001/*
002 * Copyright 2002-2020 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.web.cors.reactive;
018
019import java.util.ArrayList;
020import java.util.Arrays;
021import java.util.List;
022
023import org.apache.commons.logging.Log;
024import org.apache.commons.logging.LogFactory;
025
026import org.springframework.http.HttpHeaders;
027import org.springframework.http.HttpMethod;
028import org.springframework.http.HttpStatus;
029import org.springframework.http.server.reactive.ServerHttpRequest;
030import org.springframework.http.server.reactive.ServerHttpResponse;
031import org.springframework.lang.Nullable;
032import org.springframework.util.CollectionUtils;
033import org.springframework.web.cors.CorsConfiguration;
034import org.springframework.web.server.ServerWebExchange;
035
036/**
037 * The default implementation of {@link CorsProcessor},
038 * as defined by the <a href="https://www.w3.org/TR/cors/">CORS W3C recommendation</a>.
039 *
040 * <p>Note that when input {@link CorsConfiguration} is {@code null}, this
041 * implementation does not reject simple or actual requests outright but simply
042 * avoid adding CORS headers to the response. CORS processing is also skipped
043 * if the response already contains CORS headers.
044 *
045 * @author Sebastien Deleuze
046 * @author Rossen Stoyanchev
047 * @since 5.0
048 */
049public class DefaultCorsProcessor implements CorsProcessor {
050
051        private static final Log logger = LogFactory.getLog(DefaultCorsProcessor.class);
052
053        private static final List<String> VARY_HEADERS = Arrays.asList(
054                        HttpHeaders.ORIGIN, HttpHeaders.ACCESS_CONTROL_REQUEST_METHOD, HttpHeaders.ACCESS_CONTROL_REQUEST_HEADERS);
055
056
057        @Override
058        public boolean process(@Nullable CorsConfiguration config, ServerWebExchange exchange) {
059
060                ServerHttpRequest request = exchange.getRequest();
061                ServerHttpResponse response = exchange.getResponse();
062                HttpHeaders responseHeaders = response.getHeaders();
063
064                List<String> varyHeaders = responseHeaders.get(HttpHeaders.VARY);
065                if (varyHeaders == null) {
066                        responseHeaders.addAll(HttpHeaders.VARY, VARY_HEADERS);
067                }
068                else {
069                        for (String header : VARY_HEADERS) {
070                                if (!varyHeaders.contains(header)) {
071                                        responseHeaders.add(HttpHeaders.VARY, header);
072                                }
073                        }
074                }
075
076                if (!CorsUtils.isCorsRequest(request)) {
077                        return true;
078                }
079
080                if (responseHeaders.getFirst(HttpHeaders.ACCESS_CONTROL_ALLOW_ORIGIN) != null) {
081                        logger.trace("Skip: response already contains \"Access-Control-Allow-Origin\"");
082                        return true;
083                }
084
085                boolean preFlightRequest = CorsUtils.isPreFlightRequest(request);
086                if (config == null) {
087                        if (preFlightRequest) {
088                                rejectRequest(response);
089                                return false;
090                        }
091                        else {
092                                return true;
093                        }
094                }
095
096                return handleInternal(exchange, config, preFlightRequest);
097        }
098
099        /**
100         * Invoked when one of the CORS checks failed.
101         */
102        protected void rejectRequest(ServerHttpResponse response) {
103                response.setStatusCode(HttpStatus.FORBIDDEN);
104        }
105
106        /**
107         * Handle the given request.
108         */
109        protected boolean handleInternal(ServerWebExchange exchange,
110                        CorsConfiguration config, boolean preFlightRequest) {
111
112                ServerHttpRequest request = exchange.getRequest();
113                ServerHttpResponse response = exchange.getResponse();
114                HttpHeaders responseHeaders = response.getHeaders();
115
116                String requestOrigin = request.getHeaders().getOrigin();
117                String allowOrigin = checkOrigin(config, requestOrigin);
118                if (allowOrigin == null) {
119                        logger.debug("Reject: '" + requestOrigin + "' origin is not allowed");
120                        rejectRequest(response);
121                        return false;
122                }
123
124                HttpMethod requestMethod = getMethodToUse(request, preFlightRequest);
125                List<HttpMethod> allowMethods = checkMethods(config, requestMethod);
126                if (allowMethods == null) {
127                        logger.debug("Reject: HTTP '" + requestMethod + "' is not allowed");
128                        rejectRequest(response);
129                        return false;
130                }
131
132                List<String> requestHeaders = getHeadersToUse(request, preFlightRequest);
133                List<String> allowHeaders = checkHeaders(config, requestHeaders);
134                if (preFlightRequest && allowHeaders == null) {
135                        logger.debug("Reject: headers '" + requestHeaders + "' are not allowed");
136                        rejectRequest(response);
137                        return false;
138                }
139
140                responseHeaders.setAccessControlAllowOrigin(allowOrigin);
141
142                if (preFlightRequest) {
143                        responseHeaders.setAccessControlAllowMethods(allowMethods);
144                }
145
146                if (preFlightRequest && !allowHeaders.isEmpty()) {
147                        responseHeaders.setAccessControlAllowHeaders(allowHeaders);
148                }
149
150                if (!CollectionUtils.isEmpty(config.getExposedHeaders())) {
151                        responseHeaders.setAccessControlExposeHeaders(config.getExposedHeaders());
152                }
153
154                if (Boolean.TRUE.equals(config.getAllowCredentials())) {
155                        responseHeaders.setAccessControlAllowCredentials(true);
156                }
157
158                if (preFlightRequest && config.getMaxAge() != null) {
159                        responseHeaders.setAccessControlMaxAge(config.getMaxAge());
160                }
161
162                return true;
163        }
164
165        /**
166         * Check the origin and determine the origin for the response. The default
167         * implementation simply delegates to
168         * {@link CorsConfiguration#checkOrigin(String)}.
169         */
170        @Nullable
171        protected String checkOrigin(CorsConfiguration config, @Nullable String requestOrigin) {
172                return config.checkOrigin(requestOrigin);
173        }
174
175        /**
176         * Check the HTTP method and determine the methods for the response of a
177         * pre-flight request. The default implementation simply delegates to
178         * {@link CorsConfiguration#checkHttpMethod(HttpMethod)}.
179         */
180        @Nullable
181        protected List<HttpMethod> checkMethods(CorsConfiguration config, @Nullable HttpMethod requestMethod) {
182                return config.checkHttpMethod(requestMethod);
183        }
184
185        @Nullable
186        private HttpMethod getMethodToUse(ServerHttpRequest request, boolean isPreFlight) {
187                return (isPreFlight ? request.getHeaders().getAccessControlRequestMethod() : request.getMethod());
188        }
189
190        /**
191         * Check the headers and determine the headers for the response of a
192         * pre-flight request. The default implementation simply delegates to
193         * {@link CorsConfiguration#checkOrigin(String)}.
194         */
195        @Nullable
196
197        protected List<String> checkHeaders(CorsConfiguration config, List<String> requestHeaders) {
198                return config.checkHeaders(requestHeaders);
199        }
200
201        private List<String> getHeadersToUse(ServerHttpRequest request, boolean isPreFlight) {
202                HttpHeaders headers = request.getHeaders();
203                return (isPreFlight ? headers.getAccessControlRequestHeaders() : new ArrayList<>(headers.keySet()));
204        }
205
206}