Hacky Easter 2019 writeup

As every year hacking-lab.com carried out the annual Hacky Easter event with 27 challenges. As usual the variety of the challenges was awesome. I actually got full score this year 🙂 Many thanks to daubsi, who gave me a nudge once in a while on the last challenges (you can find his writeup here).
Easy
01 Twisted
02 Just Watch
03 Sloppy Encryption
04 Disco 2
05 Call for Papers
06 Dots
07 Shell we Argument
08 Modern Art
09 rorriM rorriM
Medium
10 Stackunderflow
11 Memeory 2.0
12 Decrypt0r
13 Symphony in HEX
14 White Box
15 Seen in Steem
16 Every-Thing
17 New Egg Design
18 Egg Storage
Hard
19 CoUmpact DiAsc
20 Scrambled Egg
21 The Hunt: Misty Jungle
22 The Hunt: Muddy Quagmire
23 The Maze
24 CAPTEG
Hidden
25 Hidden Egg #1
26 Hidden Egg #2
27 Hidden Egg #3
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nullcon HackIM 2019 – babypwn

The nullcon HackIM 2019 CTF (ctftime.org) ran from 01/02/2019, 16:30 UTC to 03/02/2019 04:30 UTC.

I did the pwn challenge babypwn, which was really fun to do. The following article contains my writeup being divided into the following sections:

Challenge description
Security mechanisms and disassembly
Signedness vulnerabilitiy
Format string vulnerabilitiy
Final exploit

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Hack The Box – Dab

This article contains my first writeup on a machine from Hack The Box. If you have not checked out Hack The Box yet, I really suggest you do. Aside from providing classical CTF-style challenges, the plattform hosts plenty of vulnerable machines (boxes), which are supposed to be exploited. The boxes tend to be geared to realistic scenarios and are thus an awesome opportunity to increase your own pen testing skills.

In order to prove the exploitation of a machine, there are two different flag files stored on each machine. The first one to acquire is a file called user.txt, which can be read by a low privileged user. The next step after initially exploiting the machine is to escalate privileges gaining access to an administrative user (root access). With this high privileged user a second file called root.txt can be read. Both files contain a flag (an md5sum), which is supposed to be submitted on the Hack The Box website rewarding you with the corresponding points for this machine.

According to those two steps/files the article is divided into the following sections:

User
    – Port Scan
    – FTP (Port 21)
    – SSH (Port 22)
    – HTTP nginx (Port 80)
    – HTTP nginx (Port 8080)
    – Back to SSH

Root
    – Initial Enumeration
    – SUID binaries
    – myexec
    – libseclogin.so
    – myexec’s password
    – ldconfig
    – Compile own shared Library

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Heap Exploitation: Off-By-One / Poison Null Byte

The goal of this article is to explain in detail how an off-by-one vulnerability on the heap also known as poison null byte can be exploited. Although this technique does not work with the latest libc, I think it can be used very good in order to demonstrate how exploits based on heap-metadata corruption work (also check out shellphish’s how2heap).

In order to do this I created a vulnerable program, which we will use as an example to create such an exploit. If you like to, you can start by analyzing and exploiting the program on your own (at least check out Environment):

–> heap.zip

Though it is not required to the exploit the program, the source-code might be helpful:

–> heap.c

The article is divided into the following sections:

–> Environment
–> Vulnerable Program
–> Heap Basics
–> Libc-Leak
–> Control Instruction Pointer
–> One Gadget
–> Final Exploit

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Hacky Easter 2018 writeup

As every year hacking-lab.com carried out the annual Hacky Easter event with 27 challenges. I could not spend as much time as I would have liked to on solving the challenges, but after all I managed to collect 25 of the 27 eggs and focused on this writeup.
Easy
01 Prison Break
02 Babylon
03 Pony Coder
04 Memeory
05 Sloppy & Paste (mobile)
06 Cooking for Hackers
07 Jigsaw
08 Disco Egg
09 Dial Trial (mobile)
Medium
10 Level Two
11 De Egg you must (not solved)
12 Patience (mobile)
13 Sagittarius…
14 Same same…
15 Manila greetings
16 git cloak –hard
17 Space Invaders
18 Egg Factory
Hard
19 Virtual Hen
20 Artist: No Name Yet (not solved)
21 Hot Dog
22 Block Jane
23 Rapbid Learning
24 ELF
Hidden
25 Hidden Egg #1
26 Hidden Egg #2
27 Hidden Egg #3

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angstromCTF 2018 – writeup hellcode

The angstromCTF 2018 (ctftime.org) ran from 16/03/2018, 20:00 UTC to 23/03/2018 00:00 UTC.

As the description on ctftime.org states, the ctf is primarily geared towards high school students but with a very wide range of challenge difficulty.

There have been a lot of interesting challenges which have been fun to do. I decided to make a writeup for the pwn challenge hellcode.

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