Decode path in getStaticFilePath (#11812)

* Decode path in getStaticFilePath

Some containers do not decode path when using getPathInfo, in case path has not been decoded there is a risk for path traversal vulnerability.

server/src/main/java/com/vaadin/server/VaadinServlet.java

@@ -28,11 +28,13 @@ import java.io.OutputStream;
 import java.io.OutputStreamWriter;
 import java.io.PrintWriter;
 import java.io.Serializable;
+import java.io.UnsupportedEncodingException;
 import java.lang.reflect.Method;
 import java.net.MalformedURLException;
 import java.net.URISyntaxException;
 import java.net.URL;
 import java.net.URLConnection;
+import java.net.URLDecoder;
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
@@ -1348,16 +1350,33 @@ public class VaadinServlet extends HttpServlet implements Constants {
      * @since 8.0
      */
     protected String getStaticFilePath(HttpServletRequest request) {
-        String pathInfo = request.getPathInfo();
-        if (pathInfo == null) {
+        if (request.getPathInfo() == null) {
             return null;
         }
+        String decodedPath = null;
+        String contextPath = null;
+        try {
+            // pathInfo should be already decoded, but some containers do not decode it,
+            // hence we use getRequestURI instead.
+            decodedPath = URLDecoder.decode(request.getRequestURI(), StandardCharsets.UTF_8.name());
+            contextPath = URLDecoder.decode(request.getContextPath(), StandardCharsets.UTF_8.name());
+        } catch (UnsupportedEncodingException e) {
+            throw new RuntimeException("An error occurred during decoding URL.",e);
+        }
+        // Possible context path needs to be removed
+        String filePath = decodedPath.substring(contextPath.length());
+        String servletPath = request.getServletPath();
+        // Possible servlet path needs to be removed
+        if (!servletPath.isEmpty() && !servletPath.equals("/VAADIN") 
+                && filePath.startsWith(servletPath)) {
+            filePath = filePath.substring(servletPath.length());
+        }
         // Servlet mapped as /* serves at /VAADIN
         // Servlet mapped as /foo/bar/* serves at /foo/bar/VAADIN
-        if (pathInfo.startsWith("/VAADIN/")) {
-            return pathInfo;
+        if (filePath.startsWith("/VAADIN/")) {
+            return filePath;
         }
-        String servletPrefixedPath = request.getServletPath() + pathInfo;
+        String servletPrefixedPath = servletPath + filePath;
         // Servlet mapped as /VAADIN/*
         if (servletPrefixedPath.startsWith("/VAADIN/")) {
             return servletPrefixedPath;

server/src/test/java/com/vaadin/server/VaadinServletTest.java

@@ -116,6 +116,8 @@ public class VaadinServletTest {
         HttpServletRequest request = Mockito.mock(HttpServletRequest.class);
         Mockito.when(request.getServletPath()).thenReturn(servletPath);
         Mockito.when(request.getPathInfo()).thenReturn(pathInfo);
+        Mockito.when(request.getRequestURI()).thenReturn("/context"+pathInfo);
+        Mockito.when(request.getContextPath()).thenReturn("/context");
         return request;
     }
 }