[No QA][ECUK] MFA re-register flow when server returns "registration required"

src/components/MultifactorAuthentication/Context/Main.tsx

@@ -10,7 +10,7 @@ import {requestValidateCodeAction} from '@libs/actions/User';
 import getPlatform from '@libs/getPlatform';
 import type {ChallengeType, MultifactorAuthenticationReason, OutcomePaths} from '@libs/MultifactorAuthentication/Biometrics/types';
 import Navigation from '@navigation/Navigation';
-import {requestAuthorizationChallenge, requestRegistrationChallenge} from '@userActions/MultifactorAuthentication';
+import {clearLocalMFAPublicKeyList, requestAuthorizationChallenge, requestRegistrationChallenge} from '@userActions/MultifactorAuthentication';
 import {processRegistration, processScenario} from '@userActions/MultifactorAuthentication/processing';
 import CONST from '@src/CONST';
 import ONYXKEYS from '@src/ONYXKEYS';
@@ -24,9 +24,8 @@ let deviceBiometricsState: OnyxEntry<DeviceBiometrics>;
 
 // Use Onyx.connectWithoutView instead of useOnyx hook to access the device biometrics state.
 // This is a non-reactive read that allows us to check the current value (hasAcceptedSoftPrompt)
-// from within the process() callback without triggering component re-renders or complicating
-// the effect's dependency list. Since we only need the latest value at specific points in the
-// MFA flow (not reactivity to changes), this is more efficient than using the useOnyx hook.
+// from within the process() callback without triggering calling it too many times during the
+// fresh registration flow
 Onyx.connectWithoutView({
     key: ONYXKEYS.DEVICE_BIOMETRICS,
     callback: (data) => {
@@ -111,6 +110,12 @@ function MultifactorAuthenticationContextProvider({children}: MultifactorAuthent
 
         // 1. Check if there's an error - stop processing
         if (error) {
+            if (error.reason === CONST.MULTIFACTOR_AUTHENTICATION.REASON.BACKEND.REGISTRATION_REQUIRED) {
+                clearLocalMFAPublicKeyList();
+                dispatch({type: 'REREGISTER'});
+                return;
+            }
+
             Navigation.navigate(ROUTES.MULTIFACTOR_AUTHENTICATION_OUTCOME.getRoute(paths.failureOutcome), {forceReplace: true});
             dispatch({type: 'SET_FLOW_COMPLETE', payload: true});
             return;

src/components/MultifactorAuthentication/Context/State.tsx

@@ -93,6 +93,7 @@ type Action =
     | {type: 'SET_FLOW_COMPLETE'; payload: boolean}
     | {type: 'SET_AUTHENTICATION_METHOD'; payload: AuthTypeInfo | undefined}
     | {type: 'INIT'; payload: InitPayload}
+    | {type: 'REREGISTER'}
     | {type: 'RESET'};
 
 /**
@@ -153,6 +154,13 @@ function stateReducer(state: MultifactorAuthenticationState, action: Action): Mu
             };
         case 'RESET':
             return DEFAULT_STATE;
+        case 'REREGISTER':
+            return {
+                ...DEFAULT_STATE,
+                scenario: state.scenario,
+                payload: state.payload,
+                outcomePaths: state.outcomePaths,
+            };
         default:
             return state;
     }

src/components/MultifactorAuthentication/Context/usePromptContent.ts

@@ -1,3 +1,4 @@
+import {useEffect, useRef} from 'react';
 import type {OnyxEntry} from 'react-native-onyx';
 import type DotLottieAnimation from '@components/LottieAnimations/types';
 import {MULTIFACTOR_AUTHENTICATION_PROMPT_UI} from '@components/MultifactorAuthentication/config';
@@ -40,10 +41,29 @@ function usePromptContent(promptType: MultifactorAuthenticationPromptType): Prom
     const [deviceBiometricsState] = useOnyx(ONYXKEYS.DEVICE_BIOMETRICS, {canBeMissing: true});
     const hasEverAcceptedSoftPrompt = deviceBiometricsState?.hasAcceptedSoftPrompt ?? false;
 
+    // This one's a real doozy. There's an edge case with the MFA flows where the user's keys were revoked
+    // server-side, but the client missed the Onyx update to clear them locally. When the client launches the MFA
+    // flow, it thinks it is already registered, so it goes directly to authentication. When it requests an
+    // authentication challenge from the server, the server throws "400 Registration required", so we need to
+    // restart the whole flow. The registration flow clears a relevant state, which causes the prompt page to
+    // change from the authentication version to the registration version briefly before we navigate away from the
+    // page. Since there is no legitimate case for the prompt page to transition from authentication =>
+    // registration, only the other way around, this ref prevents that from happening. Functionally, it acts as a
+    // latch for isReturningUser, so that once it becomes true, it'll never become false until this screen
+    // unmounts.
+    const wasPreviouslyRegisteredRef = useRef(false);
+
     const contentData = MULTIFACTOR_AUTHENTICATION_PROMPT_UI[promptType];
 
     // Returning user: server has credentials, but user hasn't approved soft prompt yet
-    const isReturningUser = hasEverAcceptedSoftPrompt && serverHasCredentials && !state.softPromptApproved;
+    const isReturningUser = wasPreviouslyRegisteredRef.current || (hasEverAcceptedSoftPrompt && serverHasCredentials && !state.softPromptApproved);
+
+    useEffect(() => {
+        if (!isReturningUser) {
+            return;
+        }
+        wasPreviouslyRegisteredRef.current = isReturningUser;
+    }, [isReturningUser]);
 
     let title: TranslationPaths = contentData.title;
     let subtitle: TranslationPaths | undefined = contentData.subtitle;
@@ -64,7 +84,8 @@ function usePromptContent(promptType: MultifactorAuthenticationPromptType): Prom
     // Display confirm button only for new users during their first biometric registration.
     // Hide it for: users who already approved the soft prompt, users who finished registration,
     // or returning users with existing server credentials. The button prompts users to enable biometrics.
-    const shouldDisplayConfirmButton = !hasEverAcceptedSoftPrompt || (!state.softPromptApproved && !state.isRegistrationComplete && !serverHasCredentials);
+    const shouldDisplayConfirmButton =
+        !hasEverAcceptedSoftPrompt || (!state.softPromptApproved && !state.isRegistrationComplete && !serverHasCredentials && !wasPreviouslyRegisteredRef.current);
 
     return {
         animation: contentData.animation,

src/libs/MultifactorAuthentication/Biometrics/VALUES.ts

@@ -205,6 +205,14 @@ const MULTIFACTOR_AUTHENTICATION_VALUES = {
     },
     API_RESPONSE_MAP,
     REASON,
+    /**
+     * Specifically meaningful values for `multifactorAuthenticationPublicKeyIDs` in the `account` Onyx key.
+     * Casting `[] as string[]` is necessary to allow us to actually store the value in Onyx. Otherwise the
+     * `as const` would mean `[]` becomes `readonly []` (readonly empty array), which is more precise,
+     * but isn't allowed to be assigned to a `string[]` field.
+     */
+    PUBLIC_KEYS_PREVIOUSLY_BUT_NOT_CURRENTLY_REGISTERED: [] as string[],
+    PUBLIC_KEYS_AUTHENTICATION_NEVER_REGISTERED: undefined,
 } as const;
 
 export {MultifactorAuthenticationCallbacks};

src/libs/actions/MultifactorAuthentication/index.ts

@@ -193,11 +193,18 @@ function markHasAcceptedSoftPrompt() {
     });
 }
 
+function clearLocalMFAPublicKeyList() {
+    Onyx.merge(ONYXKEYS.ACCOUNT, {
+        multifactorAuthenticationPublicKeyIDs: CONST.MULTIFACTOR_AUTHENTICATION.PUBLIC_KEYS_PREVIOUSLY_BUT_NOT_CURRENTLY_REGISTERED,
+    });
+}
+
 export {
     registerAuthenticationKey,
     requestRegistrationChallenge,
     requestAuthorizationChallenge,
     troubleshootMultifactorAuthentication,
     revokeMultifactorAuthenticationCredentials,
     markHasAcceptedSoftPrompt,
+    clearLocalMFAPublicKeyList,
 };

src/pages/settings/Security/SecuritySettingsPage.tsx

@@ -91,7 +91,7 @@ function SecuritySettingsPage() {
     const hasDelegates = delegates.length > 0;
     const hasDelegators = delegators.length > 0;
 
-    const hasEverRegisteredForMultifactorAuthentication = account?.multifactorAuthenticationPublicKeyIDs !== undefined;
+    const hasEverRegisteredForMultifactorAuthentication = account?.multifactorAuthenticationPublicKeyIDs !== CONST.MULTIFACTOR_AUTHENTICATION.PUBLIC_KEYS_AUTHENTICATION_NEVER_REGISTERED;
 
     const setMenuPosition = useCallback(() => {
         if (!delegateButtonRef.current) {