233 lines
8.3 KiB
C++
233 lines
8.3 KiB
C++
// Copyright 2017 Google LLC. 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/playready_pssh_generator.h>
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#include <algorithm>
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#include <memory>
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#include <set>
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#include <vector>
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#include <absl/strings/escaping.h>
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#include <glog/logging.h>
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#include <mbedtls/cipher.h>
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#include <packager/media/base/buffer_writer.h>
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#include <packager/media/base/protection_system_ids.h>
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namespace shaka {
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namespace media {
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namespace {
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const uint8_t kPlayReadyPsshBoxVersion = 0;
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// For PlayReady clients 1.0+ that support CTR keys.
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const std::string kPlayHeaderObject_4_0 =
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"<WRMHEADER "
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"xmlns=\"http://schemas.microsoft.com/DRM/2007/03/PlayReadyHeader\" "
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"version=\"4.0.0.0\"><DATA>"
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"<PROTECTINFO><KEYLEN>16</KEYLEN><ALGID>AESCTR</ALGID></PROTECTINFO>"
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"<KID>$0</KID><CHECKSUM>$1</CHECKSUM>"
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"$2</DATA></WRMHEADER>";
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// For PlayReady clients 4.0+ that support CBC keys.
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const std::string kPlayHeaderObject_4_3 =
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"<WRMHEADER "
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"xmlns=\"http://schemas.microsoft.com/DRM/2007/03/PlayReadyHeader\" "
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"version=\"4.3.0.0\"><DATA><PROTECTINFO><KIDS>"
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"<KID ALGID=\"AESCBC\" VALUE=\"$0\"></KID>"
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"</KIDS></PROTECTINFO>$1</DATA></WRMHEADER>";
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// Converts the key_id's endianness.
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std::vector<uint8_t> ConvertGuidEndianness(const std::vector<uint8_t>& input) {
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std::vector<uint8_t> output = input;
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if (output.size() > 7) { // Defensive check.
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output[0] = input[3];
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output[1] = input[2];
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output[2] = input[1];
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output[3] = input[0];
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output[4] = input[5];
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output[5] = input[4];
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output[6] = input[7];
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output[7] = input[6];
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// 8-15 are an array of bytes with no endianness.
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}
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return output;
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}
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void ReplaceString(std::string* str,
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const std::string& from,
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const std::string& to) {
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size_t location = str->find(from);
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if (location != std::string::npos) {
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str->replace(location, from.size(), to);
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}
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}
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void AesEcbEncrypt(const std::vector<uint8_t>& key,
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const std::vector<uint8_t>& plaintext,
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std::vector<uint8_t>* ciphertext) {
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CHECK_EQ(plaintext.size() % AES_BLOCK_SIZE, 0u);
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// mbedtls requires an extra block worth of output buffer.
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ciphertext->resize(plaintext.size() + AES_BLOCK_SIZE);
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mbedtls_cipher_context_t ctx;
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mbedtls_cipher_init(&ctx);
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const mbedtls_cipher_info_t* cipher_info =
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mbedtls_cipher_info_from_type(MBEDTLS_CIPHER_AES_128_ECB);
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CHECK(cipher_info);
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CHECK_EQ(mbedtls_cipher_setup(&ctx, cipher_info), 0) << "Cipher setup failed";
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CHECK_EQ(key.size(), 16u);
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CHECK_EQ(
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mbedtls_cipher_setkey(&ctx, key.data(), 8 * key.size(), MBEDTLS_ENCRYPT),
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0)
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<< "Failed to set encryption key";
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size_t output_size = 0;
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CHECK_EQ(mbedtls_cipher_crypt(&ctx, /* iv= */ NULL, /* iv_len= */ 0,
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plaintext.data(), plaintext.size(),
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ciphertext->data(), &output_size),
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0);
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// Truncate the output to the correct size.
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ciphertext->resize(plaintext.size());
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mbedtls_cipher_free(&ctx);
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}
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// Generates the data section of a PlayReady PSSH.
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// PlayReady PSSH Data is a PlayReady Header Object, which is described at
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// https://docs.microsoft.com/en-us/playready/specifications/playready-header-specification
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Status GeneratePlayReadyPsshData(const std::vector<uint8_t>& key_id,
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const std::vector<uint8_t>& key,
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const std::string& extra_header_data,
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const FourCC protection_scheme,
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std::vector<uint8_t>* output) {
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CHECK(output);
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std::vector<uint8_t> key_id_converted = ConvertGuidEndianness(key_id);
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std::vector<uint8_t> encrypted_key_id;
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AesEcbEncrypt(key, key_id_converted, &encrypted_key_id);
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std::string checksum =
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std::string(encrypted_key_id.begin(), encrypted_key_id.end())
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.substr(0, 8);
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std::string base64_checksum;
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absl::Base64Escape(checksum, &base64_checksum);
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std::string base64_key_id;
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absl::Base64Escape(
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std::string(key_id_converted.begin(), key_id_converted.end()),
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&base64_key_id);
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std::string playready_header;
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switch (protection_scheme) {
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case kAppleSampleAesProtectionScheme:
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case FOURCC_cbc1:
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case FOURCC_cbcs:
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playready_header = kPlayHeaderObject_4_3;
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ReplaceString(&playready_header, "$0", base64_key_id);
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ReplaceString(&playready_header, "$1", extra_header_data);
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break;
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case FOURCC_cenc:
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case FOURCC_cens:
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playready_header = kPlayHeaderObject_4_0;
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ReplaceString(&playready_header, "$0", base64_key_id);
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ReplaceString(&playready_header, "$1", base64_checksum);
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ReplaceString(&playready_header, "$2", extra_header_data);
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break;
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default:
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return Status(error::INVALID_ARGUMENT,
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"The provided protection scheme is not supported.");
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}
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// Create a PlayReady Record.
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// Outline in section '2.PlayReady Records' of
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// 'PlayReady Header Object' document. Note data is in little endian format.
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std::vector<uint16_t> record_value =
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std::vector<uint16_t>(playready_header.begin(), playready_header.end());
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shaka::media::BufferWriter writer_pr_record;
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uint16_t record_type =
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1; // Indicates that the record contains a rights management header.
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uint16_t record_length = record_value.size() * 2;
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writer_pr_record.AppendInt(static_cast<uint8_t>(record_type & 0xff));
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writer_pr_record.AppendInt(static_cast<uint8_t>((record_type >> 8) & 0xff));
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writer_pr_record.AppendInt(static_cast<uint8_t>(record_length & 0xff));
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writer_pr_record.AppendInt(static_cast<uint8_t>((record_length >> 8) & 0xff));
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for (auto record_item : record_value) {
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writer_pr_record.AppendInt(static_cast<uint8_t>(record_item & 0xff));
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writer_pr_record.AppendInt(static_cast<uint8_t>((record_item >> 8) & 0xff));
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}
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// Create the PlayReady Header object.
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// Outline in section '1.PlayReady Header Objects' of
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// 'PlayReady Header Object' document. Note data is in little endian format.
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shaka::media::BufferWriter writer_pr_header_object;
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uint32_t playready_header_length = writer_pr_record.Size() + 4 + 2;
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uint16_t record_count = 1;
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writer_pr_header_object.AppendInt(
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static_cast<uint8_t>(playready_header_length & 0xff));
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writer_pr_header_object.AppendInt(
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static_cast<uint8_t>((playready_header_length >> 8) & 0xff));
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writer_pr_header_object.AppendInt(
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static_cast<uint8_t>((playready_header_length >> 16) & 0xff));
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writer_pr_header_object.AppendInt(
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static_cast<uint8_t>((playready_header_length >> 24) & 0xff));
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writer_pr_header_object.AppendInt(static_cast<uint8_t>(record_count & 0xff));
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writer_pr_header_object.AppendInt(
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static_cast<uint8_t>((record_count >> 8) & 0xff));
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writer_pr_header_object.AppendBuffer(writer_pr_record);
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*output = std::vector<uint8_t>(
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writer_pr_header_object.Buffer(),
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writer_pr_header_object.Buffer() + writer_pr_header_object.Size());
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return Status::OK;
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}
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} // namespace
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PlayReadyPsshGenerator::PlayReadyPsshGenerator(
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const std::string& extra_header_data,
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FourCC protection_scheme)
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: PsshGenerator(std::vector<uint8_t>(std::begin(kPlayReadySystemId),
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std::end(kPlayReadySystemId)),
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kPlayReadyPsshBoxVersion),
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extra_header_data_(extra_header_data),
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protection_scheme_(protection_scheme) {}
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PlayReadyPsshGenerator::~PlayReadyPsshGenerator() {}
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bool PlayReadyPsshGenerator::SupportMultipleKeys() {
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return false;
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}
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std::optional<std::vector<uint8_t>>
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PlayReadyPsshGenerator::GeneratePsshDataFromKeyIdAndKey(
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const std::vector<uint8_t>& key_id,
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const std::vector<uint8_t>& key) const {
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std::vector<uint8_t> pssh_data;
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Status status = GeneratePlayReadyPsshData(key_id, key, extra_header_data_,
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protection_scheme_, &pssh_data);
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if (!status.ok()) {
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LOG(ERROR) << status.ToString();
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return std::nullopt;
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}
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return pssh_data;
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}
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std::optional<std::vector<uint8_t>>
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PlayReadyPsshGenerator::GeneratePsshDataFromKeyIds(
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const std::vector<std::vector<uint8_t>>& key_ids) const {
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UNUSED(key_ids);
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NOTIMPLEMENTED();
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return std::nullopt;
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}
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} // namespace media
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} // namespace shaka
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