2 * Copyright (c) 2000 Niels Provos. All rights reserved.
3 * Copyright (c) 2001 Markus Friedl. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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.
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.
27 RCSID("$OpenBSD: kexgex.c,v 1.22 2002/03/24 17:27:03 stevesk Exp $");
29 #include <openssl/bn.h>
41 #include "monitor_wrap.h"
45 char *client_version_string,
46 char *server_version_string,
47 char *ckexinit, int ckexinitlen,
48 char *skexinit, int skexinitlen,
49 u_char *serverhostkeyblob, int sbloblen,
50 int min, int wantbits, int max, BIGNUM *prime, BIGNUM *gen,
51 BIGNUM *client_dh_pub,
52 BIGNUM *server_dh_pub,
53 BIGNUM *shared_secret)
56 static u_char digest[EVP_MAX_MD_SIZE];
57 const EVP_MD *evp_md = EVP_sha1();
61 buffer_put_cstring(&b, client_version_string);
62 buffer_put_cstring(&b, server_version_string);
64 /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
65 buffer_put_int(&b, ckexinitlen+1);
66 buffer_put_char(&b, SSH2_MSG_KEXINIT);
67 buffer_append(&b, ckexinit, ckexinitlen);
68 buffer_put_int(&b, skexinitlen+1);
69 buffer_put_char(&b, SSH2_MSG_KEXINIT);
70 buffer_append(&b, skexinit, skexinitlen);
72 buffer_put_string(&b, serverhostkeyblob, sbloblen);
73 if (min == -1 || max == -1)
74 buffer_put_int(&b, wantbits);
76 buffer_put_int(&b, min);
77 buffer_put_int(&b, wantbits);
78 buffer_put_int(&b, max);
80 buffer_put_bignum2(&b, prime);
81 buffer_put_bignum2(&b, gen);
82 buffer_put_bignum2(&b, client_dh_pub);
83 buffer_put_bignum2(&b, server_dh_pub);
84 buffer_put_bignum2(&b, shared_secret);
89 EVP_DigestInit(&md, evp_md);
90 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
91 EVP_DigestFinal(&md, digest, NULL);
96 dump_digest("hash", digest, EVP_MD_size(evp_md));
104 kexgex_client(Kex *kex)
106 BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
107 BIGNUM *p = NULL, *g = NULL;
108 Key *server_host_key;
109 u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
110 u_int klen, kout, slen, sbloblen;
114 nbits = dh_estimate(kex->we_need * 8);
116 if (datafellows & SSH_OLD_DHGEX) {
117 debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD sent");
119 /* Old GEX request */
120 packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
121 packet_put_int(nbits);
125 debug("SSH2_MSG_KEX_DH_GEX_REQUEST sent");
127 /* New GEX request */
130 packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
132 packet_put_int(nbits);
136 fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
141 debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
142 packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP);
144 if ((p = BN_new()) == NULL)
146 packet_get_bignum2(p);
147 if ((g = BN_new()) == NULL)
149 packet_get_bignum2(g);
152 if (BN_num_bits(p) < min || BN_num_bits(p) > max)
153 fatal("DH_GEX group out of range: %d !< %d !< %d",
154 min, BN_num_bits(p), max);
156 dh = dh_new_group(g, p);
157 dh_gen_key(dh, kex->we_need * 8);
160 DHparams_print_fp(stderr, dh);
161 fprintf(stderr, "pub= ");
162 BN_print_fp(stderr, dh->pub_key);
163 fprintf(stderr, "\n");
166 debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
167 /* generate and send 'e', client DH public key */
168 packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
169 packet_put_bignum2(dh->pub_key);
172 debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
173 packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY);
176 server_host_key_blob = packet_get_string(&sbloblen);
177 server_host_key = key_from_blob(server_host_key_blob, sbloblen);
178 if (server_host_key == NULL)
179 fatal("cannot decode server_host_key_blob");
180 if (server_host_key->type != kex->hostkey_type)
181 fatal("type mismatch for decoded server_host_key_blob");
182 if (kex->verify_host_key == NULL)
183 fatal("cannot verify server_host_key");
184 if (kex->verify_host_key(server_host_key) == -1)
185 fatal("server_host_key verification failed");
187 /* DH paramter f, server public DH key */
188 if ((dh_server_pub = BN_new()) == NULL)
189 fatal("dh_server_pub == NULL");
190 packet_get_bignum2(dh_server_pub);
193 fprintf(stderr, "dh_server_pub= ");
194 BN_print_fp(stderr, dh_server_pub);
195 fprintf(stderr, "\n");
196 debug("bits %d", BN_num_bits(dh_server_pub));
200 signature = packet_get_string(&slen);
203 if (!dh_pub_is_valid(dh, dh_server_pub))
204 packet_disconnect("bad server public DH value");
207 kbuf = xmalloc(klen);
208 kout = DH_compute_key(kbuf, dh_server_pub, dh);
210 dump_digest("shared secret", kbuf, kout);
212 if ((shared_secret = BN_new()) == NULL)
213 fatal("kexgex_client: BN_new failed");
214 BN_bin2bn(kbuf, kout, shared_secret);
215 memset(kbuf, 0, klen);
218 if (datafellows & SSH_OLD_DHGEX)
221 /* calc and verify H */
223 kex->client_version_string,
224 kex->server_version_string,
225 buffer_ptr(&kex->my), buffer_len(&kex->my),
226 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
227 server_host_key_blob, sbloblen,
234 /* have keys, free DH */
236 xfree(server_host_key_blob);
237 BN_clear_free(dh_server_pub);
239 if (key_verify(server_host_key, signature, slen, hash, 20) != 1)
240 fatal("key_verify failed for server_host_key");
241 key_free(server_host_key);
244 /* save session id */
245 if (kex->session_id == NULL) {
246 kex->session_id_len = 20;
247 kex->session_id = xmalloc(kex->session_id_len);
248 memcpy(kex->session_id, hash, kex->session_id_len);
250 kex_derive_keys(kex, hash, shared_secret);
251 BN_clear_free(shared_secret);
259 kexgex_server(Kex *kex)
261 BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
262 Key *server_host_key;
264 u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
265 u_int sbloblen, klen, kout, slen;
266 int min = -1, max = -1, nbits = -1, type;
268 if (kex->load_host_key == NULL)
269 fatal("Cannot load hostkey");
270 server_host_key = kex->load_host_key(kex->hostkey_type);
271 if (server_host_key == NULL)
272 fatal("Unsupported hostkey type %d", kex->hostkey_type);
274 type = packet_read();
276 case SSH2_MSG_KEX_DH_GEX_REQUEST:
277 debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
278 min = packet_get_int();
279 nbits = packet_get_int();
280 max = packet_get_int();
281 min = MAX(DH_GRP_MIN, min);
282 max = MIN(DH_GRP_MAX, max);
284 case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
285 debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
286 nbits = packet_get_int();
289 /* unused for old GEX */
292 fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
296 if (max < min || nbits < min || max < nbits)
297 fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
300 /* Contact privileged parent */
301 dh = PRIVSEP(choose_dh(min, nbits, max));
303 packet_disconnect("Protocol error: no matching DH grp found");
305 debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
306 packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
307 packet_put_bignum2(dh->p);
308 packet_put_bignum2(dh->g);
314 /* Compute our exchange value in parallel with the client */
315 dh_gen_key(dh, kex->we_need * 8);
317 debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
318 packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);
321 if ((dh_client_pub = BN_new()) == NULL)
322 fatal("dh_client_pub == NULL");
323 packet_get_bignum2(dh_client_pub);
327 fprintf(stderr, "dh_client_pub= ");
328 BN_print_fp(stderr, dh_client_pub);
329 fprintf(stderr, "\n");
330 debug("bits %d", BN_num_bits(dh_client_pub));
334 DHparams_print_fp(stderr, dh);
335 fprintf(stderr, "pub= ");
336 BN_print_fp(stderr, dh->pub_key);
337 fprintf(stderr, "\n");
339 if (!dh_pub_is_valid(dh, dh_client_pub))
340 packet_disconnect("bad client public DH value");
343 kbuf = xmalloc(klen);
344 kout = DH_compute_key(kbuf, dh_client_pub, dh);
346 dump_digest("shared secret", kbuf, kout);
348 if ((shared_secret = BN_new()) == NULL)
349 fatal("kexgex_server: BN_new failed");
350 BN_bin2bn(kbuf, kout, shared_secret);
351 memset(kbuf, 0, klen);
354 key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
356 if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
359 /* calc H */ /* XXX depends on 'kex' */
361 kex->client_version_string,
362 kex->server_version_string,
363 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
364 buffer_ptr(&kex->my), buffer_len(&kex->my),
365 server_host_key_blob, sbloblen,
372 BN_clear_free(dh_client_pub);
374 /* save session id := H */
375 /* XXX hashlen depends on KEX */
376 if (kex->session_id == NULL) {
377 kex->session_id_len = 20;
378 kex->session_id = xmalloc(kex->session_id_len);
379 memcpy(kex->session_id, hash, kex->session_id_len);
383 /* XXX hashlen depends on KEX */
384 PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, 20));
386 /* destroy_sensitive_data(); */
388 /* send server hostkey, DH pubkey 'f' and singed H */
389 debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
390 packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
391 packet_put_string(server_host_key_blob, sbloblen);
392 packet_put_bignum2(dh->pub_key); /* f */
393 packet_put_string(signature, slen);
397 xfree(server_host_key_blob);
398 /* have keys, free DH */
401 kex_derive_keys(kex, hash, shared_secret);
402 BN_clear_free(shared_secret);