AS-REP Roasting
Last updated
Configuring
Prerequisite
Username EnumerationConfiguring
Login on
DC02with the usernameAdministratorand passwordWelcome01!.Open the "Active Directory Users and Computers" administration tool on
DC02.
3. Click on "View" and enable "Advanced Features"
4. Open "Employees", right click the user Richard and click on "Properties"
5. Open "Account" and scroll to the bottom in "Account options", then select "Do not require kerberos preauthentication".
6. Right click on Richard and select "Reset Password". Uncheck "User must change password at next logon" and fill in the password Sample123. Click on "OK"
Attacking
How it works
When pre-authentication is not required, an attack can directly send a request for authentication. The KDC will return an encrypted TGT and the attacker can extract the hash and brute-force it offline.
Tools
Executing the attack
Make sure Impacket is installed and run the GetNPUsers.py tool with the users we enumerated earlier and saved in
users.txt. The tool will check if any of the enumerated users doesn't require pre-authentication and will request a ticket which we can crack offline.
2. The tool doesn't say anything about users that don't require pre-authentication. Check if the outputfile exists and cat it:
3. The user Richard doesn't require pre-authentication and we have an hash from the TGT. Lets crack it with Hashcat and this wordlist. The Hashcat parameters are:
Crackingmode:
-a 0for using a wordlistHashmode:
-m 18200for Kerberos 5, etype 23, AS-REPList with hashes:
asreproastingPassword list:
2020-200_most_used_passwords.txt
4. We successfully cracked the password. The password for Richard is Sample123.
Defending
Recommendations
Periodically check for users that don't require pre-authentication and remove the attribute.
Check for users with the attribute:
Remove the attribute for a single user:
Check for users with the attribute and remove it:
