Validate path, query and fragment for authority-less file URLs

src/main/java/org/apache/commons/validator/routines/UrlValidator.java

@@ -384,11 +384,12 @@ public boolean isValid(final String value) {
             return false;
         }
         final String authority = uri.getRawAuthority();
-        if ("file".equals(scheme) && GenericValidator.isBlankOrNull(authority)) { // Special case - file: allows an empty authority
-            return true; // this is a local file - nothing more to do here
-        }
+        // Special case - file: allows an empty authority, so only the authority check is skipped for it;
+        // the path, query and fragment below are validated as they are for any other scheme
+        final boolean emptyFileAuthority = "file".equals(scheme) && GenericValidator.isBlankOrNull(authority);
         // Validate the authority
-        if ("file".equals(scheme) && authority != null && authority.contains(":") || !isValidAuthority(authority)) {
+        if (!emptyFileAuthority
+                && ("file".equals(scheme) && authority != null && authority.contains(":") || !isValidAuthority(authority))) {
             return false;
         }
         if (!isValidPath(uri.getRawPath()) || !isValidQuery(uri.getRawQuery()) || !isValidFragment(uri.getRawFragment())) {

src/test/java/org/apache/commons/validator/routines/UrlValidatorTest.java

@@ -152,6 +152,45 @@ public void setUp() {
         }
     }
 
+    @Test
+    void testFileSchemePath() {
+        final String[] schemes = { "file" };
+        final UrlValidator urlValidator = new UrlValidator(schemes, UrlValidator.ALLOW_LOCAL_URLS);
+
+        // an authority-less file: URL gets the same path check as one carrying an authority
+        assertFalse(urlValidator.isValid("file:///../../etc/passwd"));
+        assertFalse(urlValidator.isValid("file:/../../etc/passwd"));
+        assertFalse(urlValidator.isValid("file://localhost/../../etc/passwd"));
+
+        // percent-encoded form of the same, as covered for http in testValidator383
+        assertFalse(urlValidator.isValid("file:///..%2f..%2fetc/passwd"));
+        assertFalse(urlValidator.isValid("file:///%2e%2e/etc/passwd"));
+
+        // an opaque file: URI has no path at all, just as http:example.com has none
+        assertFalse(urlValidator.isValid("file:etc/passwd"));
+
+        assertTrue(urlValidator.isValid("file:///etc/hosts"));
+        assertTrue(urlValidator.isValid("file:/C:/path/to/dir/"));
+    }
+
+    @Test
+    void testFileSchemePathOptions() {
+        final String[] schemes = { "file" };
+
+        final UrlValidator noDoubleSlashes = new UrlValidator(schemes, UrlValidator.ALLOW_LOCAL_URLS);
+        assertFalse(noDoubleSlashes.isValid("file:///tmp/a//b"));
+        assertFalse(noDoubleSlashes.isValid("file://localhost/tmp/a//b"));
+
+        final UrlValidator allowDoubleSlashes = new UrlValidator(schemes, UrlValidator.ALLOW_LOCAL_URLS | UrlValidator.ALLOW_2_SLASHES);
+        assertTrue(allowDoubleSlashes.isValid("file:///tmp/a//b"));
+
+        final UrlValidator noFragments = new UrlValidator(schemes, UrlValidator.ALLOW_LOCAL_URLS | UrlValidator.NO_FRAGMENTS);
+        assertFalse(noFragments.isValid("file:///tmp/x#frag"));
+        assertFalse(noFragments.isValid("file://localhost/tmp/x#frag"));
+
+        assertTrue(noDoubleSlashes.isValid("file:///tmp/x#frag"));
+    }
+
     @Test
     void testFragments() {
         final String[] schemes = { "http", "https" };