linux-kernel - Re: [PATCH ghak90 V7 20/21] audit: add capcontid to set contid outside init_user

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Date:   Thu, 31 Oct 2019 10:50:57 -0400
From:   Steve Grubb <sgrubb@...hat.com>
To:     Richard Guy Briggs <rgb@...hat.com>
Cc:     Paul Moore <paul@...l-moore.com>,
        containers@...ts.linux-foundation.org, linux-api@...r.kernel.org,
        Linux-Audit Mailing List <linux-audit@...hat.com>,
        linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
        omosnace@...hat.com, dhowells@...hat.com, simo@...hat.com,
        Eric Paris <eparis@...isplace.org>,
        Serge Hallyn <serge@...lyn.com>, ebiederm@...ssion.com,
        nhorman@...driver.com, Dan Walsh <dwalsh@...hat.com>,
        mpatel@...hat.com
Subject: Re: [PATCH ghak90 V7 20/21] audit: add capcontid to set contid outside init_user_ns

Hello,

TLDR;  I see a lot of benefit to switching away from procfs for setting auid & 
sessionid.

On Wednesday, October 30, 2019 6:03:20 PM EDT Richard Guy Briggs wrote:
> > Also, for the record, removing the audit loginuid from procfs is not
> > something to take lightly, if at all; like it or not, it's part of the
> > kernel API.

It can also be used by tools to iterate processes related to one user or 
session. I use this in my Intrusion Prevention System which will land in 
audit user space at some point in the future.

> Oh, I'm quite aware of how important this change is and it was discussed
> with Steve Grubb who saw the concern and value of considering such a
> disruptive change.

Actually, I advocated for syscall. I think the gist of Eric's idea was that /
proc is the intersection of many nasty problems. By relying on it, you can't 
simplify the API to reduce the complexity. Almost no program actually needs 
access to /proc. ps does. But almost everything else is happy without it. For 
example, when you setup chroot jails, you may have to add /dev/random or /
dev/null, but almost never /proc. What does force you to add /proc is any 
entry point daemon like sshd because it needs to set the loginuid. If we 
switch away from /proc, then sshd or crond will no longer /require/ procfs to 
be available which again simplifies the system design.

> Removing proc support for auid/ses would be a
> long-term deprecation if accepted.

It might need to just be turned into readonly for a while. But then again, 
perhaps auid and session should be part of /proc/<pid>/status? Maybe this can 
be done independently and ahead of the container work so there is a migration 
path for things that read auid or session. TBH, maybe this should have been 
done from the beginning.

-Steve