barlowa124 · Oct 10, 2026
diff --git a/Xlib/xauth.py b/Xlib/xauth.py
@@ -30,6 +30,7 @@
 FamilyServerInterpreted = X.FamilyServerInterpreted
 FamilyInternetV6 = X.FamilyInternetV6
 FamilyLocal = 256
+FamilyWild = 0xFFFF
 
 class Xauthority(object):
     def __init__(self, filename = None):
@@ -120,10 +121,12 @@ def get_best_auth(self, family, address, dispno,
         matches = {}
 
         for efam, eaddr, enum, ename, edata in self.entries:
-            if enum == b'' and ename not in matches:
-                enum = num
-            if efam == family and eaddr == address and num == enum:
-                matches[ename] = edata
+            # As in libXau's XauGetBestAuthByAddr: a FamilyWild entry
+            # matches any family and address, and an empty entry number
+            # matches any display number.
+            if efam == FamilyWild or (efam == family and eaddr == address):
+                if enum == b'' or enum == num:
+                    matches[ename] = edata
 
         for t in types:
             try:

diff --git a/test/test_xauth.py b/test/test_xauth.py
@@ -0,0 +1,67 @@
+import os
+import struct
+import sys
+import tempfile
+import unittest
+
+from Xlib import xauth, error
+
+
+def _entry(family, addr, num, name, data):
+    out = struct.pack('>H', family)
+    for field in (addr, num, name, data):
+        out += struct.pack('>H', len(field)) + field
+    return out
+
+
+def _write_xauth(entries):
+    fd, path = tempfile.mkstemp()
+    try:
+        with os.fdopen(fd, 'wb') as fp:
+            fp.write(b''.join(entries))
+        return xauth.Xauthority(path)
+    finally:
+        os.unlink(path)
+
+
+class TestXauthority(unittest.TestCase):
+    def test_family_wild_matches_any_family_and_address(self):
+        # Mutter/XWayland writes FamilyWild entries with an empty display
+        # number; they are meant to match every family, address and
+        # display. See https://github.com/python-xlib/python-xlib/issues/294
+        au = _write_xauth([
+            _entry(xauth.FamilyWild, b'whatever', b'',
+                   b'MIT-MAGIC-COOKIE-1', b'cookie'),
+        ])
+        name, data = au.get_best_auth(xauth.FamilyLocal, b'other-host', 0)
+        self.assertEqual(name, b'MIT-MAGIC-COOKIE-1')
+        self.assertEqual(data, b'cookie')
+
+    def test_family_wild_empty_num_only(self):
+        au = _write_xauth([
+            _entry(xauth.FamilyWild, b'host', b'',
+                   b'MIT-MAGIC-COOKIE-1', b'cookie'),
+        ])
+        name, data = au.get_best_auth(xauth.FamilyInternet,
+                                      b'\x7f\x00\x00\x01', 42)
+        self.assertEqual(data, b'cookie')
+
+    def test_no_match_still_raises(self):
+        au = _write_xauth([
+            _entry(xauth.FamilyLocal, b'other-host', b'1',
+                   b'MIT-MAGIC-COOKIE-1', b'cookie'),
+        ])
+        self.assertRaises(error.XNoAuthError, au.get_best_auth,
+                          xauth.FamilyLocal, b'my-host', 0)
+
+    def test_exact_match_unchanged(self):
+        au = _write_xauth([
+            _entry(xauth.FamilyLocal, b'my-host', b'0',
+                   b'MIT-MAGIC-COOKIE-1', b'cookie'),
+        ])
+        name, data = au.get_best_auth(xauth.FamilyLocal, b'my-host', 0)
+        self.assertEqual(data, b'cookie')
+
+
+if __name__ == '__main__':
+    unittest.main()