blob: 69348b964df82ce547bb515dd8f356fba202c91e [file] [log] [blame]
djm@openbsd.orgb7e74ea2019-11-25 00:51:37 +00001/* $OpenBSD: kexgen.c,v 1.4 2019/11/25 00:51:37 djm Exp $ */
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +00002/*
3 * Copyright (c) 2019 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
Damien Millerd50ab3c2019-01-22 00:02:23 +110026#include "includes.h"
27
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +000028#include <sys/types.h>
29
Darren Tucker9634ffb2019-07-23 22:25:44 +100030#include <stdarg.h>
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +000031#include <stdio.h>
32#include <string.h>
33#include <signal.h>
34
35#include "sshkey.h"
36#include "kex.h"
37#include "log.h"
38#include "packet.h"
39#include "ssh2.h"
40#include "sshbuf.h"
41#include "digest.h"
42#include "ssherr.h"
43
44static int input_kex_gen_init(int, u_int32_t, struct ssh *);
45static int input_kex_gen_reply(int type, u_int32_t seq, struct ssh *ssh);
46
47static int
48kex_gen_hash(
49 int hash_alg,
50 const struct sshbuf *client_version,
51 const struct sshbuf *server_version,
djm@openbsd.orgbb956ea2019-01-23 00:30:41 +000052 const struct sshbuf *client_kexinit,
53 const struct sshbuf *server_kexinit,
54 const struct sshbuf *server_host_key_blob,
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +000055 const struct sshbuf *client_pub,
56 const struct sshbuf *server_pub,
57 const struct sshbuf *shared_secret,
58 u_char *hash, size_t *hashlen)
59{
60 struct sshbuf *b;
61 int r;
62
63 if (*hashlen < ssh_digest_bytes(hash_alg))
64 return SSH_ERR_INVALID_ARGUMENT;
65 if ((b = sshbuf_new()) == NULL)
66 return SSH_ERR_ALLOC_FAIL;
67 if ((r = sshbuf_put_stringb(b, client_version)) != 0 ||
68 (r = sshbuf_put_stringb(b, server_version)) != 0 ||
69 /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
djm@openbsd.orgbb956ea2019-01-23 00:30:41 +000070 (r = sshbuf_put_u32(b, sshbuf_len(client_kexinit) + 1)) != 0 ||
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +000071 (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 ||
djm@openbsd.orgbb956ea2019-01-23 00:30:41 +000072 (r = sshbuf_putb(b, client_kexinit)) != 0 ||
73 (r = sshbuf_put_u32(b, sshbuf_len(server_kexinit) + 1)) != 0 ||
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +000074 (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 ||
djm@openbsd.orgbb956ea2019-01-23 00:30:41 +000075 (r = sshbuf_putb(b, server_kexinit)) != 0 ||
76 (r = sshbuf_put_stringb(b, server_host_key_blob)) != 0 ||
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +000077 (r = sshbuf_put_stringb(b, client_pub)) != 0 ||
78 (r = sshbuf_put_stringb(b, server_pub)) != 0 ||
79 (r = sshbuf_putb(b, shared_secret)) != 0) {
80 sshbuf_free(b);
81 return r;
82 }
83#ifdef DEBUG_KEX
84 sshbuf_dump(b, stderr);
85#endif
86 if (ssh_digest_buffer(hash_alg, b, hash, *hashlen) != 0) {
87 sshbuf_free(b);
88 return SSH_ERR_LIBCRYPTO_ERROR;
89 }
90 sshbuf_free(b);
91 *hashlen = ssh_digest_bytes(hash_alg);
92#ifdef DEBUG_KEX
93 dump_digest("hash", hash, *hashlen);
94#endif
95 return 0;
96}
97
98int
99kex_gen_client(struct ssh *ssh)
100{
101 struct kex *kex = ssh->kex;
102 int r;
103
104 switch (kex->kex_type) {
Darren Tucker9edbd782019-03-14 10:17:28 +1100105#ifdef WITH_OPENSSL
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +0000106 case KEX_DH_GRP1_SHA1:
107 case KEX_DH_GRP14_SHA1:
108 case KEX_DH_GRP14_SHA256:
109 case KEX_DH_GRP16_SHA512:
110 case KEX_DH_GRP18_SHA512:
111 r = kex_dh_keypair(kex);
112 break;
113 case KEX_ECDH_SHA2:
114 r = kex_ecdh_keypair(kex);
115 break;
Darren Tucker9edbd782019-03-14 10:17:28 +1100116#endif
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +0000117 case KEX_C25519_SHA256:
118 r = kex_c25519_keypair(kex);
119 break;
120 case KEX_KEM_SNTRUP4591761X25519_SHA512:
121 r = kex_kem_sntrup4591761x25519_keypair(kex);
122 break;
123 default:
124 r = SSH_ERR_INVALID_ARGUMENT;
125 break;
126 }
127 if (r != 0)
128 return r;
129 if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_INIT)) != 0 ||
130 (r = sshpkt_put_stringb(ssh, kex->client_pub)) != 0 ||
131 (r = sshpkt_send(ssh)) != 0)
132 return r;
133 debug("expecting SSH2_MSG_KEX_ECDH_REPLY");
134 ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_REPLY, &input_kex_gen_reply);
135 return 0;
136}
137
138static int
139input_kex_gen_reply(int type, u_int32_t seq, struct ssh *ssh)
140{
141 struct kex *kex = ssh->kex;
142 struct sshkey *server_host_key = NULL;
143 struct sshbuf *shared_secret = NULL;
144 struct sshbuf *server_blob = NULL;
djm@openbsd.orgbb956ea2019-01-23 00:30:41 +0000145 struct sshbuf *tmp = NULL, *server_host_key_blob = NULL;
146 u_char *signature = NULL;
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +0000147 u_char hash[SSH_DIGEST_MAX_LENGTH];
djm@openbsd.orgbb956ea2019-01-23 00:30:41 +0000148 size_t slen, hashlen;
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +0000149 int r;
150
151 /* hostkey */
djm@openbsd.orgbb956ea2019-01-23 00:30:41 +0000152 if ((r = sshpkt_getb_froms(ssh, &server_host_key_blob)) != 0)
153 goto out;
154 /* sshkey_fromb() consumes its buffer, so make a copy */
155 if ((tmp = sshbuf_fromb(server_host_key_blob)) == NULL) {
156 r = SSH_ERR_ALLOC_FAIL;
157 goto out;
158 }
159 if ((r = sshkey_fromb(tmp, &server_host_key)) != 0)
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +0000160 goto out;
161 if ((r = kex_verify_host_key(ssh, server_host_key)) != 0)
162 goto out;
163
164 /* Q_S, server public key */
165 /* signed H */
166 if ((r = sshpkt_getb_froms(ssh, &server_blob)) != 0 ||
167 (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
168 (r = sshpkt_get_end(ssh)) != 0)
169 goto out;
170
171 /* compute shared secret */
172 switch (kex->kex_type) {
Darren Tucker9edbd782019-03-14 10:17:28 +1100173#ifdef WITH_OPENSSL
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +0000174 case KEX_DH_GRP1_SHA1:
175 case KEX_DH_GRP14_SHA1:
176 case KEX_DH_GRP14_SHA256:
177 case KEX_DH_GRP16_SHA512:
178 case KEX_DH_GRP18_SHA512:
179 r = kex_dh_dec(kex, server_blob, &shared_secret);
180 break;
181 case KEX_ECDH_SHA2:
182 r = kex_ecdh_dec(kex, server_blob, &shared_secret);
183 break;
Darren Tucker9edbd782019-03-14 10:17:28 +1100184#endif
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +0000185 case KEX_C25519_SHA256:
186 r = kex_c25519_dec(kex, server_blob, &shared_secret);
187 break;
188 case KEX_KEM_SNTRUP4591761X25519_SHA512:
189 r = kex_kem_sntrup4591761x25519_dec(kex, server_blob,
190 &shared_secret);
191 break;
192 default:
193 r = SSH_ERR_INVALID_ARGUMENT;
194 break;
195 }
196 if (r !=0 )
197 goto out;
198
199 /* calc and verify H */
200 hashlen = sizeof(hash);
201 if ((r = kex_gen_hash(
202 kex->hash_alg,
203 kex->client_version,
204 kex->server_version,
djm@openbsd.orgbb956ea2019-01-23 00:30:41 +0000205 kex->my,
206 kex->peer,
207 server_host_key_blob,
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +0000208 kex->client_pub,
209 server_blob,
210 shared_secret,
211 hash, &hashlen)) != 0)
212 goto out;
213
214 if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
djm@openbsd.orgb7e74ea2019-11-25 00:51:37 +0000215 kex->hostkey_alg, ssh->compat, NULL)) != 0)
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +0000216 goto out;
217
218 if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
219 r = kex_send_newkeys(ssh);
220out:
221 explicit_bzero(hash, sizeof(hash));
222 explicit_bzero(kex->c25519_client_key, sizeof(kex->c25519_client_key));
223 explicit_bzero(kex->sntrup4591761_client_key,
224 sizeof(kex->sntrup4591761_client_key));
djm@openbsd.orgbb956ea2019-01-23 00:30:41 +0000225 sshbuf_free(server_host_key_blob);
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +0000226 free(signature);
djm@openbsd.orgbb956ea2019-01-23 00:30:41 +0000227 sshbuf_free(tmp);
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +0000228 sshkey_free(server_host_key);
229 sshbuf_free(server_blob);
230 sshbuf_free(shared_secret);
231 sshbuf_free(kex->client_pub);
232 kex->client_pub = NULL;
233 return r;
234}
235
236int
237kex_gen_server(struct ssh *ssh)
238{
239 debug("expecting SSH2_MSG_KEX_ECDH_INIT");
240 ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_INIT, &input_kex_gen_init);
241 return 0;
242}
243
244static int
245input_kex_gen_init(int type, u_int32_t seq, struct ssh *ssh)
246{
247 struct kex *kex = ssh->kex;
248 struct sshkey *server_host_private, *server_host_public;
249 struct sshbuf *shared_secret = NULL;
250 struct sshbuf *server_pubkey = NULL;
251 struct sshbuf *client_pubkey = NULL;
djm@openbsd.orgbb956ea2019-01-23 00:30:41 +0000252 struct sshbuf *server_host_key_blob = NULL;
253 u_char *signature = NULL, hash[SSH_DIGEST_MAX_LENGTH];
254 size_t slen, hashlen;
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +0000255 int r;
256
257 if ((r = kex_load_hostkey(ssh, &server_host_private,
258 &server_host_public)) != 0)
259 goto out;
260
261 if ((r = sshpkt_getb_froms(ssh, &client_pubkey)) != 0 ||
262 (r = sshpkt_get_end(ssh)) != 0)
263 goto out;
264
265 /* compute shared secret */
266 switch (kex->kex_type) {
Darren Tucker9edbd782019-03-14 10:17:28 +1100267#ifdef WITH_OPENSSL
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +0000268 case KEX_DH_GRP1_SHA1:
269 case KEX_DH_GRP14_SHA1:
270 case KEX_DH_GRP14_SHA256:
271 case KEX_DH_GRP16_SHA512:
272 case KEX_DH_GRP18_SHA512:
273 r = kex_dh_enc(kex, client_pubkey, &server_pubkey,
274 &shared_secret);
275 break;
276 case KEX_ECDH_SHA2:
277 r = kex_ecdh_enc(kex, client_pubkey, &server_pubkey,
278 &shared_secret);
279 break;
Darren Tucker9edbd782019-03-14 10:17:28 +1100280#endif
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +0000281 case KEX_C25519_SHA256:
282 r = kex_c25519_enc(kex, client_pubkey, &server_pubkey,
283 &shared_secret);
284 break;
285 case KEX_KEM_SNTRUP4591761X25519_SHA512:
286 r = kex_kem_sntrup4591761x25519_enc(kex, client_pubkey,
287 &server_pubkey, &shared_secret);
288 break;
289 default:
290 r = SSH_ERR_INVALID_ARGUMENT;
291 break;
292 }
293 if (r !=0 )
294 goto out;
295
296 /* calc H */
djm@openbsd.orgbb956ea2019-01-23 00:30:41 +0000297 if ((server_host_key_blob = sshbuf_new()) == NULL) {
298 r = SSH_ERR_ALLOC_FAIL;
299 goto out;
300 }
301 if ((r = sshkey_putb(server_host_public, server_host_key_blob)) != 0)
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +0000302 goto out;
303 hashlen = sizeof(hash);
304 if ((r = kex_gen_hash(
305 kex->hash_alg,
306 kex->client_version,
307 kex->server_version,
djm@openbsd.orgbb956ea2019-01-23 00:30:41 +0000308 kex->peer,
309 kex->my,
310 server_host_key_blob,
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +0000311 client_pubkey,
312 server_pubkey,
313 shared_secret,
314 hash, &hashlen)) != 0)
315 goto out;
316
317 /* sign H */
318 if ((r = kex->sign(ssh, server_host_private, server_host_public,
319 &signature, &slen, hash, hashlen, kex->hostkey_alg)) != 0)
320 goto out;
321
322 /* send server hostkey, ECDH pubkey 'Q_S' and signed H */
323 if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_REPLY)) != 0 ||
djm@openbsd.orgbb956ea2019-01-23 00:30:41 +0000324 (r = sshpkt_put_stringb(ssh, server_host_key_blob)) != 0 ||
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +0000325 (r = sshpkt_put_stringb(ssh, server_pubkey)) != 0 ||
326 (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
327 (r = sshpkt_send(ssh)) != 0)
328 goto out;
329
330 if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
331 r = kex_send_newkeys(ssh);
332out:
333 explicit_bzero(hash, sizeof(hash));
djm@openbsd.orgbb956ea2019-01-23 00:30:41 +0000334 sshbuf_free(server_host_key_blob);
djm@openbsd.orgf1185ab2019-01-21 11:22:00 +0000335 free(signature);
336 sshbuf_free(shared_secret);
337 sshbuf_free(client_pubkey);
338 sshbuf_free(server_pubkey);
339 return r;
340}