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>
45 #define KEX_COOKIE_LEN 16
48 static void kex_kexinit_finish(Kex *);
49 static void kex_choose_conf(Kex *);
51 /* put algorithm proposal into buffer */
53 kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
59 * add a dummy cookie, the cookie will be overwritten by
60 * kex_send_kexinit(), each time a kexinit is set
62 for (i = 0; i < KEX_COOKIE_LEN; i++)
63 buffer_put_char(b, 0);
64 for (i = 0; i < PROPOSAL_MAX; i++)
65 buffer_put_cstring(b, proposal[i]);
66 buffer_put_char(b, 0); /* first_kex_packet_follows */
67 buffer_put_int(b, 0); /* uint32 reserved */
70 /* parse buffer and return algorithm proposal */
72 kex_buf2prop(Buffer *raw, int *first_kex_follows)
78 proposal = xmalloc(PROPOSAL_MAX * sizeof(char *));
81 buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
83 for (i = 0; i < KEX_COOKIE_LEN; i++)
85 /* extract kex init proposal strings */
86 for (i = 0; i < PROPOSAL_MAX; i++) {
87 proposal[i] = buffer_get_string(&b,NULL);
88 debug2("kex_parse_kexinit: %s", proposal[i]);
90 /* first kex follows / reserved */
91 i = buffer_get_char(&b);
92 if (first_kex_follows != NULL)
93 *first_kex_follows = i;
94 debug2("kex_parse_kexinit: first_kex_follows %d ", i);
95 i = buffer_get_int(&b);
96 debug2("kex_parse_kexinit: reserved %d ", i);
102 kex_prop_free(char **proposal)
106 for (i = 0; i < PROPOSAL_MAX; i++)
112 kex_protocol_error(int type, u_int32_t seq, void *ctxt)
114 error("Hm, kex protocol error: type %d seq %u", type, seq);
118 kex_reset_dispatch(void)
120 dispatch_range(SSH2_MSG_TRANSPORT_MIN,
121 SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
122 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
128 kex_reset_dispatch();
130 packet_start(SSH2_MSG_NEWKEYS);
132 /* packet_write_wait(); */
133 debug("SSH2_MSG_NEWKEYS sent");
135 debug("expecting SSH2_MSG_NEWKEYS");
136 packet_read_expect(SSH2_MSG_NEWKEYS);
138 debug("SSH2_MSG_NEWKEYS received");
141 buffer_clear(&kex->peer);
142 /* buffer_clear(&kex->my); */
143 kex->flags &= ~KEX_INIT_SENT;
149 kex_send_kexinit(Kex *kex)
156 error("kex_send_kexinit: no kex, cannot rekey");
159 if (kex->flags & KEX_INIT_SENT) {
160 debug("KEX_INIT_SENT");
165 /* generate a random cookie */
166 if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
167 fatal("kex_send_kexinit: kex proposal too short");
168 cookie = buffer_ptr(&kex->my);
169 for (i = 0; i < KEX_COOKIE_LEN; i++) {
175 packet_start(SSH2_MSG_KEXINIT);
176 packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
178 debug("SSH2_MSG_KEXINIT sent");
179 kex->flags |= KEX_INIT_SENT;
183 kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
188 Kex *kex = (Kex *)ctxt;
190 debug("SSH2_MSG_KEXINIT received");
192 fatal("kex_input_kexinit: no kex, cannot rekey");
194 ptr = packet_get_raw(&dlen);
195 buffer_append(&kex->peer, ptr, dlen);
198 for (i = 0; i < KEX_COOKIE_LEN; i++)
200 for (i = 0; i < PROPOSAL_MAX; i++)
201 xfree(packet_get_string(NULL));
202 (void) packet_get_char();
203 (void) packet_get_int();
206 kex_kexinit_finish(kex);
210 kex_setup(char *proposal[PROPOSAL_MAX])
214 kex = xmalloc(sizeof(*kex));
215 memset(kex, 0, sizeof(*kex));
216 buffer_init(&kex->peer);
217 buffer_init(&kex->my);
218 kex_prop2buf(&kex->my, proposal);
221 kex_send_kexinit(kex); /* we start */
222 kex_reset_dispatch();
228 kex_kexinit_finish(Kex *kex)
230 if (!(kex->flags & KEX_INIT_SENT))
231 kex_send_kexinit(kex);
233 kex_choose_conf(kex);
235 if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
236 kex->kex[kex->kex_type] != NULL) {
237 (kex->kex[kex->kex_type])(kex);
239 fatal("Unsupported key exchange %d", kex->kex_type);
244 choose_enc(Enc *enc, char *client, char *server)
246 char *name = match_list(client, server, NULL);
248 fatal("no matching cipher found: client %s server %s", client, server);
249 if ((enc->cipher = cipher_by_name(name)) == NULL)
250 fatal("matching cipher is not supported: %s", name);
255 enc->key_len = cipher_keylen(enc->cipher);
256 enc->block_size = cipher_blocksize(enc->cipher);
259 choose_mac(Mac *mac, char *client, char *server)
261 char *name = match_list(client, server, NULL);
263 fatal("no matching mac found: client %s server %s", client, server);
264 if (mac_init(mac, name) < 0)
265 fatal("unsupported mac %s", name);
266 /* truncate the key */
267 if (datafellows & SSH_BUG_HMAC)
274 choose_comp(Comp *comp, char *client, char *server)
276 char *name = match_list(client, server, NULL);
278 fatal("no matching comp found: client %s server %s", client, server);
279 if (strcmp(name, "zlib") == 0) {
281 } else if (strcmp(name, "none") == 0) {
284 fatal("unsupported comp %s", name);
289 choose_kex(Kex *k, char *client, char *server)
291 k->name = match_list(client, server, NULL);
294 if (strcmp(k->name, KEX_DH1) == 0) {
295 k->kex_type = KEX_DH_GRP1_SHA1;
296 } else if (strcmp(k->name, KEX_DH14) == 0) {
297 k->kex_type = KEX_DH_GRP14_SHA1;
298 } else if (strcmp(k->name, KEX_DHGEX) == 0) {
299 k->kex_type = KEX_DH_GEX_SHA1;
301 fatal("bad kex alg %s", k->name);
304 choose_hostkeyalg(Kex *k, char *client, char *server)
306 char *hostkeyalg = match_list(client, server, NULL);
307 if (hostkeyalg == NULL)
308 fatal("no hostkey alg");
309 k->hostkey_type = key_type_from_name(hostkeyalg);
310 if (k->hostkey_type == KEY_UNSPEC)
311 fatal("bad hostkey alg '%s'", hostkeyalg);
316 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
318 static int check[] = {
319 PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
324 for (idx = &check[0]; *idx != -1; idx++) {
325 if ((p = strchr(my[*idx], ',')) != NULL)
327 if ((p = strchr(peer[*idx], ',')) != NULL)
329 if (strcmp(my[*idx], peer[*idx]) != 0) {
330 debug2("proposal mismatch: my %s peer %s",
331 my[*idx], peer[*idx]);
335 debug2("proposals match");
340 kex_choose_conf(Kex *kex)
344 char **cprop, **sprop;
345 int nenc, nmac, ncomp;
347 int ctos; /* direction: if true client-to-server */
349 int first_kex_follows, type;
351 my = kex_buf2prop(&kex->my, NULL);
352 peer = kex_buf2prop(&kex->peer, &first_kex_follows);
362 /* Algorithm Negotiation */
363 for (mode = 0; mode < MODE_MAX; mode++) {
364 newkeys = xmalloc(sizeof(*newkeys));
365 memset(newkeys, 0, sizeof(*newkeys));
366 kex->newkeys[mode] = newkeys;
367 ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
368 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
369 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
370 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
371 choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
372 choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
373 choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
374 debug("kex: %s %s %s %s",
375 ctos ? "client->server" : "server->client",
380 choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
381 choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
382 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
384 for (mode = 0; mode < MODE_MAX; mode++) {
385 newkeys = kex->newkeys[mode];
386 if (need < newkeys->enc.key_len)
387 need = newkeys->enc.key_len;
388 if (need < newkeys->enc.block_size)
389 need = newkeys->enc.block_size;
390 if (need < newkeys->mac.key_len)
391 need = newkeys->mac.key_len;
393 /* XXX need runden? */
396 /* ignore the next message if the proposals do not match */
397 if (first_kex_follows && !proposals_match(my, peer) &&
398 !(datafellows & SSH_BUG_FIRSTKEX)) {
399 type = packet_read();
400 debug2("skipping next packet (type %u)", type);
408 derive_key(Kex *kex, int id, int need, u_char *hash, BIGNUM *shared_secret)
411 const EVP_MD *evp_md = EVP_sha1();
415 int mdsz = EVP_MD_size(evp_md);
416 u_char *digest = xmalloc(roundup(need, mdsz));
419 buffer_put_bignum2(&b, shared_secret);
421 /* K1 = HASH(K || H || "A" || session_id) */
422 EVP_DigestInit(&md, evp_md);
423 if (!(datafellows & SSH_BUG_DERIVEKEY))
424 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
425 EVP_DigestUpdate(&md, hash, mdsz);
426 EVP_DigestUpdate(&md, &c, 1);
427 EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
428 EVP_DigestFinal(&md, digest, NULL);
432 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
433 * Key = K1 || K2 || ... || Kn
435 for (have = mdsz; need > have; have += mdsz) {
436 EVP_DigestInit(&md, evp_md);
437 if (!(datafellows & SSH_BUG_DERIVEKEY))
438 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
439 EVP_DigestUpdate(&md, hash, mdsz);
440 EVP_DigestUpdate(&md, digest, have);
441 EVP_DigestFinal(&md, digest + have, NULL);
445 fprintf(stderr, "key '%c'== ", c);
446 dump_digest("key", digest, need);
451 Newkeys *current_keys[MODE_MAX];
455 kex_derive_keys(Kex *kex, u_char *hash, BIGNUM *shared_secret)
460 for (i = 0; i < NKEYS; i++)
461 keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret);
463 debug2("kex_derive_keys");
464 for (mode = 0; mode < MODE_MAX; mode++) {
465 current_keys[mode] = kex->newkeys[mode];
466 kex->newkeys[mode] = NULL;
467 ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
468 current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
469 current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
470 current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
475 kex_get_newkeys(int mode)
479 ret = current_keys[mode];
480 current_keys[mode] = NULL;
485 derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
486 u_int8_t cookie[8], u_int8_t id[16])
488 const EVP_MD *evp_md = EVP_md5();
490 u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE];
493 EVP_DigestInit(&md, evp_md);
495 len = BN_num_bytes(host_modulus);
496 if (len < (512 / 8) || len > sizeof(nbuf))
497 fatal("%s: bad host modulus (len %d)", __func__, len);
498 BN_bn2bin(host_modulus, nbuf);
499 EVP_DigestUpdate(&md, nbuf, len);
501 len = BN_num_bytes(server_modulus);
502 if (len < (512 / 8) || len > sizeof(nbuf))
503 fatal("%s: bad server modulus (len %d)", __func__, len);
504 BN_bn2bin(server_modulus, nbuf);
505 EVP_DigestUpdate(&md, nbuf, len);
507 EVP_DigestUpdate(&md, cookie, 8);
509 EVP_DigestFinal(&md, obuf, NULL);
510 memcpy(id, obuf, 16);
512 memset(nbuf, 0, sizeof(nbuf));
513 memset(obuf, 0, sizeof(obuf));
514 memset(&md, 0, sizeof(md));
517 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
519 dump_digest(char *msg, u_char *digest, int len)
523 fprintf(stderr, "%s\n", msg);
524 for (i = 0; i< len; i++) {
525 fprintf(stderr, "%02x", digest[i]);
527 fprintf(stderr, "\n");
529 fprintf(stderr, " ");
531 fprintf(stderr, "\n");