gh-59616: Support os.chmod(follow_symlinks=True) and os.lchmod() on Windows (GH-113049)

1 files changed, 65 insertions, 18 deletions

diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index ddbb4cd..b464a28 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -3309,6 +3309,29 @@ 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 +3354,8 @@ 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 +3372,16 @@ 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 +3392,36 @@ 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));
+            }
+            (void)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 +3551,7 @@ 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
 
@@ -3535,6 +3572,15 @@ 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
@@ -3542,9 +3588,10 @@ os_lchmod_impl(PyObject *module, path_t *path, int mode)
         path_error(path);
         return NULL;
     }
+#endif /* MS_WINDOWS */
     Py_RETURN_NONE;
 }
-#endif /* HAVE_LCHMOD */
+#endif /* HAVE_LCHMOD || MS_WINDOWS */
 
 
 #ifdef HAVE_CHFLAGS