chromecast/media/cma/pipeline/decrypt_util.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "chromecast/media/cma/pipeline/decrypt_util.h"
   6
   7 #include <openssl/aes.h>
   8 #include <string>
   9
  10 #include "base/logging.h"
  11 #include "chromecast/media/cma/base/decoder_buffer_base.h"
  12 #include "crypto/symmetric_key.h"
  13 #include "media/base/decrypt_config.h"
  14
  15 namespace chromecast {
  16 namespace media {
  17
  18 namespace {
  19
  20 class DecoderBufferClear : public DecoderBufferBase {
  21  public:
  22   explicit DecoderBufferClear(const scoped_refptr<DecoderBufferBase>& buffer);
  23
  24   // DecoderBufferBase implementation.
  25   base::TimeDelta timestamp() const override;
  26   const uint8* data() const override;
  27   uint8* writable_data() const override;
  28   int data_size() const override;
  29   const ::media::DecryptConfig* decrypt_config() const override;
  30   bool end_of_stream() const override;
  31
  32  private:
  33   ~DecoderBufferClear() override;
  34
  35   scoped_refptr<DecoderBufferBase> const buffer_;
  36
  37   DISALLOW_COPY_AND_ASSIGN(DecoderBufferClear);
  38 };
  39
  40 DecoderBufferClear::DecoderBufferClear(
  41     const scoped_refptr<DecoderBufferBase>& buffer)
  42     : buffer_(buffer) {
  43 }
  44
  45 DecoderBufferClear::~DecoderBufferClear() {
  46 }
  47
  48 base::TimeDelta DecoderBufferClear::timestamp() const {
  49   return buffer_->timestamp();
  50 }
  51
  52 const uint8* DecoderBufferClear::data() const {
  53   return buffer_->data();
  54 }
  55
  56 uint8* DecoderBufferClear::writable_data() const {
  57   return buffer_->writable_data();
  58 }
  59
  60 int DecoderBufferClear::data_size() const {
  61   return buffer_->data_size();
  62 }
  63
  64 const ::media::DecryptConfig* DecoderBufferClear::decrypt_config() const {
  65   // Buffer is clear so no decryption info.
  66   return NULL;
  67 }
  68
  69 bool DecoderBufferClear::end_of_stream() const {
  70   return buffer_->end_of_stream();
  71 }
  72
  73 }  // namespace
  74
  75 scoped_refptr<DecoderBufferBase> DecryptDecoderBuffer(
  76     const scoped_refptr<DecoderBufferBase>& buffer,
  77     crypto::SymmetricKey* key) {
  78   if (buffer->end_of_stream())
  79     return buffer;
  80
  81   const ::media::DecryptConfig* decrypt_config = buffer->decrypt_config();
  82   if (!decrypt_config || decrypt_config->iv().size() == 0)
  83     return buffer;
  84
  85   // Get the key.
  86   std::string raw_key;
  87   if (!key->GetRawKey(&raw_key)) {
  88     LOG(ERROR) << "Failed to get the underlying AES key";
  89     return buffer;
  90   }
  91   DCHECK_EQ(static_cast<int>(raw_key.length()), AES_BLOCK_SIZE);
  92   const uint8* key_u8 = reinterpret_cast<const uint8*>(raw_key.data());
  93   AES_KEY aes_key;
  94   if (AES_set_encrypt_key(key_u8, AES_BLOCK_SIZE * 8, &aes_key) != 0) {
  95     LOG(ERROR) << "Failed to set the AES key";
  96     return buffer;
  97   }
  98
  99   // Get the IV.
 100   uint8 aes_iv[AES_BLOCK_SIZE];
 101   DCHECK_EQ(static_cast<int>(decrypt_config->iv().length()),
 102             AES_BLOCK_SIZE);
 103   memcpy(aes_iv, decrypt_config->iv().data(), AES_BLOCK_SIZE);
 104
 105   // Decryption state.
 106   unsigned int encrypted_byte_offset = 0;
 107   uint8 ecount_buf[AES_BLOCK_SIZE];
 108
 109   // Perform the decryption.
 110   const std::vector< ::media::SubsampleEntry>& subsamples =
 111       decrypt_config->subsamples();
 112   uint8* data = buffer->writable_data();
 113   uint32 offset = 0;
 114   for (size_t k = 0; k < subsamples.size(); k++) {
 115     offset += subsamples[k].clear_bytes;
 116     uint32 cypher_bytes = subsamples[k].cypher_bytes;
 117     CHECK_LE(offset + cypher_bytes, buffer->data_size());
 118     AES_ctr128_encrypt(
 119         data + offset, data + offset, cypher_bytes, &aes_key,
 120         aes_iv, ecount_buf, &encrypted_byte_offset);
 121     offset += cypher_bytes;
 122   }
 123
 124   return scoped_refptr<DecoderBufferBase>(new DecoderBufferClear(buffer));
 125 }
 126
 127 }  // namespace media
 128 }  // namespace chromecast