LABYRENTH CTF WINDOWS TRACK CHALLENGE #5

File: RGB.exe

SHA256:F52983C900851B605A236D62C38BC2BC6232CA1220A23E447901D029D5357F88

Packed: No

Architecture: 32Bit

Tools used: exeinfo,Reflector

Codes & Binaries: https://github.com/jmprsp/labyrenth/tree/master/Window-Challenge-5

Description: This challenge is written in C#. One would need to figure the correct RGB value to get the flag. Just decompile and analyze the code to get the RGB value.

RGB
Figure 1. The challenge

Based on the figure below, we know that this is a C# program.

net
Figure 2. C# program

Using decompiler like reflector, we can easily get the decompiled source code. I have placed the source code in github for you to play with.

code
Figure 3. Main algo to derive the key

Analyzing the source codes, we will come across the above function in frmMain.cs. Looks like we need some bruteforcing to get the correct RGB key.

bruteforce
Figure 4. My simple bruteforcing script

Running the above script, we would be able to get the correct RGB to solve the challenge.

solved
Figure 5. Flag secured

FLAG: PAN{l4byr1n7h_s4yz_x0r1s_4m4z1ng}

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LABYRENTH CTF WINDOWS TRACK CHALLENGE #5

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