Annotation of src/usr.bin/ssh/kex.c, Revision 1.45
1.1 markus 1: /*
1.36 markus 2: * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
1.1 markus 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"
1.45 ! markus 26: RCSID("$OpenBSD: kex.c,v 1.44 2002/02/11 16:10:15 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:
1.35 itojun 46: /* prototype */
47: static void kex_kexinit_finish(Kex *);
48: static void kex_choose_conf(Kex *);
1.26 markus 49:
50: /* put algorithm proposal into buffer */
1.35 itojun 51: static void
1.26 markus 52: kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
1.1 markus 53: {
54: u_int32_t rand = 0;
55: int i;
1.26 markus 56:
57: buffer_clear(b);
1.7 markus 58: for (i = 0; i < KEX_COOKIE_LEN; i++) {
1.1 markus 59: if (i % 4 == 0)
60: rand = arc4random();
1.26 markus 61: buffer_put_char(b, rand & 0xff);
1.1 markus 62: rand >>= 8;
63: }
64: for (i = 0; i < PROPOSAL_MAX; i++)
1.26 markus 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 */
1.1 markus 68: }
69:
1.26 markus 70: /* parse buffer and return algorithm proposal */
1.35 itojun 71: static char **
1.26 markus 72: kex_buf2prop(Buffer *raw)
1.7 markus 73: {
1.26 markus 74: Buffer b;
1.7 markus 75: int i;
1.26 markus 76: char **proposal;
1.7 markus 77:
1.26 markus 78: proposal = xmalloc(PROPOSAL_MAX * sizeof(char *));
1.7 markus 79:
1.26 markus 80: buffer_init(&b);
81: buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
1.7 markus 82: /* skip cookie */
83: for (i = 0; i < KEX_COOKIE_LEN; i++)
1.26 markus 84: buffer_get_char(&b);
1.7 markus 85: /* extract kex init proposal strings */
86: for (i = 0; i < PROPOSAL_MAX; i++) {
1.26 markus 87: proposal[i] = buffer_get_string(&b,NULL);
88: debug2("kex_parse_kexinit: %s", proposal[i]);
1.7 markus 89: }
1.26 markus 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);
95: buffer_free(&b);
96: return proposal;
1.1 markus 97: }
98:
1.35 itojun 99: static void
1.26 markus 100: kex_prop_free(char **proposal)
1.1 markus 101: {
102: int i;
1.26 markus 103:
104: for (i = 0; i < PROPOSAL_MAX; i++)
105: xfree(proposal[i]);
106: xfree(proposal);
1.1 markus 107: }
108:
1.35 itojun 109: static void
1.41 markus 110: kex_protocol_error(int type, u_int32_t seq, void *ctxt)
1.1 markus 111: {
1.41 markus 112: error("Hm, kex protocol error: type %d seq %u", type, seq);
1.26 markus 113: }
1.1 markus 114:
1.35 itojun 115: static void
1.44 markus 116: kex_reset_dispatch(void)
1.29 markus 117: {
1.42 markus 118: dispatch_range(SSH2_MSG_TRANSPORT_MIN,
119: SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
1.44 markus 120: dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.29 markus 121: }
122:
123: void
1.28 markus 124: kex_finish(Kex *kex)
1.26 markus 125: {
1.44 markus 126: kex_reset_dispatch();
1.28 markus 127:
1.26 markus 128: packet_start(SSH2_MSG_NEWKEYS);
129: packet_send();
130: /* packet_write_wait(); */
131: debug("SSH2_MSG_NEWKEYS sent");
1.19 stevesk 132:
1.33 markus 133: debug("waiting for SSH2_MSG_NEWKEYS");
1.40 markus 134: packet_read_expect(SSH2_MSG_NEWKEYS);
1.26 markus 135: debug("SSH2_MSG_NEWKEYS received");
1.32 markus 136:
1.30 markus 137: kex->done = 1;
1.26 markus 138: buffer_clear(&kex->peer);
1.27 markus 139: /* buffer_clear(&kex->my); */
1.26 markus 140: kex->flags &= ~KEX_INIT_SENT;
1.32 markus 141: xfree(kex->name);
142: kex->name = NULL;
1.26 markus 143: }
1.1 markus 144:
1.26 markus 145: void
146: kex_send_kexinit(Kex *kex)
147: {
1.29 markus 148: if (kex == NULL) {
149: error("kex_send_kexinit: no kex, cannot rekey");
150: return;
151: }
1.28 markus 152: if (kex->flags & KEX_INIT_SENT) {
153: debug("KEX_INIT_SENT");
154: return;
155: }
1.30 markus 156: kex->done = 0;
1.26 markus 157: packet_start(SSH2_MSG_KEXINIT);
158: packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
159: packet_send();
160: debug("SSH2_MSG_KEXINIT sent");
161: kex->flags |= KEX_INIT_SENT;
1.1 markus 162: }
163:
1.26 markus 164: void
1.41 markus 165: kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
1.11 provos 166: {
1.26 markus 167: char *ptr;
168: int dlen;
1.31 markus 169: int i;
1.26 markus 170: Kex *kex = (Kex *)ctxt;
1.11 provos 171:
1.26 markus 172: debug("SSH2_MSG_KEXINIT received");
1.29 markus 173: if (kex == NULL)
174: fatal("kex_input_kexinit: no kex, cannot rekey");
1.11 provos 175:
1.26 markus 176: ptr = packet_get_raw(&dlen);
177: buffer_append(&kex->peer, ptr, dlen);
1.31 markus 178:
179: /* discard packet */
180: for (i = 0; i < KEX_COOKIE_LEN; i++)
181: packet_get_char();
182: for (i = 0; i < PROPOSAL_MAX; i++)
183: xfree(packet_get_string(NULL));
184: packet_get_char();
185: packet_get_int();
1.39 markus 186: packet_check_eom();
1.19 stevesk 187:
1.26 markus 188: kex_kexinit_finish(kex);
189: }
1.11 provos 190:
1.26 markus 191: Kex *
1.28 markus 192: kex_setup(char *proposal[PROPOSAL_MAX])
1.26 markus 193: {
194: Kex *kex;
1.11 provos 195:
1.26 markus 196: kex = xmalloc(sizeof(*kex));
197: memset(kex, 0, sizeof(*kex));
198: buffer_init(&kex->peer);
199: buffer_init(&kex->my);
200: kex_prop2buf(&kex->my, proposal);
1.30 markus 201: kex->done = 0;
1.26 markus 202:
203: kex_send_kexinit(kex); /* we start */
1.44 markus 204: kex_reset_dispatch();
1.26 markus 205:
206: return kex;
1.11 provos 207: }
208:
1.35 itojun 209: static void
1.26 markus 210: kex_kexinit_finish(Kex *kex)
1.1 markus 211: {
1.26 markus 212: if (!(kex->flags & KEX_INIT_SENT))
213: kex_send_kexinit(kex);
1.1 markus 214:
1.26 markus 215: kex_choose_conf(kex);
1.1 markus 216:
1.37 deraadt 217: switch (kex->kex_type) {
1.26 markus 218: case DH_GRP1_SHA1:
219: kexdh(kex);
220: break;
221: case DH_GEX_SHA1:
222: kexgex(kex);
223: break;
224: default:
225: fatal("Unsupported key exchange %d", kex->kex_type);
1.1 markus 226: }
227: }
228:
1.35 itojun 229: static void
1.1 markus 230: choose_enc(Enc *enc, char *client, char *server)
231: {
1.23 markus 232: char *name = match_list(client, server, NULL);
1.1 markus 233: if (name == NULL)
234: fatal("no matching cipher found: client %s server %s", client, server);
1.45 ! markus 235: if ((enc->cipher = cipher_by_name(name)) == NULL)
1.12 markus 236: fatal("matching cipher is not supported: %s", name);
1.1 markus 237: enc->name = name;
238: enc->enabled = 0;
239: enc->iv = NULL;
240: enc->key = NULL;
1.45 ! markus 241: enc->key_len = cipher_keylen(enc->cipher);
! 242: enc->block_size = cipher_blocksize(enc->cipher);
1.1 markus 243: }
1.35 itojun 244: static void
1.1 markus 245: choose_mac(Mac *mac, char *client, char *server)
246: {
1.23 markus 247: char *name = match_list(client, server, NULL);
1.1 markus 248: if (name == NULL)
249: fatal("no matching mac found: client %s server %s", client, server);
1.21 markus 250: if (mac_init(mac, name) < 0)
1.1 markus 251: fatal("unsupported mac %s", name);
1.21 markus 252: /* truncate the key */
253: if (datafellows & SSH_BUG_HMAC)
254: mac->key_len = 16;
1.1 markus 255: mac->name = name;
256: mac->key = NULL;
257: mac->enabled = 0;
258: }
1.35 itojun 259: static void
1.1 markus 260: choose_comp(Comp *comp, char *client, char *server)
261: {
1.23 markus 262: char *name = match_list(client, server, NULL);
1.1 markus 263: if (name == NULL)
264: fatal("no matching comp found: client %s server %s", client, server);
265: if (strcmp(name, "zlib") == 0) {
266: comp->type = 1;
267: } else if (strcmp(name, "none") == 0) {
268: comp->type = 0;
269: } else {
270: fatal("unsupported comp %s", name);
271: }
272: comp->name = name;
273: }
1.35 itojun 274: static void
1.1 markus 275: choose_kex(Kex *k, char *client, char *server)
276: {
1.23 markus 277: k->name = match_list(client, server, NULL);
1.1 markus 278: if (k->name == NULL)
279: fatal("no kex alg");
1.11 provos 280: if (strcmp(k->name, KEX_DH1) == 0) {
281: k->kex_type = DH_GRP1_SHA1;
282: } else if (strcmp(k->name, KEX_DHGEX) == 0) {
283: k->kex_type = DH_GEX_SHA1;
284: } else
1.1 markus 285: fatal("bad kex alg %s", k->name);
286: }
1.35 itojun 287: static void
1.1 markus 288: choose_hostkeyalg(Kex *k, char *client, char *server)
289: {
1.23 markus 290: char *hostkeyalg = match_list(client, server, NULL);
1.13 markus 291: if (hostkeyalg == NULL)
1.1 markus 292: fatal("no hostkey alg");
1.13 markus 293: k->hostkey_type = key_type_from_name(hostkeyalg);
294: if (k->hostkey_type == KEY_UNSPEC)
295: fatal("bad hostkey alg '%s'", hostkeyalg);
1.17 markus 296: xfree(hostkeyalg);
1.1 markus 297: }
298:
1.35 itojun 299: static void
1.27 markus 300: kex_choose_conf(Kex *kex)
1.1 markus 301: {
1.27 markus 302: Newkeys *newkeys;
1.26 markus 303: char **my, **peer;
304: char **cprop, **sprop;
1.27 markus 305: int nenc, nmac, ncomp;
1.1 markus 306: int mode;
307: int ctos; /* direction: if true client-to-server */
308: int need;
309:
1.27 markus 310: my = kex_buf2prop(&kex->my);
311: peer = kex_buf2prop(&kex->peer);
1.26 markus 312:
1.27 markus 313: if (kex->server) {
1.26 markus 314: cprop=peer;
315: sprop=my;
316: } else {
317: cprop=my;
318: sprop=peer;
319: }
1.1 markus 320:
1.30 markus 321: /* Algorithm Negotiation */
1.1 markus 322: for (mode = 0; mode < MODE_MAX; mode++) {
1.27 markus 323: newkeys = xmalloc(sizeof(*newkeys));
324: memset(newkeys, 0, sizeof(*newkeys));
1.30 markus 325: kex->newkeys[mode] = newkeys;
1.27 markus 326: ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
1.1 markus 327: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
328: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
329: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.27 markus 330: choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
331: choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
332: choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
1.2 markus 333: debug("kex: %s %s %s %s",
1.1 markus 334: ctos ? "client->server" : "server->client",
1.27 markus 335: newkeys->enc.name,
336: newkeys->mac.name,
337: newkeys->comp.name);
1.1 markus 338: }
1.27 markus 339: choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
340: choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
1.1 markus 341: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
342: need = 0;
343: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 344: newkeys = kex->newkeys[mode];
1.45 ! markus 345: if (need < newkeys->enc.key_len)
! 346: need = newkeys->enc.key_len;
! 347: if (need < newkeys->enc.block_size)
! 348: need = newkeys->enc.block_size;
1.27 markus 349: if (need < newkeys->mac.key_len)
350: need = newkeys->mac.key_len;
1.1 markus 351: }
1.7 markus 352: /* XXX need runden? */
1.27 markus 353: kex->we_need = need;
1.26 markus 354:
355: kex_prop_free(my);
356: kex_prop_free(peer);
357: }
358:
1.35 itojun 359: static u_char *
1.27 markus 360: derive_key(Kex *kex, int id, int need, u_char *hash, BIGNUM *shared_secret)
1.26 markus 361: {
362: Buffer b;
363: EVP_MD *evp_md = EVP_sha1();
364: EVP_MD_CTX md;
365: char c = id;
366: int have;
1.43 markus 367: int mdsz = EVP_MD_size(evp_md);
1.30 markus 368: u_char *digest = xmalloc(roundup(need, mdsz));
1.26 markus 369:
370: buffer_init(&b);
371: buffer_put_bignum2(&b, shared_secret);
372:
1.30 markus 373: /* K1 = HASH(K || H || "A" || session_id) */
1.26 markus 374: EVP_DigestInit(&md, evp_md);
1.34 markus 375: if (!(datafellows & SSH_BUG_DERIVEKEY))
376: EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
1.30 markus 377: EVP_DigestUpdate(&md, hash, mdsz);
378: EVP_DigestUpdate(&md, &c, 1);
1.27 markus 379: EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
1.26 markus 380: EVP_DigestFinal(&md, digest, NULL);
381:
1.30 markus 382: /*
383: * expand key:
384: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
385: * Key = K1 || K2 || ... || Kn
386: */
1.26 markus 387: for (have = mdsz; need > have; have += mdsz) {
388: EVP_DigestInit(&md, evp_md);
1.34 markus 389: if (!(datafellows & SSH_BUG_DERIVEKEY))
390: EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
1.26 markus 391: EVP_DigestUpdate(&md, hash, mdsz);
392: EVP_DigestUpdate(&md, digest, have);
393: EVP_DigestFinal(&md, digest + have, NULL);
394: }
395: buffer_free(&b);
396: #ifdef DEBUG_KEX
397: fprintf(stderr, "key '%c'== ", c);
398: dump_digest("key", digest, need);
399: #endif
400: return digest;
1.1 markus 401: }
402:
1.30 markus 403: Newkeys *current_keys[MODE_MAX];
1.27 markus 404:
1.23 markus 405: #define NKEYS 6
1.26 markus 406: void
1.27 markus 407: kex_derive_keys(Kex *kex, u_char *hash, BIGNUM *shared_secret)
1.1 markus 408: {
1.15 markus 409: u_char *keys[NKEYS];
1.27 markus 410: int i, mode, ctos;
1.1 markus 411:
412: for (i = 0; i < NKEYS; i++)
1.27 markus 413: keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret);
1.1 markus 414:
1.27 markus 415: debug("kex_derive_keys");
1.1 markus 416: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 417: current_keys[mode] = kex->newkeys[mode];
418: kex->newkeys[mode] = NULL;
1.27 markus 419: ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
1.30 markus 420: current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
421: current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
422: current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
1.1 markus 423: }
1.27 markus 424: }
425:
426: Newkeys *
427: kex_get_newkeys(int mode)
428: {
1.30 markus 429: Newkeys *ret;
430:
431: ret = current_keys[mode];
432: current_keys[mode] = NULL;
433: return ret;
1.1 markus 434: }
1.26 markus 435:
436: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
437: void
438: dump_digest(char *msg, u_char *digest, int len)
439: {
440: int i;
441:
442: fprintf(stderr, "%s\n", msg);
1.37 deraadt 443: for (i = 0; i< len; i++) {
1.26 markus 444: fprintf(stderr, "%02x", digest[i]);
445: if (i%32 == 31)
446: fprintf(stderr, "\n");
447: else if (i%8 == 7)
448: fprintf(stderr, " ");
449: }
450: fprintf(stderr, "\n");
451: }
452: #endif
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