Hi,
Our IPv6 stack scans all extension headers for routing header type
0 and drops the packet if it finds one. RFC 5095 demands to handle
a routing header type 0 like an unrecognised routing type. This
is enough to protect the own machine.
To protect a network as a firewall, we have pf which does the same
full scan in pf_walk_header6(). As pf is enabled by default, nothing
changes for most users. If you turn off pf on your router, you
should not expect extra protection.
I would like to get rid of the double scanning and the old disabled
code in the IPv6 stack.
ok?
bluhm
Index: netinet6/ip6_input.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/netinet6/ip6_input.c,v
retrieving revision 1.115
diff -u -p -u -p -r1.115 ip6_input.c
--- netinet6/ip6_input.c 17 Oct 2013 16:27:46 -0000 1.115
+++ netinet6/ip6_input.c 18 Oct 2013 17:21:52 -0000
@@ -122,7 +122,6 @@ struct ifqueue ip6intrq;
struct ip6stat ip6stat;
void ip6_init2(void *);
-int ip6_check_rh0hdr(struct mbuf *, int *);
int ip6_hopopts_input(u_int32_t *, u_int32_t *, struct mbuf **, int *);
struct mbuf *ip6_pullexthdr(struct mbuf *, size_t, int);
@@ -318,15 +317,6 @@ ip6_input(struct mbuf *m)
}
#endif
- if (ip6_check_rh0hdr(m, &off)) {
- ip6stat.ip6s_badoptions++;
- in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_discard);
- in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_hdrerr);
- icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, off);
- /* m is already freed */
- return;
- }
-
#if NPF > 0
/*
* Packet filter
@@ -705,74 +695,6 @@ ip6_input(struct mbuf *m)
return;
bad:
m_freem(m);
-}
-
-/* scan packet for RH0 routing header. Mostly stolen from pf.c:pf_test() */
-int
-ip6_check_rh0hdr(struct mbuf *m, int *offp)
-{
- struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
- struct ip6_rthdr rthdr;
- struct ip6_ext opt6;
- u_int8_t proto = ip6->ip6_nxt;
- int done = 0, lim, off, rh_cnt = 0;
-
- off = ((caddr_t)ip6 - m->m_data) + sizeof(struct ip6_hdr);
- lim = min(m->m_pkthdr.len, ntohs(ip6->ip6_plen) + sizeof(*ip6));
- do {
- switch (proto) {
- case IPPROTO_ROUTING:
- *offp = off;
- if (rh_cnt++) {
- /* more then one rh header present */
- return (1);
- }
-
- if (off + sizeof(rthdr) > lim) {
- /* packet to short to make sense */
- return (1);
- }
-
- m_copydata(m, off, sizeof(rthdr), (caddr_t)&rthdr);
-
- if (rthdr.ip6r_type == IPV6_RTHDR_TYPE_0) {
- *offp += offsetof(struct ip6_rthdr, ip6r_type);
- return (1);
- }
-
- off += (rthdr.ip6r_len + 1) * 8;
- proto = rthdr.ip6r_nxt;
- break;
- case IPPROTO_AH:
- case IPPROTO_HOPOPTS:
- case IPPROTO_DSTOPTS:
- /* get next header and header length */
- if (off + sizeof(opt6) > lim) {
- /*
- * Packet to short to make sense, we could
- * reject the packet but as a router we
- * should not do that so forward it.
- */
- return (0);
- }
-
- m_copydata(m, off, sizeof(opt6), (caddr_t)&opt6);
-
- if (proto == IPPROTO_AH)
- off += (opt6.ip6e_len + 2) * 4;
- else
- off += (opt6.ip6e_len + 1) * 8;
- proto = opt6.ip6e_nxt;
- break;
- case IPPROTO_FRAGMENT:
- default:
- /* end of header stack */
- done = 1;
- break;
- }
- } while (!done);
-
- return (0);
}
/*
Index: netinet6/route6.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/netinet6/route6.c,v
retrieving revision 1.17
diff -u -p -u -p -r1.17 route6.c
--- netinet6/route6.c 11 Jun 2008 19:00:50 -0000 1.17
+++ netinet6/route6.c 18 Oct 2013 17:59:45 -0000
@@ -44,10 +44,6 @@
#include <netinet/icmp6.h>
-#if 0
-static int ip6_rthdr0(struct mbuf *, struct ip6_hdr *, struct ip6_rthdr0 *);
-#endif
-
/*
* proto is unused
*/
@@ -68,43 +64,12 @@ route6_input(struct mbuf **mp, int *offp
}
switch (rh->ip6r_type) {
-#if 0
- /*
- * See http://www.secdev.org/conf/IPv6_RH_security-csw07.pdf
- * for why IPV6_RTHDR_TYPE_0 is banned here.
- *
- * We return ICMPv6 parameter problem so that innocent people
- * (not an attacker) would notice about the use of IPV6_RTHDR_TYPE_0.
- * Since there's no amplification, and ICMPv6 error will be rate-
- * controlled, it shouldn't cause any problem.
- * If you are concerned about this, you may want to use the following
- * code fragment:
- *
- * case IPV6_RTHDR_TYPE_0:
- * m_freem(m);
- * return (IPPROTO_DONE);
- */
case IPV6_RTHDR_TYPE_0:
- rhlen = (rh->ip6r_len + 1) << 3;
- if (rh->ip6r_segleft == 0)
- break; /* Final dst. Just ignore the header. */
/*
- * note on option length:
- * maximum rhlen: 2048
- * max mbuf m_pulldown can handle: MCLBYTES == usually 2048
- * so, here we are assuming that m_pulldown can handle
- * rhlen == 2048 case. this may not be a good thing to
- * assume - we may want to avoid pulling it up altogether.
+ * RFC 5095 specifies to handle routing header type 0
+ * the same way as an unrecognised routing type.
*/
- IP6_EXTHDR_GET(rh, struct ip6_rthdr *, m, off, rhlen);
- if (rh == NULL) {
- ip6stat.ip6s_tooshort++;
- return IPPROTO_DONE;
- }
- if (ip6_rthdr0(m, ip6, (struct ip6_rthdr0 *)rh))
- return (IPPROTO_DONE);
- break;
-#endif
+ /* FALLTHROUGH */
default:
/* unknown routing type */
if (rh->ip6r_segleft == 0) {
@@ -120,83 +85,3 @@ route6_input(struct mbuf **mp, int *offp
*offp += rhlen;
return (rh->ip6r_nxt);
}
-
-#if 0
-/*
- * Type0 routing header processing
- *
- * RFC2292 backward compatibility warning: no support for strict/loose bitmap,
- * as it was dropped between RFC1883 and RFC2460.
- */
-static int
-ip6_rthdr0(struct mbuf *m, struct ip6_hdr *ip6, struct ip6_rthdr0 *rh0)
-{
- int addrs, index;
- struct in6_addr *nextaddr, tmpaddr;
-
- if (rh0->ip6r0_segleft == 0)
- return (0);
-
- if (rh0->ip6r0_len % 2) {
- /*
- * Type 0 routing header can't contain more than 23 addresses.
- * RFC 2460: this limitation was removed since strict/loose
- * bitmap field was deleted.
- */
- ip6stat.ip6s_badoptions++;
- icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
- (caddr_t)&rh0->ip6r0_len - (caddr_t)ip6);
- return (-1);
- }
-
- if ((addrs = rh0->ip6r0_len / 2) < rh0->ip6r0_segleft) {
- ip6stat.ip6s_badoptions++;
- icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
- (caddr_t)&rh0->ip6r0_segleft - (caddr_t)ip6);
- return (-1);
- }
-
- index = addrs - rh0->ip6r0_segleft;
- rh0->ip6r0_segleft--;
- nextaddr = ((struct in6_addr *)(rh0 + 1)) + index;
-
- /*
- * reject invalid addresses. be proactive about malicious use of
- * IPv4 mapped/compat address.
- * XXX need more checks?
- */
- if (IN6_IS_ADDR_MULTICAST(nextaddr) ||
- IN6_IS_ADDR_UNSPECIFIED(nextaddr) ||
- IN6_IS_ADDR_V4MAPPED(nextaddr) ||
- IN6_IS_ADDR_V4COMPAT(nextaddr)) {
- ip6stat.ip6s_badoptions++;
- goto bad;
- }
- if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
- IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_dst) ||
- IN6_IS_ADDR_V4MAPPED(&ip6->ip6_dst) ||
- IN6_IS_ADDR_V4COMPAT(&ip6->ip6_dst)) {
- ip6stat.ip6s_badoptions++;
- goto bad;
- }
-
- /*
- * Swap the IPv6 destination address and nextaddr. Forward the packet.
- */
- tmpaddr = *nextaddr;
- *nextaddr = ip6->ip6_dst;
- if (IN6_IS_ADDR_LINKLOCAL(nextaddr))
- nextaddr->s6_addr16[1] = 0;
- ip6->ip6_dst = tmpaddr;
- if (IN6_IS_ADDR_LINKLOCAL(&ip6->ip6_dst))
- ip6->ip6_dst.s6_addr16[1] = htons(m->m_pkthdr.rcvif->if_index);
-
- ip6_forward(m, 1);
-
- return (-1); /* m would be freed in ip6_forward() */
-
- bad:
- m_freem(m);
- return (-1);
-}
-#endif
