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>
45 #define KEX_COOKIE_LEN 16
47 /* Use privilege separation for sshd */
49 struct monitor *pmonitor;
53 static void kex_kexinit_finish(Kex *);
54 static void kex_choose_conf(Kex *);
56 /* put algorithm proposal into buffer */
58 kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
64 * add a dummy cookie, the cookie will be overwritten by
65 * kex_send_kexinit(), each time a kexinit is set
67 for (i = 0; i < KEX_COOKIE_LEN; i++)
68 buffer_put_char(b, 0);
69 for (i = 0; i < PROPOSAL_MAX; i++)
70 buffer_put_cstring(b, proposal[i]);
71 buffer_put_char(b, 0); /* first_kex_packet_follows */
72 buffer_put_int(b, 0); /* uint32 reserved */
75 /* parse buffer and return algorithm proposal */
77 kex_buf2prop(Buffer *raw)
83 proposal = xmalloc(PROPOSAL_MAX * sizeof(char *));
86 buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
88 for (i = 0; i < KEX_COOKIE_LEN; i++)
90 /* extract kex init proposal strings */
91 for (i = 0; i < PROPOSAL_MAX; i++) {
92 proposal[i] = buffer_get_string(&b,NULL);
93 debug2("kex_parse_kexinit: %s", proposal[i]);
95 /* first kex follows / reserved */
96 i = buffer_get_char(&b);
97 debug2("kex_parse_kexinit: first_kex_follows %d ", i);
98 i = buffer_get_int(&b);
99 debug2("kex_parse_kexinit: reserved %d ", i);
105 kex_prop_free(char **proposal)
109 for (i = 0; i < PROPOSAL_MAX; i++)
115 kex_protocol_error(int type, u_int32_t seq, void *ctxt)
117 error("Hm, kex protocol error: type %d seq %u", type, seq);
121 kex_reset_dispatch(void)
123 dispatch_range(SSH2_MSG_TRANSPORT_MIN,
124 SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
125 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
131 kex_reset_dispatch();
133 packet_start(SSH2_MSG_NEWKEYS);
135 /* packet_write_wait(); */
136 debug("SSH2_MSG_NEWKEYS sent");
138 debug("waiting for SSH2_MSG_NEWKEYS");
139 packet_read_expect(SSH2_MSG_NEWKEYS);
141 debug("SSH2_MSG_NEWKEYS received");
144 buffer_clear(&kex->peer);
145 /* buffer_clear(&kex->my); */
146 kex->flags &= ~KEX_INIT_SENT;
152 kex_send_kexinit(Kex *kex)
159 error("kex_send_kexinit: no kex, cannot rekey");
162 if (kex->flags & KEX_INIT_SENT) {
163 debug("KEX_INIT_SENT");
168 /* generate a random cookie */
169 if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
170 fatal("kex_send_kexinit: kex proposal too short");
171 cookie = buffer_ptr(&kex->my);
172 for (i = 0; i < KEX_COOKIE_LEN; i++) {
178 packet_start(SSH2_MSG_KEXINIT);
179 packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
181 debug("SSH2_MSG_KEXINIT sent");
182 kex->flags |= KEX_INIT_SENT;
186 kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
191 Kex *kex = (Kex *)ctxt;
193 debug("SSH2_MSG_KEXINIT received");
195 fatal("kex_input_kexinit: no kex, cannot rekey");
197 ptr = packet_get_raw(&dlen);
198 buffer_append(&kex->peer, ptr, dlen);
201 for (i = 0; i < KEX_COOKIE_LEN; i++)
203 for (i = 0; i < PROPOSAL_MAX; i++)
204 xfree(packet_get_string(NULL));
205 (void) packet_get_char();
206 (void) packet_get_int();
209 kex_kexinit_finish(kex);
213 kex_setup(char *proposal[PROPOSAL_MAX])
217 kex = xmalloc(sizeof(*kex));
218 memset(kex, 0, sizeof(*kex));
219 buffer_init(&kex->peer);
220 buffer_init(&kex->my);
221 kex_prop2buf(&kex->my, proposal);
224 kex_send_kexinit(kex); /* we start */
225 kex_reset_dispatch();
231 kex_kexinit_finish(Kex *kex)
233 if (!(kex->flags & KEX_INIT_SENT))
234 kex_send_kexinit(kex);
236 kex_choose_conf(kex);
238 switch (kex->kex_type) {
246 fatal("Unsupported key exchange %d", kex->kex_type);
251 choose_enc(Enc *enc, char *client, char *server)
253 char *name = match_list(client, server, NULL);
255 fatal("no matching cipher found: client %s server %s", client, server);
256 if ((enc->cipher = cipher_by_name(name)) == NULL)
257 fatal("matching cipher is not supported: %s", name);
262 enc->key_len = cipher_keylen(enc->cipher);
263 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)
281 choose_comp(Comp *comp, char *client, char *server)
283 char *name = match_list(client, server, NULL);
285 fatal("no matching comp found: client %s server %s", client, server);
286 if (strcmp(name, "zlib") == 0) {
288 } else if (strcmp(name, "none") == 0) {
291 fatal("unsupported comp %s", name);
296 choose_kex(Kex *k, char *client, char *server)
298 k->name = match_list(client, server, NULL);
301 if (strcmp(k->name, KEX_DH1) == 0) {
302 k->kex_type = DH_GRP1_SHA1;
303 } else if (strcmp(k->name, KEX_DHGEX) == 0) {
304 k->kex_type = DH_GEX_SHA1;
306 fatal("bad kex alg %s", k->name);
309 choose_hostkeyalg(Kex *k, char *client, char *server)
311 char *hostkeyalg = match_list(client, server, NULL);
312 if (hostkeyalg == NULL)
313 fatal("no hostkey alg");
314 k->hostkey_type = key_type_from_name(hostkeyalg);
315 if (k->hostkey_type == KEY_UNSPEC)
316 fatal("bad hostkey alg '%s'", hostkeyalg);
321 kex_choose_conf(Kex *kex)
325 char **cprop, **sprop;
326 int nenc, nmac, ncomp;
328 int ctos; /* direction: if true client-to-server */
331 my = kex_buf2prop(&kex->my);
332 peer = kex_buf2prop(&kex->peer);
342 /* Algorithm Negotiation */
343 for (mode = 0; mode < MODE_MAX; mode++) {
344 newkeys = xmalloc(sizeof(*newkeys));
345 memset(newkeys, 0, sizeof(*newkeys));
346 kex->newkeys[mode] = newkeys;
347 ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
348 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
349 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
350 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
351 choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
352 choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
353 choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
354 debug("kex: %s %s %s %s",
355 ctos ? "client->server" : "server->client",
360 choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
361 choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
362 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
364 for (mode = 0; mode < MODE_MAX; mode++) {
365 newkeys = kex->newkeys[mode];
366 if (need < newkeys->enc.key_len)
367 need = newkeys->enc.key_len;
368 if (need < newkeys->enc.block_size)
369 need = newkeys->enc.block_size;
370 if (need < newkeys->mac.key_len)
371 need = newkeys->mac.key_len;
373 /* XXX need runden? */
381 derive_key(Kex *kex, int id, int need, u_char *hash, BIGNUM *shared_secret)
384 const EVP_MD *evp_md = EVP_sha1();
388 int mdsz = EVP_MD_size(evp_md);
389 u_char *digest = xmalloc(roundup(need, mdsz));
392 buffer_put_bignum2(&b, shared_secret);
394 /* K1 = HASH(K || H || "A" || session_id) */
395 EVP_DigestInit(&md, evp_md);
396 if (!(datafellows & SSH_BUG_DERIVEKEY))
397 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
398 EVP_DigestUpdate(&md, hash, mdsz);
399 EVP_DigestUpdate(&md, &c, 1);
400 EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
401 EVP_DigestFinal(&md, digest, NULL);
405 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
406 * Key = K1 || K2 || ... || Kn
408 for (have = mdsz; need > have; have += mdsz) {
409 EVP_DigestInit(&md, evp_md);
410 if (!(datafellows & SSH_BUG_DERIVEKEY))
411 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
412 EVP_DigestUpdate(&md, hash, mdsz);
413 EVP_DigestUpdate(&md, digest, have);
414 EVP_DigestFinal(&md, digest + have, NULL);
418 fprintf(stderr, "key '%c'== ", c);
419 dump_digest("key", digest, need);
424 Newkeys *current_keys[MODE_MAX];
428 kex_derive_keys(Kex *kex, u_char *hash, BIGNUM *shared_secret)
433 for (i = 0; i < NKEYS; i++)
434 keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret);
436 debug("kex_derive_keys");
437 for (mode = 0; mode < MODE_MAX; mode++) {
438 current_keys[mode] = kex->newkeys[mode];
439 kex->newkeys[mode] = NULL;
440 ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
441 current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
442 current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
443 current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
448 kex_get_newkeys(int mode)
452 ret = current_keys[mode];
453 current_keys[mode] = NULL;
457 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
459 dump_digest(char *msg, u_char *digest, int len)
463 fprintf(stderr, "%s\n", msg);
464 for (i = 0; i< len; i++) {
465 fprintf(stderr, "%02x", digest[i]);
467 fprintf(stderr, "\n");
469 fprintf(stderr, " ");
471 fprintf(stderr, "\n");