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Merge pull request apache#426 from salcho/post-ww-5083
WW-5083: Adds support for Fetch Metadata in Struts2.
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‎core/src/main/java/org/apache/struts2/interceptor/FetchMetadataInterceptor.java‎

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/*
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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*/
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package org.apache.struts2.interceptor;
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import static org.apache.struts2.interceptor.ResourceIsolationPolicy.SEC_FETCH_DEST_HEADER;
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import static org.apache.struts2.interceptor.ResourceIsolationPolicy.SEC_FETCH_MODE_HEADER;
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import static org.apache.struts2.interceptor.ResourceIsolationPolicy.SEC_FETCH_SITE_HEADER;
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import static org.apache.struts2.interceptor.ResourceIsolationPolicy.VARY_HEADER;
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import com.opensymphony.xwork2.ActionContext;
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import com.opensymphony.xwork2.ActionInvocation;
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import com.opensymphony.xwork2.interceptor.AbstractInterceptor;
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import com.opensymphony.xwork2.interceptor.PreResultListener;
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import com.opensymphony.xwork2.util.TextParseUtil;
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import java.util.HashSet;
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import java.util.Set;
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import javax.servlet.http.HttpServletRequest;
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import javax.servlet.http.HttpServletResponse;
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import org.apache.logging.log4j.LogManager;
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import org.apache.logging.log4j.Logger;
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/**
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* Interceptor that implements Fetch Metadata policy on incoming requests used to protect against
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* CSRF, XSSI, and cross-origin information leaks. Uses {@link StrutsResourceIsolationPolicy} to
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* filter the requests allowed to be processed.
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*
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* @see <a href="https://web.dev/fetch-metadata/">https://web.dev/fetch-metadata/</a>
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**/
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public class FetchMetadataInterceptor extends AbstractInterceptor {
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private static final Logger logger = LogManager.getLogger(FetchMetadataInterceptor.class);
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private static final String VARY_HEADER_VALUE = String.format("%s,%s,%s", SEC_FETCH_DEST_HEADER, SEC_FETCH_SITE_HEADER, SEC_FETCH_MODE_HEADER);
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private static final String SC_FORBIDDEN = String.valueOf(HttpServletResponse.SC_FORBIDDEN);
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private final Set<String> exemptedPaths = new HashSet<>();
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private final ResourceIsolationPolicy resourceIsolationPolicy = new StrutsResourceIsolationPolicy();
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public void setExemptedPaths(String paths){
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this.exemptedPaths.addAll(TextParseUtil.commaDelimitedStringToSet(paths));
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}
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@Override
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public String intercept(ActionInvocation invocation) throws Exception {
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ActionContext context = invocation.getInvocationContext();
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HttpServletRequest request = context.getServletRequest();
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addVaryHeaders(invocation);
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String contextPath = request.getContextPath();
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// Apply exemptions: paths/endpoints meant to be served cross-origin
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if (exemptedPaths.contains(contextPath)) {
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return invocation.invoke();
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}
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// Check if request is allowed
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if (resourceIsolationPolicy.isRequestAllowed(request)) {
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return invocation.invoke();
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}
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logger.atDebug().log(
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"Fetch metadata rejected cross-origin request to %s",
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contextPath
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);
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return SC_FORBIDDEN;
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}
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private void addVaryHeaders(ActionInvocation invocation) {
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HttpServletResponse response = invocation.getInvocationContext().getServletResponse();
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response.setHeader(VARY_HEADER, VARY_HEADER_VALUE);
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}
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}

‎core/src/main/java/org/apache/struts2/interceptor/ResourceIsolationPolicy.java‎

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/*
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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*/
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package org.apache.struts2.interceptor;
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import javax.servlet.http.HttpServletRequest;
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/**
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* Interface for the resource isolation policies to be used for fetch metadata checks.
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*
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* Resource isolation policies are designed to protect against cross origin attacks and use the
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* {@code sec-fetch-*} request headers to decide whether to accept or reject a request. Read more
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* about <a href="https://web.dev/fetch-metadata/">Fetch Metadata.</a>
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*
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* See {@link StrutsResourceIsolationPolicy} for the default implementation used.
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*
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* @see <a href="https://web.dev/fetch-metadata/">https://web.dev/fetch-metadata/</a>
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**/
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@FunctionalInterface
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public interface ResourceIsolationPolicy {
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String SEC_FETCH_SITE_HEADER = "sec-fetch-site";
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String SEC_FETCH_MODE_HEADER = "sec-fetch-mode";
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String SEC_FETCH_DEST_HEADER = "sec-fetch-dest";
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String VARY_HEADER = "Vary";
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String SAME_ORIGIN = "same-origin";
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String SAME_SITE = "same-site";
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String NONE = "none";
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String MODE_NAVIGATE = "navigate";
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String DEST_OBJECT = "object";
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String DEST_EMBED = "embed";
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String CROSS_SITE = "cross-site";
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String CORS = "cors";
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String DEST_SCRIPT = "script";
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String DEST_IMAGE = "image";
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boolean isRequestAllowed(HttpServletRequest request);
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}

‎core/src/main/java/org/apache/struts2/interceptor/StrutsResourceIsolationPolicy.java‎

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/*
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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*/
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package org.apache.struts2.interceptor;
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import org.apache.logging.log4j.util.Strings;
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import javax.servlet.http.HttpServletRequest;
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/**
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*
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* Default resource isolation policy used in {@link FetchMetadataInterceptor} that
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* implements the {@link ResourceIsolationPolicy} interface. This default policy is based on
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* <a href="https://web.dev/fetch-metadata/">https://web.dev/fetch-metadata/</a>.
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*
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* @see <a href="https://web.dev/fetch-metadata/">https://web.dev/fetch-metadata/</a>
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**/
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public final class StrutsResourceIsolationPolicy implements ResourceIsolationPolicy {
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@Override
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public boolean isRequestAllowed(HttpServletRequest request) {
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String site = request.getHeader(SEC_FETCH_SITE_HEADER);
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// Allow requests from browsers which don't send Fetch Metadata
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if (Strings.isEmpty(site)){
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return true;
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}
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// Allow same-site and browser-initiated requests
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if (SAME_ORIGIN.equals(site) || SAME_SITE.equals(site) || NONE.equals(site)) {
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return true;
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}
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// Allow simple top-level navigations except <object> and <embed>
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return isAllowedTopLevelNavigation(request);
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}
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private boolean isAllowedTopLevelNavigation(HttpServletRequest request) {
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String mode = request.getHeader(SEC_FETCH_MODE_HEADER);
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String dest = request.getHeader(SEC_FETCH_DEST_HEADER);
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boolean isSimpleTopLevelNavigation = MODE_NAVIGATE.equals(mode) || "GET".equals(request.getMethod());
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boolean isNotObjectOrEmbedRequest = !DEST_EMBED.equals(dest) && !DEST_OBJECT.equals(dest);
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return isSimpleTopLevelNavigation && isNotObjectOrEmbedRequest;
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}
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}

‎core/src/main/resources/struts-default.xml‎

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<interceptor name="annotationParameterFilter" class="com.opensymphony.xwork2.interceptor.annotations.AnnotationParameterFilterInterceptor" />
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<interceptor name="multiselect" class="org.apache.struts2.interceptor.MultiselectInterceptor" />
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<interceptor name="noop" class="org.apache.struts2.interceptor.NoOpInterceptor" />
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<interceptor name="fetchMetadata" class="org.apache.struts2.interceptor.FetchMetadataInterceptor" />
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<!-- Empty stack - performs no operations -->
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<interceptor-stack name="emptyStack">
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<interceptor-ref name="actionMappingParams"/>
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<interceptor-ref name="params"/>
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<interceptor-ref name="conversionError"/>
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<interceptor-ref name="fetchMetadata"/>
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<interceptor-ref name="validation">
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<param name="excludeMethods">input,back,cancel,browse</param>
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</interceptor-ref>

‎core/src/test/java/org/apache/struts2/interceptor/FetchMetadataInterceptorTest.java‎

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/*
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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*/
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package org.apache.struts2.interceptor;
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import static org.apache.struts2.interceptor.ResourceIsolationPolicy.SEC_FETCH_DEST_HEADER;
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import static org.apache.struts2.interceptor.ResourceIsolationPolicy.SEC_FETCH_MODE_HEADER;
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import static org.apache.struts2.interceptor.ResourceIsolationPolicy.SEC_FETCH_SITE_HEADER;
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import static org.apache.struts2.interceptor.ResourceIsolationPolicy.VARY_HEADER;
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import static org.junit.Assert.assertNotEquals;
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import com.opensymphony.xwork2.ActionContext;
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import com.opensymphony.xwork2.XWorkTestCase;
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import com.opensymphony.xwork2.mock.MockActionInvocation;
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import org.apache.struts2.ServletActionContext;
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import org.springframework.mock.web.MockHttpServletRequest;
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import org.springframework.mock.web.MockHttpServletResponse;
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import java.util.Arrays;
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public class FetchMetadataInterceptorTest extends XWorkTestCase {
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private final FetchMetadataInterceptor interceptor = new FetchMetadataInterceptor();
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private final MockActionInvocation mai = new MockActionInvocation();
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private final MockHttpServletRequest request = new MockHttpServletRequest();
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private final MockHttpServletResponse response = new MockHttpServletResponse();
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private static final String VARY_HEADER_VALUE = String.format(
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"%s,%s,%s",
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SEC_FETCH_DEST_HEADER,
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SEC_FETCH_SITE_HEADER,
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SEC_FETCH_MODE_HEADER
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);
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@Override
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protected void setUp() throws Exception {
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super.setUp();
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container.inject(interceptor);
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interceptor.setExemptedPaths("/foo,/bar");
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ServletActionContext.setRequest(request);
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ServletActionContext.setResponse(response);
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ActionContext context = ServletActionContext.getActionContext();
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mai.setInvocationContext(context);
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}
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public void testNoSite() throws Exception {
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request.removeHeader("sec-fetch-site");
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assertNotEquals("Expected interceptor to accept this request", "403",
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interceptor.intercept(mai));
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}
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public void testValidSite() throws Exception {
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for (String header : Arrays.asList("same-origin", "same-site", "none")){
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request.addHeader("sec-fetch-site", header);
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assertNotEquals("Expected interceptor to accept this request", "403",
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interceptor.intercept(mai));
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}
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}
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public void testValidTopLevelNavigation() throws Exception {
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request.addHeader("sec-fetch-mode", "navigate");
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request.addHeader("sec-fetch-dest", "script");
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request.setMethod("GET");
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assertNotEquals("Expected interceptor to accept this request", "403",
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interceptor.intercept(mai));
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}
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public void testInvalidTopLevelNavigation() throws Exception {
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for (String header : Arrays.asList("object", "embed")) {
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request.addHeader("sec-fetch-site", "foo");
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request.addHeader("sec-fetch-mode", "navigate");
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request.addHeader("sec-fetch-dest", header);
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request.setMethod("GET");
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assertEquals("Expected interceptor to NOT accept this request", "403", interceptor.intercept(mai));
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}
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}
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public void testPathInExemptedPaths() throws Exception {
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request.addHeader("sec-fetch-site", "foo");
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request.setContextPath("/foo");
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assertNotEquals("Expected interceptor to accept this request", "403",
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interceptor.intercept(mai));
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}
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public void testPathNotInExemptedPaths() throws Exception {
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request.addHeader("sec-fetch-site", "foo");
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request.setContextPath("/foobar");
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assertEquals("Expected interceptor to NOT accept this request", "403", interceptor.intercept(mai));
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}
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public void testVaryHeaderAcceptedReq() throws Exception {
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request.addHeader("sec-fetch-site", "foo");
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request.setContextPath("/foo");
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interceptor.intercept(mai);
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assertTrue("Expected vary header to be included", response.containsHeader(VARY_HEADER));
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assertEquals("Expected different vary header value", response.getHeader(VARY_HEADER), VARY_HEADER_VALUE);
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}
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public void testVaryHeaderRejectedReq() throws Exception {
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request.addHeader("sec-fetch-site", "foo");
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interceptor.intercept(mai);
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assertTrue("Expected vary header to be included", response.containsHeader(VARY_HEADER));
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assertEquals("Expected different vary header value", response.getHeader(VARY_HEADER), VARY_HEADER_VALUE);
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}
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}

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