GH-118447: Fix handling of unreadable symlinks in os.path.realpath()

Lib/posixpath.py

@@ -471,26 +471,26 @@ def realpath(filename, *, strict=False):
  if not stat.S_ISLNK(st.st_mode):
  path = newpath
  continue
+ if newpath in seen:
+ # Already seen this path
+ path = seen[newpath]
+ if path is not None:
+ # use cached value
+ continue
+ # The symlink is not resolved, so we must have a symlink loop.
+ if strict:
+ # Raise OSError(errno.ELOOP)
+ os.stat(newpath)
+ path = newpath
+ continue
+ target = os.readlink(newpath)
  except OSError:
  if strict:
  raise
  path = newpath
  continue
  # Resolve the symbolic link
- if newpath in seen:
- # Already seen this path
- path = seen[newpath]
- if path is not None:
- # use cached value
- continue
- # The symlink is not resolved, so we must have a symlink loop.
- if strict:
- # Raise OSError(errno.ELOOP)
- os.stat(newpath)
- path = newpath
- continue
  seen[newpath] = None # not resolved symlink
- target = os.readlink(newpath)
  if target.startswith(sep):
  # Symlink target is absolute; reset resolved path.
  path = sep

Lib/test/test_posixpath.py

@@ -660,6 +660,23 @@ 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).