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 1.47 2002/02/28 15:46:33 markus Exp $");
28 #include <openssl/crypto.h>
44 #define KEX_COOKIE_LEN 16
46 /* Use privilege separation for sshd */
51 static void kex_kexinit_finish(Kex *);
52 static void kex_choose_conf(Kex *);
54 /* put algorithm proposal into buffer */
56 kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
62 for (i = 0; i < KEX_COOKIE_LEN; i++) {
65 buffer_put_char(b, rand & 0xff);
68 for (i = 0; i < PROPOSAL_MAX; i++)
69 buffer_put_cstring(b, proposal[i]);
70 buffer_put_char(b, 0); /* first_kex_packet_follows */
71 buffer_put_int(b, 0); /* uint32 reserved */
74 /* parse buffer and return algorithm proposal */
76 kex_buf2prop(Buffer *raw)
82 proposal = xmalloc(PROPOSAL_MAX * sizeof(char *));
85 buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
87 for (i = 0; i < KEX_COOKIE_LEN; i++)
89 /* extract kex init proposal strings */
90 for (i = 0; i < PROPOSAL_MAX; i++) {
91 proposal[i] = buffer_get_string(&b,NULL);
92 debug2("kex_parse_kexinit: %s", proposal[i]);
94 /* first kex follows / reserved */
95 i = buffer_get_char(&b);
96 debug2("kex_parse_kexinit: first_kex_follows %d ", i);
97 i = buffer_get_int(&b);
98 debug2("kex_parse_kexinit: reserved %d ", i);
104 kex_prop_free(char **proposal)
108 for (i = 0; i < PROPOSAL_MAX; i++)
114 kex_protocol_error(int type, u_int32_t seq, void *ctxt)
116 error("Hm, kex protocol error: type %d seq %u", type, seq);
120 kex_reset_dispatch(void)
122 dispatch_range(SSH2_MSG_TRANSPORT_MIN,
123 SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
124 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
130 kex_reset_dispatch();
132 packet_start(SSH2_MSG_NEWKEYS);
134 /* packet_write_wait(); */
135 debug("SSH2_MSG_NEWKEYS sent");
137 debug("waiting for SSH2_MSG_NEWKEYS");
138 packet_read_expect(SSH2_MSG_NEWKEYS);
140 debug("SSH2_MSG_NEWKEYS received");
143 buffer_clear(&kex->peer);
144 /* buffer_clear(&kex->my); */
145 kex->flags &= ~KEX_INIT_SENT;
151 kex_send_kexinit(Kex *kex)
154 error("kex_send_kexinit: no kex, cannot rekey");
157 if (kex->flags & KEX_INIT_SENT) {
158 debug("KEX_INIT_SENT");
162 packet_start(SSH2_MSG_KEXINIT);
163 packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
165 debug("SSH2_MSG_KEXINIT sent");
166 kex->flags |= KEX_INIT_SENT;
170 kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
175 Kex *kex = (Kex *)ctxt;
177 debug("SSH2_MSG_KEXINIT received");
179 fatal("kex_input_kexinit: no kex, cannot rekey");
181 ptr = packet_get_raw(&dlen);
182 buffer_append(&kex->peer, ptr, dlen);
185 for (i = 0; i < KEX_COOKIE_LEN; i++)
187 for (i = 0; i < PROPOSAL_MAX; i++)
188 xfree(packet_get_string(NULL));
193 kex_kexinit_finish(kex);
197 kex_setup(char *proposal[PROPOSAL_MAX])
201 kex = xmalloc(sizeof(*kex));
202 memset(kex, 0, sizeof(*kex));
203 buffer_init(&kex->peer);
204 buffer_init(&kex->my);
205 kex_prop2buf(&kex->my, proposal);
208 kex_send_kexinit(kex); /* we start */
209 kex_reset_dispatch();
215 kex_kexinit_finish(Kex *kex)
217 if (!(kex->flags & KEX_INIT_SENT))
218 kex_send_kexinit(kex);
220 kex_choose_conf(kex);
222 switch (kex->kex_type) {
230 fatal("Unsupported key exchange %d", kex->kex_type);
235 choose_enc(Enc *enc, char *client, char *server)
237 char *name = match_list(client, server, NULL);
239 fatal("no matching cipher found: client %s server %s", client, server);
240 if ((enc->cipher = cipher_by_name(name)) == NULL)
241 fatal("matching cipher is not supported: %s", name);
246 enc->key_len = cipher_keylen(enc->cipher);
247 enc->block_size = cipher_blocksize(enc->cipher);
250 choose_mac(Mac *mac, char *client, char *server)
252 char *name = match_list(client, server, NULL);
254 fatal("no matching mac found: client %s server %s", client, server);
255 if (mac_init(mac, name) < 0)
256 fatal("unsupported mac %s", name);
257 /* truncate the key */
258 if (datafellows & SSH_BUG_HMAC)
265 choose_comp(Comp *comp, char *client, char *server)
267 char *name = match_list(client, server, NULL);
269 fatal("no matching comp found: client %s server %s", client, server);
270 if (strcmp(name, "zlib") == 0) {
272 } else if (strcmp(name, "none") == 0) {
275 fatal("unsupported comp %s", name);
280 choose_kex(Kex *k, char *client, char *server)
282 k->name = match_list(client, server, NULL);
285 if (strcmp(k->name, KEX_DH1) == 0) {
286 k->kex_type = DH_GRP1_SHA1;
287 } else if (strcmp(k->name, KEX_DHGEX) == 0) {
288 k->kex_type = DH_GEX_SHA1;
290 fatal("bad kex alg %s", k->name);
293 choose_hostkeyalg(Kex *k, char *client, char *server)
295 char *hostkeyalg = match_list(client, server, NULL);
296 if (hostkeyalg == NULL)
297 fatal("no hostkey alg");
298 k->hostkey_type = key_type_from_name(hostkeyalg);
299 if (k->hostkey_type == KEY_UNSPEC)
300 fatal("bad hostkey alg '%s'", hostkeyalg);
305 kex_choose_conf(Kex *kex)
309 char **cprop, **sprop;
310 int nenc, nmac, ncomp;
312 int ctos; /* direction: if true client-to-server */
315 my = kex_buf2prop(&kex->my);
316 peer = kex_buf2prop(&kex->peer);
326 /* Algorithm Negotiation */
327 for (mode = 0; mode < MODE_MAX; mode++) {
328 newkeys = xmalloc(sizeof(*newkeys));
329 memset(newkeys, 0, sizeof(*newkeys));
330 kex->newkeys[mode] = newkeys;
331 ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
332 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
333 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
334 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
335 choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
336 choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
337 choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
338 debug("kex: %s %s %s %s",
339 ctos ? "client->server" : "server->client",
344 choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
345 choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
346 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
348 for (mode = 0; mode < MODE_MAX; mode++) {
349 newkeys = kex->newkeys[mode];
350 if (need < newkeys->enc.key_len)
351 need = newkeys->enc.key_len;
352 if (need < newkeys->enc.block_size)
353 need = newkeys->enc.block_size;
354 if (need < newkeys->mac.key_len)
355 need = newkeys->mac.key_len;
357 /* XXX need runden? */
365 derive_key(Kex *kex, int id, int need, u_char *hash, BIGNUM *shared_secret)
368 const EVP_MD *evp_md = EVP_sha1();
372 int mdsz = EVP_MD_size(evp_md);
373 u_char *digest = xmalloc(roundup(need, mdsz));
376 buffer_put_bignum2(&b, shared_secret);
378 /* K1 = HASH(K || H || "A" || session_id) */
379 EVP_DigestInit(&md, evp_md);
380 if (!(datafellows & SSH_BUG_DERIVEKEY))
381 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
382 EVP_DigestUpdate(&md, hash, mdsz);
383 EVP_DigestUpdate(&md, &c, 1);
384 EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
385 EVP_DigestFinal(&md, digest, NULL);
389 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
390 * Key = K1 || K2 || ... || Kn
392 for (have = mdsz; need > have; have += mdsz) {
393 EVP_DigestInit(&md, evp_md);
394 if (!(datafellows & SSH_BUG_DERIVEKEY))
395 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
396 EVP_DigestUpdate(&md, hash, mdsz);
397 EVP_DigestUpdate(&md, digest, have);
398 EVP_DigestFinal(&md, digest + have, NULL);
402 fprintf(stderr, "key '%c'== ", c);
403 dump_digest("key", digest, need);
408 Newkeys *current_keys[MODE_MAX];
412 kex_derive_keys(Kex *kex, u_char *hash, BIGNUM *shared_secret)
417 for (i = 0; i < NKEYS; i++)
418 keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret);
420 debug("kex_derive_keys");
421 for (mode = 0; mode < MODE_MAX; mode++) {
422 current_keys[mode] = kex->newkeys[mode];
423 kex->newkeys[mode] = NULL;
424 ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
425 current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
426 current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
427 current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
432 kex_get_newkeys(int mode)
436 ret = current_keys[mode];
437 current_keys[mode] = NULL;
441 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
443 dump_digest(char *msg, u_char *digest, int len)
447 fprintf(stderr, "%s\n", msg);
448 for (i = 0; i< len; i++) {
449 fprintf(stderr, "%02x", digest[i]);
451 fprintf(stderr, "\n");
453 fprintf(stderr, " ");
455 fprintf(stderr, "\n");