biometrics/fingerprint/aidl/default/include/Session.h

/*
 * Copyright (C) 2020 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#pragma once

#include <aidl/android/hardware/biometrics/fingerprint/BnSession.h>
#include <aidl/android/hardware/biometrics/fingerprint/ISessionCallback.h>

#include "FakeFingerprintEngine.h"
#include "WorkerThread.h"

namespace aidl::android::hardware::biometrics::fingerprint {

namespace common = aidl::android::hardware::biometrics::common;
namespace keymaster = aidl::android::hardware::keymaster;

enum class SessionState {
    IDLING,
    CLOSED,
    GENERATING_CHALLENGE,
    REVOKING_CHALLENGE,
    ENROLLING,
    AUTHENTICATING,
    DETECTING_INTERACTION,
    ENUMERATING_ENROLLMENTS,
    REMOVING_ENROLLMENTS,
    GETTING_AUTHENTICATOR_ID,
    INVALIDATING_AUTHENTICATOR_ID,
    RESETTING_LOCKOUT,
};

class Session : public BnSession {
  public:
    Session(int sensorId, int userId, std::shared_ptr<ISessionCallback> cb,
            FakeFingerprintEngine* engine, WorkerThread* worker);

    ndk::ScopedAStatus generateChallenge() override;

    ndk::ScopedAStatus revokeChallenge(int64_t challenge) override;

    ndk::ScopedAStatus enroll(const keymaster::HardwareAuthToken& hat,
                              std::shared_ptr<common::ICancellationSignal>* out) override;

    ndk::ScopedAStatus authenticate(int64_t operationId,
                                    std::shared_ptr<common::ICancellationSignal>* out) override;

    ndk::ScopedAStatus detectInteraction(
            std::shared_ptr<common::ICancellationSignal>* out) override;

    ndk::ScopedAStatus enumerateEnrollments() override;

    ndk::ScopedAStatus removeEnrollments(const std::vector<int32_t>& enrollmentIds) override;

    ndk::ScopedAStatus getAuthenticatorId() override;

    ndk::ScopedAStatus invalidateAuthenticatorId() override;

    ndk::ScopedAStatus resetLockout(const keymaster::HardwareAuthToken& hat) override;

    ndk::ScopedAStatus close() override;

    ndk::ScopedAStatus onPointerDown(int32_t pointerId, int32_t x, int32_t y, float minor,
                                     float major) override;

    ndk::ScopedAStatus onPointerUp(int32_t pointerId) override;

    ndk::ScopedAStatus onUiReady() override;

    bool isClosed();

  private:
    // Crashes the HAL if it's not currently idling because that would be an invalid state machine
    // transition. Otherwise, sets the scheduled state to the given state.
    void scheduleStateOrCrash(SessionState state);

    // Crashes the HAL if the provided state doesn't match the previously scheduled state.
    // Otherwise, transitions into the provided state, clears the scheduled state, and notifies
    // the client about the transition by calling ISessionCallback#onStateChanged.
    void enterStateOrCrash(SessionState state);

    // Sets the current state to SessionState::IDLING and notifies the client about the transition
    // by calling ISessionCallback#onStateChanged.
    void enterIdling();

    // The sensor and user IDs for which this session was created.
    int32_t mSensorId;
    int32_t mUserId;

    // Callback for talking to the framework. This callback must only be called from non-binder
    // threads to prevent nested binder calls and consequently a binder thread exhaustion.
    // Practically, it means that this callback should always be called from the worker thread.
    std::shared_ptr<ISessionCallback> mCb;

    // Module that communicates to the actual fingerprint hardware, keystore, TEE, etc. In real
    // life such modules typically consume a lot of memory and are slow to initialize. This is here
    // to showcase how such a module can be used within a Session without incurring the high
    // initialization costs every time a Session is constructed.
    FakeFingerprintEngine* mEngine;

    // Worker thread that allows to schedule tasks for asynchronous execution.
    WorkerThread* mWorker;

    // Simple representation of the session's state machine. These are atomic because they can be
    // modified from both the main and the worker threads.
    std::atomic<SessionState> mScheduledState;
    std::atomic<SessionState> mCurrentState;
};

}  // namespace aidl::android::hardware::biometrics::fingerprint