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[XFRM]: Drop packets when replay counter would overflow

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According to RFC4303, section 3.3.3 we need to drop outgoing packets which
cause the replay counter to overflow:

   3.3.3.  Sequence Number Generation

   The sender's counter is initialized to 0 when an SA is established.
   The sender increments the sequence number (or ESN) counter for this
   SA and inserts the low-order 32 bits of the value into the Sequence
   Number field.  Thus, the first packet sent using a given SA will
   contain a sequence number of 1.

   If anti-replay is enabled (the default), the sender checks to ensure
   that the counter has not cycled before inserting the new value in the
   Sequence Number field.  In other words, the sender MUST NOT send a
   packet on an SA if doing so would cause the sequence number to cycle.
   An attempt to transmit a packet that would result in sequence number
   overflow is an auditable event.  The audit log entry for this event
   SHOULD include the SPI value, current date/time, Source Address,
   Destination Address, and (in IPv6) the cleartext Flow ID.

Signed-off-by: Paul Moore <paul.moore@hp.com>
Acked-by: James Morris <jmorris@namei.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Paul Moore 2007-12-21 14:59:08 -08:00 committed by David S. Miller
parent afeb14b490
commit e1af9f270b
1 changed files with 4 additions and 1 deletions
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5
net/xfrm/xfrm_output.c
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@ -57,8 +57,11 @@ static int xfrm_output_one(struct sk_buff *skb, int err)
if (x->type->flags & XFRM_TYPE_REPLAY_PROT) {
XFRM_SKB_CB(skb)->seq = ++x->replay.oseq;
if (unlikely(x->replay.oseq == 0))
if (unlikely(x->replay.oseq == 0)) {
x->replay.oseq--;
xfrm_audit_state_replay_overflow(x, skb);
goto error;
}
if (xfrm_aevent_is_on())
xfrm_replay_notify(x, XFRM_REPLAY_UPDATE);
}