[PATCH V3] audit: normalize NETFILTER_PKT

[Richard Guy Briggs]

On 2017-03-02 21:54, Paul Moore wrote:
> On Thu, Mar 2, 2017 at 9:00 PM, Richard Guy Briggs <rgb at redhat.com> wrote:
> > On 2017-03-02 19:16, Paul Moore wrote:
> >> On Wed, Mar 1, 2017 at 5:34 PM, Richard Guy Briggs <rgb at redhat.com> wrote:
> >> > On 2017-03-01 17:19, Paul Moore wrote:
> >> >> On Wed, Mar 1, 2017 at 11:28 AM, Richard Guy Briggs <rgb at redhat.com> wrote:
> >> >> > On 2017-02-28 17:22, Paul Moore wrote:
> >> >> >> On Sun, Feb 26, 2017 at 3:49 PM, Richard Guy Briggs <rgb at redhat.com> wrote:
> >> >> >> > Eliminate flipping in and out of message fields, dropping fields in the process.
> >> >> >> >
> >> >> >> > Sample raw message format IPv4 UDP:
> >> >> >> > type=NETFILTER_PKT msg=audit(1487874761.386:228):  mark=0xae8a2732 saddr=127.0.0.1 daddr=127.0.0.1 proto=17^]
> >> >> >> > Sample raw message format IPv6 ICMP6:
> >> >> >> > type=NETFILTER_PKT msg=audit(1487874761.381:227):  mark=0x223894b7 saddr=::1 daddr=::1 proto=58^]
> >> >> >> >
> >> >> >> > Issue: https://github.com/linux-audit/audit-kernel/issues/11
> >> >> >> > Test case: https://github.com/linux-audit/audit-testsuite/issues/43
> >> >> >> >
> >> >> >> > Signed-off-by: Richard Guy Briggs <rgb at redhat.com>
> >> >> >> > ---
> >> >> >> >  net/netfilter/xt_AUDIT.c |  122 ++++++++++-----------------------------------
> >> >> >> >  1 files changed, 27 insertions(+), 95 deletions(-)
> >> >> >> >
> >> >> >> > diff --git a/net/netfilter/xt_AUDIT.c b/net/netfilter/xt_AUDIT.c
> >> >> >> > index 4973cbd..945fa29 100644
> >> >> >> > --- a/net/netfilter/xt_AUDIT.c
> >> >> >> > +++ b/net/netfilter/xt_AUDIT.c
> >> >> >> > @@ -31,146 +31,78 @@ MODULE_ALIAS("ip6t_AUDIT");
> 
> ...
> 
> >> >> >> >  static unsigned int
> >> >> >> >  audit_tg(struct sk_buff *skb, const struct xt_action_param *par)
> >> >> >> >  {
> >> >> >> > -       const struct xt_audit_info *info = par->targinfo;
> >> >> >> >         struct audit_buffer *ab;
> >> >> >> > +       int fam = -1;
> >> >> >> >
> >> >> >> >         if (audit_enabled == 0)
> >> >> >> >                 goto errout;
> >> >> >> > -
> >> >> >> >         ab = audit_log_start(NULL, GFP_ATOMIC, AUDIT_NETFILTER_PKT);
> >> >> >> >         if (ab == NULL)
> >> >> >> >                 goto errout;
> >> >> >> >
> >> >> >> > -       audit_log_format(ab, "action=%hhu hook=%u len=%u inif=%s outif=%s",
> >> >> >> > -                        info->type, par->hooknum, skb->len,
> >> >> >> > -                        par->in ? par->in->name : "?",
> >> >> >> > -                        par->out ? par->out->name : "?");
> >> >> >> > -
> >> >> >> > -       if (skb->mark)
> >> >> >> > -               audit_log_format(ab, " mark=%#x", skb->mark);
> >> >> >> > -
> >> >> >> > -       if (skb->dev && skb->dev->type == ARPHRD_ETHER) {
> >> >> >> > -               audit_log_format(ab, " smac=%pM dmac=%pM macproto=0x%04x",
> >> >> >> > -                                eth_hdr(skb)->h_source, eth_hdr(skb)->h_dest,
> >> >> >> > -                                ntohs(eth_hdr(skb)->h_proto));
> >> >> >> > +       audit_log_format(ab, "mark=%#x", skb->mark ?: -1);
> >> >> >>
> >> >> >> How do Steve's userspace tools like the unset/-1 value represented
> >> >> >> when it is a hex value: -1 or 0xffffffff?
> >> >> >
> >> >> > My understanding is they are set up to cope with this.
> >> >>
> >> >> How does userspace distinguish between an unset nfmark and a nfmark of
> >> >> 0xffffffff?
> >> >
> >> > It never had to deal specifically with nfmark previously because it
> >> > wasn't included if it was blank.  Generally other values that are -1 are
> >> > interpreted by the audit userspace tools as unset (session id, auid,
> >> > etc...)
> >>
> >> Yes, I know, let me get straight to the point: should we use "mark=-1"
> >> when the nfmark is unset instead of "mark=0xffffffff"?
> >
> > I'd prefer to keep the format as it was, explicitly labelled hex.  The
> > other fields that are printed as unset, -1, come out in the logs as
> > MAX_UINT: "auid=4294967295 ses=4294967295", so I don't see any reason to
> > change that convention.  Once that field is known by userspace tools,
> > they can interpret (-i) that as -1.
> 
> Perhaps I'm missing something here, but let me ask again, how does
> userspace distinguish between an unset nfmark and a nfmark of
> 0xffffffff?

It can't.

> paul moore

- RGB

--
Richard Guy Briggs <rgb at redhat.com>
Kernel Security Engineering, Base Operating Systems, Red Hat
Remote, Ottawa, Canada
Voice: +1.647.777.2635, Internal: (81) 32635