Backport clean duplicate separators in resource URLs

Issue: SPR-16616

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -245,21 +245,7 @@ public class PathResourceResolver extends AbstractResourceResolver {
 			return true;
 		}
 		locationPath = (locationPath.endsWith("/") || locationPath.isEmpty() ? locationPath : locationPath + "/");
-		if (!resourcePath.startsWith(locationPath)) {
-			return false;
-		}
-
-		if (resourcePath.contains("%")) {
-			// 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);
-				}
-				return false;
-			}
-		}
-
-		return true;
+		return (resourcePath.startsWith(locationPath) && !isInvalidEncodedPath(resourcePath));
 	}
 
 	private String encodeIfNecessary(String path, HttpServletRequest request, Resource location) {
@@ -291,8 +277,30 @@ public class PathResourceResolver extends AbstractResourceResolver {
 	}
 
 	private boolean shouldEncodeRelativePath(Resource location) {
-		return location instanceof UrlResource &&
-				this.urlPathHelper != null && this.urlPathHelper.isUrlDecode();
+		return (location instanceof UrlResource && this.urlPathHelper != null && this.urlPathHelper.isUrlDecode());
+	}
+
+	private boolean isInvalidEncodedPath(String resourcePath) {
+		if (resourcePath.contains("%")) {
+			// Use URLDecoder (vs UriUtils) to preserve potentially decoded UTF-8 chars...
+			try {
+				String decodedPath = URLDecoder.decode(resourcePath, "UTF-8");
+				int separatorIndex = decodedPath.indexOf("..") + 2;
+				if (separatorIndex > 1 && separatorIndex < decodedPath.length()) {
+					char separator = decodedPath.charAt(separatorIndex);
+					if (separator == '/' || separator == '\\') {
+						if (logger.isTraceEnabled()) {
+							logger.trace("Resolved resource path contains \"../\" after decoding: " + resourcePath);
+						}
+					}
+					return true;
+				}
+			}
+			catch (UnsupportedEncodingException ex) {
+				// Should never happen...
+			}
+		}
+		return false;
 	}
 
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -17,6 +17,7 @@
 package org.springframework.web.servlet.resource;
 
 import java.io.IOException;
+import java.io.UnsupportedEncodingException;
 import java.net.URLDecoder;
 import java.nio.charset.Charset;
 import java.util.ArrayList;
@@ -507,6 +508,7 @@ public class ResourceHttpRequestHandler extends WebContentGenerator
 			throw new IllegalStateException("Required request attribute '" +
 					HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE + "' is not set");
 		}
+
 		path = processPath(path);
 		if (!StringUtils.hasText(path) || isInvalidPath(path)) {
 			if (logger.isTraceEnabled()) {
@@ -514,25 +516,19 @@ public class ResourceHttpRequestHandler extends WebContentGenerator
 			}
 			return null;
 		}
-		if (path.contains("%")) {
-			try {
-				// Use URLDecoder (vs UriUtils) to preserve potentially decoded UTF-8 chars
-				if (isInvalidPath(URLDecoder.decode(path, "UTF-8"))) {
-					if (logger.isTraceEnabled()) {
-						logger.trace("Ignoring invalid resource path with escape sequences [" + path + "].");
-					}
-					return null;
-				}
-			}
-			catch (IllegalArgumentException ex) {
-				// ignore
+		if (isInvalidEncodedPath(path)) {
+			if (logger.isTraceEnabled()) {
+				logger.trace("Ignoring invalid resource path with escape sequences [" + path + "]");
 			}
+			return null;
 		}
+
 		ResourceResolverChain resolveChain = new DefaultResourceResolverChain(getResourceResolvers());
 		Resource resource = resolveChain.resolveResource(request, path, getLocations());
 		if (resource == null || getResourceTransformers().isEmpty()) {
 			return resource;
 		}
+
 		ResourceTransformerChain transformChain =
 				new DefaultResourceTransformerChain(resolveChain, getResourceTransformers());
 		resource = transformChain.transform(request, resource);
@@ -540,13 +536,47 @@ public class ResourceHttpRequestHandler extends WebContentGenerator
 	}
 
 	/**
-	 * Process the given resource path to be used.
-	 * <p>The default implementation replaces any combination of leading '/' and
-	 * control characters (00-1F and 7F) with a single "/" or "". For example
-	 * {@code "  // /// ////  foo/bar"} becomes {@code "/foo/bar"}.
+	 * Process the given resource path.
+	 * <p>The default implementation replaces:
+	 * <ul>
+	 * <li>Backslash with forward slash.
+	 * <li>Duplicate occurrences of slash with a single slash.
+	 * <li>Any combination of leading slash and control characters (00-1F and 7F)
+	 * with a single "/" or "". For example {@code "  / // foo/bar"}
+	 * becomes {@code "/foo/bar"}.
+	 * </ul>
 	 * @since 3.2.12
 	 */
 	protected String processPath(String path) {
+		path = StringUtils.replace(path, "\\", "/");
+		path = cleanDuplicateSlashes(path);
+		return cleanLeadingSlash(path);
+	}
+
+	private String cleanDuplicateSlashes(String path) {
+		StringBuilder sb = null;
+		char prev = 0;
+		for (int i = 0; i < path.length(); i++) {
+			char curr = path.charAt(i);
+			try {
+				if ((curr == '/') && (prev == '/')) {
+					if (sb == null) {
+						sb = new StringBuilder(path.substring(0, i));
+					}
+					continue;
+				}
+				if (sb != null) {
+					sb.append(path.charAt(i));
+				}
+			}
+			finally {
+				prev = curr;
+			}
+		}
+		return sb != null ? sb.toString() : path;
+	}
+
+	private String cleanLeadingSlash(String path) {
 		boolean slash = false;
 		for (int i = 0; i < path.length(); i++) {
 			if (path.charAt(i) == '/') {
@@ -556,9 +586,9 @@ public class ResourceHttpRequestHandler extends WebContentGenerator
 				if (i == 0 || (i == 1 && slash)) {
 					return path;
 				}
-				path = slash ? "/" + path.substring(i) : path.substring(i);
+				path = (slash ? "/" + path.substring(i) : path.substring(i));
 				if (logger.isTraceEnabled()) {
-					logger.trace("Path after trimming leading '/' and control characters: " + path);
+					logger.trace("Path after trimming leading '/' and control characters: [" + path + "]");
 				}
 				return path;
 			}
@@ -566,6 +596,34 @@ public class ResourceHttpRequestHandler extends WebContentGenerator
 		return (slash ? "/" : "");
 	}
 
+	/**
+	 * Check whether the given path contains invalid escape sequences.
+	 * @param path the path to validate
+	 * @return {@code true} if the path is invalid, {@code false} otherwise
+	 */
+	private boolean isInvalidEncodedPath(String path) {
+		if (path.contains("%")) {
+			try {
+				// Use URLDecoder (vs UriUtils) to preserve potentially decoded UTF-8 chars
+				String decodedPath = URLDecoder.decode(path, "UTF-8");
+				if (isInvalidPath(decodedPath)) {
+					return true;
+				}
+				decodedPath = processPath(decodedPath);
+				if (isInvalidPath(decodedPath)) {
+					return true;
+				}
+			}
+			catch (IllegalArgumentException ex) {
+				// Should never happen...
+			}
+			catch (UnsupportedEncodingException ex) {
+				// Should never happen...
+			}
+		}
+		return false;
+	}
+
 	/**
 	 * Identifies invalid resource paths. By default rejects:
 	 * <ul>
@@ -580,32 +638,24 @@ public class ResourceHttpRequestHandler extends WebContentGenerator
 	 * path starts predictably with a single '/' or does not have one.
 	 * @param path the path to validate
 	 * @return {@code true} if the path is invalid, {@code false} otherwise
+	 * @since 3.0.6
 	 */
 	protected boolean isInvalidPath(String path) {
-		if (logger.isTraceEnabled()) {
-			logger.trace("Applying \"invalid path\" checks to path: " + path);
-		}
 		if (path.contains("WEB-INF") || path.contains("META-INF")) {
-			if (logger.isTraceEnabled()) {
-				logger.trace("Path contains \"WEB-INF\" or \"META-INF\".");
-			}
+			logger.trace("Path contains \"WEB-INF\" or \"META-INF\".");
 			return true;
 		}
 		if (path.contains(":/")) {
 			String relativePath = (path.charAt(0) == '/' ? path.substring(1) : path);
 			if (ResourceUtils.isUrl(relativePath) || relativePath.startsWith("url:")) {
-				if (logger.isTraceEnabled()) {
-					logger.trace("Path represents URL or has \"url:\" prefix.");
-				}
+				logger.trace("Path represents URL or has \"url:\" prefix.");
 				return true;
 			}
 		}
 		if (path.contains("..")) {
 			path = StringUtils.cleanPath(path);
 			if (path.contains("../")) {
-				if (logger.isTraceEnabled()) {
-					logger.trace("Path contains \"../\" after call to StringUtils#cleanPath.");
-				}
+				logger.trace("Path contains \"../\" after call to StringUtils#cleanPath.");
 				return true;
 			}
 		}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -46,6 +46,7 @@ import org.springframework.web.accept.ContentNegotiationManagerFactoryBean;
 import org.springframework.web.servlet.HandlerMapping;
 
 import static org.junit.Assert.*;
+import static org.mockito.Mockito.*;
 
 /**
  * Unit tests for {@link ResourceHttpRequestHandler}.
@@ -310,41 +311,84 @@ public class ResourceHttpRequestHandlerTests {
 	}
 
 	@Test
-	public void invalidPath() throws Exception {
+	public void testInvalidPath() throws Exception {
+
+		// Use mock ResourceResolver: i.e. we're only testing upfront validations...
+
+		Resource resource = mock(Resource.class);
+		when(resource.getFilename()).thenThrow(new AssertionError("Resource should not be resolved"));
+		when(resource.getInputStream()).thenThrow(new AssertionError("Resource should not be resolved"));
+		ResourceResolver resolver = mock(ResourceResolver.class);
+		when(resolver.resolveResource(any(), any(), any(), any())).thenReturn(resource);
+
+		ResourceHttpRequestHandler handler = new ResourceHttpRequestHandler();
+		handler.setLocations(Collections.singletonList(new ClassPathResource("test/", getClass())));
+		handler.setResourceResolvers(Collections.singletonList(resolver));
+		handler.setServletContext(new TestServletContext());
+		handler.afterPropertiesSet();
+
+		testInvalidPath("../testsecret/secret.txt", handler);
+		testInvalidPath("test/../../testsecret/secret.txt", handler);
+		testInvalidPath(":/../../testsecret/secret.txt", handler);
+
+		Resource location = new UrlResource(getClass().getResource("./test/"));
+		this.handler.setLocations(Collections.singletonList(location));
+		Resource secretResource = new UrlResource(getClass().getResource("testsecret/secret.txt"));
+		String secretPath = secretResource.getURL().getPath();
+
+		testInvalidPath("file:" + secretPath, handler);
+		testInvalidPath("/file:" + secretPath, handler);
+		testInvalidPath("url:" + secretPath, handler);
+		testInvalidPath("/url:" + secretPath, handler);
+		testInvalidPath("/../.." + secretPath, handler);
+		testInvalidPath("/%2E%2E/testsecret/secret.txt", handler);
+		testInvalidPath("/%2E%2E/testsecret/secret.txt", handler);
+		testInvalidPath("%2F%2F%2E%2E%2F%2F%2E%2E" + secretPath, handler);
+	}
+
+	private void testInvalidPath(String requestPath, ResourceHttpRequestHandler handler) throws Exception {
+		this.request.setAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, requestPath);
+		this.response = new MockHttpServletResponse();
+		handler.handleRequest(this.request, this.response);
+		assertEquals(HttpStatus.NOT_FOUND.value(), this.response.getStatus());
+	}
+
+	@Test
+	public void resolvePathWithTraversal() throws Exception {
 		for (HttpMethod method : HttpMethod.values()) {
 			this.request = new MockHttpServletRequest("GET", "");
 			this.response = new MockHttpServletResponse();
-			testInvalidPath(method);
+			testResolvePathWithTraversal(method);
 		}
 	}
 
-	private void testInvalidPath(HttpMethod httpMethod) throws Exception {
+	private void testResolvePathWithTraversal(HttpMethod httpMethod) throws Exception {
 		this.request.setMethod(httpMethod.name());
 
 		Resource location = new ClassPathResource("test/", getClass());
 		this.handler.setLocations(Collections.singletonList(location));
 
-		testInvalidPath(location, "../testsecret/secret.txt");
-		testInvalidPath(location, "test/../../testsecret/secret.txt");
-		testInvalidPath(location, ":/../../testsecret/secret.txt");
+		testResolvePathWithTraversal(location, "../testsecret/secret.txt");
+		testResolvePathWithTraversal(location, "test/../../testsecret/secret.txt");
+		testResolvePathWithTraversal(location, ":/../../testsecret/secret.txt");
 
 		location = new UrlResource(getClass().getResource("./test/"));
 		this.handler.setLocations(Collections.singletonList(location));
 		Resource secretResource = new UrlResource(getClass().getResource("testsecret/secret.txt"));
 		String secretPath = secretResource.getURL().getPath();
 
-		testInvalidPath(location, "file:" + secretPath);
-		testInvalidPath(location, "/file:" + secretPath);
-		testInvalidPath(location, "url:" + secretPath);
-		testInvalidPath(location, "/url:" + secretPath);
-		testInvalidPath(location, "/" + secretPath);
-		testInvalidPath(location, "////../.." + secretPath);
-		testInvalidPath(location, "/%2E%2E/testsecret/secret.txt");
-		testInvalidPath(location, "/  " + secretPath);
-		testInvalidPath(location, "url:" + secretPath);
+		testResolvePathWithTraversal(location, "file:" + secretPath);
+		testResolvePathWithTraversal(location, "/file:" + secretPath);
+		testResolvePathWithTraversal(location, "url:" + secretPath);
+		testResolvePathWithTraversal(location, "/url:" + secretPath);
+		testResolvePathWithTraversal(location, "/" + secretPath);
+		testResolvePathWithTraversal(location, "////../.." + secretPath);
+		testResolvePathWithTraversal(location, "/%2E%2E/testsecret/secret.txt");
+		testResolvePathWithTraversal(location, "%2F%2F%2E%2E%2F%2Ftestsecret/secret.txt");
+		testResolvePathWithTraversal(location, "/  " + secretPath);
 	}
 
-	private void testInvalidPath(Resource location, String requestPath) throws Exception {
+	private void testResolvePathWithTraversal(Resource location, String requestPath) throws Exception {
 		this.request.setAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, requestPath);
 		this.response = new MockHttpServletResponse();
 		this.handler.handleRequest(this.request, this.response);