[webcrypto] Reject AES-GCM tag lengths other than 32, 64, 96, 104, 112, 120, 128.

content/renderer/webcrypto/webcrypto_util.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/webcrypto_util.h"
 
 #include "base/base64.h"
 #include "base/logging.h"
 #include "third_party/WebKit/public/platform/WebCryptoAlgorithm.h"
 #include "third_party/WebKit/public/platform/WebCryptoAlgorithmParams.h"
@@ skipping 103 matching lines @@
 Status Status::ErrorUnsupported() {
   return Status("The requested operation is unsupported");
 }
 
 Status Status::ErrorUnexpected() {
   return Status("Something unexpected happened...");
 }
 
 Status Status::ErrorInvalidAesGcmTagLength() {
   return Status(
-      "The tag length is invalid: either too large or not a multiple "
-      "of 8 bits");
+      "The tag length is invalid: Must be 32, 64, 96, 104, 112, 120, or 128 "
+      "bits");
 }
 
 Status Status::ErrorGenerateKeyPublicExponent() {
   return Status("The \"publicExponent\" is either empty, zero, or too large");
 }
 
 Status Status::ErrorMissingAlgorithmImportRawKey() {
   return Status(
       "The key's algorithm must be specified when importing "
       "raw-formatted key.");
@@ skipping 185 matching lines @@
       return 128;
     default:
       NOTREACHED();
       return 0;
   }
 }
 
 }  // namespace webcrypto
 
 }  // namespace content