python · serhiy-storchaka · Dec 14, 2023 · Dec 13, 2023 · Dec 13, 2023 · Dec 13, 2023
diff --git a/Doc/library/os.rst b/Doc/library/os.rst
@@ -2062,6 +2062,7 @@ features:
       Although Windows supports :func:`chmod`, you can only set the file's
       read-only flag with it (via the ``stat.S_IWRITE`` and ``stat.S_IREAD``
       constants or a corresponding integer value).  All other bits are ignored.
+      The default value of *follow_symlinks* on Windows is ``False``.
 
       The function is limited on Emscripten and WASI, see
       :ref:`wasm-availability` for more information.
@@ -2075,6 +2076,9 @@ features:
    .. versionchanged:: 3.6
       Accepts a :term:`path-like object`.
 
+   .. versionchanged:: 3.13
+      Added support for the *follow_symlinks* argument on Windows.
+
 
 .. function:: chown(path, uid, gid, *, dir_fd=None, follow_symlinks=True)
 
@@ -2162,11 +2166,14 @@ features:
 
    .. audit-event:: os.chmod path,mode,dir_fd os.lchmod
 
-   .. availability:: Unix.
+   .. availability:: Unix, Windows.
 
    .. versionchanged:: 3.6
       Accepts a :term:`path-like object`.
 
+   .. versionchanged:: 3.13
+      Added support on Windows.
+
 .. function:: lchown(path, uid, gid)
 
    Change the owner and group id of *path* to the numeric *uid* and *gid*.  This

@@ -261,6 +261,10 @@ os
   CPU resources of a container system without having to modify the container (application code).
   (Contributed by Donghee Na in :gh:`109595`)
 
+* Add support of :func:`os.lchmod` and the *follow_symlinks* argument
+  in :func:`os.chmod` on Windows.
+  (Contributed by Serhiy Storchaka in :gh:`59616`)
+
 pathlib
 -------
 

diff --git a/Lib/os.py b/Lib/os.py
@@ -171,6 +171,7 @@ def _add(str, fn):
     _add("HAVE_FSTATAT",    "stat")
     _add("HAVE_LCHFLAGS",   "chflags")
     _add("HAVE_LCHMOD",     "chmod")
+    _add("MS_WINDOWS",      "chmod")
     if _exists("lchown"): # mac os x10.3
         _add("HAVE_LCHOWN", "chown")
     _add("HAVE_LINKAT",     "link")

diff --git a/Lib/tempfile.py b/Lib/tempfile.py
@@ -273,7 +273,7 @@ def _dont_follow_symlinks(func, path, *args):
     # Pass follow_symlinks=False, unless not supported on this platform.
     if func in _os.supports_follow_symlinks:
         func(path, *args, follow_symlinks=False)
-    elif _os.name == 'nt' or not _os.path.islink(path):
+    elif not _os.path.islink(path):
         func(path, *args)
 
 def _resetperms(path):

diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
@@ -21,8 +21,10 @@
 
 try:
     import posix
+    nt = None
 except ImportError:
-    import nt as posix
+    import nt
+    posix = nt
 
 try:
     import pwd
@@ -935,6 +937,122 @@ def test_utime(self):
         posix.utime(os_helper.TESTFN, (int(now), int(now)))
         posix.utime(os_helper.TESTFN, (now, now))
 
+    def check_chmod(self, chmod_func, target, **kwargs):
+        mode = os.stat(target).st_mode
+        try:
+            new_mode = mode & ~(stat.S_IWOTH | stat.S_IWGRP | stat.S_IWUSR)
+            chmod_func(target, new_mode, **kwargs)
+            self.assertEqual(os.stat(target).st_mode, new_mode)
+            if stat.S_ISREG(mode):
+                try:
+                    with open(target, 'wb+'):
+                        pass
+                except PermissionError:
+                    pass
+            new_mode = mode | (stat.S_IWOTH | stat.S_IWGRP | stat.S_IWUSR)
+            chmod_func(target, new_mode, **kwargs)
+            self.assertEqual(os.stat(target).st_mode, new_mode)
+            if stat.S_ISREG(mode):
+                with open(target, 'wb+'):
+                    pass
+        finally:
+            posix.chmod(target, mode)
+
+    def test_chmod_file(self):
+        self.check_chmod(posix.chmod, os_helper.TESTFN)
+
+    def tempdir(self):
+        target = os_helper.TESTFN + 'd'
+        posix.mkdir(target)
+        self.addCleanup(posix.rmdir, target)
+        return target
+
+    def test_chmod_dir(self):
+        target = self.tempdir()
+        self.check_chmod(posix.chmod, target)
+
+    @unittest.skipUnless(hasattr(posix, 'lchmod'), 'test needs os.lchmod()')
+    def test_lchmod_file(self):
+        self.check_chmod(posix.lchmod, os_helper.TESTFN)
+        self.check_chmod(posix.chmod, os_helper.TESTFN, follow_symlinks=False)
+
+    @unittest.skipUnless(hasattr(posix, 'lchmod'), 'test needs os.lchmod()')
+    def test_lchmod_dir(self):
+        target = self.tempdir()
+        self.check_chmod(posix.lchmod, target)
+        self.check_chmod(posix.chmod, target, follow_symlinks=False)
+
+    def check_chmod_link(self, chmod_func, target, link, **kwargs):
+        target_mode = os.stat(target).st_mode
+        link_mode = os.lstat(link).st_mode
+        try:
+            new_mode = target_mode & ~(stat.S_IWOTH | stat.S_IWGRP | stat.S_IWUSR)
+            chmod_func(link, new_mode, **kwargs)
+            self.assertEqual(os.stat(target).st_mode, new_mode)
+            self.assertEqual(os.lstat(link).st_mode, link_mode)
+            new_mode = target_mode | (stat.S_IWOTH | stat.S_IWGRP | stat.S_IWUSR)
+            chmod_func(link, new_mode, **kwargs)
+            self.assertEqual(os.stat(target).st_mode, new_mode)
+            self.assertEqual(os.lstat(link).st_mode, link_mode)
+        finally:
+            posix.chmod(target, target_mode)
+
+    def check_lchmod_link(self, chmod_func, target, link, **kwargs):
+        target_mode = os.stat(target).st_mode
+        link_mode = os.lstat(link).st_mode
+        new_mode = link_mode & ~(stat.S_IWOTH | stat.S_IWGRP | stat.S_IWUSR)
+        chmod_func(link, new_mode, **kwargs)
+        self.assertEqual(os.stat(target).st_mode, target_mode)
+        self.assertEqual(os.lstat(link).st_mode, new_mode)
+        new_mode = link_mode | (stat.S_IWOTH | stat.S_IWGRP | stat.S_IWUSR)
+        chmod_func(link, new_mode, **kwargs)
+        self.assertEqual(os.stat(target).st_mode, target_mode)
+        self.assertEqual(os.lstat(link).st_mode, new_mode)
+
+    @os_helper.skip_unless_symlink
+    def test_chmod_file_symlink(self):
+        target = os_helper.TESTFN
+        link = os_helper.TESTFN + '-link'
+        os.symlink(target, link)
+        self.addCleanup(posix.unlink, link)
+        if os.name == 'nt':
+            self.check_lchmod_link(posix.chmod, target, link)
+        else:
+            self.check_chmod_link(posix.chmod, target, link)
+        self.check_chmod_link(posix.chmod, target, link, follow_symlinks=True)
+
+    @os_helper.skip_unless_symlink
+    def test_chmod_dir_symlink(self):
+        target = self.tempdir()
+        link = os_helper.TESTFN + '-link'
+        os.symlink(target, link, target_is_directory=True)
+        self.addCleanup(posix.unlink, link)
+        if os.name == 'nt':
+            self.check_lchmod_link(posix.chmod, target, link)
+        else:
+            self.check_chmod_link(posix.chmod, target, link)
+        self.check_chmod_link(posix.chmod, target, link, follow_symlinks=True)
+
+    @unittest.skipUnless(hasattr(posix, 'lchmod'), 'test needs os.lchmod()')
+    @os_helper.skip_unless_symlink
+    def test_lchmod_file_symlink(self):
+        target = os_helper.TESTFN
+        link = os_helper.TESTFN + '-link'
+        os.symlink(target, link)
+        self.addCleanup(posix.unlink, link)
+        self.check_lchmod_link(posix.chmod, target, link, follow_symlinks=False)
+        self.check_lchmod_link(posix.lchmod, target, link)
+
+    @unittest.skipUnless(hasattr(posix, 'lchmod'), 'test needs os.lchmod()')
+    @os_helper.skip_unless_symlink
+    def test_lchmod_dir_symlink(self):
+        target = self.tempdir()
+        link = os_helper.TESTFN + '-link'
+        os.symlink(target, link)
+        self.addCleanup(posix.unlink, link)
+        self.check_lchmod_link(posix.chmod, target, link, follow_symlinks=False)
+        self.check_lchmod_link(posix.lchmod, target, link)
+
     def _test_chflags_regular_file(self, chflags_func, target_file, **kwargs):
         st = os.stat(target_file)
         self.assertTrue(hasattr(st, 'st_flags'))

diff --git a/Lib/test/test_shutil.py b/Lib/test/test_shutil.py
@@ -1132,10 +1132,11 @@ def test_copymode_symlink_to_symlink(self):
         os.lchmod(src_link, stat.S_IRWXO|stat.S_IRWXG)
         # link to link
         os.lchmod(dst_link, stat.S_IRWXO)
+        old_mode = os.stat(dst).st_mode
         shutil.copymode(src_link, dst_link, follow_symlinks=False)
         self.assertEqual(os.lstat(src_link).st_mode,
                          os.lstat(dst_link).st_mode)
-        self.assertNotEqual(os.stat(src).st_mode, os.stat(dst).st_mode)
+        self.assertEqual(os.stat(dst).st_mode, old_mode)
         # src link - use chmod
         os.lchmod(dst_link, stat.S_IRWXO)
         shutil.copymode(src_link, dst, follow_symlinks=False)

diff --git a/Misc/NEWS.d/next/Library/2023-12-13-17-08-21.gh-issue-59616.JNlWSs.rst b/Misc/NEWS.d/next/Library/2023-12-13-17-08-21.gh-issue-59616.JNlWSs.rst
@@ -0,0 +1,2 @@
+Add support of :func:`os.lchmod` and the *follow_symlinks* argument in
+:func:`os.chmod` on Windows.
diff --git a/Modules/clinic/posixmodule.c.h b/Modules/clinic/posixmodule.c.h
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
@@ -3309,6 +3309,27 @@ os_fchdir_impl(PyObject *module, int fd)
 }
 #endif /* HAVE_FCHDIR */
 
+#ifdef MS_WINDOWS
+# define CHMOD_DEFAULT_FOLLOW_SYMLINKS 0
+#else
+# define CHMOD_DEFAULT_FOLLOW_SYMLINKS 1
+#endif
+
+#ifdef MS_WINDOWS
+static int
+win32_lchmod(LPCWSTR path, int mode)
+{
+    DWORD attr = GetFileAttributesW(path);
+    if (attr == INVALID_FILE_ATTRIBUTES) {
+        return 0;
+    }
+    if (mode & _S_IWRITE)
+        attr &= ~FILE_ATTRIBUTE_READONLY;
+    else
+        attr |= FILE_ATTRIBUTE_READONLY;
+    return SetFileAttributesW(path, attr);
+}
+#endif
 
 /*[clinic input]
 os.chmod
@@ -3331,7 +3352,8 @@ os.chmod
         and path should be relative; path will then be relative to that
         directory.
 
-    follow_symlinks: bool = True
+    follow_symlinks: bool(c_default="CHMOD_DEFAULT_FOLLOW_SYMLINKS", \
+                          py_default="(os.name != 'nt')") = CHMOD_DEFAULT_FOLLOW_SYMLINKS
         If False, and the last element of the path is a symbolic link,
         chmod will modify the symbolic link itself instead of the file
         the link points to.
@@ -3348,20 +3370,16 @@ dir_fd and follow_symlinks may not be implemented on your platform.
 static PyObject *
 os_chmod_impl(PyObject *module, path_t *path, int mode, int dir_fd,
               int follow_symlinks)
-/*[clinic end generated code: output=5cf6a94915cc7bff input=674a14bc998de09d]*/
+/*[clinic end generated code: output=5cf6a94915cc7bff input=fcf115d174b9f3d8]*/
 {
     int result;
 
-#ifdef MS_WINDOWS
-    DWORD attr;
-#endif
-
 #ifdef HAVE_FCHMODAT
     int fchmodat_nofollow_unsupported = 0;
     int fchmodat_unsupported = 0;
 #endif
 
-#if !(defined(HAVE_FCHMODAT) || defined(HAVE_LCHMOD))
+#if !(defined(HAVE_FCHMODAT) || defined(HAVE_LCHMOD) || defined(MS_WINDOWS))
     if (follow_symlinks_specified("chmod", follow_symlinks))
         return NULL;
 #endif
@@ -3372,19 +3390,34 @@ os_chmod_impl(PyObject *module, path_t *path, int mode, int dir_fd,
     }
 
 #ifdef MS_WINDOWS
+    result = 0;
     Py_BEGIN_ALLOW_THREADS
-    attr = GetFileAttributesW(path->wide);
-    if (attr == INVALID_FILE_ATTRIBUTES)
-        result = 0;
+    if (follow_symlinks) {
+        HANDLE hfile;
+        FILE_BASIC_INFO info;
+
+        hfile = CreateFileW(path->wide,
+                            FILE_READ_ATTRIBUTES|FILE_WRITE_ATTRIBUTES,
+                            0, NULL,
+                            OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL);
+        if (hfile != INVALID_HANDLE_VALUE) {
+            if (GetFileInformationByHandleEx(hfile, FileBasicInfo,
+                                             &info, sizeof(info)))
+            {
+                if (mode & _S_IWRITE)
+                    info.FileAttributes &= ~FILE_ATTRIBUTE_READONLY;
+                else
+                    info.FileAttributes |= FILE_ATTRIBUTE_READONLY;
+                result = SetFileInformationByHandle(hfile, FileBasicInfo,
+                                                    &info, sizeof(info));
+            }
+            CloseHandle(hfile);
+        }
+    }
     else {
-        if (mode & _S_IWRITE)
-            attr &= ~FILE_ATTRIBUTE_READONLY;
-        else
-            attr |= FILE_ATTRIBUTE_READONLY;
-        result = SetFileAttributesW(path->wide, attr);
+        result = win32_lchmod(path->wide, mode);
     }
     Py_END_ALLOW_THREADS
-
     if (!result) {
         return path_error(path);
     }
@@ -3514,7 +3547,7 @@ os_fchmod_impl(PyObject *module, int fd, int mode)
 #endif /* HAVE_FCHMOD */
 
 
-#ifdef HAVE_LCHMOD
+#if defined(HAVE_LCHMOD) || defined(MS_WINDOWS)
 /*[clinic input]
 os.lchmod
 
@@ -3535,16 +3568,26 @@ os_lchmod_impl(PyObject *module, path_t *path, int mode)
     if (PySys_Audit("os.chmod", "Oii", path->object, mode, -1) < 0) {
         return NULL;
     }
+#ifdef MS_WINDOWS
+    Py_BEGIN_ALLOW_THREADS
+    res = win32_lchmod(path->wide, mode);
+    Py_END_ALLOW_THREADS
+    if (!res) {
+        path_error(path);
+        return NULL;
+    }
+#else /* MS_WINDOWS */
     Py_BEGIN_ALLOW_THREADS
     res = lchmod(path->narrow, mode);
     Py_END_ALLOW_THREADS
     if (res < 0) {
         path_error(path);
         return NULL;
     }
+#endif /* MS_WINDOWS */
     Py_RETURN_NONE;
 }
-#endif /* HAVE_LCHMOD */
+#endif /* HAVE_LCHMOD || MS_WINDOWS */
 
 
 #ifdef HAVE_CHFLAGS
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Add support of :func:`os.lchmod` and the follow_symlinks argument in
		:func:`os.chmod` on Windows.