Assert static resource location

Closes gh-33712

spring-webmvc/src/main/java/org/springframework/web/servlet/function/PathResourceLookupFunction.java

@@ -47,7 +47,7 @@ class PathResourceLookupFunction implements Function<ServerRequest, Optional<Res
 
 	public PathResourceLookupFunction(String pattern, Resource location) {
 		Assert.hasLength(pattern, "'pattern' must not be empty");
-		Assert.notNull(location, "'location' must not be null");
+		ResourceHandlerUtils.assertResourceLocation(location);
 		this.pattern = PathPatternParser.defaultInstance.parse(pattern);
 		this.location = location;
 	}

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

@@ -27,6 +27,8 @@ import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.UrlResource;
 import org.springframework.core.log.LogFormatUtils;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 import org.springframework.util.ResourceUtils;
 import org.springframework.util.StringUtils;
 import org.springframework.web.context.support.ServletContextResource;
@@ -42,6 +44,42 @@ public abstract class ResourceHandlerUtils {
 
 	private static final Log logger = LogFactory.getLog(ResourceHandlerUtils.class);
 
+	private static final String FOLDER_SEPARATOR = "/";
+
+	private static final String WINDOWS_FOLDER_SEPARATOR = "\\";
+
+
+	/**
+	 * Assert the given location is not null, and its path ends on slash.
+	 */
+	public static void assertResourceLocation(@Nullable Resource location) {
+		Assert.notNull(location, "Resource location must not be null");
+		try {
+			String path;
+			if (location instanceof UrlResource) {
+				path = location.getURL().toExternalForm();
+			}
+			else if (location instanceof ClassPathResource classPathResource) {
+				path = classPathResource.getPath();
+			}
+			else {
+				path = location.getURL().getPath();
+			}
+			assertLocationPath(path);
+		}
+		catch (IOException ex) {
+			// ignore
+		}
+	}
+
+	/**
+	 * Assert the given location path is a directory and ends on slash.
+	 */
+	public static void assertLocationPath(@Nullable String path) {
+		Assert.notNull(path, "Resource location path must not be null");
+		Assert.isTrue(path.endsWith(FOLDER_SEPARATOR) || path.endsWith(WINDOWS_FOLDER_SEPARATOR),
+				"Resource location does not end with slash: " + path);
+	}
 
 	/**
 	 * Normalize the given resource path replacing the following:

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

@@ -180,7 +180,10 @@ public class ResourceHttpRequestHandler extends WebContentGenerator
 	public void setLocations(List<Resource> locations) {
 		Assert.notNull(locations, "Locations list must not be null");
 		this.locationResources.clear();
-		this.locationResources.addAll(locations);
+		for (Resource location : locations) {
+			ResourceHandlerUtils.assertResourceLocation(location);
+			this.locationResources.add(location);
+		}
 	}
 
 	/**
@@ -493,6 +496,7 @@ public class ResourceHttpRequestHandler extends WebContentGenerator
 					charset = Charset.forName(value);
 					location = location.substring(endIndex + 1);
 				}
+				ResourceHandlerUtils.assertLocationPath(location);
 				Resource resource = applicationContext.getResource(location);
 				if (location.equals("/") && !(resource instanceof ServletContextResource)) {
 					throw new IllegalStateException(

spring-webmvc/src/test/java/org/springframework/web/servlet/config/annotation/ResourceHandlerRegistryTests.java

@@ -204,7 +204,7 @@ class ResourceHandlerRegistryTests {
 
 	@Test
 	void urlResourceWithCharset() {
-		this.registration.addResourceLocations("[charset=ISO-8859-1]file:///tmp");
+		this.registration.addResourceLocations("[charset=ISO-8859-1]file:///tmp/");
 		this.registration.resourceChain(true);
 
 		ResourceHttpRequestHandler handler = getHandler("/resources/**");

spring-webmvc/src/test/java/org/springframework/web/servlet/config/annotation/WebMvcConfigurationSupportExtensionTests.java

@@ -457,7 +457,7 @@ class WebMvcConfigurationSupportExtensionTests {
 
 		@Override
 		public void addResourceHandlers(ResourceHandlerRegistry registry) {
-			registry.addResourceHandler("/resources/**").addResourceLocations("src/test/java");
+			registry.addResourceHandler("/resources/**").addResourceLocations("src/test/java/");
 		}
 
 		@Override

spring-webmvc/src/test/resources/org/springframework/web/servlet/config/mvc-config-resources-chain.xml

@@ -23,7 +23,7 @@
 
 	<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
 		<property name="properties">
-			<value>location=file:///tmp</value>
+			<value>location=file:///tmp/</value>
 		</property>
 	</bean>