From 36d22d82aa202bb199967e9512281e9a53db42c9 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Sun, 7 Apr 2024 21:33:14 +0200
Subject: Adding upstream version 115.7.0esr.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 netwerk/protocol/about/moz.build                  |  32 ++
 netwerk/protocol/about/nsAboutBlank.cpp           |  52 ++
 netwerk/protocol/about/nsAboutBlank.h             |  32 ++
 netwerk/protocol/about/nsAboutCache.cpp           | 533 +++++++++++++++++++++
 netwerk/protocol/about/nsAboutCache.h             | 199 ++++++++
 netwerk/protocol/about/nsAboutCacheEntry.cpp      | 559 ++++++++++++++++++++++
 netwerk/protocol/about/nsAboutCacheEntry.h        |  86 ++++
 netwerk/protocol/about/nsAboutProtocolHandler.cpp | 414 ++++++++++++++++
 netwerk/protocol/about/nsAboutProtocolHandler.h   | 139 ++++++
 netwerk/protocol/about/nsAboutProtocolUtils.h     |  64 +++
 netwerk/protocol/about/nsIAboutModule.idl         | 119 +++++
 11 files changed, 2229 insertions(+)
 create mode 100644 netwerk/protocol/about/moz.build
 create mode 100644 netwerk/protocol/about/nsAboutBlank.cpp
 create mode 100644 netwerk/protocol/about/nsAboutBlank.h
 create mode 100644 netwerk/protocol/about/nsAboutCache.cpp
 create mode 100644 netwerk/protocol/about/nsAboutCache.h
 create mode 100644 netwerk/protocol/about/nsAboutCacheEntry.cpp
 create mode 100644 netwerk/protocol/about/nsAboutCacheEntry.h
 create mode 100644 netwerk/protocol/about/nsAboutProtocolHandler.cpp
 create mode 100644 netwerk/protocol/about/nsAboutProtocolHandler.h
 create mode 100644 netwerk/protocol/about/nsAboutProtocolUtils.h
 create mode 100644 netwerk/protocol/about/nsIAboutModule.idl

(limited to 'netwerk/protocol/about')

diff --git a/netwerk/protocol/about/moz.build b/netwerk/protocol/about/moz.build
new file mode 100644
index 0000000000..f130d9b07b
--- /dev/null
+++ b/netwerk/protocol/about/moz.build
@@ -0,0 +1,32 @@
+# -*- 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/.
+
+XPIDL_SOURCES += [
+    "nsIAboutModule.idl",
+]
+
+XPIDL_MODULE = "necko_about"
+
+EXPORTS += [
+    "nsAboutProtocolHandler.h",
+    "nsAboutProtocolUtils.h",
+]
+
+UNIFIED_SOURCES += [
+    "nsAboutBlank.cpp",
+    "nsAboutCache.cpp",
+    "nsAboutCacheEntry.cpp",
+    "nsAboutProtocolHandler.cpp",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul"
+
+LOCAL_INCLUDES += [
+    "/netwerk/base",
+    "/netwerk/cache2",
+]
diff --git a/netwerk/protocol/about/nsAboutBlank.cpp b/netwerk/protocol/about/nsAboutBlank.cpp
new file mode 100644
index 0000000000..88db0d2de3
--- /dev/null
+++ b/netwerk/protocol/about/nsAboutBlank.cpp
@@ -0,0 +1,52 @@
+/* -*- 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/. */
+
+#include "nsAboutBlank.h"
+#include "nsStringStream.h"
+#include "nsNetUtil.h"
+#include "nsContentUtils.h"
+#include "nsIChannel.h"
+
+NS_IMPL_ISUPPORTS(nsAboutBlank, nsIAboutModule)
+
+NS_IMETHODIMP
+nsAboutBlank::NewChannel(nsIURI* aURI, nsILoadInfo* aLoadInfo,
+                         nsIChannel** result) {
+  NS_ENSURE_ARG_POINTER(aURI);
+
+  nsCOMPtr<nsIInputStream> in;
+  nsresult rv = NS_NewCStringInputStream(getter_AddRefs(in), ""_ns);
+  if (NS_FAILED(rv)) return rv;
+
+  nsCOMPtr<nsIChannel> channel;
+  rv = NS_NewInputStreamChannelInternal(getter_AddRefs(channel), aURI,
+                                        in.forget(), "text/html"_ns, "utf-8"_ns,
+                                        aLoadInfo);
+  if (NS_FAILED(rv)) return rv;
+
+  channel.forget(result);
+  return rv;
+}
+
+NS_IMETHODIMP
+nsAboutBlank::GetURIFlags(nsIURI* aURI, uint32_t* result) {
+  *result = nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
+            nsIAboutModule::URI_CAN_LOAD_IN_CHILD |
+            nsIAboutModule::MAKE_LINKABLE |
+            nsIAboutModule::HIDE_FROM_ABOUTABOUT;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsAboutBlank::GetChromeURI(nsIURI* aURI, nsIURI** chromeURI) {
+  return NS_ERROR_ILLEGAL_VALUE;
+}
+
+nsresult nsAboutBlank::Create(REFNSIID aIID, void** aResult) {
+  RefPtr<nsAboutBlank> about = new nsAboutBlank();
+  return about->QueryInterface(aIID, aResult);
+}
+
+////////////////////////////////////////////////////////////////////////////////
diff --git a/netwerk/protocol/about/nsAboutBlank.h b/netwerk/protocol/about/nsAboutBlank.h
new file mode 100644
index 0000000000..6cb43507f5
--- /dev/null
+++ b/netwerk/protocol/about/nsAboutBlank.h
@@ -0,0 +1,32 @@
+/* -*- 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 nsAboutBlank_h__
+#define nsAboutBlank_h__
+
+#include "nsIAboutModule.h"
+
+class nsAboutBlank : public nsIAboutModule {
+ public:
+  NS_DECL_ISUPPORTS
+
+  NS_DECL_NSIABOUTMODULE
+
+  nsAboutBlank() = default;
+
+  static nsresult Create(REFNSIID aIID, void** aResult);
+
+ private:
+  virtual ~nsAboutBlank() = default;
+};
+
+#define NS_ABOUT_BLANK_MODULE_CID                    \
+  { /* 3decd6c8-30ef-11d3-8cd0-0060b0fc14a3 */       \
+    0x3decd6c8, 0x30ef, 0x11d3, {                    \
+      0x8c, 0xd0, 0x00, 0x60, 0xb0, 0xfc, 0x14, 0xa3 \
+    }                                                \
+  }
+
+#endif  // nsAboutBlank_h__
diff --git a/netwerk/protocol/about/nsAboutCache.cpp b/netwerk/protocol/about/nsAboutCache.cpp
new file mode 100644
index 0000000000..1873277a7a
--- /dev/null
+++ b/netwerk/protocol/about/nsAboutCache.cpp
@@ -0,0 +1,533 @@
+/* -*- 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/. */
+
+#include "nsAboutCache.h"
+#include "nsIInputStream.h"
+#include "nsIURI.h"
+#include "nsCOMPtr.h"
+#include "nsNetUtil.h"
+#include "nsIPipe.h"
+#include "nsContentUtils.h"
+#include "nsEscape.h"
+#include "nsAboutProtocolUtils.h"
+#include "nsPrintfCString.h"
+
+#include "nsICacheStorageService.h"
+#include "nsICacheStorage.h"
+#include "CacheFileUtils.h"
+#include "CacheObserver.h"
+
+#include "nsThreadUtils.h"
+
+using namespace mozilla::net;
+
+NS_IMPL_ISUPPORTS(nsAboutCache, nsIAboutModule)
+NS_IMPL_ISUPPORTS(nsAboutCache::Channel, nsIChannel, nsIRequest,
+                  nsICacheStorageVisitor)
+
+NS_IMETHODIMP
+nsAboutCache::NewChannel(nsIURI* aURI, nsILoadInfo* aLoadInfo,
+                         nsIChannel** result) {
+  nsresult rv;
+
+  NS_ENSURE_ARG_POINTER(aURI);
+
+  RefPtr<Channel> channel = new Channel();
+  rv = channel->Init(aURI, aLoadInfo);
+  if (NS_FAILED(rv)) return rv;
+
+  channel.forget(result);
+
+  return NS_OK;
+}
+
+nsresult nsAboutCache::Channel::Init(nsIURI* aURI, nsILoadInfo* aLoadInfo) {
+  nsresult rv;
+
+  mCancel = false;
+
+  nsCOMPtr<nsIInputStream> inputStream;
+  NS_NewPipe(getter_AddRefs(inputStream), getter_AddRefs(mStream), 16384,
+             (uint32_t)-1,
+             true,  // non-blocking input
+             false  // blocking output
+  );
+
+  nsAutoCString storageName;
+  rv = ParseURI(aURI, storageName);
+  if (NS_FAILED(rv)) return rv;
+
+  mOverview = storageName.IsEmpty();
+  if (mOverview) {
+    // ...and visit all we can
+    mStorageList.AppendElement("memory"_ns);
+    mStorageList.AppendElement("disk"_ns);
+  } else {
+    // ...and visit just the specified storage, entries will output too
+    mStorageList.AppendElement(storageName);
+  }
+
+  // The entries header is added on encounter of the first entry
+  mEntriesHeaderAdded = false;
+
+  rv = NS_NewInputStreamChannelInternal(getter_AddRefs(mChannel), aURI,
+                                        inputStream.forget(), "text/html"_ns,
+                                        "utf-8"_ns, aLoadInfo);
+  if (NS_FAILED(rv)) return rv;
+
+  mBuffer.AssignLiteral(
+      "<!DOCTYPE html>\n"
+      "<html>\n"
+      "<head>\n"
+      "  <title>Network Cache Storage Information</title>\n"
+      "  <meta charset=\"utf-8\">\n"
+      "  <meta name=\"color-scheme\" content=\"light dark\">\n"
+      "  <meta http-equiv=\"Content-Security-Policy\" content=\"default-src "
+      "chrome:; object-src 'none'\"/>\n"
+      "  <link rel=\"stylesheet\" "
+      "href=\"chrome://global/skin/in-content/info-pages.css\"/>\n"
+      "  <link rel=\"stylesheet\" "
+      "href=\"chrome://global/skin/aboutCache.css\"/>\n"
+      "</head>\n"
+      "<body class=\"aboutPageWideContainer\">\n"
+      "<h1>Information about the Network Cache Storage Service</h1>\n");
+
+  if (!mOverview) {
+    mBuffer.AppendLiteral(
+        "<a href=\"about:cache?storage=\">Back to overview</a>");
+  }
+
+  rv = FlushBuffer();
+  if (NS_FAILED(rv)) {
+    NS_WARNING("Failed to flush buffer");
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsAboutCache::Channel::AsyncOpen(nsIStreamListener* aListener) {
+  nsresult rv;
+
+  if (!mChannel) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  // Kick the walk loop.
+  rv = VisitNextStorage();
+  if (NS_FAILED(rv)) return rv;
+
+  rv = mChannel->AsyncOpen(aListener);
+  if (NS_FAILED(rv)) return rv;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsAboutCache::Channel::Open(nsIInputStream** _retval) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+nsresult nsAboutCache::Channel::ParseURI(nsIURI* uri, nsACString& storage) {
+  //
+  // about:cache[?storage=<storage-name>[&context=<context-key>]]
+  //
+  nsresult rv;
+
+  nsAutoCString path;
+  rv = uri->GetPathQueryRef(path);
+  if (NS_FAILED(rv)) return rv;
+
+  storage.Truncate();
+
+  nsACString::const_iterator start, valueStart, end;
+  path.BeginReading(start);
+  path.EndReading(end);
+
+  valueStart = end;
+  if (!FindInReadable("?storage="_ns, start, valueStart)) {
+    return NS_OK;
+  }
+
+  storage.Assign(Substring(valueStart, end));
+
+  return NS_OK;
+}
+
+nsresult nsAboutCache::Channel::VisitNextStorage() {
+  if (!mStorageList.Length()) return NS_ERROR_NOT_AVAILABLE;
+
+  mStorageName = mStorageList[0];
+  mStorageList.RemoveElementAt(0);
+
+  // Must re-dispatch since we cannot start another visit cycle
+  // from visitor callback.  The cache v1 service doesn't like it.
+  // TODO - mayhemer, bug 913828, remove this dispatch and call
+  // directly.
+  return NS_DispatchToMainThread(mozilla::NewRunnableMethod(
+      "nsAboutCache::Channel::FireVisitStorage", this,
+      &nsAboutCache::Channel::FireVisitStorage));
+}
+
+void nsAboutCache::Channel::FireVisitStorage() {
+  nsresult rv;
+
+  rv = VisitStorage(mStorageName);
+  if (NS_FAILED(rv)) {
+    nsAutoCString escaped;
+    nsAppendEscapedHTML(mStorageName, escaped);
+    mBuffer.Append(nsPrintfCString(
+        "<p>Unrecognized storage name '%s' in about:cache URL</p>",
+        escaped.get()));
+
+    rv = FlushBuffer();
+    if (NS_FAILED(rv)) {
+      NS_WARNING("Failed to flush buffer");
+    }
+
+    // Simulate finish of a visit cycle, this tries the next storage
+    // or closes the output stream (i.e. the UI loader will stop spinning)
+    OnCacheEntryVisitCompleted();
+  }
+}
+
+nsresult nsAboutCache::Channel::VisitStorage(nsACString const& storageName) {
+  nsresult rv;
+
+  rv = GetStorage(storageName, nullptr, getter_AddRefs(mStorage));
+  if (NS_FAILED(rv)) return rv;
+
+  rv = mStorage->AsyncVisitStorage(this, !mOverview);
+  if (NS_FAILED(rv)) return rv;
+
+  return NS_OK;
+}
+
+// static
+nsresult nsAboutCache::GetStorage(nsACString const& storageName,
+                                  nsILoadContextInfo* loadInfo,
+                                  nsICacheStorage** storage) {
+  nsresult rv;
+
+  nsCOMPtr<nsICacheStorageService> cacheService =
+      do_GetService("@mozilla.org/netwerk/cache-storage-service;1", &rv);
+  if (NS_FAILED(rv)) return rv;
+
+  nsCOMPtr<nsICacheStorage> cacheStorage;
+  if (storageName == "disk") {
+    rv = cacheService->DiskCacheStorage(loadInfo, getter_AddRefs(cacheStorage));
+  } else if (storageName == "memory") {
+    rv = cacheService->MemoryCacheStorage(loadInfo,
+                                          getter_AddRefs(cacheStorage));
+  } else {
+    rv = NS_ERROR_UNEXPECTED;
+  }
+  if (NS_FAILED(rv)) return rv;
+
+  cacheStorage.forget(storage);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsAboutCache::Channel::OnCacheStorageInfo(uint32_t aEntryCount,
+                                          uint64_t aConsumption,
+                                          uint64_t aCapacity,
+                                          nsIFile* aDirectory) {
+  // We need mStream for this
+  if (!mStream) {
+    return NS_ERROR_FAILURE;
+  }
+
+  mBuffer.AssignLiteral("<h2>");
+  nsAppendEscapedHTML(mStorageName, mBuffer);
+  mBuffer.AppendLiteral(
+      "</h2>\n"
+      "<table id=\"");
+  mBuffer.AppendLiteral("\">\n");
+
+  // Write out cache info
+  // Number of entries
+  mBuffer.AppendLiteral(
+      "  <tr>\n"
+      "    <th>Number of entries:</th>\n"
+      "    <td>");
+  mBuffer.AppendInt(aEntryCount);
+  mBuffer.AppendLiteral(
+      "</td>\n"
+      "  </tr>\n");
+
+  // Maximum storage size
+  mBuffer.AppendLiteral(
+      "  <tr>\n"
+      "    <th>Maximum storage size:</th>\n"
+      "    <td>");
+  mBuffer.AppendInt(aCapacity / 1024);
+  mBuffer.AppendLiteral(
+      " KiB</td>\n"
+      "  </tr>\n");
+
+  // Storage in use
+  mBuffer.AppendLiteral(
+      "  <tr>\n"
+      "    <th>Storage in use:</th>\n"
+      "    <td>");
+  mBuffer.AppendInt(aConsumption / 1024);
+  mBuffer.AppendLiteral(
+      " KiB</td>\n"
+      "  </tr>\n");
+
+  // Storage disk location
+  mBuffer.AppendLiteral(
+      "  <tr>\n"
+      "    <th>Storage disk location:</th>\n"
+      "    <td>");
+  if (aDirectory) {
+    nsAutoString path;
+    aDirectory->GetPath(path);
+    mBuffer.Append(NS_ConvertUTF16toUTF8(path));
+  } else {
+    mBuffer.AppendLiteral("none, only stored in memory");
+  }
+  mBuffer.AppendLiteral(
+      "    </td>\n"
+      "  </tr>\n");
+
+  if (mOverview) {           // The about:cache case
+    if (aEntryCount != 0) {  // Add the "List Cache Entries" link
+      mBuffer.AppendLiteral(
+          "  <tr>\n"
+          "    <td colspan=\"2\"><a href=\"about:cache?storage=");
+      nsAppendEscapedHTML(mStorageName, mBuffer);
+      mBuffer.AppendLiteral(
+          "\">List Cache Entries</a></td>\n"
+          "  </tr>\n");
+    }
+  }
+
+  mBuffer.AppendLiteral("</table>\n");
+
+  // The entries header is added on encounter of the first entry
+  mEntriesHeaderAdded = false;
+
+  nsresult rv = FlushBuffer();
+  if (NS_FAILED(rv)) {
+    NS_WARNING("Failed to flush buffer");
+  }
+
+  if (mOverview) {
+    // OnCacheEntryVisitCompleted() is not called when we do not iterate
+    // cache entries.  Since this moves forward to the next storage in
+    // the list we want to visit, artificially call it here.
+    OnCacheEntryVisitCompleted();
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsAboutCache::Channel::OnCacheEntryInfo(
+    nsIURI* aURI, const nsACString& aIdEnhance, int64_t aDataSize,
+    int64_t aAltDataSize, uint32_t aFetchCount, uint32_t aLastModified,
+    uint32_t aExpirationTime, bool aPinned, nsILoadContextInfo* aInfo) {
+  // We need mStream for this
+  if (!mStream || mCancel) {
+    // Returning a failure from this callback stops the iteration
+    return NS_ERROR_FAILURE;
+  }
+
+  if (!mEntriesHeaderAdded) {
+    mBuffer.AppendLiteral(
+        "<hr/>\n"
+        "<table id=\"entries\">\n"
+        "  <colgroup>\n"
+        "   <col id=\"col-key\">\n"
+        "   <col id=\"col-dataSize\">\n"
+        "   <col id=\"col-altDataSize\">\n"
+        "   <col id=\"col-fetchCount\">\n"
+        "   <col id=\"col-lastModified\">\n"
+        "   <col id=\"col-expires\">\n"
+        "   <col id=\"col-pinned\">\n"
+        "  </colgroup>\n"
+        "  <thead>\n"
+        "    <tr>\n"
+        "      <th>Key</th>\n"
+        "      <th>Data size</th>\n"
+        "      <th>Alternative Data size</th>\n"
+        "      <th>Fetch count</th>\n"
+        "      <th>Last Modifed</th>\n"
+        "      <th>Expires</th>\n"
+        "      <th>Pinning</th>\n"
+        "    </tr>\n"
+        "  </thead>\n");
+    mEntriesHeaderAdded = true;
+  }
+
+  // Generate a about:cache-entry URL for this entry...
+
+  nsAutoCString url;
+  url.AssignLiteral("about:cache-entry?storage=");
+  nsAppendEscapedHTML(mStorageName, url);
+
+  nsAutoCString context;
+  CacheFileUtils::AppendKeyPrefix(aInfo, context);
+  url.AppendLiteral("&amp;context=");
+  nsAppendEscapedHTML(context, url);
+
+  url.AppendLiteral("&amp;eid=");
+  nsAppendEscapedHTML(aIdEnhance, url);
+
+  nsAutoCString cacheUriSpec;
+  aURI->GetAsciiSpec(cacheUriSpec);
+  nsAutoCString escapedCacheURI;
+  nsAppendEscapedHTML(cacheUriSpec, escapedCacheURI);
+  url.AppendLiteral("&amp;uri=");
+  url += escapedCacheURI;
+
+  // Entry start...
+  mBuffer.AppendLiteral("  <tr>\n");
+
+  // URI
+  mBuffer.AppendLiteral("    <td><a href=\"");
+  mBuffer.Append(url);
+  mBuffer.AppendLiteral("\">");
+  if (!aIdEnhance.IsEmpty()) {
+    nsAppendEscapedHTML(aIdEnhance, mBuffer);
+    mBuffer.Append(':');
+  }
+  mBuffer.Append(escapedCacheURI);
+  mBuffer.AppendLiteral("</a>");
+
+  if (!context.IsEmpty()) {
+    mBuffer.AppendLiteral("<br><span title=\"Context separation key\">");
+    nsAutoCString escapedContext;
+    nsAppendEscapedHTML(context, escapedContext);
+    mBuffer.Append(escapedContext);
+    mBuffer.AppendLiteral("</span>");
+  }
+
+  mBuffer.AppendLiteral("</td>\n");
+
+  // Content length
+  mBuffer.AppendLiteral("    <td>");
+  mBuffer.AppendInt(aDataSize);
+  mBuffer.AppendLiteral(" bytes</td>\n");
+
+  // Length of alternative content
+  mBuffer.AppendLiteral("    <td>");
+  mBuffer.AppendInt(aAltDataSize);
+  mBuffer.AppendLiteral(" bytes</td>\n");
+
+  // Number of accesses
+  mBuffer.AppendLiteral("    <td>");
+  mBuffer.AppendInt(aFetchCount);
+  mBuffer.AppendLiteral("</td>\n");
+
+  // vars for reporting time
+  char buf[255];
+
+  // Last modified time
+  mBuffer.AppendLiteral("    <td>");
+  if (aLastModified) {
+    PrintTimeString(buf, sizeof(buf), aLastModified);
+    mBuffer.Append(buf);
+  } else {
+    mBuffer.AppendLiteral("No last modified time");
+  }
+  mBuffer.AppendLiteral("</td>\n");
+
+  // Expires time
+  mBuffer.AppendLiteral("    <td>");
+
+  // Bug - 633747.
+  // When expiration time is 0, we show 1970-01-01 01:00:00 which is confusing.
+  // So we check if time is 0, then we show a message, "Expired Immediately"
+  if (aExpirationTime == 0) {
+    mBuffer.AppendLiteral("Expired Immediately");
+  } else if (aExpirationTime < 0xFFFFFFFF) {
+    PrintTimeString(buf, sizeof(buf), aExpirationTime);
+    mBuffer.Append(buf);
+  } else {
+    mBuffer.AppendLiteral("No expiration time");
+  }
+  mBuffer.AppendLiteral("</td>\n");
+
+  // Pinning
+  mBuffer.AppendLiteral("    <td>");
+  if (aPinned) {
+    mBuffer.AppendLiteral("Pinned");
+  } else {
+    mBuffer.AppendLiteral("&nbsp;");
+  }
+  mBuffer.AppendLiteral("</td>\n");
+
+  // Entry is done...
+  mBuffer.AppendLiteral("  </tr>\n");
+
+  return FlushBuffer();
+}
+
+NS_IMETHODIMP
+nsAboutCache::Channel::OnCacheEntryVisitCompleted() {
+  if (!mStream) {
+    return NS_ERROR_FAILURE;
+  }
+
+  if (mEntriesHeaderAdded) {
+    mBuffer.AppendLiteral("</table>\n");
+  }
+
+  // Kick another storage visiting (from a storage that allows us.)
+  while (mStorageList.Length()) {
+    nsresult rv = VisitNextStorage();
+    if (NS_SUCCEEDED(rv)) {
+      // Expecting new round of OnCache* calls.
+      return NS_OK;
+    }
+  }
+
+  // We are done!
+  mBuffer.AppendLiteral(
+      "</body>\n"
+      "</html>\n");
+  nsresult rv = FlushBuffer();
+  if (NS_FAILED(rv)) {
+    NS_WARNING("Failed to flush buffer");
+  }
+  mStream->Close();
+
+  return NS_OK;
+}
+
+nsresult nsAboutCache::Channel::FlushBuffer() {
+  nsresult rv;
+
+  uint32_t bytesWritten;
+  rv = mStream->Write(mBuffer.get(), mBuffer.Length(), &bytesWritten);
+  mBuffer.Truncate();
+
+  if (NS_FAILED(rv)) {
+    mCancel = true;
+  }
+
+  return rv;
+}
+
+NS_IMETHODIMP
+nsAboutCache::GetURIFlags(nsIURI* aURI, uint32_t* result) {
+  *result = nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
+            nsIAboutModule::IS_SECURE_CHROME_UI;
+  return NS_OK;
+}
+
+// static
+nsresult nsAboutCache::Create(REFNSIID aIID, void** aResult) {
+  RefPtr<nsAboutCache> about = new nsAboutCache();
+  return about->QueryInterface(aIID, aResult);
+}
+
+NS_IMETHODIMP
+nsAboutCache::GetChromeURI(nsIURI* aURI, nsIURI** chromeURI) {
+  return NS_ERROR_ILLEGAL_VALUE;
+}
+
+////////////////////////////////////////////////////////////////////////////////
diff --git a/netwerk/protocol/about/nsAboutCache.h b/netwerk/protocol/about/nsAboutCache.h
new file mode 100644
index 0000000000..65292b9aae
--- /dev/null
+++ b/netwerk/protocol/about/nsAboutCache.h
@@ -0,0 +1,199 @@
+/* -*- 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 nsAboutCache_h__
+#define nsAboutCache_h__
+
+#include "nsIAboutModule.h"
+#include "nsICacheStorageVisitor.h"
+#include "nsICacheStorage.h"
+
+#include "nsString.h"
+#include "nsIChannel.h"
+#include "nsIOutputStream.h"
+#include "nsILoadContextInfo.h"
+
+#include "nsCOMPtr.h"
+#include "nsTArray.h"
+
+#define NS_FORWARD_SAFE_NSICHANNEL_SUBSET(_to)                                 \
+  NS_IMETHOD GetOriginalURI(nsIURI** aOriginalURI) override {                  \
+    return !(_to) ? NS_ERROR_NULL_POINTER                                      \
+                  : (_to)->GetOriginalURI(aOriginalURI);                       \
+  }                                                                            \
+  NS_IMETHOD SetOriginalURI(nsIURI* aOriginalURI) override {                   \
+    return !(_to) ? NS_ERROR_NULL_POINTER                                      \
+                  : (_to)->SetOriginalURI(aOriginalURI);                       \
+  }                                                                            \
+  NS_IMETHOD GetURI(nsIURI** aURI) override {                                  \
+    return !(_to) ? NS_ERROR_NULL_POINTER : (_to)->GetURI(aURI);               \
+  }                                                                            \
+  NS_IMETHOD GetOwner(nsISupports** aOwner) override {                         \
+    return !(_to) ? NS_ERROR_NULL_POINTER : (_to)->GetOwner(aOwner);           \
+  }                                                                            \
+  NS_IMETHOD SetOwner(nsISupports* aOwner) override {                          \
+    return !(_to) ? NS_ERROR_NULL_POINTER : (_to)->SetOwner(aOwner);           \
+  }                                                                            \
+  NS_IMETHOD GetNotificationCallbacks(                                         \
+      nsIInterfaceRequestor** aNotificationCallbacks) override {               \
+    return !(_to) ? NS_ERROR_NULL_POINTER                                      \
+                  : (_to)->GetNotificationCallbacks(aNotificationCallbacks);   \
+  }                                                                            \
+  NS_IMETHOD SetNotificationCallbacks(                                         \
+      nsIInterfaceRequestor* aNotificationCallbacks) override {                \
+    return !(_to) ? NS_ERROR_NULL_POINTER                                      \
+                  : (_to)->SetNotificationCallbacks(aNotificationCallbacks);   \
+  }                                                                            \
+  NS_IMETHOD GetSecurityInfo(nsITransportSecurityInfo** aSecurityInfo)         \
+      override {                                                               \
+    return !(_to) ? NS_ERROR_NULL_POINTER                                      \
+                  : (_to)->GetSecurityInfo(aSecurityInfo);                     \
+  }                                                                            \
+  NS_IMETHOD GetContentType(nsACString& aContentType) override {               \
+    return !(_to) ? NS_ERROR_NULL_POINTER                                      \
+                  : (_to)->GetContentType(aContentType);                       \
+  }                                                                            \
+  NS_IMETHOD SetContentType(const nsACString& aContentType) override {         \
+    return !(_to) ? NS_ERROR_NULL_POINTER                                      \
+                  : (_to)->SetContentType(aContentType);                       \
+  }                                                                            \
+  NS_IMETHOD GetContentCharset(nsACString& aContentCharset) override {         \
+    return !(_to) ? NS_ERROR_NULL_POINTER                                      \
+                  : (_to)->GetContentCharset(aContentCharset);                 \
+  }                                                                            \
+  NS_IMETHOD SetContentCharset(const nsACString& aContentCharset) override {   \
+    return !(_to) ? NS_ERROR_NULL_POINTER                                      \
+                  : (_to)->SetContentCharset(aContentCharset);                 \
+  }                                                                            \
+  NS_IMETHOD GetContentLength(int64_t* aContentLength) override {              \
+    return !(_to) ? NS_ERROR_NULL_POINTER                                      \
+                  : (_to)->GetContentLength(aContentLength);                   \
+  }                                                                            \
+  NS_IMETHOD SetContentLength(int64_t aContentLength) override {               \
+    return !(_to) ? NS_ERROR_NULL_POINTER                                      \
+                  : (_to)->SetContentLength(aContentLength);                   \
+  }                                                                            \
+  NS_IMETHOD GetContentDisposition(uint32_t* aContentDisposition) override {   \
+    return !(_to) ? NS_ERROR_NULL_POINTER                                      \
+                  : (_to)->GetContentDisposition(aContentDisposition);         \
+  }                                                                            \
+  NS_IMETHOD SetContentDisposition(uint32_t aContentDisposition) override {    \
+    return !(_to) ? NS_ERROR_NULL_POINTER                                      \
+                  : (_to)->SetContentDisposition(aContentDisposition);         \
+  }                                                                            \
+  NS_IMETHOD GetContentDispositionFilename(                                    \
+      nsAString& aContentDispositionFilename) override {                       \
+    return !(_to) ? NS_ERROR_NULL_POINTER                                      \
+                  : (_to)->GetContentDispositionFilename(                      \
+                        aContentDispositionFilename);                          \
+  }                                                                            \
+  NS_IMETHOD SetContentDispositionFilename(                                    \
+      const nsAString& aContentDispositionFilename) override {                 \
+    return !(_to) ? NS_ERROR_NULL_POINTER                                      \
+                  : (_to)->SetContentDispositionFilename(                      \
+                        aContentDispositionFilename);                          \
+  }                                                                            \
+  NS_IMETHOD GetContentDispositionHeader(                                      \
+      nsACString& aContentDispositionHeader) override {                        \
+    return !(_to) ? NS_ERROR_NULL_POINTER                                      \
+                  : (_to)->GetContentDispositionHeader(                        \
+                        aContentDispositionHeader);                            \
+  }                                                                            \
+  NS_IMETHOD GetLoadInfo(nsILoadInfo** aLoadInfo) override {                   \
+    return !(_to) ? NS_ERROR_NULL_POINTER : (_to)->GetLoadInfo(aLoadInfo);     \
+  }                                                                            \
+  NS_IMETHOD SetLoadInfo(nsILoadInfo* aLoadInfo) override {                    \
+    return !(_to) ? NS_ERROR_NULL_POINTER : (_to)->SetLoadInfo(aLoadInfo);     \
+  }                                                                            \
+  NS_IMETHOD GetIsDocument(bool* aIsDocument) override {                       \
+    return !(_to) ? NS_ERROR_NULL_POINTER : (_to)->GetIsDocument(aIsDocument); \
+  }                                                                            \
+  NS_IMETHOD GetCanceled(bool* aCanceled) override {                           \
+    return !(_to) ? NS_ERROR_NULL_POINTER : (_to)->GetCanceled(aCanceled);     \
+  };
+
+class nsAboutCache final : public nsIAboutModule {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIABOUTMODULE
+
+  nsAboutCache() = default;
+
+  [[nodiscard]] static nsresult Create(REFNSIID aIID, void** aResult);
+
+  [[nodiscard]] static nsresult GetStorage(nsACString const& storageName,
+                                           nsILoadContextInfo* loadInfo,
+                                           nsICacheStorage** storage);
+
+ protected:
+  virtual ~nsAboutCache() = default;
+
+  class Channel final : public nsIChannel, public nsICacheStorageVisitor {
+    NS_DECL_ISUPPORTS
+    NS_DECL_NSICACHESTORAGEVISITOR
+    NS_FORWARD_SAFE_NSIREQUEST(mChannel)
+    NS_FORWARD_SAFE_NSICHANNEL_SUBSET(mChannel)
+    NS_IMETHOD AsyncOpen(nsIStreamListener* aListener) override;
+    NS_IMETHOD Open(nsIInputStream** _retval) override;
+
+   private:
+    virtual ~Channel() = default;
+
+   public:
+    [[nodiscard]] nsresult Init(nsIURI* aURI, nsILoadInfo* aLoadInfo);
+    [[nodiscard]] nsresult ParseURI(nsIURI* uri, nsACString& storage);
+
+    // Finds a next storage we wish to visit (we use this method
+    // even there is a specified storage name, which is the only
+    // one in the list then.)  Posts FireVisitStorage() when found.
+    [[nodiscard]] nsresult VisitNextStorage();
+    // Helper method that calls VisitStorage() for the current storage.
+    // When it fails, OnCacheEntryVisitCompleted is simulated to close
+    // the output stream and thus the about:cache channel.
+    void FireVisitStorage();
+    // Kiks the visit cycle for the given storage, names can be:
+    // "disk", "memory", "appcache"
+    // Note: any newly added storage type has to be manually handled here.
+    [[nodiscard]] nsresult VisitStorage(nsACString const& storageName);
+
+    // Writes content of mBuffer to mStream and truncates
+    // the buffer.  It may fail when the input stream is closed by canceling
+    // the input stream channel.  It can be used to stop the cache iteration
+    // process.
+    [[nodiscard]] nsresult FlushBuffer();
+
+    // Whether we are showing overview status of all available
+    // storages.
+    bool mOverview = false;
+
+    // Flag initially false, that indicates the entries header has
+    // been added to the output HTML.
+    bool mEntriesHeaderAdded = false;
+
+    // Cancelation flag
+    bool mCancel = false;
+
+    // The list of all storage names we want to visit
+    nsTArray<nsCString> mStorageList;
+    nsCString mStorageName;
+    nsCOMPtr<nsICacheStorage> mStorage;
+
+    // Output data buffering and streaming output
+    nsCString mBuffer;
+    nsCOMPtr<nsIOutputStream> mStream;
+
+    // The input stream channel, the one that actually does the job
+    nsCOMPtr<nsIChannel> mChannel;
+  };
+};
+
+#define NS_ABOUT_CACHE_MODULE_CID                    \
+  { /* 9158c470-86e4-11d4-9be2-00e09872a416 */       \
+    0x9158c470, 0x86e4, 0x11d4, {                    \
+      0x9b, 0xe2, 0x00, 0xe0, 0x98, 0x72, 0xa4, 0x16 \
+    }                                                \
+  }
+
+#endif  // nsAboutCache_h__
diff --git a/netwerk/protocol/about/nsAboutCacheEntry.cpp b/netwerk/protocol/about/nsAboutCacheEntry.cpp
new file mode 100644
index 0000000000..08dfcf6ca0
--- /dev/null
+++ b/netwerk/protocol/about/nsAboutCacheEntry.cpp
@@ -0,0 +1,559 @@
+/* -*- 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 <algorithm>
+
+#include "nsAboutCacheEntry.h"
+
+#include "CacheFileUtils.h"
+#include "CacheObserver.h"
+#include "mozilla/Sprintf.h"
+#include "nsAboutCache.h"
+#include "nsAboutProtocolUtils.h"
+#include "nsContentUtils.h"
+#include "nsEscape.h"
+#include "nsIAsyncInputStream.h"
+#include "nsIAsyncOutputStream.h"
+#include "nsICacheStorage.h"
+#include "nsIPipe.h"
+#include "nsITransportSecurityInfo.h"
+#include "nsInputStreamPump.h"
+#include "nsNetUtil.h"
+
+using namespace mozilla::net;
+
+#define HEXDUMP_MAX_ROWS 16
+
+static void HexDump(uint32_t* state, const char* buf, int32_t n,
+                    nsCString& result) {
+  char temp[16];
+
+  const unsigned char* p;
+  while (n) {
+    SprintfLiteral(temp, "%08x:  ", *state);
+    result.Append(temp);
+    *state += HEXDUMP_MAX_ROWS;
+
+    p = (const unsigned char*)buf;
+
+    int32_t i, row_max = std::min(HEXDUMP_MAX_ROWS, n);
+
+    // print hex codes:
+    for (i = 0; i < row_max; ++i) {
+      SprintfLiteral(temp, "%02x  ", *p++);
+      result.Append(temp);
+    }
+    for (i = row_max; i < HEXDUMP_MAX_ROWS; ++i) {
+      result.AppendLiteral("    ");
+    }
+
+    // print ASCII glyphs if possible:
+    p = (const unsigned char*)buf;
+    for (i = 0; i < row_max; ++i, ++p) {
+      switch (*p) {
+        case '<':
+          result.AppendLiteral("&lt;");
+          break;
+        case '>':
+          result.AppendLiteral("&gt;");
+          break;
+        case '&':
+          result.AppendLiteral("&amp;");
+          break;
+        default:
+          if (*p < 0x7F && *p > 0x1F) {
+            result.Append(*p);
+          } else {
+            result.Append('.');
+          }
+      }
+    }
+
+    result.Append('\n');
+
+    buf += row_max;
+    n -= row_max;
+  }
+}
+
+//-----------------------------------------------------------------------------
+// nsAboutCacheEntry::nsISupports
+
+NS_IMPL_ISUPPORTS(nsAboutCacheEntry, nsIAboutModule)
+NS_IMPL_ISUPPORTS(nsAboutCacheEntry::Channel, nsICacheEntryOpenCallback,
+                  nsICacheEntryMetaDataVisitor, nsIStreamListener, nsIRequest,
+                  nsIChannel)
+
+//-----------------------------------------------------------------------------
+// nsAboutCacheEntry::nsIAboutModule
+
+NS_IMETHODIMP
+nsAboutCacheEntry::NewChannel(nsIURI* uri, nsILoadInfo* aLoadInfo,
+                              nsIChannel** result) {
+  NS_ENSURE_ARG_POINTER(uri);
+  nsresult rv;
+
+  RefPtr<Channel> channel = new Channel();
+  rv = channel->Init(uri, aLoadInfo);
+  if (NS_FAILED(rv)) return rv;
+
+  channel.forget(result);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsAboutCacheEntry::GetURIFlags(nsIURI* aURI, uint32_t* result) {
+  *result = nsIAboutModule::HIDE_FROM_ABOUTABOUT |
+            nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsAboutCacheEntry::GetChromeURI(nsIURI* aURI, nsIURI** chromeURI) {
+  return NS_ERROR_ILLEGAL_VALUE;
+}
+
+//-----------------------------------------------------------------------------
+// nsAboutCacheEntry::Channel
+
+nsresult nsAboutCacheEntry::Channel::Init(nsIURI* uri, nsILoadInfo* aLoadInfo) {
+  nsresult rv;
+
+  nsCOMPtr<nsIInputStream> stream;
+  rv = GetContentStream(uri, getter_AddRefs(stream));
+  if (NS_FAILED(rv)) return rv;
+
+  rv = NS_NewInputStreamChannelInternal(getter_AddRefs(mChannel), uri,
+                                        stream.forget(), "text/html"_ns,
+                                        "utf-8"_ns, aLoadInfo);
+  if (NS_FAILED(rv)) return rv;
+
+  return NS_OK;
+}
+
+nsresult nsAboutCacheEntry::Channel::GetContentStream(nsIURI* uri,
+                                                      nsIInputStream** result) {
+  nsresult rv;
+
+  // Init: (block size, maximum length)
+  nsCOMPtr<nsIAsyncInputStream> inputStream;
+  NS_NewPipe2(getter_AddRefs(inputStream), getter_AddRefs(mOutputStream), true,
+              false, 256, UINT32_MAX);
+
+  constexpr auto buffer =
+      "<!DOCTYPE html>\n"
+      "<html>\n"
+      "<head>\n"
+      "  <meta http-equiv=\"Content-Security-Policy\" content=\"default-src "
+      "chrome:; object-src 'none'\" />\n"
+      "  <meta name=\"color-scheme\" content=\"light dark\" />\n"
+      "  <title>Cache entry information</title>\n"
+      "  <link rel=\"stylesheet\" "
+      "href=\"chrome://global/skin/in-content/info-pages.css\" "
+      "type=\"text/css\"/>\n"
+      "  <link rel=\"stylesheet\" "
+      "href=\"chrome://global/skin/aboutCacheEntry.css\" type=\"text/css\"/>\n"
+      "</head>\n"
+      "<body>\n"
+      "<h1>Cache entry information</h1>\n"_ns;
+  uint32_t n;
+  rv = mOutputStream->Write(buffer.get(), buffer.Length(), &n);
+  if (NS_FAILED(rv)) return rv;
+  if (n != buffer.Length()) return NS_ERROR_UNEXPECTED;
+
+  rv = OpenCacheEntry(uri);
+  if (NS_FAILED(rv)) return rv;
+
+  inputStream.forget(result);
+  return NS_OK;
+}
+
+nsresult nsAboutCacheEntry::Channel::OpenCacheEntry(nsIURI* uri) {
+  nsresult rv;
+
+  rv = ParseURI(uri, mStorageName, getter_AddRefs(mLoadInfo), mEnhanceId,
+                getter_AddRefs(mCacheURI));
+  if (NS_FAILED(rv)) return rv;
+
+  return OpenCacheEntry();
+}
+
+nsresult nsAboutCacheEntry::Channel::OpenCacheEntry() {
+  nsresult rv;
+
+  nsCOMPtr<nsICacheStorage> storage;
+  rv = nsAboutCache::GetStorage(mStorageName, mLoadInfo,
+                                getter_AddRefs(storage));
+  if (NS_FAILED(rv)) return rv;
+
+  // Invokes OnCacheEntryAvailable()
+  rv = storage->AsyncOpenURI(
+      mCacheURI, mEnhanceId,
+      nsICacheStorage::OPEN_READONLY | nsICacheStorage::OPEN_SECRETLY, this);
+  if (NS_FAILED(rv)) return rv;
+
+  return NS_OK;
+}
+
+nsresult nsAboutCacheEntry::Channel::ParseURI(nsIURI* uri,
+                                              nsACString& storageName,
+                                              nsILoadContextInfo** loadInfo,
+                                              nsCString& enahnceID,
+                                              nsIURI** cacheUri) {
+  //
+  // about:cache-entry?storage=[string]&contenxt=[string]&eid=[string]&uri=[string]
+  //
+  nsresult rv;
+
+  nsAutoCString path;
+  rv = uri->GetPathQueryRef(path);
+  if (NS_FAILED(rv)) return rv;
+
+  nsACString::const_iterator keyBegin, keyEnd, valBegin, begin, end;
+  path.BeginReading(begin);
+  path.EndReading(end);
+
+  keyBegin = begin;
+  keyEnd = end;
+  if (!FindInReadable("?storage="_ns, keyBegin, keyEnd)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  valBegin = keyEnd;  // the value of the storage key starts after the key
+
+  keyBegin = keyEnd;
+  keyEnd = end;
+  if (!FindInReadable("&context="_ns, keyBegin, keyEnd)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  storageName.Assign(Substring(valBegin, keyBegin));
+  valBegin = keyEnd;  // the value of the context key starts after the key
+
+  keyBegin = keyEnd;
+  keyEnd = end;
+  if (!FindInReadable("&eid="_ns, keyBegin, keyEnd)) return NS_ERROR_FAILURE;
+
+  nsAutoCString contextKey(Substring(valBegin, keyBegin));
+  valBegin = keyEnd;  // the value of the eid key starts after the key
+
+  keyBegin = keyEnd;
+  keyEnd = end;
+  if (!FindInReadable("&uri="_ns, keyBegin, keyEnd)) return NS_ERROR_FAILURE;
+
+  enahnceID.Assign(Substring(valBegin, keyBegin));
+
+  valBegin = keyEnd;  // the value of the uri key starts after the key
+  nsAutoCString uriSpec(Substring(valBegin, end));  // uri is the last one
+
+  // Uf... parsing done, now get some objects from it...
+
+  nsCOMPtr<nsILoadContextInfo> info = CacheFileUtils::ParseKey(contextKey);
+  if (!info) return NS_ERROR_FAILURE;
+  info.forget(loadInfo);
+
+  rv = NS_NewURI(cacheUri, uriSpec);
+  if (NS_FAILED(rv)) return rv;
+
+  return NS_OK;
+}
+
+//-----------------------------------------------------------------------------
+// nsICacheEntryOpenCallback implementation
+//-----------------------------------------------------------------------------
+
+NS_IMETHODIMP
+nsAboutCacheEntry::Channel::OnCacheEntryCheck(nsICacheEntry* aEntry,
+                                              uint32_t* result) {
+  *result = nsICacheEntryOpenCallback::ENTRY_WANTED;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsAboutCacheEntry::Channel::OnCacheEntryAvailable(nsICacheEntry* entry,
+                                                  bool isNew, nsresult status) {
+  nsresult rv;
+
+  mWaitingForData = false;
+  if (entry) {
+    rv = WriteCacheEntryDescription(entry);
+  } else {
+    rv = WriteCacheEntryUnavailable();
+  }
+  if (NS_FAILED(rv)) return rv;
+
+  if (!mWaitingForData) {
+    // Data is not expected, close the output of content now.
+    CloseContent();
+  }
+
+  return NS_OK;
+}
+
+//-----------------------------------------------------------------------------
+// Print-out helper methods
+//-----------------------------------------------------------------------------
+
+#define APPEND_ROW(label, value) \
+  PR_BEGIN_MACRO                 \
+  buffer.AppendLiteral(          \
+      "  <tr>\n"                 \
+      "    <th>");               \
+  buffer.AppendLiteral(label);   \
+  buffer.AppendLiteral(          \
+      ":</th>\n"                 \
+      "    <td>");               \
+  buffer.Append(value);          \
+  buffer.AppendLiteral(          \
+      "</td>\n"                  \
+      "  </tr>\n");              \
+  PR_END_MACRO
+
+nsresult nsAboutCacheEntry::Channel::WriteCacheEntryDescription(
+    nsICacheEntry* entry) {
+  nsresult rv;
+  // This method appears to run in a situation where the run-time stack
+  // should have plenty of space, so allocating a large string on the
+  // stack is OK.
+  nsAutoCStringN<4097> buffer;
+  uint32_t n;
+
+  nsAutoCString str;
+
+  rv = entry->GetKey(str);
+  if (NS_FAILED(rv)) return rv;
+
+  buffer.AssignLiteral(
+      "<table>\n"
+      "  <tr>\n"
+      "    <th>key:</th>\n"
+      "    <td id=\"td-key\">");
+
+  // Test if the key is actually a URI
+  nsCOMPtr<nsIURI> uri;
+  rv = NS_NewURI(getter_AddRefs(uri), str);
+
+  nsAutoCString escapedStr;
+  nsAppendEscapedHTML(str, escapedStr);
+
+  // javascript: and data: URLs should not be linkified
+  // since clicking them can cause scripts to run - bug 162584
+  if (NS_SUCCEEDED(rv) &&
+      !(uri->SchemeIs("javascript") || uri->SchemeIs("data"))) {
+    buffer.AppendLiteral("<a href=\"");
+    buffer.Append(escapedStr);
+    buffer.AppendLiteral("\">");
+    buffer.Append(escapedStr);
+    buffer.AppendLiteral("</a>");
+    uri = nullptr;
+  } else {
+    buffer.Append(escapedStr);
+  }
+  buffer.AppendLiteral(
+      "</td>\n"
+      "  </tr>\n");
+
+  // temp vars for reporting
+  char timeBuf[255];
+  uint32_t u = 0;
+  nsAutoCString s;
+
+  // Fetch Count
+  s.Truncate();
+  entry->GetFetchCount(&u);
+  s.AppendInt(u);
+  APPEND_ROW("fetch count", s);
+
+  // Last Fetched
+  entry->GetLastFetched(&u);
+  if (u) {
+    PrintTimeString(timeBuf, sizeof(timeBuf), u);
+    APPEND_ROW("last fetched", timeBuf);
+  } else {
+    APPEND_ROW("last fetched", "No last fetch time (bug 1000338)");
+  }
+
+  // Last Modified
+  entry->GetLastModified(&u);
+  if (u) {
+    PrintTimeString(timeBuf, sizeof(timeBuf), u);
+    APPEND_ROW("last modified", timeBuf);
+  } else {
+    APPEND_ROW("last modified", "No last modified time (bug 1000338)");
+  }
+
+  // Expiration Time
+  entry->GetExpirationTime(&u);
+
+  // Bug - 633747.
+  // When expiration time is 0, we show 1970-01-01 01:00:00 which is confusing.
+  // So we check if time is 0, then we show a message, "Expired Immediately"
+  if (u == 0) {
+    APPEND_ROW("expires", "Expired Immediately");
+  } else if (u < 0xFFFFFFFF) {
+    PrintTimeString(timeBuf, sizeof(timeBuf), u);
+    APPEND_ROW("expires", timeBuf);
+  } else {
+    APPEND_ROW("expires", "No expiration time");
+  }
+
+  // Data Size
+  s.Truncate();
+  uint32_t dataSize;
+  if (NS_FAILED(entry->GetStorageDataSize(&dataSize))) dataSize = 0;
+  s.AppendInt(
+      (int32_t)dataSize);  // XXX nsICacheEntryInfo interfaces should be fixed.
+  s.AppendLiteral(" B");
+  APPEND_ROW("Data size", s);
+
+  // TODO - mayhemer
+  // Here used to be a link to the disk file (in the old cache for entries that
+  // did not fit any of the block files, in the new cache every time).
+  // I'd rather have a small set of buttons here to action on the entry:
+  // 1. save the content
+  // 2. save as a complete HTTP response (response head, headers, content)
+  // 3. doom the entry
+  // A new bug(s) should be filed here.
+
+  // Security Info
+  nsCOMPtr<nsITransportSecurityInfo> securityInfo;
+  entry->GetSecurityInfo(getter_AddRefs(securityInfo));
+  if (securityInfo) {
+    APPEND_ROW("Security", "This is a secure document.");
+  } else {
+    APPEND_ROW(
+        "Security",
+        "This document does not have any security info associated with it.");
+  }
+
+  buffer.AppendLiteral(
+      "</table>\n"
+      "<hr/>\n"
+      "<table>\n");
+
+  mBuffer = &buffer;  // make it available for OnMetaDataElement().
+  entry->VisitMetaData(this);
+  mBuffer = nullptr;
+
+  buffer.AppendLiteral("</table>\n");
+  mOutputStream->Write(buffer.get(), buffer.Length(), &n);
+  buffer.Truncate();
+
+  // Provide a hexdump of the data
+  if (!dataSize) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIInputStream> stream;
+  entry->OpenInputStream(0, getter_AddRefs(stream));
+  if (!stream) {
+    return NS_OK;
+  }
+
+  RefPtr<nsInputStreamPump> pump;
+  rv = nsInputStreamPump::Create(getter_AddRefs(pump), stream);
+  if (NS_FAILED(rv)) {
+    return NS_OK;  // just ignore
+  }
+
+  rv = pump->AsyncRead(this);
+  if (NS_FAILED(rv)) {
+    return NS_OK;  // just ignore
+  }
+
+  mWaitingForData = true;
+  return NS_OK;
+}
+
+nsresult nsAboutCacheEntry::Channel::WriteCacheEntryUnavailable() {
+  uint32_t n;
+  constexpr auto buffer = "The cache entry you selected is not available."_ns;
+  mOutputStream->Write(buffer.get(), buffer.Length(), &n);
+  return NS_OK;
+}
+
+//-----------------------------------------------------------------------------
+// nsICacheEntryMetaDataVisitor implementation
+//-----------------------------------------------------------------------------
+
+NS_IMETHODIMP
+nsAboutCacheEntry::Channel::OnMetaDataElement(char const* key,
+                                              char const* value) {
+  mBuffer->AppendLiteral(
+      "  <tr>\n"
+      "    <th>");
+  mBuffer->Append(key);
+  mBuffer->AppendLiteral(
+      ":</th>\n"
+      "    <td>");
+  nsAppendEscapedHTML(nsDependentCString(value), *mBuffer);
+  mBuffer->AppendLiteral(
+      "</td>\n"
+      "  </tr>\n");
+
+  return NS_OK;
+}
+
+//-----------------------------------------------------------------------------
+// nsIStreamListener implementation
+//-----------------------------------------------------------------------------
+
+NS_IMETHODIMP
+nsAboutCacheEntry::Channel::OnStartRequest(nsIRequest* request) {
+  mHexDumpState = 0;
+
+  constexpr auto buffer = "<hr/>\n<pre>"_ns;
+  uint32_t n;
+  return mOutputStream->Write(buffer.get(), buffer.Length(), &n);
+}
+
+NS_IMETHODIMP
+nsAboutCacheEntry::Channel::OnDataAvailable(nsIRequest* request,
+                                            nsIInputStream* aInputStream,
+                                            uint64_t aOffset, uint32_t aCount) {
+  uint32_t n;
+  return aInputStream->ReadSegments(&nsAboutCacheEntry::Channel::PrintCacheData,
+                                    this, aCount, &n);
+}
+
+/* static */
+nsresult nsAboutCacheEntry::Channel::PrintCacheData(
+    nsIInputStream* aInStream, void* aClosure, const char* aFromSegment,
+    uint32_t aToOffset, uint32_t aCount, uint32_t* aWriteCount) {
+  nsAboutCacheEntry::Channel* a =
+      static_cast<nsAboutCacheEntry::Channel*>(aClosure);
+
+  nsCString buffer;
+  HexDump(&a->mHexDumpState, aFromSegment, aCount, buffer);
+
+  uint32_t n;
+  a->mOutputStream->Write(buffer.get(), buffer.Length(), &n);
+
+  *aWriteCount = aCount;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsAboutCacheEntry::Channel::OnStopRequest(nsIRequest* request,
+                                          nsresult result) {
+  constexpr auto buffer = "</pre>\n"_ns;
+  uint32_t n;
+  mOutputStream->Write(buffer.get(), buffer.Length(), &n);
+
+  CloseContent();
+
+  return NS_OK;
+}
+
+void nsAboutCacheEntry::Channel::CloseContent() {
+  constexpr auto buffer = "</body>\n</html>\n"_ns;
+  uint32_t n;
+  mOutputStream->Write(buffer.get(), buffer.Length(), &n);
+
+  mOutputStream->Close();
+  mOutputStream = nullptr;
+}
diff --git a/netwerk/protocol/about/nsAboutCacheEntry.h b/netwerk/protocol/about/nsAboutCacheEntry.h
new file mode 100644
index 0000000000..76f8649061
--- /dev/null
+++ b/netwerk/protocol/about/nsAboutCacheEntry.h
@@ -0,0 +1,86 @@
+/* -*- 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/. */
+
+#ifndef nsAboutCacheEntry_h__
+#define nsAboutCacheEntry_h__
+
+#include "nsIAboutModule.h"
+#include "nsICacheEntryOpenCallback.h"
+#include "nsICacheEntry.h"
+#include "nsIStreamListener.h"
+#include "nsString.h"
+#include "nsCOMPtr.h"
+#include "nsIChannel.h"
+
+class nsIAsyncOutputStream;
+class nsIInputStream;
+class nsILoadContextInfo;
+class nsIURI;
+
+class nsAboutCacheEntry final : public nsIAboutModule {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIABOUTMODULE
+
+ private:
+  virtual ~nsAboutCacheEntry() = default;
+
+  class Channel final : public nsICacheEntryOpenCallback,
+                        public nsICacheEntryMetaDataVisitor,
+                        public nsIStreamListener,
+                        public nsIChannel {
+   public:
+    NS_DECL_ISUPPORTS
+    NS_DECL_NSICACHEENTRYOPENCALLBACK
+    NS_DECL_NSICACHEENTRYMETADATAVISITOR
+    NS_DECL_NSIREQUESTOBSERVER
+    NS_DECL_NSISTREAMLISTENER
+    NS_FORWARD_SAFE_NSICHANNEL(mChannel)
+    NS_FORWARD_SAFE_NSIREQUEST(mChannel)
+
+    Channel() = default;
+
+   private:
+    virtual ~Channel() = default;
+
+   public:
+    [[nodiscard]] nsresult Init(nsIURI* uri, nsILoadInfo* aLoadInfo);
+
+    [[nodiscard]] nsresult GetContentStream(nsIURI*, nsIInputStream**);
+    [[nodiscard]] nsresult OpenCacheEntry(nsIURI*);
+    [[nodiscard]] nsresult OpenCacheEntry();
+    [[nodiscard]] nsresult WriteCacheEntryDescription(nsICacheEntry*);
+    [[nodiscard]] nsresult WriteCacheEntryUnavailable();
+    [[nodiscard]] nsresult ParseURI(nsIURI* uri, nsACString& storageName,
+                                    nsILoadContextInfo** loadInfo,
+                                    nsCString& enahnceID, nsIURI** cacheUri);
+    void CloseContent();
+
+    [[nodiscard]] static nsresult PrintCacheData(
+        nsIInputStream* aInStream, void* aClosure, const char* aFromSegment,
+        uint32_t aToOffset, uint32_t aCount, uint32_t* aWriteCount);
+
+   private:
+    nsCString mStorageName, mEnhanceId;
+    nsCOMPtr<nsILoadContextInfo> mLoadInfo;
+    nsCOMPtr<nsIURI> mCacheURI;
+
+    nsCString* mBuffer{nullptr};
+    nsCOMPtr<nsIAsyncOutputStream> mOutputStream;
+    bool mWaitingForData{false};
+    uint32_t mHexDumpState{0};
+
+    nsCOMPtr<nsIChannel> mChannel;
+  };
+};
+
+#define NS_ABOUT_CACHE_ENTRY_MODULE_CID              \
+  { /* 7fa5237d-b0eb-438f-9e50-ca0166e63788 */       \
+    0x7fa5237d, 0xb0eb, 0x438f, {                    \
+      0x9e, 0x50, 0xca, 0x01, 0x66, 0xe6, 0x37, 0x88 \
+    }                                                \
+  }
+
+#endif  // nsAboutCacheEntry_h__
diff --git a/netwerk/protocol/about/nsAboutProtocolHandler.cpp b/netwerk/protocol/about/nsAboutProtocolHandler.cpp
new file mode 100644
index 0000000000..fe69c7ec02
--- /dev/null
+++ b/netwerk/protocol/about/nsAboutProtocolHandler.cpp
@@ -0,0 +1,414 @@
+/* -*- 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/. */
+
+#include "base/basictypes.h"
+#include "mozilla/ArrayUtils.h"
+
+#include "nsAboutProtocolHandler.h"
+#include "nsIURI.h"
+#include "nsIAboutModule.h"
+#include "nsContentUtils.h"
+#include "nsString.h"
+#include "nsNetCID.h"
+#include "nsAboutProtocolUtils.h"
+#include "nsError.h"
+#include "nsNetUtil.h"
+#include "nsIObjectInputStream.h"
+#include "nsIObjectOutputStream.h"
+#include "nsIWritablePropertyBag2.h"
+#include "nsIChannel.h"
+#include "nsIScriptError.h"
+#include "nsIClassInfoImpl.h"
+
+#include "mozilla/ipc/URIUtils.h"
+
+namespace mozilla {
+namespace net {
+
+static NS_DEFINE_CID(kNestedAboutURICID, NS_NESTEDABOUTURI_CID);
+
+static bool IsSafeForUntrustedContent(nsIAboutModule* aModule, nsIURI* aURI) {
+  uint32_t flags;
+  nsresult rv = aModule->GetURIFlags(aURI, &flags);
+  NS_ENSURE_SUCCESS(rv, false);
+
+  return (flags & nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT) != 0;
+}
+
+static bool IsSafeToLinkForUntrustedContent(nsIURI* aURI) {
+  nsAutoCString path;
+  aURI->GetPathQueryRef(path);
+
+  int32_t f = path.FindChar('#');
+  if (f >= 0) {
+    path.SetLength(f);
+  }
+
+  f = path.FindChar('?');
+  if (f >= 0) {
+    path.SetLength(f);
+  }
+
+  ToLowerCase(path);
+
+  // The about modules for these URL types have the
+  // URI_SAFE_FOR_UNTRUSTED_CONTENT and MAKE_LINKABLE flags set.
+  return path.EqualsLiteral("blank") || path.EqualsLiteral("logo") ||
+         path.EqualsLiteral("srcdoc");
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+NS_IMPL_ISUPPORTS(nsAboutProtocolHandler, nsIProtocolHandler,
+                  nsIProtocolHandlerWithDynamicFlags, nsISupportsWeakReference)
+
+////////////////////////////////////////////////////////////////////////////////
+// nsIProtocolHandler methods:
+
+NS_IMETHODIMP
+nsAboutProtocolHandler::GetScheme(nsACString& result) {
+  result.AssignLiteral("about");
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsAboutProtocolHandler::GetFlagsForURI(nsIURI* aURI, uint32_t* aFlags) {
+  // First use the default (which is "unsafe for content"):
+  *aFlags = URI_NORELATIVE | URI_NOAUTH | URI_DANGEROUS_TO_LOAD |
+            URI_SCHEME_NOT_SELF_LINKABLE;
+
+  // Now try to see if this URI overrides the default:
+  nsCOMPtr<nsIAboutModule> aboutMod;
+  nsresult rv = NS_GetAboutModule(aURI, getter_AddRefs(aboutMod));
+  if (NS_FAILED(rv)) {
+    // Swallow this and just tell the consumer the default:
+    return NS_OK;
+  }
+  uint32_t aboutModuleFlags = 0;
+  rv = aboutMod->GetURIFlags(aURI, &aboutModuleFlags);
+  // This should never happen, so pass back the error:
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Secure (https) pages can load safe about pages without becoming
+  // mixed content.
+  if (aboutModuleFlags & nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT) {
+    *aFlags |= URI_IS_POTENTIALLY_TRUSTWORTHY;
+    // about: pages can only be loaded by unprivileged principals
+    // if they are marked as LINKABLE
+    if (aboutModuleFlags & nsIAboutModule::MAKE_LINKABLE) {
+      // Replace URI_DANGEROUS_TO_LOAD with URI_LOADABLE_BY_ANYONE.
+      *aFlags &= ~URI_DANGEROUS_TO_LOAD;
+      *aFlags |= URI_LOADABLE_BY_ANYONE;
+    }
+  }
+  return NS_OK;
+}
+
+// static
+nsresult nsAboutProtocolHandler::CreateNewURI(const nsACString& aSpec,
+                                              const char* aCharset,
+                                              nsIURI* aBaseURI,
+                                              nsIURI** aResult) {
+  *aResult = nullptr;
+  nsresult rv;
+
+  // Use a simple URI to parse out some stuff first
+  nsCOMPtr<nsIURI> url;
+  rv = NS_MutateURI(new nsSimpleURI::Mutator()).SetSpec(aSpec).Finalize(url);
+
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  if (IsSafeToLinkForUntrustedContent(url)) {
+    // We need to indicate that this baby is safe.  Use an inner URI that
+    // no one but the security manager will see.  Make sure to preserve our
+    // path, in case someone decides to hardcode checks for particular
+    // about: URIs somewhere.
+    nsAutoCString spec;
+    rv = url->GetPathQueryRef(spec);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    spec.InsertLiteral("moz-safe-about:", 0);
+
+    nsCOMPtr<nsIURI> inner;
+    rv = NS_NewURI(getter_AddRefs(inner), spec);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    rv = NS_MutateURI(new nsNestedAboutURI::Mutator())
+             .Apply(&nsINestedAboutURIMutator::InitWithBase, inner, aBaseURI)
+             .SetSpec(aSpec)
+             .Finalize(url);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  url.swap(*aResult);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsAboutProtocolHandler::NewChannel(nsIURI* uri, nsILoadInfo* aLoadInfo,
+                                   nsIChannel** result) {
+  NS_ENSURE_ARG_POINTER(uri);
+
+  // about:what you ask?
+  nsCOMPtr<nsIAboutModule> aboutMod;
+  nsresult rv = NS_GetAboutModule(uri, getter_AddRefs(aboutMod));
+
+  nsAutoCString path;
+  nsresult rv2 = NS_GetAboutModuleName(uri, path);
+  if (NS_SUCCEEDED(rv2) && path.EqualsLiteral("srcdoc")) {
+    // about:srcdoc is meant to be unresolvable, yet is included in the
+    // about lookup tables so that it can pass security checks when used in
+    // a srcdoc iframe.  To ensure that it stays unresolvable, we pretend
+    // that it doesn't exist.
+    rv = NS_ERROR_FACTORY_NOT_REGISTERED;
+  }
+
+  if (NS_SUCCEEDED(rv)) {
+    // The standard return case:
+    rv = aboutMod->NewChannel(uri, aLoadInfo, result);
+    if (NS_SUCCEEDED(rv)) {
+      // Not all implementations of nsIAboutModule::NewChannel()
+      // set the LoadInfo on the newly created channel yet, as
+      // an interim solution we set the LoadInfo here if not
+      // available on the channel. Bug 1087720
+      nsCOMPtr<nsILoadInfo> loadInfo = (*result)->LoadInfo();
+      if (aLoadInfo != loadInfo) {
+        NS_ASSERTION(false,
+                     "nsIAboutModule->newChannel(aURI, aLoadInfo) needs to "
+                     "set LoadInfo");
+        AutoTArray<nsString, 2> params = {
+            u"nsIAboutModule->newChannel(aURI)"_ns,
+            u"nsIAboutModule->newChannel(aURI, aLoadInfo)"_ns};
+        nsContentUtils::ReportToConsole(
+            nsIScriptError::warningFlag, "Security by Default"_ns,
+            nullptr,  // aDocument
+            nsContentUtils::eNECKO_PROPERTIES, "APIDeprecationWarning", params);
+        (*result)->SetLoadInfo(aLoadInfo);
+      }
+
+      // If this URI is safe for untrusted content, enforce that its
+      // principal be based on the channel's originalURI by setting the
+      // owner to null.
+      // Note: this relies on aboutMod's newChannel implementation
+      // having set the proper originalURI, which probably isn't ideal.
+      if (IsSafeForUntrustedContent(aboutMod, uri)) {
+        (*result)->SetOwner(nullptr);
+      }
+
+      RefPtr<nsNestedAboutURI> aboutURI;
+      nsresult rv2 =
+          uri->QueryInterface(kNestedAboutURICID, getter_AddRefs(aboutURI));
+      if (NS_SUCCEEDED(rv2) && aboutURI->GetBaseURI()) {
+        nsCOMPtr<nsIWritablePropertyBag2> writableBag =
+            do_QueryInterface(*result);
+        if (writableBag) {
+          writableBag->SetPropertyAsInterface(u"baseURI"_ns,
+                                              aboutURI->GetBaseURI());
+        }
+      }
+    }
+    return rv;
+  }
+
+  // mumble...
+
+  if (rv == NS_ERROR_FACTORY_NOT_REGISTERED) {
+    // This looks like an about: we don't know about.  Convert
+    // this to an invalid URI error.
+    rv = NS_ERROR_MALFORMED_URI;
+  }
+
+  return rv;
+}
+
+NS_IMETHODIMP
+nsAboutProtocolHandler::AllowPort(int32_t port, const char* scheme,
+                                  bool* _retval) {
+  // don't override anything.
+  *_retval = false;
+  return NS_OK;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// Safe about protocol handler impl
+
+NS_IMPL_ISUPPORTS(nsSafeAboutProtocolHandler, nsIProtocolHandler,
+                  nsISupportsWeakReference)
+
+// nsIProtocolHandler methods:
+
+NS_IMETHODIMP
+nsSafeAboutProtocolHandler::GetScheme(nsACString& result) {
+  result.AssignLiteral("moz-safe-about");
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsSafeAboutProtocolHandler::NewChannel(nsIURI* uri, nsILoadInfo* aLoadInfo,
+                                       nsIChannel** result) {
+  *result = nullptr;
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+NS_IMETHODIMP
+nsSafeAboutProtocolHandler::AllowPort(int32_t port, const char* scheme,
+                                      bool* _retval) {
+  // don't override anything.
+  *_retval = false;
+  return NS_OK;
+}
+
+////////////////////////////////////////////////////////////
+// nsNestedAboutURI implementation
+
+NS_IMPL_CLASSINFO(nsNestedAboutURI, nullptr, nsIClassInfo::THREADSAFE,
+                  NS_NESTEDABOUTURI_CID);
+// Empty CI getter. We only need nsIClassInfo for Serialization
+NS_IMPL_CI_INTERFACE_GETTER0(nsNestedAboutURI)
+
+NS_INTERFACE_MAP_BEGIN(nsNestedAboutURI)
+  if (aIID.Equals(kNestedAboutURICID)) {
+    foundInterface = static_cast<nsIURI*>(this);
+  } else
+    NS_IMPL_QUERY_CLASSINFO(nsNestedAboutURI)
+NS_INTERFACE_MAP_END_INHERITING(nsSimpleNestedURI)
+
+// nsISerializable
+
+NS_IMETHODIMP
+nsNestedAboutURI::Read(nsIObjectInputStream* aStream) {
+  MOZ_ASSERT_UNREACHABLE("Use nsIURIMutator.read() instead");
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+nsresult nsNestedAboutURI::ReadPrivate(nsIObjectInputStream* aStream) {
+  nsresult rv = nsSimpleNestedURI::ReadPrivate(aStream);
+  if (NS_FAILED(rv)) return rv;
+
+  bool haveBase;
+  rv = aStream->ReadBoolean(&haveBase);
+  if (NS_FAILED(rv)) return rv;
+
+  if (haveBase) {
+    nsCOMPtr<nsISupports> supports;
+    rv = aStream->ReadObject(true, getter_AddRefs(supports));
+    if (NS_FAILED(rv)) return rv;
+
+    mBaseURI = do_QueryInterface(supports, &rv);
+    if (NS_FAILED(rv)) return rv;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsNestedAboutURI::Write(nsIObjectOutputStream* aStream) {
+  nsresult rv = nsSimpleNestedURI::Write(aStream);
+  if (NS_FAILED(rv)) return rv;
+
+  rv = aStream->WriteBoolean(mBaseURI != nullptr);
+  if (NS_FAILED(rv)) return rv;
+
+  if (mBaseURI) {
+    // A previous iteration of this code wrote out mBaseURI as nsISupports
+    // and then read it in as nsIURI, which is non-kosher when mBaseURI
+    // implements more than just a single line of interfaces and the
+    // canonical nsISupports* isn't the one a static_cast<> of mBaseURI
+    // would produce.  For backwards compatibility with existing
+    // serializations we continue to write mBaseURI as nsISupports but
+    // switch to reading it as nsISupports, with a post-read QI to get to
+    // nsIURI.
+    rv = aStream->WriteCompoundObject(mBaseURI, NS_GET_IID(nsISupports), true);
+    if (NS_FAILED(rv)) return rv;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP_(void)
+nsNestedAboutURI::Serialize(mozilla::ipc::URIParams& aParams) {
+  using namespace mozilla::ipc;
+
+  NestedAboutURIParams params;
+  URIParams nestedParams;
+
+  nsSimpleNestedURI::Serialize(nestedParams);
+  params.nestedParams() = nestedParams;
+
+  if (mBaseURI) {
+    SerializeURI(mBaseURI, params.baseURI());
+  }
+
+  aParams = params;
+}
+
+bool nsNestedAboutURI::Deserialize(const mozilla::ipc::URIParams& aParams) {
+  using namespace mozilla::ipc;
+
+  if (aParams.type() != URIParams::TNestedAboutURIParams) {
+    NS_ERROR("Received unknown parameters from the other process!");
+    return false;
+  }
+
+  const NestedAboutURIParams& params = aParams.get_NestedAboutURIParams();
+  if (!nsSimpleNestedURI::Deserialize(params.nestedParams())) {
+    return false;
+  }
+
+  mBaseURI = nullptr;
+  if (params.baseURI()) {
+    mBaseURI = DeserializeURI(*params.baseURI());
+  }
+  return true;
+}
+
+// nsSimpleURI
+/* virtual */ nsSimpleURI* nsNestedAboutURI::StartClone(
+    nsSimpleURI::RefHandlingEnum aRefHandlingMode, const nsACString& aNewRef) {
+  // Sadly, we can't make use of nsSimpleNestedURI::StartClone here.
+  // However, this function is expected to exactly match that function,
+  // aside from the "new ns***URI()" call.
+  NS_ENSURE_TRUE(mInnerURI, nullptr);
+
+  nsCOMPtr<nsIURI> innerClone;
+  nsresult rv = NS_OK;
+  if (aRefHandlingMode == eHonorRef) {
+    innerClone = mInnerURI;
+  } else if (aRefHandlingMode == eReplaceRef) {
+    rv = NS_GetURIWithNewRef(mInnerURI, aNewRef, getter_AddRefs(innerClone));
+  } else {
+    rv = NS_GetURIWithoutRef(mInnerURI, getter_AddRefs(innerClone));
+  }
+
+  if (NS_FAILED(rv)) {
+    return nullptr;
+  }
+
+  nsNestedAboutURI* url = new nsNestedAboutURI(innerClone, mBaseURI);
+  SetRefOnClone(url, aRefHandlingMode, aNewRef);
+
+  return url;
+}
+
+// Queries this list of interfaces. If none match, it queries mURI.
+NS_IMPL_NSIURIMUTATOR_ISUPPORTS(nsNestedAboutURI::Mutator, nsIURISetters,
+                                nsIURIMutator, nsISerializable,
+                                nsINestedAboutURIMutator)
+
+NS_IMETHODIMP
+nsNestedAboutURI::Mutate(nsIURIMutator** aMutator) {
+  RefPtr<nsNestedAboutURI::Mutator> mutator = new nsNestedAboutURI::Mutator();
+  nsresult rv = mutator->InitFromURI(this);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+  mutator.forget(aMutator);
+  return NS_OK;
+}
+
+}  // namespace net
+}  // namespace mozilla
diff --git a/netwerk/protocol/about/nsAboutProtocolHandler.h b/netwerk/protocol/about/nsAboutProtocolHandler.h
new file mode 100644
index 0000000000..1a15400361
--- /dev/null
+++ b/netwerk/protocol/about/nsAboutProtocolHandler.h
@@ -0,0 +1,139 @@
+/* -*- 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 nsAboutProtocolHandler_h___
+#define nsAboutProtocolHandler_h___
+
+#include "nsIProtocolHandler.h"
+#include "nsSimpleNestedURI.h"
+#include "nsWeakReference.h"
+#include "mozilla/Attributes.h"
+#include "nsIURIMutator.h"
+
+class nsIURI;
+
+namespace mozilla {
+namespace net {
+
+class nsAboutProtocolHandler : public nsIProtocolHandlerWithDynamicFlags,
+                               public nsIProtocolHandler,
+                               public nsSupportsWeakReference {
+ public:
+  NS_DECL_ISUPPORTS
+
+  // nsIProtocolHandler methods:
+  NS_DECL_NSIPROTOCOLHANDLER
+  NS_DECL_NSIPROTOCOLHANDLERWITHDYNAMICFLAGS
+
+  // nsAboutProtocolHandler methods:
+  nsAboutProtocolHandler() = default;
+
+  static nsresult CreateNewURI(const nsACString& aSpec, const char* aCharset,
+                               nsIURI* aBaseURI, nsIURI** result);
+
+ private:
+  virtual ~nsAboutProtocolHandler() = default;
+};
+
+class nsSafeAboutProtocolHandler final : public nsIProtocolHandler,
+                                         public nsSupportsWeakReference {
+ public:
+  NS_DECL_ISUPPORTS
+
+  // nsIProtocolHandler methods:
+  NS_DECL_NSIPROTOCOLHANDLER
+
+  // nsSafeAboutProtocolHandler methods:
+  nsSafeAboutProtocolHandler() = default;
+
+ private:
+  ~nsSafeAboutProtocolHandler() = default;
+};
+
+// Class to allow us to propagate the base URI to about:blank correctly
+class nsNestedAboutURI final : public nsSimpleNestedURI {
+ private:
+  nsNestedAboutURI(nsIURI* aInnerURI, nsIURI* aBaseURI)
+      : nsSimpleNestedURI(aInnerURI), mBaseURI(aBaseURI) {}
+  nsNestedAboutURI() : nsSimpleNestedURI() {}
+  virtual ~nsNestedAboutURI() = default;
+
+ public:
+  // Override QI so we can QI to our CID as needed
+  NS_IMETHOD QueryInterface(REFNSIID aIID, void** aInstancePtr) override;
+
+  // Override StartClone(), the nsISerializable methods, and
+  virtual nsSimpleURI* StartClone(RefHandlingEnum aRefHandlingMode,
+                                  const nsACString& newRef) override;
+  NS_IMETHOD Mutate(nsIURIMutator** _retval) override;
+  NS_IMETHOD_(void) Serialize(ipc::URIParams& aParams) override;
+
+  // nsISerializable
+  NS_IMETHOD Read(nsIObjectInputStream* aStream) override;
+  NS_IMETHOD Write(nsIObjectOutputStream* aStream) override;
+
+  nsIURI* GetBaseURI() const { return mBaseURI; }
+
+ protected:
+  nsCOMPtr<nsIURI> mBaseURI;
+  bool Deserialize(const mozilla::ipc::URIParams&);
+  nsresult ReadPrivate(nsIObjectInputStream* stream);
+
+ public:
+  class Mutator final : public nsIURIMutator,
+                        public BaseURIMutator<nsNestedAboutURI>,
+                        public nsISerializable,
+                        public nsINestedAboutURIMutator {
+    NS_DECL_ISUPPORTS
+    NS_FORWARD_SAFE_NSIURISETTERS_RET(mURI)
+
+    explicit Mutator() = default;
+
+   private:
+    virtual ~Mutator() = default;
+
+    [[nodiscard]] NS_IMETHOD Deserialize(
+        const mozilla::ipc::URIParams& aParams) override {
+      return InitFromIPCParams(aParams);
+    }
+
+    NS_IMETHOD
+    Write(nsIObjectOutputStream* aOutputStream) override {
+      return NS_ERROR_NOT_IMPLEMENTED;
+    }
+
+    [[nodiscard]] NS_IMETHOD Read(nsIObjectInputStream* aStream) override {
+      return InitFromInputStream(aStream);
+    }
+
+    [[nodiscard]] NS_IMETHOD Finalize(nsIURI** aURI) override {
+      mURI.forget(aURI);
+      return NS_OK;
+    }
+
+    [[nodiscard]] NS_IMETHOD SetSpec(const nsACString& aSpec,
+                                     nsIURIMutator** aMutator) override {
+      if (aMutator) {
+        NS_ADDREF(*aMutator = this);
+      }
+      return InitFromSpec(aSpec);
+    }
+
+    [[nodiscard]] NS_IMETHOD InitWithBase(nsIURI* aInnerURI,
+                                          nsIURI* aBaseURI) override {
+      mURI = new nsNestedAboutURI(aInnerURI, aBaseURI);
+      return NS_OK;
+    }
+
+    friend class nsNestedAboutURI;
+  };
+
+  friend BaseURIMutator<nsNestedAboutURI>;
+};
+
+}  // namespace net
+}  // namespace mozilla
+
+#endif /* nsAboutProtocolHandler_h___ */
diff --git a/netwerk/protocol/about/nsAboutProtocolUtils.h b/netwerk/protocol/about/nsAboutProtocolUtils.h
new file mode 100644
index 0000000000..68d1f4d54b
--- /dev/null
+++ b/netwerk/protocol/about/nsAboutProtocolUtils.h
@@ -0,0 +1,64 @@
+/* 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 nsAboutProtocolUtils_h
+#define nsAboutProtocolUtils_h
+
+#include "nsIURI.h"
+#include "nsString.h"
+#include "nsReadableUtils.h"
+#include "nsIAboutModule.h"
+#include "nsServiceManagerUtils.h"
+#include "prtime.h"
+
+[[nodiscard]] inline nsresult NS_GetAboutModuleName(nsIURI* aAboutURI,
+                                                    nsCString& aModule) {
+  NS_ASSERTION(aAboutURI->SchemeIs("about"),
+               "should be used only on about: URIs");
+
+  MOZ_TRY(aAboutURI->GetPathQueryRef(aModule));
+
+  int32_t f = aModule.FindCharInSet("#?"_ns);
+  if (f != kNotFound) {
+    aModule.Truncate(f);
+  }
+
+  // convert to lowercase, as all about: modules are lowercase
+  ToLowerCase(aModule);
+  return NS_OK;
+}
+
+[[nodiscard]] inline bool NS_IsContentAccessibleAboutURI(nsIURI* aURI) {
+  MOZ_ASSERT(aURI->SchemeIs("about"), "Should be used only on about: URIs");
+  nsAutoCString name;
+  if (NS_WARN_IF(NS_FAILED(NS_GetAboutModuleName(aURI, name)))) {
+    return true;
+  }
+  return name.EqualsLiteral("blank") || name.EqualsLiteral("srcdoc");
+}
+
+inline nsresult NS_GetAboutModule(nsIURI* aAboutURI, nsIAboutModule** aModule) {
+  MOZ_ASSERT(aAboutURI, "Must have URI");
+
+  nsAutoCString contractID;
+  MOZ_TRY(NS_GetAboutModuleName(aAboutURI, contractID));
+
+  // look up a handler to deal with "what"
+  contractID.InsertLiteral(NS_ABOUT_MODULE_CONTRACTID_PREFIX, 0);
+
+  return CallGetService(contractID.get(), aModule);
+}
+
+inline PRTime SecondsToPRTime(uint32_t t_sec) {
+  return (PRTime)t_sec * PR_USEC_PER_SEC;
+}
+
+inline void PrintTimeString(char* buf, uint32_t bufsize, uint32_t t_sec) {
+  PRExplodedTime et;
+  PRTime t_usec = SecondsToPRTime(t_sec);
+  PR_ExplodeTime(t_usec, PR_LocalTimeParameters, &et);
+  PR_FormatTime(buf, bufsize, "%Y-%m-%d %H:%M:%S", &et);
+}
+
+#endif
diff --git a/netwerk/protocol/about/nsIAboutModule.idl b/netwerk/protocol/about/nsIAboutModule.idl
new file mode 100644
index 0000000000..db82dad11d
--- /dev/null
+++ b/netwerk/protocol/about/nsIAboutModule.idl
@@ -0,0 +1,119 @@
+/* -*- Mode: C++; tab-width: 2; 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 nsIChannel;
+interface nsILoadInfo;
+
+[scriptable, uuid(c0c19db9-1b5a-4ac5-b656-ed6f8149fa48)]
+interface nsIAboutModule : nsISupports
+{
+
+    /**
+     * Constructs a new channel for the about protocol module.
+     *
+     * @param aURI the uri of the new channel
+     * @param aLoadInfo the loadinfo of the new channel
+     */
+    nsIChannel newChannel(in nsIURI aURI,
+                          in nsILoadInfo aLoadInfo);
+
+    /**
+     * A flag that indicates whether a URI should be run with content
+     * privileges. If it is, the about: protocol handler will enforce that
+     * the principal of channels created for it be based on their
+     * originalURI or URI (depending on the channel flags), by setting
+     * their "owner" to null.
+     * If content needs to be able to link to this URI, specify
+     * URI_CONTENT_LINKABLE as well.
+     */
+    const unsigned long URI_SAFE_FOR_UNTRUSTED_CONTENT = (1 << 0);
+
+    /**
+     * A flag that indicates whether script should be enabled for the
+     * given about: URI even if it's disabled in general.
+     */
+    const unsigned long ALLOW_SCRIPT = (1 << 1);
+
+    /**
+     * A flag that indicates whether this about: URI doesn't want to be listed
+     * in about:about, especially if it's not useful without a query string.
+     */
+    const unsigned long HIDE_FROM_ABOUTABOUT = (1 << 2);
+
+    /**
+     * A flag that indicates whether this about: URI wants Indexed DB enabled.
+     */
+    const unsigned long ENABLE_INDEXED_DB = (1 << 3);
+
+    /**
+     * A flag that indicates that this URI can be loaded in a child process
+     */
+    const unsigned long URI_CAN_LOAD_IN_CHILD = (1 << 4);
+
+    /**
+     * A flag that indicates that this URI must be loaded in a child process
+     */
+    const unsigned long URI_MUST_LOAD_IN_CHILD = (1 << 5);
+
+    /**
+     * Obsolete. This flag no longer has any effect and will be removed in future.
+     */
+    const unsigned long MAKE_UNLINKABLE = (1 << 6);
+
+    /**
+     * A flag that indicates that this URI should be linkable from content.
+     * Ignored unless URI_SAFE_FOR_UNTRUSTED_CONTENT is also specified.
+     *
+     * When adding a new about module with this flag make sure to also update
+     * IsSafeToLinkForUntrustedContent() in nsAboutProtocolHandler.cpp
+     */
+    const unsigned long MAKE_LINKABLE = (1 << 7);
+
+    /**
+     * A flag that indicates that this URI can be loaded in the privileged
+     * activity stream content process if said process is enabled. Ignored unless
+     * URI_MUST_LOAD_IN_CHILD is also specified.
+     */
+    const unsigned long URI_CAN_LOAD_IN_PRIVILEGEDABOUT_PROCESS = (1 << 8);
+
+    /**
+     * A flag that indicates that this URI must be loaded in an extension process (if available).
+     */
+    const unsigned long URI_MUST_LOAD_IN_EXTENSION_PROCESS = (1 << 9);
+
+    /**
+     * A flag that indicates that this about: URI needs to allow unsanitized content.
+     * Only to be used by about:home and about:newtab.
+     */
+    const unsigned long ALLOW_UNSANITIZED_CONTENT = (1 << 10);
+
+    /**
+     * A flag that indicates that this about: URI is a secure chrome UI
+     */
+    const unsigned long IS_SECURE_CHROME_UI = (1 << 11);
+
+    /**
+     * A method to get the flags that apply to a given about: URI.  The URI
+     * passed in is guaranteed to be one of the URIs that this module
+     * registered to deal with.
+     */
+    unsigned long getURIFlags(in nsIURI aURI);
+
+    /**
+     * A method to get the chrome URI that corresponds to a given about URI.
+     */
+    nsIURI getChromeURI(in nsIURI aURI);
+};
+
+%{C++
+
+#define NS_ABOUT_MODULE_CONTRACTID        "@mozilla.org/network/protocol/about;1"
+#define NS_ABOUT_MODULE_CONTRACTID_PREFIX NS_ABOUT_MODULE_CONTRACTID "?what="
+#define NS_ABOUT_MODULE_CONTRACTID_LENGTH 49      // strlen(NS_ABOUT_MODULE_CONTRACTID_PREFIX)
+
+%}
-- 
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