Consistent encoded path evaluation in ResourceHttpRequestHandler and co

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.
@@ -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.nio.charset.StandardCharsets;
@@ -251,21 +252,7 @@ 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, @Nullable HttpServletRequest request, Resource location) {
@@ -289,8 +276,30 @@ 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

@@ -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;
@@ -66,24 +67,23 @@ import org.springframework.web.util.UrlPathHelper;
  * according to the guidelines of Page Speed, YSlow, etc.
  *
  * <p>The {@linkplain #setLocations "locations"} property takes a list of Spring
- * {@link Resource} locations from which static resources are allowed to
- * be served by this handler. Resources could be served from a classpath location,
- * e.g. "classpath:/META-INF/public-web-resources/", allowing convenient packaging
+ * {@link Resource} locations from which static resources are allowed to be served
+ * by this handler. Resources could be served from a classpath location, e.g.
+ * "classpath:/META-INF/public-web-resources/", allowing convenient packaging
  * and serving of resources such as .js, .css, and others in jar files.
  *
  * <p>This request handler may also be configured with a
  * {@link #setResourceResolvers(List) resourcesResolver} and
  * {@link #setResourceTransformers(List) resourceTransformer} chains to support
- * arbitrary resolution and transformation of resources being served. By default a
- * {@link PathResourceResolver} simply finds resources based on the configured
- * "locations". An application can configure additional resolvers and
- * transformers such as the {@link VersionResourceResolver} which can resolve
- * and prepare URLs for resources with a version in the URL.
+ * arbitrary resolution and transformation of resources being served. By default
+ * a {@link PathResourceResolver} simply finds resources based on the configured
+ * "locations". An application can configure additional resolvers and transformers
+ * such as the {@link VersionResourceResolver} which can resolve and prepare URLs
+ * for resources with a version in the URL.
  *
- * <p>This handler also properly evaluates the {@code Last-Modified} header (if
- * present) so that a {@code 304} status code will be returned as appropriate,
- * avoiding unnecessary overhead for resources that are already cached by the
- * client.
+ * <p>This handler also properly evaluates the {@code Last-Modified} header
+ * (if present) so that a {@code 304} status code will be returned as appropriate,
+ * avoiding unnecessary overhead for resources that are already cached by the client.
  *
  * @author Keith Donald
  * @author Jeremy Grelle
@@ -510,6 +510,7 @@ 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()) {
@@ -517,57 +518,25 @@ public class ResourceHttpRequestHandler extends WebContentGenerator
 			}
 			return null;
 		}
-		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)) {
-					if (logger.isTraceEnabled()) {
-						logger.trace("Ignoring invalid resource path with escape sequences [" + path + "].");
-					}
-					return null;
-				}
-				decodedPath = processPath(decodedPath);
-				if (isInvalidPath(decodedPath)) {
-					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);
 		return resource;
 	}
 
-	/**
-	 * 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;
@@ -601,9 +570,9 @@ 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;
 			}
@@ -611,6 +580,31 @@ 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 | UnsupportedEncodingException ex) {
+				// Should never happen...
+			}
+		}
+		return false;
+	}
+
 	/**
 	 * Identifies invalid resource paths. By default rejects:
 	 * <ul>
@@ -627,36 +621,45 @@ public class ResourceHttpRequestHandler extends WebContentGenerator
 	 * @return {@code true} if the path is invalid, {@code false} otherwise
 	 */
 	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;
 			}
 		}
 		return false;
 	}
 
+	/**
+	 * 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);
+	}
+
 	/**
 	 * Determine the media type for the given request and the resource matched
 	 * to it. This implementation tries to determine the MediaType based on the