1 /* $OpenBSD: kex.c,v 1.86 2010/09/22 05:01:29 djm Exp $ */
4 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 #include <sys/param.h>
37 #include <openssl/crypto.h>
54 #if OPENSSL_VERSION_NUMBER >= 0x00907000L
55 # if defined(HAVE_EVP_SHA256)
56 # define evp_ssh_sha256 EVP_sha256
58 extern const EVP_MD *evp_ssh_sha256(void);
63 static void kex_kexinit_finish(Kex *);
64 static void kex_choose_conf(Kex *);
66 /* Validate KEX method name list */
68 kex_names_valid(const char *names)
72 if (names == NULL || strcmp(names, "") == 0)
74 s = cp = xstrdup(names);
75 for ((p = strsep(&cp, ",")); p && *p != '\0';
76 (p = strsep(&cp, ","))) {
77 if (strcmp(p, KEX_DHGEX_SHA256) != 0 &&
78 strcmp(p, KEX_DHGEX_SHA1) != 0 &&
79 strcmp(p, KEX_DH14) != 0 &&
80 strcmp(p, KEX_DH1) != 0 &&
81 (strncmp(p, KEX_ECDH_SHA2_STEM,
82 sizeof(KEX_ECDH_SHA2_STEM) - 1) != 0 ||
83 kex_ecdh_name_to_nid(p) == -1)) {
84 error("Unsupported KEX algorithm \"%.100s\"", p);
89 debug3("kex names ok: [%s]", names);
94 /* Put algorithm proposal into buffer. */
95 #ifndef NONE_CIPHER_ENABLED
98 /* Also used in sshconnect2.c. */
101 kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
107 * add a dummy cookie, the cookie will be overwritten by
108 * kex_send_kexinit(), each time a kexinit is set
110 for (i = 0; i < KEX_COOKIE_LEN; i++)
111 buffer_put_char(b, 0);
112 for (i = 0; i < PROPOSAL_MAX; i++)
113 buffer_put_cstring(b, proposal[i]);
114 buffer_put_char(b, 0); /* first_kex_packet_follows */
115 buffer_put_int(b, 0); /* uint32 reserved */
118 /* parse buffer and return algorithm proposal */
120 kex_buf2prop(Buffer *raw, int *first_kex_follows)
126 proposal = xcalloc(PROPOSAL_MAX, sizeof(char *));
129 buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
131 for (i = 0; i < KEX_COOKIE_LEN; i++)
133 /* extract kex init proposal strings */
134 for (i = 0; i < PROPOSAL_MAX; i++) {
135 proposal[i] = buffer_get_cstring(&b,NULL);
136 debug2("kex_parse_kexinit: %s", proposal[i]);
138 /* first kex follows / reserved */
139 i = buffer_get_char(&b);
140 if (first_kex_follows != NULL)
141 *first_kex_follows = i;
142 debug2("kex_parse_kexinit: first_kex_follows %d ", i);
143 i = buffer_get_int(&b);
144 debug2("kex_parse_kexinit: reserved %u ", i);
150 kex_prop_free(char **proposal)
154 for (i = 0; i < PROPOSAL_MAX; i++)
161 kex_protocol_error(int type, u_int32_t seq, void *ctxt)
163 error("Hm, kex protocol error: type %d seq %u", type, seq);
167 kex_reset_dispatch(void)
169 dispatch_range(SSH2_MSG_TRANSPORT_MIN,
170 SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
171 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
177 kex_reset_dispatch();
179 packet_start(SSH2_MSG_NEWKEYS);
181 /* packet_write_wait(); */
182 debug("SSH2_MSG_NEWKEYS sent");
184 debug("expecting SSH2_MSG_NEWKEYS");
185 packet_read_expect(SSH2_MSG_NEWKEYS);
187 debug("SSH2_MSG_NEWKEYS received");
190 buffer_clear(&kex->peer);
191 /* buffer_clear(&kex->my); */
192 kex->flags &= ~KEX_INIT_SENT;
198 kex_send_kexinit(Kex *kex)
205 error("kex_send_kexinit: no kex, cannot rekey");
208 if (kex->flags & KEX_INIT_SENT) {
209 debug("KEX_INIT_SENT");
214 /* generate a random cookie */
215 if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
216 fatal("kex_send_kexinit: kex proposal too short");
217 cookie = buffer_ptr(&kex->my);
218 for (i = 0; i < KEX_COOKIE_LEN; i++) {
224 packet_start(SSH2_MSG_KEXINIT);
225 packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
227 debug("SSH2_MSG_KEXINIT sent");
228 kex->flags |= KEX_INIT_SENT;
233 kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
237 Kex *kex = (Kex *)ctxt;
239 debug("SSH2_MSG_KEXINIT received");
241 fatal("kex_input_kexinit: no kex, cannot rekey");
243 ptr = packet_get_raw(&dlen);
244 buffer_append(&kex->peer, ptr, dlen);
247 for (i = 0; i < KEX_COOKIE_LEN; i++)
249 for (i = 0; i < PROPOSAL_MAX; i++)
250 xfree(packet_get_string(NULL));
251 (void) packet_get_char();
252 (void) packet_get_int();
255 kex_kexinit_finish(kex);
259 kex_setup(char *proposal[PROPOSAL_MAX])
263 kex = xcalloc(1, sizeof(*kex));
264 buffer_init(&kex->peer);
265 buffer_init(&kex->my);
266 kex_prop2buf(&kex->my, proposal);
269 kex_send_kexinit(kex); /* we start */
270 kex_reset_dispatch();
276 kex_kexinit_finish(Kex *kex)
278 if (!(kex->flags & KEX_INIT_SENT))
279 kex_send_kexinit(kex);
281 kex_choose_conf(kex);
283 if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
284 kex->kex[kex->kex_type] != NULL) {
285 (kex->kex[kex->kex_type])(kex);
287 fatal("Unsupported key exchange %d", kex->kex_type);
292 choose_enc(Enc *enc, char *client, char *server)
294 char *name = match_list(client, server, NULL);
296 fatal("no matching cipher found: client %s server %s",
298 if ((enc->cipher = cipher_by_name(name)) == NULL)
299 fatal("matching cipher is not supported: %s", name);
304 enc->key_len = cipher_keylen(enc->cipher);
305 enc->block_size = cipher_blocksize(enc->cipher);
309 choose_mac(Mac *mac, char *client, char *server)
311 char *name = match_list(client, server, NULL);
313 fatal("no matching mac found: client %s server %s",
315 if (mac_setup(mac, name) < 0)
316 fatal("unsupported mac %s", name);
317 /* truncate the key */
318 if (datafellows & SSH_BUG_HMAC)
326 choose_comp(Comp *comp, char *client, char *server)
328 char *name = match_list(client, server, NULL);
330 fatal("no matching comp found: client %s server %s", client, server);
331 if (strcmp(name, "zlib@openssh.com") == 0) {
332 comp->type = COMP_DELAYED;
333 } else if (strcmp(name, "zlib") == 0) {
334 comp->type = COMP_ZLIB;
335 } else if (strcmp(name, "none") == 0) {
336 comp->type = COMP_NONE;
338 fatal("unsupported comp %s", name);
344 choose_kex(Kex *k, char *client, char *server)
346 k->name = match_list(client, server, NULL);
348 fatal("Unable to negotiate a key exchange method");
349 if (strcmp(k->name, KEX_DH1) == 0) {
350 k->kex_type = KEX_DH_GRP1_SHA1;
351 k->evp_md = EVP_sha1();
352 } else if (strcmp(k->name, KEX_DH14) == 0) {
353 k->kex_type = KEX_DH_GRP14_SHA1;
354 k->evp_md = EVP_sha1();
355 } else if (strcmp(k->name, KEX_DHGEX_SHA1) == 0) {
356 k->kex_type = KEX_DH_GEX_SHA1;
357 k->evp_md = EVP_sha1();
358 #if OPENSSL_VERSION_NUMBER >= 0x00907000L
359 } else if (strcmp(k->name, KEX_DHGEX_SHA256) == 0) {
360 k->kex_type = KEX_DH_GEX_SHA256;
361 k->evp_md = evp_ssh_sha256();
362 } else if (strncmp(k->name, KEX_ECDH_SHA2_STEM,
363 sizeof(KEX_ECDH_SHA2_STEM) - 1) == 0) {
364 k->kex_type = KEX_ECDH_SHA2;
365 k->evp_md = kex_ecdh_name_to_evpmd(k->name);
368 fatal("bad kex alg %s", k->name);
372 choose_hostkeyalg(Kex *k, char *client, char *server)
374 char *hostkeyalg = match_list(client, server, NULL);
375 if (hostkeyalg == NULL)
376 fatal("no hostkey alg");
377 k->hostkey_type = key_type_from_name(hostkeyalg);
378 if (k->hostkey_type == KEY_UNSPEC)
379 fatal("bad hostkey alg '%s'", hostkeyalg);
384 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
386 static int check[] = {
387 PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
392 for (idx = &check[0]; *idx != -1; idx++) {
393 if ((p = strchr(my[*idx], ',')) != NULL)
395 if ((p = strchr(peer[*idx], ',')) != NULL)
397 if (strcmp(my[*idx], peer[*idx]) != 0) {
398 debug2("proposal mismatch: my %s peer %s",
399 my[*idx], peer[*idx]);
403 debug2("proposals match");
408 kex_choose_conf(Kex *kex)
412 char **cprop, **sprop;
413 int nenc, nmac, ncomp;
414 u_int mode, ctos, need;
415 int first_kex_follows, type;
416 #ifdef NONE_CIPHER_ENABLED
420 my = kex_buf2prop(&kex->my, NULL);
421 peer = kex_buf2prop(&kex->peer, &first_kex_follows);
431 /* Check whether server offers roaming */
434 roaming = match_list(KEX_RESUME, peer[PROPOSAL_KEX_ALGS], NULL);
441 /* Algorithm Negotiation */
442 #ifdef NONE_CIPHER_ENABLED
443 auth_flag = packet_get_authentication_state();
444 debug ("AUTH STATE is %d", auth_flag);
446 for (mode = 0; mode < MODE_MAX; mode++) {
447 newkeys = xcalloc(1, sizeof(*newkeys));
448 kex->newkeys[mode] = newkeys;
449 ctos = (!kex->server && mode == MODE_OUT) ||
450 (kex->server && mode == MODE_IN);
451 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
452 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
453 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
454 choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
455 choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
456 choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
457 #ifdef NONE_CIPHER_ENABLED
458 debug("REQUESTED ENC.NAME is '%s'", newkeys->enc.name);
459 if (strcmp(newkeys->enc.name, "none") == 0) {
460 debug("Requesting NONE. Authflag is %d", auth_flag);
462 debug("None requested post authentication.");
464 fatal("Pre-authentication none cipher requests "
468 debug("kex: %s %s %s %s",
469 ctos ? "client->server" : "server->client",
474 choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
475 choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
476 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
478 for (mode = 0; mode < MODE_MAX; mode++) {
479 newkeys = kex->newkeys[mode];
480 if (need < newkeys->enc.key_len)
481 need = newkeys->enc.key_len;
482 if (need < newkeys->enc.block_size)
483 need = newkeys->enc.block_size;
484 if (need < newkeys->mac.key_len)
485 need = newkeys->mac.key_len;
487 /* XXX need runden? */
490 /* ignore the next message if the proposals do not match */
491 if (first_kex_follows && !proposals_match(my, peer) &&
492 !(datafellows & SSH_BUG_FIRSTKEX)) {
493 type = packet_read();
494 debug2("skipping next packet (type %u)", type);
502 derive_key(Kex *kex, int id, u_int need, u_char *hash, u_int hashlen,
503 BIGNUM *shared_secret)
512 if ((mdsz = EVP_MD_size(kex->evp_md)) <= 0)
513 fatal("bad kex md size %d", mdsz);
514 digest = xmalloc(roundup(need, mdsz));
517 buffer_put_bignum2(&b, shared_secret);
519 /* K1 = HASH(K || H || "A" || session_id) */
520 EVP_DigestInit(&md, kex->evp_md);
521 if (!(datafellows & SSH_BUG_DERIVEKEY))
522 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
523 EVP_DigestUpdate(&md, hash, hashlen);
524 EVP_DigestUpdate(&md, &c, 1);
525 EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
526 EVP_DigestFinal(&md, digest, NULL);
530 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
531 * Key = K1 || K2 || ... || Kn
533 for (have = mdsz; need > have; have += mdsz) {
534 EVP_DigestInit(&md, kex->evp_md);
535 if (!(datafellows & SSH_BUG_DERIVEKEY))
536 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
537 EVP_DigestUpdate(&md, hash, hashlen);
538 EVP_DigestUpdate(&md, digest, have);
539 EVP_DigestFinal(&md, digest + have, NULL);
543 fprintf(stderr, "key '%c'== ", c);
544 dump_digest("key", digest, need);
549 Newkeys *current_keys[MODE_MAX];
553 kex_derive_keys(Kex *kex, u_char *hash, u_int hashlen, BIGNUM *shared_secret)
558 for (i = 0; i < NKEYS; i++) {
559 keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, hashlen,
563 debug2("kex_derive_keys");
564 for (mode = 0; mode < MODE_MAX; mode++) {
565 current_keys[mode] = kex->newkeys[mode];
566 kex->newkeys[mode] = NULL;
567 ctos = (!kex->server && mode == MODE_OUT) ||
568 (kex->server && mode == MODE_IN);
569 current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
570 current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
571 current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
576 kex_get_newkeys(int mode)
580 ret = current_keys[mode];
581 current_keys[mode] = NULL;
586 derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
587 u_int8_t cookie[8], u_int8_t id[16])
589 const EVP_MD *evp_md = EVP_md5();
591 u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE];
594 EVP_DigestInit(&md, evp_md);
596 len = BN_num_bytes(host_modulus);
597 if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
598 fatal("%s: bad host modulus (len %d)", __func__, len);
599 BN_bn2bin(host_modulus, nbuf);
600 EVP_DigestUpdate(&md, nbuf, len);
602 len = BN_num_bytes(server_modulus);
603 if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
604 fatal("%s: bad server modulus (len %d)", __func__, len);
605 BN_bn2bin(server_modulus, nbuf);
606 EVP_DigestUpdate(&md, nbuf, len);
608 EVP_DigestUpdate(&md, cookie, 8);
610 EVP_DigestFinal(&md, obuf, NULL);
611 memcpy(id, obuf, 16);
613 memset(nbuf, 0, sizeof(nbuf));
614 memset(obuf, 0, sizeof(obuf));
615 memset(&md, 0, sizeof(md));
618 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
620 dump_digest(char *msg, u_char *digest, int len)
624 fprintf(stderr, "%s\n", msg);
625 for (i = 0; i < len; i++) {
626 fprintf(stderr, "%02x", digest[i]);
628 fprintf(stderr, "\n");
630 fprintf(stderr, " ");
632 fprintf(stderr, "\n");