Annotation of src/usr.bin/ssh/kex.c, Revision 1.46
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"
1.46 ! markus 26: RCSID("$OpenBSD: kex.c,v 1.45 2002/02/14 23:41:01 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);
1.46 ! markus 135: packet_check_eom();
1.26 markus 136: debug("SSH2_MSG_NEWKEYS received");
1.32 markus 137:
1.30 markus 138: kex->done = 1;
1.26 markus 139: buffer_clear(&kex->peer);
1.27 markus 140: /* buffer_clear(&kex->my); */
1.26 markus 141: kex->flags &= ~KEX_INIT_SENT;
1.32 markus 142: xfree(kex->name);
143: kex->name = NULL;
1.26 markus 144: }
1.1 markus 145:
1.26 markus 146: void
147: kex_send_kexinit(Kex *kex)
148: {
1.29 markus 149: if (kex == NULL) {
150: error("kex_send_kexinit: no kex, cannot rekey");
151: return;
152: }
1.28 markus 153: if (kex->flags & KEX_INIT_SENT) {
154: debug("KEX_INIT_SENT");
155: return;
156: }
1.30 markus 157: kex->done = 0;
1.26 markus 158: packet_start(SSH2_MSG_KEXINIT);
159: packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
160: packet_send();
161: debug("SSH2_MSG_KEXINIT sent");
162: kex->flags |= KEX_INIT_SENT;
1.1 markus 163: }
164:
1.26 markus 165: void
1.41 markus 166: kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
1.11 provos 167: {
1.26 markus 168: char *ptr;
169: int dlen;
1.31 markus 170: int i;
1.26 markus 171: Kex *kex = (Kex *)ctxt;
1.11 provos 172:
1.26 markus 173: debug("SSH2_MSG_KEXINIT received");
1.29 markus 174: if (kex == NULL)
175: fatal("kex_input_kexinit: no kex, cannot rekey");
1.11 provos 176:
1.26 markus 177: ptr = packet_get_raw(&dlen);
178: buffer_append(&kex->peer, ptr, dlen);
1.31 markus 179:
180: /* discard packet */
181: for (i = 0; i < KEX_COOKIE_LEN; i++)
182: packet_get_char();
183: for (i = 0; i < PROPOSAL_MAX; i++)
184: xfree(packet_get_string(NULL));
185: packet_get_char();
186: packet_get_int();
1.39 markus 187: packet_check_eom();
1.19 stevesk 188:
1.26 markus 189: kex_kexinit_finish(kex);
190: }
1.11 provos 191:
1.26 markus 192: Kex *
1.28 markus 193: kex_setup(char *proposal[PROPOSAL_MAX])
1.26 markus 194: {
195: Kex *kex;
1.11 provos 196:
1.26 markus 197: kex = xmalloc(sizeof(*kex));
198: memset(kex, 0, sizeof(*kex));
199: buffer_init(&kex->peer);
200: buffer_init(&kex->my);
201: kex_prop2buf(&kex->my, proposal);
1.30 markus 202: kex->done = 0;
1.26 markus 203:
204: kex_send_kexinit(kex); /* we start */
1.44 markus 205: kex_reset_dispatch();
1.26 markus 206:
207: return kex;
1.11 provos 208: }
209:
1.35 itojun 210: static void
1.26 markus 211: kex_kexinit_finish(Kex *kex)
1.1 markus 212: {
1.26 markus 213: if (!(kex->flags & KEX_INIT_SENT))
214: kex_send_kexinit(kex);
1.1 markus 215:
1.26 markus 216: kex_choose_conf(kex);
1.1 markus 217:
1.37 deraadt 218: switch (kex->kex_type) {
1.26 markus 219: case DH_GRP1_SHA1:
220: kexdh(kex);
221: break;
222: case DH_GEX_SHA1:
223: kexgex(kex);
224: break;
225: default:
226: fatal("Unsupported key exchange %d", kex->kex_type);
1.1 markus 227: }
228: }
229:
1.35 itojun 230: static void
1.1 markus 231: choose_enc(Enc *enc, char *client, char *server)
232: {
1.23 markus 233: char *name = match_list(client, server, NULL);
1.1 markus 234: if (name == NULL)
235: fatal("no matching cipher found: client %s server %s", client, server);
1.45 markus 236: if ((enc->cipher = cipher_by_name(name)) == NULL)
1.12 markus 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;
1.45 markus 242: enc->key_len = cipher_keylen(enc->cipher);
243: enc->block_size = cipher_blocksize(enc->cipher);
1.1 markus 244: }
1.35 itojun 245: static void
1.1 markus 246: choose_mac(Mac *mac, char *client, char *server)
247: {
1.23 markus 248: char *name = match_list(client, server, NULL);
1.1 markus 249: if (name == NULL)
250: fatal("no matching mac found: client %s server %s", client, server);
1.21 markus 251: if (mac_init(mac, name) < 0)
1.1 markus 252: fatal("unsupported mac %s", name);
1.21 markus 253: /* truncate the key */
254: if (datafellows & SSH_BUG_HMAC)
255: mac->key_len = 16;
1.1 markus 256: mac->name = name;
257: mac->key = NULL;
258: mac->enabled = 0;
259: }
1.35 itojun 260: static void
1.1 markus 261: choose_comp(Comp *comp, char *client, char *server)
262: {
1.23 markus 263: char *name = match_list(client, server, NULL);
1.1 markus 264: if (name == NULL)
265: fatal("no matching comp found: client %s server %s", client, server);
266: if (strcmp(name, "zlib") == 0) {
267: comp->type = 1;
268: } else if (strcmp(name, "none") == 0) {
269: comp->type = 0;
270: } else {
271: fatal("unsupported comp %s", name);
272: }
273: comp->name = name;
274: }
1.35 itojun 275: static void
1.1 markus 276: choose_kex(Kex *k, char *client, char *server)
277: {
1.23 markus 278: k->name = match_list(client, server, NULL);
1.1 markus 279: if (k->name == NULL)
280: fatal("no kex alg");
1.11 provos 281: if (strcmp(k->name, KEX_DH1) == 0) {
282: k->kex_type = DH_GRP1_SHA1;
283: } else if (strcmp(k->name, KEX_DHGEX) == 0) {
284: k->kex_type = DH_GEX_SHA1;
285: } else
1.1 markus 286: fatal("bad kex alg %s", k->name);
287: }
1.35 itojun 288: static void
1.1 markus 289: choose_hostkeyalg(Kex *k, char *client, char *server)
290: {
1.23 markus 291: char *hostkeyalg = match_list(client, server, NULL);
1.13 markus 292: if (hostkeyalg == NULL)
1.1 markus 293: fatal("no hostkey alg");
1.13 markus 294: k->hostkey_type = key_type_from_name(hostkeyalg);
295: if (k->hostkey_type == KEY_UNSPEC)
296: fatal("bad hostkey alg '%s'", hostkeyalg);
1.17 markus 297: xfree(hostkeyalg);
1.1 markus 298: }
299:
1.35 itojun 300: static void
1.27 markus 301: kex_choose_conf(Kex *kex)
1.1 markus 302: {
1.27 markus 303: Newkeys *newkeys;
1.26 markus 304: char **my, **peer;
305: char **cprop, **sprop;
1.27 markus 306: int nenc, nmac, ncomp;
1.1 markus 307: int mode;
308: int ctos; /* direction: if true client-to-server */
309: int need;
310:
1.27 markus 311: my = kex_buf2prop(&kex->my);
312: peer = kex_buf2prop(&kex->peer);
1.26 markus 313:
1.27 markus 314: if (kex->server) {
1.26 markus 315: cprop=peer;
316: sprop=my;
317: } else {
318: cprop=my;
319: sprop=peer;
320: }
1.1 markus 321:
1.30 markus 322: /* Algorithm Negotiation */
1.1 markus 323: for (mode = 0; mode < MODE_MAX; mode++) {
1.27 markus 324: newkeys = xmalloc(sizeof(*newkeys));
325: memset(newkeys, 0, sizeof(*newkeys));
1.30 markus 326: kex->newkeys[mode] = newkeys;
1.27 markus 327: ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
1.1 markus 328: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
329: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
330: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.27 markus 331: choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
332: choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
333: choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
1.2 markus 334: debug("kex: %s %s %s %s",
1.1 markus 335: ctos ? "client->server" : "server->client",
1.27 markus 336: newkeys->enc.name,
337: newkeys->mac.name,
338: newkeys->comp.name);
1.1 markus 339: }
1.27 markus 340: choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
341: choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
1.1 markus 342: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
343: need = 0;
344: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 345: newkeys = kex->newkeys[mode];
1.45 markus 346: if (need < newkeys->enc.key_len)
347: need = newkeys->enc.key_len;
348: if (need < newkeys->enc.block_size)
349: need = newkeys->enc.block_size;
1.27 markus 350: if (need < newkeys->mac.key_len)
351: need = newkeys->mac.key_len;
1.1 markus 352: }
1.7 markus 353: /* XXX need runden? */
1.27 markus 354: kex->we_need = need;
1.26 markus 355:
356: kex_prop_free(my);
357: kex_prop_free(peer);
358: }
359:
1.35 itojun 360: static u_char *
1.27 markus 361: derive_key(Kex *kex, int id, int need, u_char *hash, BIGNUM *shared_secret)
1.26 markus 362: {
363: Buffer b;
364: EVP_MD *evp_md = EVP_sha1();
365: EVP_MD_CTX md;
366: char c = id;
367: int have;
1.43 markus 368: int mdsz = EVP_MD_size(evp_md);
1.30 markus 369: u_char *digest = xmalloc(roundup(need, mdsz));
1.26 markus 370:
371: buffer_init(&b);
372: buffer_put_bignum2(&b, shared_secret);
373:
1.30 markus 374: /* K1 = HASH(K || H || "A" || session_id) */
1.26 markus 375: EVP_DigestInit(&md, evp_md);
1.34 markus 376: if (!(datafellows & SSH_BUG_DERIVEKEY))
377: EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
1.30 markus 378: EVP_DigestUpdate(&md, hash, mdsz);
379: EVP_DigestUpdate(&md, &c, 1);
1.27 markus 380: EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
1.26 markus 381: EVP_DigestFinal(&md, digest, NULL);
382:
1.30 markus 383: /*
384: * expand key:
385: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
386: * Key = K1 || K2 || ... || Kn
387: */
1.26 markus 388: for (have = mdsz; need > have; have += mdsz) {
389: EVP_DigestInit(&md, evp_md);
1.34 markus 390: if (!(datafellows & SSH_BUG_DERIVEKEY))
391: EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
1.26 markus 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);
1.37 deraadt 444: for (i = 0; i< len; i++) {
1.26 markus 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