Support multi-factor authentication with email link sign in

FirebaseAuth/Sources/Backend/FIRAuthBackend.m

@@ -805,15 +805,31 @@ - (void)verifyPassword:(FIRVerifyPasswordRequest *)request
 - (void)emailLinkSignin:(FIREmailLinkSignInRequest *)request
                callback:(FIREmailLinkSigninResponseCallback)callback {
   FIREmailLinkSignInResponse *response = [[FIREmailLinkSignInResponse alloc] init];
-  [self postWithRequest:request
-               response:response
-               callback:^(NSError *error) {
-                 if (error) {
-                   callback(nil, error);
+  [self
+      postWithRequest:request
+             response:response
+             callback:^(NSError *error) {
+               if (error) {
+                 callback(nil, error);
+               } else {
+                 if (!response.IDToken && response.MFAInfo) {
+#if TARGET_OS_IOS
+                   NSMutableArray<FIRMultiFactorInfo *> *multiFactorInfo = [NSMutableArray array];
+                   for (FIRAuthProtoMFAEnrollment *MFAEnrollment in response.MFAInfo) {
+                     FIRPhoneMultiFactorInfo *info =
+                         [[FIRPhoneMultiFactorInfo alloc] initWithProto:MFAEnrollment];
+                     [multiFactorInfo addObject:info];
+                   }
+                   NSError *multiFactorRequiredError = [FIRAuthErrorUtils
+                       secondFactorRequiredErrorWithPendingCredential:response.MFAPendingCredential
+                                                                hints:multiFactorInfo];
+                   callback(nil, multiFactorRequiredError);
+#endif
                  } else {
                    callback(response, nil);
                  }
-               }];
+               }
+             }];
 }
 
 - (void)secureToken:(FIRSecureTokenRequest *)request

FirebaseAuth/Sources/Backend/RPC/FIREmailLinkSignInResponse.h

@@ -16,6 +16,7 @@
 #import <Foundation/Foundation.h>
 
 #import "FirebaseAuth/Sources/Backend/FIRAuthRPCResponse.h"
+#import "FirebaseAuth/Sources/Backend/RPC/Proto/FIRAuthProtoMFAEnrollment.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -39,6 +40,11 @@ NS_ASSUME_NONNULL_BEGIN
  */
 @property(nonatomic, strong, readonly, nullable) NSString *refreshToken;
 
+/** @property localID
+    @brief The Firebase Auth user ID.
+ */
+@property(nonatomic, strong, readonly, nullable) NSString *localID;
+
 /** @property approximateExpirationDate
     @brief The approximate expiration date of the access token.
  */
@@ -49,6 +55,17 @@ NS_ASSUME_NONNULL_BEGIN
  */
 @property(nonatomic, assign) BOOL isNewUser;
 
+/** @property MFAPendingCredential
+    @brief An opaque string that functions as proof that the user has successfully passed the first
+   factor check.
+*/
+@property(nonatomic, strong, readonly, nullable) NSString *MFAPendingCredential;
+
+/** @property MFAInfo
+    @brief Info on which multi-factor authentication providers are enabled.
+*/
+@property(nonatomic, strong, readonly, nullable) NSArray<FIRAuthProtoMFAEnrollment *> *MFAInfo;
+
 @end
 
 NS_ASSUME_NONNULL_END

FirebaseAuth/Sources/Backend/RPC/FIREmailLinkSignInResponse.m

@@ -21,6 +21,7 @@
 @implementation FIREmailLinkSignInResponse
 
 - (BOOL)setWithDictionary:(NSDictionary *)dictionary error:(NSError *_Nullable *_Nullable)error {
+  _localID = [dictionary[@"localId"] copy];
   _email = [dictionary[@"email"] copy];
   _IDToken = [dictionary[@"idToken"] copy];
   _isNewUser = [dictionary[@"isNewUser"] boolValue];
@@ -29,6 +30,18 @@ - (BOOL)setWithDictionary:(NSDictionary *)dictionary error:(NSError *_Nullable *
       [dictionary[@"expiresIn"] isKindOfClass:[NSString class]]
           ? [NSDate dateWithTimeIntervalSinceNow:[dictionary[@"expiresIn"] doubleValue]]
           : nil;
+  if (dictionary[@"mfaInfo"] != nil) {
+    NSMutableArray<FIRAuthProtoMFAEnrollment *> *MFAInfo = [NSMutableArray array];
+    NSArray *MFAInfoDataArray = dictionary[@"mfaInfo"];
+    for (NSDictionary *MFAInfoData in MFAInfoDataArray) {
+      FIRAuthProtoMFAEnrollment *MFAEnrollment =
+          [[FIRAuthProtoMFAEnrollment alloc] initWithDictionary:MFAInfoData];
+      [MFAInfo addObject:MFAEnrollment];
+    }
+    _MFAInfo = MFAInfo;
+  }
+  _MFAPendingCredential = [dictionary[@"mfaPendingCredential"] copy];
+
   return YES;
 }
 

FirebaseAuth/Sources/Backend/RPC/FIRVerifyAssertionResponse.h

@@ -205,8 +205,15 @@ NS_ASSUME_NONNULL_BEGIN
  */
 @property(nonatomic, copy, nullable) NSString *pendingToken;
 
+/** @property MFAPendingCredential
+    @brief An opaque string that functions as proof that the user has successfully passed the first
+   factor check.
+*/
 @property(nonatomic, strong, readonly, nullable) NSString *MFAPendingCredential;
 
+/** @property MFAInfo
+    @brief Info on which multi-factor authentication providers are enabled.
+*/
 @property(nonatomic, strong, readonly, nullable) NSArray<FIRAuthProtoMFAEnrollment *> *MFAInfo;
 
 @end

FirebaseAuth/Sources/Backend/RPC/FIRVerifyPasswordResponse.h

@@ -66,8 +66,15 @@ NS_ASSUME_NONNULL_BEGIN
  */
 @property(nonatomic, strong, readonly, nullable) NSURL *photoURL;
 
+/** @property MFAPendingCredential
+    @brief An opaque string that functions as proof that the user has successfully passed the first
+   factor check.
+*/
 @property(nonatomic, strong, readonly, nullable) NSString *MFAPendingCredential;
 
+/** @property MFAInfo
+    @brief Info on which multi-factor authentication providers are enabled.
+*/
 @property(nonatomic, strong, readonly, nullable) NSArray<FIRAuthProtoMFAEnrollment *> *MFAInfo;
 
 @end