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;
018
019import java.io.IOException;
020import java.nio.charset.Charset;
021import java.util.ArrayList;
022import java.util.List;
023import javax.servlet.http.HttpServletRequest;
024import javax.servlet.http.HttpServletResponse;
025
026import org.apache.commons.logging.Log;
027import org.apache.commons.logging.LogFactory;
028
029import org.springframework.http.HttpHeaders;
030import org.springframework.http.HttpMethod;
031import org.springframework.http.HttpStatus;
032import org.springframework.http.server.ServerHttpRequest;
033import org.springframework.http.server.ServerHttpResponse;
034import org.springframework.http.server.ServletServerHttpRequest;
035import org.springframework.http.server.ServletServerHttpResponse;
036import org.springframework.util.CollectionUtils;
037import org.springframework.web.util.WebUtils;
038
039/**
040 * The default implementation of {@link CorsProcessor}, as defined by the
041 * <a href="https://www.w3.org/TR/cors/">CORS W3C recommendation</a>.
042 *
043 * <p>Note that when input {@link CorsConfiguration} is {@code null}, this
044 * implementation does not reject simple or actual requests outright but simply
045 * avoid adding CORS headers to the response. CORS processing is also skipped
046 * if the response already contains CORS headers, or if the request is detected
047 * as a same-origin one.
048 *
049 * @author Sebastien Deleuze
050 * @author Rossen Stoyanchev
051 * @since 4.2
052 */
053public class DefaultCorsProcessor implements CorsProcessor {
054
055        private static final Charset UTF8_CHARSET = Charset.forName("UTF-8");
056
057        private static final Log logger = LogFactory.getLog(DefaultCorsProcessor.class);
058
059
060        @Override
061        @SuppressWarnings("resource")
062        public boolean processRequest(CorsConfiguration config, HttpServletRequest request, HttpServletResponse response)
063                        throws IOException {
064
065                if (!CorsUtils.isCorsRequest(request)) {
066                        return true;
067                }
068
069                ServletServerHttpResponse serverResponse = new ServletServerHttpResponse(response);
070                if (responseHasCors(serverResponse)) {
071                        logger.debug("Skip CORS processing: response already contains \"Access-Control-Allow-Origin\" header");
072                        return true;
073                }
074
075                ServletServerHttpRequest serverRequest = new ServletServerHttpRequest(request);
076                if (WebUtils.isSameOrigin(serverRequest)) {
077                        logger.debug("Skip CORS processing: request is from same origin");
078                        return true;
079                }
080
081                boolean preFlightRequest = CorsUtils.isPreFlightRequest(request);
082                if (config == null) {
083                        if (preFlightRequest) {
084                                rejectRequest(serverResponse);
085                                return false;
086                        }
087                        else {
088                                return true;
089                        }
090                }
091
092                return handleInternal(serverRequest, serverResponse, config, preFlightRequest);
093        }
094
095        private boolean responseHasCors(ServerHttpResponse response) {
096                try {
097                        return (response.getHeaders().getAccessControlAllowOrigin() != null);
098                }
099                catch (NullPointerException npe) {
100                        // SPR-11919 and https://issues.jboss.org/browse/WFLY-3474
101                        return false;
102                }
103        }
104
105        /**
106         * Invoked when one of the CORS checks failed.
107         * The default implementation sets the response status to 403 and writes
108         * "Invalid CORS request" to the response.
109         */
110        protected void rejectRequest(ServerHttpResponse response) throws IOException {
111                response.setStatusCode(HttpStatus.FORBIDDEN);
112                response.getBody().write("Invalid CORS request".getBytes(UTF8_CHARSET));
113        }
114
115        /**
116         * Handle the given request.
117         */
118        protected boolean handleInternal(ServerHttpRequest request, ServerHttpResponse response,
119                        CorsConfiguration config, boolean preFlightRequest) throws IOException {
120
121                String requestOrigin = request.getHeaders().getOrigin();
122                String allowOrigin = checkOrigin(config, requestOrigin);
123
124                HttpMethod requestMethod = getMethodToUse(request, preFlightRequest);
125                List<HttpMethod> allowMethods = checkMethods(config, requestMethod);
126
127                List<String> requestHeaders = getHeadersToUse(request, preFlightRequest);
128                List<String> allowHeaders = checkHeaders(config, requestHeaders);
129
130                if (allowOrigin == null || allowMethods == null || (preFlightRequest && allowHeaders == null)) {
131                        rejectRequest(response);
132                        return false;
133                }
134
135                HttpHeaders responseHeaders = response.getHeaders();
136                responseHeaders.setAccessControlAllowOrigin(allowOrigin);
137                responseHeaders.add(HttpHeaders.VARY, HttpHeaders.ORIGIN);
138
139                if (preFlightRequest) {
140                        responseHeaders.setAccessControlAllowMethods(allowMethods);
141                }
142
143                if (preFlightRequest && !allowHeaders.isEmpty()) {
144                        responseHeaders.setAccessControlAllowHeaders(allowHeaders);
145                }
146
147                if (!CollectionUtils.isEmpty(config.getExposedHeaders())) {
148                        responseHeaders.setAccessControlExposeHeaders(config.getExposedHeaders());
149                }
150
151                if (Boolean.TRUE.equals(config.getAllowCredentials())) {
152                        responseHeaders.setAccessControlAllowCredentials(true);
153                }
154
155                if (preFlightRequest && config.getMaxAge() != null) {
156                        responseHeaders.setAccessControlMaxAge(config.getMaxAge());
157                }
158
159                response.flush();
160                return true;
161        }
162
163        /**
164         * Check the origin and determine the origin for the response. The default
165         * implementation simply delegates to
166         * {@link org.springframework.web.cors.CorsConfiguration#checkOrigin(String)}.
167         */
168        protected String checkOrigin(CorsConfiguration config, String requestOrigin) {
169                return config.checkOrigin(requestOrigin);
170        }
171
172        /**
173         * Check the HTTP method and determine the methods for the response of a
174         * pre-flight request. The default implementation simply delegates to
175         * {@link org.springframework.web.cors.CorsConfiguration#checkHttpMethod(HttpMethod)}.
176         */
177        protected List<HttpMethod> checkMethods(CorsConfiguration config, HttpMethod requestMethod) {
178                return config.checkHttpMethod(requestMethod);
179        }
180
181        private HttpMethod getMethodToUse(ServerHttpRequest request, boolean isPreFlight) {
182                return (isPreFlight ? request.getHeaders().getAccessControlRequestMethod() : request.getMethod());
183        }
184
185        /**
186         * Check the headers and determine the headers for the response of a
187         * pre-flight request. The default implementation simply delegates to
188         * {@link org.springframework.web.cors.CorsConfiguration#checkOrigin(String)}.
189         */
190        protected List<String> checkHeaders(CorsConfiguration config, List<String> requestHeaders) {
191                return config.checkHeaders(requestHeaders);
192        }
193
194        private List<String> getHeadersToUse(ServerHttpRequest request, boolean isPreFlight) {
195                HttpHeaders headers = request.getHeaders();
196                return (isPreFlight ? headers.getAccessControlRequestHeaders() : new ArrayList<String>(headers.keySet()));
197        }
198
199}