1 files changed, 110 insertions, 0 deletions
diff --git a/app/src/main/kotlin/com/pitchedapps/frost/utils/BiometricUtils.kt b/app/src/main/kotlin/com/pitchedapps/frost/utils/BiometricUtils.kt
new file mode 100644
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+++ b/app/src/main/kotlin/com/pitchedapps/frost/utils/BiometricUtils.kt
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+/*
+ * Copyright 2019 Allan Wang
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package com.pitchedapps.frost.utils
+
+import android.content.Context
+import android.hardware.fingerprint.FingerprintManager
+import android.os.Build
+import androidx.biometric.BiometricPrompt
+import androidx.fragment.app.FragmentActivity
+import ca.allanwang.kau.utils.string
+import com.pitchedapps.frost.R
+import kotlinx.coroutines.CompletableDeferred
+import java.util.concurrent.Executor
+import java.util.concurrent.ExecutorService
+import java.util.concurrent.Executors
+
+typealias BiometricDeferred = CompletableDeferred<BiometricPrompt.CryptoObject?>
+
+/**
+ * Container for [BiometricPrompt]
+ * Inspired by coroutine's CommonPool
+ */
+object BiometricUtils {
+
+    private val executor: Executor
+        get() = pool ?: getOrCreatePoolSync()
+
+    @Volatile
+    private var pool: ExecutorService? = null
+
+    private var lastUnlockTime = -1L
+
+    private const val UNLOCK_TIME_INTERVAL = 15 * 60 * 1000
+
+    /**
+     * Checks if biometric authentication is possible
+     * Currently, this means checking for enrolled fingerprints
+     */
+    @Suppress("DEPRECATION")
+    fun isSupported(context: Context): Boolean {
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) return false
+        val fingerprintManager = context.getSystemService(FingerprintManager::class.java) ?: return false
+        return fingerprintManager.isHardwareDetected && fingerprintManager.hasEnrolledFingerprints()
+    }
+
+    private fun getOrCreatePoolSync(): Executor =
+        pool ?: Executors.newSingleThreadExecutor().also { pool = it }
+
+    private fun shouldPrompt(context: Context): Boolean {
+        return Prefs.biometricsEnabled && System.currentTimeMillis() - lastUnlockTime > UNLOCK_TIME_INTERVAL
+    }
+
+    fun authenticate(activity: FragmentActivity, force: Boolean = false): BiometricDeferred {
+        val deferred: BiometricDeferred = CompletableDeferred()
+        if (!force && !shouldPrompt(activity)) {
+            deferred.complete(null)
+            return deferred
+        }
+        val info = BiometricPrompt.PromptInfo.Builder()
+            .setTitle(activity.string(R.string.biometrics_prompt_title))
+            .setNegativeButtonText(activity.string(R.string.kau_cancel))
+            .build()
+        BiometricPrompt(activity, executor, Callback(activity, deferred)).authenticate(info)
+        return deferred
+    }
+
+    private class Callback(val activity: FragmentActivity, val deferred: BiometricDeferred) :
+        BiometricPrompt.AuthenticationCallback() {
+        override fun onAuthenticationError(errorCode: Int, errString: CharSequence) {
+            deferred.cancel()
+            activity.finish()
+        }
+
+        override fun onAuthenticationSucceeded(result: BiometricPrompt.AuthenticationResult) {
+            lastUnlockTime = System.currentTimeMillis()
+            deferred.complete(result.cryptoObject)
+        }
+
+        override fun onAuthenticationFailed() {
+            deferred.cancel()
+            activity.finish()
+        }
+    }
+
+    /**
+     * For completeness we provide a shutdown function.
+     * In practice, we initialize the executor only when it is first used,
+     * and keep it alive throughout the app lifecycle, as it will be used an arbitrary number of times,
+     * with unknown frequency
+     */
+    @Synchronized
+    fun shutdown() {
+        pool?.shutdown()
+        pool = null
+    }
+}