Reactive OAuth 2.0 logout handler resolves registrationId

Closes gh-11378

oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/oidc/web/server/logout/OidcClientInitiatedServerLogoutSuccessHandler.java

@@ -18,7 +18,8 @@ package org.springframework.security.oauth2.client.oidc.web.server.logout;
 
 import java.net.URI;
 import java.nio.charset.StandardCharsets;
-import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
 
 import reactor.core.publisher.Mono;
 
@@ -85,7 +86,7 @@ public class OidcClientInitiatedServerLogoutSuccessHandler implements ServerLogo
 						return Mono.empty();
 					}
 					String idToken = idToken(authentication);
-					String postLogoutRedirectUri = postLogoutRedirectUri(exchange.getExchange().getRequest());
+					String postLogoutRedirectUri = postLogoutRedirectUri(exchange.getExchange().getRequest(), clientRegistration);
 					return Mono.just(endpointUri(endSessionEndpoint, idToken, postLogoutRedirectUri));
 				})
 				.switchIfEmpty(
@@ -119,7 +120,7 @@ public class OidcClientInitiatedServerLogoutSuccessHandler implements ServerLogo
 		return ((OidcUser) authentication.getPrincipal()).getIdToken().getTokenValue();
 	}
 
-	private String postLogoutRedirectUri(ServerHttpRequest request) {
+	private String postLogoutRedirectUri(ServerHttpRequest request, ClientRegistration clientRegistration) {
 		if (this.postLogoutRedirectUri == null) {
 			return null;
 		}
@@ -129,8 +130,13 @@ public class OidcClientInitiatedServerLogoutSuccessHandler implements ServerLogo
 				.replaceQuery(null)
 				.fragment(null)
 				.build();
+
+		Map<String, String> uriVariables = new HashMap<>();
+		uriVariables.put("baseUrl", uriComponents.toUriString());
+		uriVariables.put("registrationId", clientRegistration.getRegistrationId());
+
 		return UriComponentsBuilder.fromUriString(this.postLogoutRedirectUri)
-				.buildAndExpand(Collections.singletonMap("baseUrl", uriComponents.toUriString()))
+				.buildAndExpand(uriVariables)
 				.toUriString();
 		// @formatter:on
 	}

oauth2/oauth2-client/src/test/java/org/springframework/security/oauth2/client/oidc/web/server/logout/OidcClientInitiatedServerLogoutSuccessHandlerTests.java

@@ -163,6 +163,22 @@ public class OidcClientInitiatedServerLogoutSuccessHandlerTests {
 				+ "post_logout_redirect_uri=https://rp.example.org/context?forwardUrl%3Dsecured%253Fparam%253Dtrue");
 	}
 
+	@Test
+	public void logoutWhenUsingPostLogoutRedirectUriTemplateThenBuildsItForRedirectExpanded()
+			throws IOException, ServletException {
+		OAuth2AuthenticationToken token = new OAuth2AuthenticationToken(TestOidcUsers.create(),
+				AuthorityUtils.NO_AUTHORITIES, this.registration.getRegistrationId());
+		given(this.exchange.getPrincipal()).willReturn(Mono.just(token));
+		MockServerHttpRequest request = MockServerHttpRequest.get("https://rp.example.org/").build();
+		given(this.exchange.getRequest()).willReturn(request);
+		WebFilterExchange f = new WebFilterExchange(this.exchange, this.chain);
+		this.handler.setPostLogoutRedirectUri("{baseUrl}/{registrationId}");
+		this.handler.onLogoutSuccess(f, token).block();
+		assertThat(redirectedUrl(this.exchange)).isEqualTo(String.format(
+				"https://endpoint?" + "id_token_hint=id-token&" + "post_logout_redirect_uri=https://rp.example.org/%s",
+				this.registration.getRegistrationId()));
+	}
+
 	@Test
 	public void setPostLogoutRedirectUriWhenGivenNullThenThrowsException() {
 		assertThatIllegalArgumentException().isThrownBy(() -> this.handler.setPostLogoutRedirectUri((URI) null));