pythonGH-118447: Fix handling of unreadable symlinks in `os.path.real…

…path()` (python#118489)

Co-authored-by: Nice Zombies <nineteendo19d0@gmail.com>
(cherry picked from commit caf6064)

Lib/posixpath.py

@@ -491,8 +491,16 @@ def _joinrealpath(path, rest, strict, seen):
  else:
  # Return already resolved part + rest of the path unchanged.
  return join(newpath, rest), False
+ try:
+ target = os.readlink(newpath)
+ except OSError:
+ if strict:
+ raise
+ else:
+ # Return already resolved part + rest of the path unchanged.
+ return join(newpath, rest), False
  seen[newpath] = None # not resolved symlink
- path, ok = _joinrealpath(path, os.readlink(newpath), strict, seen)
+ path, ok = _joinrealpath(path, target, strict, seen)
  if not ok:
  return join(path, rest), False
  seen[newpath] = path # resolved symlink

Lib/test/test_posixpath.py

@@ -641,6 +641,23 @@ def test_realpath_resolve_first(self):
  safe_rmdir(ABSTFN + "/k")
  safe_rmdir(ABSTFN)
 
+ @os_helper.skip_unless_symlink
+ @skip_if_ABSTFN_contains_backslash
+ @unittest.skipIf(os.chmod not in os.supports_follow_symlinks, "Can't set symlink permissions")
+ def test_realpath_unreadable_symlink(self):
+ try:
+ os.symlink(ABSTFN+"1", ABSTFN)
+ os.chmod(ABSTFN, 0o000, follow_symlinks=False)
+ self.assertEqual(realpath(ABSTFN), ABSTFN)
+ self.assertEqual(realpath(ABSTFN + '/foo'), ABSTFN + '/foo')
+ self.assertEqual(realpath(ABSTFN + '/../foo'), dirname(ABSTFN) + '/foo')
+ self.assertEqual(realpath(ABSTFN + '/foo/..'), ABSTFN)
+ with self.assertRaises(PermissionError):
+ realpath(ABSTFN, strict=True)
+ finally:
+ os.chmod(ABSTFN, 0o755, follow_symlinks=False)
+ os.unlink(ABSTFN)
+
  def test_relpath(self):
  (real_getcwd, os.getcwd) = (os.getcwd, lambda: r"/home/user/bar")
  try:

Misc/NEWS.d/next/Library/2024-05-01-22-24-05.gh-issue-110863.GjYBbq.rst

@@ -0,0 +1,2 @@
+:func:`os.path.realpath` now suppresses any :exc:`OSError` from
+:func:`os.readlink` when *strict* mode is disabled (the default).