, true, true],
+
+      ["about:test-content-linkable", true, true, true],
+
+      // Because this page doesn't have SAFE_FOR_UNTRUSTED, the web can't link to it:
+      ["about:test-unknown-linkable", false, false, true],
+    ],
+  ],
+  [
+    "about:test-content-unlinkable",
+    [
+      ["about:test-chrome-privs", false, false, true],
+
+      // Can't link to unlinkable content if we're not sure it's privileged:
+      ["about:test-unknown-unlinkable", false, false, true],
+
+      ["about:test-content-unlinkable", true, true, true],
+      ["about:test-content-unlinkable2", true, true, true],
+      ["about:test-content-unlinkable2?foo", true, true, true],
+      ["about:test-content-unlinkable2?foo#bar", true, true, true],
+      ["about:test-content-unlinkable2#bar", true, true, true],
+
+      ["about:test-content-linkable", true, true, true],
+      ["about:test-unknown-linkable", false, false, true],
+    ],
+  ],
+  [
+    "about:test-unknown-linkable",
+    [
+      ["about:test-chrome-privs", false, false, true],
+
+      // Linkable content can't link to unlinkable content.
+      ["about:test-unknown-unlinkable", false, false, true],
+
+      ["about:test-content-unlinkable", false, false, true],
+      ["about:test-content-unlinkable2", false, false, true],
+      ["about:test-content-unlinkable2?foo", false, false, true],
+      ["about:test-content-unlinkable2?foo#bar", false, false, true],
+      ["about:test-content-unlinkable2#bar", false, false, true],
+
+      // ... but it can link to other linkable content.
+      ["about:test-content-linkable", true, true, true],
+
+      // Can link to ourselves:
+      ["about:test-unknown-linkable", true, true, true],
+
+      // Because this page doesn't have SAFE_FOR_UNTRUSTED, the web can't link to it:
+      ["about:test-unknown-linkable2", false, false, true],
+    ],
+  ],
+  [
+    "about:test-content-linkable",
+    [
+      ["about:test-chrome-privs", false, false, true],
+
+      // Linkable content can't link to unlinkable content.
+      ["about:test-unknown-unlinkable", false, false, true],
+
+      ["about:test-content-unlinkable", false, false, true],
+
+      // ... but it can link to itself and other linkable content.
+      ["about:test-content-linkable", true, true, true],
+      ["about:test-content-linkable2", true, true, true],
+
+      // Because this page doesn't have SAFE_FOR_UNTRUSTED, the web can't link to it:
+      ["about:test-unknown-linkable", false, false, true],
+    ],
+  ],
+]);
+
+function testURL(
+  source,
+  target,
+  canLoad,
+  canLoadWithoutInherit,
+  canCreate,
+  flags
+) {
+  function getPrincipalDesc(principal) {
+    if (principal.spec != "") {
+      return principal.spec;
+    }
+    if (principal.isSystemPrincipal) {
+      return "system principal";
+    }
+    if (principal.isNullPrincipal) {
+      return "null principal";
+    }
+    return "unknown principal";
+  }
+  let threw = false;
+  let targetURI;
+  try {
+    targetURI = Services.io.newURI(target);
+  } catch (ex) {
+    ok(
+      !canCreate,
+      "Shouldn't be passing URIs that we can't create. Failed to create: " +
+        target
+    );
+    return;
+  }
+  ok(
+    canCreate,
+    "Created a URI for " +
+      target +
+      " which should " +
+      (canCreate ? "" : "not ") +
+      "be possible."
+  );
+  try {
+    ssm.checkLoadURIWithPrincipal(source, targetURI, flags);
+  } catch (ex) {
+    info(ex.message);
+    threw = true;
+  }
+  let inheritDisallowed = flags & ssm.DISALLOW_INHERIT_PRINCIPAL;
+  let shouldThrow = inheritDisallowed ? !canLoadWithoutInherit : !canLoad;
+  ok(
+    threw == shouldThrow,
+    "Should " +
+      (shouldThrow ? "" : "not ") +
+      "throw an error when loading " +
+      target +
+      " from " +
+      getPrincipalDesc(source) +
+      (inheritDisallowed ? " without" : " with") +
+      " principal inheritance."
+  );
+}
+
+add_task(async function () {
+  // In this test we want to verify both http and https load
+  // restrictions, hence we explicitly switch off the https-first
+  // upgrading mechanism.
+  await SpecialPowers.pushPrefEnv({
+    set: [["dom.security.https_first", false]],
+  });
+
+  await kAboutPagesRegistered;
+  let baseFlags = ssm.STANDARD | ssm.DONT_REPORT_ERRORS;
+  for (let [sourceString, targetsAndExpectations] of URLs) {
+    let source;
+    if (sourceString.startsWith("about:test-chrome-privs")) {
+      source = ssm.getSystemPrincipal();
+    } else {
+      source = ssm.createContentPrincipal(Services.io.newURI(sourceString), {});
+    }
+    for (let [
+      target,
+      canLoad,
+      canLoadWithoutInherit,
+      canCreate,
+    ] of targetsAndExpectations) {
+      testURL(
+        source,
+        target,
+        canLoad,
+        canLoadWithoutInherit,
+        canCreate,
+        baseFlags
+      );
+      testURL(
+        source,
+        target,
+        canLoad,
+        canLoadWithoutInherit,
+        canCreate,
+        baseFlags | ssm.DISALLOW_INHERIT_PRINCIPAL
+      );
+    }
+  }
+
+  // Now test blob URIs, which we need to do in-content.
+  await BrowserTestUtils.withNewTab(
+    "http://www.example.com/",
+    async function (browser) {
+      await SpecialPowers.spawn(
+        browser,
+        [testURL.toString()],
+        async function (testURLFn) {
+          // eslint-disable-next-line no-shadow , no-eval
+          let testURL = eval("(" + testURLFn + ")");
+          // eslint-disable-next-line no-shadow
+          let ssm = Services.scriptSecurityManager;
+          // eslint-disable-next-line no-shadow
+          let baseFlags = ssm.STANDARD | ssm.DONT_REPORT_ERRORS;
+          // eslint-disable-next-line no-unused-vars
+          let b = new content.Blob(["I am a blob"]);
+          let contentBlobURI = content.URL.createObjectURL(b);
+          let contentPrincipal = content.document.nodePrincipal;
+          // Loading this blob URI from the content page should work:
+          testURL(
+            contentPrincipal,
+            contentBlobURI,
+            true,
+            true,
+            true,
+            baseFlags
+          );
+          testURL(
+            contentPrincipal,
+            contentBlobURI,
+            true,
+            true,
+            true,
+            baseFlags | ssm.DISALLOW_INHERIT_PRINCIPAL
+          );
+
+          testURL(
+            contentPrincipal,
+            "view-source:" + contentBlobURI,
+            false,
+            false,
+            true,
+            baseFlags
+          );
+          testURL(
+            contentPrincipal,
+            "view-source:" + contentBlobURI,
+            false,
+            false,
+            true,
+            baseFlags | ssm.DISALLOW_INHERIT_PRINCIPAL
+          );
+        }
+      );
+    }
+  );
+});
diff --git a/caps/tests/mochitest/chrome.ini b/caps/tests/mochitest/chrome.ini
new file mode 100644
index 0000000000..776afa34e4
--- /dev/null
+++ b/caps/tests/mochitest/chrome.ini
@@ -0,0 +1,12 @@
+[DEFAULT]
+skip-if = os == 'android'
+support-files =
+  file_data.txt
+  file_disableScript.html
+  !/caps/tests/mochitest/file_data.txt
+  !/caps/tests/mochitest/file_disableScript.html
+
+[test_bug995943.xhtml]
+skip-if = (verify && debug && (os == 'mac'))
+[test_addonMayLoad.html]
+[test_disableScript.xhtml]
diff --git a/caps/tests/mochitest/file_bug1367586-followon.html b/caps/tests/mochitest/file_bug1367586-followon.html
new file mode 100644
index 0000000000..3b648ce746
--- /dev/null
+++ b/caps/tests/mochitest/file_bug1367586-followon.html
@@ -0,0 +1 @@
+<body>Follow-on navigation content</body>
diff --git a/caps/tests/mochitest/file_bug1367586-redirect.sjs b/caps/tests/mochitest/file_bug1367586-redirect.sjs
new file mode 100644
index 0000000000..12a980155f
--- /dev/null
+++ b/caps/tests/mochitest/file_bug1367586-redirect.sjs
@@ -0,0 +1,8 @@
+function handleRequest(aRequest, aResponse) {
+  aResponse.setStatusLine(aRequest.httpVersion, 302, "Moved");
+  aResponse.setHeader(
+    "Location",
+    "http://mochi.test:8888/tests/caps/tests/mochitest/file_bug1367586-target.html"
+  );
+  aResponse.write("To be redirected to target");
+}
diff --git a/caps/tests/mochitest/file_bug1367586-target.html b/caps/tests/mochitest/file_bug1367586-target.html
new file mode 100644
index 0000000000..e2a2fde20d
--- /dev/null
+++ b/caps/tests/mochitest/file_bug1367586-target.html
@@ -0,0 +1,6 @@
+<head><script>
+window.addEventListener("pageshow", function(event) {
+    parent.ok(!event.persisted, "Should not load from bfcache");
+});
+</script></head>
+<body>Redirect target content</body>
diff --git a/caps/tests/mochitest/file_data.txt b/caps/tests/mochitest/file_data.txt
new file mode 100644
index 0000000000..26d7bd8488
--- /dev/null
+++ b/caps/tests/mochitest/file_data.txt
@@ -0,0 +1 @@
+server data fetched over XHR
diff --git a/caps/tests/mochitest/file_disableScript.html b/caps/tests/mochitest/file_disableScript.html
new file mode 100644
index 0000000000..f4888cd586
--- /dev/null
+++ b/caps/tests/mochitest/file_disableScript.html
@@ -0,0 +1,11 @@
+<!DOCTYPE html>
+<html>
+<head>
+<script>
+var gFiredOnload = false;
+var gFiredOnclick = false;
+</script>
+</head>
+<body onload="gFiredOnload = true;" onclick="gFiredOnclick = true;">
+</body>
+</html>
diff --git a/caps/tests/mochitest/mochitest.ini b/caps/tests/mochitest/mochitest.ini
new file mode 100644
index 0000000000..9036a3ac23
--- /dev/null
+++ b/caps/tests/mochitest/mochitest.ini
@@ -0,0 +1,18 @@
+[DEFAULT]
+support-files =
+  file_bug1367586-followon.html
+  file_bug1367586-redirect.sjs
+  file_bug1367586-target.html
+  file_data.txt
+  file_disableScript.html
+  !/js/xpconnect/tests/mochitest/file_empty.html
+
+[test_bug246699.html]
+[test_bug292789.html]
+skip-if = os == 'android'
+[test_bug423375.html]
+[test_bug470804.html]
+[test_bug1367586.html]
+skip-if =
+  http3
+[test_disallowInheritPrincipal.html]
diff --git a/caps/tests/mochitest/resource_test_file.html b/caps/tests/mochitest/resource_test_file.html
new file mode 100644
index 0000000000..8201bd70e0
--- /dev/null
+++ b/caps/tests/mochitest/resource_test_file.html
@@ -0,0 +1,2 @@
+<!DOCTYPE html>
+<html><head><title>resource test file</title></head><body></body></html>
diff --git a/caps/tests/mochitest/test_addonMayLoad.html b/caps/tests/mochitest/test_addonMayLoad.html
new file mode 100644
index 0000000000..2d5e5e59f1
--- /dev/null
+++ b/caps/tests/mochitest/test_addonMayLoad.html
@@ -0,0 +1,95 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1180921
+-->
+<head>
+  <meta charset="utf-8">
+  <title>Test for Bug 1180921</title>
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="chrome://global/skin"/>
+  <link rel="stylesheet" type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"/>
+  <script type="application/javascript">
+
+  /** Test for Bug 1180921 */
+  let module = Cu.getGlobalForObject(Services);
+  let ssm = Services.scriptSecurityManager;
+
+  function StubPolicy(id, subdomain) {
+    /* globals MatchPatternSet */
+    return new module.WebExtensionPolicy({
+      id,
+      mozExtensionHostname: id,
+      baseURL: `file:///{id}`,
+
+      allowedOrigins: new MatchPatternSet([`*://${subdomain}.example.org/*`]),
+      localizeCallback(string) {},
+    });
+  }
+
+  /* globals WebExtensionPolicy */
+  let policyA = StubPolicy("addona", "test1");
+  let policyB = StubPolicy("addonb", "test2");
+  policyA.active = true;
+  policyB.active = true;
+
+  SimpleTest.waitForExplicitFinish();
+  SimpleTest.registerCleanupFunction(function() {
+    policyA.active = false;
+    policyB.active = false;
+  });
+
+  function tryLoad(sb, uri) {
+    let p = new Promise(function(resolve, reject) {
+      Cu.exportFunction(resolve, sb, { defineAs: "finish" });
+      Cu.exportFunction(reject, sb, { defineAs: "error" });
+      sb.eval("try { (function () { " +
+              "  var xhr = new XMLHttpRequest();" +
+              "  xhr.onreadystatechange = function() { if (xhr.readyState == XMLHttpRequest.DONE) { finish(xhr.status == 200); } };" +
+              "  xhr.open('GET', '" + uri + "', true);" +
+              "  xhr.send();" +
+              "})() } catch (e) { error(e); }");
+    });
+    return p;
+  }
+
+  let addonA = new Cu.Sandbox(ssm.createContentPrincipal(Services.io.newURI("moz-extension://addonA/"), {}),
+                              {wantGlobalProperties: ["XMLHttpRequest"]});
+  let addonB = new Cu.Sandbox(ssm.createContentPrincipal(Services.io.newURI("moz-extension://addonB/"), {}),
+                              {wantGlobalProperties: ["XMLHttpRequest"]});
+
+  function uriForDomain(d) { return d + "/tests/caps/tests/mochitest/file_data.txt"; }
+
+  tryLoad(addonA, uriForDomain("http://test4.example.org"))
+  .then(function(success) {
+    ok(!success, "cross-origin load should fail for addon A");
+    return tryLoad(addonA, uriForDomain("http://test1.example.org"));
+  }).then(function(success) {
+    ok(success, "allowlisted cross-origin load of test1 should succeed for addon A");
+    return tryLoad(addonB, uriForDomain("http://test1.example.org"));
+  }).then(function(success) {
+    ok(!success, "non-allowlisted cross-origin load of test1 should fail for addon B");
+    return tryLoad(addonB, uriForDomain("http://test2.example.org"));
+  }).then(function(success) {
+    ok(success, "allowlisted cross-origin load of test2 should succeed for addon B");
+    return tryLoad(addonA, uriForDomain("http://test2.example.org"));
+  }).then(function(success) {
+    ok(!success, "non-allowlisted cross-origin load of test2 should fail for addon A");
+    SimpleTest.finish();
+  }, function(e) {
+    ok(false, "Rejected promise chain: " + e);
+    SimpleTest.finish();
+  });
+
+  </script>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1180921">Mozilla Bug 1180921</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+
+</div>
+<pre id="test">
+</pre>
+</body>
+</html>
diff --git a/caps/tests/mochitest/test_bug1367586.html b/caps/tests/mochitest/test_bug1367586.html
new file mode 100644
index 0000000000..d95693c94d
--- /dev/null
+++ b/caps/tests/mochitest/test_bug1367586.html
@@ -0,0 +1,50 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1367586
+-->
+<head>
+  <title>Test for Bug 1367586</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<iframe id="load-frame"></iframe>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+
+var frm = document.getElementById("load-frame");
+var step = 0;
+
+window.addEventListener("load", () => {
+  frm.contentWindow.location = "http://mochi.test:8888/tests/caps/tests/mochitest/file_bug1367586-redirect.sjs";
+  frm.addEventListener("load", function() {
+    ++step;
+    SimpleTest.executeSoon((function(_step, _frm) {
+      switch (_step) {
+      case 1:
+        is(_frm.contentWindow.location.href, "http://mochi.test:8888/tests/caps/tests/mochitest/file_bug1367586-target.html",
+           "Redirected to the expected target in step 1");
+        _frm.contentWindow.location = "http://mochi.test:8888/tests/caps/tests/mochitest/file_bug1367586-followon.html";
+        break;
+      case 2:
+        is(_frm.contentWindow.location.href, "http://mochi.test:8888/tests/caps/tests/mochitest/file_bug1367586-followon.html",
+           "Navigated to the expected URL in step 2");
+        _frm.contentWindow.history.back();
+        break;
+      case 3:
+        is(_frm.contentWindow.location.href, "http://mochi.test:8888/tests/caps/tests/mochitest/file_bug1367586-target.html",
+           "Seeing the correct URL when navigating back in step 3");
+        SimpleTest.finish();
+        break;
+      }
+    }).bind(window, step, frm));
+  });
+});
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/caps/tests/mochitest/test_bug246699.html b/caps/tests/mochitest/test_bug246699.html
new file mode 100644
index 0000000000..9ff25c110a
--- /dev/null
+++ b/caps/tests/mochitest/test_bug246699.html
@@ -0,0 +1,60 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=246699
+-->
+<head>
+  <title>Test for Bug 246699</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=246699">Mozilla Bug 246699</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+<iframe id="load-frame"></iframe>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+/**
+ * Test for Bug 246699
+ * (should produce stack information for caps errors)
+ */
+function isError(e) {
+  return e.constructor.name === "Error" || e.constructor.name === "TypeError";
+}
+
+function hasStack(e) {
+  return isError(e) && /inciteCaps/.test(e.stack);
+}
+
+function inciteCaps(f) {
+    try {
+        f();
+        return "operation succeeded";
+    } catch (e) {
+        if (hasStack(e)) {
+          return "denied-stack";
+        }
+        return "unexpected: " + e;
+    }
+}
+
+function tryChromeLoad() {
+    window.frames[0].location = "chrome://global/content/mozilla.html";
+}
+
+function tryComponentsClasses() {
+    return SpecialPowers.unwrap(SpecialPowers.Cc)["@mozilla.org/dummy;1"];
+}
+
+
+is(inciteCaps(tryChromeLoad), "denied-stack",
+   "should get stack for content-loading-chrome rejection");
+is(inciteCaps(tryComponentsClasses), "denied-stack",
+   "should get stack for SpecialPowers.Components.classes rejection");
+</script>
+</pre>
+</body>
+</html>
diff --git a/caps/tests/mochitest/test_bug292789.html b/caps/tests/mochitest/test_bug292789.html
new file mode 100644
index 0000000000..cd177dfd5b
--- /dev/null
+++ b/caps/tests/mochitest/test_bug292789.html
@@ -0,0 +1,121 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=292789
+-->
+<head>
+  <title>Test for Bug 292789</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=292789">Mozilla Bug 292789</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+  <script src="chrome://global/content/treeUtils.js"></script>
+  <script type="application/javascript" src="chrome://mozapps/content/update/history.js"></script>
+  <script id="resjs" type="application/javascript"></script>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+/** Test for Bug 292789
+ *
+ * Selectively allow access to allowlisted chrome packages
+ * even for ALLOW_CHROME mechanisms (<script>, <img> etc)
+ */
+
+/* import-globals-from ../../../toolkit/content/treeUtils.js */
+/* import-globals-from ../../../toolkit/mozapps/update/content/history.js */
+
+SimpleTest.waitForExplicitFinish();
+
+let ChromeUtils = {
+  import() { return {}; },
+};
+
+/** <script src=""> test */
+function testScriptSrc(aCallback) {
+    is(typeof gTreeUtils.sort, "function",
+       "content can still load <script> from chrome://global");
+
+    /** Try to find an export from history.js.  We will find it if it is
+     *  improperly not blocked, otherwise it will be "undefined".
+     */
+    is(typeof gUpdateHistory, "undefined",
+       "content should not be able to load <script> from chrome://mozapps");
+
+    /** make sure the last one didn't pass because someone
+     *  moved history.js
+     */
+    var resjs = document.getElementById("resjs");
+    resjs.onload = scriptOnload;
+    resjs.src = "resource://gre/chrome/toolkit/content/mozapps/update/history.js";
+    document.getElementById("content").appendChild(resjs);
+
+    function scriptOnload() {
+      is(typeof gUpdateHistory.onLoad, "function",
+         "history.js has not moved unexpectedly");
+
+      // trigger the callback
+      if (aCallback)
+        aCallback();
+    }
+}
+
+/** <img src=""> tests */
+var img_global = "chrome://global/skin/media/error.png";
+var img_mozapps = "chrome://mozapps/skin/extensions/extensionGeneric.svg";
+var res_mozapps = "resource://gre/chrome/toolkit/skin/classic/mozapps/extensions/extensionGeneric.svg";
+
+var imgTests = [[img_global, "success"],
+                [img_mozapps, "fail"],
+                [res_mozapps, "success"]];
+
+var curImgTest = 0;
+
+function runImgTest() {
+    var test = imgTests[curImgTest++];
+    var callback = curImgTest == imgTests.length ? finishTest : runImgTest;
+    loadImage(test[0], test[1], callback);
+}
+
+function finishTest() {
+  SimpleTest.finish();
+}
+
+function fail(event) {
+    is("fail", event.target.expected,
+       "content should not be allowed to load " + event.target.src);
+    if (event.target.callback)
+      event.target.callback();
+}
+
+function success(event) {
+    is("success", event.target.expected,
+       "content should be able to load " + event.target.src);
+    if (event.target.callback)
+      event.target.callback();
+}
+
+function loadImage(uri, expect, callback) {
+    var img = document.createElement("img");
+    img.onerror = fail;
+    img.onload = success;
+    img.expected = expect;
+    img.callback = callback;
+    img.src = uri;
+    // document.getElementById("content").appendChild(img);
+}
+
+// Start off the script src test, and have it start the img tests when complete.
+// Temporarily allow content to access all resource:// URIs.
+SpecialPowers.pushPrefEnv({
+  set: [
+    ["security.all_resource_uri_content_accessible", true],
+  ],
+}, () => testScriptSrc(runImgTest));
+</script>
+</pre>
+</body>
+</html>
diff --git a/caps/tests/mochitest/test_bug423375.html b/caps/tests/mochitest/test_bug423375.html
new file mode 100644
index 0000000000..2ae1dfb923
--- /dev/null
+++ b/caps/tests/mochitest/test_bug423375.html
@@ -0,0 +1,43 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=423375
+-->
+<head>
+  <title>Test for Bug 423375</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=423375">Mozilla Bug 423375</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+<iframe id="load-frame"></iframe>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+/**
+ *Test for Bug 423375
+ *(content shouldn't be able to load chrome: or resource:)
+ */
+function tryLoad(url) {
+    try {
+        window.frames[0].location = url;
+        return "loaded";
+    } catch (e) {
+        if (/Access.*denied/.test(String(e))) {
+          return "denied";
+        }
+        return "unexpected: " + e;
+    }
+}
+
+is(tryLoad("chrome://global/content/mozilla.html"), "denied",
+   "content should have been prevented from loading chrome: URL");
+is(tryLoad("resource://gre-resources/html.css"), "denied",
+   "content should have been prevented from loading resource: URL");
+</script>
+</pre>
+</body>
+</html>
diff --git a/caps/tests/mochitest/test_bug470804.html b/caps/tests/mochitest/test_bug470804.html
new file mode 100644
index 0000000000..26da479af6
--- /dev/null
+++ b/caps/tests/mochitest/test_bug470804.html
@@ -0,0 +1,41 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=470804
+-->
+<head>
+  <title>Test for Bug 470804</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=470804">Mozilla Bug 470804</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+
+</div>
+<pre id="test">
+<script type="application/javascript">
+
+/** Test for Bug 470804
+    Passing a null targetURL to checkLoadURIWithPrincipal shouldn't crash
+ */
+
+const nsIScriptSecurityManager = SpecialPowers.Ci.nsIScriptSecurityManager;
+var secMan = SpecialPowers.Services.scriptSecurityManager;
+var principal = SpecialPowers.wrap(document).nodePrincipal;
+isnot(principal, undefined, "Should have a principal");
+isnot(principal, null, "Should have a non-null principal");
+is(principal.isSystemPrincipal, false,
+   "Shouldn't have system principal here");
+try {
+  secMan.checkLoadURIWithPrincipal(principal, null,
+                                   nsIScriptSecurityManager.STANDARD);
+} catch (e) {
+  // throwing is fine, it's just crashing that's bad
+}
+ok(true, "Survival: we should get here without crashing");
+</script>
+</pre>
+</body>
+</html>
diff --git a/caps/tests/mochitest/test_bug995943.xhtml b/caps/tests/mochitest/test_bug995943.xhtml
new file mode 100644
index 0000000000..0ba95f548d
--- /dev/null
+++ b/caps/tests/mochitest/test_bug995943.xhtml
@@ -0,0 +1,111 @@
+<?xml version="1.0"?>
+<?xml-stylesheet type="text/css" href="chrome://global/skin"?>
+<?xml-stylesheet type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"?>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=995943
+-->
+<window title="Mozilla Bug 995943"
+        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+
+  <!-- test results are displayed in the html:body -->
+  <body xmlns="http://www.w3.org/1999/xhtml">
+  <a href="https://bugzilla.mozilla.org/show_bug.cgi?id=995943"
+     target="_blank">Mozilla Bug 995943</a>
+  </body>
+
+  <!-- test code goes here -->
+  <script type="application/javascript">
+  <![CDATA[
+  function debug(msg) { info(msg); }
+
+  /** Test for CAPS file:// URI prefs. */
+  SimpleTest.waitForExplicitFinish();
+  SimpleTest.requestCompleteLog();
+  if (navigator.userAgent.includes("Mac OS X 10.10"))
+    SimpleTest.expectAssertions(5, 11); // See bug 1067022, 1307988
+  else if (Services.appinfo.OS == "WINNT")
+    SimpleTest.expectAssertions(0, 1); // See bug 1067022
+  else
+    SimpleTest.expectAssertions(0, 9); // See bug 1305241, 1145314
+
+  var rootdir = Services.appinfo.OS == "WINNT" ? "file:///C:" : "file:///";
+
+  function checkLoadFileURI(domain, shouldLoad) {
+    debug("Invoking checkLoadFileURI with domain: " + domain + ", shouldLoad: " + shouldLoad);
+    return new Promise(function(resolve, reject) {
+      $('ifr').addEventListener('load', function l1() {
+        debug("Invoked l1 for " + domain);
+        $('ifr').removeEventListener('load', l1);
+        function l2() {
+          debug("Invoked l2 for " + domain);
+          $('ifr').removeEventListener('load', l2);
+          ok(shouldLoad, "Successfully loaded file:// URI for domain: " + domain);
+          resolve();
+        }
+        $('ifr').addEventListener('load', l2);
+        try {
+          window[0].wrappedJSObject.location = rootdir;
+          debug("Successfully navigated for " + domain);
+        } catch (e) {
+          ok(!shouldLoad && /denied|insecure/.test(e),
+             "Prevented loading of file:// URI for domain: " + domain + " - " + e);
+          $('ifr').removeEventListener('load', l2);
+          resolve();
+        }
+      });
+      let targetURI = domain + '/tests/js/xpconnect/tests/mochitest/file_empty.html';
+      debug("Navigating iframe to " + targetURI);
+      $('ifr').contentWindow.location = targetURI;
+    });
+  }
+
+  function pushPrefs(prefs) {
+    return SpecialPowers.pushPrefEnv({ set: prefs });
+  }
+
+  function popPrefs() {
+    return new Promise(function(resolve) { SpecialPowers.popPrefEnv(resolve); });
+  }
+
+  var gGoCount = 0;
+  function go() {
+    debug("Invoking go for window with id: " + window.windowGlobalChild.innerWindowId);
+    is(++gGoCount, 1, "Should only call go once!");
+    checkLoadFileURI('http://example.com', false).then(
+      pushPrefs.bind(null, [['capability.policy.policynames', ' somepolicy '],
+                            ['capability.policy.somepolicy.checkloaduri.enabled', 'AlLAcCeSs'],
+                            ['capability.policy.somepolicy.sites', 'http://example.com']]))
+    .then(checkLoadFileURI.bind(null, 'http://example.com', true))
+    .then(popPrefs)
+    .then(checkLoadFileURI.bind(null, 'http://example.com', false))
+    .then(
+      pushPrefs.bind(null, [['capability.policy.policynames', ',somepolicy, someotherpolicy, '],
+                            ['capability.policy.somepolicy.checkloaduri.enabled', 'allaccess'],
+                            ['capability.policy.someotherpolicy.checkloaduri.enabled', 'nope'],
+                            ['capability.policy.somepolicy.sites', ' http://example.org   test1.example.com https://test2.example.com '],
+                            ['capability.policy.someotherpolicy.sites', 'http://example.net ']]))
+    .then(checkLoadFileURI.bind(null, 'http://example.org', true))
+    .then(checkLoadFileURI.bind(null, 'http://test2.example.com', false))
+    .then(checkLoadFileURI.bind(null, 'https://test2.example.com', true))
+    .then(checkLoadFileURI.bind(null, 'http://sub1.test2.example.com', false))
+    .then(checkLoadFileURI.bind(null, 'https://sub1.test2.example.com', true))
+    .then(checkLoadFileURI.bind(null, 'http://example.net', false))
+    .then(checkLoadFileURI.bind(null, 'http://test1.example.com', true))
+    .then(checkLoadFileURI.bind(null, 'https://test1.example.com', true))
+    .then(checkLoadFileURI.bind(null, 'http://sub1.test1.example.com', true))
+    .then(checkLoadFileURI.bind(null, 'https://sub1.test1.example.com', true))
+    .then(pushPrefs.bind(null, [['capability.policy.someotherpolicy.checkloaduri.enabled', 'allAccess']]))
+    .then(checkLoadFileURI.bind(null, 'http://example.net', true))
+    .then(popPrefs)
+    .then(popPrefs)
+    .then(checkLoadFileURI.bind(null, 'http://example.net', false))
+    .then(SimpleTest.finish.bind(SimpleTest));
+
+  }
+  addLoadEvent(go);
+
+  ]]>
+  </script>
+  <iframe id="ifr" type="content" />
+</window>
diff --git a/caps/tests/mochitest/test_disableScript.xhtml b/caps/tests/mochitest/test_disableScript.xhtml
new file mode 100644
index 0000000000..8c16c13bc3
--- /dev/null
+++ b/caps/tests/mochitest/test_disableScript.xhtml
@@ -0,0 +1,330 @@
+<?xml version="1.0"?>
+<?xml-stylesheet type="text/css" href="chrome://global/skin"?>
+<?xml-stylesheet type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"?>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=840488
+-->
+<window title="Mozilla Bug 840488"
+        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+
+  <!-- test results are displayed in the html:body -->
+  <body xmlns="http://www.w3.org/1999/xhtml">
+  <a href="https://bugzilla.mozilla.org/show_bug.cgi?id=840488"
+     target="_blank">Mozilla Bug 840488</a>
+  </body>
+
+  <iframe id="root" name="root" type="content"/>
+  <iframe id="chromeFrame" name="chromeFrame" type="content"/>
+
+  <!-- test code goes here -->
+  <script type="application/javascript">
+  /* eslint-disable mozilla/no-useless-parameters, no-redeclare, no-undef */
+  <![CDATA[
+
+  /** Test for all the different ways that script can be disabled for a given global. */
+
+  SimpleTest.waitForExplicitFinish();
+  const ssm = Services.scriptSecurityManager;
+  function makeURI(uri) { return Services.io.newURI(uri); }
+  const path = "/tests/caps/tests/mochitest/file_disableScript.html";
+  const uri = "http://www.example.com" + path;
+  var rootFrame = document.getElementById('root');
+  var chromeFrame = document.getElementById('chromeFrame');
+  navigateFrame(rootFrame, uri + "?name=rootframe").then(function() {
+    navigateFrame(chromeFrame, "file_disableScript.html").then(go);
+  });
+
+  function navigateFrame(ifr, src) {
+    return new Promise(resolve => {
+      function onload() {
+        ifr.removeEventListener('load', onload);
+        resolve();
+      }
+      ifr.addEventListener('load', onload, false);
+      ifr.setAttribute('src', src);
+    });
+  }
+
+  function navigateBack(ifr) {
+    return new Promise(resolve => {
+
+      // pageshow events don't fire on the iframe element, so we need to use the
+      // chrome event handler for the docshell.
+      var browser = ifr.contentWindow.docShell.chromeEventHandler;
+      function onpageshow(evt) {
+        info("Navigated back. Persisted: " + evt.persisted);
+        browser.removeEventListener('pageshow', onpageshow);
+        resolve();
+      }
+      browser.addEventListener('pageshow', onpageshow, false);
+      ifr.contentWindow.history.back();
+    });
+  }
+
+  function addFrame(parentWin, name, expectOnload) {
+    let ifr = parentWin.document.createElement('iframe');
+    parentWin.document.body.appendChild(ifr);
+    ifr.setAttribute('name', name);
+    return new Promise(resolve => {
+      // We need to append 'name' to avoid running afoul of recursive frame detection.
+      let frameURI = uri + "?name=" + name;
+      navigateFrame(ifr, frameURI).then(function() {
+        is(String(ifr.contentWindow.location), frameURI, "Successful load");
+        is(!!ifr.contentWindow.wrappedJSObject.gFiredOnload, expectOnload,
+           "onload should only fire when scripts are enabled");
+        resolve();
+      });
+    });
+  }
+
+  function checkScriptEnabled(win, expectEnabled) {
+    win.wrappedJSObject.gFiredOnclick = false;
+    win.document.body.dispatchEvent(new win.Event('click'));
+    is(win.wrappedJSObject.gFiredOnclick, expectEnabled, "Checking script-enabled for " + win.name + " (" + win.location + ")");
+  }
+
+  function setScriptEnabled(win, enabled) {
+    win.browsingContext.allowJavascript = enabled;
+  }
+
+  function testList(expectEnabled, win, list, idx) {
+    idx = idx || 0;
+    return new Promise(resolve => {
+      let target = list[idx] + path;
+      info("Testing scriptability for: " + target + ". expecting " + expectEnabled);
+      navigateFrame(win.frameElement, target).then(function() {
+        checkScriptEnabled(win, expectEnabled);
+        if (idx == list.length - 1)
+          resolve();
+        else
+        testList(expectEnabled, win, list, idx + 1).then(function() { resolve(); });
+      });
+    });
+  }
+
+  function testDomainPolicy(defaultScriptability, exceptions, superExceptions,
+                            exempt, notExempt, set, superSet, win) {
+    // Populate our sets.
+    for (var e of exceptions)
+      set.add(makeURI(e));
+    for (var e of superExceptions)
+      superSet.add(makeURI(e));
+
+    return testList(defaultScriptability, win, notExempt).then(function() {
+      return testList(!defaultScriptability, win, exempt);
+    });
+  }
+
+  function setScriptEnabledForBrowser(enabled) {
+    var prefname = "javascript.enabled";
+    Services.prefs.setBoolPref(prefname, enabled);
+  }
+
+  function reloadFrame(frame) {
+    return new Promise(resolve => {
+      frame.addEventListener('load', function onload() {
+        resolve();
+        frame.removeEventListener('load', onload);
+      }, false);
+      frame.contentWindow.location.reload(true);
+    });
+  }
+
+  function go() {
+    var rootWin = rootFrame.contentWindow;
+    var chromeWin = chromeFrame.contentWindow;
+
+    // Test simple docshell enable/disable.
+    checkScriptEnabled(rootWin, true);
+    setScriptEnabled(rootWin, false);
+    checkScriptEnabled(rootWin, false);
+    setScriptEnabled(rootWin, true);
+    checkScriptEnabled(rootWin, true);
+
+    // Privileged frames are immune to docshell flags.
+    ok(chromeWin.document.nodePrincipal.isSystemPrincipal, "Sanity check for System Principal");
+    setScriptEnabled(chromeWin, false);
+    checkScriptEnabled(chromeWin, true);
+    setScriptEnabled(chromeWin, true);
+
+    // Play around with the docshell tree and make sure everything works as
+    // we expect.
+    addFrame(rootWin, 'parent', true).then(function() {
+      checkScriptEnabled(rootWin[0], true);
+      return addFrame(rootWin[0], 'childA', true);
+    }).then(function() {
+      checkScriptEnabled(rootWin[0][0], true);
+      setScriptEnabled(rootWin[0], false);
+      checkScriptEnabled(rootWin, true);
+      checkScriptEnabled(rootWin[0], false);
+      checkScriptEnabled(rootWin[0][0], false);
+      return addFrame(rootWin[0], 'childB', false);
+    }).then(function() {
+      checkScriptEnabled(rootWin[0][1], false);
+      setScriptEnabled(rootWin[0][0], false);
+      setScriptEnabled(rootWin[0], true);
+      checkScriptEnabled(rootWin[0], true);
+      checkScriptEnabled(rootWin[0][0], false);
+      setScriptEnabled(rootWin[0][0], true);
+
+      // Flags are inherited from the parent docshell at attach time. Note that
+      // the flag itself is inherited, regardless of whether or not scripts are
+      // currently allowed on the parent (which could depend on the parent's
+      // parent). Check that.
+      checkScriptEnabled(rootWin[0][1], false);
+      setScriptEnabled(rootWin[0], false);
+      setScriptEnabled(rootWin[0][1], true);
+      return addFrame(rootWin[0][1], 'grandchild', false);
+    }).then(function() {
+      checkScriptEnabled(rootWin[0], false);
+      checkScriptEnabled(rootWin[0][1], false);
+      checkScriptEnabled(rootWin[0][1][0], false);
+      setScriptEnabled(rootWin[0], true);
+      checkScriptEnabled(rootWin[0], true);
+      checkScriptEnabled(rootWin[0][1], true);
+      checkScriptEnabled(rootWin[0][1][0], true);
+
+    // Try navigating two frames, then munging docshell scriptability, then
+    // pulling the frames out of the bfcache to make sure that flags are
+    // properly propagated to inactive inner windows. We do this both for an
+    // 'own' docshell, as well as for an ancestor docshell.
+      return navigateFrame(rootWin[0][0].frameElement, rootWin[0][0].location + '-navigated');
+    }).then(function() { return navigateFrame(rootWin[0][1][0].frameElement, rootWin[0][1][0].location + '-navigated'); })
+      .then(function() {
+      checkScriptEnabled(rootWin[0][0], true);
+      checkScriptEnabled(rootWin[0][1][0], true);
+      setScriptEnabled(rootWin[0][0], false);
+      setScriptEnabled(rootWin[0][1], false);
+      checkScriptEnabled(rootWin[0][0], false);
+      checkScriptEnabled(rootWin[0][1][0], false);
+      return navigateBack(rootWin[0][0].frameElement);
+    }).then(function() { return navigateBack(rootWin[0][1][0].frameElement); })
+      .then(function() {
+      checkScriptEnabled(rootWin[0][0], false);
+      checkScriptEnabled(rootWin[0][1][0], false);
+
+    // Disable JS via the global pref pref. This is only guaranteed to have an effect
+    // for subsequent loads.
+      setScriptEnabledForBrowser(false);
+      return reloadFrame(rootFrame);
+    }).then(function() {
+      checkScriptEnabled(rootWin, false);
+      checkScriptEnabled(chromeWin, true);
+      setScriptEnabledForBrowser(true);
+      return reloadFrame(rootFrame);
+    }).then(function() {
+      checkScriptEnabled(rootWin, true);
+
+    // Play around with dynamically blocking script for a given global.
+    // This takes effect immediately.
+      Cu.blockScriptForGlobal(rootWin);
+      Cu.blockScriptForGlobal(rootWin);
+      Cu.unblockScriptForGlobal(rootWin);
+      checkScriptEnabled(rootWin, false);
+      Cu.unblockScriptForGlobal(rootWin);
+      checkScriptEnabled(rootWin, true);
+      Cu.blockScriptForGlobal(rootWin);
+      try {
+        Cu.blockScriptForGlobal(chromeWin);
+        ok(false, "Should have thrown");
+      } catch (e) {
+        ok(/may not be disabled/.test(e),
+           "Shouldn't be able to programmatically block script for system globals");
+      }
+      return reloadFrame(rootFrame);
+    }).then(function() {
+      checkScriptEnabled(rootWin, true);
+
+    // Test system-wide domain policy. This only takes effect for subsequently-
+    // loaded globals.
+
+    // Check the basic semantics of the sets.
+    is(ssm.domainPolicyActive, false, "not enabled");
+    window.policy = ssm.activateDomainPolicy();
+    ok(policy instanceof Ci.nsIDomainPolicy, "Got a policy");
+    try {
+      ssm.activateDomainPolicy();
+      ok(false, "Should have thrown");
+    } catch (e) {
+      ok(true, "can't have two live domain policies");
+    }
+    var sbRef = policy.superBlocklist;
+    isnot(sbRef, null, "superBlocklist non-null");
+    ok(!sbRef.contains(makeURI('http://www.example.com')));
+    sbRef.add(makeURI('http://www.example.com/foopy'));
+    ok(sbRef.contains(makeURI('http://www.example.com')));
+    sbRef.remove(makeURI('http://www.example.com'));
+    ok(!sbRef.contains(makeURI('http://www.example.com')));
+    sbRef.add(makeURI('http://www.example.com/foopy/this.that/'));
+    ok(sbRef.contains(makeURI('http://www.example.com/baz')));
+    ok(!sbRef.contains(makeURI('https://www.example.com')));
+    ok(!sbRef.contains(makeURI('https://www.example.com:88')));
+    ok(!sbRef.contains(makeURI('http://foo.www.example.com')));
+    ok(sbRef.containsSuperDomain(makeURI('http://foo.www.example.com')));
+    ok(sbRef.containsSuperDomain(makeURI('http://foo.bar.www.example.com')));
+    ok(!sbRef.containsSuperDomain(makeURI('http://foo.bar.www.exxample.com')));
+    ok(!sbRef.containsSuperDomain(makeURI('http://example.com')));
+    ok(!sbRef.containsSuperDomain(makeURI('http://com/this.that/')));
+    ok(!sbRef.containsSuperDomain(makeURI('https://foo.www.example.com')));
+    ok(sbRef.contains(makeURI('http://www.example.com')));
+    policy.deactivate();
+    is(ssm.domainPolicyActive, false, "back to inactive");
+    ok(!sbRef.contains(makeURI('http://www.example.com')),
+       "Disabling domain policy clears the set");
+    policy = ssm.activateDomainPolicy();
+    ok(policy.superBlocklist);
+    isnot(sbRef, policy.superBlocklist, "Mint new sets each time!");
+    policy.deactivate();
+    is(policy.blocklist, null, "blocklist nulled out");
+    policy = ssm.activateDomainPolicy();
+    isnot(policy.blocklist, null, "non-null again");
+    isnot(policy.blocklist, sbRef, "freshly minted");
+    policy.deactivate();
+
+    //
+    // Now, create and apply a mock-policy. We check the same policy both as
+    // a blocklist and as a allowlist.
+    //
+
+    window.testPolicy = {
+      // The policy.
+      exceptions: ['http://test1.example.com', 'http://example.com'],
+      superExceptions: ['http://test2.example.org', 'https://test1.example.com'],
+
+      // The testcases.
+      exempt: ['http://test1.example.com', 'http://example.com',
+               'http://test2.example.org', 'http://sub1.test2.example.org',
+               'https://sub1.test1.example.com'],
+
+      notExempt: ['http://test2.example.com', 'http://sub1.test1.example.com',
+                  'http://www.example.com', 'https://test2.example.com',
+                  'https://example.com', 'http://test1.example.org'],
+    };
+
+    policy = ssm.activateDomainPolicy();
+    info("Testing Blocklist-style Domain Policy");
+    return testDomainPolicy(true, testPolicy.exceptions,
+                            testPolicy.superExceptions, testPolicy.exempt,
+                            testPolicy.notExempt, policy.blocklist,
+                            policy.superBlocklist, rootWin);
+  }).then(function() {
+    policy.deactivate();
+    policy = ssm.activateDomainPolicy();
+    info("Testing Allowlist-style Domain Policy");
+    setScriptEnabledForBrowser(false);
+    return testDomainPolicy(false, testPolicy.exceptions,
+                            testPolicy.superExceptions, testPolicy.exempt,
+                            testPolicy.notExempt, policy.allowlist,
+                            policy.superAllowlist, rootWin);
+  }).then(function() {
+    setScriptEnabledForBrowser(true);
+    policy.deactivate();
+
+    SimpleTest.finish();
+    });
+  }
+
+  ]]>
+  </script>
+</window>
diff --git a/caps/tests/mochitest/test_disallowInheritPrincipal.html b/caps/tests/mochitest/test_disallowInheritPrincipal.html
new file mode 100644
index 0000000000..308ee61320
--- /dev/null
+++ b/caps/tests/mochitest/test_disallowInheritPrincipal.html
@@ -0,0 +1,58 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=732413
+-->
+<head>
+  <title>Test for Bug 732413</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=732413">Mozilla Bug 732413</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+
+</div>
+<pre id="test">
+<script type="application/javascript">
+
+/** Test for Bug 732413
+    Passing DISALLOW_INHERIT_PRINCIPAL flag should be effective even if
+    aPrincipal is the system principal.
+ */
+
+const nsIScriptSecurityManager = SpecialPowers.Ci.nsIScriptSecurityManager;
+var secMan = SpecialPowers.Cc["@mozilla.org/scriptsecuritymanager;1"]
+                       .getService(nsIScriptSecurityManager);
+var sysPrincipal = secMan.getSystemPrincipal();
+isnot(sysPrincipal, undefined, "Should have a principal");
+isnot(sysPrincipal, null, "Should have a non-null principal");
+is(sysPrincipal.isSystemPrincipal, true,
+   "Should have system principal here");
+
+
+var inheritingURI = SpecialPowers.Services.io.newURI("javascript:1+1");
+
+// First try a normal call to checkLoadURIWithPrincipal
+try {
+  secMan.checkLoadURIWithPrincipal(sysPrincipal, inheritingURI,
+                                   nsIScriptSecurityManager.STANDARD);
+  ok(true, "checkLoadURI allowed the load");
+} catch (e) {
+  ok(false, "checkLoadURI failed unexpectedly: " + e);
+}
+
+// Now call checkLoadURIWithPrincipal with DISALLOW_INHERIT_PRINCIPAL
+try {
+  secMan.checkLoadURIWithPrincipal(sysPrincipal, inheritingURI,
+                                   nsIScriptSecurityManager.DISALLOW_INHERIT_PRINCIPAL);
+  ok(false, "checkLoadURI allowed the load unexpectedly");
+} catch (e) {
+  ok(true, "checkLoadURI prevented load of principal-inheriting URI");
+}
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/caps/tests/unit/test_ipv6_host_literal.js b/caps/tests/unit/test_ipv6_host_literal.js
new file mode 100644
index 0000000000..cde7d82d7e
--- /dev/null
+++ b/caps/tests/unit/test_ipv6_host_literal.js
@@ -0,0 +1,38 @@
+var ssm = Services.scriptSecurityManager;
+function makeURI(uri) {
+  return Services.io.newURI(uri);
+}
+
+function testIPV6Host(aHost, aExpected) {
+  var ipv6Host = ssm.createContentPrincipal(makeURI(aHost), {});
+  Assert.equal(ipv6Host.origin, aExpected);
+}
+
+function run_test() {
+  testIPV6Host("http://[::1]/", "http://[::1]");
+
+  testIPV6Host(
+    "http://[2001:db8:85a3:8d3:1319:8a2e:370:7348]/",
+    "http://[2001:db8:85a3:8d3:1319:8a2e:370:7348]"
+  );
+
+  testIPV6Host(
+    "http://[2001:db8:85a3:8d3:1319:8a2e:370:7348]:443/",
+    "http://[2001:db8:85a3:8d3:1319:8a2e:370:7348]:443"
+  );
+
+  testIPV6Host(
+    "http://[2001:db8:85a3::1319:8a2e:370:7348]/",
+    "http://[2001:db8:85a3:0:1319:8a2e:370:7348]"
+  );
+
+  testIPV6Host(
+    "http://[20D1:0000:3238:DFE1:63:0000:0000:FEFB]/",
+    "http://[20d1:0:3238:dfe1:63::fefb]"
+  );
+
+  testIPV6Host(
+    "http://[20D1:0:3238:DFE1:63::FEFB]/",
+    "http://[20d1:0:3238:dfe1:63::fefb]"
+  );
+}
diff --git a/caps/tests/unit/test_oa_partitionKey_pattern.js b/caps/tests/unit/test_oa_partitionKey_pattern.js
new file mode 100644
index 0000000000..5d0625018f
--- /dev/null
+++ b/caps/tests/unit/test_oa_partitionKey_pattern.js
@@ -0,0 +1,159 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * Tests origin attributes partitionKey pattern matching.
+ */
+
+"use strict";
+
+function testMatch(oa, pattern, shouldMatch = true) {
+  let msg = `Origin attributes should ${
+    shouldMatch ? "match" : "not match"
+  } pattern.`;
+  msg += ` oa: ${JSON.stringify(oa)} - pattern: ${JSON.stringify(pattern)}`;
+  Assert.equal(
+    ChromeUtils.originAttributesMatchPattern(oa, pattern),
+    shouldMatch,
+    msg
+  );
+}
+
+function getPartitionKey(scheme, baseDomain, port) {
+  if (!scheme || !baseDomain) {
+    return "";
+  }
+  return `(${scheme},${baseDomain}${port ? `,${port}` : ``})`;
+}
+
+function getOAWithPartitionKey(scheme, baseDomain, port, oa = {}) {
+  oa.partitionKey = getPartitionKey(scheme, baseDomain, port);
+  return oa;
+}
+
+/**
+ * Tests that an OriginAttributesPattern which is empty or only has an empty
+ * partitionKeyPattern matches any partitionKey.
+ */
+add_task(async function test_empty_pattern_matches_any() {
+  let list = [
+    getOAWithPartitionKey("https", "example.com"),
+    getOAWithPartitionKey("http", "example.net", 8080),
+    getOAWithPartitionKey(),
+  ];
+
+  for (let oa of list) {
+    testMatch(oa, {});
+    testMatch(oa, { partitionKeyPattern: {} });
+  }
+});
+
+/**
+ * Tests that if a partitionKeyPattern is passed, but the partitionKey is
+ * invalid, the pattern match will always fail.
+ */
+add_task(async function test_invalid_pk() {
+  let list = [
+    "()",
+    "(,,)",
+    "(https)",
+    "(https,,)",
+    "(example.com)",
+    "(http,example.com,invalid)",
+    "(http,example.com,8000,1000)",
+  ].map(partitionKey => ({ partitionKey }));
+
+  for (let oa of list) {
+    testMatch(oa, {});
+    testMatch(oa, { partitionKeyPattern: {} });
+    testMatch(
+      oa,
+      { partitionKeyPattern: { baseDomain: "example.com" } },
+      false
+    );
+    testMatch(oa, { partitionKeyPattern: { scheme: "https" } }, false);
+  }
+});
+
+/**
+ * Tests that if a pattern sets "partitionKey" it takes precedence over "partitionKeyPattern".
+ */
+add_task(async function test_string_overwrites_pattern() {
+  let oa = getOAWithPartitionKey("https", "example.com", 8080, {
+    userContextId: 2,
+  });
+
+  testMatch(oa, { partitionKey: oa.partitionKey });
+  testMatch(oa, {
+    partitionKey: oa.partitionKey,
+    partitionKeyPattern: { baseDomain: "example.com" },
+  });
+  testMatch(oa, {
+    partitionKey: oa.partitionKey,
+    partitionKeyPattern: { baseDomain: "example.net" },
+  });
+  testMatch(
+    oa,
+    {
+      partitionKey: getPartitionKey("https", "example.net"),
+      partitionKeyPattern: { scheme: "https", baseDomain: "example.com" },
+    },
+    false
+  );
+});
+
+/**
+ * Tests that we can match parts of a partitionKey by setting
+ * partitionKeyPattern.
+ */
+add_task(async function test_pattern() {
+  let a = getOAWithPartitionKey("https", "example.com", 8080, {
+    userContextId: 2,
+  });
+  let b = getOAWithPartitionKey("https", "example.com", undefined, {
+    privateBrowsingId: 1,
+  });
+
+  for (let oa of [a, b]) {
+    // Match
+    testMatch(oa, { partitionKeyPattern: { scheme: "https" } });
+    testMatch(oa, {
+      partitionKeyPattern: { scheme: "https", baseDomain: "example.com" },
+    });
+    testMatch(
+      oa,
+      {
+        partitionKeyPattern: {
+          scheme: "https",
+          baseDomain: "example.com",
+          port: 8080,
+        },
+      },
+      oa == a
+    );
+    testMatch(oa, {
+      partitionKeyPattern: { baseDomain: "example.com" },
+    });
+    testMatch(
+      oa,
+      {
+        partitionKeyPattern: { port: 8080 },
+      },
+      oa == a
+    );
+
+    // Mismatch
+    testMatch(oa, { partitionKeyPattern: { scheme: "http" } }, false);
+    testMatch(
+      oa,
+      { partitionKeyPattern: { baseDomain: "example.net" } },
+      false
+    );
+    testMatch(oa, { partitionKeyPattern: { port: 8443 } }, false);
+    testMatch(
+      oa,
+      { partitionKeyPattern: { scheme: "https", baseDomain: "example.net" } },
+      false
+    );
+  }
+});
diff --git a/caps/tests/unit/test_origin.js b/caps/tests/unit/test_origin.js
new file mode 100644
index 0000000000..c0cbc2996a
--- /dev/null
+++ b/caps/tests/unit/test_origin.js
@@ -0,0 +1,323 @@
+var ssm = Services.scriptSecurityManager;
+function makeURI(uri) {
+  return Services.io.newURI(uri);
+}
+
+function checkThrows(f) {
+  var threw = false;
+  try {
+    f();
+  } catch (e) {
+    threw = true;
+  }
+  Assert.ok(threw);
+}
+
+function checkCrossOrigin(a, b) {
+  Assert.ok(!a.equals(b));
+  Assert.ok(!a.equalsConsideringDomain(b));
+  Assert.ok(!a.subsumes(b));
+  Assert.ok(!a.subsumesConsideringDomain(b));
+  Assert.ok(!b.subsumes(a));
+  Assert.ok(!b.subsumesConsideringDomain(a));
+}
+
+function checkOriginAttributes(prin, attrs, suffix) {
+  attrs = attrs || {};
+  Assert.equal(
+    prin.originAttributes.inIsolatedMozBrowser,
+    attrs.inIsolatedMozBrowser || false
+  );
+  Assert.equal(prin.originSuffix, suffix || "");
+  Assert.equal(ChromeUtils.originAttributesToSuffix(attrs), suffix || "");
+  Assert.ok(
+    ChromeUtils.originAttributesMatchPattern(prin.originAttributes, attrs)
+  );
+  if (!prin.isNullPrincipal && !prin.origin.startsWith("[")) {
+    Assert.ok(ssm.createContentPrincipalFromOrigin(prin.origin).equals(prin));
+  } else {
+    checkThrows(() => ssm.createContentPrincipalFromOrigin(prin.origin));
+  }
+}
+
+function checkSandboxOriginAttributes(arr, attrs, options) {
+  options = options || {};
+  var sandbox = Cu.Sandbox(arr, options);
+  checkOriginAttributes(
+    Cu.getObjectPrincipal(sandbox),
+    attrs,
+    ChromeUtils.originAttributesToSuffix(attrs)
+  );
+}
+
+// utility function useful for debugging
+// eslint-disable-next-line no-unused-vars
+function printAttrs(name, attrs) {
+  info(
+    name +
+      " {\n" +
+      "\tuserContextId: " +
+      attrs.userContextId +
+      ",\n" +
+      "\tinIsolatedMozBrowser: " +
+      attrs.inIsolatedMozBrowser +
+      ",\n" +
+      "\tprivateBrowsingId: '" +
+      attrs.privateBrowsingId +
+      "',\n" +
+      "\tfirstPartyDomain: '" +
+      attrs.firstPartyDomain +
+      "'\n}"
+  );
+}
+
+function checkValues(attrs, values) {
+  values = values || {};
+  // printAttrs("attrs", attrs);
+  // printAttrs("values", values);
+  Assert.equal(attrs.userContextId, values.userContextId || 0);
+  Assert.equal(
+    attrs.inIsolatedMozBrowser,
+    values.inIsolatedMozBrowser || false
+  );
+  Assert.equal(attrs.privateBrowsingId, values.privateBrowsingId || "");
+  Assert.equal(attrs.firstPartyDomain, values.firstPartyDomain || "");
+}
+
+function run_test() {
+  // Attributeless origins.
+  Assert.equal(ssm.getSystemPrincipal().origin, "[System Principal]");
+  checkOriginAttributes(ssm.getSystemPrincipal());
+  var exampleOrg = ssm.createContentPrincipal(
+    makeURI("http://example.org"),
+    {}
+  );
+  Assert.equal(exampleOrg.origin, "http://example.org");
+  checkOriginAttributes(exampleOrg);
+  var exampleCom = ssm.createContentPrincipal(
+    makeURI("https://www.example.com:123"),
+    {}
+  );
+  Assert.equal(exampleCom.origin, "https://www.example.com:123");
+  checkOriginAttributes(exampleCom);
+  var nullPrin = Cu.getObjectPrincipal(new Cu.Sandbox(null));
+  Assert.ok(
+    /^moz-nullprincipal:\{([0-9]|[a-z]|\-){36}\}$/.test(nullPrin.origin)
+  );
+  checkOriginAttributes(nullPrin);
+  var ipv6Prin = ssm.createContentPrincipal(
+    makeURI("https://[2001:db8::ff00:42:8329]:123"),
+    {}
+  );
+  Assert.equal(ipv6Prin.origin, "https://[2001:db8::ff00:42:8329]:123");
+  checkOriginAttributes(ipv6Prin);
+  var ipv6NPPrin = ssm.createContentPrincipal(
+    makeURI("https://[2001:db8::ff00:42:8329]"),
+    {}
+  );
+  Assert.equal(ipv6NPPrin.origin, "https://[2001:db8::ff00:42:8329]");
+  checkOriginAttributes(ipv6NPPrin);
+  var ep = Cu.getObjectPrincipal(
+    Cu.Sandbox([exampleCom, nullPrin, exampleOrg])
+  );
+  checkOriginAttributes(ep);
+  checkCrossOrigin(exampleCom, exampleOrg);
+  checkCrossOrigin(exampleOrg, nullPrin);
+
+  // nsEP origins should be in lexical order.
+  Assert.equal(
+    ep.origin,
+    `[Expanded Principal [${exampleCom.origin}, ${nullPrin.origin}, ${exampleOrg.origin}]]`
+  );
+
+  // Make sure createContentPrincipal does what the rest of gecko does.
+  Assert.ok(
+    exampleOrg.equals(
+      Cu.getObjectPrincipal(new Cu.Sandbox("http://example.org"))
+    )
+  );
+
+  //
+  // Test origin attributes.
+  //
+
+  // Just browser.
+  var exampleOrg_browser = ssm.createContentPrincipal(
+    makeURI("http://example.org"),
+    { inIsolatedMozBrowser: true }
+  );
+  var nullPrin_browser = ssm.createNullPrincipal({
+    inIsolatedMozBrowser: true,
+  });
+  checkOriginAttributes(
+    exampleOrg_browser,
+    { inIsolatedMozBrowser: true },
+    "^inBrowser=1"
+  );
+  checkOriginAttributes(
+    nullPrin_browser,
+    { inIsolatedMozBrowser: true },
+    "^inBrowser=1"
+  );
+  Assert.equal(exampleOrg_browser.origin, "http://example.org^inBrowser=1");
+
+  // First party Uri
+  var exampleOrg_firstPartyDomain = ssm.createContentPrincipal(
+    makeURI("http://example.org"),
+    { firstPartyDomain: "example.org" }
+  );
+  checkOriginAttributes(
+    exampleOrg_firstPartyDomain,
+    { firstPartyDomain: "example.org" },
+    "^firstPartyDomain=example.org"
+  );
+  Assert.equal(
+    exampleOrg_firstPartyDomain.origin,
+    "http://example.org^firstPartyDomain=example.org"
+  );
+
+  // Just userContext.
+  var exampleOrg_userContext = ssm.createContentPrincipal(
+    makeURI("http://example.org"),
+    { userContextId: 42 }
+  );
+  checkOriginAttributes(
+    exampleOrg_userContext,
+    { userContextId: 42 },
+    "^userContextId=42"
+  );
+  Assert.equal(
+    exampleOrg_userContext.origin,
+    "http://example.org^userContextId=42"
+  );
+
+  checkSandboxOriginAttributes(null, {});
+  checkSandboxOriginAttributes("http://example.org", {});
+  checkSandboxOriginAttributes(
+    "http://example.org",
+    {},
+    { originAttributes: {} }
+  );
+  checkSandboxOriginAttributes(["http://example.org"], {});
+  checkSandboxOriginAttributes(
+    ["http://example.org"],
+    {},
+    { originAttributes: {} }
+  );
+
+  // Check that all of the above are cross-origin.
+  checkCrossOrigin(exampleOrg_browser, nullPrin_browser);
+  checkCrossOrigin(exampleOrg_firstPartyDomain, exampleOrg);
+  checkCrossOrigin(exampleOrg_userContext, exampleOrg);
+
+  // Check Principal kinds.
+  function checkKind(prin, kind) {
+    Assert.equal(prin.isNullPrincipal, kind == "nullPrincipal");
+    Assert.equal(prin.isContentPrincipal, kind == "contentPrincipal");
+    Assert.equal(prin.isExpandedPrincipal, kind == "expandedPrincipal");
+    Assert.equal(prin.isSystemPrincipal, kind == "systemPrincipal");
+  }
+  checkKind(ssm.createNullPrincipal({}), "nullPrincipal");
+  checkKind(
+    ssm.createContentPrincipal(makeURI("http://www.example.com"), {}),
+    "contentPrincipal"
+  );
+  checkKind(
+    Cu.getObjectPrincipal(
+      Cu.Sandbox([
+        ssm.createContentPrincipal(makeURI("http://www.example.com"), {}),
+      ])
+    ),
+    "expandedPrincipal"
+  );
+  checkKind(ssm.getSystemPrincipal(), "systemPrincipal");
+
+  //
+  // Test Origin Attribute Manipulation
+  //
+
+  // check that we can create an empty origin attributes dict with default
+  // members and values.
+  var emptyAttrs = ChromeUtils.fillNonDefaultOriginAttributes({});
+  checkValues(emptyAttrs);
+
+  var uri = "http://example.org";
+  var tests = [
+    ["", {}],
+    ["^userContextId=3", { userContextId: 3 }],
+    ["^inBrowser=1", { inIsolatedMozBrowser: true }],
+    ["^firstPartyDomain=example.org", { firstPartyDomain: "example.org" }],
+  ];
+
+  // check that we can create an origin attributes from an origin properly
+  tests.forEach(t => {
+    let attrs = ChromeUtils.createOriginAttributesFromOrigin(uri + t[0]);
+    checkValues(attrs, t[1]);
+    Assert.equal(ChromeUtils.originAttributesToSuffix(attrs), t[0]);
+  });
+
+  // check that we can create an origin attributes from a dict properly
+  tests.forEach(t => {
+    let attrs = ChromeUtils.fillNonDefaultOriginAttributes(t[1]);
+    checkValues(attrs, t[1]);
+    Assert.equal(ChromeUtils.originAttributesToSuffix(attrs), t[0]);
+  });
+
+  // each row in the dflt_tests array has these values:
+  // [0] - the suffix used to create an origin attribute from
+  // [1] - the expected result of creating an origin attributes from [0]
+  // [2] - the expected result after setting userContextId to the default
+  // [3] - the expected result of creating a suffix from [2]
+  var dflt_tests = [
+    ["", {}, {}, ""],
+    ["^userContextId=3", { userContextId: 3 }, {}, ""],
+  ];
+
+  // check that we can set the userContextId to default properly
+  dflt_tests.forEach(t => {
+    let orig = ChromeUtils.createOriginAttributesFromOrigin(uri + t[0]);
+    checkValues(orig, t[1]);
+    let mod = orig;
+    mod.userContextId = 0;
+    checkValues(mod, t[2]);
+    Assert.equal(ChromeUtils.originAttributesToSuffix(mod), t[3]);
+  });
+
+  // each row in the dflt2_tests array has these values:
+  // [0] - the suffix used to create an origin attribute from
+  // [1] - the expected result of creating an origin attributes from [0]
+  // [2] - the expected result after setting firstPartyUri to the default
+  // [3] - the expected result of creating a suffix from [2]
+  var dflt2_tests = [
+    ["", {}, {}, ""],
+    ["^firstPartyDomain=foo.com", { firstPartyDomain: "foo.com" }, {}, ""],
+  ];
+
+  // check that we can set the userContextId to default properly
+  dflt2_tests.forEach(t => {
+    let orig = ChromeUtils.createOriginAttributesFromOrigin(uri + t[0]);
+    checkValues(orig, t[1]);
+    let mod = orig;
+    mod.firstPartyDomain = "";
+    checkValues(mod, t[2]);
+    Assert.equal(ChromeUtils.originAttributesToSuffix(mod), t[3]);
+  });
+
+  var fileURI = makeURI("file:///foo/bar").QueryInterface(Ci.nsIFileURL);
+  var fileTests = [
+    [true, fileURI.spec],
+    [false, "file://UNIVERSAL_FILE_URI_ORIGIN"],
+  ];
+  fileTests.forEach(t => {
+    Services.prefs.setBoolPref("security.fileuri.strict_origin_policy", t[0]);
+    var filePrin = ssm.createContentPrincipal(fileURI, {});
+    Assert.equal(filePrin.origin, t[1]);
+  });
+  Services.prefs.clearUserPref("security.fileuri.strict_origin_policy");
+
+  var aboutBlankURI = makeURI("about:blank");
+  var aboutBlankPrin = ssm.createContentPrincipal(aboutBlankURI, {});
+  Assert.ok(
+    /^moz-nullprincipal:\{([0-9]|[a-z]|\-){36}\}$/.test(aboutBlankPrin.origin)
+  );
+}
diff --git a/caps/tests/unit/test_precursor_principal.js b/caps/tests/unit/test_precursor_principal.js
new file mode 100644
index 0000000000..37c1ae13bc
--- /dev/null
+++ b/caps/tests/unit/test_precursor_principal.js
@@ -0,0 +1,259 @@
+"use strict";
+const { TestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TestUtils.sys.mjs"
+);
+const { XPCShellContentUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/XPCShellContentUtils.sys.mjs"
+);
+const { ExtensionTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/ExtensionXPCShellUtils.sys.mjs"
+);
+
+XPCShellContentUtils.init(this);
+ExtensionTestUtils.init(this);
+
+const server = XPCShellContentUtils.createHttpServer({
+  hosts: ["example.com", "example.org"],
+});
+
+server.registerPathHandler("/static_frames", (request, response) => {
+  response.setHeader("Content-Type", "text/html");
+  response.write(`
+    <iframe name="same_origin" sandbox="allow-scripts allow-same-origin" src="http://example.com/frame"></iframe>
+    <iframe name="same_origin_sandbox" sandbox="allow-scripts" src="http://example.com/frame"></iframe>
+    <iframe name="cross_origin" sandbox="allow-scripts allow-same-origin" src="http://example.org/frame"></iframe>
+    <iframe name="cross_origin_sandbox" sandbox="allow-scripts" src="http://example.org/frame"></iframe>
+    <iframe name="data_uri" sandbox="allow-scripts allow-same-origin" src="data:text/html,<h1>Data Subframe</h1>"></iframe>
+    <iframe name="data_uri_sandbox" sandbox="allow-scripts" src="data:text/html,<h1>Data Subframe</h1>"></iframe>
+    <iframe name="srcdoc" sandbox="allow-scripts allow-same-origin" srcdoc="<h1>Srcdoc Subframe</h1>"></iframe>
+    <iframe name="srcdoc_sandbox" sandbox="allow-scripts" srcdoc="<h1>Srcdoc Subframe</h1>"></iframe>
+    <iframe name="blank" sandbox="allow-scripts allow-same-origin"></iframe>
+    <iframe name="blank_sandbox" sandbox="allow-scripts"></iframe>
+    <iframe name="redirect_com" sandbox="allow-scripts allow-same-origin" src="/redirect?com"></iframe>
+    <iframe name="redirect_com_sandbox" sandbox="allow-scripts" src="/redirect?com"></iframe>
+    <iframe name="redirect_org" sandbox="allow-scripts allow-same-origin" src="/redirect?org"></iframe>
+    <iframe name="redirect_org_sandbox" sandbox="allow-scripts" src="/redirect?org"></iframe>
+    <iframe name="ext_redirect_com_com" sandbox="allow-scripts allow-same-origin" src="/ext_redirect?com"></iframe>
+    <iframe name="ext_redirect_com_com_sandbox" sandbox="allow-scripts" src="/ext_redirect?com"></iframe>
+    <iframe name="ext_redirect_org_com" sandbox="allow-scripts allow-same-origin" src="http://example.org/ext_redirect?com"></iframe>
+    <iframe name="ext_redirect_org_com_sandbox" sandbox="allow-scripts" src="http://example.org/ext_redirect?com"></iframe>
+    <iframe name="ext_redirect_com_org" sandbox="allow-scripts allow-same-origin" src="/ext_redirect?org"></iframe>
+    <iframe name="ext_redirect_com_org_sandbox" sandbox="allow-scripts" src="/ext_redirect?org"></iframe>
+    <iframe name="ext_redirect_org_org" sandbox="allow-scripts allow-same-origin" src="http://example.org/ext_redirect?org"></iframe>
+    <iframe name="ext_redirect_org_org_sandbox" sandbox="allow-scripts" src="http://example.org/ext_redirect?org"></iframe>
+    <iframe name="ext_redirect_com_data" sandbox="allow-scripts allow-same-origin" src="/ext_redirect?data"></iframe>
+    <iframe name="ext_redirect_com_data_sandbox" sandbox="allow-scripts" src="/ext_redirect?data"></iframe>
+    <iframe name="ext_redirect_org_data" sandbox="allow-scripts allow-same-origin" src="http://example.org/ext_redirect?data"></iframe>
+    <iframe name="ext_redirect_org_data_sandbox" sandbox="allow-scripts" src="http://example.org/ext_redirect?data"></iframe>
+
+    <!-- XXX(nika): These aren't static as they perform loads dynamically - perhaps consider testing them separately? -->
+    <iframe name="client_replace_org_blank" sandbox="allow-scripts allow-same-origin" src="http://example.org/client_replace?blank"></iframe>
+    <iframe name="client_replace_org_blank_sandbox" sandbox="allow-scripts" src="http://example.org/client_replace?blank"></iframe>
+    <iframe name="client_replace_org_data" sandbox="allow-scripts allow-same-origin" src="http://example.org/client_replace?data"></iframe>
+    <iframe name="client_replace_org_data_sandbox" sandbox="allow-scripts" src="http://example.org/client_replace?data"></iframe>
+  `);
+});
+
+server.registerPathHandler("/frame", (request, response) => {
+  response.setHeader("Content-Type", "text/html");
+  response.write(`<h1>HTTP Subframe</h1>`);
+});
+
+server.registerPathHandler("/redirect", (request, response) => {
+  let redirect;
+  if (request.queryString == "com") {
+    redirect = "http://example.com/frame";
+  } else if (request.queryString == "org") {
+    redirect = "http://example.org/frame";
+  } else {
+    response.setStatusLine(request.httpVersion, 404, "Not found");
+    return;
+  }
+
+  response.setStatusLine(request.httpVersion, 302, "Found");
+  response.setHeader("Location", redirect);
+});
+
+server.registerPathHandler("/client_replace", (request, response) => {
+  let redirect;
+  if (request.queryString == "blank") {
+    redirect = "about:blank";
+  } else if (request.queryString == "data") {
+    redirect = "data:text/html,<h1>Data Subframe</h1>";
+  } else {
+    response.setStatusLine(request.httpVersion, 404, "Not found");
+    return;
+  }
+
+  response.setHeader("Content-Type", "text/html");
+  response.write(`
+    <script>
+      window.location.replace(${JSON.stringify(redirect)});
+    </script>
+  `);
+});
+
+add_task(async function sandboxed_precursor() {
+  // Bug 1725345: Make XPCShellContentUtils.createHttpServer support https
+  Services.prefs.setBoolPref("dom.security.https_first", false);
+
+  let extension = await ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "<all_urls>"],
+    },
+    background() {
+      // eslint-disable-next-line no-undef
+      browser.webRequest.onBeforeRequest.addListener(
+        details => {
+          let url = new URL(details.url);
+          if (!url.pathname.includes("ext_redirect")) {
+            return {};
+          }
+
+          let redirectUrl;
+          if (url.search == "?com") {
+            redirectUrl = "http://example.com/frame";
+          } else if (url.search == "?org") {
+            redirectUrl = "http://example.org/frame";
+          } else if (url.search == "?data") {
+            redirectUrl = "data:text/html,<h1>Data Subframe</h1>";
+          }
+          return { redirectUrl };
+        },
+        { urls: ["<all_urls>"] },
+        ["blocking"]
+      );
+    },
+  });
+  await extension.startup();
+
+  registerCleanupFunction(async function () {
+    await extension.unload();
+  });
+
+  for (let userContextId of [undefined, 1]) {
+    let comURI = Services.io.newURI("http://example.com");
+    let comPrin = Services.scriptSecurityManager.createContentPrincipal(
+      comURI,
+      { userContextId }
+    );
+    let orgURI = Services.io.newURI("http://example.org");
+    let orgPrin = Services.scriptSecurityManager.createContentPrincipal(
+      orgURI,
+      { userContextId }
+    );
+
+    let page = await XPCShellContentUtils.loadContentPage(
+      "http://example.com/static_frames",
+      {
+        remote: true,
+        remoteSubframes: true,
+        userContextId,
+      }
+    );
+    let bc = page.browsingContext;
+
+    ok(
+      bc.currentWindowGlobal.documentPrincipal.equals(comPrin),
+      "toplevel principal matches"
+    );
+
+    // XXX: This is sketchy as heck, but it's also the easiest way to wait for
+    // the `window.location.replace` loads to finish.
+    await TestUtils.waitForCondition(
+      () =>
+        bc.children.every(
+          child =>
+            !child.currentWindowGlobal.documentURI.spec.includes(
+              "/client_replace"
+            )
+        ),
+      "wait for every client_replace global to be replaced"
+    );
+
+    let principals = {};
+    for (let child of bc.children) {
+      notEqual(child.name, "", "child frames must have names");
+      ok(!(child.name in principals), "duplicate child frame name");
+      principals[child.name] = child.currentWindowGlobal.documentPrincipal;
+    }
+
+    function principal_is(name, expected) {
+      let principal = principals[name];
+      info(`${name} = ${principal.origin}`);
+      ok(principal.equals(expected), `${name} is correct`);
+    }
+    function precursor_is(name, precursor) {
+      let principal = principals[name];
+      info(`${name} = ${principal.origin}`);
+      ok(principal.isNullPrincipal, `${name} is null`);
+      ok(
+        principal.precursorPrincipal.equals(precursor),
+        `${name} has the correct precursor`
+      );
+    }
+
+    // Basic loads should have the principals or precursor principals for the
+    // document being loaded.
+    principal_is("same_origin", comPrin);
+    precursor_is("same_origin_sandbox", comPrin);
+
+    principal_is("cross_origin", orgPrin);
+    precursor_is("cross_origin_sandbox", orgPrin);
+
+    // Loads of a data: URI should complete with a sandboxed principal based on
+    // the principal which tried to perform the load.
+    precursor_is("data_uri", comPrin);
+    precursor_is("data_uri_sandbox", comPrin);
+
+    // Loads which inherit principals, such as srcdoc an about:blank loads,
+    // should also inherit sandboxed precursor principals.
+    principal_is("srcdoc", comPrin);
+    precursor_is("srcdoc_sandbox", comPrin);
+
+    principal_is("blank", comPrin);
+    precursor_is("blank_sandbox", comPrin);
+
+    // Redirects shouldn't interfere with the final principal, and it should be
+    // based only on the final URI.
+    principal_is("redirect_com", comPrin);
+    precursor_is("redirect_com_sandbox", comPrin);
+
+    principal_is("redirect_org", orgPrin);
+    precursor_is("redirect_org_sandbox", orgPrin);
+
+    // Extension redirects should act like normal redirects, and still resolve
+    // with the principal or sandboxed principal of the final URI.
+    principal_is("ext_redirect_com_com", comPrin);
+    precursor_is("ext_redirect_com_com_sandbox", comPrin);
+
+    principal_is("ext_redirect_com_org", orgPrin);
+    precursor_is("ext_redirect_com_org_sandbox", orgPrin);
+
+    principal_is("ext_redirect_org_com", comPrin);
+    precursor_is("ext_redirect_org_com_sandbox", comPrin);
+
+    principal_is("ext_redirect_org_org", orgPrin);
+    precursor_is("ext_redirect_org_org_sandbox", orgPrin);
+
+    // When an extension redirects to a data: URI, we use the last non-data: URI
+    // in the chain as the precursor principal.
+    // FIXME: This should perhaps use the extension's principal instead?
+    precursor_is("ext_redirect_com_data", comPrin);
+    precursor_is("ext_redirect_com_data_sandbox", comPrin);
+
+    precursor_is("ext_redirect_org_data", orgPrin);
+    precursor_is("ext_redirect_org_data_sandbox", orgPrin);
+
+    // Check that navigations triggred by script within the frames will have the
+    // correct behaviour when navigating to blank and data URIs.
+    principal_is("client_replace_org_blank", orgPrin);
+    precursor_is("client_replace_org_blank_sandbox", orgPrin);
+
+    precursor_is("client_replace_org_data", orgPrin);
+    precursor_is("client_replace_org_data_sandbox", orgPrin);
+
+    await page.close();
+  }
+  Services.prefs.clearUserPref("dom.security.https_first");
+});
diff --git a/caps/tests/unit/test_site_origin.js b/caps/tests/unit/test_site_origin.js
new file mode 100644
index 0000000000..bbde787f00
--- /dev/null
+++ b/caps/tests/unit/test_site_origin.js
@@ -0,0 +1,184 @@
+const scriptSecMan = Services.scriptSecurityManager;
+
+// SystemPrincipal checks
+let systemPrincipal = scriptSecMan.getSystemPrincipal();
+Assert.ok(systemPrincipal.isSystemPrincipal);
+Assert.equal(systemPrincipal.origin, "[System Principal]");
+Assert.equal(systemPrincipal.originNoSuffix, "[System Principal]");
+Assert.equal(systemPrincipal.siteOrigin, "[System Principal]");
+Assert.equal(systemPrincipal.siteOriginNoSuffix, "[System Principal]");
+
+// ContentPrincipal checks
+let uri1 = Services.io.newURI("http://example.com");
+let prinicpal1 = scriptSecMan.createContentPrincipal(uri1, {
+  userContextId: 11,
+});
+Assert.ok(prinicpal1.isContentPrincipal);
+Assert.equal(prinicpal1.origin, "http://example.com^userContextId=11");
+Assert.equal(prinicpal1.originNoSuffix, "http://example.com");
+Assert.equal(prinicpal1.siteOrigin, "http://example.com^userContextId=11");
+Assert.equal(prinicpal1.siteOriginNoSuffix, "http://example.com");
+
+let uri2 = Services.io.newURI("http://test1.example.com");
+let prinicpal2 = scriptSecMan.createContentPrincipal(uri2, {
+  userContextId: 22,
+});
+Assert.ok(prinicpal2.isContentPrincipal);
+Assert.equal(prinicpal2.origin, "http://test1.example.com^userContextId=22");
+Assert.equal(prinicpal2.originNoSuffix, "http://test1.example.com");
+Assert.equal(prinicpal2.siteOrigin, "http://example.com^userContextId=22");
+Assert.equal(prinicpal2.siteOriginNoSuffix, "http://example.com");
+
+let uri3 = Services.io.newURI("https://test1.test2.example.com:5555");
+let prinicpal3 = scriptSecMan.createContentPrincipal(uri3, {
+  userContextId: 5555,
+});
+Assert.ok(prinicpal3.isContentPrincipal);
+Assert.equal(
+  prinicpal3.origin,
+  "https://test1.test2.example.com:5555^userContextId=5555"
+);
+Assert.equal(prinicpal3.originNoSuffix, "https://test1.test2.example.com:5555");
+Assert.equal(prinicpal3.siteOrigin, "https://example.com^userContextId=5555");
+Assert.equal(prinicpal3.siteOriginNoSuffix, "https://example.com");
+
+let uri4 = Services.io.newURI("https://.example.com:6666");
+let prinicpal4 = scriptSecMan.createContentPrincipal(uri4, {
+  userContextId: 6666,
+});
+Assert.ok(prinicpal4.isContentPrincipal);
+Assert.equal(prinicpal4.origin, "https://.example.com:6666^userContextId=6666");
+Assert.equal(prinicpal4.originNoSuffix, "https://.example.com:6666");
+Assert.equal(prinicpal4.siteOrigin, "https://.example.com^userContextId=6666");
+Assert.equal(prinicpal4.siteOriginNoSuffix, "https://.example.com");
+
+let aboutURI = Services.io.newURI("about:preferences");
+let aboutPrincipal = scriptSecMan.createContentPrincipal(aboutURI, {
+  userContextId: 66,
+});
+Assert.ok(aboutPrincipal.isContentPrincipal);
+Assert.equal(aboutPrincipal.origin, "about:preferences^userContextId=66");
+Assert.equal(aboutPrincipal.originNoSuffix, "about:preferences");
+Assert.equal(aboutPrincipal.siteOrigin, "about:preferences^userContextId=66");
+Assert.equal(aboutPrincipal.siteOriginNoSuffix, "about:preferences");
+
+let viewSourceURI = Services.io.newURI(
+  "view-source:https://test1.test2.example.com"
+);
+let viewSourcePrincipal = scriptSecMan.createContentPrincipal(viewSourceURI, {
+  userContextId: 101,
+});
+Assert.ok(viewSourcePrincipal.isContentPrincipal);
+Assert.ok(viewSourcePrincipal.schemeIs("view-source"));
+Assert.equal(
+  viewSourcePrincipal.origin,
+  "https://test1.test2.example.com^userContextId=101"
+);
+Assert.equal(
+  viewSourcePrincipal.originNoSuffix,
+  "https://test1.test2.example.com"
+);
+Assert.equal(
+  viewSourcePrincipal.siteOrigin,
+  "https://example.com^userContextId=101"
+);
+Assert.equal(viewSourcePrincipal.siteOriginNoSuffix, "https://example.com");
+
+let mozExtensionURI = Services.io.newURI(
+  "moz-extension://924f966d-c93b-4fbf-968a-16608461663c/meh.txt"
+);
+let mozExtensionPrincipal = scriptSecMan.createContentPrincipal(
+  mozExtensionURI,
+  {
+    userContextId: 102,
+  }
+);
+Assert.ok(mozExtensionPrincipal.isContentPrincipal);
+Assert.ok(mozExtensionPrincipal.schemeIs("moz-extension"));
+Assert.equal(
+  mozExtensionPrincipal.origin,
+  "moz-extension://924f966d-c93b-4fbf-968a-16608461663c^userContextId=102"
+);
+Assert.equal(
+  mozExtensionPrincipal.originNoSuffix,
+  "moz-extension://924f966d-c93b-4fbf-968a-16608461663c"
+);
+Assert.equal(
+  mozExtensionPrincipal.siteOrigin,
+  "moz-extension://924f966d-c93b-4fbf-968a-16608461663c^userContextId=102"
+);
+Assert.equal(
+  mozExtensionPrincipal.siteOriginNoSuffix,
+  "moz-extension://924f966d-c93b-4fbf-968a-16608461663c"
+);
+
+let localhostURI = Services.io.newURI(" http://localhost:44203");
+let localhostPrincipal = scriptSecMan.createContentPrincipal(localhostURI, {
+  userContextId: 144,
+});
+Assert.ok(localhostPrincipal.isContentPrincipal);
+Assert.ok(localhostPrincipal.schemeIs("http"));
+Assert.equal(
+  localhostPrincipal.origin,
+  "http://localhost:44203^userContextId=144"
+);
+Assert.equal(localhostPrincipal.originNoSuffix, "http://localhost:44203");
+Assert.equal(
+  localhostPrincipal.siteOrigin,
+  "http://localhost^userContextId=144"
+);
+Assert.equal(localhostPrincipal.siteOriginNoSuffix, "http://localhost");
+
+// NullPrincipal checks
+let nullPrincipal = scriptSecMan.createNullPrincipal({ userContextId: 33 });
+Assert.ok(nullPrincipal.isNullPrincipal);
+Assert.ok(nullPrincipal.origin.includes("moz-nullprincipal"));
+Assert.ok(nullPrincipal.origin.includes("^userContextId=33"));
+Assert.ok(nullPrincipal.originNoSuffix.includes("moz-nullprincipal"));
+Assert.ok(!nullPrincipal.originNoSuffix.includes("^userContextId=33"));
+Assert.ok(nullPrincipal.siteOrigin.includes("moz-nullprincipal"));
+Assert.ok(nullPrincipal.siteOrigin.includes("^userContextId=33"));
+Assert.ok(nullPrincipal.siteOriginNoSuffix.includes("moz-nullprincipal"));
+Assert.ok(!nullPrincipal.siteOriginNoSuffix.includes("^userContextId=33"));
+
+// ExpandedPrincipal checks
+let expandedPrincipal = Cu.getObjectPrincipal(Cu.Sandbox([prinicpal2]));
+Assert.ok(expandedPrincipal.isExpandedPrincipal);
+Assert.equal(
+  expandedPrincipal.origin,
+  "[Expanded Principal [http://test1.example.com^userContextId=22]]^userContextId=22"
+);
+Assert.equal(
+  expandedPrincipal.originNoSuffix,
+  "[Expanded Principal [http://test1.example.com^userContextId=22]]"
+);
+Assert.equal(
+  expandedPrincipal.siteOrigin,
+  "[Expanded Principal [http://test1.example.com^userContextId=22]]^userContextId=22"
+);
+Assert.equal(
+  expandedPrincipal.siteOriginNoSuffix,
+  "[Expanded Principal [http://test1.example.com^userContextId=22]]"
+);
+
+let ipv6URI = Services.io.newURI("https://[2001:db8::ff00:42:8329]:123");
+let ipv6Principal = scriptSecMan.createContentPrincipal(ipv6URI, {
+  userContextId: 6,
+});
+Assert.ok(ipv6Principal.isContentPrincipal);
+Assert.equal(
+  ipv6Principal.origin,
+  "https://[2001:db8::ff00:42:8329]:123^userContextId=6"
+);
+Assert.equal(
+  ipv6Principal.originNoSuffix,
+  "https://[2001:db8::ff00:42:8329]:123"
+);
+Assert.equal(
+  ipv6Principal.siteOrigin,
+  "https://[2001:db8::ff00:42:8329]^userContextId=6"
+);
+Assert.equal(
+  ipv6Principal.siteOriginNoSuffix,
+  "https://[2001:db8::ff00:42:8329]"
+);
diff --git a/caps/tests/unit/test_uri_escaping.js b/caps/tests/unit/test_uri_escaping.js
new file mode 100644
index 0000000000..7feb581295
--- /dev/null
+++ b/caps/tests/unit/test_uri_escaping.js
@@ -0,0 +1,28 @@
+var ssm = Services.scriptSecurityManager;
+
+function makeURI(uri) {
+  return Services.io.newURI(uri);
+}
+
+function createPrincipal(aURI) {
+  try {
+    var uri = makeURI(aURI);
+    var principal = ssm.createContentPrincipal(uri, {});
+    return principal;
+  } catch (e) {
+    return null;
+  }
+}
+
+function run_test() {
+  Assert.equal(createPrincipal("http://test^test/foo^bar#x^y"), null);
+
+  Assert.equal(createPrincipal("http://test^test/foo\\bar"), null);
+
+  Assert.equal(createPrincipal("http://test:2^3/foo\\bar"), null);
+
+  Assert.equal(
+    createPrincipal("http://test/foo^bar").exposableSpec,
+    "http://test/foo%5Ebar"
+  );
+}
diff --git a/caps/tests/unit/xpcshell.ini b/caps/tests/unit/xpcshell.ini
new file mode 100644
index 0000000000..9ff2b22617
--- /dev/null
+++ b/caps/tests/unit/xpcshell.ini
@@ -0,0 +1,11 @@
+[DEFAULT]
+head =
+
+[test_origin.js]
+[test_uri_escaping.js]
+[test_ipv6_host_literal.js]
+[test_oa_partitionKey_pattern.js]
+[test_site_origin.js]
+[test_precursor_principal.js]
+firefox-appdir = browser
+skip-if = toolkit == 'android'