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>

1 files changed, 206 insertions, 1 deletions

diff --git a/net/xfrm/xfrm_replay.c b/net/xfrm/xfrm_replay.c
index 42d68f324874..50589ea9d6a8 100644
--- a/net/xfrm/xfrm_replay.c
+++ b/net/xfrm/xfrm_replay.c
@@ -1,5 +1,21 @@
 /*
  * 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 <net/xfrm.h>
@@ -125,6 +141,178 @@ static void xfrm_replay_advance(struct xfrm_state *x, __be32 net_seq)
                 xfrm_replay_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 seq = ntohl(net_seq);
+        u32 diff =  replay_esn->seq - seq;
+        u32 pos = (replay_esn->seq - 1) % replay_esn->replay_window;
+
+        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;
+        }
+
+        if (pos >= diff) {
+                bitnr = (pos - diff) % replay_esn->replay_window;
+                nr = bitnr >> 5;
+                bitnr = bitnr & 0x1F;
+                if (replay_esn->bmp[nr] & (1U << bitnr))
+                        goto err_replay;
+        } 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);
+                        }
+
+                        bitnr = (pos + diff) % replay_esn->replay_window;
+                        nr = bitnr >> 5;
+                        bitnr = bitnr & 0x1F;
+                        replay_esn->bmp[nr] |= (1U << bitnr);
+                } else {
+                        nr = replay_esn->replay_window >> 5;
+                        for (i = 0; i <= nr; i++)
+                                replay_esn->bmp[i] = 0;
+
+                        bitnr = (pos + diff) % replay_esn->replay_window;
+                        nr = bitnr >> 5;
+                        bitnr = bitnr & 0x1F;
+                        replay_esn->bmp[nr] |= (1U << bitnr);
+                }
+
+                replay_esn->seq = seq;
+        } else {
+                diff = replay_esn->seq - seq;
+
+                if (pos >= diff) {
+                        bitnr = (pos - diff) % replay_esn->replay_window;
+                        nr = bitnr >> 5;
+                        bitnr = bitnr & 0x1F;
+                        replay_esn->bmp[nr] |= (1U << bitnr);
+                } 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)))
+                xfrm_replay_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 struct xfrm_replay xfrm_replay_legacy = {
         .advance        = xfrm_replay_advance,
         .check          = xfrm_replay_check,
@@ -132,9 +320,26 @@ static struct xfrm_replay xfrm_replay_legacy = {
         .overflow       = xfrm_replay_overflow,
 };
 
+static struct xfrm_replay xfrm_replay_bmp = {
+        .advance        = xfrm_replay_advance_bmp,
+        .check          = xfrm_replay_check_bmp,
+        .notify         = xfrm_replay_notify_bmp,
+        .overflow       = xfrm_replay_overflow_bmp,
+};
+
 int xfrm_init_replay(struct xfrm_state *x)
 {
-        x->repl = &xfrm_replay_legacy;
+        struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
+
+        if (replay_esn) {
+                if (replay_esn->replay_window >
+                    replay_esn->bmp_len * sizeof(__u32))
+                        return -EINVAL;
+
+                x->repl = &xfrm_replay_bmp;
+        } else
+                x->repl = &xfrm_replay_legacy;
+
 
         return 0;
 }