1 /* $OpenBSD: kex.c,v 1.86 2010/09/22 05:01:29 djm Exp $ */
3 * Copyright (c) 2000, 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.
28 #include <sys/param.h>
36 #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 /* used in sshconnect.c as well as kex.c */
97 kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
103 * add a dummy cookie, the cookie will be overwritten by
104 * kex_send_kexinit(), each time a kexinit is set
106 for (i = 0; i < KEX_COOKIE_LEN; i++)
107 buffer_put_char(b, 0);
108 for (i = 0; i < PROPOSAL_MAX; i++)
109 buffer_put_cstring(b, proposal[i]);
110 buffer_put_char(b, 0); /* first_kex_packet_follows */
111 buffer_put_int(b, 0); /* uint32 reserved */
114 /* parse buffer and return algorithm proposal */
116 kex_buf2prop(Buffer *raw, int *first_kex_follows)
122 proposal = xcalloc(PROPOSAL_MAX, sizeof(char *));
125 buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
127 for (i = 0; i < KEX_COOKIE_LEN; i++)
129 /* extract kex init proposal strings */
130 for (i = 0; i < PROPOSAL_MAX; i++) {
131 proposal[i] = buffer_get_cstring(&b,NULL);
132 debug2("kex_parse_kexinit: %s", proposal[i]);
134 /* first kex follows / reserved */
135 i = buffer_get_char(&b);
136 if (first_kex_follows != NULL)
137 *first_kex_follows = i;
138 debug2("kex_parse_kexinit: first_kex_follows %d ", i);
139 i = buffer_get_int(&b);
140 debug2("kex_parse_kexinit: reserved %u ", i);
146 kex_prop_free(char **proposal)
150 for (i = 0; i < PROPOSAL_MAX; i++)
157 kex_protocol_error(int type, u_int32_t seq, void *ctxt)
159 error("Hm, kex protocol error: type %d seq %u", type, seq);
163 kex_reset_dispatch(void)
165 dispatch_range(SSH2_MSG_TRANSPORT_MIN,
166 SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
167 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
173 kex_reset_dispatch();
175 packet_start(SSH2_MSG_NEWKEYS);
177 /* packet_write_wait(); */
178 debug("SSH2_MSG_NEWKEYS sent");
180 debug("expecting SSH2_MSG_NEWKEYS");
181 packet_read_expect(SSH2_MSG_NEWKEYS);
183 debug("SSH2_MSG_NEWKEYS received");
186 buffer_clear(&kex->peer);
187 /* buffer_clear(&kex->my); */
188 kex->flags &= ~KEX_INIT_SENT;
194 kex_send_kexinit(Kex *kex)
201 error("kex_send_kexinit: no kex, cannot rekey");
204 if (kex->flags & KEX_INIT_SENT) {
205 debug("KEX_INIT_SENT");
210 /* generate a random cookie */
211 if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
212 fatal("kex_send_kexinit: kex proposal too short");
213 cookie = buffer_ptr(&kex->my);
214 for (i = 0; i < KEX_COOKIE_LEN; i++) {
220 packet_start(SSH2_MSG_KEXINIT);
221 packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
223 debug("SSH2_MSG_KEXINIT sent");
224 kex->flags |= KEX_INIT_SENT;
229 kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
233 Kex *kex = (Kex *)ctxt;
235 debug("SSH2_MSG_KEXINIT received");
237 fatal("kex_input_kexinit: no kex, cannot rekey");
239 ptr = packet_get_raw(&dlen);
240 buffer_append(&kex->peer, ptr, dlen);
243 for (i = 0; i < KEX_COOKIE_LEN; i++)
245 for (i = 0; i < PROPOSAL_MAX; i++)
246 xfree(packet_get_string(NULL));
247 (void) packet_get_char();
248 (void) packet_get_int();
251 kex_kexinit_finish(kex);
255 kex_setup(char *proposal[PROPOSAL_MAX])
259 kex = xcalloc(1, sizeof(*kex));
260 buffer_init(&kex->peer);
261 buffer_init(&kex->my);
262 kex_prop2buf(&kex->my, proposal);
265 kex_send_kexinit(kex); /* we start */
266 kex_reset_dispatch();
272 kex_kexinit_finish(Kex *kex)
274 if (!(kex->flags & KEX_INIT_SENT))
275 kex_send_kexinit(kex);
277 kex_choose_conf(kex);
279 if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
280 kex->kex[kex->kex_type] != NULL) {
281 (kex->kex[kex->kex_type])(kex);
283 fatal("Unsupported key exchange %d", kex->kex_type);
288 choose_enc(Enc *enc, char *client, char *server)
290 char *name = match_list(client, server, NULL);
292 fatal("no matching cipher found: client %s server %s",
294 if ((enc->cipher = cipher_by_name(name)) == NULL)
295 fatal("matching cipher is not supported: %s", name);
300 enc->key_len = cipher_keylen(enc->cipher);
301 enc->block_size = cipher_blocksize(enc->cipher);
305 choose_mac(Mac *mac, char *client, char *server)
307 char *name = match_list(client, server, NULL);
309 fatal("no matching mac found: client %s server %s",
311 if (mac_setup(mac, name) < 0)
312 fatal("unsupported mac %s", name);
313 /* truncate the key */
314 if (datafellows & SSH_BUG_HMAC)
322 choose_comp(Comp *comp, char *client, char *server)
324 char *name = match_list(client, server, NULL);
326 fatal("no matching comp found: client %s server %s", client, server);
327 if (strcmp(name, "zlib@openssh.com") == 0) {
328 comp->type = COMP_DELAYED;
329 } else if (strcmp(name, "zlib") == 0) {
330 comp->type = COMP_ZLIB;
331 } else if (strcmp(name, "none") == 0) {
332 comp->type = COMP_NONE;
334 fatal("unsupported comp %s", name);
340 choose_kex(Kex *k, char *client, char *server)
342 k->name = match_list(client, server, NULL);
344 fatal("Unable to negotiate a key exchange method");
345 if (strcmp(k->name, KEX_DH1) == 0) {
346 k->kex_type = KEX_DH_GRP1_SHA1;
347 k->evp_md = EVP_sha1();
348 } else if (strcmp(k->name, KEX_DH14) == 0) {
349 k->kex_type = KEX_DH_GRP14_SHA1;
350 k->evp_md = EVP_sha1();
351 } else if (strcmp(k->name, KEX_DHGEX_SHA1) == 0) {
352 k->kex_type = KEX_DH_GEX_SHA1;
353 k->evp_md = EVP_sha1();
354 #if OPENSSL_VERSION_NUMBER >= 0x00907000L
355 } else if (strcmp(k->name, KEX_DHGEX_SHA256) == 0) {
356 k->kex_type = KEX_DH_GEX_SHA256;
357 k->evp_md = evp_ssh_sha256();
358 } else if (strncmp(k->name, KEX_ECDH_SHA2_STEM,
359 sizeof(KEX_ECDH_SHA2_STEM) - 1) == 0) {
360 k->kex_type = KEX_ECDH_SHA2;
361 k->evp_md = kex_ecdh_name_to_evpmd(k->name);
364 fatal("bad kex alg %s", k->name);
368 choose_hostkeyalg(Kex *k, char *client, char *server)
370 char *hostkeyalg = match_list(client, server, NULL);
371 if (hostkeyalg == NULL)
372 fatal("no hostkey alg");
373 k->hostkey_type = key_type_from_name(hostkeyalg);
374 if (k->hostkey_type == KEY_UNSPEC)
375 fatal("bad hostkey alg '%s'", hostkeyalg);
380 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
382 static int check[] = {
383 PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
388 for (idx = &check[0]; *idx != -1; idx++) {
389 if ((p = strchr(my[*idx], ',')) != NULL)
391 if ((p = strchr(peer[*idx], ',')) != NULL)
393 if (strcmp(my[*idx], peer[*idx]) != 0) {
394 debug2("proposal mismatch: my %s peer %s",
395 my[*idx], peer[*idx]);
399 debug2("proposals match");
404 kex_choose_conf(Kex *kex)
408 char **cprop, **sprop;
409 int nenc, nmac, ncomp;
410 u_int mode, ctos, need;
411 int first_kex_follows, type;
416 auth_flag = packet_authentication_state();
418 debug ("AUTH STATE IS %d", auth_flag);
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 for (mode = 0; mode < MODE_MAX; mode++) {
443 newkeys = xcalloc(1, sizeof(*newkeys));
444 kex->newkeys[mode] = newkeys;
445 ctos = (!kex->server && mode == MODE_OUT) ||
446 (kex->server && mode == MODE_IN);
447 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
448 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
449 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
450 choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
451 choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
452 choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
453 debug("REQUESTED ENC.NAME is '%s'", newkeys->enc.name);
454 if (strcmp(newkeys->enc.name, "none") == 0) {
455 debug("Requesting NONE. Authflag is %d", auth_flag);
456 if (auth_flag == 1) {
457 debug("None requested post authentication.");
459 fatal("Pre-authentication none cipher requests are not allowed.");
462 debug("kex: %s %s %s %s",
463 ctos ? "client->server" : "server->client",
467 /* client starts withctos = 0 && log flag = 0 and no log*/
468 /* 2nd client pass ctos=1 and flag = 1 so no log*/
469 /* server starts with ctos =1 && log_flag = 0 so log */
470 /* 2nd sever pass ctos = 1 && log flag = 1 so no log*/
472 if (ctos && !log_flag) {
473 logit("SSH: Server;Ltype: Kex;Remote: %s-%d;Enc: %s;MAC: %s;Comp: %s",
482 choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
483 choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
484 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
486 for (mode = 0; mode < MODE_MAX; mode++) {
487 newkeys = kex->newkeys[mode];
488 if (need < newkeys->enc.key_len)
489 need = newkeys->enc.key_len;
490 if (need < newkeys->enc.block_size)
491 need = newkeys->enc.block_size;
492 if (need < newkeys->mac.key_len)
493 need = newkeys->mac.key_len;
495 /* XXX need runden? */
498 /* ignore the next message if the proposals do not match */
499 if (first_kex_follows && !proposals_match(my, peer) &&
500 !(datafellows & SSH_BUG_FIRSTKEX)) {
501 type = packet_read();
502 debug2("skipping next packet (type %u)", type);
510 derive_key(Kex *kex, int id, u_int need, u_char *hash, u_int hashlen,
511 BIGNUM *shared_secret)
520 if ((mdsz = EVP_MD_size(kex->evp_md)) <= 0)
521 fatal("bad kex md size %d", mdsz);
522 digest = xmalloc(roundup(need, mdsz));
525 buffer_put_bignum2(&b, shared_secret);
527 /* K1 = HASH(K || H || "A" || session_id) */
528 EVP_DigestInit(&md, kex->evp_md);
529 if (!(datafellows & SSH_BUG_DERIVEKEY))
530 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
531 EVP_DigestUpdate(&md, hash, hashlen);
532 EVP_DigestUpdate(&md, &c, 1);
533 EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
534 EVP_DigestFinal(&md, digest, NULL);
538 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
539 * Key = K1 || K2 || ... || Kn
541 for (have = mdsz; need > have; have += mdsz) {
542 EVP_DigestInit(&md, kex->evp_md);
543 if (!(datafellows & SSH_BUG_DERIVEKEY))
544 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
545 EVP_DigestUpdate(&md, hash, hashlen);
546 EVP_DigestUpdate(&md, digest, have);
547 EVP_DigestFinal(&md, digest + have, NULL);
551 fprintf(stderr, "key '%c'== ", c);
552 dump_digest("key", digest, need);
557 Newkeys *current_keys[MODE_MAX];
561 kex_derive_keys(Kex *kex, u_char *hash, u_int hashlen, BIGNUM *shared_secret)
566 for (i = 0; i < NKEYS; i++) {
567 keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, hashlen,
571 debug2("kex_derive_keys");
572 for (mode = 0; mode < MODE_MAX; mode++) {
573 current_keys[mode] = kex->newkeys[mode];
574 kex->newkeys[mode] = NULL;
575 ctos = (!kex->server && mode == MODE_OUT) ||
576 (kex->server && mode == MODE_IN);
577 current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
578 current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
579 current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
584 kex_get_newkeys(int mode)
588 ret = current_keys[mode];
589 current_keys[mode] = NULL;
594 derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
595 u_int8_t cookie[8], u_int8_t id[16])
597 const EVP_MD *evp_md = EVP_md5();
599 u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE];
602 EVP_DigestInit(&md, evp_md);
604 len = BN_num_bytes(host_modulus);
605 if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
606 fatal("%s: bad host modulus (len %d)", __func__, len);
607 BN_bn2bin(host_modulus, nbuf);
608 EVP_DigestUpdate(&md, nbuf, len);
610 len = BN_num_bytes(server_modulus);
611 if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
612 fatal("%s: bad server modulus (len %d)", __func__, len);
613 BN_bn2bin(server_modulus, nbuf);
614 EVP_DigestUpdate(&md, nbuf, len);
616 EVP_DigestUpdate(&md, cookie, 8);
618 EVP_DigestFinal(&md, obuf, NULL);
619 memcpy(id, obuf, 16);
621 memset(nbuf, 0, sizeof(nbuf));
622 memset(obuf, 0, sizeof(obuf));
623 memset(&md, 0, sizeof(md));
626 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
628 dump_digest(char *msg, u_char *digest, int len)
632 fprintf(stderr, "%s\n", msg);
633 for (i = 0; i < len; i++) {
634 fprintf(stderr, "%02x", digest[i]);
636 fprintf(stderr, "\n");
638 fprintf(stderr, " ");
640 fprintf(stderr, "\n");