From fd4b5453df74e249987553b12c14ad75fafa4991 Mon Sep 17 00:00:00 2001 From: Barney Gale Date: Wed, 13 Nov 2024 22:59:32 +0000 Subject: [PATCH] GH-118289: Fix handling of non-directories in `posixpath.realpath()` (#120127) In strict mode, raise `NotADirectoryError` if we encounter a non-directory while we still have path parts left to process. We use a `part_count` variable rather than `len(rest)` because the `rest` stack also contains markers for unresolved symlinks. --- Lib/posixpath.py | 18 ++++-- Lib/test/test_posixpath.py | 59 +++++++++++++++++++ ...-06-05-19-09-36.gh-issue-118289.moL9_d.rst | 2 + 3 files changed, 75 insertions(+), 4 deletions(-) create mode 100644 Misc/NEWS.d/next/Library/2024-06-05-19-09-36.gh-issue-118289.moL9_d.rst diff --git a/Lib/posixpath.py b/Lib/posixpath.py index fccca4e066b76f..db72ded8826056 100644 --- a/Lib/posixpath.py +++ b/Lib/posixpath.py @@ -412,6 +412,10 @@ def _realpath(filename, strict=False, sep=sep, curdir=curdir, pardir=pardir, # very fast way of spelling list(reversed(...)). rest = filename.split(sep)[::-1] + # Number of unprocessed parts in 'rest'. This can differ from len(rest) + # later, because 'rest' might contain markers for unresolved symlinks. + part_count = len(rest) + # The resolved path, which is absolute throughout this function. # Note: getcwd() returns a normalized and symlink-free path. path = sep if filename.startswith(sep) else getcwd() @@ -426,12 +430,13 @@ def _realpath(filename, strict=False, sep=sep, curdir=curdir, pardir=pardir, # by *maxlinks*, this is used instead of *seen* to detect symlink loops. link_count = 0 - while rest: + while part_count: name = rest.pop() if name is None: # resolved symlink target seen[rest.pop()] = path continue + part_count -= 1 if not name or name == curdir: # current dir continue @@ -444,8 +449,11 @@ def _realpath(filename, strict=False, sep=sep, curdir=curdir, pardir=pardir, else: newpath = path + sep + name try: - st = lstat(newpath) - if not stat.S_ISLNK(st.st_mode): + st_mode = lstat(newpath).st_mode + if not stat.S_ISLNK(st_mode): + if strict and part_count and not stat.S_ISDIR(st_mode): + raise OSError(errno.ENOTDIR, os.strerror(errno.ENOTDIR), + newpath) path = newpath continue elif maxlinks is not None: @@ -487,7 +495,9 @@ def _realpath(filename, strict=False, sep=sep, curdir=curdir, pardir=pardir, rest.append(newpath) rest.append(None) # Push the unresolved symlink target parts onto the stack. - rest.extend(target.split(sep)[::-1]) + target_parts = target.split(sep)[::-1] + rest.extend(target_parts) + part_count += len(target_parts) return path diff --git a/Lib/test/test_posixpath.py b/Lib/test/test_posixpath.py index ca5cf42f8fcd71..b39255ebc79ac1 100644 --- a/Lib/test/test_posixpath.py +++ b/Lib/test/test_posixpath.py @@ -695,6 +695,65 @@ def test_realpath_unreadable_symlink(self): os.chmod(ABSTFN, 0o755, follow_symlinks=False) os.unlink(ABSTFN) + @skip_if_ABSTFN_contains_backslash + def test_realpath_nonterminal_file(self): + try: + with open(ABSTFN, 'w') as f: + f.write('test_posixpath wuz ere') + self.assertEqual(realpath(ABSTFN, strict=False), ABSTFN) + self.assertEqual(realpath(ABSTFN, strict=True), ABSTFN) + self.assertEqual(realpath(ABSTFN + "/", strict=False), ABSTFN) + self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/", strict=True) + self.assertEqual(realpath(ABSTFN + "/.", strict=False), ABSTFN) + self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/.", strict=True) + self.assertEqual(realpath(ABSTFN + "/..", strict=False), dirname(ABSTFN)) + self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/..", strict=True) + self.assertEqual(realpath(ABSTFN + "/subdir", strict=False), ABSTFN + "/subdir") + self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/subdir", strict=True) + finally: + os_helper.unlink(ABSTFN) + + @os_helper.skip_unless_symlink + @skip_if_ABSTFN_contains_backslash + def test_realpath_nonterminal_symlink_to_file(self): + try: + with open(ABSTFN + "1", 'w') as f: + f.write('test_posixpath wuz ere') + os.symlink(ABSTFN + "1", ABSTFN) + self.assertEqual(realpath(ABSTFN, strict=False), ABSTFN + "1") + self.assertEqual(realpath(ABSTFN, strict=True), ABSTFN + "1") + self.assertEqual(realpath(ABSTFN + "/", strict=False), ABSTFN + "1") + self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/", strict=True) + self.assertEqual(realpath(ABSTFN + "/.", strict=False), ABSTFN + "1") + self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/.", strict=True) + self.assertEqual(realpath(ABSTFN + "/..", strict=False), dirname(ABSTFN)) + self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/..", strict=True) + self.assertEqual(realpath(ABSTFN + "/subdir", strict=False), ABSTFN + "1/subdir") + self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/subdir", strict=True) + finally: + os_helper.unlink(ABSTFN) + + @os_helper.skip_unless_symlink + @skip_if_ABSTFN_contains_backslash + def test_realpath_nonterminal_symlink_to_symlinks_to_file(self): + try: + with open(ABSTFN + "2", 'w') as f: + f.write('test_posixpath wuz ere') + os.symlink(ABSTFN + "2", ABSTFN + "1") + os.symlink(ABSTFN + "1", ABSTFN) + self.assertEqual(realpath(ABSTFN, strict=False), ABSTFN + "2") + self.assertEqual(realpath(ABSTFN, strict=True), ABSTFN + "2") + self.assertEqual(realpath(ABSTFN + "/", strict=False), ABSTFN + "2") + self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/", strict=True) + self.assertEqual(realpath(ABSTFN + "/.", strict=False), ABSTFN + "2") + self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/.", strict=True) + self.assertEqual(realpath(ABSTFN + "/..", strict=False), dirname(ABSTFN)) + self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/..", strict=True) + self.assertEqual(realpath(ABSTFN + "/subdir", strict=False), ABSTFN + "2/subdir") + self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/subdir", strict=True) + finally: + os_helper.unlink(ABSTFN) + def test_relpath(self): (real_getcwd, os.getcwd) = (os.getcwd, lambda: r"/home/user/bar") try: diff --git a/Misc/NEWS.d/next/Library/2024-06-05-19-09-36.gh-issue-118289.moL9_d.rst b/Misc/NEWS.d/next/Library/2024-06-05-19-09-36.gh-issue-118289.moL9_d.rst new file mode 100644 index 00000000000000..522572e160ba7b --- /dev/null +++ b/Misc/NEWS.d/next/Library/2024-06-05-19-09-36.gh-issue-118289.moL9_d.rst @@ -0,0 +1,2 @@ +:func:`!posixpath.realpath` now raises :exc:`NotADirectoryError` when *strict* +mode is enabled and a non-directory path with a trailing slash is supplied.