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.
27 #include <openssl/crypto.h>
44 #define KEX_COOKIE_LEN 16
46 #if OPENSSL_VERSION_NUMBER >= 0x00907000L
47 # if defined(HAVE_EVP_SHA256)
48 # define evp_ssh_sha256 EVP_sha256
50 extern const EVP_MD *evp_ssh_sha256(void);
55 static void kex_kexinit_finish(Kex *);
56 static void kex_choose_conf(Kex *);
58 /* put algorithm proposal into buffer */
60 kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
66 * add a dummy cookie, the cookie will be overwritten by
67 * kex_send_kexinit(), each time a kexinit is set
69 for (i = 0; i < KEX_COOKIE_LEN; i++)
70 buffer_put_char(b, 0);
71 for (i = 0; i < PROPOSAL_MAX; i++)
72 buffer_put_cstring(b, proposal[i]);
73 buffer_put_char(b, 0); /* first_kex_packet_follows */
74 buffer_put_int(b, 0); /* uint32 reserved */
77 /* parse buffer and return algorithm proposal */
79 kex_buf2prop(Buffer *raw, int *first_kex_follows)
85 proposal = xmalloc(PROPOSAL_MAX * sizeof(char *));
88 buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
90 for (i = 0; i < KEX_COOKIE_LEN; i++)
92 /* extract kex init proposal strings */
93 for (i = 0; i < PROPOSAL_MAX; i++) {
94 proposal[i] = buffer_get_string(&b,NULL);
95 debug2("kex_parse_kexinit: %s", proposal[i]);
97 /* first kex follows / reserved */
98 i = buffer_get_char(&b);
99 if (first_kex_follows != NULL)
100 *first_kex_follows = i;
101 debug2("kex_parse_kexinit: first_kex_follows %d ", i);
102 i = buffer_get_int(&b);
103 debug2("kex_parse_kexinit: reserved %d ", i);
109 kex_prop_free(char **proposal)
113 for (i = 0; i < PROPOSAL_MAX; i++)
119 kex_protocol_error(int type, u_int32_t seq, void *ctxt)
121 error("Hm, kex protocol error: type %d seq %u", type, seq);
125 kex_reset_dispatch(void)
127 dispatch_range(SSH2_MSG_TRANSPORT_MIN,
128 SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
129 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
135 kex_reset_dispatch();
137 packet_start(SSH2_MSG_NEWKEYS);
139 /* packet_write_wait(); */
140 debug("SSH2_MSG_NEWKEYS sent");
142 debug("expecting SSH2_MSG_NEWKEYS");
143 packet_read_expect(SSH2_MSG_NEWKEYS);
145 debug("SSH2_MSG_NEWKEYS received");
148 buffer_clear(&kex->peer);
149 /* buffer_clear(&kex->my); */
150 kex->flags &= ~KEX_INIT_SENT;
156 kex_send_kexinit(Kex *kex)
163 error("kex_send_kexinit: no kex, cannot rekey");
166 if (kex->flags & KEX_INIT_SENT) {
167 debug("KEX_INIT_SENT");
172 /* generate a random cookie */
173 if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
174 fatal("kex_send_kexinit: kex proposal too short");
175 cookie = buffer_ptr(&kex->my);
176 for (i = 0; i < KEX_COOKIE_LEN; i++) {
182 packet_start(SSH2_MSG_KEXINIT);
183 packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
185 debug("SSH2_MSG_KEXINIT sent");
186 kex->flags |= KEX_INIT_SENT;
190 kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
194 Kex *kex = (Kex *)ctxt;
196 debug("SSH2_MSG_KEXINIT received");
198 fatal("kex_input_kexinit: no kex, cannot rekey");
200 ptr = packet_get_raw(&dlen);
201 buffer_append(&kex->peer, ptr, dlen);
204 for (i = 0; i < KEX_COOKIE_LEN; i++)
206 for (i = 0; i < PROPOSAL_MAX; i++)
207 xfree(packet_get_string(NULL));
208 (void) packet_get_char();
209 (void) packet_get_int();
212 kex_kexinit_finish(kex);
216 kex_setup(char *proposal[PROPOSAL_MAX])
220 kex = xmalloc(sizeof(*kex));
221 memset(kex, 0, sizeof(*kex));
222 buffer_init(&kex->peer);
223 buffer_init(&kex->my);
224 kex_prop2buf(&kex->my, proposal);
227 kex_send_kexinit(kex); /* we start */
228 kex_reset_dispatch();
234 kex_kexinit_finish(Kex *kex)
236 if (!(kex->flags & KEX_INIT_SENT))
237 kex_send_kexinit(kex);
239 kex_choose_conf(kex);
241 if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
242 kex->kex[kex->kex_type] != NULL) {
243 (kex->kex[kex->kex_type])(kex);
245 fatal("Unsupported key exchange %d", kex->kex_type);
250 choose_enc(Enc *enc, char *client, char *server)
252 char *name = match_list(client, server, NULL);
254 fatal("no matching cipher found: client %s server %s", client, server);
255 if ((enc->cipher = cipher_by_name(name)) == NULL)
256 fatal("matching cipher is not supported: %s", name);
261 enc->key_len = cipher_keylen(enc->cipher);
262 enc->block_size = cipher_blocksize(enc->cipher);
266 choose_mac(Mac *mac, char *client, char *server)
268 char *name = match_list(client, server, NULL);
270 fatal("no matching mac found: client %s server %s", client, server);
271 if (mac_init(mac, name) < 0)
272 fatal("unsupported mac %s", name);
273 /* truncate the key */
274 if (datafellows & SSH_BUG_HMAC)
282 choose_comp(Comp *comp, char *client, char *server)
284 char *name = match_list(client, server, NULL);
286 fatal("no matching comp found: client %s server %s", client, server);
287 if (strcmp(name, "zlib@openssh.com") == 0) {
288 comp->type = COMP_DELAYED;
289 } else if (strcmp(name, "zlib") == 0) {
290 comp->type = COMP_ZLIB;
291 } else if (strcmp(name, "none") == 0) {
292 comp->type = COMP_NONE;
294 fatal("unsupported comp %s", name);
300 choose_kex(Kex *k, char *client, char *server)
302 k->name = match_list(client, server, NULL);
305 if (strcmp(k->name, KEX_DH1) == 0) {
306 k->kex_type = KEX_DH_GRP1_SHA1;
307 k->evp_md = EVP_sha1();
308 } else if (strcmp(k->name, KEX_DH14) == 0) {
309 k->kex_type = KEX_DH_GRP14_SHA1;
310 k->evp_md = EVP_sha1();
311 } else if (strcmp(k->name, KEX_DHGEX_SHA1) == 0) {
312 k->kex_type = KEX_DH_GEX_SHA1;
313 k->evp_md = EVP_sha1();
314 #if OPENSSL_VERSION_NUMBER >= 0x00907000L
315 } else if (strcmp(k->name, KEX_DHGEX_SHA256) == 0) {
316 k->kex_type = KEX_DH_GEX_SHA256;
317 k->evp_md = evp_ssh_sha256();
320 fatal("bad kex alg %s", k->name);
324 choose_hostkeyalg(Kex *k, char *client, char *server)
326 char *hostkeyalg = match_list(client, server, NULL);
327 if (hostkeyalg == NULL)
328 fatal("no hostkey alg");
329 k->hostkey_type = key_type_from_name(hostkeyalg);
330 if (k->hostkey_type == KEY_UNSPEC)
331 fatal("bad hostkey alg '%s'", hostkeyalg);
336 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
338 static int check[] = {
339 PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
344 for (idx = &check[0]; *idx != -1; idx++) {
345 if ((p = strchr(my[*idx], ',')) != NULL)
347 if ((p = strchr(peer[*idx], ',')) != NULL)
349 if (strcmp(my[*idx], peer[*idx]) != 0) {
350 debug2("proposal mismatch: my %s peer %s",
351 my[*idx], peer[*idx]);
355 debug2("proposals match");
360 kex_choose_conf(Kex *kex)
364 char **cprop, **sprop;
365 int nenc, nmac, ncomp;
366 u_int mode, ctos, need;
367 int first_kex_follows, type;
369 my = kex_buf2prop(&kex->my, NULL);
370 peer = kex_buf2prop(&kex->peer, &first_kex_follows);
380 /* Algorithm Negotiation */
381 for (mode = 0; mode < MODE_MAX; mode++) {
382 newkeys = xmalloc(sizeof(*newkeys));
383 memset(newkeys, 0, sizeof(*newkeys));
384 kex->newkeys[mode] = newkeys;
385 ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
386 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
387 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
388 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
389 choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
390 choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
391 choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
392 debug("kex: %s %s %s %s",
393 ctos ? "client->server" : "server->client",
398 choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
399 choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
400 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
402 for (mode = 0; mode < MODE_MAX; mode++) {
403 newkeys = kex->newkeys[mode];
404 if (need < newkeys->enc.key_len)
405 need = newkeys->enc.key_len;
406 if (need < newkeys->enc.block_size)
407 need = newkeys->enc.block_size;
408 if (need < newkeys->mac.key_len)
409 need = newkeys->mac.key_len;
411 /* XXX need runden? */
414 /* ignore the next message if the proposals do not match */
415 if (first_kex_follows && !proposals_match(my, peer) &&
416 !(datafellows & SSH_BUG_FIRSTKEX)) {
417 type = packet_read();
418 debug2("skipping next packet (type %u)", type);
426 derive_key(Kex *kex, int id, u_int need, u_char *hash, u_int hashlen,
427 BIGNUM *shared_secret)
436 if ((mdsz = EVP_MD_size(kex->evp_md)) <= 0)
437 fatal("bad kex md size %d", mdsz);
438 digest = xmalloc(roundup(need, mdsz));
441 buffer_put_bignum2(&b, shared_secret);
443 /* K1 = HASH(K || H || "A" || session_id) */
444 EVP_DigestInit(&md, kex->evp_md);
445 if (!(datafellows & SSH_BUG_DERIVEKEY))
446 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
447 EVP_DigestUpdate(&md, hash, hashlen);
448 EVP_DigestUpdate(&md, &c, 1);
449 EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
450 EVP_DigestFinal(&md, digest, NULL);
454 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
455 * Key = K1 || K2 || ... || Kn
457 for (have = mdsz; need > have; have += mdsz) {
458 EVP_DigestInit(&md, kex->evp_md);
459 if (!(datafellows & SSH_BUG_DERIVEKEY))
460 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
461 EVP_DigestUpdate(&md, hash, hashlen);
462 EVP_DigestUpdate(&md, digest, have);
463 EVP_DigestFinal(&md, digest + have, NULL);
467 fprintf(stderr, "key '%c'== ", c);
468 dump_digest("key", digest, need);
473 Newkeys *current_keys[MODE_MAX];
477 kex_derive_keys(Kex *kex, u_char *hash, u_int hashlen, BIGNUM *shared_secret)
482 for (i = 0; i < NKEYS; i++) {
483 keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, hashlen,
487 debug2("kex_derive_keys");
488 for (mode = 0; mode < MODE_MAX; mode++) {
489 current_keys[mode] = kex->newkeys[mode];
490 kex->newkeys[mode] = NULL;
491 ctos = (!kex->server && mode == MODE_OUT) ||
492 (kex->server && mode == MODE_IN);
493 current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
494 current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
495 current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
500 kex_get_newkeys(int mode)
504 ret = current_keys[mode];
505 current_keys[mode] = NULL;
510 derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
511 u_int8_t cookie[8], u_int8_t id[16])
513 const EVP_MD *evp_md = EVP_md5();
515 u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE];
518 EVP_DigestInit(&md, evp_md);
520 len = BN_num_bytes(host_modulus);
521 if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
522 fatal("%s: bad host modulus (len %d)", __func__, len);
523 BN_bn2bin(host_modulus, nbuf);
524 EVP_DigestUpdate(&md, nbuf, len);
526 len = BN_num_bytes(server_modulus);
527 if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
528 fatal("%s: bad server modulus (len %d)", __func__, len);
529 BN_bn2bin(server_modulus, nbuf);
530 EVP_DigestUpdate(&md, nbuf, len);
532 EVP_DigestUpdate(&md, cookie, 8);
534 EVP_DigestFinal(&md, obuf, NULL);
535 memcpy(id, obuf, 16);
537 memset(nbuf, 0, sizeof(nbuf));
538 memset(obuf, 0, sizeof(obuf));
539 memset(&md, 0, sizeof(md));
542 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
544 dump_digest(char *msg, u_char *digest, int len)
548 fprintf(stderr, "%s\n", msg);
549 for (i = 0; i< len; i++) {
550 fprintf(stderr, "%02x", digest[i]);
552 fprintf(stderr, "\n");
554 fprintf(stderr, " ");
556 fprintf(stderr, "\n");