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linux/net/xfrm/xfrm_replay.c
Steffen Klassert 3b59df46a4 xfrm: Workaround incompatibility of ESN and async crypto 
ESN for esp is defined in RFC 4303. This RFC assumes that the
sequence number counters are always up to date. However,
this is not true if an async crypto algorithm is employed.

If the sequence number counters are not up to date on sequence
number check, we may incorrectly update the upper 32 bit of
the sequence number. This leads to a DOS.

We workaround this by comparing the upper sequence number,
(used for authentication) with the upper sequence number
computed after the async processing. We drop the packet
if these numbers are different.

To do this, we introduce a recheck function that does this
check in the ESN case.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
2012-09-04 14:09:45 -04:00

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/*
* xfrm_replay.c - xfrm replay detection, derived from xfrm_state.c.
*
* Copyright (C) 2010 secunet Security Networks AG
* Copyright (C) 2010 Steffen Klassert <steffen.klassert@secunet.com>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License along with
* this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include <linux/export.h>
#include <net/xfrm.h>
u32 xfrm_replay_seqhi(struct xfrm_state *x, __be32 net_seq)
{
u32 seq, seq_hi, bottom;
struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
if (!(x->props.flags & XFRM_STATE_ESN))
return 0;
seq = ntohl(net_seq);
seq_hi = replay_esn->seq_hi;
bottom = replay_esn->seq - replay_esn->replay_window + 1;
if (likely(replay_esn->seq >= replay_esn->replay_window - 1)) {
/* A. same subspace */
if (unlikely(seq < bottom))
seq_hi++;
} else {
/* B. window spans two subspaces */
if (unlikely(seq >= bottom))
seq_hi--;
}
return seq_hi;
}
static void xfrm_replay_notify(struct xfrm_state *x, int event)
{
struct km_event c;
/* we send notify messages in case
* 1. we updated on of the sequence numbers, and the seqno difference
* is at least x->replay_maxdiff, in this case we also update the
* timeout of our timer function
* 2. if x->replay_maxage has elapsed since last update,
* and there were changes
*
* The state structure must be locked!
*/
switch (event) {
case XFRM_REPLAY_UPDATE:
if (x->replay_maxdiff &&
(x->replay.seq - x->preplay.seq < x->replay_maxdiff) &&
(x->replay.oseq - x->preplay.oseq < x->replay_maxdiff)) {
if (x->xflags & XFRM_TIME_DEFER)
event = XFRM_REPLAY_TIMEOUT;
else
return;
}
break;
case XFRM_REPLAY_TIMEOUT:
if (memcmp(&x->replay, &x->preplay,
sizeof(struct xfrm_replay_state)) == 0) {
x->xflags |= XFRM_TIME_DEFER;
return;
}
break;
}
memcpy(&x->preplay, &x->replay, sizeof(struct xfrm_replay_state));
c.event = XFRM_MSG_NEWAE;
c.data.aevent = event;
km_state_notify(x, &c);
if (x->replay_maxage &&
!mod_timer(&x->rtimer, jiffies + x->replay_maxage))
x->xflags &= ~XFRM_TIME_DEFER;
}
static int xfrm_replay_overflow(struct xfrm_state *x, struct sk_buff *skb)
{
int err = 0;
struct net *net = xs_net(x);
if (x->type->flags & XFRM_TYPE_REPLAY_PROT) {
XFRM_SKB_CB(skb)->seq.output.low = ++x->replay.oseq;
if (unlikely(x->replay.oseq == 0)) {
x->replay.oseq--;
xfrm_audit_state_replay_overflow(x, skb);
err = -EOVERFLOW;
return err;
}
if (xfrm_aevent_is_on(net))
x->repl->notify(x, XFRM_REPLAY_UPDATE);
}
return err;
}
static int xfrm_replay_check(struct xfrm_state *x,
struct sk_buff *skb, __be32 net_seq)
{
u32 diff;
u32 seq = ntohl(net_seq);
if (!x->props.replay_window)
return 0;
if (unlikely(seq == 0))
goto err;
if (likely(seq > x->replay.seq))
return 0;
diff = x->replay.seq - seq;
if (diff >= min_t(unsigned int, x->props.replay_window,
sizeof(x->replay.bitmap) * 8)) {
x->stats.replay_window++;
goto err;
}
if (x->replay.bitmap & (1U << diff)) {
x->stats.replay++;
goto err;
}
return 0;
err:
xfrm_audit_state_replay(x, skb, net_seq);
return -EINVAL;
}
static void xfrm_replay_advance(struct xfrm_state *x, __be32 net_seq)
{
u32 diff;
u32 seq = ntohl(net_seq);
if (!x->props.replay_window)
return;
if (seq > x->replay.seq) {
diff = seq - x->replay.seq;
if (diff < x->props.replay_window)
x->replay.bitmap = ((x->replay.bitmap) << diff) | 1;
else
x->replay.bitmap = 1;
x->replay.seq = seq;
} else {
diff = x->replay.seq - seq;
x->replay.bitmap |= (1U << diff);
}
if (xfrm_aevent_is_on(xs_net(x)))
x->repl->notify(x, XFRM_REPLAY_UPDATE);
}
static int xfrm_replay_overflow_bmp(struct xfrm_state *x, struct sk_buff *skb)
{
int err = 0;
struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
struct net *net = xs_net(x);
if (x->type->flags & XFRM_TYPE_REPLAY_PROT) {
XFRM_SKB_CB(skb)->seq.output.low = ++replay_esn->oseq;
if (unlikely(replay_esn->oseq == 0)) {
replay_esn->oseq--;
xfrm_audit_state_replay_overflow(x, skb);
err = -EOVERFLOW;
return err;
}
if (xfrm_aevent_is_on(net))
x->repl->notify(x, XFRM_REPLAY_UPDATE);
}
return err;
}
static int xfrm_replay_check_bmp(struct xfrm_state *x,
struct sk_buff *skb, __be32 net_seq)
{
unsigned int bitnr, nr;
struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
u32 pos;
u32 seq = ntohl(net_seq);
u32 diff = replay_esn->seq - seq;
if (!replay_esn->replay_window)
return 0;
if (unlikely(seq == 0))
goto err;
if (likely(seq > replay_esn->seq))
return 0;
if (diff >= replay_esn->replay_window) {
x->stats.replay_window++;
goto err;
}
pos = (replay_esn->seq - 1) % replay_esn->replay_window;
if (pos >= diff)
bitnr = (pos - diff) % replay_esn->replay_window;
else
bitnr = replay_esn->replay_window - (diff - pos);
nr = bitnr >> 5;
bitnr = bitnr & 0x1F;
if (replay_esn->bmp[nr] & (1U << bitnr))
goto err_replay;
return 0;
err_replay:
x->stats.replay++;
err:
xfrm_audit_state_replay(x, skb, net_seq);
return -EINVAL;
}
static void xfrm_replay_advance_bmp(struct xfrm_state *x, __be32 net_seq)
{
unsigned int bitnr, nr, i;
u32 diff;
struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
u32 seq = ntohl(net_seq);
u32 pos = (replay_esn->seq - 1) % replay_esn->replay_window;
if (!replay_esn->replay_window)
return;
if (seq > replay_esn->seq) {
diff = seq - replay_esn->seq;
if (diff < replay_esn->replay_window) {
for (i = 1; i < diff; i++) {
bitnr = (pos + i) % replay_esn->replay_window;
nr = bitnr >> 5;
bitnr = bitnr & 0x1F;
replay_esn->bmp[nr] &= ~(1U << bitnr);
}
} else {
nr = (replay_esn->replay_window - 1) >> 5;
for (i = 0; i <= nr; i++)
replay_esn->bmp[i] = 0;
}
bitnr = (pos + diff) % replay_esn->replay_window;
replay_esn->seq = seq;
} else {
diff = replay_esn->seq - seq;
if (pos >= diff)
bitnr = (pos - diff) % replay_esn->replay_window;
else
bitnr = replay_esn->replay_window - (diff - pos);
}
nr = bitnr >> 5;
bitnr = bitnr & 0x1F;
replay_esn->bmp[nr] |= (1U << bitnr);
if (xfrm_aevent_is_on(xs_net(x)))
x->repl->notify(x, XFRM_REPLAY_UPDATE);
}
static void xfrm_replay_notify_bmp(struct xfrm_state *x, int event)
{
struct km_event c;
struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
struct xfrm_replay_state_esn *preplay_esn = x->preplay_esn;
/* we send notify messages in case
* 1. we updated on of the sequence numbers, and the seqno difference
* is at least x->replay_maxdiff, in this case we also update the
* timeout of our timer function
* 2. if x->replay_maxage has elapsed since last update,
* and there were changes
*
* The state structure must be locked!
*/
switch (event) {
case XFRM_REPLAY_UPDATE:
if (x->replay_maxdiff &&
(replay_esn->seq - preplay_esn->seq < x->replay_maxdiff) &&
(replay_esn->oseq - preplay_esn->oseq < x->replay_maxdiff)) {
if (x->xflags & XFRM_TIME_DEFER)
event = XFRM_REPLAY_TIMEOUT;
else
return;
}
break;
case XFRM_REPLAY_TIMEOUT:
if (memcmp(x->replay_esn, x->preplay_esn,
xfrm_replay_state_esn_len(replay_esn)) == 0) {
x->xflags |= XFRM_TIME_DEFER;
return;
}
break;
}
memcpy(x->preplay_esn, x->replay_esn,
xfrm_replay_state_esn_len(replay_esn));
c.event = XFRM_MSG_NEWAE;
c.data.aevent = event;
km_state_notify(x, &c);
if (x->replay_maxage &&
!mod_timer(&x->rtimer, jiffies + x->replay_maxage))
x->xflags &= ~XFRM_TIME_DEFER;
}
static int xfrm_replay_overflow_esn(struct xfrm_state *x, struct sk_buff *skb)
{
int err = 0;
struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
struct net *net = xs_net(x);
if (x->type->flags & XFRM_TYPE_REPLAY_PROT) {
XFRM_SKB_CB(skb)->seq.output.low = ++replay_esn->oseq;
XFRM_SKB_CB(skb)->seq.output.hi = replay_esn->oseq_hi;
if (unlikely(replay_esn->oseq == 0)) {
XFRM_SKB_CB(skb)->seq.output.hi = ++replay_esn->oseq_hi;
if (replay_esn->oseq_hi == 0) {
replay_esn->oseq--;
replay_esn->oseq_hi--;
xfrm_audit_state_replay_overflow(x, skb);
err = -EOVERFLOW;
return err;
}
}
if (xfrm_aevent_is_on(net))
x->repl->notify(x, XFRM_REPLAY_UPDATE);
}
return err;
}
static int xfrm_replay_check_esn(struct xfrm_state *x,
struct sk_buff *skb, __be32 net_seq)
{
unsigned int bitnr, nr;
u32 diff;
struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
u32 pos;
u32 seq = ntohl(net_seq);
u32 wsize = replay_esn->replay_window;
u32 top = replay_esn->seq;
u32 bottom = top - wsize + 1;
if (!wsize)
return 0;
if (unlikely(seq == 0 && replay_esn->seq_hi == 0 &&
(replay_esn->seq < replay_esn->replay_window - 1)))
goto err;
diff = top - seq;
if (likely(top >= wsize - 1)) {
/* A. same subspace */
if (likely(seq > top) || seq < bottom)
return 0;
} else {
/* B. window spans two subspaces */
if (likely(seq > top && seq < bottom))
return 0;
if (seq >= bottom)
diff = ~seq + top + 1;
}
if (diff >= replay_esn->replay_window) {
x->stats.replay_window++;
goto err;
}
pos = (replay_esn->seq - 1) % replay_esn->replay_window;
if (pos >= diff)
bitnr = (pos - diff) % replay_esn->replay_window;
else
bitnr = replay_esn->replay_window - (diff - pos);
nr = bitnr >> 5;
bitnr = bitnr & 0x1F;
if (replay_esn->bmp[nr] & (1U << bitnr))
goto err_replay;
return 0;
err_replay:
x->stats.replay++;
err:
xfrm_audit_state_replay(x, skb, net_seq);
return -EINVAL;
}
static int xfrm_replay_recheck_esn(struct xfrm_state *x,
struct sk_buff *skb, __be32 net_seq)
{
if (unlikely(XFRM_SKB_CB(skb)->seq.input.hi !=
htonl(xfrm_replay_seqhi(x, net_seq)))) {
x->stats.replay_window++;
return -EINVAL;
}
return xfrm_replay_check_esn(x, skb, net_seq);
}
static void xfrm_replay_advance_esn(struct xfrm_state *x, __be32 net_seq)
{
unsigned int bitnr, nr, i;
int wrap;
u32 diff, pos, seq, seq_hi;
struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
if (!replay_esn->replay_window)
return;
seq = ntohl(net_seq);
pos = (replay_esn->seq - 1) % replay_esn->replay_window;
seq_hi = xfrm_replay_seqhi(x, net_seq);
wrap = seq_hi - replay_esn->seq_hi;
if ((!wrap && seq > replay_esn->seq) || wrap > 0) {
if (likely(!wrap))
diff = seq - replay_esn->seq;
else
diff = ~replay_esn->seq + seq + 1;
if (diff < replay_esn->replay_window) {
for (i = 1; i < diff; i++) {
bitnr = (pos + i) % replay_esn->replay_window;
nr = bitnr >> 5;
bitnr = bitnr & 0x1F;
replay_esn->bmp[nr] &= ~(1U << bitnr);
}
} else {
nr = (replay_esn->replay_window - 1) >> 5;
for (i = 0; i <= nr; i++)
replay_esn->bmp[i] = 0;
}
bitnr = (pos + diff) % replay_esn->replay_window;
replay_esn->seq = seq;
if (unlikely(wrap > 0))
replay_esn->seq_hi++;
} else {
diff = replay_esn->seq - seq;
if (pos >= diff)
bitnr = (pos - diff) % replay_esn->replay_window;
else
bitnr = replay_esn->replay_window - (diff - pos);
}
nr = bitnr >> 5;
bitnr = bitnr & 0x1F;
replay_esn->bmp[nr] |= (1U << bitnr);
if (xfrm_aevent_is_on(xs_net(x)))
x->repl->notify(x, XFRM_REPLAY_UPDATE);
}
static struct xfrm_replay xfrm_replay_legacy = {
.advance = xfrm_replay_advance,
.check = xfrm_replay_check,
.recheck = xfrm_replay_check,
.notify = xfrm_replay_notify,
.overflow = xfrm_replay_overflow,
};
static struct xfrm_replay xfrm_replay_bmp = {
.advance = xfrm_replay_advance_bmp,
.check = xfrm_replay_check_bmp,
.recheck = xfrm_replay_check_bmp,
.notify = xfrm_replay_notify_bmp,
.overflow = xfrm_replay_overflow_bmp,
};
static struct xfrm_replay xfrm_replay_esn = {
.advance = xfrm_replay_advance_esn,
.check = xfrm_replay_check_esn,
.recheck = xfrm_replay_recheck_esn,
.notify = xfrm_replay_notify_bmp,
.overflow = xfrm_replay_overflow_esn,
};
int xfrm_init_replay(struct xfrm_state *x)
{
struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
if (replay_esn) {
if (replay_esn->replay_window >
replay_esn->bmp_len * sizeof(__u32) * 8)
return -EINVAL;
if ((x->props.flags & XFRM_STATE_ESN) && replay_esn->replay_window == 0)
return -EINVAL;
if ((x->props.flags & XFRM_STATE_ESN) && x->replay_esn)
x->repl = &xfrm_replay_esn;
else
x->repl = &xfrm_replay_bmp;
} else
x->repl = &xfrm_replay_legacy;
return 0;
}
EXPORT_SYMBOL(xfrm_init_replay);
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