Difficulty:

  • Easy (Author)
  • Baby (Specki)

Notes:

  • Many anti-debugging checks. Probably hard to circumvent
  • Ghidra does not like DotNet Binaries by default. Disassembly is practically unusable

Rabbit Holes:

Solution:

  • Decompile in dnSpy
  • Find √¨nitialCheck function that validates args
  • Find hardcoded check comparing input to decryption of encoded constant
  • Copy&Paste decription Routine into seperate program(solve.cs), decrypt encoded constant and print to console
  • Run reme.dll with password from previous step (CanIHazFlag?)
  • WIN

Flag

CSCG{CanIHazFlag?}

Remediation:

  • Do not use two-way encryption for securing secrets --> use one-way and only store hash
  • Do not hardcode passwords inside decryption function