add additional isLeadingPath method that resolves symlinks

src/main/org/apache/tools/ant/util/FileUtils.java

@@ -1210,6 +1210,36 @@ public class FileUtils {
         return p.startsWith(l);
     }
 
+    /**
+     * Learn whether one path "leads" another.
+     *
+     * @param leading The leading path, must not be null, must be absolute.
+     * @param path The path to check, must not be null, must be absolute.
+     * @param resolveSymlinks whether symbolic links shall be resolved
+     * prior to comparing the paths.
+     * @return true if path starts with leading; false otherwise.
+     * @since Ant 1.9.13
+     * @throws IOException if resolveSymlinks is true and invoking
+     * getCanonicaPath on either argument throws an exception
+     */
+    public boolean isLeadingPath(File leading, File path, boolean resolveSymlinks)
+        throws IOException {
+        if (!resolveSymlinks) {
+            return isLeadingPath(leading, path);
+        }
+        String l = leading.getCanonicalPath();
+        String p = path.getCanonicalPath();
+        if (l.equals(p)) {
+            return true;
+        }
+        // ensure that l ends with a /
+        // so we never think /foo was a parent directory of /foobar
+        if (!l.endsWith(File.separator)) {
+            l += File.separator;
+        }
+        return p.startsWith(l);
+    }
+
     /**
      * Constructs a <code>file:</code> URI that represents the
      * external form of the given pathname.

src/tests/junit/org/apache/tools/ant/util/FileUtilsTest.java

@@ -32,6 +32,7 @@ import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
+import static org.junit.Assume.assumeFalse;
 import static org.junit.Assume.assumeTrue;
 
 /**
@@ -603,6 +604,36 @@ public class FileUtilsTest {
         assertFalse(FILE_UTILS.isLeadingPath(new File("/foo"), new File("/foo/../..")));
     }
 
+    /**
+     * @see "https://bz.apache.org/bugzilla/show_bug.cgi?id=62502"
+     */
+    @Test
+    public void isLeadingPathCanonicalVersionCannotBeFooledByTooManyDoubleDots() throws IOException {
+        assertFalse(FILE_UTILS.isLeadingPath(new File("/foo"), new File("/foo/../../bar"), true));
+        assertFalse(FILE_UTILS.isLeadingPath(new File("c:\\foo"), new File("c:\\foo\\..\\..\\bar"), true));
+        assertFalse(FILE_UTILS.isLeadingPath(new File("/foo"), new File("/foo/../.."), true));
+    }
+
+    @Test
+    public void isLeadingPathCanonicalVersionWorksAsExpectedOnUnix() throws IOException {
+        assumeFalse("Test doesn't run on DOS", Os.isFamily("dos"));
+        assertTrue(FILE_UTILS.isLeadingPath(new File("/foo"), new File("/foo/bar"), true));
+        assertTrue(FILE_UTILS.isLeadingPath(new File("/foo"), new File("/foo/baz/../bar"), true));
+        assertTrue(FILE_UTILS.isLeadingPath(new File("/foo"), new File("/foo/../foo/bar"), true));
+        assertFalse(FILE_UTILS.isLeadingPath(new File("/foo"), new File("/foobar"), true));
+        assertFalse(FILE_UTILS.isLeadingPath(new File("/foo"), new File("/bar"), true));
+    }
+
+    @Test
+    public void isLeadingPathCanonicalVersionWorksAsExpectedOnDos() throws IOException {
+        assumeTrue("Test only runs on DOS", Os.isFamily("dos"));
+        assertTrue(FILE_UTILS.isLeadingPath(new File("C:\\foo"), new File("C:\\foo\\bar"), true));
+        assertTrue(FILE_UTILS.isLeadingPath(new File("C:\\foo"), new File("C:\\foo\\baz\\..\\bar"), true));
+        assertTrue(FILE_UTILS.isLeadingPath(new File("C:\\foo"), new File("C:\\foo\\..\\foo\\bar"), true));
+        assertFalse(FILE_UTILS.isLeadingPath(new File("C:\\foo"), new File("C:\\foobar"), true));
+        assertFalse(FILE_UTILS.isLeadingPath(new File("C:\\foo"), new File("C:\\bar"), true));
+    }
+
     /**
      * adapt file separators to local conventions
      */