We can forge the return value of `snprintf` and overread the stack.
Also we can craft a ROP chain byte by byte using the nonce token.

[writeup](https://ptr-yudai.hatenablog.com/entry/2019/06/03/113943#pwnable-410pts-otp_server)

Original writeup (https://ptr-yudai.hatenablog.com/entry/2019/06/03/113943#pwnable-410pts-otp_server).