2 * Copyright (c) 2000 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 1.29 2001/04/04 14:34:58 markus Exp $");
28 #include <openssl/crypto.h>
44 #define KEX_COOKIE_LEN 16
46 void kex_kexinit_finish(Kex *kex);
47 void kex_choose_conf(Kex *k);
49 /* put algorithm proposal into buffer */
51 kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
57 for (i = 0; i < KEX_COOKIE_LEN; i++) {
60 buffer_put_char(b, rand & 0xff);
63 for (i = 0; i < PROPOSAL_MAX; i++)
64 buffer_put_cstring(b, proposal[i]);
65 buffer_put_char(b, 0); /* first_kex_packet_follows */
66 buffer_put_int(b, 0); /* uint32 reserved */
69 /* parse buffer and return algorithm proposal */
71 kex_buf2prop(Buffer *raw)
77 proposal = xmalloc(PROPOSAL_MAX * sizeof(char *));
80 buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
82 for (i = 0; i < KEX_COOKIE_LEN; i++)
84 /* extract kex init proposal strings */
85 for (i = 0; i < PROPOSAL_MAX; i++) {
86 proposal[i] = buffer_get_string(&b,NULL);
87 debug2("kex_parse_kexinit: %s", proposal[i]);
89 /* first kex follows / reserved */
90 i = buffer_get_char(&b);
91 debug2("kex_parse_kexinit: first_kex_follows %d ", i);
92 i = buffer_get_int(&b);
93 debug2("kex_parse_kexinit: reserved %d ", i);
99 kex_prop_free(char **proposal)
103 for (i = 0; i < PROPOSAL_MAX; i++)
109 kex_protocol_error(int type, int plen, void *ctxt)
111 error("Hm, kex protocol error: type %d plen %d", type, plen);
115 kex_clear_dispatch(void)
119 /* Numbers 30-49 are used for kex packets */
120 for (i = 30; i <= 49; i++)
121 dispatch_set(i, &kex_protocol_error);
129 kex_clear_dispatch();
131 packet_start(SSH2_MSG_NEWKEYS);
133 /* packet_write_wait(); */
134 debug("SSH2_MSG_NEWKEYS sent");
136 debug("waiting for SSH2_MSG_NEWKEYS");
137 packet_read_expect(&plen, SSH2_MSG_NEWKEYS);
138 debug("SSH2_MSG_NEWKEYS received");
140 buffer_clear(&kex->peer);
141 /* buffer_clear(&kex->my); */
142 kex->flags &= ~KEX_INIT_SENT;
146 kex_send_kexinit(Kex *kex)
149 error("kex_send_kexinit: no kex, cannot rekey");
152 if (kex->flags & KEX_INIT_SENT) {
153 debug("KEX_INIT_SENT");
156 packet_start(SSH2_MSG_KEXINIT);
157 packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
159 debug("SSH2_MSG_KEXINIT sent");
160 kex->flags |= KEX_INIT_SENT;
164 kex_input_kexinit(int type, int plen, void *ctxt)
168 Kex *kex = (Kex *)ctxt;
170 debug("SSH2_MSG_KEXINIT received");
172 fatal("kex_input_kexinit: no kex, cannot rekey");
174 ptr = packet_get_raw(&dlen);
175 buffer_append(&kex->peer, ptr, dlen);
177 kex_kexinit_finish(kex);
181 kex_setup(char *proposal[PROPOSAL_MAX])
185 kex = xmalloc(sizeof(*kex));
186 memset(kex, 0, sizeof(*kex));
187 buffer_init(&kex->peer);
188 buffer_init(&kex->my);
189 kex_prop2buf(&kex->my, proposal);
192 kex_send_kexinit(kex); /* we start */
193 kex_clear_dispatch();
194 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
200 kex_kexinit_finish(Kex *kex)
202 if (!(kex->flags & KEX_INIT_SENT))
203 kex_send_kexinit(kex);
205 kex_choose_conf(kex);
207 switch(kex->kex_type) {
215 fatal("Unsupported key exchange %d", kex->kex_type);
220 choose_enc(Enc *enc, char *client, char *server)
222 char *name = match_list(client, server, NULL);
224 fatal("no matching cipher found: client %s server %s", client, server);
225 enc->cipher = cipher_by_name(name);
226 if (enc->cipher == NULL)
227 fatal("matching cipher is not supported: %s", name);
234 choose_mac(Mac *mac, char *client, char *server)
236 char *name = match_list(client, server, NULL);
238 fatal("no matching mac found: client %s server %s", client, server);
239 if (mac_init(mac, name) < 0)
240 fatal("unsupported mac %s", name);
241 /* truncate the key */
242 if (datafellows & SSH_BUG_HMAC)
249 choose_comp(Comp *comp, char *client, char *server)
251 char *name = match_list(client, server, NULL);
253 fatal("no matching comp found: client %s server %s", client, server);
254 if (strcmp(name, "zlib") == 0) {
256 } else if (strcmp(name, "none") == 0) {
259 fatal("unsupported comp %s", name);
264 choose_kex(Kex *k, char *client, char *server)
266 k->name = match_list(client, server, NULL);
269 if (strcmp(k->name, KEX_DH1) == 0) {
270 k->kex_type = DH_GRP1_SHA1;
271 } else if (strcmp(k->name, KEX_DHGEX) == 0) {
272 k->kex_type = DH_GEX_SHA1;
274 fatal("bad kex alg %s", k->name);
277 choose_hostkeyalg(Kex *k, char *client, char *server)
279 char *hostkeyalg = match_list(client, server, NULL);
280 if (hostkeyalg == NULL)
281 fatal("no hostkey alg");
282 k->hostkey_type = key_type_from_name(hostkeyalg);
283 if (k->hostkey_type == KEY_UNSPEC)
284 fatal("bad hostkey alg '%s'", hostkeyalg);
289 kex_choose_conf(Kex *kex)
293 char **cprop, **sprop;
294 int nenc, nmac, ncomp;
296 int ctos; /* direction: if true client-to-server */
299 my = kex_buf2prop(&kex->my);
300 peer = kex_buf2prop(&kex->peer);
310 for (mode = 0; mode < MODE_MAX; mode++) {
311 newkeys = xmalloc(sizeof(*newkeys));
312 memset(newkeys, 0, sizeof(*newkeys));
313 kex->keys[mode] = newkeys;
314 ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
315 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
316 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
317 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
318 choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
319 choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
320 choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
321 debug("kex: %s %s %s %s",
322 ctos ? "client->server" : "server->client",
327 choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
328 choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
329 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
331 for (mode = 0; mode < MODE_MAX; mode++) {
332 newkeys = kex->keys[mode];
333 if (need < newkeys->enc.cipher->key_len)
334 need = newkeys->enc.cipher->key_len;
335 if (need < newkeys->enc.cipher->block_size)
336 need = newkeys->enc.cipher->block_size;
337 if (need < newkeys->mac.key_len)
338 need = newkeys->mac.key_len;
340 /* XXX need runden? */
348 derive_key(Kex *kex, int id, int need, u_char *hash, BIGNUM *shared_secret)
351 EVP_MD *evp_md = EVP_sha1();
355 int mdsz = evp_md->md_size;
356 u_char *digest = xmalloc(((need+mdsz-1)/mdsz)*mdsz);
359 buffer_put_bignum2(&b, shared_secret);
361 EVP_DigestInit(&md, evp_md);
362 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b)); /* shared_secret K */
363 EVP_DigestUpdate(&md, hash, mdsz); /* transport-06 */
364 EVP_DigestUpdate(&md, &c, 1); /* key id */
365 EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
366 EVP_DigestFinal(&md, digest, NULL);
369 for (have = mdsz; need > have; have += mdsz) {
370 EVP_DigestInit(&md, evp_md);
371 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
372 EVP_DigestUpdate(&md, hash, mdsz);
373 EVP_DigestUpdate(&md, digest, have);
374 EVP_DigestFinal(&md, digest + have, NULL);
378 fprintf(stderr, "key '%c'== ", c);
379 dump_digest("key", digest, need);
384 Newkeys *x_newkeys[MODE_MAX];
388 kex_derive_keys(Kex *kex, u_char *hash, BIGNUM *shared_secret)
394 for (i = 0; i < NKEYS; i++)
395 keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret);
397 debug("kex_derive_keys");
398 for (mode = 0; mode < MODE_MAX; mode++) {
399 newkeys = kex->keys[mode];
400 ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
401 newkeys->enc.iv = keys[ctos ? 0 : 1];
402 newkeys->enc.key = keys[ctos ? 2 : 3];
403 newkeys->mac.key = keys[ctos ? 4 : 5];
404 x_newkeys[mode] = newkeys;
409 kex_get_newkeys(int mode)
411 return x_newkeys[mode];
414 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
416 dump_digest(char *msg, u_char *digest, int len)
420 fprintf(stderr, "%s\n", msg);
421 for (i = 0; i< len; i++){
422 fprintf(stderr, "%02x", digest[i]);
424 fprintf(stderr, "\n");
426 fprintf(stderr, " ");
428 fprintf(stderr, "\n");