Hi and welcome.
I believe this should work with the TWAPI SSPI package http://twapi.sourceforge.net/v4.0/sspi.html
You may need ASN too https://core.tcl.tk/tcllib/doc/trunk/embedded/www/tcllib/files/modules/asn/asn.html
best wishes Brian
I forgot to mention, that we use Ubuntu 14.04 on our Server where the NaviServer is installed.
The AD is on another Server installed.
TWAPI SSPI requires Windows.