Re: [PATCH v7 0/3] fanotify: Allow user space to pass back additional audit info

[Paul Moore]

On Wed, Feb 8, 2023 at 10:27 AM Steve Grubb <sgrubb@xxxxxxxxxx> wrote:
> On Wednesday, February 8, 2023 10:03:24 AM EST Paul Moore wrote:
> > On Wed, Feb 8, 2023 at 7:08 AM Jan Kara <jack@xxxxxxx> wrote:
> > > On Tue 07-02-23 09:54:11, Paul Moore wrote:
> > > > On Tue, Feb 7, 2023 at 7:09 AM Jan Kara <jack@xxxxxxx> wrote:
> > > > > On Fri 03-02-23 16:35:13, Richard Guy Briggs wrote:
> > > > > > The Fanotify API can be used for access control by requesting
> > > > > > permission
> > > > > > event notification. The user space tooling that uses it may have a
> > > > > > complicated policy that inherently contains additional context for
> > > > > > the
> > > > > > decision. If this information were available in the audit trail,
> > > > > > policy
> > > > > > writers can close the loop on debugging policy. Also, if this
> > > > > > additional
> > > > > > information were available, it would enable the creation of tools
> > > > > > that
> > > > > > can suggest changes to the policy similar to how audit2allow can
> > > > > > help
> > > > > > refine labeled security.
> > > > > >
> > > > > > This patchset defines a new flag (FAN_INFO) and new extensions that
> > > > > > define additional information which are appended after the response
> > > > > > structure returned from user space on a permission event.  The
> > > > > > appended
> > > > > > information is organized with headers containing a type and size
> > > > > > that
> > > > > > can be delegated to interested subsystems.  One new information
> > > > > > type is
> > > > > > defined to audit the triggering rule number.
> > > > > >
> > > > > > A newer kernel will work with an older userspace and an older
> > > > > > kernel
> > > > > > will behave as expected and reject a newer userspace, leaving it up
> > > > > > to
> > > > > > the newer userspace to test appropriately and adapt as necessary.
> > > > > > This
> > > > > > is done by providing a a fully-formed FAN_INFO extension but
> > > > > > setting the
> > > > > > fd to FAN_NOFD.  On a capable kernel, it will succeed but issue no
> > > > > > audit
> > > > > > record, whereas on an older kernel it will fail.
> > > > > >
> > > > > > The audit function was updated to log the additional information in
> > > > > > the
> > > > > > AUDIT_FANOTIFY record. The following are examples of the new record
> > > > > >
> > > > > > format:
> > > > > >   type=FANOTIFY msg=audit(1600385147.372:590): resp=2 fan_type=1
> > > > > >   fan_info=3137 subj_trust=3 obj_trust=5 type=FANOTIFY
> > > > > >   msg=audit(1659730979.839:284): resp=1 fan_type=0 fan_info=0
> > > > > >   subj_trust=2 obj_trust=2> > >
> > > > > Thanks! I've applied this series to my tree.
> > > >
> > > > While I think this version of the patchset is fine, for future
> > > > reference it would have been nice if you had waited for my ACK on
> > > > patch 3/3; while Steve maintains his userspace tools, I'm the one
> > > > responsible for maintaining the Linux Kernel's audit subsystem.
> > >
> > > Aha, I'm sorry for that. I had the impression that on the last version of
> > > the series you've said you don't see anything for which the series should
> > > be respun so once Steve's objections where addressed and you were silent
> > > for a few days, I thought you consider the thing settled... My bad.
> >
> > That's understandable, especially given inconsistencies across
> > subsystems.  If it helps, if I'm going to ACK something I make it
> > explicit with a proper 'Acked-by: ...' line in my reply; if I say
> > something looks good but there is no explicit ACK, there is usually
> > something outstanding that needs to be resolved, e.g. questions,
> > additional testing, etc.
> >
> > In this particular case I posed some questions in that thread and
> > never saw a reply with any answers, hence the lack of an ACK.  While I
> > think the patches were reasonable, I withheld my ACK until the
> > questions were answered ... which they never were from what I can
> > tell, we just saw a new patchset with changes.
> >
> > /me shrugs
>
> Paul,
>
> I reread the thread. You only had a request to change if/else to a switch
> construct only if there was a respin for the 3F. You otherwise said get
> Steve's input and the 3F borders on being overly clever. Both were addressed.
> If you had other questions that needed answers on, please restate them to
> expedite approval of this set of patches. As far as I can tell, all comments
> are addressed.

Steve,

It might be helpful to reread my reply below:

https://lore.kernel.org/linux-audit/CAHC9VhRWDD6Tk6AEmgoobBkcVKRYbVOte7-F0TGJD2dRk7NKxw@xxxxxxxxxxxxxx/

You'll see that I made a comment in that email about not following
Richard's explanation about "encoding the zero" (the patch was
encoding a "?" to the best I could tell).  I was hoping for some
clarification from Richard on his comments, and I never saw anything
in my inbox.  I just checked the archives on lore and I don't see
anything there either.

-- 
paul-moore.com