From eb9c65e975347f80dee05c3e34deedb7f6537bb3 Mon Sep 17 00:00:00 2001
From: Matthew Chen <matthew@signal.org>
Date: Wed, 28 Mar 2018 12:32:57 -0400
Subject: [PATCH] Improve handling of local authentication errors.

---
 Signal/src/util/OWSScreenLock.swift | 16 ++++++++++++----
 Signal/src/util/OWSScreenLockUI.m   | 10 ++++++++++
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/Signal/src/util/OWSScreenLock.swift b/Signal/src/util/OWSScreenLock.swift
index d8ae13f3b..4b19231ba 100644
--- a/Signal/src/util/OWSScreenLock.swift
+++ b/Signal/src/util/OWSScreenLock.swift
@@ -11,6 +11,7 @@ import LocalAuthentication
         case success
         case cancel
         case failure(error:String)
+        case unexpectedFailure(error:String)
     }
 
     @objc public let screenLockTimeoutDefault = 15 * kMinuteInterval
@@ -122,6 +123,8 @@ import LocalAuthentication
                                         switch outcome {
                                         case .failure(let error):
                                             completion(self.authenticationError(errorDescription: error))
+                                        case .unexpectedFailure(let error):
+                                            completion(self.authenticationError(errorDescription: error))
                                         case .success:
                                             self.setIsScreenLockEnabled(value: true)
                                             completion(nil)
@@ -144,6 +147,8 @@ import LocalAuthentication
                                         switch outcome {
                                         case .failure(let error):
                                             completion(self.authenticationError(errorDescription: error))
+                                        case .unexpectedFailure(let error):
+                                            completion(self.authenticationError(errorDescription: error))
                                         case .success:
                                             self.setIsScreenLockEnabled(value: false)
                                             completion(nil)
@@ -155,6 +160,7 @@ import LocalAuthentication
 
     @objc public func tryToUnlockScreenLock(success: @escaping (() -> Void),
                                             failure: @escaping ((Error) -> Void),
+                                            unexpectedFailure: @escaping ((Error) -> Void),
                                             cancel: @escaping (() -> Void)) {
         guard !ignoreUnlockUntilActive else {
             DispatchQueue.main.async {
@@ -171,6 +177,8 @@ import LocalAuthentication
                                         switch outcome {
                                         case .failure(let error):
                                             failure(self.authenticationError(errorDescription: error))
+                                        case .unexpectedFailure(let error):
+                                            unexpectedFailure(self.authenticationError(errorDescription: error))
                                         case .success:
                                             success()
                                         case .cancel:
@@ -215,7 +223,7 @@ import LocalAuthentication
             case .success:
                 owsFail("\(self.logTag) local authentication unexpected success")
                 completion(.failure(error:defaultErrorDescription))
-            case .cancel, .failure:
+            case .cancel, .failure, .unexpectedFailure:
                 completion(outcome)
             }
             return
@@ -235,7 +243,7 @@ import LocalAuthentication
                 case .success:
                     owsFail("\(self.logTag) local authentication unexpected success")
                     completion(.failure(error:defaultErrorDescription))
-                case .cancel, .failure:
+                case .cancel, .failure, .unexpectedFailure:
                     completion(outcome)
                 }
             }
@@ -296,10 +304,10 @@ import LocalAuthentication
                                                          comment: "Indicates that Touch ID/Face ID/Phone Passcode is 'locked out' on this device due to authentication failures."))
             case .invalidContext:
                 owsFail("\(self.logTag) context not valid.")
-                return .failure(error:defaultErrorDescription)
+                return .unexpectedFailure(error:defaultErrorDescription)
             case .notInteractive:
                 owsFail("\(self.logTag) context not interactive.")
-                return .failure(error:defaultErrorDescription)
+                return .unexpectedFailure(error:defaultErrorDescription)
             }
         }
         return .failure(error:defaultErrorDescription)
diff --git a/Signal/src/util/OWSScreenLockUI.m b/Signal/src/util/OWSScreenLockUI.m
index 41e24c563..9cdfde474 100644
--- a/Signal/src/util/OWSScreenLockUI.m
+++ b/Signal/src/util/OWSScreenLockUI.m
@@ -202,6 +202,16 @@ NS_ASSUME_NONNULL_BEGIN
 
             [self showScreenLockFailureAlertWithMessage:error.localizedDescription];
         }
+        unexpectedFailure:^(NSError *error) {
+            DDLogInfo(@"%@ unlock screen lock unexpectedly failed.", self.logTag);
+
+            // Local Authentication isn't working properly.
+            // This isn't covered by the docs or the forums but in practice
+            // it appears to be effective to retry again after waiting a bit.
+            dispatch_async(dispatch_get_main_queue(), ^{
+                [self clearAuthUIWhenActive];
+            });
+        }
         cancel:^{
             DDLogInfo(@"%@ unlock screen lock cancelled.", self.logTag);