xfrm: Add support for IPsec extended sequence numbers

This patch adds support for IPsec extended sequence numbers (esn)
as defined in RFC 4303. The bits to manage the anti-replay window
are based on a patch from Alex Badea.

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>

2 files changed, 193 insertions, 1 deletions

diff --git a/net/xfrm/xfrm_input.c b/net/xfrm/xfrm_input.c
index 55d5f5c3d119..872065ca7f8c 100644
--- a/net/xfrm/xfrm_input.c
+++ b/net/xfrm/xfrm_input.c
@@ -107,6 +107,7 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
         struct net *net = dev_net(skb->dev);
         int err;
         __be32 seq;
+        __be32 seq_hi;
         struct xfrm_state *x;
         xfrm_address_t *daddr;
         struct xfrm_mode *inner_mode;
@@ -184,7 +185,10 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
 
                 spin_unlock(&x->lock);
 
+                seq_hi = htonl(xfrm_replay_seqhi(x, seq));
+
                 XFRM_SKB_CB(skb)->seq.input.low = seq;
+                XFRM_SKB_CB(skb)->seq.input.hi = seq_hi;
 
                 nexthdr = x->type->input(x, skb);
 
diff --git a/net/xfrm/xfrm_replay.c b/net/xfrm/xfrm_replay.c
index 50589ea9d6a8..2f5be5b15740 100644
--- a/net/xfrm/xfrm_replay.c
+++ b/net/xfrm/xfrm_replay.c
@@ -20,6 +20,31 @@
 
 #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;
@@ -313,6 +338,160 @@ static void xfrm_replay_notify_bmp(struct xfrm_state *x, int event)
                 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 seq = ntohl(net_seq);
+        u32 pos = (replay_esn->seq - 1) % replay_esn->replay_window;
+        u32 wsize = replay_esn->replay_window;
+        u32 top = replay_esn->seq;
+        u32 bottom = top - wsize + 1;
+
+        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;
+        }
+
+        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_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);
+                        }
+
+                        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;
+
+                if (unlikely(wrap > 0))
+                        replay_esn->seq_hi++;
+        } 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 struct xfrm_replay xfrm_replay_legacy = {
         .advance        = xfrm_replay_advance,
         .check          = xfrm_replay_check,
@@ -327,6 +506,13 @@ static struct xfrm_replay xfrm_replay_bmp = {
         .overflow       = xfrm_replay_overflow_bmp,
 };
 
+static struct xfrm_replay xfrm_replay_esn = {
+        .advance        = xfrm_replay_advance_esn,
+        .check          = xfrm_replay_check_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;
@@ -336,11 +522,13 @@ int xfrm_init_replay(struct xfrm_state *x)
                     replay_esn->bmp_len * sizeof(__u32))
                         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);