From 03654763148f9a3878b8b70c30d1ffce2fca3dff Mon Sep 17 00:00:00 2001 From: Sylvain Rochet Date: Sun, 26 Apr 2015 20:40:53 +0200 Subject: ppp: mppe: discard late packet in stateless mode When PPP is used over a link which does not guarantee packet ordering, we might get late MPPE packets. This is a problem because MPPE must be kept synchronized and the current implementation does not drop them and rekey 4095 times instead of 0, which is wrong. In order to prevent rekeying about a whole count space times (~ 4095 times), drop packets which are not within the forward 4096/2 window and increase sanity error counter. Signed-off-by: Sylvain Rochet Signed-off-by: David S. Miller --- drivers/net/ppp/ppp_mppe.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/net/ppp/ppp_mppe.c b/drivers/net/ppp/ppp_mppe.c index 692ee0ff0db1..05005c660d4d 100644 --- a/drivers/net/ppp/ppp_mppe.c +++ b/drivers/net/ppp/ppp_mppe.c @@ -533,6 +533,13 @@ mppe_decompress(void *arg, unsigned char *ibuf, int isize, unsigned char *obuf, */ if (!state->stateful) { + /* Discard late packet */ + if ((ccount - state->ccount) % MPPE_CCOUNT_SPACE + > MPPE_CCOUNT_SPACE / 2) { + state->sanity_errors++; + goto sanity_error; + } + /* RFC 3078, sec 8.1. Rekey for every packet. */ while (state->ccount != ccount) { mppe_rekey(state, 0); -- cgit v1.2.3