If you've upgraded toFirebase Authentication with Identity Platform, you can authenticate your users withFirebase using the OpenID Connect (OIDC) compliant provider of your choice. Thismakes it possible to use identity providers not natively supported by Firebase.

Before you begin

To sign in users using an OIDC provider, you must first collect some informationfrom the provider:

• Client ID: A string unique to the provider that identifies your app. Yourprovider might assign you a different client ID for each platform you support.This is one of the values of theaud claim in ID tokens issued by yourprovider.

• Client secret: A secret string that the provider uses to confirm ownershipof a client ID. For every client ID, you will need a matching client secret.(This value is required only if you're using theauth code flow, which isstrongly recommended.)

• Issuer: A string that identifies your provider. This value must be a URLthat, when appended with/.well-known/openid-configuration, is the locationof the provider's OIDC discovery document. For example, if the issuer ishttps://auth.example.com, the discovery document must be available athttps://auth.example.com/.well-known/openid-configuration.

After you have the above information, enable OpenID Connect as a sign-inprovider for your Firebase project:

1. Add Firebase to your Android project.

2. If you haven't upgraded toFirebase Authentication with Identity Platform, do so. OpenID Connect authenticationis only available in upgraded projects.

3. On theSign-in providerspage of theFirebase console, clickAdd new provider, and then clickOpenID Connect.

4. Select whether you will be using theauthorization code flow or theimplicit grant flow.

   You should use always the code flow if your provider supports it. Theimplicit flow is less secure and using it is strongly discouraged.

5. Give a name to this provider. Note the provider ID that's generated:something likeoidc.example-provider. You'll need this ID when you addsign-in code to your app.

6. Specify your client ID and client secret, and your provider's issuer string.These values must exactly match the values your provider assigned to you.

7. Save your changes.

Handle the sign-in flow with the Firebase SDK

If you are building an Android app, the easiest way to authenticate your userswith Firebase using your OIDC provider is to handle the entire sign-in flow withthe Firebase Android SDK.

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

1. Construct an instance of anOAuthProvider using itsBuilder with theprovider's ID

   Kotlin

   valproviderBuilder=OAuthProvider.newBuilder("oidc.example-provider")
   GenericIdpActivity.kt

   Java

   OAuthProvider.BuilderproviderBuilder=OAuthProvider.newBuilder("oidc.example-provider");
   GenericIdpActivity.java

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

   Kotlin

   // Target specific email with login hint.providerBuilder.addCustomParameter("login_hint","user@example.com")
   GenericIdpActivity.kt

   Java

   // Target specific email with login hint.providerBuilder.addCustomParameter("login_hint","user@example.com");
   GenericIdpActivity.java

   Check with your OIDC provider for the parameters they support. Note that you can't pass Firebase-required parameters withsetCustomParameters(). These parameters areclient_id,response_type,redirect_uri,state,scope andresponse_mode.

3. Optional: Specify additional OAuth 2.0 scopes beyond basic profile thatyou want to request from the authentication provider.

   Kotlin

   // Request read access to a user's email addresses.// This must be preconfigured in the app's API permissions.providerBuilder.scopes=listOf("mail.read","calendars.read")
   GenericIdpActivity.kt

   Java

   // Request read access to a user's email addresses.// This must be preconfigured in the app's API permissions.List<String>scopes=newArrayList<String>(){{add("mail.read");add("calendars.read");}};providerBuilder.setScopes(scopes);
   GenericIdpActivity.java

   Check with your OIDC provider for the scopes they use.

4. Authenticate with Firebase using the OAuth provider object. Note that unlikeother FirebaseAuthoperations, this will take control of your UI by popping up aCustom Chrome Tab.As a result, do not reference your Activity in theOnSuccessListenerandOnFailureListener that you attach as they will immediately detach whenthe operation starts the UI.

   You should first check if you've already received a response. Signing in withthis method puts your Activity in the background, which means that it can bereclaimed by the system during the sign in flow. In order to make sure thatyou don't make the user try again if this happens, you should check if aresult is already present.

   To check if there is a pending result, callgetPendingAuthResult:

   Kotlin

   valpendingResultTask=firebaseAuth.pendingAuthResultif(pendingResultTask!=null){// There's something already here! Finish the sign-in for your user.pendingResultTask.addOnSuccessListener{// User is signed in.// IdP data available in// authResult.getAdditionalUserInfo().getProfile().// The OAuth access token can also be retrieved:// ((OAuthCredential)authResult.getCredential()).getAccessToken().// The OAuth secret can be retrieved by calling:// ((OAuthCredential)authResult.getCredential()).getSecret().}.addOnFailureListener{// Handle failure.}}else{// There's no pending result so you need to start the sign-in flow.// See below.}
   GenericIdpActivity.kt

   Java

   Task<AuthResult>pendingResultTask=firebaseAuth.getPendingAuthResult();if(pendingResultTask!=null){// There's something already here! Finish the sign-in for your user.pendingResultTask.addOnSuccessListener(newOnSuccessListener<AuthResult>(){@OverridepublicvoidonSuccess(AuthResultauthResult){// User is signed in.// IdP data available in// authResult.getAdditionalUserInfo().getProfile().// The OAuth access token can also be retrieved:// ((OAuthCredential)authResult.getCredential()).getAccessToken().// The OAuth secret can be retrieved by calling:// ((OAuthCredential)authResult.getCredential()).getSecret().}}).addOnFailureListener(newOnFailureListener(){@OverridepublicvoidonFailure(@NonNullExceptione){// Handle failure.}});}else{// There's no pending result so you need to start the sign-in flow.// See below.}
   GenericIdpActivity.java

   To start the sign in flow, callstartActivityForSignInWithProvider:

   Kotlin

   firebaseAuth.startActivityForSignInWithProvider(activity,provider.build()).addOnSuccessListener{// User is signed in.// IdP data available in// authResult.getAdditionalUserInfo().getProfile().// The OAuth access token can also be retrieved:// ((OAuthCredential)authResult.getCredential()).getAccessToken().// The OAuth secret can be retrieved by calling:// ((OAuthCredential)authResult.getCredential()).getSecret().}.addOnFailureListener{// Handle failure.}
   GenericIdpActivity.kt

   Java

   firebaseAuth.startActivityForSignInWithProvider(/* activity= */this,provider.build()).addOnSuccessListener(newOnSuccessListener<AuthResult>(){@OverridepublicvoidonSuccess(AuthResultauthResult){// User is signed in.// IdP data available in// authResult.getAdditionalUserInfo().getProfile().// The OAuth access token can also be retrieved:// ((OAuthCredential)authResult.getCredential()).getAccessToken().// The OAuth secret can be retrieved by calling:// ((OAuthCredential)authResult.getCredential()).getSecret().}}).addOnFailureListener(newOnFailureListener(){@OverridepublicvoidonFailure(@NonNullExceptione){// Handle failure.}});
   GenericIdpActivity.java

5. While the above examples focus on sign-in flows, you also have theability to link an OIDC provider to an existing user usingstartActivityForLinkWithProvider. For example, you can link multipleproviders to the same user allowing them to sign in with either.

   Kotlin

   // The user is already signed-in.valfirebaseUser=firebaseAuth.currentUser!!firebaseUser.startActivityForLinkWithProvider(activity,provider.build()).addOnSuccessListener{// Provider credential is linked to the current user.// IdP data available in// authResult.getAdditionalUserInfo().getProfile().// The OAuth access token can also be retrieved:// authResult.getCredential().getAccessToken().// The OAuth secret can be retrieved by calling:// authResult.getCredential().getSecret().}.addOnFailureListener{// Handle failure.}
   GenericIdpActivity.kt

   Java

   // The user is already signed-in.FirebaseUserfirebaseUser=firebaseAuth.getCurrentUser();firebaseUser.startActivityForLinkWithProvider(/* activity= */this,provider.build()).addOnSuccessListener(newOnSuccessListener<AuthResult>(){@OverridepublicvoidonSuccess(AuthResultauthResult){// Provider credential is linked to the current user.// IdP data available in// authResult.getAdditionalUserInfo().getProfile().// The OAuth access token can also be retrieved:// authResult.getCredential().getAccessToken().// The OAuth secret can be retrieved by calling:// authResult.getCredential().getSecret().}}).addOnFailureListener(newOnFailureListener(){@OverridepublicvoidonFailure(@NonNullExceptione){// Handle failure.}});
   GenericIdpActivity.java

6. The same pattern can be used withstartActivityForReauthenticateWithProvider which can be used to retrievefresh credentials for sensitive operations that require recent login.

   Kotlin

   // The user is already signed-in.valfirebaseUser=firebaseAuth.currentUser!!firebaseUser.startActivityForReauthenticateWithProvider(activity,provider.build()).addOnSuccessListener{// User is re-authenticated with fresh tokens and// should be able to perform sensitive operations// like account deletion and email or password// update.}.addOnFailureListener{// Handle failure.}
   GenericIdpActivity.kt

   Java

   // The user is already signed-in.FirebaseUserfirebaseUser=firebaseAuth.getCurrentUser();firebaseUser.startActivityForReauthenticateWithProvider(/* activity= */this,provider.build()).addOnSuccessListener(newOnSuccessListener<AuthResult>(){@OverridepublicvoidonSuccess(AuthResultauthResult){// User is re-authenticated with fresh tokens and// should be able to perform sensitive operations// like account deletion and email or password// update.}}).addOnFailureListener(newOnFailureListener(){@OverridepublicvoidonFailure(@NonNullExceptione){// Handle failure.}});
   GenericIdpActivity.java

Handle the sign-in flow manually

If you've already implemented the OpenID Connect sign-in flow in your app, youcan use the ID token directly to authenticate with Firebase:

valproviderId="oidc.example-provider"// As registered in Firebase console.valcredential=oAuthCredential(providerId){setIdToken(idToken)// ID token from OpenID Connect flow.}Firebase.auth.signInWithCredential(credential).addOnSuccessListener{authResult->// User is signed in.// IdP data available in://    authResult.additionalUserInfo.profile}.addOnFailureListener{e->// Handle failure.}
GenericIdpActivity.kt

AuthCredentialcredential=OAuthProvider.newCredentialBuilder("oidc.example-provider")// As registered in Firebase console..setIdToken(idToken)// ID token from OpenID Connect flow..build();FirebaseAuth.getInstance().signInWithCredential(credential).addOnSuccessListener(newOnSuccessListener<AuthResult>(){@OverridepublicvoidonSuccess(AuthResultauthResult){// User is signed in.// IdP data available in://    authResult.getAdditionalUserInfo().getProfile()}}).addOnFailureListener(newOnFailureListener(){@OverridepublicvoidonFailure(@NonNullExceptione){// Handle failure.}});
GenericIdpActivity.java

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 theFirebaseUser 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:

Firebase.auth.signOut()
MainActivity.kt

FirebaseAuth.getInstance().signOut();
MainActivity.java