git: 2eddb410f789 - main - pf: accept IP options for IGMP and ICMP6 MLD
- Go to: [ bottom of page ] [ top of archives ] [ this month ]
Date: Wed, 23 Jul 2025 14:23:48 UTC
The branch main has been updated by kp:
URL: https://cgit.FreeBSD.org/src/commit/?id=2eddb410f7892ff637bbf058b58f2644f329e8d9
commit 2eddb410f7892ff637bbf058b58f2644f329e8d9
Author: Kristof Provost <kp@FreeBSD.org>
AuthorDate: 2025-07-16 12:40:05 +0000
Commit: Kristof Provost <kp@FreeBSD.org>
CommitDate: 2025-07-23 13:35:44 +0000
pf: accept IP options for IGMP and ICMP6 MLD
IGMP and ICMP6 MLD packets always have the router alert option set.
pf blocked IPv4 options and IPv6 option header by default. This
forced users to set allow-opts in pf rules.
Better let multicast work by default. Detect router alerts by
parsing IP options and hop by hop headers. If the packet has only
this option and is a multicast control packet, do not block it due
to bad options.
tested by otto@; OK sashan@
Relnotes: yes
Obtained from: OpenBSD, bluhm <bluhm@openbsd.org>, 214dd8280c
Sponsored by: Rubicon Communications, LLC ("Netgate")
---
sys/net/pfvar.h | 3 ++
sys/netpfil/pf/pf.c | 132 +++++++++++++++++++++++++++++++++++++++++++++-------
2 files changed, 117 insertions(+), 18 deletions(-)
diff --git a/sys/net/pfvar.h b/sys/net/pfvar.h
index 452a8eb4024b..efc884398e7b 100644
--- a/sys/net/pfvar.h
+++ b/sys/net/pfvar.h
@@ -1676,6 +1676,9 @@ struct pf_pdesc {
u_int32_t fragoff; /* fragment header offset */
u_int32_t jumbolen; /* length from v6 jumbo header */
u_int32_t badopts; /* v4 options or v6 routing headers */
+#define PF_OPT_OTHER 0x0001
+#define PF_OPT_JUMBO 0x0002
+#define PF_OPT_ROUTER_ALERT 0x0004
u_int16_t *ip_sum;
u_int16_t flags; /* Let SCRUB trigger behavior in
diff --git a/sys/netpfil/pf/pf.c b/sys/netpfil/pf/pf.c
index 1310445c4063..0a951815656e 100644
--- a/sys/netpfil/pf/pf.c
+++ b/sys/netpfil/pf/pf.c
@@ -375,6 +375,8 @@ static u_int16_t pf_calc_mss(struct pf_addr *, sa_family_t,
int, u_int16_t);
static int pf_check_proto_cksum(struct mbuf *, int, int,
u_int8_t, sa_family_t);
+static int pf_walk_option(struct pf_pdesc *, struct ip *,
+ int, int, u_short *);
static int pf_walk_header(struct pf_pdesc *, struct ip *, u_short *);
#ifdef INET6
static int pf_walk_option6(struct pf_pdesc *, struct ip6_hdr *,
@@ -9797,6 +9799,55 @@ pf_dummynet_route(struct pf_pdesc *pd, struct pf_kstate *s,
return (0);
}
+static int
+pf_walk_option(struct pf_pdesc *pd, struct ip *h, int off, int end,
+ u_short *reason)
+{
+ uint8_t type, length, opts[15 * 4 - sizeof(struct ip)];
+
+ MPASS(end - off <= sizeof(opts));
+ m_copydata(pd->m, off, end - off, opts);
+ end -= off;
+ off = 0;
+
+ while (off < end) {
+ type = opts[off];
+ if (type == IPOPT_EOL)
+ break;
+ if (type == IPOPT_NOP) {
+ off++;
+ continue;
+ }
+ if (off + 2 > end) {
+ DPFPRINTF(PF_DEBUG_MISC, ("IP length opt\n"));
+ REASON_SET(reason, PFRES_IPOPTIONS);
+ return (PF_DROP);
+ }
+ length = opts[off + 1];
+ if (length < 2) {
+ DPFPRINTF(PF_DEBUG_MISC, ("IP short opt\n"));
+ REASON_SET(reason, PFRES_IPOPTIONS);
+ return (PF_DROP);
+ }
+ if (off + length > end) {
+ DPFPRINTF(PF_DEBUG_MISC, ("IP long opt\n"));
+ REASON_SET(reason, PFRES_IPOPTIONS);
+ return (PF_DROP);
+ }
+ switch (type) {
+ case IPOPT_RA:
+ pd->badopts |= PF_OPT_ROUTER_ALERT;
+ break;
+ default:
+ pd->badopts |= PF_OPT_OTHER;
+ break;
+ }
+ off += length;
+ }
+
+ return (PF_PASS);
+}
+
static int
pf_walk_header(struct pf_pdesc *pd, struct ip *h, u_short *reason)
{
@@ -9809,11 +9860,20 @@ pf_walk_header(struct pf_pdesc *pd, struct ip *h, u_short *reason)
REASON_SET(reason, PFRES_SHORT);
return (PF_DROP);
}
- if (hlen != sizeof(struct ip))
- pd->badopts++;
+ if (hlen != sizeof(struct ip)) {
+ if (pf_walk_option(pd, h, pd->off + sizeof(struct ip),
+ pd->off + hlen, reason) != PF_PASS)
+ return (PF_DROP);
+ /* header options which contain only padding is fishy */
+ if (pd->badopts == 0)
+ pd->badopts |= PF_OPT_OTHER;
+ }
end = pd->off + ntohs(h->ip_len);
pd->off += hlen;
pd->proto = h->ip_p;
+ /* IGMP packets have router alert options, allow them */
+ if (pd->proto == IPPROTO_IGMP)
+ pd->badopts &= ~PF_OPT_ROUTER_ALERT;
/* stop walking over non initial fragments */
if ((h->ip_off & htons(IP_OFFMASK)) != 0)
return (PF_PASS);
@@ -9870,7 +9930,10 @@ pf_walk_option6(struct pf_pdesc *pd, struct ip6_hdr *h, int off, int end,
return (PF_DROP);
}
switch (opt.ip6o_type) {
+ case IP6OPT_PADN:
+ break;
case IP6OPT_JUMBO:
+ pd->badopts |= PF_OPT_JUMBO;
if (pd->jumbolen != 0) {
DPFPRINTF(PF_DEBUG_MISC, ("IPv6 multiple jumbo"));
REASON_SET(reason, PFRES_IPOPTIONS);
@@ -9895,7 +9958,11 @@ pf_walk_option6(struct pf_pdesc *pd, struct ip6_hdr *h, int off, int end,
return (PF_DROP);
}
break;
+ case IP6OPT_ROUTER_ALERT:
+ pd->badopts |= PF_OPT_ROUTER_ALERT;
+ break;
default:
+ pd->badopts |= PF_OPT_OTHER;
break;
}
off += sizeof(opt) + opt.ip6o_len;
@@ -9909,6 +9976,7 @@ pf_walk_header6(struct pf_pdesc *pd, struct ip6_hdr *h, u_short *reason)
{
struct ip6_frag frag;
struct ip6_ext ext;
+ struct icmp6_hdr icmp6;
struct ip6_rthdr rthdr;
uint32_t end;
int hdr_cnt, fraghdr_cnt = 0, rthdr_cnt = 0;
@@ -9920,9 +9988,22 @@ pf_walk_header6(struct pf_pdesc *pd, struct ip6_hdr *h, u_short *reason)
for (hdr_cnt = 0; hdr_cnt < PF_HDR_LIMIT; hdr_cnt++) {
switch (pd->proto) {
case IPPROTO_ROUTING:
- case IPPROTO_HOPOPTS:
case IPPROTO_DSTOPTS:
- pd->badopts++;
+ pd->badopts |= PF_OPT_OTHER;
+ break;
+ case IPPROTO_HOPOPTS:
+ if (!pf_pull_hdr(pd->m, pd->off, &ext, sizeof(ext),
+ NULL, reason, AF_INET6)) {
+ DPFPRINTF(PF_DEBUG_MISC, ("IPv6 short exthdr\n"));
+ return (PF_DROP);
+ }
+ if (pf_walk_option6(pd, h, pd->off + sizeof(ext),
+ pd->off + (ext.ip6e_len + 1) * 8,
+ reason) != PF_PASS)
+ return (PF_DROP);
+ /* option header which contains only padding is fishy */
+ if (pd->badopts == 0)
+ pd->badopts |= PF_OPT_OTHER;
break;
}
switch (pd->proto) {
@@ -10001,18 +10082,11 @@ pf_walk_header6(struct pf_pdesc *pd, struct ip6_hdr *h, u_short *reason)
/* reassembly needs the ext header before the frag */
if (pd->fragoff == 0)
pd->extoff = pd->off;
- if (pd->proto == IPPROTO_HOPOPTS && pd->fragoff == 0) {
- if (pf_walk_option6(pd, h,
- pd->off + sizeof(ext),
- pd->off + (ext.ip6e_len + 1) * 8, reason)
- != PF_PASS)
- return (PF_DROP);
- if (ntohs(h->ip6_plen) == 0 && pd->jumbolen != 0) {
- DPFPRINTF(PF_DEBUG_MISC,
- ("IPv6 missing jumbo"));
- REASON_SET(reason, PFRES_IPOPTIONS);
- return (PF_DROP);
- }
+ if (pd->proto == IPPROTO_HOPOPTS && pd->fragoff == 0 &&
+ ntohs(h->ip6_plen) == 0 && pd->jumbolen != 0) {
+ DPFPRINTF(PF_DEBUG_MISC, ("IPv6 missing jumbo\n"));
+ REASON_SET(reason, PFRES_IPOPTIONS);
+ return (PF_DROP);
}
if (pd->proto == IPPROTO_AH)
pd->off += (ext.ip6e_len + 2) * 4;
@@ -10020,10 +10094,32 @@ pf_walk_header6(struct pf_pdesc *pd, struct ip6_hdr *h, u_short *reason)
pd->off += (ext.ip6e_len + 1) * 8;
pd->proto = ext.ip6e_nxt;
break;
+ case IPPROTO_ICMPV6:
+ /* fragments may be short, ignore inner header then */
+ if (pd->fragoff != 0 && end < pd->off + sizeof(icmp6)) {
+ pd->off = pd->fragoff;
+ pd->proto = IPPROTO_FRAGMENT;
+ return (PF_PASS);
+ }
+ if (!pf_pull_hdr(pd->m, pd->off, &icmp6, sizeof(icmp6),
+ NULL, reason, AF_INET6)) {
+ DPFPRINTF(PF_DEBUG_MISC,
+ ("IPv6 short icmp6hdr\n"));
+ return (PF_DROP);
+ }
+ /* ICMP multicast packets have router alert options */
+ switch (icmp6.icmp6_type) {
+ case MLD_LISTENER_QUERY:
+ case MLD_LISTENER_REPORT:
+ case MLD_LISTENER_DONE:
+ case MLDV2_LISTENER_REPORT:
+ pd->badopts &= ~PF_OPT_ROUTER_ALERT;
+ break;
+ }
+ return (PF_PASS);
case IPPROTO_TCP:
case IPPROTO_UDP:
case IPPROTO_SCTP:
- case IPPROTO_ICMPV6:
/* fragments may be short, ignore inner header then */
if (pd->fragoff != 0 && end < pd->off +
(pd->proto == IPPROTO_TCP ? sizeof(struct tcphdr) :
@@ -10733,7 +10829,7 @@ done:
if (s)
memcpy(&pd.act, &s->act, sizeof(s->act));
- if (action == PF_PASS && pd.badopts && !pd.act.allow_opts) {
+ if (action == PF_PASS && pd.badopts != 0 && !pd.act.allow_opts) {
action = PF_DROP;
REASON_SET(&reason, PFRES_IPOPTIONS);
pd.act.log = PF_LOG_FORCE;