Add support for v0.3 of the encrypted WebM specification.

media/crypto/aes_decryptor.cc

 // Copyright (c) 2012 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 "media/crypto/aes_decryptor.h"
 
 #include <vector>
 
 #include "base/logging.h"
 #include "base/stl_util.h"
@@ skipping 267 matching lines @@
   // what should happen when a frame fails the integrity check.
   // http://wiki.webmproject.org/encryption/webm-encryption-rfc
   if (checksum_size > 0 &&
       !key->hmac_key().empty() &&
       !CheckData(*encrypted, key->hmac_key())) {
     DVLOG(1) << "Integrity check failed.";
     decrypt_cb.Run(kError, NULL);
     return;
   }
 
-  // TODO(strobe): Currently, presence of checksum is used to indicate the use
-  // of normal or WebM decryption keys. Consider a more explicit signaling
-  // mechanism and the removal of the webm_decryption_key member.
-  crypto::SymmetricKey* decryption_key = (checksum_size > 0) ?
-      key->webm_decryption_key() : key->decryption_key();
-  scoped_refptr<DecoderBuffer> decrypted =
-      DecryptData(*encrypted, decryption_key);
-  if (!decrypted) {
-    DVLOG(1) << "Decryption failed.";
-    decrypt_cb.Run(kError, NULL);
-    return;
+  scoped_refptr<DecoderBuffer> decrypted;
+  // An empty iv string signals that the frame is unencrypted.
+  if (encrypted->GetDecryptConfig()->iv().empty()) {
+    int data_offset = encrypted->GetDecryptConfig()->data_offset();
+    const uint8* frame =
+        reinterpret_cast<const uint8*>(encrypted->GetData() + data_offset);
+    int frame_size = encrypted->GetDataSize() - data_offset;
+    decrypted = DecoderBuffer::CopyFrom(frame, frame_size);

[xhwang, 2012/08/01 00:45:41]

decrypted = DecoderBuffer::CopyFrom(encrypted->GetData() + data_offset,
encrypted->GetDataSize() - data_offset);

[fgalligan1, 2012/08/01 01:36:10]

Done.

+  } else {
+    // TODO(strobe): Currently, presence of checksum is used to indicate the use
+    // of normal or WebM decryption keys. Consider a more explicit signaling
+    // mechanism and the removal of the webm_decryption_key member.
+    crypto::SymmetricKey* decryption_key = (checksum_size > 0) ?
+        key->webm_decryption_key() : key->decryption_key();
+    decrypted = DecryptData(*encrypted, decryption_key);
+    if (!decrypted) {
+      DVLOG(1) << "Decryption failed.";
+      decrypt_cb.Run(kError, NULL);
+      return;
+    }
   }
 
   decrypted->SetTimestamp(encrypted->GetTimestamp());
   decrypted->SetDuration(encrypted->GetDuration());
   decrypt_cb.Run(kSuccess, decrypted);
 }
 
 void AesDecryptor::SetKey(const std::string& key_id,
                           scoped_ptr<DecryptionKey> decryption_key) {
   base::AutoLock auto_lock(key_map_lock_);
@@ skipping 40 matching lines @@
     return false;
 
   hmac_key_ = DeriveKey(secret_, kWebmHmacSeed, kWebmSha1DigestSize);
   if (hmac_key_.empty())
     return false;
 
   return true;
 }
 
 }  // namespace media