Adding upstream version 86.0.1.upstream/86.0.1upstream

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

1 files changed, 653 insertions, 0 deletions

diff --git a/netwerk/protocol/res/SubstitutingProtocolHandler.cpp b/netwerk/protocol/res/SubstitutingProtocolHandler.cpp
new file mode 100644
index 0000000000..baf368761b
--- /dev/null
+++ b/netwerk/protocol/res/SubstitutingProtocolHandler.cpp
@@ -0,0 +1,653 @@
+/* -*- 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 "mozilla/ModuleUtils.h"
+#include "mozilla/Unused.h"
+#include "mozilla/chrome/RegistryMessageUtils.h"
+#include "mozilla/dom/ContentParent.h"
+
+#include "SubstitutingProtocolHandler.h"
+#include "SubstitutingURL.h"
+#include "SubstitutingJARURI.h"
+#include "nsIChannel.h"
+#include "nsIIOService.h"
+#include "nsIFile.h"
+#include "nsNetCID.h"
+#include "nsNetUtil.h"
+#include "nsReadableUtils.h"
+#include "nsURLHelper.h"
+#include "nsEscape.h"
+#include "nsIObjectInputStream.h"
+#include "nsIObjectOutputStream.h"
+#include "nsIClassInfoImpl.h"
+
+using mozilla::dom::ContentParent;
+
+namespace mozilla {
+namespace net {
+
+// Log module for Substituting Protocol logging. We keep the pre-existing module
+// name of "nsResProtocol" to avoid disruption.
+static LazyLogModule gResLog("nsResProtocol");
+
+static NS_DEFINE_CID(kSubstitutingURLCID, NS_SUBSTITUTINGURL_CID);
+static NS_DEFINE_CID(kSubstitutingJARURIImplCID,
+                     NS_SUBSTITUTINGJARURI_IMPL_CID);
+
+//---------------------------------------------------------------------------------
+// SubstitutingURL : overrides nsStandardURL::GetFile to provide nsIFile
+// resolution
+//---------------------------------------------------------------------------------
+
+// The list of interfaces should be in sync with nsStandardURL
+// Queries this list of interfaces. If none match, it queries mURI.
+NS_IMPL_NSIURIMUTATOR_ISUPPORTS(SubstitutingURL::Mutator, nsIURISetters,
+                                nsIURIMutator, nsIStandardURLMutator,
+                                nsIURLMutator, nsIFileURLMutator,
+                                nsISerializable)
+
+NS_IMPL_CLASSINFO(SubstitutingURL, nullptr, nsIClassInfo::THREADSAFE,
+                  NS_SUBSTITUTINGURL_CID)
+// Empty CI getter. We only need nsIClassInfo for Serialization
+NS_IMPL_CI_INTERFACE_GETTER0(SubstitutingURL)
+
+NS_IMPL_ADDREF_INHERITED(SubstitutingURL, nsStandardURL)
+NS_IMPL_RELEASE_INHERITED(SubstitutingURL, nsStandardURL)
+NS_IMPL_QUERY_INTERFACE_CI_INHERITED0(SubstitutingURL, nsStandardURL)
+
+nsresult SubstitutingURL::EnsureFile() {
+  nsAutoCString ourScheme;
+  nsresult rv = GetScheme(ourScheme);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Get the handler associated with this scheme. It would be nice to just
+  // pass this in when constructing SubstitutingURLs, but we need a generic
+  // factory constructor.
+  nsCOMPtr<nsIIOService> io = do_GetIOService(&rv);
+  nsCOMPtr<nsIProtocolHandler> handler;
+  rv = io->GetProtocolHandler(ourScheme.get(), getter_AddRefs(handler));
+  NS_ENSURE_SUCCESS(rv, rv);
+  nsCOMPtr<nsISubstitutingProtocolHandler> substHandler =
+      do_QueryInterface(handler);
+  MOZ_ASSERT(substHandler);
+
+  nsAutoCString spec;
+  rv = substHandler->ResolveURI(this, spec);
+  if (NS_FAILED(rv)) return rv;
+
+  nsAutoCString scheme;
+  rv = net_ExtractURLScheme(spec, scheme);
+  if (NS_FAILED(rv)) return rv;
+
+  // Bug 585869:
+  // In most cases, the scheme is jar if it's not file.
+  // Regardless, net_GetFileFromURLSpec should be avoided
+  // when the scheme isn't file.
+  if (!scheme.EqualsLiteral("file")) return NS_ERROR_NO_INTERFACE;
+
+  return net_GetFileFromURLSpec(spec, getter_AddRefs(mFile));
+}
+
+/* virtual */
+nsStandardURL* SubstitutingURL::StartClone() {
+  SubstitutingURL* clone = new SubstitutingURL();
+  return clone;
+}
+
+void SubstitutingURL::Serialize(ipc::URIParams& aParams) {
+  nsStandardURL::Serialize(aParams);
+  aParams.get_StandardURLParams().isSubstituting() = true;
+}
+
+// SubstitutingJARURI
+
+SubstitutingJARURI::SubstitutingJARURI(nsIURL* source, nsIJARURI* resolved)
+    : mSource(source), mResolved(resolved) {}
+
+// SubstitutingJARURI::nsIURI
+
+NS_IMETHODIMP
+SubstitutingJARURI::Equals(nsIURI* aOther, bool* aResult) {
+  return EqualsInternal(aOther, eHonorRef, aResult);
+}
+
+NS_IMETHODIMP
+SubstitutingJARURI::EqualsExceptRef(nsIURI* aOther, bool* aResult) {
+  return EqualsInternal(aOther, eIgnoreRef, aResult);
+}
+
+nsresult SubstitutingJARURI::EqualsInternal(nsIURI* aOther,
+                                            RefHandlingEnum aRefHandlingMode,
+                                            bool* aResult) {
+  *aResult = false;
+  if (!aOther) {
+    return NS_OK;
+  }
+
+  nsresult rv;
+  RefPtr<SubstitutingJARURI> other;
+  rv =
+      aOther->QueryInterface(kSubstitutingJARURIImplCID, getter_AddRefs(other));
+  if (NS_FAILED(rv)) {
+    return NS_OK;
+  }
+
+  // We only need to check the source as the resolved URI is the same for a
+  // given source
+  return aRefHandlingMode == eHonorRef
+             ? mSource->Equals(other->mSource, aResult)
+             : mSource->EqualsExceptRef(other->mSource, aResult);
+}
+
+// SubstitutingJARURI::nsISerializable
+
+NS_IMETHODIMP
+SubstitutingJARURI::Read(nsIObjectInputStream* aStream) {
+  MOZ_ASSERT(!mSource);
+  MOZ_ASSERT(!mResolved);
+  NS_ENSURE_ARG_POINTER(aStream);
+
+  nsresult rv;
+  nsCOMPtr<nsISupports> source;
+  rv = aStream->ReadObject(true, getter_AddRefs(source));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mSource = do_QueryInterface(source, &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsISupports> resolved;
+  rv = aStream->ReadObject(true, getter_AddRefs(resolved));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mResolved = do_QueryInterface(resolved, &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SubstitutingJARURI::Write(nsIObjectOutputStream* aStream) {
+  NS_ENSURE_ARG_POINTER(aStream);
+
+  nsresult rv;
+  rv = aStream->WriteCompoundObject(mSource, NS_GET_IID(nsISupports), true);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = aStream->WriteCompoundObject(mResolved, NS_GET_IID(nsISupports), true);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return NS_OK;
+}
+
+NS_IMPL_CLASSINFO(SubstitutingJARURI, nullptr, nsIClassInfo::MAIN_THREAD_ONLY,
+                  NS_SUBSTITUTINGJARURI_CID)
+
+NS_IMPL_ADDREF(SubstitutingJARURI)
+NS_IMPL_RELEASE(SubstitutingJARURI)
+
+NS_INTERFACE_MAP_BEGIN(SubstitutingJARURI)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIURI)
+  NS_INTERFACE_MAP_ENTRY(nsIJARURI)
+  NS_INTERFACE_MAP_ENTRY(nsIURL)
+  NS_INTERFACE_MAP_ENTRY(nsIStandardURL)
+  NS_INTERFACE_MAP_ENTRY(nsISerializable)
+  if (aIID.Equals(kSubstitutingJARURIImplCID)) {
+    foundInterface = static_cast<nsIURI*>(this);
+  } else
+    NS_INTERFACE_MAP_ENTRY(nsIURI)
+  NS_IMPL_QUERY_CLASSINFO(SubstitutingJARURI)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CI_INTERFACE_GETTER(SubstitutingJARURI, nsIURI, nsIJARURI, nsIURL,
+                            nsIStandardURL, nsISerializable)
+
+SubstitutingProtocolHandler::SubstitutingProtocolHandler(const char* aScheme,
+                                                         uint32_t aFlags,
+                                                         bool aEnforceFileOrJar)
+    : mScheme(aScheme),
+      mSubstitutionsLock("SubstitutingProtocolHandler::mSubstitutions"),
+      mSubstitutions(16),
+      mEnforceFileOrJar(aEnforceFileOrJar) {
+  mFlags.emplace(aFlags);
+  ConstructInternal();
+}
+
+SubstitutingProtocolHandler::SubstitutingProtocolHandler(const char* aScheme)
+    : mScheme(aScheme),
+      mSubstitutionsLock("SubstitutingProtocolHandler::mSubstitutions"),
+      mSubstitutions(16),
+      mEnforceFileOrJar(true) {
+  ConstructInternal();
+}
+
+void SubstitutingProtocolHandler::ConstructInternal() {
+  nsresult rv;
+  mIOService = do_GetIOService(&rv);
+  MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv) && mIOService);
+}
+
+//
+// IPC marshalling.
+//
+
+nsresult SubstitutingProtocolHandler::CollectSubstitutions(
+    nsTArray<SubstitutionMapping>& aMappings) {
+  AutoReadLock lock(mSubstitutionsLock);
+  for (auto iter = mSubstitutions.ConstIter(); !iter.Done(); iter.Next()) {
+    SubstitutionEntry& entry = iter.Data();
+    nsCOMPtr<nsIURI> uri = entry.baseURI;
+    SerializedURI serialized;
+    if (uri) {
+      nsresult rv = uri->GetSpec(serialized.spec);
+      NS_ENSURE_SUCCESS(rv, rv);
+    }
+    SubstitutionMapping substitution = {mScheme, nsCString(iter.Key()),
+                                        serialized, entry.flags};
+    aMappings.AppendElement(substitution);
+  }
+
+  return NS_OK;
+}
+
+nsresult SubstitutingProtocolHandler::SendSubstitution(const nsACString& aRoot,
+                                                       nsIURI* aBaseURI,
+                                                       uint32_t aFlags) {
+  if (GeckoProcessType_Content == XRE_GetProcessType()) {
+    return NS_OK;
+  }
+
+  nsTArray<ContentParent*> parents;
+  ContentParent::GetAll(parents);
+  if (!parents.Length()) {
+    return NS_OK;
+  }
+
+  SubstitutionMapping mapping;
+  mapping.scheme = mScheme;
+  mapping.path = aRoot;
+  if (aBaseURI) {
+    nsresult rv = aBaseURI->GetSpec(mapping.resolvedURI.spec);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+  mapping.flags = aFlags;
+
+  for (uint32_t i = 0; i < parents.Length(); i++) {
+    Unused << parents[i]->SendRegisterChromeItem(mapping);
+  }
+
+  return NS_OK;
+}
+
+//----------------------------------------------------------------------------
+// nsIProtocolHandler
+//----------------------------------------------------------------------------
+
+nsresult SubstitutingProtocolHandler::GetScheme(nsACString& result) {
+  result = mScheme;
+  return NS_OK;
+}
+
+nsresult SubstitutingProtocolHandler::GetDefaultPort(int32_t* result) {
+  *result = -1;
+  return NS_OK;
+}
+
+nsresult SubstitutingProtocolHandler::GetProtocolFlags(uint32_t* result) {
+  if (mFlags.isNothing()) {
+    NS_WARNING(
+        "Trying to get protocol flags the wrong way - use "
+        "nsIProtocolHandlerWithDynamicFlags instead");
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  *result = mFlags.ref();
+  return NS_OK;
+}
+
+nsresult SubstitutingProtocolHandler::NewURI(const nsACString& aSpec,
+                                             const char* aCharset,
+                                             nsIURI* aBaseURI,
+                                             nsIURI** aResult) {
+  // unescape any %2f and %2e to make sure nsStandardURL coalesces them.
+  // Later net_GetFileFromURLSpec() will do a full unescape and we want to
+  // treat them the same way the file system will. (bugs 380994, 394075)
+  nsresult rv;
+  nsAutoCString spec;
+  const char* src = aSpec.BeginReading();
+  const char* end = aSpec.EndReading();
+  const char* last = src;
+
+  spec.SetCapacity(aSpec.Length() + 1);
+  for (; src < end; ++src) {
+    if (*src == '%' && (src < end - 2) && *(src + 1) == '2') {
+      char ch = '\0';
+      if (*(src + 2) == 'f' || *(src + 2) == 'F') {
+        ch = '/';
+      } else if (*(src + 2) == 'e' || *(src + 2) == 'E') {
+        ch = '.';
+      }
+
+      if (ch) {
+        if (last < src) {
+          spec.Append(last, src - last);
+        }
+        spec.Append(ch);
+        src += 2;
+        last = src + 1;  // src will be incremented by the loop
+      }
+    }
+    if (*src == '?' || *src == '#') {
+      break;  // Don't escape %2f and %2e in the query or ref parts of the URI
+    }
+  }
+
+  if (last < end) {
+    spec.Append(last, end - last);
+  }
+
+  nsCOMPtr<nsIURI> base(aBaseURI);
+  nsCOMPtr<nsIURL> uri;
+  rv = NS_MutateURI(new SubstitutingURL::Mutator())
+           .Apply(NS_MutatorMethod(&nsIStandardURLMutator::Init,
+                                   nsIStandardURL::URLTYPE_STANDARD, -1, spec,
+                                   aCharset, base, nullptr))
+           .Finalize(uri);
+  if (NS_FAILED(rv)) return rv;
+
+  nsAutoCString host;
+  rv = uri->GetHost(host);
+  if (NS_FAILED(rv)) return rv;
+
+  // "android" is the only root that would return the RESOLVE_JAR_URI flag
+  // see nsResProtocolHandler::GetSubstitutionInternal
+  if (MustResolveJAR(host)) {
+    return ResolveJARURI(uri, aResult);
+  }
+
+  uri.forget(aResult);
+  return NS_OK;
+}
+
+nsresult SubstitutingProtocolHandler::ResolveJARURI(nsIURL* aURL,
+                                                    nsIURI** aResult) {
+  nsAutoCString spec;
+  nsresult rv = ResolveURI(aURL, spec);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIURI> resolvedURI;
+  rv = NS_NewURI(getter_AddRefs(resolvedURI), spec);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIURI> innermostURI = NS_GetInnermostURI(resolvedURI);
+  nsAutoCString scheme;
+  innermostURI->GetScheme(scheme);
+
+  // We only ever want to resolve to a local jar.
+  NS_ENSURE_TRUE(scheme.EqualsLiteral("file"), NS_ERROR_UNEXPECTED);
+
+  nsCOMPtr<nsIJARURI> jarURI(do_QueryInterface(resolvedURI));
+  if (!jarURI) {
+    // This substitution does not resolve to a jar: URL, so we just
+    // return the plain SubstitutionURL
+    nsCOMPtr<nsIURI> url = aURL;
+    url.forget(aResult);
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIJARURI> result = new SubstitutingJARURI(aURL, jarURI);
+  result.forget(aResult);
+
+  return rv;
+}
+
+nsresult SubstitutingProtocolHandler::NewChannel(nsIURI* uri,
+                                                 nsILoadInfo* aLoadInfo,
+                                                 nsIChannel** result) {
+  NS_ENSURE_ARG_POINTER(uri);
+  NS_ENSURE_ARG_POINTER(aLoadInfo);
+
+  nsAutoCString spec;
+  nsresult rv = ResolveURI(uri, spec);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIURI> newURI;
+  rv = NS_NewURI(getter_AddRefs(newURI), spec);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // We don't want to allow the inner protocol handler to modify the result
+  // principal URI since we want either |uri| or anything pre-set by upper
+  // layers to prevail.
+  nsCOMPtr<nsIURI> savedResultPrincipalURI;
+  rv =
+      aLoadInfo->GetResultPrincipalURI(getter_AddRefs(savedResultPrincipalURI));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = NS_NewChannelInternal(result, newURI, aLoadInfo);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = aLoadInfo->SetResultPrincipalURI(savedResultPrincipalURI);
+  NS_ENSURE_SUCCESS(rv, rv);
+  rv = (*result)->SetOriginalURI(uri);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return SubstituteChannel(uri, aLoadInfo, result);
+}
+
+nsresult SubstitutingProtocolHandler::AllowPort(int32_t port,
+                                                const char* scheme,
+                                                bool* _retval) {
+  // don't override anything.
+  *_retval = false;
+  return NS_OK;
+}
+
+//----------------------------------------------------------------------------
+// nsISubstitutingProtocolHandler
+//----------------------------------------------------------------------------
+
+nsresult SubstitutingProtocolHandler::SetSubstitution(const nsACString& root,
+                                                      nsIURI* baseURI) {
+  // Add-ons use this API but they should not be able to make anything
+  // content-accessible.
+  return SetSubstitutionWithFlags(root, baseURI, 0);
+}
+
+nsresult SubstitutingProtocolHandler::SetSubstitutionWithFlags(
+    const nsACString& origRoot, nsIURI* baseURI, uint32_t flags) {
+  nsAutoCString root;
+  ToLowerCase(origRoot, root);
+
+  if (!baseURI) {
+    {
+      AutoWriteLock lock(mSubstitutionsLock);
+      mSubstitutions.Remove(root);
+    }
+
+    return SendSubstitution(root, baseURI, flags);
+  }
+
+  // If baseURI isn't a same-scheme URI, we can set the substitution
+  // immediately.
+  nsAutoCString scheme;
+  nsresult rv = baseURI->GetScheme(scheme);
+  NS_ENSURE_SUCCESS(rv, rv);
+  if (!scheme.Equals(mScheme)) {
+    if (mEnforceFileOrJar && !scheme.EqualsLiteral("file") &&
+        !scheme.EqualsLiteral("jar") && !scheme.EqualsLiteral("app") &&
+        !scheme.EqualsLiteral("resource")) {
+      NS_WARNING("Refusing to create substituting URI to non-file:// target");
+      return NS_ERROR_INVALID_ARG;
+    }
+
+    {
+      AutoWriteLock lock(mSubstitutionsLock);
+      SubstitutionEntry& entry = mSubstitutions.GetOrInsert(root);
+      entry.baseURI = baseURI;
+      entry.flags = flags;
+    }
+
+    return SendSubstitution(root, baseURI, flags);
+  }
+
+  // baseURI is a same-type substituting URI, let's resolve it first.
+  nsAutoCString newBase;
+  rv = ResolveURI(baseURI, newBase);
+  if (NS_FAILED(rv)) return rv;
+
+  nsCOMPtr<nsIURI> newBaseURI;
+  rv =
+      mIOService->NewURI(newBase, nullptr, nullptr, getter_AddRefs(newBaseURI));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  {
+    AutoWriteLock lock(mSubstitutionsLock);
+    SubstitutionEntry& entry = mSubstitutions.GetOrInsert(root);
+    entry.baseURI = newBaseURI;
+    entry.flags = flags;
+  }
+
+  return SendSubstitution(root, newBaseURI, flags);
+}
+
+nsresult SubstitutingProtocolHandler::GetSubstitution(
+    const nsACString& origRoot, nsIURI** result) {
+  NS_ENSURE_ARG_POINTER(result);
+
+  nsAutoCString root;
+  ToLowerCase(origRoot, root);
+
+  {
+    AutoReadLock lock(mSubstitutionsLock);
+    SubstitutionEntry entry;
+    if (mSubstitutions.Get(root, &entry)) {
+      nsCOMPtr<nsIURI> baseURI = entry.baseURI;
+      baseURI.forget(result);
+      return NS_OK;
+    }
+  }
+
+  uint32_t flags;
+  return GetSubstitutionInternal(root, result, &flags);
+}
+
+nsresult SubstitutingProtocolHandler::GetSubstitutionFlags(
+    const nsACString& root, uint32_t* flags) {
+#ifdef DEBUG
+  nsAutoCString lcRoot;
+  ToLowerCase(root, lcRoot);
+  MOZ_ASSERT(root.Equals(lcRoot),
+             "GetSubstitutionFlags should never receive mixed-case root name");
+#endif
+
+  *flags = 0;
+
+  {
+    AutoReadLock lock(mSubstitutionsLock);
+
+    SubstitutionEntry entry;
+    if (mSubstitutions.Get(root, &entry)) {
+      *flags = entry.flags;
+      return NS_OK;
+    }
+  }
+
+  nsCOMPtr<nsIURI> baseURI;
+  return GetSubstitutionInternal(root, getter_AddRefs(baseURI), flags);
+}
+
+nsresult SubstitutingProtocolHandler::HasSubstitution(
+    const nsACString& origRoot, bool* result) {
+  NS_ENSURE_ARG_POINTER(result);
+
+  nsAutoCString root;
+  ToLowerCase(origRoot, root);
+
+  *result = HasSubstitution(root);
+  return NS_OK;
+}
+
+nsresult SubstitutingProtocolHandler::ResolveURI(nsIURI* uri,
+                                                 nsACString& result) {
+  nsresult rv;
+
+  nsAutoCString host;
+  nsAutoCString path;
+  nsAutoCString pathname;
+
+  nsCOMPtr<nsIURL> url = do_QueryInterface(uri);
+  if (!url) {
+    return NS_ERROR_MALFORMED_URI;
+  }
+
+  rv = uri->GetAsciiHost(host);
+  if (NS_FAILED(rv)) return rv;
+
+  rv = uri->GetPathQueryRef(path);
+  if (NS_FAILED(rv)) return rv;
+
+  rv = url->GetFilePath(pathname);
+  if (NS_FAILED(rv)) return rv;
+
+  if (ResolveSpecialCases(host, path, pathname, result)) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIURI> baseURI;
+  rv = GetSubstitution(host, getter_AddRefs(baseURI));
+  if (NS_FAILED(rv)) return rv;
+
+  // Unescape the path so we can perform some checks on it.
+  NS_UnescapeURL(pathname);
+  if (pathname.FindChar('\\') != -1) {
+    return NS_ERROR_MALFORMED_URI;
+  }
+
+  // Some code relies on an empty path resolving to a file rather than a
+  // directory.
+  NS_ASSERTION(path.CharAt(0) == '/', "Path must begin with '/'");
+  if (path.Length() == 1) {
+    rv = baseURI->GetSpec(result);
+  } else {
+    // Make sure we always resolve the path as file-relative to our target URI.
+    // When the baseURI is a nsIFileURL, and the directory it points to doesn't
+    // exist, it doesn't end with a /. In that case, a file-relative resolution
+    // is going to pick something in the parent directory, so we resolve using
+    // an absolute path derived from the full path in that case.
+    nsCOMPtr<nsIFileURL> baseDir = do_QueryInterface(baseURI);
+    if (baseDir) {
+      nsAutoCString basePath;
+      rv = baseURI->GetFilePath(basePath);
+      if (NS_SUCCEEDED(rv) && !StringEndsWith(basePath, "/"_ns)) {
+        // Cf. the assertion above, path already starts with a /, so prefixing
+        // with a string that doesn't end with one will leave us wit the right
+        // amount of /.
+        path.Insert(basePath, 0);
+      } else {
+        // Allow to fall through below.
+        baseDir = nullptr;
+      }
+    }
+    if (!baseDir) {
+      path.Insert('.', 0);
+    }
+    rv = baseURI->Resolve(path, result);
+  }
+
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  if (MOZ_LOG_TEST(gResLog, LogLevel::Debug)) {
+    nsAutoCString spec;
+    uri->GetAsciiSpec(spec);
+    MOZ_LOG(gResLog, LogLevel::Debug,
+            ("%s\n -> %s\n", spec.get(), PromiseFlatCString(result).get()));
+  }
+  return rv;
+}
+
+}  // namespace net
+}  // namespace mozilla