pythongh-118486: Support mkdir(mode=0o700) on Windows

Author: zooba

Doc/library/os.rst

@@ -2430,6 +2430,10 @@ 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
    <dir_fd>`.
 
@@ -2444,6 +2448,9 @@ features:
    .. versionchanged:: 3.6
       Accepts a :term:`path-like object`.
 
+   .. versionchanged:: 3.13
+      Windows now handles a *mode* of ``0o700``.
+
 
 .. function:: makedirs(name, mode=0o777, exist_ok=False)
 

Lib/test/test_tempfile.py

@@ -13,6 +13,7 @@
 import weakref
 import gc
 import shutil
+import subprocess
 from unittest import mock
 
 import unittest
@@ -803,6 +804,33 @@ 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.removeprefix(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

Misc/NEWS.d/next/Windows/2024-05-01-20-57-09.gh-issue-118486.K44KJG.rst

@@ -0,0 +1,2 @@
+:func:`os.mkdir` now accepts *mode* of ``0o700`` to restrict the new
+directory to the current user.

Modules/posixmodule.c

@@ -37,6 +37,8 @@
 #  include <winioctl.h>
 #  include <lmcons.h>             // UNLEN
 #  include "osdefs.h"             // SEP
+#  include <aclapi.h>             // SetEntriesInAcl
+#  include <sddl.h>               // SDDL_REVISION_1
 #  if defined(MS_WINDOWS_DESKTOP) || defined(MS_WINDOWS_SYSTEM)
 #    define HAVE_SYMLINK
 #  endif /* MS_WINDOWS_DESKTOP | MS_WINDOWS_SYSTEM */
@@ -5539,6 +5541,133 @@ os__path_normpath_impl(PyObject *module, PyObject *path)
     return result;
 }
 
+#ifdef MS_WINDOWS
+
+/* We centralise SECURITY_ATTRIBUTE initialization based around
+templates that will probably mostly match common POSIX mode settings.
+The _Py_SECURITY_ATTRIBUTE_DATA structure contains temporary data, as
+a constructed SECURITY_ATTRIBUTE structure typically refers to memory
+that has to be alive while it's being used.
+
+Typical use will look like:
+    SECURITY_ATTRIBUTES *pSecAttr = NULL;
+    struct _Py_SECURITY_ATTRIBUTE_DATA secAttrData;
+    int error, error2;
+
+    Py_BEGIN_ALLOW_THREADS
+    switch (mode) {
+    case 0x1C0: // 0o700
+        error = initializeMkdir700SecurityAttributes(&pSecAttr, &secAttrData);
+        break;
+    ...
+    default:
+        error = initializeDefaultSecurityAttributes(&pSecAttr, &secAttrData);
+        break;
+    }
+
+    if (!error) {
+        // do operation, passing pSecAttr
+    }
+
+    // Unconditionally clear secAttrData.
+    error2 = clearSecurityAttributes(&pSecAttr, &secAttrData);
+    if (!error) {
+        error = error2;
+    }
+    Py_END_ALLOW_THREADS
+
+    if (error) {
+      PyErr_SetFromWindowsErr(error);
+      return NULL;
+    }
+*/
+
+struct _Py_SECURITY_ATTRIBUTE_DATA {
+    SECURITY_ATTRIBUTES securityAttributes;
+    PACL acl;
+    SECURITY_DESCRIPTOR sd;
+    EXPLICIT_ACCESS_W ea[4];
+};
+
+static int
+initializeDefaultSecurityAttributes(
+    PSECURITY_ATTRIBUTES *securityAttributes,
+    struct _Py_SECURITY_ATTRIBUTE_DATA *data
+) {
+    assert(securityAttributes);
+    assert(data);
+    *securityAttributes = NULL;
+    memset(data, 0, sizeof(*data));
+    return 0;
+}
+
+static int
+initializeMkdir700SecurityAttributes(
+    PSECURITY_ATTRIBUTES *securityAttributes,
+    struct _Py_SECURITY_ATTRIBUTE_DATA *data
+) {
+    assert(securityAttributes);
+    assert(data);
+    *securityAttributes = NULL;
+    memset(data, 0, sizeof(*data));
+
+    if (!InitializeSecurityDescriptor(&data->sd, SECURITY_DESCRIPTOR_REVISION)
+        || !SetSecurityDescriptorGroup(&data->sd, NULL, TRUE)) {
+        return GetLastError();
+    }
+
+    data->securityAttributes.nLength = sizeof(SECURITY_ATTRIBUTES);
+    data->ea[0].grfAccessPermissions = GENERIC_ALL;
+    data->ea[0].grfAccessMode = SET_ACCESS;
+    data->ea[0].grfInheritance = SUB_CONTAINERS_AND_OBJECTS_INHERIT;
+    data->ea[0].Trustee.TrusteeForm = TRUSTEE_IS_NAME;
+    data->ea[0].Trustee.TrusteeType = TRUSTEE_IS_ALIAS;
+    data->ea[0].Trustee.ptstrName = L"CURRENT_USER";
+
+    data->ea[1].grfAccessPermissions = GENERIC_ALL;
+    data->ea[1].grfAccessMode = SET_ACCESS;
+    data->ea[1].grfInheritance = SUB_CONTAINERS_AND_OBJECTS_INHERIT;
+    data->ea[1].Trustee.TrusteeForm = TRUSTEE_IS_NAME;
+    data->ea[1].Trustee.TrusteeType = TRUSTEE_IS_ALIAS;
+    data->ea[1].Trustee.ptstrName = L"SYSTEM";
+
+    data->ea[2].grfAccessPermissions = GENERIC_ALL;
+    data->ea[2].grfAccessMode = SET_ACCESS;
+    data->ea[2].grfInheritance = SUB_CONTAINERS_AND_OBJECTS_INHERIT;
+    data->ea[2].Trustee.TrusteeForm = TRUSTEE_IS_NAME;
+    data->ea[2].Trustee.TrusteeType = TRUSTEE_IS_ALIAS;
+    data->ea[2].Trustee.ptstrName = L"ADMINISTRATORS";
+
+    int r = SetEntriesInAclW(3, data->ea, NULL, &data->acl);
+    if (r) {
+        return r;
+    }
+    if (!SetSecurityDescriptorDacl(&data->sd, TRUE, data->acl, FALSE)) {
+        return GetLastError();
+    }
+    data->securityAttributes.lpSecurityDescriptor = &data->sd;
+    *securityAttributes = &data->securityAttributes;
+    return 0;
+}
+
+static int
+clearSecurityAttributes(
+    PSECURITY_ATTRIBUTES *securityAttributes,
+    struct _Py_SECURITY_ATTRIBUTE_DATA *data
+) {
+    assert(securityAttributes);
+    assert(data);
+    *securityAttributes = NULL;
+    if (data->acl) {
+        if (LocalFree((void *)data->acl)) {
+            return GetLastError();
+        }
+    }
+    return 0;
+}
+
+#endif
+
 /*[clinic input]
 os.mkdir
 
@@ -5568,6 +5697,12 @@ os_mkdir_impl(PyObject *module, path_t *path, int mode, int dir_fd)
 /*[clinic end generated code: output=a70446903abe821f input=a61722e1576fab03]*/
 {
     int result;
+#ifdef MS_WINDOWS
+    int error = 0;
+    int pathError = 0;
+    SECURITY_ATTRIBUTES *pSecAttr = NULL;
+    struct _Py_SECURITY_ATTRIBUTE_DATA secAttrData;
+#endif
 #ifdef HAVE_MKDIRAT
     int mkdirat_unavailable = 0;
 #endif
@@ -5579,11 +5714,30 @@ 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);
+    switch (mode) {
+    case 0x1C0: // 0o700
+        error = initializeMkdir700SecurityAttributes(&pSecAttr, &secAttrData);
+        break;
+    default:
+        error = initializeDefaultSecurityAttributes(&pSecAttr, &secAttrData);
+        break;
+    }
+    if (!error) {
+        result = CreateDirectoryW(path->wide, pSecAttr);
+        error = clearSecurityAttributes(&pSecAttr, &secAttrData);
+    } else {
+        // Ignore errors - we have a more interesting one already
+        clearSecurityAttributes(&pSecAttr, &secAttrData);
+    }
     Py_END_ALLOW_THREADS
 
-    if (!result)
+    if (error) {
+        PyErr_SetFromWindowsErr(error);
+        return NULL;
+    }
+    if (!result) {
         return path_error(path);
+    }
 #else
     Py_BEGIN_ALLOW_THREADS
 #if HAVE_MKDIRAT