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

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Message-ID: <20191101150927.c5sf3n5ezfg2eano@madcap2.tricolour.ca>
Date:   Fri, 1 Nov 2019 11:09:27 -0400
From:   Richard Guy Briggs <rgb@...hat.com>
To:     Steve Grubb <sgrubb@...hat.com>
Cc:     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 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.

> -Steve

- RGB

--
Richard Guy Briggs <rgb@...hat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635