netdev - [PATCH 2/2] ppp: mppe: discard late packet in stateless mode

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Sun, 26 Apr 2015 20:40:53 +0200
From:	Sylvain Rochet <sylvain.rochet@...secur.com>
To:	Paul Mackerras <paulus@...ba.org>, linux-ppp@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>
Cc:	Sylvain Rochet <sylvain.rochet@...secur.com>
Subject: [PATCH 2/2] 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 <sylvain.rochet@...secur.com>
---
 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 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);
-- 
2.1.4

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html