Implement verify() for HMAC using NSS

content/renderer/webcrypto_impl_nss.cc

 // Copyright 2013 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 "content/renderer/webcrypto_impl.h"
 
 #include <pk11pub.h>
 #include <sechash.h>
+#include <vector>
 
 #include "base/logging.h"
 #include "crypto/nss_util.h"
 #include "crypto/scoped_nss_types.h"
+#include "crypto/secure_util.h"
 #include "third_party/WebKit/public/platform/WebArrayBuffer.h"
 #include "third_party/WebKit/public/platform/WebCryptoAlgorithm.h"
 #include "third_party/WebKit/public/platform/WebCryptoAlgorithmParams.h"
 
 namespace content {
 
 namespace {
 
 class SymKeyHandle : public WebKit::WebCryptoKeyHandle {
  public:
@@ skipping 219 matching lines @@
       break;
     }
     default:
       return false;
   }
 
   *buffer = result;
   return true;
 }
 
+bool WebCryptoImpl::VerifySignatureInternal(
+    const WebKit::WebCryptoAlgorithm& algorithm,
+    const WebKit::WebCryptoKey& key,
+    const unsigned char* signature,
+    unsigned signature_size,
+    const unsigned char* data,
+    unsigned data_size,
+    bool* signature_match) {
+  switch (algorithm.id()) {
+    case WebKit::WebCryptoAlgorithmIdHmac: {
+      WebKit::WebArrayBuffer result;
+      if (!SignInternal(algorithm, key, data, data_size, &result)) {
+        return false;
+      }
+
+      // Handling of truncated signatures is underspecified in the WebCrypto
+      // spec, so here we fail verification if a truncated signature is being
+      // verified.
+      // See https://www.w3.org/Bugs/Public/show_bug.cgi?id=23097
+      *signature_match =
+          crypto::SecureMemEqual(result.data(), signature, signature_size) &&

[eroman, 2013/09/26 00:10:43]

This is incorrect: the size check needs to be done BEFORE the comparison,
otherwise it may out of bounds.

Please add a regression test where signature_size is > result.byteLength()

[Bryan Eyler, 2013/09/26 00:18:07]

Done.

+          result.byteLength() == signature_size;
+
+      break;
+    }
+    default:
+      return false;
+  }
+
+  return true;
+}
+
 }  // namespace content