Annotation of src/usr.bin/ssh/kex.c, Revision 1.40
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"
1.40 ! markus 26: RCSID("$OpenBSD: kex.c,v 1.39 2001/12/28 12:14:27 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
1.38 djm 110: kex_protocol_error(int type, int plen, u_int32_t seq, void *ctxt)
1.1 markus 111: {
1.33 markus 112: error("Hm, kex protocol error: type %d plen %d", type, plen);
1.26 markus 113: }
1.1 markus 114:
1.35 itojun 115: static void
1.29 markus 116: kex_clear_dispatch(void)
117: {
118: int i;
119:
120: /* Numbers 30-49 are used for kex packets */
121: for (i = 30; i <= 49; i++)
122: dispatch_set(i, &kex_protocol_error);
123: }
124:
125: void
1.28 markus 126: kex_finish(Kex *kex)
1.26 markus 127: {
1.29 markus 128: kex_clear_dispatch();
1.28 markus 129:
1.26 markus 130: packet_start(SSH2_MSG_NEWKEYS);
131: packet_send();
132: /* packet_write_wait(); */
133: debug("SSH2_MSG_NEWKEYS sent");
1.19 stevesk 134:
1.33 markus 135: debug("waiting for SSH2_MSG_NEWKEYS");
1.40 ! markus 136: packet_read_expect(SSH2_MSG_NEWKEYS);
1.26 markus 137: debug("SSH2_MSG_NEWKEYS received");
1.32 markus 138:
1.30 markus 139: kex->done = 1;
1.26 markus 140: buffer_clear(&kex->peer);
1.27 markus 141: /* buffer_clear(&kex->my); */
1.26 markus 142: kex->flags &= ~KEX_INIT_SENT;
1.32 markus 143: xfree(kex->name);
144: kex->name = NULL;
1.26 markus 145: }
1.1 markus 146:
1.26 markus 147: void
148: kex_send_kexinit(Kex *kex)
149: {
1.29 markus 150: if (kex == NULL) {
151: error("kex_send_kexinit: no kex, cannot rekey");
152: return;
153: }
1.28 markus 154: if (kex->flags & KEX_INIT_SENT) {
155: debug("KEX_INIT_SENT");
156: return;
157: }
1.30 markus 158: kex->done = 0;
1.26 markus 159: packet_start(SSH2_MSG_KEXINIT);
160: packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
161: packet_send();
162: debug("SSH2_MSG_KEXINIT sent");
163: kex->flags |= KEX_INIT_SENT;
1.1 markus 164: }
165:
1.26 markus 166: void
1.38 djm 167: kex_input_kexinit(int type, int plen, u_int32_t seq, void *ctxt)
1.11 provos 168: {
1.26 markus 169: char *ptr;
170: int dlen;
1.31 markus 171: int i;
1.26 markus 172: Kex *kex = (Kex *)ctxt;
1.11 provos 173:
1.26 markus 174: debug("SSH2_MSG_KEXINIT received");
1.29 markus 175: if (kex == NULL)
176: fatal("kex_input_kexinit: no kex, cannot rekey");
1.11 provos 177:
1.26 markus 178: ptr = packet_get_raw(&dlen);
179: buffer_append(&kex->peer, ptr, dlen);
1.31 markus 180:
181: /* discard packet */
182: for (i = 0; i < KEX_COOKIE_LEN; i++)
183: packet_get_char();
184: for (i = 0; i < PROPOSAL_MAX; i++)
185: xfree(packet_get_string(NULL));
186: packet_get_char();
187: packet_get_int();
1.39 markus 188: packet_check_eom();
1.19 stevesk 189:
1.26 markus 190: kex_kexinit_finish(kex);
191: }
1.11 provos 192:
1.26 markus 193: Kex *
1.28 markus 194: kex_setup(char *proposal[PROPOSAL_MAX])
1.26 markus 195: {
196: Kex *kex;
1.11 provos 197:
1.26 markus 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);
1.30 markus 203: kex->done = 0;
1.26 markus 204:
205: kex_send_kexinit(kex); /* we start */
1.29 markus 206: kex_clear_dispatch();
207: dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.26 markus 208:
209: return kex;
1.11 provos 210: }
211:
1.35 itojun 212: static void
1.26 markus 213: kex_kexinit_finish(Kex *kex)
1.1 markus 214: {
1.26 markus 215: if (!(kex->flags & KEX_INIT_SENT))
216: kex_send_kexinit(kex);
1.1 markus 217:
1.26 markus 218: kex_choose_conf(kex);
1.1 markus 219:
1.37 deraadt 220: switch (kex->kex_type) {
1.26 markus 221: case DH_GRP1_SHA1:
222: kexdh(kex);
223: break;
224: case DH_GEX_SHA1:
225: kexgex(kex);
226: break;
227: default:
228: fatal("Unsupported key exchange %d", kex->kex_type);
1.1 markus 229: }
230: }
231:
1.35 itojun 232: static void
1.1 markus 233: choose_enc(Enc *enc, char *client, char *server)
234: {
1.23 markus 235: char *name = match_list(client, server, NULL);
1.1 markus 236: if (name == NULL)
237: fatal("no matching cipher found: client %s server %s", client, server);
1.12 markus 238: enc->cipher = cipher_by_name(name);
239: if (enc->cipher == NULL)
240: fatal("matching cipher is not supported: %s", name);
1.1 markus 241: enc->name = name;
242: enc->enabled = 0;
243: enc->iv = NULL;
244: enc->key = NULL;
245: }
1.35 itojun 246: static void
1.1 markus 247: choose_mac(Mac *mac, char *client, char *server)
248: {
1.23 markus 249: char *name = match_list(client, server, NULL);
1.1 markus 250: if (name == NULL)
251: fatal("no matching mac found: client %s server %s", client, server);
1.21 markus 252: if (mac_init(mac, name) < 0)
1.1 markus 253: fatal("unsupported mac %s", name);
1.21 markus 254: /* truncate the key */
255: if (datafellows & SSH_BUG_HMAC)
256: mac->key_len = 16;
1.1 markus 257: mac->name = name;
258: mac->key = NULL;
259: mac->enabled = 0;
260: }
1.35 itojun 261: static void
1.1 markus 262: choose_comp(Comp *comp, char *client, char *server)
263: {
1.23 markus 264: char *name = match_list(client, server, NULL);
1.1 markus 265: if (name == NULL)
266: fatal("no matching comp found: client %s server %s", client, server);
267: if (strcmp(name, "zlib") == 0) {
268: comp->type = 1;
269: } else if (strcmp(name, "none") == 0) {
270: comp->type = 0;
271: } else {
272: fatal("unsupported comp %s", name);
273: }
274: comp->name = name;
275: }
1.35 itojun 276: static void
1.1 markus 277: choose_kex(Kex *k, char *client, char *server)
278: {
1.23 markus 279: k->name = match_list(client, server, NULL);
1.1 markus 280: if (k->name == NULL)
281: fatal("no kex alg");
1.11 provos 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;
286: } else
1.1 markus 287: fatal("bad kex alg %s", k->name);
288: }
1.35 itojun 289: static void
1.1 markus 290: choose_hostkeyalg(Kex *k, char *client, char *server)
291: {
1.23 markus 292: char *hostkeyalg = match_list(client, server, NULL);
1.13 markus 293: if (hostkeyalg == NULL)
1.1 markus 294: fatal("no hostkey alg");
1.13 markus 295: k->hostkey_type = key_type_from_name(hostkeyalg);
296: if (k->hostkey_type == KEY_UNSPEC)
297: fatal("bad hostkey alg '%s'", hostkeyalg);
1.17 markus 298: xfree(hostkeyalg);
1.1 markus 299: }
300:
1.35 itojun 301: static void
1.27 markus 302: kex_choose_conf(Kex *kex)
1.1 markus 303: {
1.27 markus 304: Newkeys *newkeys;
1.26 markus 305: char **my, **peer;
306: char **cprop, **sprop;
1.27 markus 307: int nenc, nmac, ncomp;
1.1 markus 308: int mode;
309: int ctos; /* direction: if true client-to-server */
310: int need;
311:
1.27 markus 312: my = kex_buf2prop(&kex->my);
313: peer = kex_buf2prop(&kex->peer);
1.26 markus 314:
1.27 markus 315: if (kex->server) {
1.26 markus 316: cprop=peer;
317: sprop=my;
318: } else {
319: cprop=my;
320: sprop=peer;
321: }
1.1 markus 322:
1.30 markus 323: /* Algorithm Negotiation */
1.1 markus 324: for (mode = 0; mode < MODE_MAX; mode++) {
1.27 markus 325: newkeys = xmalloc(sizeof(*newkeys));
326: memset(newkeys, 0, sizeof(*newkeys));
1.30 markus 327: kex->newkeys[mode] = newkeys;
1.27 markus 328: ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
1.1 markus 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;
1.27 markus 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]);
1.2 markus 335: debug("kex: %s %s %s %s",
1.1 markus 336: ctos ? "client->server" : "server->client",
1.27 markus 337: newkeys->enc.name,
338: newkeys->mac.name,
339: newkeys->comp.name);
1.1 markus 340: }
1.27 markus 341: choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
342: choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
1.1 markus 343: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
344: need = 0;
345: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 346: newkeys = kex->newkeys[mode];
1.27 markus 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;
1.1 markus 353: }
1.7 markus 354: /* XXX need runden? */
1.27 markus 355: kex->we_need = need;
1.26 markus 356:
357: kex_prop_free(my);
358: kex_prop_free(peer);
359: }
360:
1.35 itojun 361: static u_char *
1.27 markus 362: derive_key(Kex *kex, int id, int need, u_char *hash, BIGNUM *shared_secret)
1.26 markus 363: {
364: Buffer b;
365: EVP_MD *evp_md = EVP_sha1();
366: EVP_MD_CTX md;
367: char c = id;
368: int have;
369: int mdsz = evp_md->md_size;
1.30 markus 370: u_char *digest = xmalloc(roundup(need, mdsz));
1.26 markus 371:
372: buffer_init(&b);
373: buffer_put_bignum2(&b, shared_secret);
374:
1.30 markus 375: /* K1 = HASH(K || H || "A" || session_id) */
1.26 markus 376: EVP_DigestInit(&md, evp_md);
1.34 markus 377: if (!(datafellows & SSH_BUG_DERIVEKEY))
378: EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
1.30 markus 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);
1.34 markus 391: if (!(datafellows & SSH_BUG_DERIVEKEY))
392: EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
1.26 markus 393: EVP_DigestUpdate(&md, hash, mdsz);
394: EVP_DigestUpdate(&md, digest, have);
395: EVP_DigestFinal(&md, digest + have, NULL);
396: }
397: buffer_free(&b);
398: #ifdef DEBUG_KEX
399: fprintf(stderr, "key '%c'== ", c);
400: dump_digest("key", digest, need);
401: #endif
402: return digest;
1.1 markus 403: }
404:
1.30 markus 405: Newkeys *current_keys[MODE_MAX];
1.27 markus 406:
1.23 markus 407: #define NKEYS 6
1.26 markus 408: void
1.27 markus 409: kex_derive_keys(Kex *kex, u_char *hash, BIGNUM *shared_secret)
1.1 markus 410: {
1.15 markus 411: u_char *keys[NKEYS];
1.27 markus 412: int i, mode, ctos;
1.1 markus 413:
414: for (i = 0; i < NKEYS; i++)
1.27 markus 415: keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret);
1.1 markus 416:
1.27 markus 417: debug("kex_derive_keys");
1.1 markus 418: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 419: current_keys[mode] = kex->newkeys[mode];
420: kex->newkeys[mode] = NULL;
1.27 markus 421: ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
1.30 markus 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];
1.1 markus 425: }
1.27 markus 426: }
427:
428: Newkeys *
429: kex_get_newkeys(int mode)
430: {
1.30 markus 431: Newkeys *ret;
432:
433: ret = current_keys[mode];
434: current_keys[mode] = NULL;
435: return ret;
1.1 markus 436: }
1.26 markus 437:
438: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
439: void
440: dump_digest(char *msg, u_char *digest, int len)
441: {
442: int i;
443:
444: fprintf(stderr, "%s\n", msg);
1.37 deraadt 445: for (i = 0; i< len; i++) {
1.26 markus 446: fprintf(stderr, "%02x", digest[i]);
447: if (i%32 == 31)
448: fprintf(stderr, "\n");
449: else if (i%8 == 7)
450: fprintf(stderr, " ");
451: }
452: fprintf(stderr, "\n");
453: }
454: #endif
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