From ee4dd2a078fd3e01a5fc9028fb1c279a8570d4f5 Mon Sep 17 00:00:00 2001
From: Simone Bordet <simone.bordet@gmail.com>
Date: Tue, 29 Jun 2021 00:07:56 +0200
Subject: [PATCH] Issue #6473 - Improve alias checking in PathResource.

* Reverted %-escape handling for URI query parts.
* Performing canonicalization in ServletContext.getResource(),
  and improving alias checking in ContextHandler.getResource().
* Performing canonicalization checks in Resource.addPath() to avoid
  navigation above of the root.
* Test added and fixed.
* Various cleanups.

Signed-off-by: Simone Bordet <simone.bordet@gmail.com>
---
 .../java/org/eclipse/jetty/http/HttpURI.java  | 67 +++++++++----------
 .../org/eclipse/jetty/http/HttpURITest.java   | 20 ++++++
 .../maven/plugin/JettyWebAppContext.java      | 16 +++--
 .../jetty/rewrite/handler/RedirectUtil.java   |  4 +-
 .../rewrite/handler/ValidUrlRuleTest.java     | 14 +++-
 .../jetty/server/handler/ContextHandler.java  |  6 +-
 .../jetty/server/handler/ResourceHandler.java |  2 +
 .../jetty/server/HttpConnectionTest.java      |  6 ++
 .../ContextHandlerGetResourceTest.java        | 21 ++++--
 .../eclipse/jetty/servlet/RequestURITest.java |  6 +-
 .../java/org/eclipse/jetty/util/URIUtil.java  |  1 -
 .../jetty/util/resource/FileResource.java     |  7 +-
 .../jetty/util/resource/PathResource.java     | 25 ++++---
 .../eclipse/jetty/util/resource/Resource.java |  1 +
 .../jetty/util/resource/URLResource.java      |  7 +-
 .../jetty/util/URIUtilCanonicalPathTest.java  | 20 ++++++
 .../jetty/util/resource/ResourceTest.java     | 18 +++++
 17 files changed, 167 insertions(+), 74 deletions(-)

diff --git a/jetty-http/src/main/java/org/eclipse/jetty/http/HttpURI.java b/jetty-http/src/main/java/org/eclipse/jetty/http/HttpURI.java
index 5dc6db1302aa..0a2e758caf39 100644
--- a/jetty-http/src/main/java/org/eclipse/jetty/http/HttpURI.java
+++ b/jetty-http/src/main/java/org/eclipse/jetty/http/HttpURI.java
@@ -36,7 +36,7 @@
 /**
  * Http URI.
  * Parse an HTTP URI from a string or byte array.  Given a URI
- * <code>http://user@host:port/path;param1/%2e/info;param2?query#fragment</code>
+ * {@code http://user@host:port/path;param1/%2e/info;param2?query#fragment}
  * this class will split it into the following optional elements:<ul>
  * <li>{@link #getScheme()} - http:</li>
  * <li>{@link #getAuthority()} - //name@host:port</li>
@@ -65,11 +65,13 @@
  * Thus this class avoid and/or detects such ambiguities. Furthermore, by decoding characters and
  * removing parameters before relative path normalization, ambiguous paths will be resolved in such
  * a way to be non-standard-but-non-ambiguous to down stream interpretation of the decoded path string.
- * The violations are recorded and available by API such as {@link #hasViolation(Violation)} so that requests
+ * The violations are recorded and available by API such as {@link #hasAmbiguousSegment()} so that requests
  * containing them may be rejected in case the non-standard-but-non-ambiguous interpretations
- * are not satisfactory for a given compliance configuration.   Implementations that wish to
- * process ambiguous URI paths must configure the compliance modes to accept them and then perform
- * their own decoding of {@link #getPath()}.
+ * are not satisfactory for a given compliance configuration.
+ * </p>
+ * <p>
+ * Implementations that wish to process ambiguous URI paths must configure the compliance modes
+ * to accept them and then perform their own decoding of {@link #getPath()}.
  * </p>
  * <p>
  * If there are multiple path parameters, only the last one is returned by {@link #getParam()}.
@@ -95,30 +97,30 @@ private enum State
     /**
      * Violations of safe URI interpretations
      */
-    public enum Violation
+    enum Violation
     {
         /**
-         * Ambiguous path segments e.g. <code>/foo/%2E%2E/bar</code>
+         * Ambiguous path segments e.g. {@code /foo/%2E%2E/bar}
          */
         SEGMENT("Ambiguous path segments"),
         /**
-         * Ambiguous path separator within a URI segment e.g. <code>/foo%2Fbar</code>
+         * Ambiguous path separator within a URI segment e.g. {@code /foo%2Fbar}
          */
         SEPARATOR("Ambiguous path separator"),
         /**
-         * Ambiguous path parameters within a URI segment e.g. <code>/foo/..;/bar</code>
+         * Ambiguous path parameters within a URI segment e.g. {@code /foo/..;/bar}
          */
         PARAM("Ambiguous path parameters"),
         /**
-         * Ambiguous double encoding within a URI segment e.g. <code>/%2557EB-INF</code>
+         * Ambiguous double encoding within a URI segment e.g. {@code /%2557EB-INF}
          */
         ENCODING("Ambiguous double encoding"),
         /**
-         * Ambiguous empty segments e.g. <code>/foo//bar</code>
+         * Ambiguous empty segments e.g. {@code /foo//bar}
          */
         EMPTY("Ambiguous empty segments"),
         /**
-         * Non standard UTF-16 encoding eg <code>/foo%u2192bar</code>.
+         * Non standard UTF-16 encoding eg {@code /foo%u2192bar}.
          */
         UTF16("Non standard UTF-16 encoding");
 
@@ -338,7 +340,7 @@ private void parse(State state, final String uri, final int offset, final int en
         int encodedValue = 0; // the partial encoded value
         boolean dot = false; // set to true if the path contains . or .. segments
 
-        for (int i = 0; i < end; i++)
+        for (int i = offset; i < end; i++)
         {
             char c = uri.charAt(i);
 
@@ -567,6 +569,8 @@ else if (c == '/')
                             switch (encodedValue)
                             {
                                 case 0:
+                                    // Byte 0 cannot be present in a UTF-8 sequence in any position
+                                    // other than as the NUL ASCII byte which we do not wish to allow.
                                     throw new IllegalArgumentException("Illegal character in path");
                                 case '/':
                                     _violations.add(Violation.SEPARATOR);
@@ -653,26 +657,11 @@ else if (c == '/')
                 }
                 case QUERY:
                 {
-                    switch (c)
+                    if (c == '#')
                     {
-                        case '%':
-                            encodedCharacters = 2;
-                            break;
-                        case 'u':
-                        case 'U':
-                            if (encodedCharacters == 1)
-                                _violations.add(Violation.UTF16);
-                            encodedCharacters = 0;
-                            break;
-                        case '#':
-                            _query = uri.substring(mark, i);
-                            mark = i + 1;
-                            state = State.FRAGMENT;
-                            encodedCharacters = 0;
-                            break;
-                        default:
-                            encodedCharacters = 0;
-                            break;
+                        _query = uri.substring(mark, i);
+                        mark = i + 1;
+                        state = State.FRAGMENT;
                     }
                     break;
                 }
@@ -687,7 +676,9 @@ else if (c == '/')
                     break;
                 }
                 default:
+                {
                     throw new IllegalStateException(state.toString());
+                }
             }
         }
 
@@ -741,8 +732,8 @@ else if (_path != null)
         {
             // The RFC requires this to be canonical before decoding, but this can leave dot segments and dot dot segments
             // which are not canonicalized and could be used in an attempt to bypass security checks.
-            String decodeNonCanonical = URIUtil.decodePath(_path);
-            _decodedPath = URIUtil.canonicalPath(decodeNonCanonical);
+            String decodedNonCanonical = URIUtil.decodePath(_path);
+            _decodedPath = URIUtil.canonicalPath(decodedNonCanonical);
             if (_decodedPath == null)
                 throw new IllegalArgumentException("Bad URI");
         }
@@ -763,7 +754,8 @@ private void checkSegment(String uri, int segment, int end, boolean param)
         // This method is called once for every segment parsed.
         // A URI like "/foo/" has two segments: "foo" and an empty segment.
         // Empty segments are only ambiguous if they are not the last segment
-        // So if this method is called for any segment and we have previously seen an empty segment, then it was ambiguous
+        // So if this method is called for any segment and we have previously
+        // seen an empty segment, then it was ambiguous.
         if (_emptySegment)
             _violations.add(Violation.EMPTY);
 
@@ -843,7 +835,8 @@ public boolean hasAmbiguousEncoding()
     }
 
     /**
-     * @return True if the URI has either an {@link #hasAmbiguousSegment()} or {@link #hasAmbiguousSeparator()}.
+     * @return True if the URI has either an {@link #hasAmbiguousSegment()} or {@link #hasAmbiguousEmptySegment()}
+     * or {@link #hasAmbiguousSeparator()} or {@link #hasAmbiguousParameter()}
      */
     public boolean isAmbiguous()
     {
@@ -858,7 +851,7 @@ public boolean hasViolations()
         return !_violations.isEmpty();
     }
 
-    public boolean hasViolation(Violation violation)
+    boolean hasViolation(Violation violation)
     {
         return _violations.contains(violation);
     }
diff --git a/jetty-http/src/test/java/org/eclipse/jetty/http/HttpURITest.java b/jetty-http/src/test/java/org/eclipse/jetty/http/HttpURITest.java
index 2489c75cf34e..28be9c41f0ba 100644
--- a/jetty-http/src/test/java/org/eclipse/jetty/http/HttpURITest.java
+++ b/jetty-http/src/test/java/org/eclipse/jetty/http/HttpURITest.java
@@ -322,6 +322,7 @@ public static Stream<Arguments> decodePathTests()
                 {"/f%6f%6F/bar", "/foo/bar", EnumSet.noneOf(Violation.class)},
                 {"/f%u006f%u006F/bar", "/foo/bar", EnumSet.of(Violation.UTF16)},
                 {"/f%u0001%u0001/bar", "/f\001\001/bar", EnumSet.of(Violation.UTF16)},
+                {"/foo/%u20AC/bar", "/foo/\u20AC/bar", EnumSet.of(Violation.UTF16)},
 
                 // illegal paths
                 {"//host/../path/info", null, EnumSet.noneOf(Violation.class)},
@@ -333,6 +334,9 @@ public static Stream<Arguments> decodePathTests()
                 {"/path/%u000X/info", null, EnumSet.noneOf(Violation.class)},
                 {"/path/Fo%u0000/info", null, EnumSet.noneOf(Violation.class)},
                 {"/path/Fo%00/info", null, EnumSet.noneOf(Violation.class)},
+                {"/path/Foo/info%u0000", null, EnumSet.noneOf(Violation.class)},
+                {"/path/Foo/info%00", null, EnumSet.noneOf(Violation.class)},
+                {"/path/%U20AC", null, EnumSet.noneOf(Violation.class)},
                 {"%2e%2e/info", null, EnumSet.noneOf(Violation.class)},
                 {"%u002e%u002e/info", null, EnumSet.noneOf(Violation.class)},
                 {"%2e%2e;/info", null, EnumSet.noneOf(Violation.class)},
@@ -769,4 +773,20 @@ public void testCompareToJavaNetURI(String input, String scheme, String host, In
         assertThat("[" + input + "] .fragment", httpUri.getFragment(), is(javaUri.getFragment()));
         assertThat("[" + input + "] .toString", httpUri.toString(), is(javaUri.toASCIIString()));
     }
+
+    public static Stream<Arguments> queryData()
+    {
+        return Stream.of(
+            new String[]{"/path?p=%U20AC", "p=%U20AC"},
+            new String[]{"/path?p=%u20AC", "p=%u20AC"}
+        ).map(Arguments::of);
+    }
+
+    @ParameterizedTest
+    @MethodSource("queryData")
+    public void testEncodedQuery(String input, String expectedQuery)
+    {
+        HttpURI httpURI = new HttpURI(input);
+        assertThat("[" + input + "] .query", httpURI.getQuery(), is(expectedQuery));
+    }
 }
diff --git a/jetty-maven-plugin/src/main/java/org/eclipse/jetty/maven/plugin/JettyWebAppContext.java b/jetty-maven-plugin/src/main/java/org/eclipse/jetty/maven/plugin/JettyWebAppContext.java
index d2efd9018989..8108b9d2ac21 100644
--- a/jetty-maven-plugin/src/main/java/org/eclipse/jetty/maven/plugin/JettyWebAppContext.java
+++ b/jetty-maven-plugin/src/main/java/org/eclipse/jetty/maven/plugin/JettyWebAppContext.java
@@ -39,6 +39,7 @@
 import org.eclipse.jetty.servlet.ServletHolder;
 import org.eclipse.jetty.servlet.ServletMapping;
 import org.eclipse.jetty.util.StringUtil;
+import org.eclipse.jetty.util.URIUtil;
 import org.eclipse.jetty.util.log.Log;
 import org.eclipse.jetty.util.log.Logger;
 import org.eclipse.jetty.util.resource.Resource;
@@ -450,12 +451,17 @@ public Resource getResource(String uriInContext) throws MalformedURLException
         // If no regular resource exists check for access to /WEB-INF/lib or /WEB-INF/classes
         if ((resource == null || !resource.exists()) && uriInContext != null && _classes != null)
         {
+            // Canonicalize again to look for the resource inside /WEB-INF subdirectories.
+            String uri = URIUtil.canonicalPath(uriInContext);
+            if (uri == null)
+                return null;
+
             try
             {
                 // Replace /WEB-INF/classes with candidates for the classpath
-                if (uriInContext.startsWith(WEB_INF_CLASSES_PREFIX))
+                if (uri.startsWith(WEB_INF_CLASSES_PREFIX))
                 {
-                    if (uriInContext.equalsIgnoreCase(WEB_INF_CLASSES_PREFIX) || uriInContext.equalsIgnoreCase(WEB_INF_CLASSES_PREFIX + "/"))
+                    if (uri.equalsIgnoreCase(WEB_INF_CLASSES_PREFIX) || uri.equalsIgnoreCase(WEB_INF_CLASSES_PREFIX + "/"))
                     {
                         //exact match for a WEB-INF/classes, so preferentially return the resource matching the web-inf classes
                         //rather than the test classes
@@ -471,7 +477,7 @@ else if (_testClasses != null)
                         int i = 0;
                         while (res == null && (i < _webInfClasses.size()))
                         {
-                            String newPath = StringUtil.replace(uriInContext, WEB_INF_CLASSES_PREFIX, _webInfClasses.get(i).getPath());
+                            String newPath = StringUtil.replace(uri, WEB_INF_CLASSES_PREFIX, _webInfClasses.get(i).getPath());
                             res = Resource.newResource(newPath);
                             if (!res.exists())
                             {
@@ -482,11 +488,11 @@ else if (_testClasses != null)
                         return res;
                     }
                 }
-                else if (uriInContext.startsWith(WEB_INF_LIB_PREFIX))
+                else if (uri.startsWith(WEB_INF_LIB_PREFIX))
                 {
                     // Return the real jar file for all accesses to
                     // /WEB-INF/lib/*.jar
-                    String jarName = StringUtil.strip(uriInContext, WEB_INF_LIB_PREFIX);
+                    String jarName = StringUtil.strip(uri, WEB_INF_LIB_PREFIX);
                     if (jarName.startsWith("/") || jarName.startsWith("\\"))
                         jarName = jarName.substring(1);
                     if (jarName.length() == 0)
diff --git a/jetty-rewrite/src/main/java/org/eclipse/jetty/rewrite/handler/RedirectUtil.java b/jetty-rewrite/src/main/java/org/eclipse/jetty/rewrite/handler/RedirectUtil.java
index 4754173ca315..43347ca26196 100644
--- a/jetty-rewrite/src/main/java/org/eclipse/jetty/rewrite/handler/RedirectUtil.java
+++ b/jetty-rewrite/src/main/java/org/eclipse/jetty/rewrite/handler/RedirectUtil.java
@@ -53,12 +53,12 @@ public static String toRedirectURL(final HttpServletRequest request, String loca
                 String path = request.getRequestURI();
                 String parent = (path.endsWith("/")) ? path : URIUtil.parentPath(path);
                 location = URIUtil.canonicalURI(URIUtil.addEncodedPaths(parent, location));
-                if (!location.startsWith("/"))
+                if (location != null && !location.startsWith("/"))
                     url.append('/');
             }
 
             if (location == null)
-                throw new IllegalStateException("path cannot be above root");
+                throw new IllegalStateException("redirect path cannot be above root");
             url.append(location);
 
             location = url.toString();
diff --git a/jetty-rewrite/src/test/java/org/eclipse/jetty/rewrite/handler/ValidUrlRuleTest.java b/jetty-rewrite/src/test/java/org/eclipse/jetty/rewrite/handler/ValidUrlRuleTest.java
index fff775784b97..b060f29d13ee 100644
--- a/jetty-rewrite/src/test/java/org/eclipse/jetty/rewrite/handler/ValidUrlRuleTest.java
+++ b/jetty-rewrite/src/test/java/org/eclipse/jetty/rewrite/handler/ValidUrlRuleTest.java
@@ -24,6 +24,7 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 @SuppressWarnings("unused")
@@ -75,6 +76,12 @@ public void testInvalidUrlWithReason() throws Exception
 
     @Test
     public void testInvalidJsp() throws Exception
+    {
+        assertThrows(IllegalArgumentException.class, () -> _request.setURIPathQuery("/jsp/bean1.jsp%00"));
+    }
+
+    @Test
+    public void testInvalidJspWithNullByte() throws Exception
     {
         _rule.setCode("405");
         _rule.setReason("foo");
@@ -87,6 +94,12 @@ public void testInvalidJsp() throws Exception
         assertEquals("foo", _response.getReason());
     }
 
+    @Test
+    public void testInvalidShamrock() throws Exception
+    {
+        assertThrows(IllegalArgumentException.class, () -> _request.setURIPathQuery("/jsp/shamrock-%00%E2%98%98.jsp"));
+    }
+
     @Test
     public void testValidShamrock() throws Exception
     {
@@ -110,4 +123,3 @@ public void testCharacters() throws Exception
         //@checkstyle-enable-check : IllegalTokenText
     }
 }
-
diff --git a/jetty-server/src/main/java/org/eclipse/jetty/server/handler/ContextHandler.java b/jetty-server/src/main/java/org/eclipse/jetty/server/handler/ContextHandler.java
index c7c93a6fab66..69955da56852 100644
--- a/jetty-server/src/main/java/org/eclipse/jetty/server/handler/ContextHandler.java
+++ b/jetty-server/src/main/java/org/eclipse/jetty/server/handler/ContextHandler.java
@@ -1942,11 +1942,6 @@ public Resource getResource(String path) throws MalformedURLException
         if (_baseResource == null)
             return null;
 
-        // Does the path go above the current scope?
-        path = URIUtil.canonicalPath(path);
-        if (path == null)
-            return null;
-
         try
         {
             Resource resource = _baseResource.addPath(path);
@@ -2299,6 +2294,7 @@ else if (path.charAt(0) != '/')
         @Override
         public URL getResource(String path) throws MalformedURLException
         {
+            path = URIUtil.canonicalPath(path);
             if (path == null)
                 return null;
             Resource resource = ContextHandler.this.getResource(path);
diff --git a/jetty-server/src/main/java/org/eclipse/jetty/server/handler/ResourceHandler.java b/jetty-server/src/main/java/org/eclipse/jetty/server/handler/ResourceHandler.java
index 43709a297223..e98f20410d3a 100644
--- a/jetty-server/src/main/java/org/eclipse/jetty/server/handler/ResourceHandler.java
+++ b/jetty-server/src/main/java/org/eclipse/jetty/server/handler/ResourceHandler.java
@@ -187,7 +187,9 @@ public Resource getResource(String path)
                 }
             }
             else if (_context != null)
+            {
                 r = _context.getResource(path);
+            }
 
             if ((r == null || !r.exists()) && path.endsWith("/jetty-dir.css"))
                 r = getStylesheet();
diff --git a/jetty-server/src/test/java/org/eclipse/jetty/server/HttpConnectionTest.java b/jetty-server/src/test/java/org/eclipse/jetty/server/HttpConnectionTest.java
index 9ce41675f850..29ab15308e75 100644
--- a/jetty-server/src/test/java/org/eclipse/jetty/server/HttpConnectionTest.java
+++ b/jetty-server/src/test/java/org/eclipse/jetty/server/HttpConnectionTest.java
@@ -829,6 +829,12 @@ public void testBadUTF8FallsbackTo8859() throws Exception
         Log.getLogger(HttpParser.class).info("badMessage: bad encoding expected ...");
         String response;
 
+        response = connector.getResponse("GET /foo/bar%c0%00 HTTP/1.1\r\n" +
+            "Host: localhost\r\n" +
+            "Connection: close\r\n" +
+            "\r\n");
+        checkContains(response, 0, "HTTP/1.1 400");
+
         response = connector.getResponse("GET /bad/utf8%c1 HTTP/1.1\r\n" +
             "Host: localhost\r\n" +
             "Connection: close\r\n" +
diff --git a/jetty-server/src/test/java/org/eclipse/jetty/server/handler/ContextHandlerGetResourceTest.java b/jetty-server/src/test/java/org/eclipse/jetty/server/handler/ContextHandlerGetResourceTest.java
index f3b26d86fd07..a82c14a07e8d 100644
--- a/jetty-server/src/test/java/org/eclipse/jetty/server/handler/ContextHandlerGetResourceTest.java
+++ b/jetty-server/src/test/java/org/eclipse/jetty/server/handler/ContextHandlerGetResourceTest.java
@@ -235,16 +235,23 @@ public void testDoesNotExistResource() throws Exception
     @Test
     public void testAlias() throws Exception
     {
-        Resource resource = context.getResource("/./index.html");
-        assertNotNull(resource);
-        assertFalse(resource.isAlias());
+        String path = "/./index.html";
+        Resource resource = context.getResource(path);
+        assertNull(resource);
+        URL resourceURL = context.getServletContext().getResource(path);
+        assertFalse(resourceURL.getPath().contains("/./"));
 
-        resource = context.getResource("/down/../index.html");
-        assertNotNull(resource);
-        assertFalse(resource.isAlias());
+        path = "/down/../index.html";
+        resource = context.getResource(path);
+        assertNull(resource);
+        resourceURL = context.getServletContext().getResource(path);
+        assertFalse(resourceURL.getPath().contains("/../"));
 
-        resource = context.getResource("//index.html");
+        path = "//index.html";
+        resource = context.getResource(path);
         assertNull(resource);
+        resourceURL = context.getServletContext().getResource(path);
+        assertNull(resourceURL);
     }
 
     @ParameterizedTest
diff --git a/jetty-servlet/src/test/java/org/eclipse/jetty/servlet/RequestURITest.java b/jetty-servlet/src/test/java/org/eclipse/jetty/servlet/RequestURITest.java
index 02ac7ebaedb1..32ec194a78ed 100644
--- a/jetty-servlet/src/test/java/org/eclipse/jetty/servlet/RequestURITest.java
+++ b/jetty-servlet/src/test/java/org/eclipse/jetty/servlet/RequestURITest.java
@@ -74,7 +74,8 @@ public static Stream<Arguments> data()
         ret.add(Arguments.of("/hello%u0025world", "/hello%u0025world", null));
         ret.add(Arguments.of("/hello-euro-%E2%82%AC", "/hello-euro-%E2%82%AC", null));
         ret.add(Arguments.of("/hello-euro?%E2%82%AC", "/hello-euro", "%E2%82%AC"));
-        // test the ascii control characters (just for completeness)
+        // Test the ascii control characters (just for completeness).
+        // Zero is not allowed in UTF-8 sequences so start from 1.
         for (int i = 0x1; i < 0x1f; i++)
         {
             String raw = String.format("/hello%%%02Xworld", i);
@@ -84,6 +85,9 @@ public static Stream<Arguments> data()
         return ret.stream();
     }
 
+    // TODO: add "dataWithZero" and test for 400 responses.
+    //  Add other bad ones like %XY, %1G, ..;, ., \000, etc.
+
     @SuppressWarnings("serial")
     public static class RequestUriServlet extends HttpServlet
     {
diff --git a/jetty-util/src/main/java/org/eclipse/jetty/util/URIUtil.java b/jetty-util/src/main/java/org/eclipse/jetty/util/URIUtil.java
index 3c6f7a53d343..6817072ad721 100644
--- a/jetty-util/src/main/java/org/eclipse/jetty/util/URIUtil.java
+++ b/jetty-util/src/main/java/org/eclipse/jetty/util/URIUtil.java
@@ -537,7 +537,6 @@ public static String decodePath(String path, int offset, int length)
         {
             throw new IllegalArgumentException("cannot decode URI", e);
         }
-
     }
 
     /* Decode a URI path and strip parameters of ISO-8859-1 path
diff --git a/jetty-util/src/main/java/org/eclipse/jetty/util/resource/FileResource.java b/jetty-util/src/main/java/org/eclipse/jetty/util/resource/FileResource.java
index 40ead6f17972..c3d77b329c42 100644
--- a/jetty-util/src/main/java/org/eclipse/jetty/util/resource/FileResource.java
+++ b/jetty-util/src/main/java/org/eclipse/jetty/util/resource/FileResource.java
@@ -270,8 +270,11 @@ public Resource addPath(String path)
     {
         assertValidPath(path);
 
-        if (path == null)
-            throw new MalformedURLException();
+        // Check that the path is within the root,
+        // but use the original path to create the
+        // resource, to preserve aliasing.
+        if (URIUtil.canonicalPath(path) == null)
+            throw new MalformedURLException(path);
 
         if ("/".equals(path))
             return this;
diff --git a/jetty-util/src/main/java/org/eclipse/jetty/util/resource/PathResource.java b/jetty-util/src/main/java/org/eclipse/jetty/util/resource/PathResource.java
index 22f936a62cfd..3c58739016b6 100644
--- a/jetty-util/src/main/java/org/eclipse/jetty/util/resource/PathResource.java
+++ b/jetty-util/src/main/java/org/eclipse/jetty/util/resource/PathResource.java
@@ -94,8 +94,11 @@ private Path checkAliasPath()
         if (!abs.isAbsolute())
             abs = path.toAbsolutePath();
 
+        // Any normalization difference means it's an alias,
+        // and we don't want to bother further to follow
+        // symlinks as it's an alias anyway.
         Path normal = path.normalize();
-        if (!abs.equals(normal))
+        if (!isSameName(abs, normal))
             return normal;
 
         try
@@ -105,11 +108,8 @@ private Path checkAliasPath()
             if (Files.exists(path))
             {
                 Path real = abs.toRealPath(FOLLOW_LINKS);
-
                 if (!isSameName(abs, real))
-                {
                     return real;
-                }
             }
         }
         catch (IOException e)
@@ -361,20 +361,23 @@ public boolean isSame(Resource resource)
     }
 
     @Override
-    public Resource addPath(final String subpath) throws IOException
+    public Resource addPath(final String subPath) throws IOException
     {
-        if ((subpath == null) || (subpath.length() == 0))
-            throw new MalformedURLException(subpath);
+        // Check that the path is within the root,
+        // but use the original path to create the
+        // resource, to preserve aliasing.
+        if (URIUtil.canonicalPath(subPath) == null)
+            throw new MalformedURLException(subPath);
 
-        if ("/".equals(subpath))
+        if ("/".equals(subPath))
             return this;
 
-        // subpaths are always under PathResource
-        // compensate for input subpaths like "/subdir"
+        // Sub-paths are always under PathResource
+        // compensate for input sub-paths like "/subdir"
         // where default resolve behavior would be
         // to treat that like an absolute path
 
-        return new PathResource(this, subpath);
+        return new PathResource(this, subPath);
     }
 
     private void assertValidPath(Path path)
diff --git a/jetty-util/src/main/java/org/eclipse/jetty/util/resource/Resource.java b/jetty-util/src/main/java/org/eclipse/jetty/util/resource/Resource.java
index dc443becffb3..45744360415f 100644
--- a/jetty-util/src/main/java/org/eclipse/jetty/util/resource/Resource.java
+++ b/jetty-util/src/main/java/org/eclipse/jetty/util/resource/Resource.java
@@ -555,6 +555,7 @@ public String getListHTML(String base, boolean parent) throws IOException
      */
     public String getListHTML(String base, boolean parent, String query) throws IOException
     {
+        base = URIUtil.canonicalPath(base);
         if (base == null || !isDirectory())
             return null;
 
diff --git a/jetty-util/src/main/java/org/eclipse/jetty/util/resource/URLResource.java b/jetty-util/src/main/java/org/eclipse/jetty/util/resource/URLResource.java
index 054f4d0d5ab6..40d68abdf56c 100644
--- a/jetty-util/src/main/java/org/eclipse/jetty/util/resource/URLResource.java
+++ b/jetty-util/src/main/java/org/eclipse/jetty/util/resource/URLResource.java
@@ -271,8 +271,11 @@ public String[] list()
     public Resource addPath(String path)
         throws IOException
     {
-        if (path == null)
-            throw new MalformedURLException("null path");
+        // Check that the path is within the root,
+        // but use the original path to create the
+        // resource, to preserve aliasing.
+        if (URIUtil.canonicalPath(path) == null)
+            throw new MalformedURLException(path);
 
         return newResource(URIUtil.addEncodedPaths(_url.toExternalForm(), URIUtil.encodePath(path)), _useCaches);
     }
diff --git a/jetty-util/src/test/java/org/eclipse/jetty/util/URIUtilCanonicalPathTest.java b/jetty-util/src/test/java/org/eclipse/jetty/util/URIUtilCanonicalPathTest.java
index c40ff6a83c7e..a52a64444d2a 100644
--- a/jetty-util/src/test/java/org/eclipse/jetty/util/URIUtilCanonicalPathTest.java
+++ b/jetty-util/src/test/java/org/eclipse/jetty/util/URIUtilCanonicalPathTest.java
@@ -151,7 +151,9 @@ public void testCanonicalPath(String input, String expectedResult)
 
         // Check canonicalURI
         if (expectedResult == null)
+        {
             assertThat(URIUtil.canonicalURI(input), nullValue());
+        }
         else
         {
             // mostly encodedURI will be the same
@@ -162,4 +164,22 @@ public void testCanonicalPath(String input, String expectedResult)
         }
     }
 
+    public static Stream<Arguments> queries()
+    {
+        String[][] data =
+            {
+                {"/ctx/../dir?/../index.html", "/dir?/../index.html"},
+                {"/get-files?file=/etc/passwd", "/get-files?file=/etc/passwd"},
+                {"/get-files?file=../../../../../passwd", "/get-files?file=../../../../../passwd"}
+            };
+        return Stream.of(data).map(Arguments::of);
+    }
+
+    @ParameterizedTest
+    @MethodSource("queries")
+    public void testQuery(String input, String expectedPath)
+    {
+        String actual = URIUtil.canonicalURI(input);
+        assertThat(actual, is(expectedPath));
+    }
 }
diff --git a/jetty-util/src/test/java/org/eclipse/jetty/util/resource/ResourceTest.java b/jetty-util/src/test/java/org/eclipse/jetty/util/resource/ResourceTest.java
index c93dc731ed74..5d7c7b29dc5a 100644
--- a/jetty-util/src/test/java/org/eclipse/jetty/util/resource/ResourceTest.java
+++ b/jetty-util/src/test/java/org/eclipse/jetty/util/resource/ResourceTest.java
@@ -21,6 +21,7 @@
 import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
+import java.net.MalformedURLException;
 import java.net.URI;
 import java.net.URL;
 import java.nio.file.Path;
@@ -45,6 +46,8 @@
 import static org.hamcrest.Matchers.startsWith;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 public class ResourceTest
 {
@@ -325,4 +328,19 @@ public void testEqualsWindowsCaseInsensitiveDrive() throws Exception
 
         assertEquals(rb, ra);
     }
+
+    @Test
+    public void testClimbAboveBase() throws Exception
+    {
+        Resource resource = Resource.newResource("/foo/bar");
+        assertThrows(MalformedURLException.class, () -> resource.addPath(".."));
+
+        Resource same = resource.addPath(".");
+        assertNotNull(same);
+        assertTrue(same.isAlias());
+
+        assertThrows(MalformedURLException.class, () -> resource.addPath("./.."));
+
+        assertThrows(MalformedURLException.class, () -> resource.addPath("./../bar"));
+    }
 }