/* $NetBSD: if_stf.c,v 1.109 2022/09/03 02:47:59 thorpej Exp $ */ /* $KAME: if_stf.c,v 1.62 2001/06/07 22:32:16 itojun Exp $ */ /* * Copyright (C) 2000 WIDE Project. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the project nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ /* * 6to4 interface, based on RFC3056. * * 6to4 interface is NOT capable of link-layer (I mean, IPv4) multicasting. * There is no address mapping defined from IPv6 multicast address to IPv4 * address. Therefore, we do not have IFF_MULTICAST on the interface. * * Due to the lack of address mapping for link-local addresses, we cannot * throw packets toward link-local addresses (fe80::x). Also, we cannot throw * packets to link-local multicast addresses (ff02::x). * * Here are interesting symptoms due to the lack of link-local address: * * Unicast routing exchange: * - RIPng: Impossible. Uses link-local multicast packet toward ff02::9, * and link-local addresses as nexthop. * - OSPFv6: Impossible. OSPFv6 assumes that there's link-local address * assigned to the link, and makes use of them. Also, HELLO packets use * link-local multicast addresses (ff02::5 and ff02::6). * - BGP4+: Maybe. You can only use global address as nexthop, and global * address as TCP endpoint address. * * Multicast routing protocols: * - PIM: Hello packet cannot be used to discover adjacent PIM routers. * Adjacent PIM routers must be configured manually (is it really spec-wise * correct thing to do?). * * ICMPv6: * - Redirects cannot be used due to the lack of link-local address. * * stf interface does not have, and will not need, a link-local address. * It seems to have no real benefit and does not help the above symptoms much. * Even if we assign link-locals to interface, we cannot really * use link-local unicast/multicast on top of 6to4 cloud (since there's no * encapsulation defined for link-local address), and the above analysis does * not change. RFC3056 does not mandate the assignment of link-local address * either. * * 6to4 interface has security issues. Refer to * http://playground.iijlab.net/i-d/draft-itojun-ipv6-transition-abuse-00.txt * for details. The code tries to filter out some of malicious packets. * Note that there is no way to be 100% secure. */ #include __KERNEL_RCSID(0, "$NetBSD: if_stf.c,v 1.109 2022/09/03 02:47:59 thorpej Exp $"); #ifdef _KERNEL_OPT #include "opt_inet.h" #include "stf.h" #endif #ifndef INET6 #error "pseudo-device stf requires options INET6" #endif #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "ioconf.h" #define IN6_IS_ADDR_6TO4(x) (ntohs((x)->s6_addr16[0]) == 0x2002) #define GET_V4(x) ((const struct in_addr *)(&(x)->s6_addr16[1])) struct stf_softc { struct ifnet sc_if; /* common area */ struct route sc_ro; const struct encaptab *encap_cookie; LIST_ENTRY(stf_softc) sc_list; }; static LIST_HEAD(, stf_softc) stf_softc_list; static int stf_clone_create(struct if_clone *, int); static int stf_clone_destroy(struct ifnet *); struct if_clone stf_cloner = IF_CLONE_INITIALIZER("stf", stf_clone_create, stf_clone_destroy); static int ip_stf_ttl = STF_TTL; extern struct domain inetdomain; static const struct encapsw in_stf_encapsw = { .encapsw4 = { .pr_input = in_stf_input, .pr_ctlinput = NULL, } }; static int stf_encapcheck(struct mbuf *, int, int, void *); static struct in6_ifaddr *stf_getsrcifa6(struct ifnet *); static int stf_output(struct ifnet *, struct mbuf *, const struct sockaddr *, const struct rtentry *); static int isrfc1918addr(const struct in_addr *); static int stf_checkaddr4(struct stf_softc *, const struct in_addr *, struct ifnet *); static int stf_checkaddr6(struct stf_softc *, const struct in6_addr *, struct ifnet *); static void stf_rtrequest(int, struct rtentry *, const struct rt_addrinfo *); static int stf_ioctl(struct ifnet *, u_long, void *); /* ARGSUSED */ void stfattach(int count) { /* * Nothing to do here, initialization is handled by the * module initialization code in stfinit() below). */ } static void stfinit(void) { LIST_INIT(&stf_softc_list); if_clone_attach(&stf_cloner); } static int stfdetach(void) { int error = 0; if (!LIST_EMPTY(&stf_softc_list)) error = EBUSY; if (error == 0) if_clone_detach(&stf_cloner); return error; } static int stf_clone_create(struct if_clone *ifc, int unit) { struct stf_softc *sc; int error; sc = malloc(sizeof(struct stf_softc), M_DEVBUF, M_WAIT|M_ZERO); if_initname(&sc->sc_if, ifc->ifc_name, unit); error = encap_lock_enter(); if (error) { free(sc, M_DEVBUF); return error; } if (LIST_FIRST(&stf_softc_list) != NULL) { /* Only one stf interface is allowed. */ encap_lock_exit(); free(sc, M_DEVBUF); return EEXIST; } sc->encap_cookie = encap_attach_func(AF_INET, IPPROTO_IPV6, stf_encapcheck, &in_stf_encapsw, sc); encap_lock_exit(); if (sc->encap_cookie == NULL) { printf("%s: unable to attach encap\n", if_name(&sc->sc_if)); free(sc, M_DEVBUF); return EIO; /* XXX */ } sc->sc_if.if_mtu = STF_MTU; sc->sc_if.if_flags = 0; sc->sc_if.if_ioctl = stf_ioctl; sc->sc_if.if_output = stf_output; sc->sc_if.if_type = IFT_STF; sc->sc_if.if_dlt = DLT_NULL; if_attach(&sc->sc_if); if_alloc_sadl(&sc->sc_if); bpf_attach(&sc->sc_if, DLT_NULL, sizeof(u_int)); LIST_INSERT_HEAD(&stf_softc_list, sc, sc_list); return 0; } static int stf_clone_destroy(struct ifnet *ifp) { struct stf_softc *sc = (void *) ifp; encap_lock_enter(); LIST_REMOVE(sc, sc_list); encap_detach(sc->encap_cookie); encap_lock_exit(); bpf_detach(ifp); if_detach(ifp); rtcache_free(&sc->sc_ro); free(sc, M_DEVBUF); return 0; } static int stf_encapcheck(struct mbuf *m, int off, int proto, void *arg) { struct ip ip; struct in6_ifaddr *ia6; struct stf_softc *sc; struct in_addr a, b; sc = (struct stf_softc *)arg; if (sc == NULL) return 0; if ((sc->sc_if.if_flags & IFF_UP) == 0) return 0; /* IFF_LINK0 means "no decapsulation" */ if ((sc->sc_if.if_flags & IFF_LINK0) != 0) return 0; if (proto != IPPROTO_IPV6) return 0; m_copydata(m, 0, sizeof(ip), (void *)&ip); if (ip.ip_v != 4) return 0; ia6 = stf_getsrcifa6(&sc->sc_if); if (ia6 == NULL) return 0; /* * check if IPv4 dst matches the IPv4 address derived from the * local 6to4 address. * success on: dst = 10.1.1.1, ia6->ia_addr = 2002:0a01:0101:... */ if (memcmp(GET_V4(&ia6->ia_addr.sin6_addr), &ip.ip_dst, sizeof(ip.ip_dst)) != 0) return 0; /* * check if IPv4 src matches the IPv4 address derived from the * local 6to4 address masked by prefixmask. * success on: src = 10.1.1.1, ia6->ia_addr = 2002:0a00:.../24 * fail on: src = 10.1.1.1, ia6->ia_addr = 2002:0b00:.../24 */ memset(&a, 0, sizeof(a)); a.s_addr = GET_V4(&ia6->ia_addr.sin6_addr)->s_addr; a.s_addr &= GET_V4(&ia6->ia_prefixmask.sin6_addr)->s_addr; b = ip.ip_src; b.s_addr &= GET_V4(&ia6->ia_prefixmask.sin6_addr)->s_addr; if (a.s_addr != b.s_addr) return 0; /* stf interface makes single side match only */ return 32; } static struct in6_ifaddr * stf_getsrcifa6(struct ifnet *ifp) { struct ifaddr *ifa; struct in_ifaddr *ia4; struct sockaddr_in6 *sin6; struct in_addr in; int s; s = pserialize_read_enter(); IFADDR_READER_FOREACH(ifa, ifp) { if (ifa->ifa_addr->sa_family != AF_INET6) continue; sin6 = (struct sockaddr_in6 *)ifa->ifa_addr; if (!IN6_IS_ADDR_6TO4(&sin6->sin6_addr)) continue; memcpy(&in, GET_V4(&sin6->sin6_addr), sizeof(in)); ia4 = in_get_ia(in); if (ia4 == NULL) continue; pserialize_read_exit(s); /* TODO NOMPSAFE */ return (struct in6_ifaddr *)ifa; } pserialize_read_exit(s); return NULL; } static int stf_output(struct ifnet *ifp, struct mbuf *m, const struct sockaddr *dst, const struct rtentry *rt0) { struct rtentry *rt; struct stf_softc *sc; const struct sockaddr_in6 *dst6; const struct in_addr *in4; uint8_t tos; struct ip *ip; struct ip6_hdr *ip6; struct in6_ifaddr *ia6; union { struct sockaddr dst; struct sockaddr_in dst4; } u; sc = (struct stf_softc*)ifp; dst6 = (const struct sockaddr_in6 *)dst; /* just in case */ if ((ifp->if_flags & IFF_UP) == 0) { m_freem(m); return ENETDOWN; } /* * If we don't have an ip4 address that match my inner ip6 address, * we shouldn't generate output. Without this check, we'll end up * using wrong IPv4 source. */ ia6 = stf_getsrcifa6(ifp); if (ia6 == NULL) { m_freem(m); if_statinc(ifp, if_oerrors); return ENETDOWN; } if (m->m_len < sizeof(*ip6)) { m = m_pullup(m, sizeof(*ip6)); if (m == NULL) { if_statinc(ifp, if_oerrors); return ENOBUFS; } } ip6 = mtod(m, struct ip6_hdr *); tos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; /* * Pickup the right outer dst addr from the list of candidates. * ip6_dst has priority as it may be able to give us shorter IPv4 hops. */ if (IN6_IS_ADDR_6TO4(&ip6->ip6_dst)) in4 = GET_V4(&ip6->ip6_dst); else if (IN6_IS_ADDR_6TO4(&dst6->sin6_addr)) in4 = GET_V4(&dst6->sin6_addr); else { m_freem(m); if_statinc(ifp, if_oerrors); return ENETUNREACH; } bpf_mtap_af(ifp, AF_INET6, m, BPF_D_OUT); M_PREPEND(m, sizeof(struct ip), M_DONTWAIT); if (m && m->m_len < sizeof(struct ip)) m = m_pullup(m, sizeof(struct ip)); if (m == NULL) { if_statinc(ifp, if_oerrors); return ENOBUFS; } ip = mtod(m, struct ip *); memset(ip, 0, sizeof(*ip)); bcopy(GET_V4(&((struct sockaddr_in6 *)&ia6->ia_addr)->sin6_addr), &ip->ip_src, sizeof(ip->ip_src)); memcpy(&ip->ip_dst, in4, sizeof(ip->ip_dst)); ip->ip_p = IPPROTO_IPV6; ip->ip_ttl = ip_stf_ttl; ip->ip_len = htons(m->m_pkthdr.len); if (ifp->if_flags & IFF_LINK1) ip_ecn_ingress(ECN_ALLOWED, &ip->ip_tos, &tos); else ip_ecn_ingress(ECN_NOCARE, &ip->ip_tos, &tos); sockaddr_in_init(&u.dst4, &ip->ip_dst, 0); if ((rt = rtcache_lookup(&sc->sc_ro, &u.dst)) == NULL) { m_freem(m); if_statinc(ifp, if_oerrors); return ENETUNREACH; } /* If the route constitutes infinite encapsulation, punt. */ if (rt->rt_ifp == ifp) { rtcache_unref(rt, &sc->sc_ro); rtcache_free(&sc->sc_ro); m_freem(m); if_statinc(ifp, if_oerrors); return ENETUNREACH; } rtcache_unref(rt, &sc->sc_ro); if_statadd2(ifp, if_opackets, 1, if_obytes, m->m_pkthdr.len - sizeof(struct ip)); return ip_output(m, NULL, &sc->sc_ro, 0, NULL, NULL); } static int isrfc1918addr(const struct in_addr *in) { /* * returns 1 if private address range: * 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 */ if ((ntohl(in->s_addr) & 0xff000000) >> 24 == 10 || (ntohl(in->s_addr) & 0xfff00000) >> 16 == 172 * 256 + 16 || (ntohl(in->s_addr) & 0xffff0000) >> 16 == 192 * 256 + 168) return 1; return 0; } static int stf_checkaddr4(struct stf_softc *sc, const struct in_addr *in, struct ifnet *inifp /*incoming interface*/) { struct in_ifaddr *ia4; /* * reject packets with the following address: * 224.0.0.0/4 0.0.0.0/8 127.0.0.0/8 255.0.0.0/8 */ if (IN_MULTICAST(in->s_addr)) return -1; switch ((ntohl(in->s_addr) & 0xff000000) >> 24) { case 0: case 127: case 255: return -1; } /* * reject packets with private address range. * (requirement from RFC3056 section 2 1st paragraph) */ if (isrfc1918addr(in)) return -1; /* * reject packet with IPv4 link-local (169.254.0.0/16), * as suggested in draft-savola-v6ops-6to4-security-00.txt */ if (((ntohl(in->s_addr) & 0xff000000) >> 24) == 169 && ((ntohl(in->s_addr) & 0x00ff0000) >> 16) == 254) return -1; /* * reject packets with broadcast */ IN_ADDRLIST_READER_FOREACH(ia4) { if ((ia4->ia_ifa.ifa_ifp->if_flags & IFF_BROADCAST) == 0) continue; if (in->s_addr == ia4->ia_broadaddr.sin_addr.s_addr) return -1; } /* * perform ingress filter */ if (sc && (sc->sc_if.if_flags & IFF_LINK2) == 0 && inifp) { struct sockaddr_in sin; struct rtentry *rt; memset(&sin, 0, sizeof(sin)); sin.sin_family = AF_INET; sin.sin_len = sizeof(struct sockaddr_in); sin.sin_addr = *in; rt = rtalloc1((struct sockaddr *)&sin, 0); if (!rt || rt->rt_ifp != inifp) { #if 0 log(LOG_WARNING, "%s: packet from 0x%x dropped " "due to ingress filter\n", if_name(&sc->sc_if), (uint32_t)ntohl(sin.sin_addr.s_addr)); #endif if (rt) rt_unref(rt); return -1; } rt_unref(rt); } return 0; } static int stf_checkaddr6(struct stf_softc *sc, const struct in6_addr *in6, struct ifnet *inifp /*incoming interface*/) { /* * check 6to4 addresses */ if (IN6_IS_ADDR_6TO4(in6)) return stf_checkaddr4(sc, GET_V4(in6), inifp); /* * reject anything that look suspicious. the test is implemented * in ip6_input too, but we check here as well to * (1) reject bad packets earlier, and * (2) to be safe against future ip6_input change. */ if (IN6_IS_ADDR_V4COMPAT(in6) || IN6_IS_ADDR_V4MAPPED(in6)) return -1; /* * reject link-local and site-local unicast * as suggested in draft-savola-v6ops-6to4-security-00.txt */ if (IN6_IS_ADDR_LINKLOCAL(in6) || IN6_IS_ADDR_SITELOCAL(in6)) return -1; /* * reject node-local and link-local multicast * as suggested in draft-savola-v6ops-6to4-security-00.txt */ if (IN6_IS_ADDR_MC_NODELOCAL(in6) || IN6_IS_ADDR_MC_LINKLOCAL(in6)) return -1; return 0; } void in_stf_input(struct mbuf *m, int off, int proto, void *eparg) { int s; struct stf_softc *sc = eparg; struct ip *ip; struct ip6_hdr *ip6; uint8_t otos, itos; struct ifnet *ifp; size_t pktlen; KASSERT(sc != NULL); if (proto != IPPROTO_IPV6) { m_freem(m); return; } ip = mtod(m, struct ip *); if ((sc->sc_if.if_flags & IFF_UP) == 0) { m_freem(m); return; } ifp = &sc->sc_if; /* * perform sanity check against outer src/dst. * for source, perform ingress filter as well. */ if (stf_checkaddr4(sc, &ip->ip_dst, NULL) < 0 || stf_checkaddr4(sc, &ip->ip_src, m_get_rcvif_NOMPSAFE(m)) < 0) { m_freem(m); return; } otos = ip->ip_tos; m_adj(m, off); if (m->m_len < sizeof(*ip6)) { m = m_pullup(m, sizeof(*ip6)); if (!m) return; } ip6 = mtod(m, struct ip6_hdr *); /* * perform sanity check against inner src/dst. * for source, perform ingress filter as well. */ if (stf_checkaddr6(sc, &ip6->ip6_dst, NULL) < 0 || stf_checkaddr6(sc, &ip6->ip6_src, m_get_rcvif_NOMPSAFE(m)) < 0) { m_freem(m); return; } itos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; if ((ifp->if_flags & IFF_LINK1) != 0) ip_ecn_egress(ECN_ALLOWED, &otos, &itos); else ip_ecn_egress(ECN_NOCARE, &otos, &itos); ip6->ip6_flow &= ~htonl(0xff << 20); ip6->ip6_flow |= htonl((uint32_t)itos << 20); pktlen = m->m_pkthdr.len; m_set_rcvif(m, ifp); bpf_mtap_af(ifp, AF_INET6, m, BPF_D_IN); /* * Put the packet to the network layer input queue according to the * specified address family. * See net/if_gif.c for possible issues with packet processing * reorder due to extra queueing. */ s = splnet(); if (__predict_true(pktq_enqueue(ip6_pktq, m, 0))) { if_statadd2(ifp, if_ipackets, 1, if_ibytes, pktlen); } else { m_freem(m); } splx(s); return; } /* ARGSUSED */ static void stf_rtrequest(int cmd, struct rtentry *rt, const struct rt_addrinfo *info) { if (rt != NULL) { struct stf_softc *sc; sc = LIST_FIRST(&stf_softc_list); rt->rt_rmx.rmx_mtu = (sc != NULL) ? sc->sc_if.if_mtu : STF_MTU; } } static int stf_ioctl(struct ifnet *ifp, u_long cmd, void *data) { struct ifaddr *ifa; struct ifreq *ifr = data; struct sockaddr_in6 *sin6; int error; error = 0; switch (cmd) { case SIOCINITIFADDR: ifa = (struct ifaddr *)data; if (ifa == NULL || ifa->ifa_addr->sa_family != AF_INET6) { error = EAFNOSUPPORT; break; } sin6 = (struct sockaddr_in6 *)ifa->ifa_addr; if (IN6_IS_ADDR_6TO4(&sin6->sin6_addr) && !isrfc1918addr(GET_V4(&sin6->sin6_addr))) { ifa->ifa_rtrequest = stf_rtrequest; ifp->if_flags |= IFF_UP; } else error = EINVAL; break; case SIOCADDMULTI: case SIOCDELMULTI: if (ifr != NULL && ifreq_getaddr(cmd, ifr)->sa_family == AF_INET6) ; else error = EAFNOSUPPORT; break; case SIOCSIFMTU: if (ifr->ifr_mtu < STF_MTU_MIN || ifr->ifr_mtu > STF_MTU_MAX) return EINVAL; else if ((error = ifioctl_common(ifp, cmd, data)) == ENETRESET) error = 0; break; default: error = ifioctl_common(ifp, cmd, data); break; } return error; } /* * Module infrastructure */ #include "if_module.h" IF_MODULE(MODULE_CLASS_DRIVER, stf, NULL)