Revert "TUN-1736: Missing headers when passing an invalid path"

This reverts commit 3c93d9b300.

streamhandler/request.go

@@ -45,7 +45,16 @@ func H2RequestHeadersToH1Request(h2 []h2mux.Header, h1 *http.Request) error {
 			// Otherwise the host header will be based on the origin URL
 			h1.Host = header.Value
 		case ":path":
-			h1.URL.Path = header.Value
+			u, err := url.Parse(header.Value)
+			if err != nil {
+				return fmt.Errorf("unparseable path")
+			}
+			resolved := h1.URL.ResolveReference(u)
+			// prevent escaping base URL
+			if !strings.HasPrefix(resolved.String(), h1.URL.String()) {
+				return fmt.Errorf("invalid path")
+			}
+			h1.URL = resolved
 		case "content-length":
 			contentLength, err := strconv.ParseInt(header.Value, 10, 64)
 			if err != nil {