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authorSteffen Klassert <steffen.klassert@secunet.com>2012-09-04 00:03:29 +0000
committerDavid S. Miller <davem@davemloft.net>2012-09-04 14:09:45 -0400
commit3b59df46a449ec9975146d71318c4777ad086744 (patch)
tree8ba7e6186ef90c4bffe553504c33f40054704f94
parent37159ef2c1ae1e696b24b260b241209a19f92c60 (diff)
downloadvexpress-lsk-3b59df46a449ec9975146d71318c4777ad086744.tar.gz
xfrm: Workaround incompatibility of ESN and async crypto
ESN for esp is defined in RFC 4303. This RFC assumes that the sequence number counters are always up to date. However, this is not true if an async crypto algorithm is employed. If the sequence number counters are not up to date on sequence number check, we may incorrectly update the upper 32 bit of the sequence number. This leads to a DOS. We workaround this by comparing the upper sequence number, (used for authentication) with the upper sequence number computed after the async processing. We drop the packet if these numbers are different. To do this, we introduce a recheck function that does this check in the ESN case. 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>
-rw-r--r--include/net/xfrm.h3
-rw-r--r--net/xfrm/xfrm_input.c2
-rw-r--r--net/xfrm/xfrm_replay.c15
3 files changed, 19 insertions, 1 deletions
diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 976a81abe1a..639dd1316d3 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -273,6 +273,9 @@ struct xfrm_replay {
int (*check)(struct xfrm_state *x,
struct sk_buff *skb,
__be32 net_seq);
+ int (*recheck)(struct xfrm_state *x,
+ struct sk_buff *skb,
+ __be32 net_seq);
void (*notify)(struct xfrm_state *x, int event);
int (*overflow)(struct xfrm_state *x, struct sk_buff *skb);
};
diff --git a/net/xfrm/xfrm_input.c b/net/xfrm/xfrm_input.c
index 54a0dc2e2f8..ab2bb42fe09 100644
--- a/net/xfrm/xfrm_input.c
+++ b/net/xfrm/xfrm_input.c
@@ -212,7 +212,7 @@ resume:
/* only the first xfrm gets the encap type */
encap_type = 0;
- if (async && x->repl->check(x, skb, seq)) {
+ if (async && x->repl->recheck(x, skb, seq)) {
XFRM_INC_STATS(net, LINUX_MIB_XFRMINSTATESEQERROR);
goto drop_unlock;
}
diff --git a/net/xfrm/xfrm_replay.c b/net/xfrm/xfrm_replay.c
index 2f6d11d04a2..3efb07d3eb2 100644
--- a/net/xfrm/xfrm_replay.c
+++ b/net/xfrm/xfrm_replay.c
@@ -420,6 +420,18 @@ err:
return -EINVAL;
}
+static int xfrm_replay_recheck_esn(struct xfrm_state *x,
+ struct sk_buff *skb, __be32 net_seq)
+{
+ if (unlikely(XFRM_SKB_CB(skb)->seq.input.hi !=
+ htonl(xfrm_replay_seqhi(x, net_seq)))) {
+ x->stats.replay_window++;
+ return -EINVAL;
+ }
+
+ return xfrm_replay_check_esn(x, skb, net_seq);
+}
+
static void xfrm_replay_advance_esn(struct xfrm_state *x, __be32 net_seq)
{
unsigned int bitnr, nr, i;
@@ -479,6 +491,7 @@ static void xfrm_replay_advance_esn(struct xfrm_state *x, __be32 net_seq)
static struct xfrm_replay xfrm_replay_legacy = {
.advance = xfrm_replay_advance,
.check = xfrm_replay_check,
+ .recheck = xfrm_replay_check,
.notify = xfrm_replay_notify,
.overflow = xfrm_replay_overflow,
};
@@ -486,6 +499,7 @@ static struct xfrm_replay xfrm_replay_legacy = {
static struct xfrm_replay xfrm_replay_bmp = {
.advance = xfrm_replay_advance_bmp,
.check = xfrm_replay_check_bmp,
+ .recheck = xfrm_replay_check_bmp,
.notify = xfrm_replay_notify_bmp,
.overflow = xfrm_replay_overflow_bmp,
};
@@ -493,6 +507,7 @@ static struct xfrm_replay xfrm_replay_bmp = {
static struct xfrm_replay xfrm_replay_esn = {
.advance = xfrm_replay_advance_esn,
.check = xfrm_replay_check_esn,
+ .recheck = xfrm_replay_recheck_esn,
.notify = xfrm_replay_notify_bmp,
.overflow = xfrm_replay_overflow_esn,
};