Allow to set an authentication manager for back-channel logout in ServerHttpSecurity

config/src/main/java/org/springframework/security/config/web/server/OidcBackChannelLogoutReactiveAuthenticationManager.java

@@ -64,14 +64,14 @@
  * "https://openid.net/specs/openid-connect-backchannel-1_0.html">OIDC Back-Channel
  * Logout</a>
  */
-final class OidcBackChannelLogoutReactiveAuthenticationManager implements ReactiveAuthenticationManager {
+public final class OidcBackChannelLogoutReactiveAuthenticationManager implements ReactiveAuthenticationManager {
 
 	private ReactiveJwtDecoderFactory<ClientRegistration> logoutTokenDecoderFactory;
 
 	/**
 	 * Construct an {@link OidcBackChannelLogoutReactiveAuthenticationManager}
 	 */
-	OidcBackChannelLogoutReactiveAuthenticationManager() {
+	public OidcBackChannelLogoutReactiveAuthenticationManager() {
 		Function<ClientRegistration, OAuth2TokenValidator<Jwt>> jwtValidator = (clientRegistration) -> JwtValidators
 			.createDefaultWithValidators(new OidcBackChannelLogoutTokenValidator(clientRegistration));
 		this.logoutTokenDecoderFactory = (clientRegistration) -> {
@@ -130,7 +130,7 @@ private Mono<Jwt> decode(ClientRegistration registration, String token) {
 	 * correspond to the {@link ClientRegistration} associated with the OIDC logout token.
 	 * @param logoutTokenDecoderFactory the {@link JwtDecoderFactory} to use
 	 */
-	void setLogoutTokenDecoderFactory(ReactiveJwtDecoderFactory<ClientRegistration> logoutTokenDecoderFactory) {
+	public void setLogoutTokenDecoderFactory(ReactiveJwtDecoderFactory<ClientRegistration> logoutTokenDecoderFactory) {
 		Assert.notNull(logoutTokenDecoderFactory, "logoutTokenDecoderFactory cannot be null");
 		this.logoutTokenDecoderFactory = logoutTokenDecoderFactory;
 	}

config/src/main/java/org/springframework/security/config/web/server/OidcBackChannelLogoutTokenValidator.java

@@ -46,7 +46,7 @@
  * "https://openid.net/specs/openid-connect-backchannel-1_0.html#Validation">the OIDC
  * Back-Channel Logout spec</a>
  */
-final class OidcBackChannelLogoutTokenValidator implements OAuth2TokenValidator<Jwt> {
+public final class OidcBackChannelLogoutTokenValidator implements OAuth2TokenValidator<Jwt> {
 
 	private static final String LOGOUT_VALIDATION_URL = "https://openid.net/specs/openid-connect-backchannel-1_0.html#Validation";
 
@@ -56,7 +56,7 @@ final class OidcBackChannelLogoutTokenValidator implements OAuth2TokenValidator<
 
 	private final String issuer;
 
-	OidcBackChannelLogoutTokenValidator(ClientRegistration clientRegistration) {
+	public OidcBackChannelLogoutTokenValidator(ClientRegistration clientRegistration) {
 		this.audience = clientRegistration.getClientId();
 		String issuer = clientRegistration.getProviderDetails().getIssuerUri();
 		Assert.hasText(issuer, "Provider issuer cannot be null");

config/src/main/java/org/springframework/security/config/web/server/ServerHttpSecurity.java

@@ -5600,7 +5600,7 @@ public final class BackChannelLogoutConfigurer {
 
 			private ServerAuthenticationConverter authenticationConverter;
 
-			private final ReactiveAuthenticationManager authenticationManager = new OidcBackChannelLogoutReactiveAuthenticationManager();
+			private ReactiveAuthenticationManager authenticationManager;
 
 			private Supplier<ServerLogoutHandler> logoutHandler = this::logoutHandler;
 
@@ -5613,6 +5613,9 @@ private ServerAuthenticationConverter authenticationConverter() {
 			}
 
 			private ReactiveAuthenticationManager authenticationManager() {
+				if (this.authenticationManager == null) {
+					this.authenticationManager = new OidcBackChannelLogoutReactiveAuthenticationManager();
+				}
 				return this.authenticationManager;
 			}
 
@@ -5745,6 +5748,41 @@ public BackChannelLogoutConfigurer logoutHandler(ServerLogoutHandler logoutHandl
 				return this;
 			}
 
+			/**
+			 * Configure a custom instance of the authentication manager used for
+			 * back-channel logout.
+			 *
+			 * <p>
+			 * By default, a new instance of
+			 * {@link OidcBackChannelLogoutReactiveAuthenticationManager} will be created.
+			 * If you want to customize the authentication manager, you can use this
+			 * method.
+			 *
+			 * <p>
+			 * For example, if you want to customize the WebClient instance for fetching
+			 * the JWKS keys in the logout process, you can configure Back-Channel Logout
+			 * in the following way:
+			 *
+			 * <pre>
+			 * 	http
+			 *     	.oidcLogout((oidc) -&gt; oidc
+			 *     		.backChannel(config -> {
+			 *     			var logoutTokenDecoderFactory = new CustomOidcLogoutTokenDecoderFactory();
+			 * 				var manager = new OidcBackChannelLogoutReactiveAuthenticationManager();
+			 * 				manager.setLogoutTokenDecoderFactory(logoutTokenDecoderFactory);
+			 * 				config.authenticationManager(manager);
+			 *			}))
+			 *     	);
+			 * </pre>
+			 * @param authenticationManager the {@link ReactiveAuthenticationManager} to
+			 * use as replacement of the default used authentication manager
+			 * @return {@link BackChannelLogoutConfigurer} for further customizations
+			 * @since 6.5
+			 */
+			public void setAuthenticationManager(ReactiveAuthenticationManager authenticationManager) {
+				this.authenticationManager = authenticationManager;
+			}
+
 			void configure(ServerHttpSecurity http) {
 				ServerLogoutHandler oidcLogout = this.logoutHandler.get();
 				ServerLogoutHandler sessionLogout = new SecurityContextServerLogoutHandler();

config/src/test/java/org/springframework/security/config/web/server/OidcLogoutSpecTests.java

@@ -379,6 +379,35 @@ void logoutWhenCustomComponentsThenUses() {
 		verify(sessionRegistry, atLeastOnce()).removeSessionInformation(any(OidcLogoutToken.class));
 	}
 
+	@Test
+	void logoutCustomAuthenticationManagerThenUses() {
+		this.spring
+			.register(WebServerConfig.class, OidcProviderConfig.class, WithCustomAuthenticationManagerConfig.class)
+			.autowire();
+		String registrationId = this.clientRegistration.getRegistrationId();
+		String sessionId = login();
+		String logoutToken = this.test.get()
+			.uri("/token/logout")
+			.cookie("SESSION", sessionId)
+			.exchange()
+			.expectStatus()
+			.isOk()
+			.returnResult(String.class)
+			.getResponseBody()
+			.blockFirst();
+		this.test.post()
+			.uri(this.web.url("/logout/connect/back-channel/" + registrationId).toString())
+			.body(BodyInserters.fromFormData("logout_token", logoutToken))
+			.exchange()
+			.expectStatus()
+			.isOk();
+		this.test.get().uri("/token/logout").cookie("SESSION", sessionId).exchange().expectStatus().isUnauthorized();
+		ReactiveOidcSessionRegistry sessionRegistry = this.spring.getContext()
+			.getBean(ReactiveOidcSessionRegistry.class);
+		verify(sessionRegistry, atLeastOnce()).saveSessionInformation(any());
+		verify(sessionRegistry, atLeastOnce()).removeSessionInformation(any(OidcLogoutToken.class));
+	}
+
 	@Test
 	void logoutWhenProviderIssuerMissingThen5xxServerError() {
 		this.spring.register(WebServerConfig.class, OidcProviderConfig.class, ProviderIssuerMissingConfig.class)
@@ -628,6 +657,35 @@ ReactiveOidcSessionRegistry sessionRegistry() {
 
 	}
 
+	@Configuration
+	@EnableWebFluxSecurity
+	@Import(RegistrationConfig.class)
+	static class WithCustomAuthenticationManagerConfig {
+
+		ReactiveOidcSessionRegistry sessionRegistry = spy(new InMemoryReactiveOidcSessionRegistry());
+
+		@Bean
+		@Order(1)
+		SecurityWebFilterChain filters(ServerHttpSecurity http) throws Exception {
+			// @formatter:off
+			http
+					.authorizeExchange((authorize) -> authorize.anyExchange().authenticated())
+					.oauth2Login(Customizer.withDefaults())
+					.oidcLogout((oidc) -> oidc.backChannel((backChannel) -> {
+						backChannel.setAuthenticationManager(new OidcBackChannelLogoutReactiveAuthenticationManager());
+					}));
+			// @formatter:on
+
+			return http.build();
+		}
+
+		@Bean
+		ReactiveOidcSessionRegistry sessionRegistry() {
+			return this.sessionRegistry;
+		}
+
+	}
+
 	@Configuration
 	@EnableWebFluxSecurity
 	@Import(RegistrationConfig.class)