media/cdm/proxy_decryptor.cc

// Copyright 2013 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 "media/cdm/proxy_decryptor.h"

#include <cstring>

#include "base/bind.h"
#include "base/callback_helpers.h"
#include "base/logging.h"
#include "base/stl_util.h"
#include "base/strings/string_util.h"
#include "media/base/cdm_callback_promise.h"
#include "media/base/cdm_config.h"
#include "media/base/cdm_factory.h"
#include "media/base/cdm_key_information.h"
#include "media/base/key_systems.h"
#include "media/base/media_permission.h"
#include "media/cdm/json_web_key.h"
#include "media/cdm/key_system_names.h"

namespace media {

// Special system code to signal a closed persistent session in a SessionError()
// call. This is needed because there is no SessionClosed() call in the prefixed
// EME API.
const int kSessionClosedSystemCode = 29127;

ProxyDecryptor::PendingGenerateKeyRequestData::PendingGenerateKeyRequestData(
    EmeInitDataType init_data_type,
    const std::vector<uint8>& init_data)
    : init_data_type(init_data_type), init_data(init_data) {
}

ProxyDecryptor::PendingGenerateKeyRequestData::
    ~PendingGenerateKeyRequestData() {
}

ProxyDecryptor::ProxyDecryptor(MediaPermission* media_permission,
                               bool use_hw_secure_codecs,
                               const KeyAddedCB& key_added_cb,
                               const KeyErrorCB& key_error_cb,
                               const KeyMessageCB& key_message_cb)
    : is_creating_cdm_(false),
      media_permission_(media_permission),
      use_hw_secure_codecs_(use_hw_secure_codecs),
      key_added_cb_(key_added_cb),
      key_error_cb_(key_error_cb),
      key_message_cb_(key_message_cb),
      is_clear_key_(false),
      weak_ptr_factory_(this) {
  DCHECK(media_permission);
  DCHECK(!key_added_cb_.is_null());
  DCHECK(!key_error_cb_.is_null());
  DCHECK(!key_message_cb_.is_null());
}

ProxyDecryptor::~ProxyDecryptor() {
  // Destroy the decryptor explicitly before destroying the plugin.
  media_keys_.reset();
}

void ProxyDecryptor::CreateCdm(CdmFactory* cdm_factory,
                               const std::string& key_system,
                               const GURL& security_origin,
                               const CdmContextReadyCB& cdm_context_ready_cb) {
  DVLOG(1) << __FUNCTION__ << ": key_system = " << key_system;
  DCHECK(!is_creating_cdm_);
  DCHECK(!media_keys_);

  // TODO(sandersd): Trigger permissions check here and use it to determine
  // distinctive identifier support, instead of always requiring the
  // permission. http://crbug.com/455271
  CdmConfig cdm_config;
  cdm_config.allow_distinctive_identifier = true;
  cdm_config.allow_persistent_state = true;
  cdm_config.use_hw_secure_codecs = use_hw_secure_codecs_;

  is_creating_cdm_ = true;

  base::WeakPtr<ProxyDecryptor> weak_this = weak_ptr_factory_.GetWeakPtr();
  cdm_factory->Create(
      key_system, security_origin, cdm_config,
      base::Bind(&ProxyDecryptor::OnSessionMessage, weak_this),
      base::Bind(&ProxyDecryptor::OnSessionClosed, weak_this),
      base::Bind(&ProxyDecryptor::OnLegacySessionError, weak_this),
      base::Bind(&ProxyDecryptor::OnSessionKeysChange, weak_this),
      base::Bind(&ProxyDecryptor::OnSessionExpirationUpdate, weak_this),
      base::Bind(&ProxyDecryptor::OnCdmCreated, weak_this, key_system,
                 security_origin, cdm_context_ready_cb));
}

void ProxyDecryptor::OnCdmCreated(const std::string& key_system,
                                  const GURL& security_origin,
                                  const CdmContextReadyCB& cdm_context_ready_cb,
                                  scoped_ptr<MediaKeys> cdm,
                                  const std::string& /* error_message */) {
  is_creating_cdm_ = false;

  if (!cdm) {
    cdm_context_ready_cb.Run(nullptr);
  } else {
    key_system_ = key_system;
    security_origin_ = security_origin;
    is_clear_key_ = IsClearKey(key_system) || IsExternalClearKey(key_system);
    media_keys_ = cdm.Pass();

    cdm_context_ready_cb.Run(media_keys_->GetCdmContext());
  }

  for (const auto& request : pending_requests_)
    GenerateKeyRequestInternal(request->init_data_type, request->init_data);

  pending_requests_.clear();
}

void ProxyDecryptor::GenerateKeyRequest(EmeInitDataType init_data_type,
                                        const uint8* init_data,
                                        int init_data_length) {
  std::vector<uint8> init_data_vector(init_data, init_data + init_data_length);

  if (is_creating_cdm_) {
    pending_requests_.push_back(
        new PendingGenerateKeyRequestData(init_data_type, init_data_vector));
    return;
  }

  GenerateKeyRequestInternal(init_data_type, init_data_vector);
}

// Returns true if |data| is prefixed with |header| and has data after the
// |header|.
bool HasHeader(const std::vector<uint8>& data, const std::string& header) {
  return data.size() > header.size() &&
         std::equal(header.begin(), header.end(), data.begin());
}

// Removes the first |length| items from |data|.
void StripHeader(std::vector<uint8>& data, size_t length) {
  data.erase(data.begin(), data.begin() + length);
}

void ProxyDecryptor::GenerateKeyRequestInternal(
    EmeInitDataType init_data_type,
    const std::vector<uint8>& init_data) {
  DVLOG(1) << __FUNCTION__;
  DCHECK(!is_creating_cdm_);

  if (!media_keys_) {
    OnLegacySessionError(std::string(), MediaKeys::NOT_SUPPORTED_ERROR, 0,
                         "CDM creation failed.");
    return;
  }

  const char kPrefixedApiPersistentSessionHeader[] = "PERSISTENT|";
  const char kPrefixedApiLoadSessionHeader[] = "LOAD_SESSION|";

  SessionCreationType session_creation_type = TemporarySession;
  std::vector<uint8> stripped_init_data = init_data;
  if (HasHeader(init_data, kPrefixedApiLoadSessionHeader)) {
    session_creation_type = LoadSession;
    StripHeader(stripped_init_data, strlen(kPrefixedApiLoadSessionHeader));
  } else if (HasHeader(init_data, kPrefixedApiPersistentSessionHeader)) {
    session_creation_type = PersistentSession;
    StripHeader(stripped_init_data,
                strlen(kPrefixedApiPersistentSessionHeader));
  }

  scoped_ptr<NewSessionCdmPromise> promise(new CdmCallbackPromise<std::string>(
      base::Bind(&ProxyDecryptor::SetSessionId, weak_ptr_factory_.GetWeakPtr(),
                 session_creation_type),
      base::Bind(&ProxyDecryptor::OnLegacySessionError,
                 weak_ptr_factory_.GetWeakPtr(),
                 std::string())));  // No session id until created.

  if (session_creation_type == LoadSession) {
    media_keys_->LoadSession(
        MediaKeys::PERSISTENT_LICENSE_SESSION,
        std::string(
            reinterpret_cast<const char*>(vector_as_array(&stripped_init_data)),
            stripped_init_data.size()),
        promise.Pass());
    return;
  }

  MediaKeys::SessionType session_type =
      session_creation_type == PersistentSession
          ? MediaKeys::PERSISTENT_LICENSE_SESSION
          : MediaKeys::TEMPORARY_SESSION;

  // No permission required when AesDecryptor is used or when the key system is
  // external clear key.
  DCHECK(!key_system_.empty());
  if (CanUseAesDecryptor(key_system_) || IsExternalClearKey(key_system_)) {
    OnPermissionStatus(session_type, init_data_type, stripped_init_data,
                       promise.Pass(), true /* granted */);
    return;
  }

#if defined(OS_CHROMEOS) || defined(OS_ANDROID)
  media_permission_->RequestPermission(
      MediaPermission::PROTECTED_MEDIA_IDENTIFIER, security_origin_,
      base::Bind(&ProxyDecryptor::OnPermissionStatus,
                 weak_ptr_factory_.GetWeakPtr(), session_type, init_data_type,
                 stripped_init_data, base::Passed(&promise)));
#else
  OnPermissionStatus(session_type, init_data_type, stripped_init_data,
                     promise.Pass(), true /* granted */);
#endif
}

void ProxyDecryptor::OnPermissionStatus(
    MediaKeys::SessionType session_type,
    EmeInitDataType init_data_type,
    const std::vector<uint8>& init_data,
    scoped_ptr<NewSessionCdmPromise> promise,
    bool granted) {
  // ProxyDecryptor is only used by Prefixed EME, where RequestPermission() is
  // only for triggering the permission UI. Later CheckPermission() will be
  // called (e.g. in PlatformVerificationFlow on ChromeOS; in BrowserCdmManager
  // on Android) and the permission status will be evaluated then.
  DVLOG_IF(1, !granted) << "Permission request rejected.";

  media_keys_->CreateSessionAndGenerateRequest(session_type, init_data_type,
                                               init_data, promise.Pass());
}

void ProxyDecryptor::AddKey(const uint8* key,
                            int key_length,
                            const uint8* init_data,
                            int init_data_length,
                            const std::string& session_id) {
  DVLOG(1) << "AddKey()";

  if (!media_keys_) {
    OnLegacySessionError(std::string(), MediaKeys::INVALID_STATE_ERROR, 0,
                         "CDM is not available.");
    return;
  }

  // In the prefixed API, the session parameter provided to addKey() is
  // optional, so use the single existing session if it exists.
  std::string new_session_id(session_id);
  if (new_session_id.empty()) {
    if (active_sessions_.size() == 1) {
      base::hash_map<std::string, bool>::iterator it = active_sessions_.begin();
      new_session_id = it->first;
    } else {
      OnLegacySessionError(std::string(), MediaKeys::NOT_SUPPORTED_ERROR, 0,
                           "SessionId not specified.");
      return;
    }
  }

  scoped_ptr<SimpleCdmPromise> promise(new CdmCallbackPromise<>(
      base::Bind(&ProxyDecryptor::GenerateKeyAdded,
                 weak_ptr_factory_.GetWeakPtr(), session_id),
      base::Bind(&ProxyDecryptor::OnLegacySessionError,
                 weak_ptr_factory_.GetWeakPtr(), session_id)));

  // EME WD spec only supports a single array passed to the CDM. For
  // Clear Key using v0.1b, both arrays are used (|init_data| is key_id).
  // Since the EME WD spec supports the key as a JSON Web Key,
  // convert the 2 arrays to a JWK and pass it as the single array.
  if (is_clear_key_) {
    // Decryptor doesn't support empty key ID (see http://crbug.com/123265).
    // So ensure a non-empty value is passed.
    if (!init_data) {
      static const uint8 kDummyInitData[1] = {0};
      init_data = kDummyInitData;
      init_data_length = arraysize(kDummyInitData);
    }

    std::string jwk =
        GenerateJWKSet(key, key_length, init_data, init_data_length);
    DCHECK(!jwk.empty());
    media_keys_->UpdateSession(new_session_id,
                               std::vector<uint8_t>(jwk.begin(), jwk.end()),
                               promise.Pass());
    return;
  }

  media_keys_->UpdateSession(new_session_id,
                             std::vector<uint8_t>(key, key + key_length),
                             promise.Pass());
}

void ProxyDecryptor::CancelKeyRequest(const std::string& session_id) {
  DVLOG(1) << "CancelKeyRequest()";

  if (!media_keys_) {
    OnLegacySessionError(std::string(), MediaKeys::INVALID_STATE_ERROR, 0,
                         "CDM is not available.");
    return;
  }

  scoped_ptr<SimpleCdmPromise> promise(new CdmCallbackPromise<>(
      base::Bind(&ProxyDecryptor::OnSessionClosed,
                 weak_ptr_factory_.GetWeakPtr(), session_id),
      base::Bind(&ProxyDecryptor::OnLegacySessionError,
                 weak_ptr_factory_.GetWeakPtr(), session_id)));
  media_keys_->RemoveSession(session_id, promise.Pass());
}

void ProxyDecryptor::OnSessionMessage(const std::string& session_id,
                                      MediaKeys::MessageType message_type,
                                      const std::vector<uint8>& message,
                                      const GURL& legacy_destination_url) {
  // Assumes that OnSessionCreated() has been called before this.

  // For ClearKey, convert the message from JSON into just passing the key
  // as the message. If unable to extract the key, return the message unchanged.
  if (is_clear_key_) {
    std::vector<uint8> key;
    if (ExtractFirstKeyIdFromLicenseRequest(message, &key)) {
      key_message_cb_.Run(session_id, key, legacy_destination_url);
      return;
    }
  }

  key_message_cb_.Run(session_id, message, legacy_destination_url);
}

void ProxyDecryptor::OnSessionKeysChange(const std::string& session_id,
                                         bool has_additional_usable_key,
                                         CdmKeysInfo keys_info) {
  // EME v0.1b doesn't support this event.
}

void ProxyDecryptor::OnSessionExpirationUpdate(
    const std::string& session_id,
    const base::Time& new_expiry_time) {
  // EME v0.1b doesn't support this event.
}

void ProxyDecryptor::GenerateKeyAdded(const std::string& session_id) {
  // EME WD doesn't support this event, but it is needed for EME v0.1b.
  key_added_cb_.Run(session_id);
}

void ProxyDecryptor::OnSessionClosed(const std::string& session_id) {
  base::hash_map<std::string, bool>::iterator it =
      active_sessions_.find(session_id);

  // Latest EME spec separates closing a session ("allows an application to
  // indicate that it no longer needs the session") and actually closing the
  // session (done by the CDM at any point "such as in response to a close()
  // call, when the session is no longer needed, or when system resources are
  // lost.") Thus the CDM may cause 2 close() events -- one to resolve the
  // close() promise, and a second to actually close the session. Prefixed EME
  // only expects 1 close event, so drop the second (and subsequent) events.
  // However, this means we can't tell if the CDM is generating spurious close()
  // events.
  if (it == active_sessions_.end())
    return;

  if (it->second) {
    OnLegacySessionError(session_id, MediaKeys::NOT_SUPPORTED_ERROR,
                         kSessionClosedSystemCode,
                         "Do not close persistent sessions.");
  }
  active_sessions_.erase(it);
}

void ProxyDecryptor::OnLegacySessionError(const std::string& session_id,
                                          MediaKeys::Exception exception_code,
                                          uint32 system_code,
                                          const std::string& error_message) {
  // Convert |error_name| back to MediaKeys::KeyError if possible. Prefixed
  // EME has different error message, so all the specific error events will
  // get lost.
  MediaKeys::KeyError error_code;
  switch (exception_code) {
    case MediaKeys::CLIENT_ERROR:
      error_code = MediaKeys::kClientError;
      break;
    case MediaKeys::OUTPUT_ERROR:
      error_code = MediaKeys::kOutputError;
      break;
    default:
      // This will include all other CDM4 errors and any error generated
      // by CDM5 or later.
      error_code = MediaKeys::kUnknownError;
      break;
  }
  key_error_cb_.Run(session_id, error_code, system_code);
}

void ProxyDecryptor::SetSessionId(SessionCreationType session_type,
                                  const std::string& session_id) {
  // Loaded sessions are considered persistent.
  bool is_persistent =
      session_type == PersistentSession || session_type == LoadSession;
  active_sessions_.insert(std::make_pair(session_id, is_persistent));

  // For LoadSession(), generate the KeyAdded event.
  if (session_type == LoadSession)
    GenerateKeyAdded(session_id);
}

}  // namespace media