/* $OpenBSD: pf_norm.c,v 1.71 2003/08/14 19:00:12 jason Exp $ */ /* * Copyright 2001 Niels Provos * 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. */ #include "pflog.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef INET6 #include #endif /* INET6 */ #include struct pf_frent { LIST_ENTRY(pf_frent) fr_next; struct ip *fr_ip; struct mbuf *fr_m; }; struct pf_frcache { LIST_ENTRY(pf_frcache) fr_next; uint16_t fr_off; uint16_t fr_end; }; #define PFFRAG_SEENLAST 0x0001 /* Seen the last fragment for this */ #define PFFRAG_NOBUFFER 0x0002 /* Non-buffering fragment cache */ #define PFFRAG_DROP 0x0004 /* Drop all fragments */ #define BUFFER_FRAGMENTS(fr) (!((fr)->fr_flags & PFFRAG_NOBUFFER)) struct pf_fragment { RB_ENTRY(pf_fragment) fr_entry; TAILQ_ENTRY(pf_fragment) frag_next; struct in_addr fr_src; struct in_addr fr_dst; u_int8_t fr_p; /* protocol of this fragment */ u_int8_t fr_flags; /* status flags */ u_int16_t fr_id; /* fragment id for reassemble */ u_int16_t fr_max; /* fragment data max */ u_int32_t fr_timeout; #define fr_queue fr_u.fru_queue #define fr_cache fr_u.fru_cache union { LIST_HEAD(pf_fragq, pf_frent) fru_queue; /* buffering */ LIST_HEAD(pf_cacheq, pf_frcache) fru_cache; /* non-buf */ } fr_u; }; TAILQ_HEAD(pf_fragqueue, pf_fragment) pf_fragqueue; TAILQ_HEAD(pf_cachequeue, pf_fragment) pf_cachequeue; static __inline int pf_frag_compare(struct pf_fragment *, struct pf_fragment *); RB_HEAD(pf_frag_tree, pf_fragment) pf_frag_tree, pf_cache_tree; RB_PROTOTYPE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare); RB_GENERATE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare); /* Private prototypes */ void pf_ip2key(struct pf_fragment *, struct ip *); void pf_remove_fragment(struct pf_fragment *); void pf_flush_fragments(void); void pf_free_fragment(struct pf_fragment *); struct pf_fragment *pf_find_fragment(struct ip *, struct pf_frag_tree *); struct mbuf *pf_reassemble(struct mbuf **, struct pf_fragment *, struct pf_frent *, int); struct mbuf *pf_fragcache(struct mbuf **, struct ip*, struct pf_fragment *, int, int, int *); u_int16_t pf_cksum_fixup(u_int16_t, u_int16_t, u_int16_t); int pf_normalize_tcpopt(struct pf_rule *, struct mbuf *, struct tcphdr *, int); #define DPFPRINTF(x) if (pf_status.debug >= PF_DEBUG_MISC) \ { printf("%s: ", __func__); printf x ;} /* Globals */ struct pool pf_frent_pl, pf_frag_pl, pf_cache_pl, pf_cent_pl; struct pool pf_state_scrub_pl; int pf_nfrents, pf_ncache; void pf_normalize_init(void) { pool_init(&pf_frent_pl, sizeof(struct pf_frent), 0, 0, 0, "pffrent", NULL); pool_init(&pf_frag_pl, sizeof(struct pf_fragment), 0, 0, 0, "pffrag", NULL); pool_init(&pf_cache_pl, sizeof(struct pf_fragment), 0, 0, 0, "pffrcache", NULL); pool_init(&pf_cent_pl, sizeof(struct pf_frcache), 0, 0, 0, "pffrcent", NULL); pool_init(&pf_state_scrub_pl, sizeof(struct pf_state_scrub), 0, 0, 0, "pfstscr", NULL); pool_sethiwat(&pf_frag_pl, PFFRAG_FRAG_HIWAT); pool_sethardlimit(&pf_frent_pl, PFFRAG_FRENT_HIWAT, NULL, 0); pool_sethardlimit(&pf_cache_pl, PFFRAG_FRCACHE_HIWAT, NULL, 0); pool_sethardlimit(&pf_cent_pl, PFFRAG_FRCENT_HIWAT, NULL, 0); TAILQ_INIT(&pf_fragqueue); TAILQ_INIT(&pf_cachequeue); } static __inline int pf_frag_compare(struct pf_fragment *a, struct pf_fragment *b) { int diff; if ((diff = a->fr_id - b->fr_id)) return (diff); else if ((diff = a->fr_p - b->fr_p)) return (diff); else if (a->fr_src.s_addr < b->fr_src.s_addr) return (-1); else if (a->fr_src.s_addr > b->fr_src.s_addr) return (1); else if (a->fr_dst.s_addr < b->fr_dst.s_addr) return (-1); else if (a->fr_dst.s_addr > b->fr_dst.s_addr) return (1); return (0); } void pf_purge_expired_fragments(void) { struct pf_fragment *frag; u_int32_t expire = time.tv_sec - pf_default_rule.timeout[PFTM_FRAG]; while ((frag = TAILQ_LAST(&pf_fragqueue, pf_fragqueue)) != NULL) { KASSERT(BUFFER_FRAGMENTS(frag)); if (frag->fr_timeout > expire) break; DPFPRINTF(("expiring %d(%p)\n", frag->fr_id, frag)); pf_free_fragment(frag); } while ((frag = TAILQ_LAST(&pf_cachequeue, pf_cachequeue)) != NULL) { KASSERT(!BUFFER_FRAGMENTS(frag)); if (frag->fr_timeout > expire) break; DPFPRINTF(("expiring %d(%p)\n", frag->fr_id, frag)); pf_free_fragment(frag); KASSERT(TAILQ_EMPTY(&pf_cachequeue) || TAILQ_LAST(&pf_cachequeue, pf_cachequeue) != frag); } } /* * Try to flush old fragments to make space for new ones */ void pf_flush_fragments(void) { struct pf_fragment *frag; int goal; goal = pf_nfrents * 9 / 10; DPFPRINTF(("trying to free > %d frents\n", pf_nfrents - goal)); while (goal < pf_nfrents) { frag = TAILQ_LAST(&pf_fragqueue, pf_fragqueue); if (frag == NULL) break; pf_free_fragment(frag); } goal = pf_ncache * 9 / 10; DPFPRINTF(("trying to free > %d cache entries\n", pf_ncache - goal)); while (goal < pf_ncache) { frag = TAILQ_LAST(&pf_cachequeue, pf_cachequeue); if (frag == NULL) break; pf_free_fragment(frag); } } /* Frees the fragments and all associated entries */ void pf_free_fragment(struct pf_fragment *frag) { struct pf_frent *frent; struct pf_frcache *frcache; /* Free all fragments */ if (BUFFER_FRAGMENTS(frag)) { for (frent = LIST_FIRST(&frag->fr_queue); frent; frent = LIST_FIRST(&frag->fr_queue)) { LIST_REMOVE(frent, fr_next); m_freem(frent->fr_m); pool_put(&pf_frent_pl, frent); pf_nfrents--; } } else { for (frcache = LIST_FIRST(&frag->fr_cache); frcache; frcache = LIST_FIRST(&frag->fr_cache)) { LIST_REMOVE(frcache, fr_next); KASSERT(LIST_EMPTY(&frag->fr_cache) || LIST_FIRST(&frag->fr_cache)->fr_off > frcache->fr_end); pool_put(&pf_cent_pl, frcache); pf_ncache--; } } pf_remove_fragment(frag); } void pf_ip2key(struct pf_fragment *key, struct ip *ip) { key->fr_p = ip->ip_p; key->fr_id = ip->ip_id; key->fr_src.s_addr = ip->ip_src.s_addr; key->fr_dst.s_addr = ip->ip_dst.s_addr; } struct pf_fragment * pf_find_fragment(struct ip *ip, struct pf_frag_tree *tree) { struct pf_fragment key; struct pf_fragment *frag; pf_ip2key(&key, ip); frag = RB_FIND(pf_frag_tree, tree, &key); if (frag != NULL) { /* XXX Are we sure we want to update the timeout? */ frag->fr_timeout = time.tv_sec; if (BUFFER_FRAGMENTS(frag)) { TAILQ_REMOVE(&pf_fragqueue, frag, frag_next); TAILQ_INSERT_HEAD(&pf_fragqueue, frag, frag_next); } else { TAILQ_REMOVE(&pf_cachequeue, frag, frag_next); TAILQ_INSERT_HEAD(&pf_cachequeue, frag, frag_next); } } return (frag); } /* Removes a fragment from the fragment queue and frees the fragment */ void pf_remove_fragment(struct pf_fragment *frag) { if (BUFFER_FRAGMENTS(frag)) { RB_REMOVE(pf_frag_tree, &pf_frag_tree, frag); TAILQ_REMOVE(&pf_fragqueue, frag, frag_next); pool_put(&pf_frag_pl, frag); } else { RB_REMOVE(pf_frag_tree, &pf_cache_tree, frag); TAILQ_REMOVE(&pf_cachequeue, frag, frag_next); pool_put(&pf_cache_pl, frag); } } #define FR_IP_OFF(fr) ((ntohs((fr)->fr_ip->ip_off) & IP_OFFMASK) << 3) struct mbuf * pf_reassemble(struct mbuf **m0, struct pf_fragment *frag, struct pf_frent *frent, int mff) { struct mbuf *m = *m0, *m2; struct pf_frent *frea, *next; struct pf_frent *frep = NULL; struct ip *ip = frent->fr_ip; int hlen = ip->ip_hl << 2; u_int16_t off = (ntohs(ip->ip_off) & IP_OFFMASK) << 3; u_int16_t ip_len = ntohs(ip->ip_len) - ip->ip_hl * 4; u_int16_t max = ip_len + off; KASSERT(frag == NULL || BUFFER_FRAGMENTS(frag)); /* Strip off ip header */ m->m_data += hlen; m->m_len -= hlen; /* Create a new reassembly queue for this packet */ if (frag == NULL) { frag = pool_get(&pf_frag_pl, PR_NOWAIT); if (frag == NULL) { pf_flush_fragments(); frag = pool_get(&pf_frag_pl, PR_NOWAIT); if (frag == NULL) goto drop_fragment; } frag->fr_flags = 0; frag->fr_max = 0; frag->fr_src = frent->fr_ip->ip_src; frag->fr_dst = frent->fr_ip->ip_dst; frag->fr_p = frent->fr_ip->ip_p; frag->fr_id = frent->fr_ip->ip_id; frag->fr_timeout = time.tv_sec; LIST_INIT(&frag->fr_queue); RB_INSERT(pf_frag_tree, &pf_frag_tree, frag); TAILQ_INSERT_HEAD(&pf_fragqueue, frag, frag_next); /* We do not have a previous fragment */ frep = NULL; goto insert; } /* * Find a fragment after the current one: * - off contains the real shifted offset. */ LIST_FOREACH(frea, &frag->fr_queue, fr_next) { if (FR_IP_OFF(frea) > off) break; frep = frea; } KASSERT(frep != NULL || frea != NULL); if (frep != NULL && FR_IP_OFF(frep) + ntohs(frep->fr_ip->ip_len) - frep->fr_ip->ip_hl * 4 > off) { u_int16_t precut; precut = FR_IP_OFF(frep) + ntohs(frep->fr_ip->ip_len) - frep->fr_ip->ip_hl * 4 - off; if (precut >= ip_len) goto drop_fragment; m_adj(frent->fr_m, precut); DPFPRINTF(("overlap -%d\n", precut)); /* Enforce 8 byte boundaries */ ip->ip_off = htons(ntohs(ip->ip_off) + (precut >> 3)); off = (ntohs(ip->ip_off) & IP_OFFMASK) << 3; ip_len -= precut; ip->ip_len = htons(ip_len); } for (; frea != NULL && ip_len + off > FR_IP_OFF(frea); frea = next) { u_int16_t aftercut; aftercut = ip_len + off - FR_IP_OFF(frea); DPFPRINTF(("adjust overlap %d\n", aftercut)); if (aftercut < ntohs(frea->fr_ip->ip_len) - frea->fr_ip->ip_hl * 4) { frea->fr_ip->ip_len = htons(ntohs(frea->fr_ip->ip_len) - aftercut); frea->fr_ip->ip_off = htons(ntohs(frea->fr_ip->ip_off) + (aftercut >> 3)); m_adj(frea->fr_m, aftercut); break; } /* This fragment is completely overlapped, loose it */ next = LIST_NEXT(frea, fr_next); m_freem(frea->fr_m); LIST_REMOVE(frea, fr_next); pool_put(&pf_frent_pl, frea); pf_nfrents--; } insert: /* Update maximum data size */ if (frag->fr_max < max) frag->fr_max = max; /* This is the last segment */ if (!mff) frag->fr_flags |= PFFRAG_SEENLAST; if (frep == NULL) LIST_INSERT_HEAD(&frag->fr_queue, frent, fr_next); else LIST_INSERT_AFTER(frep, frent, fr_next); /* Check if we are completely reassembled */ if (!(frag->fr_flags & PFFRAG_SEENLAST)) return (NULL); /* Check if we have all the data */ off = 0; for (frep = LIST_FIRST(&frag->fr_queue); frep; frep = next) { next = LIST_NEXT(frep, fr_next); off += ntohs(frep->fr_ip->ip_len) - frep->fr_ip->ip_hl * 4; if (off < frag->fr_max && (next == NULL || FR_IP_OFF(next) != off)) { DPFPRINTF(("missing fragment at %d, next %d, max %d\n", off, next == NULL ? -1 : FR_IP_OFF(next), frag->fr_max)); return (NULL); } } DPFPRINTF(("%d < %d?\n", off, frag->fr_max)); if (off < frag->fr_max) return (NULL); /* We have all the data */ frent = LIST_FIRST(&frag->fr_queue); KASSERT(frent != NULL); if ((frent->fr_ip->ip_hl << 2) + off > IP_MAXPACKET) { DPFPRINTF(("drop: too big: %d\n", off)); pf_free_fragment(frag); return (NULL); } next = LIST_NEXT(frent, fr_next); /* Magic from ip_input */ ip = frent->fr_ip; m = frent->fr_m; m2 = m->m_next; m->m_next = NULL; m_cat(m, m2); pool_put(&pf_frent_pl, frent); pf_nfrents--; for (frent = next; frent != NULL; frent = next) { next = LIST_NEXT(frent, fr_next); m2 = frent->fr_m; pool_put(&pf_frent_pl, frent); pf_nfrents--; m_cat(m, m2); } ip->ip_src = frag->fr_src; ip->ip_dst = frag->fr_dst; /* Remove from fragment queue */ pf_remove_fragment(frag); hlen = ip->ip_hl << 2; ip->ip_len = htons(off + hlen); m->m_len += hlen; m->m_data -= hlen; /* some debugging cruft by sklower, below, will go away soon */ /* XXX this should be done elsewhere */ if (m->m_flags & M_PKTHDR) { int plen = 0; for (m2 = m; m2; m2 = m2->m_next) plen += m2->m_len; m->m_pkthdr.len = plen; } DPFPRINTF(("complete: %p(%d)\n", m, ntohs(ip->ip_len))); return (m); drop_fragment: /* Oops - fail safe - drop packet */ pool_put(&pf_frent_pl, frent); pf_nfrents--; m_freem(m); return (NULL); } struct mbuf * pf_fragcache(struct mbuf **m0, struct ip *h, struct pf_fragment *frag, int mff, int drop, int *nomem) { struct mbuf *m = *m0; struct pf_frcache *frp, *fra, *cur = NULL; int ip_len = ntohs(h->ip_len) - (h->ip_hl << 2); u_int16_t off = ntohs(h->ip_off) << 3; u_int16_t max = ip_len + off; int hosed = 0; KASSERT(frag == NULL || !BUFFER_FRAGMENTS(frag)); /* Create a new range queue for this packet */ if (frag == NULL) { frag = pool_get(&pf_cache_pl, PR_NOWAIT); if (frag == NULL) { pf_flush_fragments(); frag = pool_get(&pf_cache_pl, PR_NOWAIT); if (frag == NULL) goto no_mem; } /* Get an entry for the queue */ cur = pool_get(&pf_cent_pl, PR_NOWAIT); if (cur == NULL) { pool_put(&pf_cache_pl, frag); goto no_mem; } pf_ncache++; frag->fr_flags = PFFRAG_NOBUFFER; frag->fr_max = 0; frag->fr_src = h->ip_src; frag->fr_dst = h->ip_dst; frag->fr_p = h->ip_p; frag->fr_id = h->ip_id; frag->fr_timeout = time.tv_sec; cur->fr_off = off; cur->fr_end = max; LIST_INIT(&frag->fr_cache); LIST_INSERT_HEAD(&frag->fr_cache, cur, fr_next); RB_INSERT(pf_frag_tree, &pf_cache_tree, frag); TAILQ_INSERT_HEAD(&pf_cachequeue, frag, frag_next); DPFPRINTF(("fragcache[%d]: new %d-%d\n", h->ip_id, off, max)); goto pass; } /* * Find a fragment after the current one: * - off contains the real shifted offset. */ frp = NULL; LIST_FOREACH(fra, &frag->fr_cache, fr_next) { if (fra->fr_off > off) break; frp = fra; } KASSERT(frp != NULL || fra != NULL); if (frp != NULL) { int precut; precut = frp->fr_end - off; if (precut >= ip_len) { /* Fragment is entirely a duplicate */ DPFPRINTF(("fragcache[%d]: dead (%d-%d) %d-%d\n", h->ip_id, frp->fr_off, frp->fr_end, off, max)); goto drop_fragment; } if (precut == 0) { /* They are adjacent. Fixup cache entry */ DPFPRINTF(("fragcache[%d]: adjacent (%d-%d) %d-%d\n", h->ip_id, frp->fr_off, frp->fr_end, off, max)); frp->fr_end = max; } else if (precut > 0) { /* The first part of this payload overlaps with a * fragment that has already been passed. * Need to trim off the first part of the payload. * But to do so easily, we need to create another * mbuf to throw the original header into. */ DPFPRINTF(("fragcache[%d]: chop %d (%d-%d) %d-%d\n", h->ip_id, precut, frp->fr_off, frp->fr_end, off, max)); off += precut; max -= precut; /* Update the previous frag to encompas this one */ frp->fr_end = max; if (!drop) { /* XXX Optimization opportunity * This is a very heavy way to trim the payload. * we could do it much faster by diddling mbuf * internals but that would be even less legible * than this mbuf magic. For my next trick, * I'll pull a rabbit out of my laptop. */ *m0 = m_copym2(m, 0, h->ip_hl << 2, M_NOWAIT); if (*m0 == NULL) goto no_mem; KASSERT((*m0)->m_next == NULL); m_adj(m, precut + (h->ip_hl << 2)); m_cat(*m0, m); m = *m0; if (m->m_flags & M_PKTHDR) { int plen = 0; struct mbuf *t; for (t = m; t; t = t->m_next) plen += t->m_len; m->m_pkthdr.len = plen; } h = mtod(m, struct ip *); KASSERT((int)m->m_len == ntohs(h->ip_len) - precut); h->ip_off = htons(ntohs(h->ip_off) + (precut >> 3)); h->ip_len = htons(ntohs(h->ip_len) - precut); } else { hosed++; } } else { /* There is a gap between fragments */ DPFPRINTF(("fragcache[%d]: gap %d (%d-%d) %d-%d\n", h->ip_id, -precut, frp->fr_off, frp->fr_end, off, max)); cur = pool_get(&pf_cent_pl, PR_NOWAIT); if (cur == NULL) goto no_mem; pf_ncache++; cur->fr_off = off; cur->fr_end = max; LIST_INSERT_AFTER(frp, cur, fr_next); } } if (fra != NULL) { int aftercut; int merge = 0; aftercut = max - fra->fr_off; if (aftercut == 0) { /* Adjacent fragments */ DPFPRINTF(("fragcache[%d]: adjacent %d-%d (%d-%d)\n", h->ip_id, off, max, fra->fr_off, fra->fr_end)); fra->fr_off = off; merge = 1; } else if (aftercut > 0) { /* Need to chop off the tail of this fragment */ DPFPRINTF(("fragcache[%d]: chop %d %d-%d (%d-%d)\n", h->ip_id, aftercut, off, max, fra->fr_off, fra->fr_end)); fra->fr_off = off; max -= aftercut; merge = 1; if (!drop) { m_adj(m, -aftercut); if (m->m_flags & M_PKTHDR) { int plen = 0; struct mbuf *t; for (t = m; t; t = t->m_next) plen += t->m_len; m->m_pkthdr.len = plen; } h = mtod(m, struct ip *); KASSERT((int)m->m_len == ntohs(h->ip_len) - aftercut); h->ip_len = htons(ntohs(h->ip_len) - aftercut); } else { hosed++; } } else { /* There is a gap between fragments */ DPFPRINTF(("fragcache[%d]: gap %d %d-%d (%d-%d)\n", h->ip_id, -aftercut, off, max, fra->fr_off, fra->fr_end)); cur = pool_get(&pf_cent_pl, PR_NOWAIT); if (cur == NULL) goto no_mem; pf_ncache++; cur->fr_off = off; cur->fr_end = max; LIST_INSERT_BEFORE(fra, cur, fr_next); } /* Need to glue together two seperate fragment descriptors */ if (merge) { if (cur && fra->fr_off <= cur->fr_end) { /* Need to merge in a previous 'cur' */ DPFPRINTF(("fragcache[%d]: adjacent(merge " "%d-%d) %d-%d (%d-%d)\n", h->ip_id, cur->fr_off, cur->fr_end, off, max, fra->fr_off, fra->fr_end)); fra->fr_off = cur->fr_off; LIST_REMOVE(cur, fr_next); pool_put(&pf_cent_pl, cur); pf_ncache--; cur = NULL; } else if (frp && fra->fr_off <= frp->fr_end) { /* Need to merge in a modified 'frp' */ KASSERT(cur == NULL); DPFPRINTF(("fragcache[%d]: adjacent(merge " "%d-%d) %d-%d (%d-%d)\n", h->ip_id, frp->fr_off, frp->fr_end, off, max, fra->fr_off, fra->fr_end)); fra->fr_off = frp->fr_off; LIST_REMOVE(frp, fr_next); pool_put(&pf_cent_pl, frp); pf_ncache--; frp = NULL; } } } if (hosed) { /* * We must keep tracking the overall fragment even when * we're going to drop it anyway so that we know when to * free the overall descriptor. Thus we drop the frag late. */ goto drop_fragment; } pass: /* Update maximum data size */ if (frag->fr_max < max) frag->fr_max = max; /* This is the last segment */ if (!mff) frag->fr_flags |= PFFRAG_SEENLAST; /* Check if we are completely reassembled */ if ((frag->fr_flags & PFFRAG_SEENLAST) && LIST_FIRST(&frag->fr_cache)->fr_off == 0 && LIST_FIRST(&frag->fr_cache)->fr_end == frag->fr_max) { /* Remove from fragment queue */ DPFPRINTF(("fragcache[%d]: done 0-%d\n", h->ip_id, frag->fr_max)); pf_free_fragment(frag); } return (m); no_mem: *nomem = 1; /* Still need to pay attention to !IP_MF */ if (!mff && frag) frag->fr_flags |= PFFRAG_SEENLAST; m_freem(m); return (NULL); drop_fragment: /* Still need to pay attention to !IP_MF */ if (!mff && frag) frag->fr_flags |= PFFRAG_SEENLAST; if (drop) { /* This fragment has been deemed bad. Don't reass */ if ((frag->fr_flags & PFFRAG_DROP) == 0) DPFPRINTF(("fragcache[%d]: dropping overall fragment\n", h->ip_id)); frag->fr_flags |= PFFRAG_DROP; } m_freem(m); return (NULL); } int pf_normalize_ip(struct mbuf **m0, int dir, struct ifnet *ifp, u_short *reason) { struct mbuf *m = *m0; struct pf_rule *r; struct pf_frent *frent; struct pf_fragment *frag = NULL; 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; r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); while (r != NULL) { r->evaluations++; if (r->ifp != NULL && r->ifp != ifp) 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.not)) 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.not)) r = r->skip[PF_SKIP_DST_ADDR].ptr; else break; } if (r == NULL) return (PF_PASS); else r->packets++; /* Check for illegal packets */ if (hlen < (int)sizeof(struct ip)) goto drop; if (hlen > ntohs(h->ip_len)) 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); /* 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; if ((r->rule_flag & (PFRULE_FRAGCROP|PFRULE_FRAGDROP)) == 0) { /* Fully buffer all of the fragments */ frag = pf_find_fragment(h, &pf_frag_tree); /* Check if we saw the last fragment already */ if (frag != NULL && (frag->fr_flags & PFFRAG_SEENLAST) && max > frag->fr_max) goto bad; /* Get an entry for the fragment queue */ frent = pool_get(&pf_frent_pl, PR_NOWAIT); if (frent == NULL) { REASON_SET(reason, PFRES_MEMORY); return (PF_DROP); } pf_nfrents++; frent->fr_ip = h; frent->fr_m = m; /* Might return a completely reassembled mbuf, or NULL */ DPFPRINTF(("reass frag %d @ %d-%d\n", h->ip_id, fragoff, max)); *m0 = m = pf_reassemble(m0, frag, frent, mff); if (m == NULL) return (PF_DROP); if (frag && (frag->fr_flags & PFFRAG_DROP)) goto drop; h = mtod(m, struct ip *); } else { /* non-buffering fragment cache (drops or masks overlaps) */ int nomem = 0; if (dir == PF_OUT) { if (m_tag_find(m, PACKET_TAG_PF_FRAGCACHE, NULL) != NULL) { /* Already passed the fragment cache in the * input direction. If we continued, it would * appear to be a dup and would be dropped. */ goto fragment_pass; } } frag = pf_find_fragment(h, &pf_cache_tree); /* Check if we saw the last fragment already */ if (frag != NULL && (frag->fr_flags & PFFRAG_SEENLAST) && max > frag->fr_max) { if (r->rule_flag & PFRULE_FRAGDROP) frag->fr_flags |= PFFRAG_DROP; goto bad; } *m0 = m = pf_fragcache(m0, h, frag, mff, (r->rule_flag & PFRULE_FRAGDROP) ? 1 : 0, &nomem); if (m == NULL) { if (nomem) goto no_mem; goto drop; } if (dir == PF_IN) { struct m_tag *mtag; mtag = m_tag_get(PACKET_TAG_PF_FRAGCACHE, 0, M_NOWAIT); if (mtag == NULL) goto no_mem; m_tag_prepend(m, mtag); } if (frag && (frag->fr_flags & PFFRAG_DROP)) goto drop; goto fragment_pass; } no_fragment: /* At this point, only IP_DF is allowed in ip_off */ h->ip_off &= htons(IP_DF); /* Enforce a minimum ttl, may cause endless packet loops */ if (r->min_ttl && h->ip_ttl < r->min_ttl) h->ip_ttl = r->min_ttl; if (r->rule_flag & PFRULE_RANDOMID) h->ip_id = ip_randomid(); return (PF_PASS); fragment_pass: /* Enforce a minimum ttl, may cause endless packet loops */ if (r->min_ttl && h->ip_ttl < r->min_ttl) h->ip_ttl = r->min_ttl; return (PF_PASS); no_mem: REASON_SET(reason, PFRES_MEMORY); if (r != NULL && r->log) PFLOG_PACKET(ifp, h, m, AF_INET, dir, *reason, r, NULL, NULL); return (PF_DROP); drop: REASON_SET(reason, PFRES_NORM); if (r != NULL && r->log) PFLOG_PACKET(ifp, h, m, AF_INET, dir, *reason, r, NULL, NULL); return (PF_DROP); bad: DPFPRINTF(("dropping bad fragment\n")); /* Free assoicated fragments */ if (frag != NULL) pf_free_fragment(frag); REASON_SET(reason, PFRES_FRAG); if (r != NULL && r->log) PFLOG_PACKET(ifp, h, m, AF_INET, dir, *reason, r, NULL, NULL); return (PF_DROP); } #ifdef INET6 int pf_normalize_ip6(struct mbuf **m0, int dir, struct ifnet *ifp, u_short *reason) { struct mbuf *m = *m0; struct pf_rule *r; struct ip6_hdr *h = mtod(m, struct ip6_hdr *); 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; u_int16_t fragoff = 0; int optend; int ooff; u_int8_t proto; int terminal; r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); while (r != NULL) { r->evaluations++; if (r->ifp != NULL && r->ifp != ifp) 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.not)) 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.not)) r = r->skip[PF_SKIP_DST_ADDR].ptr; else break; } if (r == NULL) return (PF_PASS); else r->packets++; /* Check for illegal packets */ if (sizeof(struct ip6_hdr) + IPV6_MAXPACKET < m->m_pkthdr.len) goto drop; 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; 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; 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; /* Enforce a minimum ttl, may cause endless packet loops */ if (r->min_ttl && h->ip6_hlim < r->min_ttl) h->ip6_hlim = r->min_ttl; return (PF_PASS); fragment: if (ntohs(h->ip6_plen) == 0 || jumbolen) goto drop; plen = ntohs(h->ip6_plen); if (!pf_pull_hdr(m, off, &frag, sizeof(frag), NULL, NULL, AF_INET6)) goto shortpkt; fragoff = ntohs(frag.ip6f_offlg & IP6F_OFF_MASK); if (fragoff + (plen - off - sizeof(frag)) > IPV6_MAXPACKET) goto badfrag; /* do something about it */ return (PF_PASS); shortpkt: REASON_SET(reason, PFRES_SHORT); if (r != NULL && r->log) PFLOG_PACKET(ifp, h, m, AF_INET6, dir, *reason, r, NULL, NULL); return (PF_DROP); drop: REASON_SET(reason, PFRES_NORM); if (r != NULL && r->log) PFLOG_PACKET(ifp, h, m, AF_INET6, dir, *reason, r, NULL, NULL); return (PF_DROP); badfrag: REASON_SET(reason, PFRES_FRAG); if (r != NULL && r->log) PFLOG_PACKET(ifp, h, m, AF_INET6, dir, *reason, r, NULL, NULL); return (PF_DROP); } #endif int pf_normalize_tcp(int dir, struct ifnet *ifp, 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; r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); while (r != NULL) { r->evaluations++; if (r->ifp != NULL && r->ifp != ifp) 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.not)) 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.not)) 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 { rm = r; break; } } if (rm == NULL) return (PF_PASS); else r->packets++; 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) flags &= ~TH_FIN; } 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_cksum_fixup(th->th_sum, ov, nv); rewrite = 1; } /* Remove urgent pointer, if TH_URG is not set */ if (!(flags & TH_URG) && th->th_urp) { th->th_sum = pf_cksum_fixup(th->th_sum, th->th_urp, 0); th->th_urp = 0; rewrite = 1; } /* Process options */ if (r->max_mss && pf_normalize_tcpopt(r, m, th, off)) rewrite = 1; /* copy back packet headers if we sanitized */ if (rewrite) m_copyback(m, off, sizeof(*th), th); return (PF_PASS); tcp_drop: REASON_SET(&reason, PFRES_NORM); if (rm != NULL && r->log) PFLOG_PACKET(ifp, h, m, AF_INET, dir, reason, r, NULL, NULL); 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_int8_t hdr[60]; u_int8_t *opt; KASSERT(src->scrub == NULL); src->scrub = pool_get(&pf_state_scrub_pl, PR_NOWAIT); if (src->scrub == NULL) return (1); bzero(src->scrub, sizeof(*src->scrub)); 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: /* FALLTHROUH */ 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 = arc4random(); } /* FALLTHROUGH */ default: hlen -= opt[1]; opt += opt[1]; break; } } } return (0); } void pf_normalize_tcp_cleanup(struct pf_state *state) { if (state->src.scrub) pool_put(&pf_state_scrub_pl, state->src.scrub); if (state->dst.scrub) pool_put(&pf_state_scrub_pl, 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_peer *src, struct pf_state_peer *dst, int *writeback) { u_int8_t hdr[60]; u_int8_t *opt; int copyback = 0; KASSERT(src->scrub || dst->scrub); /* * 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 (dst->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: /* FALLTHROUH */ 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 (opt[1] >= TCPOLEN_TIMESTAMP) { u_int32_t ts_value; if (src->scrub && (src->scrub->pfss_flags & PFSS_TIMESTAMP)) { memcpy(&ts_value, &opt[2], sizeof(u_int32_t)); ts_value = htonl(ntohl(ts_value) + src->scrub->pfss_ts_mod); pf_change_a(&opt[2], &th->th_sum, ts_value, 0); copyback = 1; } if (dst->scrub && (dst->scrub->pfss_flags & PFSS_TIMESTAMP)) { memcpy(&ts_value, &opt[6], sizeof(u_int32_t)); ts_value = htonl(ntohl(ts_value) - dst->scrub->pfss_ts_mod); pf_change_a(&opt[6], &th->th_sum, ts_value, 0); copyback = 1; } } /* FALLTHROUGH */ default: hlen -= opt[1]; opt += opt[1]; 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)); } } /* I have a dream.... TCP segment reassembly.... */ return (0); } int pf_normalize_tcpopt(struct pf_rule *r, struct mbuf *m, struct tcphdr *th, int off) { u_int16_t *mss; int thoff; int opt, cnt, optlen = 0; int rewrite = 0; u_char *optp; thoff = th->th_off << 2; cnt = thoff - sizeof(struct tcphdr); optp = mtod(m, caddr_t) + off + sizeof(struct tcphdr); 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_cksum_fixup(th->th_sum, *mss, htons(r->max_mss)); *mss = htons(r->max_mss); rewrite = 1; } break; default: break; } } return (rewrite); }