media_cas_client/plugin/include/policy_engine.h

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

#ifndef WIDEVINE_CAS_POLICY_ENGINE_H_
#define WIDEVINE_CAS_POLICY_ENGINE_H_

#include <map>
#include <memory>
#include <string>

#include "cas_util.h"
#include "clock.h"
#include "crypto_session.h"
#include "license_key_status.h"
#include "license_protocol.pb.h"
#include "timer.h"

namespace wvcas {

// This acts as an oracle that basically says "Yes(true) you may still decrypt
// or no(false) you may not decrypt this data anymore."
// TODO(jfore): Just pass in a function object? OnTimerEvent can be a
class PolicyEngine : public wvutil::TimerHandler {
  typedef enum {
    kLicenseStateInitial,
    kLicenseStatePending,  // if license is issued for sometime in the future
    kLicenseStateCanPlay,
    kLicenseStateNeedRenewal,
    kLicenseStateWaitingLicenseUpdate,
    kLicenseStateExpired
  } LicenseState;

 public:
  // The default constructor.
  PolicyEngine() {}
  virtual ~PolicyEngine() {}

  virtual void initialize(std::shared_ptr<CryptoSession> crypto_session,
                          CasEventListener* event_listener) {
    license_keys_ = CreateLicenseKeys();
    clock_ = CreateClock();
    event_listener_ = event_listener;
    crypto_session_ = crypto_session;
  }

  // The value returned should be taken as a hint rather than an absolute
  // status. It is computed during the last call to either SetLicense/
  // UpdateLicense/OnTimerEvent/BeginDecryption and may be out of sync
  // depending on the amount of time elapsed. The current decryption
  // status is not calculated to avoid overhead in the decryption path.
  virtual bool CanDecryptContent(const KeyId& key_id) const;

  // The value returned indicates if a license renewal is allowed under the
  // current policy.
  virtual bool CanRenew() const { return policy_.can_renew(); }

  // The value returned indicates if the license is persisted to non-volatile
  // storage for offline use.
  virtual bool CanPersist() const { return policy_.can_persist(); }

  // The value returned indicates whether or not the client id should be
  // included in renewal requests.
  virtual bool always_include_client_id() const {
    return policy_.always_include_client_id();
  }

  // The value returned is the current license id.
  virtual const video_widevine::LicenseIdentification& license_id() const {
    return license_id_;
  }

  virtual const std::string& renewal_server_url() const {
    return policy_.renewal_server_url();
  }

  // SetLicense is used in handling the initial license response. It stores
  // an exact copy of the policy information stored in the license.
  // The license state transitions to kLicenseStateCanPlay if the license
  // permits playback.
  virtual void SetLicense(const video_widevine::License& license);

  // UpdateLicense is used in handling a license response for a renewal request.
  // The response may only contain any policy fields that have changed. In this
  // case an exact copy is not what we want to happen. We also will receive an
  // updated license_start_time from the server. The license will transition to
  // kLicenseStateCanPlay if the license permits playback.
  virtual void UpdateLicense(const video_widevine::License& license);

  // Call this on first decrypt to set the start of playback.
  virtual void BeginDecryption(void);

  // OnTimerEvent is called when a timer fires. It notifies the Policy Engine
  // that the timer has fired and dispatches the relevant events through
  // |event_listener_|.
  virtual void OnTimerEvent() override;

  // Used to update the currently loaded entitled content keys.
  virtual void SetEntitledLicenseKeys(
      const std::vector<WidevinePsshData_EntitledKey>& entitled_keys);

  // Used to query if the current license state is expired.
  virtual bool IsExpired() const {
    return license_state_ == kLicenseStateExpired;
  }

  // for offline save and restore
  int64_t GetPlaybackStartTime() const { return playback_start_time_; }
  int64_t GetLastPlaybackTime() const { return last_playback_time_; }
  int64_t GetGracePeriodEndTime() const { return grace_period_end_time_; }
  void RestorePlaybackTimes(int64_t playback_start_time,
                            int64_t last_playback_time,
                            int64_t grace_period_end_time);

  PolicyEngine(const PolicyEngine&) = delete;
  PolicyEngine& operator=(const PolicyEngine&) = delete;

 private:
  // Notifies updates in keys information and fire OnKeysChange event if
  // key changes.
  void NotifyKeysChange(KeyStatus new_status);

  void NotifyLicenseExpired(LicenseState key_status);

  bool HasLicenseOrPlaybackDurationExpired(int64_t current_time);

  // Notifies updates in expiry time and fire OnExpirationUpdate event if
  // expiry time changes.
  void NotifyExpirationUpdate(int64_t current_time);

  // Notify listeners of the current renewal url.
  void NotifyRenewalServerUpdate();

  // Guard against clock rollbacks
  int64_t GetCurrentTime();

  LicenseState license_state_ = kLicenseStateInitial;

  void CheckDeviceHdcpStatus();

  // Gets the clock time that the license expires based on whether we have
  // started playing.  This takes into account GetHardLicenseExpiryTime.
  int64_t GetExpiryTime(int64_t current_time,
                        bool ignore_soft_enforce_playback_duration);

  void CheckDeviceHdcpStatusOnTimer(int64_t current_time);

  bool HasPlaybackStarted(int64_t current_time) {
    if (playback_start_time_ == 0) return false;

    const int64_t playback_time = current_time - playback_start_time_;
    return playback_time >= policy_.play_start_grace_period_seconds();
  }

  // Gets the clock time that the rental duration will expire, using the license
  // duration if one is not present.
  int64_t GetRentalExpiryTime();

  // Gets the clock time that the license expires.  This is the hard limit that
  // all license types must obey at all times.
  int64_t GetHardLicenseExpiryTime();

  bool HasRenewalDelayExpired(int64_t current_time);

  bool HasRenewalRetryIntervalExpired(int64_t current_time);

  void UpdateRenewalRequest(int64_t current_time);

  virtual std::unique_ptr<wvcas::LicenseKeys> CreateLicenseKeys();

  virtual std::unique_ptr<wvutil::Clock> CreateClock();

  // This is the current policy information for this license. This gets updated
  // as license renewals occur.
  video_widevine::License::Policy policy_;

  // This is the license id field from server response. This data gets passed
  // back to the server in each renewal request. When we get a renewal response
  // from the license server we will get an updated id field.
  video_widevine::LicenseIdentification license_id_;

  // The server returns the license start time in the license/license renewal
  // response based off the request time sent by the client in the
  // license request/renewal
  int64_t license_start_time_ = 0;
  int64_t playback_start_time_ = 0;
  int64_t last_playback_time_ = 0;
  int64_t grace_period_end_time_ = 0;
  bool last_expiry_time_set_ = false;
  bool was_expired_on_load_ = false;

  // This is used as a reference point for policy management. This value
  // represents an offset from license_start_time_. This is used to
  // calculate the time where renewal retries should occur.
  int64_t next_renewal_time_ = 0;

  CasEventListener* event_listener_ = nullptr;

  // Keys associated with license - holds allowed usage, usage constraints,
  // and current status (KeyStatus)
  std::unique_ptr<LicenseKeys> license_keys_;
  std::unique_ptr<wvutil::Clock> clock_;
  // to assist in clock rollback checks
  int64_t last_recorded_current_time_ = 0;
  int64_t last_expiry_time_ = 0;
  int64_t next_device_check_ = 0;
  std::shared_ptr<wvcas::CryptoSession> crypto_session_;
  uint32_t current_resolution_ = 0;
  std::string renewal_server_url_;
};

}  // namespace wvcas

#endif  // WIDEVINE_CAS_POLICY_ENGINE_H_