linux-kernel - Re: [RFC] Capabilities still can't be inherited by normal programs

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Message-ID: <20121210145950.GC8137@sergelap>
Date:	Mon, 10 Dec 2012 08:59:50 -0600
From:	Serge Hallyn <serge.hallyn@...onical.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	"Andrew G. Morgan" <morgan@...nel.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Casey Schaufler <casey@...aufler-ca.com>,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	Kees Cook <keescook@...omium.org>,
	James Morris <james.l.morris@...cle.com>,
	Eric Paris <eparis@...hat.com>,
	"Serge E. Hallyn" <serge@...onical.com>,
	Markku Savela <msa@...h.iki.fi>
Subject: Re: [RFC] Capabilities still can't be inherited by normal programs

Quoting Andy Lutomirski (luto@...capital.net):
> It's especially bad because granting CAP_DAC_READ_SEARCH to user "foo"
> doesn't mean anything.  Is he authorized to back things up to
> encrypted storage?

We're talking about privileges at the kernel level here, and there is
no way this could be expressed at that level.

Higher level tools could/should certainly be exposing things at this
level.

BUT

You *are* doing a good job of making me feel that we should have
per-user fI xattrs or acls.  Sudo is popular because people like to say
"user joe can run foo with privilege".  Most people will never want to
be bothered to say "user joe can run foo with CAP_XYZ" (versus "as
root"), but I do think we could get programs/packages to do that.

Note that another difficulty here likes in the age-old, as yet
unanswered imo, question of "how do I easily figure out what caps I need
to run my program."  A few years ago I pointed to this (perhaps in
mostly private emails, don't recall) as something to be solved, but
the solution escapes me.

-serge
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