7MS #640: Tales of Pentest Pwnage – Part 63

7 Minute Security

This was my favorite pentest tale of pwnage to date! There’s a lot to cover in this episode so I’m going to try and bullet out the TLDR version here:

• Sprinkled farmer files around the environment
• Found high-priv boxes with WebClient enabled
• Added “ghost” machine to the Active Directory (we’ll call it GHOSTY)
• RBCD attack to be able to impersonate a domain admin using the CIFS/SMB service against the victim system where some higher-priv users were sitting
• Use net.py to add myself to local admin on the victim host
• Find a vulnerable service to hijack and have run an evil, TGT-gathering Rubeus.exe – found that Credential Guard was cramping my style!
• Pulled the TGT from a host not protected with Credential Guard
• Figured out the stolen user’s account has some “write” privileges to a domain controller
• Use rbcd.py to delegate from GHOSTY and to the domain controller
• Request a TGT for GHOSTY
• Use getST.py to impersonate CIFS using a domain admin account on the domain controller (important thing here was to specify the DC by its FQDN, not just hostname)
• Final move: use the domain admin ccache file to leverage net.py and add myself to the Active Directory Administrators group