Fixed MultiProtocolURL.resolveBackpath to handle remaining '..' segments

source/net/yacy/cora/document/id/MultiProtocolURL.java

@@ -474,7 +474,17 @@ public class MultiProtocolURL implements Serializable, Comparable<MultiProtocolU
         escape();
     }
 
-    //  resolve '..'
+    /**
+     * Resolve '..' segments in the path.
+     * For standard pseudo algorithms, see :
+     * <ul>
+     * <li>https://tools.ietf.org/html/rfc3986#section-5.2.4</li>
+     * <li>https://url.spec.whatwg.org/#path-state</li>
+     * <li>https://www.w3.org/TR/url/#relative-path-state</li>
+     * </ul>
+     * @param path URL path part : must not be null
+     * @return the path with '..' segments resolved
+     */
     private static final String resolveBackpath(final String path) {
         String p = path;
         if (p.isEmpty() || p.charAt(0) != '/') { p = "/" + p; }
@@ -486,6 +496,14 @@ public class MultiProtocolURL implements Serializable, Comparable<MultiProtocolU
             p = matcher.replaceAll("");
             matcher.reset(p);
         }
+        /* Let's remove any eventual remaining but inappropriate '..' segments at the beginning. 
+         * See https://tools.ietf.org/html/rfc3986#section-5.2.4 -> parts 2.C and 2.D */
+        while(p.startsWith("/../")) {
+        	p = p.substring(3);
+        }
+        if(p.equals("/..")) {
+        	p = "/";
+        }
         return p.equals("") ? "/" : p;
     }
 

test/java/net/yacy/cora/document/id/MultiProtocolURLTest.java

@@ -38,15 +38,17 @@ public class MultiProtocolURLTest {
         String[][] testStrings = new String[][]{
             new String[]{"/..home", "/..home"},
             new String[]{"/test/..home/test.html", "/test/..home/test.html"},
-            new String[]{"/../", "/../"},
-            new String[]{"/..", "/.."},
             new String[]{"/test/..", "/"},
             new String[]{"/test/../", "/"},
             new String[]{"/test/test2/..", "/test"},
             new String[]{"/test/test2/../", "/test/"},
             new String[]{"/test/test2/../hallo", "/test/hallo"},
             new String[]{"/test/test2/../hallo/", "/test/hallo/"},
-            new String[]{"/home/..test/../hallo/../", "/home/"}
+            new String[]{"/home/..test/../hallo/../", "/home/"},
+            /* No path segments prior to the '..' segment : '..' still has to be removed (See https://tools.ietf.org/html/rfc3986#section-5.2.4 -> parts 2.C and 2.D )*/
+            new String[]{"/../", "/"},
+            new String[]{"/..", "/"},
+            new String[]{"/../../../image.jpg", "/image.jpg"}
         };
         String testhost = "http://localhost";
         for (int i = 0; i < testStrings.length; i++) {
@@ -223,7 +225,7 @@ public class MultiProtocolURLTest {
      * Test of getFileExtension method, of class MultiProtocolURL.
      */
     @Test
-    public void testGetFileExtension() throws MalformedURLException {
+    public void testGetFileExtension() {
         Map<String, String> testurls = new HashMap<String, String>();
         //  key=testurl, value=result
         testurls.put("path/file.xml","xml"); // easiest