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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.
This commit is contained in:
Barney Gale 2024-11-13 22:59:32 +00:00 committed by GitHub
parent c695e37a3f
commit fd4b5453df
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GPG Key ID: B5690EEEBB952194
3 changed files with 75 additions and 4 deletions
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18
Lib/posixpath.py
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@ -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

59
Lib/test/test_posixpath.py
View File

@ -695,6 +695,65 @@ class PosixPathTest(unittest.TestCase):
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:

2
Misc/NEWS.d/next/Library/2024-06-05-19-09-36.gh-issue-118289.moL9_d.rst Normal file
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@ -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.