/*- * SPDX-License-Identifier: BSD-2-Clause * * Copyright 2001 Niels Provos * Copyright 2011-2018 Alexander Bluhm * 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 __FBSDID("$FreeBSD$"); #include "opt_inet.h" #include "opt_inet6.h" #include "opt_pf.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef INET6 #include #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 /* pointers to queue element */ struct pf_frent *fr_firstoff[PF_FRAG_ENTRY_POINTS]; /* count entries between pointers */ uint8_t fr_entries[PF_FRAG_ENTRY_POINTS]; 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 */ u_int16_t fr_holes; /* number of holes in the queue */ 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 */ }; VNET_DEFINE_STATIC(struct mtx, pf_frag_mtx); #define V_pf_frag_mtx VNET(pf_frag_mtx) #define PF_FRAG_LOCK() mtx_lock(&V_pf_frag_mtx) #define PF_FRAG_UNLOCK() mtx_unlock(&V_pf_frag_mtx) #define PF_FRAG_ASSERT() mtx_assert(&V_pf_frag_mtx, MA_OWNED) VNET_DEFINE(uma_zone_t, pf_state_scrub_z); /* XXX: shared with pfsync */ VNET_DEFINE_STATIC(uma_zone_t, pf_frent_z); #define V_pf_frent_z VNET(pf_frent_z) VNET_DEFINE_STATIC(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); VNET_DEFINE_STATIC(struct pf_fragqueue, pf_fragqueue); #define V_pf_fragqueue VNET(pf_fragqueue) RB_HEAD(pf_frag_tree, pf_fragment); VNET_DEFINE_STATIC(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 struct pf_frent *pf_create_fragment(u_short *); static int pf_frent_holes(struct pf_frent *frent); static struct pf_fragment *pf_find_fragment(struct pf_fragment_cmp *key, struct pf_frag_tree *tree); static inline int pf_frent_index(struct pf_frent *); static int pf_frent_insert(struct pf_fragment *, struct pf_frent *, struct pf_frent *); void pf_frent_remove(struct pf_fragment *, struct pf_frent *); struct pf_frent *pf_frent_previous(struct pf_fragment *, struct pf_frent *); static struct pf_fragment *pf_fillup_fragment(struct pf_fragment_cmp *, struct pf_frent *, u_short *); static struct mbuf *pf_join_fragment(struct pf_fragment *); #ifdef INET 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 *); #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); mtx_init(&V_pf_frag_mtx, "pf fragments", NULL, MTX_DEF); 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); mtx_destroy(&V_pf_frag_mtx); } 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) { u_int32_t expire = time_uptime - V_pf_default_rule.timeout[PFTM_FRAG]; pf_purge_fragments(expire); } void pf_purge_fragments(uint32_t expire) { struct pf_fragment *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(); KASSERT(frag, ("frag != NULL")); 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); } /* * Calculate the additional holes that were created in the fragment * queue by inserting this fragment. A fragment in the middle * creates one more hole by splitting. For each connected side, * it loses one hole. * Fragment entry must be in the queue when calling this function. */ static int pf_frent_holes(struct pf_frent *frent) { struct pf_frent *prev = TAILQ_PREV(frent, pf_fragq, fr_next); struct pf_frent *next = TAILQ_NEXT(frent, fr_next); int holes = 1; if (prev == NULL) { if (frent->fe_off == 0) holes--; } else { KASSERT(frent->fe_off != 0, ("frent->fe_off != 0")); if (frent->fe_off == prev->fe_off + prev->fe_len) holes--; } if (next == NULL) { if (!frent->fe_mff) holes--; } else { KASSERT(frent->fe_mff, ("frent->fe_mff")); if (next->fe_off == frent->fe_off + frent->fe_len) holes--; } return holes; } static inline int pf_frent_index(struct pf_frent *frent) { /* * We have an array of 16 entry points to the queue. A full size * 65535 octet IP packet can have 8192 fragments. So the queue * traversal length is at most 512 and at most 16 entry points are * checked. We need 128 additional bytes on a 64 bit architecture. */ CTASSERT(((u_int16_t)0xffff &~ 7) / (0x10000 / PF_FRAG_ENTRY_POINTS) == 16 - 1); CTASSERT(((u_int16_t)0xffff >> 3) / PF_FRAG_ENTRY_POINTS == 512 - 1); return frent->fe_off / (0x10000 / PF_FRAG_ENTRY_POINTS); } static int pf_frent_insert(struct pf_fragment *frag, struct pf_frent *frent, struct pf_frent *prev) { int index; CTASSERT(PF_FRAG_ENTRY_LIMIT <= 0xff); /* * A packet has at most 65536 octets. With 16 entry points, each one * spawns 4096 octets. We limit these to 64 fragments each, which * means on average every fragment must have at least 64 octets. */ index = pf_frent_index(frent); if (frag->fr_entries[index] >= PF_FRAG_ENTRY_LIMIT) return ENOBUFS; frag->fr_entries[index]++; if (prev == NULL) { TAILQ_INSERT_HEAD(&frag->fr_queue, frent, fr_next); } else { KASSERT(prev->fe_off + prev->fe_len <= frent->fe_off, ("overlapping fragment")); TAILQ_INSERT_AFTER(&frag->fr_queue, prev, frent, fr_next); } if (frag->fr_firstoff[index] == NULL) { KASSERT(prev == NULL || pf_frent_index(prev) < index, ("prev == NULL || pf_frent_index(pref) < index")); frag->fr_firstoff[index] = frent; } else { if (frent->fe_off < frag->fr_firstoff[index]->fe_off) { KASSERT(prev == NULL || pf_frent_index(prev) < index, ("prev == NULL || pf_frent_index(pref) < index")); frag->fr_firstoff[index] = frent; } else { KASSERT(prev != NULL, ("prev != NULL")); KASSERT(pf_frent_index(prev) == index, ("pf_frent_index(prev) == index")); } } frag->fr_holes += pf_frent_holes(frent); return 0; } void pf_frent_remove(struct pf_fragment *frag, struct pf_frent *frent) { #ifdef INVARIANTS struct pf_frent *prev = TAILQ_PREV(frent, pf_fragq, fr_next); #endif struct pf_frent *next = TAILQ_NEXT(frent, fr_next); int index; frag->fr_holes -= pf_frent_holes(frent); index = pf_frent_index(frent); KASSERT(frag->fr_firstoff[index] != NULL, ("frent not found")); if (frag->fr_firstoff[index]->fe_off == frent->fe_off) { if (next == NULL) { frag->fr_firstoff[index] = NULL; } else { KASSERT(frent->fe_off + frent->fe_len <= next->fe_off, ("overlapping fragment")); if (pf_frent_index(next) == index) { frag->fr_firstoff[index] = next; } else { frag->fr_firstoff[index] = NULL; } } } else { KASSERT(frag->fr_firstoff[index]->fe_off < frent->fe_off, ("frag->fr_firstoff[index]->fe_off < frent->fe_off")); KASSERT(prev != NULL, ("prev != NULL")); KASSERT(prev->fe_off + prev->fe_len <= frent->fe_off, ("overlapping fragment")); KASSERT(pf_frent_index(prev) == index, ("pf_frent_index(prev) == index")); } TAILQ_REMOVE(&frag->fr_queue, frent, fr_next); KASSERT(frag->fr_entries[index] > 0, ("No fragments remaining")); frag->fr_entries[index]--; } struct pf_frent * pf_frent_previous(struct pf_fragment *frag, struct pf_frent *frent) { struct pf_frent *prev, *next; int index; /* * If there are no fragments after frag, take the final one. Assume * that the global queue is not empty. */ prev = TAILQ_LAST(&frag->fr_queue, pf_fragq); KASSERT(prev != NULL, ("prev != NULL")); if (prev->fe_off <= frent->fe_off) return prev; /* * We want to find a fragment entry that is before frag, but still * close to it. Find the first fragment entry that is in the same * entry point or in the first entry point after that. As we have * already checked that there are entries behind frag, this will * succeed. */ for (index = pf_frent_index(frent); index < PF_FRAG_ENTRY_POINTS; index++) { prev = frag->fr_firstoff[index]; if (prev != NULL) break; } KASSERT(prev != NULL, ("prev != NULL")); /* * In prev we may have a fragment from the same entry point that is * before frent, or one that is just one position behind frent. * In the latter case, we go back one step and have the predecessor. * There may be none if the new fragment will be the first one. */ if (prev->fe_off > frent->fe_off) { prev = TAILQ_PREV(prev, pf_fragq, fr_next); if (prev == NULL) return NULL; KASSERT(prev->fe_off <= frent->fe_off, ("prev->fe_off <= frent->fe_off")); return prev; } /* * In prev is the first fragment of the entry point. The offset * of frag is behind it. Find the closest previous fragment. */ for (next = TAILQ_NEXT(prev, fr_next); next != NULL; next = TAILQ_NEXT(next, fr_next)) { if (next->fe_off > frent->fe_off) break; prev = next; } return prev; } 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; int old_index, new_index; PF_FRAG_ASSERT(); /* No empty fragments. */ if (frent->fe_len == 0) { DPFPRINTF(("bad fragment: len 0\n")); goto bad_fragment; } /* All fragments are 8 byte aligned. */ if (frent->fe_mff && (frent->fe_len & 0x7)) { DPFPRINTF(("bad fragment: mff and len %d\n", 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\n", frent->fe_off + frent->fe_len)); goto bad_fragment; } DPFPRINTF((key->frc_af == AF_INET ? "reass frag %d @ %d-%d\n" : "reass frag %#08x @ %d-%d\n", 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; memset(frag->fr_firstoff, 0, sizeof(frag->fr_firstoff)); memset(frag->fr_entries, 0, sizeof(frag->fr_entries)); frag->fr_timeout = time_uptime; frag->fr_maxlen = frent->fe_len; frag->fr_holes = 1; 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, cannot fail. */ pf_frent_insert(frag, frent, NULL); 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 neighbors for newly inserted fragment */ prev = pf_frent_previous(frag, frent); if (prev == NULL) { after = TAILQ_FIRST(&frag->fr_queue); KASSERT(after != NULL, ("after != NULL")); } else { after = TAILQ_NEXT(prev, fr_next); } 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\n", 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\n", aftercut)); if (aftercut < after->fe_len) { m_adj(after->fe_m, aftercut); old_index = pf_frent_index(after); after->fe_off += aftercut; after->fe_len -= aftercut; new_index = pf_frent_index(after); if (old_index != new_index) { DPFPRINTF(("frag index %d, new %d", old_index, new_index)); /* Fragment switched queue as fe_off changed */ after->fe_off -= aftercut; after->fe_len += aftercut; /* Remove restored fragment from old queue */ pf_frent_remove(frag, after); after->fe_off += aftercut; after->fe_len -= aftercut; /* Insert into correct queue */ if (pf_frent_insert(frag, after, prev)) { DPFPRINTF( ("fragment requeue limit exceeded")); m_freem(after->fe_m); uma_zfree(V_pf_frent_z, after); /* There is not way to recover */ goto bad_fragment; } } break; } /* This fragment is completely overlapped, lose it. */ next = TAILQ_NEXT(after, fr_next); pf_frent_remove(frag, after); m_freem(after->fe_m); uma_zfree(V_pf_frent_z, after); } /* If part of the queue gets too long, there is not way to recover. */ if (pf_frent_insert(frag, frent, prev)) { DPFPRINTF(("fragment queue limit exceeded\n")); goto bad_fragment; } return (frag); bad_fragment: REASON_SET(reason, PFRES_FRAG); drop_fragment: uma_zfree(V_pf_frent_z, frent); return (NULL); } 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 (frag->fr_holes) { DPFPRINTF(("frag %d, holes %d\n", frag->fr_id, frag->fr_holes)); 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_sum = pf_cksum_fixup(ip->ip_sum, ip->ip_len, htons(hdrlen + total), 0); ip->ip_len = htons(hdrlen + total); ip->ip_sum = pf_cksum_fixup(ip->ip_sum, ip->ip_off, ip->ip_off & ~(IP_MF|IP_OFFMASK), 0); ip->ip_off &= ~(IP_MF|IP_OFFMASK); if (hdrlen + total > IP_MAXPACKET) { DPFPRINTF(("drop: too big: %d\n", 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 (frag->fr_holes) { DPFPRINTF(("frag %d, holes %d\n", frag->fr_id, frag->fr_holes)); PF_FRAG_UNLOCK(); 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")); extoff = frent->fe_extoff; maxlen = frag->fr_maxlen; frag_id = frag->fr_id; 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\n", 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)\n", 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, bool forward) { struct mbuf *m = *m0, *t; struct ip6_hdr *hdr; 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 { hdr = mtod(m, struct ip6_hdr *); proto = hdr->ip6_nxt; hdr->ip6_nxt = IPPROTO_FRAGMENT; } /* In case of link-local traffic we'll need a scope set. */ hdr = mtod(m, struct ip6_hdr *); in6_setscope(&hdr->ip6_src, ifp, NULL); in6_setscope(&hdr->ip6_dst, ifp, NULL); /* The MTU must be a multiple of 8 bytes, or we risk doing the * fragmentation wrong. */ maxlen = maxlen & ~7; /* * 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\n", error)); action = PF_DROP; } for (; 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) if (forward) { MPASS(m->m_pkthdr.rcvif != NULL); ip6_forward(m, 0); } else { (void)ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL); } else m_freem(m); } return (action); } #endif /* INET6 */ #ifdef INET int pf_normalize_ip(struct mbuf **m0, int dir, struct pfi_kkif *kif, u_short *reason, struct pf_pdesc *pd) { struct mbuf *m = *m0; struct pf_krule *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 tag = -1; int verdict; int srs; PF_RULES_RASSERT(); r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); /* Check if there any scrub rules. Lack of scrub rules means enforced * packet normalization operation just like in OpenBSD. */ srs = (r != NULL); while (r != NULL) { pf_counter_u64_add(&r->evaluations, 1); if (pfi_kkif_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 (srs) { /* With scrub rules present IPv4 normalization happens only * if one of rules has matched and it's not a "no scrub" rule */ if (r == NULL || r->action == PF_NOSCRUB) return (PF_PASS); pf_counter_u64_critical_enter(); pf_counter_u64_add_protected(&r->packets[dir == PF_OUT], 1); pf_counter_u64_add_protected(&r->bytes[dir == PF_OUT], pd->tot_len); pf_counter_u64_critical_exit(); } else if ((!V_pf_status.reass && (h->ip_off & htons(IP_MF | IP_OFFMASK)))) { /* With no scrub rules IPv4 fragment reassembly depends on the * global switch. Fragments can be dropped early if reassembly * is disabled. */ REASON_SET(reason, PFRES_NORM); goto drop; } /* 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 or we're in no-df mode */ if ((((r && r->rule_flag & PFRULE_NODF) || (V_pf_status.reass & PF_REASS_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; /* 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; } if (r==NULL || !(r->rule_flag & PFRULE_FRAGMENT_NOREASS)) { 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); } } if (r != NULL) { int scrub_flags = pf_rule_to_scrub_flags(r->rule_flag); pf_scrub_ip(&m, scrub_flags, 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_kkif *kif, u_short *reason, struct pf_pdesc *pd) { struct mbuf *m = *m0; struct pf_krule *r; struct ip6_hdr *h = mtod(m, struct ip6_hdr *); int extoff; int off; struct ip6_ext ext; struct ip6_opt opt; struct ip6_frag frag; u_int32_t plen; int optend; int ooff; u_int8_t proto; int terminal; int srs; PF_RULES_RASSERT(); r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); /* Check if there any scrub rules. Lack of scrub rules means enforced * packet normalization operation just like in OpenBSD. */ srs = (r != NULL); while (r != NULL) { pf_counter_u64_add(&r->evaluations, 1); if (pfi_kkif_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 (srs) { /* With scrub rules present IPv6 normalization happens only * if one of rules has matched and it's not a "no scrub" rule */ if (r == NULL || r->action == PF_NOSCRUB) return (PF_PASS); pf_counter_u64_critical_enter(); pf_counter_u64_add_protected(&r->packets[dir == PF_OUT], 1); pf_counter_u64_add_protected(&r->bytes[dir == PF_OUT], pd->tot_len); pf_counter_u64_critical_exit(); } /* Check for illegal packets */ if (sizeof(struct ip6_hdr) + IPV6_MAXPACKET < m->m_pkthdr.len) goto drop; plen = ntohs(h->ip6_plen); /* jumbo payload option not supported */ if (plen == 0) 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; if (opt.ip6o_type == IP6OPT_JUMBO) goto drop; ooff += sizeof(opt) + opt.ip6o_len; } while (ooff < optend); off = optend; proto = ext.ip6e_nxt; break; default: terminal = 1; break; } } while (!terminal); if (sizeof(struct ip6_hdr) + plen > m->m_pkthdr.len) goto shortpkt; if (r != NULL) { int scrub_flags = pf_rule_to_scrub_flags(r->rule_flag); pf_scrub_ip6(&m, scrub_flags, r->min_ttl, r->set_tos); } return (PF_PASS); fragment: 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_kkif *kif, struct mbuf *m, int ipoff, int off, void *h, struct pf_pdesc *pd) { struct pf_krule *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; int srs; PF_RULES_RASSERT(); r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); /* Check if there any scrub rules. Lack of scrub rules means enforced * packet normalization operation just like in OpenBSD. */ srs = (r != NULL); while (r != NULL) { pf_counter_u64_add(&r->evaluations, 1); if (pfi_kkif_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 (srs) { /* With scrub rules present TCP normalization happens only * if one of rules has matched and it's not a "no scrub" rule */ if (rm == NULL || rm->action == PF_NOSCRUB) return (PF_PASS); pf_counter_u64_critical_enter(); pf_counter_u64_add_protected(&r->packets[dir == PF_OUT], 1); pf_counter_u64_add_protected(&r->bytes[dir == PF_OUT], pd->tot_len); pf_counter_u64_critical_exit(); } if (rm && 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; } /* Set MSS for old-style scrub rules. * The function performs its own copyback. */ if (rm != NULL && rm->max_mss) pf_normalize_mss(m, off, pd, rm->max_mss); /* 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_kstate *state) { uma_zfree(V_pf_state_scrub_z, state->src.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_kstate *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; size_t startoff; 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) { startoff = opt - (hdr + sizeof(struct tcphdr)); 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??\n")); 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_patch_32_unaligned(m, &th->th_sum, &opt[2], htonl(tsval + src->scrub->pfss_ts_mod), PF_ALGNMNT(startoff), 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_patch_32_unaligned(m, &th->th_sum, &opt[6], htonl(tsecr), PF_ALGNMNT(startoff), 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); } int pf_normalize_mss(struct mbuf *m, int off, struct pf_pdesc *pd, u_int16_t maxmss) { struct tcphdr *th = &pd->hdr.tcp; u_int16_t *mss; int thoff; int opt, cnt, optlen = 0; u_char opts[TCP_MAXOLEN]; u_char *optp = opts; size_t startoff; thoff = th->th_off << 2; cnt = thoff - sizeof(struct tcphdr); if (cnt > 0 && !pf_pull_hdr(m, off + sizeof(*th), opts, cnt, NULL, NULL, pd->af)) return (0); for (; cnt > 0; cnt -= optlen, optp += optlen) { startoff = optp - opts; 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)) > maxmss) { pf_patch_16_unaligned(m, &th->th_sum, mss, htons(maxmss), PF_ALGNMNT(startoff), 0); m_copyback(m, off + sizeof(*th), thoff - sizeof(*th), opts); m_copyback(m, off, sizeof(*th), (caddr_t)th); } break; default: break; } } return (0); } u_int16_t pf_rule_to_scrub_flags(u_int32_t rule_flags) { /* * Translate pf_krule->rule_flag to pf_krule->scrub_flags. * The pf_scrub_ip functions have been adapted to the new style of pass * rules but they might get called if old scrub rules are used. */ int scrub_flags = 0; if (rule_flags & PFRULE_SET_TOS) { scrub_flags |= PFSTATE_SETTOS; } if (rule_flags & PFRULE_RANDOMID) scrub_flags |= PFSTATE_RANDOMID; return scrub_flags; } #ifdef INET 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 & PFSTATE_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 & PFSTATE_SETTOS) { u_int16_t ov, nv; ov = *(u_int16_t *)h; h->ip_tos = tos | (h->ip_tos & IPTOS_ECN_MASK); 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 & PFSTATE_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 void pf_scrub_ip6(struct mbuf **m0, u_int32_t flags, u_int8_t min_ttl, u_int8_t tos) { 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; /* Enforce tos. Set traffic class bits */ if (flags & PFSTATE_SETTOS) { h->ip6_flow &= IPV6_FLOWLABEL_MASK | IPV6_VERSION_MASK; h->ip6_flow |= htonl((tos | IPV6_ECN(h)) << 20); } } #endif