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 1.33 2001/04/05 10:42:50 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");
141 buffer_clear(&kex->peer);
142 /* buffer_clear(&kex->my); */
143 kex->flags &= ~KEX_INIT_SENT;
149 kex_send_kexinit(Kex *kex)
152 error("kex_send_kexinit: no kex, cannot rekey");
155 if (kex->flags & KEX_INIT_SENT) {
156 debug("KEX_INIT_SENT");
160 packet_start(SSH2_MSG_KEXINIT);
161 packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
163 debug("SSH2_MSG_KEXINIT sent");
164 kex->flags |= KEX_INIT_SENT;
168 kex_input_kexinit(int type, int plen, void *ctxt)
173 Kex *kex = (Kex *)ctxt;
175 debug("SSH2_MSG_KEXINIT received");
177 fatal("kex_input_kexinit: no kex, cannot rekey");
179 ptr = packet_get_raw(&dlen);
180 buffer_append(&kex->peer, ptr, dlen);
183 for (i = 0; i < KEX_COOKIE_LEN; i++)
185 for (i = 0; i < PROPOSAL_MAX; i++)
186 xfree(packet_get_string(NULL));
191 kex_kexinit_finish(kex);
195 kex_setup(char *proposal[PROPOSAL_MAX])
199 kex = xmalloc(sizeof(*kex));
200 memset(kex, 0, sizeof(*kex));
201 buffer_init(&kex->peer);
202 buffer_init(&kex->my);
203 kex_prop2buf(&kex->my, proposal);
206 kex_send_kexinit(kex); /* we start */
207 kex_clear_dispatch();
208 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
214 kex_kexinit_finish(Kex *kex)
216 if (!(kex->flags & KEX_INIT_SENT))
217 kex_send_kexinit(kex);
219 kex_choose_conf(kex);
221 switch(kex->kex_type) {
229 fatal("Unsupported key exchange %d", kex->kex_type);
234 choose_enc(Enc *enc, char *client, char *server)
236 char *name = match_list(client, server, NULL);
238 fatal("no matching cipher found: client %s server %s", client, server);
239 enc->cipher = cipher_by_name(name);
240 if (enc->cipher == NULL)
241 fatal("matching cipher is not supported: %s", name);
248 choose_mac(Mac *mac, char *client, char *server)
250 char *name = match_list(client, server, NULL);
252 fatal("no matching mac found: client %s server %s", client, server);
253 if (mac_init(mac, name) < 0)
254 fatal("unsupported mac %s", name);
255 /* truncate the key */
256 if (datafellows & SSH_BUG_HMAC)
263 choose_comp(Comp *comp, char *client, char *server)
265 char *name = match_list(client, server, NULL);
267 fatal("no matching comp found: client %s server %s", client, server);
268 if (strcmp(name, "zlib") == 0) {
270 } else if (strcmp(name, "none") == 0) {
273 fatal("unsupported comp %s", name);
278 choose_kex(Kex *k, char *client, char *server)
280 k->name = match_list(client, server, NULL);
283 if (strcmp(k->name, KEX_DH1) == 0) {
284 k->kex_type = DH_GRP1_SHA1;
285 } else if (strcmp(k->name, KEX_DHGEX) == 0) {
286 k->kex_type = DH_GEX_SHA1;
288 fatal("bad kex alg %s", k->name);
291 choose_hostkeyalg(Kex *k, char *client, char *server)
293 char *hostkeyalg = match_list(client, server, NULL);
294 if (hostkeyalg == NULL)
295 fatal("no hostkey alg");
296 k->hostkey_type = key_type_from_name(hostkeyalg);
297 if (k->hostkey_type == KEY_UNSPEC)
298 fatal("bad hostkey alg '%s'", hostkeyalg);
303 kex_choose_conf(Kex *kex)
307 char **cprop, **sprop;
308 int nenc, nmac, ncomp;
310 int ctos; /* direction: if true client-to-server */
313 my = kex_buf2prop(&kex->my);
314 peer = kex_buf2prop(&kex->peer);
324 /* Algorithm Negotiation */
325 for (mode = 0; mode < MODE_MAX; mode++) {
326 newkeys = xmalloc(sizeof(*newkeys));
327 memset(newkeys, 0, sizeof(*newkeys));
328 kex->newkeys[mode] = newkeys;
329 ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
330 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
331 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
332 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
333 choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
334 choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
335 choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
336 debug("kex: %s %s %s %s",
337 ctos ? "client->server" : "server->client",
342 choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
343 choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
344 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
346 for (mode = 0; mode < MODE_MAX; mode++) {
347 newkeys = kex->newkeys[mode];
348 if (need < newkeys->enc.cipher->key_len)
349 need = newkeys->enc.cipher->key_len;
350 if (need < newkeys->enc.cipher->block_size)
351 need = newkeys->enc.cipher->block_size;
352 if (need < newkeys->mac.key_len)
353 need = newkeys->mac.key_len;
355 /* XXX need runden? */
363 derive_key(Kex *kex, int id, int need, u_char *hash, BIGNUM *shared_secret)
366 EVP_MD *evp_md = EVP_sha1();
370 int mdsz = evp_md->md_size;
371 u_char *digest = xmalloc(roundup(need, mdsz));
374 buffer_put_bignum2(&b, shared_secret);
376 /* K1 = HASH(K || H || "A" || session_id) */
377 EVP_DigestInit(&md, evp_md);
378 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
379 EVP_DigestUpdate(&md, hash, mdsz);
380 EVP_DigestUpdate(&md, &c, 1);
381 EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
382 EVP_DigestFinal(&md, digest, NULL);
386 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
387 * Key = K1 || K2 || ... || Kn
389 for (have = mdsz; need > have; have += mdsz) {
390 EVP_DigestInit(&md, evp_md);
391 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
392 EVP_DigestUpdate(&md, hash, mdsz);
393 EVP_DigestUpdate(&md, digest, have);
394 EVP_DigestFinal(&md, digest + have, NULL);
398 fprintf(stderr, "key '%c'== ", c);
399 dump_digest("key", digest, need);
404 Newkeys *current_keys[MODE_MAX];
408 kex_derive_keys(Kex *kex, u_char *hash, BIGNUM *shared_secret)
413 for (i = 0; i < NKEYS; i++)
414 keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret);
416 debug("kex_derive_keys");
417 for (mode = 0; mode < MODE_MAX; mode++) {
418 current_keys[mode] = kex->newkeys[mode];
419 kex->newkeys[mode] = NULL;
420 ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
421 current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
422 current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
423 current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
428 kex_get_newkeys(int mode)
432 ret = current_keys[mode];
433 current_keys[mode] = NULL;
437 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
439 dump_digest(char *msg, u_char *digest, int len)
443 fprintf(stderr, "%s\n", msg);
444 for (i = 0; i< len; i++){
445 fprintf(stderr, "%02x", digest[i]);
447 fprintf(stderr, "\n");
449 fprintf(stderr, " ");
451 fprintf(stderr, "\n");