Codehead's Corner
Random ramblings on hacking, coding, fighting with infrastructure and general tech
Posted: 9 Nov 2017 by Codehead
7 minute read

After completing the video lectures of the Security Tube Linux 64 bit Assembler Expert course (SLAE64), a series of assessments must be completed to gain certification. This is the forth assignment; create a custom encoder/decoder to disguise a shellcode payload.

Many security and threat monitoring tools rely on signature matching to identify bad code. A good way to avoid signature based detection is to obscure the content of a payload with encryption or encoding. The same payload can be repeatedly disguised with different obfuscation schemes. Creating a new encoding method is much simpler than building a new payload.

For the assignment, we will design a simple encoding scheme, create an encoding script to disguise our shellcode and write a decoder stub which we will deploy with the payload to rebuild the original code on the fly.


Categories: SLAE64 Assembler Shellcode
Posted: 8 Oct 2017 by Codehead
2 minute read

A pretty simple crypto challenge, but the technique is applicable to more complex problems.

Challenge

The smart home system has the function of remote monitoring of what is happening in the home and every few minutes sends pictures of the surveillance cameras to the owner of the house. You successfully intercepted the network traffic of this system, however, its creators took care of the security of their users data and encrypted the pictures. Decrypt the provided image and you will find the flag.

SECRET_ENCRYPTED.PNG


Categories: Hacking CTF
Posted: 20 Sep 2017 by Codehead
3 minute read

I was expecting a keygen or licence key cracking based on the title of this challenge, so revisiting some old protocols that I haven’t used in anger for ages was a nice surprise. The challenge blurb was pretty minimal:

Challenge

Serial

nc misc.chal.csaw.io 4239


Categories: Hacking CTF
Posted: 5 Sep 2016 by Codehead
2 minute read

I almost missed the Tokyo Westerns CTF. I stumbled across the event on the last day and wasn’t able to spend too long on it. I managed a few of challenges, mainly the PPC category. However, I wanted to write up the ‘Glance’ image manipulation challenge for future reference.

Challenge

I saw this through a gap of the door on a train.


Categories: Hacking CTF
Posted: 21 Aug 2016 by Codehead
12 minute read

The LabyREnth competition ran from 15th July to 14th Aug. I only managed to find time to do the first Windows challenge. It was a tricky one and I was only able to work at it in fits and starts, often with days or weeks between sessions. However, I learnt quite a few handy new things while working on it, so I’m writing this as a reference for myself and as an example of the dead-ends and rabbit holes of the analysis process for those who are interested.


Categories: Hacking CTF
Posted: 17 Apr 2016 by Codehead
2 minute read

Challenge:

Welcome to Vertinet.

This problem follows the same specifications as the previous Verticode problem, except that you have to solve many of them by developing a client to communicate with the server available at problems1.2016q1.sctf.io:50000. Good luck.


Categories: Hacking CTF
Posted: 17 Apr 2016 by Codehead
3 minute read

This was a nice little challenge from sCTF 2016. I’m trying to work on more tricky stuff, but this one looked like fun and I couldn’t resist.

Challenge:

Welcome to Verticode, the new method of translating text into vertical codes.


Categories: Hacking CTF
Posted: 27 Mar 2016 by Codehead
7 minute read

I only managed one task in the 2016 VolgaCTF, but it was a fun one. Coding a tic tac toe bot.

Challenge:

Tic-Tac-Toe

An important step towards the strong AI is the ability of an artificial agent to solve a well-defined problem. 
A project by the name 'tic-tac-toe' was one of such test problems. It's still up...

nc tic-tac-toe.2016.volgactf.ru 45679

Categories: Hacking CTF
Posted: 21 Feb 2016 by Codehead
3 minute read

Challenge:

File Checker (rev60)

Description:

My friend sent me this file. He told that if I manage to reverse it, I’ll have access to all his devices. My misfortune that I don’t know anything about reversing :/


Categories: Hacking CTF
Posted: 21 Feb 2016 by Codehead
2 minute read

Challenge:

FlagStore (exp70)

Description:

Here’s the ultimate flag store. Store and retrieve your flags whenever you want.


Categories: Hacking CTF
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