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f-stack/freebsd/netpfil/pf/pf_norm.c

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/*-
* 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 "opt_inet.h"
#include "opt_inet6.h"
#include "opt_pf.h"
#include <sys/param.h>
#include <sys/kernel.h>
#include <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
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