TryHackMe-Empline

In this post , I will be sharing my writeup for THM Empline room , which was a medium difficulty machine , This machine had ssh ,mysql and web server running ,the foothold was related to finding a subdomain on which a vulnerable version of opencats was running , which we can exploit using XXE through which we were able to perform LFI (Local File Inclusion). With that we were able to read config.php which had credentials for mysql and we logged in to retrieve user hash , after cracking the hash we were able to ssh into the machine . For privilege escalation we found that ruby had capability set on it which allowed us to change ownership of any file folder.

NMAP

22/tcp open  ssh     syn-ack ttl 63 OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey:
| 2048 c0:d5:41:ee:a4:d0:83:0c:97:0d:75:cc:7b:10:7f:76 (RSA)
| ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDR9CEnxhm89ZCC+SGhOpO28srSTnL5lQtnqd4NaT7hTT6N1NrRZQ5DoB6cBI+YlaqYe3I4Ud3y7RF3ESms8L21hbpQus2UYxbWOl+/s3muDp
Zww1nvI5k9oJguQaLG1EroU8tee7yhPID0+285jbk5AZY72pc7NLOMLvFDijArOhj9kIcsPLVTaxzQ6Di+xwXYdiKO0F3Y7GgMMSszIeigvZEDhNnNW0Z1puMYbtTgmvJH6LpzMSEC+32iNRGlvb
jebE9Ehh+tGiOuHKXT1uexrt7gbkjp3lJteV5034a7G1t/Vi3JJoj9tMV/CrvgeDDncbT5NNaSA6/ynLLENqSP
| 256 83:82:f9:69:19:7d:0d:5c:53:65:d5:54:f6:45:db:74 (ECDSA)
| ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBFhf+BTt0YGudpgOROEuqs4YuIhT1ve23uvZkHhN9lYSpK9WcHI2K5IXIi+XgPeSk/VIQLsRUA
0kOqbsuoxN+u0=
| 256 4f:91:3e:8b:69:69:09:70:0e:82:26:28:5c:84:71:c9 (ED25519)
|_ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIDkr5yXgnawt7un+3Tf0TJ+sZTrbVIY0TDbitiu2eHpf
80/tcp open http syn-ack ttl 63 Apache httpd 2.4.29 ((Ubuntu))
| http-methods:
|_ Supported Methods: HEAD GET POST OPTIONS
|_http-server-header: Apache/2.4.29 (Ubuntu)
|_http-title: Empline
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
3306/tcp open mysql syn-ack ttl 63 MySQL 5.5.5-10.1.48-MariaDB-0ubuntu0.18.04.1
| mysql-info:
| Protocol: 10
| Version: 5.5.5-10.1.48-MariaDB-0ubuntu0.18.04.1
| Thread ID: 85
| Capabilities flags: 63487
| Some Capabilities: ConnectWithDatabase, IgnoreSpaceBeforeParenthesis, IgnoreSigpipes, Speaks41ProtocolNew, SupportsTransactions, ODBCClient, Spe
aks41ProtocolOld, Support41Auth, FoundRows, DontAllowDatabaseTableColumn, LongColumnFlag, LongPassword, SupportsLoadDataLocal, InteractiveClient, Su
pportsCompression, SupportsAuthPlugins, SupportsMultipleResults, SupportsMultipleStatments
| Status: Autocommit
| Salt: 3[Qe)7{&IzMS7Y9RnVB*
|_ Auth Plugin Name: mysql_native_password
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

PORT 80 (HTTP)

On the web server we can see a page which looks like a static html template , so running gobuster on the site for fuzzing for files

But this didn’t find much files , but looking at the source code we found a subdomain

So let’s add this to /etc/hosts file

This brings us to a page where it says opencats

We can search for exploits available if any

And we found a XXE exploit which would allows us to perform Local File Inclusion (LFI), for the exploit to work we need to install python-docx and then we can run the exploit to see if we can read passwd file

Trying to fuzz for files on subdomain

I didn’t find any php files so adding them with -x I found config.php

We can now use the same exploit by supplying config.php file to read

After connecting to database since the port was open we can get user creds

Putting those hashes on crackstation we can get george's password

Privilege Escalation

We can check for sudo -l and see if we have permissions to run anything as root

Next we can check for crontabs if there's a script running in a background

We see nothing in crontabs as well , we can look for SUID binaries

No interesting SUID’s here that we can utilize , so next thing to check is for linux capabilities and what capabilities in linux are that things that the root user can do his permissions are broken down into some permissions like changing setting suid or changing ownership of folders

Here we can see ruby has those capabilities set and can change ownership of the directories with chown

Following the documentation of ruby we can look for changing ownership of files/folders

And we see that root’s directory is now owned by george , we can add ssh public key in authorized_keys file and see if we can get ssh session as root user but it won't work because in sshd_config file it's configured to not allow root to login through ssh

Now there are so many ways here we can change ownership of /etc/ and either allow root to login through ssh (but that would require ssh to restart), add a new root user entry in /etc/shadow or edit sudoers file

We need to now revert the file permissions as it needs to be owned by root user

References

BS CS undergraduate | CTF Player