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upstream: fix all-zero check in kexc25519_shared_key

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from markus@ ok djm@

OpenBSD-Commit-ID: 60b1d364e0d9d34d1d1ef1620cb92e36cf06712d
This commit is contained in:
djm@openbsd.org 2019-01-21 09:49:37 +00:00 committed by Damien Miller
parent 9d1a9771d0
commit f3ebaffd87
1 changed files with 7 additions and 5 deletions
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12
kexc25519.c
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@ -1,4 +1,4 @@
/* $OpenBSD: kexc25519.c,v 1.11 2018/12/27 03:25:25 djm Exp $ */ /* $OpenBSD: kexc25519.c,v 1.12 2019/01/21 09:49:37 djm Exp $ */
/* /*
* Copyright (c) 2001, 2013 Markus Friedl. All rights reserved. * Copyright (c) 2001, 2013 Markus Friedl. All rights reserved.
* Copyright (c) 2010 Damien Miller. All rights reserved. * Copyright (c) 2010 Damien Miller. All rights reserved.
@ -64,14 +64,16 @@ kexc25519_shared_key(const u_char key[CURVE25519_SIZE],
const u_char pub[CURVE25519_SIZE], struct sshbuf *out) const u_char pub[CURVE25519_SIZE], struct sshbuf *out)
{ {
u_char shared_key[CURVE25519_SIZE]; u_char shared_key[CURVE25519_SIZE];
u_char zero[CURVE25519_SIZE];
int r; int r;
/* Check for all-zero public key */ crypto_scalarmult_curve25519(shared_key, key, pub);
explicit_bzero(shared_key, CURVE25519_SIZE);
if (timingsafe_bcmp(pub, shared_key, CURVE25519_SIZE) == 0) /* Check for all-zero shared secret */
explicit_bzero(zero, CURVE25519_SIZE);
if (timingsafe_bcmp(zero, shared_key, CURVE25519_SIZE) == 0)
return SSH_ERR_KEY_INVALID_EC_VALUE; return SSH_ERR_KEY_INVALID_EC_VALUE;
crypto_scalarmult_curve25519(shared_key, key, pub);
#ifdef DEBUG_KEXECDH #ifdef DEBUG_KEXECDH
dump_digest("shared secret", shared_key, CURVE25519_SIZE); dump_digest("shared secret", shared_key, CURVE25519_SIZE);
#endif #endif