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
48 int
kex_ecdh_name_to_nid(const char * kexname)49 kex_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
56 const EVP_MD *
kex_ecdh_name_to_evpmd(const char * kexname)57 kex_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
66 void
kex_ecdh_hash(const EVP_MD * evp_md,const EC_GROUP * ec_group,char * client_version_string,char * server_version_string,char * ckexinit,int ckexinitlen,char * skexinit,int skexinitlen,u_char * serverhostkeyblob,int sbloblen,const EC_POINT * client_dh_pub,const EC_POINT * server_dh_pub,const BIGNUM * shared_secret,u_char ** hash,u_int * hashlen)67 kex_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