netdev - Re: [PATCH ghak90 V8 13/16] audit: track container nesting

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Date:   Wed, 5 Feb 2020 18:05:52 -0500
From:   Paul Moore <paul@...l-moore.com>
To:     Richard Guy Briggs <rgb@...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 V8 13/16] audit: track container nesting

On Thu, Jan 30, 2020 at 2:28 PM Richard Guy Briggs <rgb@...hat.com> wrote:
> On 2020-01-22 16:29, Paul Moore wrote:
> > On Tue, Dec 31, 2019 at 2:51 PM Richard Guy Briggs <rgb@...hat.com> wrote:
> > >
> > > Track the parent container of a container to be able to filter and
> > > report nesting.
> > >
> > > Now that we have a way to track and check the parent container of a
> > > container, modify the contid field format to be able to report that
> > > nesting using a carrat ("^") separator to indicate nesting.  The
> > > original field format was "contid=<contid>" for task-associated records
> > > and "contid=<contid>[,<contid>[...]]" for network-namespace-associated
> > > records.  The new field format is
> > > "contid=<contid>[^<contid>[...]][,<contid>[...]]".
> >
> > Let's make sure we always use a comma as a separator, even when
> > recording the parent information, for example:
> > "contid=<contid>[,^<contid>[...]][,<contid>[...]]"
>
> The intent here is to clearly indicate and separate nesting from
> parallel use of several containers by one netns.  If we do away with
> that distinction, then we lose that inheritance accountability and
> should really run the list through a "uniq" function to remove the
> produced redundancies.  This clear inheritance is something Steve was
> looking for since tracking down individual events/records to show that
> inheritance was not aways feasible due to rolled logs or search effort.

Perhaps my example wasn't clear.  I'm not opposed to the little
carat/hat character indicating a container's parent, I just think it
would be good to also include a comma *in*addition* to the carat/hat.

> > > Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> > > ---
> > >  include/linux/audit.h |  1 +
> > >  kernel/audit.c        | 53 +++++++++++++++++++++++++++++++++++++++++++--------
> > >  kernel/audit.h        |  1 +
> > >  kernel/auditfilter.c  | 17 ++++++++++++++++-
> > >  kernel/auditsc.c      |  2 +-
> > >  5 files changed, 64 insertions(+), 10 deletions(-)
> >
> > ...
> >
> > > diff --git a/kernel/audit.c b/kernel/audit.c
> > > index ef8e07524c46..68be59d1a89b 100644
> > > --- a/kernel/audit.c
> > > +++ b/kernel/audit.c
> >
> > > @@ -492,6 +493,7 @@ void audit_switch_task_namespaces(struct nsproxy *ns, struct task_struct *p)
> > >                 audit_netns_contid_add(new->net_ns, contid);
> > >  }
> > >
> > > +void audit_log_contid(struct audit_buffer *ab, u64 contid);
> >
> > If we need a forward declaration, might as well just move it up near
> > the top of the file with the rest of the declarations.
>
> Ok.
>
> > > +void audit_log_contid(struct audit_buffer *ab, u64 contid)
> > > +{
> > > +       struct audit_contobj *cont = NULL, *prcont = NULL;
> > > +       int h;
> >
> > It seems safer to pass the audit container ID object and not the u64.
>
> It would also be faster, but in some places it isn't available such as
> for ptrace and signal targets.  This also links back to the drop record
> refcounts to hold onto the contobj until process exit, or signal
> delivery.
>
> What we could do is to supply two potential parameters, a contobj and/or
> a contid, and have it use the contobj if it is valid, otherwise, use the
> contid, as is done for names and paths supplied to audit_log_name().

Let's not do multiple parameters, that begs for misuse, let's take the
wrapper function route:

 func a(int id) {
   // important stuff
 }

 func ao(struct obj) {
   a(obj.id);
 }

... and we can add a comment that you *really* should be using the
variant that passes an object.

> > > @@ -2705,9 +2741,10 @@ int audit_set_contid(struct task_struct *task, u64 contid)
> > >         if (!ab)
> > >                 return rc;
> > >
> > > -       audit_log_format(ab,
> > > -                        "op=set opid=%d contid=%llu old-contid=%llu",
> > > -                        task_tgid_nr(task), contid, oldcontid);
> > > +       audit_log_format(ab, "op=set opid=%d contid=", task_tgid_nr(task));
> > > +       audit_log_contid(ab, contid);
> > > +       audit_log_format(ab, " old-contid=");
> > > +       audit_log_contid(ab, oldcontid);
> >
> > This is an interesting case where contid and old-contid are going to
> > be largely the same, only the first (current) ID is going to be
> > different; do we want to duplicate all of those IDs?
>
> At first when I read your comment, I thought we could just take contid
> and drop oldcontid, but if it fails, we still want all the information,
> so given the way I've set up the search code in userspace, listing only
> the newest contid in the contid field and all the rest in oldcontid
> could be a good compromise.

This is along the lines of what I was thinking.

-- 
paul moore
www.paul-moore.com