Wei's

PicoCTF - Safe Opener

26 Sep 2022 picoCTF 

Challenge

Tags

PicoCTF 2022 / Reverse Engineering

Description

Can you open this safe?
I forgot the key to my safe but this program is supposed to help me with retrieving the lost key. Can you help me unlock my safe?
Put the password you recover into the picoCTF flag format like:
picoCTF{password}

Writeup

  1. Download the progrem SafeOpener.java. There is a method named openSafe used to check if password correct. String encodedkey is password which was transferd to byte array and encode.
  2. We can derive the password by decoding string encodedkey. Add four lines to openSafe method.
  3. Execute the program. Here’s flag! picoCTF{pl3as3_l3t_m3_1nt0_th3_saf3} ٩(^ᴗ^)۶

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