Refactor BiometricAuthenticator and add proper support for retries (#1627)

Author: msfjarvis

CHANGELOG.md

@@ -23,6 +23,7 @@ All notable changes to this project will be documented in this file.
 -   .gpg-id file generated by APS did not work with pass CLI
 -   All but the latest launcher shortcut would have an empty icon
 -   When prompted to select a GPG key during onboarding, the app would crash if the user did not make a selection in OpenKeychain
+-   Biometric authentication prompts no longer inexplicably dismiss when an incorrect biometric is entered
 
 ### Changed
 

app/src/main/java/dev/msfjarvis/aps/ui/main/LaunchActivity.kt

@@ -14,6 +14,7 @@ import dev.msfjarvis.aps.ui.crypto.BasePgpActivity
 import dev.msfjarvis.aps.ui.crypto.DecryptActivity
 import dev.msfjarvis.aps.ui.passwords.PasswordStore
 import dev.msfjarvis.aps.util.auth.BiometricAuthenticator
+import dev.msfjarvis.aps.util.auth.BiometricAuthenticator.Result
 import dev.msfjarvis.aps.util.extensions.sharedPrefs
 import dev.msfjarvis.aps.util.settings.PreferenceKeys
 
@@ -23,18 +24,19 @@ class LaunchActivity : AppCompatActivity() {
     super.onCreate(savedInstanceState)
     val prefs = sharedPrefs
     if (prefs.getBoolean(PreferenceKeys.BIOMETRIC_AUTH, false)) {
-      BiometricAuthenticator.authenticate(this) {
-        when (it) {
-          is BiometricAuthenticator.Result.Success -> {
+      BiometricAuthenticator.authenticate(this) { result ->
+        when (result) {
+          is Result.Success -> {
             startTargetActivity(false)
           }
-          is BiometricAuthenticator.Result.HardwareUnavailableOrDisabled -> {
+          is Result.HardwareUnavailableOrDisabled -> {
             prefs.edit { remove(PreferenceKeys.BIOMETRIC_AUTH) }
             startTargetActivity(false)
           }
-          is BiometricAuthenticator.Result.Failure, BiometricAuthenticator.Result.Cancelled -> {
+          is Result.Failure, Result.Cancelled -> {
             finish()
           }
+          is Result.Retry -> {}
         }
       }
     } else {

app/src/main/java/dev/msfjarvis/aps/ui/settings/GeneralSettings.kt

@@ -17,6 +17,7 @@ import de.Maxr1998.modernpreferences.helpers.singleChoice
 import de.Maxr1998.modernpreferences.preferences.choice.SelectionItem
 import dev.msfjarvis.aps.R
 import dev.msfjarvis.aps.util.auth.BiometricAuthenticator
+import dev.msfjarvis.aps.util.auth.BiometricAuthenticator.Result
 import dev.msfjarvis.aps.util.extensions.sharedPrefs
 import dev.msfjarvis.aps.util.settings.PreferenceKeys
 
@@ -73,11 +74,12 @@ class GeneralSettings(private val activity: FragmentActivity) : SettingsProvider
           activity.sharedPrefs.edit {
             BiometricAuthenticator.authenticate(activity) { result ->
               when (result) {
-                is BiometricAuthenticator.Result.Success -> {
+                is Result.Success -> {
                   // Apply the changes
                   putBoolean(PreferenceKeys.BIOMETRIC_AUTH, checked)
                   enabled = true
                 }
+                is Result.Retry -> {}
                 else -> {
                   // If any error occurs, revert back to the previous
                   // state. This

app/src/main/java/dev/msfjarvis/aps/ui/sshkeygen/SshKeyGenActivity.kt

@@ -22,6 +22,7 @@ import dev.msfjarvis.aps.R
 import dev.msfjarvis.aps.databinding.ActivitySshKeygenBinding
 import dev.msfjarvis.aps.injection.prefs.GitPreferences
 import dev.msfjarvis.aps.util.auth.BiometricAuthenticator
+import dev.msfjarvis.aps.util.auth.BiometricAuthenticator.Result
 import dev.msfjarvis.aps.util.extensions.keyguardManager
 import dev.msfjarvis.aps.util.extensions.viewBinding
 import dev.msfjarvis.aps.util.git.sshj.SshKey
@@ -121,17 +122,17 @@ class SshKeyGenActivity : AppCompatActivity() {
         if (requireAuthentication) {
           val result =
             withContext(Dispatchers.Main) {
-              suspendCoroutine<BiometricAuthenticator.Result> { cont ->
+              suspendCoroutine<Result> { cont ->
                 BiometricAuthenticator.authenticate(
                   this@SshKeyGenActivity,
                   R.string.biometric_prompt_title_ssh_keygen
-                ) {
+                ) { result ->
                   // Do not cancel on failed attempts as these are handled by the authenticator UI.
-                  if (it !is BiometricAuthenticator.Result.Failure) cont.resume(it)
+                  if (result !is Result.Retry) cont.resume(result)
                 }
               }
             }
-          if (result !is BiometricAuthenticator.Result.Success)
+          if (result !is Result.Success)
             throw UserNotAuthenticatedException(getString(R.string.biometric_auth_generic_failure))
         }
         keyGenType.generateKey(requireAuthentication)

app/src/main/java/dev/msfjarvis/aps/util/auth/BiometricAuthenticator.kt

@@ -21,10 +21,28 @@ object BiometricAuthenticator {
   private const val validAuthenticators =
     Authenticators.DEVICE_CREDENTIAL or Authenticators.BIOMETRIC_WEAK
 
+  /**
+   * Sealed class to wrap [BiometricPrompt]'s [Int]-based return codes into more easily-interpreted
+   * types.
+   */
   sealed class Result {
+
+    /** Biometric authentication was a success. */
     data class Success(val cryptoObject: BiometricPrompt.CryptoObject?) : Result()
+
+    /** Biometric authentication has irreversibly failed. */
     data class Failure(val code: Int?, val message: CharSequence) : Result()
+
+    /**
+     * An incorrect biometric was entered, but the prompt UI is offering the option to retry the
+     * operation.
+     */
+    object Retry : Result()
+
+    /** The biometric hardware is unavailable or disabled on a software or hardware level. */
     object HardwareUnavailableOrDisabled : Result()
+
+    /** The prompt was dismissed. */
     object Cancelled : Result()
   }
 
@@ -56,18 +74,35 @@ object BiometricAuthenticator {
               BiometricPrompt.ERROR_NO_DEVICE_CREDENTIAL -> {
                 Result.HardwareUnavailableOrDisabled
               }
-              else ->
+              BiometricPrompt.ERROR_LOCKOUT,
+              BiometricPrompt.ERROR_LOCKOUT_PERMANENT,
+              BiometricPrompt.ERROR_NO_SPACE,
+              BiometricPrompt.ERROR_TIMEOUT,
+              BiometricPrompt.ERROR_VENDOR -> {
+                Result.Failure(
+                  errorCode,
+                  activity.getString(R.string.biometric_auth_error_reason, errString)
+                )
+              }
+              BiometricPrompt.ERROR_UNABLE_TO_PROCESS -> {
+                Result.Retry
+              }
+              // We cover all guaranteed values above, but [errorCode] is still an Int at the end of
+              // the day so a
+              // catch-all else will always be required.
+              else -> {
                 Result.Failure(
                   errorCode,
                   activity.getString(R.string.biometric_auth_error_reason, errString)
                 )
+              }
             }
           )
         }
 
         override fun onAuthenticationFailed() {
           super.onAuthenticationFailed()
-          callback(Result.Failure(null, activity.getString(R.string.biometric_auth_error)))
+          callback(Result.Retry)
         }
 
         override fun onAuthenticationSucceeded(result: BiometricPrompt.AuthenticationResult) {

app/src/main/java/dev/msfjarvis/aps/util/git/operation/GitOperation.kt

@@ -22,6 +22,7 @@ import dev.msfjarvis.aps.data.repo.PasswordRepository
 import dev.msfjarvis.aps.ui.sshkeygen.SshKeyGenActivity
 import dev.msfjarvis.aps.ui.sshkeygen.SshKeyImportActivity
 import dev.msfjarvis.aps.util.auth.BiometricAuthenticator
+import dev.msfjarvis.aps.util.auth.BiometricAuthenticator.Result.*
 import dev.msfjarvis.aps.util.git.GitCommandExecutor
 import dev.msfjarvis.aps.util.git.sshj.ContinuationContainerActivity
 import dev.msfjarvis.aps.util.git.sshj.SshAuthMethod
@@ -172,17 +173,17 @@ abstract class GitOperation(protected val callingActivity: FragmentActivity) {
                   BiometricAuthenticator.authenticate(
                     callingActivity,
                     R.string.biometric_prompt_title_ssh_auth
-                  ) { if (it !is BiometricAuthenticator.Result.Failure) cont.resume(it) }
+                  ) { result -> if (result !is Failure) cont.resume(result) }
                 }
               }
             when (result) {
-              is BiometricAuthenticator.Result.Success -> {
+              is Success -> {
                 registerAuthProviders(SshAuthMethod.SshKey(authActivity))
               }
-              is BiometricAuthenticator.Result.Cancelled -> {
+              is Cancelled -> {
                 return Err(SSHException(DisconnectReason.AUTH_CANCELLED_BY_USER))
               }
-              is BiometricAuthenticator.Result.Failure -> {
+              is Failure -> {
                 throw IllegalStateException("Biometric authentication failures should be ignored")
               }
               else -> {