moebius#223: Consider blocking top level window data: URIs (part 1/3 without tests)

https://github.com/MoonchildProductions/moebius/pull/223

22 files changed, 515 insertions, 1 deletions

diff --git a/docshell/base/nsDocShell.cpp b/docshell/base/nsDocShell.cpp
index 58c182cbb..ae97a7c9e 100644
--- a/docshell/base/nsDocShell.cpp
+++ b/docshell/base/nsDocShell.cpp
@@ -42,6 +42,7 @@
 
 #include "nsArray.h"
 #include "nsArrayUtils.h"
+#include "nsContentSecurityManager.h"
 #include "nsICaptivePortalService.h"
 #include "nsIDOMStorage.h"
 #include "nsIContentViewer.h"
@@ -9884,6 +9885,15 @@ nsDocShell::InternalLoad(nsIURI* aURI,
     contentType = nsIContentPolicy::TYPE_DOCUMENT;
   }
 
+  if (!nsContentSecurityManager::AllowTopLevelNavigationToDataURI(
+        aURI,
+        contentType,
+        aTriggeringPrincipal,
+        (aLoadType == LOAD_NORMAL_EXTERNAL))) {
+    // logging to console happens within AllowTopLevelNavigationToDataURI
+    return NS_OK;
+  }
+
   // If there's no targetDocShell, that means we are about to create a new window,
   // perform a content policy check before creating the window.
   if (!targetDocShell) {
@@ -10232,8 +10242,11 @@ nsDocShell::InternalLoad(nsIURI* aURI,
     }
   }
 
+  bool loadFromExternal = false;
+
   // Before going any further vet loads initiated by external programs.
   if (aLoadType == LOAD_NORMAL_EXTERNAL) {
+    loadFromExternal = true;
     // Disallow external chrome: loads targetted at content windows
     bool isChrome = false;
     if (NS_SUCCEEDED(aURI->SchemeIs("chrome", &isChrome)) && isChrome) {
@@ -10724,7 +10737,7 @@ nsDocShell::InternalLoad(nsIURI* aURI,
                         nsINetworkPredictor::PREDICT_LOAD, this, nullptr);
 
   nsCOMPtr<nsIRequest> req;
-  rv = DoURILoad(aURI, aOriginalURI, aLoadReplace, aReferrer,
+  rv = DoURILoad(aURI, aOriginalURI, aLoadReplace, loadFromExternal, aReferrer,
                  !(aFlags & INTERNAL_LOAD_FLAGS_DONT_SEND_REFERRER),
                  aReferrerPolicy,
                  aTriggeringPrincipal, principalToInherit, aTypeHint,
@@ -10804,6 +10817,7 @@ nsresult
 nsDocShell::DoURILoad(nsIURI* aURI,
                       nsIURI* aOriginalURI,
                       bool aLoadReplace,
+                      bool aLoadFromExternal,
                       nsIURI* aReferrerURI,
                       bool aSendReferrer,
                       uint32_t aReferrerPolicy,
diff --git a/docshell/base/nsDocShell.h b/docshell/base/nsDocShell.h
index 3ca9e0b34..549d7f540 100644
--- a/docshell/base/nsDocShell.h
+++ b/docshell/base/nsDocShell.h
@@ -369,6 +369,7 @@ protected:
   nsresult DoURILoad(nsIURI* aURI,
                      nsIURI* aOriginalURI,
                      bool aLoadReplace,
+                     bool aLoadFromExternal,
                      nsIURI* aReferrer,
                      bool aSendReferrer,
                      uint32_t aReferrerPolicy,
diff --git a/dom/locales/en-US/chrome/security/security.properties b/dom/locales/en-US/chrome/security/security.properties
index 8b66cc265..c0b80996c 100644
--- a/dom/locales/en-US/chrome/security/security.properties
+++ b/dom/locales/en-US/chrome/security/security.properties
@@ -81,3 +81,6 @@ MimeTypeMismatch=The resource from “%1$S” was blocked due to MIME type misma
 XCTOHeaderValueMissing=X-Content-Type-Options header warning: value was “%1$S”; did you mean to send “nosniff”?
 
 BlockScriptWithWrongMimeType=Script from “%1$S” was blocked because of a disallowed MIME type.
+
+# LOCALIZATION NOTE: Do not translate "data: URI".
+BlockTopLevelDataURINavigation=Navigation to toplevel data: URI not allowed (Blocked loading of: “%1$S”)
diff --git a/dom/security/nsContentSecurityManager.cpp b/dom/security/nsContentSecurityManager.cpp
index c4e1ed8e1..069e7d6a7 100644
--- a/dom/security/nsContentSecurityManager.cpp
+++ b/dom/security/nsContentSecurityManager.cpp
@@ -1,13 +1,16 @@
 #include "nsContentSecurityManager.h"
+#include "nsEscape.h"
 #include "nsIChannel.h"
 #include "nsIHttpChannelInternal.h"
 #include "nsIStreamListener.h"
 #include "nsILoadInfo.h"
+#include "nsIOService.h"
 #include "nsContentUtils.h"
 #include "nsCORSListenerProxy.h"
 #include "nsIStreamListener.h"
 #include "nsIDocument.h"
 #include "nsMixedContentBlocker.h"
+#include "nsNullPrincipal.h"
 
 #include "mozilla/dom/Element.h"
 
@@ -15,6 +18,66 @@ NS_IMPL_ISUPPORTS(nsContentSecurityManager,
                   nsIContentSecurityManager,
                   nsIChannelEventSink)
 
+/* static */ bool
+nsContentSecurityManager::AllowTopLevelNavigationToDataURI(
+  nsIURI* aURI,
+  nsContentPolicyType aContentPolicyType,
+  nsIPrincipal* aTriggeringPrincipal,
+  bool aLoadFromExternal)
+{
+  // Let's block all toplevel document navigations to a data: URI.
+  // In all cases where the toplevel document is navigated to a
+  // data: URI the triggeringPrincipal is a codeBasePrincipal, or
+  // a NullPrincipal. In other cases, e.g. typing a data: URL into
+  // the URL-Bar, the triggeringPrincipal is a SystemPrincipal;
+  // we don't want to block those loads. Only exception, loads coming
+  // from an external applicaton (e.g. Thunderbird) don't load
+  // using a codeBasePrincipal, but we want to block those loads.
+  if (!mozilla::net::nsIOService::BlockToplevelDataUriNavigations()) {
+    return true;
+  }
+  if (aContentPolicyType != nsIContentPolicy::TYPE_DOCUMENT) {
+    return true;
+  }
+  bool isDataURI =
+    (NS_SUCCEEDED(aURI->SchemeIs("data", &isDataURI)) && isDataURI);
+  if (!isDataURI) {
+    return true;
+  }
+  // Whitelist data: images as long as they are not SVGs
+  nsAutoCString filePath;
+  aURI->GetFilePath(filePath);
+  if (StringBeginsWith(filePath, NS_LITERAL_CSTRING("image/")) &&
+      !StringBeginsWith(filePath, NS_LITERAL_CSTRING("image/svg+xml"))) {
+    return true;
+  }
+  // Whitelist data: PDFs and JSON
+  if (StringBeginsWith(filePath, NS_LITERAL_CSTRING("application/pdf")) ||
+      StringBeginsWith(filePath, NS_LITERAL_CSTRING("application/json"))) {
+    return true;
+  }
+  if (!aLoadFromExternal &&
+      nsContentUtils::IsSystemPrincipal(aTriggeringPrincipal)) {
+    return true;
+  }
+  nsAutoCString dataSpec;
+  aURI->GetSpec(dataSpec);
+  if (dataSpec.Length() > 50) {
+    dataSpec.Truncate(50);
+    dataSpec.AppendLiteral("...");
+  }
+  NS_ConvertUTF8toUTF16 specUTF16(NS_UnescapeURL(dataSpec));
+  const char16_t* params[] = { specUTF16.get() };
+  nsContentUtils::ReportToConsole(nsIScriptError::warningFlag,
+                                  NS_LITERAL_CSTRING("DATA_URI_BLOCKED"),
+                                  // no doc available, log to browser console
+                                  nullptr,
+                                  nsContentUtils::eSECURITY_PROPERTIES,
+                                  "BlockTopLevelDataURINavigation",
+                                  params, ArrayLength(params));
+  return false;
+}
+
 static nsresult
 ValidateSecurityFlags(nsILoadInfo* aLoadInfo)
 {
@@ -478,6 +541,27 @@ nsContentSecurityManager::AsyncOnChannelRedirect(nsIChannel* aOldChannel,
     }
   }
 
+  // Redirecting to a toplevel data: URI is not allowed, hence we pass
+  // a NullPrincipal as the TriggeringPrincipal to
+  // AllowTopLevelNavigationToDataURI() which definitely blocks any
+  // data: URI load.
+  nsCOMPtr<nsILoadInfo> newLoadInfo = aNewChannel->GetLoadInfo();
+  if (newLoadInfo) {
+    nsCOMPtr<nsIURI> uri;
+    nsresult rv = NS_GetFinalChannelURI(aNewChannel, getter_AddRefs(uri));
+    NS_ENSURE_SUCCESS(rv, rv);
+    nsCOMPtr<nsIPrincipal> nullTriggeringPrincipal = nsNullPrincipal::Create();
+    if (!nsContentSecurityManager::AllowTopLevelNavigationToDataURI(
+          uri,
+          newLoadInfo->GetExternalContentPolicyType(),
+          nullTriggeringPrincipal,
+          false)) {
+        // logging to console happens within AllowTopLevelNavigationToDataURI
+      aOldChannel->Cancel(NS_ERROR_DOM_BAD_URI);
+      return NS_ERROR_DOM_BAD_URI;
+    }
+  }
+
   // Also verify that the redirecting server is allowed to redirect to the
   // given URI
   nsCOMPtr<nsIPrincipal> oldPrincipal;
diff --git a/dom/security/nsContentSecurityManager.h b/dom/security/nsContentSecurityManager.h
index 912c0e89f..09b6c86aa 100644
--- a/dom/security/nsContentSecurityManager.h
+++ b/dom/security/nsContentSecurityManager.h
@@ -32,6 +32,11 @@ public:
   static nsresult doContentSecurityCheck(nsIChannel* aChannel,
                                          nsCOMPtr<nsIStreamListener>& aInAndOutListener);
 
+  static bool AllowTopLevelNavigationToDataURI(nsIURI* aURI,
+                                               nsContentPolicyType aContentPolicyType,
+                                               nsIPrincipal* aTriggeringPrincipal,
+                                               bool aLoadFromExternal);
+
 private:
   static nsresult CheckChannel(nsIChannel* aChannel);
 
diff --git a/dom/security/test/general/browser.ini b/dom/security/test/general/browser.ini
new file mode 100644
index 000000000..97ddae3bf
--- /dev/null
+++ b/dom/security/test/general/browser.ini
@@ -0,0 +1,5 @@
+[DEFAULT]
+[browser_test_toplevel_data_navigations.js]
+support-files =
+  file_toplevel_data_navigations.sjs
+  file_toplevel_data_meta_redirect.html
diff --git a/dom/security/test/general/browser_test_toplevel_data_navigations.js b/dom/security/test/general/browser_test_toplevel_data_navigations.js
new file mode 100644
index 000000000..a13a6350e
--- /dev/null
+++ b/dom/security/test/general/browser_test_toplevel_data_navigations.js
@@ -0,0 +1,54 @@
+/* eslint-disable mozilla/no-arbitrary-setTimeout */
+
+"use strict";
+
+const kDataBody = "toplevel navigation to data: URI allowed";
+const kDataURI = "data:text/html,<body>" + kDataBody + "</body>";
+const kTestPath = getRootDirectory(gTestPath)
+                  .replace("chrome://mochitests/content", "http://example.com")
+const kRedirectURI = kTestPath + "file_toplevel_data_navigations.sjs";
+const kMetaRedirectURI = kTestPath + "file_toplevel_data_meta_redirect.html";
+
+add_task(async function test_nav_data_uri() {
+  await SpecialPowers.pushPrefEnv({
+    "set": [["security.data_uri.block_toplevel_data_uri_navigations", true]],
+  });
+  await BrowserTestUtils.withNewTab(kDataURI, async function(browser) {
+    await ContentTask.spawn(gBrowser.selectedBrowser, {kDataBody}, async function({kDataBody}) { // eslint-disable-line
+     is(content.document.body.innerHTML, kDataBody,
+        "data: URI navigation from system should be allowed");
+    });
+  });
+});
+
+add_task(async function test_nav_data_uri_redirect() {
+  await SpecialPowers.pushPrefEnv({
+    "set": [["security.data_uri.block_toplevel_data_uri_navigations", true]],
+  });
+  let tab = BrowserTestUtils.addTab(gBrowser, kRedirectURI);
+  registerCleanupFunction(async function() {
+    await BrowserTestUtils.removeTab(tab);
+  });
+  // wait to make sure data: URI did not load before checking that it got blocked
+  await new Promise(resolve => setTimeout(resolve, 500));
+  await ContentTask.spawn(gBrowser.selectedBrowser, {}, async function() {
+    is(content.document.body.innerHTML, "",
+       "data: URI navigation after server redirect should be blocked");
+  });
+});
+
+add_task(async function test_nav_data_uri_meta_redirect() {
+  await SpecialPowers.pushPrefEnv({
+    "set": [["security.data_uri.block_toplevel_data_uri_navigations", true]],
+  });
+  let tab = BrowserTestUtils.addTab(gBrowser, kMetaRedirectURI);
+  registerCleanupFunction(async function() {
+    await BrowserTestUtils.removeTab(tab);
+  });
+  // wait to make sure data: URI did not load before checking that it got blocked
+  await new Promise(resolve => setTimeout(resolve, 500));
+  await ContentTask.spawn(gBrowser.selectedBrowser, {}, async function() {
+    is(content.document.body.innerHTML, "",
+       "data: URI navigation after meta redirect should be blocked");
+  });
+});
diff --git a/dom/security/test/general/file_block_toplevel_data_navigation.html b/dom/security/test/general/file_block_toplevel_data_navigation.html
new file mode 100644
index 000000000..5fbfdfdef
--- /dev/null
+++ b/dom/security/test/general/file_block_toplevel_data_navigation.html
@@ -0,0 +1,14 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Toplevel data navigation</title>
+</head>
+<body>
+test1: clicking data: URI tries to navigate window<br/>
+<a id="testlink" href="data:text/html,<body>toplevel data: URI navigations should be blocked</body>">click me</a>
+<script>
+  document.getElementById('testlink').click();
+</script>
+</body>
+</html>
diff --git a/dom/security/test/general/file_block_toplevel_data_navigation2.html b/dom/security/test/general/file_block_toplevel_data_navigation2.html
new file mode 100644
index 000000000..e0308e1ae
--- /dev/null
+++ b/dom/security/test/general/file_block_toplevel_data_navigation2.html
@@ -0,0 +1,29 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Toplevel data navigation</title>
+</head>
+<body>
+test2: data: URI in iframe tries to window.open(data:, _blank);<br/>
+<iframe id="testFrame" src=""></iframe>
+<script>
+  let DATA_URI = `data:text/html,<body><script>
+    var win = window.open("data:text/html,<body>toplevel data: URI navigations should be blocked</body>", "_blank");
+    setTimeout(function () {
+      var result = win.document.body.innerHTML === "" ? "blocked" : "navigated";
+      parent.postMessage(result, "*");
+      win.close();
+    }, 1000);
+    <\/script></body>`;
+
+  window.addEventListener("message", receiveMessage);
+  function receiveMessage(event) {
+    window.removeEventListener("message", receiveMessage);
+    // propagate the information back to the caller
+    window.opener.postMessage(event.data, "*");
+  }
+  document.getElementById('testFrame').src = DATA_URI;
+</script>
+</body>
+</html>
diff --git a/dom/security/test/general/file_block_toplevel_data_navigation3.html b/dom/security/test/general/file_block_toplevel_data_navigation3.html
new file mode 100644
index 000000000..34aeddab3
--- /dev/null
+++ b/dom/security/test/general/file_block_toplevel_data_navigation3.html
@@ -0,0 +1,13 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Toplevel data navigation</title>
+</head>
+<body>
+test3: performing data: URI navigation through win.loc.href<br/>
+<script>
+  window.location.href = "data:text/html,<body>toplevel data: URI navigations should be blocked</body>";
+</script>
+</body>
+</html>
diff --git a/dom/security/test/general/file_block_toplevel_data_redirect.sjs b/dom/security/test/general/file_block_toplevel_data_redirect.sjs
new file mode 100644
index 000000000..64e294cab
--- /dev/null
+++ b/dom/security/test/general/file_block_toplevel_data_redirect.sjs
@@ -0,0 +1,14 @@
+// Custom *.sjs file specifically for the needs of Bug:
+// Bug 1394554 - Block toplevel data: URI navigations after redirect
+
+var DATA_URI =
+  "<body>toplevel data: URI navigations after redirect should be blocked</body>";
+
+function handleRequest(request, response)
+{
+  // avoid confusing cache behaviors
+  response.setHeader("Cache-Control", "no-cache", false);
+
+  response.setStatusLine("1.1", 302, "Found");
+  response.setHeader("Location", "data:text/html," + escape(DATA_URI), false);
+}
diff --git a/dom/security/test/general/file_toplevel_data_meta_redirect.html b/dom/security/test/general/file_toplevel_data_meta_redirect.html
new file mode 100644
index 000000000..f4f5deb52
--- /dev/null
+++ b/dom/security/test/general/file_toplevel_data_meta_redirect.html
@@ -0,0 +1,10 @@
+<html>

+<body>

+<head>

+  <meta http-equiv="refresh"

+        content="0; url='data:text/html,<body>toplevel meta redirect to data: URI should be blocked</body>'">

+</head>

+<body>

+Meta Redirect to data: URI

+</body>

+</html>

diff --git a/dom/security/test/general/file_toplevel_data_navigations.sjs b/dom/security/test/general/file_toplevel_data_navigations.sjs
new file mode 100644
index 000000000..501b833e5
--- /dev/null
+++ b/dom/security/test/general/file_toplevel_data_navigations.sjs
@@ -0,0 +1,14 @@
+// Custom *.sjs file specifically for the needs of Bug:
+// Bug 1394554 - Block toplevel data: URI navigations after redirect
+
+var DATA_URI =
+  "data:text/html,<body>toplevel data: URI navigations after redirect should be blocked</body>";
+
+function handleRequest(request, response)
+{
+  // avoid confusing cache behaviors
+  response.setHeader("Cache-Control", "no-cache", false);
+
+  response.setStatusLine("1.1", 302, "Found");
+  response.setHeader("Location", DATA_URI, false);
+}
diff --git a/dom/security/test/general/mochitest.ini b/dom/security/test/general/mochitest.ini
index 70c0c9fb6..f3bcca072 100644
--- a/dom/security/test/general/mochitest.ini
+++ b/dom/security/test/general/mochitest.ini
@@ -3,7 +3,19 @@ support-files =
   file_contentpolicytype_targeted_link_iframe.sjs
   file_nosniff_testserver.sjs
   file_block_script_wrong_mime_server.sjs
+  file_block_toplevel_data_navigation.html
+  file_block_toplevel_data_navigation2.html
+  file_block_toplevel_data_navigation3.html
+  file_block_toplevel_data_redirect.sjs
 
 [test_contentpolicytype_targeted_link_iframe.html]
 [test_nosniff.html]
 [test_block_script_wrong_mime.html]
+[test_block_toplevel_data_navigation.html]
+skip-if = toolkit == 'android' # intermittent failure
+[test_block_toplevel_data_img_navigation.html]
+skip-if = toolkit == 'android' # intermittent failure
+[test_allow_opening_data_pdf.html]
+skip-if = toolkit == 'android'
+[test_allow_opening_data_json.html]
+skip-if = toolkit == 'android'
diff --git a/dom/security/test/general/test_allow_opening_data_json.html b/dom/security/test/general/test_allow_opening_data_json.html
new file mode 100644
index 000000000..1530a24e8
--- /dev/null
+++ b/dom/security/test/general/test_allow_opening_data_json.html
@@ -0,0 +1,39 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Bug 1403814: Allow toplevel data URI navigation data:application/json</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<script class="testbody" type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+
+function test_toplevel_data_json() {
+  const DATA_JSON = "data:application/json,{'my_json_key':'my_json_value'}";
+
+  let win = window.open(DATA_JSON);
+  let wrappedWin = SpecialPowers.wrap(win);
+
+  // Unfortunately we can't detect whether the JSON has loaded or not using some
+  // event, hence we are constantly polling location.href till we see that
+  // the data: URI appears. Test times out on failure.
+  var jsonLoaded = setInterval(function() {
+    if (wrappedWin.document.location.href.startsWith("data:application/json")) {
+      clearInterval(jsonLoaded);
+      ok(true, "navigating to data:application/json allowed");
+      wrappedWin.close();
+      SimpleTest.finish();
+    }
+  }, 200);
+}
+
+SpecialPowers.pushPrefEnv({
+  set: [["security.data_uri.block_toplevel_data_uri_navigations", true]]
+}, test_toplevel_data_json);
+
+</script>
+</body>
+</html>
diff --git a/dom/security/test/general/test_allow_opening_data_pdf.html b/dom/security/test/general/test_allow_opening_data_pdf.html
new file mode 100644
index 000000000..6b51fe57b
--- /dev/null
+++ b/dom/security/test/general/test_allow_opening_data_pdf.html
@@ -0,0 +1,41 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Bug 1398692: Allow toplevel navigation to a data:application/pdf</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<script class="testbody" type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+
+function test_toplevel_data_pdf() {
+  // The PDF contains one page and it is a 3/72" square, the minimum allowed by the spec
+  const DATA_PDF =
+    "data:application/pdf;base64,JVBERi0xLjANCjEgMCBvYmo8PC9UeXBlL0NhdGFsb2cvUGFnZXMgMiAwIFI+PmVuZG9iaiAyIDAgb2JqPDwvVHlwZS9QYWdlcy9LaWRzWzMgMCBSXS9Db3VudCAxPj5lbmRvYmogMyAwIG9iajw8L1R5cGUvUGFnZS9NZWRpYUJveFswIDAgMyAzXT4+ZW5kb2JqDQp4cmVmDQowIDQNCjAwMDAwMDAwMDAgNjU1MzUgZg0KMDAwMDAwMDAxMCAwMDAwMCBuDQowMDAwMDAwMDUzIDAwMDAwIG4NCjAwMDAwMDAxMDIgMDAwMDAgbg0KdHJhaWxlcjw8L1NpemUgNC9Sb290IDEgMCBSPj4NCnN0YXJ0eHJlZg0KMTQ5DQolRU9G";
+
+  let win = window.open(DATA_PDF);
+  let wrappedWin = SpecialPowers.wrap(win);
+
+  // Unfortunately we can't detect whether the PDF has loaded or not using some
+  // event, hence we are constantly polling location.href till we see that
+  // the data: URI appears. Test times out on failure.
+  var pdfLoaded = setInterval(function() {
+    if (wrappedWin.document.location.href.startsWith("data:application/pdf")) {
+      clearInterval(pdfLoaded);
+      ok(true, "navigating to data:application/pdf allowed");
+      wrappedWin.close();
+      SimpleTest.finish();
+    }
+  }, 200);
+}
+
+SpecialPowers.pushPrefEnv({
+  set: [["security.data_uri.block_toplevel_data_uri_navigations", true]]
+}, test_toplevel_data_pdf);
+
+</script>
+</body>
+</html>
diff --git a/dom/security/test/general/test_block_toplevel_data_img_navigation.html b/dom/security/test/general/test_block_toplevel_data_img_navigation.html
new file mode 100644
index 000000000..2b8f62760
--- /dev/null
+++ b/dom/security/test/general/test_block_toplevel_data_img_navigation.html
@@ -0,0 +1,51 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Bug 1396798: Do not block toplevel data: navigation to image (except svgs)</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<script class="testbody" type="text/javascript">
+SpecialPowers.setBoolPref("security.data_uri.block_toplevel_data_uri_navigations", true);
+SimpleTest.registerCleanupFunction(() => {
+  SpecialPowers.clearUserPref("security.data_uri.block_toplevel_data_uri_navigations");
+});
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.requestFlakyTimeout("have to test that top level data:image loading is blocked/allowed");
+
+function test_toplevel_data_image() {
+  const DATA_PNG =
+    "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==";
+  let win1 = window.open(DATA_PNG);
+  let wrappedWin1 = SpecialPowers.wrap(win1);
+  setTimeout(function () {
+    let images = wrappedWin1.document.getElementsByTagName('img'); 
+    is(images.length, 1, "Loading data:image/png should be allowed");
+    is(images[0].src, DATA_PNG, "Sanity: img src matches");
+    wrappedWin1.close();
+    test_toplevel_data_image_svg();
+  }, 1000);
+}
+
+function test_toplevel_data_image_svg() {
+  const DATA_SVG =
+    "data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHdpZHRoPSIxNiIgaGVpZ2h0PSIxNiIgdmlld0JveD0iMCAwIDE2IDE2Ij4KICA8cGF0aCBkPSJNOCwxMkwzLDcsNCw2bDQsNCw0LTQsMSwxWiIgZmlsbD0iIzZBNkE2QSIgLz4KPC9zdmc+Cg==";
+  let win2 = window.open(DATA_SVG);
+  let wrappedWin2 = SpecialPowers.wrap(win2);
+  setTimeout(function () {
+    isnot(wrappedWin2.document.documentElement.localName, "svg",
+          "Loading data:image/svg+xml should be blocked");
+    wrappedWin2.close();
+    SimpleTest.finish();
+  }, 1000);
+}
+
+// fire up the tests
+test_toplevel_data_image();
+
+</script>
+</body>
+</html>
diff --git a/dom/security/test/general/test_block_toplevel_data_navigation.html b/dom/security/test/general/test_block_toplevel_data_navigation.html
new file mode 100644
index 000000000..fc91f2ec0
--- /dev/null
+++ b/dom/security/test/general/test_block_toplevel_data_navigation.html
@@ -0,0 +1,90 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Bug 1331351 - Block top level window data: URI navigations</title>
+  <!-- Including SimpleTest.js so we can use waitForExplicitFinish !-->
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<script class="testbody" type="text/javascript">
+SpecialPowers.setBoolPref("security.data_uri.block_toplevel_data_uri_navigations", true);
+SimpleTest.registerCleanupFunction(() => {
+  SpecialPowers.clearUserPref("security.data_uri.block_toplevel_data_uri_navigations");
+});
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.requestFlakyTimeout("have to test that top level data: URI navgiation is blocked");
+
+function test1() {
+  // simple data: URI click navigation should be prevented
+  let TEST_FILE = "file_block_toplevel_data_navigation.html";
+  let win1 = window.open(TEST_FILE);
+  var readyStateCheckInterval = setInterval(function() {
+    let state = win1.document.readyState;
+    if (state === "interactive" || state === "complete") {
+      clearInterval(readyStateCheckInterval);
+      ok(win1.document.body.innerHTML.indexOf("test1:") !== -1,
+         "toplevel data: URI navigation through click() should be blocked");
+      win1.close();
+      test2();
+    }
+  }, 200);
+}
+
+function test2() {
+  // data: URI in iframe which opens data: URI in _blank should be blocked 
+  let win2 = window.open("file_block_toplevel_data_navigation2.html");
+  window.addEventListener("message", receiveMessage);
+  function receiveMessage(event) {
+    window.removeEventListener("message", receiveMessage);
+    is(event.data, "blocked",
+      "data: URI navigation using _blank from data: URI should be blocked");
+    win2.close();
+    test3();
+  }
+}
+
+function test3() {
+  // navigating to a data: URI using window.location.href should be blocked
+  let win3 = window.open("file_block_toplevel_data_navigation3.html");
+  setTimeout(function () {
+    ok(win3.document.body.innerHTML.indexOf("test3:") !== -1,
+      "data: URI navigation through win.loc.href should be blocked");
+    win3.close();
+    test4();
+  }, 1000);
+}
+
+function test4() {
+  // navigating to a data: URI using window.open() should be blocked
+  let win4 = window.open("data:text/html,<body>toplevel data: URI navigations should be blocked</body>");
+  setTimeout(function () {
+    // Please note that the data: URI will be displayed in the URL-Bar but not
+    // loaded, hence we rather rely on document.body than document.location
+    is(win4.document.body.innerHTML, "",
+      "navigating to a data: URI using window.open() should be blocked");
+    test5();
+  }, 1000);
+}
+
+function test5() {
+  // navigating to a URI which redirects to a data: URI using window.open() should be blocked
+  let win5 = window.open("file_block_toplevel_data_redirect.sjs");
+  setTimeout(function () {
+    // Please note that the data: URI will be displayed in the URL-Bar but not
+    // loaded, hence we rather rely on document.body than document.location
+    is(SpecialPowers.wrap(win5).document.body.innerHTML, "",
+      "navigating to URI which redirects to a data: URI using window.open() should be blocked");
+    win5.close();
+    SimpleTest.finish();
+  }, 1000);
+}
+
+// fire up the tests
+test1();
+
+</script>
+</body>
+</html>
diff --git a/dom/security/test/moz.build b/dom/security/test/moz.build
index ddb4e9b89..946959dee 100644
--- a/dom/security/test/moz.build
+++ b/dom/security/test/moz.build
@@ -27,5 +27,6 @@ MOCHITEST_CHROME_MANIFESTS += [
 BROWSER_CHROME_MANIFESTS += [
     'contentverifier/browser.ini',
     'csp/browser.ini',
+    'general/browser.ini',
     'hsts/browser.ini',
 ]
diff --git a/modules/libpref/init/all.js b/modules/libpref/init/all.js
index 182de4a11..ccc59269b 100644
--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -5564,6 +5564,12 @@ pref("security.mixed_content.use_hsts", true);
 // Approximately 1 week default cache for HSTS priming failures
 pref ("security.mixed_content.hsts_priming_cache_timeout", 10080);
 
+// TODO: Bug 1380959: Block toplevel data: URI navigations
+// If true, all toplevel data: URI navigations will be blocked.
+// Please note that manually entering a data: URI in the
+// URL-Bar will not be blocked when flipping this pref.
+pref("security.data_uri.block_toplevel_data_uri_navigations", false);
+
 // Disable Storage api in release builds.
 #ifdef NIGHTLY_BUILD
 pref("dom.storageManager.enabled", true);
diff --git a/netwerk/base/nsIOService.cpp b/netwerk/base/nsIOService.cpp
index 0da79c18a..8b7f31f99 100644
--- a/netwerk/base/nsIOService.cpp
+++ b/netwerk/base/nsIOService.cpp
@@ -173,6 +173,8 @@ uint32_t   nsIOService::gDefaultSegmentCount = 24;
 
 bool nsIOService::sTelemetryEnabled = false;
 
+bool nsIOService::sBlockToplevelDataUriNavigations = false;
+
 ////////////////////////////////////////////////////////////////////////////////
 
 nsIOService::nsIOService()
@@ -251,6 +253,8 @@ nsIOService::Init()
         NS_WARNING("failed to get observer service");
 
     Preferences::AddBoolVarCache(&sTelemetryEnabled, "toolkit.telemetry.enabled", false);
+    Preferences::AddBoolVarCache(&sBlockToplevelDataUriNavigations,
+                                 "security.data_uri.block_toplevel_data_uri_navigations", false);
     Preferences::AddBoolVarCache(&mOfflineMirrorsConnectivity, OFFLINE_MIRRORS_CONNECTIVITY, true);
 
     gIOService = this;
@@ -1876,5 +1880,11 @@ nsIOService::SpeculativeAnonymousConnect2(nsIURI *aURI,
     return SpeculativeConnectInternal(aURI, aPrincipal, aCallbacks, true);
 }
 
+/*static*/ bool
+nsIOService::BlockToplevelDataUriNavigations()
+{
+  return sBlockToplevelDataUriNavigations;
+}
+
 } // namespace net
 } // namespace mozilla
diff --git a/netwerk/base/nsIOService.h b/netwerk/base/nsIOService.h
index 7ac23b791..e592c4d1c 100644
--- a/netwerk/base/nsIOService.h
+++ b/netwerk/base/nsIOService.h
@@ -95,6 +95,8 @@ public:
 
     bool IsLinkUp();
 
+    static bool BlockToplevelDataUriNavigations();
+
     // Used to trigger a recheck of the captive portal status
     nsresult RecheckCaptivePortal();
 private:
@@ -176,6 +178,8 @@ private:
 
     static bool                          sTelemetryEnabled;
 
+    static bool                          sBlockToplevelDataUriNavigations;
+
     // These timestamps are needed for collecting telemetry on PR_Connect,
     // PR_ConnectContinue and PR_Close blocking time.  If we spend very long
     // time in any of these functions we want to know if and what network