Do not require a key before processing unencrypted frames within a potentially encrypted stream.

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 214 matching lines @@
       break;
     default:
       NOTREACHED();
   }
 }
 
 void AesDecryptor::Decrypt(StreamType stream_type,
                            const scoped_refptr<DecoderBuffer>& encrypted,
                            const DecryptCB& decrypt_cb) {
   CHECK(encrypted->GetDecryptConfig());
-  const std::string& key_id = encrypted->GetDecryptConfig()->key_id();
-
-  DecryptionKey* key = GetKey(key_id);
-  if (!key) {
-    DVLOG(1) << "Could not find a matching key for the given key ID.";
-    decrypt_cb.Run(kNoKey, 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();
     decrypted = DecoderBuffer::CopyFrom(encrypted->GetData() + data_offset,
                                         encrypted->GetDataSize() - data_offset);
   } else {
+    const std::string& key_id = encrypted->GetDecryptConfig()->key_id();
+    DecryptionKey* key = GetKey(key_id);
+    if (!key) {
+      DVLOG(1) << "Could not find a matching key for the given key ID.";
+      decrypt_cb.Run(kNoKey, NULL);
+      return;
+    }
+
     crypto::SymmetricKey* 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());
@@ skipping 67 matching lines @@
 bool AesDecryptor::DecryptionKey::Init() {
   CHECK(!secret_.empty());
   decryption_key_.reset(crypto::SymmetricKey::Import(
       crypto::SymmetricKey::AES, secret_));
   if (!decryption_key_.get())
     return false;
   return true;
 }
 
 }  // namespace media