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src/sys/net/pf_norm.c

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/* $OpenBSD: pf_norm.c,v 1.230 2024/04/22 13:30:22 bluhm Exp $ */
/*
* Copyright 2001 Niels Provos <provos@citi.umich.edu>
* Copyright 2009 Henning Brauer <henning@openbsd.org>
* Copyright 2011-2018 Alexander Bluhm <bluhm@openbsd.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "pflog.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/filio.h>
#include <sys/fcntl.h>
#include <sys/socket.h>
#include <sys/kernel.h>
#include <sys/time.h>
#include <sys/pool.h>
#include <sys/syslog.h>
#include <sys/mutex.h>
#include <net/if.h>
#include <net/if_var.h>
#include <net/if_pflog.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip_var.h>
#include <netinet/ip_icmp.h>
#include <netinet/tcp.h>
#include <netinet/tcp_seq.h>
#include <netinet/tcp_fsm.h>
#include <netinet/udp.h>
#ifdef INET6
#include <netinet6/in6_var.h>
#include <netinet/ip6.h>
#include <netinet6/ip6_var.h>
#include <netinet/icmp6.h>
#include <netinet6/nd6.h>
#endif /* INET6 */
#include <net/pfvar.h>
#include <net/pfvar_priv.h>
struct pf_frent {
TAILQ_ENTRY(pf_frent) fr_next;
struct mbuf *fe_m;
u_int16_t fe_hdrlen; /* ipv4 header length with ip options
ipv6, extension, fragment header */
u_int16_t fe_extoff; /* last extension header offset or 0 */
u_int16_t fe_len; /* fragment length */
u_int16_t fe_off; /* fragment offset */
u_int16_t fe_mff; /* more fragment flag */
};
RB_HEAD(pf_frag_tree, pf_fragment);
struct pf_frnode {
struct pf_addr fn_src; /* ip source address */
struct pf_addr fn_dst; /* ip destination address */
sa_family_t fn_af; /* address family */
u_int8_t fn_proto; /* protocol for fragments in fn_tree */
u_int8_t fn_direction; /* pf packet direction */
u_int32_t fn_fragments; /* number of entries in fn_tree */
u_int32_t fn_gen; /* fr_gen of newest entry in fn_tree */
RB_ENTRY(pf_frnode) fn_entry;
struct pf_frag_tree fn_tree; /* matching fragments, lookup by id */
};
struct pf_fragment {
struct pf_frent *fr_firstoff[PF_FRAG_ENTRY_POINTS];
/* pointers to queue element */
u_int8_t fr_entries[PF_FRAG_ENTRY_POINTS];
/* count entries between pointers */
RB_ENTRY(pf_fragment) fr_entry;
TAILQ_ENTRY(pf_fragment) frag_next;
TAILQ_HEAD(pf_fragq, pf_frent) fr_queue;
u_int32_t fr_id; /* fragment id for reassemble */
int32_t fr_timeout;
u_int32_t fr_gen; /* generation number (per pf_frnode) */
u_int16_t fr_maxlen; /* maximum length of single fragment */
u_int16_t fr_holes; /* number of holes in the queue */
struct pf_frnode *fr_node; /* ip src/dst/proto/af for fragments */
};
struct pf_fragment_tag {
u_int16_t ft_hdrlen; /* header length of reassembled pkt */
u_int16_t ft_extoff; /* last extension header offset or 0 */
u_int16_t ft_maxlen; /* maximum fragment payload length */
};
TAILQ_HEAD(pf_fragqueue, pf_fragment) pf_fragqueue;
static __inline int pf_frnode_compare(struct pf_frnode *,
struct pf_frnode *);
RB_HEAD(pf_frnode_tree, pf_frnode) pf_frnode_tree;
RB_PROTOTYPE(pf_frnode_tree, pf_frnode, fn_entry, pf_frnode_compare);
RB_GENERATE(pf_frnode_tree, pf_frnode, fn_entry, pf_frnode_compare);
static __inline int pf_frag_compare(struct pf_fragment *,
struct pf_fragment *);
RB_PROTOTYPE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare);
RB_GENERATE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare);
/* Private prototypes */
void pf_flush_fragments(void);
void pf_free_fragment(struct pf_fragment *);
struct pf_fragment *pf_find_fragment(struct pf_frnode *, u_int32_t);
struct pf_frent *pf_create_fragment(u_short *);
int pf_frent_holes(struct pf_frent *);
static inline int pf_frent_index(struct pf_frent *);
int pf_frent_insert(struct pf_fragment *,
struct pf_frent *, struct pf_frent *);
void pf_frent_remove(struct pf_fragment *,
struct pf_frent *);
struct pf_frent *pf_frent_previous(struct pf_fragment *,
struct pf_frent *);
struct pf_fragment *pf_fillup_fragment(struct pf_frnode *, u_int32_t,
struct pf_frent *, u_short *);
struct mbuf *pf_join_fragment(struct pf_fragment *);
int pf_reassemble(struct mbuf **, int, u_short *);
#ifdef INET6
int pf_reassemble6(struct mbuf **, struct ip6_frag *,
u_int16_t, u_int16_t, int, u_short *);
#endif /* INET6 */
/* Globals */
struct pool pf_frent_pl, pf_frag_pl, pf_frnode_pl;
struct pool pf_state_scrub_pl;
struct mutex pf_frag_mtx;
#define PF_FRAG_LOCK_INIT() mtx_init(&pf_frag_mtx, IPL_SOFTNET)
void
pf_normalize_init(void)
{
pool_init(&pf_frent_pl, sizeof(struct pf_frent), 0,
IPL_SOFTNET, 0, "pffrent", NULL);
pool_init(&pf_frnode_pl, sizeof(struct pf_frnode), 0,
IPL_SOFTNET, 0, "pffrnode", NULL);
pool_init(&pf_frag_pl, sizeof(struct pf_fragment), 0,
IPL_SOFTNET, 0, "pffrag", NULL);
pool_init(&pf_state_scrub_pl, sizeof(struct pf_state_scrub), 0,
IPL_SOFTNET, 0, "pfstscr", NULL);
pool_sethiwat(&pf_frag_pl, PFFRAG_FRAG_HIWAT);
pool_sethardlimit(&pf_frent_pl, PFFRAG_FRENT_HIWAT, NULL, 0);
TAILQ_INIT(&pf_fragqueue);
PF_FRAG_LOCK_INIT();
}
static __inline int
pf_frnode_compare(struct pf_frnode *a, struct pf_frnode *b)
{
int diff;
if ((diff = a->fn_proto - b->fn_proto) != 0)
return (diff);
if ((diff = a->fn_af - b->fn_af) != 0)
return (diff);
if ((diff = pf_addr_compare(&a->fn_src, &b->fn_src, a->fn_af)) != 0)
return (diff);
if ((diff = pf_addr_compare(&a->fn_dst, &b->fn_dst, a->fn_af)) != 0)
return (diff);
return (0);
}
static __inline int
pf_frag_compare(struct pf_fragment *a, struct pf_fragment *b)
{
int diff;
if ((diff = a->fr_id - b->fr_id) != 0)
return (diff);
return (0);
}
void
pf_purge_expired_fragments(void)
{
struct pf_fragment *frag;
int32_t expire;
PF_ASSERT_UNLOCKED();
expire = getuptime() - pf_default_rule.timeout[PFTM_FRAG];
PF_FRAG_LOCK();
while ((frag = TAILQ_LAST(&pf_fragqueue, pf_fragqueue)) != NULL) {
if (frag->fr_timeout > expire)
break;
DPFPRINTF(LOG_NOTICE, "expiring %d(%p)", frag->fr_id, frag);
pf_free_fragment(frag);
}
PF_FRAG_UNLOCK();
}
/*
* Try to flush old fragments to make space for new ones
*/
void
pf_flush_fragments(void)
{
struct pf_fragment *frag;
u_int goal;
goal = pf_status.fragments * 9 / 10;
DPFPRINTF(LOG_NOTICE, "trying to free > %u frents",
pf_status.fragments - goal);
while (goal < pf_status.fragments) {
if ((frag = TAILQ_LAST(&pf_fragqueue, pf_fragqueue)) == NULL)
break;
pf_free_fragment(frag);
}
}
/*
* Remove a fragment from the fragment queue, free its fragment entries,
* and free the fragment itself.
*/
void
pf_free_fragment(struct pf_fragment *frag)
{
struct pf_frent *frent;
struct pf_frnode *frnode;
frnode = frag->fr_node;
RB_REMOVE(pf_frag_tree, &frnode->fn_tree, frag);
KASSERT(frnode->fn_fragments >= 1);
frnode->fn_fragments--;
if (frnode->fn_fragments == 0) {
KASSERT(RB_EMPTY(&frnode->fn_tree));
RB_REMOVE(pf_frnode_tree, &pf_frnode_tree, frnode);
pool_put(&pf_frnode_pl, frnode);
}
TAILQ_REMOVE(&pf_fragqueue, frag, frag_next);
/* Free all fragment entries */
while ((frent = TAILQ_FIRST(&frag->fr_queue)) != NULL) {
TAILQ_REMOVE(&frag->fr_queue, frent, fr_next);
pf_status.ncounters[NCNT_FRAG_REMOVALS]++;
m_freem(frent->fe_m);
pool_put(&pf_frent_pl, frent);
pf_status.fragments--;
}
pool_put(&pf_frag_pl, frag);
}
struct pf_fragment *
pf_find_fragment(struct pf_frnode *key, u_int32_t id)
{
struct pf_fragment *frag, idkey;
struct pf_frnode *frnode;
u_int32_t stale;
frnode = RB_FIND(pf_frnode_tree, &pf_frnode_tree, key);
pf_status.ncounters[NCNT_FRAG_SEARCH]++;
if (frnode == NULL)
return (NULL);
KASSERT(frnode->fn_fragments >= 1);
idkey.fr_id = id;
frag = RB_FIND(pf_frag_tree, &frnode->fn_tree, &idkey);
if (frag == NULL)
return (NULL);
/*
* Limit the number of fragments we accept for each (proto,src,dst,af)
* combination (aka pf_frnode), so we can deal better with a high rate
* of fragments. Problem analysis is in RFC 4963.
* Store the current generation for each pf_frnode in fn_gen and on
* lookup discard 'stale' fragments (pf_fragment, based on the fr_gen
* member). Instead of adding another button interpret the pf fragment
* timeout in multiples of 200 fragments. This way the default of 60s
* means: pf_fragment objects older than 60*200 = 12,000 generations
* are considered stale.
*/
stale = pf_default_rule.timeout[PFTM_FRAG] * PF_FRAG_STALE;
if ((frnode->fn_gen - frag->fr_gen) >= stale) {
DPFPRINTF(LOG_NOTICE, "stale fragment %d(%p), gen %u, num %u",
frag->fr_id, frag, frag->fr_gen, frnode->fn_fragments);
pf_free_fragment(frag);
return (NULL);
}
TAILQ_REMOVE(&pf_fragqueue, frag, frag_next);
TAILQ_INSERT_HEAD(&pf_fragqueue, frag, frag_next);
return (frag);
}
struct pf_frent *
pf_create_fragment(u_short *reason)
{
struct pf_frent *frent;
frent = pool_get(&pf_frent_pl, PR_NOWAIT);
if (frent == NULL) {
pf_flush_fragments();
frent = pool_get(&pf_frent_pl, PR_NOWAIT);
if (frent == NULL) {
REASON_SET(reason, PFRES_MEMORY);
return (NULL);
}
}
pf_status.fragments++;
return (frent);
}
/*
* Calculate the additional holes that were created in the fragment
* queue by inserting this fragment. A fragment in the middle
* creates one more hole by splitting. For each connected side,
* it loses one hole.
* Fragment entry must be in the queue when calling this function.
*/
int
pf_frent_holes(struct pf_frent *frent)
{
struct pf_frent *prev = TAILQ_PREV(frent, pf_fragq, fr_next);
struct pf_frent *next = TAILQ_NEXT(frent, fr_next);
int holes = 1;
if (prev == NULL) {
if (frent->fe_off == 0)
holes--;
} else {
KASSERT(frent->fe_off != 0);
if (frent->fe_off == prev->fe_off + prev->fe_len)
holes--;
}
if (next == NULL) {
if (!frent->fe_mff)
holes--;
} else {
KASSERT(frent->fe_mff);
if (next->fe_off == frent->fe_off + frent->fe_len)
holes--;
}
return holes;
}
static inline int
pf_frent_index(struct pf_frent *frent)
{
/*
* We have an array of 16 entry points to the queue. A full size
* 65535 octet IP packet can have 8192 fragments. So the queue
* traversal length is at most 512 and at most 16 entry points are
* checked. We need 128 additional bytes on a 64 bit architecture.
*/
CTASSERT(((u_int16_t)0xffff &~ 7) / (0x10000 / PF_FRAG_ENTRY_POINTS) ==
16 - 1);
CTASSERT(((u_int16_t)0xffff >> 3) / PF_FRAG_ENTRY_POINTS == 512 - 1);
return frent->fe_off / (0x10000 / PF_FRAG_ENTRY_POINTS);
}
int
pf_frent_insert(struct pf_fragment *frag, struct pf_frent *frent,
struct pf_frent *prev)
{
CTASSERT(PF_FRAG_ENTRY_LIMIT <= 0xff);
int index;
/*
* A packet has at most 65536 octets. With 16 entry points, each one
* spawns 4096 octets. We limit these to 64 fragments each, which
* means on average every fragment must have at least 64 octets.
*/
index = pf_frent_index(frent);
if (frag->fr_entries[index] >= PF_FRAG_ENTRY_LIMIT)
return ENOBUFS;
frag->fr_entries[index]++;
if (prev == NULL) {
TAILQ_INSERT_HEAD(&frag->fr_queue, frent, fr_next);
} else {
KASSERT(prev->fe_off + prev->fe_len <= frent->fe_off);
TAILQ_INSERT_AFTER(&frag->fr_queue, prev, frent, fr_next);
}
pf_status.ncounters[NCNT_FRAG_INSERT]++;
if (frag->fr_firstoff[index] == NULL) {
KASSERT(prev == NULL || pf_frent_index(prev) < index);
frag->fr_firstoff[index] = frent;
} else {
if (frent->fe_off < frag->fr_firstoff[index]->fe_off) {
KASSERT(prev == NULL || pf_frent_index(prev) < index);
frag->fr_firstoff[index] = frent;
} else {
KASSERT(prev != NULL);
KASSERT(pf_frent_index(prev) == index);
}
}
frag->fr_holes += pf_frent_holes(frent);
return 0;
}
void
pf_frent_remove(struct pf_fragment *frag, struct pf_frent *frent)
{
#ifdef DIAGNOSTIC
struct pf_frent *prev = TAILQ_PREV(frent, pf_fragq, fr_next);
#endif
struct pf_frent *next = TAILQ_NEXT(frent, fr_next);
int index;
frag->fr_holes -= pf_frent_holes(frent);
index = pf_frent_index(frent);
KASSERT(frag->fr_firstoff[index] != NULL);
if (frag->fr_firstoff[index]->fe_off == frent->fe_off) {
if (next == NULL) {
frag->fr_firstoff[index] = NULL;
} else {
KASSERT(frent->fe_off + frent->fe_len <= next->fe_off);
if (pf_frent_index(next) == index) {
frag->fr_firstoff[index] = next;
} else {
frag->fr_firstoff[index] = NULL;
}
}
} else {
KASSERT(frag->fr_firstoff[index]->fe_off < frent->fe_off);
KASSERT(prev != NULL);
KASSERT(prev->fe_off + prev->fe_len <= frent->fe_off);
KASSERT(pf_frent_index(prev) == index);
}
TAILQ_REMOVE(&frag->fr_queue, frent, fr_next);
pf_status.ncounters[NCNT_FRAG_REMOVALS]++;
KASSERT(frag->fr_entries[index] > 0);
frag->fr_entries[index]--;
}
struct pf_frent *
pf_frent_previous(struct pf_fragment *frag, struct pf_frent *frent)
{
struct pf_frent *prev, *next;
int index;
/*
* If there are no fragments after frag, take the final one. Assume
* that the global queue is not empty.
*/
prev = TAILQ_LAST(&frag->fr_queue, pf_fragq);
KASSERT(prev != NULL);
if (prev->fe_off <= frent->fe_off)
return prev;
/*
* We want to find a fragment entry that is before frag, but still
* close to it. Find the first fragment entry that is in the same
* entry point or in the first entry point after that. As we have
* already checked that there are entries behind frag, this will
* succeed.
*/
for (index = pf_frent_index(frent); index < PF_FRAG_ENTRY_POINTS;
index++) {
prev = frag->fr_firstoff[index];
if (prev != NULL)
break;
}
KASSERT(prev != NULL);
/*
* In prev we may have a fragment from the same entry point that is
* before frent, or one that is just one position behind frent.
* In the latter case, we go back one step and have the predecessor.
* There may be none if the new fragment will be the first one.
*/
if (prev->fe_off > frent->fe_off) {
prev = TAILQ_PREV(prev, pf_fragq, fr_next);
if (prev == NULL)
return NULL;
KASSERT(prev->fe_off <= frent->fe_off);
return prev;
}
/*
* In prev is the first fragment of the entry point. The offset
* of frag is behind it. Find the closest previous fragment.
*/
for (next = TAILQ_NEXT(prev, fr_next); next != NULL;
next = TAILQ_NEXT(next, fr_next)) {
if (next->fe_off > frent->fe_off)
break;
prev = next;
}
return prev;
}
struct pf_fragment *
pf_fillup_fragment(struct pf_frnode *key, u_int32_t id,
struct pf_frent *frent, u_short *reason)
{
struct pf_frent *after, *next, *prev;
struct pf_fragment *frag;
struct pf_frnode *frnode;
u_int16_t total;
/* No empty fragments */
if (frent->fe_len == 0) {
DPFPRINTF(LOG_NOTICE, "bad fragment: len 0");
goto bad_fragment;
}
/* All fragments are 8 byte aligned */
if (frent->fe_mff && (frent->fe_len & 0x7)) {
DPFPRINTF(LOG_NOTICE, "bad fragment: mff and len %d",
frent->fe_len);
goto bad_fragment;
}
/* Respect maximum length, IP_MAXPACKET == IPV6_MAXPACKET */
if (frent->fe_off + frent->fe_len > IP_MAXPACKET) {
DPFPRINTF(LOG_NOTICE, "bad fragment: max packet %d",
frent->fe_off + frent->fe_len);
goto bad_fragment;
}
DPFPRINTF(LOG_INFO, key->fn_af == AF_INET ?
"reass frag %d @ %d-%d" : "reass frag %#08x @ %d-%d",
id, frent->fe_off, frent->fe_off + frent->fe_len);
/* Fully buffer all of the fragments in this fragment queue */
frag = pf_find_fragment(key, id);
/* Create a new reassembly queue for this packet */
if (frag == NULL) {
frag = pool_get(&pf_frag_pl, PR_NOWAIT);
if (frag == NULL) {
pf_flush_fragments();
frag = pool_get(&pf_frag_pl, PR_NOWAIT);
if (frag == NULL) {
REASON_SET(reason, PFRES_MEMORY);
goto drop_fragment;
}
}
frnode = RB_FIND(pf_frnode_tree, &pf_frnode_tree, key);
if (frnode == NULL) {
frnode = pool_get(&pf_frnode_pl, PR_NOWAIT);
if (frnode == NULL) {
pf_flush_fragments();
frnode = pool_get(&pf_frnode_pl, PR_NOWAIT);
if (frnode == NULL) {
REASON_SET(reason, PFRES_MEMORY);
pool_put(&pf_frag_pl, frag);
goto drop_fragment;
}
}
*frnode = *key;
RB_INIT(&frnode->fn_tree);
frnode->fn_fragments = 0;
frnode->fn_gen = 0;
}
memset(frag->fr_firstoff, 0, sizeof(frag->fr_firstoff));
memset(frag->fr_entries, 0, sizeof(frag->fr_entries));
TAILQ_INIT(&frag->fr_queue);
frag->fr_id = id;
frag->fr_timeout = getuptime();
frag->fr_gen = frnode->fn_gen++;
frag->fr_maxlen = frent->fe_len;
frag->fr_holes = 1;
frag->fr_node = frnode;
/* RB_INSERT cannot fail as pf_find_fragment() found nothing */
RB_INSERT(pf_frag_tree, &frnode->fn_tree, frag);
frnode->fn_fragments++;
if (frnode->fn_fragments == 1)
RB_INSERT(pf_frnode_tree, &pf_frnode_tree, frnode);
TAILQ_INSERT_HEAD(&pf_fragqueue, frag, frag_next);
/* We do not have a previous fragment, cannot fail. */
pf_frent_insert(frag, frent, NULL);
return (frag);
}
KASSERT(!TAILQ_EMPTY(&frag->fr_queue));
KASSERT(frag->fr_node);
/* Remember maximum fragment len for refragmentation */
if (frent->fe_len > frag->fr_maxlen)
frag->fr_maxlen = frent->fe_len;
/* Maximum data we have seen already */
total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off +
TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len;
/* Non terminal fragments must have more fragments flag */
if (frent->fe_off + frent->fe_len < total && !frent->fe_mff)
goto free_ipv6_fragment;
/* Check if we saw the last fragment already */
if (!TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_mff) {
if (frent->fe_off + frent->fe_len > total ||
(frent->fe_off + frent->fe_len == total && frent->fe_mff))
goto free_ipv6_fragment;
} else {
if (frent->fe_off + frent->fe_len == total && !frent->fe_mff)
goto free_ipv6_fragment;
}
/* Find neighbors for newly inserted fragment */
prev = pf_frent_previous(frag, frent);
if (prev == NULL) {
after = TAILQ_FIRST(&frag->fr_queue);
KASSERT(after != NULL);
} else {
after = TAILQ_NEXT(prev, fr_next);
}
if (prev != NULL && prev->fe_off + prev->fe_len > frent->fe_off) {
u_int16_t precut;
#ifdef INET6
if (frag->fr_node->fn_af == AF_INET6)
goto free_ipv6_fragment;
#endif /* INET6 */
precut = prev->fe_off + prev->fe_len - frent->fe_off;
if (precut >= frent->fe_len) {
DPFPRINTF(LOG_NOTICE, "new frag overlapped");
goto drop_fragment;
}
DPFPRINTF(LOG_NOTICE, "frag head overlap %d", precut);
m_adj(frent->fe_m, precut);
frent->fe_off += precut;
frent->fe_len -= precut;
}
for (; after != NULL && frent->fe_off + frent->fe_len > after->fe_off;
after = next) {
u_int16_t aftercut;
#ifdef INET6
if (frag->fr_node->fn_af == AF_INET6)
goto free_ipv6_fragment;
#endif /* INET6 */
aftercut = frent->fe_off + frent->fe_len - after->fe_off;
if (aftercut < after->fe_len) {
int old_index, new_index;
DPFPRINTF(LOG_NOTICE, "frag tail overlap %d", aftercut);
m_adj(after->fe_m, aftercut);
old_index = pf_frent_index(after);
after->fe_off += aftercut;
after->fe_len -= aftercut;
new_index = pf_frent_index(after);
if (old_index != new_index) {
DPFPRINTF(LOG_DEBUG, "frag index %d, new %d",
old_index, new_index);
/* Fragment switched queue as fe_off changed */
after->fe_off -= aftercut;
after->fe_len += aftercut;
/* Remove restored fragment from old queue */
pf_frent_remove(frag, after);
after->fe_off += aftercut;
after->fe_len -= aftercut;
/* Insert into correct queue */
if (pf_frent_insert(frag, after, prev)) {
DPFPRINTF(LOG_WARNING,
"fragment requeue limit exceeded");
m_freem(after->fe_m);
pool_put(&pf_frent_pl, after);
pf_status.fragments--;
/* There is not way to recover */
goto free_fragment;
}
}
break;
}
/* This fragment is completely overlapped, lose it */
DPFPRINTF(LOG_NOTICE, "old frag overlapped");
next = TAILQ_NEXT(after, fr_next);
pf_frent_remove(frag, after);
m_freem(after->fe_m);
pool_put(&pf_frent_pl, after);
pf_status.fragments--;
}
/* If part of the queue gets too long, there is not way to recover. */
if (pf_frent_insert(frag, frent, prev)) {
DPFPRINTF(LOG_WARNING, "fragment queue limit exceeded");
goto free_fragment;
}
return (frag);
free_ipv6_fragment:
if (frag->fr_node->fn_af == AF_INET)
goto bad_fragment;
/*
* RFC 5722, Errata 3089: When reassembling an IPv6 datagram, if one
* or more its constituent fragments is determined to be an overlapping
* fragment, the entire datagram (and any constituent fragments) MUST
* be silently discarded.
*/
DPFPRINTF(LOG_NOTICE, "flush overlapping fragments");
free_fragment:
pf_free_fragment(frag);
bad_fragment:
REASON_SET(reason, PFRES_FRAG);
drop_fragment:
pool_put(&pf_frent_pl, frent);
pf_status.fragments--;
return (NULL);
}
struct mbuf *
pf_join_fragment(struct pf_fragment *frag)
{
struct mbuf *m, *m2;
struct pf_frent *frent;
frent = TAILQ_FIRST(&frag->fr_queue);
TAILQ_REMOVE(&frag->fr_queue, frent, fr_next);
pf_status.ncounters[NCNT_FRAG_REMOVALS]++;
m = frent->fe_m;
/* Strip off any trailing bytes */
if ((frent->fe_hdrlen + frent->fe_len) < m->m_pkthdr.len)
m_adj(m, (frent->fe_hdrlen + frent->fe_len) - m->m_pkthdr.len);
/* Magic from ip_input */
m2 = m->m_next;
m->m_next = NULL;
m_cat(m, m2);
pool_put(&pf_frent_pl, frent);
pf_status.fragments--;
while ((frent = TAILQ_FIRST(&frag->fr_queue)) != NULL) {
TAILQ_REMOVE(&frag->fr_queue, frent, fr_next);
pf_status.ncounters[NCNT_FRAG_REMOVALS]++;
m2 = frent->fe_m;
/* Strip off ip header */
m_adj(m2, frent->fe_hdrlen);
/* Strip off any trailing bytes */
if (frent->fe_len < m2->m_pkthdr.len)
m_adj(m2, frent->fe_len - m2->m_pkthdr.len);
pool_put(&pf_frent_pl, frent);
pf_status.fragments--;
m_removehdr(m2);
m_cat(m, m2);
}
/* Remove from fragment queue */
pf_free_fragment(frag);
return (m);
}
int
pf_reassemble(struct mbuf **m0, int dir, u_short *reason)
{
struct mbuf *m = *m0;
struct ip *ip = mtod(m, struct ip *);
struct pf_frent *frent;
struct pf_fragment *frag;
struct pf_frnode key;
u_int16_t total, hdrlen;
/* Get an entry for the fragment queue */
if ((frent = pf_create_fragment(reason)) == NULL)
return (PF_DROP);
frent->fe_m = m;
frent->fe_hdrlen = ip->ip_hl << 2;
frent->fe_extoff = 0;
frent->fe_len = ntohs(ip->ip_len) - (ip->ip_hl << 2);
frent->fe_off = (ntohs(ip->ip_off) & IP_OFFMASK) << 3;
frent->fe_mff = ntohs(ip->ip_off) & IP_MF;
key.fn_src.v4 = ip->ip_src;
key.fn_dst.v4 = ip->ip_dst;
key.fn_af = AF_INET;
key.fn_proto = ip->ip_p;
key.fn_direction = dir;
if ((frag = pf_fillup_fragment(&key, ip->ip_id, frent, reason))
== NULL)
return (PF_DROP);
/* The mbuf is part of the fragment entry, no direct free or access */
m = *m0 = NULL;
if (frag->fr_holes) {
DPFPRINTF(LOG_DEBUG, "frag %d, holes %d",
frag->fr_id, frag->fr_holes);
return (PF_PASS); /* drop because *m0 is NULL, no error */
}
/* We have all the data */
frent = TAILQ_FIRST(&frag->fr_queue);
KASSERT(frent != NULL);
total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off +
TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len;
hdrlen = frent->fe_hdrlen;
m = *m0 = pf_join_fragment(frag);
frag = NULL;
m_calchdrlen(m);
ip = mtod(m, struct ip *);
ip->ip_len = htons(hdrlen + total);
ip->ip_off &= ~(IP_MF|IP_OFFMASK);
if (hdrlen + total > IP_MAXPACKET) {
DPFPRINTF(LOG_NOTICE, "drop: too big: %d", total);
ip->ip_len = 0;
REASON_SET(reason, PFRES_SHORT);
/* PF_DROP requires a valid mbuf *m0 in pf_test() */
return (PF_DROP);
}
DPFPRINTF(LOG_INFO, "complete: %p(%d)", m, ntohs(ip->ip_len));
return (PF_PASS);
}
#ifdef INET6
int
pf_reassemble6(struct mbuf **m0, struct ip6_frag *fraghdr,
u_int16_t hdrlen, u_int16_t extoff, int dir, u_short *reason)
{
struct mbuf *m = *m0;
struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
struct m_tag *mtag;
struct pf_fragment_tag *ftag;
struct pf_frent *frent;
struct pf_fragment *frag;
struct pf_frnode key;
int off;
u_int16_t total, maxlen;
u_int8_t proto;
/* Get an entry for the fragment queue */
if ((frent = pf_create_fragment(reason)) == NULL)
return (PF_DROP);
frent->fe_m = m;
frent->fe_hdrlen = hdrlen;
frent->fe_extoff = extoff;
frent->fe_len = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - hdrlen;
frent->fe_off = ntohs(fraghdr->ip6f_offlg & IP6F_OFF_MASK);
frent->fe_mff = fraghdr->ip6f_offlg & IP6F_MORE_FRAG;
key.fn_src.v6 = ip6->ip6_src;
key.fn_dst.v6 = ip6->ip6_dst;
key.fn_af = AF_INET6;
/* Only the first fragment's protocol is relevant */
key.fn_proto = 0;
key.fn_direction = dir;
if ((frag = pf_fillup_fragment(&key, fraghdr->ip6f_ident, frent,
reason)) == NULL)
return (PF_DROP);
/* The mbuf is part of the fragment entry, no direct free or access */
m = *m0 = NULL;
if (frag->fr_holes) {
DPFPRINTF(LOG_DEBUG, "frag %#08x, holes %d",
frag->fr_id, frag->fr_holes);
return (PF_PASS); /* drop because *m0 is NULL, no error */
}
/* We have all the data */
frent = TAILQ_FIRST(&frag->fr_queue);
KASSERT(frent != NULL);
extoff = frent->fe_extoff;
maxlen = frag->fr_maxlen;
total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off +
TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len;
hdrlen = frent->fe_hdrlen - sizeof(struct ip6_frag);
m = *m0 = pf_join_fragment(frag);
frag = NULL;
/* Take protocol from first fragment header */
if ((m = m_getptr(m, hdrlen + offsetof(struct ip6_frag, ip6f_nxt),
&off)) == NULL)
panic("%s: short frag mbuf chain", __func__);
proto = *(mtod(m, caddr_t) + off);
m = *m0;
/* Delete frag6 header */
if (frag6_deletefraghdr(m, hdrlen) != 0)
goto fail;
m_calchdrlen(m);
if ((mtag = m_tag_get(PACKET_TAG_PF_REASSEMBLED, sizeof(struct
pf_fragment_tag), M_NOWAIT)) == NULL)
goto fail;
ftag = (struct pf_fragment_tag *)(mtag + 1);
ftag->ft_hdrlen = hdrlen;
ftag->ft_extoff = extoff;
ftag->ft_maxlen = maxlen;
m_tag_prepend(m, mtag);
ip6 = mtod(m, struct ip6_hdr *);
ip6->ip6_plen = htons(hdrlen - sizeof(struct ip6_hdr) + total);
if (extoff) {
/* Write protocol into next field of last extension header */
if ((m = m_getptr(m, extoff + offsetof(struct ip6_ext,
ip6e_nxt), &off)) == NULL)
panic("%s: short ext mbuf chain", __func__);
*(mtod(m, caddr_t) + off) = proto;
m = *m0;
} else
ip6->ip6_nxt = proto;
if (hdrlen - sizeof(struct ip6_hdr) + total > IPV6_MAXPACKET) {
DPFPRINTF(LOG_NOTICE, "drop: too big: %d", total);
ip6->ip6_plen = 0;
REASON_SET(reason, PFRES_SHORT);
/* PF_DROP requires a valid mbuf *m0 in pf_test6() */
return (PF_DROP);
}
DPFPRINTF(LOG_INFO, "complete: %p(%d)", m, ntohs(ip6->ip6_plen));
return (PF_PASS);
fail:
REASON_SET(reason, PFRES_MEMORY);
/* PF_DROP requires a valid mbuf *m0 in pf_test6(), will free later */
return (PF_DROP);
}
int
pf_refragment6(struct mbuf **m0, struct m_tag *mtag, struct sockaddr_in6 *dst,
struct ifnet *ifp, struct rtentry *rt)
{
struct mbuf *m = *m0;
struct mbuf_list ml;
struct pf_fragment_tag *ftag = (struct pf_fragment_tag *)(mtag + 1);
u_int32_t mtu;
u_int16_t hdrlen, extoff, maxlen;
u_int8_t proto;
int error;
hdrlen = ftag->ft_hdrlen;
extoff = ftag->ft_extoff;
maxlen = ftag->ft_maxlen;
m_tag_delete(m, mtag);
mtag = NULL;
ftag = NULL;
/* Checksum must be calculated for the whole packet */
in6_proto_cksum_out(m, NULL);
if (extoff) {
int off;
/* Use protocol from next field of last extension header */
if ((m = m_getptr(m, extoff + offsetof(struct ip6_ext,
ip6e_nxt), &off)) == NULL)
panic("%s: short ext mbuf chain", __func__);
proto = *(mtod(m, caddr_t) + off);
*(mtod(m, caddr_t) + off) = IPPROTO_FRAGMENT;
m = *m0;
} else {
struct ip6_hdr *hdr;
hdr = mtod(m, struct ip6_hdr *);
proto = hdr->ip6_nxt;
hdr->ip6_nxt = IPPROTO_FRAGMENT;
}
/*
* Maxlen may be less than 8 iff there was only a single
* fragment. As it was fragmented before, add a fragment
* header also for a single fragment. If total or maxlen
* is less than 8, ip6_fragment() will return EMSGSIZE and
* we drop the packet.
*/
mtu = hdrlen + sizeof(struct ip6_frag) + maxlen;
error = ip6_fragment(m, &ml, hdrlen, proto, mtu);
*m0 = NULL; /* ip6_fragment() has consumed original packet. */
if (error) {
DPFPRINTF(LOG_NOTICE, "refragment error %d", error);
return (PF_DROP);
}
while ((m = ml_dequeue(&ml)) != NULL) {
m->m_pkthdr.pf.flags |= PF_TAG_REFRAGMENTED;
if (ifp == NULL) {
ip6_forward(m, NULL, 0);
} else if ((u_long)m->m_pkthdr.len <= ifp->if_mtu) {
ifp->if_output(ifp, m, sin6tosa(dst), rt);
} else {
icmp6_error(m, ICMP6_PACKET_TOO_BIG, 0, ifp->if_mtu);
}
}
return (PF_PASS);
}
#endif /* INET6 */
int
pf_normalize_ip(struct pf_pdesc *pd, u_short *reason)
{
struct ip *h = mtod(pd->m, struct ip *);
u_int16_t fragoff = (ntohs(h->ip_off) & IP_OFFMASK) << 3;
u_int16_t mff = (ntohs(h->ip_off) & IP_MF);
if (!fragoff && !mff)
goto no_fragment;
/* Clear IP_DF if we're in no-df mode */
if (pf_status.reass & PF_REASS_NODF && h->ip_off & htons(IP_DF))
h->ip_off &= htons(~IP_DF);
/* 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(LOG_NOTICE, "bad fragment: IP_DF");
REASON_SET(reason, PFRES_FRAG);
return (PF_DROP);
}
if (!pf_status.reass)
return (PF_PASS); /* no reassembly */
/* Returns PF_DROP or m is NULL or completely reassembled mbuf */
PF_FRAG_LOCK();
if (pf_reassemble(&pd->m, pd->dir, reason) != PF_PASS) {
PF_FRAG_UNLOCK();
return (PF_DROP);
}
PF_FRAG_UNLOCK();
if (pd->m == NULL)
return (PF_PASS); /* packet has been reassembled, no error */
h = mtod(pd->m, struct ip *);
no_fragment:
/* At this point, only IP_DF is allowed in ip_off */
if (h->ip_off & ~htons(IP_DF))
h->ip_off &= htons(IP_DF);
return (PF_PASS);
}
#ifdef INET6
int
pf_normalize_ip6(struct pf_pdesc *pd, u_short *reason)
{
struct ip6_frag frag;
if (pd->fragoff == 0)
goto no_fragment;
if (!pf_pull_hdr(pd->m, pd->fragoff, &frag, sizeof(frag), reason,
AF_INET6))
return (PF_DROP);
if (!pf_status.reass)
return (PF_PASS); /* no reassembly */
/* Returns PF_DROP or m is NULL or completely reassembled mbuf */
PF_FRAG_LOCK();
if (pf_reassemble6(&pd->m, &frag, pd->fragoff + sizeof(frag),
pd->extoff, pd->dir, reason) != PF_PASS) {
PF_FRAG_UNLOCK();
return (PF_DROP);
}
PF_FRAG_UNLOCK();
if (pd->m == NULL)
return (PF_PASS); /* packet has been reassembled, no error */
no_fragment:
return (PF_PASS);
}
#endif /* INET6 */
struct pf_state_scrub *
pf_state_scrub_get(void)
{
return (pool_get(&pf_state_scrub_pl, PR_NOWAIT | PR_ZERO));
}
void
pf_state_scrub_put(struct pf_state_scrub *scrub)
{
pool_put(&pf_state_scrub_pl, scrub);
}
int
pf_normalize_tcp_alloc(struct pf_state_peer *src)
{
src->scrub = pf_state_scrub_get();
if (src->scrub == NULL)
return (ENOMEM);
return (0);
}
int
pf_normalize_tcp(struct pf_pdesc *pd)
{
struct tcphdr *th = &pd->hdr.tcp;
u_short reason;
u_int8_t flags;
u_int rewrite = 0;
flags = th->th_flags;
if (flags & TH_SYN) {
/* Illegal packet */
if (flags & TH_RST)
goto tcp_drop;
if (flags & TH_FIN) /* XXX why clear instead of drop? */
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|TH_PUSH|TH_URG))
goto tcp_drop;
}
/* If flags changed, or reserved data set, then adjust */
if (flags != th->th_flags || th->th_x2 != 0) {
/* hack: set 4-bit th_x2 = 0 */
u_int8_t *th_off = (u_int8_t*)(&th->th_ack+1);
pf_patch_8(pd, th_off, th->th_off << 4, PF_HI);
pf_patch_8(pd, &th->th_flags, flags, PF_LO);
rewrite = 1;
}
/* Remove urgent pointer, if TH_URG is not set */
if (!(flags & TH_URG) && th->th_urp) {
pf_patch_16(pd, &th->th_urp, 0);
rewrite = 1;
}
/* copy back packet headers if we sanitized */
if (rewrite) {
m_copyback(pd->m, pd->off, sizeof(*th), th, M_NOWAIT);
}
return (PF_PASS);
tcp_drop:
REASON_SET(&reason, PFRES_NORM);
return (PF_DROP);
}
int
pf_normalize_tcp_init(struct pf_pdesc *pd, struct pf_state_peer *src)
{
struct tcphdr *th = &pd->hdr.tcp;
u_int32_t tsval, tsecr;
int olen;
u_int8_t opts[MAX_TCPOPTLEN], *opt;
KASSERT(src->scrub == NULL);
if (pf_normalize_tcp_alloc(src) != 0)
return (1);
switch (pd->af) {
case AF_INET: {
struct ip *h = mtod(pd->m, struct ip *);
src->scrub->pfss_ttl = h->ip_ttl;
break;
}
#ifdef INET6
case AF_INET6: {
struct ip6_hdr *h = mtod(pd->m, struct ip6_hdr *);
src->scrub->pfss_ttl = h->ip6_hlim;
break;
}
#endif /* INET6 */
default:
unhandled_af(pd->af);
}
/*
* 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);
olen = (th->th_off << 2) - sizeof(*th);
if (olen < TCPOLEN_TIMESTAMP || !pf_pull_hdr(pd->m,
pd->off + sizeof(*th), opts, olen, NULL, pd->af))
return (0);
opt = opts;
while ((opt = pf_find_tcpopt(opt, opts, olen,
TCPOPT_TIMESTAMP, TCPOLEN_TIMESTAMP)) != NULL) {
src->scrub->pfss_flags |= PFSS_TIMESTAMP;
src->scrub->pfss_ts_mod = 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);
opt += opt[1];
}
return (0);
}
void
pf_normalize_tcp_cleanup(struct pf_state *state)
{
if (state->src.scrub)
pool_put(&pf_state_scrub_pl, state->src.scrub);
if (state->dst.scrub)
pool_put(&pf_state_scrub_pl, state->dst.scrub);
/* Someday... flush the TCP segment reassembly descriptors. */
}
int
pf_normalize_tcp_stateful(struct pf_pdesc *pd, u_short *reason,
struct pf_state *state, struct pf_state_peer *src,
struct pf_state_peer *dst, int *writeback)
{
struct tcphdr *th = &pd->hdr.tcp;
struct timeval uptime;
u_int tsval_from_last;
u_int32_t tsval, tsecr;
int copyback = 0;
int got_ts = 0;
int olen;
u_int8_t opts[MAX_TCPOPTLEN], *opt;
KASSERT(src->scrub || dst->scrub);
/*
* Enforce the minimum TTL seen for this connection. Negate a common
* technique to evade an intrusion detection system and confuse
* firewall state code.
*/
switch (pd->af) {
case AF_INET:
if (src->scrub) {
struct ip *h = mtod(pd->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;
#ifdef INET6
case AF_INET6:
if (src->scrub) {
struct ip6_hdr *h = mtod(pd->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 */
default:
unhandled_af(pd->af);
}
olen = (th->th_off << 2) - sizeof(*th);
if (olen >= TCPOLEN_TIMESTAMP &&
((src->scrub && (src->scrub->pfss_flags & PFSS_TIMESTAMP)) ||
(dst->scrub && (dst->scrub->pfss_flags & PFSS_TIMESTAMP))) &&
pf_pull_hdr(pd->m, pd->off + sizeof(*th), opts, olen, NULL,
pd->af)) {
/* Modulate the timestamps. Can be used for NAT detection, OS
* uptime determination or reboot detection.
*/
opt = opts;
while ((opt = pf_find_tcpopt(opt, opts, olen,
TCPOPT_TIMESTAMP, TCPOLEN_TIMESTAMP)) != NULL) {
u_int8_t *ts = opt + 2;
u_int8_t *tsr = opt + 6;
if (got_ts) {
/* Huh? Multiple timestamps!? */
if (pf_status.debug >= LOG_NOTICE) {
log(LOG_NOTICE,
"pf: %s: multiple TS??", __func__);
pf_print_state(state);
addlog("\n");
}
REASON_SET(reason, PFRES_TS);
return (PF_DROP);
}
memcpy(&tsval, ts, sizeof(u_int32_t));
memcpy(&tsecr, tsr, sizeof(u_int32_t));
/* modulate TS */
if (tsval && src->scrub &&
(src->scrub->pfss_flags & PFSS_TIMESTAMP)) {
/* tsval used further on */
tsval = ntohl(tsval);
pf_patch_32_unaligned(pd,
ts, htonl(tsval + src->scrub->pfss_ts_mod),
PF_ALGNMNT(ts - opts));
copyback = 1;
}
/* modulate TS reply if any (!0) */
if (tsecr && dst->scrub &&
(dst->scrub->pfss_flags & PFSS_TIMESTAMP)) {
/* tsecr used further on */
tsecr = ntohl(tsecr) - dst->scrub->pfss_ts_mod;
pf_patch_32_unaligned(pd,
tsr, htonl(tsecr), PF_ALGNMNT(tsr - opts));
copyback = 1;
}
got_ts = 1;
opt += opt[1];
}
if (copyback) {
/* Copyback the options, caller copies back header */
*writeback = 1;
m_copyback(pd->m, pd->off + sizeof(*th), olen, opts, M_NOWAIT);
}
}
/*
* 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 ||
getuptime() - state->creation > TS_MAX_CONN)) {
if (pf_status.debug >= LOG_NOTICE) {
log(LOG_NOTICE, "pf: src idled out of PAWS ");
pf_print_state(state);
addlog("\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 (pf_status.debug >= LOG_NOTICE) {
log(LOG_NOTICE, "pf: dst idled out of PAWS ");
pf_print_state(state);
addlog("\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 = 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 */
timersub(&uptime, &src->scrub->pfss_last, &delta_ts);
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(LOG_NOTICE, "Timestamp failed %c%c%c%c",
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(LOG_NOTICE, " tsval: %u tsecr: %u "
"+ticks: %u idle: %llu.%06lus", tsval, tsecr,
tsval_from_last, (long long)delta_ts.tv_sec,
delta_ts.tv_usec);
DPFPRINTF(LOG_NOTICE, " src->tsval: %u tsecr: %u",
src->scrub->pfss_tsval, src->scrub->pfss_tsecr);
DPFPRINTF(LOG_NOTICE, " dst->tsval: %u tsecr: %u "
"tsval0: %u", dst->scrub->pfss_tsval,
dst->scrub->pfss_tsecr, dst->scrub->pfss_tsval0);
if (pf_status.debug >= LOG_NOTICE) {
log(LOG_NOTICE, "pf: ");
pf_print_state(state);
pf_print_flags(th->th_flags);
addlog("\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 (pf_status.debug >= LOG_NOTICE) {
log(LOG_NOTICE,
"pf: did not receive expected RFC1323 "
"timestamp");
pf_print_state(state);
pf_print_flags(th->th_flags);
addlog("\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 (pf_status.debug >= LOG_NOTICE && dst->scrub &&
(dst->scrub->pfss_flags & PFSS_TIMESTAMP)) {
/* Don't warn if other host rejected RFC1323 */
log(LOG_NOTICE,
"pf: broken RFC1323 stack did not "
"timestamp data packet. Disabled PAWS "
"security.");
pf_print_state(state);
pf_print_flags(th->th_flags);
addlog("\n");
}
}
}
/*
* Update PAWS values
*/
if (got_ts && src->scrub && PFSS_TIMESTAMP == (src->scrub->pfss_flags &
(PFSS_PAWS_IDLED|PFSS_TIMESTAMP))) {
getmicrouptime(&src->scrub->pfss_last);
if (SEQ_GEQ(tsval, src->scrub->pfss_tsval) ||
(src->scrub->pfss_flags & PFSS_PAWS) == 0)
src->scrub->pfss_tsval = tsval;
if (tsecr) {
if (SEQ_GEQ(tsecr, src->scrub->pfss_tsecr) ||
(src->scrub->pfss_flags & PFSS_PAWS) == 0)
src->scrub->pfss_tsecr = tsecr;
if ((src->scrub->pfss_flags & PFSS_PAWS) == 0 &&
(SEQ_LT(tsval, src->scrub->pfss_tsval0) ||
src->scrub->pfss_tsval0 == 0)) {
/* tsval0 MUST be the lowest timestamp */
src->scrub->pfss_tsval0 = tsval;
}
/* Only fully initialized after a TS gets echoed */
if ((src->scrub->pfss_flags & PFSS_PAWS) == 0)
src->scrub->pfss_flags |= PFSS_PAWS;
}
}
/* I have a dream.... TCP segment reassembly.... */
return (0);
}
int
pf_normalize_mss(struct pf_pdesc *pd, u_int16_t maxmss)
{
int olen, optsoff;
u_int8_t opts[MAX_TCPOPTLEN], *opt;
olen = (pd->hdr.tcp.th_off << 2) - sizeof(struct tcphdr);
optsoff = pd->off + sizeof(struct tcphdr);
if (olen < TCPOLEN_MAXSEG ||
!pf_pull_hdr(pd->m, optsoff, opts, olen, NULL, pd->af))
return (0);
opt = opts;
while ((opt = pf_find_tcpopt(opt, opts, olen,
TCPOPT_MAXSEG, TCPOLEN_MAXSEG)) != NULL) {
u_int16_t mss;
u_int8_t *mssp = opt + 2;
memcpy(&mss, mssp, sizeof(mss));
if (ntohs(mss) > maxmss) {
size_t mssoffopts = mssp - opts;
pf_patch_16_unaligned(pd, &mss,
htons(maxmss), PF_ALGNMNT(mssoffopts));
m_copyback(pd->m, optsoff + mssoffopts,
sizeof(mss), &mss, M_NOWAIT);
m_copyback(pd->m, pd->off,
sizeof(struct tcphdr), &pd->hdr.tcp, M_NOWAIT);
}
opt += opt[1];
}
return (0);
}
void
pf_scrub(struct mbuf *m, u_int16_t flags, sa_family_t af, u_int8_t min_ttl,
u_int8_t tos)
{
struct ip *h = mtod(m, struct ip *);
#ifdef INET6
struct ip6_hdr *h6 = mtod(m, struct ip6_hdr *);
#endif /* INET6 */
u_int16_t old;
/* Clear IP_DF if no-df was requested */
if (flags & PFSTATE_NODF && af == AF_INET && h->ip_off & htons(IP_DF)) {
old = h->ip_off;
h->ip_off &= htons(~IP_DF);
pf_cksum_fixup(&h->ip_sum, old, h->ip_off, 0);
}
/* Enforce a minimum ttl, may cause endless packet loops */
if (min_ttl && af == AF_INET && h->ip_ttl < min_ttl) {
old = h->ip_ttl;
h->ip_ttl = min_ttl;
pf_cksum_fixup(&h->ip_sum, old, h->ip_ttl, 0);
}
#ifdef INET6
if (min_ttl && af == AF_INET6 && h6->ip6_hlim < min_ttl)
h6->ip6_hlim = min_ttl;
#endif /* INET6 */
/* Enforce tos */
if (flags & PFSTATE_SETTOS) {
if (af == AF_INET) {
/*
* ip_tos is 8 bit field at offset 1. Use 16 bit value
* at offset 0.
*/
old = *(u_int16_t *)h;
h->ip_tos = tos | (h->ip_tos & IPTOS_ECN_MASK);
pf_cksum_fixup(&h->ip_sum, old, *(u_int16_t *)h, 0);
}
#ifdef INET6
if (af == AF_INET6) {
/* drugs are unable to explain such idiocy */
h6->ip6_flow &= ~htonl(0x0fc00000);
h6->ip6_flow |= htonl(((u_int32_t)tos) << 20);
}
#endif /* INET6 */
}
/* random-id, but not for fragments */
if (flags & PFSTATE_RANDOMID && af == AF_INET &&
!(h->ip_off & ~htons(IP_DF))) {
old = h->ip_id;
h->ip_id = htons(ip_randomid());
pf_cksum_fixup(&h->ip_sum, old, h->ip_id, 0);
}
}
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