Annotation of src/usr.bin/ssh/kex.c, Revision 1.32
1.1 markus 1: /*
2: * Copyright (c) 2000 Markus Friedl. All rights reserved.
3: *
4: * Redistribution and use in source and binary forms, with or without
5: * modification, are permitted provided that the following conditions
6: * are met:
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.
12: *
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.
23: */
24:
25: #include "includes.h"
1.32 ! markus 26: RCSID("$OpenBSD: kex.c,v 1.31 2001/04/04 22:04:34 markus Exp $");
1.18 markus 27:
28: #include <openssl/crypto.h>
1.1 markus 29:
30: #include "ssh2.h"
31: #include "xmalloc.h"
32: #include "buffer.h"
33: #include "bufaux.h"
1.7 markus 34: #include "packet.h"
1.1 markus 35: #include "compat.h"
1.18 markus 36: #include "cipher.h"
1.1 markus 37: #include "kex.h"
1.13 markus 38: #include "key.h"
1.18 markus 39: #include "log.h"
1.21 markus 40: #include "mac.h"
1.23 markus 41: #include "match.h"
1.26 markus 42: #include "dispatch.h"
1.1 markus 43:
1.7 markus 44: #define KEX_COOKIE_LEN 16
45:
1.26 markus 46: void kex_kexinit_finish(Kex *kex);
47: void kex_choose_conf(Kex *k);
48:
49: /* put algorithm proposal into buffer */
50: void
51: kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
1.1 markus 52: {
53: u_int32_t rand = 0;
54: int i;
1.26 markus 55:
56: buffer_clear(b);
1.7 markus 57: for (i = 0; i < KEX_COOKIE_LEN; i++) {
1.1 markus 58: if (i % 4 == 0)
59: rand = arc4random();
1.26 markus 60: buffer_put_char(b, rand & 0xff);
1.1 markus 61: rand >>= 8;
62: }
63: for (i = 0; i < PROPOSAL_MAX; i++)
1.26 markus 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 */
1.1 markus 67: }
68:
1.26 markus 69: /* parse buffer and return algorithm proposal */
70: char **
71: kex_buf2prop(Buffer *raw)
1.7 markus 72: {
1.26 markus 73: Buffer b;
1.7 markus 74: int i;
1.26 markus 75: char **proposal;
1.7 markus 76:
1.26 markus 77: proposal = xmalloc(PROPOSAL_MAX * sizeof(char *));
1.7 markus 78:
1.26 markus 79: buffer_init(&b);
80: buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
1.7 markus 81: /* skip cookie */
82: for (i = 0; i < KEX_COOKIE_LEN; i++)
1.26 markus 83: buffer_get_char(&b);
1.7 markus 84: /* extract kex init proposal strings */
85: for (i = 0; i < PROPOSAL_MAX; i++) {
1.26 markus 86: proposal[i] = buffer_get_string(&b,NULL);
87: debug2("kex_parse_kexinit: %s", proposal[i]);
1.7 markus 88: }
1.26 markus 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);
94: buffer_free(&b);
95: return proposal;
1.1 markus 96: }
97:
98: void
1.26 markus 99: kex_prop_free(char **proposal)
1.1 markus 100: {
101: int i;
1.26 markus 102:
103: for (i = 0; i < PROPOSAL_MAX; i++)
104: xfree(proposal[i]);
105: xfree(proposal);
1.1 markus 106: }
107:
1.26 markus 108: void
109: kex_protocol_error(int type, int plen, void *ctxt)
1.1 markus 110: {
1.26 markus 111: error("Hm, kex protocol error: type %d plen %d", type, plen);
112: }
1.1 markus 113:
1.26 markus 114: void
1.29 markus 115: kex_clear_dispatch(void)
116: {
117: int i;
118:
119: /* Numbers 30-49 are used for kex packets */
120: for (i = 30; i <= 49; i++)
121: dispatch_set(i, &kex_protocol_error);
122: }
123:
124: void
1.28 markus 125: kex_finish(Kex *kex)
1.26 markus 126: {
1.29 markus 127: int plen;
128:
129: kex_clear_dispatch();
1.28 markus 130:
1.26 markus 131: packet_start(SSH2_MSG_NEWKEYS);
132: packet_send();
133: /* packet_write_wait(); */
134: debug("SSH2_MSG_NEWKEYS sent");
1.19 stevesk 135:
1.28 markus 136: debug("waiting for SSH2_MSG_NEWKEYS");
137: packet_read_expect(&plen, SSH2_MSG_NEWKEYS);
1.26 markus 138: debug("SSH2_MSG_NEWKEYS received");
1.32 ! markus 139:
1.30 markus 140: kex->done = 1;
1.26 markus 141: buffer_clear(&kex->peer);
1.27 markus 142: /* buffer_clear(&kex->my); */
1.26 markus 143: kex->flags &= ~KEX_INIT_SENT;
1.32 ! markus 144: xfree(kex->name);
! 145: kex->name = NULL;
1.26 markus 146: }
1.1 markus 147:
1.26 markus 148: void
149: kex_send_kexinit(Kex *kex)
150: {
1.29 markus 151: if (kex == NULL) {
152: error("kex_send_kexinit: no kex, cannot rekey");
153: return;
154: }
1.28 markus 155: if (kex->flags & KEX_INIT_SENT) {
156: debug("KEX_INIT_SENT");
157: return;
158: }
1.30 markus 159: kex->done = 0;
1.26 markus 160: packet_start(SSH2_MSG_KEXINIT);
161: packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
162: packet_send();
163: debug("SSH2_MSG_KEXINIT sent");
164: kex->flags |= KEX_INIT_SENT;
1.1 markus 165: }
166:
1.26 markus 167: void
168: kex_input_kexinit(int type, int plen, void *ctxt)
1.11 provos 169: {
1.26 markus 170: char *ptr;
171: int dlen;
1.31 markus 172: int i;
1.26 markus 173: Kex *kex = (Kex *)ctxt;
1.11 provos 174:
1.26 markus 175: debug("SSH2_MSG_KEXINIT received");
1.29 markus 176: if (kex == NULL)
177: fatal("kex_input_kexinit: no kex, cannot rekey");
1.11 provos 178:
1.26 markus 179: ptr = packet_get_raw(&dlen);
180: buffer_append(&kex->peer, ptr, dlen);
1.31 markus 181:
182: /* discard packet */
183: for (i = 0; i < KEX_COOKIE_LEN; i++)
184: packet_get_char();
185: for (i = 0; i < PROPOSAL_MAX; i++)
186: xfree(packet_get_string(NULL));
187: packet_get_char();
188: packet_get_int();
189: packet_done();
1.19 stevesk 190:
1.26 markus 191: kex_kexinit_finish(kex);
192: }
1.11 provos 193:
1.26 markus 194: Kex *
1.28 markus 195: kex_setup(char *proposal[PROPOSAL_MAX])
1.26 markus 196: {
197: Kex *kex;
1.11 provos 198:
1.26 markus 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);
1.30 markus 204: kex->done = 0;
1.26 markus 205:
206: kex_send_kexinit(kex); /* we start */
1.29 markus 207: kex_clear_dispatch();
208: dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.26 markus 209:
210: return kex;
1.11 provos 211: }
212:
1.26 markus 213: void
214: kex_kexinit_finish(Kex *kex)
1.1 markus 215: {
1.26 markus 216: if (!(kex->flags & KEX_INIT_SENT))
217: kex_send_kexinit(kex);
1.1 markus 218:
1.26 markus 219: kex_choose_conf(kex);
1.1 markus 220:
1.26 markus 221: switch(kex->kex_type) {
222: case DH_GRP1_SHA1:
223: kexdh(kex);
224: break;
225: case DH_GEX_SHA1:
226: kexgex(kex);
227: break;
228: default:
229: fatal("Unsupported key exchange %d", kex->kex_type);
1.1 markus 230: }
231: }
232:
233: void
234: choose_enc(Enc *enc, char *client, char *server)
235: {
1.23 markus 236: char *name = match_list(client, server, NULL);
1.1 markus 237: if (name == NULL)
238: fatal("no matching cipher found: client %s server %s", client, server);
1.12 markus 239: enc->cipher = cipher_by_name(name);
240: if (enc->cipher == NULL)
241: fatal("matching cipher is not supported: %s", name);
1.1 markus 242: enc->name = name;
243: enc->enabled = 0;
244: enc->iv = NULL;
245: enc->key = NULL;
246: }
247: void
248: choose_mac(Mac *mac, char *client, char *server)
249: {
1.23 markus 250: char *name = match_list(client, server, NULL);
1.1 markus 251: if (name == NULL)
252: fatal("no matching mac found: client %s server %s", client, server);
1.21 markus 253: if (mac_init(mac, name) < 0)
1.1 markus 254: fatal("unsupported mac %s", name);
1.21 markus 255: /* truncate the key */
256: if (datafellows & SSH_BUG_HMAC)
257: mac->key_len = 16;
1.1 markus 258: mac->name = name;
259: mac->key = NULL;
260: mac->enabled = 0;
261: }
262: void
263: choose_comp(Comp *comp, char *client, char *server)
264: {
1.23 markus 265: char *name = match_list(client, server, NULL);
1.1 markus 266: if (name == NULL)
267: fatal("no matching comp found: client %s server %s", client, server);
268: if (strcmp(name, "zlib") == 0) {
269: comp->type = 1;
270: } else if (strcmp(name, "none") == 0) {
271: comp->type = 0;
272: } else {
273: fatal("unsupported comp %s", name);
274: }
275: comp->name = name;
276: }
277: void
278: choose_kex(Kex *k, char *client, char *server)
279: {
1.23 markus 280: k->name = match_list(client, server, NULL);
1.1 markus 281: if (k->name == NULL)
282: fatal("no kex alg");
1.11 provos 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;
287: } else
1.1 markus 288: fatal("bad kex alg %s", k->name);
289: }
290: void
291: choose_hostkeyalg(Kex *k, char *client, char *server)
292: {
1.23 markus 293: char *hostkeyalg = match_list(client, server, NULL);
1.13 markus 294: if (hostkeyalg == NULL)
1.1 markus 295: fatal("no hostkey alg");
1.13 markus 296: k->hostkey_type = key_type_from_name(hostkeyalg);
297: if (k->hostkey_type == KEY_UNSPEC)
298: fatal("bad hostkey alg '%s'", hostkeyalg);
1.17 markus 299: xfree(hostkeyalg);
1.1 markus 300: }
301:
1.26 markus 302: void
1.27 markus 303: kex_choose_conf(Kex *kex)
1.1 markus 304: {
1.27 markus 305: Newkeys *newkeys;
1.26 markus 306: char **my, **peer;
307: char **cprop, **sprop;
1.27 markus 308: int nenc, nmac, ncomp;
1.1 markus 309: int mode;
310: int ctos; /* direction: if true client-to-server */
311: int need;
312:
1.27 markus 313: my = kex_buf2prop(&kex->my);
314: peer = kex_buf2prop(&kex->peer);
1.26 markus 315:
1.27 markus 316: if (kex->server) {
1.26 markus 317: cprop=peer;
318: sprop=my;
319: } else {
320: cprop=my;
321: sprop=peer;
322: }
1.1 markus 323:
1.30 markus 324: /* Algorithm Negotiation */
1.1 markus 325: for (mode = 0; mode < MODE_MAX; mode++) {
1.27 markus 326: newkeys = xmalloc(sizeof(*newkeys));
327: memset(newkeys, 0, sizeof(*newkeys));
1.30 markus 328: kex->newkeys[mode] = newkeys;
1.27 markus 329: ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
1.1 markus 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;
1.27 markus 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]);
1.2 markus 336: debug("kex: %s %s %s %s",
1.1 markus 337: ctos ? "client->server" : "server->client",
1.27 markus 338: newkeys->enc.name,
339: newkeys->mac.name,
340: newkeys->comp.name);
1.1 markus 341: }
1.27 markus 342: choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
343: choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
1.1 markus 344: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
345: need = 0;
346: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 347: newkeys = kex->newkeys[mode];
1.27 markus 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;
1.1 markus 354: }
1.7 markus 355: /* XXX need runden? */
1.27 markus 356: kex->we_need = need;
1.26 markus 357:
358: kex_prop_free(my);
359: kex_prop_free(peer);
360: }
361:
362: u_char *
1.27 markus 363: derive_key(Kex *kex, int id, int need, u_char *hash, BIGNUM *shared_secret)
1.26 markus 364: {
365: Buffer b;
366: EVP_MD *evp_md = EVP_sha1();
367: EVP_MD_CTX md;
368: char c = id;
369: int have;
370: int mdsz = evp_md->md_size;
1.30 markus 371: u_char *digest = xmalloc(roundup(need, mdsz));
1.26 markus 372:
373: buffer_init(&b);
374: buffer_put_bignum2(&b, shared_secret);
375:
1.30 markus 376: /* K1 = HASH(K || H || "A" || session_id) */
1.26 markus 377: EVP_DigestInit(&md, evp_md);
1.30 markus 378: EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
379: EVP_DigestUpdate(&md, hash, mdsz);
380: EVP_DigestUpdate(&md, &c, 1);
1.27 markus 381: EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
1.26 markus 382: EVP_DigestFinal(&md, digest, NULL);
383:
1.30 markus 384: /*
385: * expand key:
386: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
387: * Key = K1 || K2 || ... || Kn
388: */
1.26 markus 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);
395: }
396: buffer_free(&b);
397: #ifdef DEBUG_KEX
398: fprintf(stderr, "key '%c'== ", c);
399: dump_digest("key", digest, need);
400: #endif
401: return digest;
1.1 markus 402: }
403:
1.30 markus 404: Newkeys *current_keys[MODE_MAX];
1.27 markus 405:
1.23 markus 406: #define NKEYS 6
1.26 markus 407: void
1.27 markus 408: kex_derive_keys(Kex *kex, u_char *hash, BIGNUM *shared_secret)
1.1 markus 409: {
1.15 markus 410: u_char *keys[NKEYS];
1.27 markus 411: int i, mode, ctos;
1.1 markus 412:
413: for (i = 0; i < NKEYS; i++)
1.27 markus 414: keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret);
1.1 markus 415:
1.27 markus 416: debug("kex_derive_keys");
1.1 markus 417: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 418: current_keys[mode] = kex->newkeys[mode];
419: kex->newkeys[mode] = NULL;
1.27 markus 420: ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
1.30 markus 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];
1.1 markus 424: }
1.27 markus 425: }
426:
427: Newkeys *
428: kex_get_newkeys(int mode)
429: {
1.30 markus 430: Newkeys *ret;
431:
432: ret = current_keys[mode];
433: current_keys[mode] = NULL;
434: return ret;
1.1 markus 435: }
1.26 markus 436:
437: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
438: void
439: dump_digest(char *msg, u_char *digest, int len)
440: {
441: int i;
442:
443: fprintf(stderr, "%s\n", msg);
444: for (i = 0; i< len; i++){
445: fprintf(stderr, "%02x", digest[i]);
446: if (i%32 == 31)
447: fprintf(stderr, "\n");
448: else if (i%8 == 7)
449: fprintf(stderr, " ");
450: }
451: fprintf(stderr, "\n");
452: }
453: #endif
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