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From: Terry Lambert <terry@lambert.org>
Message-Id: <199604292130.OAA05136@phaeton.artisoft.com>
Subject: Re: Password in a directory
To: helio@compuland.com.br (Helio Coelho Junior)
Date: Mon, 29 Apr 1996 14:30:24 -0700 (MST)
Cc: questions@FreeBSD.ORG
In-Reply-To: <199604280016.VAA01732@sv.compuland.com.br> from "Helio Coelho Junior" at Apr 27, 96 09:16:33 pm
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> Is it possible to put a password in a directory, so the
> user need to type to have access granted ?

No.  Because:

1)	Credentials are associated with processes; they are not
	seperate authentication instances (this is an error in
	the design of UNIX).

2)	You can't associate another credential to indicate
	an "authenticated user" of a directory.  There is
	one credential for a process.

3)	You can't associate an authentication instance with a
	presence of a process "in" a hierarchy because of the
	concept of "current directory" (this is another error
	in the design of UNIX).

4)	There is no way for the kernel to call back to the user
	to request an authentication at access time.  You *could*
	set up a kludge based on an error followed by an ioctl()
	that swould have to be built into a library interface used
	by all code.  It would be a pain to do, since every
	application would require changes.  This is because UNIX
	does not support a "broadcast port" mechanism. Supporting
	such a mechanism would require (1) terminal dependence of
	all applications (that's how VMS does it), or an automaton
	per terminal type (not practical), or a callback/requester
	(assumes credentials are associated with a session manager
	and the user is running in a graphica environemnt (that's
	how UnixWare handles NetWare client authorization and
	why SMBFS is a bad idea on FreeBSD and Linux).

If you have a specialized application, you could hack it, on the
assumption that only someone running the application and using it
to authenticate, or root, would ever access the directory.


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.