12a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)// Copyright (c) 2013 The Chromium Authors. All rights reserved. 22a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)// Use of this source code is governed by a BSD-style license that can be 32a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)// found in the LICENSE file. 42a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) 52a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)#include "media/webm/webm_crypto_helpers.h" 62a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) 72a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)#include "base/logging.h" 82a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)#include "base/sys_byteorder.h" 92a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)#include "media/base/decrypt_config.h" 102a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)#include "media/webm/webm_constants.h" 112a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) 122a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)namespace media { 132a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)namespace { 142a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) 152a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)// Generates a 16 byte CTR counter block. The CTR counter block format is a 162a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)// CTR IV appended with a CTR block counter. |iv| is an 8 byte CTR IV. 172a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)// |iv_size| is the size of |iv| in btyes. Returns a string of 182a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)// kDecryptionKeySize bytes. 192a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)std::string GenerateWebMCounterBlock(const uint8* iv, int iv_size) { 202a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) std::string counter_block(reinterpret_cast<const char*>(iv), iv_size); 212a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) counter_block.append(DecryptConfig::kDecryptionKeySize - iv_size, 0); 222a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) return counter_block; 232a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)} 242a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) 252a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)} // namespace anonymous 262a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) 272a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)scoped_ptr<DecryptConfig> WebMCreateDecryptConfig( 282a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) const uint8* data, int data_size, 292a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) const uint8* key_id, int key_id_size) { 302a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) if (data_size < kWebMSignalByteSize) { 312a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) DVLOG(1) << "Got a block from an encrypted stream with no data."; 327d4cd473f85ac64c3747c96c277f9e506a0d2246Torne (Richard Coles) return scoped_ptr<DecryptConfig>(); 332a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) } 342a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) 352a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) uint8 signal_byte = data[0]; 362a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) int frame_offset = sizeof(signal_byte); 372a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) 382a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) // Setting the DecryptConfig object of the buffer while leaving the 392a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) // initialization vector empty will tell the decryptor that the frame is 402a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) // unencrypted. 412a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) std::string counter_block; 422a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) 432a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) if (signal_byte & kWebMFlagEncryptedFrame) { 442a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) if (data_size < kWebMSignalByteSize + kWebMIvSize) { 452a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) DVLOG(1) << "Got an encrypted block with not enough data " << data_size; 467d4cd473f85ac64c3747c96c277f9e506a0d2246Torne (Richard Coles) return scoped_ptr<DecryptConfig>(); 472a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) } 482a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) counter_block = GenerateWebMCounterBlock(data + frame_offset, kWebMIvSize); 492a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) frame_offset += kWebMIvSize; 502a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) } 512a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) 522a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) scoped_ptr<DecryptConfig> config(new DecryptConfig( 532a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) std::string(reinterpret_cast<const char*>(key_id), key_id_size), 542a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) counter_block, 552a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) frame_offset, 562a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) std::vector<SubsampleEntry>())); 572a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) return config.Pass(); 582a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)} 592a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) 602a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)} // namespace media 61