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 1.26 2001/04/03 19:53:29 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_send_newkeys(void)
117 packet_start(SSH2_MSG_NEWKEYS);
119 /* packet_write_wait(); */
120 debug("SSH2_MSG_NEWKEYS sent");
124 kex_input_newkeys(int type, int plen, void *ctxt)
129 debug("SSH2_MSG_NEWKEYS received");
131 for (i = 30; i <= 49; i++)
132 dispatch_set(i, &kex_protocol_error);
133 buffer_clear(&kex->peer);
134 buffer_clear(&kex->my);
135 kex->flags &= ~KEX_INIT_SENT;
139 kex_send_kexinit(Kex *kex)
141 packet_start(SSH2_MSG_KEXINIT);
142 packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
144 debug("SSH2_MSG_KEXINIT sent");
145 kex->flags |= KEX_INIT_SENT;
149 kex_input_kexinit(int type, int plen, void *ctxt)
153 Kex *kex = (Kex *)ctxt;
155 dispatch_set(SSH2_MSG_KEXINIT, &kex_protocol_error);
156 debug("SSH2_MSG_KEXINIT received");
158 ptr = packet_get_raw(&dlen);
159 buffer_append(&kex->peer, ptr, dlen);
161 kex_kexinit_finish(kex);
165 kex_start(char *proposal[PROPOSAL_MAX])
170 kex = xmalloc(sizeof(*kex));
171 memset(kex, 0, sizeof(*kex));
172 buffer_init(&kex->peer);
173 buffer_init(&kex->my);
174 kex_prop2buf(&kex->my, proposal);
177 kex_send_kexinit(kex); /* we start */
178 /* Numbers 30-49 are used for kex packets */
179 for (i = 30; i <= 49; i++)
180 dispatch_set(i, kex_protocol_error);
182 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
183 dispatch_set(SSH2_MSG_NEWKEYS, &kex_input_newkeys);
188 kex_kexinit_finish(Kex *kex)
190 if (!(kex->flags & KEX_INIT_SENT))
191 kex_send_kexinit(kex);
193 kex_choose_conf(kex);
195 switch(kex->kex_type) {
203 fatal("Unsupported key exchange %d", kex->kex_type);
208 choose_enc(Enc *enc, char *client, char *server)
210 char *name = match_list(client, server, NULL);
212 fatal("no matching cipher found: client %s server %s", client, server);
213 enc->cipher = cipher_by_name(name);
214 if (enc->cipher == NULL)
215 fatal("matching cipher is not supported: %s", name);
222 choose_mac(Mac *mac, char *client, char *server)
224 char *name = match_list(client, server, NULL);
226 fatal("no matching mac found: client %s server %s", client, server);
227 if (mac_init(mac, name) < 0)
228 fatal("unsupported mac %s", name);
229 /* truncate the key */
230 if (datafellows & SSH_BUG_HMAC)
237 choose_comp(Comp *comp, char *client, char *server)
239 char *name = match_list(client, server, NULL);
241 fatal("no matching comp found: client %s server %s", client, server);
242 if (strcmp(name, "zlib") == 0) {
244 } else if (strcmp(name, "none") == 0) {
247 fatal("unsupported comp %s", name);
252 choose_kex(Kex *k, char *client, char *server)
254 k->name = match_list(client, server, NULL);
257 if (strcmp(k->name, KEX_DH1) == 0) {
258 k->kex_type = DH_GRP1_SHA1;
259 } else if (strcmp(k->name, KEX_DHGEX) == 0) {
260 k->kex_type = DH_GEX_SHA1;
262 fatal("bad kex alg %s", k->name);
265 choose_hostkeyalg(Kex *k, char *client, char *server)
267 char *hostkeyalg = match_list(client, server, NULL);
268 if (hostkeyalg == NULL)
269 fatal("no hostkey alg");
270 k->hostkey_type = key_type_from_name(hostkeyalg);
271 if (k->hostkey_type == KEY_UNSPEC)
272 fatal("bad hostkey alg '%s'", hostkeyalg);
277 kex_choose_conf(Kex *k)
280 char **cprop, **sprop;
282 int ctos; /* direction: if true client-to-server */
285 my = kex_buf2prop(&k->my);
286 peer = kex_buf2prop(&k->peer);
296 for (mode = 0; mode < MODE_MAX; mode++) {
297 int nenc, nmac, ncomp;
298 ctos = (!k->server && mode == MODE_OUT) || (k->server && mode == MODE_IN);
299 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
300 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
301 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
302 choose_enc (&k->enc [mode], cprop[nenc], sprop[nenc]);
303 choose_mac (&k->mac [mode], cprop[nmac], sprop[nmac]);
304 choose_comp(&k->comp[mode], cprop[ncomp], sprop[ncomp]);
305 debug("kex: %s %s %s %s",
306 ctos ? "client->server" : "server->client",
311 choose_kex(k, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
312 choose_hostkeyalg(k, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
313 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
315 for (mode = 0; mode < MODE_MAX; mode++) {
316 if (need < k->enc[mode].cipher->key_len)
317 need = k->enc[mode].cipher->key_len;
318 if (need < k->enc[mode].cipher->block_size)
319 need = k->enc[mode].cipher->block_size;
320 if (need < k->mac[mode].key_len)
321 need = k->mac[mode].key_len;
323 /* XXX need runden? */
332 derive_key(int id, int need, u_char *hash, BIGNUM *shared_secret)
335 EVP_MD *evp_md = EVP_sha1();
339 int mdsz = evp_md->md_size;
340 u_char *digest = xmalloc(((need+mdsz-1)/mdsz)*mdsz);
343 buffer_put_bignum2(&b, shared_secret);
345 EVP_DigestInit(&md, evp_md);
346 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b)); /* shared_secret K */
347 EVP_DigestUpdate(&md, hash, mdsz); /* transport-06 */
348 EVP_DigestUpdate(&md, &c, 1); /* key id */
349 EVP_DigestUpdate(&md, hash, mdsz); /* session id */
350 EVP_DigestFinal(&md, digest, NULL);
353 for (have = mdsz; need > have; have += mdsz) {
354 EVP_DigestInit(&md, evp_md);
355 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
356 EVP_DigestUpdate(&md, hash, mdsz);
357 EVP_DigestUpdate(&md, digest, have);
358 EVP_DigestFinal(&md, digest + have, NULL);
362 fprintf(stderr, "key '%c'== ", c);
363 dump_digest("key", digest, need);
370 kex_derive_keys(Kex *k, u_char *hash, BIGNUM *shared_secret)
377 for (i = 0; i < NKEYS; i++)
378 keys[i] = derive_key('A'+i, k->we_need, hash, shared_secret);
380 for (mode = 0; mode < MODE_MAX; mode++) {
381 ctos = (!k->server && mode == MODE_OUT) || (k->server && mode == MODE_IN);
382 k->enc[mode].iv = keys[ctos ? 0 : 1];
383 k->enc[mode].key = keys[ctos ? 2 : 3];
384 k->mac[mode].key = keys[ctos ? 4 : 5];
388 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
390 dump_digest(char *msg, u_char *digest, int len)
394 fprintf(stderr, "%s\n", msg);
395 for (i = 0; i< len; i++){
396 fprintf(stderr, "%02x", digest[i]);
398 fprintf(stderr, "\n");
400 fprintf(stderr, " ");
402 fprintf(stderr, "\n");