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 1.41 2001/12/28 15:06:00 markus Exp $");
28 #include <openssl/crypto.h>
44 #define KEX_COOKIE_LEN 16
47 static void kex_kexinit_finish(Kex *);
48 static void kex_choose_conf(Kex *);
50 /* put algorithm proposal into buffer */
52 kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
58 for (i = 0; i < KEX_COOKIE_LEN; i++) {
61 buffer_put_char(b, rand & 0xff);
64 for (i = 0; i < PROPOSAL_MAX; i++)
65 buffer_put_cstring(b, proposal[i]);
66 buffer_put_char(b, 0); /* first_kex_packet_follows */
67 buffer_put_int(b, 0); /* uint32 reserved */
70 /* parse buffer and return algorithm proposal */
72 kex_buf2prop(Buffer *raw)
78 proposal = xmalloc(PROPOSAL_MAX * sizeof(char *));
81 buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
83 for (i = 0; i < KEX_COOKIE_LEN; i++)
85 /* extract kex init proposal strings */
86 for (i = 0; i < PROPOSAL_MAX; i++) {
87 proposal[i] = buffer_get_string(&b,NULL);
88 debug2("kex_parse_kexinit: %s", proposal[i]);
90 /* first kex follows / reserved */
91 i = buffer_get_char(&b);
92 debug2("kex_parse_kexinit: first_kex_follows %d ", i);
93 i = buffer_get_int(&b);
94 debug2("kex_parse_kexinit: reserved %d ", i);
100 kex_prop_free(char **proposal)
104 for (i = 0; i < PROPOSAL_MAX; i++)
110 kex_protocol_error(int type, u_int32_t seq, void *ctxt)
112 error("Hm, kex protocol error: type %d seq %u", type, seq);
116 kex_clear_dispatch(void)
120 /* Numbers 30-49 are used for kex packets */
121 for (i = 30; i <= 49; i++)
122 dispatch_set(i, &kex_protocol_error);
128 kex_clear_dispatch();
130 packet_start(SSH2_MSG_NEWKEYS);
132 /* packet_write_wait(); */
133 debug("SSH2_MSG_NEWKEYS sent");
135 debug("waiting for SSH2_MSG_NEWKEYS");
136 packet_read_expect(SSH2_MSG_NEWKEYS);
137 debug("SSH2_MSG_NEWKEYS received");
140 buffer_clear(&kex->peer);
141 /* buffer_clear(&kex->my); */
142 kex->flags &= ~KEX_INIT_SENT;
148 kex_send_kexinit(Kex *kex)
151 error("kex_send_kexinit: no kex, cannot rekey");
154 if (kex->flags & KEX_INIT_SENT) {
155 debug("KEX_INIT_SENT");
159 packet_start(SSH2_MSG_KEXINIT);
160 packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
162 debug("SSH2_MSG_KEXINIT sent");
163 kex->flags |= KEX_INIT_SENT;
167 kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
172 Kex *kex = (Kex *)ctxt;
174 debug("SSH2_MSG_KEXINIT received");
176 fatal("kex_input_kexinit: no kex, cannot rekey");
178 ptr = packet_get_raw(&dlen);
179 buffer_append(&kex->peer, ptr, dlen);
182 for (i = 0; i < KEX_COOKIE_LEN; i++)
184 for (i = 0; i < PROPOSAL_MAX; i++)
185 xfree(packet_get_string(NULL));
190 kex_kexinit_finish(kex);
194 kex_setup(char *proposal[PROPOSAL_MAX])
198 kex = xmalloc(sizeof(*kex));
199 memset(kex, 0, sizeof(*kex));
200 buffer_init(&kex->peer);
201 buffer_init(&kex->my);
202 kex_prop2buf(&kex->my, proposal);
205 kex_send_kexinit(kex); /* we start */
206 kex_clear_dispatch();
207 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
213 kex_kexinit_finish(Kex *kex)
215 if (!(kex->flags & KEX_INIT_SENT))
216 kex_send_kexinit(kex);
218 kex_choose_conf(kex);
220 switch (kex->kex_type) {
228 fatal("Unsupported key exchange %d", kex->kex_type);
233 choose_enc(Enc *enc, char *client, char *server)
235 char *name = match_list(client, server, NULL);
237 fatal("no matching cipher found: client %s server %s", client, server);
238 enc->cipher = cipher_by_name(name);
239 if (enc->cipher == NULL)
240 fatal("matching cipher is not supported: %s", name);
247 choose_mac(Mac *mac, char *client, char *server)
249 char *name = match_list(client, server, NULL);
251 fatal("no matching mac found: client %s server %s", client, server);
252 if (mac_init(mac, name) < 0)
253 fatal("unsupported mac %s", name);
254 /* truncate the key */
255 if (datafellows & SSH_BUG_HMAC)
262 choose_comp(Comp *comp, char *client, char *server)
264 char *name = match_list(client, server, NULL);
266 fatal("no matching comp found: client %s server %s", client, server);
267 if (strcmp(name, "zlib") == 0) {
269 } else if (strcmp(name, "none") == 0) {
272 fatal("unsupported comp %s", name);
277 choose_kex(Kex *k, char *client, char *server)
279 k->name = match_list(client, server, NULL);
282 if (strcmp(k->name, KEX_DH1) == 0) {
283 k->kex_type = DH_GRP1_SHA1;
284 } else if (strcmp(k->name, KEX_DHGEX) == 0) {
285 k->kex_type = DH_GEX_SHA1;
287 fatal("bad kex alg %s", k->name);
290 choose_hostkeyalg(Kex *k, char *client, char *server)
292 char *hostkeyalg = match_list(client, server, NULL);
293 if (hostkeyalg == NULL)
294 fatal("no hostkey alg");
295 k->hostkey_type = key_type_from_name(hostkeyalg);
296 if (k->hostkey_type == KEY_UNSPEC)
297 fatal("bad hostkey alg '%s'", hostkeyalg);
302 kex_choose_conf(Kex *kex)
306 char **cprop, **sprop;
307 int nenc, nmac, ncomp;
309 int ctos; /* direction: if true client-to-server */
312 my = kex_buf2prop(&kex->my);
313 peer = kex_buf2prop(&kex->peer);
323 /* Algorithm Negotiation */
324 for (mode = 0; mode < MODE_MAX; mode++) {
325 newkeys = xmalloc(sizeof(*newkeys));
326 memset(newkeys, 0, sizeof(*newkeys));
327 kex->newkeys[mode] = newkeys;
328 ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
329 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
330 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
331 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
332 choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
333 choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
334 choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
335 debug("kex: %s %s %s %s",
336 ctos ? "client->server" : "server->client",
341 choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
342 choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
343 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
345 for (mode = 0; mode < MODE_MAX; mode++) {
346 newkeys = kex->newkeys[mode];
347 if (need < newkeys->enc.cipher->key_len)
348 need = newkeys->enc.cipher->key_len;
349 if (need < newkeys->enc.cipher->block_size)
350 need = newkeys->enc.cipher->block_size;
351 if (need < newkeys->mac.key_len)
352 need = newkeys->mac.key_len;
354 /* XXX need runden? */
362 derive_key(Kex *kex, int id, int need, u_char *hash, BIGNUM *shared_secret)
365 EVP_MD *evp_md = EVP_sha1();
369 int mdsz = evp_md->md_size;
370 u_char *digest = xmalloc(roundup(need, mdsz));
373 buffer_put_bignum2(&b, shared_secret);
375 /* K1 = HASH(K || H || "A" || session_id) */
376 EVP_DigestInit(&md, evp_md);
377 if (!(datafellows & SSH_BUG_DERIVEKEY))
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 if (!(datafellows & SSH_BUG_DERIVEKEY))
392 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
393 EVP_DigestUpdate(&md, hash, mdsz);
394 EVP_DigestUpdate(&md, digest, have);
395 EVP_DigestFinal(&md, digest + have, NULL);
399 fprintf(stderr, "key '%c'== ", c);
400 dump_digest("key", digest, need);
405 Newkeys *current_keys[MODE_MAX];
409 kex_derive_keys(Kex *kex, u_char *hash, BIGNUM *shared_secret)
414 for (i = 0; i < NKEYS; i++)
415 keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret);
417 debug("kex_derive_keys");
418 for (mode = 0; mode < MODE_MAX; mode++) {
419 current_keys[mode] = kex->newkeys[mode];
420 kex->newkeys[mode] = NULL;
421 ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
422 current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
423 current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
424 current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
429 kex_get_newkeys(int mode)
433 ret = current_keys[mode];
434 current_keys[mode] = NULL;
438 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
440 dump_digest(char *msg, u_char *digest, int len)
444 fprintf(stderr, "%s\n", msg);
445 for (i = 0; i< len; i++) {
446 fprintf(stderr, "%02x", digest[i]);
448 fprintf(stderr, "\n");
450 fprintf(stderr, " ");
452 fprintf(stderr, "\n");