1 /* $OpenBSD: kex.c,v 1.79 2007/06/05 06:52:37 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>
56 #define KEX_COOKIE_LEN 16
58 #if OPENSSL_VERSION_NUMBER >= 0x00907000L
59 # if defined(HAVE_EVP_SHA256)
60 # define evp_ssh_sha256 EVP_sha256
62 extern const EVP_MD *evp_ssh_sha256(void);
67 static void kex_kexinit_finish(Kex *);
68 static void kex_choose_conf(Kex *);
70 /* put algorithm proposal into buffer */
71 /* used in sshconnect.c as well as kex.c */
73 kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
79 * add a dummy cookie, the cookie will be overwritten by
80 * kex_send_kexinit(), each time a kexinit is set
82 for (i = 0; i < KEX_COOKIE_LEN; i++)
83 buffer_put_char(b, 0);
84 for (i = 0; i < PROPOSAL_MAX; i++)
85 buffer_put_cstring(b, proposal[i]);
86 buffer_put_char(b, 0); /* first_kex_packet_follows */
87 buffer_put_int(b, 0); /* uint32 reserved */
90 /* parse buffer and return algorithm proposal */
92 kex_buf2prop(Buffer *raw, int *first_kex_follows)
98 proposal = xcalloc(PROPOSAL_MAX, sizeof(char *));
101 buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
103 for (i = 0; i < KEX_COOKIE_LEN; i++)
105 /* extract kex init proposal strings */
106 for (i = 0; i < PROPOSAL_MAX; i++) {
107 proposal[i] = buffer_get_string(&b,NULL);
108 debug2("kex_parse_kexinit: %s", proposal[i]);
110 /* first kex follows / reserved */
111 i = buffer_get_char(&b);
112 if (first_kex_follows != NULL)
113 *first_kex_follows = i;
114 debug2("kex_parse_kexinit: first_kex_follows %d ", i);
115 i = buffer_get_int(&b);
116 debug2("kex_parse_kexinit: reserved %u ", i);
122 kex_prop_free(char **proposal)
126 for (i = 0; i < PROPOSAL_MAX; i++)
133 kex_protocol_error(int type, u_int32_t seq, void *ctxt)
135 error("Hm, kex protocol error: type %d seq %u", type, seq);
139 kex_reset_dispatch(void)
141 dispatch_range(SSH2_MSG_TRANSPORT_MIN,
142 SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
143 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
149 kex_reset_dispatch();
151 packet_start(SSH2_MSG_NEWKEYS);
153 /* packet_write_wait(); */
154 debug("SSH2_MSG_NEWKEYS sent");
156 debug("expecting SSH2_MSG_NEWKEYS");
157 packet_read_expect(SSH2_MSG_NEWKEYS);
159 debug("SSH2_MSG_NEWKEYS received");
162 buffer_clear(&kex->peer);
163 /* buffer_clear(&kex->my); */
164 kex->flags &= ~KEX_INIT_SENT;
170 kex_send_kexinit(Kex *kex)
177 error("kex_send_kexinit: no kex, cannot rekey");
180 if (kex->flags & KEX_INIT_SENT) {
181 debug("KEX_INIT_SENT");
186 /* generate a random cookie */
187 if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
188 fatal("kex_send_kexinit: kex proposal too short");
189 cookie = buffer_ptr(&kex->my);
190 for (i = 0; i < KEX_COOKIE_LEN; i++) {
196 packet_start(SSH2_MSG_KEXINIT);
197 packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
199 debug("SSH2_MSG_KEXINIT sent");
200 kex->flags |= KEX_INIT_SENT;
205 kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
209 Kex *kex = (Kex *)ctxt;
211 debug("SSH2_MSG_KEXINIT received");
213 fatal("kex_input_kexinit: no kex, cannot rekey");
215 ptr = packet_get_raw(&dlen);
216 buffer_append(&kex->peer, ptr, dlen);
219 for (i = 0; i < KEX_COOKIE_LEN; i++)
221 for (i = 0; i < PROPOSAL_MAX; i++)
222 xfree(packet_get_string(NULL));
223 (void) packet_get_char();
224 (void) packet_get_int();
227 kex_kexinit_finish(kex);
231 kex_setup(char *proposal[PROPOSAL_MAX])
235 kex = xcalloc(1, sizeof(*kex));
236 buffer_init(&kex->peer);
237 buffer_init(&kex->my);
238 kex_prop2buf(&kex->my, proposal);
241 kex_send_kexinit(kex); /* we start */
242 kex_reset_dispatch();
248 kex_kexinit_finish(Kex *kex)
250 if (!(kex->flags & KEX_INIT_SENT))
251 kex_send_kexinit(kex);
253 kex_choose_conf(kex);
255 if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
256 kex->kex[kex->kex_type] != NULL) {
257 (kex->kex[kex->kex_type])(kex);
259 fatal("Unsupported key exchange %d", kex->kex_type);
264 choose_enc(Enc *enc, char *client, char *server)
266 char *name = match_list(client, server, NULL);
268 fatal("no matching cipher found: client %s server %s",
270 if ((enc->cipher = cipher_by_name(name)) == NULL)
271 fatal("matching cipher is not supported: %s", name);
276 enc->key_len = cipher_keylen(enc->cipher);
277 enc->block_size = cipher_blocksize(enc->cipher);
281 choose_mac(Mac *mac, char *client, char *server)
283 char *name = match_list(client, server, NULL);
285 fatal("no matching mac found: client %s server %s",
287 if (mac_setup(mac, name) < 0)
288 fatal("unsupported mac %s", name);
289 /* truncate the key */
290 if (datafellows & SSH_BUG_HMAC)
298 choose_comp(Comp *comp, char *client, char *server)
300 char *name = match_list(client, server, NULL);
302 fatal("no matching comp found: client %s server %s", client, server);
303 if (strcmp(name, "zlib@openssh.com") == 0) {
304 comp->type = COMP_DELAYED;
305 } else if (strcmp(name, "zlib") == 0) {
306 comp->type = COMP_ZLIB;
307 } else if (strcmp(name, "none") == 0) {
308 comp->type = COMP_NONE;
310 fatal("unsupported comp %s", name);
316 choose_kex(Kex *k, char *client, char *server)
318 k->name = match_list(client, server, NULL);
320 fatal("Unable to negotiate a key exchange method");
321 if (strcmp(k->name, KEX_DH1) == 0) {
322 k->kex_type = KEX_DH_GRP1_SHA1;
323 k->evp_md = EVP_sha1();
324 } else if (strcmp(k->name, KEX_DH14) == 0) {
325 k->kex_type = KEX_DH_GRP14_SHA1;
326 k->evp_md = EVP_sha1();
327 } else if (strcmp(k->name, KEX_DHGEX_SHA1) == 0) {
328 k->kex_type = KEX_DH_GEX_SHA1;
329 k->evp_md = EVP_sha1();
330 #if OPENSSL_VERSION_NUMBER >= 0x00907000L
331 } else if (strcmp(k->name, KEX_DHGEX_SHA256) == 0) {
332 k->kex_type = KEX_DH_GEX_SHA256;
333 k->evp_md = evp_ssh_sha256();
336 } else if (strncmp(k->name, KEX_GSS_GEX_SHA1_ID,
337 sizeof(KEX_GSS_GEX_SHA1_ID) - 1) == 0) {
338 k->kex_type = KEX_GSS_GEX_SHA1;
339 k->evp_md = EVP_sha1();
340 } else if (strncmp(k->name, KEX_GSS_GRP1_SHA1_ID,
341 sizeof(KEX_GSS_GRP1_SHA1_ID) - 1) == 0) {
342 k->kex_type = KEX_GSS_GRP1_SHA1;
343 k->evp_md = EVP_sha1();
344 } else if (strncmp(k->name, KEX_GSS_GRP14_SHA1_ID,
345 sizeof(KEX_GSS_GRP14_SHA1_ID) - 1) == 0) {
346 k->kex_type = KEX_GSS_GRP14_SHA1;
347 k->evp_md = EVP_sha1();
350 fatal("bad kex alg %s", k->name);
354 choose_hostkeyalg(Kex *k, char *client, char *server)
356 char *hostkeyalg = match_list(client, server, NULL);
357 if (hostkeyalg == NULL)
358 fatal("no hostkey alg");
359 k->hostkey_type = key_type_from_name(hostkeyalg);
360 if (k->hostkey_type == KEY_UNSPEC)
361 fatal("bad hostkey alg '%s'", hostkeyalg);
366 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
368 static int check[] = {
369 PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
374 for (idx = &check[0]; *idx != -1; idx++) {
375 if ((p = strchr(my[*idx], ',')) != NULL)
377 if ((p = strchr(peer[*idx], ',')) != NULL)
379 if (strcmp(my[*idx], peer[*idx]) != 0) {
380 debug2("proposal mismatch: my %s peer %s",
381 my[*idx], peer[*idx]);
385 debug2("proposals match");
390 kex_choose_conf(Kex *kex)
394 char **cprop, **sprop;
395 int nenc, nmac, ncomp;
396 u_int mode, ctos, need;
397 int first_kex_follows, type;
401 auth_flag = packet_authentication_state();
403 debug ("AUTH STATE IS %d", auth_flag);
405 my = kex_buf2prop(&kex->my, NULL);
406 peer = kex_buf2prop(&kex->peer, &first_kex_follows);
416 /* Algorithm Negotiation */
417 for (mode = 0; mode < MODE_MAX; mode++) {
418 newkeys = xcalloc(1, sizeof(*newkeys));
419 kex->newkeys[mode] = newkeys;
420 ctos = (!kex->server && mode == MODE_OUT) ||
421 (kex->server && mode == MODE_IN);
422 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
423 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
424 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
425 choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
426 choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
427 choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
428 debug("REQUESTED ENC.NAME is '%s'", newkeys->enc.name);
429 if (strcmp(newkeys->enc.name, "none") == 0) {
430 debug("Requesting NONE. Authflag is %d", auth_flag);
431 if (auth_flag == 1) {
432 debug("None requested post authentication.");
434 fatal("Pre-authentication none cipher requests are not allowed.");
437 debug("kex: %s %s %s %s",
438 ctos ? "client->server" : "server->client",
443 choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
444 choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
445 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
447 for (mode = 0; mode < MODE_MAX; mode++) {
448 newkeys = kex->newkeys[mode];
449 if (need < newkeys->enc.key_len)
450 need = newkeys->enc.key_len;
451 if (need < newkeys->enc.block_size)
452 need = newkeys->enc.block_size;
453 if (need < newkeys->mac.key_len)
454 need = newkeys->mac.key_len;
456 /* XXX need runden? */
459 /* ignore the next message if the proposals do not match */
460 if (first_kex_follows && !proposals_match(my, peer) &&
461 !(datafellows & SSH_BUG_FIRSTKEX)) {
462 type = packet_read();
463 debug2("skipping next packet (type %u)", type);
471 derive_key(Kex *kex, int id, u_int need, u_char *hash, u_int hashlen,
472 BIGNUM *shared_secret)
481 if ((mdsz = EVP_MD_size(kex->evp_md)) <= 0)
482 fatal("bad kex md size %d", mdsz);
483 digest = xmalloc(roundup(need, mdsz));
486 buffer_put_bignum2(&b, shared_secret);
488 /* K1 = HASH(K || H || "A" || session_id) */
489 EVP_DigestInit(&md, kex->evp_md);
490 if (!(datafellows & SSH_BUG_DERIVEKEY))
491 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
492 EVP_DigestUpdate(&md, hash, hashlen);
493 EVP_DigestUpdate(&md, &c, 1);
494 EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
495 EVP_DigestFinal(&md, digest, NULL);
499 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
500 * Key = K1 || K2 || ... || Kn
502 for (have = mdsz; need > have; have += mdsz) {
503 EVP_DigestInit(&md, kex->evp_md);
504 if (!(datafellows & SSH_BUG_DERIVEKEY))
505 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
506 EVP_DigestUpdate(&md, hash, hashlen);
507 EVP_DigestUpdate(&md, digest, have);
508 EVP_DigestFinal(&md, digest + have, NULL);
512 fprintf(stderr, "key '%c'== ", c);
513 dump_digest("key", digest, need);
518 Newkeys *current_keys[MODE_MAX];
522 kex_derive_keys(Kex *kex, u_char *hash, u_int hashlen, BIGNUM *shared_secret)
527 for (i = 0; i < NKEYS; i++) {
528 keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, hashlen,
532 debug2("kex_derive_keys");
533 for (mode = 0; mode < MODE_MAX; mode++) {
534 current_keys[mode] = kex->newkeys[mode];
535 kex->newkeys[mode] = NULL;
536 ctos = (!kex->server && mode == MODE_OUT) ||
537 (kex->server && mode == MODE_IN);
538 current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
539 current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
540 current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
545 kex_get_newkeys(int mode)
549 ret = current_keys[mode];
550 current_keys[mode] = NULL;
555 derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
556 u_int8_t cookie[8], u_int8_t id[16])
558 const EVP_MD *evp_md = EVP_md5();
560 u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE];
563 EVP_DigestInit(&md, evp_md);
565 len = BN_num_bytes(host_modulus);
566 if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
567 fatal("%s: bad host modulus (len %d)", __func__, len);
568 BN_bn2bin(host_modulus, nbuf);
569 EVP_DigestUpdate(&md, nbuf, len);
571 len = BN_num_bytes(server_modulus);
572 if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
573 fatal("%s: bad server modulus (len %d)", __func__, len);
574 BN_bn2bin(server_modulus, nbuf);
575 EVP_DigestUpdate(&md, nbuf, len);
577 EVP_DigestUpdate(&md, cookie, 8);
579 EVP_DigestFinal(&md, obuf, NULL);
580 memcpy(id, obuf, 16);
582 memset(nbuf, 0, sizeof(nbuf));
583 memset(obuf, 0, sizeof(obuf));
584 memset(&md, 0, sizeof(md));
587 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
589 dump_digest(char *msg, u_char *digest, int len)
593 fprintf(stderr, "%s\n", msg);
594 for (i = 0; i < len; i++) {
595 fprintf(stderr, "%02x", digest[i]);
597 fprintf(stderr, "\n");
599 fprintf(stderr, " ");
601 fprintf(stderr, "\n");