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>
40 #include "openbsd-compat/openssl-compat.h"
56 static int input_kex_dh_gex_group(int, u_int32_t, struct ssh *);
57 static int input_kex_dh_gex_reply(int, u_int32_t, struct ssh *);
60 kexgex_client(struct ssh *ssh)
62 struct kex *kex = ssh->kex;
66 nbits = dh_estimate(kex->dh_need * 8);
68 kex->min = DH_GRP_MIN;
69 kex->max = DH_GRP_MAX;
71 if (datafellows & SSH_BUG_DHGEX_LARGE)
72 kex->nbits = MINIMUM(kex->nbits, 4096);
74 if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST)) != 0 ||
75 (r = sshpkt_put_u32(ssh, kex->min)) != 0 ||
76 (r = sshpkt_put_u32(ssh, kex->nbits)) != 0 ||
77 (r = sshpkt_put_u32(ssh, kex->max)) != 0 ||
78 (r = sshpkt_send(ssh)) != 0)
80 debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent",
81 kex->min, kex->nbits, kex->max);
83 fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
84 kex->min, kex->nbits, kex->max);
86 ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP,
87 &input_kex_dh_gex_group);
94 input_kex_dh_gex_group(int type, u_int32_t seq, struct ssh *ssh)
96 struct kex *kex = ssh->kex;
97 BIGNUM *p = NULL, *g = NULL;
98 const BIGNUM *pub_key;
101 debug("got SSH2_MSG_KEX_DH_GEX_GROUP");
103 if ((p = BN_new()) == NULL ||
104 (g = BN_new()) == NULL) {
105 r = SSH_ERR_ALLOC_FAIL;
108 if ((r = sshpkt_get_bignum2(ssh, p)) != 0 ||
109 (r = sshpkt_get_bignum2(ssh, g)) != 0 ||
110 (r = sshpkt_get_end(ssh)) != 0)
112 if ((bits = BN_num_bits(p)) < 0 ||
113 (u_int)bits < kex->min || (u_int)bits > kex->max) {
114 r = SSH_ERR_DH_GEX_OUT_OF_RANGE;
117 if ((kex->dh = dh_new_group(g, p)) == NULL) {
118 r = SSH_ERR_ALLOC_FAIL;
121 p = g = NULL; /* belong to kex->dh now */
123 /* generate and send 'e', client DH public key */
124 if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
126 DH_get0_key(kex->dh, &pub_key, NULL);
127 if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_INIT)) != 0 ||
128 (r = sshpkt_put_bignum2(ssh, pub_key)) != 0 ||
129 (r = sshpkt_send(ssh)) != 0)
131 debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
133 DHparams_print_fp(stderr, kex->dh);
134 fprintf(stderr, "pub= ");
135 BN_print_fp(stderr, pub_key);
136 fprintf(stderr, "\n");
138 ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP, NULL);
139 ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REPLY, &input_kex_dh_gex_reply);
148 input_kex_dh_gex_reply(int type, u_int32_t seq, struct ssh *ssh)
150 struct kex *kex = ssh->kex;
151 BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
152 const BIGNUM *pub_key, *dh_p, *dh_g;
153 struct sshkey *server_host_key = NULL;
154 u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL;
155 u_char hash[SSH_DIGEST_MAX_LENGTH];
156 size_t klen = 0, slen, sbloblen, hashlen;
159 debug("got SSH2_MSG_KEX_DH_GEX_REPLY");
160 if (kex->verify_host_key == NULL) {
161 r = SSH_ERR_INVALID_ARGUMENT;
165 if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
167 (r = sshkey_from_blob(server_host_key_blob, sbloblen,
168 &server_host_key)) != 0)
170 if (server_host_key->type != kex->hostkey_type ||
171 (kex->hostkey_type == KEY_ECDSA &&
172 server_host_key->ecdsa_nid != kex->hostkey_nid)) {
173 r = SSH_ERR_KEY_TYPE_MISMATCH;
176 if (kex->verify_host_key(server_host_key, ssh) == -1) {
177 r = SSH_ERR_SIGNATURE_INVALID;
180 /* DH parameter f, server public DH key */
181 if ((dh_server_pub = BN_new()) == NULL) {
182 r = SSH_ERR_ALLOC_FAIL;
186 if ((r = sshpkt_get_bignum2(ssh, dh_server_pub)) != 0 ||
187 (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
188 (r = sshpkt_get_end(ssh)) != 0)
191 fprintf(stderr, "dh_server_pub= ");
192 BN_print_fp(stderr, dh_server_pub);
193 fprintf(stderr, "\n");
194 debug("bits %d", BN_num_bits(dh_server_pub));
196 if (!dh_pub_is_valid(kex->dh, dh_server_pub)) {
197 sshpkt_disconnect(ssh, "bad server public DH value");
198 r = SSH_ERR_MESSAGE_INCOMPLETE;
202 klen = DH_size(kex->dh);
203 if ((kbuf = malloc(klen)) == NULL ||
204 (shared_secret = BN_new()) == NULL) {
205 r = SSH_ERR_ALLOC_FAIL;
208 if ((kout = DH_compute_key(kbuf, dh_server_pub, kex->dh)) < 0 ||
209 BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
210 r = SSH_ERR_LIBCRYPTO_ERROR;
214 dump_digest("shared secret", kbuf, kout);
216 if (ssh->compat & SSH_OLD_DHGEX)
217 kex->min = kex->max = -1;
219 /* calc and verify H */
220 DH_get0_key(kex->dh, &pub_key, NULL);
221 DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g);
222 hashlen = sizeof(hash);
223 if ((r = kexgex_hash(
225 kex->client_version_string,
226 kex->server_version_string,
227 sshbuf_ptr(kex->my), sshbuf_len(kex->my),
228 sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
229 server_host_key_blob, sbloblen,
230 kex->min, kex->nbits, kex->max,
235 hash, &hashlen)) != 0)
238 if ((r = sshkey_verify(server_host_key, signature, slen, hash,
239 hashlen, kex->hostkey_alg, ssh->compat)) != 0)
242 /* save session id */
243 if (kex->session_id == NULL) {
244 kex->session_id_len = hashlen;
245 kex->session_id = malloc(kex->session_id_len);
246 if (kex->session_id == NULL) {
247 r = SSH_ERR_ALLOC_FAIL;
250 memcpy(kex->session_id, hash, kex->session_id_len);
253 if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
254 r = kex_send_newkeys(ssh);
256 explicit_bzero(hash, sizeof(hash));
259 BN_clear_free(dh_server_pub);
261 explicit_bzero(kbuf, klen);
264 BN_clear_free(shared_secret);
265 sshkey_free(server_host_key);
266 free(server_host_key_blob);
270 #endif /* WITH_OPENSSL */