Add support for encrypted WebM files as defined in the RFC.

Add support for encrypted WebM files as defined in the RFC.

The WebM parser now reads the HMAC and IV from every encrypted
Block and stores that information in the DecryptorConfig object.
Added two new elements ContentEncAESSettings and
AESSettingsCipherMode used by encrypted WebM files.

This is a new code review of
https://chromiumcodereview.appspot.com/10535029/ patch set 17 after
patch set 16 was reverted.

BUG=119845
TEST=media_unittests


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=147654

[xhwang, 2012-07-20 00:52:16]

LGTM

FYI, the MockDecryptor CL is in the commit queue. If it's landed first, you may
need to rebase again (sorry!). But fortunately this rebase should be super easy:
you just need to drop most (if not all) of your changes in
FFmepgVideoDecoderTest as it doesn't care about real decryption now.

[commit-bot: I haz the power, 2012-07-20 13:38:57]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/fgalligan@chromium.org/10810026/8001

[commit-bot: I haz the power, 2012-07-20 14:54:12]

Change committed as 147654

[Ryan Sleevi, 2012-07-23 21:50:58]

Crypto drive-by

https://chromiumcodereview.appspot.com/10810026/diff/8001/media/crypto/aes_de...
File media/crypto/aes_decryptor.cc (right):

https://chromiumcodereview.appspot.com/10810026/diff/8001/media/crypto/aes_de...
media/crypto/aes_decryptor.cc:81: input.GetDecryptConfig()->checksum_size()) !=
0)
Note: crypto::HMAC specifically exposes a Verify method to avoid timing issues
with memcmp that may leak keying material.

[fgalligan, 2012-07-24 05:35:00]

Thanks.

I have a CL that uses VerifyTruncated().
https://chromiumcodereview.appspot.com/10800091


On Mon, Jul 23, 2012 at 2:50 PM, <rsleevi@chromium.org> wrote:

> Crypto drive-by
>
>
> https://chromiumcodereview.**appspot.com/10810026/diff/**
>
8001/media/crypto/aes_**decryptor.cc<https://chromiumcodereview.appspot.com/10810026/diff/8001/media/crypto/aes_decryptor.cc>
> File media/crypto/aes_decryptor.cc (right):
>
> https://chromiumcodereview.**appspot.com/10810026/diff/**
>
8001/media/crypto/aes_**decryptor.cc#newcode81<https://chromiumcodereview.appspot.com/10810026/diff/8001/media/crypto/aes_decryptor.cc#newcode81>
> media/crypto/aes_decryptor.cc:**81:
> input.GetDecryptConfig()->**checksum_size()) != 0)
> Note: crypto::HMAC specifically exposes a Verify method to avoid timing
> issues with memcmp that may leak keying material.
>
>
https://chromiumcodereview.**appspot.com/10810026/<https://chromiumcodereview...
>