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freebsd/sys/netpfil/pf/pf_norm.c
Gleb Smirnoff 75bf2db380 Move new pf includes to the pf directory. The pfvar.h remain 
in net, to avoid compatibility breakage for no sake.

The future plan is to split most of non-kernel parts of
pfvar.h into pf.h, and then make pfvar.h a kernel only
include breaking compatibility.

Discussed with:		bz
2013-10-27 16:25:57 +00:00

2000 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);
/* use mtag from concatenated mbuf chain */
pd->pf_mtag = pf_find_mtag(m);
#ifdef DIAGNOSTIC
if (pd->pf_mtag == NULL) {
printf("%s: pf_find_mtag returned NULL(1)\n", __func__);
if ((pd->pf_mtag = pf_get_mtag(m)) == NULL) {
m_freem(m);
*m0 = NULL;
goto no_mem;
}
}
#endif
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->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;
}
/* use mtag from copied and trimmed mbuf chain */
pd->pf_mtag = pf_find_mtag(m);
#ifdef DIAGNOSTIC
if (pd->pf_mtag == NULL) {
printf("%s: pf_find_mtag returned NULL(2)\n", __func__);
if ((pd->pf_mtag = pf_get_mtag(m)) == NULL) {
m_freem(m);
*m0 = NULL;
goto no_mem;
}
}
#endif
if (dir == PF_IN)
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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