Support for parsing encrypted WebM streams by src.

media/webm/webm_crypt_helpers.h

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.

[ddorwin, 2012/09/01 16:46:41]

Same as the other helper file - two files for one function. Are there others
that might end up in this file or can we merge the files?

[fgalligan1, 2013/03/09 01:10:59]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_WEBM_WEBM_CRYPT_HELPERS_H_
+#define MEDIA_WEBM_WEBM_CRYPT_HELPERS_H_
+
+#include "base/basictypes.h"
+
+#include "base/memory/scoped_ptr.h"
+#include "media/base/decoder_buffer.h"
+
+namespace media {
+
+// Returns an initialized DecoderBuffer which can be sent to the Decryptor if

[ddorwin, 2012/09/01 16:46:41]

nit: , which

+// the stream is encrypted or sent to the Decoder if the stream is not
+// encrypted. Currently encrypted streams must be WebM.

[xhwang, 2012/08/29 05:08:14]

This function should not worry about how the buffer is handled (by the Decryptor
or decoder).

[ddorwin, 2012/09/01 16:46:41]

Isn't the "Currently..." sentence implicit in the name?

+// Every encrypted Block has an HMAC and IV prepended to it.
+// Current encrypted WebM request for comments specification is here
+// http://wiki.webmproject.org/encryption/webm-encryption-rfc
+// If encrypted, skip past the HMAC to get the buffer. Encrypted buffers

[ddorwin, 2012/09/01 16:46:41]

This probably needs to be updated to handle verified but unencrypted blocks.

[fgalligan1, 2013/03/09 01:10:59]

hmac removed.

+// must include the IV and the encrypted frame because the decryptor will
+// verify this data before decryption. The HMAC and IV will be copied into
+// DecryptConfig.
+scoped_refptr<DecoderBuffer> WebMCopyBufferCheckIfEncrypted(

[ddorwin, 2012/09/01 16:46:41]

The function name does not "flow" - it's two separate fragments. How about
something like WebMCopyBufferWithEncryptionCheck?
What does "CheckIfEncrypted" mean anyway? It's really just checking as part of
the implementation. Maybe this should be WebMCopyPossiblyEncryptedBuffer?

+    const uint8* data, int data_size,
+    const uint8* key_id, int key_id_size);

[xhwang, 2012/08/29 05:08:14]

The only reason we use pointer/size for initData is that it *can* be large for
ISO. For webm key_id is always smallish. So feel free to use std::string for
key_id for webm specific code.

+
+}  // webkit_media

[ddorwin, 2012/09/01 16:46:41]

media

[fgalligan1, 2013/03/09 01:10:59]

Done.

+
+#endif  // MEDIA_WEBM_WEBM_CRYPT_HELPERS_H_