1/* $OpenBSD: kexecdh.c,v 1.3 2010/09/22 05:01:29 djm Exp $ */
2/*
3 * Copyright (c) 2001 Markus Friedl.  All rights reserved.
4 * Copyright (c) 2010 Damien Miller.  All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27#include "includes.h"
28
29#ifdef OPENSSL_HAS_ECC
30
31#include <sys/types.h>
32
33#include <signal.h>
34#include <string.h>
35
36#include <openssl/bn.h>
37#include <openssl/evp.h>
38#include <openssl/ec.h>
39#include <openssl/ecdh.h>
40
41#include "buffer.h"
42#include "ssh2.h"
43#include "key.h"
44#include "cipher.h"
45#include "kex.h"
46#include "log.h"
47
48int
49kex_ecdh_name_to_nid(const char *kexname)
50{
51	if (strlen(kexname) < sizeof(KEX_ECDH_SHA2_STEM) - 1)
52		fatal("%s: kexname too short \"%s\"", __func__, kexname);
53	return key_curve_name_to_nid(kexname + sizeof(KEX_ECDH_SHA2_STEM) - 1);
54}
55
56const EVP_MD *
57kex_ecdh_name_to_evpmd(const char *kexname)
58{
59	int nid = kex_ecdh_name_to_nid(kexname);
60
61	if (nid == -1)
62		fatal("%s: unsupported ECDH curve \"%s\"", __func__, kexname);
63	return key_ec_nid_to_evpmd(nid);
64}
65
66void
67kex_ecdh_hash(
68    const EVP_MD *evp_md,
69    const EC_GROUP *ec_group,
70    char *client_version_string,
71    char *server_version_string,
72    char *ckexinit, int ckexinitlen,
73    char *skexinit, int skexinitlen,
74    u_char *serverhostkeyblob, int sbloblen,
75    const EC_POINT *client_dh_pub,
76    const EC_POINT *server_dh_pub,
77    const BIGNUM *shared_secret,
78    u_char **hash, u_int *hashlen)
79{
80	Buffer b;
81	EVP_MD_CTX md;
82	static u_char digest[EVP_MAX_MD_SIZE];
83
84	buffer_init(&b);
85	buffer_put_cstring(&b, client_version_string);
86	buffer_put_cstring(&b, server_version_string);
87
88	/* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
89	buffer_put_int(&b, ckexinitlen+1);
90	buffer_put_char(&b, SSH2_MSG_KEXINIT);
91	buffer_append(&b, ckexinit, ckexinitlen);
92	buffer_put_int(&b, skexinitlen+1);
93	buffer_put_char(&b, SSH2_MSG_KEXINIT);
94	buffer_append(&b, skexinit, skexinitlen);
95
96	buffer_put_string(&b, serverhostkeyblob, sbloblen);
97	buffer_put_ecpoint(&b, ec_group, client_dh_pub);
98	buffer_put_ecpoint(&b, ec_group, server_dh_pub);
99	buffer_put_bignum2(&b, shared_secret);
100
101#ifdef DEBUG_KEX
102	buffer_dump(&b);
103#endif
104	EVP_DigestInit(&md, evp_md);
105	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
106	EVP_DigestFinal(&md, digest, NULL);
107
108	buffer_free(&b);
109
110#ifdef DEBUG_KEX
111	dump_digest("hash", digest, EVP_MD_size(evp_md));
112#endif
113	*hash = digest;
114	*hashlen = EVP_MD_size(evp_md);
115}
116
117#endif /* OPENSSL_HAS_ECC */
118