Date:   Fri, 1 Nov 2019 11:21:18 -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 2019-11-01 11:13, Steve Grubb wrote:
> On Friday, November 1, 2019 11:09:27 AM EDT Richard Guy Briggs 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.
> 
> This also sounds good to me. But I still think loginuid and audit sessionid 
> should get written in /proc/<pid>/status so that all process information is 
> consolidated in one place.

I don't have a problem adding auid/sessionid to /proc/<pid>/status with
other related information, but it is disruptive to deprecate the
existing interface which could be a seperate step.

> -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

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