I'm sorry, I'm very far from an expert in GSS/krb5.  In particular, I've 
never used NFS and gssd together, so I have no personal experience.  
Maybe someone else on the list can help?
For questions like this, our default has been "what does knfsd do?"  Do 
you happen to know if knfsd accepts "shorthostname(a)REALM.COM" as a root 
user?
Daniel
On 1/18/20 11:50 PM, Pushpesh Sharma wrote:
 Hi All,
 Any pointers are appreciated..
 -pushpesh
 *From:* Pushpesh Sharma <pushpeshs(a)vmware.com>
 *Sent:* Thursday, January 16, 2020 7:45 PM
 *To:* devel(a)lists.nfs-ganesha.org
 *Subject:* [NFS-Ganesha-Devel] Default KRB Principal name with new 
 rpc.gssd
 Hi All,
 We are trying to use ganehsa with KRB. On NFS client centos7.5 we are 
 joining Active Directory based using sssd(AD based KRB Realm). For 
 root user we are getting krb ticket using kinit and valid AD user.
 Client principal while joining domain using sssd a default principal 
 of shorthostname$(a)REALM.COM <mailto:shorthostname$@REALM.COM> is 
 always generated. gss.rpcd by default send this principal as principal 
 user name to ganesha server. Client do have other principal like 
 nfs/client_fdqn(a)REALM.COM <mailto:nfs/client_fdqn@REALM.COM>. But as 
 per rpc.gssd documentation <mailto:rpc.gssd%20documentation> as well 
 first choice would be shorthostname$(a)REALM.COM 
 <mailto:shorthostname$@REALM.COM>.
 Due to this server always recognize root user as someone else i.e. 
 shorthostname$(a)REALM.COM <mailto:shorthostname$@REALM.COM>.
 We do see in src/idmapper/idmapper.c 
<
https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub....
 handling for mapping three principal patterns  nfs/* , root/*, host/* 
 to uid=0, gid=0. So this left shorthostname$(a)REALM.COM 
 <mailto:horthostname$@REALM.COM> principal not being recognized as root.
 We are of the opinion that doing a small fix in above idmapper code to 
 add this pattern as well can fix this issue.
 But we wanted to know any security concern around it? Or if the client 
 behavior can be change in any way, so we don’t need this fix?
 If we try removing this shorthostname$(a)REALM.COM 
 <mailto:shorthostname$@REALM.COM>principal after domain join, sssd 
 cannot be re-loaded and complains about not finding this principal.
 Thanks
 -pushpesh
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