1 /* $OpenBSD: kexdhs.c,v 1.24 2016/05/02 10:26:04 djm Exp $ */
2 /*
3 * Copyright (c) 2001 Markus Friedl. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26 #include "includes.h"
27
28 #ifdef WITH_OPENSSL
29
30 #include <sys/types.h>
31
32 #include <stdarg.h>
33 #include <string.h>
34 #include <signal.h>
35
36 #include <openssl/dh.h>
37
38 #include "sshkey.h"
39 #include "cipher.h"
40 #include "digest.h"
41 #include "kex.h"
42 #include "log.h"
43 #include "packet.h"
44 #include "dh.h"
45 #include "ssh2.h"
46
47 #include "dispatch.h"
48 #include "compat.h"
49 #include "ssherr.h"
50 #include "sshbuf.h"
51
52 static int input_kex_dh_init(int, u_int32_t, void *);
53
54 int
kexdh_server(struct ssh * ssh)55 kexdh_server(struct ssh *ssh)
56 {
57 struct kex *kex = ssh->kex;
58 int r;
59
60 /* generate server DH public key */
61 switch (kex->kex_type) {
62 case KEX_DH_GRP1_SHA1:
63 kex->dh = dh_new_group1();
64 break;
65 case KEX_DH_GRP14_SHA1:
66 case KEX_DH_GRP14_SHA256:
67 kex->dh = dh_new_group14();
68 break;
69 case KEX_DH_GRP16_SHA512:
70 kex->dh = dh_new_group16();
71 break;
72 case KEX_DH_GRP18_SHA512:
73 kex->dh = dh_new_group18();
74 break;
75 default:
76 r = SSH_ERR_INVALID_ARGUMENT;
77 goto out;
78 }
79 if (kex->dh == NULL) {
80 r = SSH_ERR_ALLOC_FAIL;
81 goto out;
82 }
83 if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
84 goto out;
85
86 debug("expecting SSH2_MSG_KEXDH_INIT");
87 ssh_dispatch_set(ssh, SSH2_MSG_KEXDH_INIT, &input_kex_dh_init);
88 r = 0;
89 out:
90 return r;
91 }
92
93 int
input_kex_dh_init(int type,u_int32_t seq,void * ctxt)94 input_kex_dh_init(int type, u_int32_t seq, void *ctxt)
95 {
96 struct ssh *ssh = ctxt;
97 struct kex *kex = ssh->kex;
98 BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
99 struct sshkey *server_host_public, *server_host_private;
100 u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL;
101 u_char hash[SSH_DIGEST_MAX_LENGTH];
102 size_t sbloblen, slen;
103 size_t klen = 0, hashlen;
104 int kout, r;
105
106 if (kex->load_host_public_key == NULL ||
107 kex->load_host_private_key == NULL) {
108 r = SSH_ERR_INVALID_ARGUMENT;
109 goto out;
110 }
111 server_host_public = kex->load_host_public_key(kex->hostkey_type,
112 kex->hostkey_nid, ssh);
113 server_host_private = kex->load_host_private_key(kex->hostkey_type,
114 kex->hostkey_nid, ssh);
115 if (server_host_public == NULL) {
116 r = SSH_ERR_NO_HOSTKEY_LOADED;
117 goto out;
118 }
119
120 /* key, cert */
121 if ((dh_client_pub = BN_new()) == NULL) {
122 r = SSH_ERR_ALLOC_FAIL;
123 goto out;
124 }
125 if ((r = sshpkt_get_bignum2(ssh, dh_client_pub)) != 0 ||
126 (r = sshpkt_get_end(ssh)) != 0)
127 goto out;
128
129 #ifdef DEBUG_KEXDH
130 fprintf(stderr, "dh_client_pub= ");
131 BN_print_fp(stderr, dh_client_pub);
132 fprintf(stderr, "\n");
133 debug("bits %d", BN_num_bits(dh_client_pub));
134 #endif
135
136 #ifdef DEBUG_KEXDH
137 DHparams_print_fp(stderr, kex->dh);
138 fprintf(stderr, "pub= ");
139 BN_print_fp(stderr, kex->dh->pub_key);
140 fprintf(stderr, "\n");
141 #endif
142 if (!dh_pub_is_valid(kex->dh, dh_client_pub)) {
143 sshpkt_disconnect(ssh, "bad client public DH value");
144 r = SSH_ERR_MESSAGE_INCOMPLETE;
145 goto out;
146 }
147
148 klen = DH_size(kex->dh);
149 if ((kbuf = malloc(klen)) == NULL ||
150 (shared_secret = BN_new()) == NULL) {
151 r = SSH_ERR_ALLOC_FAIL;
152 goto out;
153 }
154 if ((kout = DH_compute_key(kbuf, dh_client_pub, kex->dh)) < 0 ||
155 BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
156 r = SSH_ERR_LIBCRYPTO_ERROR;
157 goto out;
158 }
159 #ifdef DEBUG_KEXDH
160 dump_digest("shared secret", kbuf, kout);
161 #endif
162 if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
163 &sbloblen)) != 0)
164 goto out;
165 /* calc H */
166 hashlen = sizeof(hash);
167 if ((r = kex_dh_hash(
168 kex->hash_alg,
169 kex->client_version_string,
170 kex->server_version_string,
171 sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
172 sshbuf_ptr(kex->my), sshbuf_len(kex->my),
173 server_host_key_blob, sbloblen,
174 dh_client_pub,
175 kex->dh->pub_key,
176 shared_secret,
177 hash, &hashlen)) != 0)
178 goto out;
179
180 /* save session id := H */
181 if (kex->session_id == NULL) {
182 kex->session_id_len = hashlen;
183 kex->session_id = malloc(kex->session_id_len);
184 if (kex->session_id == NULL) {
185 r = SSH_ERR_ALLOC_FAIL;
186 goto out;
187 }
188 memcpy(kex->session_id, hash, kex->session_id_len);
189 }
190
191 /* sign H */
192 if ((r = kex->sign(server_host_private, server_host_public, &signature,
193 &slen, hash, hashlen, kex->hostkey_alg, ssh->compat)) < 0)
194 goto out;
195
196 /* destroy_sensitive_data(); */
197
198 /* send server hostkey, DH pubkey 'f' and singed H */
199 if ((r = sshpkt_start(ssh, SSH2_MSG_KEXDH_REPLY)) != 0 ||
200 (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
201 (r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 || /* f */
202 (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
203 (r = sshpkt_send(ssh)) != 0)
204 goto out;
205
206 if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
207 r = kex_send_newkeys(ssh);
208 out:
209 explicit_bzero(hash, sizeof(hash));
210 DH_free(kex->dh);
211 kex->dh = NULL;
212 if (dh_client_pub)
213 BN_clear_free(dh_client_pub);
214 if (kbuf) {
215 explicit_bzero(kbuf, klen);
216 free(kbuf);
217 }
218 if (shared_secret)
219 BN_clear_free(shared_secret);
220 free(server_host_key_blob);
221 free(signature);
222 return r;
223 }
224 #endif /* WITH_OPENSSL */
225