Annotation of src/usr.bin/ssh/kex.c, Revision 1.43
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"
1.43 ! markus 26: RCSID("$OpenBSD: kex.c,v 1.42 2002/01/11 13:39:36 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
1.29 markus 116: kex_clear_dispatch(void)
117: {
1.42 markus 118: dispatch_range(SSH2_MSG_TRANSPORT_MIN,
119: SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
1.29 markus 120: }
121:
122: void
1.28 markus 123: kex_finish(Kex *kex)
1.26 markus 124: {
1.29 markus 125: kex_clear_dispatch();
1.28 markus 126:
1.26 markus 127: packet_start(SSH2_MSG_NEWKEYS);
128: packet_send();
129: /* packet_write_wait(); */
130: debug("SSH2_MSG_NEWKEYS sent");
1.19 stevesk 131:
1.33 markus 132: debug("waiting for SSH2_MSG_NEWKEYS");
1.40 markus 133: packet_read_expect(SSH2_MSG_NEWKEYS);
1.26 markus 134: debug("SSH2_MSG_NEWKEYS received");
1.32 markus 135:
1.30 markus 136: kex->done = 1;
1.26 markus 137: buffer_clear(&kex->peer);
1.27 markus 138: /* buffer_clear(&kex->my); */
1.26 markus 139: kex->flags &= ~KEX_INIT_SENT;
1.32 markus 140: xfree(kex->name);
141: kex->name = NULL;
1.26 markus 142: }
1.1 markus 143:
1.26 markus 144: void
145: kex_send_kexinit(Kex *kex)
146: {
1.29 markus 147: if (kex == NULL) {
148: error("kex_send_kexinit: no kex, cannot rekey");
149: return;
150: }
1.28 markus 151: if (kex->flags & KEX_INIT_SENT) {
152: debug("KEX_INIT_SENT");
153: return;
154: }
1.30 markus 155: kex->done = 0;
1.26 markus 156: packet_start(SSH2_MSG_KEXINIT);
157: packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
158: packet_send();
159: debug("SSH2_MSG_KEXINIT sent");
160: kex->flags |= KEX_INIT_SENT;
1.1 markus 161: }
162:
1.26 markus 163: void
1.41 markus 164: kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
1.11 provos 165: {
1.26 markus 166: char *ptr;
167: int dlen;
1.31 markus 168: int i;
1.26 markus 169: Kex *kex = (Kex *)ctxt;
1.11 provos 170:
1.26 markus 171: debug("SSH2_MSG_KEXINIT received");
1.29 markus 172: if (kex == NULL)
173: fatal("kex_input_kexinit: no kex, cannot rekey");
1.11 provos 174:
1.26 markus 175: ptr = packet_get_raw(&dlen);
176: buffer_append(&kex->peer, ptr, dlen);
1.31 markus 177:
178: /* discard packet */
179: for (i = 0; i < KEX_COOKIE_LEN; i++)
180: packet_get_char();
181: for (i = 0; i < PROPOSAL_MAX; i++)
182: xfree(packet_get_string(NULL));
183: packet_get_char();
184: packet_get_int();
1.39 markus 185: packet_check_eom();
1.19 stevesk 186:
1.26 markus 187: kex_kexinit_finish(kex);
188: }
1.11 provos 189:
1.26 markus 190: Kex *
1.28 markus 191: kex_setup(char *proposal[PROPOSAL_MAX])
1.26 markus 192: {
193: Kex *kex;
1.11 provos 194:
1.26 markus 195: kex = xmalloc(sizeof(*kex));
196: memset(kex, 0, sizeof(*kex));
197: buffer_init(&kex->peer);
198: buffer_init(&kex->my);
199: kex_prop2buf(&kex->my, proposal);
1.30 markus 200: kex->done = 0;
1.26 markus 201:
202: kex_send_kexinit(kex); /* we start */
1.29 markus 203: kex_clear_dispatch();
204: dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
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);
1.12 markus 235: enc->cipher = cipher_by_name(name);
236: if (enc->cipher == NULL)
237: fatal("matching cipher is not supported: %s", name);
1.1 markus 238: enc->name = name;
239: enc->enabled = 0;
240: enc->iv = NULL;
241: enc->key = NULL;
242: }
1.35 itojun 243: static void
1.1 markus 244: choose_mac(Mac *mac, char *client, char *server)
245: {
1.23 markus 246: char *name = match_list(client, server, NULL);
1.1 markus 247: if (name == NULL)
248: fatal("no matching mac found: client %s server %s", client, server);
1.21 markus 249: if (mac_init(mac, name) < 0)
1.1 markus 250: fatal("unsupported mac %s", name);
1.21 markus 251: /* truncate the key */
252: if (datafellows & SSH_BUG_HMAC)
253: mac->key_len = 16;
1.1 markus 254: mac->name = name;
255: mac->key = NULL;
256: mac->enabled = 0;
257: }
1.35 itojun 258: static void
1.1 markus 259: choose_comp(Comp *comp, char *client, char *server)
260: {
1.23 markus 261: char *name = match_list(client, server, NULL);
1.1 markus 262: if (name == NULL)
263: fatal("no matching comp found: client %s server %s", client, server);
264: if (strcmp(name, "zlib") == 0) {
265: comp->type = 1;
266: } else if (strcmp(name, "none") == 0) {
267: comp->type = 0;
268: } else {
269: fatal("unsupported comp %s", name);
270: }
271: comp->name = name;
272: }
1.35 itojun 273: static void
1.1 markus 274: choose_kex(Kex *k, char *client, char *server)
275: {
1.23 markus 276: k->name = match_list(client, server, NULL);
1.1 markus 277: if (k->name == NULL)
278: fatal("no kex alg");
1.11 provos 279: if (strcmp(k->name, KEX_DH1) == 0) {
280: k->kex_type = DH_GRP1_SHA1;
281: } else if (strcmp(k->name, KEX_DHGEX) == 0) {
282: k->kex_type = DH_GEX_SHA1;
283: } else
1.1 markus 284: fatal("bad kex alg %s", k->name);
285: }
1.35 itojun 286: static void
1.1 markus 287: choose_hostkeyalg(Kex *k, char *client, char *server)
288: {
1.23 markus 289: char *hostkeyalg = match_list(client, server, NULL);
1.13 markus 290: if (hostkeyalg == NULL)
1.1 markus 291: fatal("no hostkey alg");
1.13 markus 292: k->hostkey_type = key_type_from_name(hostkeyalg);
293: if (k->hostkey_type == KEY_UNSPEC)
294: fatal("bad hostkey alg '%s'", hostkeyalg);
1.17 markus 295: xfree(hostkeyalg);
1.1 markus 296: }
297:
1.35 itojun 298: static void
1.27 markus 299: kex_choose_conf(Kex *kex)
1.1 markus 300: {
1.27 markus 301: Newkeys *newkeys;
1.26 markus 302: char **my, **peer;
303: char **cprop, **sprop;
1.27 markus 304: int nenc, nmac, ncomp;
1.1 markus 305: int mode;
306: int ctos; /* direction: if true client-to-server */
307: int need;
308:
1.27 markus 309: my = kex_buf2prop(&kex->my);
310: peer = kex_buf2prop(&kex->peer);
1.26 markus 311:
1.27 markus 312: if (kex->server) {
1.26 markus 313: cprop=peer;
314: sprop=my;
315: } else {
316: cprop=my;
317: sprop=peer;
318: }
1.1 markus 319:
1.30 markus 320: /* Algorithm Negotiation */
1.1 markus 321: for (mode = 0; mode < MODE_MAX; mode++) {
1.27 markus 322: newkeys = xmalloc(sizeof(*newkeys));
323: memset(newkeys, 0, sizeof(*newkeys));
1.30 markus 324: kex->newkeys[mode] = newkeys;
1.27 markus 325: ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
1.1 markus 326: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
327: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
328: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.27 markus 329: choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
330: choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
331: choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
1.2 markus 332: debug("kex: %s %s %s %s",
1.1 markus 333: ctos ? "client->server" : "server->client",
1.27 markus 334: newkeys->enc.name,
335: newkeys->mac.name,
336: newkeys->comp.name);
1.1 markus 337: }
1.27 markus 338: choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
339: choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
1.1 markus 340: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
341: need = 0;
342: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 343: newkeys = kex->newkeys[mode];
1.27 markus 344: if (need < newkeys->enc.cipher->key_len)
345: need = newkeys->enc.cipher->key_len;
346: if (need < newkeys->enc.cipher->block_size)
347: need = newkeys->enc.cipher->block_size;
348: if (need < newkeys->mac.key_len)
349: need = newkeys->mac.key_len;
1.1 markus 350: }
1.7 markus 351: /* XXX need runden? */
1.27 markus 352: kex->we_need = need;
1.26 markus 353:
354: kex_prop_free(my);
355: kex_prop_free(peer);
356: }
357:
1.35 itojun 358: static u_char *
1.27 markus 359: derive_key(Kex *kex, int id, int need, u_char *hash, BIGNUM *shared_secret)
1.26 markus 360: {
361: Buffer b;
362: EVP_MD *evp_md = EVP_sha1();
363: EVP_MD_CTX md;
364: char c = id;
365: int have;
1.43 ! markus 366: int mdsz = EVP_MD_size(evp_md);
1.30 markus 367: u_char *digest = xmalloc(roundup(need, mdsz));
1.26 markus 368:
369: buffer_init(&b);
370: buffer_put_bignum2(&b, shared_secret);
371:
1.30 markus 372: /* K1 = HASH(K || H || "A" || session_id) */
1.26 markus 373: EVP_DigestInit(&md, evp_md);
1.34 markus 374: if (!(datafellows & SSH_BUG_DERIVEKEY))
375: EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
1.30 markus 376: EVP_DigestUpdate(&md, hash, mdsz);
377: EVP_DigestUpdate(&md, &c, 1);
1.27 markus 378: EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
1.26 markus 379: EVP_DigestFinal(&md, digest, NULL);
380:
1.30 markus 381: /*
382: * expand key:
383: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
384: * Key = K1 || K2 || ... || Kn
385: */
1.26 markus 386: for (have = mdsz; need > have; have += mdsz) {
387: EVP_DigestInit(&md, evp_md);
1.34 markus 388: if (!(datafellows & SSH_BUG_DERIVEKEY))
389: EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
1.26 markus 390: EVP_DigestUpdate(&md, hash, mdsz);
391: EVP_DigestUpdate(&md, digest, have);
392: EVP_DigestFinal(&md, digest + have, NULL);
393: }
394: buffer_free(&b);
395: #ifdef DEBUG_KEX
396: fprintf(stderr, "key '%c'== ", c);
397: dump_digest("key", digest, need);
398: #endif
399: return digest;
1.1 markus 400: }
401:
1.30 markus 402: Newkeys *current_keys[MODE_MAX];
1.27 markus 403:
1.23 markus 404: #define NKEYS 6
1.26 markus 405: void
1.27 markus 406: kex_derive_keys(Kex *kex, u_char *hash, BIGNUM *shared_secret)
1.1 markus 407: {
1.15 markus 408: u_char *keys[NKEYS];
1.27 markus 409: int i, mode, ctos;
1.1 markus 410:
411: for (i = 0; i < NKEYS; i++)
1.27 markus 412: keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret);
1.1 markus 413:
1.27 markus 414: debug("kex_derive_keys");
1.1 markus 415: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 416: current_keys[mode] = kex->newkeys[mode];
417: kex->newkeys[mode] = NULL;
1.27 markus 418: ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
1.30 markus 419: current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
420: current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
421: current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
1.1 markus 422: }
1.27 markus 423: }
424:
425: Newkeys *
426: kex_get_newkeys(int mode)
427: {
1.30 markus 428: Newkeys *ret;
429:
430: ret = current_keys[mode];
431: current_keys[mode] = NULL;
432: return ret;
1.1 markus 433: }
1.26 markus 434:
435: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
436: void
437: dump_digest(char *msg, u_char *digest, int len)
438: {
439: int i;
440:
441: fprintf(stderr, "%s\n", msg);
1.37 deraadt 442: for (i = 0; i< len; i++) {
1.26 markus 443: fprintf(stderr, "%02x", digest[i]);
444: if (i%32 == 31)
445: fprintf(stderr, "\n");
446: else if (i%8 == 7)
447: fprintf(stderr, " ");
448: }
449: fprintf(stderr, "\n");
450: }
451: #endif
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