Implementation of subresource integrity attribute for secure origins.

Source/core/frame/SubresourceIntegrity.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 "config.h"
+#include "core/frame/SubresourceIntegrity.h"
+
+#include "platform/Crypto.h"
+#include "public/platform/WebCrypto.h"
+#include "public/platform/WebCryptoAlgorithm.h"
+#include "wtf/text/Base64.h"
+#include "wtf/text/StringUTF8Adaptor.h"
+#include "wtf/text/WTFString.h"
+
+namespace blink {
+
+static bool DigestsEqual(const DigestValue& digest1, const DigestValue& digest2)
+{
+    if (digest1.size() != digest2.size())
+        return false;
+
+    for (size_t i = 0; i < digest1.size(); i++) {
+        if (digest1[i] != digest2[i])
+            return false;
+    }
+
+    return true;
+}
+
+// TODO(jww) If CheckSubresourceIntegrity fails, Blink should create a console
+// message to alert the developer of the failure.
+bool SubresourceIntegrity::CheckSubresourceIntegrity(const String& source, const String& integrity)
+{
+    Vector<char> hashVector;
+    base64Decode(integrity, hashVector);

[Mike West, 2014/09/13 03:44:31]

Please add some TODOs about parsing the `ni:///` syntax to extract the algorithm
and expected hash, and about supporting multiple sets of integrity metadata, as
discussed in the agility section.

+
+    StringUTF8Adaptor normalizedSource(source, StringUTF8Adaptor::Normalize, WTF::EntitiesForUnencodables);
+
+    DigestValue digest;
+    bool digestSuccess = computeDigest(HashAlgorithmSha256, normalizedSource.data(), normalizedSource.length(), digest);
+
+    if (digestSuccess) {
+        DigestValue convertedHashVector;
+        convertedHashVector.append(reinterpret_cast<uint8_t*>(hashVector.data()), hashVector.size());
+        return DigestsEqual(digest, convertedHashVector);
+    }
+
+    return false;
+}
+
+} // namespace blink