From 91e3669e01245185569d09e9e6e11641282971ee Mon Sep 17 00:00:00 2001 From: Steve Dower Date: Fri, 24 May 2024 18:27:13 +0100 Subject: [PATCH] [3.8] gh-118486: Support mkdir(mode=0o700) on Windows (GH-118488) (GH-118742) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Co-authored-by: Łukasz Langa --- Doc/library/os.rst | 7 +++ Doc/whatsnew/3.8.rst | 16 +++++++ Lib/test/test_os.py | 12 +++++ Lib/test/test_tempfile.py | 28 ++++++++++++ ...-05-01-20-57-09.gh-issue-118486.K44KJG.rst | 4 ++ Modules/posixmodule.c | 44 +++++++++++++++++-- 6 files changed, 108 insertions(+), 3 deletions(-) create mode 100644 Misc/NEWS.d/next/Security/2024-05-01-20-57-09.gh-issue-118486.K44KJG.rst diff --git a/Doc/library/os.rst b/Doc/library/os.rst index d0a37a8bbdbf05..736a59a9216b6f 100644 --- a/Doc/library/os.rst +++ b/Doc/library/os.rst @@ -1909,6 +1909,10 @@ features: platform-dependent. On some platforms, they are ignored and you should call :func:`chmod` explicitly to set them. + On Windows, a *mode* of ``0o700`` is specifically handled to apply access + control to the new directory such that only the current user and + administrators have access. Other values of *mode* are ignored. + This function can also support :ref:`paths relative to directory descriptors `. @@ -1923,6 +1927,9 @@ features: .. versionchanged:: 3.6 Accepts a :term:`path-like object`. + .. versionchanged:: 3.8.20 + Windows now handles a *mode* of ``0o700``. + .. function:: makedirs(name, mode=0o777, exist_ok=False) diff --git a/Doc/whatsnew/3.8.rst b/Doc/whatsnew/3.8.rst index de4dd856877543..4cd581a189147e 100644 --- a/Doc/whatsnew/3.8.rst +++ b/Doc/whatsnew/3.8.rst @@ -1046,6 +1046,13 @@ treat junctions as links. (Contributed by Steve Dower in :issue:`37834`.) +As of 3.8.20, :func:`os.mkdir` and :func:`os.makedirs` on Windows now support +passing a *mode* value of ``0o700`` to apply access control to the new +directory. This implicitly affects :func:`tempfile.mkdtemp` and is a +mitigation for CVE-2024-4030. Other values for *mode* continue to be +ignored. +(Contributed by Steve Dower in :gh:`118486`.) + os.path ------- @@ -1252,6 +1259,15 @@ in a standardized and extensible format, and offers several other benefits. (Contributed by C.A.M. Gerlach in :issue:`36268`.) +tempfile +-------- + +As of 3.8.20 on Windows, the default mode ``0o700`` used by +:func:`tempfile.mkdtemp` now limits access to the new directory due to +changes to :func:`os.mkdir`. This is a mitigation for CVE-2024-4030. +(Contributed by Steve Dower in :gh:`118486`.) + + threading --------- diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py index 5302b1ce575d4e..84f78c222982a8 100644 --- a/Lib/test/test_os.py +++ b/Lib/test/test_os.py @@ -1380,6 +1380,18 @@ def test_exist_ok_existing_regular_file(self): self.assertRaises(OSError, os.makedirs, path, exist_ok=True) os.remove(path) + @unittest.skipUnless(os.name == 'nt', "requires Windows") + def test_win32_mkdir_700(self): + base = support.TESTFN + path = os.path.abspath(os.path.join(support.TESTFN, 'dir')) + os.mkdir(path, mode=0o700) + out = subprocess.check_output(["cacls.exe", path, "/s"], encoding="oem") + os.rmdir(path) + self.assertEqual( + out.strip(), + f'{path} "D:P(A;OICI;FA;;;SY)(A;OICI;FA;;;BA)(A;OICI;FA;;;OW)"', + ) + def tearDown(self): path = os.path.join(support.TESTFN, 'dir1', 'dir2', 'dir3', 'dir4', 'dir5', 'dir6') diff --git a/Lib/test/test_tempfile.py b/Lib/test/test_tempfile.py index 8cb36f38a2a35c..c1fdcea04bb935 100644 --- a/Lib/test/test_tempfile.py +++ b/Lib/test/test_tempfile.py @@ -11,6 +11,7 @@ import contextlib import stat import weakref +import subprocess from unittest import mock import unittest @@ -760,6 +761,33 @@ def test_mode(self): finally: os.rmdir(dir) + @unittest.skipUnless(os.name == "nt", "Only on Windows.") + def test_mode_win32(self): + # Use icacls.exe to extract the users with some level of access + # Main thing we are testing is that the BUILTIN\Users group has + # no access. The exact ACL is going to vary based on which user + # is running the test. + dir = self.do_create() + try: + out = subprocess.check_output(["icacls.exe", dir], encoding="oem").casefold() + finally: + os.rmdir(dir) + + dir = dir.casefold() + users = set() + found_user = False + for line in out.strip().splitlines(): + acl = None + # First line of result includes our directory + if line.startswith(dir): + acl = line[len(dir):].strip() + elif line and line[:1].isspace(): + acl = line.strip() + if acl: + users.add(acl.partition(":")[0]) + + self.assertNotIn(r"BUILTIN\Users".casefold(), users) + def test_collision_with_existing_file(self): # mkdtemp tries another name when a file with # the chosen name already exists diff --git a/Misc/NEWS.d/next/Security/2024-05-01-20-57-09.gh-issue-118486.K44KJG.rst b/Misc/NEWS.d/next/Security/2024-05-01-20-57-09.gh-issue-118486.K44KJG.rst new file mode 100644 index 00000000000000..a28a4e5cdb6991 --- /dev/null +++ b/Misc/NEWS.d/next/Security/2024-05-01-20-57-09.gh-issue-118486.K44KJG.rst @@ -0,0 +1,4 @@ +:func:`os.mkdir` on Windows now accepts *mode* of ``0o700`` to restrict +the new directory to the current user. This fixes CVE-2024-4030 +affecting :func:`tempfile.mkdtemp` in scenarios where the base temporary +directory is more permissive than the default. diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c index d7edabe5da08d1..2ec8458cb51bfb 100644 --- a/Modules/posixmodule.c +++ b/Modules/posixmodule.c @@ -40,6 +40,12 @@ #include "pycore_pystate.h" /* _PyRuntime */ #include "pythread.h" #include "structmember.h" + +#ifdef MS_WINDOWS +# include // SetEntriesInAcl +# include // SDDL_REVISION_1 +#endif + #ifndef MS_WINDOWS # include "posixmodule.h" #else @@ -4122,7 +4128,6 @@ os__path_splitroot_impl(PyObject *module, path_t *path) #endif /* MS_WINDOWS */ - /*[clinic input] os.mkdir @@ -4151,6 +4156,12 @@ os_mkdir_impl(PyObject *module, path_t *path, int mode, int dir_fd) /*[clinic end generated code: output=a70446903abe821f input=e965f68377e9b1ce]*/ { int result; +#ifdef MS_WINDOWS + int error = 0; + int pathError = 0; + SECURITY_ATTRIBUTES secAttr = { sizeof(secAttr) }; + SECURITY_ATTRIBUTES *pSecAttr = NULL; +#endif if (PySys_Audit("os.mkdir", "Oii", path->object, mode, dir_fd == DEFAULT_DIR_FD ? -1 : dir_fd) < 0) { @@ -4159,11 +4170,38 @@ os_mkdir_impl(PyObject *module, path_t *path, int mode, int dir_fd) #ifdef MS_WINDOWS Py_BEGIN_ALLOW_THREADS - result = CreateDirectoryW(path->wide, NULL); + if (mode == 0700 /* 0o700 */) { + ULONG sdSize; + pSecAttr = &secAttr; + // Set a discretionary ACL (D) that is protected (P) and includes + // inheritable (OICI) entries that allow (A) full control (FA) to + // SYSTEM (SY), Administrators (BA), and the owner (OW). + if (!ConvertStringSecurityDescriptorToSecurityDescriptorW( + L"D:P(A;OICI;FA;;;SY)(A;OICI;FA;;;BA)(A;OICI;FA;;;OW)", + SDDL_REVISION_1, + &secAttr.lpSecurityDescriptor, + &sdSize + )) { + error = GetLastError(); + } + } + if (!error) { + result = CreateDirectoryW(path->wide, pSecAttr); + if (secAttr.lpSecurityDescriptor && + // uncommonly, LocalFree returns non-zero on error, but still uses + // GetLastError() to see what the error code is + LocalFree(secAttr.lpSecurityDescriptor)) { + error = GetLastError(); + } + } Py_END_ALLOW_THREADS - if (!result) + if (error) { + return PyErr_SetFromWindowsErr(error); + } + if (!result) { return path_error(path); + } #else Py_BEGIN_ALLOW_THREADS #if HAVE_MKDIRAT