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[3.12] gh-112278: Improve error handling in wmi module and tests (GH-117818) #117899

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Merged
merged 1 commit into from
Apr 15, 2024
Merged

[3.12] gh-112278: Improve error handling in wmi module and tests (GH-117818) #117899

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28 changes: 21 additions & 7 deletions Lib/test/test_wmi.py
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Original file line number Diff line number Diff line change
@@ -1,17 +1,31 @@
# Test the internal _wmi module on Windows
# This is used by the platform module, and potentially others

import time
import unittest
from test.support import import_helper, requires_resource
from test.support import import_helper, requires_resource, LOOPBACK_TIMEOUT


# Do this first so test will be skipped if module doesn't exist
_wmi = import_helper.import_module('_wmi', required_on=['win'])


def wmi_exec_query(query):
# gh-112278: WMI maybe slow response when first call.
try:
return _wmi.exec_query(query)
except BrokenPipeError:
pass
except WindowsError as e:
if e.winerror != 258:
raise
time.sleep(LOOPBACK_TIMEOUT)
return _wmi.exec_query(query)


class WmiTests(unittest.TestCase):
def test_wmi_query_os_version(self):
r = _wmi.exec_query("SELECT Version FROM Win32_OperatingSystem").split("\0")
r = wmi_exec_query("SELECT Version FROM Win32_OperatingSystem").split("\0")
self.assertEqual(1, len(r))
k, eq, v = r[0].partition("=")
self.assertEqual("=", eq, r[0])
Expand All @@ -28,7 +42,7 @@ def test_wmi_query_repeated(self):
def test_wmi_query_error(self):
# Invalid queries fail with OSError
try:
_wmi.exec_query("SELECT InvalidColumnName FROM InvalidTableName")
wmi_exec_query("SELECT InvalidColumnName FROM InvalidTableName")
except OSError as ex:
if ex.winerror & 0xFFFFFFFF == 0x80041010:
# This is the expected error code. All others should fail the test
Expand All @@ -42,19 +56,19 @@ def test_wmi_query_repeated_error(self):
def test_wmi_query_not_select(self):
# Queries other than SELECT are blocked to avoid potential exploits
with self.assertRaises(ValueError):
_wmi.exec_query("not select, just in case someone tries something")
wmi_exec_query("not select, just in case someone tries something")

@requires_resource('cpu')
def test_wmi_query_overflow(self):
# Ensure very big queries fail
# Test multiple times to ensure consistency
for _ in range(2):
with self.assertRaises(OSError):
_wmi.exec_query("SELECT * FROM CIM_DataFile")
wmi_exec_query("SELECT * FROM CIM_DataFile")

def test_wmi_query_multiple_rows(self):
# Multiple instances should have an extra null separator
r = _wmi.exec_query("SELECT ProcessId FROM Win32_Process WHERE ProcessId < 1000")
r = wmi_exec_query("SELECT ProcessId FROM Win32_Process WHERE ProcessId < 1000")
self.assertFalse(r.startswith("\0"), r)
self.assertFalse(r.endswith("\0"), r)
it = iter(r.split("\0"))
Expand All @@ -69,6 +83,6 @@ def test_wmi_query_threads(self):
from concurrent.futures import ThreadPoolExecutor
query = "SELECT ProcessId FROM Win32_Process WHERE ProcessId < 1000"
with ThreadPoolExecutor(4) as pool:
task = [pool.submit(_wmi.exec_query, query) for _ in range(32)]
task = [pool.submit(wmi_exec_query, query) for _ in range(32)]
for t in task:
self.assertRegex(t.result(), "ProcessId=")
91 changes: 73 additions & 18 deletions PC/_wmimodule.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,11 @@
// Version history
// 2022-08: Initial contribution (Steve Dower)

// clinic/_wmimodule.cpp.h uses internal pycore_modsupport.h API
#ifndef Py_BUILD_CORE_BUILTIN
# define Py_BUILD_CORE_MODULE 1
#endif

#define _WIN32_DCOM
#include <Windows.h>
#include <comdef.h>
Expand Down Expand Up @@ -39,6 +44,8 @@ struct _query_data {
LPCWSTR query;
HANDLE writePipe;
HANDLE readPipe;
HANDLE initEvent;
HANDLE connectEvent;
};


Expand Down Expand Up @@ -75,12 +82,18 @@ _query_thread(LPVOID param)
IID_IWbemLocator, (LPVOID *)&locator
);
}
if (SUCCEEDED(hr) && !SetEvent(data->initEvent)) {
hr = HRESULT_FROM_WIN32(GetLastError());
}
if (SUCCEEDED(hr)) {
hr = locator->ConnectServer(
bstr_t(L"ROOT\\CIMV2"),
NULL, NULL, 0, NULL, 0, 0, &services
);
}
if (SUCCEEDED(hr) && !SetEvent(data->connectEvent)) {
hr = HRESULT_FROM_WIN32(GetLastError());
}
if (SUCCEEDED(hr)) {
hr = CoSetProxyBlanket(
services, RPC_C_AUTHN_WINNT, RPC_C_AUTHZ_NONE, NULL,
Expand Down Expand Up @@ -184,6 +197,24 @@ _query_thread(LPVOID param)
}


static DWORD
wait_event(HANDLE event, DWORD timeout)
{
DWORD err = 0;
switch (WaitForSingleObject(event, timeout)) {
case WAIT_OBJECT_0:
break;
case WAIT_TIMEOUT:
err = WAIT_TIMEOUT;
break;
default:
err = GetLastError();
break;
}
return err;
}


/*[clinic input]
_wmi.exec_query

Expand Down Expand Up @@ -226,7 +257,11 @@ _wmi_exec_query_impl(PyObject *module, PyObject *query)

Py_BEGIN_ALLOW_THREADS

if (!CreatePipe(&data.readPipe, &data.writePipe, NULL, 0)) {
data.initEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
data.connectEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
if (!data.initEvent || !data.connectEvent ||
!CreatePipe(&data.readPipe, &data.writePipe, NULL, 0))
{
err = GetLastError();
} else {
hThread = CreateThread(NULL, 0, _query_thread, (LPVOID*)&data, 0, NULL);
Expand All @@ -238,6 +273,19 @@ _wmi_exec_query_impl(PyObject *module, PyObject *query)
}
}

// gh-112278: If current user doesn't have permission to query the WMI, the
// function IWbemLocator::ConnectServer will hang for 5 seconds, and there
// is no way to specify the timeout. So we use an Event object to simulate
// a timeout. The initEvent will be set after COM initialization, it will
// take a longer time when first initialized. The connectEvent will be set
// after connected to WMI.
if (!err) {
err = wait_event(data.initEvent, 1000);
if (!err) {
err = wait_event(data.connectEvent, 100);
}
}

while (!err) {
if (ReadFile(
data.readPipe,
Expand All @@ -259,28 +307,35 @@ _wmi_exec_query_impl(PyObject *module, PyObject *query)
CloseHandle(data.readPipe);
}

// Allow the thread some time to clean up
switch (WaitForSingleObject(hThread, 1000)) {
case WAIT_OBJECT_0:
// Thread ended cleanly
if (!GetExitCodeThread(hThread, (LPDWORD)&err)) {
err = GetLastError();
}
break;
case WAIT_TIMEOUT:
// Probably stuck - there's not much we can do, unfortunately
if (err == 0 || err == ERROR_BROKEN_PIPE) {
err = WAIT_TIMEOUT;
if (hThread) {
// Allow the thread some time to clean up
int thread_err;
switch (WaitForSingleObject(hThread, 100)) {
case WAIT_OBJECT_0:
// Thread ended cleanly
if (!GetExitCodeThread(hThread, (LPDWORD)&thread_err)) {
thread_err = GetLastError();
}
break;
case WAIT_TIMEOUT:
// Probably stuck - there's not much we can do, unfortunately
thread_err = WAIT_TIMEOUT;
break;
default:
thread_err = GetLastError();
break;
}
break;
default:
// An error on our side is more likely to be relevant than one from
// the thread, but if we don't have one on our side we'll take theirs.
if (err == 0 || err == ERROR_BROKEN_PIPE) {
err = GetLastError();
err = thread_err;
}
break;

CloseHandle(hThread);
}

CloseHandle(hThread);
CloseHandle(data.initEvent);
CloseHandle(data.connectEvent);
hThread = NULL;

Py_END_ALLOW_THREADS
Expand Down