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 1.51 2002/06/24 14:55:38 markus Exp $");
28 #include <openssl/crypto.h>
49 #define KEX_COOKIE_LEN 16
51 /* Use privilege separation for sshd */
53 struct monitor *pmonitor;
57 static void kex_kexinit_finish(Kex *);
58 static void kex_choose_conf(Kex *);
60 /* put algorithm proposal into buffer */
62 kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
68 * add a dummy cookie, the cookie will be overwritten by
69 * kex_send_kexinit(), each time a kexinit is set
71 for (i = 0; i < KEX_COOKIE_LEN; i++)
72 buffer_put_char(b, 0);
73 for (i = 0; i < PROPOSAL_MAX; i++)
74 buffer_put_cstring(b, proposal[i]);
75 buffer_put_char(b, 0); /* first_kex_packet_follows */
76 buffer_put_int(b, 0); /* uint32 reserved */
79 /* parse buffer and return algorithm proposal */
81 kex_buf2prop(Buffer *raw)
87 proposal = xmalloc(PROPOSAL_MAX * sizeof(char *));
90 buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
92 for (i = 0; i < KEX_COOKIE_LEN; i++)
94 /* extract kex init proposal strings */
95 for (i = 0; i < PROPOSAL_MAX; i++) {
96 proposal[i] = buffer_get_string(&b,NULL);
97 debug2("kex_parse_kexinit: %s", proposal[i]);
99 /* first kex follows / reserved */
100 i = buffer_get_char(&b);
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("waiting for 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)
195 Kex *kex = (Kex *)ctxt;
197 debug("SSH2_MSG_KEXINIT received");
199 fatal("kex_input_kexinit: no kex, cannot rekey");
201 ptr = packet_get_raw(&dlen);
202 buffer_append(&kex->peer, ptr, dlen);
205 for (i = 0; i < KEX_COOKIE_LEN; i++)
207 for (i = 0; i < PROPOSAL_MAX; i++)
208 xfree(packet_get_string(NULL));
209 (void) packet_get_char();
210 (void) packet_get_int();
213 kex_kexinit_finish(kex);
217 kex_setup(char *proposal[PROPOSAL_MAX])
221 kex = xmalloc(sizeof(*kex));
222 memset(kex, 0, sizeof(*kex));
223 buffer_init(&kex->peer);
224 buffer_init(&kex->my);
225 kex_prop2buf(&kex->my, proposal);
228 kex_send_kexinit(kex); /* we start */
229 kex_reset_dispatch();
235 kex_kexinit_finish(Kex *kex)
237 if (!(kex->flags & KEX_INIT_SENT))
238 kex_send_kexinit(kex);
240 kex_choose_conf(kex);
242 switch (kex->kex_type) {
255 fatal("Unsupported key exchange %d", kex->kex_type);
260 choose_enc(Enc *enc, char *client, char *server)
262 char *name = match_list(client, server, NULL);
264 fatal("no matching cipher found: client %s server %s", client, server);
265 if ((enc->cipher = cipher_by_name(name)) == NULL)
266 fatal("matching cipher is not supported: %s", name);
271 enc->key_len = cipher_keylen(enc->cipher);
272 enc->block_size = cipher_blocksize(enc->cipher);
275 choose_mac(Mac *mac, char *client, char *server)
277 char *name = match_list(client, server, NULL);
279 fatal("no matching mac found: client %s server %s", client, server);
280 if (mac_init(mac, name) < 0)
281 fatal("unsupported mac %s", name);
282 /* truncate the key */
283 if (datafellows & SSH_BUG_HMAC)
290 choose_comp(Comp *comp, char *client, char *server)
292 char *name = match_list(client, server, NULL);
294 fatal("no matching comp found: client %s server %s", client, server);
295 if (strcmp(name, "zlib") == 0) {
297 } else if (strcmp(name, "none") == 0) {
300 fatal("unsupported comp %s", name);
305 choose_kex(Kex *k, char *client, char *server)
307 k->name = match_list(client, server, NULL);
309 fatal("No key exchange algorithm");
310 if (strcmp(k->name, KEX_DH1) == 0) {
311 k->kex_type = DH_GRP1_SHA1;
312 } else if (strcmp(k->name, KEX_DHGEX) == 0) {
313 k->kex_type = DH_GEX_SHA1;
315 } else if (strncmp(k->name, KEX_GSS_SHA1, sizeof(KEX_GSS_SHA1)-1) == 0) {
316 k->kex_type = GSS_GRP1_SHA1;
319 fatal("bad kex alg %s", k->name);
322 choose_hostkeyalg(Kex *k, char *client, char *server)
324 char *hostkeyalg = match_list(client, server, NULL);
325 if (hostkeyalg == NULL)
326 fatal("no hostkey alg");
327 k->hostkey_type = key_type_from_name(hostkeyalg);
328 if (k->hostkey_type == KEY_UNSPEC)
329 fatal("bad hostkey alg '%s'", hostkeyalg);
334 kex_choose_conf(Kex *kex)
338 char **cprop, **sprop;
339 int nenc, nmac, ncomp;
341 int ctos; /* direction: if true client-to-server */
344 my = kex_buf2prop(&kex->my);
345 peer = kex_buf2prop(&kex->peer);
355 /* Algorithm Negotiation */
356 for (mode = 0; mode < MODE_MAX; mode++) {
357 newkeys = xmalloc(sizeof(*newkeys));
358 memset(newkeys, 0, sizeof(*newkeys));
359 kex->newkeys[mode] = newkeys;
360 ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
361 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
362 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
363 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
364 choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
365 choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
366 choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
367 debug("kex: %s %s %s %s",
368 ctos ? "client->server" : "server->client",
373 choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
374 choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
375 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
377 for (mode = 0; mode < MODE_MAX; mode++) {
378 newkeys = kex->newkeys[mode];
379 if (need < newkeys->enc.key_len)
380 need = newkeys->enc.key_len;
381 if (need < newkeys->enc.block_size)
382 need = newkeys->enc.block_size;
383 if (need < newkeys->mac.key_len)
384 need = newkeys->mac.key_len;
386 /* XXX need runden? */
394 derive_key(Kex *kex, int id, int need, u_char *hash, BIGNUM *shared_secret)
397 const EVP_MD *evp_md = EVP_sha1();
401 int mdsz = EVP_MD_size(evp_md);
402 u_char *digest = xmalloc(roundup(need, mdsz));
405 buffer_put_bignum2(&b, shared_secret);
407 /* K1 = HASH(K || H || "A" || session_id) */
408 EVP_DigestInit(&md, evp_md);
409 if (!(datafellows & SSH_BUG_DERIVEKEY))
410 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
411 EVP_DigestUpdate(&md, hash, mdsz);
412 EVP_DigestUpdate(&md, &c, 1);
413 EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
414 EVP_DigestFinal(&md, digest, NULL);
418 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
419 * Key = K1 || K2 || ... || Kn
421 for (have = mdsz; need > have; have += mdsz) {
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, digest, have);
427 EVP_DigestFinal(&md, digest + have, NULL);
431 fprintf(stderr, "key '%c'== ", c);
432 dump_digest("key", digest, need);
437 Newkeys *current_keys[MODE_MAX];
441 kex_derive_keys(Kex *kex, u_char *hash, BIGNUM *shared_secret)
446 for (i = 0; i < NKEYS; i++)
447 keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret);
449 debug("kex_derive_keys");
450 for (mode = 0; mode < MODE_MAX; mode++) {
451 current_keys[mode] = kex->newkeys[mode];
452 kex->newkeys[mode] = NULL;
453 ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
454 current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
455 current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
456 current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
461 kex_get_newkeys(int mode)
465 ret = current_keys[mode];
466 current_keys[mode] = NULL;
470 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
472 dump_digest(char *msg, u_char *digest, int len)
476 fprintf(stderr, "%s\n", msg);
477 for (i = 0; i< len; i++) {
478 fprintf(stderr, "%02x", digest[i]);
480 fprintf(stderr, "\n");
482 fprintf(stderr, " ");
484 fprintf(stderr, "\n");