linux-kernel - Re: [PATCH v4 3/4] fanotify,audit: Allow audit to use the full permission event response

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Date:   Thu, 8 Sep 2022 22:41:44 -0400
From:   Richard Guy Briggs <rgb@...hat.com>
To:     Steve Grubb <sgrubb@...hat.com>
Cc:     Paul Moore <paul@...l-moore.com>, Jan Kara <jack@...e.cz>,
        Linux-Audit Mailing List <linux-audit@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org, Eric Paris <eparis@...isplace.org>,
        Amir Goldstein <amir73il@...il.com>
Subject: Re: [PATCH v4 3/4] fanotify,audit: Allow audit to use the full
 permission event response

On 2022-09-08 22:20, Steve Grubb wrote:
> On Thursday, September 8, 2022 5:22:15 PM EDT Paul Moore wrote:
> > On Thu, Sep 8, 2022 at 5:14 PM Steve Grubb <sgrubb@...hat.com> wrote:
> > > On Wednesday, September 7, 2022 4:23:49 PM EDT Paul Moore wrote:
> > > > On Wed, Sep 7, 2022 at 4:11 PM Steve Grubb <sgrubb@...hat.com> wrote:
> > > > > On Wednesday, September 7, 2022 2:43:54 PM EDT Richard Guy Briggs 
> wrote:
> > > > > > > > Ultimately I guess I'll leave it upto audit subsystem what it
> > > > > > > > wants
> > > > > > > > to
> > > > > > > > have in its struct fanotify_response_info_audit_rule because
> > > > > > > > for
> > > > > > > > fanotify subsystem, it is just an opaque blob it is passing.
> > > > > > > 
> > > > > > > In that case, let's stick with leveraging the type/len fields in
> > > > > > > the
> > > > > > > fanotify_response_info_header struct, that should give us all the
> > > > > > > flexibility we need.
> > > > > > > 
> > > > > > > Richard and Steve, it sounds like Steve is already aware of
> > > > > > > additional
> > > > > > > information that he wants to send via the
> > > > > > > fanotify_response_info_audit_rule struct, please include that in
> > > > > > > the
> > > > > > > next revision of this patchset.  I don't want to get this merged
> > > > > > > and
> > > > > > > then soon after have to hack in additional info.
> > > > > > 
> > > > > > Steve, please define the type and name of this additional field.
> > > > > 
> > > > > Maybe extra_data, app_data, or extra_info. Something generic that can
> > > > > be
> > > > > reused by any application. Default to 0 if not present.
> > > > 
> > > > I think the point is being missed ... The idea is to not speculate on
> > > > additional fields, as discussed we have ways to handle that, the issue
> > > > was that Steve implied that he already had ideas for "things" he
> > > > wanted to add.  If there are "things" that need to be added, let's do
> > > > that now, however if there is just speculation that maybe someday we
> > > > might need to add something else we can leave that until later.
> > > 
> > > This is not speculation. I know what I want to put there. I know you want
> > > to pin it down to exactly what it is. However, when this started a
> > > couple years back, one of the concerns was that we're building something
> > > specific to 1 user of fanotify. And that it would be better for all
> > > future users to have a generic facility that everyone could use if they
> > > wanted to. That's why I'm suggesting something generic, its so this is
> > > not special purpose that doesn't fit any other use case.
> > 
> > Well, we are talking specifically about fanotify in this thread and
> > dealing with data structures that are specific to fanotify.  I can
> > understand wanting to future proof things, but based on what we've
> > seen in this thread I think we are all set in this regard.
> 
> I'm trying to abide by what was suggested by the fs-devel folks. I can live 
> with it. But if you want to make something non-generic for all users of 
> fanotify, call the new field "trusted". This would decern when a decision was 
> made because the file was untrusted or access denied for another reason.

So, "u32 trusted;" ?  How would you like that formatted?
"fan_trust={0|1}"

> > You mention that you know what you want to put in the struct, why not
> > share the details with all of us so we are all on the same page and
> > can have a proper discussion.
> 
> Because I want to abide by the original agreement and not impose opinionated 
> requirements that serve no one else. I'd rather have something anyone can 
> use. I want to play nice.

If someone else wants to use something, why not give them a type of
their own other than FAN_RESPONSE_INFO_AUDIT_RULE that they can shape
however they like?

> -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