Merge branch 'reset-settings-on-migration-failure'

10 files changed, 304 insertions, 124 deletions

diff --git a/ios/MullvadVPN.xcodeproj/project.pbxproj b/ios/MullvadVPN.xcodeproj/project.pbxproj
index 4f7aaa8a3e..042c517930 100644
--- a/ios/MullvadVPN.xcodeproj/project.pbxproj
+++ b/ios/MullvadVPN.xcodeproj/project.pbxproj
@@ -293,6 +293,7 @@
 		58E0729F28814ACC008902F8 /* WireGuardLogLevel+Logging.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58E0729E28814ACC008902F8 /* WireGuardLogLevel+Logging.swift */; };
 		58E072A128814B0E008902F8 /* MullvadEndpoint+WgEndpoint.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58E072A028814B0E008902F8 /* MullvadEndpoint+WgEndpoint.swift */; };
 		58E0A98827C8F46300FE6BDD /* Tunnel.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58E0A98727C8F46300FE6BDD /* Tunnel.swift */; };
+		58E11188292FA11F009FCA84 /* SettingsMigrationUIHandler.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58E11187292FA11F009FCA84 /* SettingsMigrationUIHandler.swift */; };
 		58E20771274672CA00DE5D77 /* LaunchViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58E20770274672CA00DE5D77 /* LaunchViewController.swift */; };
 		58E25F812837BBBB002CFB2C /* SceneDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58E25F802837BBBB002CFB2C /* SceneDelegate.swift */; };
 		58E511E628DDDEAC00B0BCDE /* CodingErrors+CustomErrorDescription.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58E511E528DDDEAC00B0BCDE /* CodingErrors+CustomErrorDescription.swift */; };
@@ -788,6 +789,7 @@
 		58E072A028814B0E008902F8 /* MullvadEndpoint+WgEndpoint.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "MullvadEndpoint+WgEndpoint.swift"; sourceTree = "<group>"; };
 		58E072A428814C28008902F8 /* TunnelMonitorDelegate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TunnelMonitorDelegate.swift; sourceTree = "<group>"; };
 		58E0A98727C8F46300FE6BDD /* Tunnel.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Tunnel.swift; sourceTree = "<group>"; };
+		58E11187292FA11F009FCA84 /* SettingsMigrationUIHandler.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SettingsMigrationUIHandler.swift; sourceTree = "<group>"; };
 		58E20770274672CA00DE5D77 /* LaunchViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = LaunchViewController.swift; sourceTree = "<group>"; };
 		58E25F802837BBBB002CFB2C /* SceneDelegate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SceneDelegate.swift; sourceTree = "<group>"; };
 		58E511E028DDB7F100B0BCDE /* WrappingError.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = WrappingError.swift; sourceTree = "<group>"; };
@@ -1026,20 +1028,20 @@
 			path = MullvadREST;
 			sourceTree = "<group>";
 		};
-		068CE57129278F5F00A068BB /* SettingsMigration */ = {
+		068CE57129278F5F00A068BB /* Migrations */ = {
 			isa = PBXGroup;
 			children = (
-				068CE5732927B7A400A068BB /* Migration.swift */,
 				068CE56F29278F5300A068BB /* MigrationFromV1ToV2.swift */,
 			);
-			path = SettingsMigration;
+			path = Migrations;
 			sourceTree = "<group>";
 		};
 		580F8B88281A79A7002E0998 /* SettingsManager */ = {
 			isa = PBXGroup;
 			children = (
-				068CE57129278F5F00A068BB /* SettingsMigration */,
+				068CE57129278F5F00A068BB /* Migrations */,
 				06410DFD292CE18F00AFC18C /* KeychainSettingsStore.swift */,
+				068CE5732927B7A400A068BB /* Migration.swift */,
 				58FF2C02281BDE02009EF542 /* SettingsManager.swift */,
 				06410E03292D0F7100AFC18C /* SettingsParser.swift */,
 				06410E06292D108E00AFC18C /* SettingsStore.swift */,
@@ -1410,6 +1412,7 @@
 				58CCA0152242560B004F3011 /* UIColor+Palette.swift */,
 				585CA70E25F8C44600B47C62 /* UIMetrics.swift */,
 				58F7CA872692E34000FC59FD /* WireguardKeysContentView.swift */,
+				58E11187292FA11F009FCA84 /* SettingsMigrationUIHandler.swift */,
 			);
 			path = MullvadVPN;
 			sourceTree = "<group>";
@@ -2261,6 +2264,7 @@
 				5888AD83227B11080051EB06 /* SelectLocationCell.swift in Sources */,
 				5891BF1C25E3E3EB006D6FB0 /* Bundle+ProductVersion.swift in Sources */,
 				5878A26F2907E7E00096FC88 /* ProblemReportInteractor.swift in Sources */,
+				58E11188292FA11F009FCA84 /* SettingsMigrationUIHandler.swift in Sources */,
 				5807E2C02432038B00F5FF30 /* String+Split.swift in Sources */,
 				58677712290976FB006F721F /* SettingsInteractor.swift in Sources */,
 				58CE5E66224146200008646E /* LoginViewController.swift in Sources */,
diff --git a/ios/MullvadVPN/AppDelegate.swift b/ios/MullvadVPN/AppDelegate.swift
index b11ada5f7c..1721f80261 100644
--- a/ios/MullvadVPN/AppDelegate.swift
+++ b/ios/MullvadVPN/AppDelegate.swift
@@ -110,28 +110,48 @@ class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterD
         setupNotificationHandler()
         addApplicationNotifications(application: application)
 
-        let setupTunnelManagerOperation =
-            AsyncBlockOperation(dispatchQueue: .main) { operation in
-                SettingsManager.migrateStore(with: self.proxyFactory) { error in
-                    precondition(error == nil)
-
-                    self.tunnelManager.loadConfiguration { error in
-                        // TODO: avoid throwing fatal error and show the problem report UI instead.
-                        if let error = error {
-                            fatalError(error.localizedDescription)
-                        }
+        let migrateSettingsOperation = AsyncBlockOperation(dispatchQueue: .main) { operation in
+            SettingsManager.migrateStore(with: self.proxyFactory) { error in
+                guard let error = error else {
+                    operation.finish()
+                    return
+                }
 
-                        self.logger.debug("Finished initialization.")
+                guard let migrationUIHandler = application.connectedScenes.compactMap({ scene in
+                    return scene.delegate as? SettingsMigrationUIHandler
+                }).first else {
+                    operation.finish()
+                    return
+                }
 
-                        NotificationManager.shared.updateNotifications()
-                        self.storePaymentManager.startPaymentQueueMonitoring()
+                migrationUIHandler.showMigrationError(error) {
+                    operation.finish()
+                }
+            }
+        }
 
-                        operation.finish()
+        let loadTunnelConfigurationOperation =
+            AsyncBlockOperation(dispatchQueue: .main) { operation in
+                self.tunnelManager.loadConfiguration { error in
+                    // TODO: avoid throwing fatal error and show the problem report UI instead.
+                    if let error = error {
+                        fatalError(error.localizedDescription)
                     }
+
+                    self.logger.debug("Finished initialization.")
+
+                    NotificationManager.shared.updateNotifications()
+                    self.storePaymentManager.startPaymentQueueMonitoring()
+
+                    operation.finish()
                 }
             }
+        loadTunnelConfigurationOperation.addDependency(migrateSettingsOperation)
 
-        operationQueue.addOperation(setupTunnelManagerOperation)
+        operationQueue.addOperations(
+            [migrateSettingsOperation, loadTunnelConfigurationOperation],
+            waitUntilFinished: false
+        )
 
         return true
     }
diff --git a/ios/MullvadVPN/SceneDelegate.swift b/ios/MullvadVPN/SceneDelegate.swift
index 27fbfa7bf2..03f6bc3674 100644
--- a/ios/MullvadVPN/SceneDelegate.swift
+++ b/ios/MullvadVPN/SceneDelegate.swift
@@ -19,7 +19,7 @@ class SceneDelegate: UIResponder, UIWindowSceneDelegate, UISplitViewControllerDe
     SettingsNavigationControllerDelegate, ConnectViewControllerDelegate,
     OutOfTimeViewControllerDelegate, SelectLocationViewControllerDelegate,
     RevokedDeviceViewControllerDelegate, NotificationManagerDelegate, TunnelObserver,
-    RelayCacheTrackerObserver
+    RelayCacheTrackerObserver, SettingsMigrationUIHandler
 {
     private let logger = Logger(label: "SceneDelegate")
 
@@ -952,4 +952,64 @@ class SceneDelegate: UIResponder, UIWindowSceneDelegate, UISplitViewControllerDe
         }
         return nil
     }
+
+    // MARK: - SettingsMigrationUIHandler
+
+    func showMigrationError(_ error: Error, completionHandler: @escaping () -> Void) {
+        let alertController = UIAlertController(
+            title: NSLocalizedString(
+                "ALERT_TITLE",
+                tableName: "SettingsMigrationUI",
+                value: "Settings migration error",
+                comment: ""
+            ),
+            message: Self.migrationErrorReason(error),
+            preferredStyle: .alert
+        )
+        alertController.addAction(
+            UIAlertAction(
+                title: NSLocalizedString("OK", tableName: "SettingsMigrationUI", comment: ""),
+                style: .default,
+                handler: { _ in
+                    completionHandler()
+                }
+            )
+        )
+
+        if let rootViewController = window?.rootViewController {
+            rootViewController.present(alertController, animated: true)
+        } else {
+            completionHandler()
+        }
+    }
+
+    private static func migrationErrorReason(_ error: Error) -> String {
+        if error is UnsupportedSettingsVersionError {
+            return NSLocalizedString(
+                "NEWER_STORED_SETTINGS_ERROR",
+                tableName: "SettingsMigrationUI",
+                value: """
+                The version of settings stored on device is from a newer app than is currently \
+                running. Settings will be reset to defaults.
+                """,
+                comment: ""
+            )
+        } else if let error = error as? SettingsMigrationError,
+                  error.underlyingError is REST.Error
+        {
+            return NSLocalizedString(
+                "NETWORK_ERROR",
+                tableName: "SettingsMigrationUI",
+                value: "Network error occurred. Settings will be reset to defaults.",
+                comment: ""
+            )
+        } else {
+            return NSLocalizedString(
+                "INTERNAL_ERROR",
+                tableName: "SettingsMigrationUI",
+                value: "Internal error occurred. Settings will be reset to defaults.",
+                comment: ""
+            )
+        }
+    }
 }
diff --git a/ios/MullvadVPN/SettingsManager/KeychainSettingsStore.swift b/ios/MullvadVPN/SettingsManager/KeychainSettingsStore.swift
index f98ee06a6f..eb662b8d11 100644
--- a/ios/MullvadVPN/SettingsManager/KeychainSettingsStore.swift
+++ b/ios/MullvadVPN/SettingsManager/KeychainSettingsStore.swift
@@ -11,10 +11,12 @@ import MullvadTypes
 import Security
 
 class KeychainSettingsStore: SettingsStore {
-    let keychainServiceName: String
+    let serviceName: String
+    let accessGroup: String
 
-    init(keychainServiceName: String) {
-        self.keychainServiceName = keychainServiceName
+    init(serviceName: String, accessGroup: String) {
+        self.serviceName = serviceName
+        self.accessGroup = accessGroup
     }
 
     func read(key: SettingsKey) throws -> Data {
@@ -89,14 +91,14 @@ class KeychainSettingsStore: SettingsStore {
     private func createDefaultAttributes(item: SettingsKey) -> [CFString: Any] {
         return [
             kSecClass: kSecClassGenericPassword,
-            kSecAttrService: keychainServiceName,
+            kSecAttrService: serviceName,
             kSecAttrAccount: item.rawValue,
         ]
     }
 
     private func createAccessAttributes() -> [CFString: Any] {
         return [
-            kSecAttrAccessGroup: ApplicationConfiguration.securityGroupIdentifier,
+            kSecAttrAccessGroup: accessGroup,
             kSecAttrAccessible: kSecAttrAccessibleAfterFirstUnlock,
         ]
     }
diff --git a/ios/MullvadVPN/SettingsManager/SettingsMigration/Migration.swift b/ios/MullvadVPN/SettingsManager/Migration.swift
index 79704c7b9b..79704c7b9b 100644
--- a/ios/MullvadVPN/SettingsManager/SettingsMigration/Migration.swift
+++ b/ios/MullvadVPN/SettingsManager/Migration.swift
diff --git a/ios/MullvadVPN/SettingsManager/SettingsMigration/MigrationFromV1ToV2.swift b/ios/MullvadVPN/SettingsManager/Migrations/MigrationFromV1ToV2.swift
index ea95cb9632..34956cd1e0 100644
--- a/ios/MullvadVPN/SettingsManager/SettingsMigration/MigrationFromV1ToV2.swift
+++ b/ios/MullvadVPN/SettingsManager/Migrations/MigrationFromV1ToV2.swift
@@ -19,8 +19,8 @@ class MigrationFromV1ToV2: Migration {
     private var accountTask: Cancellable?
     private var deviceTask: Cancellable?
 
-    private var accountCompletion: OperationCompletion<REST.AccountData, REST.Error>?
-    private var devicesCompletion: OperationCompletion<[REST.Device], REST.Error>?
+    private var accountCompletion: OperationCompletion<REST.AccountData, REST.Error> = .cancelled
+    private var devicesCompletion: OperationCompletion<[REST.Device], REST.Error> = .cancelled
 
     private let legacySettings: LegacyTunnelSettings
 
@@ -42,6 +42,18 @@ class MigrationFromV1ToV2: Migration {
     ) {
         let storedAccountNumber = legacySettings.accountNumber
 
+        // Store last used account number.
+        logger.debug("Store legacy account number as last used account.")
+        do {
+            if let accountData = storedAccountNumber.data(using: .utf8) {
+                try store.write(accountData, for: .lastUsedAccount)
+            } else {
+                logger.error("Failed to encode account number into utf-8 data.")
+            }
+        } catch {
+            logger.error(error: error, message: "Failed to store last used account.")
+        }
+
         // Fetch remote data concurrently.
         logger.debug("Fetching account and device data...")
         let dispatchGroup = DispatchGroup()
@@ -67,27 +79,16 @@ class MigrationFromV1ToV2: Migration {
         }
 
         dispatchGroup.notify(queue: .main) {
-            switch (self.accountCompletion, self.devicesCompletion) {
-            case let (.success(accountData), .success(deviceData)):
-                // Migrate settings if all data is available.
-
-                let result = Result {
-                    try self.migrateSettings(
-                        store: store,
-                        parser: parser,
-                        settings: self.legacySettings,
-                        accountData: accountData,
-                        devices: deviceData
-                    )
-                }
-
-                completion(result.error)
-
-            default:
-                let errors = [self.accountCompletion?.error, self.devicesCompletion?.error]
-                    .compactMap { $0 }
-                completion(MigrateLegacySettingsError(underlyingErrors: errors))
+            let result = Result {
+                try self.migrateSettings(
+                    store: store,
+                    parser: parser,
+                    settings: self.legacySettings,
+                    accountData: try self.accountCompletion.get(),
+                    devices: try self.devicesCompletion.get()
+                )
             }
+            completion(result.error)
         }
     }
 
@@ -163,15 +164,3 @@ class MigrationFromV1ToV2: Migration {
         try store.write(deviceData, for: .deviceState)
     }
 }
-
-struct MigrateLegacySettingsError: WrappingError {
-    let underlyingErrors: [REST.Error]
-
-    var underlyingError: Error? {
-        return underlyingErrors.first
-    }
-
-    var errorDescription: String? {
-        return "Failed to migrate legacy settings to v2"
-    }
-}
diff --git a/ios/MullvadVPN/SettingsManager/SettingsManager.swift b/ios/MullvadVPN/SettingsManager/SettingsManager.swift
index f0e88185b1..2940937ae4 100644
--- a/ios/MullvadVPN/SettingsManager/SettingsManager.swift
+++ b/ios/MullvadVPN/SettingsManager/SettingsManager.swift
@@ -16,8 +16,15 @@ private let accountTokenKey = "accountToken"
 private let accountExpiryKey = "accountExpiry"
 
 enum SettingsManager {
+    private static let logger = Logger(label: "SettingsManager")
+
+    private static let store: SettingsStore = KeychainSettingsStore(
+        serviceName: keychainServiceName,
+        accessGroup: ApplicationConfiguration.securityGroupIdentifier
+    )
+
     private static func makeParser() -> SettingsParser {
-        SettingsParser(decoder: JSONDecoder(), encoder: JSONEncoder())
+        return SettingsParser(decoder: JSONDecoder(), encoder: JSONEncoder())
     }
 
     // MARK: - Last used account
@@ -50,23 +57,29 @@ enum SettingsManager {
         }
     }
 
-    private static let store: SettingsStore = KeychainSettingsStore(
-        keychainServiceName: keychainServiceName
-    )
-
     // MARK: - Settings
 
     static func readSettings() throws -> TunnelSettingsV2 {
-        let data = try store.read(key: .settings)
+        let storedVersion: Int
+        let data: Data
         let parser = makeParser()
 
-        let version = try parser.parseVersion(data: data)
-        let currentVersion = SchemaVersion.current.rawValue
+        do {
+            data = try store.read(key: .settings)
+            storedVersion = try parser.parseVersion(data: data)
+        } catch {
+            throw ReadSettingsVersionError(underlyingError: error)
+        }
+
+        let currentVersion = SchemaVersion.current
 
-        if version == currentVersion {
+        if storedVersion == currentVersion.rawValue {
             return try parser.parsePayload(as: TunnelSettingsV2.self, from: data)
         } else {
-            throw UnsupportedVersionSettings(storedVersion: version, currentVersion: currentVersion)
+            throw UnsupportedSettingsVersionError(
+                storedVersion: storedVersion,
+                currentVersion: currentVersion
+            )
         }
     }
 
@@ -95,21 +108,38 @@ enum SettingsManager {
 
     // MARK: - Migration
 
+    /// Migrate settings store if needed.
+    ///
+    /// The error returned in `completion` handler is set to `nil` upon success or when no
+    /// migration is not needed.
+    ///
+    /// The following types of error are expected to be returned by this method:
+    /// `SettingsMigrationError`, `UnsupportedSettingsVersionError`, `ReadSettingsVersionError`.
     static func migrateStore(
         with restFactory: REST.ProxyFactory,
         completion: @escaping (Error?) -> Void
     ) {
+        let handleCompletion = { (error: Error?) in
+            // Reset store upon failure to migrate settings.
+            if error != nil {
+                self.resetStore()
+            }
+            completion(error)
+        }
+
         if let legacySettings = readLegacySettings() {
             migrateLegacySettings(
                 restFactory: restFactory,
                 legacySettings: legacySettings,
-                completion: completion
+                completion: handleCompletion
             )
         } else {
-            migrateModernSettings(completion: completion)
+            migrateModernSettings(completion: handleCompletion)
         }
     }
 
+    // MARK: - Private
+
     private static func migrateLegacySettings(
         restFactory: REST.ProxyFactory,
         legacySettings: LegacyTunnelSettings,
@@ -124,22 +154,17 @@ enum SettingsManager {
 
         migration.migrate(with: store, parser: parser) { error in
             if let error = error {
-                logger.error(
-                    error: error,
-                    message: "Failed to migrate from legacy settings to v2."
+                let migrationError = SettingsMigrationError(
+                    sourceVersion: .v1,
+                    targetVersion: .v2,
+                    underlyingError: error
                 )
 
-                completion(error)
-            } else {
-                let userDefaults = UserDefaults.standard
-
-                logger.debug("Remove legacy settings from keychain.")
-                Self.deleteLegacySettings()
+                logger.error(error: migrationError)
 
-                logger.debug("Remove legacy settings from user defaults.")
-
-                userDefaults.removeObject(forKey: accountTokenKey)
-                userDefaults.removeObject(forKey: accountExpiryKey)
+                completion(migrationError)
+            } else {
+                Self.deleteAllLegacySettings()
 
                 completion(nil)
             }
@@ -147,66 +172,68 @@ enum SettingsManager {
     }
 
     private static func migrateModernSettings(completion: @escaping (Error?) -> Void) {
-        let parser = makeParser()
-
         do {
+            let parser = makeParser()
             let settingsData = try store.read(key: .settings)
             let settingsVersion = try parser.parseVersion(data: settingsData)
 
             if settingsVersion != SchemaVersion.current.rawValue {
-                let error = UnsupportedVersionSettings(
+                let error = UnsupportedSettingsVersionError(
                     storedVersion: settingsVersion,
-                    currentVersion: SchemaVersion.current.rawValue
+                    currentVersion: SchemaVersion.current
                 )
 
-                logger.error(
-                    error: error,
-                    message: "Encountered an unknown version."
-                )
+                logger.error(error: error, message: "Encountered an unknown version.")
 
                 completion(error)
-
             } else {
                 completion(nil)
             }
-
         } catch .itemNotFound as KeychainError {
             completion(nil)
         } catch {
-            completion(error)
+            completion(ReadSettingsVersionError(underlyingError: error))
         }
     }
 
-    // MARK: - Legacy settings
+    /// Removes all legacy settings, device state and tunnel settings but keeps the last used
+    /// account number stored.
+    private static func resetStore() {
+        logger.debug("Reset store.")
 
-    private static func readLegacySettings() -> LegacyTunnelSettings? {
-        let storedAccountNumber = UserDefaults.standard.string(forKey: accountTokenKey)
-
-        guard let storedAccountNumber = storedAccountNumber else {
-            logger.debug("Account number is not found in user defaults. Nothing to migrate.")
-
-            return nil
+        do {
+            try store.delete(key: .deviceState)
+        } catch {
+            if (error as? KeychainError) != .itemNotFound {
+                logger.error(error: error, message: "Failed to delete device state.")
+            }
         }
 
-        // Set legacy account number as last used.
-        logger.debug("Found legacy account number.")
-        logger.debug("Store last used account.")
-
         do {
-            try Self.setLastUsedAccount(storedAccountNumber)
+            try store.delete(key: .settings)
         } catch {
-            logger.error(
-                error: error,
-                message: "Failed to store last used account."
-            )
+            if (error as? KeychainError) != .itemNotFound {
+                logger.error(error: error, message: "Failed to delete settings.")
+            }
+        }
+
+        Self.deleteAllLegacySettings()
+    }
+
+    // MARK: - Legacy settings
+
+    private static func readLegacySettings() -> LegacyTunnelSettings? {
+        guard let storedAccountNumber = UserDefaults.standard.string(forKey: accountTokenKey) else {
+            logger.debug("Legacy account number is not found in user defaults. Nothing to migrate.")
+            return nil
         }
 
         // List legacy settings stored in keychain.
-        logger.debug("Read legacy settings...")
+        logger.debug("List legacy settings in keychain...")
 
         var storedSettings: [LegacyTunnelSettings] = []
         do {
-            storedSettings = try Self.readLegacySettings()
+            storedSettings = try findAllLegacySettingsInKeychain()
         } catch .itemNotFound as KeychainError {
             logger.debug("Legacy settings are not found in keychain.")
 
@@ -236,11 +263,7 @@ enum SettingsManager {
         return matchingSettings
     }
 
-    // MARK: - Legacy settings support
-
-    private static let logger = Logger(label: "SettingsManager")
-
-    static func readLegacySettings() throws -> [LegacyTunnelSettings] {
+    private static func findAllLegacySettingsInKeychain() throws -> [LegacyTunnelSettings] {
         let query: [CFString: Any] = [
             kSecClass: kSecClassGenericPassword,
             kSecAttrService: keychainServiceName,
@@ -287,7 +310,17 @@ enum SettingsManager {
             }
     }
 
-    static func deleteLegacySettings() {
+    private static func deleteAllLegacySettings() {
+        logger.debug("Remove legacy settings from keychain.")
+        deleteLegacySettingsFromKeychain()
+
+        logger.debug("Remove legacy settings from user defaults.")
+        let userDefaults = UserDefaults.standard
+        userDefaults.removeObject(forKey: accountTokenKey)
+        userDefaults.removeObject(forKey: accountExpiryKey)
+    }
+
+    private static func deleteLegacySettingsFromKeychain() {
         let query: [CFString: Any] = [
             kSecClass: kSecClassGenericPassword,
             kSecAttrService: keychainServiceName,
@@ -362,11 +395,53 @@ enum SettingsKey: String, CaseIterable {
     case lastUsedAccount = "LastUsedAccount"
 }
 
-struct UnsupportedVersionSettings: LocalizedError {
-    let storedVersion, currentVersion: Int
+/// An error type describing a failure to read or parse settings version.
+struct ReadSettingsVersionError: LocalizedError, WrappingError {
+    private let inner: Error
+
+    var underlyingError: Error? {
+        return inner
+    }
+
+    var errorDescription: String? {
+        return "Failed to read settings version."
+    }
+
+    init(underlyingError: Error) {
+        inner = underlyingError
+    }
+}
+
+/// An error returned when stored settings version is unknown to the currently running app.
+struct UnsupportedSettingsVersionError: LocalizedError {
+    let storedVersion: Int
+    let currentVersion: SchemaVersion
 
     var errorDescription: String? {
-        return "Stored settings version was not the same as current version, stored version: \(storedVersion), current version: \(currentVersion)"
+        return """
+        Stored settings version was not the same as current version, \
+        stored version: \(storedVersion), current version: \(currentVersion)
+        """
+    }
+}
+
+/// A wrapper type for errors returned by concrete migrations.
+struct SettingsMigrationError: LocalizedError, WrappingError {
+    private let inner: Error
+    let sourceVersion, targetVersion: SchemaVersion
+
+    var underlyingError: Error? {
+        return inner
+    }
+
+    var errorDescription: String? {
+        return "Failed to migrate settings from \(sourceVersion) to \(targetVersion)."
+    }
+
+    init(sourceVersion: SchemaVersion, targetVersion: SchemaVersion, underlyingError: Error) {
+        self.sourceVersion = sourceVersion
+        self.targetVersion = targetVersion
+        inner = underlyingError
     }
 }
 
diff --git a/ios/MullvadVPN/SettingsManager/TunnelSettingsV2.swift b/ios/MullvadVPN/SettingsManager/TunnelSettingsV2.swift
index 6c0ada1415..76b794eba9 100644
--- a/ios/MullvadVPN/SettingsManager/TunnelSettingsV2.swift
+++ b/ios/MullvadVPN/SettingsManager/TunnelSettingsV2.swift
@@ -14,7 +14,10 @@ import class WireGuardKitTypes.PrivateKey
 import class WireGuardKitTypes.PublicKey
 
 /// Settings and device state schema versions.
-enum SchemaVersion: Int {
+enum SchemaVersion: Int, Equatable {
+    /// Legacy settings format, stored as `TunnelSettingsV1`.
+    case v1 = 1
+
     /// New settings format, stored as `TunnelSettingsV2`.
     case v2 = 2
 
diff --git a/ios/MullvadVPN/SettingsMigrationUIHandler.swift b/ios/MullvadVPN/SettingsMigrationUIHandler.swift
new file mode 100644
index 0000000000..949458e394
--- /dev/null
+++ b/ios/MullvadVPN/SettingsMigrationUIHandler.swift
@@ -0,0 +1,13 @@
+//
+//  SettingsMigrationUIHandler.swift
+//  MullvadVPN
+//
+//  Created by pronebird on 24/11/2022.
+//  Copyright © 2022 Mullvad VPN AB. All rights reserved.
+//
+
+import Foundation
+
+protocol SettingsMigrationUIHandler {
+    func showMigrationError(_ error: Error, completionHandler: @escaping () -> Void)
+}
diff --git a/ios/Operations/OperationCompletion.swift b/ios/Operations/OperationCompletion.swift
index 0e004bfe50..49a34e0884 100644
--- a/ios/Operations/OperationCompletion.swift
+++ b/ios/Operations/OperationCompletion.swift
@@ -65,6 +65,14 @@ public enum OperationCompletion<Success, Failure: Error> {
         }
     }
 
+    public func get() throws -> Success {
+        if let result = result {
+            return try result.get()
+        } else {
+            throw OperationCancellationError()
+        }
+    }
+
     public func map<NewSuccess>(_ block: (Success) -> NewSuccess)
         -> OperationCompletion<NewSuccess, Failure>
     {
@@ -143,3 +151,9 @@ public enum OperationCompletion<Success, Failure: Error> {
         return mapError { $0 }
     }
 }
+
+public struct OperationCancellationError: LocalizedError {
+    public var errorDescription: String? {
+        return "Operation was cancelled."
+    }
+}