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   StreamId stream_id() const override;
  26   base::TimeDelta timestamp() const override;
  27   void set_timestamp(const base::TimeDelta& timestamp) override;
  28   const uint8* data() const override;
  29   uint8* writable_data() const override;
  30   size_t data_size() const override;
  31   const ::media::DecryptConfig* decrypt_config() const override;
  32   bool end_of_stream() const override;
  33
  34  private:
  35   ~DecoderBufferClear() override;
  36
  37   scoped_refptr<DecoderBufferBase> const buffer_;
  38
  39   DISALLOW_COPY_AND_ASSIGN(DecoderBufferClear);
  40 };
  41
  42 DecoderBufferClear::DecoderBufferClear(
  43     const scoped_refptr<DecoderBufferBase>& buffer)
  44     : buffer_(buffer) {
  45 }
  46
  47 DecoderBufferClear::~DecoderBufferClear() {
  48 }
  49
  50 StreamId DecoderBufferClear::stream_id() const {
  51   return buffer_->stream_id();
  52 }
  53
  54 base::TimeDelta DecoderBufferClear::timestamp() const {
  55   return buffer_->timestamp();
  56 }
  57
  58 void DecoderBufferClear::set_timestamp(const base::TimeDelta& timestamp) {
  59   buffer_->set_timestamp(timestamp);
  60 }
  61
  62 const uint8* DecoderBufferClear::data() const {
  63   return buffer_->data();
  64 }
  65
  66 uint8* DecoderBufferClear::writable_data() const {
  67   return buffer_->writable_data();
  68 }
  69
  70 size_t DecoderBufferClear::data_size() const {
  71   return buffer_->data_size();
  72 }
  73
  74 const ::media::DecryptConfig* DecoderBufferClear::decrypt_config() const {
  75   // Buffer is clear so no decryption info.
  76   return NULL;
  77 }
  78
  79 bool DecoderBufferClear::end_of_stream() const {
  80   return buffer_->end_of_stream();
  81 }
  82
  83 }  // namespace
  84
  85 scoped_refptr<DecoderBufferBase> DecryptDecoderBuffer(
  86     const scoped_refptr<DecoderBufferBase>& buffer,
  87     crypto::SymmetricKey* key) {
  88   if (buffer->end_of_stream())
  89     return buffer;
  90
  91   const ::media::DecryptConfig* decrypt_config = buffer->decrypt_config();
  92   if (!decrypt_config || decrypt_config->iv().size() == 0)
  93     return buffer;
  94
  95   // Get the key.
  96   std::string raw_key;
  97   if (!key->GetRawKey(&raw_key)) {
  98     LOG(ERROR) << "Failed to get the underlying AES key";
  99     return buffer;
 100   }
 101   DCHECK_EQ(static_cast<int>(raw_key.length()), AES_BLOCK_SIZE);
 102   const uint8* key_u8 = reinterpret_cast<const uint8*>(raw_key.data());
 103   AES_KEY aes_key;
 104   if (AES_set_encrypt_key(key_u8, AES_BLOCK_SIZE * 8, &aes_key) != 0) {
 105     LOG(ERROR) << "Failed to set the AES key";
 106     return buffer;
 107   }
 108
 109   // Get the IV.
 110   uint8 aes_iv[AES_BLOCK_SIZE];
 111   DCHECK_EQ(static_cast<int>(decrypt_config->iv().length()),
 112             AES_BLOCK_SIZE);
 113   memcpy(aes_iv, decrypt_config->iv().data(), AES_BLOCK_SIZE);
 114
 115   // Decryption state.
 116   unsigned int encrypted_byte_offset = 0;
 117   uint8 ecount_buf[AES_BLOCK_SIZE];
 118
 119   // Perform the decryption.
 120   const std::vector< ::media::SubsampleEntry>& subsamples =
 121       decrypt_config->subsamples();
 122   uint8* data = buffer->writable_data();
 123   uint32 offset = 0;
 124   for (size_t k = 0; k < subsamples.size(); k++) {
 125     offset += subsamples[k].clear_bytes;
 126     uint32 cypher_bytes = subsamples[k].cypher_bytes;
 127     CHECK_LE(static_cast<size_t>(offset + cypher_bytes), buffer->data_size());
 128     AES_ctr128_encrypt(
 129         data + offset, data + offset, cypher_bytes, &aes_key,
 130         aes_iv, ecount_buf, &encrypted_byte_offset);
 131     offset += cypher_bytes;
 132   }
 133
 134   return scoped_refptr<DecoderBufferBase>(new DecoderBufferClear(buffer));
 135 }
 136
 137 }  // namespace media
 138 }  // namespace chromecast