diff options
Diffstat (limited to 'freebsd/sys/netpfil/pf/pf_norm.c')
| -rw-r--r-- | freebsd/sys/netpfil/pf/pf_norm.c | 1843 |
1 files changed, 1843 insertions, 0 deletions
diff --git a/freebsd/sys/netpfil/pf/pf_norm.c b/freebsd/sys/netpfil/pf/pf_norm.c new file mode 100644 index 00000000..86d2c8eb --- /dev/null +++ b/freebsd/sys/netpfil/pf/pf_norm.c @@ -0,0 +1,1843 @@ +#include <machine/rtems-bsd-kernel-space.h> + +/*- + * Copyright 2001 Niels Provos <provos@citi.umich.edu> + * Copyright 2011 Alexander Bluhm <bluhm@openbsd.org> + * 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. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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. + * + * $OpenBSD: pf_norm.c,v 1.114 2009/01/29 14:11:45 henning Exp $ + */ + +#include <sys/cdefs.h> +__FBSDID("$FreeBSD$"); + +#include <rtems/bsd/local/opt_inet.h> +#include <rtems/bsd/local/opt_inet6.h> +#include <rtems/bsd/local/opt_pf.h> + +#include <rtems/bsd/sys/param.h> +#include <sys/kernel.h> +#include <rtems/bsd/sys/lock.h> +#include <sys/mbuf.h> +#include <sys/mutex.h> +#include <sys/refcount.h> +#include <sys/rwlock.h> +#include <sys/socket.h> + +#include <net/if.h> +#include <net/vnet.h> +#include <net/pfvar.h> +#include <net/if_pflog.h> + +#include <netinet/in.h> +#include <netinet/ip.h> +#include <netinet/ip_var.h> +#include <netinet6/ip6_var.h> +#include <netinet/tcp.h> +#include <netinet/tcp_fsm.h> +#include <netinet/tcp_seq.h> + +#ifdef INET6 +#include <netinet/ip6.h> +#endif /* INET6 */ + +struct pf_frent { + TAILQ_ENTRY(pf_frent) fr_next; + struct mbuf *fe_m; + uint16_t fe_hdrlen; /* ipv4 header length with ip options + ipv6, extension, fragment header */ + uint16_t fe_extoff; /* last extension header offset or 0 */ + uint16_t fe_len; /* fragment length */ + uint16_t fe_off; /* fragment offset */ + uint16_t fe_mff; /* more fragment flag */ +}; + +struct pf_fragment_cmp { + struct pf_addr frc_src; + struct pf_addr frc_dst; + uint32_t frc_id; + sa_family_t frc_af; + uint8_t frc_proto; +}; + +struct pf_fragment { + struct pf_fragment_cmp fr_key; +#define fr_src fr_key.frc_src +#define fr_dst fr_key.frc_dst +#define fr_id fr_key.frc_id +#define fr_af fr_key.frc_af +#define fr_proto fr_key.frc_proto + + RB_ENTRY(pf_fragment) fr_entry; + TAILQ_ENTRY(pf_fragment) frag_next; + uint32_t fr_timeout; + uint16_t fr_maxlen; /* maximum length of single fragment */ + TAILQ_HEAD(pf_fragq, pf_frent) fr_queue; +}; + +struct pf_fragment_tag { + uint16_t ft_hdrlen; /* header length of reassembled pkt */ + uint16_t ft_extoff; /* last extension header offset or 0 */ + uint16_t ft_maxlen; /* maximum fragment payload length */ + uint32_t ft_id; /* fragment id */ +}; + +static struct mtx pf_frag_mtx; +MTX_SYSINIT(pf_frag_mtx, &pf_frag_mtx, "pf fragments", MTX_DEF); +#define PF_FRAG_LOCK() mtx_lock(&pf_frag_mtx) +#define PF_FRAG_UNLOCK() mtx_unlock(&pf_frag_mtx) +#define PF_FRAG_ASSERT() mtx_assert(&pf_frag_mtx, MA_OWNED) + +VNET_DEFINE(uma_zone_t, pf_state_scrub_z); /* XXX: shared with pfsync */ + +static VNET_DEFINE(uma_zone_t, pf_frent_z); +#define V_pf_frent_z VNET(pf_frent_z) +static VNET_DEFINE(uma_zone_t, pf_frag_z); +#define V_pf_frag_z VNET(pf_frag_z) + +TAILQ_HEAD(pf_fragqueue, pf_fragment); +TAILQ_HEAD(pf_cachequeue, pf_fragment); +static VNET_DEFINE(struct pf_fragqueue, pf_fragqueue); +#define V_pf_fragqueue VNET(pf_fragqueue) +RB_HEAD(pf_frag_tree, pf_fragment); +static VNET_DEFINE(struct pf_frag_tree, pf_frag_tree); +#define V_pf_frag_tree VNET(pf_frag_tree) +static int pf_frag_compare(struct pf_fragment *, + struct pf_fragment *); +static RB_PROTOTYPE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare); +static RB_GENERATE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare); + +static void pf_flush_fragments(void); +static void pf_free_fragment(struct pf_fragment *); +static void pf_remove_fragment(struct pf_fragment *); +static int pf_normalize_tcpopt(struct pf_rule *, struct mbuf *, + struct tcphdr *, int, sa_family_t); +static struct pf_frent *pf_create_fragment(u_short *); +static struct pf_fragment *pf_find_fragment(struct pf_fragment_cmp *key, + struct pf_frag_tree *tree); +static struct pf_fragment *pf_fillup_fragment(struct pf_fragment_cmp *, + struct pf_frent *, u_short *); +static int pf_isfull_fragment(struct pf_fragment *); +static struct mbuf *pf_join_fragment(struct pf_fragment *); +#ifdef INET +static void pf_scrub_ip(struct mbuf **, uint32_t, uint8_t, uint8_t); +static int pf_reassemble(struct mbuf **, struct ip *, int, u_short *); +#endif /* INET */ +#ifdef INET6 +static int pf_reassemble6(struct mbuf **, struct ip6_hdr *, + struct ip6_frag *, uint16_t, uint16_t, u_short *); +static void pf_scrub_ip6(struct mbuf **, uint8_t); +#endif /* INET6 */ + +#define DPFPRINTF(x) do { \ + if (V_pf_status.debug >= PF_DEBUG_MISC) { \ + printf("%s: ", __func__); \ + printf x ; \ + } \ +} while(0) + +#ifdef INET +static void +pf_ip2key(struct ip *ip, int dir, struct pf_fragment_cmp *key) +{ + + key->frc_src.v4 = ip->ip_src; + key->frc_dst.v4 = ip->ip_dst; + key->frc_af = AF_INET; + key->frc_proto = ip->ip_p; + key->frc_id = ip->ip_id; +} +#endif /* INET */ + +void +pf_normalize_init(void) +{ + + V_pf_frag_z = uma_zcreate("pf frags", sizeof(struct pf_fragment), + NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); + V_pf_frent_z = uma_zcreate("pf frag entries", sizeof(struct pf_frent), + NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); + V_pf_state_scrub_z = uma_zcreate("pf state scrubs", + sizeof(struct pf_state_scrub), NULL, NULL, NULL, NULL, + UMA_ALIGN_PTR, 0); + + V_pf_limits[PF_LIMIT_FRAGS].zone = V_pf_frent_z; + V_pf_limits[PF_LIMIT_FRAGS].limit = PFFRAG_FRENT_HIWAT; + uma_zone_set_max(V_pf_frent_z, PFFRAG_FRENT_HIWAT); + uma_zone_set_warning(V_pf_frent_z, "PF frag entries limit reached"); + + TAILQ_INIT(&V_pf_fragqueue); +} + +void +pf_normalize_cleanup(void) +{ + + uma_zdestroy(V_pf_state_scrub_z); + uma_zdestroy(V_pf_frent_z); + uma_zdestroy(V_pf_frag_z); +} + +static int +pf_frag_compare(struct pf_fragment *a, struct pf_fragment *b) +{ + int diff; + + if ((diff = a->fr_id - b->fr_id) != 0) + return (diff); + if ((diff = a->fr_proto - b->fr_proto) != 0) + return (diff); + if ((diff = a->fr_af - b->fr_af) != 0) + return (diff); + if ((diff = pf_addr_cmp(&a->fr_src, &b->fr_src, a->fr_af)) != 0) + return (diff); + if ((diff = pf_addr_cmp(&a->fr_dst, &b->fr_dst, a->fr_af)) != 0) + return (diff); + return (0); +} + +void +pf_purge_expired_fragments(void) +{ + struct pf_fragment *frag; + u_int32_t expire = time_uptime - + V_pf_default_rule.timeout[PFTM_FRAG]; + + PF_FRAG_LOCK(); + while ((frag = TAILQ_LAST(&V_pf_fragqueue, pf_fragqueue)) != NULL) { + if (frag->fr_timeout > expire) + break; + + DPFPRINTF(("expiring %d(%p)\n", frag->fr_id, frag)); + pf_free_fragment(frag); + } + + PF_FRAG_UNLOCK(); +} + +/* + * Try to flush old fragments to make space for new ones + */ +static void +pf_flush_fragments(void) +{ + struct pf_fragment *frag; + int goal; + + PF_FRAG_ASSERT(); + + goal = uma_zone_get_cur(V_pf_frent_z) * 9 / 10; + DPFPRINTF(("trying to free %d frag entriess\n", goal)); + while (goal < uma_zone_get_cur(V_pf_frent_z)) { + frag = TAILQ_LAST(&V_pf_fragqueue, pf_fragqueue); + if (frag) + pf_free_fragment(frag); + else + break; + } +} + +/* Frees the fragments and all associated entries */ +static void +pf_free_fragment(struct pf_fragment *frag) +{ + struct pf_frent *frent; + + PF_FRAG_ASSERT(); + + /* Free all fragments */ + for (frent = TAILQ_FIRST(&frag->fr_queue); frent; + frent = TAILQ_FIRST(&frag->fr_queue)) { + TAILQ_REMOVE(&frag->fr_queue, frent, fr_next); + + m_freem(frent->fe_m); + uma_zfree(V_pf_frent_z, frent); + } + + pf_remove_fragment(frag); +} + +static struct pf_fragment * +pf_find_fragment(struct pf_fragment_cmp *key, struct pf_frag_tree *tree) +{ + struct pf_fragment *frag; + + PF_FRAG_ASSERT(); + + frag = RB_FIND(pf_frag_tree, tree, (struct pf_fragment *)key); + if (frag != NULL) { + /* XXX Are we sure we want to update the timeout? */ + frag->fr_timeout = time_uptime; + TAILQ_REMOVE(&V_pf_fragqueue, frag, frag_next); + TAILQ_INSERT_HEAD(&V_pf_fragqueue, frag, frag_next); + } + + return (frag); +} + +/* Removes a fragment from the fragment queue and frees the fragment */ +static void +pf_remove_fragment(struct pf_fragment *frag) +{ + + PF_FRAG_ASSERT(); + + RB_REMOVE(pf_frag_tree, &V_pf_frag_tree, frag); + TAILQ_REMOVE(&V_pf_fragqueue, frag, frag_next); + uma_zfree(V_pf_frag_z, frag); +} + +static struct pf_frent * +pf_create_fragment(u_short *reason) +{ + struct pf_frent *frent; + + PF_FRAG_ASSERT(); + + frent = uma_zalloc(V_pf_frent_z, M_NOWAIT); + if (frent == NULL) { + pf_flush_fragments(); + frent = uma_zalloc(V_pf_frent_z, M_NOWAIT); + if (frent == NULL) { + REASON_SET(reason, PFRES_MEMORY); + return (NULL); + } + } + + return (frent); +} + +static struct pf_fragment * +pf_fillup_fragment(struct pf_fragment_cmp *key, struct pf_frent *frent, + u_short *reason) +{ + struct pf_frent *after, *next, *prev; + struct pf_fragment *frag; + uint16_t total; + + PF_FRAG_ASSERT(); + + /* No empty fragments. */ + if (frent->fe_len == 0) { + DPFPRINTF(("bad fragment: len 0")); + goto bad_fragment; + } + + /* All fragments are 8 byte aligned. */ + if (frent->fe_mff && (frent->fe_len & 0x7)) { + DPFPRINTF(("bad fragment: mff and len %d", frent->fe_len)); + goto bad_fragment; + } + + /* Respect maximum length, IP_MAXPACKET == IPV6_MAXPACKET. */ + if (frent->fe_off + frent->fe_len > IP_MAXPACKET) { + DPFPRINTF(("bad fragment: max packet %d", + frent->fe_off + frent->fe_len)); + goto bad_fragment; + } + + DPFPRINTF((key->frc_af == AF_INET ? + "reass frag %d @ %d-%d" : "reass frag %#08x @ %d-%d", + key->frc_id, frent->fe_off, frent->fe_off + frent->fe_len)); + + /* Fully buffer all of the fragments in this fragment queue. */ + frag = pf_find_fragment(key, &V_pf_frag_tree); + + /* Create a new reassembly queue for this packet. */ + if (frag == NULL) { + frag = uma_zalloc(V_pf_frag_z, M_NOWAIT); + if (frag == NULL) { + pf_flush_fragments(); + frag = uma_zalloc(V_pf_frag_z, M_NOWAIT); + if (frag == NULL) { + REASON_SET(reason, PFRES_MEMORY); + goto drop_fragment; + } + } + + *(struct pf_fragment_cmp *)frag = *key; + frag->fr_timeout = time_uptime; + frag->fr_maxlen = frent->fe_len; + TAILQ_INIT(&frag->fr_queue); + + RB_INSERT(pf_frag_tree, &V_pf_frag_tree, frag); + TAILQ_INSERT_HEAD(&V_pf_fragqueue, frag, frag_next); + + /* We do not have a previous fragment. */ + TAILQ_INSERT_HEAD(&frag->fr_queue, frent, fr_next); + + return (frag); + } + + KASSERT(!TAILQ_EMPTY(&frag->fr_queue), ("!TAILQ_EMPTY()->fr_queue")); + + /* Remember maximum fragment len for refragmentation. */ + if (frent->fe_len > frag->fr_maxlen) + frag->fr_maxlen = frent->fe_len; + + /* Maximum data we have seen already. */ + total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off + + TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len; + + /* Non terminal fragments must have more fragments flag. */ + if (frent->fe_off + frent->fe_len < total && !frent->fe_mff) + goto bad_fragment; + + /* Check if we saw the last fragment already. */ + if (!TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_mff) { + if (frent->fe_off + frent->fe_len > total || + (frent->fe_off + frent->fe_len == total && frent->fe_mff)) + goto bad_fragment; + } else { + if (frent->fe_off + frent->fe_len == total && !frent->fe_mff) + goto bad_fragment; + } + + /* Find a fragment after the current one. */ + prev = NULL; + TAILQ_FOREACH(after, &frag->fr_queue, fr_next) { + if (after->fe_off > frent->fe_off) + break; + prev = after; + } + + KASSERT(prev != NULL || after != NULL, + ("prev != NULL || after != NULL")); + + if (prev != NULL && prev->fe_off + prev->fe_len > frent->fe_off) { + uint16_t precut; + + precut = prev->fe_off + prev->fe_len - frent->fe_off; + if (precut >= frent->fe_len) + goto bad_fragment; + DPFPRINTF(("overlap -%d", precut)); + m_adj(frent->fe_m, precut); + frent->fe_off += precut; + frent->fe_len -= precut; + } + + for (; after != NULL && frent->fe_off + frent->fe_len > after->fe_off; + after = next) { + uint16_t aftercut; + + aftercut = frent->fe_off + frent->fe_len - after->fe_off; + DPFPRINTF(("adjust overlap %d", aftercut)); + if (aftercut < after->fe_len) { + m_adj(after->fe_m, aftercut); + after->fe_off += aftercut; + after->fe_len -= aftercut; + break; + } + + /* This fragment is completely overlapped, lose it. */ + next = TAILQ_NEXT(after, fr_next); + m_freem(after->fe_m); + TAILQ_REMOVE(&frag->fr_queue, after, fr_next); + uma_zfree(V_pf_frent_z, after); + } + + if (prev == NULL) + TAILQ_INSERT_HEAD(&frag->fr_queue, frent, fr_next); + else + TAILQ_INSERT_AFTER(&frag->fr_queue, prev, frent, fr_next); + + return (frag); + +bad_fragment: + REASON_SET(reason, PFRES_FRAG); +drop_fragment: + uma_zfree(V_pf_frent_z, frent); + return (NULL); +} + +static int +pf_isfull_fragment(struct pf_fragment *frag) +{ + struct pf_frent *frent, *next; + uint16_t off, total; + + /* Check if we are completely reassembled */ + if (TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_mff) + return (0); + + /* Maximum data we have seen already */ + total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off + + TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len; + + /* Check if we have all the data */ + off = 0; + for (frent = TAILQ_FIRST(&frag->fr_queue); frent; frent = next) { + next = TAILQ_NEXT(frent, fr_next); + + off += frent->fe_len; + if (off < total && (next == NULL || next->fe_off != off)) { + DPFPRINTF(("missing fragment at %d, next %d, total %d", + off, next == NULL ? -1 : next->fe_off, total)); + return (0); + } + } + DPFPRINTF(("%d < %d?", off, total)); + if (off < total) + return (0); + KASSERT(off == total, ("off == total")); + + return (1); +} + +static struct mbuf * +pf_join_fragment(struct pf_fragment *frag) +{ + struct mbuf *m, *m2; + struct pf_frent *frent, *next; + + frent = TAILQ_FIRST(&frag->fr_queue); + next = TAILQ_NEXT(frent, fr_next); + + m = frent->fe_m; + m_adj(m, (frent->fe_hdrlen + frent->fe_len) - m->m_pkthdr.len); + uma_zfree(V_pf_frent_z, frent); + for (frent = next; frent != NULL; frent = next) { + next = TAILQ_NEXT(frent, fr_next); + + m2 = frent->fe_m; + /* Strip off ip header. */ + m_adj(m2, frent->fe_hdrlen); + /* Strip off any trailing bytes. */ + m_adj(m2, frent->fe_len - m2->m_pkthdr.len); + + uma_zfree(V_pf_frent_z, frent); + m_cat(m, m2); + } + + /* Remove from fragment queue. */ + pf_remove_fragment(frag); + + return (m); +} + +#ifdef INET +static int +pf_reassemble(struct mbuf **m0, struct ip *ip, int dir, u_short *reason) +{ + struct mbuf *m = *m0; + struct pf_frent *frent; + struct pf_fragment *frag; + struct pf_fragment_cmp key; + uint16_t total, hdrlen; + + /* Get an entry for the fragment queue */ + if ((frent = pf_create_fragment(reason)) == NULL) + return (PF_DROP); + + frent->fe_m = m; + frent->fe_hdrlen = ip->ip_hl << 2; + frent->fe_extoff = 0; + frent->fe_len = ntohs(ip->ip_len) - (ip->ip_hl << 2); + frent->fe_off = (ntohs(ip->ip_off) & IP_OFFMASK) << 3; + frent->fe_mff = ntohs(ip->ip_off) & IP_MF; + + pf_ip2key(ip, dir, &key); + + if ((frag = pf_fillup_fragment(&key, frent, reason)) == NULL) + return (PF_DROP); + + /* The mbuf is part of the fragment entry, no direct free or access */ + m = *m0 = NULL; + + if (!pf_isfull_fragment(frag)) + return (PF_PASS); /* drop because *m0 is NULL, no error */ + + /* We have all the data */ + frent = TAILQ_FIRST(&frag->fr_queue); + KASSERT(frent != NULL, ("frent != NULL")); + total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off + + TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len; + hdrlen = frent->fe_hdrlen; + + m = *m0 = pf_join_fragment(frag); + frag = NULL; + + if (m->m_flags & M_PKTHDR) { + int plen = 0; + for (m = *m0; m; m = m->m_next) + plen += m->m_len; + m = *m0; + m->m_pkthdr.len = plen; + } + + ip = mtod(m, struct ip *); + ip->ip_len = htons(hdrlen + total); + ip->ip_off &= ~(IP_MF|IP_OFFMASK); + + if (hdrlen + total > IP_MAXPACKET) { + DPFPRINTF(("drop: too big: %d", total)); + ip->ip_len = 0; + REASON_SET(reason, PFRES_SHORT); + /* PF_DROP requires a valid mbuf *m0 in pf_test() */ + return (PF_DROP); + } + + DPFPRINTF(("complete: %p(%d)\n", m, ntohs(ip->ip_len))); + return (PF_PASS); +} +#endif /* INET */ + +#ifdef INET6 +static int +pf_reassemble6(struct mbuf **m0, struct ip6_hdr *ip6, struct ip6_frag *fraghdr, + uint16_t hdrlen, uint16_t extoff, u_short *reason) +{ + struct mbuf *m = *m0; + struct pf_frent *frent; + struct pf_fragment *frag; + struct pf_fragment_cmp key; + struct m_tag *mtag; + struct pf_fragment_tag *ftag; + int off; + uint32_t frag_id; + uint16_t total, maxlen; + uint8_t proto; + + PF_FRAG_LOCK(); + + /* Get an entry for the fragment queue. */ + if ((frent = pf_create_fragment(reason)) == NULL) { + PF_FRAG_UNLOCK(); + return (PF_DROP); + } + + frent->fe_m = m; + frent->fe_hdrlen = hdrlen; + frent->fe_extoff = extoff; + frent->fe_len = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - hdrlen; + frent->fe_off = ntohs(fraghdr->ip6f_offlg & IP6F_OFF_MASK); + frent->fe_mff = fraghdr->ip6f_offlg & IP6F_MORE_FRAG; + + key.frc_src.v6 = ip6->ip6_src; + key.frc_dst.v6 = ip6->ip6_dst; + key.frc_af = AF_INET6; + /* Only the first fragment's protocol is relevant. */ + key.frc_proto = 0; + key.frc_id = fraghdr->ip6f_ident; + + if ((frag = pf_fillup_fragment(&key, frent, reason)) == NULL) { + PF_FRAG_UNLOCK(); + return (PF_DROP); + } + + /* The mbuf is part of the fragment entry, no direct free or access. */ + m = *m0 = NULL; + + if (!pf_isfull_fragment(frag)) { + PF_FRAG_UNLOCK(); + return (PF_PASS); /* Drop because *m0 is NULL, no error. */ + } + + /* We have all the data. */ + extoff = frent->fe_extoff; + maxlen = frag->fr_maxlen; + frag_id = frag->fr_id; + frent = TAILQ_FIRST(&frag->fr_queue); + KASSERT(frent != NULL, ("frent != NULL")); + total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off + + TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len; + hdrlen = frent->fe_hdrlen - sizeof(struct ip6_frag); + + m = *m0 = pf_join_fragment(frag); + frag = NULL; + + PF_FRAG_UNLOCK(); + + /* Take protocol from first fragment header. */ + m = m_getptr(m, hdrlen + offsetof(struct ip6_frag, ip6f_nxt), &off); + KASSERT(m, ("%s: short mbuf chain", __func__)); + proto = *(mtod(m, caddr_t) + off); + m = *m0; + + /* Delete frag6 header */ + if (ip6_deletefraghdr(m, hdrlen, M_NOWAIT) != 0) + goto fail; + + if (m->m_flags & M_PKTHDR) { + int plen = 0; + for (m = *m0; m; m = m->m_next) + plen += m->m_len; + m = *m0; + m->m_pkthdr.len = plen; + } + + if ((mtag = m_tag_get(PF_REASSEMBLED, sizeof(struct pf_fragment_tag), + M_NOWAIT)) == NULL) + goto fail; + ftag = (struct pf_fragment_tag *)(mtag + 1); + ftag->ft_hdrlen = hdrlen; + ftag->ft_extoff = extoff; + ftag->ft_maxlen = maxlen; + ftag->ft_id = frag_id; + m_tag_prepend(m, mtag); + + ip6 = mtod(m, struct ip6_hdr *); + ip6->ip6_plen = htons(hdrlen - sizeof(struct ip6_hdr) + total); + if (extoff) { + /* Write protocol into next field of last extension header. */ + m = m_getptr(m, extoff + offsetof(struct ip6_ext, ip6e_nxt), + &off); + KASSERT(m, ("%s: short mbuf chain", __func__)); + *(mtod(m, char *) + off) = proto; + m = *m0; + } else + ip6->ip6_nxt = proto; + + if (hdrlen - sizeof(struct ip6_hdr) + total > IPV6_MAXPACKET) { + DPFPRINTF(("drop: too big: %d", total)); + ip6->ip6_plen = 0; + REASON_SET(reason, PFRES_SHORT); + /* PF_DROP requires a valid mbuf *m0 in pf_test6(). */ + return (PF_DROP); + } + + DPFPRINTF(("complete: %p(%d)", m, ntohs(ip6->ip6_plen))); + return (PF_PASS); + +fail: + REASON_SET(reason, PFRES_MEMORY); + /* PF_DROP requires a valid mbuf *m0 in pf_test6(), will free later. */ + return (PF_DROP); +} +#endif /* INET6 */ + +#ifdef INET6 +int +pf_refragment6(struct ifnet *ifp, struct mbuf **m0, struct m_tag *mtag) +{ + struct mbuf *m = *m0, *t; + struct pf_fragment_tag *ftag = (struct pf_fragment_tag *)(mtag + 1); + struct pf_pdesc pd; + uint32_t frag_id; + uint16_t hdrlen, extoff, maxlen; + uint8_t proto; + int error, action; + + hdrlen = ftag->ft_hdrlen; + extoff = ftag->ft_extoff; + maxlen = ftag->ft_maxlen; + frag_id = ftag->ft_id; + m_tag_delete(m, mtag); + mtag = NULL; + ftag = NULL; + + if (extoff) { + int off; + + /* Use protocol from next field of last extension header */ + m = m_getptr(m, extoff + offsetof(struct ip6_ext, ip6e_nxt), + &off); + KASSERT((m != NULL), ("pf_refragment6: short mbuf chain")); + proto = *(mtod(m, caddr_t) + off); + *(mtod(m, char *) + off) = IPPROTO_FRAGMENT; + m = *m0; + } else { + struct ip6_hdr *hdr; + + hdr = mtod(m, struct ip6_hdr *); + proto = hdr->ip6_nxt; + hdr->ip6_nxt = IPPROTO_FRAGMENT; + } + + /* + * Maxlen may be less than 8 if there was only a single + * fragment. As it was fragmented before, add a fragment + * header also for a single fragment. If total or maxlen + * is less than 8, ip6_fragment() will return EMSGSIZE and + * we drop the packet. + */ + error = ip6_fragment(ifp, m, hdrlen, proto, maxlen, frag_id); + m = (*m0)->m_nextpkt; + (*m0)->m_nextpkt = NULL; + if (error == 0) { + /* The first mbuf contains the unfragmented packet. */ + m_freem(*m0); + *m0 = NULL; + action = PF_PASS; + } else { + /* Drop expects an mbuf to free. */ + DPFPRINTF(("refragment error %d", error)); + action = PF_DROP; + } + for (t = m; m; m = t) { + t = m->m_nextpkt; + m->m_nextpkt = NULL; + m->m_flags |= M_SKIP_FIREWALL; + memset(&pd, 0, sizeof(pd)); + pd.pf_mtag = pf_find_mtag(m); + if (error == 0) + ip6_forward(m, 0); + else + m_freem(m); + } + + return (action); +} +#endif /* INET6 */ + +#ifdef INET +int +pf_normalize_ip(struct mbuf **m0, int dir, struct pfi_kif *kif, u_short *reason, + struct pf_pdesc *pd) +{ + struct mbuf *m = *m0; + struct pf_rule *r; + struct ip *h = mtod(m, struct ip *); + int mff = (ntohs(h->ip_off) & IP_MF); + int hlen = h->ip_hl << 2; + u_int16_t fragoff = (ntohs(h->ip_off) & IP_OFFMASK) << 3; + u_int16_t max; + int ip_len; + int ip_off; + int tag = -1; + int verdict; + + PF_RULES_RASSERT(); + + r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); + while (r != NULL) { + r->evaluations++; + if (pfi_kif_match(r->kif, kif) == r->ifnot) + r = r->skip[PF_SKIP_IFP].ptr; + else if (r->direction && r->direction != dir) + r = r->skip[PF_SKIP_DIR].ptr; + else if (r->af && r->af != AF_INET) + r = r->skip[PF_SKIP_AF].ptr; + else if (r->proto && r->proto != h->ip_p) + r = r->skip[PF_SKIP_PROTO].ptr; + else if (PF_MISMATCHAW(&r->src.addr, + (struct pf_addr *)&h->ip_src.s_addr, AF_INET, + r->src.neg, kif, M_GETFIB(m))) + r = r->skip[PF_SKIP_SRC_ADDR].ptr; + else if (PF_MISMATCHAW(&r->dst.addr, + (struct pf_addr *)&h->ip_dst.s_addr, AF_INET, + r->dst.neg, NULL, M_GETFIB(m))) + r = r->skip[PF_SKIP_DST_ADDR].ptr; + else if (r->match_tag && !pf_match_tag(m, r, &tag, + pd->pf_mtag ? pd->pf_mtag->tag : 0)) + r = TAILQ_NEXT(r, entries); + else + break; + } + + if (r == NULL || r->action == PF_NOSCRUB) + return (PF_PASS); + else { + r->packets[dir == PF_OUT]++; + r->bytes[dir == PF_OUT] += pd->tot_len; + } + + /* Check for illegal packets */ + if (hlen < (int)sizeof(struct ip)) { + REASON_SET(reason, PFRES_NORM); + goto drop; + } + + if (hlen > ntohs(h->ip_len)) { + REASON_SET(reason, PFRES_NORM); + goto drop; + } + + /* Clear IP_DF if the rule uses the no-df option */ + if (r->rule_flag & PFRULE_NODF && h->ip_off & htons(IP_DF)) { + u_int16_t ip_off = h->ip_off; + + h->ip_off &= htons(~IP_DF); + h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0); + } + + /* We will need other tests here */ + if (!fragoff && !mff) + goto no_fragment; + + /* We're dealing with a fragment now. Don't allow fragments + * with IP_DF to enter the cache. If the flag was cleared by + * no-df above, fine. Otherwise drop it. + */ + if (h->ip_off & htons(IP_DF)) { + DPFPRINTF(("IP_DF\n")); + goto bad; + } + + ip_len = ntohs(h->ip_len) - hlen; + ip_off = (ntohs(h->ip_off) & IP_OFFMASK) << 3; + + /* All fragments are 8 byte aligned */ + if (mff && (ip_len & 0x7)) { + DPFPRINTF(("mff and %d\n", ip_len)); + goto bad; + } + + /* Respect maximum length */ + if (fragoff + ip_len > IP_MAXPACKET) { + DPFPRINTF(("max packet %d\n", fragoff + ip_len)); + goto bad; + } + max = fragoff + ip_len; + + /* Fully buffer all of the fragments + * Might return a completely reassembled mbuf, or NULL */ + PF_FRAG_LOCK(); + DPFPRINTF(("reass frag %d @ %d-%d\n", h->ip_id, fragoff, max)); + verdict = pf_reassemble(m0, h, dir, reason); + PF_FRAG_UNLOCK(); + + if (verdict != PF_PASS) + return (PF_DROP); + + m = *m0; + if (m == NULL) + return (PF_DROP); + + h = mtod(m, struct ip *); + + no_fragment: + /* At this point, only IP_DF is allowed in ip_off */ + if (h->ip_off & ~htons(IP_DF)) { + u_int16_t ip_off = h->ip_off; + + h->ip_off &= htons(IP_DF); + h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0); + } + + pf_scrub_ip(&m, r->rule_flag, r->min_ttl, r->set_tos); + + return (PF_PASS); + + bad: + DPFPRINTF(("dropping bad fragment\n")); + REASON_SET(reason, PFRES_FRAG); + drop: + if (r != NULL && r->log) + PFLOG_PACKET(kif, m, AF_INET, dir, *reason, r, NULL, NULL, pd, + 1); + + return (PF_DROP); +} +#endif + +#ifdef INET6 +int +pf_normalize_ip6(struct mbuf **m0, int dir, struct pfi_kif *kif, + u_short *reason, struct pf_pdesc *pd) +{ + struct mbuf *m = *m0; + struct pf_rule *r; + struct ip6_hdr *h = mtod(m, struct ip6_hdr *); + int extoff; + int off; + struct ip6_ext ext; + struct ip6_opt opt; + struct ip6_opt_jumbo jumbo; + struct ip6_frag frag; + u_int32_t jumbolen = 0, plen; + int optend; + int ooff; + u_int8_t proto; + int terminal; + + PF_RULES_RASSERT(); + + r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); + while (r != NULL) { + r->evaluations++; + if (pfi_kif_match(r->kif, kif) == r->ifnot) + r = r->skip[PF_SKIP_IFP].ptr; + else if (r->direction && r->direction != dir) + r = r->skip[PF_SKIP_DIR].ptr; + else if (r->af && r->af != AF_INET6) + r = r->skip[PF_SKIP_AF].ptr; +#if 0 /* header chain! */ + else if (r->proto && r->proto != h->ip6_nxt) + r = r->skip[PF_SKIP_PROTO].ptr; +#endif + else if (PF_MISMATCHAW(&r->src.addr, + (struct pf_addr *)&h->ip6_src, AF_INET6, + r->src.neg, kif, M_GETFIB(m))) + r = r->skip[PF_SKIP_SRC_ADDR].ptr; + else if (PF_MISMATCHAW(&r->dst.addr, + (struct pf_addr *)&h->ip6_dst, AF_INET6, + r->dst.neg, NULL, M_GETFIB(m))) + r = r->skip[PF_SKIP_DST_ADDR].ptr; + else + break; + } + + if (r == NULL || r->action == PF_NOSCRUB) + return (PF_PASS); + else { + r->packets[dir == PF_OUT]++; + r->bytes[dir == PF_OUT] += pd->tot_len; + } + + /* Check for illegal packets */ + if (sizeof(struct ip6_hdr) + IPV6_MAXPACKET < m->m_pkthdr.len) + goto drop; + + extoff = 0; + off = sizeof(struct ip6_hdr); + proto = h->ip6_nxt; + terminal = 0; + do { + switch (proto) { + case IPPROTO_FRAGMENT: + goto fragment; + break; + case IPPROTO_AH: + case IPPROTO_ROUTING: + case IPPROTO_DSTOPTS: + if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL, + NULL, AF_INET6)) + goto shortpkt; + extoff = off; + if (proto == IPPROTO_AH) + off += (ext.ip6e_len + 2) * 4; + else + off += (ext.ip6e_len + 1) * 8; + proto = ext.ip6e_nxt; + break; + case IPPROTO_HOPOPTS: + if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL, + NULL, AF_INET6)) + goto shortpkt; + extoff = off; + optend = off + (ext.ip6e_len + 1) * 8; + ooff = off + sizeof(ext); + do { + if (!pf_pull_hdr(m, ooff, &opt.ip6o_type, + sizeof(opt.ip6o_type), NULL, NULL, + AF_INET6)) + goto shortpkt; + if (opt.ip6o_type == IP6OPT_PAD1) { + ooff++; + continue; + } + if (!pf_pull_hdr(m, ooff, &opt, sizeof(opt), + NULL, NULL, AF_INET6)) + goto shortpkt; + if (ooff + sizeof(opt) + opt.ip6o_len > optend) + goto drop; + switch (opt.ip6o_type) { + case IP6OPT_JUMBO: + if (h->ip6_plen != 0) + goto drop; + if (!pf_pull_hdr(m, ooff, &jumbo, + sizeof(jumbo), NULL, NULL, + AF_INET6)) + goto shortpkt; + memcpy(&jumbolen, jumbo.ip6oj_jumbo_len, + sizeof(jumbolen)); + jumbolen = ntohl(jumbolen); + if (jumbolen <= IPV6_MAXPACKET) + goto drop; + if (sizeof(struct ip6_hdr) + jumbolen != + m->m_pkthdr.len) + goto drop; + break; + default: + break; + } + ooff += sizeof(opt) + opt.ip6o_len; + } while (ooff < optend); + + off = optend; + proto = ext.ip6e_nxt; + break; + default: + terminal = 1; + break; + } + } while (!terminal); + + /* jumbo payload option must be present, or plen > 0 */ + if (ntohs(h->ip6_plen) == 0) + plen = jumbolen; + else + plen = ntohs(h->ip6_plen); + if (plen == 0) + goto drop; + if (sizeof(struct ip6_hdr) + plen > m->m_pkthdr.len) + goto shortpkt; + + pf_scrub_ip6(&m, r->min_ttl); + + return (PF_PASS); + + fragment: + /* Jumbo payload packets cannot be fragmented. */ + plen = ntohs(h->ip6_plen); + if (plen == 0 || jumbolen) + goto drop; + if (sizeof(struct ip6_hdr) + plen > m->m_pkthdr.len) + goto shortpkt; + + if (!pf_pull_hdr(m, off, &frag, sizeof(frag), NULL, NULL, AF_INET6)) + goto shortpkt; + + /* Offset now points to data portion. */ + off += sizeof(frag); + + /* Returns PF_DROP or *m0 is NULL or completely reassembled mbuf. */ + if (pf_reassemble6(m0, h, &frag, off, extoff, reason) != PF_PASS) + return (PF_DROP); + m = *m0; + if (m == NULL) + return (PF_DROP); + + pd->flags |= PFDESC_IP_REAS; + return (PF_PASS); + + shortpkt: + REASON_SET(reason, PFRES_SHORT); + if (r != NULL && r->log) + PFLOG_PACKET(kif, m, AF_INET6, dir, *reason, r, NULL, NULL, pd, + 1); + return (PF_DROP); + + drop: + REASON_SET(reason, PFRES_NORM); + if (r != NULL && r->log) + PFLOG_PACKET(kif, m, AF_INET6, dir, *reason, r, NULL, NULL, pd, + 1); + return (PF_DROP); +} +#endif /* INET6 */ + +int +pf_normalize_tcp(int dir, struct pfi_kif *kif, struct mbuf *m, int ipoff, + int off, void *h, struct pf_pdesc *pd) +{ + struct pf_rule *r, *rm = NULL; + struct tcphdr *th = pd->hdr.tcp; + int rewrite = 0; + u_short reason; + u_int8_t flags; + sa_family_t af = pd->af; + + PF_RULES_RASSERT(); + + r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); + while (r != NULL) { + r->evaluations++; + if (pfi_kif_match(r->kif, kif) == r->ifnot) + r = r->skip[PF_SKIP_IFP].ptr; + else if (r->direction && r->direction != dir) + r = r->skip[PF_SKIP_DIR].ptr; + else if (r->af && r->af != af) + r = r->skip[PF_SKIP_AF].ptr; + else if (r->proto && r->proto != pd->proto) + r = r->skip[PF_SKIP_PROTO].ptr; + else if (PF_MISMATCHAW(&r->src.addr, pd->src, af, + r->src.neg, kif, M_GETFIB(m))) + r = r->skip[PF_SKIP_SRC_ADDR].ptr; + else if (r->src.port_op && !pf_match_port(r->src.port_op, + r->src.port[0], r->src.port[1], th->th_sport)) + r = r->skip[PF_SKIP_SRC_PORT].ptr; + else if (PF_MISMATCHAW(&r->dst.addr, pd->dst, af, + r->dst.neg, NULL, M_GETFIB(m))) + r = r->skip[PF_SKIP_DST_ADDR].ptr; + else if (r->dst.port_op && !pf_match_port(r->dst.port_op, + r->dst.port[0], r->dst.port[1], th->th_dport)) + r = r->skip[PF_SKIP_DST_PORT].ptr; + else if (r->os_fingerprint != PF_OSFP_ANY && !pf_osfp_match( + pf_osfp_fingerprint(pd, m, off, th), + r->os_fingerprint)) + r = TAILQ_NEXT(r, entries); + else { + rm = r; + break; + } + } + + if (rm == NULL || rm->action == PF_NOSCRUB) + return (PF_PASS); + else { + r->packets[dir == PF_OUT]++; + r->bytes[dir == PF_OUT] += pd->tot_len; + } + + if (rm->rule_flag & PFRULE_REASSEMBLE_TCP) + pd->flags |= PFDESC_TCP_NORM; + + flags = th->th_flags; + if (flags & TH_SYN) { + /* Illegal packet */ + if (flags & TH_RST) + goto tcp_drop; + + if (flags & TH_FIN) + goto tcp_drop; + } else { + /* Illegal packet */ + if (!(flags & (TH_ACK|TH_RST))) + goto tcp_drop; + } + + if (!(flags & TH_ACK)) { + /* These flags are only valid if ACK is set */ + if ((flags & TH_FIN) || (flags & TH_PUSH) || (flags & TH_URG)) + goto tcp_drop; + } + + /* Check for illegal header length */ + if (th->th_off < (sizeof(struct tcphdr) >> 2)) + goto tcp_drop; + + /* If flags changed, or reserved data set, then adjust */ + if (flags != th->th_flags || th->th_x2 != 0) { + u_int16_t ov, nv; + + ov = *(u_int16_t *)(&th->th_ack + 1); + th->th_flags = flags; + th->th_x2 = 0; + nv = *(u_int16_t *)(&th->th_ack + 1); + + th->th_sum = pf_proto_cksum_fixup(m, th->th_sum, ov, nv, 0); + rewrite = 1; + } + + /* Remove urgent pointer, if TH_URG is not set */ + if (!(flags & TH_URG) && th->th_urp) { + th->th_sum = pf_proto_cksum_fixup(m, th->th_sum, th->th_urp, + 0, 0); + th->th_urp = 0; + rewrite = 1; + } + + /* Process options */ + if (r->max_mss && pf_normalize_tcpopt(r, m, th, off, pd->af)) + rewrite = 1; + + /* copy back packet headers if we sanitized */ + if (rewrite) + m_copyback(m, off, sizeof(*th), (caddr_t)th); + + return (PF_PASS); + + tcp_drop: + REASON_SET(&reason, PFRES_NORM); + if (rm != NULL && r->log) + PFLOG_PACKET(kif, m, AF_INET, dir, reason, r, NULL, NULL, pd, + 1); + return (PF_DROP); +} + +int +pf_normalize_tcp_init(struct mbuf *m, int off, struct pf_pdesc *pd, + struct tcphdr *th, struct pf_state_peer *src, struct pf_state_peer *dst) +{ + u_int32_t tsval, tsecr; + u_int8_t hdr[60]; + u_int8_t *opt; + + KASSERT((src->scrub == NULL), + ("pf_normalize_tcp_init: src->scrub != NULL")); + + src->scrub = uma_zalloc(V_pf_state_scrub_z, M_ZERO | M_NOWAIT); + if (src->scrub == NULL) + return (1); + + switch (pd->af) { +#ifdef INET + case AF_INET: { + struct ip *h = mtod(m, struct ip *); + src->scrub->pfss_ttl = h->ip_ttl; + break; + } +#endif /* INET */ +#ifdef INET6 + case AF_INET6: { + struct ip6_hdr *h = mtod(m, struct ip6_hdr *); + src->scrub->pfss_ttl = h->ip6_hlim; + break; + } +#endif /* INET6 */ + } + + + /* + * All normalizations below are only begun if we see the start of + * the connections. They must all set an enabled bit in pfss_flags + */ + if ((th->th_flags & TH_SYN) == 0) + return (0); + + + if (th->th_off > (sizeof(struct tcphdr) >> 2) && src->scrub && + pf_pull_hdr(m, off, hdr, th->th_off << 2, NULL, NULL, pd->af)) { + /* Diddle with TCP options */ + int hlen; + opt = hdr + sizeof(struct tcphdr); + hlen = (th->th_off << 2) - sizeof(struct tcphdr); + while (hlen >= TCPOLEN_TIMESTAMP) { + switch (*opt) { + case TCPOPT_EOL: /* FALLTHROUGH */ + case TCPOPT_NOP: + opt++; + hlen--; + break; + case TCPOPT_TIMESTAMP: + if (opt[1] >= TCPOLEN_TIMESTAMP) { + src->scrub->pfss_flags |= + PFSS_TIMESTAMP; + src->scrub->pfss_ts_mod = + htonl(arc4random()); + + /* note PFSS_PAWS not set yet */ + memcpy(&tsval, &opt[2], + sizeof(u_int32_t)); + memcpy(&tsecr, &opt[6], + sizeof(u_int32_t)); + src->scrub->pfss_tsval0 = ntohl(tsval); + src->scrub->pfss_tsval = ntohl(tsval); + src->scrub->pfss_tsecr = ntohl(tsecr); + getmicrouptime(&src->scrub->pfss_last); + } + /* FALLTHROUGH */ + default: + hlen -= MAX(opt[1], 2); + opt += MAX(opt[1], 2); + break; + } + } + } + + return (0); +} + +void +pf_normalize_tcp_cleanup(struct pf_state *state) +{ + if (state->src.scrub) + uma_zfree(V_pf_state_scrub_z, state->src.scrub); + if (state->dst.scrub) + uma_zfree(V_pf_state_scrub_z, state->dst.scrub); + + /* Someday... flush the TCP segment reassembly descriptors. */ +} + +int +pf_normalize_tcp_stateful(struct mbuf *m, int off, struct pf_pdesc *pd, + u_short *reason, struct tcphdr *th, struct pf_state *state, + struct pf_state_peer *src, struct pf_state_peer *dst, int *writeback) +{ + struct timeval uptime; + u_int32_t tsval, tsecr; + u_int tsval_from_last; + u_int8_t hdr[60]; + u_int8_t *opt; + int copyback = 0; + int got_ts = 0; + + KASSERT((src->scrub || dst->scrub), + ("%s: src->scrub && dst->scrub!", __func__)); + + /* + * Enforce the minimum TTL seen for this connection. Negate a common + * technique to evade an intrusion detection system and confuse + * firewall state code. + */ + switch (pd->af) { +#ifdef INET + case AF_INET: { + if (src->scrub) { + struct ip *h = mtod(m, struct ip *); + if (h->ip_ttl > src->scrub->pfss_ttl) + src->scrub->pfss_ttl = h->ip_ttl; + h->ip_ttl = src->scrub->pfss_ttl; + } + break; + } +#endif /* INET */ +#ifdef INET6 + case AF_INET6: { + if (src->scrub) { + struct ip6_hdr *h = mtod(m, struct ip6_hdr *); + if (h->ip6_hlim > src->scrub->pfss_ttl) + src->scrub->pfss_ttl = h->ip6_hlim; + h->ip6_hlim = src->scrub->pfss_ttl; + } + break; + } +#endif /* INET6 */ + } + + if (th->th_off > (sizeof(struct tcphdr) >> 2) && + ((src->scrub && (src->scrub->pfss_flags & PFSS_TIMESTAMP)) || + (dst->scrub && (dst->scrub->pfss_flags & PFSS_TIMESTAMP))) && + pf_pull_hdr(m, off, hdr, th->th_off << 2, NULL, NULL, pd->af)) { + /* Diddle with TCP options */ + int hlen; + opt = hdr + sizeof(struct tcphdr); + hlen = (th->th_off << 2) - sizeof(struct tcphdr); + while (hlen >= TCPOLEN_TIMESTAMP) { + switch (*opt) { + case TCPOPT_EOL: /* FALLTHROUGH */ + case TCPOPT_NOP: + opt++; + hlen--; + break; + case TCPOPT_TIMESTAMP: + /* Modulate the timestamps. Can be used for + * NAT detection, OS uptime determination or + * reboot detection. + */ + + if (got_ts) { + /* Huh? Multiple timestamps!? */ + if (V_pf_status.debug >= PF_DEBUG_MISC) { + DPFPRINTF(("multiple TS??")); + pf_print_state(state); + printf("\n"); + } + REASON_SET(reason, PFRES_TS); + return (PF_DROP); + } + if (opt[1] >= TCPOLEN_TIMESTAMP) { + memcpy(&tsval, &opt[2], + sizeof(u_int32_t)); + if (tsval && src->scrub && + (src->scrub->pfss_flags & + PFSS_TIMESTAMP)) { + tsval = ntohl(tsval); + pf_change_proto_a(m, &opt[2], + &th->th_sum, + htonl(tsval + + src->scrub->pfss_ts_mod), + 0); + copyback = 1; + } + + /* Modulate TS reply iff valid (!0) */ + memcpy(&tsecr, &opt[6], + sizeof(u_int32_t)); + if (tsecr && dst->scrub && + (dst->scrub->pfss_flags & + PFSS_TIMESTAMP)) { + tsecr = ntohl(tsecr) + - dst->scrub->pfss_ts_mod; + pf_change_proto_a(m, &opt[6], + &th->th_sum, htonl(tsecr), + 0); + copyback = 1; + } + got_ts = 1; + } + /* FALLTHROUGH */ + default: + hlen -= MAX(opt[1], 2); + opt += MAX(opt[1], 2); + break; + } + } + if (copyback) { + /* Copyback the options, caller copys back header */ + *writeback = 1; + m_copyback(m, off + sizeof(struct tcphdr), + (th->th_off << 2) - sizeof(struct tcphdr), hdr + + sizeof(struct tcphdr)); + } + } + + + /* + * Must invalidate PAWS checks on connections idle for too long. + * The fastest allowed timestamp clock is 1ms. That turns out to + * be about 24 days before it wraps. XXX Right now our lowerbound + * TS echo check only works for the first 12 days of a connection + * when the TS has exhausted half its 32bit space + */ +#define TS_MAX_IDLE (24*24*60*60) +#define TS_MAX_CONN (12*24*60*60) /* XXX remove when better tsecr check */ + + getmicrouptime(&uptime); + if (src->scrub && (src->scrub->pfss_flags & PFSS_PAWS) && + (uptime.tv_sec - src->scrub->pfss_last.tv_sec > TS_MAX_IDLE || + time_uptime - state->creation > TS_MAX_CONN)) { + if (V_pf_status.debug >= PF_DEBUG_MISC) { + DPFPRINTF(("src idled out of PAWS\n")); + pf_print_state(state); + printf("\n"); + } + src->scrub->pfss_flags = (src->scrub->pfss_flags & ~PFSS_PAWS) + | PFSS_PAWS_IDLED; + } + if (dst->scrub && (dst->scrub->pfss_flags & PFSS_PAWS) && + uptime.tv_sec - dst->scrub->pfss_last.tv_sec > TS_MAX_IDLE) { + if (V_pf_status.debug >= PF_DEBUG_MISC) { + DPFPRINTF(("dst idled out of PAWS\n")); + pf_print_state(state); + printf("\n"); + } + dst->scrub->pfss_flags = (dst->scrub->pfss_flags & ~PFSS_PAWS) + | PFSS_PAWS_IDLED; + } + + if (got_ts && src->scrub && dst->scrub && + (src->scrub->pfss_flags & PFSS_PAWS) && + (dst->scrub->pfss_flags & PFSS_PAWS)) { + /* Validate that the timestamps are "in-window". + * RFC1323 describes TCP Timestamp options that allow + * measurement of RTT (round trip time) and PAWS + * (protection against wrapped sequence numbers). PAWS + * gives us a set of rules for rejecting packets on + * long fat pipes (packets that were somehow delayed + * in transit longer than the time it took to send the + * full TCP sequence space of 4Gb). We can use these + * rules and infer a few others that will let us treat + * the 32bit timestamp and the 32bit echoed timestamp + * as sequence numbers to prevent a blind attacker from + * inserting packets into a connection. + * + * RFC1323 tells us: + * - The timestamp on this packet must be greater than + * or equal to the last value echoed by the other + * endpoint. The RFC says those will be discarded + * since it is a dup that has already been acked. + * This gives us a lowerbound on the timestamp. + * timestamp >= other last echoed timestamp + * - The timestamp will be less than or equal to + * the last timestamp plus the time between the + * last packet and now. The RFC defines the max + * clock rate as 1ms. We will allow clocks to be + * up to 10% fast and will allow a total difference + * or 30 seconds due to a route change. And this + * gives us an upperbound on the timestamp. + * timestamp <= last timestamp + max ticks + * We have to be careful here. Windows will send an + * initial timestamp of zero and then initialize it + * to a random value after the 3whs; presumably to + * avoid a DoS by having to call an expensive RNG + * during a SYN flood. Proof MS has at least one + * good security geek. + * + * - The TCP timestamp option must also echo the other + * endpoints timestamp. The timestamp echoed is the + * one carried on the earliest unacknowledged segment + * on the left edge of the sequence window. The RFC + * states that the host will reject any echoed + * timestamps that were larger than any ever sent. + * This gives us an upperbound on the TS echo. + * tescr <= largest_tsval + * - The lowerbound on the TS echo is a little more + * tricky to determine. The other endpoint's echoed + * values will not decrease. But there may be + * network conditions that re-order packets and + * cause our view of them to decrease. For now the + * only lowerbound we can safely determine is that + * the TS echo will never be less than the original + * TS. XXX There is probably a better lowerbound. + * Remove TS_MAX_CONN with better lowerbound check. + * tescr >= other original TS + * + * It is also important to note that the fastest + * timestamp clock of 1ms will wrap its 32bit space in + * 24 days. So we just disable TS checking after 24 + * days of idle time. We actually must use a 12d + * connection limit until we can come up with a better + * lowerbound to the TS echo check. + */ + struct timeval delta_ts; + int ts_fudge; + + + /* + * PFTM_TS_DIFF is how many seconds of leeway to allow + * a host's timestamp. This can happen if the previous + * packet got delayed in transit for much longer than + * this packet. + */ + if ((ts_fudge = state->rule.ptr->timeout[PFTM_TS_DIFF]) == 0) + ts_fudge = V_pf_default_rule.timeout[PFTM_TS_DIFF]; + + /* Calculate max ticks since the last timestamp */ +#define TS_MAXFREQ 1100 /* RFC max TS freq of 1Khz + 10% skew */ +#define TS_MICROSECS 1000000 /* microseconds per second */ + delta_ts = uptime; + timevalsub(&delta_ts, &src->scrub->pfss_last); + tsval_from_last = (delta_ts.tv_sec + ts_fudge) * TS_MAXFREQ; + tsval_from_last += delta_ts.tv_usec / (TS_MICROSECS/TS_MAXFREQ); + + if ((src->state >= TCPS_ESTABLISHED && + dst->state >= TCPS_ESTABLISHED) && + (SEQ_LT(tsval, dst->scrub->pfss_tsecr) || + SEQ_GT(tsval, src->scrub->pfss_tsval + tsval_from_last) || + (tsecr && (SEQ_GT(tsecr, dst->scrub->pfss_tsval) || + SEQ_LT(tsecr, dst->scrub->pfss_tsval0))))) { + /* Bad RFC1323 implementation or an insertion attack. + * + * - Solaris 2.6 and 2.7 are known to send another ACK + * after the FIN,FIN|ACK,ACK closing that carries + * an old timestamp. + */ + + DPFPRINTF(("Timestamp failed %c%c%c%c\n", + SEQ_LT(tsval, dst->scrub->pfss_tsecr) ? '0' : ' ', + SEQ_GT(tsval, src->scrub->pfss_tsval + + tsval_from_last) ? '1' : ' ', + SEQ_GT(tsecr, dst->scrub->pfss_tsval) ? '2' : ' ', + SEQ_LT(tsecr, dst->scrub->pfss_tsval0)? '3' : ' ')); + DPFPRINTF((" tsval: %u tsecr: %u +ticks: %u " + "idle: %jus %lums\n", + tsval, tsecr, tsval_from_last, + (uintmax_t)delta_ts.tv_sec, + delta_ts.tv_usec / 1000)); + DPFPRINTF((" src->tsval: %u tsecr: %u\n", + src->scrub->pfss_tsval, src->scrub->pfss_tsecr)); + DPFPRINTF((" dst->tsval: %u tsecr: %u tsval0: %u" + "\n", dst->scrub->pfss_tsval, + dst->scrub->pfss_tsecr, dst->scrub->pfss_tsval0)); + if (V_pf_status.debug >= PF_DEBUG_MISC) { + pf_print_state(state); + pf_print_flags(th->th_flags); + printf("\n"); + } + REASON_SET(reason, PFRES_TS); + return (PF_DROP); + } + + /* XXX I'd really like to require tsecr but it's optional */ + + } else if (!got_ts && (th->th_flags & TH_RST) == 0 && + ((src->state == TCPS_ESTABLISHED && dst->state == TCPS_ESTABLISHED) + || pd->p_len > 0 || (th->th_flags & TH_SYN)) && + src->scrub && dst->scrub && + (src->scrub->pfss_flags & PFSS_PAWS) && + (dst->scrub->pfss_flags & PFSS_PAWS)) { + /* Didn't send a timestamp. Timestamps aren't really useful + * when: + * - connection opening or closing (often not even sent). + * but we must not let an attacker to put a FIN on a + * data packet to sneak it through our ESTABLISHED check. + * - on a TCP reset. RFC suggests not even looking at TS. + * - on an empty ACK. The TS will not be echoed so it will + * probably not help keep the RTT calculation in sync and + * there isn't as much danger when the sequence numbers + * got wrapped. So some stacks don't include TS on empty + * ACKs :-( + * + * To minimize the disruption to mostly RFC1323 conformant + * stacks, we will only require timestamps on data packets. + * + * And what do ya know, we cannot require timestamps on data + * packets. There appear to be devices that do legitimate + * TCP connection hijacking. There are HTTP devices that allow + * a 3whs (with timestamps) and then buffer the HTTP request. + * If the intermediate device has the HTTP response cache, it + * will spoof the response but not bother timestamping its + * packets. So we can look for the presence of a timestamp in + * the first data packet and if there, require it in all future + * packets. + */ + + if (pd->p_len > 0 && (src->scrub->pfss_flags & PFSS_DATA_TS)) { + /* + * Hey! Someone tried to sneak a packet in. Or the + * stack changed its RFC1323 behavior?!?! + */ + if (V_pf_status.debug >= PF_DEBUG_MISC) { + DPFPRINTF(("Did not receive expected RFC1323 " + "timestamp\n")); + pf_print_state(state); + pf_print_flags(th->th_flags); + printf("\n"); + } + REASON_SET(reason, PFRES_TS); + return (PF_DROP); + } + } + + + /* + * We will note if a host sends his data packets with or without + * timestamps. And require all data packets to contain a timestamp + * if the first does. PAWS implicitly requires that all data packets be + * timestamped. But I think there are middle-man devices that hijack + * TCP streams immediately after the 3whs and don't timestamp their + * packets (seen in a WWW accelerator or cache). + */ + if (pd->p_len > 0 && src->scrub && (src->scrub->pfss_flags & + (PFSS_TIMESTAMP|PFSS_DATA_TS|PFSS_DATA_NOTS)) == PFSS_TIMESTAMP) { + if (got_ts) + src->scrub->pfss_flags |= PFSS_DATA_TS; + else { + src->scrub->pfss_flags |= PFSS_DATA_NOTS; + if (V_pf_status.debug >= PF_DEBUG_MISC && dst->scrub && + (dst->scrub->pfss_flags & PFSS_TIMESTAMP)) { + /* Don't warn if other host rejected RFC1323 */ + DPFPRINTF(("Broken RFC1323 stack did not " + "timestamp data packet. Disabled PAWS " + "security.\n")); + pf_print_state(state); + pf_print_flags(th->th_flags); + printf("\n"); + } + } + } + + + /* + * Update PAWS values + */ + if (got_ts && src->scrub && PFSS_TIMESTAMP == (src->scrub->pfss_flags & + (PFSS_PAWS_IDLED|PFSS_TIMESTAMP))) { + getmicrouptime(&src->scrub->pfss_last); + if (SEQ_GEQ(tsval, src->scrub->pfss_tsval) || + (src->scrub->pfss_flags & PFSS_PAWS) == 0) + src->scrub->pfss_tsval = tsval; + + if (tsecr) { + if (SEQ_GEQ(tsecr, src->scrub->pfss_tsecr) || + (src->scrub->pfss_flags & PFSS_PAWS) == 0) + src->scrub->pfss_tsecr = tsecr; + + if ((src->scrub->pfss_flags & PFSS_PAWS) == 0 && + (SEQ_LT(tsval, src->scrub->pfss_tsval0) || + src->scrub->pfss_tsval0 == 0)) { + /* tsval0 MUST be the lowest timestamp */ + src->scrub->pfss_tsval0 = tsval; + } + + /* Only fully initialized after a TS gets echoed */ + if ((src->scrub->pfss_flags & PFSS_PAWS) == 0) + src->scrub->pfss_flags |= PFSS_PAWS; + } + } + + /* I have a dream.... TCP segment reassembly.... */ + return (0); +} + +static int +pf_normalize_tcpopt(struct pf_rule *r, struct mbuf *m, struct tcphdr *th, + int off, sa_family_t af) +{ + u_int16_t *mss; + int thoff; + int opt, cnt, optlen = 0; + int rewrite = 0; + u_char opts[TCP_MAXOLEN]; + u_char *optp = opts; + + thoff = th->th_off << 2; + cnt = thoff - sizeof(struct tcphdr); + + if (cnt > 0 && !pf_pull_hdr(m, off + sizeof(*th), opts, cnt, + NULL, NULL, af)) + return (rewrite); + + for (; cnt > 0; cnt -= optlen, optp += optlen) { + opt = optp[0]; + if (opt == TCPOPT_EOL) + break; + if (opt == TCPOPT_NOP) + optlen = 1; + else { + if (cnt < 2) + break; + optlen = optp[1]; + if (optlen < 2 || optlen > cnt) + break; + } + switch (opt) { + case TCPOPT_MAXSEG: + mss = (u_int16_t *)(optp + 2); + if ((ntohs(*mss)) > r->max_mss) { + th->th_sum = pf_proto_cksum_fixup(m, + th->th_sum, *mss, htons(r->max_mss), 0); + *mss = htons(r->max_mss); + rewrite = 1; + } + break; + default: + break; + } + } + + if (rewrite) + m_copyback(m, off + sizeof(*th), thoff - sizeof(*th), opts); + + return (rewrite); +} + +#ifdef INET +static void +pf_scrub_ip(struct mbuf **m0, u_int32_t flags, u_int8_t min_ttl, u_int8_t tos) +{ + struct mbuf *m = *m0; + struct ip *h = mtod(m, struct ip *); + + /* Clear IP_DF if no-df was requested */ + if (flags & PFRULE_NODF && h->ip_off & htons(IP_DF)) { + u_int16_t ip_off = h->ip_off; + + h->ip_off &= htons(~IP_DF); + h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0); + } + + /* Enforce a minimum ttl, may cause endless packet loops */ + if (min_ttl && h->ip_ttl < min_ttl) { + u_int16_t ip_ttl = h->ip_ttl; + + h->ip_ttl = min_ttl; + h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_ttl, h->ip_ttl, 0); + } + + /* Enforce tos */ + if (flags & PFRULE_SET_TOS) { + u_int16_t ov, nv; + + ov = *(u_int16_t *)h; + h->ip_tos = tos; + nv = *(u_int16_t *)h; + + h->ip_sum = pf_cksum_fixup(h->ip_sum, ov, nv, 0); + } + + /* random-id, but not for fragments */ + if (flags & PFRULE_RANDOMID && !(h->ip_off & ~htons(IP_DF))) { + uint16_t ip_id = h->ip_id; + + ip_fillid(h); + h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_id, h->ip_id, 0); + } +} +#endif /* INET */ + +#ifdef INET6 +static void +pf_scrub_ip6(struct mbuf **m0, u_int8_t min_ttl) +{ + struct mbuf *m = *m0; + struct ip6_hdr *h = mtod(m, struct ip6_hdr *); + + /* Enforce a minimum ttl, may cause endless packet loops */ + if (min_ttl && h->ip6_hlim < min_ttl) + h->ip6_hlim = min_ttl; +} +#endif |