You can let your users authenticate with Firebase using OAuth providers such asGitHub by integrating generic OAuth Login into your app using the Firebase SDK tocarry out the end to end sign-in flow.

Before you begin

To sign in users using GitHub accounts, you must first enable GitHub as a sign-inprovider for your Firebase project:

Use Swift Package Manager to install and manage Firebase dependencies.

1. In Xcode, with your app project open, navigate toFile > Add Packages.
2. When prompted, add the Firebase Apple platforms SDK repository:

  https://github.com/firebase/firebase-ios-sdk.git

Note: New projects should use the default (latest) SDK version, but you can choose an older version if needed.
3. Choose theFirebase Authentication library.
4. Add the-ObjC flag to theOther Linker Flags section of your target's build settings.
5. When finished, Xcode will automatically begin resolving and downloading your dependencies in the background.

Now, perform some configuration steps:

1. In theFirebase console, open theAuth section.
2. On theSign in method tab, enable theGitHub provider.
3. Add theClient ID andClient Secret from that provider's developer console to the provider configuration:
   1. Register your app as a developer application on GitHub and get your app's OAuth 2.0Client ID andClient Secret.
   2. Make sure your FirebaseOAuth redirect URI (e.g.my-app-12345.firebaseapp.com/__/auth/handler) is set as yourAuthorization callback URL in your app's settings page on yourGitHub app's config.
4. ClickSave.

Handle the sign-in flow with the Firebase SDK

To handle the sign-in flow with the Firebase Apple platforms SDK, follow these steps:

1. Add custom URL schemes to your Xcode project:

   1. Open your project configuration: double-click the project name in the left tree view. Select your app from theTARGETS section, then select theInfo tab, and expand theURL Types section.
   2. Click the+ button, and add your Encoded App ID as a URL scheme. You can find your Encoded App ID on theGeneral Settings page of the Firebase console, in the section for your iOS app. Leave the other fields blank.

      When completed, your config should look something similar to the following (but with your application-specific values):

      

2. Create an instance of anOAuthProvider using the provider IDgithub.com.

   Swift

   varprovider=OAuthProvider(providerID:"github.com")

   Objective-C

   FIROAuthProvider*provider=[FIROAuthProviderproviderWithProviderID:@"github.com"];

3. Optional: Specify additional custom OAuth parameters that you want tosend with the OAuth request.

   Swift

   provider.customParameters=["allow_signup":"false"]

   Objective-C

   [providersetCustomParameters:@{@"allow_signup":@"false"}];

   For the parameters GitHub supports, see theGitHub OAuth documentation.Note that you can't pass Firebase-required parameters withsetCustomParameters. These parameters areclient_id,redirect_uri,response_type,scope andstate.

4. Optional: Specify additional OAuth 2.0 scopes beyond basic profile thatyou want to request from the authentication provider. If your applicationrequires access to private user data from GitHub APIs, you'll need torequest permissions to access GitHub APIs underAPI Permissions in theGitHub developer console. Requested OAuth scopes must be exact matches tothe preconfigured ones in the app's API permissions.

   Swift

   // Request read access to a user's email addresses.// This must be preconfigured in the app's API permissions.provider.scopes=["user:email"]

   Objective-C

   // Request read access to a user's email addresses.// This must be preconfigured in the app's API permissions.[providersetScopes:@[@"user:email"]];

   To learn more, refer to theGitHub scopes documentation.

5. Optional: If you want to customize the way your app presents theSFSafariViewController orUIWebView whendisplaying the reCAPTCHA to the user, create a custom class that conformsto theAuthUIDelegate protocol, and pass it tocredentialWithUIDelegate.

6. Authenticate with Firebase using the OAuth provider object.

   Swift

   provider.getCredentialWith(nil){credential,erroriniferror!=nil{// Handle error.}ifcredential!=nil{Auth().signIn(with:credential){authResult,erroriniferror!=nil{// Handle error.}// User is signed in.// IdP data available in authResult.additionalUserInfo.profile.guardletoauthCredential=authResult.credentialas?OAuthCredentialelse{return}// GitHub OAuth access token can also be retrieved by:// oauthCredential.accessToken// GitHub OAuth ID token can be retrieved by calling:// oauthCredential.idToken}}}

   Objective-C

   [providergetCredentialWithUIDelegate:nilcompletion:^(FIRAuthCredential*_Nullablecredential,NSError*_Nullableerror){if(error){// Handle error.}if(credential){[[FIRAuthauth]signInWithCredential:credentialcompletion:^(FIRAuthDataResult*_NullableauthResult,NSError*_Nullableerror){if(error){// Handle error.}// User is signed in.// IdP data available in authResult.additionalUserInfo.profile.FIROAuthCredential*oauthCredential=(FIROAuthCredential*)authResult.credential;// GitHub OAuth access token can also be retrieved by:// oauthCredential.accessToken// GitHub OAuth ID token can be retrieved by calling:// oauthCredential.idToken}];}}];

   Using the OAuth access token, you can call theGitHub API.

   For example, to get basic profile information, you can call the REST API,passing the access token in theAuthorization header:

   https://api.github.com/user

7. While the above examples focus on sign-in flows, you also have theability to link a GitHub provider to an existing user. For example, you canlink multiple providers to the same user allowing them to sign in with either.

   Swift

   Auth().currentUser.link(withCredential:credential){authResult,erroriniferror!=nil{// Handle error.}// GitHub credential is linked to the current user.// IdP data available in authResult.additionalUserInfo.profile.// GitHub OAuth access token can also be retrieved by:// (authResult.credential as? OAuthCredential)?.accessToken// GitHub OAuth ID token can be retrieved by calling:// (authResult.credential as? OAuthCredential)?.idToken}

   Objective-C

   [[FIRAuthauth].currentUserlinkWithCredential:credentialcompletion:^(FIRAuthDataResult*_NullableauthResult,NSError*_Nullableerror){if(error){// Handle error.}// GitHub credential is linked to the current user.// IdP data available in authResult.additionalUserInfo.profile.// GitHub OAuth access token is can also be retrieved by:// ((FIROAuthCredential *)authResult.credential).accessToken// GitHub OAuth ID token can be retrieved by calling:// ((FIROAuthCredential *)authResult.credential).idToken}];

8. The same pattern can be used withreauthenticateWithCredential which canbe used to retrieve fresh credentials for sensitive operations that requirerecent login.

   Swift

   Auth().currentUser.reauthenticateWithCredential(withCredential:credential){authResult,erroriniferror!=nil{// Handle error.}// User is re-authenticated with fresh tokens minted and// should be able to perform sensitive operations like account// deletion and email or password update.// IdP data available in result.additionalUserInfo.profile.// Additional OAuth access token is can also be retrieved by:// (authResult.credential as? OAuthCredential)?.accessToken// GitHub OAuth ID token can be retrieved by calling:// (authResult.credential as? OAuthCredential)?.idToken}

   Objective-C

   [[FIRAuthauth].currentUserreauthenticateWithCredential:credentialcompletion:^(FIRAuthDataResult*_NullableauthResult,NSError*_Nullableerror){if(error){// Handle error.}// User is re-authenticated with fresh tokens minted and// should be able to perform sensitive operations like account// deletion and email or password update.// IdP data available in result.additionalUserInfo.profile.// Additional OAuth access token is can also be retrieved by:// ((FIROAuthCredential *)authResult.credential).accessToken// GitHub OAuth ID token can be retrieved by calling:// ((FIROAuthCredential *)authResult.credential).idToken}];

// Sign-in with an OAuth credential.provider.getCredentialWith(nil){credential,errorin// An account with the same email already exists.if(errorasNSError?)?.code==AuthErrorCode.accountExistsWithDifferentCredential.rawValue{// Get pending credential and email of existing account.letexistingAcctEmail=(error!asNSError).userInfo[AuthErrorUserInfoEmailKey]as!StringletpendingCred=(error!asNSError).userInfo[AuthErrorUserInfoUpdatedCredentialKey]as!AuthCredential// Lookup existing account identifier by the email.Auth.auth().fetchProviders(forEmail:existingAcctEmail){providers,errorin// Existing email/password account.if(providers?.contains(EmailAuthProviderID))!{// Existing password account for email. Ask user to provide the password of the// existing account.// Sign in with existing account.Auth.auth().signIn(withEmail:existingAcctEmail,password:password){user,errorin// Successfully signed in.ifuser!=nil{// Link pending credential to account.Auth.auth().currentUser?.linkAndRetrieveData(with:pendingCred){result,errorin// ...}}}}}return}// Other errors.iferror!=nil{// handle the error.return}// Sign in with the credential.ifcredential!=nil{Auth.auth().signInAndRetrieveData(with:credential!){result,erroriniferror!=nil{// handle the error.return}}}}

// Sign-in with an OAuth credential.[providergetCredentialWithUIDelegate:nilcompletion:^(FIRAuthCredential*_Nullablecredential,NSError*_Nullableerror){// An account with the same email already exists.if(error.code==FIRAuthErrorCodeAccountExistsWithDifferentCredential){// Get pending credential and email of existing account.NSString*existingAcctEmail=error.userInfo[FIRAuthErrorUserInfoEmailKey];FIRAuthCredential*pendingCred=error.userInfo[FIRAuthErrorUserInfoUpdatedCredentialKey];// Lookup existing account identifier by the email.[[FIRAuthauth]fetchProvidersForEmail:existingAcctEmailcompletion:^(NSArray<NSString*>*_Nullableproviders,NSError*_Nullableerror){// Existing email/password account.if([providerscontainsObject:FIREmailAuthProviderID]){// Existing password account for email. Ask user to provide the password of the// existing account.// Sign in with existing account.[[FIRAuthauth]signInWithEmail:existingAcctEmailpassword:passwordcompletion:^(FIRUser*user,NSError*error){// Successfully signed in.if(user){// Link pending credential to account.[[FIRAuthauth].currentUserlinkWithCredential:pendingCredcompletion:^(FIRUser*_Nullableuser,NSError*_Nullableerror){// ...}];}}];}}];return;}// Other errors.if(error){// handle the error.return;}// Sign in with the credential.if(credential){[[FIRAuthauth]signInAndRetrieveDataWithCredential:credentialcompletion:^(FIRAuthDataResult*_NullableauthResult,NSError*_Nullableerror){if(error){// handle the error.return;}}];}}];

Next steps

After a user signs in for the first time, a new user account is created andlinked to the credentials—that is, the user name and password, phonenumber, or auth provider information—the user signed in with. This newaccount is stored as part of your Firebase project, and can be used to identifya user across every app in your project, regardless of how the user signs in.

• In your apps, you can get the user's basic profile information from theUser object. SeeManage Users.

• In yourFirebase Realtime Database andCloud StorageSecurity Rules, you can get the signed-in user's unique user ID from theauth variable, and use it to control what data a user can access.

You can allow users to sign in to your app using multiple authenticationproviders bylinking auth provider credentials to anexisting user account.

To sign out a user, callsignOut:.

letfirebaseAuth=Auth.auth()do{tryfirebaseAuth.signOut()}catchletsignOutErrorasNSError{print("Error signing out: %@",signOutError)}

NSError*signOutError;BOOLstatus=[[FIRAuthauth]signOut:&signOutError];if(!status){NSLog(@"Error signing out: %@",signOutError);return;}

You may also want to add error handling code for the full range of authentication errors. SeeHandle Errors.