xfrm: Support anti-replay window size bigger than 32 packets
As it is, the anti-replay bitmap in struct xfrm_replay_state can only accomodate 32 packets. Even though it is possible to configure anti-replay window sizes up to 255 packets from userspace. So we reject any packet with a sequence number within the configured window but outside the bitmap. With this patch, we represent the anti-replay window as a bitmap of variable length that can be accessed via the new struct xfrm_replay_state_esn. Thus, we have no limit on the window size anymore. To use the new anti-replay window implementantion, new userspace tools are required. We leave the old implementation untouched to stay in sync with old userspace tools. 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>
This commit is contained in:
Steffen Klassert
David S. Miller
parent
9fdc4883d9
commit
97e15c3a85
1 changed files with 206 additions and 1 deletions
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@ -1,5 +1,21 @@
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/*
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* xfrm_replay.c - xfrm replay detection, derived from xfrm_state.c.
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*
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* Copyright (C) 2010 secunet Security Networks AG
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* Copyright (C) 2010 Steffen Klassert <steffen.klassert@secunet.com>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms and conditions of the GNU General Public License,
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* version 2, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include <net/xfrm.h>
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@ -125,6 +141,178 @@ static void xfrm_replay_advance(struct xfrm_state *x, __be32 net_seq)
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xfrm_replay_notify(x, XFRM_REPLAY_UPDATE);
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}
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static int xfrm_replay_overflow_bmp(struct xfrm_state *x, struct sk_buff *skb)
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{
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int err = 0;
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struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
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struct net *net = xs_net(x);
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if (x->type->flags & XFRM_TYPE_REPLAY_PROT) {
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XFRM_SKB_CB(skb)->seq.output.low = ++replay_esn->oseq;
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if (unlikely(replay_esn->oseq == 0)) {
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replay_esn->oseq--;
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xfrm_audit_state_replay_overflow(x, skb);
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err = -EOVERFLOW;
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return err;
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}
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if (xfrm_aevent_is_on(net))
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x->repl->notify(x, XFRM_REPLAY_UPDATE);
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}
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return err;
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}
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static int xfrm_replay_check_bmp(struct xfrm_state *x,
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struct sk_buff *skb, __be32 net_seq)
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{
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unsigned int bitnr, nr;
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struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
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u32 seq = ntohl(net_seq);
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u32 diff = replay_esn->seq - seq;
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u32 pos = (replay_esn->seq - 1) % replay_esn->replay_window;
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if (unlikely(seq == 0))
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goto err;
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if (likely(seq > replay_esn->seq))
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return 0;
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if (diff >= replay_esn->replay_window) {
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x->stats.replay_window++;
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goto err;
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}
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if (pos >= diff) {
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bitnr = (pos - diff) % replay_esn->replay_window;
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nr = bitnr >> 5;
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bitnr = bitnr & 0x1F;
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if (replay_esn->bmp[nr] & (1U << bitnr))
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goto err_replay;
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} else {
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bitnr = replay_esn->replay_window - (diff - pos);
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nr = bitnr >> 5;
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bitnr = bitnr & 0x1F;
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if (replay_esn->bmp[nr] & (1U << bitnr))
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goto err_replay;
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}
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return 0;
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err_replay:
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x->stats.replay++;
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err:
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xfrm_audit_state_replay(x, skb, net_seq);
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return -EINVAL;
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}
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static void xfrm_replay_advance_bmp(struct xfrm_state *x, __be32 net_seq)
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{
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unsigned int bitnr, nr, i;
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u32 diff;
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struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
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u32 seq = ntohl(net_seq);
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u32 pos = (replay_esn->seq - 1) % replay_esn->replay_window;
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if (!replay_esn->replay_window)
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return;
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if (seq > replay_esn->seq) {
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diff = seq - replay_esn->seq;
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if (diff < replay_esn->replay_window) {
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for (i = 1; i < diff; i++) {
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bitnr = (pos + i) % replay_esn->replay_window;
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nr = bitnr >> 5;
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bitnr = bitnr & 0x1F;
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replay_esn->bmp[nr] &= ~(1U << bitnr);
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}
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bitnr = (pos + diff) % replay_esn->replay_window;
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nr = bitnr >> 5;
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bitnr = bitnr & 0x1F;
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replay_esn->bmp[nr] |= (1U << bitnr);
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} else {
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nr = replay_esn->replay_window >> 5;
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for (i = 0; i <= nr; i++)
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replay_esn->bmp[i] = 0;
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bitnr = (pos + diff) % replay_esn->replay_window;
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nr = bitnr >> 5;
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bitnr = bitnr & 0x1F;
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replay_esn->bmp[nr] |= (1U << bitnr);
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}
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replay_esn->seq = seq;
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} else {
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diff = replay_esn->seq - seq;
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if (pos >= diff) {
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bitnr = (pos - diff) % replay_esn->replay_window;
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nr = bitnr >> 5;
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bitnr = bitnr & 0x1F;
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replay_esn->bmp[nr] |= (1U << bitnr);
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} else {
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bitnr = replay_esn->replay_window - (diff - pos);
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nr = bitnr >> 5;
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bitnr = bitnr & 0x1F;
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replay_esn->bmp[nr] |= (1U << bitnr);
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}
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}
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if (xfrm_aevent_is_on(xs_net(x)))
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xfrm_replay_notify(x, XFRM_REPLAY_UPDATE);
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}
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static void xfrm_replay_notify_bmp(struct xfrm_state *x, int event)
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{
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struct km_event c;
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struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
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struct xfrm_replay_state_esn *preplay_esn = x->preplay_esn;
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/* we send notify messages in case
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* 1. we updated on of the sequence numbers, and the seqno difference
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* is at least x->replay_maxdiff, in this case we also update the
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* timeout of our timer function
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* 2. if x->replay_maxage has elapsed since last update,
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* and there were changes
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*
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* The state structure must be locked!
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*/
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switch (event) {
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case XFRM_REPLAY_UPDATE:
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if (x->replay_maxdiff &&
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(replay_esn->seq - preplay_esn->seq < x->replay_maxdiff) &&
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(replay_esn->oseq - preplay_esn->oseq < x->replay_maxdiff)) {
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if (x->xflags & XFRM_TIME_DEFER)
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event = XFRM_REPLAY_TIMEOUT;
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else
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return;
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}
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break;
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case XFRM_REPLAY_TIMEOUT:
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if (memcmp(x->replay_esn, x->preplay_esn,
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xfrm_replay_state_esn_len(replay_esn)) == 0) {
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x->xflags |= XFRM_TIME_DEFER;
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return;
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}
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break;
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}
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memcpy(x->preplay_esn, x->replay_esn,
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xfrm_replay_state_esn_len(replay_esn));
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c.event = XFRM_MSG_NEWAE;
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c.data.aevent = event;
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km_state_notify(x, &c);
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if (x->replay_maxage &&
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!mod_timer(&x->rtimer, jiffies + x->replay_maxage))
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x->xflags &= ~XFRM_TIME_DEFER;
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}
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static struct xfrm_replay xfrm_replay_legacy = {
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.advance = xfrm_replay_advance,
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.check = xfrm_replay_check,
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@ -132,9 +320,26 @@ static struct xfrm_replay xfrm_replay_legacy = {
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.overflow = xfrm_replay_overflow,
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};
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static struct xfrm_replay xfrm_replay_bmp = {
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.advance = xfrm_replay_advance_bmp,
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.check = xfrm_replay_check_bmp,
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.notify = xfrm_replay_notify_bmp,
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.overflow = xfrm_replay_overflow_bmp,
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};
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int xfrm_init_replay(struct xfrm_state *x)
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{
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x->repl = &xfrm_replay_legacy;
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struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
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if (replay_esn) {
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if (replay_esn->replay_window >
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replay_esn->bmp_len * sizeof(__u32))
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return -EINVAL;
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x->repl = &xfrm_replay_bmp;
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} else
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x->repl = &xfrm_replay_legacy;
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return 0;
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}
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