Re: [RFC PATCH ghak9 0/3] audit: Record the path of FDs passed to *at(2) syscalls

Paul Moore
2018-08-02T23:16:27Z

On Thu, Jul 26, 2018 at 4:12 AM Ondrej Mosnacek <omosnace@redhat.com> wrote:
> On Wed, Jul 25, 2018 at 3:11 PM Steve Grubb <sgrubb@redhat.com> wrote:
> > On Wednesday, July 25, 2018 9:02:50 AM EDT Ondrej Mosnacek wrote:
> > > On Wed, Jul 25, 2018 at 2:48 PM Steve Grubb <sgrubb@redhat.com> wrote:
> > > > On Wednesday, July 25, 2018 3:44:07 AM EDT Ondrej Mosnacek wrote:
> > > > > On Wed, Jul 25, 2018 at 3:11 AM Steve Grubb <sgrubb@redhat.com> wrote:
> > > > > > On Tuesday, July 24, 2018 6:15:54 PM EDT Paul Moore wrote:
> > > > > > > On Tue, Jul 24, 2018 at 10:12 AM Ondrej Mosnacek
> > > > > > > <omosnace@redhat.com>
> > > > > > >
> > > > > > > > Beyond that, there is really no information in the records that
> > > > > > > > would
> > > > > > > > allow reconstructing which PARENT path belongs to which
> > > > > > > > CREATE/DELETE
> > > > > > > > path... (Intuitively you can guess that src will come before dst,
> > > > > > > > but
> > > > > > > > that is not very reliable.) I think a "parent inode" field in the
> > > > > > > > PATH
> > > > > > > > records could fix this, but maybe there is a better solution...
> > > > > > >
> > > > > > > I have my suspicions, but I would be curious to hear from Steve how
> > > > > > > the reconstruction is typically handled.
> > > > > >
> > > > > > For any *at function when the dirfd is not AT_FDCWD, it goes badly.
> > > > > > If
> > > > > > its a old style syscall without the dirfd, then if the first
> > > > > > character
> > > > > > is '/' use that. Otherwise concatonate cwd and path and pass it to
> > > > > > realpath to sort out.
> > > > >
> > > > > In that case it seems the best fix for openat() et al. would be to
> > > > > somehow always force outputting the full path when dirfd != AT_FDCWD.
> > > > > Hopefully that won't require too much hacking around...
> > > >
> > > > What is asked for is the full path that dirfd was opened with. I can take
> > > > care of everything else.
> > >
> > > But where/how should that path be logged? In case of renameat(), for
> > > example, we have 6 (!) path components:
> > > <src_dir>/<src_parent>/<src_child> and <dst_dir>/<dst_parent>/<dst_child>
> > >
> > > (I am assuming the child paths always represent just the last path
> > > component based on the observed inodes of the parent/child records.)
> > >
> > > Current record format can distinguish between PARENT and child
> > > (DELETE/CREATE), but there is no nametype for the dirfd path. That's
> > > why I am leaning towards just logging the full "<*_dir>/<*_parent>"
> > > path in the PARENT record. Or do you prefer that we add a new nametype
> > > for the dirfd path?
> >
> > You could make a new nametype so that we can make sense of it. But do you
> > have all of the required information for a PATH record? I thought that you
> > were making a new record type since you have abbreviated information.
>
> I think it should be possible to collect that information by putting
> hooks in the right places of the filesystem code (and fixing the
> current ones).
>
> To be honest, the reason why I had jumped right to making a new record
> type was Paul's wording in the issue description ("We may need a new
> auxiliary record type since this is neither the cwd or path." ...

For future reference, when I say "may" I do really mean it; it *may*
be a good idea, but it *may* also be a garbage idea ;)

--
paul moore