Hack The Box – Rope

This article contains my writeup on the machine Rope from Hack The Box. I really enjoyed the box, since it provides a total of three custom binaries, which are supposed to be exploited 🙂

The article is divided into the following parts:

User
    – Initial Recon
    – httpserver
    – Leak Memory Address
    – Exploit Format String Vulnerability
    – Escalating from john to r4j (readlogs)

Root
    – Local Recon
    – contact
    – Bruteforce
    – Libc Leak
    – Final Exploit

Continue reading “Hack The Box – Rope”

HACKvent19 writeup

This year’s HACKvent was hosted on the brand new Hacking-Lab 2.0 plattform. Each day from the 1st of december until the 24th a new challenge is published raising in difficulty. The flag format changed from HV18-xxxx-xxxx-xxxx-xxxx-xxxx to HV19{...}. After all I managed to solve all 28 challenges 🙂
Hidden
HV19.H1 Hidden One
HV19.H2 Hidden Two
HV19.H3 Hidden Three
HV19.H4 Hidden Four
Easy
HV19.01 censored
HV19.02 Triangulation
HV19.03 Hodor, Hodor, Hodor
HV19.04 password policy circumvention
HV19.05 Santa Parcel Tracking
HV19.06 bacon and eggs
HV19.07 Santa Rider
Medium
HV19.08 SmileNcryptor 4.0
HV19.09 Santas Quick Response 3.0
HV19.10 Guess what
HV19.11 Frolicsome Santa Jokes API
HV19.12 back to basic
HV19.13 TrieMe
HV19.14 Achtung das Flag
Hard
HV19.15 Santa’s Workshop
HV19.16 B0rked Calculator
HV19.17 Unicode Portal
HV19.18 Dance with me
HV19.19 U+1F385
HV19.20 i want to play a game
HV19.21 Happy Christmas 256
Leet
HV19.22 The command … is lost
HV19.23 Internet Data Archive
HV19.24 ham radio

Continue reading “HACKvent19 writeup”

Google CTF 2019 (Quals) – Quantum Key Distribution

This years online qualification for the Google Capture The Flag finals (ctftime.org) ran from 22/06/2019, 00:01 UTC to 23/06/2019 23:59 UTC.

As last year, there were plenty of diversified challenges, which were worked out very well.

I tried to take at least a look at as much challenges as possible and solved the challenge Quantum Key Distribution, which was relatively easy based on the amounts of solves. Within this article I want to share my writeup on this challenge.

The writeup is divided into the following sections:

Continue reading “Google CTF 2019 (Quals) – Quantum Key Distribution”

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
Continue reading “Hacky Easter 2019 writeup”

VolgaCTF 2019 Qualifier – Blind

The VolgaCTF 2019 Qualifier (ctftime.org) took place from 29/03/2019, 15:00 UTC to 31/03/2019 15:00 UTC.

There has been a really interesting RSA crypto challenge called Blind, which I would like to share with you in this writeup.

The article is divided into the following sections:

Challenge description
What does the script do?
Blind RSA Signature
Retrieving the Flag

Continue reading “VolgaCTF 2019 Qualifier – Blind”

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

Continue reading “nullcon HackIM 2019 – babypwn”

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

Continue reading “Hack The Box – Dab”

HACKvent18 writeup

For the sixth time in a row now hacking-lab.com carried out the annual HACKvent. Each day from the 1st of december until the 24th a new challenge is published. I would have loved to spend more time on it, but time is a rare resource especially on the days before christmas 😉 After all I managed to solve 21 of 24 tasks:

Easy
Day 01: Just Another Bar Code
Day 02: Me
Day 03: Catch me
Day 04: pirating like in the 90ies
Day 05: OSINT 1
Day 06: Mondrian
Day 07: flappy.pl
Medium
Day 08: Advent Snail
Day 09: fake xmass balls
Day 10: >_ Run, Node, Run
Day 11: Crypt-o-Math 3.0
Day 12: SmartWishList
Day 13: flappy’s revenge
Day 14: power in the shell
Hard
Day 15: Watch Me
Day 16: Pay 100 Bitcoins
Day 17: Faster KEy Exchange
Day 18: Be Evil
Day 19: PromoCode
Day 20: I want to play a game
Day 21: muffinCTF (Day 1)
Day 22: muffinCTF (Day 2)
Day 23: muffinCTF (Day 3)
Final
Day 24: Take the red pill, take the blue pill

Continue reading “HACKvent18 writeup”

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

Continue reading “Heap Exploitation: Off-By-One / Poison Null Byte”