Social Authentication

Social authentication is a multi-step authentication flow, allowing you to sign a user into an account or link them with an existing one.

Both native platforms and web support creating a credential which can then be passed to the signInWithCredential or linkWithCredential methods. Alternatively on web platforms, you can trigger the authentication process via a popup or redirect.

Google

Most configuration is already setup when using Google Sign-In with Firebase, however you need to ensure your machine's SHA1 key has been configured for use with Android. You can see how to generate the key on the Installation documentation.

Ensure the "Google" sign-in provider is enabled on the Firebase Console.

If your user signs in with Google, after having already manually registered an account, their authentication provider will automatically change to Google, due to Firebase Authentications concept of trusted providers. You can find out more about this here.

On native platforms, a 3rd party library is required to trigger the authentication flow.

Install the official google_sign_in plugin:

pubspec.yaml
dependencies:
google_sign_in: "^4.5.1"

Once installed, trigger the sign-in flow and create a new credential:

import 'package:google_sign_in/google_sign_in.dart';
Future<UserCredential> signInWithGoogle() async {
// Trigger the authentication flow
final GoogleSignInAccount googleUser = await GoogleSignIn().signIn();
// Obtain the auth details from the request
final GoogleSignInAuthentication googleAuth = await googleUser.authentication;
// Create a new credential
final GoogleAuthCredential credential = GoogleAuthProvider.credential(
accessToken: googleAuth.accessToken,
idToken: googleAuth.idToken,
);
// Once signed in, return the UserCredential
return await FirebaseAuth.instance.signInWithCredential(credential);
}

Facebook

Before getting started setup your Facebook Developer App and follow the setup process to enable Facebook Login.

Ensure the "Facebook" sign-in provider is enabled on the Firebase Console. with the Facebook App ID and Secret set.

On native platforms, a 3rd party library is required to both install the Facebook SDK and trigger the authentication flow.

Install the flutter_facebook_auth plugin:

pubspec.yaml
dependencies:
flutter_facebook_auth: "^0.3.0"

You will need to follow the steps in the plugin documentation to ensure that both the Android & iOS Facebook SDKs have been initialized correctly. Once complete, trigger the sign-in flow, create a Facebook credential and sign the user in:

import 'package:flutter_facebook_auth/flutter_facebook_auth.dart';
Future<UserCredential> signInWithFacebook() async {
// Trigger the sign-in flow
final LoginResult result = await FacebookAuth.instance.login();
// Create a credential from the access token
final FacebookAuthCredential facebookAuthCredential =
FacebookAuthProvider.credential(result.accessToken.token);
// Once signed in, return the UserCredential
return await FirebaseAuth.instance.signInWithCredential(facebookAuthCredential);
}

Apple

Apple announced that any applications using 3rd party login services (such as Facebook, Twitter, Google etc) must also have an Apple Sign-In method. Apple Sign-In is not required for Android devices.

To integrate Apple Sign-In on your iOS application, you will need to install a 3rd party library to authenticate with Apple. Once authentication is successful, a Firebase credential can then be used to sign the user into Firebase with their Apple account

The example below is based on sign_in_with_apple Flutter package.

import 'dart:math';
import 'dart:convert';
import 'dart:io';
import 'package:crypto/crypto.dart';
import 'package:sign_in_with_apple/sign_in_with_apple.dart';
import 'package:firebase_auth/firebase_auth.dart';
String _createNonce(int length) {
final random = Random();
final charCodes = List<int>.generate(length, (_) {
int codeUnit;
switch (random.nextInt(3)) {
case 0:
codeUnit = random.nextInt(10) + 48;
break;
case 1:
codeUnit = random.nextInt(26) + 65;
break;
case 2:
codeUnit = random.nextInt(26) + 97;
break;
}
return codeUnit;
});
return String.fromCharCodes(charCodes);
}
Future<OAuthCredential> _createAppleOAuthCred() async {
final nonce = _createNonce(32);
final nativeAppleCred = Platform.isIOS
? await SignInWithApple.getAppleIDCredential(
scopes: [
AppleIDAuthorizationScopes.email,
AppleIDAuthorizationScopes.fullName,
],
nonce: sha256.convert(utf8.encode(nonce)).toString(),
)
: await SignInWithApple.getAppleIDCredential(
scopes: [
AppleIDAuthorizationScopes.email,
AppleIDAuthorizationScopes.fullName,
],
webAuthenticationOptions: WebAuthenticationOptions(
redirectUri: Uri.parse(
'https://your-project-name.firebaseapp.com/__/auth/handler'),
clientId: 'your.app.bundle.name',
),
nonce: sha256.convert(utf8.encode(nonce)).toString(),
);
return new OAuthCredential(
providerId: "apple.com", // MUST be "apple.com"
signInMethod: "oauth", // MUST be "oauth"
accessToken: nativeAppleCred.identityToken, // propagate Apple ID token to BOTH accessToken and idToken parameters
idToken: nativeAppleCred.identityToken,
rawNonce: nonce,
);
}
// sign in with Apple OAuth2 credential:
final oauthCred = await _createAppleOAuthCred();
await FirebaseAuth.instance.signInWithCredential(oauthCred);
// or link Apple OAuth2 credential to existing account:
final oauthCred = await _createAppleOAuthCred();
await FirebaseAuth.instance.currentUser.linkWithCredential(oauthCred);

Twitter

Ensure the "Twitter" sign-in provider is enabled on the Firebase Console with an API Key and API Secret set.

On native platforms, a 3rd party library is required to both install the Twitter SDK and trigger the authentication flow.

Install the flutter_twitter_login plugin:

pubspec.yaml
dependencies:
flutter_twitter_login: ^1.1.0

You will need to ensure that your application in the Twitter Developer Portal has a callback URL of twittersdk:// for Android, and twitterkit-CONSUMERKEY:// for iOS. Once complete, trigger the sign-in flow, create a Twitter credential and sign the user in:

import 'package:flutter_twitter_login/flutter_twitter_login.dart';
Future<UserCredential> signInWithTwitter() async {
// Create a TwitterLogin instance
final TwitterLogin twitterLogin = new TwitterLogin(
consumerKey: '<your consumer key>',
consumerSecret:' <your consumer secret>',
);
// Trigger the sign-in flow
final TwitterLoginResult loginResult = await twitterLogin.authorize();
// Get the Logged In session
final TwitterSession twitterSession = loginResult.session;
// Create a credential from the access token
final AuthCredential twitterAuthCredential =
TwitterAuthProvider.credential(accessToken: twitterSession.token, secret: twitterSession.secret);
// Once signed in, return the UserCredential
return await FirebaseAuth.instance.signInWithCredential(twitterAuthCredential);
}

Please note there is an outstanding issue with this package, regarding iOS and the use of UIWebView which is deprecated.

GitHub

Ensure that you have setup an OAuth App from your GitHub Developer Settings and that the "GitHub" sign-in provider is enabled on the Firebase Console with the Client ID and Secret are set, with the callback URL set in the GitHub app.

On native platforms, a 3rd party library is required to both install the GitHub SDK and trigger the authentication flow.

Install the github_sign_in plugin:

pubspec.yaml
dependencies:
github_sign_in: ^0.0.1

You will need to populate the GitHubSignIn instance with your GitHub Client ID, GitHub Client Secret and also a Redirect URL (Firebase callback url). Once complete trigger the sign-in flow, create a GitHub credential and sign the user in:

import 'package:github_sign_in/github_sign_in.dart';
Future<UserCredential> signInWithGitHub() async {
// Create a GitHubSignIn instance
final GitHubSignIn gitHubSignIn = GitHubSignIn(
clientId: clientId,
clientSecret: clientSecret,
redirectUrl: 'https://my-project.firebaseapp.com/__/auth/handler');
// Trigger the sign-in flow
final result = await gitHubSignIn.signIn(context);
// Create a credential from the access token
final AuthCredential githubAuthCredential = GithubAuthProvider.credential(result.token);
// Once signed in, return the UserCredential
return await FirebaseAuth.instance.signInWithCredential(githubAuthCredential);
}