xfrm: Move IPsec replay detection functions to a separate file

To support multiple versions of replay detection, we move the replay
detection functions to a separate file and make them accessible
via function pointers contained in the struct xfrm_replay.

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, 141 insertions, 0 deletions

diff --git a/net/xfrm/xfrm_replay.c b/net/xfrm/xfrm_replay.c
new file mode 100644
index 0000000..42d68f3
--- /dev/null
+++ b/net/xfrm/xfrm_replay.c
@@ -0,0 +1,141 @@
+/*
+ * xfrm_replay.c - xfrm replay detection, derived from xfrm_state.c.
+ */
+
+#include <net/xfrm.h>
+
+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 (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)))
+		xfrm_replay_notify(x, XFRM_REPLAY_UPDATE);
+}
+
+static struct xfrm_replay xfrm_replay_legacy = {
+	.advance	= xfrm_replay_advance,
+	.check		= xfrm_replay_check,
+	.notify		= xfrm_replay_notify,
+	.overflow	= xfrm_replay_overflow,
+};
+
+int xfrm_init_replay(struct xfrm_state *x)
+{
+	x->repl = &xfrm_replay_legacy;
+
+	return 0;
+}
+EXPORT_SYMBOL(xfrm_init_replay);