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

content/renderer/webcrypto/shared_crypto_unittest.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 "content/renderer/webcrypto/shared_crypto.h"
 
 #include <algorithm>
 #include <string>
 #include <vector>
 
@@ skipping 1978 matching lines @@
     EXPECT_STATUS(Status::Error(),
                   AesGcmDecrypt(key,
                                 test_iv,
                                 test_additional_data,
                                 test_tag_size_bits,
                                 test_cipher_text,
                                 Corrupted(test_authentication_tag),
                                 &plain_text));
 
     // Try different incorrect tag lengths
-    uint8 kAlternateTagLengths[] = {8, 96, 120, 128, 160, 255};
+    uint8 kAlternateTagLengths[] = {0, 8, 96, 120, 128, 160, 255};

[eroman, 2014/02/20 01:28:22]

Previously, decrypting with taglength=0 would succeed, so added it to the
failure tests.

     for (size_t tag_i = 0; tag_i < arraysize(kAlternateTagLengths); ++tag_i) {
       unsigned int wrong_tag_size_bits = kAlternateTagLengths[tag_i];
       if (test_tag_size_bits == wrong_tag_size_bits)
         continue;
       EXPECT_STATUS_ERROR(AesGcmDecrypt(key,
                                         test_iv,
                                         test_additional_data,
                                         wrong_tag_size_bits,
                                         test_cipher_text,
                                         test_authentication_tag,
                                         &plain_text));
     }
   }
 }
 
 }  // namespace webcrypto
 
 }  // namespace content