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bpo-39899: os.path.expanduser(): don't guess other Windows users' home directories if the basename of the current user's home directory doesn't match their username. (GH-18841) 

This makes `ntpath.expanduser()` match `pathlib.Path.expanduser()` in this regard, and is more in line with `posixpath.expanduser()`'s cautious approach.

Also remove the near-duplicate implementation of `expanduser()` in pathlib, and by doing so fix a bug where KeyError could be raised when expanding another user's home directory.
This commit is contained in:
Barney Gale 2021-04-07 23:50:13 +01:00 committed by GitHub
parent df5dc1c7a5
commit 3f3d82b848
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7 changed files with 63 additions and 68 deletions
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4
Doc/library/os.path.rst
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@ -175,8 +175,8 @@ the :mod:`glob` module.)
On Windows, :envvar:`USERPROFILE` will be used if set, otherwise a combination
of :envvar:`HOMEPATH` and :envvar:`HOMEDRIVE` will be used. An initial
``~user`` is handled by stripping the last directory component from the created
user path derived above.
``~user`` is handled by checking that the last directory component of the current
user's home directory matches :envvar:`USERNAME`, and replacing it if so.
If the expansion fails or if the path does not begin with a tilde, the path is
returned unchanged.

10
Doc/library/pathlib.rst
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@ -705,7 +705,10 @@ call fails (for example because the path doesn't exist).
.. classmethod:: Path.home()
Return a new path object representing the user's home directory (as
returned by :func:`os.path.expanduser` with ``~`` construct)::
returned by :func:`os.path.expanduser` with ``~`` construct). If the home
directory can't be resolved, :exc:`RuntimeError` is raised.
::
>>> Path.home()
PosixPath('/home/antoine')
@ -773,7 +776,10 @@ call fails (for example because the path doesn't exist).
.. method:: Path.expanduser()
Return a new path with expanded ``~`` and ``~user`` constructs,
as returned by :meth:`os.path.expanduser`::
as returned by :meth:`os.path.expanduser`. If a home directory can't be
resolved, :exc:`RuntimeError` is raised.
::
>>> p = PosixPath('~/films/Monty Python')
>>> p.expanduser()

18
Lib/ntpath.py
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@ -312,12 +312,24 @@ def expanduser(path):
drive = ''
userhome = join(drive, os.environ['HOMEPATH'])
if i != 1: #~user
# Try to guess user home directory. By default all users directories
# are located in the same place and are named by corresponding
# usernames. If current user home directory points to nonstandard
# place, this guess is likely wrong, and so we bail out.
current_user = os.environ.get('USERNAME')
if current_user != basename(userhome):
return path
target_user = path[1:i]
if isinstance(target_user, bytes):
target_user = os.fsdecode(target_user)
if target_user != current_user:
userhome = join(dirname(userhome), target_user)
if isinstance(path, bytes):
userhome = os.fsencode(userhome)
if i != 1: #~user
userhome = join(dirname(userhome), path[1:i])
return userhome + path[i:]

51
Lib/pathlib.py
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@ -246,34 +246,6 @@ class _WindowsFlavour(_Flavour):
# It's a path on a network drive => 'file://host/share/a/b'
return 'file:' + urlquote_from_bytes(path.as_posix().encode('utf-8'))
def gethomedir(self, username):
if 'USERPROFILE' in os.environ:
userhome = os.environ['USERPROFILE']
elif 'HOMEPATH' in os.environ:
try:
drv = os.environ['HOMEDRIVE']
except KeyError:
drv = ''
userhome = drv + os.environ['HOMEPATH']
else:
raise RuntimeError("Can't determine home directory")
if username:
# Try to guess user home directory. By default all users
# directories are located in the same place and are named by
# corresponding usernames. If current user home directory points
# to nonstandard place, this guess is likely wrong.
if os.environ['USERNAME'] != username:
drv, root, parts = self.parse_parts((userhome,))
if parts[-1] != os.environ['USERNAME']:
raise RuntimeError("Can't determine home directory "
"for %r" % username)
parts[-1] = username
if drv or root:
userhome = drv + root + self.join(parts[1:])
else:
userhome = self.join(parts)
return userhome
class _PosixFlavour(_Flavour):
sep = '/'
@ -364,21 +336,6 @@ class _PosixFlavour(_Flavour):
bpath = bytes(path)
return 'file://' + urlquote_from_bytes(bpath)
def gethomedir(self, username):
if not username:
try:
return os.environ['HOME']
except KeyError:
import pwd
return pwd.getpwuid(os.getuid()).pw_dir
else:
import pwd
try:
return pwd.getpwnam(username).pw_dir
except KeyError:
raise RuntimeError("Can't determine home directory "
"for %r" % username)
_windows_flavour = _WindowsFlavour()
_posix_flavour = _PosixFlavour()
@ -463,6 +420,8 @@ class _NormalAccessor(_Accessor):
getcwd = os.getcwd
expanduser = staticmethod(os.path.expanduser)
_normal_accessor = _NormalAccessor()
@ -1105,7 +1064,7 @@ class Path(PurePath):
"""Return a new path pointing to the user's home directory (as
returned by os.path.expanduser('~')).
"""
return cls(cls()._flavour.gethomedir(None))
return cls("~").expanduser()
def samefile(self, other_path):
"""Return whether other_path is the same or not as this file
@ -1517,7 +1476,9 @@ class Path(PurePath):
"""
if (not (self._drv or self._root) and
self._parts and self._parts[0][:1] == '~'):
homedir = self._flavour.gethomedir(self._parts[0][1:])
homedir = self._accessor.expanduser(self._parts[0])
if homedir[:1] == "~":
raise RuntimeError("Could not determine home directory.")
return self._from_parts([homedir] + self._parts[1:])
return self

43
Lib/test/test_ntpath.py
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@ -503,34 +503,47 @@ class TestNtpath(NtpathTestCase):
env.clear()
tester('ntpath.expanduser("~test")', '~test')
env['HOMEPATH'] = 'eric\\idle'
env['HOMEDRIVE'] = 'C:\\'
tester('ntpath.expanduser("~test")', 'C:\\eric\\test')
tester('ntpath.expanduser("~")', 'C:\\eric\\idle')
env['HOMEPATH'] = 'Users\\eric'
env['USERNAME'] = 'eric'
tester('ntpath.expanduser("~test")', 'C:\\Users\\test')
tester('ntpath.expanduser("~")', 'C:\\Users\\eric')
del env['HOMEDRIVE']
tester('ntpath.expanduser("~test")', 'eric\\test')
tester('ntpath.expanduser("~")', 'eric\\idle')
tester('ntpath.expanduser("~test")', 'Users\\test')
tester('ntpath.expanduser("~")', 'Users\\eric')
env.clear()
env['USERPROFILE'] = 'C:\\eric\\idle'
tester('ntpath.expanduser("~test")', 'C:\\eric\\test')
tester('ntpath.expanduser("~")', 'C:\\eric\\idle')
env['USERPROFILE'] = 'C:\\Users\\eric'
env['USERNAME'] = 'eric'
tester('ntpath.expanduser("~test")', 'C:\\Users\\test')
tester('ntpath.expanduser("~")', 'C:\\Users\\eric')
tester('ntpath.expanduser("~test\\foo\\bar")',
'C:\\eric\\test\\foo\\bar')
'C:\\Users\\test\\foo\\bar')
tester('ntpath.expanduser("~test/foo/bar")',
'C:\\eric\\test/foo/bar')
'C:\\Users\\test/foo/bar')
tester('ntpath.expanduser("~\\foo\\bar")',
'C:\\eric\\idle\\foo\\bar')
'C:\\Users\\eric\\foo\\bar')
tester('ntpath.expanduser("~/foo/bar")',
'C:\\eric\\idle/foo/bar')
'C:\\Users\\eric/foo/bar')
# bpo-36264: ignore `HOME` when set on windows
env.clear()
env['HOME'] = 'F:\\'
env['USERPROFILE'] = 'C:\\eric\\idle'
tester('ntpath.expanduser("~test")', 'C:\\eric\\test')
tester('ntpath.expanduser("~")', 'C:\\eric\\idle')
env['USERPROFILE'] = 'C:\\Users\\eric'
env['USERNAME'] = 'eric'
tester('ntpath.expanduser("~test")', 'C:\\Users\\test')
tester('ntpath.expanduser("~")', 'C:\\Users\\eric')
# bpo-39899: don't guess another user's home directory if
# `%USERNAME% != basename(%USERPROFILE%)`
env.clear()
env['USERPROFILE'] = 'C:\\Users\\eric'
env['USERNAME'] = 'idle'
tester('ntpath.expanduser("~test")', '~test')
tester('ntpath.expanduser("~")', 'C:\\Users\\eric')
@unittest.skipUnless(nt, "abspath requires 'nt' module")
def test_abspath(self):

2
Lib/test/test_pathlib.py
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@ -2609,7 +2609,7 @@ class WindowsPathTest(_BasePathTest, unittest.TestCase):
env.pop('USERNAME', None)
self.assertEqual(p1.expanduser(),
P('C:/Users/alice/My Documents'))
self.assertRaises(KeyError, p2.expanduser)
self.assertRaises(RuntimeError, p2.expanduser)
env['USERNAME'] = 'alice'
self.assertEqual(p2.expanduser(),
P('C:/Users/alice/My Documents'))

3
Misc/NEWS.d/next/Library/2020-03-09-20-36-07.bpo-39899.9adF3E.rst Normal file
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@ -0,0 +1,3 @@
:func:`os.path.expanduser()` now refuses to guess Windows home directories if the basename of current user's home directory does not match their username.
:meth:`pathlib.Path.expanduser()` and :meth:`~pathlib.Path.home()` now consistently raise :exc:`RuntimeError` exception when a home directory cannot be resolved. Previously a :exc:`KeyError` exception could be raised on Windows when the ``"USERNAME"`` environment variable was unset.