Bug 1609474 - Handle if extensions.webextensions.remote changes during runtime for the purposes of Eval/JS Load Telemetry r=robwu,ckerschb

Differential Revision: https://phabricator.services.mozilla.com/D60034

--HG--
extra : moz-landing-system : lando

dom/security/nsContentSecurityUtils.cpp

@@ -291,6 +291,11 @@ class EvalUsageNotificationRunnable final : public Runnable {
   uint32_t mColumnNumber;
 };
 
+// The Web Extension process pref may be toggled during a session, at which
+// point stuff may be loaded in the parent process but we would send telemetry
+// for it. Avoid this by observing if the pref ever was disabled.
+static bool sWebExtensionsRemoteWasEverDisabled = false;
+
 /* static */
 bool nsContentSecurityUtils::IsEvalAllowed(JSContext* cx,
                                            bool aIsSystemPrincipal,
@@ -377,11 +382,18 @@ bool nsContentSecurityUtils::IsEvalAllowed(JSContext* cx,
 
   if (XRE_IsE10sParentProcess() &&
       !StaticPrefs::extensions_webextensions_remote()) {
+    sWebExtensionsRemoteWasEverDisabled = true;
     MOZ_LOG(sCSMLog, LogLevel::Debug,
             ("Allowing eval() in parent process because the web extension "
              "process is disabled"));
     return true;
   }
+  if (XRE_IsE10sParentProcess() && sWebExtensionsRemoteWasEverDisabled) {
+    MOZ_LOG(sCSMLog, LogLevel::Debug,
+            ("Allowing eval() in parent process because the web extension "
+             "process was disabled at some point"));
+    return true;
+  }
 
   // We permit these two common idioms to get access to the global JS object
   if (!aScript.IsEmpty() &&
@@ -737,12 +749,20 @@ bool nsContentSecurityUtils::ValidateScriptFilename(const char* aFilename,
 
   if (XRE_IsE10sParentProcess() &&
       !StaticPrefs::extensions_webextensions_remote()) {
+    sWebExtensionsRemoteWasEverDisabled = true;
     MOZ_LOG(sCSMLog, LogLevel::Debug,
             ("Allowing a javascript load of %s because the web extension "
              "process is disabled.",
              aFilename));
     return true;
   }
+  if (XRE_IsE10sParentProcess() && sWebExtensionsRemoteWasEverDisabled) {
+    MOZ_LOG(sCSMLog, LogLevel::Debug,
+            ("Allowing a javascript load of %s because the web extension "
+             "process was disabled at some point.",
+             aFilename));
+    return true;
+  }
 
   NS_ConvertUTF8toUTF16 filenameU(aFilename);
   if (StringBeginsWith(filenameU, NS_LITERAL_STRING("chrome://"))) {