118 lines
3.9 KiB
C++
118 lines
3.9 KiB
C++
// Copyright 2016 Google Inc. All rights reserved.
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//
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file or at
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// https://developers.google.com/open-source/licenses/bsd
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#include "packager/media/base/decryptor_source.h"
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#include "packager/base/logging.h"
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#include "packager/base/stl_util.h"
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#include "packager/media/base/aes_decryptor.h"
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#include "packager/media/base/aes_pattern_cryptor.h"
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namespace shaka {
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namespace media {
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DecryptorSource::DecryptorSource(KeySource* key_source)
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: key_source_(key_source) {
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CHECK(key_source);
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}
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DecryptorSource::~DecryptorSource() {
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STLDeleteValues(&decryptor_map_);
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}
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bool DecryptorSource::DecryptSampleBuffer(const DecryptConfig* decrypt_config,
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uint8_t* buffer,
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size_t buffer_size) {
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DCHECK(decrypt_config);
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DCHECK(buffer);
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// Get the decryptor object.
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AesCryptor* decryptor;
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auto found = decryptor_map_.find(decrypt_config->key_id());
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if (found == decryptor_map_.end()) {
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// Create new AesDecryptor based on decryption mode.
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EncryptionKey key;
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Status status(key_source_->GetKey(decrypt_config->key_id(), &key));
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if (!status.ok()) {
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LOG(ERROR) << "Error retrieving decryption key: " << status;
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return false;
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}
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scoped_ptr<AesCryptor> aes_decryptor;
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switch (decrypt_config->protection_scheme()) {
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case FOURCC_cenc:
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aes_decryptor.reset(new AesCtrDecryptor);
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break;
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case FOURCC_cbc1:
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aes_decryptor.reset(new AesCbcDecryptor(kNoPadding));
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break;
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case FOURCC_cens:
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aes_decryptor.reset(new AesPatternCryptor(
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decrypt_config->crypt_byte_block(),
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decrypt_config->skip_byte_block(),
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AesPatternCryptor::kEncryptIfCryptByteBlockRemaining,
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AesCryptor::kDontUseConstantIv,
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scoped_ptr<AesCryptor>(new AesCtrDecryptor())));
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break;
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case FOURCC_cbcs:
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aes_decryptor.reset(new AesPatternCryptor(
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decrypt_config->crypt_byte_block(),
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decrypt_config->skip_byte_block(),
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AesPatternCryptor::kEncryptIfCryptByteBlockRemaining,
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AesCryptor::kUseConstantIv,
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scoped_ptr<AesCryptor>(new AesCbcDecryptor(kNoPadding))));
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break;
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default:
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LOG(ERROR) << "Unsupported protection scheme: "
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<< decrypt_config->protection_scheme();
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return false;
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}
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if (!aes_decryptor->InitializeWithIv(key.key, decrypt_config->iv())) {
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LOG(ERROR) << "Failed to initialize AesDecryptor for decryption.";
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return false;
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}
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decryptor = aes_decryptor.release();
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decryptor_map_[decrypt_config->key_id()] = decryptor;
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} else {
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decryptor = found->second;
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}
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if (!decryptor->SetIv(decrypt_config->iv())) {
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LOG(ERROR) << "Invalid initialization vector.";
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return false;
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}
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if (decrypt_config->subsamples().empty()) {
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// Sample not encrypted using subsample encryption. Decrypt whole.
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if (!decryptor->Crypt(buffer, buffer_size, buffer)) {
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LOG(ERROR) << "Error during bulk sample decryption.";
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return false;
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}
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return true;
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}
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// Subsample decryption.
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const std::vector<SubsampleEntry>& subsamples = decrypt_config->subsamples();
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uint8_t* current_ptr = buffer;
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const uint8_t* const buffer_end = buffer + buffer_size;
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for (const auto& subsample : subsamples) {
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if ((current_ptr + subsample.clear_bytes + subsample.cipher_bytes) >
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buffer_end) {
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LOG(ERROR) << "Subsamples overflow sample buffer.";
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return false;
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}
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current_ptr += subsample.clear_bytes;
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if (!decryptor->Crypt(current_ptr, subsample.cipher_bytes, current_ptr)) {
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LOG(ERROR) << "Error decrypting subsample buffer.";
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return false;
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}
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current_ptr += subsample.cipher_bytes;
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}
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return true;
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}
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} // namespace media
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} // namespace shaka
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