upstream commit

add a comment about implicitly-expected checks to
sshkey_ec_validate_public()

Upstream-ID: 74a7f71c28f7c13a50f89fc78e7863b9cd61713f

Author: djmdjm

sshkey.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: sshkey.c,v 1.39 2016/09/26 21:16:11 djm Exp $ */
+/* $OpenBSD: sshkey.c,v 1.40 2016/10/04 21:34:40 djm Exp $ */
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  * Copyright (c) 2008 Alexander von Gernler.  All rights reserved.
@@ -2864,6 +2864,14 @@ sshkey_ec_validate_public(const EC_GROUP *group, const EC_POINT *public)
 	BIGNUM *order, *x, *y, *tmp;
 	int ret = SSH_ERR_KEY_INVALID_EC_VALUE;
 
+	/*
+	 * NB. This assumes OpenSSL has already verified that the public
+	 * point lies on the curve. This is done by EC_POINT_oct2point()
+	 * implicitly calling EC_POINT_is_on_curve(). If this code is ever
+	 * reachable with public points not unmarshalled using
+	 * EC_POINT_oct2point then the caller will need to explicitly check.
+	 */
+
 	if ((bnctx = BN_CTX_new()) == NULL)
 		return SSH_ERR_ALLOC_FAIL;
 	BN_CTX_start(bnctx);