2 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 RCSID("$OpenBSD: kex.c,v 1.60 2004/06/21 17:36:31 avsm Exp $");
28 #include <openssl/crypto.h>
49 #define KEX_COOKIE_LEN 16
52 static void kex_kexinit_finish(Kex *);
53 static void kex_choose_conf(Kex *);
55 /* put algorithm proposal into buffer */
57 kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
63 * add a dummy cookie, the cookie will be overwritten by
64 * kex_send_kexinit(), each time a kexinit is set
66 for (i = 0; i < KEX_COOKIE_LEN; i++)
67 buffer_put_char(b, 0);
68 for (i = 0; i < PROPOSAL_MAX; i++)
69 buffer_put_cstring(b, proposal[i]);
70 buffer_put_char(b, 0); /* first_kex_packet_follows */
71 buffer_put_int(b, 0); /* uint32 reserved */
74 /* parse buffer and return algorithm proposal */
76 kex_buf2prop(Buffer *raw, int *first_kex_follows)
82 proposal = xmalloc(PROPOSAL_MAX * sizeof(char *));
85 buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
87 for (i = 0; i < KEX_COOKIE_LEN; i++)
89 /* extract kex init proposal strings */
90 for (i = 0; i < PROPOSAL_MAX; i++) {
91 proposal[i] = buffer_get_string(&b,NULL);
92 debug2("kex_parse_kexinit: %s", proposal[i]);
94 /* first kex follows / reserved */
95 i = buffer_get_char(&b);
96 if (first_kex_follows != NULL)
97 *first_kex_follows = i;
98 debug2("kex_parse_kexinit: first_kex_follows %d ", i);
99 i = buffer_get_int(&b);
100 debug2("kex_parse_kexinit: reserved %d ", i);
106 kex_prop_free(char **proposal)
110 for (i = 0; i < PROPOSAL_MAX; i++)
116 kex_protocol_error(int type, u_int32_t seq, void *ctxt)
118 error("Hm, kex protocol error: type %d seq %u", type, seq);
122 kex_reset_dispatch(void)
124 dispatch_range(SSH2_MSG_TRANSPORT_MIN,
125 SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
126 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
132 kex_reset_dispatch();
134 packet_start(SSH2_MSG_NEWKEYS);
136 /* packet_write_wait(); */
137 debug("SSH2_MSG_NEWKEYS sent");
139 debug("expecting SSH2_MSG_NEWKEYS");
140 packet_read_expect(SSH2_MSG_NEWKEYS);
142 debug("SSH2_MSG_NEWKEYS received");
145 buffer_clear(&kex->peer);
146 /* buffer_clear(&kex->my); */
147 kex->flags &= ~KEX_INIT_SENT;
153 kex_send_kexinit(Kex *kex)
160 error("kex_send_kexinit: no kex, cannot rekey");
163 if (kex->flags & KEX_INIT_SENT) {
164 debug("KEX_INIT_SENT");
169 /* generate a random cookie */
170 if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
171 fatal("kex_send_kexinit: kex proposal too short");
172 cookie = buffer_ptr(&kex->my);
173 for (i = 0; i < KEX_COOKIE_LEN; i++) {
179 packet_start(SSH2_MSG_KEXINIT);
180 packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
182 debug("SSH2_MSG_KEXINIT sent");
183 kex->flags |= KEX_INIT_SENT;
187 kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
192 Kex *kex = (Kex *)ctxt;
194 debug("SSH2_MSG_KEXINIT received");
196 fatal("kex_input_kexinit: no kex, cannot rekey");
198 ptr = packet_get_raw(&dlen);
199 buffer_append(&kex->peer, ptr, dlen);
202 for (i = 0; i < KEX_COOKIE_LEN; i++)
204 for (i = 0; i < PROPOSAL_MAX; i++)
205 xfree(packet_get_string(NULL));
206 (void) packet_get_char();
207 (void) packet_get_int();
210 kex_kexinit_finish(kex);
214 kex_setup(char *proposal[PROPOSAL_MAX])
218 kex = xmalloc(sizeof(*kex));
219 memset(kex, 0, sizeof(*kex));
220 buffer_init(&kex->peer);
221 buffer_init(&kex->my);
222 kex_prop2buf(&kex->my, proposal);
225 kex_send_kexinit(kex); /* we start */
226 kex_reset_dispatch();
232 kex_kexinit_finish(Kex *kex)
234 if (!(kex->flags & KEX_INIT_SENT))
235 kex_send_kexinit(kex);
237 kex_choose_conf(kex);
239 if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
240 kex->kex[kex->kex_type] != NULL) {
241 (kex->kex[kex->kex_type])(kex);
243 fatal("Unsupported key exchange %d", kex->kex_type);
248 choose_enc(Enc *enc, char *client, char *server)
250 char *name = match_list(client, server, NULL);
252 fatal("no matching cipher found: client %s server %s", client, server);
253 if ((enc->cipher = cipher_by_name(name)) == NULL)
254 fatal("matching cipher is not supported: %s", name);
259 enc->key_len = cipher_keylen(enc->cipher);
260 enc->block_size = cipher_blocksize(enc->cipher);
263 choose_mac(Mac *mac, char *client, char *server)
265 char *name = match_list(client, server, NULL);
267 fatal("no matching mac found: client %s server %s", client, server);
268 if (mac_init(mac, name) < 0)
269 fatal("unsupported mac %s", name);
270 /* truncate the key */
271 if (datafellows & SSH_BUG_HMAC)
278 choose_comp(Comp *comp, char *client, char *server)
280 char *name = match_list(client, server, NULL);
282 fatal("no matching comp found: client %s server %s", client, server);
283 if (strcmp(name, "zlib") == 0) {
285 } else if (strcmp(name, "none") == 0) {
288 fatal("unsupported comp %s", name);
293 choose_kex(Kex *k, char *client, char *server)
295 k->name = match_list(client, server, NULL);
298 if (strcmp(k->name, KEX_DH1) == 0) {
299 k->kex_type = KEX_DH_GRP1_SHA1;
300 } else if (strcmp(k->name, KEX_DH14) == 0) {
301 k->kex_type = KEX_DH_GRP14_SHA1;
302 } else if (strcmp(k->name, KEX_DHGEX) == 0) {
303 k->kex_type = KEX_DH_GEX_SHA1;
305 } else if (strncmp(k->name, KEX_GSS_SHA1, sizeof(KEX_GSS_SHA1)-1) == 0) {
306 k->kex_type = KEX_GSS_GRP1_SHA1;
309 fatal("bad kex alg %s", k->name);
312 choose_hostkeyalg(Kex *k, char *client, char *server)
314 char *hostkeyalg = match_list(client, server, NULL);
315 if (hostkeyalg == NULL)
316 fatal("no hostkey alg");
317 k->hostkey_type = key_type_from_name(hostkeyalg);
318 if (k->hostkey_type == KEY_UNSPEC)
319 fatal("bad hostkey alg '%s'", hostkeyalg);
324 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
326 static int check[] = {
327 PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
332 for (idx = &check[0]; *idx != -1; idx++) {
333 if ((p = strchr(my[*idx], ',')) != NULL)
335 if ((p = strchr(peer[*idx], ',')) != NULL)
337 if (strcmp(my[*idx], peer[*idx]) != 0) {
338 debug2("proposal mismatch: my %s peer %s",
339 my[*idx], peer[*idx]);
343 debug2("proposals match");
348 kex_choose_conf(Kex *kex)
352 char **cprop, **sprop;
353 int nenc, nmac, ncomp;
355 int ctos; /* direction: if true client-to-server */
357 int first_kex_follows, type;
359 my = kex_buf2prop(&kex->my, NULL);
360 peer = kex_buf2prop(&kex->peer, &first_kex_follows);
370 /* Algorithm Negotiation */
371 for (mode = 0; mode < MODE_MAX; mode++) {
372 newkeys = xmalloc(sizeof(*newkeys));
373 memset(newkeys, 0, sizeof(*newkeys));
374 kex->newkeys[mode] = newkeys;
375 ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
376 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
377 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
378 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
379 choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
380 choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
381 choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
382 debug("kex: %s %s %s %s",
383 ctos ? "client->server" : "server->client",
388 choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
389 choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
390 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
392 for (mode = 0; mode < MODE_MAX; mode++) {
393 newkeys = kex->newkeys[mode];
394 if (need < newkeys->enc.key_len)
395 need = newkeys->enc.key_len;
396 if (need < newkeys->enc.block_size)
397 need = newkeys->enc.block_size;
398 if (need < newkeys->mac.key_len)
399 need = newkeys->mac.key_len;
401 /* XXX need runden? */
404 /* ignore the next message if the proposals do not match */
405 if (first_kex_follows && !proposals_match(my, peer) &&
406 !(datafellows & SSH_BUG_FIRSTKEX)) {
407 type = packet_read();
408 debug2("skipping next packet (type %u)", type);
416 derive_key(Kex *kex, int id, int need, u_char *hash, BIGNUM *shared_secret)
419 const EVP_MD *evp_md = EVP_sha1();
423 int mdsz = EVP_MD_size(evp_md);
424 u_char *digest = xmalloc(roundup(need, mdsz));
427 buffer_put_bignum2(&b, shared_secret);
429 /* K1 = HASH(K || H || "A" || session_id) */
430 EVP_DigestInit(&md, evp_md);
431 if (!(datafellows & SSH_BUG_DERIVEKEY))
432 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
433 EVP_DigestUpdate(&md, hash, mdsz);
434 EVP_DigestUpdate(&md, &c, 1);
435 EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
436 EVP_DigestFinal(&md, digest, NULL);
440 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
441 * Key = K1 || K2 || ... || Kn
443 for (have = mdsz; need > have; have += mdsz) {
444 EVP_DigestInit(&md, evp_md);
445 if (!(datafellows & SSH_BUG_DERIVEKEY))
446 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
447 EVP_DigestUpdate(&md, hash, mdsz);
448 EVP_DigestUpdate(&md, digest, have);
449 EVP_DigestFinal(&md, digest + have, NULL);
453 fprintf(stderr, "key '%c'== ", c);
454 dump_digest("key", digest, need);
459 Newkeys *current_keys[MODE_MAX];
463 kex_derive_keys(Kex *kex, u_char *hash, BIGNUM *shared_secret)
468 for (i = 0; i < NKEYS; i++)
469 keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret);
471 debug2("kex_derive_keys");
472 for (mode = 0; mode < MODE_MAX; mode++) {
473 current_keys[mode] = kex->newkeys[mode];
474 kex->newkeys[mode] = NULL;
475 ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
476 current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
477 current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
478 current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
483 kex_get_newkeys(int mode)
487 ret = current_keys[mode];
488 current_keys[mode] = NULL;
493 derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
494 u_int8_t cookie[8], u_int8_t id[16])
496 const EVP_MD *evp_md = EVP_md5();
498 u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE];
501 EVP_DigestInit(&md, evp_md);
503 len = BN_num_bytes(host_modulus);
504 if (len < (512 / 8) || len > sizeof(nbuf))
505 fatal("%s: bad host modulus (len %d)", __func__, len);
506 BN_bn2bin(host_modulus, nbuf);
507 EVP_DigestUpdate(&md, nbuf, len);
509 len = BN_num_bytes(server_modulus);
510 if (len < (512 / 8) || len > sizeof(nbuf))
511 fatal("%s: bad server modulus (len %d)", __func__, len);
512 BN_bn2bin(server_modulus, nbuf);
513 EVP_DigestUpdate(&md, nbuf, len);
515 EVP_DigestUpdate(&md, cookie, 8);
517 EVP_DigestFinal(&md, obuf, NULL);
518 memcpy(id, obuf, 16);
520 memset(nbuf, 0, sizeof(nbuf));
521 memset(obuf, 0, sizeof(obuf));
522 memset(&md, 0, sizeof(md));
525 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
527 dump_digest(char *msg, u_char *digest, int len)
531 fprintf(stderr, "%s\n", msg);
532 for (i = 0; i< len; i++) {
533 fprintf(stderr, "%02x", digest[i]);
535 fprintf(stderr, "\n");
537 fprintf(stderr, " ");
539 fprintf(stderr, "\n");