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Does libcurl support Kerberos constrained delegation?

From: Sachin Nikumbh <>
Date: Sun, 8 Jul 2018 22:25:08 -0400


I am looking at libcurl’s support on Kerberos delegation.

The only thing I found is CURLOPT_GSSAPI_DELEGATION added in 7.22.0.

However, there are several issues with this option:

   1. Looks like this option is for the original Kerberos v5 delegation
   (unconstrained delegation for any services), not the Microsoft Kerberos
   protocol extension for constrained delegation.
   2. It’s using GSSAPI. So does it work natively on Windows with SSPI?

The preferred way to do Kerberos delegation is to do protocol transition
(S4U2Self) and Constrained delegation (S4U2Proxy).

Is this supported in libcurl?

If not, is there any plan to support it?


Received on 2018-07-09