[PATCH V3] audit: normalize NETFILTER_PKT

[Paul Moore]

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 void audit_ip4(struct audit_buffer *ab, struct sk_buff *skb)
> +static bool audit_ip4(struct audit_buffer *ab, struct sk_buff *skb)
>  {
>         struct iphdr _iph;
>         const struct iphdr *ih;
>
>         ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);

It seems like we should be using skb_network_offset(skb) instead of 0
above, yes?  Granted, this isn't new, but let's fix it.

> -       if (!ih) {
> -               audit_log_format(ab, " truncated=1");
> -               return;
> -       }
> +       if (!ih)
> +               return false;
>
> -       audit_log_format(ab, " saddr=%pI4 daddr=%pI4 ipid=%hu proto=%hhu",
> -               &ih->saddr, &ih->daddr, ntohs(ih->id), ih->protocol);
> +       audit_log_format(ab, " saddr=%pI4 daddr=%pI4 proto=%hhu",
> +                        &ih->saddr, &ih->daddr, ih->protocol);
>
> -       if (ntohs(ih->frag_off) & IP_OFFSET) {
> -               audit_log_format(ab, " frag=1");
> -               return;
> -       }
> -
> -       audit_proto(ab, skb, ih->protocol, ih->ihl * 4);
> +       return true;
>  }

...

>  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?

-- 
paul moore
www.paul-moore.com