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

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Date:   Fri, 1 Nov 2019 12:22:11 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Richard Guy Briggs <rgb@...hat.com>
Cc:     Steve Grubb <sgrubb@...hat.com>, nhorman@...driver.com,
        linux-api@...r.kernel.org, containers@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>, dhowells@...hat.com,
        Linux-Audit Mailing List <linux-audit@...hat.com>,
        netfilter-devel@...r.kernel.org, ebiederm@...ssion.com,
        simo@...hat.com, netdev@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, Eric Paris <eparis@...isplace.org>,
        mpatel@...hat.com, Serge Hallyn <serge@...lyn.com>
Subject: Re: [PATCH ghak90 V7 20/21] audit: add capcontid to set contid
 outside init_user_ns

On Fri, Nov 1, 2019 at 11:10 AM Richard Guy Briggs <rgb@...hat.com> wrote:
> On 2019-10-31 10:50, Steve Grubb wrote:
> > 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.
>
> How about making loginuid/contid/capcontid writable only via netlink but
> still provide the /proc interface for reading?  Deprecation of proc can
> be left as a decision for later.  This way sshd/crond/getty don't need
> /proc, but the info is still there for tools that want to read it.

Just so there is no confusion for the next patchset: I think it would
be a mistake to include any changes to loginuid in your next patchset,
even as a "RFC" at the end.  Also, barring some shocking comments from
Eric relating to the imminent death of /proc in containers, I think it
would also be a mistake to include the netlink API.

Let's keep it small and focused :)

-- 
paul moore
www.paul-moore.com