Add reactive interfaces for CSRF request handling

Issue gh-11959

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

@@ -147,6 +147,8 @@ import org.springframework.security.web.server.context.WebSessionServerSecurityC
 import org.springframework.security.web.server.csrf.CsrfServerLogoutHandler;
 import org.springframework.security.web.server.csrf.CsrfWebFilter;
 import org.springframework.security.web.server.csrf.ServerCsrfTokenRepository;
+import org.springframework.security.web.server.csrf.ServerCsrfTokenRequestAttributeHandler;
+import org.springframework.security.web.server.csrf.ServerCsrfTokenRequestHandler;
 import org.springframework.security.web.server.csrf.WebSessionServerCsrfTokenRepository;
 import org.springframework.security.web.server.header.CacheControlServerHttpHeadersWriter;
 import org.springframework.security.web.server.header.CompositeServerHttpHeadersWriter;
@@ -1852,12 +1854,28 @@ public class ServerHttpSecurity {
 		 * @param enabled true if should read from multipart form body, else false.
 		 * Default is false
 		 * @return the {@link CsrfSpec} for additional configuration
+		 * @deprecated Use
+		 * {@link ServerCsrfTokenRequestAttributeHandler#setTokenFromMultipartDataEnabled(boolean)}
+		 * instead
 		 */
+		@Deprecated
 		public CsrfSpec tokenFromMultipartDataEnabled(boolean enabled) {
 			this.filter.setTokenFromMultipartDataEnabled(enabled);
 			return this;
 		}
 
+		/**
+		 * Specifies a {@link ServerCsrfTokenRequestHandler} that is used to make the
+		 * {@code CsrfToken} available as an exchange attribute.
+		 * @param requestHandler the {@link ServerCsrfTokenRequestHandler} to use
+		 * @return the {@link CsrfSpec} for additional configuration
+		 * @since 5.8
+		 */
+		public CsrfSpec csrfTokenRequestHandler(ServerCsrfTokenRequestHandler requestHandler) {
+			this.filter.setRequestHandler(requestHandler);
+			return this;
+		}
+
 		/**
 		 * Allows method chaining to continue configuring the {@link ServerHttpSecurity}
 		 * @return the {@link ServerHttpSecurity} to continue configuring

config/src/main/kotlin/org/springframework/security/config/web/server/ServerCsrfDsl.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,6 +19,7 @@ package org.springframework.security.config.web.server
 import org.springframework.security.web.server.authorization.ServerAccessDeniedHandler
 import org.springframework.security.web.server.csrf.CsrfWebFilter
 import org.springframework.security.web.server.csrf.ServerCsrfTokenRepository
+import org.springframework.security.web.server.csrf.ServerCsrfTokenRequestHandler
 import org.springframework.security.web.server.util.matcher.ServerWebExchangeMatcher
 
 /**
@@ -33,13 +34,17 @@ import org.springframework.security.web.server.util.matcher.ServerWebExchangeMat
  * is enabled.
  * @property tokenFromMultipartDataEnabled if true, the [CsrfWebFilter] should try to resolve the actual CSRF
  * token from the body of multipart data requests.
+ * @property csrfTokenRequestHandler the  [ServerCsrfTokenRequestHandler] that is used to make the CSRF token
+ * available as an exchange attribute
  */
 @ServerSecurityMarker
 class ServerCsrfDsl {
     var accessDeniedHandler: ServerAccessDeniedHandler? = null
     var csrfTokenRepository: ServerCsrfTokenRepository? = null
     var requireCsrfProtectionMatcher: ServerWebExchangeMatcher? = null
+    @Deprecated("Use 'csrfTokenRequestHandler' instead")
     var tokenFromMultipartDataEnabled: Boolean? = null
+    var csrfTokenRequestHandler: ServerCsrfTokenRequestHandler? = null
 
     private var disabled = false
 
@@ -56,6 +61,7 @@ class ServerCsrfDsl {
             csrfTokenRepository?.also { csrf.csrfTokenRepository(csrfTokenRepository) }
             requireCsrfProtectionMatcher?.also { csrf.requireCsrfProtectionMatcher(requireCsrfProtectionMatcher) }
             tokenFromMultipartDataEnabled?.also { csrf.tokenFromMultipartDataEnabled(tokenFromMultipartDataEnabled!!) }
+            csrfTokenRequestHandler?.also { csrf.csrfTokenRequestHandler(csrfTokenRequestHandler) }
             if (disabled) {
                 csrf.disable()
             }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -64,8 +64,11 @@ import org.springframework.security.web.server.context.SecurityContextServerWebE
 import org.springframework.security.web.server.context.ServerSecurityContextRepository;
 import org.springframework.security.web.server.context.WebSessionServerSecurityContextRepository;
 import org.springframework.security.web.server.csrf.CsrfServerLogoutHandler;
+import org.springframework.security.web.server.csrf.CsrfToken;
 import org.springframework.security.web.server.csrf.CsrfWebFilter;
+import org.springframework.security.web.server.csrf.DefaultCsrfToken;
 import org.springframework.security.web.server.csrf.ServerCsrfTokenRepository;
+import org.springframework.security.web.server.csrf.ServerCsrfTokenRequestHandler;
 import org.springframework.security.web.server.savedrequest.ServerRequestCache;
 import org.springframework.security.web.server.savedrequest.WebSessionServerRequestCache;
 import org.springframework.test.util.ReflectionTestUtils;
@@ -84,6 +87,7 @@ import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.BDDMockito.given;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
 import static org.springframework.security.config.Customizer.withDefaults;
@@ -500,6 +504,28 @@ public class ServerHttpSecurityTests {
 		verify(customServerCsrfTokenRepository).loadToken(any());
 	}
 
+	@Test
+	public void postWhenCustomRequestHandlerThenUsed() {
+		CsrfToken csrfToken = new DefaultCsrfToken("headerName", "paramName", "tokenValue");
+		given(this.csrfTokenRepository.loadToken(any(ServerWebExchange.class))).willReturn(Mono.just(csrfToken));
+		given(this.csrfTokenRepository.generateToken(any(ServerWebExchange.class))).willReturn(Mono.empty());
+		ServerCsrfTokenRequestHandler requestHandler = mock(ServerCsrfTokenRequestHandler.class);
+		given(requestHandler.resolveCsrfTokenValue(any(ServerWebExchange.class), any(CsrfToken.class)))
+				.willReturn(Mono.just(csrfToken.getToken()));
+		// @formatter:off
+		this.http.csrf((csrf) -> csrf
+			.csrfTokenRepository(this.csrfTokenRepository)
+			.csrfTokenRequestHandler(requestHandler)
+		);
+		// @formatter:on
+		WebTestClient client = buildClient();
+		client.post().uri("/").exchange().expectStatus().isOk();
+		verify(this.csrfTokenRepository, times(2)).loadToken(any(ServerWebExchange.class));
+		verify(this.csrfTokenRepository).generateToken(any(ServerWebExchange.class));
+		verify(requestHandler).handle(any(ServerWebExchange.class), any());
+		verify(requestHandler).resolveCsrfTokenValue(any(ServerWebExchange.class), any());
+	}
+
 	@Test
 	public void shouldConfigureRequestCacheForOAuth2LoginAuthenticationEntryPointAndSuccessHandler() {
 		ServerRequestCache requestCache = spy(new WebSessionServerRequestCache());

config/src/test/kotlin/org/springframework/security/config/web/server/ServerCsrfDslTests.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -24,6 +24,7 @@ import org.junit.jupiter.api.extension.ExtendWith
 import org.springframework.beans.factory.annotation.Autowired
 import org.springframework.context.ApplicationContext
 import org.springframework.context.annotation.Bean
+import org.springframework.context.annotation.Configuration
 import org.springframework.http.MediaType
 import org.springframework.security.config.annotation.web.reactive.EnableWebFluxSecurity
 import org.springframework.security.config.test.SpringTestContext
@@ -33,6 +34,8 @@ import org.springframework.security.web.server.authorization.ServerAccessDeniedH
 import org.springframework.security.web.server.csrf.CsrfToken
 import org.springframework.security.web.server.csrf.DefaultCsrfToken
 import org.springframework.security.web.server.csrf.ServerCsrfTokenRepository
+import org.springframework.security.web.server.csrf.ServerCsrfTokenRequestAttributeHandler
+import org.springframework.security.web.server.csrf.ServerCsrfTokenRequestHandler
 import org.springframework.security.web.server.csrf.WebSessionServerCsrfTokenRepository
 import org.springframework.security.web.server.util.matcher.PathPatternParserServerWebExchangeMatcher
 import org.springframework.test.web.reactive.server.WebTestClient
@@ -299,4 +302,55 @@ class ServerCsrfDslTests {
             }
         }
     }
+
+    @Test
+    fun `csrf when custom request handler then handler used`() {
+        this.spring.register(CustomRequestHandlerConfig::class.java).autowire()
+        mockkObject(CustomRequestHandlerConfig.REPOSITORY)
+        every {
+            CustomRequestHandlerConfig.REPOSITORY.loadToken(any())
+        } returns Mono.just(this.token)
+        mockkObject(CustomRequestHandlerConfig.HANDLER)
+        every {
+            CustomRequestHandlerConfig.HANDLER.handle(any(), any())
+        } returns Unit
+        every {
+            CustomRequestHandlerConfig.HANDLER.resolveCsrfTokenValue(any(), any())
+        } returns Mono.just(this.token.token)
+
+        this.client.post()
+            .uri("/")
+            .exchange()
+            .expectStatus().isOk
+        verify(exactly = 2) { CustomRequestHandlerConfig.REPOSITORY.loadToken(any()) }
+        verify(exactly = 1) { CustomRequestHandlerConfig.HANDLER.resolveCsrfTokenValue(any(), any()) }
+        verify(exactly = 1) { CustomRequestHandlerConfig.HANDLER.handle(any(), any()) }
+    }
+
+    @Configuration
+    @EnableWebFluxSecurity
+    @EnableWebFlux
+    open class CustomRequestHandlerConfig {
+        companion object {
+            val REPOSITORY: ServerCsrfTokenRepository = WebSessionServerCsrfTokenRepository()
+            val HANDLER: ServerCsrfTokenRequestHandler = ServerCsrfTokenRequestAttributeHandler()
+        }
+
+        @Bean
+        open fun springWebFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
+            return http {
+                csrf {
+                    csrfTokenRepository = REPOSITORY
+                    csrfTokenRequestHandler = HANDLER
+                }
+            }
+        }
+
+        @RestController
+        internal class TestController {
+            @PostMapping("/")
+            fun home() {
+            }
+        }
+    }
 }

web/src/main/java/org/springframework/security/web/server/csrf/CsrfWebFilter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,12 +23,8 @@ import java.util.Set;
 
 import reactor.core.publisher.Mono;
 
-import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpStatus;
-import org.springframework.http.MediaType;
-import org.springframework.http.codec.multipart.FormFieldPart;
-import org.springframework.http.server.reactive.ServerHttpRequest;
 import org.springframework.security.crypto.codec.Utf8;
 import org.springframework.security.web.server.authorization.HttpStatusServerAccessDeniedHandler;
 import org.springframework.security.web.server.authorization.ServerAccessDeniedHandler;
@@ -63,6 +59,7 @@ import org.springframework.web.server.WebFilterChain;
  *
  * @author Rob Winch
  * @author Parikshit Dutta
+ * @author Steve Riesenberg
  * @since 5.0
  */
 public class CsrfWebFilter implements WebFilter {
@@ -86,7 +83,7 @@ public class CsrfWebFilter implements WebFilter {
 	private ServerAccessDeniedHandler accessDeniedHandler = new HttpStatusServerAccessDeniedHandler(
 			HttpStatus.FORBIDDEN);
 
-	private boolean isTokenFromMultipartDataEnabled;
+	private ServerCsrfTokenRequestHandler requestHandler = new ServerCsrfTokenRequestAttributeHandler();
 
 	public void setAccessDeniedHandler(ServerAccessDeniedHandler accessDeniedHandler) {
 		Assert.notNull(accessDeniedHandler, "accessDeniedHandler");
@@ -103,14 +100,34 @@ public class CsrfWebFilter implements WebFilter {
 		this.requireCsrfProtectionMatcher = requireCsrfProtectionMatcher;
 	}
 
+	/**
+	 * Specifies a {@link ServerCsrfTokenRequestHandler} that is used to make the
+	 * {@code CsrfToken} available as an exchange attribute.
+	 * <p>
+	 * The default is {@link ServerCsrfTokenRequestAttributeHandler}.
+	 * @param requestHandler the {@link ServerCsrfTokenRequestHandler} to use
+	 * @since 5.8
+	 */
+	public void setRequestHandler(ServerCsrfTokenRequestHandler requestHandler) {
+		Assert.notNull(requestHandler, "requestHandler cannot be null");
+		this.requestHandler = requestHandler;
+	}
+
 	/**
 	 * Specifies if the {@code CsrfWebFilter} should try to resolve the actual CSRF token
 	 * from the body of multipart data requests.
 	 * @param tokenFromMultipartDataEnabled true if should read from multipart form body,
 	 * else false. Default is false
+	 * @deprecated Use
+	 * {@link ServerCsrfTokenRequestAttributeHandler#setTokenFromMultipartDataEnabled(boolean)}
+	 * instead
 	 */
+	@Deprecated
 	public void setTokenFromMultipartDataEnabled(boolean tokenFromMultipartDataEnabled) {
-		this.isTokenFromMultipartDataEnabled = tokenFromMultipartDataEnabled;
+		if (this.requestHandler instanceof ServerCsrfTokenRequestAttributeHandler) {
+			((ServerCsrfTokenRequestAttributeHandler) this.requestHandler)
+					.setTokenFromMultipartDataEnabled(tokenFromMultipartDataEnabled);
+		}
 	}
 
 	@Override
@@ -138,30 +155,14 @@ public class CsrfWebFilter implements WebFilter {
 	}
 
 	private Mono<Boolean> containsValidCsrfToken(ServerWebExchange exchange, CsrfToken expected) {
-		return exchange.getFormData().flatMap((data) -> Mono.justOrEmpty(data.getFirst(expected.getParameterName())))
-				.switchIfEmpty(Mono.justOrEmpty(exchange.getRequest().getHeaders().getFirst(expected.getHeaderName())))
-				.switchIfEmpty(tokenFromMultipartData(exchange, expected))
+		return this.requestHandler.resolveCsrfTokenValue(exchange, expected)
 				.map((actual) -> equalsConstantTime(actual, expected.getToken()));
 	}
 
-	private Mono<String> tokenFromMultipartData(ServerWebExchange exchange, CsrfToken expected) {
-		if (!this.isTokenFromMultipartDataEnabled) {
-			return Mono.empty();
-		}
-		ServerHttpRequest request = exchange.getRequest();
-		HttpHeaders headers = request.getHeaders();
-		MediaType contentType = headers.getContentType();
-		if (!MediaType.MULTIPART_FORM_DATA.isCompatibleWith(contentType)) {
-			return Mono.empty();
-		}
-		return exchange.getMultipartData().map((d) -> d.getFirst(expected.getParameterName())).cast(FormFieldPart.class)
-				.map(FormFieldPart::value);
-	}
-
 	private Mono<Void> continueFilterChain(ServerWebExchange exchange, WebFilterChain chain) {
 		return Mono.defer(() -> {
 			Mono<CsrfToken> csrfToken = csrfToken(exchange);
-			exchange.getAttributes().put(CsrfToken.class.getName(), csrfToken);
+			this.requestHandler.handle(exchange, csrfToken);
 			return chain.filter(exchange);
 		});
 	}

web/src/main/java/org/springframework/security/web/server/csrf/ServerCsrfTokenRequestAttributeHandler.java

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2002-2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.security.web.server.csrf;
+
+import reactor.core.publisher.Mono;
+
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.MediaType;
+import org.springframework.http.codec.multipart.FormFieldPart;
+import org.springframework.http.server.reactive.ServerHttpRequest;
+import org.springframework.util.Assert;
+import org.springframework.web.server.ServerWebExchange;
+
+/**
+ * An implementation of the {@link ServerCsrfTokenRequestHandler} interface that is
+ * capable of making the {@link CsrfToken} available as an exchange attribute and
+ * resolving the token value as either a form data value or header of the request.
+ *
+ * @author Steve Riesenberg
+ * @since 5.8
+ */
+public class ServerCsrfTokenRequestAttributeHandler implements ServerCsrfTokenRequestHandler {
+
+	private boolean isTokenFromMultipartDataEnabled;
+
+	@Override
+	public void handle(ServerWebExchange exchange, Mono<CsrfToken> csrfToken) {
+		Assert.notNull(exchange, "exchange cannot be null");
+		Assert.notNull(csrfToken, "csrfToken cannot be null");
+		exchange.getAttributes().put(CsrfToken.class.getName(), csrfToken);
+	}
+
+	@Override
+	public Mono<String> resolveCsrfTokenValue(ServerWebExchange exchange, CsrfToken csrfToken) {
+		return ServerCsrfTokenRequestHandler.super.resolveCsrfTokenValue(exchange, csrfToken)
+				.switchIfEmpty(tokenFromMultipartData(exchange, csrfToken));
+	}
+
+	/**
+	 * Specifies if the {@code ServerCsrfTokenRequestResolver} should try to resolve the
+	 * actual CSRF token from the body of multipart data requests.
+	 * @param tokenFromMultipartDataEnabled true if should read from multipart form body,
+	 * else false. Default is false
+	 */
+	public void setTokenFromMultipartDataEnabled(boolean tokenFromMultipartDataEnabled) {
+		this.isTokenFromMultipartDataEnabled = tokenFromMultipartDataEnabled;
+	}
+
+	private Mono<String> tokenFromMultipartData(ServerWebExchange exchange, CsrfToken expected) {
+		if (!this.isTokenFromMultipartDataEnabled) {
+			return Mono.empty();
+		}
+		ServerHttpRequest request = exchange.getRequest();
+		HttpHeaders headers = request.getHeaders();
+		MediaType contentType = headers.getContentType();
+		if (!MediaType.MULTIPART_FORM_DATA.isCompatibleWith(contentType)) {
+			return Mono.empty();
+		}
+		return exchange.getMultipartData().map((d) -> d.getFirst(expected.getParameterName())).cast(FormFieldPart.class)
+				.map(FormFieldPart::value);
+	}
+
+}

web/src/main/java/org/springframework/security/web/server/csrf/ServerCsrfTokenRequestHandler.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2002-2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.security.web.server.csrf;
+
+import reactor.core.publisher.Mono;
+
+import org.springframework.util.Assert;
+import org.springframework.web.server.ServerWebExchange;
+
+/**
+ * A callback interface that is used to make the {@link CsrfToken} created by the
+ * {@link ServerCsrfTokenRepository} available as an exchange attribute. Implementations
+ * of this interface may choose to perform additional tasks or customize how the token is
+ * made available to the application through exchange attributes.
+ *
+ * @author Steve Riesenberg
+ * @since 5.8
+ * @see ServerCsrfTokenRequestAttributeHandler
+ */
+@FunctionalInterface
+public interface ServerCsrfTokenRequestHandler extends ServerCsrfTokenRequestResolver {
+
+	/**
+	 * Handles a request using a {@link CsrfToken}.
+	 * @param exchange the {@code ServerWebExchange} with the request being handled
+	 * @param csrfToken the {@code Mono<CsrfToken>} created by the
+	 * {@link ServerCsrfTokenRepository}
+	 */
+	void handle(ServerWebExchange exchange, Mono<CsrfToken> csrfToken);
+
+	@Override
+	default Mono<String> resolveCsrfTokenValue(ServerWebExchange exchange, CsrfToken csrfToken) {
+		Assert.notNull(exchange, "exchange cannot be null");
+		Assert.notNull(csrfToken, "csrfToken cannot be null");
+		return exchange.getFormData().flatMap((data) -> Mono.justOrEmpty(data.getFirst(csrfToken.getParameterName())))
+				.switchIfEmpty(
+						Mono.justOrEmpty(exchange.getRequest().getHeaders().getFirst(csrfToken.getHeaderName())));
+	}
+
+}

web/src/main/java/org/springframework/security/web/server/csrf/ServerCsrfTokenRequestResolver.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2002-2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.security.web.server.csrf;
+
+import reactor.core.publisher.Mono;
+
+import org.springframework.web.server.ServerWebExchange;
+
+/**
+ * Implementations of this interface are capable of resolving the token value of a
+ * {@link CsrfToken} from the provided {@code ServerWebExchange}. Used by the
+ * {@link CsrfWebFilter}.
+ *
+ * @author Steve Riesenberg
+ * @since 5.8
+ * @see ServerCsrfTokenRequestAttributeHandler
+ */
+@FunctionalInterface
+public interface ServerCsrfTokenRequestResolver {
+
+	/**
+	 * Returns the token value resolved from the provided {@code ServerWebExchange} and
+	 * {@link CsrfToken} or {@code Mono.empty()} if not available.
+	 * @param exchange the {@code ServerWebExchange} with the request being processed
+	 * @param csrfToken the {@link CsrfToken} created by the
+	 * {@link ServerCsrfTokenRepository}
+	 * @return the token value resolved from the request
+	 */
+	Mono<String> resolveCsrfTokenValue(ServerWebExchange exchange, CsrfToken csrfToken);
+
+}

web/src/test/java/org/springframework/security/web/server/csrf/CsrfWebFilterTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -34,13 +34,17 @@ import org.springframework.test.web.reactive.server.WebTestClient;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;
 import org.springframework.web.reactive.function.BodyInserters;
+import org.springframework.web.server.ServerWebExchange;
 import org.springframework.web.server.WebFilterChain;
 import org.springframework.web.server.WebSession;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.BDDMockito.given;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
 
 /**
@@ -65,6 +69,15 @@ public class CsrfWebFilterTests {
 
 	private MockServerWebExchange post = MockServerWebExchange.from(MockServerHttpRequest.post("/"));
 
+	@Test
+	public void setRequestHandlerWhenNullThenThrowsIllegalArgumentException() {
+		// @formatter:off
+		assertThatIllegalArgumentException()
+				.isThrownBy(() -> this.csrfFilter.setRequestHandler(null))
+				.withMessage("requestHandler cannot be null");
+		// @formatter:on
+	}
+
 	@Test
 	public void filterWhenGetThenSessionNotCreatedAndChainContinues() {
 		PublisherProbe<Void> chainResult = PublisherProbe.empty();
@@ -145,6 +158,28 @@ public class CsrfWebFilterTests {
 		chainResult.assertWasSubscribed();
 	}
 
+	@Test
+	public void filterWhenRequestHandlerSetThenUsed() {
+		ServerCsrfTokenRequestHandler requestHandler = mock(ServerCsrfTokenRequestHandler.class);
+		given(requestHandler.resolveCsrfTokenValue(any(ServerWebExchange.class), any(CsrfToken.class)))
+				.willReturn(Mono.just(this.token.getToken()));
+		this.csrfFilter.setRequestHandler(requestHandler);
+
+		PublisherProbe<Void> chainResult = PublisherProbe.empty();
+		given(this.chain.filter(any())).willReturn(chainResult.mono());
+		this.csrfFilter.setCsrfTokenRepository(this.repository);
+		given(this.repository.loadToken(any())).willReturn(Mono.just(this.token));
+		given(this.repository.generateToken(any())).willReturn(Mono.just(this.token));
+		this.post = MockServerWebExchange
+				.from(MockServerHttpRequest.post("/").header(this.token.getHeaderName(), this.token.getToken()));
+		Mono<Void> result = this.csrfFilter.filter(this.post, this.chain);
+		StepVerifier.create(result).verifyComplete();
+		chainResult.assertWasSubscribed();
+
+		verify(requestHandler).handle(eq(this.post), any());
+		verify(requestHandler).resolveCsrfTokenValue(this.post, this.token);
+	}
+
 	@Test
 	// gh-8452
 	public void matchesRequireCsrfProtectionWhenNonStandardHTTPMethodIsUsed() {

web/src/test/java/org/springframework/security/web/server/csrf/ServerCsrfTokenRequestAttributeHandlerTests.java

@@ -0,0 +1,132 @@
+/*
+ * Copyright 2002-2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.security.web.server.csrf;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import reactor.core.publisher.Mono;
+import reactor.test.StepVerifier;
+
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.MediaType;
+import org.springframework.mock.http.server.reactive.MockServerHttpRequest;
+import org.springframework.mock.web.server.MockServerWebExchange;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+
+/**
+ * Tests for {@link ServerCsrfTokenRequestAttributeHandler}.
+ *
+ * @author Steve Riesenberg
+ * @since 5.8
+ */
+public class ServerCsrfTokenRequestAttributeHandlerTests {
+
+	private ServerCsrfTokenRequestAttributeHandler handler;
+
+	private MockServerWebExchange exchange;
+
+	private CsrfToken token;
+
+	@BeforeEach
+	public void setUp() {
+		this.handler = new ServerCsrfTokenRequestAttributeHandler();
+		this.exchange = MockServerWebExchange.builder(MockServerHttpRequest.get("/")).build();
+		this.token = new DefaultCsrfToken("headerName", "paramName", "csrfTokenValue");
+	}
+
+	@Test
+	public void handleWhenExchangeIsNullThenThrowsIllegalArgumentException() {
+		// @formatter:off
+		assertThatIllegalArgumentException()
+				.isThrownBy(() -> this.handler.handle(null, Mono.just(this.token)))
+				.withMessage("exchange cannot be null");
+		// @formatter:on
+	}
+
+	@Test
+	public void handleWhenCsrfTokenIsNullThenThrowsIllegalArgumentException() {
+		// @formatter:off
+		assertThatIllegalArgumentException()
+				.isThrownBy(() -> this.handler.handle(this.exchange, null))
+				.withMessage("csrfToken cannot be null");
+		// @formatter:on
+	}
+
+	@Test
+	public void handleWhenValidParametersThenExchangeAttributeSet() {
+		Mono<CsrfToken> csrfToken = Mono.just(this.token);
+		this.handler.handle(this.exchange, csrfToken);
+		Mono<CsrfToken> csrfTokenAttribute = this.exchange.getAttribute(CsrfToken.class.getName());
+		assertThat(csrfTokenAttribute).isNotNull();
+		assertThat(csrfTokenAttribute).isEqualTo(csrfToken);
+	}
+
+	@Test
+	public void resolveCsrfTokenValueWhenExchangeIsNullThenThrowsIllegalArgumentException() {
+		// @formatter:off
+		assertThatIllegalArgumentException()
+				.isThrownBy(() -> this.handler.resolveCsrfTokenValue(null, this.token))
+				.withMessage("exchange cannot be null");
+		// @formatter:on
+	}
+
+	@Test
+	public void resolveCsrfTokenValueWhenCsrfTokenIsNullThenThrowsIllegalArgumentException() {
+		// @formatter:off
+		assertThatIllegalArgumentException()
+				.isThrownBy(() -> this.handler.resolveCsrfTokenValue(this.exchange, null))
+				.withMessage("csrfToken cannot be null");
+		// @formatter:on
+	}
+
+	@Test
+	public void resolveCsrfTokenValueWhenTokenNotSetThenReturnsEmptyMono() {
+		Mono<String> csrfToken = this.handler.resolveCsrfTokenValue(this.exchange, this.token);
+		StepVerifier.create(csrfToken).verifyComplete();
+	}
+
+	@Test
+	public void resolveCsrfTokenValueWhenFormDataSetThenReturnsTokenValue() {
+		this.exchange = MockServerWebExchange.builder(MockServerHttpRequest.post("/")
+				.header(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_FORM_URLENCODED_VALUE)
+				.body(this.token.getParameterName() + "=" + this.token.getToken())).build();
+		Mono<String> csrfToken = this.handler.resolveCsrfTokenValue(this.exchange, this.token);
+		StepVerifier.create(csrfToken).expectNext(this.token.getToken()).verifyComplete();
+	}
+
+	@Test
+	public void resolveCsrfTokenValueWhenHeaderSetThenReturnsTokenValue() {
+		this.exchange = MockServerWebExchange.builder(MockServerHttpRequest.post("/")
+				.header(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_FORM_URLENCODED_VALUE)
+				.header(this.token.getHeaderName(), this.token.getToken())).build();
+		Mono<String> csrfToken = this.handler.resolveCsrfTokenValue(this.exchange, this.token);
+		StepVerifier.create(csrfToken).expectNext(this.token.getToken()).verifyComplete();
+	}
+
+	@Test
+	public void resolveCsrfTokenValueWhenHeaderAndFormDataSetThenFormDataIsPreferred() {
+		this.exchange = MockServerWebExchange.builder(MockServerHttpRequest.post("/")
+				.header(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_FORM_URLENCODED_VALUE)
+				.header(this.token.getHeaderName(), "header")
+				.body(this.token.getParameterName() + "=" + this.token.getToken())).build();
+		Mono<String> csrfToken = this.handler.resolveCsrfTokenValue(this.exchange, this.token);
+		StepVerifier.create(csrfToken).expectNext(this.token.getToken()).verifyComplete();
+	}
+
+}