Windows Credential Guard with MSLSA

[Seshan Parameswaran]

I am not looking to get the TGT Session Key but rather achieve the same functionality that AllowTGTSessionKey would with credential cache stored in MSLSA, that is obtain TGT and Service Tickets, in a Linux environment, with MSLSA fronting Credential Guard that the LSA APIs would be interacting with to retrieve the TGT and service tickets.  The scenario in a gist is as follows in Linux environment


  1.  When the credential cache is stored in MSLSA, we can set the LSA Kerberos parameter AllowTgtSessionKey and use MIT library to retrieve the TGT.
  2.  With Windows Credential Guard,  it is not possible to enable sharing the TGT session keys with applications using the AllowTgtSessionKey as it is maintained and managed by Windows Credential Guard.  However with Windows MIT Library it seems to be possible to invoke innate API calls as you have mentioned to obtain the TGT.  When it comes to Linux, I am not aware of any such API or patch for that matter, that when used would work seamlessly with Windows Credential Guard.  I am looking for this specific information.
From: Srinivas Cheruku <srinivas.cheruku at gmail.com>
Date: Sunday, June 26, 2022 at 10:32 PM
To: Sam Hartman <hartmans at debian.org>, Seshan Parameswaran <seshan.parameswaran at oracle.com>, krbdev at mit.edu <krbdev at mit.edu>
Subject: [External] : Re: Windows Credential Guard with MSLSA
Yes, when using MS LSA APIs (CyberSafe implementation) and retrieving tickets we don’t need to set AllowTgtSessionKey registry as MS LSA APIs are able to get the tgt and service tickets for you and the code don’t need to know the session keys.

We even tested with Credential Guard (some months back) running and MS LSA APIs were able to get tickets without any issues on Windows.

Can I know why you want get the TGT session key when using MS LSA APIs?

I haven’t use MS LSA library for Linux and so I am not very sure on this.

Thanks,
Srini


From: krbdev <krbdev-bounces at mit.edu> on behalf of Sam Hartman <hartmans at debian.org>
Date: Friday, 24 June 2022 at 20:28
To: Seshan Parameswaran <seshan.parameswaran at oracle.com>, krbdev at mit.edu <krbdev at mit.edu>
Subject: Re: Windows Credential Guard with MSLSA

It used to be the case that the MSLSA cache would work reasonably well
without TGT keys available.
Namely, if you retrieved a ticket the cache would ask the LSA to get the
ticket for you,.
Does this no longer work?
If this does work, does it meet your needs?
If not, what functionality are you missing?
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