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Tag: delegation

A Case Study in Wagging the Dog: Computer Takeover

Last month, Elad Shamir released a phenomenal, in depth post on abusing resource-based constrained delegation (RBCD) in Active Directory. One of the big points he discusses is that if the TrustedToAuthForDelegation UserAccountControl flag is not set, the S4U2self process will still work but the resulting TGS is not FORWARDABLE. This resulting service ticket will fail for traditional constrained delegation, but will still work in the S4U2proxy process for resource-based constrained delegation. Does the first paragraph sound like Greek? Check out these resources so it makes it bit more sense: Matan Hart’s BlackHat Asia 2017 “Delegate to the Top” talk and…

The Most Dangerous User Right You (Probably) Have Never Heard Of

I find Windows user rights pretty interesting. Separate from machine/domain object DACLs, user rights govern things like “by what method can specific users log into a particular system” and are managed under User Rights Assignment in Group Policy. Sidenote: I recently integrated privilege enumeration into PowerUp in the Get-ProcessTokenPrivilege function, with -Special returning ‘privileged’ privileges. SeEnableDelegationPrivilege One user right I overlooked, until Ben Campbell’s post on constrained delegation, was SeEnableDelegationPrivilege. This right governs whether a user account can “Enable computer and user accounts to be trusted for delegation.” Part of the reason I overlooked it is stated right in the…

S4U2Pwnage

[Edit 9/29/18] For a better weaponization of constrained delegation abuse, check out the “s4u” section of the From Kekeo to Rubeus post. Several weeks ago my workmate Lee Christensen (who helped develop this post and material) and I spent some time diving into Active Directory’s S4U2Self and S4U2Proxy protocol extensions. Then, just recently, Benjamin Delpy and Ben Campbell had an interesting public conversation about the same topic on Twitter. This culminated with Benjamin releasing a modification to Kekeo that allows for easy abuse of S4U misconfigurations. As I was writing this, Ben also published an excellent post on this very topic, which…