Initial biometric authentication support (#541)

* [WIP] Initial biometric authentication support

* Redirect decryption app shortcut to go through LaunchActivity

* UserPreference: Clear existing shortcuts when toggling password auth

Clears out any auth-bypassed entries that exist

* Fix hilarious copypasta derp

Signed-off-by: Harsh Shandilya <msfjarvis@gmail.com>

2 files changed, 77 insertions, 0 deletions

diff --git a/app/src/main/java/com/zeapo/pwdstore/utils/auth/AuthenticationResult.kt b/app/src/main/java/com/zeapo/pwdstore/utils/auth/AuthenticationResult.kt
new file mode 100644
index 00000000..d8530ba3
--- /dev/null
+++ b/app/src/main/java/com/zeapo/pwdstore/utils/auth/AuthenticationResult.kt
@@ -0,0 +1,14 @@
+package com.zeapo.pwdstore.utils.auth
+
+import androidx.biometric.BiometricPrompt
+
+internal sealed class AuthenticationResult {
+    internal data class Success(val cryptoObject: BiometricPrompt.CryptoObject?) :
+            AuthenticationResult()
+    internal data class RecoverableError(val code: Int, val message: CharSequence) :
+            AuthenticationResult()
+    internal data class UnrecoverableError(val code: Int, val message: CharSequence) :
+            AuthenticationResult()
+    internal object Failure : AuthenticationResult()
+    internal object Cancelled : AuthenticationResult()
+}
diff --git a/app/src/main/java/com/zeapo/pwdstore/utils/auth/Authenticator.kt b/app/src/main/java/com/zeapo/pwdstore/utils/auth/Authenticator.kt
new file mode 100644
index 00000000..5139ef01
--- /dev/null
+++ b/app/src/main/java/com/zeapo/pwdstore/utils/auth/Authenticator.kt
@@ -0,0 +1,63 @@
+package com.zeapo.pwdstore.utils.auth
+
+import android.os.Handler
+import android.util.Log
+import androidx.biometric.BiometricManager
+import androidx.biometric.BiometricPrompt
+import androidx.fragment.app.FragmentActivity
+import com.zeapo.pwdstore.R
+
+internal class Authenticator(
+        private val fragmentActivity: FragmentActivity,
+        private val callback: (AuthenticationResult) -> Unit
+) {
+    private val handler = Handler()
+    private val biometricManager = BiometricManager.from(fragmentActivity)
+
+    private val authCallback = object : BiometricPrompt.AuthenticationCallback() {
+
+        override fun onAuthenticationError(errorCode: Int, errString: CharSequence) {
+            super.onAuthenticationError(errorCode, errString)
+            Log.d(TAG,"Error: $errorCode: $errString")
+            callback(AuthenticationResult.UnrecoverableError(errorCode, errString))
+        }
+
+        override fun onAuthenticationFailed() {
+            super.onAuthenticationFailed()
+            Log.d(TAG, "Failed")
+            callback(AuthenticationResult.Failure)
+        }
+
+        override fun onAuthenticationSucceeded(result: BiometricPrompt.AuthenticationResult) {
+            super.onAuthenticationSucceeded(result)
+            Log.d(TAG, "Success")
+            callback(AuthenticationResult.Success(result.cryptoObject))
+        }
+    }
+
+    private val biometricPrompt = BiometricPrompt(
+            fragmentActivity,
+            { runnable -> handler.post(runnable) },
+            authCallback
+    )
+
+    private val promptInfo = BiometricPrompt.PromptInfo.Builder()
+            .setTitle(fragmentActivity.getString(R.string.biometric_prompt_title))
+            .setNegativeButtonText(fragmentActivity.getString(R.string.biometric_prompt_negative_text))
+            .build()
+
+    fun authenticate() {
+        if (biometricManager.canAuthenticate() != BiometricManager.BIOMETRIC_SUCCESS) {
+            callback(AuthenticationResult.UnrecoverableError(
+                    0,
+                    fragmentActivity.getString(R.string.biometric_prompt_no_hardware)
+            ))
+        } else {
+            biometricPrompt.authenticate(promptInfo)
+        }
+    }
+
+    companion object {
+        private const val TAG = "Authenticator"
+    }
+}