This binary uses stack cookies to prevent exploitation, but all hope is not lost. Read the flag from flag.txt anyways! The binary can be found at /home/what_the_flag/ on the shell server. You can solve this problem interactively here. The source can be found here.

hint:How can you enter a correct password, but still overflow the buffer? Think about what terminates gets(). Also, the file name that you want to open is already in the binary!

https://picoctf.com/problem-static/binary/WhatTheFlag/what_the_flag.html