HeaderWriterFilter writes headers at beginning

Add support for HeaderWriterFilter to write headers at the beginning of the request

Fixes: gh-6501

Author: ankurpathak

config/src/test/java/org/springframework/security/config/annotation/authentication/configurers/HeadersConfigurerJavaTests.java

@@ -0,0 +1,131 @@
+/*
+ * Copyright 2002-2019 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
+ *
+ *      http://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.config.annotation.authentication.configurers;
+
+import javax.servlet.Filter;
+import javax.servlet.ServletException;
+import java.io.IOException;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import org.springframework.mock.web.MockFilterChain;
+import org.springframework.mock.web.MockHttpServletRequest;
+import org.springframework.mock.web.MockHttpServletResponse;
+import org.springframework.mock.web.MockServletContext;
+import org.springframework.security.config.annotation.ObjectPostProcessor;
+import org.springframework.security.config.annotation.web.builders.HttpSecurity;
+import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
+import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
+import org.springframework.security.web.header.HeaderWriterFilter;
+import org.springframework.web.context.ConfigurableWebApplicationContext;
+import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link HeadersConfigurer}.
+ *
+ * @author Ankur Pathak
+ */
+public class HeadersConfigurerJavaTests {
+
+	private boolean allowCircularReferences = false;
+	private MockServletContext servletContext;
+	private MockHttpServletRequest request;
+	private MockHttpServletResponse response;
+	private MockFilterChain chain;
+	private ConfigurableWebApplicationContext context;
+
+
+	@Before
+	public void setUp() {
+		this.servletContext = new MockServletContext();
+		this.request = new MockHttpServletRequest(this.servletContext, "GET", "");
+		this.response = new MockHttpServletResponse();
+		this.chain = new MockFilterChain();
+	}
+
+
+	@After
+	public void cleanup(){
+		if (this.context != null){
+			this.context.close();
+		}
+	}
+
+
+	@EnableWebSecurity
+	public static class HeadersAtTheBeginningOfRequestConfig extends WebSecurityConfigurerAdapter {
+		@Override
+		protected void configure(HttpSecurity http) throws Exception {
+			http
+					.headers()
+					.addObjectPostProcessor(new ObjectPostProcessor<HeaderWriterFilter>() {
+						@Override
+						public HeaderWriterFilter postProcess(HeaderWriterFilter filter) {
+							filter.setShouldWriteHeadersEagerly(true);
+							return filter;
+						}
+					});
+		}
+	}
+
+	@Test
+	public void headersWrittenAtBeginningOfRequest() throws IOException, ServletException {
+		this.context = loadConfig(HeadersAtTheBeginningOfRequestConfig.class);
+		this.request.setSecure(true);
+		getSpringSecurityFilterChain().doFilter(this.request, this.response, this.chain);
+		assertThat(getResponseHeaders()).containsAllEntriesOf(new LinkedHashMap<String, String>(){{
+			put("X-Content-Type-Options", "nosniff");
+			put("X-Frame-Options", "DENY");
+			put("Strict-Transport-Security", "max-age=31536000 ; includeSubDomains");
+			put("Cache-Control", "no-cache, no-store, max-age=0, must-revalidate");
+			put("Expires", "0");
+			put("Pragma", "no-cache");
+			put("X-XSS-Protection", "1; mode=block");
+		}});
+	}
+
+
+	@SuppressWarnings("unchecked")
+	private Map<String, String > getResponseHeaders() {
+		Map<String, String> headers = new LinkedHashMap<>();
+		this.response.getHeaderNames().forEach(name -> {
+			List values = this.response.getHeaderValues(name);
+			headers.put(name, String.join(",", values));
+		});
+		return headers;
+	}
+
+	private ConfigurableWebApplicationContext loadConfig(Class<?>... configs) {
+		AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext();
+		context.register(configs);
+		context.setAllowCircularReferences(this.allowCircularReferences);
+		context.setServletContext(this.servletContext);
+		context.refresh();
+		return context;
+	}
+
+	private Filter getSpringSecurityFilterChain() {
+		return this.context.getBean("springSecurityFilterChain", Filter.class);
+	}
+}

web/src/main/java/org/springframework/security/web/header/HeaderWriterFilter.java

@@ -51,6 +51,11 @@ public class HeaderWriterFilter extends OncePerRequestFilter {
 	 */
 	private final HeaderWriter headerWriter;
 
+	/**
+	 * Indicates whether to write the headers at the beginning of the request.
+	 */
+	private boolean shouldWriteHeadersEagerly = false;
+
 	/**
 	 * Creates a new instance.
 	 *
@@ -67,18 +72,41 @@ protected void doFilterInternal(HttpServletRequest request,
 			HttpServletResponse response, FilterChain filterChain)
 			throws ServletException, IOException {
 
+		if (this.shouldWriteHeadersEagerly) {
+			doHeadersBefore(request, response, filterChain);
+		} else {
+			doHeadersAfter(request, response, filterChain);
+		}
+	}
+
+	private void doHeadersBefore(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws IOException, ServletException {
+		this.headerWriter.writeHeaders(request, response);
+		filterChain.doFilter(request, response);
+	}
+
+	private void doHeadersAfter(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws IOException, ServletException {
 		HeaderWriterResponse headerWriterResponse = new HeaderWriterResponse(request,
 				response, this.headerWriter);
 		HeaderWriterRequest headerWriterRequest = new HeaderWriterRequest(request,
 				headerWriterResponse);
-
 		try {
 			filterChain.doFilter(headerWriterRequest, headerWriterResponse);
 		} finally {
 			headerWriterResponse.writeHeaders();
 		}
 	}
 
+	/**
+	 * Allow writing headers at the beginning of the request.
+	 *
+	 * @param shouldWriteHeadersEagerly boolean to allow writing headers at the beginning of the request.
+	 * @author Ankur Pathak
+	 * @since 5.2
+	 */
+	public void setShouldWriteHeadersEagerly(boolean shouldWriteHeadersEagerly) {
+		this.shouldWriteHeadersEagerly = shouldWriteHeadersEagerly;
+	}
+
 	static class HeaderWriterResponse extends OnCommittedResponseWrapper {
 		private final HttpServletRequest request;
 		private final HeaderWriter headerWriter;

web/src/test/java/org/springframework/security/web/header/HeaderWriterFilterTests.java

@@ -136,4 +136,25 @@ public void doFilterWhenRequestContainsIncludeThenHeadersStillWritten() throws E
 
 		verifyNoMoreInteractions(this.writer1);
 	}
+
+	@Test
+	public void headersWrittenAtBeginningOfRequest() throws Exception {
+		HeaderWriterFilter filter = new HeaderWriterFilter(
+				Collections.singletonList(this.writer1));
+		filter.setShouldWriteHeadersEagerly(true);
+
+		MockHttpServletRequest request = new MockHttpServletRequest();
+		MockHttpServletResponse response = new MockHttpServletResponse();
+
+		filter.doFilter(request, response, new FilterChain() {
+			@Override
+			public void doFilter(ServletRequest request, ServletResponse response)
+					throws IOException, ServletException {
+				verify(HeaderWriterFilterTests.this.writer1).writeHeaders(
+						any(HttpServletRequest.class), any(HttpServletResponse.class));
+			}
+		});
+
+		verifyNoMoreInteractions(this.writer1);
+	}
 }