1 /* $OpenBSD: kex.c,v 1.80 2008/09/06 12:24:13 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>
57 #define KEX_COOKIE_LEN 16
59 #if OPENSSL_VERSION_NUMBER >= 0x00907000L
60 # if defined(HAVE_EVP_SHA256)
61 # define evp_ssh_sha256 EVP_sha256
63 extern const EVP_MD *evp_ssh_sha256(void);
68 static void kex_kexinit_finish(Kex *);
69 static void kex_choose_conf(Kex *);
71 /* put algorithm proposal into buffer */
72 /* used in sshconnect.c as well as kex.c */
74 kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
80 * add a dummy cookie, the cookie will be overwritten by
81 * kex_send_kexinit(), each time a kexinit is set
83 for (i = 0; i < KEX_COOKIE_LEN; i++)
84 buffer_put_char(b, 0);
85 for (i = 0; i < PROPOSAL_MAX; i++)
86 buffer_put_cstring(b, proposal[i]);
87 buffer_put_char(b, 0); /* first_kex_packet_follows */
88 buffer_put_int(b, 0); /* uint32 reserved */
91 /* parse buffer and return algorithm proposal */
93 kex_buf2prop(Buffer *raw, int *first_kex_follows)
99 proposal = xcalloc(PROPOSAL_MAX, sizeof(char *));
102 buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
104 for (i = 0; i < KEX_COOKIE_LEN; i++)
106 /* extract kex init proposal strings */
107 for (i = 0; i < PROPOSAL_MAX; i++) {
108 proposal[i] = buffer_get_string(&b,NULL);
109 debug2("kex_parse_kexinit: %s", proposal[i]);
111 /* first kex follows / reserved */
112 i = buffer_get_char(&b);
113 if (first_kex_follows != NULL)
114 *first_kex_follows = i;
115 debug2("kex_parse_kexinit: first_kex_follows %d ", i);
116 i = buffer_get_int(&b);
117 debug2("kex_parse_kexinit: reserved %u ", i);
123 kex_prop_free(char **proposal)
127 for (i = 0; i < PROPOSAL_MAX; i++)
134 kex_protocol_error(int type, u_int32_t seq, void *ctxt)
136 error("Hm, kex protocol error: type %d seq %u", type, seq);
140 kex_reset_dispatch(void)
142 dispatch_range(SSH2_MSG_TRANSPORT_MIN,
143 SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
144 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
150 kex_reset_dispatch();
152 packet_start(SSH2_MSG_NEWKEYS);
154 /* packet_write_wait(); */
155 debug("SSH2_MSG_NEWKEYS sent");
157 debug("expecting SSH2_MSG_NEWKEYS");
158 packet_read_expect(SSH2_MSG_NEWKEYS);
160 debug("SSH2_MSG_NEWKEYS received");
163 buffer_clear(&kex->peer);
164 /* buffer_clear(&kex->my); */
165 kex->flags &= ~KEX_INIT_SENT;
171 kex_send_kexinit(Kex *kex)
178 error("kex_send_kexinit: no kex, cannot rekey");
181 if (kex->flags & KEX_INIT_SENT) {
182 debug("KEX_INIT_SENT");
187 /* generate a random cookie */
188 if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
189 fatal("kex_send_kexinit: kex proposal too short");
190 cookie = buffer_ptr(&kex->my);
191 for (i = 0; i < KEX_COOKIE_LEN; i++) {
197 packet_start(SSH2_MSG_KEXINIT);
198 packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
200 debug("SSH2_MSG_KEXINIT sent");
201 kex->flags |= KEX_INIT_SENT;
206 kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
210 Kex *kex = (Kex *)ctxt;
212 debug("SSH2_MSG_KEXINIT received");
214 fatal("kex_input_kexinit: no kex, cannot rekey");
216 ptr = packet_get_raw(&dlen);
217 buffer_append(&kex->peer, ptr, dlen);
220 for (i = 0; i < KEX_COOKIE_LEN; i++)
222 for (i = 0; i < PROPOSAL_MAX; i++)
223 xfree(packet_get_string(NULL));
224 (void) packet_get_char();
225 (void) packet_get_int();
228 kex_kexinit_finish(kex);
232 kex_setup(char *proposal[PROPOSAL_MAX])
236 kex = xcalloc(1, sizeof(*kex));
237 buffer_init(&kex->peer);
238 buffer_init(&kex->my);
239 kex_prop2buf(&kex->my, proposal);
242 kex_send_kexinit(kex); /* we start */
243 kex_reset_dispatch();
249 kex_kexinit_finish(Kex *kex)
251 if (!(kex->flags & KEX_INIT_SENT))
252 kex_send_kexinit(kex);
254 kex_choose_conf(kex);
256 if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
257 kex->kex[kex->kex_type] != NULL) {
258 (kex->kex[kex->kex_type])(kex);
260 fatal("Unsupported key exchange %d", kex->kex_type);
265 choose_enc(Enc *enc, char *client, char *server)
267 char *name = match_list(client, server, NULL);
269 fatal("no matching cipher found: client %s server %s",
271 if ((enc->cipher = cipher_by_name(name)) == NULL)
272 fatal("matching cipher is not supported: %s", name);
277 enc->key_len = cipher_keylen(enc->cipher);
278 enc->block_size = cipher_blocksize(enc->cipher);
282 choose_mac(Mac *mac, char *client, char *server)
284 char *name = match_list(client, server, NULL);
286 fatal("no matching mac found: client %s server %s",
288 if (mac_setup(mac, name) < 0)
289 fatal("unsupported mac %s", name);
290 /* truncate the key */
291 if (datafellows & SSH_BUG_HMAC)
299 choose_comp(Comp *comp, char *client, char *server)
301 char *name = match_list(client, server, NULL);
303 fatal("no matching comp found: client %s server %s", client, server);
304 if (strcmp(name, "zlib@openssh.com") == 0) {
305 comp->type = COMP_DELAYED;
306 } else if (strcmp(name, "zlib") == 0) {
307 comp->type = COMP_ZLIB;
308 } else if (strcmp(name, "none") == 0) {
309 comp->type = COMP_NONE;
311 fatal("unsupported comp %s", name);
317 choose_kex(Kex *k, char *client, char *server)
319 k->name = match_list(client, server, NULL);
321 fatal("Unable to negotiate a key exchange method");
322 if (strcmp(k->name, KEX_DH1) == 0) {
323 k->kex_type = KEX_DH_GRP1_SHA1;
324 k->evp_md = EVP_sha1();
325 } else if (strcmp(k->name, KEX_DH14) == 0) {
326 k->kex_type = KEX_DH_GRP14_SHA1;
327 k->evp_md = EVP_sha1();
328 } else if (strcmp(k->name, KEX_DHGEX_SHA1) == 0) {
329 k->kex_type = KEX_DH_GEX_SHA1;
330 k->evp_md = EVP_sha1();
331 #if OPENSSL_VERSION_NUMBER >= 0x00907000L
332 } else if (strcmp(k->name, KEX_DHGEX_SHA256) == 0) {
333 k->kex_type = KEX_DH_GEX_SHA256;
334 k->evp_md = evp_ssh_sha256();
337 } else if (strncmp(k->name, KEX_GSS_GEX_SHA1_ID,
338 sizeof(KEX_GSS_GEX_SHA1_ID) - 1) == 0) {
339 k->kex_type = KEX_GSS_GEX_SHA1;
340 k->evp_md = EVP_sha1();
341 } else if (strncmp(k->name, KEX_GSS_GRP1_SHA1_ID,
342 sizeof(KEX_GSS_GRP1_SHA1_ID) - 1) == 0) {
343 k->kex_type = KEX_GSS_GRP1_SHA1;
344 k->evp_md = EVP_sha1();
345 } else if (strncmp(k->name, KEX_GSS_GRP14_SHA1_ID,
346 sizeof(KEX_GSS_GRP14_SHA1_ID) - 1) == 0) {
347 k->kex_type = KEX_GSS_GRP14_SHA1;
348 k->evp_md = EVP_sha1();
351 fatal("bad kex alg %s", k->name);
355 choose_hostkeyalg(Kex *k, char *client, char *server)
357 char *hostkeyalg = match_list(client, server, NULL);
358 if (hostkeyalg == NULL)
359 fatal("no hostkey alg");
360 k->hostkey_type = key_type_from_name(hostkeyalg);
361 if (k->hostkey_type == KEY_UNSPEC)
362 fatal("bad hostkey alg '%s'", hostkeyalg);
367 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
369 static int check[] = {
370 PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
375 for (idx = &check[0]; *idx != -1; idx++) {
376 if ((p = strchr(my[*idx], ',')) != NULL)
378 if ((p = strchr(peer[*idx], ',')) != NULL)
380 if (strcmp(my[*idx], peer[*idx]) != 0) {
381 debug2("proposal mismatch: my %s peer %s",
382 my[*idx], peer[*idx]);
386 debug2("proposals match");
391 kex_choose_conf(Kex *kex)
395 char **cprop, **sprop;
396 int nenc, nmac, ncomp;
397 u_int mode, ctos, need;
398 int first_kex_follows, type;
403 auth_flag = packet_authentication_state();
405 debug ("AUTH STATE IS %d", auth_flag);
407 my = kex_buf2prop(&kex->my, NULL);
408 peer = kex_buf2prop(&kex->peer, &first_kex_follows);
418 /* Algorithm Negotiation */
419 for (mode = 0; mode < MODE_MAX; mode++) {
420 newkeys = xcalloc(1, sizeof(*newkeys));
421 kex->newkeys[mode] = newkeys;
422 ctos = (!kex->server && mode == MODE_OUT) ||
423 (kex->server && mode == MODE_IN);
424 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
425 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
426 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
427 choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
428 choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
429 choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
430 debug("REQUESTED ENC.NAME is '%s'", newkeys->enc.name);
431 if (strcmp(newkeys->enc.name, "none") == 0) {
432 debug("Requesting NONE. Authflag is %d", auth_flag);
433 if (auth_flag == 1) {
434 debug("None requested post authentication.");
436 fatal("Pre-authentication none cipher requests are not allowed.");
439 debug("kex: %s %s %s %s",
440 ctos ? "client->server" : "server->client",
444 /* client starts withctos = 0 && log flag = 0 and no log*/
445 /* 2nd client pass ctos=1 and flag = 1 so no log*/
446 /* server starts with ctos =1 && log_flag = 0 so log */
447 /* 2nd sever pass ctos = 1 && log flag = 1 so no log*/
449 if (ctos && !log_flag) {
450 logit("SSH: Server;Ltype: Kex;Remote: %s-%d;Enc: %s;MAC: %s;Comp: %s",
459 choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
460 choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
461 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
463 for (mode = 0; mode < MODE_MAX; mode++) {
464 newkeys = kex->newkeys[mode];
465 if (need < newkeys->enc.key_len)
466 need = newkeys->enc.key_len;
467 if (need < newkeys->enc.block_size)
468 need = newkeys->enc.block_size;
469 if (need < newkeys->mac.key_len)
470 need = newkeys->mac.key_len;
472 /* XXX need runden? */
475 /* ignore the next message if the proposals do not match */
476 if (first_kex_follows && !proposals_match(my, peer) &&
477 !(datafellows & SSH_BUG_FIRSTKEX)) {
478 type = packet_read();
479 debug2("skipping next packet (type %u)", type);
487 derive_key(Kex *kex, int id, u_int need, u_char *hash, u_int hashlen,
488 BIGNUM *shared_secret)
497 if ((mdsz = EVP_MD_size(kex->evp_md)) <= 0)
498 fatal("bad kex md size %d", mdsz);
499 digest = xmalloc(roundup(need, mdsz));
502 buffer_put_bignum2(&b, shared_secret);
504 /* K1 = HASH(K || H || "A" || session_id) */
505 EVP_DigestInit(&md, kex->evp_md);
506 if (!(datafellows & SSH_BUG_DERIVEKEY))
507 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
508 EVP_DigestUpdate(&md, hash, hashlen);
509 EVP_DigestUpdate(&md, &c, 1);
510 EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
511 EVP_DigestFinal(&md, digest, NULL);
515 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
516 * Key = K1 || K2 || ... || Kn
518 for (have = mdsz; need > have; have += mdsz) {
519 EVP_DigestInit(&md, kex->evp_md);
520 if (!(datafellows & SSH_BUG_DERIVEKEY))
521 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
522 EVP_DigestUpdate(&md, hash, hashlen);
523 EVP_DigestUpdate(&md, digest, have);
524 EVP_DigestFinal(&md, digest + have, NULL);
528 fprintf(stderr, "key '%c'== ", c);
529 dump_digest("key", digest, need);
534 Newkeys *current_keys[MODE_MAX];
538 kex_derive_keys(Kex *kex, u_char *hash, u_int hashlen, BIGNUM *shared_secret)
543 for (i = 0; i < NKEYS; i++) {
544 keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, hashlen,
548 debug2("kex_derive_keys");
549 for (mode = 0; mode < MODE_MAX; mode++) {
550 current_keys[mode] = kex->newkeys[mode];
551 kex->newkeys[mode] = NULL;
552 ctos = (!kex->server && mode == MODE_OUT) ||
553 (kex->server && mode == MODE_IN);
554 current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
555 current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
556 current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
561 kex_get_newkeys(int mode)
565 ret = current_keys[mode];
566 current_keys[mode] = NULL;
571 derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
572 u_int8_t cookie[8], u_int8_t id[16])
574 const EVP_MD *evp_md = EVP_md5();
576 u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE];
579 EVP_DigestInit(&md, evp_md);
581 len = BN_num_bytes(host_modulus);
582 if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
583 fatal("%s: bad host modulus (len %d)", __func__, len);
584 BN_bn2bin(host_modulus, nbuf);
585 EVP_DigestUpdate(&md, nbuf, len);
587 len = BN_num_bytes(server_modulus);
588 if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
589 fatal("%s: bad server modulus (len %d)", __func__, len);
590 BN_bn2bin(server_modulus, nbuf);
591 EVP_DigestUpdate(&md, nbuf, len);
593 EVP_DigestUpdate(&md, cookie, 8);
595 EVP_DigestFinal(&md, obuf, NULL);
596 memcpy(id, obuf, 16);
598 memset(nbuf, 0, sizeof(nbuf));
599 memset(obuf, 0, sizeof(obuf));
600 memset(&md, 0, sizeof(md));
603 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
605 dump_digest(char *msg, u_char *digest, int len)
609 fprintf(stderr, "%s\n", msg);
610 for (i = 0; i < len; i++) {
611 fprintf(stderr, "%02x", digest[i]);
613 fprintf(stderr, "\n");
615 fprintf(stderr, " ");
617 fprintf(stderr, "\n");