[webcrypto] Support 256-bit AES-GCM for OpenSSL implementation.

content/child/webcrypto/openssl/aes_gcm_openssl.cc

 // 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 <vector>
 #include <openssl/evp.h>
 
 #include "base/logging.h"
 #include "content/child/webcrypto/crypto_data.h"
 #include "content/child/webcrypto/openssl/aes_key_openssl.h"
 #include "content/child/webcrypto/openssl/key_openssl.h"
 #include "content/child/webcrypto/openssl/util_openssl.h"
 #include "content/child/webcrypto/status.h"
 #include "content/child/webcrypto/webcrypto_util.h"
 #include "crypto/openssl_util.h"
 #include "crypto/scoped_openssl_types.h"
 #include "third_party/WebKit/public/platform/WebCryptoAlgorithmParams.h"
 
 namespace content {
 
 namespace webcrypto {
 
 namespace {
 
 const EVP_AEAD* GetAesGcmAlgorithmFromKeySize(unsigned int key_size_bytes) {
   switch (key_size_bytes) {
     case 16:
       return EVP_aead_aes_128_gcm();
-    // TODO(eroman): Hook up 256-bit support when it is available.
+    case 32:
+      return EVP_aead_aes_256_gcm();
     default:
       return NULL;
   }
 }
 
 Status AesGcmEncryptDecrypt(EncryptOrDecrypt mode,
                             const blink::WebCryptoAlgorithm& algorithm,
                             const blink::WebCryptoKey& key,
                             const CryptoData& data,
                             std::vector<uint8_t>* buffer) {
@@ skipping 94 matching lines @@
 
 }  // namespace
 
 AlgorithmImplementation* CreatePlatformAesGcmImplementation() {
   return new AesGcmImplementation;
 }
 
 }  // namespace webcrypto
 
 }  // namespace content