android/libwvdrmengine/cdm/src/wv_content_decryption_module.cpp

// Copyright 2018 Google LLC. All Rights Reserved. This file and proprietary
// source code may only be used and distributed under the Widevine License
// Agreement.

#include "wv_content_decryption_module.h"

#include <algorithm>
#include <iterator>

#include "cdm_client_property_set.h"
#include "cdm_engine.h"
#include "cdm_engine_factory.h"
#include "initialization_data.h"
#include "license.h"
#include "log.h"
#include "properties.h"
#include "service_certificate.h"
#include "string_conversions.h"
#include "wv_cdm_constants.h"
#include "wv_cdm_event_listener.h"
#include "wv_metrics.pb.h"

namespace {
const int kCdmTimerDurationSeconds = 1;
}

namespace wvcdm {

std::mutex WvContentDecryptionModule::session_sharing_id_generation_lock_;

WvContentDecryptionModule::WvContentDecryptionModule() {}

WvContentDecryptionModule::~WvContentDecryptionModule() {
  CryptoSession::DisableDelayedTermination();
  CloseAllCdms();
  CryptoSession::TryTerminate();
  DisableTimerAndWaitForExit();
}

bool WvContentDecryptionModule::IsSupported(const std::string& init_data_type) {
  return InitializationData(init_data_type).is_supported();
}

bool WvContentDecryptionModule::IsCenc(const std::string& init_data_type) {
  return InitializationData(init_data_type).is_cenc();
}

bool WvContentDecryptionModule::IsWebm(const std::string& init_data_type) {
  return InitializationData(init_data_type).is_webm();
}

bool WvContentDecryptionModule::IsHls(const std::string& init_data_type) {
  return InitializationData(init_data_type).is_hls();
}

bool WvContentDecryptionModule::IsAudio(const std::string& init_data_type) {
  return InitializationData(init_data_type).is_audio();
}

CdmResponseType WvContentDecryptionModule::OpenSession(
    const CdmKeySystem& key_system, CdmClientPropertySet* property_set,
    const CdmIdentifier& identifier, WvCdmEventListener* event_listener,
    CdmSessionId* session_id) {
  if (property_set && property_set->is_session_sharing_enabled()) {
    std::unique_lock<std::mutex> auto_lock(session_sharing_id_generation_lock_);
    if (property_set->session_sharing_id() == 0)
      property_set->set_session_sharing_id(GenerateSessionSharingId());
  }

  CdmEngine* cdm_engine = EnsureCdmForIdentifier(identifier);
  CdmResponseType sts = cdm_engine->OpenSession(key_system, property_set,
                                                event_listener, session_id);
  if (sts == NO_ERROR) {
    std::unique_lock<std::mutex> auto_lock(cdms_lock_);
    cdm_by_session_id_[*session_id] = cdm_engine;
  }
  return sts;
}

CdmResponseType WvContentDecryptionModule::CloseSession(
    const CdmSessionId& session_id) {
  LOGV("Closing session ID: %s", session_id.c_str());
  CdmEngine* cdm_engine = GetCdmForSessionId(session_id);
  // TODO(rfrias): Avoid reusing the error codes from CdmEngine.
  if (!cdm_engine) return SESSION_NOT_FOUND_1;
  const CdmResponseType sts = cdm_engine->CloseSession(session_id);
  if (sts == NO_ERROR) {
    std::unique_lock<std::mutex> auto_lock(cdms_lock_);
    cdm_by_session_id_.erase(session_id);
  }
  return sts;
}

bool WvContentDecryptionModule::IsOpenSession(const CdmSessionId& session_id) {
  CdmEngine* cdm_engine = GetCdmForSessionId(session_id);
  return cdm_engine && cdm_engine->IsOpenSession(session_id);
}

CdmResponseType WvContentDecryptionModule::GenerateKeyRequest(
    const CdmSessionId& session_id, const CdmKeySetId& key_set_id,
    const std::string& init_data_type, const CdmInitData& init_data,
    const CdmLicenseType license_type, CdmAppParameterMap& app_parameters,
    CdmClientPropertySet* property_set, const CdmIdentifier& identifier,
    CdmKeyRequest* key_request) {
  CdmEngine* cdm_engine = EnsureCdmForIdentifier(identifier);
  CdmResponseType sts;
  if (license_type == kLicenseTypeRelease) {
    sts = cdm_engine->OpenKeySetSession(key_set_id, property_set, nullptr);
    if (sts != NO_ERROR) return sts;
    std::unique_lock<std::mutex> auto_lock(cdms_lock_);
    cdm_by_session_id_[key_set_id] = cdm_engine;
  }

  const SecurityLevel requested_security_level =
      property_set && property_set->security_level().compare(
                          wvcdm::QUERY_VALUE_SECURITY_LEVEL_L3) == 0
          ? wvcdm::kLevel3
          : wvcdm::kLevelDefault;

  std::string oec_version;
  sts = cdm_engine->QueryStatus(requested_security_level,
                                QUERY_KEY_OEMCRYPTO_API_VERSION, &oec_version);
  if (sts != NO_ERROR) {
    return sts;
  }
  InitializationData initialization_data(init_data_type, init_data,
                                         oec_version);

  sts = cdm_engine->GenerateKeyRequest(session_id, key_set_id,
                                       initialization_data, license_type,
                                       app_parameters, key_request);
  if (license_type == kLicenseTypeRelease && sts != KEY_MESSAGE) {
    cdm_engine->CloseKeySetSession(key_set_id);
    std::unique_lock<std::mutex> auto_lock(cdms_lock_);
    cdm_by_session_id_.erase(key_set_id);
  }
  return sts;
}

CdmResponseType WvContentDecryptionModule::AddKey(
    const CdmSessionId& session_id, const CdmKeyResponse& key_data,
    CdmKeySetId* key_set_id) {
  CdmEngine* cdm_engine = session_id.empty() ? GetCdmForSessionId(*key_set_id)
                                             : GetCdmForSessionId(session_id);
  if (!cdm_engine) return SESSION_NOT_FOUND_3;
  // Save key_set_id, as CDM will return an empty key_set_id on release
  CdmKeySetId release_key_set_id;
  if (session_id.empty() && key_set_id != nullptr) {
    release_key_set_id = *key_set_id;
  }
  CdmResponseType sts;
  CdmLicenseType license_type;
  sts = cdm_engine->AddKey(session_id, key_data, &license_type, key_set_id);
  // Empty session id indicates license type release.
  if (sts == KEY_ADDED && session_id.empty()) {
    cdm_engine->CloseKeySetSession(release_key_set_id);
    std::unique_lock<std::mutex> auto_lock(cdms_lock_);
    cdm_by_session_id_.erase(release_key_set_id);
  }
  return sts;
}

CdmResponseType WvContentDecryptionModule::RestoreKey(
    const CdmSessionId& session_id, const CdmKeySetId& key_set_id) {
  CdmEngine* cdm_engine = GetCdmForSessionId(session_id);
  if (!cdm_engine) return SESSION_NOT_FOUND_4;
  CdmResponseType sts;
  sts = cdm_engine->RestoreKey(session_id, key_set_id);
  return sts;
}

CdmResponseType WvContentDecryptionModule::RemoveKeys(
    const CdmSessionId& session_id) {
  CdmEngine* cdm_engine = GetCdmForSessionId(session_id);
  if (!cdm_engine) return SESSION_NOT_FOUND_5;
  CdmResponseType sts = cdm_engine->RemoveKeys(session_id);
  return sts;
}

CdmResponseType WvContentDecryptionModule::QueryStatus(
    SecurityLevel security_level, const std::string& key, std::string* value) {
  CdmEngine* cdm_engine = EnsureCdmForIdentifier(kDefaultCdmIdentifier);
  return cdm_engine->QueryStatus(security_level, key, value);
}

CdmResponseType WvContentDecryptionModule::QuerySessionStatus(
    const CdmSessionId& session_id, CdmQueryMap* key_info) {
  CdmEngine* cdm_engine = GetCdmForSessionId(session_id);
  if (!cdm_engine) return SESSION_NOT_FOUND_8;
  return cdm_engine->QuerySessionStatus(session_id, key_info);
}

CdmResponseType WvContentDecryptionModule::QueryKeyStatus(
    const CdmSessionId& session_id, CdmQueryMap* key_info) {
  CdmEngine* cdm_engine = GetCdmForSessionId(session_id);
  if (!cdm_engine) return SESSION_NOT_FOUND_9;
  CdmResponseType sts;
  sts = cdm_engine->QueryKeyStatus(session_id, key_info);
  return sts;
}

CdmResponseType WvContentDecryptionModule::QueryOemCryptoSessionId(
    const CdmSessionId& session_id, CdmQueryMap* response) {
  CdmEngine* cdm_engine = GetCdmForSessionId(session_id);
  if (!cdm_engine) return SESSION_NOT_FOUND_10;
  return cdm_engine->QueryOemCryptoSessionId(session_id, response);
}

bool WvContentDecryptionModule::IsSecurityLevelSupported(
    CdmSecurityLevel level) {
  return CdmEngine::IsSecurityLevelSupported(level);
}

CdmResponseType WvContentDecryptionModule::GetProvisioningRequest(
    CdmCertificateType cert_type, const std::string& cert_authority,
    const CdmIdentifier& identifier, const std::string& service_certificate,
    SecurityLevel requested_security_level, CdmProvisioningRequest* request,
    std::string* default_url) {
  CdmEngine* cdm_engine = EnsureCdmForIdentifier(identifier);
  return cdm_engine->GetProvisioningRequest(
      cert_type, cert_authority, service_certificate, requested_security_level,
      request, default_url);
}

CdmResponseType WvContentDecryptionModule::HandleProvisioningResponse(
    const CdmIdentifier& identifier, CdmProvisioningResponse& response,
    SecurityLevel requested_security_level, std::string* cert,
    std::string* wrapped_key) {
  CdmEngine* cdm_engine = EnsureCdmForIdentifier(identifier);
  return cdm_engine->HandleProvisioningResponse(
      response, requested_security_level, cert, wrapped_key);
}

CdmResponseType WvContentDecryptionModule::Unprovision(
    CdmSecurityLevel level, const CdmIdentifier& identifier) {
  CdmEngine* cdm_engine = EnsureCdmForIdentifier(identifier);
  // Persistent state is deleted on unprovisioning. The L3 OEMCrypto device
  // key may however remain in memory until |OEMCrypto_Terminate| is called.
  // It is not regenerated until |OEMCrypto_Initialize| is called.
  // Enable immediate OEMCrypto termination and re-initalization on
  // unprovisioning.
  CryptoSession::DisableDelayedTermination();
  return cdm_engine->Unprovision(level);
}

bool WvContentDecryptionModule::IsProvisioned(CdmSecurityLevel security_level,
                                              const std::string& origin,
                                              const std::string& spoid,
                                              bool atsc_mode_enabled) {
  FileSystem file_system;
  file_system.set_origin(origin);
  file_system.set_identifier(spoid + origin);
  DeviceFiles device_files(&file_system);
  device_files.Init(security_level);
  return device_files.HasCertificate(atsc_mode_enabled);
}

CdmResponseType WvContentDecryptionModule::GetUsageInfo(
    const std::string& app_id, const CdmIdentifier& identifier,
    CdmUsageInfo* usage_info) {
  CdmEngine* cdm_engine = EnsureCdmForIdentifier(identifier);
  int error_detail = NO_ERROR;
  return cdm_engine->GetUsageInfo(app_id, &error_detail, usage_info);
}

CdmResponseType WvContentDecryptionModule::GetUsageInfo(
    const std::string& app_id, const CdmSecureStopId& ssid,
    const CdmIdentifier& identifier, CdmUsageInfo* usage_info) {
  CdmEngine* cdm_engine = EnsureCdmForIdentifier(identifier);
  int error_detail = NO_ERROR;
  return cdm_engine->GetUsageInfo(app_id, ssid, &error_detail, usage_info);
}

CdmResponseType WvContentDecryptionModule::RemoveAllUsageInfo(
    const std::string& app_id, const CdmIdentifier& identifier) {
  CdmEngine* cdm_engine = EnsureCdmForIdentifier(identifier);
  return cdm_engine->RemoveAllUsageInfo(app_id);
}

CdmResponseType WvContentDecryptionModule::RemoveUsageInfo(
    const std::string& app_id, const CdmIdentifier& identifier,
    const CdmSecureStopId& secure_stop_id) {
  CdmEngine* cdm_engine = EnsureCdmForIdentifier(identifier);
  return cdm_engine->RemoveUsageInfo(app_id, secure_stop_id);
}

CdmResponseType WvContentDecryptionModule::ReleaseUsageInfo(
    const CdmUsageInfoReleaseMessage& message,
    const CdmIdentifier& identifier) {
  CdmEngine* cdm_engine = EnsureCdmForIdentifier(identifier);
  return cdm_engine->ReleaseUsageInfo(message);
}

CdmResponseType WvContentDecryptionModule::GetSecureStopIds(
    const std::string& app_id, const CdmIdentifier& identifier,
    std::vector<CdmSecureStopId>* ssids) {
  if (ssids == nullptr) {
    LOGE("Secure stop IDs destination not provided");
    return PARAMETER_NULL;
  }

  CdmEngine* cdm_engine = EnsureCdmForIdentifier(identifier);
  const CdmResponseType sts =
      cdm_engine->ListUsageIds(app_id, kSecurityLevelL1, nullptr, ssids);
  std::vector<CdmSecureStopId> secure_stop_ids;
  const CdmResponseType sts_l3 = cdm_engine->ListUsageIds(
      app_id, kSecurityLevelL3, nullptr, &secure_stop_ids);
  ssids->insert(ssids->end(), secure_stop_ids.begin(), secure_stop_ids.end());
  return sts_l3 != NO_ERROR ? sts_l3 : sts;
}

CdmResponseType WvContentDecryptionModule::Decrypt(
    const CdmSessionId& session_id, bool validate_key_id,
    const CdmDecryptionParameters& parameters) {
  return DecryptV16(session_id, validate_key_id,
                    CdmDecryptionParametersV16::from_v15(parameters));
}

CdmResponseType WvContentDecryptionModule::DecryptV16(
    const CdmSessionId& session_id, bool validate_key_id,
    const CdmDecryptionParametersV16& parameters) {
  // First find the CdmEngine that has the given session_id.  If we are using
  // key sharing, the shared session will still be in the same CdmEngine.
  CdmEngine* cdm_engine = GetCdmForSessionId(session_id);
  if (!cdm_engine) {
    LOGE("Decrypt session ID not found: %s", session_id.c_str());
    return SESSION_NOT_FOUND_18;
  }

  CdmSessionId local_session_id = session_id;
  if (validate_key_id && Properties::GetSessionSharingId(session_id) != 0) {
    bool status =
        cdm_engine->FindSessionForKey(parameters.key_id, &local_session_id);
    if (!status) {
      bool is_any_protected = std::any_of(
          std::begin(parameters.samples), std::end(parameters.samples),
          [](const CdmDecryptionSample& sample) -> bool {
            return std::any_of(
                std::begin(sample.subsamples), std::end(sample.subsamples),
                [](const CdmDecryptionSubsample& subsample) -> bool {
                  return subsample.protected_bytes > 0;
                });
          });

      // A key does not need to be loaded if
      // (a) the content consists of one or more samples and is entirely
      //     clear data
      // (b) (legacy) the content consists of clear lead/frame in a single
      //     subsample. In earlier releases content was presented for decryption
      //     as individual subsamples. If the clear frame is broken up across
      //     multiple subsamples decryption, requests should be rejected
      //     (b/110251447)
      // TODO(b/149524614): Remove support for the legacy case
      if (is_any_protected ||
          (parameters.observe_legacy_fields && parameters.samples.size() == 1 &&
           parameters.samples[0].subsamples.size() == 1 &&
           !(parameters.samples[0].subsamples[0].flags &
                 OEMCrypto_FirstSubsample &&
             parameters.samples[0].subsamples[0].flags &
                 OEMCrypto_LastSubsample))) {
        return KEY_NOT_FOUND_IN_SESSION;
      }
    }
  }
  return cdm_engine->DecryptV16(local_session_id, parameters);
}

void WvContentDecryptionModule::NotifyResolution(const CdmSessionId& session_id,
                                                 uint32_t width,
                                                 uint32_t height) {
  CdmEngine* cdm_engine = GetCdmForSessionId(session_id);
  if (!cdm_engine) return;
  cdm_engine->NotifyResolution(session_id, width, height);
}

bool WvContentDecryptionModule::IsValidServiceCertificate(
    const std::string& certificate) {
  ServiceCertificate cert;
  CdmResponseType status = cert.Init(certificate);
  if (status != NO_ERROR) return false;
  return cert.has_certificate();
}

CdmResponseType WvContentDecryptionModule::GetMetrics(
    std::vector<drm_metrics::WvCdmMetrics>* metrics, bool* full_list_returned) {
  if (!metrics || !full_list_returned) {
    return PARAMETER_NULL;
  }
  std::unique_lock<std::mutex> auto_lock(cdms_lock_);
  for (auto& key_value_pair : cdms_) {
    const CdmIdentifier& identifier = key_value_pair.first;
    drm_metrics::WvCdmMetrics metric;
    const CdmResponseType status = GetMetricsInternal(identifier, &metric);
    if (status == NO_ERROR) {
      metrics->push_back(metric);
    } else {
      LOGD("GetMetrics call failed: cdm identifier=%u, error=%d",
           identifier.unique_id, status);
    }
  }
  // With no streaming activities, |cdms_| size would be zero,
  // treat it as a non full list in that case.
  *full_list_returned = !cdms_.empty() && metrics->size() == cdms_.size();

  // We only return error if no metrics is returned when cdms_ is not empty.
  //  - metrics && cdms_ sizes can both be zero, returns NO_ERROR
  //  - metrics size <= cdms_, returns NO_ERROR
  //  - metrics is empty, but cdms_ is not, returns UNKNOWN_ERROR
  return (metrics->empty() && !cdms_.empty()) ? UNKNOWN_ERROR : NO_ERROR;
}

CdmResponseType WvContentDecryptionModule::GetMetrics(
    const CdmIdentifier& identifier, drm_metrics::WvCdmMetrics* metrics) {
  if (!metrics) {
    return PARAMETER_NULL;
  }
  std::unique_lock<std::mutex> auto_lock(cdms_lock_);
  return GetMetricsInternal(identifier, metrics);
}

CdmResponseType WvContentDecryptionModule::GetMetricsInternal(
    const CdmIdentifier& identifier, drm_metrics::WvCdmMetrics* metrics) {
  // Note: Caller should lock before calling.
  auto it = cdms_.find(identifier);
  if (it == cdms_.end()) {
    LOGE("Cdm Identifier not found");
    // TODO(blueeyes): Add a better error.
    return UNKNOWN_ERROR;
  }
  return it->second.cdm_engine->GetMetricsSnapshot(metrics) ? NO_ERROR
                                                            : UNKNOWN_ERROR;
}

WvContentDecryptionModule::CdmInfo::CdmInfo()
    : cdm_engine(CdmEngineFactory::CreateCdmEngine(&file_system)) {}

CdmEngine* WvContentDecryptionModule::EnsureCdmForIdentifier(
    const CdmIdentifier& identifier) {
  CdmEngine* cdm_engine;
  bool enable_timer = false;
  {
    std::unique_lock<std::mutex> auto_lock(cdms_lock_);
    if (cdms_.size() == 0) enable_timer = true;
    if (cdms_.find(identifier) == cdms_.end()) {
      // Accessing the map entry will create a new instance using the default
      // constructor. We then need to provide it with two pieces of info: The
      // origin provided by the app and an identifier that uniquely identifies
      // this CDM. We concatenate all pieces of the CdmIdentifier in order to
      // create an ID that is unique to that identifier.
      cdms_[identifier].file_system.set_origin(identifier.origin);
      cdms_[identifier].file_system.set_identifier(identifier.spoid +
                                                   identifier.origin);
      cdms_[identifier].cdm_engine->SetAppPackageName(
          identifier.app_package_name);
      cdms_[identifier].cdm_engine->SetSpoid(identifier.spoid);
      cdms_[identifier].cdm_engine->SetUserId(identifier.user_id);
    }
    cdm_engine = cdms_[identifier].cdm_engine.get();
  }
  // Do not enable timer while holding on to the |cdms_lock_|
  if (enable_timer) EnableTimer();

  return cdm_engine;
}

CdmEngine* WvContentDecryptionModule::GetCdmForSessionId(
    const std::string& session_id) {
  std::unique_lock<std::mutex> auto_lock(cdms_lock_);
  // Use find to avoid creating empty entries when not found.
  auto it = cdm_by_session_id_.find(session_id);
  if (it == cdm_by_session_id_.end()) return nullptr;
  return it->second;
}

void WvContentDecryptionModule::CloseAllCdms() {
  std::unique_lock<std::mutex> auto_lock(cdms_lock_);
  cdm_by_session_id_.clear();
  cdms_.clear();
}

CdmResponseType WvContentDecryptionModule::CloseCdm(
    const CdmIdentifier& cdm_identifier) {
  std::unique_lock<std::mutex> auto_lock(cdms_lock_);
  auto it = cdms_.find(cdm_identifier);
  if (it == cdms_.end()) {
    LOGE("Cdm Identifier not found");
    // TODO(blueeyes): Create a better error.
    return UNKNOWN_ERROR;
  }
  // Remove any sessions that point to this engine.
  for (auto session_it = cdm_by_session_id_.begin();
       session_it != cdm_by_session_id_.end();) {
    if (session_it->second == it->second.cdm_engine.get()) {
      session_it = cdm_by_session_id_.erase(session_it);
    } else {
      ++session_it;
    }
  }
  cdms_.erase(it);
  return NO_ERROR;
}

CdmResponseType WvContentDecryptionModule::SetDebugIgnoreKeyboxCount(
    uint32_t count) {
  return CdmEngine::SetDebugIgnoreKeyboxCount(count);
}

CdmResponseType WvContentDecryptionModule::SetDecryptHash(
    const std::string& hash_data, CdmSessionId* id) {
  if (id == nullptr) {
    LOGE("Cdm session ID not provided");
    return PARAMETER_NULL;
  }

  uint32_t frame_number;
  std::string hash;
  CdmResponseType res =
      CdmEngine::ParseDecryptHashString(hash_data, id, &frame_number, &hash);

  if (res != NO_ERROR) return res;

  CdmEngine* cdm_engine = GetCdmForSessionId(*id);

  if (!cdm_engine) {
    LOGE("Unable to find CdmEngine");
    return SESSION_NOT_FOUND_20;
  }

  res = cdm_engine->SetDecryptHash(*id, frame_number, hash);
  return res;
}

CdmResponseType WvContentDecryptionModule::GetDecryptHashError(
    const CdmSessionId& session_id, std::string* hash_error_string) {
  CdmEngine* cdm_engine = GetCdmForSessionId(session_id);

  if (!cdm_engine) {
    LOGE("Unable to find CdmEngine");
    return SESSION_NOT_FOUND_20;
  }
  return cdm_engine->GetDecryptHashError(session_id, hash_error_string);
}

void WvContentDecryptionModule::EnableTimer() {
  std::unique_lock<std::mutex> auto_lock(timer_lock_);
  if (!timer_.IsRunning()) timer_.Start(this, kCdmTimerDurationSeconds);
}

void WvContentDecryptionModule::DisableTimer() {
  std::unique_lock<std::mutex> auto_lock(timer_lock_);
  if (timer_.IsRunning()) {
    timer_.Stop(false);
  }
}

void WvContentDecryptionModule::DisableTimerAndWaitForExit() {
  std::unique_lock<std::mutex> auto_lock(timer_lock_);
  if (timer_.IsRunning()) {
    timer_.Stop(true);
  }
}

void WvContentDecryptionModule::OnTimerEvent() {
  bool disable_timer = false;
  {
    std::unique_lock<std::mutex> auto_lock(cdms_lock_);
    for (auto it = cdms_.begin(); it != cdms_.end(); ++it) {
      LoggingUidSetter set_uid(it->first.user_id);
      it->second.cdm_engine->OnTimerEvent();
    }
    if (cdms_.empty()) {
      // The following code cannot be attributed to any app uid.
      LoggingUidSetter set_uid(UNKNOWN_UID);
      if (CryptoSession::TryTerminate()) {
        // If CryptoSession is in a state to be terminated, try acquiring the
        // |timer_lock_| before deciding whether to disable the timer. If the
        // lock cannot be acquired, there is no need to disable the timer.
        // The |timer_lock_| is either being held by
        // * EnableTimer - This does not appear possible, but if it did
        //   happen |OnTimerEvent| will be called again. The timer can be
        //   disabled during a future call.
        // * DisableTimer - If so, allow that call to disable the timer. No
        //   need to call to disable it here.
        // * DisableTimerAndWaitForExit - If so, allow that call to disable
        //   the timer. No need to call to disable it here. Note that
        //   |DisableTimerAndWaitForExit| will try to stop the timer but
        //   wait for it to exit. This might kick off the timer thread one
        //   last time, which will call into OnTimerEvent. Calling
        //   |DisableTimer| here will result in deadlock.
        if (timer_lock_.try_lock()) {
          disable_timer = true;
          timer_lock_.unlock();
        }
      }
    }
  }

  // Release |cdms_lock_| before attempting to disable the timer
  if (disable_timer) {
    DisableTimer();
  }
}

uint32_t WvContentDecryptionModule::GenerateSessionSharingId() {
  static int next_session_sharing_id = 0;
  return ++next_session_sharing_id;
}

CdmResponseType WvContentDecryptionModule::ListStoredLicenses(
    CdmSecurityLevel security_level, const CdmIdentifier& identifier,
    std::vector<CdmKeySetId>* key_set_ids) {
  CdmEngine* cdm_engine = EnsureCdmForIdentifier(identifier);
  return cdm_engine->ListStoredLicenses(security_level, key_set_ids);
}

CdmResponseType WvContentDecryptionModule::GetOfflineLicenseState(
    const CdmKeySetId& key_set_id, CdmSecurityLevel security_level,
    const CdmIdentifier& identifier, CdmOfflineLicenseState* license_state) {
  CdmEngine* cdm_engine = EnsureCdmForIdentifier(identifier);
  return cdm_engine->GetOfflineLicenseState(key_set_id, security_level,
                                            license_state);
}

CdmResponseType WvContentDecryptionModule::RemoveOfflineLicense(
    const CdmKeySetId& key_set_id, CdmSecurityLevel security_level,
    const CdmIdentifier& identifier) {
  CdmEngine* cdm_engine = EnsureCdmForIdentifier(identifier);
  return cdm_engine->RemoveOfflineLicense(key_set_id, security_level);
}

CdmResponseType WvContentDecryptionModule::SetPlaybackId(
    const CdmSessionId& session_id, const std::string& playback_id) {
  LOGV("Setting session ID %s playback ID %s", session_id.c_str(),
       playback_id.c_str());
  CdmEngine* cdm_engine = GetCdmForSessionId(session_id);
  if (!cdm_engine) return SESSION_NOT_FOUND_23;
  return cdm_engine->SetPlaybackId(session_id, playback_id);
}

CdmResponseType WvContentDecryptionModule::GetSessionUserId(
    const CdmSessionId& session_id, uint32_t* user_id) {
  if (!user_id) return PARAMETER_NULL;
  CdmEngine* cdm_engine = GetCdmForSessionId(session_id);
  if (!cdm_engine) return SESSION_NOT_FOUND_23;
  *user_id = cdm_engine->GetUserId();
  return NO_ERROR;
}
}  // namespace wvcdm