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/*
* SPDX-License-Identifier: ISC
*
* Copyright (c) 2019-2020 Robert Manner <robert.manner@oneidentity.com>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/*
* This is an open source non-commercial project. Dear PVS-Studio, please check it.
* PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
*/
#include "sudo_python_module.h"
#include "sudo_util.h"
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
static int
_verify_import(const char *file_path)
{
debug_decl(_verify_import, PYTHON_DEBUG_INTERNAL);
// Check mode and owner similar to what we do in open_sudoers().
// This is to help avoid loading a potentially insecure module.
struct stat sb;
if (stat(file_path, &sb) != 0) {
PyErr_Format(PyExc_ImportError, "Failed to stat file '%s'", file_path);
debug_return_int(SUDO_RC_ERROR);
}
if (sb.st_uid != ROOT_UID) {
PyErr_Format(PyExc_ImportError, "File '%s' must be owned by uid %d", file_path, ROOT_UID);
debug_return_int(SUDO_RC_ERROR);
}
if ((sb.st_mode & (S_IWGRP|S_IWOTH)) != 0) {
PyErr_Format(PyExc_ImportError, "File '%s' must be only be writable by owner", file_path);
debug_return_int(SUDO_RC_ERROR);
}
debug_return_int(SUDO_RC_OK);
}
static PyObject *
_sudo_ImportBlocker__Init(PyObject *py_self, PyObject *py_args)
{
debug_decl(_sudo_ImportBlocker__Init, PYTHON_DEBUG_C_CALLS);
py_debug_python_call("ImportBlocker", "__init__", py_args, NULL, PYTHON_DEBUG_C_CALLS);
PyObject *py_meta_path = NULL;
if (!PyArg_UnpackTuple(py_args, "sudo.ImportBlocker.__init__", 2, 2, &py_self, &py_meta_path))
goto cleanup;
if (PyObject_SetAttrString(py_self, "meta_path", py_meta_path) != 0)
goto cleanup;
cleanup:
if (PyErr_Occurred())
debug_return_ptr(NULL);
debug_return_ptr_pynone;
}
static PyObject *
_sudo_ImportBlocker__find_module(PyObject *py_self, PyObject *py_args)
{
debug_decl(_sudo_ImportBlocker__find_module, PYTHON_DEBUG_C_CALLS);
PyObject *py_fullname = NULL, *py_path = NULL, *py_meta_path = NULL,
*py_meta_path_iterator = NULL, *py_finder = NULL,
*py_importer = NULL, *py_import_path = NULL;
py_debug_python_call("ImportBlocker", "find_module", py_args, NULL, PYTHON_DEBUG_C_CALLS);
if (!PyArg_UnpackTuple(py_args, "sudo.ImportBlocker.find_module", 2, 3, &py_self, &py_fullname, &py_path))
goto cleanup;
py_meta_path = PyObject_GetAttrString(py_self, "meta_path");
if (py_meta_path == NULL)
goto cleanup;
py_meta_path_iterator = PyObject_GetIter(py_meta_path);
if (py_meta_path_iterator == NULL)
goto cleanup;
while ((py_finder = PyIter_Next(py_meta_path_iterator)) != NULL) {
py_importer = PyObject_CallMethod(py_finder, "find_module", "(OO)",
py_fullname, py_path);
if (py_importer == NULL) {
goto cleanup;
}
if (py_importer != Py_None) { // the import could be resolved
if (PyObject_HasAttrString(py_importer, "get_filename")) {
// there is a file associated with the import (.py, .so, etc)
py_import_path = PyObject_CallMethod(py_importer, "get_filename", "");
const char *import_path = PyUnicode_AsUTF8(py_import_path);
sudo_debug_printf(SUDO_DEBUG_DIAG, "ImportBlocker: verifying permissions "
"on file '%s'\n", import_path);
if (_verify_import(import_path) != SUDO_RC_OK)
goto cleanup;
Py_CLEAR(py_import_path);
} else {
sudo_debug_printf(SUDO_DEBUG_DIAG, "ImportBlocker: internal module import '%s'\n",
PyUnicode_AsUTF8(py_fullname));
}
goto cleanup;
}
Py_CLEAR(py_importer);
Py_CLEAR(py_finder);
}
Py_CLEAR(py_importer);
py_importer = Py_None;
Py_INCREF(py_importer);
cleanup:
Py_CLEAR(py_meta_path_iterator);
Py_CLEAR(py_meta_path);
Py_CLEAR(py_finder);
Py_CLEAR(py_import_path);
if (PyErr_Occurred()) {
Py_CLEAR(py_importer);
debug_return_ptr(NULL);
}
debug_return_ptr(py_importer);
}
static PyMethodDef _sudo_ImportBlocker_class_methods[] =
{
{"__init__", _sudo_ImportBlocker__Init, METH_VARARGS, ""},
{"find_module", _sudo_ImportBlocker__find_module, METH_VARARGS, ""},
{NULL, NULL, 0, NULL}
};
// This possibly can be replaced with PySys_AddAuditHook for python >= 3.8
//
// This function is equivalent of the python call:
// sys.meta_path = [sudo.ImportBlocker(sys.meta_path)]
int
sudo_module_register_importblocker(void)
{
debug_decl(sudo_module_register_importblocker, PYTHON_DEBUG_C_CALLS);
int rc = SUDO_RC_ERROR;
PyObject *py_meta_path = NULL, *py_import_blocker_cls = NULL,
*py_import_blocker = NULL;
py_meta_path = PySys_GetObject("meta_path"); // note: borrowed reference
if (py_meta_path == NULL) {
PyErr_Format(sudo_exc_SudoException, "'sys.meta_path' is not available. "
"Unable to register import blocker hook which is meant to "
"verify that no such module get loaded by the sudo python plugins"
"which are writable by others than root.");
goto cleanup;
}
Py_INCREF(py_meta_path);
py_import_blocker_cls = sudo_module_create_class("sudo.ImportBlocker", _sudo_ImportBlocker_class_methods, NULL);
if (py_import_blocker_cls == NULL)
goto cleanup;
// call the constructor
py_import_blocker = PyObject_CallFunctionObjArgs(py_import_blocker_cls, py_meta_path, NULL);
if (py_import_blocker == NULL)
goto cleanup;
Py_DECREF(py_meta_path);
py_meta_path = PyList_New(1);
if (py_meta_path == NULL)
goto cleanup;
if (PyList_SetItem(py_meta_path, 0, py_import_blocker) != 0)
goto cleanup;
py_import_blocker = NULL; // list has stolen it
if (PySys_SetObject("meta_path", py_meta_path) != 0) {
goto cleanup;
}
rc = SUDO_RC_OK;
cleanup:
Py_CLEAR(py_meta_path);
Py_CLEAR(py_import_blocker);
Py_CLEAR(py_import_blocker_cls);
debug_return_int(rc);
}
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