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PasswordGuesser

by 9uantum / ckc9759

Rating: 4.0

PasswordGuesser THCON 2024

Challenge

password-guesser

Understanding the challenge

  • The description suggests that there is a secret hidden in the source code of the password-guesser and secret is given when we give password.
  • There is also a file password-guesser.elf
  • Maybe we have to decompile it to get the secret.
  • Assuming it is written in python lets move forward.

Solution

  • To decompile ELF file written in python there is a tool pyinstxtractor so lets decompile it using this tool. decompiler-output dcompiled
  • Decompiled folder contains many files but we are interested in password-guesser.pyc because it is the main file and it contains the secret.
  • It is a compiled python file so we have to decompile it also.
  • It can be decompiled using tool 'uncompyle6'. flag
  • In the reveal function f1-f13 arranged in ascending order is the base64 encoded flag.
f1 = "Zm"
f2 = "xh"
f3 = "Zz1U"
f4 = "SEN"
f5 = "PTntz"
f6 = "b01V"
f7 = "Q0h"
f8 = "fNF90a"
f9 = "DNf"
f10 = "RklM"
f11 = "RV9z"
f12 = "aVozf"
f13 = "Q=="
  • base64 encoded flag
ZmxhZz1USENPTntzb01VQ0hfNF90aDNfRklMRV9zaVozfQ==
  • base64 decoded
flag=THCON{soMUCH_4_th3_FILE_siZ3}

flag : THCON{soMUCH_4_th3_FILE_siZ3}

Original writeup (https://github.com/2-quantum/THCON-2k24/blob/main/passwordguesser/passwordguesser.md).

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