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 1.25 2001/03/29 21:17:39 markus Exp $");
28 #include <openssl/crypto.h>
29 #include <openssl/bio.h>
30 #include <openssl/bn.h>
31 #include <openssl/pem.h>
46 #define KEX_COOKIE_LEN 16
49 kex_init(char *myproposal[PROPOSAL_MAX])
51 int first_kex_packet_follows = 0;
52 u_char cookie[KEX_COOKIE_LEN];
55 Buffer *ki = xmalloc(sizeof(*ki));
56 for (i = 0; i < KEX_COOKIE_LEN; i++) {
59 cookie[i] = rand & 0xff;
63 buffer_append(ki, (char *)cookie, sizeof cookie);
64 for (i = 0; i < PROPOSAL_MAX; i++)
65 buffer_put_cstring(ki, myproposal[i]);
66 buffer_put_char(ki, first_kex_packet_follows);
67 buffer_put_int(ki, 0); /* uint32 reserved */
71 /* send kexinit, parse and save reply */
74 Buffer *my_kexinit, Buffer *peer_kexint,
75 char *peer_proposal[PROPOSAL_MAX])
81 debug("send KEXINIT");
82 packet_start(SSH2_MSG_KEXINIT);
83 packet_put_raw(buffer_ptr(my_kexinit), buffer_len(my_kexinit));
89 * read and save raw KEXINIT payload in buffer. this is used during
90 * computation of the session_id and the session keys.
92 debug("wait KEXINIT");
93 packet_read_expect(&plen, SSH2_MSG_KEXINIT);
94 ptr = packet_get_raw(&plen);
95 buffer_append(peer_kexint, ptr, plen);
97 /* parse packet and save algorithm proposal */
99 for (i = 0; i < KEX_COOKIE_LEN; i++)
101 /* extract kex init proposal strings */
102 for (i = 0; i < PROPOSAL_MAX; i++) {
103 peer_proposal[i] = packet_get_string(NULL);
104 debug("got kexinit: %s", peer_proposal[i]);
106 /* first kex follow / reserved */
107 i = packet_get_char();
108 debug("first kex follow: %d ", i);
109 i = packet_get_int();
110 debug("reserved: %d ", i);
117 dump_digest(u_char *digest, int len)
120 for (i = 0; i< len; i++){
121 fprintf(stderr, "%02x", digest[i]);
123 fprintf(stderr, " ");
125 fprintf(stderr, "\n");
131 char *client_version_string,
132 char *server_version_string,
133 char *ckexinit, int ckexinitlen,
134 char *skexinit, int skexinitlen,
135 char *serverhostkeyblob, int sbloblen,
136 BIGNUM *client_dh_pub,
137 BIGNUM *server_dh_pub,
138 BIGNUM *shared_secret)
141 static u_char digest[EVP_MAX_MD_SIZE];
142 EVP_MD *evp_md = EVP_sha1();
146 buffer_put_string(&b, client_version_string, strlen(client_version_string));
147 buffer_put_string(&b, server_version_string, strlen(server_version_string));
149 /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
150 buffer_put_int(&b, ckexinitlen+1);
151 buffer_put_char(&b, SSH2_MSG_KEXINIT);
152 buffer_append(&b, ckexinit, ckexinitlen);
153 buffer_put_int(&b, skexinitlen+1);
154 buffer_put_char(&b, SSH2_MSG_KEXINIT);
155 buffer_append(&b, skexinit, skexinitlen);
157 buffer_put_string(&b, serverhostkeyblob, sbloblen);
158 buffer_put_bignum2(&b, client_dh_pub);
159 buffer_put_bignum2(&b, server_dh_pub);
160 buffer_put_bignum2(&b, shared_secret);
166 EVP_DigestInit(&md, evp_md);
167 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
168 EVP_DigestFinal(&md, digest, NULL);
173 dump_digest(digest, evp_md->md_size);
180 char *client_version_string,
181 char *server_version_string,
182 char *ckexinit, int ckexinitlen,
183 char *skexinit, int skexinitlen,
184 char *serverhostkeyblob, int sbloblen,
185 int min, int wantbits, int max, BIGNUM *prime, BIGNUM *gen,
186 BIGNUM *client_dh_pub,
187 BIGNUM *server_dh_pub,
188 BIGNUM *shared_secret)
191 static u_char digest[EVP_MAX_MD_SIZE];
192 EVP_MD *evp_md = EVP_sha1();
196 buffer_put_string(&b, client_version_string, strlen(client_version_string));
197 buffer_put_string(&b, server_version_string, strlen(server_version_string));
199 /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
200 buffer_put_int(&b, ckexinitlen+1);
201 buffer_put_char(&b, SSH2_MSG_KEXINIT);
202 buffer_append(&b, ckexinit, ckexinitlen);
203 buffer_put_int(&b, skexinitlen+1);
204 buffer_put_char(&b, SSH2_MSG_KEXINIT);
205 buffer_append(&b, skexinit, skexinitlen);
207 buffer_put_string(&b, serverhostkeyblob, sbloblen);
208 if (min == -1 || max == -1)
209 buffer_put_int(&b, wantbits);
211 buffer_put_int(&b, min);
212 buffer_put_int(&b, wantbits);
213 buffer_put_int(&b, max);
215 buffer_put_bignum2(&b, prime);
216 buffer_put_bignum2(&b, gen);
217 buffer_put_bignum2(&b, client_dh_pub);
218 buffer_put_bignum2(&b, server_dh_pub);
219 buffer_put_bignum2(&b, shared_secret);
225 EVP_DigestInit(&md, evp_md);
226 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
227 EVP_DigestFinal(&md, digest, NULL);
232 dump_digest(digest, evp_md->md_size);
238 derive_key(int id, int need, u_char *hash, BIGNUM *shared_secret)
241 EVP_MD *evp_md = EVP_sha1();
245 int mdsz = evp_md->md_size;
246 u_char *digest = xmalloc(((need+mdsz-1)/mdsz)*mdsz);
249 buffer_put_bignum2(&b, shared_secret);
251 EVP_DigestInit(&md, evp_md);
252 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b)); /* shared_secret K */
253 EVP_DigestUpdate(&md, hash, mdsz); /* transport-06 */
254 EVP_DigestUpdate(&md, &c, 1); /* key id */
255 EVP_DigestUpdate(&md, hash, mdsz); /* session id */
256 EVP_DigestFinal(&md, digest, NULL);
259 for (have = mdsz; need > have; have += mdsz) {
260 EVP_DigestInit(&md, evp_md);
261 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
262 EVP_DigestUpdate(&md, hash, mdsz);
263 EVP_DigestUpdate(&md, digest, have);
264 EVP_DigestFinal(&md, digest + have, NULL);
268 fprintf(stderr, "Digest '%c'== ", c);
269 dump_digest(digest, need);
275 choose_enc(Enc *enc, char *client, char *server)
277 char *name = match_list(client, server, NULL);
279 fatal("no matching cipher found: client %s server %s", client, server);
280 enc->cipher = cipher_by_name(name);
281 if (enc->cipher == NULL)
282 fatal("matching cipher is not supported: %s", name);
289 choose_mac(Mac *mac, char *client, char *server)
291 char *name = match_list(client, server, NULL);
293 fatal("no matching mac found: client %s server %s", client, server);
294 if (mac_init(mac, name) < 0)
295 fatal("unsupported mac %s", name);
296 /* truncate the key */
297 if (datafellows & SSH_BUG_HMAC)
304 choose_comp(Comp *comp, char *client, char *server)
306 char *name = match_list(client, server, NULL);
308 fatal("no matching comp found: client %s server %s", client, server);
309 if (strcmp(name, "zlib") == 0) {
311 } else if (strcmp(name, "none") == 0) {
314 fatal("unsupported comp %s", name);
319 choose_kex(Kex *k, char *client, char *server)
321 k->name = match_list(client, server, NULL);
324 if (strcmp(k->name, KEX_DH1) == 0) {
325 k->kex_type = DH_GRP1_SHA1;
326 } else if (strcmp(k->name, KEX_DHGEX) == 0) {
327 k->kex_type = DH_GEX_SHA1;
329 fatal("bad kex alg %s", k->name);
332 choose_hostkeyalg(Kex *k, char *client, char *server)
334 char *hostkeyalg = match_list(client, server, NULL);
335 if (hostkeyalg == NULL)
336 fatal("no hostkey alg");
337 k->hostkey_type = key_type_from_name(hostkeyalg);
338 if (k->hostkey_type == KEY_UNSPEC)
339 fatal("bad hostkey alg '%s'", hostkeyalg);
344 kex_choose_conf(char *cprop[PROPOSAL_MAX], char *sprop[PROPOSAL_MAX], int server)
347 int ctos; /* direction: if true client-to-server */
351 k = xmalloc(sizeof(*k));
352 memset(k, 0, sizeof(*k));
355 for (mode = 0; mode < MODE_MAX; mode++) {
356 int nenc, nmac, ncomp;
357 ctos = (!k->server && mode == MODE_OUT) || (k->server && mode == MODE_IN);
358 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
359 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
360 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
361 choose_enc (&k->enc [mode], cprop[nenc], sprop[nenc]);
362 choose_mac (&k->mac [mode], cprop[nmac], sprop[nmac]);
363 choose_comp(&k->comp[mode], cprop[ncomp], sprop[ncomp]);
364 debug("kex: %s %s %s %s",
365 ctos ? "client->server" : "server->client",
370 choose_kex(k, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
371 choose_hostkeyalg(k, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
372 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
374 for (mode = 0; mode < MODE_MAX; mode++) {
375 if (need < k->enc[mode].cipher->key_len)
376 need = k->enc[mode].cipher->key_len;
377 if (need < k->enc[mode].cipher->block_size)
378 need = k->enc[mode].cipher->block_size;
379 if (need < k->mac[mode].key_len)
380 need = k->mac[mode].key_len;
382 /* XXX need runden? */
389 kex_derive_keys(Kex *k, u_char *hash, BIGNUM *shared_secret)
396 for (i = 0; i < NKEYS; i++)
397 keys[i] = derive_key('A'+i, k->we_need, hash, shared_secret);
399 for (mode = 0; mode < MODE_MAX; mode++) {
400 ctos = (!k->server && mode == MODE_OUT) || (k->server && mode == MODE_IN);
401 k->enc[mode].iv = keys[ctos ? 0 : 1];
402 k->enc[mode].key = keys[ctos ? 2 : 3];
403 k->mac[mode].key = keys[ctos ? 4 : 5];