Bug 1641905 - ThirdPartyUtil::IsThirdPartyWindow returns different values in fission - use the principal to inherit for about:blank channels, r=dimi

Differential Revision: https://phabricator.services.mozilla.com/D81558

dom/base/ThirdPartyUtil.cpp

@@ -100,7 +100,9 @@ nsresult ThirdPartyUtil::IsThirdPartyInternal(const nsCString& aFirstDomain,
   nsresult rv = GetBaseDomain(aSecondURI, secondDomain);
   LOG(("ThirdPartyUtil::IsThirdPartyInternal %s =? %s", aFirstDomain.get(),
        secondDomain.get()));
-  if (NS_FAILED(rv)) return rv;
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
 
   *aResult = IsThirdPartyInternal(aFirstDomain, secondDomain);
   return NS_OK;
@@ -161,7 +163,9 @@ ThirdPartyUtil::IsThirdPartyURI(nsIURI* aFirstURI, nsIURI* aSecondURI,
 
   nsAutoCString firstHost;
   nsresult rv = GetBaseDomain(aFirstURI, firstHost);
-  if (NS_FAILED(rv)) return rv;
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
 
   return IsThirdPartyInternal(firstHost, aSecondURI, aResult);
 }
@@ -275,25 +279,58 @@ ThirdPartyUtil::IsThirdPartyChannel(nsIChannel* aChannel, nsIURI* aURI,
   }
 
   bool parentIsThird = false;
+  nsAutoCString channelDomain;
 
   // Obtain the URI from the channel, and its base domain.
   nsCOMPtr<nsIURI> channelURI;
   rv = NS_GetFinalChannelURI(aChannel, getter_AddRefs(channelURI));
-  if (NS_FAILED(rv)) return rv;
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
 
-  nsAutoCString channelDomain;
-  rv = GetBaseDomain(channelURI, channelDomain);
-  if (NS_FAILED(rv)) return rv;
+  BasePrincipal* loadingPrincipal = nullptr;
+  nsCOMPtr<nsILoadInfo> loadInfo = aChannel->LoadInfo();
 
   if (!doForce) {
-    nsCOMPtr<nsILoadInfo> loadInfo = aChannel->LoadInfo();
     parentIsThird = loadInfo->GetIsInThirdPartyContext();
     if (!parentIsThird && loadInfo->GetExternalContentPolicyType() !=
                               nsIContentPolicy::TYPE_DOCUMENT) {
       // Check if the channel itself is third-party to its own requestor.
-      // Unforunately, we have to go through the loading principal.
-      BasePrincipal* loadingPrincipal =
-          BasePrincipal::Cast(loadInfo->GetLoadingPrincipal());
+      // Unfortunately, we have to go through the loading principal.
+      loadingPrincipal = BasePrincipal::Cast(loadInfo->GetLoadingPrincipal());
+    }
+  }
+
+  // Special consideration must be done for about:blank URIs because those
+  // inherit the principal from the parent context. For them, let's consider the
+  // principal URI.
+  if (NS_IsAboutBlank(channelURI)) {
+    nsCOMPtr<nsIPrincipal> principalToInherit =
+        loadInfo->FindPrincipalToInherit(aChannel);
+    if (!principalToInherit) {
+      *aResult = true;
+      return NS_OK;
+    }
+
+    rv = principalToInherit->GetBaseDomain(channelDomain);
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+
+    if (loadingPrincipal) {
+      rv = loadingPrincipal->IsThirdPartyPrincipal(principalToInherit,
+                                                   &parentIsThird);
+      if (NS_FAILED(rv)) {
+        return rv;
+      }
+    }
+  } else {
+    rv = GetBaseDomain(channelURI, channelDomain);
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+
+    if (loadingPrincipal) {
       rv = loadingPrincipal->IsThirdPartyURI(channelURI, &parentIsThird);
       if (NS_FAILED(rv)) {
         return rv;