1 /* $OpenBSD: kexgexc.c,v 1.27 2018/02/07 02:06:51 jsing Exp $ */
3 * Copyright (c) 2000 Niels Provos. All rights reserved.
4 * Copyright (c) 2001 Markus Friedl. All rights reserved.
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
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.
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.
31 #include <sys/types.h>
33 #include <openssl/dh.h>
54 static int input_kex_dh_gex_group(int, u_int32_t, struct ssh *);
55 static int input_kex_dh_gex_reply(int, u_int32_t, struct ssh *);
58 kexgex_client(struct ssh *ssh)
60 struct kex *kex = ssh->kex;
64 nbits = dh_estimate(kex->dh_need * 8);
66 kex->min = DH_GRP_MIN;
67 kex->max = DH_GRP_MAX;
69 if (datafellows & SSH_BUG_DHGEX_LARGE)
70 kex->nbits = MINIMUM(kex->nbits, 4096);
72 if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST)) != 0 ||
73 (r = sshpkt_put_u32(ssh, kex->min)) != 0 ||
74 (r = sshpkt_put_u32(ssh, kex->nbits)) != 0 ||
75 (r = sshpkt_put_u32(ssh, kex->max)) != 0 ||
76 (r = sshpkt_send(ssh)) != 0)
78 debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent",
79 kex->min, kex->nbits, kex->max);
81 fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
82 kex->min, kex->nbits, kex->max);
84 ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP,
85 &input_kex_dh_gex_group);
92 input_kex_dh_gex_group(int type, u_int32_t seq, struct ssh *ssh)
94 struct kex *kex = ssh->kex;
95 BIGNUM *p = NULL, *g = NULL;
98 debug("got SSH2_MSG_KEX_DH_GEX_GROUP");
100 if ((p = BN_new()) == NULL ||
101 (g = BN_new()) == NULL) {
102 r = SSH_ERR_ALLOC_FAIL;
105 if ((r = sshpkt_get_bignum2(ssh, p)) != 0 ||
106 (r = sshpkt_get_bignum2(ssh, g)) != 0 ||
107 (r = sshpkt_get_end(ssh)) != 0)
109 if ((bits = BN_num_bits(p)) < 0 ||
110 (u_int)bits < kex->min || (u_int)bits > kex->max) {
111 r = SSH_ERR_DH_GEX_OUT_OF_RANGE;
114 if ((kex->dh = dh_new_group(g, p)) == NULL) {
115 r = SSH_ERR_ALLOC_FAIL;
118 p = g = NULL; /* belong to kex->dh now */
120 /* generate and send 'e', client DH public key */
121 if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0 ||
122 (r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_INIT)) != 0 ||
123 (r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 ||
124 (r = sshpkt_send(ssh)) != 0)
126 debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
128 DHparams_print_fp(stderr, kex->dh);
129 fprintf(stderr, "pub= ");
130 BN_print_fp(stderr, kex->dh->pub_key);
131 fprintf(stderr, "\n");
133 ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP, NULL);
134 ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REPLY, &input_kex_dh_gex_reply);
143 input_kex_dh_gex_reply(int type, u_int32_t seq, struct ssh *ssh)
145 struct kex *kex = ssh->kex;
146 BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
147 struct sshkey *server_host_key = NULL;
148 u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL;
149 u_char hash[SSH_DIGEST_MAX_LENGTH];
150 size_t klen = 0, slen, sbloblen, hashlen;
153 debug("got SSH2_MSG_KEX_DH_GEX_REPLY");
154 if (kex->verify_host_key == NULL) {
155 r = SSH_ERR_INVALID_ARGUMENT;
159 if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
161 (r = sshkey_from_blob(server_host_key_blob, sbloblen,
162 &server_host_key)) != 0)
164 if (server_host_key->type != kex->hostkey_type ||
165 (kex->hostkey_type == KEY_ECDSA &&
166 server_host_key->ecdsa_nid != kex->hostkey_nid)) {
167 r = SSH_ERR_KEY_TYPE_MISMATCH;
170 if (kex->verify_host_key(server_host_key, ssh) == -1) {
171 r = SSH_ERR_SIGNATURE_INVALID;
174 /* DH parameter f, server public DH key */
175 if ((dh_server_pub = BN_new()) == NULL) {
176 r = SSH_ERR_ALLOC_FAIL;
180 if ((r = sshpkt_get_bignum2(ssh, dh_server_pub)) != 0 ||
181 (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
182 (r = sshpkt_get_end(ssh)) != 0)
185 fprintf(stderr, "dh_server_pub= ");
186 BN_print_fp(stderr, dh_server_pub);
187 fprintf(stderr, "\n");
188 debug("bits %d", BN_num_bits(dh_server_pub));
190 if (!dh_pub_is_valid(kex->dh, dh_server_pub)) {
191 sshpkt_disconnect(ssh, "bad server public DH value");
192 r = SSH_ERR_MESSAGE_INCOMPLETE;
196 klen = DH_size(kex->dh);
197 if ((kbuf = malloc(klen)) == NULL ||
198 (shared_secret = BN_new()) == NULL) {
199 r = SSH_ERR_ALLOC_FAIL;
202 if ((kout = DH_compute_key(kbuf, dh_server_pub, kex->dh)) < 0 ||
203 BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
204 r = SSH_ERR_LIBCRYPTO_ERROR;
208 dump_digest("shared secret", kbuf, kout);
210 if (ssh->compat & SSH_OLD_DHGEX)
211 kex->min = kex->max = -1;
213 /* calc and verify H */
214 hashlen = sizeof(hash);
215 if ((r = kexgex_hash(
217 kex->client_version_string,
218 kex->server_version_string,
219 sshbuf_ptr(kex->my), sshbuf_len(kex->my),
220 sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
221 server_host_key_blob, sbloblen,
222 kex->min, kex->nbits, kex->max,
223 kex->dh->p, kex->dh->g,
227 hash, &hashlen)) != 0)
230 if ((r = sshkey_verify(server_host_key, signature, slen, hash,
231 hashlen, kex->hostkey_alg, ssh->compat)) != 0)
234 /* save session id */
235 if (kex->session_id == NULL) {
236 kex->session_id_len = hashlen;
237 kex->session_id = malloc(kex->session_id_len);
238 if (kex->session_id == NULL) {
239 r = SSH_ERR_ALLOC_FAIL;
242 memcpy(kex->session_id, hash, kex->session_id_len);
245 if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
246 r = kex_send_newkeys(ssh);
248 explicit_bzero(hash, sizeof(hash));
251 BN_clear_free(dh_server_pub);
253 explicit_bzero(kbuf, klen);
256 BN_clear_free(shared_secret);
257 sshkey_free(server_host_key);
258 free(server_host_key_blob);
262 #endif /* WITH_OPENSSL */