android-15.0.0_r3/s

/*
 * Copyright (C) 2023 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.
 */

package com.android.systemui.authentication.domain.interactor

import android.app.admin.flags.Flags
import android.os.UserHandle
import com.android.internal.widget.LockPatternUtils
import com.android.internal.widget.LockPatternView
import com.android.internal.widget.LockscreenCredential
import com.android.systemui.authentication.data.repository.AuthenticationRepository
import com.android.systemui.authentication.shared.model.AuthenticationMethodModel
import com.android.systemui.authentication.shared.model.AuthenticationMethodModel.Password
import com.android.systemui.authentication.shared.model.AuthenticationMethodModel.Pattern
import com.android.systemui.authentication.shared.model.AuthenticationMethodModel.Pin
import com.android.systemui.authentication.shared.model.AuthenticationPatternCoordinate
import com.android.systemui.authentication.shared.model.AuthenticationWipeModel
import com.android.systemui.authentication.shared.model.AuthenticationWipeModel.WipeTarget
import com.android.systemui.dagger.SysUISingleton
import com.android.systemui.dagger.qualifiers.Application
import com.android.systemui.dagger.qualifiers.Background
import com.android.systemui.user.domain.interactor.SelectedUserInteractor
import com.android.systemui.util.time.SystemClock
import javax.inject.Inject
import kotlin.math.max
import kotlin.time.Duration
import kotlin.time.Duration.Companion.seconds
import kotlinx.coroutines.CoroutineDispatcher
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.delay
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.MutableSharedFlow
import kotlinx.coroutines.flow.SharedFlow
import kotlinx.coroutines.flow.SharingStarted
import kotlinx.coroutines.flow.StateFlow
import kotlinx.coroutines.flow.asSharedFlow
import kotlinx.coroutines.flow.combine
import kotlinx.coroutines.flow.map
import kotlinx.coroutines.flow.stateIn
import kotlinx.coroutines.launch

/**
 * Hosts application business logic related to user authentication.
 *
 * Note: there is a distinction between authentication (determining a user's identity) and device
 * entry (dismissing the lockscreen). For logic that is specific to device entry, please use
 * `DeviceEntryInteractor` instead.
 */
@SysUISingleton
class AuthenticationInteractor
@Inject
constructor(
    @Application private val applicationScope: CoroutineScope,
    @Background private val backgroundDispatcher: CoroutineDispatcher,
    private val repository: AuthenticationRepository,
    private val selectedUserInteractor: SelectedUserInteractor,
) {
    /**
     * The currently-configured authentication method. This determines how the authentication
     * challenge needs to be completed in order to unlock an otherwise locked device.
     *
     * Note: there may be other ways to unlock the device that "bypass" the need for this
     * authentication challenge (notably, biometrics like fingerprint or face unlock).
     *
     * Note: by design, this is a [Flow] and not a [StateFlow]; a consumer who wishes to get a
     * snapshot of the current authentication method without establishing a collector of the flow
     * can do so by invoking [getAuthenticationMethod].
     *
     * Note: this layer adds the synthetic authentication method of "swipe" which is special. When
     * the current authentication method is "swipe", the user does not need to complete any
     * authentication challenge to unlock the device; they just need to dismiss the lockscreen to
     * get past it. This also means that the value of `DeviceEntryInteractor#isUnlocked` remains
     * `true` even when the lockscreen is showing and still needs to be dismissed by the user to
     * proceed.
     */
    val authenticationMethod: Flow<AuthenticationMethodModel> = repository.authenticationMethod

    /**
     * Whether the auto confirm feature is enabled for the currently-selected user.
     *
     * Note that the length of the PIN is also important to take into consideration, please see
     * [hintedPinLength].
     */
    val isAutoConfirmEnabled: StateFlow<Boolean> =
        combine(repository.isAutoConfirmFeatureEnabled, repository.hasLockoutOccurred) {
                featureEnabled,
                hasLockoutOccurred ->
                // Disable auto-confirm if lockout occurred since the last successful
                // authentication attempt.
                featureEnabled && !hasLockoutOccurred
            }
            .stateIn(
                scope = applicationScope,
                started = SharingStarted.WhileSubscribed(),
                initialValue = false,
            )

    /** The length of the hinted PIN, or `null` if pin length hint should not be shown. */
    val hintedPinLength: StateFlow<Int?> =
        isAutoConfirmEnabled
            .map { isAutoConfirmEnabled ->
                repository.getPinLength().takeIf {
                    isAutoConfirmEnabled && it == repository.hintedPinLength
                }
            }
            .stateIn(
                scope = applicationScope,
                // Make sure this is kept as WhileSubscribed or we can run into a bug where the
                // downstream continues to receive old/stale/cached values.
                started = SharingStarted.WhileSubscribed(),
                initialValue = null,
            )

    /** Whether the pattern should be visible for the currently-selected user. */
    val isPatternVisible: StateFlow<Boolean> = repository.isPatternVisible

    private val _onAuthenticationResult = MutableSharedFlow<Boolean>()
    /**
     * Emits the outcome (successful or unsuccessful) whenever a PIN/Pattern/Password security
     * challenge is attempted by the user in order to unlock the device.
     */
    val onAuthenticationResult: SharedFlow<Boolean> = _onAuthenticationResult.asSharedFlow()

    /** Whether the "enhanced PIN privacy" setting is enabled for the current user. */
    val isPinEnhancedPrivacyEnabled: StateFlow<Boolean> = repository.isPinEnhancedPrivacyEnabled

    /**
     * The number of failed authentication attempts for the selected user since the last successful
     * authentication.
     */
    val failedAuthenticationAttempts: StateFlow<Int> = repository.failedAuthenticationAttempts

    /**
     * Timestamp for when the current lockout (aka "throttling") will end, allowing the user to
     * attempt authentication again. Returns `null` if no lockout is active.
     *
     * To be notified whenever a lockout is started, the caller should subscribe to
     * [onAuthenticationResult].
     *
     * Note that the value is in milliseconds and matches [SystemClock.elapsedRealtime].
     *
     * Also note that the value may change when the selected user is changed.
     */
    val lockoutEndTimestamp: Long?
        get() = repository.lockoutEndTimestamp

    /**
     * Models an imminent wipe risk to the user, profile, or device upon further unsuccessful
     * authentication attempts.
     *
     * Returns `null` when there is no risk of wipe yet, or when there's no wipe policy set by the
     * DevicePolicyManager.
     */
    val upcomingWipe: Flow<AuthenticationWipeModel?> =
        repository.failedAuthenticationAttempts.map { failedAttempts ->
            val failedAttemptsBeforeWipe = repository.getMaxFailedUnlockAttemptsForWipe()
            if (failedAttemptsBeforeWipe == 0) {
                return@map null // There is no restriction.
            }

            // The user has a DevicePolicyManager that requests a user/profile to be wiped after N
            // attempts. Once the grace period is reached, show a dialog every time as a clear
            // warning until the deletion fires.
            val remainingAttemptsBeforeWipe = max(0, failedAttemptsBeforeWipe - failedAttempts)
            if (remainingAttemptsBeforeWipe >= LockPatternUtils.FAILED_ATTEMPTS_BEFORE_WIPE_GRACE) {
                return@map null // There is no current risk of wiping the device.
            }

            AuthenticationWipeModel(
                wipeTarget = getWipeTarget(),
                failedAttempts = failedAttempts,
                remainingAttempts = remainingAttemptsBeforeWipe,
            )
        }

    /**
     * Returns the currently-configured authentication method. This determines how the
     * authentication challenge needs to be completed in order to unlock an otherwise locked device.
     *
     * Note: there may be other ways to unlock the device that "bypass" the need for this
     * authentication challenge (notably, biometrics like fingerprint or face unlock).
     *
     * Note: by design, this is offered as a convenience method alongside [authenticationMethod].
     * The flow should be used for code that wishes to stay up-to-date its logic as the
     * authentication changes over time and this method should be used for simple code that only
     * needs to check the current value.
     */
    suspend fun getAuthenticationMethod() = repository.getAuthenticationMethod()

    /**
     * Attempts to authenticate the user and unlock the device. May trigger lockout or wipe the
     * user/profile/device data upon failure.
     *
     * If [tryAutoConfirm] is `true`, authentication is attempted if and only if the auth method
     * supports auto-confirming, and the input's length is at least the required length. Otherwise,
     * `AuthenticationResult.SKIPPED` is returned.
     *
     * @param input The input from the user to try to authenticate with. This can be a list of
     *   different things, based on the current authentication method.
     * @param tryAutoConfirm `true` if called while the user inputs the code, without an explicit
     *   request to validate.
     * @return The result of this authentication attempt.
     */
    suspend fun authenticate(
        input: List<Any>,
        tryAutoConfirm: Boolean = false
    ): AuthenticationResult {
        if (input.isEmpty()) {
            throw IllegalArgumentException("Input was empty!")
        }

        val authMethod = getAuthenticationMethod()
        if (shouldSkipAuthenticationAttempt(authMethod, tryAutoConfirm, input.size)) {
            return AuthenticationResult.SKIPPED
        }

        // Attempt to authenticate:
        val credential = authMethod.createCredential(input) ?: return AuthenticationResult.SKIPPED
        val authenticationResult = repository.checkCredential(credential)
        credential.zeroize()

        if (authenticationResult.isSuccessful) {
            repository.reportAuthenticationAttempt(isSuccessful = true)
            _onAuthenticationResult.emit(true)

            // Force a garbage collection in an attempt to erase any credentials left in memory.
            // Do it after a 5-sec delay to avoid making the bouncer dismiss animation janky.
            initiateGarbageCollection(delay = 5.seconds)

            return AuthenticationResult.SUCCEEDED
        }

        // Authentication failed.
        repository.reportAuthenticationAttempt(isSuccessful = false)

        if (authenticationResult.lockoutDurationMs > 0) {
            // Lockout has been triggered.
            repository.reportLockoutStarted(authenticationResult.lockoutDurationMs)
        }

        _onAuthenticationResult.emit(false)
        return AuthenticationResult.FAILED
    }

    private suspend fun shouldSkipAuthenticationAttempt(
        authenticationMethod: AuthenticationMethodModel,
        isAutoConfirmAttempt: Boolean,
        inputLength: Int,
    ): Boolean {
        return when {
            // Lockout is active, the UI layer should not have called this; skip the attempt.
            repository.lockoutEndTimestamp != null -> true
            // Auto-confirm attempt when the feature is not enabled; skip the attempt.
            isAutoConfirmAttempt && !isAutoConfirmEnabled.value -> true
            // The pin is too short; skip only if this is an auto-confirm attempt.
            authenticationMethod == Pin && authenticationMethod.isInputTooShort(inputLength) ->
                isAutoConfirmAttempt
            // The input is too short.
            authenticationMethod.isInputTooShort(inputLength) -> true
            else -> false
        }
    }

    private suspend fun AuthenticationMethodModel.isInputTooShort(inputLength: Int): Boolean {
        return when (this) {
            Pattern -> inputLength < repository.minPatternLength
            Password -> inputLength < repository.minPasswordLength
            Pin -> inputLength < repository.getPinLength()
            else -> false
        }
    }

    /**
     * @return Whether the current user, managed profile or whole device is next at risk of wipe.
     */
    private suspend fun getWipeTarget(): WipeTarget {
        // Check which profile has the strictest policy for failed authentication attempts.
        val userToBeWiped = repository.getProfileWithMinFailedUnlockAttemptsForWipe()
        val primaryUser =
            if (Flags.headlessSingleUserFixes()) {
                selectedUserInteractor.getMainUserId() ?: UserHandle.USER_SYSTEM
            } else {
                UserHandle.USER_SYSTEM
            }
        return when (userToBeWiped) {
            selectedUserInteractor.getSelectedUserId() ->
                if (userToBeWiped == primaryUser) {
                    WipeTarget.WholeDevice
                } else {
                    WipeTarget.User
                }

            // Shouldn't happen at this stage; this is to maintain legacy behavior.
            UserHandle.USER_NULL -> WipeTarget.WholeDevice
            else -> WipeTarget.ManagedProfile
        }
    }

    private fun AuthenticationMethodModel.createCredential(
        input: List<Any>
    ): LockscreenCredential? {
        return when (this) {
            is Pin -> LockscreenCredential.createPin(input.joinToString(""))
            is Password -> LockscreenCredential.createPassword(input.joinToString(""))
            is Pattern ->
                LockscreenCredential.createPattern(
                    input
                        .map { it as AuthenticationPatternCoordinate }
                        .map { LockPatternView.Cell.of(it.y, it.x) }
                )
            else -> null
        }
    }

    private suspend fun initiateGarbageCollection(delay: Duration) {
        applicationScope.launch(backgroundDispatcher) {
            delay(delay)
            System.gc()
            System.runFinalization()
            System.gc()
        }
    }

    companion object {
        const val TAG = "AuthenticationInteractor"
    }
}

/** Result of a user authentication attempt. */
enum class AuthenticationResult {
    /** Authentication succeeded. */
    SUCCEEDED,
    /** Authentication failed. */
    FAILED,
    /** Authentication was not performed, e.g. due to insufficient input. */
    SKIPPED,
}