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-rw-r--r--kexgen.c339
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1/* $OpenBSD: kexgen.c,v 1.2 2019/01/23 00:30:41 djm Exp $ */
2/*
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
26#include "includes.h"
27
28#include <sys/types.h>
29
30#include <stdio.h>
31#include <string.h>
32#include <signal.h>
33
34#include "sshkey.h"
35#include "kex.h"
36#include "log.h"
37#include "packet.h"
38#include "ssh2.h"
39#include "sshbuf.h"
40#include "digest.h"
41#include "ssherr.h"
42
43static int input_kex_gen_init(int, u_int32_t, struct ssh *);
44static int input_kex_gen_reply(int type, u_int32_t seq, struct ssh *ssh);
45
46static int
47kex_gen_hash(
48 int hash_alg,
49 const struct sshbuf *client_version,
50 const struct sshbuf *server_version,
51 const struct sshbuf *client_kexinit,
52 const struct sshbuf *server_kexinit,
53 const struct sshbuf *server_host_key_blob,
54 const struct sshbuf *client_pub,
55 const struct sshbuf *server_pub,
56 const struct sshbuf *shared_secret,
57 u_char *hash, size_t *hashlen)
58{
59 struct sshbuf *b;
60 int r;
61
62 if (*hashlen < ssh_digest_bytes(hash_alg))
63 return SSH_ERR_INVALID_ARGUMENT;
64 if ((b = sshbuf_new()) == NULL)
65 return SSH_ERR_ALLOC_FAIL;
66 if ((r = sshbuf_put_stringb(b, client_version)) != 0 ||
67 (r = sshbuf_put_stringb(b, server_version)) != 0 ||
68 /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
69 (r = sshbuf_put_u32(b, sshbuf_len(client_kexinit) + 1)) != 0 ||
70 (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 ||
71 (r = sshbuf_putb(b, client_kexinit)) != 0 ||
72 (r = sshbuf_put_u32(b, sshbuf_len(server_kexinit) + 1)) != 0 ||
73 (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 ||
74 (r = sshbuf_putb(b, server_kexinit)) != 0 ||
75 (r = sshbuf_put_stringb(b, server_host_key_blob)) != 0 ||
76 (r = sshbuf_put_stringb(b, client_pub)) != 0 ||
77 (r = sshbuf_put_stringb(b, server_pub)) != 0 ||
78 (r = sshbuf_putb(b, shared_secret)) != 0) {
79 sshbuf_free(b);
80 return r;
81 }
82#ifdef DEBUG_KEX
83 sshbuf_dump(b, stderr);
84#endif
85 if (ssh_digest_buffer(hash_alg, b, hash, *hashlen) != 0) {
86 sshbuf_free(b);
87 return SSH_ERR_LIBCRYPTO_ERROR;
88 }
89 sshbuf_free(b);
90 *hashlen = ssh_digest_bytes(hash_alg);
91#ifdef DEBUG_KEX
92 dump_digest("hash", hash, *hashlen);
93#endif
94 return 0;
95}
96
97int
98kex_gen_client(struct ssh *ssh)
99{
100 struct kex *kex = ssh->kex;
101 int r;
102
103 switch (kex->kex_type) {
104#ifdef WITH_OPENSSL
105 case KEX_DH_GRP1_SHA1:
106 case KEX_DH_GRP14_SHA1:
107 case KEX_DH_GRP14_SHA256:
108 case KEX_DH_GRP16_SHA512:
109 case KEX_DH_GRP18_SHA512:
110 r = kex_dh_keypair(kex);
111 break;
112 case KEX_ECDH_SHA2:
113 r = kex_ecdh_keypair(kex);
114 break;
115#endif
116 case KEX_C25519_SHA256:
117 r = kex_c25519_keypair(kex);
118 break;
119 case KEX_KEM_SNTRUP4591761X25519_SHA512:
120 r = kex_kem_sntrup4591761x25519_keypair(kex);
121 break;
122 default:
123 r = SSH_ERR_INVALID_ARGUMENT;
124 break;
125 }
126 if (r != 0)
127 return r;
128 if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_INIT)) != 0 ||
129 (r = sshpkt_put_stringb(ssh, kex->client_pub)) != 0 ||
130 (r = sshpkt_send(ssh)) != 0)
131 return r;
132 debug("expecting SSH2_MSG_KEX_ECDH_REPLY");
133 ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_REPLY, &input_kex_gen_reply);
134 return 0;
135}
136
137static int
138input_kex_gen_reply(int type, u_int32_t seq, struct ssh *ssh)
139{
140 struct kex *kex = ssh->kex;
141 struct sshkey *server_host_key = NULL;
142 struct sshbuf *shared_secret = NULL;
143 struct sshbuf *server_blob = NULL;
144 struct sshbuf *tmp = NULL, *server_host_key_blob = NULL;
145 u_char *signature = NULL;
146 u_char hash[SSH_DIGEST_MAX_LENGTH];
147 size_t slen, hashlen;
148 int r;
149
150 /* hostkey */
151 if ((r = sshpkt_getb_froms(ssh, &server_host_key_blob)) != 0)
152 goto out;
153 /* sshkey_fromb() consumes its buffer, so make a copy */
154 if ((tmp = sshbuf_fromb(server_host_key_blob)) == NULL) {
155 r = SSH_ERR_ALLOC_FAIL;
156 goto out;
157 }
158 if ((r = sshkey_fromb(tmp, &server_host_key)) != 0)
159 goto out;
160 if ((r = kex_verify_host_key(ssh, server_host_key)) != 0)
161 goto out;
162
163 /* Q_S, server public key */
164 /* signed H */
165 if ((r = sshpkt_getb_froms(ssh, &server_blob)) != 0 ||
166 (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
167 (r = sshpkt_get_end(ssh)) != 0)
168 goto out;
169
170 /* compute shared secret */
171 switch (kex->kex_type) {
172#ifdef WITH_OPENSSL
173 case KEX_DH_GRP1_SHA1:
174 case KEX_DH_GRP14_SHA1:
175 case KEX_DH_GRP14_SHA256:
176 case KEX_DH_GRP16_SHA512:
177 case KEX_DH_GRP18_SHA512:
178 r = kex_dh_dec(kex, server_blob, &shared_secret);
179 break;
180 case KEX_ECDH_SHA2:
181 r = kex_ecdh_dec(kex, server_blob, &shared_secret);
182 break;
183#endif
184 case KEX_C25519_SHA256:
185 r = kex_c25519_dec(kex, server_blob, &shared_secret);
186 break;
187 case KEX_KEM_SNTRUP4591761X25519_SHA512:
188 r = kex_kem_sntrup4591761x25519_dec(kex, server_blob,
189 &shared_secret);
190 break;
191 default:
192 r = SSH_ERR_INVALID_ARGUMENT;
193 break;
194 }
195 if (r !=0 )
196 goto out;
197
198 /* calc and verify H */
199 hashlen = sizeof(hash);
200 if ((r = kex_gen_hash(
201 kex->hash_alg,
202 kex->client_version,
203 kex->server_version,
204 kex->my,
205 kex->peer,
206 server_host_key_blob,
207 kex->client_pub,
208 server_blob,
209 shared_secret,
210 hash, &hashlen)) != 0)
211 goto out;
212
213 if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
214 kex->hostkey_alg, ssh->compat)) != 0)
215 goto out;
216
217 if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
218 r = kex_send_newkeys(ssh);
219out:
220 explicit_bzero(hash, sizeof(hash));
221 explicit_bzero(kex->c25519_client_key, sizeof(kex->c25519_client_key));
222 explicit_bzero(kex->sntrup4591761_client_key,
223 sizeof(kex->sntrup4591761_client_key));
224 sshbuf_free(server_host_key_blob);
225 free(signature);
226 sshbuf_free(tmp);
227 sshkey_free(server_host_key);
228 sshbuf_free(server_blob);
229 sshbuf_free(shared_secret);
230 sshbuf_free(kex->client_pub);
231 kex->client_pub = NULL;
232 return r;
233}
234
235int
236kex_gen_server(struct ssh *ssh)
237{
238 debug("expecting SSH2_MSG_KEX_ECDH_INIT");
239 ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_INIT, &input_kex_gen_init);
240 return 0;
241}
242
243static int
244input_kex_gen_init(int type, u_int32_t seq, struct ssh *ssh)
245{
246 struct kex *kex = ssh->kex;
247 struct sshkey *server_host_private, *server_host_public;
248 struct sshbuf *shared_secret = NULL;
249 struct sshbuf *server_pubkey = NULL;
250 struct sshbuf *client_pubkey = NULL;
251 struct sshbuf *server_host_key_blob = NULL;
252 u_char *signature = NULL, hash[SSH_DIGEST_MAX_LENGTH];
253 size_t slen, hashlen;
254 int r;
255
256 if ((r = kex_load_hostkey(ssh, &server_host_private,
257 &server_host_public)) != 0)
258 goto out;
259
260 if ((r = sshpkt_getb_froms(ssh, &client_pubkey)) != 0 ||
261 (r = sshpkt_get_end(ssh)) != 0)
262 goto out;
263
264 /* compute shared secret */
265 switch (kex->kex_type) {
266#ifdef WITH_OPENSSL
267 case KEX_DH_GRP1_SHA1:
268 case KEX_DH_GRP14_SHA1:
269 case KEX_DH_GRP14_SHA256:
270 case KEX_DH_GRP16_SHA512:
271 case KEX_DH_GRP18_SHA512:
272 r = kex_dh_enc(kex, client_pubkey, &server_pubkey,
273 &shared_secret);
274 break;
275 case KEX_ECDH_SHA2:
276 r = kex_ecdh_enc(kex, client_pubkey, &server_pubkey,
277 &shared_secret);
278 break;
279#endif
280 case KEX_C25519_SHA256:
281 r = kex_c25519_enc(kex, client_pubkey, &server_pubkey,
282 &shared_secret);
283 break;
284 case KEX_KEM_SNTRUP4591761X25519_SHA512:
285 r = kex_kem_sntrup4591761x25519_enc(kex, client_pubkey,
286 &server_pubkey, &shared_secret);
287 break;
288 default:
289 r = SSH_ERR_INVALID_ARGUMENT;
290 break;
291 }
292 if (r !=0 )
293 goto out;
294
295 /* calc H */
296 if ((server_host_key_blob = sshbuf_new()) == NULL) {
297 r = SSH_ERR_ALLOC_FAIL;
298 goto out;
299 }
300 if ((r = sshkey_putb(server_host_public, server_host_key_blob)) != 0)
301 goto out;
302 hashlen = sizeof(hash);
303 if ((r = kex_gen_hash(
304 kex->hash_alg,
305 kex->client_version,
306 kex->server_version,
307 kex->peer,
308 kex->my,
309 server_host_key_blob,
310 client_pubkey,
311 server_pubkey,
312 shared_secret,
313 hash, &hashlen)) != 0)
314 goto out;
315
316 /* sign H */
317 if ((r = kex->sign(ssh, server_host_private, server_host_public,
318 &signature, &slen, hash, hashlen, kex->hostkey_alg)) != 0)
319 goto out;
320
321 /* send server hostkey, ECDH pubkey 'Q_S' and signed H */
322 if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_REPLY)) != 0 ||
323 (r = sshpkt_put_stringb(ssh, server_host_key_blob)) != 0 ||
324 (r = sshpkt_put_stringb(ssh, server_pubkey)) != 0 ||
325 (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
326 (r = sshpkt_send(ssh)) != 0)
327 goto out;
328
329 if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
330 r = kex_send_newkeys(ssh);
331out:
332 explicit_bzero(hash, sizeof(hash));
333 sshbuf_free(server_host_key_blob);
334 free(signature);
335 sshbuf_free(shared_secret);
336 sshbuf_free(client_pubkey);
337 sshbuf_free(server_pubkey);
338 return r;
339}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-13 16:18:41 +0000