Adjust error response in ResourceUrlEncodingFilter

Failure to find the lookup path now results in 400 instead of 500
reflecting the presence of some issue with the input path.

Closes gh-23508

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

@@ -96,10 +96,7 @@ public class ResourceUrlEncodingFilter extends GenericFilterBean {
 				String lookupPath = pathHelper.getLookupPathForRequest(this);
 				this.indexLookupPath = requestUri.lastIndexOf(lookupPath);
 				if (this.indexLookupPath == -1) {
-					throw new IllegalStateException(
+					throw new LookupPathIndexException(lookupPath, requestUri);
-							"Failed to find lookupPath '" + lookupPath + "' within requestUri '" + requestUri + "'. " +
-							"Does the path have invalid encoded characters for characterEncoding '" +
-							getRequest().getCharacterEncoding() + "'?");
 				}
 				this.prefixLookupPath = requestUri.substring(0, this.indexLookupPath);
 				if ("/".equals(lookupPath) && !"/".equals(requestUri)) {
@@ -164,4 +161,14 @@ public class ResourceUrlEncodingFilter extends GenericFilterBean {
 		}
 	}
 
+
+	@SuppressWarnings("serial")
+	static class LookupPathIndexException extends IllegalArgumentException {
+
+		LookupPathIndexException(String lookupPath, String requestUri) {
+			super("Failed to find lookupPath '" + lookupPath + "' within requestUri '" + requestUri + "'. " +
+					"This could be because the path has invalid encoded characters or isn't normalized.");
+		}
+	}
+
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * 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.
@@ -20,6 +20,7 @@ import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
 import org.springframework.util.Assert;
+import org.springframework.web.bind.ServletRequestBindingException;
 import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;
 
 /**
@@ -48,7 +49,12 @@ public class ResourceUrlProviderExposingInterceptor extends HandlerInterceptorAd
 	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
 			throws Exception {
 
-		request.setAttribute(RESOURCE_URL_PROVIDER_ATTR, this.resourceUrlProvider);
+		try {
+			request.setAttribute(RESOURCE_URL_PROVIDER_ATTR, this.resourceUrlProvider);
+		}
+		catch (ResourceUrlEncodingFilter.LookupPathIndexException ex) {
+			throw new ServletRequestBindingException(ex.getMessage(), ex);
+		}
 		return true;
 	}
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * 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.
@@ -19,7 +19,9 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import javax.servlet.FilterChain;
 import javax.servlet.ServletException;
+import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
 import org.junit.Before;
@@ -28,6 +30,7 @@ import org.junit.Test;
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.mock.web.test.MockHttpServletRequest;
 import org.springframework.mock.web.test.MockHttpServletResponse;
+import org.springframework.web.bind.ServletRequestBindingException;
 
 import static org.junit.Assert.*;
 
@@ -155,14 +158,36 @@ public class ResourceUrlEncodingFilterTests {
 				"/resources/bar-11e16cf79faee7ac698c805cf28248d2.css?foo=bar&url=https://example.org#something");
 	}
 
+	@Test // gh-23508
+	public void invalidLookupPath() throws Exception {
+		MockHttpServletRequest request = new MockHttpServletRequest();
+		request.setRequestURI("/a/b/../logo.png");
+		request.setServletPath("/a/logo.png");
+
+			this.filter.doFilter(request, new MockHttpServletResponse(), (req, res) -> {
+				try {
+					ResourceUrlProviderExposingInterceptor interceptor =
+							new ResourceUrlProviderExposingInterceptor(this.urlProvider);
+
+					interceptor.preHandle((HttpServletRequest) req, (HttpServletResponse) res, new Object());
+					fail();
+				}
+				catch (Exception ex) {
+					assertEquals(ServletRequestBindingException.class, ex.getClass());
+				}
+			});
+	}
+
 	private void testEncodeUrl(MockHttpServletRequest request, String url, String expected)
 			throws ServletException, IOException {
 
-		this.filter.doFilter(request, new MockHttpServletResponse(), (req, res) -> {
+		FilterChain chain = (req, res) -> {
 			req.setAttribute(ResourceUrlProviderExposingInterceptor.RESOURCE_URL_PROVIDER_ATTR, this.urlProvider);
 			String result = ((HttpServletResponse) res).encodeURL(url);
 			assertEquals(expected, result);
-		});
+		};
+
+		this.filter.doFilter(request, new MockHttpServletResponse(), chain);
 	}
 
 }