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freebsd/sys/netpfil/pf/pf_norm.c
Gleb Smirnoff 0e4f18aa68 o In pf_normalize_ip() we don't need mtag in 
!(PFRULE_FRAGCROP|PFRULE_FRAGDROP) case.
o In the (PFRULE_FRAGCROP|PFRULE_FRAGDROP) case we should allocate mtag
  if we don't find any.

Tested by:	Ian FREISLICH <ianf cloudseed.co.za>
2014-05-17 12:30:27 +00:00

1985 lines
54 KiB
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/*-
* Copyright 2001 Niels Provos <provos@citi.umich.edu>
* 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/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 <netinet/tcp.h>
#include <netinet/tcp_fsm.h>
#include <netinet/tcp_seq.h>
#ifdef INET6
#include <netinet/ip6.h>
#endif /* INET6 */
struct pf_frent {
LIST_ENTRY(pf_frent) fr_next;
union {
struct {
struct ip *_fr_ip;
struct mbuf *_fr_m;
} _frag;
struct {
uint16_t _fr_off;
uint16_t _fr_end;
} _cache;
} _u;
};
#define fr_ip _u._frag._fr_ip
#define fr_m _u._frag._fr_m
#define fr_off _u._cache._fr_off
#define fr_end _u._cache._fr_end
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 */
#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))
u_int16_t fr_id; /* fragment id for reassemble */
u_int16_t fr_max; /* fragment data max */
u_int32_t fr_timeout;
LIST_HEAD(, pf_frent) fr_queue;
};
static struct mtx pf_frag_mtx;
#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)
static VNET_DEFINE(struct pf_cachequeue, pf_cachequeue);
#define V_pf_cachequeue VNET(pf_cachequeue)
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 VNET_DEFINE(struct pf_frag_tree, pf_cache_tree);
#define V_pf_cache_tree VNET(pf_cache_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);
/* Private prototypes */
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);
#ifdef INET
static void pf_ip2key(struct pf_fragment *, struct ip *);
static void pf_scrub_ip(struct mbuf **, u_int32_t, u_int8_t,
u_int8_t);
static void pf_flush_fragments(void);
static struct pf_fragment *pf_find_fragment(struct ip *, struct pf_frag_tree *);
static struct mbuf *pf_reassemble(struct mbuf **, struct pf_fragment **,
struct pf_frent *, int);
static struct mbuf *pf_fragcache(struct mbuf **, struct ip*,
struct pf_fragment **, int, int, int *);
#endif /* INET */
#ifdef INET6
static void pf_scrub_ip6(struct mbuf **, u_int8_t);
#endif
#define DPFPRINTF(x) do { \
if (V_pf_status.debug >= PF_DEBUG_MISC) { \
printf("%s: ", __func__); \
printf x ; \
} \
} while(0)
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");
mtx_init(&pf_frag_mtx, "pf fragments", NULL, MTX_DEF);
TAILQ_INIT(&V_pf_fragqueue);
TAILQ_INIT(&V_pf_cachequeue);
}
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(&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))
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_uptime -
V_pf_default_rule.timeout[PFTM_FRAG];
PF_FRAG_LOCK();
while ((frag = TAILQ_LAST(&V_pf_fragqueue, pf_fragqueue)) != NULL) {
KASSERT((BUFFER_FRAGMENTS(frag)),
("BUFFER_FRAGMENTS(frag) == 0: %s", __FUNCTION__));
if (frag->fr_timeout > expire)
break;
DPFPRINTF(("expiring %d(%p)\n", frag->fr_id, frag));
pf_free_fragment(frag);
}
while ((frag = TAILQ_LAST(&V_pf_cachequeue, pf_cachequeue)) != NULL) {
KASSERT((!BUFFER_FRAGMENTS(frag)),
("BUFFER_FRAGMENTS(frag) != 0: %s", __FUNCTION__));
if (frag->fr_timeout > expire)
break;
DPFPRINTF(("expiring %d(%p)\n", frag->fr_id, frag));
pf_free_fragment(frag);
KASSERT((TAILQ_EMPTY(&V_pf_cachequeue) ||
TAILQ_LAST(&V_pf_cachequeue, pf_cachequeue) != frag),
("!(TAILQ_EMPTY() || TAILQ_LAST() == farg): %s",
__FUNCTION__));
}
PF_FRAG_UNLOCK();
}
#ifdef INET
/*
* Try to flush old fragments to make space for new ones
*/
static void
pf_flush_fragments(void)
{
struct pf_fragment *frag, *cache;
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);
cache = TAILQ_LAST(&V_pf_cachequeue, pf_cachequeue);
if (cache)
pf_free_fragment(cache);
if (frag == NULL && cache == NULL)
break;
}
}
#endif /* INET */
/* 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 */
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);
uma_zfree(V_pf_frent_z, frent);
}
} else {
for (frent = LIST_FIRST(&frag->fr_queue); frent;
frent = LIST_FIRST(&frag->fr_queue)) {
LIST_REMOVE(frent, fr_next);
KASSERT((LIST_EMPTY(&frag->fr_queue) ||
LIST_FIRST(&frag->fr_queue)->fr_off >
frent->fr_end),
("! (LIST_EMPTY() || LIST_FIRST()->fr_off >"
" frent->fr_end): %s", __func__));
uma_zfree(V_pf_frent_z, frent);
}
}
pf_remove_fragment(frag);
}
#ifdef INET
static 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;
}
static struct pf_fragment *
pf_find_fragment(struct ip *ip, struct pf_frag_tree *tree)
{
struct pf_fragment key;
struct pf_fragment *frag;
PF_FRAG_ASSERT();
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_uptime;
if (BUFFER_FRAGMENTS(frag)) {
TAILQ_REMOVE(&V_pf_fragqueue, frag, frag_next);
TAILQ_INSERT_HEAD(&V_pf_fragqueue, frag, frag_next);
} else {
TAILQ_REMOVE(&V_pf_cachequeue, frag, frag_next);
TAILQ_INSERT_HEAD(&V_pf_cachequeue, frag, frag_next);
}
}
return (frag);
}
#endif /* INET */
/* Removes a fragment from the fragment queue and frees the fragment */
static void
pf_remove_fragment(struct pf_fragment *frag)
{
PF_FRAG_ASSERT();
if (BUFFER_FRAGMENTS(frag)) {
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);
} else {
RB_REMOVE(pf_frag_tree, &V_pf_cache_tree, frag);
TAILQ_REMOVE(&V_pf_cachequeue, frag, frag_next);
uma_zfree(V_pf_frag_z, frag);
}
}
#ifdef INET
#define FR_IP_OFF(fr) ((ntohs((fr)->fr_ip->ip_off) & IP_OFFMASK) << 3)
static 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;
PF_FRAG_ASSERT();
KASSERT((*frag == NULL || BUFFER_FRAGMENTS(*frag)),
("! (*frag == NULL || BUFFER_FRAGMENTS(*frag)): %s", __FUNCTION__));
/* Strip off ip header */
m->m_data += hlen;
m->m_len -= hlen;
/* 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)
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_uptime;
LIST_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 */
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),
("!(frep != NULL || frea != NULL): %s", __FUNCTION__));;
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, lose it */
next = LIST_NEXT(frea, fr_next);
m_freem(frea->fr_m);
LIST_REMOVE(frea, fr_next);
uma_zfree(V_pf_frent_z, frea);
}
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), ("frent == NULL: %s", __FUNCTION__));
if ((frent->fr_ip->ip_hl << 2) + off > IP_MAXPACKET) {
DPFPRINTF(("drop: too big: %d\n", off));
pf_free_fragment(*frag);
*frag = NULL;
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);
uma_zfree(V_pf_frent_z, frent);
for (frent = next; frent != NULL; frent = next) {
next = LIST_NEXT(frent, fr_next);
m2 = frent->fr_m;
uma_zfree(V_pf_frent_z, frent);
m->m_pkthdr.csum_flags &= m2->m_pkthdr.csum_flags;
m->m_pkthdr.csum_data += m2->m_pkthdr.csum_data;
m_cat(m, m2);
}
while (m->m_pkthdr.csum_data & 0xffff0000)
m->m_pkthdr.csum_data = (m->m_pkthdr.csum_data & 0xffff) +
(m->m_pkthdr.csum_data >> 16);
ip->ip_src = (*frag)->fr_src;
ip->ip_dst = (*frag)->fr_dst;
/* Remove from fragment queue */
pf_remove_fragment(*frag);
*frag = NULL;
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 */
uma_zfree(V_pf_frent_z, frent);
m_freem(m);
return (NULL);
}
static 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_frent *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;
PF_FRAG_ASSERT();
KASSERT((*frag == NULL || !BUFFER_FRAGMENTS(*frag)),
("!(*frag == NULL || !BUFFER_FRAGMENTS(*frag)): %s", __FUNCTION__));
/* Create a new range 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)
goto no_mem;
}
/* Get an entry for the queue */
cur = uma_zalloc(V_pf_frent_z, M_NOWAIT);
if (cur == NULL) {
uma_zfree(V_pf_frag_z, *frag);
*frag = NULL;
goto no_mem;
}
(*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_uptime;
cur->fr_off = off;
cur->fr_end = max;
LIST_INIT(&(*frag)->fr_queue);
LIST_INSERT_HEAD(&(*frag)->fr_queue, cur, fr_next);
RB_INSERT(pf_frag_tree, &V_pf_cache_tree, *frag);
TAILQ_INSERT_HEAD(&V_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_queue, fr_next) {
if (fra->fr_off > off)
break;
frp = fra;
}
KASSERT((frp != NULL || fra != NULL),
("!(frp != NULL || fra != NULL): %s", __FUNCTION__));
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 encompass 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_dup(m, M_NOWAIT);
if (*m0 == NULL)
goto no_mem;
/* From KAME Project : We have missed this! */
m_adj(*m0, (h->ip_hl << 2) -
(*m0)->m_pkthdr.len);
KASSERT(((*m0)->m_next == NULL),
("(*m0)->m_next != NULL: %s",
__FUNCTION__));
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),
("m->m_len != ntohs(h->ip_len) - precut: %s",
__FUNCTION__));
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 = uma_zalloc(V_pf_frent_z, M_NOWAIT);
if (cur == NULL)
goto no_mem;
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),
("m->m_len != ntohs(h->ip_len) - aftercut: %s",
__FUNCTION__));
h->ip_len = htons(ntohs(h->ip_len) - aftercut);
} else {
hosed++;
}
} else if (frp == NULL) {
/* 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 = uma_zalloc(V_pf_frent_z, M_NOWAIT);
if (cur == NULL)
goto no_mem;
cur->fr_off = off;
cur->fr_end = max;
LIST_INSERT_BEFORE(fra, cur, fr_next);
}
/* Need to glue together two separate 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);
uma_zfree(V_pf_frent_z, cur);
cur = NULL;
} else if (frp && fra->fr_off <= frp->fr_end) {
/* Need to merge in a modified 'frp' */
KASSERT((cur == NULL), ("cur != NULL: %s",
__FUNCTION__));
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);
uma_zfree(V_pf_frent_z, frp);
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_queue)->fr_off == 0 &&
LIST_FIRST(&(*frag)->fr_queue)->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);
*frag = NULL;
}
return (m);
no_mem:
*nomem = 1;
/* Still need to pay attention to !IP_MF */
if (!mff && *frag != NULL)
(*frag)->fr_flags |= PFFRAG_SEENLAST;
m_freem(m);
return (NULL);
drop_fragment:
/* Still need to pay attention to !IP_MF */
if (!mff && *frag != NULL)
(*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 pfi_kif *kif, u_short *reason,
struct pf_pdesc *pd)
{
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;
int tag = -1;
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))
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)) {
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;
if ((r->rule_flag & (PFRULE_FRAGCROP|PFRULE_FRAGDROP)) == 0) {
/* Fully buffer all of the fragments */
PF_FRAG_LOCK();
frag = pf_find_fragment(h, &V_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 = uma_zalloc(V_pf_frent_z, M_NOWAIT);
if (frent == NULL) {
PF_FRAG_UNLOCK();
REASON_SET(reason, PFRES_MEMORY);
return (PF_DROP);
}
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);
PF_FRAG_UNLOCK();
if (m == NULL)
return (PF_DROP);
if (frag != NULL && (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 && pd->pf_mtag &&
pd->pf_mtag->flags & PF_TAG_FRAGCACHE) {
/*
* 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;
}
PF_FRAG_LOCK();
frag = pf_find_fragment(h, &V_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);
PF_FRAG_UNLOCK();
if (m == NULL) {
if (nomem)
goto no_mem;
goto drop;
}
if (dir == PF_IN) {
/* Use mtag from copied and trimmed mbuf chain. */
pd->pf_mtag = pf_get_mtag(m);
if (pd->pf_mtag == NULL) {
m_freem(m);
*m0 = NULL;
goto no_mem;
}
pd->pf_mtag->flags |= PF_TAG_FRAGCACHE;
}
if (frag != NULL && (frag->fr_flags & PFFRAG_DROP))
goto drop;
goto fragment_pass;
}
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);
}
/* not missing a return here */
fragment_pass:
pf_scrub_ip(&m, r->rule_flag, r->min_ttl, r->set_tos);
if ((r->rule_flag & (PFRULE_FRAGCROP|PFRULE_FRAGDROP)) == 0)
pd->flags |= PFDESC_IP_REAS;
return (PF_PASS);
no_mem:
REASON_SET(reason, PFRES_MEMORY);
if (r != NULL && r->log)
PFLOG_PACKET(kif, m, AF_INET, 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_INET, dir, *reason, r, NULL, NULL, pd,
1);
return (PF_DROP);
bad:
DPFPRINTF(("dropping bad fragment\n"));
/* Free associated fragments */
if (frag != NULL) {
pf_free_fragment(frag);
PF_FRAG_UNLOCK();
}
REASON_SET(reason, PFRES_FRAG);
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 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;
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;
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;
pf_scrub_ip6(&m, 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 */
/* remember to set 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);
badfrag:
REASON_SET(reason, PFRES_FRAG);
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)
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, 0);
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, 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_a(&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_a(&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_cksum_fixup(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))) {
u_int16_t ip_id = h->ip_id;
h->ip_id = ip_randomid();
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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