Re: uid string

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From: Brent Callaghan (Brent.Callaghan@eng.sun.com)
Date: 06/30/99-03:46:59 PM Z


Date: Wed, 30 Jun 1999 13:46:59 -0700 (PDT)
From: Brent Callaghan <Brent.Callaghan@eng.sun.com>
Message-Id: <199906302046.NAA01098@terra.eng.sun.com>
Subject: Re: uid string


Rick Macklem writes:
> ... Adding "@dns_domain" doesn't seem to add much either, since
> the client should already know the dns_domain of the server (or at least the
> IP address) and user names aren't normally administered on a dns_domain
> basis anyhow.

Ah, but the server isn't necessarily in the same domain
as the one in which the user is administered.



> One thought would be to tie the "uid string" to the authentication system
> being used. For example, 

It would be nice to use a pre-existing scheme for identifying users,
such as that of Kerberos.  However, I think it would be a mistake
to tie the string format to the client's authentication. For instance,
how do you identify users who created files on the server through a
different authentication scheme from that used by the client ?



> On implementation of a uid string in a Unix-like system:
> - Getting from a uid number to the login name is going to be a Royal Pain in..
>   for a kernel based implementation. The implementor will either have to put
>   getpwnam(), getpwuid() and all the baggage that it needs, such as a NIS
>   client in the kernel, or the kernel threads will have to "porpoise" out of
>   the kernel to make the calls. 

Right. It will require more work for UNIX clients and servers that
currently have it easy with NFS v2 & v3 through the direct use
of uid/gid when using AUTH_SYS.  However, if you're going to use
any kind of secure authentication, then you're stuck with doing
some kind of mapping anyway.  

You don't need to put a NIS client in the kernel.  It's easy
to to upcalls to a daemon that'll do all the name service 
jiggerypokery.  As long as you cache the mappings, the client
or server performance needn't suffer.

	Brent


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