1 /* $OpenBSD: kexgexs.c,v 1.33 2018/04/10 00:10:49 djm 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.
37 #include <openssl/dh.h>
51 #include "monitor_wrap.h"
57 static int input_kex_dh_gex_request(int, u_int32_t, struct ssh *);
58 static int input_kex_dh_gex_init(int, u_int32_t, struct ssh *);
61 kexgex_server(struct ssh *ssh)
63 ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST,
64 &input_kex_dh_gex_request);
65 debug("expecting SSH2_MSG_KEX_DH_GEX_REQUEST");
70 input_kex_dh_gex_request(int type, u_int32_t seq, struct ssh *ssh)
72 struct kex *kex = ssh->kex;
74 u_int min = 0, max = 0, nbits = 0;
76 debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
77 if ((r = sshpkt_get_u32(ssh, &min)) != 0 ||
78 (r = sshpkt_get_u32(ssh, &nbits)) != 0 ||
79 (r = sshpkt_get_u32(ssh, &max)) != 0 ||
80 (r = sshpkt_get_end(ssh)) != 0)
85 min = MAXIMUM(DH_GRP_MIN, min);
86 max = MINIMUM(DH_GRP_MAX, max);
87 nbits = MAXIMUM(DH_GRP_MIN, nbits);
88 nbits = MINIMUM(DH_GRP_MAX, nbits);
90 if (kex->max < kex->min || kex->nbits < kex->min ||
91 kex->max < kex->nbits || kex->max < DH_GRP_MIN) {
92 r = SSH_ERR_DH_GEX_OUT_OF_RANGE;
96 /* Contact privileged parent */
97 kex->dh = PRIVSEP(choose_dh(min, nbits, max));
98 if (kex->dh == NULL) {
99 sshpkt_disconnect(ssh, "no matching DH grp found");
100 r = SSH_ERR_ALLOC_FAIL;
103 debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
104 if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_GROUP)) != 0 ||
105 (r = sshpkt_put_bignum2(ssh, kex->dh->p)) != 0 ||
106 (r = sshpkt_put_bignum2(ssh, kex->dh->g)) != 0 ||
107 (r = sshpkt_send(ssh)) != 0)
110 /* Compute our exchange value in parallel with the client */
111 if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
114 debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
115 ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_INIT, &input_kex_dh_gex_init);
122 input_kex_dh_gex_init(int type, u_int32_t seq, struct ssh *ssh)
124 struct kex *kex = ssh->kex;
125 BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
126 struct sshkey *server_host_public, *server_host_private;
127 u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL;
128 u_char hash[SSH_DIGEST_MAX_LENGTH];
129 size_t sbloblen, slen;
130 size_t klen = 0, hashlen;
133 if (kex->load_host_public_key == NULL ||
134 kex->load_host_private_key == NULL) {
135 r = SSH_ERR_INVALID_ARGUMENT;
138 server_host_public = kex->load_host_public_key(kex->hostkey_type,
139 kex->hostkey_nid, ssh);
140 server_host_private = kex->load_host_private_key(kex->hostkey_type,
141 kex->hostkey_nid, ssh);
142 if (server_host_public == NULL) {
143 r = SSH_ERR_NO_HOSTKEY_LOADED;
148 if ((dh_client_pub = BN_new()) == NULL) {
149 r = SSH_ERR_ALLOC_FAIL;
152 if ((r = sshpkt_get_bignum2(ssh, dh_client_pub)) != 0 ||
153 (r = sshpkt_get_end(ssh)) != 0)
157 fprintf(stderr, "dh_client_pub= ");
158 BN_print_fp(stderr, dh_client_pub);
159 fprintf(stderr, "\n");
160 debug("bits %d", BN_num_bits(dh_client_pub));
164 DHparams_print_fp(stderr, kex->dh);
165 fprintf(stderr, "pub= ");
166 BN_print_fp(stderr, kex->dh->pub_key);
167 fprintf(stderr, "\n");
169 if (!dh_pub_is_valid(kex->dh, dh_client_pub)) {
170 sshpkt_disconnect(ssh, "bad client public DH value");
171 r = SSH_ERR_MESSAGE_INCOMPLETE;
175 klen = DH_size(kex->dh);
176 if ((kbuf = malloc(klen)) == NULL ||
177 (shared_secret = BN_new()) == NULL) {
178 r = SSH_ERR_ALLOC_FAIL;
181 if ((kout = DH_compute_key(kbuf, dh_client_pub, kex->dh)) < 0 ||
182 BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
183 r = SSH_ERR_LIBCRYPTO_ERROR;
187 dump_digest("shared secret", kbuf, kout);
189 if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
193 hashlen = sizeof(hash);
194 if ((r = kexgex_hash(
196 kex->client_version_string,
197 kex->server_version_string,
198 sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
199 sshbuf_ptr(kex->my), sshbuf_len(kex->my),
200 server_host_key_blob, sbloblen,
201 kex->min, kex->nbits, kex->max,
202 kex->dh->p, kex->dh->g,
206 hash, &hashlen)) != 0)
209 /* save session id := H */
210 if (kex->session_id == NULL) {
211 kex->session_id_len = hashlen;
212 kex->session_id = malloc(kex->session_id_len);
213 if (kex->session_id == NULL) {
214 r = SSH_ERR_ALLOC_FAIL;
217 memcpy(kex->session_id, hash, kex->session_id_len);
221 if ((r = kex->sign(server_host_private, server_host_public, &signature,
222 &slen, hash, hashlen, kex->hostkey_alg, ssh->compat)) < 0)
225 /* destroy_sensitive_data(); */
227 /* send server hostkey, DH pubkey 'f' and signed H */
228 if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REPLY)) != 0 ||
229 (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
230 (r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 || /* f */
231 (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
232 (r = sshpkt_send(ssh)) != 0)
235 if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
236 r = kex_send_newkeys(ssh);
240 BN_clear_free(dh_client_pub);
242 explicit_bzero(kbuf, klen);
245 BN_clear_free(shared_secret);
246 free(server_host_key_blob);
250 #endif /* WITH_OPENSSL */