Chromecast: adds a media pipeline feeding data to CMA device backends.

chromecast/media/cma/pipeline/decrypt_util.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chromecast/media/cma/pipeline/decrypt_util.h"
+
+#include <openssl/aes.h>
+#include <string>
+
+#include "base/logging.h"
+#include "chromecast/media/cma/base/decoder_buffer_base.h"
+#include "crypto/symmetric_key.h"
+#include "media/base/decrypt_config.h"
+
+namespace chromecast {
+namespace media {
+
+namespace {
+
+class DecoderBufferClear : public DecoderBufferBase {
+ public:
+  explicit DecoderBufferClear(const scoped_refptr<DecoderBufferBase>& buffer);
+
+  // DecoderBufferBase implementation.
+  base::TimeDelta timestamp() const override;
+  const uint8* data() const override;
+  uint8* writable_data() const override;
+  int data_size() const override;
+  const ::media::DecryptConfig* decrypt_config() const override;
+  bool end_of_stream() const override;
+
+ private:
+  virtual ~DecoderBufferClear();
+
+  scoped_refptr<DecoderBufferBase> const buffer_;
+
+  DISALLOW_COPY_AND_ASSIGN(DecoderBufferClear);
+};
+
+DecoderBufferClear::DecoderBufferClear(
+    const scoped_refptr<DecoderBufferBase>& buffer)
+    : buffer_(buffer) {
+}
+
+DecoderBufferClear::~DecoderBufferClear() {
+}
+
+base::TimeDelta DecoderBufferClear::timestamp() const {
+  return buffer_->timestamp();
+}
+
+const uint8* DecoderBufferClear::data() const {
+  return buffer_->data();
+}
+
+uint8* DecoderBufferClear::writable_data() const {
+  return buffer_->writable_data();
+}
+
+int DecoderBufferClear::data_size() const {
+  return buffer_->data_size();
+}
+
+const ::media::DecryptConfig* DecoderBufferClear::decrypt_config() const {
+  // Buffer is clear so no decryption info.
+  return NULL;
+}
+
+bool DecoderBufferClear::end_of_stream() const {
+  return buffer_->end_of_stream();
+}
+
+}  // namespace
+
+scoped_refptr<DecoderBufferBase> DecryptDecoderBuffer(
+    const scoped_refptr<DecoderBufferBase>& buffer,
+    crypto::SymmetricKey* key) {
+  if (buffer->end_of_stream())
+    return buffer;
+
+  const ::media::DecryptConfig* decrypt_config = buffer->decrypt_config();
+  if (!decrypt_config || decrypt_config->iv().size() == 0)
+    return buffer;
+
+  // Get the key.
+  std::string raw_key;
+  if (!key->GetRawKey(&raw_key)) {
+    LOG(ERROR) << "Failed to get the underlying AES key";
+    return buffer;
+  }
+  DCHECK_EQ(static_cast<int>(raw_key.length()), AES_BLOCK_SIZE);
+  const uint8* key_u8 = reinterpret_cast<const uint8*>(raw_key.data());
+  AES_KEY aes_key;
+  if (AES_set_encrypt_key(key_u8, AES_BLOCK_SIZE * 8, &aes_key) != 0) {
+    LOG(ERROR) << "Failed to set the AES key";
+    return buffer;
+  }
+
+  // Get the IV.
+  uint8 aes_iv[AES_BLOCK_SIZE];
+  DCHECK_EQ(static_cast<int>(decrypt_config->iv().length()),
+            AES_BLOCK_SIZE);
+  memcpy(aes_iv, decrypt_config->iv().data(), AES_BLOCK_SIZE);
+
+  // Decryption state.
+  unsigned int encrypted_byte_offset = 0;
+  uint8 ecount_buf[AES_BLOCK_SIZE];
+
+  // Perform the decryption.
+  const std::vector< ::media::SubsampleEntry>& subsamples =
+      decrypt_config->subsamples();
+  uint8* data = buffer->writable_data();
+  uint32 offset = 0;
+  for (size_t k = 0; k < subsamples.size(); k++) {
+    offset += subsamples[k].clear_bytes;
+    uint32 cypher_bytes = subsamples[k].cypher_bytes;
+    CHECK_LE(offset + cypher_bytes, buffer->data_size());
+    AES_ctr128_encrypt(
+        data + offset, data + offset, cypher_bytes, &aes_key,
+        aes_iv, ecount_buf, &encrypted_byte_offset);
+    offset += cypher_bytes;
+  }
+
+  return scoped_refptr<DecoderBufferBase>(new DecoderBufferClear(buffer));
+}
+
+}  // namespace media
+}  // namespace chromecast