spring-security/docs/modules/ROOT/pages/reactive/oauth2/login/advanced.adoc

[[webflux-oauth2-login-advanced]]
= Advanced Configuration

The OAuth 2.0 Authorization Framework defines the https://tools.ietf.org/html/rfc6749#section-3[Protocol Endpoints] as follows:

The authorization process utilizes two authorization server endpoints (HTTP resources):

* Authorization Endpoint: Used by the client to obtain authorization from the resource owner via user-agent redirection.
* Token Endpoint: Used by the client to exchange an authorization grant for an access token, typically with client authentication.

As well as one client endpoint:

* Redirection Endpoint: Used by the authorization server to return responses containing authorization credentials to the client via the resource owner user-agent.

The OpenID Connect Core 1.0 specification defines the https://openid.net/specs/openid-connect-core-1_0.html#UserInfo[UserInfo Endpoint] as follows:

The UserInfo Endpoint is an OAuth 2.0 Protected Resource that returns claims about the authenticated end-user.
To obtain the requested claims about the end-user, the client makes a request to the UserInfo Endpoint by using an access token obtained through OpenID Connect Authentication.
These claims are normally represented by a JSON object that contains a collection of name-value pairs for the claims.

`ServerHttpSecurity.oauth2Login()` provides a number of configuration options for customizing OAuth 2.0 Login.

The following code shows the complete configuration options available for the `oauth2Login()` DSL:

.OAuth2 Login Configuration Options
====
.Java
[source,java,role="primary"]
----
@Configuration
@EnableWebFluxSecurity
public class OAuth2LoginSecurityConfig {

	@Bean
	SecurityWebFilterChain springSecurityFilterChain(ServerHttpSecurity http) {
		http
			.oauth2Login(oauth2 -> oauth2
				.authenticationConverter(this.authenticationConverter())
				.authenticationMatcher(this.authenticationMatcher())
				.authenticationManager(this.authenticationManager())
				.authenticationSuccessHandler(this.authenticationSuccessHandler())
				.authenticationFailureHandler(this.authenticationFailureHandler())
				.clientRegistrationRepository(this.clientRegistrationRepository())
				.authorizedClientRepository(this.authorizedClientRepository())
				.authorizedClientService(this.authorizedClientService())
				.authorizationRequestResolver(this.authorizationRequestResolver())
				.authorizationRequestRepository(this.authorizationRequestRepository())
				.securityContextRepository(this.securityContextRepository())
			);

		return http.build();
	}
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
@Configuration
@EnableWebFluxSecurity
class OAuth2LoginSecurityConfig {

    @Bean
    fun securityWebFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
        http {
            oauth2Login {
                authenticationConverter = authenticationConverter()
                authenticationMatcher = authenticationMatcher()
                authenticationManager = authenticationManager()
                authenticationSuccessHandler = authenticationSuccessHandler()
                authenticationFailureHandler = authenticationFailureHandler()
                clientRegistrationRepository = clientRegistrationRepository()
                authorizedClientRepository = authorizedClientRepository()
                authorizedClientService = authorizedClientService()
                authorizationRequestResolver = authorizationRequestResolver()
                authorizationRequestRepository = authorizationRequestRepository()
                securityContextRepository = securityContextRepository()
            }
        }

        return http.build()
    }
}
----
====

The following sections go into more detail on each of the configuration options available:

* <<webflux-oauth2-login-advanced-login-page, OAuth 2.0 Login Page>>
* <<webflux-oauth2-login-advanced-redirection-endpoint, Redirection Endpoint>>
* <<webflux-oauth2-login-advanced-userinfo-endpoint, UserInfo Endpoint>>
* <<webflux-oauth2-login-advanced-idtoken-verify, ID Token Signature Verification>>
* <<webflux-oauth2-login-advanced-oidc-logout, OpenID Connect 1.0 Logout>>


[[webflux-oauth2-login-advanced-login-page]]
== OAuth 2.0 Login Page

By default, the OAuth 2.0 Login Page is auto-generated by the `LoginPageGeneratingWebFilter`.
The default login page shows each configured OAuth Client with its `ClientRegistration.clientName` as a link, which is capable of initiating the Authorization Request (or OAuth 2.0 Login).

[NOTE]
In order for `LoginPageGeneratingWebFilter` to show links for configured OAuth Clients, the registered `ReactiveClientRegistrationRepository` needs to also implement `Iterable<ClientRegistration>`.
See `InMemoryReactiveClientRegistrationRepository` for reference.

The link's destination for each OAuth Client defaults to the following:

`+"/oauth2/authorization/{registrationId}"+`

The following line shows an example:

[source,html]
----
<a href="/oauth2/authorization/google">Google</a>
----

To override the default login page, configure the `exceptionHandling().authenticationEntryPoint()` and (optionally) `oauth2Login().authorizationRequestResolver()`.

The following listing shows an example:

.OAuth2 Login Page Configuration
====
.Java
[source,java,role="primary",subs="-attributes"]
----
@Configuration
@EnableWebFluxSecurity
public class OAuth2LoginSecurityConfig {

	@Bean
	public SecurityWebFilterChain securityWebFilterChain(ServerHttpSecurity http) {
		http
			.exceptionHandling(exceptionHandling -> exceptionHandling
				.authenticationEntryPoint(new RedirectServerAuthenticationEntryPoint("/login/oauth2"))
			)
			.oauth2Login(oauth2 -> oauth2
				.authorizationRequestResolver(this.authorizationRequestResolver())
			);

		return http.build();
	}

	private ServerOAuth2AuthorizationRequestResolver authorizationRequestResolver() {
		ServerWebExchangeMatcher authorizationRequestMatcher =
				new PathPatternParserServerWebExchangeMatcher(
						"/login/oauth2/authorization/{registrationId}");

		return new DefaultServerOAuth2AuthorizationRequestResolver(
				this.clientRegistrationRepository(), authorizationRequestMatcher);
	}

	...
}
----

.Kotlin
[source,kotlin,role="secondary",subs="-attributes"]
----
@Configuration
@EnableWebFluxSecurity
class OAuth2LoginSecurityConfig {

    @Bean
    fun securityWebFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
        http {
            exceptionHandling {
                authenticationEntryPoint = RedirectServerAuthenticationEntryPoint("/login/oauth2")
            }
            oauth2Login {
                authorizationRequestResolver = authorizationRequestResolver()
            }
        }

        return http.build()
    }

    private fun authorizationRequestResolver(): ServerOAuth2AuthorizationRequestResolver {
        val authorizationRequestMatcher: ServerWebExchangeMatcher = PathPatternParserServerWebExchangeMatcher(
            "/login/oauth2/authorization/{registrationId}"
        )

        return DefaultServerOAuth2AuthorizationRequestResolver(
            clientRegistrationRepository(), authorizationRequestMatcher
        )
    }

    ...
}
----
====

[IMPORTANT]
You need to provide a `@Controller` with a `@RequestMapping("/login/oauth2")` that is capable of rendering the custom login page.

[TIP]
====
As noted earlier, configuring `oauth2Login().authorizationRequestResolver()` is optional.
However, if you choose to customize it, ensure the link to each OAuth Client matches the pattern provided through the `ServerWebExchangeMatcher`.

The following line shows an example:

[source,html]
----
<a href="/login/oauth2/authorization/google">Google</a>
----
====


[[webflux-oauth2-login-advanced-redirection-endpoint]]
== Redirection Endpoint

The Redirection Endpoint is used by the Authorization Server for returning the Authorization Response (which contains the authorization credentials) to the client via the Resource Owner user-agent.

[TIP]
OAuth 2.0 Login leverages the Authorization Code Grant.
Therefore, the authorization credential is the authorization code.

The default Authorization Response redirection endpoint is `+/login/oauth2/code/{registrationId}+`.

If you would like to customize the Authorization Response redirection endpoint, configure it as shown in the following example:

.Redirection Endpoint Configuration
====
.Java
[source,java,role="primary",subs="-attributes"]
----
@Configuration
@EnableWebFluxSecurity
public class OAuth2LoginSecurityConfig {

	@Bean
	public SecurityWebFilterChain securityWebFilterChain(ServerHttpSecurity http) {
		http
			.oauth2Login(oauth2 -> oauth2
				.authenticationMatcher(new PathPatternParserServerWebExchangeMatcher("/login/oauth2/callback/{registrationId}"))
			);

		return http.build();
	}
}
----

.Kotlin
[source,kotlin,role="secondary",subs="-attributes"]
----
@Configuration
@EnableWebFluxSecurity
class OAuth2LoginSecurityConfig {

    @Bean
    fun securityWebFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
        http {
            oauth2Login {
                authenticationMatcher = PathPatternParserServerWebExchangeMatcher("/login/oauth2/callback/{registrationId}")
            }
        }

        return http.build()
    }
}
----
====

[IMPORTANT]
====
You also need to ensure the `ClientRegistration.redirectUri` matches the custom Authorization Response redirection endpoint.

The following listing shows an example:

.Java
[source,java,role="primary",subs="-attributes"]
----
return CommonOAuth2Provider.GOOGLE.getBuilder("google")
	.clientId("google-client-id")
	.clientSecret("google-client-secret")
	.redirectUri("{baseUrl}/login/oauth2/callback/{registrationId}")
	.build();
----

.Kotlin
[source,kotlin,role="secondary",subs="-attributes"]
----
return CommonOAuth2Provider.GOOGLE.getBuilder("google")
    .clientId("google-client-id")
    .clientSecret("google-client-secret")
    .redirectUri("{baseUrl}/login/oauth2/callback/{registrationId}")
    .build()
----
====


[[webflux-oauth2-login-advanced-userinfo-endpoint]]
== UserInfo Endpoint

The UserInfo Endpoint includes a number of configuration options, as described in the following sub-sections:

* <<webflux-oauth2-login-advanced-map-authorities, Mapping User Authorities>>
* <<webflux-oauth2-login-advanced-oauth2-user-service, OAuth 2.0 UserService>>
* <<webflux-oauth2-login-advanced-oidc-user-service, OpenID Connect 1.0 UserService>>


[[webflux-oauth2-login-advanced-map-authorities]]
=== Mapping User Authorities

After the user successfully authenticates with the OAuth 2.0 Provider, the `OAuth2User.getAuthorities()` (or `OidcUser.getAuthorities()`) contains a list of granted authorities populated from `OAuth2UserRequest.getAccessToken().getScopes()` and prefixed with `SCOPE_`.
These granted authorities may be mapped to a new set of `GrantedAuthority` instances, which will be supplied to `OAuth2AuthenticationToken` when completing the authentication.

[TIP]
`OAuth2AuthenticationToken.getAuthorities()` is used for authorizing requests, such as in `hasRole('USER')` or `hasRole('ADMIN')`.

There are a couple of options to choose from when mapping user authorities:

* <<webflux-oauth2-login-advanced-map-authorities-grantedauthoritiesmapper, Using a GrantedAuthoritiesMapper>>
* <<webflux-oauth2-login-advanced-map-authorities-reactiveoauth2userservice, Delegation-based strategy with ReactiveOAuth2UserService>>


[[webflux-oauth2-login-advanced-map-authorities-grantedauthoritiesmapper]]
==== Using a GrantedAuthoritiesMapper

The `GrantedAuthoritiesMapper` is given a list of granted authorities which contains a special authority of type `OAuth2UserAuthority` and the authority string `OAUTH2_USER` (or `OidcUserAuthority` and the authority string `OIDC_USER`).

Register a `GrantedAuthoritiesMapper` `@Bean` to have it automatically applied to the configuration, as shown in the following example:

.Granted Authorities Mapper Configuration
====
.Java
[source,java,role="primary"]
----
@Configuration
@EnableWebFluxSecurity
public class OAuth2LoginSecurityConfig {

	@Bean
	public SecurityWebFilterChain securityWebFilterChain(ServerHttpSecurity http) {
		http
			...
			.oauth2Login(withDefaults());

		return http.build();
	}

	@Bean
	public GrantedAuthoritiesMapper userAuthoritiesMapper() {
		return (authorities) -> {
			Set<GrantedAuthority> mappedAuthorities = new HashSet<>();

			authorities.forEach(authority -> {
				if (OidcUserAuthority.class.isInstance(authority)) {
					OidcUserAuthority oidcUserAuthority = (OidcUserAuthority)authority;

					OidcIdToken idToken = oidcUserAuthority.getIdToken();
					OidcUserInfo userInfo = oidcUserAuthority.getUserInfo();

					// Map the claims found in idToken and/or userInfo
					// to one or more GrantedAuthority's and add it to mappedAuthorities

				} else if (OAuth2UserAuthority.class.isInstance(authority)) {
					OAuth2UserAuthority oauth2UserAuthority = (OAuth2UserAuthority)authority;

					Map<String, Object> userAttributes = oauth2UserAuthority.getAttributes();

					// Map the attributes found in userAttributes
					// to one or more GrantedAuthority's and add it to mappedAuthorities

				}
			});

			return mappedAuthorities;
		};
	}
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
@Configuration
@EnableWebFluxSecurity
class OAuth2LoginSecurityConfig {

    @Bean
    fun securityWebFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
        http {
            oauth2Login { }
        }

        return http.build()
    }

    @Bean
    fun userAuthoritiesMapper(): GrantedAuthoritiesMapper = GrantedAuthoritiesMapper { authorities: Collection<GrantedAuthority> ->
        val mappedAuthorities = emptySet<GrantedAuthority>()

        authorities.forEach { authority ->
            if (authority is OidcUserAuthority) {
                val idToken = authority.idToken
                val userInfo = authority.userInfo
                // Map the claims found in idToken and/or userInfo
                // to one or more GrantedAuthority's and add it to mappedAuthorities
            } else if (authority is OAuth2UserAuthority) {
                val userAttributes = authority.attributes
                // Map the attributes found in userAttributes
                // to one or more GrantedAuthority's and add it to mappedAuthorities
            }
        }

        mappedAuthorities
    }
}
----
====

[[webflux-oauth2-login-advanced-map-authorities-reactiveoauth2userservice]]
==== Delegation-based strategy with ReactiveOAuth2UserService

This strategy is advanced compared to using a `GrantedAuthoritiesMapper`, however, it's also more flexible as it gives you access to the `OAuth2UserRequest` and `OAuth2User` (when using an OAuth 2.0 UserService) or `OidcUserRequest` and `OidcUser` (when using an OpenID Connect 1.0 UserService).

The `OAuth2UserRequest` (and `OidcUserRequest`) provides you access to the associated `OAuth2AccessToken`, which is very useful in the cases where the _delegator_ needs to fetch authority information from a protected resource before it can map the custom authorities for the user.

The following example shows how to implement and configure a delegation-based strategy using an OpenID Connect 1.0 UserService:

.ReactiveOAuth2UserService Configuration
====
.Java
[source,java,role="primary"]
----
@Configuration
@EnableWebFluxSecurity
public class OAuth2LoginSecurityConfig {

	@Bean
	public SecurityWebFilterChain securityWebFilterChain(ServerHttpSecurity http) {
		http
			...
			.oauth2Login(withDefaults());

		return http.build();
	}

	@Bean
	public ReactiveOAuth2UserService<OidcUserRequest, OidcUser> oidcUserService() {
		final OidcReactiveOAuth2UserService delegate = new OidcReactiveOAuth2UserService();

		return (userRequest) -> {
			// Delegate to the default implementation for loading a user
			return delegate.loadUser(userRequest)
					.flatMap((oidcUser) -> {
						OAuth2AccessToken accessToken = userRequest.getAccessToken();
						Set<GrantedAuthority> mappedAuthorities = new HashSet<>();

						// TODO
						// 1) Fetch the authority information from the protected resource using accessToken
						// 2) Map the authority information to one or more GrantedAuthority's and add it to mappedAuthorities

						// 3) Create a copy of oidcUser but use the mappedAuthorities instead
						oidcUser = new DefaultOidcUser(mappedAuthorities, oidcUser.getIdToken(), oidcUser.getUserInfo());

						return Mono.just(oidcUser);
					});
		};
	}
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
@Configuration
@EnableWebFluxSecurity
class OAuth2LoginSecurityConfig {

    @Bean
    fun securityWebFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
        http {
            oauth2Login { }
        }

        return http.build()
    }

    @Bean
    fun oidcUserService(): ReactiveOAuth2UserService<OidcUserRequest, OidcUser> {
        val delegate = OidcReactiveOAuth2UserService()

        return ReactiveOAuth2UserService { userRequest ->
            // Delegate to the default implementation for loading a user
            delegate.loadUser(userRequest)
                .flatMap { oidcUser ->
                    val accessToken = userRequest.accessToken
                    val mappedAuthorities = mutableSetOf<GrantedAuthority>()

                    // TODO
                    // 1) Fetch the authority information from the protected resource using accessToken
                    // 2) Map the authority information to one or more GrantedAuthority's and add it to mappedAuthorities
                    // 3) Create a copy of oidcUser but use the mappedAuthorities instead
                    val mappedOidcUser = DefaultOidcUser(mappedAuthorities, oidcUser.idToken, oidcUser.userInfo)

                    Mono.just(mappedOidcUser)
                }
        }
    }
}
----
====


[[webflux-oauth2-login-advanced-oauth2-user-service]]
=== OAuth 2.0 UserService

`DefaultReactiveOAuth2UserService` is an implementation of a `ReactiveOAuth2UserService` that supports standard OAuth 2.0 Provider's.

[NOTE]
`ReactiveOAuth2UserService` obtains the user attributes of the end-user (the resource owner) from the UserInfo Endpoint (by using the access token granted to the client during the authorization flow) and returns an `AuthenticatedPrincipal` in the form of an `OAuth2User`.

`DefaultReactiveOAuth2UserService` uses a `WebClient` when requesting the user attributes at the UserInfo Endpoint.

If you need to customize the pre-processing of the UserInfo Request and/or the post-handling of the UserInfo Response, you will need to provide `DefaultReactiveOAuth2UserService.setWebClient()` with a custom configured `WebClient`.

Whether you customize `DefaultReactiveOAuth2UserService` or provide your own implementation of `ReactiveOAuth2UserService`, you'll need to configure it as shown in the following example:

====
.Java
[source,java,role="primary"]
----
@Configuration
@EnableWebFluxSecurity
public class OAuth2LoginSecurityConfig {

	@Bean
	public SecurityWebFilterChain securityWebFilterChain(ServerHttpSecurity http) {
		http
			...
			.oauth2Login(withDefaults());

		return http.build();
	}

	@Bean
	public ReactiveOAuth2UserService<OAuth2UserRequest, OAuth2User> oauth2UserService() {
		...
	}
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
@Configuration
@EnableWebFluxSecurity
class OAuth2LoginSecurityConfig {

    @Bean
    fun securityWebFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
        http {
            oauth2Login { }
        }

        return http.build()
    }

    @Bean
    fun oauth2UserService(): ReactiveOAuth2UserService<OAuth2UserRequest, OAuth2User> {
        // ...
    }
}
----
====


[[webflux-oauth2-login-advanced-oidc-user-service]]
=== OpenID Connect 1.0 UserService

`OidcReactiveOAuth2UserService` is an implementation of a `ReactiveOAuth2UserService` that supports OpenID Connect 1.0 Provider's.

The `OidcReactiveOAuth2UserService` leverages the `DefaultReactiveOAuth2UserService` when requesting the user attributes at the UserInfo Endpoint.

If you need to customize the pre-processing of the UserInfo Request and/or the post-handling of the UserInfo Response, you will need to provide `OidcReactiveOAuth2UserService.setOauth2UserService()` with a custom configured `ReactiveOAuth2UserService`.

Whether you customize `OidcReactiveOAuth2UserService` or provide your own implementation of `ReactiveOAuth2UserService` for OpenID Connect 1.0 Provider's, you'll need to configure it as shown in the following example:

====
.Java
[source,java,role="primary"]
----
@Configuration
@EnableWebFluxSecurity
public class OAuth2LoginSecurityConfig {

	@Bean
	public SecurityWebFilterChain securityWebFilterChain(ServerHttpSecurity http) {
		http
			...
			.oauth2Login(withDefaults());

		return http.build();
	}

	@Bean
	public ReactiveOAuth2UserService<OidcUserRequest, OidcUser> oidcUserService() {
		...
	}
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
@Configuration
@EnableWebFluxSecurity
class OAuth2LoginSecurityConfig {

    @Bean
    fun securityWebFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
        http {
            oauth2Login { }
        }

        return http.build()
    }

    @Bean
    fun oidcUserService(): ReactiveOAuth2UserService<OidcUserRequest, OidcUser> {
        // ...
    }
}
----
====


[[webflux-oauth2-login-advanced-idtoken-verify]]
== ID Token Signature Verification

OpenID Connect 1.0 Authentication introduces the https://openid.net/specs/openid-connect-core-1_0.html#IDToken[ID Token], which is a security token that contains Claims about the Authentication of an End-User by an Authorization Server when used by a Client.

The ID Token is represented as a https://tools.ietf.org/html/rfc7519[JSON Web Token] (JWT) and MUST be signed using https://tools.ietf.org/html/rfc7515[JSON Web Signature] (JWS).

The `ReactiveOidcIdTokenDecoderFactory` provides a `ReactiveJwtDecoder` used for `OidcIdToken` signature verification. The default algorithm is `RS256` but may be different when assigned during client registration.
For these cases, a resolver may be configured to return the expected JWS algorithm assigned for a specific client.

The JWS algorithm resolver is a `Function` that accepts a `ClientRegistration` and returns the expected `JwsAlgorithm` for the client, eg. `SignatureAlgorithm.RS256` or `MacAlgorithm.HS256`

The following code shows how to configure the `OidcIdTokenDecoderFactory` `@Bean` to default to `MacAlgorithm.HS256` for all `ClientRegistration`:

====
.Java
[source,java,role="primary"]
----
@Bean
public ReactiveJwtDecoderFactory<ClientRegistration> idTokenDecoderFactory() {
	ReactiveOidcIdTokenDecoderFactory idTokenDecoderFactory = new ReactiveOidcIdTokenDecoderFactory();
	idTokenDecoderFactory.setJwsAlgorithmResolver(clientRegistration -> MacAlgorithm.HS256);
	return idTokenDecoderFactory;
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
@Bean
fun idTokenDecoderFactory(): ReactiveJwtDecoderFactory<ClientRegistration> {
    val idTokenDecoderFactory = ReactiveOidcIdTokenDecoderFactory()
    idTokenDecoderFactory.setJwsAlgorithmResolver { MacAlgorithm.HS256 }
    return idTokenDecoderFactory
}
----
====

[NOTE]
For MAC based algorithms such as `HS256`, `HS384` or `HS512`, the `client-secret` corresponding to the `client-id` is used as the symmetric key for signature verification.

[TIP]
If more than one `ClientRegistration` is configured for OpenID Connect 1.0 Authentication, the JWS algorithm resolver may evaluate the provided `ClientRegistration` to determine which algorithm to return.


[[webflux-oauth2-login-advanced-oidc-logout]]
== OpenID Connect 1.0 Logout

OpenID Connect Session Management 1.0 allows the ability to log out the End-User at the Provider using the Client.
One of the strategies available is https://openid.net/specs/openid-connect-rpinitiated-1_0.html[RP-Initiated Logout].

If the OpenID Provider supports both Session Management and https://openid.net/specs/openid-connect-discovery-1_0.html[Discovery], the client may obtain the `end_session_endpoint` `URL` from the OpenID Provider's https://openid.net/specs/openid-connect-session-1_0.html#OPMetadata[Discovery Metadata].
This can be achieved by configuring the `ClientRegistration` with the `issuer-uri`, as in the following example:

[source,yaml]
----
spring:
  security:
    oauth2:
      client:
        registration:
          okta:
            client-id: okta-client-id
            client-secret: okta-client-secret
            ...
        provider:
          okta:
            issuer-uri: https://dev-1234.oktapreview.com
----

...and the `OidcClientInitiatedServerLogoutSuccessHandler`, which implements RP-Initiated Logout, may be configured as follows:

====
.Java
[source,java,role="primary",subs="-attributes"]
----
@Configuration
@EnableWebFluxSecurity
public class OAuth2LoginSecurityConfig {

	@Autowired
	private ReactiveClientRegistrationRepository clientRegistrationRepository;

	@Bean
	public SecurityWebFilterChain securityWebFilterChain(ServerHttpSecurity http) {
		http
			.authorizeExchange(authorize -> authorize
				.anyExchange().authenticated()
			)
			.oauth2Login(withDefaults())
			.logout(logout -> logout
				.logoutSuccessHandler(oidcLogoutSuccessHandler())
			);

		return http.build();
	}

	private ServerLogoutSuccessHandler oidcLogoutSuccessHandler() {
		OidcClientInitiatedServerLogoutSuccessHandler oidcLogoutSuccessHandler =
				new OidcClientInitiatedServerLogoutSuccessHandler(this.clientRegistrationRepository);

		// Sets the location that the End-User's User Agent will be redirected to
		// after the logout has been performed at the Provider
		oidcLogoutSuccessHandler.setPostLogoutRedirectUri("{baseUrl}");

		return oidcLogoutSuccessHandler;
	}
}
----

.Kotlin
[source,kotlin,role="secondary",subs="-attributes"]
----
@Configuration
@EnableWebFluxSecurity
class OAuth2LoginSecurityConfig {

    @Autowired
    private lateinit var clientRegistrationRepository: ReactiveClientRegistrationRepository

    @Bean
    fun securityWebFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
        http {
            authorizeExchange {
                authorize(anyExchange, authenticated)
            }
            oauth2Login { }
            logout {
                logoutSuccessHandler = oidcLogoutSuccessHandler()
            }
        }

        return http.build()
    }

    private fun oidcLogoutSuccessHandler(): ServerLogoutSuccessHandler {
        val oidcLogoutSuccessHandler = OidcClientInitiatedServerLogoutSuccessHandler(clientRegistrationRepository)

        // Sets the location that the End-User's User Agent will be redirected to
        // after the logout has been performed at the Provider
        oidcLogoutSuccessHandler.setPostLogoutRedirectUri("{baseUrl}")
        return oidcLogoutSuccessHandler
    }
}
----
====

NOTE: `OidcClientInitiatedServerLogoutSuccessHandler` supports the `+{baseUrl}+` placeholder.
If used, the application's base URL, like `https://app.example.org`, will replace it at request time.