org.springframework.security.web.server.csrf.CsrfWebFilter Maven / Gradle / Ivy
/*
* 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.MessageDigest;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
import reactor.core.publisher.Mono;
import org.springframework.http.HttpMethod;
import org.springframework.http.HttpStatus;
import org.springframework.security.crypto.codec.Utf8;
import org.springframework.security.web.server.authorization.HttpStatusServerAccessDeniedHandler;
import org.springframework.security.web.server.authorization.ServerAccessDeniedHandler;
import org.springframework.security.web.server.util.matcher.ServerWebExchangeMatcher;
import org.springframework.security.web.server.util.matcher.ServerWebExchangeMatcher.MatchResult;
import org.springframework.util.Assert;
import org.springframework.web.server.ServerWebExchange;
import org.springframework.web.server.WebFilter;
import org.springframework.web.server.WebFilterChain;
/**
*
* Applies
* CSRF
* protection using a synchronizer token pattern. Developers are required to ensure that
* {@link CsrfWebFilter} is invoked for any request that allows state to change. Typically
* this just means that they should ensure their web application follows proper REST
* semantics (i.e. do not change state with the HTTP methods GET, HEAD, TRACE, OPTIONS).
*
*
*
* Typically the {@link ServerCsrfTokenRepository} implementation chooses to store the
* {@link CsrfToken} in {@link org.springframework.web.server.WebSession} with
* {@link WebSessionServerCsrfTokenRepository}. This is preferred to storing the token in
* a cookie which can be modified by a client application.
*
*
* The {@code Mono<CsrfToken>} is exposes as a request attribute with the name of
* {@code CsrfToken.class.getName()}. If the token is new it will automatically be saved
* at the time it is subscribed.
*
*
* @author Rob Winch
* @author Parikshit Dutta
* @author Steve Riesenberg
* @since 5.0
*/
public class CsrfWebFilter implements WebFilter {
public static final ServerWebExchangeMatcher DEFAULT_CSRF_MATCHER = new DefaultRequireCsrfProtectionMatcher();
/**
* The attribute name to use when marking a given request as one that should not be
* filtered.
*
* To use, set the attribute on your {@link ServerWebExchange}:
* CsrfWebFilter.skipExchange(exchange);
*
*/
private static final String SHOULD_NOT_FILTER = "SHOULD_NOT_FILTER" + CsrfWebFilter.class.getName();
private ServerWebExchangeMatcher requireCsrfProtectionMatcher = DEFAULT_CSRF_MATCHER;
private ServerCsrfTokenRepository csrfTokenRepository = new WebSessionServerCsrfTokenRepository();
private ServerAccessDeniedHandler accessDeniedHandler = new HttpStatusServerAccessDeniedHandler(
HttpStatus.FORBIDDEN);
private ServerCsrfTokenRequestHandler requestHandler = new XorServerCsrfTokenRequestAttributeHandler();
public void setAccessDeniedHandler(ServerAccessDeniedHandler accessDeniedHandler) {
Assert.notNull(accessDeniedHandler, "accessDeniedHandler");
this.accessDeniedHandler = accessDeniedHandler;
}
public void setCsrfTokenRepository(ServerCsrfTokenRepository csrfTokenRepository) {
Assert.notNull(csrfTokenRepository, "csrfTokenRepository cannot be null");
this.csrfTokenRepository = csrfTokenRepository;
}
public void setRequireCsrfProtectionMatcher(ServerWebExchangeMatcher requireCsrfProtectionMatcher) {
Assert.notNull(requireCsrfProtectionMatcher, "requireCsrfProtectionMatcher cannot be null");
this.requireCsrfProtectionMatcher = requireCsrfProtectionMatcher;
}
/**
* Specifies a {@link ServerCsrfTokenRequestHandler} that is used to make the
* {@code CsrfToken} available as an exchange attribute.
*
* The default is {@link XorServerCsrfTokenRequestAttributeHandler}.
* @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;
}
@Override
public Mono filter(ServerWebExchange exchange, WebFilterChain chain) {
if (Boolean.TRUE.equals(exchange.getAttribute(SHOULD_NOT_FILTER))) {
return chain.filter(exchange).then(Mono.empty());
}
return this.requireCsrfProtectionMatcher.matches(exchange)
.filter(MatchResult::isMatch)
.filter((matchResult) -> !exchange.getAttributes().containsKey(CsrfToken.class.getName()))
.flatMap((m) -> validateToken(exchange))
.flatMap((m) -> continueFilterChain(exchange, chain))
.switchIfEmpty(continueFilterChain(exchange, chain).then(Mono.empty()))
.onErrorResume(CsrfException.class, (ex) -> this.accessDeniedHandler.handle(exchange, ex));
}
public static void skipExchange(ServerWebExchange exchange) {
exchange.getAttributes().put(SHOULD_NOT_FILTER, Boolean.TRUE);
}
private Mono validateToken(ServerWebExchange exchange) {
return this.csrfTokenRepository.loadToken(exchange)
.switchIfEmpty(Mono.defer(() -> Mono.error(new CsrfException("An expected CSRF token cannot be found"))))
.filterWhen((expected) -> containsValidCsrfToken(exchange, expected))
.switchIfEmpty(Mono.defer(() -> Mono.error(new CsrfException("Invalid CSRF Token"))))
.then();
}
private Mono containsValidCsrfToken(ServerWebExchange exchange, CsrfToken expected) {
return this.requestHandler.resolveCsrfTokenValue(exchange, expected)
.map((actual) -> equalsConstantTime(actual, expected.getToken()));
}
private Mono continueFilterChain(ServerWebExchange exchange, WebFilterChain chain) {
return Mono.defer(() -> {
Mono csrfToken = csrfToken(exchange);
this.requestHandler.handle(exchange, csrfToken);
return chain.filter(exchange);
});
}
private Mono csrfToken(ServerWebExchange exchange) {
return this.csrfTokenRepository.loadToken(exchange).switchIfEmpty(generateToken(exchange));
}
/**
* Constant time comparison to prevent against timing attacks.
* @param expected
* @param actual
* @return
*/
private static boolean equalsConstantTime(String expected, String actual) {
if (expected == actual) {
return true;
}
if (expected == null || actual == null) {
return false;
}
// Encode after ensure that the string is not null
byte[] expectedBytes = Utf8.encode(expected);
byte[] actualBytes = Utf8.encode(actual);
return MessageDigest.isEqual(expectedBytes, actualBytes);
}
private Mono generateToken(ServerWebExchange exchange) {
return this.csrfTokenRepository.generateToken(exchange)
.delayUntil((token) -> this.csrfTokenRepository.saveToken(exchange, token))
.cache();
}
private static class DefaultRequireCsrfProtectionMatcher implements ServerWebExchangeMatcher {
private static final Set ALLOWED_METHODS = new HashSet<>(
Arrays.asList(HttpMethod.GET, HttpMethod.HEAD, HttpMethod.TRACE, HttpMethod.OPTIONS));
@Override
public Mono matches(ServerWebExchange exchange) {
return Mono.just(exchange.getRequest())
.flatMap((r) -> Mono.justOrEmpty(r.getMethod()))
.filter(ALLOWED_METHODS::contains)
.flatMap((m) -> MatchResult.notMatch())
.switchIfEmpty(MatchResult.match());
}
}
}