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/strings/string_util.h"
#include "media/base/cdm_callback_promise.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::ProxyDecryptor(MediaPermission* media_permission,
                               const KeyAddedCB& key_added_cb,
                               const KeyErrorCB& key_error_cb,
                               const KeyMessageCB& key_message_cb)
    : 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();
}

CdmContext* ProxyDecryptor::GetCdmContext() {
  return media_keys_ ? media_keys_->GetCdmContext() : nullptr;
}

bool ProxyDecryptor::InitializeCDM(CdmFactory* cdm_factory,
                                   const std::string& key_system,
                                   const GURL& security_origin) {
  DVLOG(1) << "InitializeCDM: key_system = " << key_system;

  DCHECK(!media_keys_);
  media_keys_ = CreateMediaKeys(cdm_factory, key_system, security_origin);
  if (!media_keys_)
    return false;

  is_clear_key_ =
      IsClearKey(key_system) || IsExternalClearKey(key_system);
  return true;
}

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

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

bool ProxyDecryptor::GenerateKeyRequest(const std::string& init_data_type,
                                        const uint8* init_data,
                                        int init_data_length) {
  DVLOG(1) << "GenerateKeyRequest()";
  const char kPrefixedApiPersistentSessionHeader[] = "PERSISTENT|";
  const char kPrefixedApiLoadSessionHeader[] = "LOAD_SESSION|";

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

  scoped_ptr<NewSessionCdmPromise> promise(
      new CdmCallbackPromise<std::string>(
          base::Bind(&ProxyDecryptor::SetSessionId,
                     weak_ptr_factory_.GetWeakPtr(),
                     session_creation_type),
          base::Bind(&ProxyDecryptor::OnSessionError,
                     weak_ptr_factory_.GetWeakPtr(),
                     std::string())));  // No session id until created.
  uint8* init_data_vector_data =
      (init_data_vector.size() > 0) ? &init_data_vector[0] : nullptr;

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

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

  media_keys_->CreateSessionAndGenerateRequest(
      session_type, init_data_type, init_data_vector_data,
      init_data_vector.size(), promise.Pass());
  return true;
}

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()";

  // 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 {
      OnSessionError(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::OnSessionError,
                 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,
                               reinterpret_cast<const uint8*>(jwk.data()),
                               jwk.size(), promise.Pass());
    return;
  }

  media_keys_->UpdateSession(new_session_id, key, key_length, promise.Pass());
}

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

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

scoped_ptr<MediaKeys> ProxyDecryptor::CreateMediaKeys(
    CdmFactory* cdm_factory,
    const std::string& key_system,
    const GURL& security_origin) {
  base::WeakPtr<ProxyDecryptor> weak_this = weak_ptr_factory_.GetWeakPtr();
  return cdm_factory->Create(
      key_system,
      security_origin,
      base::Bind(&ProxyDecryptor::OnSessionMessage, weak_this),
      base::Bind(&ProxyDecryptor::OnSessionClosed, weak_this),
      base::Bind(&ProxyDecryptor::OnSessionError, weak_this),
      base::Bind(&ProxyDecryptor::OnSessionKeysChange, weak_this),
      base::Bind(&ProxyDecryptor::OnSessionExpirationUpdate, weak_this));
}

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) {
    OnSessionError(session_id, MediaKeys::NOT_SUPPORTED_ERROR,
                   kSessionClosedSystemCode,
                   "Do not close persistent sessions.");
  }
  active_sessions_.erase(it);
}

void ProxyDecryptor::OnSessionError(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