upstream commit
ban all-zero curve25519 keys as recommended by latest
CFRG curves draft; ok markus
diff --git a/kexc25519.c b/kexc25519.c
index b6e6c40..8d8cd4a 100644
--- a/kexc25519.c
+++ b/kexc25519.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexc25519.c,v 1.8 2015/01/19 20:16:15 markus Exp $ */
+/* $OpenBSD: kexc25519.c,v 1.9 2015/03/26 07:00:04 djm Exp $ */
/*
* Copyright (c) 2001, 2013 Markus Friedl. All rights reserved.
* Copyright (c) 2010 Damien Miller. All rights reserved.
@@ -66,6 +66,11 @@
u_char shared_key[CURVE25519_SIZE];
int r;
+ /* Check for all-zero public key */
+ explicit_bzero(shared_key, CURVE25519_SIZE);
+ if (timingsafe_bcmp(pub, shared_key, CURVE25519_SIZE) == 0)
+ return SSH_ERR_KEY_INVALID_EC_VALUE;
+
crypto_scalarmult_curve25519(shared_key, key, pub);
#ifdef DEBUG_KEXECDH
dump_digest("shared secret", shared_key, CURVE25519_SIZE);