On Thu, Feb 23, 2017 at 10:51 AM, Richard Guy Briggs <rgb@xxxxxxxxxx> wrote:
> On 2017-02-23 06:20, Florian Westphal wrote:
>> Richard Guy Briggs <rgb@xxxxxxxxxx> 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
www.paul-moore.com
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