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jsing@openbsd.org7cd31632018-02-07 02:06:50 +00001/* $OpenBSD: kexgexc.c,v 1.27 2018/02/07 02:06:51 jsing Exp $ */
Damien Miller8e7fb332003-02-24 12:03:03 +11002/*
3 * Copyright (c) 2000 Niels Provos. All rights reserved.
4 * Copyright (c) 2001 Markus Friedl. 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"
Damien Miller8e7fb332003-02-24 12:03:03 +110028
Damien Miller72ef7c12015-01-15 02:21:31 +110029#ifdef WITH_OPENSSL
30
Damien Millerd7834352006-08-05 12:39:39 +100031#include <sys/types.h>
32
Damien Miller4499f4c2010-11-20 15:15:49 +110033#include <openssl/dh.h>
34
Damien Millerded319c2006-09-01 15:38:36 +100035#include <stdarg.h>
Damien Millera7a73ee2006-08-05 11:37:59 +100036#include <stdio.h>
Damien Millere3476ed2006-07-24 14:13:33 +100037#include <string.h>
Damien Millerd7834352006-08-05 12:39:39 +100038#include <signal.h>
Damien Millere3476ed2006-07-24 14:13:33 +100039
Damien Miller48f54b92018-09-13 12:13:50 +100040#include "openbsd-compat/openssl-compat.h"
41
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000042#include "sshkey.h"
Damien Millerd7834352006-08-05 12:39:39 +100043#include "cipher.h"
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000044#include "digest.h"
Damien Miller8e7fb332003-02-24 12:03:03 +110045#include "kex.h"
46#include "log.h"
47#include "packet.h"
48#include "dh.h"
49#include "ssh2.h"
50#include "compat.h"
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000051#include "dispatch.h"
52#include "ssherr.h"
53#include "sshbuf.h"
deraadt@openbsd.org9136ec12016-09-12 01:22:38 +000054#include "misc.h"
Damien Miller8e7fb332003-02-24 12:03:03 +110055
markus@openbsd.org2ae666a2017-05-30 14:23:52 +000056static int input_kex_dh_gex_group(int, u_int32_t, struct ssh *);
57static int input_kex_dh_gex_reply(int, u_int32_t, struct ssh *);
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000058
59int
60kexgex_client(struct ssh *ssh)
Damien Miller8e7fb332003-02-24 12:03:03 +110061{
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000062 struct kex *kex = ssh->kex;
63 int r;
64 u_int nbits;
Damien Miller8e7fb332003-02-24 12:03:03 +110065
Damien Miller76eea4a2014-01-26 09:37:25 +110066 nbits = dh_estimate(kex->dh_need * 8);
Damien Miller8e7fb332003-02-24 12:03:03 +110067
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000068 kex->min = DH_GRP_MIN;
69 kex->max = DH_GRP_MAX;
70 kex->nbits = nbits;
dtucker@openbsd.orgb282fec2015-05-26 23:23:40 +000071 if (datafellows & SSH_BUG_DHGEX_LARGE)
deraadt@openbsd.org9136ec12016-09-12 01:22:38 +000072 kex->nbits = MINIMUM(kex->nbits, 4096);
djm@openbsd.org318be282015-04-13 02:04:08 +000073 /* New GEX request */
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)
79 goto out;
80 debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent",
81 kex->min, kex->nbits, kex->max);
Damien Miller8e7fb332003-02-24 12:03:03 +110082#ifdef DEBUG_KEXDH
83 fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000084 kex->min, kex->nbits, kex->max);
Damien Miller8e7fb332003-02-24 12:03:03 +110085#endif
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000086 ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP,
87 &input_kex_dh_gex_group);
88 r = 0;
89 out:
90 return r;
91}
Damien Miller8e7fb332003-02-24 12:03:03 +110092
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000093static int
markus@openbsd.org2ae666a2017-05-30 14:23:52 +000094input_kex_dh_gex_group(int type, u_int32_t seq, struct ssh *ssh)
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000095{
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000096 struct kex *kex = ssh->kex;
97 BIGNUM *p = NULL, *g = NULL;
djm@openbsd.org482d23b2018-09-13 02:08:33 +000098 const BIGNUM *pub_key;
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000099 int r, bits;
Damien Miller8e7fb332003-02-24 12:03:03 +1100100
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000101 debug("got SSH2_MSG_KEX_DH_GEX_GROUP");
Damien Miller8e7fb332003-02-24 12:03:03 +1100102
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000103 if ((p = BN_new()) == NULL ||
104 (g = BN_new()) == NULL) {
105 r = SSH_ERR_ALLOC_FAIL;
106 goto out;
107 }
108 if ((r = sshpkt_get_bignum2(ssh, p)) != 0 ||
109 (r = sshpkt_get_bignum2(ssh, g)) != 0 ||
110 (r = sshpkt_get_end(ssh)) != 0)
111 goto out;
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;
115 goto out;
116 }
117 if ((kex->dh = dh_new_group(g, p)) == NULL) {
118 r = SSH_ERR_ALLOC_FAIL;
119 goto out;
120 }
121 p = g = NULL; /* belong to kex->dh now */
Damien Miller8e7fb332003-02-24 12:03:03 +1100122
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000123 /* generate and send 'e', client DH public key */
djm@openbsd.org482d23b2018-09-13 02:08:33 +0000124 if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
125 goto out;
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 ||
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000129 (r = sshpkt_send(ssh)) != 0)
130 goto out;
131 debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
Damien Miller8e7fb332003-02-24 12:03:03 +1100132#ifdef DEBUG_KEXDH
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000133 DHparams_print_fp(stderr, kex->dh);
Damien Miller8e7fb332003-02-24 12:03:03 +1100134 fprintf(stderr, "pub= ");
djm@openbsd.org482d23b2018-09-13 02:08:33 +0000135 BN_print_fp(stderr, pub_key);
Damien Miller8e7fb332003-02-24 12:03:03 +1100136 fprintf(stderr, "\n");
137#endif
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000138 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);
140 r = 0;
141out:
jsing@openbsd.org7cd31632018-02-07 02:06:50 +0000142 BN_clear_free(p);
143 BN_clear_free(g);
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000144 return r;
145}
Damien Miller8e7fb332003-02-24 12:03:03 +1100146
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000147static int
markus@openbsd.org2ae666a2017-05-30 14:23:52 +0000148input_kex_dh_gex_reply(int type, u_int32_t seq, struct ssh *ssh)
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000149{
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000150 struct kex *kex = ssh->kex;
151 BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
djm@openbsd.org482d23b2018-09-13 02:08:33 +0000152 const BIGNUM *pub_key, *dh_p, *dh_g;
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000153 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;
157 int kout, r;
Damien Miller8e7fb332003-02-24 12:03:03 +1100158
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000159 debug("got SSH2_MSG_KEX_DH_GEX_REPLY");
160 if (kex->verify_host_key == NULL) {
161 r = SSH_ERR_INVALID_ARGUMENT;
162 goto out;
163 }
Damien Miller8e7fb332003-02-24 12:03:03 +1100164 /* key, cert */
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000165 if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
166 &sbloblen)) != 0 ||
167 (r = sshkey_from_blob(server_host_key_blob, sbloblen,
168 &server_host_key)) != 0)
169 goto out;
djm@openbsd.org5104db72015-01-26 06:10:03 +0000170 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;
174 goto out;
175 }
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000176 if (kex->verify_host_key(server_host_key, ssh) == -1) {
177 r = SSH_ERR_SIGNATURE_INVALID;
178 goto out;
179 }
Damien Millerad6b14d2006-06-13 13:00:41 +1000180 /* DH parameter f, server public DH key */
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000181 if ((dh_server_pub = BN_new()) == NULL) {
182 r = SSH_ERR_ALLOC_FAIL;
183 goto out;
184 }
185 /* signed H */
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)
189 goto out;
Damien Miller8e7fb332003-02-24 12:03:03 +1100190#ifdef DEBUG_KEXDH
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));
195#endif
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000196 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;
199 goto out;
200 }
Damien Miller8e7fb332003-02-24 12:03:03 +1100201
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000202 klen = DH_size(kex->dh);
203 if ((kbuf = malloc(klen)) == NULL ||
204 (shared_secret = BN_new()) == NULL) {
205 r = SSH_ERR_ALLOC_FAIL;
206 goto out;
207 }
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;
211 goto out;
212 }
Damien Miller8e7fb332003-02-24 12:03:03 +1100213#ifdef DEBUG_KEXDH
214 dump_digest("shared secret", kbuf, kout);
215#endif
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000216 if (ssh->compat & SSH_OLD_DHGEX)
217 kex->min = kex->max = -1;
Damien Miller8e7fb332003-02-24 12:03:03 +1100218
219 /* calc and verify H */
djm@openbsd.org482d23b2018-09-13 02:08:33 +0000220 DH_get0_key(kex->dh, &pub_key, NULL);
221 DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g);
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000222 hashlen = sizeof(hash);
223 if ((r = kexgex_hash(
Damien Millerb3051d02014-01-10 10:58:53 +1100224 kex->hash_alg,
Damien Miller8e7fb332003-02-24 12:03:03 +1100225 kex->client_version_string,
226 kex->server_version_string,
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000227 sshbuf_ptr(kex->my), sshbuf_len(kex->my),
228 sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
Damien Miller8e7fb332003-02-24 12:03:03 +1100229 server_host_key_blob, sbloblen,
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000230 kex->min, kex->nbits, kex->max,
djm@openbsd.org482d23b2018-09-13 02:08:33 +0000231 dh_p, dh_g,
232 pub_key,
Damien Miller8e7fb332003-02-24 12:03:03 +1100233 dh_server_pub,
Damien Miller19bb3a52005-11-05 15:19:35 +1100234 shared_secret,
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000235 hash, &hashlen)) != 0)
236 goto out;
Damien Miller19bb3a52005-11-05 15:19:35 +1100237
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000238 if ((r = sshkey_verify(server_host_key, signature, slen, hash,
djm@openbsd.org04c7e282017-12-18 02:25:15 +0000239 hashlen, kex->hostkey_alg, ssh->compat)) != 0)
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000240 goto out;
Damien Miller8e7fb332003-02-24 12:03:03 +1100241
242 /* save session id */
243 if (kex->session_id == NULL) {
Damien Miller19bb3a52005-11-05 15:19:35 +1100244 kex->session_id_len = hashlen;
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000245 kex->session_id = malloc(kex->session_id_len);
246 if (kex->session_id == NULL) {
247 r = SSH_ERR_ALLOC_FAIL;
248 goto out;
249 }
Damien Miller8e7fb332003-02-24 12:03:03 +1100250 memcpy(kex->session_id, hash, kex->session_id_len);
251 }
Damien Miller8e7fb332003-02-24 12:03:03 +1100252
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000253 if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
254 r = kex_send_newkeys(ssh);
255 out:
256 explicit_bzero(hash, sizeof(hash));
257 DH_free(kex->dh);
258 kex->dh = NULL;
jsing@openbsd.org7cd31632018-02-07 02:06:50 +0000259 BN_clear_free(dh_server_pub);
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000260 if (kbuf) {
261 explicit_bzero(kbuf, klen);
262 free(kbuf);
263 }
jsing@openbsd.org7cd31632018-02-07 02:06:50 +0000264 BN_clear_free(shared_secret);
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000265 sshkey_free(server_host_key);
266 free(server_host_key_blob);
267 free(signature);
268 return r;
Damien Miller8e7fb332003-02-24 12:03:03 +1100269}
Damien Miller72ef7c12015-01-15 02:21:31 +1100270#endif /* WITH_OPENSSL */