Re: [PATCH V3] audit: normalize NETFILTER_PKT

On Wed, Mar 1, 2017 at 11:28 AM, Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: > On 2017-02-28 17:22, Paul Moore wrote: >> On Sun, Feb 26, 2017 at 3:49 PM, Richard Guy Briggs <rgb(a)redhat.com&gt; 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(a)redhat.com&gt; >> > --- >> > 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. > > Yes, I agree. How does this even work now? Maybe the MAC header hasn't > been added yet (or has already been processed and stripped off) so that > skb->data is already pointing at the network header and hence has an > offset of 0. Can you be more explicit and elaborate to say if this what > you were thinking? Unfortunately, not really, I haven't thought through of all the situations and it has been a long time since I've had to worry about things like this. I think we are in agreement that it needs to change, so let's just make the change.

> This should be a seperate bug fix patch rather than fixing it in the > noise of this substantial re-arrangement. That's fine, but please send it as one patchset. Also, to get ahead of the next likely question, no I don't think the skb_network_offset() fix is -stable worthy at the moment.

>> > - 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? > > My understanding is they are set up to cope with this. How does userspace distinguish between an unset nfmark and a nfmark of 0xffffffff?

paul moore