Re: [PATCH 3/3] XFRM: Drop packets when replay counter would overflow

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(a)hp.com&gt;

--- net/xfrm/xfrm_output.c | 5 ++++- 1 files changed, 4 insertions(+), 1 deletions(-) diff --git a/net/xfrm/xfrm_output.c b/net/xfrm/xfrm_output.c index eb3333b..284eeef 100644 --- a/net/xfrm/xfrm_output.c +++ b/net/xfrm/xfrm_output.c @@ -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); } -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html