Handy-Shellcode | picoCTF 2019 | Done By Ishara Abeythissa
done by Ishara Abeythissa
Hey everyone welcome to the latest picoCTF 2019 challenges in this year started at September 27. And still having very very competitive situation inside the arena. So I started doing challenges here and i found pretty cool challenge called handy-shellcode. first of first Let’s see whats going on :)
As you can see they provide us vulnerable binary file and source code of it. So let’s download it and review the code.
First of first I refer main function and inside the main function you can see developer create buff array with char type and after the first argument the buff variable send to the vuln function with stored user input. if you read my previous articles related to buffer overflow gets and puts functions allow to buffer overflow inside the memory. so now all are cleared. now we need to find shellcode to give as input.
shellcode — \x31\xc0\x50\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x89\xc1\x89\xc2\xb0\x0b\xcd\x80\x31\xc0\x40\xcd\x80
you can use this shell-code and print it with python :).
according to above image shell code successfully execute inside the vuln application. now we need to execute this inside the pico shell. let’s create python payload for this.
you can take this script in below link
Now let’s run the script :)
hope you enjoy. keep in touch for more than amazing challenges will be soon. Happy Hacking :)