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@xxxxxxxxxxx>
---
net/xfrm/xfrm_replay.c | 185 +++++++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 184 insertions(+), 1 deletions(-)
diff --git a/net/xfrm/xfrm_replay.c b/net/xfrm/xfrm_replay.c
index 598ca4c..be2c9eb 100644
--- a/net/xfrm/xfrm_replay.c
+++ b/net/xfrm/xfrm_replay.c
@@ -141,6 +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,
@@ -148,9 +320,20 @@ 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;
+ if (x->replay_esn)
+ x->repl = &xfrm_replay_bmp;
+ else
+ x->repl = &xfrm_replay_legacy;
+
return 0;
}
--
1.7.0.4
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