org.springframework.security.web.server.csrf.CsrfWebFilter Maven / Gradle / Ivy
/*
* Copyright 2002-2020 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.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;
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
* @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 boolean isTokenFromMultipartDataEnabled;
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 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
*/
public void setTokenFromMultipartDataEnabled(boolean tokenFromMultipartDataEnabled) {
this.isTokenFromMultipartDataEnabled = tokenFromMultipartDataEnabled;
}
@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 exchange.getFormData().flatMap((data) -> Mono.justOrEmpty(data.getFirst(expected.getParameterName())))
.switchIfEmpty(Mono.justOrEmpty(exchange.getRequest().getHeaders().getFirst(expected.getHeaderName())))
.switchIfEmpty(tokenFromMultipartData(exchange, expected))
.map((actual) -> equalsConstantTime(actual, expected.getToken()));
}
private Mono tokenFromMultipartData(ServerWebExchange exchange, CsrfToken expected) {
if (!this.isTokenFromMultipartDataEnabled) {
return Mono.empty();
}
ServerHttpRequest request = exchange.getRequest();
HttpHeaders headers = request.getHeaders();
MediaType contentType = headers.getContentType();
if (!contentType.includes(MediaType.MULTIPART_FORM_DATA)) {
return Mono.empty();
}
return exchange.getMultipartData().map((d) -> d.getFirst(expected.getParameterName())).cast(FormFieldPart.class)
.map(FormFieldPart::value);
}
private Mono continueFilterChain(ServerWebExchange exchange, WebFilterChain chain) {
return Mono.defer(() -> {
Mono csrfToken = csrfToken(exchange);
exchange.getAttributes().put(CsrfToken.class.getName(), 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) {
byte[] expectedBytes = bytesUtf8(expected);
byte[] actualBytes = bytesUtf8(actual);
return MessageDigest.isEqual(expectedBytes, actualBytes);
}
private static byte[] bytesUtf8(String s) {
// need to check if Utf8.encode() runs in constant time (probably not).
// This may leak length of string.
return (s != null) ? Utf8.encode(s) : null;
}
private Mono generateToken(ServerWebExchange exchange) {
return this.csrfTokenRepository.generateToken(exchange)
.delayUntil((token) -> this.csrfTokenRepository.saveToken(exchange, token));
}
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());
}
}
}