Re: [PATCH V2] audit: normalize NETFILTER_PKT

On Thu, Feb 23, 2017 at 12:13 PM, Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: > On 2017-02-23 12:06, Paul Moore wrote: >> On Thu, Feb 23, 2017 at 12:04 PM, Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: >> > On 2017-02-23 11:57, Paul Moore wrote: >> >> On Thu, Feb 23, 2017 at 10:51 AM, Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: >> >> > On 2017-02-23 06:20, Florian Westphal wrote: >> >> >> Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: >> >> >> > Simplify and eliminate flipping in and out of message fields, relying on nfmark >> >> >> > the way we do for audit_key. >> >> >> > >> >> >> > +struct nfpkt_par { >> >> >> > + int ipv; >> >> >> > + const void *saddr; >> >> >> > + const void *daddr; >> >> >> > + u8 proto; >> >> >> > +}; >> >> >> >> >> >> This is problematic, see below for why. >> >> >> >> >> >> > -static void audit_ip4(struct audit_buffer *ab, struct sk_buff *skb) >> >> >> > +static void audit_ip4(struct audit_buffer *ab, struct sk_buff *skb, struct nfpkt_par *apar) >> >> >> > { >> >> >> > struct iphdr _iph; >> >> >> > const struct iphdr *ih; >> >> >> > >> >> >> > + apar->ipv = 4; >> >> >> > ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph); >> >> >> > - if (!ih) { >> >> >> > - audit_log_format(ab, " truncated=1"); >> >> >> > + if (!ih) >> >> >> > return; >> >> >> >> >> >> Removing this "truncated" has the consequence that this can later log >> >> >> "saddr=0.0.0.0 daddr=0.0.0.0" if we return here. >> >> >> >> >> >> This cannot happen for ip(6)tables because ip stack discards broken l3 headers >> >> >> before the netfilter hooks get called, but its possible with NFPROTO_BRIDGE. >> >> >> >> >> >> Perhaps you will need to change audit_ip4/6 to return "false" when it can't >> >> >> get the l3 information now so we only log zero addresses when the packet >> >> >> really did contain them. >> >> > >> >> > Ok, to clarify the implications, are you saying that handing a NULL >> >> > pointer to "saddr=%pI4" will print "0.0.0.0" rather than "(none)" or "?" >> >> >> >> My initial reaction is that if the packet is so badly >> >> truncated/malformed that we don't have a full IP header than we should >> >> just refrain from logging the packet; it's too malformed/garbage to >> >> offer any useful information and the normal packet processing should >> >> result in the packet being discarded anyway. >> > >> > Which is why I wanted the ethertype, but that can be coded into the nfmark. >> >> If the packet is garbage (garbage without any payload in this case), >> what does it matter? It's noise. > > It could be an indicator that either the logging rules or the filter > rules need honing, or even that there is a bug in the network code. Elaborate on this please, I still don't see how logging the ethertype is helpful for a malformed packet.

paul moore