Hello
On Tue, May 03, 2022 at 10:44:48AM +0200, Claudio Jeker wrote:
</snip>
>
> The RFC does not use the usual MUST to enforce any of this.
> So yes, we should probably not be too strict because there is no way to
> force accept the packet when pf_walk_header() returns PF_DROP.
>
> I agree that the TTL MUST be 1. Also the destination address must be a
> multicast address (IGMP to a unicast IP makes no sense).
>
updated diff below requires destination address to be multicast for IGMP.
thanks and
regards
sashan
--------8<----------------8<----------------8<----------------8<--------
diff --git a/sys/net/pf.c b/sys/net/pf.c
index f15e1ead8c0..feb7965c427 100644
--- a/sys/net/pf.c
+++ b/sys/net/pf.c
@@ -6456,8 +6456,15 @@ pf_walk_header(struct pf_pdesc *pd, struct ip *h,
u_short *reason)
pd->off += hlen;
pd->proto = h->ip_p;
/* IGMP packets have router alert options, allow them */
- if (pd->proto == IPPROTO_IGMP)
+ if (pd->proto == IPPROTO_IGMP) {
+ /* According to RFC 1112 ttl must be set to 1. */
+ if ((h->ip_ttl != 1) || !IN_MULTICAST(h->ip_dst.s_addr)) {
+ DPFPRINTF(LOG_NOTICE, "TTL in IGMP must be 1");
+ REASON_SET(reason, PFRES_IPOPTIONS);
+ return (PF_DROP);
+ }
CLR(pd->badopts, PF_OPT_ROUTER_ALERT);
+ }
/* stop walking over non initial fragments */
if ((h->ip_off & htons(IP_OFFMASK)) != 0)
return (PF_PASS);
@@ -6698,6 +6705,19 @@ pf_walk_header6(struct pf_pdesc *pd, struct ip6_hdr *h,
u_short *reason)
case MLD_LISTENER_REPORT:
case MLD_LISTENER_DONE:
case MLDV2_LISTENER_REPORT:
+ /*
+ * According to RFC 2710 all MLD messages are
+ * sent with hop-limit (ttl) set to 1, and link
+ * local source address. If either one is
+ * missing then MLD message is invalid and
+ * should be discarded.
+ */
+ if ((h->ip6_hlim != 1) ||
+ !IN6_IS_ADDR_LINKLOCAL(&h->ip6_src)) {
+ DPFPRINTF(LOG_NOTICE, "invalid MLD");
+ REASON_SET(reason, PFRES_IPOPTIONS);
+ return (PF_DROP);
+ }
CLR(pd->badopts, PF_OPT_ROUTER_ALERT);
break;
}
