| Message ID | 1430073653-22131-3-git-send-email-sylvain.rochet@finsecur.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
diff --git a/drivers/net/ppp/ppp_mppe.c b/drivers/net/ppp/ppp_mppe.c index 692ee0f..05005c6 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);
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 <sylvain.rochet@finsecur.com> --- drivers/net/ppp/ppp_mppe.c | 7 +++++++ 1 file changed, 7 insertions(+)