Part 2.3: Is policy list subsumed under subsuming policy?

third_party/WebKit/Source/core/frame/csp/SourceListDirective.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/frame/csp/SourceListDirective.h"
 
 #include "core/frame/csp/CSPSource.h"
 #include "core/frame/csp/ContentSecurityPolicy.h"
 #include "platform/network/ContentSecurityPolicyParsers.h"
 #include "platform/weborigin/KURL.h"
@@ skipping 557 matching lines @@
 
   return false;
 }
 
 HeapVector<Member<CSPSource>> SourceListDirective::getIntersectCSPSources(
     HeapVector<Member<CSPSource>> otherVector) {
   HeapVector<Member<CSPSource>> normalized;
   for (const auto& aCspSource : m_list) {
     Member<CSPSource> matchedCspSource(nullptr);
     for (const auto& bCspSource : otherVector) {
-      if ((matchedCspSource = bCspSource->intersect(aCspSource)))
+      if (aCspSource->isSchemeOnly() && bCspSource->isSchemeOnly()) {

[Mike West, 2016/11/17 10:58:31]

Nit: I guess I reviewed this earlier, but looking at it not, |sourceA| seems a
lot clearer than |aCspSource|.

+        if (Member<CSPSource> intersection =
+                bCspSource->intersect(aCspSource)) {
+          matchedCspSource = intersection;
+          break;
+        }
+      }
+      if (bCspSource->subsumes(aCspSource)) {

[amalika, 2016/11/09 17:53:46]

We always want to preserve the CSPSource we are currently considering instead of
just finding intersaction.

This is to handle the case:

Example 3:
A: https://example.com http://example.com/foo
B: http://example.com/foo https://example.com


However, as soon as we know it is subsumed by bCSPSource, we can break out of
the loop.

+        matchedCspSource = aCspSource;
         break;
+      }
+      if (Member<CSPSource> intersection = bCspSource->intersect(aCspSource))
+        matchedCspSource = intersection;
     }
     if (matchedCspSource)
       normalized.append(matchedCspSource);
   }
   return normalized;
 }
 
 DEFINE_TRACE(SourceListDirective) {
   visitor->trace(m_policy);
   visitor->trace(m_list);
   CSPDirective::trace(visitor);
 }
 
 }  // namespace blink