From 6514cd85bfe198df399d3f6d6a3325b21572c031 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Emilio=20Cobos=20=C3=81lvarez?= <emilio@crisal.io>
Date: Thu, 30 Jul 2020 08:55:24 +0000
Subject: [PATCH] Bug 1655933 - Allow images from non-static documents to get
 reused in their static clones without validation. r=tnikkel

This allows to print images that we'd otherwise reload.

Differential Revision: https://phabricator.services.mozilla.com/D85263
---
 image/imgLoader.cpp  | 21 ++++++---------------
 image/imgRequest.cpp | 23 +++++++++++++++++++++++
 image/imgRequest.h   |  4 ++++
 3 files changed, 33 insertions(+), 15 deletions(-)

diff --git a/image/imgLoader.cpp b/image/imgLoader.cpp
index d26ae7a0b5a0..f5f5bd1f52e9 100644
--- a/image/imgLoader.cpp
+++ b/image/imgLoader.cpp
@@ -672,7 +672,7 @@ static bool ShouldLoadCachedImage(imgRequest* aImgRequest,
   /* Call content policies on cached images - Bug 1082837
    * Cached images are keyed off of the first uri in a redirect chain.
    * Hence content policies don't get a chance to test the intermediate hops
-   * or the final desitnation.  Here we test the final destination using
+   * or the final destination.  Here we test the final destination using
    * mFinalURI off of the imgRequest and passing it into content policies.
    * For Mixed Content Blocker, we do an additional check to determine if any
    * of the intermediary hops went through an insecure redirect with the
@@ -1845,18 +1845,7 @@ bool imgLoader::ValidateEntry(
 
   bool validateRequest = false;
 
-  // If the request's loadId is the same as the aLoadingDocument, then it is ok
-  // to use this one because it has already been validated for this context.
-  //
-  // XXX: nullptr seems to be a 'special' key value that indicates that NO
-  //      validation is required.
-  // XXX: we also check the window ID because the loadID() can return a reused
-  //      pointer of a document. This can still happen for non-document image
-  //      cache entries.
-  void* key = (void*)aLoadingDocument;
-  uint64_t innerWindowID =
-      aLoadingDocument ? aLoadingDocument->InnerWindowID() : 0;
-  if (request->LoadId() != key || request->InnerWindowID() != innerWindowID) {
+  if (!request->CanReuseWithoutValidation(aLoadingDocument)) {
     // If we would need to revalidate this entry, but we're being told to
     // bypass the cache, we don't allow this entry to be used.
     if (aLoadFlags & nsIRequest::LOAD_BYPASS_CACHE) {
@@ -1876,10 +1865,10 @@ bool imgLoader::ValidateEntry(
             ("imgLoader::ValidateEntry validating cache entry. "
              "validateRequest = %d",
              validateRequest));
-  } else if (!key && MOZ_LOG_TEST(gImgLog, LogLevel::Debug)) {
+  } else if (!aLoadingDocument && MOZ_LOG_TEST(gImgLog, LogLevel::Debug)) {
     MOZ_LOG(gImgLog, LogLevel::Debug,
             ("imgLoader::ValidateEntry BYPASSING cache validation for %s "
-             "because of NULL LoadID",
+             "because of NULL loading document",
              aURI->GetSpecOrDefault().get()));
   }
 
@@ -1954,6 +1943,8 @@ bool imgLoader::ValidateEntry(
   if (validateRequest && aCanMakeNewChannel) {
     LOG_SCOPE(gImgLog, "imgLoader::ValidateRequest |cache hit| must validate");
 
+    uint64_t innerWindowID =
+        aLoadingDocument ? aLoadingDocument->InnerWindowID() : 0;
     return ValidateRequestWithNewChannel(
         request, aURI, aInitialDocumentURI, aReferrerInfo, aLoadGroup,
         aObserver, aLoadingDocument, innerWindowID, aLoadFlags, aLoadPolicyType,
diff --git a/image/imgRequest.cpp b/image/imgRequest.cpp
index bcb9803b245a..e3630b5c47f9 100644
--- a/image/imgRequest.cpp
+++ b/image/imgRequest.cpp
@@ -148,6 +148,29 @@ nsresult imgRequest::Init(nsIURI* aURI, nsIURI* aFinalURI,
   return NS_OK;
 }
 
+bool imgRequest::CanReuseWithoutValidation(dom::Document* aDoc) const {
+  // If the request's loadId is the same as the aLoadingDocument, then it is ok
+  // to use this one because it has already been validated for this context.
+  // XXX: nullptr seems to be a 'special' key value that indicates that NO
+  //      validation is required.
+  // XXX: we also check the window ID because the loadID() can return a reused
+  //      pointer of a document. This can still happen for non-document image
+  //      cache entries.
+  void* key = (void*)aDoc;
+  uint64_t innerWindowID = aDoc ? aDoc->InnerWindowID() : 0;
+  if (LoadId() == key && InnerWindowID() == innerWindowID) {
+    return true;
+  }
+
+  // As a special-case, if this is a print preview document, also validate on
+  // the original document. This allows to print uncacheable images.
+  if (dom::Document* original = aDoc ? aDoc->GetOriginalDocument() : nullptr) {
+    return CanReuseWithoutValidation(original);
+  }
+
+  return false;
+}
+
 void imgRequest::ClearLoader() { mLoader = nullptr; }
 
 already_AddRefed<ProgressTracker> imgRequest::GetProgressTracker() const {
diff --git a/image/imgRequest.h b/image/imgRequest.h
index d94915bd2458..e2f6a8a637e1 100644
--- a/image/imgRequest.h
+++ b/image/imgRequest.h
@@ -74,6 +74,10 @@ class imgRequest final : public nsIStreamListener,
   // Callers must call imgRequestProxy::Notify later.
   void AddProxy(imgRequestProxy* proxy);
 
+  // Whether a given document is allowed to reuse this request without any
+  // revalidation.
+  bool CanReuseWithoutValidation(mozilla::dom::Document*) const;
+
   nsresult RemoveProxy(imgRequestProxy* proxy, nsresult aStatus);
 
   // Cancel, but also ensure that all work done in Init() is undone. Call this