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 1.64 2005/07/25 11:59:39 markus 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)
191 Kex *kex = (Kex *)ctxt;
193 debug("SSH2_MSG_KEXINIT received");
195 fatal("kex_input_kexinit: no kex, cannot rekey");
197 ptr = packet_get_raw(&dlen);
198 buffer_append(&kex->peer, ptr, dlen);
201 for (i = 0; i < KEX_COOKIE_LEN; i++)
203 for (i = 0; i < PROPOSAL_MAX; i++)
204 xfree(packet_get_string(NULL));
205 (void) packet_get_char();
206 (void) packet_get_int();
209 kex_kexinit_finish(kex);
213 kex_setup(char *proposal[PROPOSAL_MAX])
217 kex = xmalloc(sizeof(*kex));
218 memset(kex, 0, sizeof(*kex));
219 buffer_init(&kex->peer);
220 buffer_init(&kex->my);
221 kex_prop2buf(&kex->my, proposal);
224 kex_send_kexinit(kex); /* we start */
225 kex_reset_dispatch();
231 kex_kexinit_finish(Kex *kex)
233 if (!(kex->flags & KEX_INIT_SENT))
234 kex_send_kexinit(kex);
236 kex_choose_conf(kex);
238 if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
239 kex->kex[kex->kex_type] != NULL) {
240 (kex->kex[kex->kex_type])(kex);
242 fatal("Unsupported key exchange %d", kex->kex_type);
247 choose_enc(Enc *enc, char *client, char *server)
249 char *name = match_list(client, server, NULL);
251 fatal("no matching cipher found: client %s server %s", client, server);
252 if ((enc->cipher = cipher_by_name(name)) == NULL)
253 fatal("matching cipher is not supported: %s", name);
258 enc->key_len = cipher_keylen(enc->cipher);
259 enc->block_size = cipher_blocksize(enc->cipher);
262 choose_mac(Mac *mac, char *client, char *server)
264 char *name = match_list(client, server, NULL);
266 fatal("no matching mac found: client %s server %s", client, server);
267 if (mac_init(mac, name) < 0)
268 fatal("unsupported mac %s", name);
269 /* truncate the key */
270 if (datafellows & SSH_BUG_HMAC)
277 choose_comp(Comp *comp, char *client, char *server)
279 char *name = match_list(client, server, NULL);
281 fatal("no matching comp found: client %s server %s", client, server);
282 if (strcmp(name, "zlib@openssh.com") == 0) {
283 comp->type = COMP_DELAYED;
284 } else if (strcmp(name, "zlib") == 0) {
285 comp->type = COMP_ZLIB;
286 } else if (strcmp(name, "none") == 0) {
287 comp->type = COMP_NONE;
289 fatal("unsupported comp %s", name);
294 choose_kex(Kex *k, char *client, char *server)
296 k->name = match_list(client, server, NULL);
299 if (strcmp(k->name, KEX_DH1) == 0) {
300 k->kex_type = KEX_DH_GRP1_SHA1;
301 } else if (strcmp(k->name, KEX_DH14) == 0) {
302 k->kex_type = KEX_DH_GRP14_SHA1;
303 } else if (strcmp(k->name, KEX_DHGEX) == 0) {
304 k->kex_type = KEX_DH_GEX_SHA1;
306 } else if (strncmp(k->name, KEX_GSS_SHA1, sizeof(KEX_GSS_SHA1)-1) == 0) {
307 k->kex_type = KEX_GSS_GRP1_SHA1;
310 fatal("bad kex alg %s", k->name);
313 choose_hostkeyalg(Kex *k, char *client, char *server)
315 char *hostkeyalg = match_list(client, server, NULL);
316 if (hostkeyalg == NULL)
317 fatal("no hostkey alg");
318 k->hostkey_type = key_type_from_name(hostkeyalg);
319 if (k->hostkey_type == KEY_UNSPEC)
320 fatal("bad hostkey alg '%s'", hostkeyalg);
325 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
327 static int check[] = {
328 PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
333 for (idx = &check[0]; *idx != -1; idx++) {
334 if ((p = strchr(my[*idx], ',')) != NULL)
336 if ((p = strchr(peer[*idx], ',')) != NULL)
338 if (strcmp(my[*idx], peer[*idx]) != 0) {
339 debug2("proposal mismatch: my %s peer %s",
340 my[*idx], peer[*idx]);
344 debug2("proposals match");
349 kex_choose_conf(Kex *kex)
353 char **cprop, **sprop;
354 int nenc, nmac, ncomp;
355 u_int mode, ctos, need;
356 int first_kex_follows, type;
358 my = kex_buf2prop(&kex->my, NULL);
359 peer = kex_buf2prop(&kex->peer, &first_kex_follows);
369 /* Algorithm Negotiation */
370 for (mode = 0; mode < MODE_MAX; mode++) {
371 newkeys = xmalloc(sizeof(*newkeys));
372 memset(newkeys, 0, sizeof(*newkeys));
373 kex->newkeys[mode] = newkeys;
374 ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
375 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
376 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
377 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
378 choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
379 choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
380 choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
381 debug("kex: %s %s %s %s",
382 ctos ? "client->server" : "server->client",
387 choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
388 choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
389 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
391 for (mode = 0; mode < MODE_MAX; mode++) {
392 newkeys = kex->newkeys[mode];
393 if (need < newkeys->enc.key_len)
394 need = newkeys->enc.key_len;
395 if (need < newkeys->enc.block_size)
396 need = newkeys->enc.block_size;
397 if (need < newkeys->mac.key_len)
398 need = newkeys->mac.key_len;
400 /* XXX need runden? */
403 /* ignore the next message if the proposals do not match */
404 if (first_kex_follows && !proposals_match(my, peer) &&
405 !(datafellows & SSH_BUG_FIRSTKEX)) {
406 type = packet_read();
407 debug2("skipping next packet (type %u)", type);
415 derive_key(Kex *kex, int id, u_int need, u_char *hash, BIGNUM *shared_secret)
418 const EVP_MD *evp_md = EVP_sha1();
422 int mdsz = EVP_MD_size(evp_md);
426 fatal("derive_key: mdsz < 0");
427 digest = xmalloc(roundup(need, mdsz));
430 buffer_put_bignum2(&b, shared_secret);
432 /* K1 = HASH(K || H || "A" || session_id) */
433 EVP_DigestInit(&md, evp_md);
434 if (!(datafellows & SSH_BUG_DERIVEKEY))
435 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
436 EVP_DigestUpdate(&md, hash, mdsz);
437 EVP_DigestUpdate(&md, &c, 1);
438 EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
439 EVP_DigestFinal(&md, digest, NULL);
443 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
444 * Key = K1 || K2 || ... || Kn
446 for (have = mdsz; need > have; have += mdsz) {
447 EVP_DigestInit(&md, evp_md);
448 if (!(datafellows & SSH_BUG_DERIVEKEY))
449 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
450 EVP_DigestUpdate(&md, hash, mdsz);
451 EVP_DigestUpdate(&md, digest, have);
452 EVP_DigestFinal(&md, digest + have, NULL);
456 fprintf(stderr, "key '%c'== ", c);
457 dump_digest("key", digest, need);
462 Newkeys *current_keys[MODE_MAX];
466 kex_derive_keys(Kex *kex, u_char *hash, BIGNUM *shared_secret)
471 for (i = 0; i < NKEYS; i++)
472 keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret);
474 debug2("kex_derive_keys");
475 for (mode = 0; mode < MODE_MAX; mode++) {
476 current_keys[mode] = kex->newkeys[mode];
477 kex->newkeys[mode] = NULL;
478 ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
479 current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
480 current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
481 current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
486 kex_get_newkeys(int mode)
490 ret = current_keys[mode];
491 current_keys[mode] = NULL;
496 derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
497 u_int8_t cookie[8], u_int8_t id[16])
499 const EVP_MD *evp_md = EVP_md5();
501 u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE];
504 EVP_DigestInit(&md, evp_md);
506 len = BN_num_bytes(host_modulus);
507 if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
508 fatal("%s: bad host modulus (len %d)", __func__, len);
509 BN_bn2bin(host_modulus, nbuf);
510 EVP_DigestUpdate(&md, nbuf, len);
512 len = BN_num_bytes(server_modulus);
513 if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
514 fatal("%s: bad server modulus (len %d)", __func__, len);
515 BN_bn2bin(server_modulus, nbuf);
516 EVP_DigestUpdate(&md, nbuf, len);
518 EVP_DigestUpdate(&md, cookie, 8);
520 EVP_DigestFinal(&md, obuf, NULL);
521 memcpy(id, obuf, 16);
523 memset(nbuf, 0, sizeof(nbuf));
524 memset(obuf, 0, sizeof(obuf));
525 memset(&md, 0, sizeof(md));
528 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
530 dump_digest(char *msg, u_char *digest, int len)
534 fprintf(stderr, "%s\n", msg);
535 for (i = 0; i< len; i++) {
536 fprintf(stderr, "%02x", digest[i]);
538 fprintf(stderr, "\n");
540 fprintf(stderr, " ");
542 fprintf(stderr, "\n");