Re: [PATCH V2] audit: normalize NETFILTER_PKT

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.

paul moore