Fix location checks for servlet 3 resources

SPR-12354 applied new checks to make sure that served static resources
are under authorized locations.

Prior to this change, serving static resources from Servlet 3 locations
such as "/webjars/" would not work since those locations can be within
one of the JARs on path. In that case, the checkLocation method would
return false and disallow serving that static resource.

This change fixes this issue by making sure to call the
`ServletContextResource.getPath()` method for servlet context resources.

Note that there's a known workaround for this issue, which is using a
classpath scheme as location, such as:
"classpath:/META-INF/resources/webjars/" instead of "/webjars".

Issue: SPR-12432
(cherry picked from commit 161d3e3)

Author: bclozel

spring-webmvc/src/main/java/org/springframework/web/servlet/resource/ResourceHttpRequestHandler.java

@@ -21,7 +21,6 @@
 import java.io.UnsupportedEncodingException;
 import java.net.URLDecoder;
 import java.util.List;
-
 import javax.activation.FileTypeMap;
 import javax.activation.MimetypesFileTypeMap;
 import javax.servlet.ServletException;
@@ -30,6 +29,7 @@
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.Resource;
@@ -43,6 +43,7 @@
 import org.springframework.util.StringUtils;
 import org.springframework.web.HttpRequestHandler;
 import org.springframework.web.context.request.ServletWebRequest;
+import org.springframework.web.context.support.ServletContextResource;
 import org.springframework.web.servlet.HandlerMapping;
 import org.springframework.web.servlet.support.WebContentGenerator;
 
@@ -300,13 +301,17 @@ private boolean isResourceUnderLocation(Resource resource, Resource location) th
 		}
 		String resourcePath;
 		String locationPath;
-		if (resource instanceof ClassPathResource) {
+		if (resource instanceof UrlResource) {
+			resourcePath = resource.getURL().toExternalForm();
+			locationPath = location.getURL().toExternalForm();
+		}
+		else if (resource instanceof ClassPathResource) {
 			resourcePath = ((ClassPathResource) resource).getPath();
 			locationPath = ((ClassPathResource) location).getPath();
 		}
-		else if (resource instanceof UrlResource) {
-			resourcePath = resource.getURL().toExternalForm();
-			locationPath = location.getURL().toExternalForm();
+		else if (resource instanceof ServletContextResource) {
+			resourcePath = ((ServletContextResource) resource).getPath();
+			locationPath = ((ServletContextResource) location).getPath();
 		}
 		else {
 			resourcePath = resource.getURL().getPath();
@@ -317,7 +322,7 @@ else if (resource instanceof UrlResource) {
 			return false;
 		}
 		if (resourcePath.contains("%")) {
-			// Use URLDecoder (vs UriUtils) to preserve potentially decoded UTF-8 chars
+			// Use URLDecoder (vs UriUtils) to preserve potentially decoded UTF-8 chars...
 			if (URLDecoder.decode(resourcePath, "UTF-8").contains("../")) {
 				if (logger.isTraceEnabled()) {
 					logger.trace("Resolved resource path contains \"../\" after decoding: " + resourcePath);

spring-webmvc/src/test/java/org/springframework/web/servlet/resource/ResourceHttpRequestHandlerTests.java

@@ -16,18 +16,14 @@
 
 package org.springframework.web.servlet.resource;
 
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertSame;
-import static org.junit.Assert.assertTrue;
-
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
-
 import javax.servlet.http.HttpServletResponse;
 
 import org.junit.Before;
 import org.junit.Test;
+
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.UrlResource;
@@ -37,6 +33,8 @@
 import org.springframework.web.HttpRequestMethodNotSupportedException;
 import org.springframework.web.servlet.HandlerMapping;
 
+import static org.junit.Assert.*;
+
 /**
  * @author Keith Donald
  * @author Jeremy Grelle
@@ -127,7 +125,6 @@ public void getResourceFromSubDirectoryOfAlternatePath() throws Exception {
 		assertEquals("function foo() { console.log(\"hello world\"); }", response.getContentAsString());
 	}
 
-
 	@Test
 	public void invalidPath() throws Exception {
 		MockHttpServletRequest request = new MockHttpServletRequest();
@@ -159,6 +156,18 @@ public void invalidPath() throws Exception {
 		testInvalidPath(location, "url:" + secretPath, request, response);
 	}
 
+	private void testInvalidPath(Resource location, String requestPath,
+			MockHttpServletRequest request, MockHttpServletResponse response) throws Exception {
+
+		request.setAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, requestPath);
+		response = new MockHttpServletResponse();
+		this.handler.handleRequest(request, response);
+		if (!location.createRelative(requestPath).exists() && !requestPath.contains(":")) {
+			fail(requestPath + " doesn't actually exist as a relative path");
+		}
+		assertEquals(404, response.getStatus());
+	}
+
 	@Test
 	public void ignoreInvalidEscapeSequence() throws Exception {
 		MockHttpServletRequest request = new MockHttpServletRequest();
@@ -192,7 +201,7 @@ public void processPath() throws Exception {
 		assertEquals("/foo/bar", this.handler.processPath("  // /// ////  foo/bar"));
 		assertEquals("/foo/bar", this.handler.processPath((char) 1 + " / " + (char) 127 + " // foo/bar"));
 
-		// root ot empty path
+		// root or empty path
 		assertEquals("", this.handler.processPath("   "));
 		assertEquals("/", this.handler.processPath("/"));
 		assertEquals("/", this.handler.processPath("///"));
@@ -243,15 +252,15 @@ public void missingResourcePath() throws Exception {
 		assertEquals(404, response.getStatus());
 	}
 
-	@Test(expected=IllegalStateException.class)
+	@Test(expected = IllegalStateException.class)
 	public void noPathWithinHandlerMappingAttribute() throws Exception {
 		MockHttpServletRequest request = new MockHttpServletRequest();
 		request.setMethod("GET");
 		MockHttpServletResponse response = new MockHttpServletResponse();
 		handler.handleRequest(request, response);
 	}
 
-	@Test(expected=HttpRequestMethodNotSupportedException.class)
+	@Test(expected = HttpRequestMethodNotSupportedException.class)
 	public void unsupportedHttpMethod() throws Exception {
 		MockHttpServletRequest request = new MockHttpServletRequest();
 		request.setAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, "/foo.css");
@@ -270,16 +279,6 @@ public void resourceNotFound() throws Exception {
 		assertEquals(404, response.getStatus());
 	}
 
-	private void testInvalidPath(Resource location, String requestPath,
-			MockHttpServletRequest request, MockHttpServletResponse response) throws Exception {
-
-		request.setAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, requestPath);
-		response = new MockHttpServletResponse();
-		this.handler.handleRequest(request, response);
-		assertTrue(location.createRelative(requestPath).exists());
-		assertEquals(404, response.getStatus());
-	}
-
 
 	private static class TestServletContext extends MockServletContext {