Branch data Line data Source code
1 : : /* $OpenBSD: kexecdhs.c,v 1.10 2014/02/02 03:44:31 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 : : #include <sys/types.h>
30 : : #include <string.h>
31 : : #include <signal.h>
32 : :
33 : : #include "xmalloc.h"
34 : : #include "buffer.h"
35 : : #include "key.h"
36 : : #include "cipher.h"
37 : : #include "kex.h"
38 : : #include "log.h"
39 : : #include "packet.h"
40 : : #include "ssh2.h"
41 : :
42 : : #ifdef OPENSSL_HAS_ECC
43 : :
44 : : #include <openssl/ecdh.h>
45 : :
46 : : void
47 : 24 : kexecdh_server(Kex *kex)
48 : : {
49 : : EC_POINT *client_public;
50 : : EC_KEY *server_key;
51 : : const EC_GROUP *group;
52 : : BIGNUM *shared_secret;
53 : : Key *server_host_private, *server_host_public;
54 : 24 : u_char *server_host_key_blob = NULL, *signature = NULL;
55 : : u_char *kbuf, *hash;
56 : : u_int klen, slen, sbloblen, hashlen;
57 : :
58 [ - + ]: 24 : if ((server_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL)
59 : 0 : fatal("%s: EC_KEY_new_by_curve_name failed", __func__);
60 [ - + ]: 24 : if (EC_KEY_generate_key(server_key) != 1)
61 : 0 : fatal("%s: EC_KEY_generate_key failed", __func__);
62 : 24 : group = EC_KEY_get0_group(server_key);
63 : :
64 : : #ifdef DEBUG_KEXECDH
65 : : fputs("server private key:\n", stderr);
66 : : key_dump_ec_key(server_key);
67 : : #endif
68 : :
69 [ + - ][ - + ]: 24 : if (kex->load_host_public_key == NULL ||
70 : 24 : kex->load_host_private_key == NULL)
71 : 0 : fatal("Cannot load hostkey");
72 : 24 : server_host_public = kex->load_host_public_key(kex->hostkey_type);
73 [ - + ]: 24 : if (server_host_public == NULL)
74 : 0 : fatal("Unsupported hostkey type %d", kex->hostkey_type);
75 : 24 : server_host_private = kex->load_host_private_key(kex->hostkey_type);
76 : :
77 : 24 : debug("expecting SSH2_MSG_KEX_ECDH_INIT");
78 : 24 : packet_read_expect(SSH2_MSG_KEX_ECDH_INIT);
79 [ - + ]: 24 : if ((client_public = EC_POINT_new(group)) == NULL)
80 : 0 : fatal("%s: EC_POINT_new failed", __func__);
81 : 24 : packet_get_ecpoint(group, client_public);
82 [ - + ]: 24 : packet_check_eom();
83 : :
84 [ - + ]: 24 : if (key_ec_validate_public(group, client_public) != 0)
85 : 0 : fatal("%s: invalid client public key", __func__);
86 : :
87 : : #ifdef DEBUG_KEXECDH
88 : : fputs("client public key:\n", stderr);
89 : : key_dump_ec_point(group, client_public);
90 : : #endif
91 : :
92 : : /* Calculate shared_secret */
93 : 24 : klen = (EC_GROUP_get_degree(group) + 7) / 8;
94 : 24 : kbuf = xmalloc(klen);
95 [ - + ]: 24 : if (ECDH_compute_key(kbuf, klen, client_public,
96 : : server_key, NULL) != (int)klen)
97 : 0 : fatal("%s: ECDH_compute_key failed", __func__);
98 : :
99 : : #ifdef DEBUG_KEXDH
100 : : dump_digest("shared secret", kbuf, klen);
101 : : #endif
102 [ - + ]: 24 : if ((shared_secret = BN_new()) == NULL)
103 : 0 : fatal("%s: BN_new failed", __func__);
104 [ - + ]: 24 : if (BN_bin2bn(kbuf, klen, shared_secret) == NULL)
105 : 0 : fatal("%s: BN_bin2bn failed", __func__);
106 : 24 : explicit_bzero(kbuf, klen);
107 : 24 : free(kbuf);
108 : :
109 : : /* calc H */
110 : 24 : key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
111 : 48 : kex_ecdh_hash(
112 : : kex->hash_alg,
113 : : group,
114 : : kex->client_version_string,
115 : : kex->server_version_string,
116 : 24 : buffer_ptr(&kex->peer), buffer_len(&kex->peer),
117 : 24 : buffer_ptr(&kex->my), buffer_len(&kex->my),
118 : : server_host_key_blob, sbloblen,
119 : : client_public,
120 : : EC_KEY_get0_public_key(server_key),
121 : : shared_secret,
122 : : &hash, &hashlen
123 : : );
124 : 24 : EC_POINT_clear_free(client_public);
125 : :
126 : : /* save session id := H */
127 [ + - ]: 24 : if (kex->session_id == NULL) {
128 : 24 : kex->session_id_len = hashlen;
129 : 24 : kex->session_id = xmalloc(kex->session_id_len);
130 : 24 : memcpy(kex->session_id, hash, kex->session_id_len);
131 : : }
132 : :
133 : : /* sign H */
134 : 24 : kex->sign(server_host_private, server_host_public, &signature, &slen,
135 : : hash, hashlen);
136 : :
137 : : /* destroy_sensitive_data(); */
138 : :
139 : : /* send server hostkey, ECDH pubkey 'Q_S' and signed H */
140 : 24 : packet_start(SSH2_MSG_KEX_ECDH_REPLY);
141 : 24 : packet_put_string(server_host_key_blob, sbloblen);
142 : 24 : packet_put_ecpoint(group, EC_KEY_get0_public_key(server_key));
143 : 24 : packet_put_string(signature, slen);
144 : 24 : packet_send();
145 : :
146 : 24 : free(signature);
147 : 24 : free(server_host_key_blob);
148 : : /* have keys, free server key */
149 : 24 : EC_KEY_free(server_key);
150 : :
151 : 24 : kex_derive_keys_bn(kex, hash, hashlen, shared_secret);
152 : 24 : BN_clear_free(shared_secret);
153 : 24 : kex_finish(kex);
154 : 24 : }
155 : : #else /* OPENSSL_HAS_ECC */
156 : : void
157 : : kexecdh_server(Kex *kex)
158 : : {
159 : : fatal("ECC support is not enabled");
160 : : }
161 : : #endif /* OPENSSL_HAS_ECC */
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