318 lines
10 KiB
C++
318 lines
10 KiB
C++
// Copyright 2014 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 "media/base/widevine_encryptor_source.h"
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#include "base/base64.h"
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#include "base/json/json_reader.h"
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#include "base/json/json_writer.h"
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#include "base/time/time.h"
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#include "base/threading/platform_thread.h"
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#include "base/values.h"
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#include "media/base/http_fetcher.h"
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#include "media/base/request_signer.h"
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// TODO: Move media/mp4/rcheck.h to media/base/. Remove this definition and use
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// RCHECK in rcheck.h instead.
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#define RCHECK(x) \
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do { \
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if (!(x)) { \
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LOG(ERROR) << "Failure while processing: " << #x; \
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return false; \
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} \
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} while (0)
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namespace {
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const char kLicenseStatusOK[] = "OK";
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// Server may return INTERNAL_ERROR intermittently, which is a transient error
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// and the next client request may succeed without problem.
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const char kLicenseStatusTransientError[] = "INTERNAL_ERROR";
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// Number of times to retry requesting keys in case of a transient error from
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// the server.
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const int kNumTransientErrorRetries = 5;
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const int kFirstRetryDelayMilliseconds = 1000;
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bool Base64StringToBytes(const std::string& base64_string,
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std::vector<uint8>* bytes) {
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DCHECK(bytes);
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std::string str;
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if (!base::Base64Decode(base64_string, &str))
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return false;
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bytes->assign(str.begin(), str.end());
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return true;
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}
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bool GetKeyAndKeyId(const base::DictionaryValue& track_dict,
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std::vector<uint8>* key,
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std::vector<uint8>* key_id) {
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DCHECK(key);
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DCHECK(key_id);
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std::string key_base64_string;
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RCHECK(track_dict.GetString("key", &key_base64_string));
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VLOG(2) << "Key:" << key_base64_string;
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RCHECK(Base64StringToBytes(key_base64_string, key));
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std::string key_id_base64_string;
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RCHECK(track_dict.GetString("key_id", &key_id_base64_string));
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VLOG(2) << "Keyid:" << key_id_base64_string;
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RCHECK(Base64StringToBytes(key_id_base64_string, key_id));
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return true;
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}
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bool GetPssh(const base::DictionaryValue& track_dict,
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std::vector<uint8>* pssh) {
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DCHECK(pssh);
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// TODO: Add support for multiple pssh.
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const base::ListValue* pssh_list;
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RCHECK(track_dict.GetList("pssh", &pssh_list));
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// Invariant check. We don't want to crash in release mode if possible.
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// The following code handles it gracefully if GetSize() does not return 1.
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DCHECK_EQ(1, pssh_list->GetSize());
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const base::DictionaryValue* pssh_dict;
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RCHECK(pssh_list->GetDictionary(0, &pssh_dict));
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std::string drm_type;
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RCHECK(pssh_dict->GetString("drm_type", &drm_type));
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if (drm_type != "WIDEVINE") {
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LOG(ERROR) << "Expecting drm_type 'WIDEVINE', get '" << drm_type << "'.";
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return false;
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}
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std::string pssh_base64_string;
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RCHECK(pssh_dict->GetString("data", &pssh_base64_string));
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VLOG(2) << "Pssh:" << pssh_base64_string;
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RCHECK(Base64StringToBytes(pssh_base64_string, pssh));
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return true;
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}
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} // namespace
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namespace media {
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WidevineEncryptorSource::WidevineEncryptorSource(
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const std::string& server_url,
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const std::string& content_id,
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TrackType track_type,
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scoped_ptr<RequestSigner> signer)
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: http_fetcher_(new SimpleHttpFetcher()),
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server_url_(server_url),
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content_id_(content_id),
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track_type_(track_type),
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signer_(signer.Pass()) {
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DCHECK(signer_);
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}
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WidevineEncryptorSource::~WidevineEncryptorSource() {}
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Status WidevineEncryptorSource::Initialize() {
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std::string request;
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FillRequest(content_id_, &request);
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std::string message;
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Status status = SignRequest(request, &message);
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if (!status.ok())
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return status;
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VLOG(1) << "Message: " << message;
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std::string raw_response;
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int64 sleep_duration = kFirstRetryDelayMilliseconds;
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// Perform client side retries if seeing server transient error to workaround
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// server limitation.
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for (int i = 0; i < kNumTransientErrorRetries; ++i) {
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status = http_fetcher_->Post(server_url_, message, &raw_response);
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if (!status.ok())
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return status;
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VLOG(1) << "Retry [" << i << "] Response:" << raw_response;
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std::string response;
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if (!DecodeResponse(raw_response, &response)) {
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return Status(error::SERVER_ERROR,
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"Failed to decode response '" + raw_response + "'.");
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}
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bool transient_error = false;
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if (ExtractEncryptionKey(response, &transient_error))
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return Status::OK;
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if (!transient_error) {
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return Status(
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error::SERVER_ERROR,
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"Failed to extract encryption key from '" + response + "'.");
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}
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// Exponential backoff.
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if (i != kNumTransientErrorRetries - 1) {
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base::PlatformThread::Sleep(
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base::TimeDelta::FromMilliseconds(sleep_duration));
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sleep_duration *= 2;
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}
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}
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return Status(error::SERVER_ERROR,
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"Failed to recover from server internal error.");
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}
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WidevineEncryptorSource::TrackType
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WidevineEncryptorSource::GetTrackTypeFromString(
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const std::string& track_type_string) {
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if (track_type_string == "SD")
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return TRACK_TYPE_SD;
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if (track_type_string == "HD")
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return TRACK_TYPE_HD;
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if (track_type_string == "AUDIO")
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return TRACK_TYPE_AUDIO;
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LOG(WARNING) << "Unexpected track type: " << track_type_string;
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return TRACK_TYPE_UNKNOWN;
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}
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void WidevineEncryptorSource::set_http_fetcher(
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scoped_ptr<HttpFetcher> http_fetcher) {
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http_fetcher_ = http_fetcher.Pass();
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}
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void WidevineEncryptorSource::FillRequest(const std::string& content_id,
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std::string* request) {
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DCHECK(request);
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std::string content_id_base64_string;
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base::Base64Encode(content_id, &content_id_base64_string);
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base::DictionaryValue request_dict;
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request_dict.SetString("content_id", content_id_base64_string);
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// TODO: Determine the need for policy.
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request_dict.SetString("policy", "");
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// Build tracks.
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base::ListValue* tracks = new base::ListValue();
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base::DictionaryValue* track_sd = new base::DictionaryValue();
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track_sd->SetString("type", "SD");
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tracks->Append(track_sd);
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base::DictionaryValue* track_hd = new base::DictionaryValue();
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track_hd->SetString("type", "HD");
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tracks->Append(track_hd);
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base::DictionaryValue* track_audio = new base::DictionaryValue();
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track_audio->SetString("type", "AUDIO");
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tracks->Append(track_audio);
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request_dict.Set("tracks", tracks);
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// Build DRM types.
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base::ListValue* drm_types = new base::ListValue();
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drm_types->AppendString("WIDEVINE");
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request_dict.Set("drm_types", drm_types);
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base::JSONWriter::Write(&request_dict, request);
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}
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Status WidevineEncryptorSource::SignRequest(const std::string& request,
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std::string* signed_request) {
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DCHECK(signed_request);
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// Sign the request.
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std::string signature;
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if (!signer_->GenerateSignature(request, &signature))
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return Status(error::INTERNAL_ERROR, "Signature generation failed.");
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// Encode request and signature using Base64 encoding.
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std::string request_base64_string;
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base::Base64Encode(request, &request_base64_string);
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std::string signature_base64_string;
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base::Base64Encode(signature, &signature_base64_string);
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base::DictionaryValue signed_request_dict;
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signed_request_dict.SetString("request", request_base64_string);
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signed_request_dict.SetString("signature", signature_base64_string);
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signed_request_dict.SetString("signer", signer_->signer_name());
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base::JSONWriter::Write(&signed_request_dict, signed_request);
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return Status::OK;
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}
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bool WidevineEncryptorSource::DecodeResponse(const std::string& raw_response,
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std::string* response) {
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DCHECK(response);
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// Extract base64 formatted response from JSON formatted raw response.
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scoped_ptr<base::Value> root(base::JSONReader::Read(raw_response));
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if (!root) {
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LOG(ERROR) << "'" << raw_response << "' is not in JSON format.";
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return false;
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}
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const base::DictionaryValue* response_dict = NULL;
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RCHECK(root->GetAsDictionary(&response_dict));
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std::string response_base64_string;
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RCHECK(response_dict->GetString("response", &response_base64_string));
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RCHECK(base::Base64Decode(response_base64_string, response));
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return true;
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}
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bool WidevineEncryptorSource::IsExpectedTrackType(
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const std::string& track_type_string) {
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return track_type_ == GetTrackTypeFromString(track_type_string);
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}
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bool WidevineEncryptorSource::ExtractEncryptionKey(const std::string& response,
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bool* transient_error) {
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DCHECK(transient_error);
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*transient_error = false;
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scoped_ptr<base::Value> root(base::JSONReader::Read(response));
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if (!root) {
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LOG(ERROR) << "'" << response << "' is not in JSON format.";
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return false;
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}
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const base::DictionaryValue* license_dict = NULL;
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RCHECK(root->GetAsDictionary(&license_dict));
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std::string license_status;
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RCHECK(license_dict->GetString("status", &license_status));
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if (license_status != kLicenseStatusOK) {
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LOG(ERROR) << "Received non-OK license response: " << response;
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*transient_error = (license_status == kLicenseStatusTransientError);
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return false;
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}
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const base::ListValue* tracks;
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RCHECK(license_dict->GetList("tracks", &tracks));
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for (base::ListValue::const_iterator it = tracks->begin();
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it != tracks->end();
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++it) {
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const base::DictionaryValue* track_dict;
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RCHECK((*it)->GetAsDictionary(&track_dict));
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std::string track_type;
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RCHECK(track_dict->GetString("type", &track_type));
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if (!IsExpectedTrackType(track_type))
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continue;
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std::vector<uint8> key_id;
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std::vector<uint8> key;
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std::vector<uint8> pssh;
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if (!GetKeyAndKeyId(*track_dict, &key, &key_id) ||
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!GetPssh(*track_dict, &pssh))
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return false;
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set_key_id(key_id);
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set_key(key);
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set_pssh(pssh);
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return true;
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}
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LOG(ERROR) << "Cannot find key of type " << track_type_ << " from '"
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<< response << "'.";
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return false;
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}
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} // namespace media
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