Pārlūkot izejas kodu

Add reactive support for BREACH

Closes gh-11959
Steve Riesenberg 3 gadi atpakaļ
vecāks
revīzija
f462134e87

+ 35 - 0
config/src/test/java/org/springframework/security/config/web/server/ServerHttpSecurityTests.java

@@ -33,6 +33,8 @@ import reactor.core.publisher.Mono;
 import reactor.test.publisher.TestPublisher;
 
 import org.springframework.http.HttpStatus;
+import org.springframework.mock.http.server.reactive.MockServerHttpRequest;
+import org.springframework.mock.web.server.MockServerWebExchange;
 import org.springframework.security.authentication.ReactiveAuthenticationManager;
 import org.springframework.security.authentication.TestingAuthenticationToken;
 import org.springframework.security.config.annotation.web.reactive.ServerHttpSecurityConfigurationBuilder;
@@ -69,6 +71,7 @@ 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.csrf.XorServerCsrfTokenRequestAttributeHandler;
 import org.springframework.security.web.server.savedrequest.ServerRequestCache;
 import org.springframework.security.web.server.savedrequest.WebSessionServerRequestCache;
 import org.springframework.test.util.ReflectionTestUtils;
@@ -526,6 +529,38 @@ public class ServerHttpSecurityTests {
 		verify(requestHandler).resolveCsrfTokenValue(any(ServerWebExchange.class), any());
 	}
 
+	@Test
+	public void postWhenServerXorCsrfTokenRequestAttributeHandlerThenOk() {
+		CsrfToken csrfToken = new DefaultCsrfToken("X-CSRF-TOKEN", "_csrf", "token");
+		given(this.csrfTokenRepository.loadToken(any(ServerWebExchange.class))).willReturn(Mono.just(csrfToken));
+		given(this.csrfTokenRepository.generateToken(any(ServerWebExchange.class))).willReturn(Mono.empty());
+		ServerCsrfTokenRequestHandler requestHandler = new XorServerCsrfTokenRequestAttributeHandler();
+		// @formatter:off
+		this.http.csrf((csrf) -> csrf
+			.csrfTokenRepository(this.csrfTokenRepository)
+			.csrfTokenRequestHandler(requestHandler)
+		);
+		// @formatter:on
+
+		// Generate masked CSRF token value
+		ServerWebExchange exchange = MockServerWebExchange.from(MockServerHttpRequest.get("/").build());
+		requestHandler.handle(exchange, Mono.just(csrfToken));
+		Mono<CsrfToken> csrfTokenAttribute = exchange.getAttribute(CsrfToken.class.getName());
+		String actualTokenValue = csrfTokenAttribute.map(CsrfToken::getToken).block();
+		assertThat(actualTokenValue).isNotEqualTo(csrfToken.getToken());
+
+		WebTestClient client = buildClient();
+		// @formatter:off
+		client.post()
+				.uri("/")
+				.header(csrfToken.getHeaderName(), actualTokenValue)
+				.exchange()
+				.expectStatus().isOk();
+		// @formatter:on
+		verify(this.csrfTokenRepository, times(2)).loadToken(any(ServerWebExchange.class));
+		verify(this.csrfTokenRepository).generateToken(any(ServerWebExchange.class));
+	}
+
 	@Test
 	public void shouldConfigureRequestCacheForOAuth2LoginAuthenticationEntryPointAndSuccessHandler() {
 		ServerRequestCache requestCache = spy(new WebSessionServerRequestCache());

+ 42 - 1
docs/modules/ROOT/pages/reactive/exploits/csrf.adoc

@@ -106,13 +106,54 @@ fun springSecurityFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain
 -----
 ====
 
+[[webflux-csrf-configure-request-handler]]
+==== Configure ServerCsrfTokenRequestHandler
+
+Spring Security's https://docs.spring.io/spring-security/site/docs/current/api/org/springframework/security/web/server/csrf/CsrfWebFilter.html[`CsrfWebFilter`] exposes a https://docs.spring.io/spring-security/site/docs/current/api/org/springframework/security/web/csrf/CsrfToken.html[`Mono<CsrfToken>`] as a `ServerWebExchange` attribute named `org.springframework.security.web.server.csrf.CsrfToken` with the help of a https://docs.spring.io/spring-security/site/docs/current/api/org/springframework/security/web/server/csrf/ServerCsrfTokenRequestHandler.html[`ServerCsrfTokenRequestHandler`].
+The default implementation is `ServerCsrfTokenRequestAttributeHandler`.
+
+An alternate implementation `XorServerCsrfTokenRequestAttributeHandler` is available to provide protection for BREACH (see https://github.com/spring-projects/spring-security/issues/4001[gh-4001]).
+
+You can configure `XorServerCsrfTokenRequestAttributeHandler` using the following Java configuration:
+
+.Configure BREACH protection
+====
+.Java
+[source,java,role="primary"]
+-----
+@Bean
+public SecurityWebFilterChain springSecurityFilterChain(ServerHttpSecurity http) {
+	http
+		// ...
+		.csrf(csrf -> csrf
+			.csrfTokenRequestHandler(new XorServerCsrfTokenRequestAttributeHandler())
+		)
+	return http.build();
+}
+-----
+
+.Kotlin
+[source,kotlin,role="secondary"]
+-----
+@Bean
+fun springSecurityFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
+    return http {
+        // ...
+        csrf {
+            csrfTokenRequestHandler = XorServerCsrfTokenRequestAttributeHandler()
+        }
+    }
+}
+-----
+====
+
 [[webflux-csrf-include]]
 === Include the CSRF Token
 
 In order for the xref:features/exploits/csrf.adoc#csrf-protection-stp[synchronizer token pattern] to protect against CSRF attacks, we must include the actual CSRF token in the HTTP request.
 This must be included in a part of the request (i.e. form parameter, HTTP header, etc) that is not automatically included in the HTTP request by the browser.
 
-Spring Security's https://docs.spring.io/spring-security/site/docs/current/api/org/springframework/security/web/server/csrf/CsrfWebFilter.html[CsrfWebFilter] exposes a https://docs.spring.io/spring-security/site/docs/current/api/org/springframework/security/web/csrf/CsrfToken.html[Mono<CsrfToken>] as a `ServerWebExchange` attribute named `org.springframework.security.web.server.csrf.CsrfToken`.
+<<webflux-csrf-configure-request-handler,We've seen>> that the `Mono<CsrfToken>` is exposed as a `ServerWebExchange` attribute.
 This means that any view technology can access the `Mono<CsrfToken>` to expose the expected token as either a <<webflux-csrf-include-form-attr,form>> or <<webflux-csrf-include-ajax-meta,meta tag>>.
 
 [[webflux-csrf-include-subscribe]]

+ 116 - 0
web/src/main/java/org/springframework/security/web/server/csrf/XorServerCsrfTokenRequestAttributeHandler.java

@@ -0,0 +1,116 @@
+/*
+ * 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 java.security.SecureRandom;
+import java.util.Base64;
+
+import reactor.core.publisher.Mono;
+
+import org.springframework.security.crypto.codec.Utf8;
+import org.springframework.util.Assert;
+import org.springframework.web.server.ServerWebExchange;
+
+/**
+ * An implementation of the {@link ServerCsrfTokenRequestAttributeHandler} and
+ * {@link ServerCsrfTokenRequestResolver} interfaces that is capable of masking the value
+ * of the {@link CsrfToken} on each request and resolving the raw token value from the
+ * masked value as either a form data value or header of the request.
+ *
+ * @author Steve Riesenberg
+ * @since 5.8
+ */
+public final class XorServerCsrfTokenRequestAttributeHandler extends ServerCsrfTokenRequestAttributeHandler {
+
+	private SecureRandom secureRandom = new SecureRandom();
+
+	/**
+	 * Specifies the {@code SecureRandom} used to generate random bytes that are used to
+	 * mask the value of the {@link CsrfToken} on each request.
+	 * @param secureRandom the {@code SecureRandom} to use to generate random bytes
+	 */
+	public void setSecureRandom(SecureRandom secureRandom) {
+		Assert.notNull(secureRandom, "secureRandom cannot be null");
+		this.secureRandom = secureRandom;
+	}
+
+	@Override
+	public void handle(ServerWebExchange exchange, Mono<CsrfToken> csrfToken) {
+		Assert.notNull(exchange, "exchange cannot be null");
+		Assert.notNull(csrfToken, "csrfToken cannot be null");
+		Mono<CsrfToken> updatedCsrfToken = csrfToken.map((token) -> new DefaultCsrfToken(token.getHeaderName(),
+				token.getParameterName(), createXoredCsrfToken(this.secureRandom, token.getToken())));
+		super.handle(exchange, updatedCsrfToken);
+	}
+
+	@Override
+	public Mono<String> resolveCsrfTokenValue(ServerWebExchange exchange, CsrfToken csrfToken) {
+		return super.resolveCsrfTokenValue(exchange, csrfToken)
+				.flatMap((actualToken) -> Mono.justOrEmpty(getTokenValue(actualToken, csrfToken.getToken())));
+	}
+
+	private static String getTokenValue(String actualToken, String token) {
+		byte[] actualBytes;
+		try {
+			actualBytes = Base64.getUrlDecoder().decode(actualToken);
+		}
+		catch (Exception ex) {
+			return null;
+		}
+
+		byte[] tokenBytes = Utf8.encode(token);
+		int tokenSize = tokenBytes.length;
+		if (actualBytes.length < tokenSize) {
+			return null;
+		}
+
+		// extract token and random bytes
+		int randomBytesSize = actualBytes.length - tokenSize;
+		byte[] xoredCsrf = new byte[tokenSize];
+		byte[] randomBytes = new byte[randomBytesSize];
+
+		System.arraycopy(actualBytes, 0, randomBytes, 0, randomBytesSize);
+		System.arraycopy(actualBytes, randomBytesSize, xoredCsrf, 0, tokenSize);
+
+		byte[] csrfBytes = xorCsrf(randomBytes, xoredCsrf);
+		return Utf8.decode(csrfBytes);
+	}
+
+	private static String createXoredCsrfToken(SecureRandom secureRandom, String token) {
+		byte[] tokenBytes = Utf8.encode(token);
+		byte[] randomBytes = new byte[tokenBytes.length];
+		secureRandom.nextBytes(randomBytes);
+
+		byte[] xoredBytes = xorCsrf(randomBytes, tokenBytes);
+		byte[] combinedBytes = new byte[tokenBytes.length + randomBytes.length];
+		System.arraycopy(randomBytes, 0, combinedBytes, 0, randomBytes.length);
+		System.arraycopy(xoredBytes, 0, combinedBytes, randomBytes.length, xoredBytes.length);
+
+		return Base64.getUrlEncoder().encodeToString(combinedBytes);
+	}
+
+	private static byte[] xorCsrf(byte[] randomBytes, byte[] csrfBytes) {
+		int len = Math.min(randomBytes.length, csrfBytes.length);
+		byte[] xoredCsrf = new byte[len];
+		System.arraycopy(csrfBytes, 0, xoredCsrf, 0, csrfBytes.length);
+		for (int i = 0; i < len; i++) {
+			xoredCsrf[i] ^= randomBytes[i];
+		}
+		return xoredCsrf;
+	}
+
+}

+ 50 - 4
web/src/test/java/org/springframework/security/web/server/csrf/CsrfWebFilterTests.java

@@ -180,6 +180,44 @@ public class CsrfWebFilterTests {
 		verify(requestHandler).resolveCsrfTokenValue(this.post, this.token);
 	}
 
+	@Test
+	public void filterWhenXorServerCsrfTokenRequestProcessorAndValidTokenThenSuccess() {
+		PublisherProbe<Void> chainResult = PublisherProbe.empty();
+		given(this.chain.filter(any())).willReturn(chainResult.mono());
+		this.csrfFilter.setCsrfTokenRepository(this.repository);
+		given(this.repository.generateToken(any())).willReturn(Mono.just(this.token));
+		given(this.repository.loadToken(any())).willReturn(Mono.just(this.token));
+		XorServerCsrfTokenRequestAttributeHandler requestHandler = new XorServerCsrfTokenRequestAttributeHandler();
+		this.csrfFilter.setRequestHandler(requestHandler);
+		StepVerifier.create(this.csrfFilter.filter(this.get, this.chain)).verifyComplete();
+		chainResult.assertWasSubscribed();
+
+		Mono<CsrfToken> csrfTokenAttribute = this.get.getAttribute(CsrfToken.class.getName());
+		assertThat(csrfTokenAttribute).isNotNull();
+		StepVerifier.create(csrfTokenAttribute)
+				.consumeNextWith((csrfToken) -> this.post = MockServerWebExchange
+						.from(MockServerHttpRequest.post("/").header(csrfToken.getHeaderName(), csrfToken.getToken())))
+				.verifyComplete();
+
+		StepVerifier.create(this.csrfFilter.filter(this.post, this.chain)).verifyComplete();
+		chainResult.assertWasSubscribed();
+	}
+
+	@Test
+	public void filterWhenXorServerCsrfTokenRequestProcessorAndRawTokenThenAccessDeniedException() {
+		PublisherProbe<Void> chainResult = PublisherProbe.empty();
+		this.csrfFilter.setCsrfTokenRepository(this.repository);
+		given(this.repository.loadToken(any())).willReturn(Mono.just(this.token));
+		XorServerCsrfTokenRequestAttributeHandler requestHandler = new XorServerCsrfTokenRequestAttributeHandler();
+		this.csrfFilter.setRequestHandler(requestHandler);
+		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.assertWasNotSubscribed();
+		assertThat(this.post.getResponse().getStatusCode()).isEqualTo(HttpStatus.FORBIDDEN);
+	}
+
 	@Test
 	// gh-8452
 	public void matchesRequireCsrfProtectionWhenNonStandardHTTPMethodIsUsed() {
@@ -215,7 +253,9 @@ public class CsrfWebFilterTests {
 	@Test
 	public void filterWhenMultipartFormDataAndEnabledThenGranted() {
 		this.csrfFilter.setCsrfTokenRepository(this.repository);
-		this.csrfFilter.setTokenFromMultipartDataEnabled(true);
+		ServerCsrfTokenRequestAttributeHandler requestHandler = new ServerCsrfTokenRequestAttributeHandler();
+		requestHandler.setTokenFromMultipartDataEnabled(true);
+		this.csrfFilter.setRequestHandler(requestHandler);
 		given(this.repository.loadToken(any())).willReturn(Mono.just(this.token));
 		given(this.repository.generateToken(any())).willReturn(Mono.just(this.token));
 		WebTestClient client = WebTestClient.bindToController(new OkController()).webFilter(this.csrfFilter).build();
@@ -227,7 +267,9 @@ public class CsrfWebFilterTests {
 	@Test
 	public void filterWhenPostAndMultipartFormDataEnabledAndNoBodyProvided() {
 		this.csrfFilter.setCsrfTokenRepository(this.repository);
-		this.csrfFilter.setTokenFromMultipartDataEnabled(true);
+		ServerCsrfTokenRequestAttributeHandler requestHandler = new ServerCsrfTokenRequestAttributeHandler();
+		requestHandler.setTokenFromMultipartDataEnabled(true);
+		this.csrfFilter.setRequestHandler(requestHandler);
 		given(this.repository.loadToken(any())).willReturn(Mono.just(this.token));
 		given(this.repository.generateToken(any())).willReturn(Mono.just(this.token));
 		WebTestClient client = WebTestClient.bindToController(new OkController()).webFilter(this.csrfFilter).build();
@@ -238,7 +280,9 @@ public class CsrfWebFilterTests {
 	@Test
 	public void filterWhenFormDataAndEnabledThenGranted() {
 		this.csrfFilter.setCsrfTokenRepository(this.repository);
-		this.csrfFilter.setTokenFromMultipartDataEnabled(true);
+		ServerCsrfTokenRequestAttributeHandler requestHandler = new ServerCsrfTokenRequestAttributeHandler();
+		requestHandler.setTokenFromMultipartDataEnabled(true);
+		this.csrfFilter.setRequestHandler(requestHandler);
 		given(this.repository.loadToken(any())).willReturn(Mono.just(this.token));
 		given(this.repository.generateToken(any())).willReturn(Mono.just(this.token));
 		WebTestClient client = WebTestClient.bindToController(new OkController()).webFilter(this.csrfFilter).build();
@@ -250,7 +294,9 @@ public class CsrfWebFilterTests {
 	@Test
 	public void filterWhenMultipartMixedAndEnabledThenNotRead() {
 		this.csrfFilter.setCsrfTokenRepository(this.repository);
-		this.csrfFilter.setTokenFromMultipartDataEnabled(true);
+		ServerCsrfTokenRequestAttributeHandler requestHandler = new ServerCsrfTokenRequestAttributeHandler();
+		requestHandler.setTokenFromMultipartDataEnabled(true);
+		this.csrfFilter.setRequestHandler(requestHandler);
 		given(this.repository.loadToken(any())).willReturn(Mono.just(this.token));
 		WebTestClient client = WebTestClient.bindToController(new OkController()).webFilter(this.csrfFilter).build();
 		client.post().uri("/").contentType(MediaType.MULTIPART_MIXED)

+ 171 - 0
web/src/test/java/org/springframework/security/web/server/csrf/XorServerCsrfTokenRequestAttributeHandlerTests.java

@@ -0,0 +1,171 @@
+/*
+ * 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 java.security.SecureRandom;
+import java.util.Arrays;
+import java.util.Base64;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.mockito.stubbing.Answer;
+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;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.BDDMockito.willAnswer;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+
+/**
+ * Tests for {@link XorServerCsrfTokenRequestAttributeHandler}.
+ *
+ * @author Steve Riesenberg
+ * @since 5.8
+ */
+public class XorServerCsrfTokenRequestAttributeHandlerTests {
+
+	private static final byte[] XOR_CSRF_TOKEN_BYTES = new byte[] { 1, 1, 1, 96, 99, 98 };
+
+	private static final String XOR_CSRF_TOKEN_VALUE = Base64.getEncoder().encodeToString(XOR_CSRF_TOKEN_BYTES);
+
+	private XorServerCsrfTokenRequestAttributeHandler handler;
+
+	private MockServerWebExchange exchange;
+
+	private CsrfToken token;
+
+	private SecureRandom secureRandom;
+
+	@BeforeEach
+	public void setUp() {
+		this.handler = new XorServerCsrfTokenRequestAttributeHandler();
+		this.exchange = MockServerWebExchange.builder(MockServerHttpRequest.get("/")).build();
+		this.token = new DefaultCsrfToken("headerName", "paramName", "abc");
+		this.secureRandom = mock(SecureRandom.class);
+	}
+
+	@Test
+	public void setSecureRandomWhenNullThenThrowsIllegalArgumentException() {
+		assertThatIllegalArgumentException().isThrownBy(() -> this.handler.setSecureRandom(null))
+				.withMessage("secureRandom cannot be null");
+	}
+
+	@Test
+	public void handleWhenExchangeIsNullThenThrowsIllegalArgumentException() {
+		assertThatIllegalArgumentException().isThrownBy(() -> this.handler.handle(null, Mono.just(this.token)))
+				.withMessage("exchange cannot be null");
+	}
+
+	@Test
+	public void handleWhenCsrfTokenIsNullThenThrowsIllegalArgumentException() {
+		assertThatIllegalArgumentException().isThrownBy(() -> this.handler.handle(this.exchange, null))
+				.withMessage("csrfToken cannot be null");
+	}
+
+	@Test
+	public void handleWhenSecureRandomSetThenUsed() {
+		this.handler.setSecureRandom(this.secureRandom);
+		this.handler.handle(this.exchange, Mono.just(this.token));
+		Mono<CsrfToken> csrfTokenAttribute = this.exchange.getAttribute(CsrfToken.class.getName());
+		assertThat(csrfTokenAttribute).isNotNull();
+		StepVerifier.create(csrfTokenAttribute).expectNextCount(1).verifyComplete();
+		verify(this.secureRandom).nextBytes(anyByteArray());
+	}
+
+	@Test
+	public void handleWhenValidParametersThenExchangeAttributeSet() {
+		willAnswer(fillByteArray()).given(this.secureRandom).nextBytes(anyByteArray());
+
+		this.handler.setSecureRandom(this.secureRandom);
+		this.handler.handle(this.exchange, Mono.just(this.token));
+		Mono<CsrfToken> csrfTokenAttribute = this.exchange.getAttribute(CsrfToken.class.getName());
+		assertThat(csrfTokenAttribute).isNotNull();
+		// @formatter:off
+		StepVerifier.create(csrfTokenAttribute)
+				.assertNext((csrfToken) -> assertThat(csrfToken.getToken()).isEqualTo(XOR_CSRF_TOKEN_VALUE))
+				.verifyComplete();
+		// @formatter:on
+		verify(this.secureRandom).nextBytes(anyByteArray());
+	}
+
+	@Test
+	public void resolveCsrfTokenValueWhenExchangeIsNullThenThrowsIllegalArgumentException() {
+		assertThatIllegalArgumentException().isThrownBy(() -> this.handler.resolveCsrfTokenValue(null, this.token))
+				.withMessage("exchange cannot be null");
+	}
+
+	@Test
+	public void resolveCsrfTokenValueWhenCsrfTokenIsNullThenThrowsIllegalArgumentException() {
+		assertThatIllegalArgumentException().isThrownBy(() -> this.handler.resolveCsrfTokenValue(this.exchange, null))
+				.withMessage("csrfToken cannot be null");
+	}
+
+	@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() + "=" + XOR_CSRF_TOKEN_VALUE)).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(), XOR_CSRF_TOKEN_VALUE)).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() + "=" + XOR_CSRF_TOKEN_VALUE)).build();
+		Mono<String> csrfToken = this.handler.resolveCsrfTokenValue(this.exchange, this.token);
+		StepVerifier.create(csrfToken).expectNext(this.token.getToken()).verifyComplete();
+	}
+
+	private static Answer<Void> fillByteArray() {
+		return (invocation) -> {
+			byte[] bytes = invocation.getArgument(0);
+			Arrays.fill(bytes, (byte) 1);
+			return null;
+		};
+	}
+
+	private static byte[] anyByteArray() {
+		return any(byte[].class);
+	}
+
+}