mirror of https://github.com/python/cpython
bpo-31512: Add non-elevated symlink support for Windows (GH-3652)
This commit is contained in:
Vidar Tonaas Fauske
Steve Dower
parent
8709490f48
commit
0e10766574
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@ -2699,19 +2699,15 @@ features:
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as a directory if *target_is_directory* is ``True`` or a file symlink (the
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default) otherwise. On non-Windows platforms, *target_is_directory* is ignored.
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Symbolic link support was introduced in Windows 6.0 (Vista). :func:`symlink`
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will raise a :exc:`NotImplementedError` on Windows versions earlier than 6.0.
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This function can support :ref:`paths relative to directory descriptors
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<dir_fd>`.
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.. note::
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On Windows, the *SeCreateSymbolicLinkPrivilege* is required in order to
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successfully create symlinks. This privilege is not typically granted to
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regular users but is available to accounts which can escalate privileges
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to the administrator level. Either obtaining the privilege or running your
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application as an administrator are ways to successfully create symlinks.
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On newer versions of Windows 10, unprivileged accounts can create symlinks
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if Developer Mode is enabled. When Developer Mode is not available/enabled,
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the *SeCreateSymbolicLinkPrivilege* privilege is required, or the process
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must be run as an administrator.
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:exc:`OSError` is raised when the function is called by an unprivileged
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@ -2729,6 +2725,9 @@ features:
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object` for *src* and *dst*.
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.. versionchanged:: 3.8
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Added support for unelevated symlinks on Windows with Developer Mode.
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.. function:: sync()
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@ -0,0 +1,2 @@
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With the Windows 10 Creators Update, non-elevated users can now create
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symlinks as long as the computer has Developer Mode enabled.
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@ -284,10 +284,7 @@ extern char *ctermid_r(char *);
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#include <windows.h>
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#include <shellapi.h> /* for ShellExecute() */
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#include <lmcons.h> /* for UNLEN */
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#ifdef SE_CREATE_SYMBOLIC_LINK_NAME /* Available starting with Vista */
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#define HAVE_SYMLINK
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static int win32_can_symlink = 0;
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#endif
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#endif /* _MSC_VER */
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#ifndef MAXPATHLEN
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@ -7755,26 +7752,6 @@ os_readlink_impl(PyObject *module, path_t *path, int dir_fd)
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#if defined(MS_WINDOWS)
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/* Grab CreateSymbolicLinkW dynamically from kernel32 */
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static BOOLEAN (CALLBACK *Py_CreateSymbolicLinkW)(LPCWSTR, LPCWSTR, DWORD) = NULL;
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static int
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check_CreateSymbolicLink(void)
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{
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HINSTANCE hKernel32;
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/* only recheck */
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if (Py_CreateSymbolicLinkW)
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return 1;
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Py_BEGIN_ALLOW_THREADS
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hKernel32 = GetModuleHandleW(L"KERNEL32");
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*(FARPROC*)&Py_CreateSymbolicLinkW = GetProcAddress(hKernel32,
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"CreateSymbolicLinkW");
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Py_END_ALLOW_THREADS
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return Py_CreateSymbolicLinkW != NULL;
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}
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/* Remove the last portion of the path - return 0 on success */
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static int
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_dirnameW(WCHAR *path)
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@ -7878,33 +7855,57 @@ os_symlink_impl(PyObject *module, path_t *src, path_t *dst,
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{
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#ifdef MS_WINDOWS
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DWORD result;
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DWORD flags = 0;
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/* Assumed true, set to false if detected to not be available. */
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static int windows_has_symlink_unprivileged_flag = TRUE;
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#else
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int result;
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#endif
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#ifdef MS_WINDOWS
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if (!check_CreateSymbolicLink()) {
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PyErr_SetString(PyExc_NotImplementedError,
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"CreateSymbolicLink functions not found");
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return NULL;
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}
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if (!win32_can_symlink) {
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PyErr_SetString(PyExc_OSError, "symbolic link privilege not held");
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return NULL;
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}
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#endif
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#ifdef MS_WINDOWS
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if (windows_has_symlink_unprivileged_flag) {
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/* Allow non-admin symlinks if system allows it. */
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flags |= SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE;
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}
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Py_BEGIN_ALLOW_THREADS
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_Py_BEGIN_SUPPRESS_IPH
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/* if src is a directory, ensure target_is_directory==1 */
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target_is_directory |= _check_dirW(src->wide, dst->wide);
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result = Py_CreateSymbolicLinkW(dst->wide, src->wide,
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target_is_directory);
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/* if src is a directory, ensure flags==1 (target_is_directory bit) */
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if (target_is_directory || _check_dirW(src->wide, dst->wide)) {
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flags |= SYMBOLIC_LINK_FLAG_DIRECTORY;
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}
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result = CreateSymbolicLinkW(dst->wide, src->wide, flags);
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_Py_END_SUPPRESS_IPH
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Py_END_ALLOW_THREADS
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if (windows_has_symlink_unprivileged_flag && !result &&
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ERROR_INVALID_PARAMETER == GetLastError()) {
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Py_BEGIN_ALLOW_THREADS
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_Py_BEGIN_SUPPRESS_IPH
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/* This error might be caused by
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SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE not being supported.
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Try again, and update windows_has_symlink_unprivileged_flag if we
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are successful this time.
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NOTE: There is a risk of a race condition here if there are other
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conditions than the flag causing ERROR_INVALID_PARAMETER, and
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another process (or thread) changes that condition in between our
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calls to CreateSymbolicLink.
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*/
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flags &= ~(SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE);
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result = CreateSymbolicLinkW(dst->wide, src->wide, flags);
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_Py_END_SUPPRESS_IPH
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Py_END_ALLOW_THREADS
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if (result || ERROR_INVALID_PARAMETER != GetLastError()) {
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windows_has_symlink_unprivileged_flag = FALSE;
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}
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}
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if (!result)
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return path_error2(src, dst);
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@ -13469,35 +13470,6 @@ static PyMethodDef posix_methods[] = {
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{NULL, NULL} /* Sentinel */
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};
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#if defined(HAVE_SYMLINK) && defined(MS_WINDOWS)
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static int
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enable_symlink()
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{
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HANDLE tok;
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TOKEN_PRIVILEGES tok_priv;
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LUID luid;
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if (!OpenProcessToken(GetCurrentProcess(), TOKEN_ALL_ACCESS, &tok))
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return 0;
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if (!LookupPrivilegeValue(NULL, SE_CREATE_SYMBOLIC_LINK_NAME, &luid))
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return 0;
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tok_priv.PrivilegeCount = 1;
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tok_priv.Privileges[0].Luid = luid;
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tok_priv.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
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if (!AdjustTokenPrivileges(tok, FALSE, &tok_priv,
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sizeof(TOKEN_PRIVILEGES),
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(PTOKEN_PRIVILEGES) NULL, (PDWORD) NULL))
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return 0;
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/* ERROR_NOT_ALL_ASSIGNED returned when the privilege can't be assigned. */
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return GetLastError() == ERROR_NOT_ALL_ASSIGNED ? 0 : 1;
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}
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#endif /* defined(HAVE_SYMLINK) && defined(MS_WINDOWS) */
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static int
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all_ins(PyObject *m)
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{
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@ -14105,10 +14077,6 @@ INITFUNC(void)
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PyObject *list;
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const char * const *trace;
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#if defined(HAVE_SYMLINK) && defined(MS_WINDOWS)
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win32_can_symlink = enable_symlink();
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#endif
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m = PyModule_Create(&posixmodule);
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if (m == NULL)
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return NULL;
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@ -45,6 +45,11 @@ typedef struct {
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FIELD_OFFSET(_Py_REPARSE_DATA_BUFFER, GenericReparseBuffer)
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#define _Py_MAXIMUM_REPARSE_DATA_BUFFER_SIZE ( 16 * 1024 )
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// Defined in WinBase.h in 'recent' versions of Windows 10 SDK
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#ifndef SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE
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#define SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE 0x2
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#endif
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#ifdef __cplusplus
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}
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#endif
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