linux-kernel - Re: NFS4 authentification / fsuid

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Message-ID: <20070830214431.GF10808@fieldses.org>
Date:	Thu, 30 Aug 2007 17:44:31 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Trond Myklebust <trond.myklebust@....uio.no>
Cc:	Jan Engelhardt <jengelh@...putergmbh.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: NFS4 authentification / fsuid

On Thu, Aug 30, 2007 at 11:04:00AM -0400, Trond Myklebust wrote:
> With CIFS or other password based protocols (including RPCSEC_GSS)

Well, rpcsec_gss isn't inherently password based, and you can
authenticate in some way that doesn't actually give away your password
(or other long-lived credential).

> What I'm saying is that the superuser can pretty much do whatever it
> takes to grab either your kerberos password (e.g. install a keyboard
> listener), a stored credential (read the contents of your kerberos
> on-disk credential cache), or s/he can access the cached contents of the
> file by hunting through /dev/kmem.
> 
> IOW: There is no such thing as security on a root-compromised machine.

And in theory a kernel could provide *some* guarantees against root,
right?  (Is there some reason a unix-like kernel must provide such
things as /dev/kmem?)

--b.
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