Annotation of src/usr.bin/ssh/kex.c, Revision 1.12.2.5
1.1 markus 1: /*
1.12.2.5! miod 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"
1.12.2.5! miod 26: RCSID("$OpenBSD: kex.c,v 1.36 2001/06/25 08:25:37 markus Exp $");
1.1 markus 27:
1.4 markus 28: #include <openssl/crypto.h>
1.1 markus 29:
1.12.2.1 jason 30: #include "ssh2.h"
31: #include "xmalloc.h"
32: #include "buffer.h"
33: #include "bufaux.h"
34: #include "packet.h"
35: #include "compat.h"
36: #include "cipher.h"
1.1 markus 37: #include "kex.h"
1.12.2.1 jason 38: #include "key.h"
39: #include "log.h"
40: #include "mac.h"
1.12.2.3 jason 41: #include "match.h"
1.12.2.4 jason 42: #include "dispatch.h"
1.1 markus 43:
1.7 markus 44: #define KEX_COOKIE_LEN 16
45:
1.12.2.5! miod 46: /* prototype */
! 47: static void kex_kexinit_finish(Kex *);
! 48: static void kex_choose_conf(Kex *);
1.12.2.4 jason 49:
50: /* put algorithm proposal into buffer */
1.12.2.5! miod 51: static void
1.12.2.4 jason 52: kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
1.1 markus 53: {
54: u_int32_t rand = 0;
55: int i;
1.12.2.4 jason 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();
1.12.2.4 jason 61: buffer_put_char(b, rand & 0xff);
1.1 markus 62: rand >>= 8;
63: }
64: for (i = 0; i < PROPOSAL_MAX; i++)
1.12.2.4 jason 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:
1.12.2.4 jason 70: /* parse buffer and return algorithm proposal */
1.12.2.5! miod 71: static char **
1.12.2.4 jason 72: kex_buf2prop(Buffer *raw)
1.7 markus 73: {
1.12.2.4 jason 74: Buffer b;
1.7 markus 75: int i;
1.12.2.4 jason 76: char **proposal;
1.7 markus 77:
1.12.2.4 jason 78: proposal = xmalloc(PROPOSAL_MAX * sizeof(char *));
1.7 markus 79:
1.12.2.4 jason 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++)
1.12.2.4 jason 84: buffer_get_char(&b);
1.7 markus 85: /* extract kex init proposal strings */
86: for (i = 0; i < PROPOSAL_MAX; i++) {
1.12.2.4 jason 87: proposal[i] = buffer_get_string(&b,NULL);
88: debug2("kex_parse_kexinit: %s", proposal[i]);
1.7 markus 89: }
1.12.2.4 jason 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;
1.7 markus 97: }
98:
1.12.2.5! miod 99: static void
1.12.2.4 jason 100: kex_prop_free(char **proposal)
1.3 markus 101: {
102: int i;
1.11 provos 103:
1.12.2.4 jason 104: for (i = 0; i < PROPOSAL_MAX; i++)
105: xfree(proposal[i]);
106: xfree(proposal);
1.1 markus 107: }
108:
1.12.2.5! miod 109: static void
1.12.2.4 jason 110: kex_protocol_error(int type, int plen, void *ctxt)
1.1 markus 111: {
1.12.2.4 jason 112: error("Hm, kex protocol error: type %d plen %d", type, plen);
1.1 markus 113: }
114:
1.12.2.5! miod 115: static void
1.12.2.4 jason 116: kex_clear_dispatch(void)
1.1 markus 117: {
1.12.2.4 jason 118: int i;
1.1 markus 119:
1.12.2.4 jason 120: /* Numbers 30-49 are used for kex packets */
121: for (i = 30; i <= 49; i++)
122: dispatch_set(i, &kex_protocol_error);
123: }
1.1 markus 124:
1.12.2.4 jason 125: void
126: kex_finish(Kex *kex)
127: {
128: int plen;
1.12.2.1 jason 129:
1.12.2.4 jason 130: kex_clear_dispatch();
1.1 markus 131:
1.12.2.4 jason 132: packet_start(SSH2_MSG_NEWKEYS);
133: packet_send();
134: /* packet_write_wait(); */
135: debug("SSH2_MSG_NEWKEYS sent");
1.1 markus 136:
1.12.2.4 jason 137: debug("waiting for SSH2_MSG_NEWKEYS");
138: packet_read_expect(&plen, SSH2_MSG_NEWKEYS);
139: debug("SSH2_MSG_NEWKEYS received");
140:
141: kex->done = 1;
142: buffer_clear(&kex->peer);
143: /* buffer_clear(&kex->my); */
144: kex->flags &= ~KEX_INIT_SENT;
145: xfree(kex->name);
146: kex->name = NULL;
147: }
1.1 markus 148:
1.12.2.4 jason 149: void
150: kex_send_kexinit(Kex *kex)
151: {
152: if (kex == NULL) {
153: error("kex_send_kexinit: no kex, cannot rekey");
154: return;
155: }
156: if (kex->flags & KEX_INIT_SENT) {
157: debug("KEX_INIT_SENT");
158: return;
159: }
160: kex->done = 0;
161: packet_start(SSH2_MSG_KEXINIT);
162: packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
163: packet_send();
164: debug("SSH2_MSG_KEXINIT sent");
165: kex->flags |= KEX_INIT_SENT;
1.1 markus 166: }
167:
1.12.2.4 jason 168: void
169: kex_input_kexinit(int type, int plen, void *ctxt)
1.11 provos 170: {
1.12.2.4 jason 171: char *ptr;
172: int dlen;
173: int i;
174: Kex *kex = (Kex *)ctxt;
1.11 provos 175:
1.12.2.4 jason 176: debug("SSH2_MSG_KEXINIT received");
177: if (kex == NULL)
178: fatal("kex_input_kexinit: no kex, cannot rekey");
1.11 provos 179:
1.12.2.4 jason 180: ptr = packet_get_raw(&dlen);
181: buffer_append(&kex->peer, ptr, dlen);
1.12.2.1 jason 182:
1.12.2.4 jason 183: /* discard packet */
184: for (i = 0; i < KEX_COOKIE_LEN; i++)
185: packet_get_char();
186: for (i = 0; i < PROPOSAL_MAX; i++)
187: xfree(packet_get_string(NULL));
188: packet_get_char();
189: packet_get_int();
190: packet_done();
1.11 provos 191:
1.12.2.4 jason 192: kex_kexinit_finish(kex);
193: }
1.11 provos 194:
1.12.2.4 jason 195: Kex *
196: kex_setup(char *proposal[PROPOSAL_MAX])
197: {
198: Kex *kex;
1.11 provos 199:
1.12.2.4 jason 200: kex = xmalloc(sizeof(*kex));
201: memset(kex, 0, sizeof(*kex));
202: buffer_init(&kex->peer);
203: buffer_init(&kex->my);
204: kex_prop2buf(&kex->my, proposal);
205: kex->done = 0;
206:
207: kex_send_kexinit(kex); /* we start */
208: kex_clear_dispatch();
209: dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
210:
211: return kex;
1.11 provos 212: }
213:
1.12.2.5! miod 214: static void
1.12.2.4 jason 215: kex_kexinit_finish(Kex *kex)
1.1 markus 216: {
1.12.2.4 jason 217: if (!(kex->flags & KEX_INIT_SENT))
218: kex_send_kexinit(kex);
1.1 markus 219:
1.12.2.4 jason 220: kex_choose_conf(kex);
1.1 markus 221:
1.12.2.4 jason 222: switch(kex->kex_type) {
223: case DH_GRP1_SHA1:
224: kexdh(kex);
225: break;
226: case DH_GEX_SHA1:
227: kexgex(kex);
228: break;
229: default:
230: fatal("Unsupported key exchange %d", kex->kex_type);
1.1 markus 231: }
232: }
233:
1.12.2.5! miod 234: static void
1.1 markus 235: choose_enc(Enc *enc, char *client, char *server)
236: {
1.12.2.3 jason 237: char *name = match_list(client, server, NULL);
1.1 markus 238: if (name == NULL)
239: fatal("no matching cipher found: client %s server %s", client, server);
1.12 markus 240: enc->cipher = cipher_by_name(name);
241: if (enc->cipher == NULL)
242: fatal("matching cipher is not supported: %s", name);
1.1 markus 243: enc->name = name;
244: enc->enabled = 0;
245: enc->iv = NULL;
246: enc->key = NULL;
247: }
1.12.2.5! miod 248: static void
1.1 markus 249: choose_mac(Mac *mac, char *client, char *server)
250: {
1.12.2.3 jason 251: char *name = match_list(client, server, NULL);
1.1 markus 252: if (name == NULL)
253: fatal("no matching mac found: client %s server %s", client, server);
1.12.2.1 jason 254: if (mac_init(mac, name) < 0)
1.1 markus 255: fatal("unsupported mac %s", name);
1.12.2.1 jason 256: /* truncate the key */
257: if (datafellows & SSH_BUG_HMAC)
258: mac->key_len = 16;
1.1 markus 259: mac->name = name;
260: mac->key = NULL;
261: mac->enabled = 0;
262: }
1.12.2.5! miod 263: static void
1.1 markus 264: choose_comp(Comp *comp, char *client, char *server)
265: {
1.12.2.3 jason 266: char *name = match_list(client, server, NULL);
1.1 markus 267: if (name == NULL)
268: fatal("no matching comp found: client %s server %s", client, server);
269: if (strcmp(name, "zlib") == 0) {
270: comp->type = 1;
271: } else if (strcmp(name, "none") == 0) {
272: comp->type = 0;
273: } else {
274: fatal("unsupported comp %s", name);
275: }
276: comp->name = name;
277: }
1.12.2.5! miod 278: static void
1.1 markus 279: choose_kex(Kex *k, char *client, char *server)
280: {
1.12.2.3 jason 281: k->name = match_list(client, server, NULL);
1.1 markus 282: if (k->name == NULL)
283: fatal("no kex alg");
1.11 provos 284: if (strcmp(k->name, KEX_DH1) == 0) {
285: k->kex_type = DH_GRP1_SHA1;
286: } else if (strcmp(k->name, KEX_DHGEX) == 0) {
287: k->kex_type = DH_GEX_SHA1;
288: } else
1.1 markus 289: fatal("bad kex alg %s", k->name);
290: }
1.12.2.5! miod 291: static void
1.1 markus 292: choose_hostkeyalg(Kex *k, char *client, char *server)
293: {
1.12.2.3 jason 294: char *hostkeyalg = match_list(client, server, NULL);
1.12.2.1 jason 295: if (hostkeyalg == NULL)
1.1 markus 296: fatal("no hostkey alg");
1.12.2.1 jason 297: k->hostkey_type = key_type_from_name(hostkeyalg);
298: if (k->hostkey_type == KEY_UNSPEC)
299: fatal("bad hostkey alg '%s'", hostkeyalg);
300: xfree(hostkeyalg);
1.1 markus 301: }
302:
1.12.2.5! miod 303: static void
1.12.2.4 jason 304: kex_choose_conf(Kex *kex)
1.1 markus 305: {
1.12.2.4 jason 306: Newkeys *newkeys;
307: char **my, **peer;
308: char **cprop, **sprop;
309: int nenc, nmac, ncomp;
1.1 markus 310: int mode;
311: int ctos; /* direction: if true client-to-server */
312: int need;
313:
1.12.2.4 jason 314: my = kex_buf2prop(&kex->my);
315: peer = kex_buf2prop(&kex->peer);
1.1 markus 316:
1.12.2.4 jason 317: if (kex->server) {
318: cprop=peer;
319: sprop=my;
320: } else {
321: cprop=my;
322: sprop=peer;
323: }
324:
325: /* Algorithm Negotiation */
1.1 markus 326: for (mode = 0; mode < MODE_MAX; mode++) {
1.12.2.4 jason 327: newkeys = xmalloc(sizeof(*newkeys));
328: memset(newkeys, 0, sizeof(*newkeys));
329: kex->newkeys[mode] = newkeys;
330: ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
1.1 markus 331: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
332: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
333: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.12.2.4 jason 334: choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
335: choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
336: choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
1.2 markus 337: debug("kex: %s %s %s %s",
1.1 markus 338: ctos ? "client->server" : "server->client",
1.12.2.4 jason 339: newkeys->enc.name,
340: newkeys->mac.name,
341: newkeys->comp.name);
1.1 markus 342: }
1.12.2.4 jason 343: choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
344: choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
1.1 markus 345: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
346: need = 0;
347: for (mode = 0; mode < MODE_MAX; mode++) {
1.12.2.4 jason 348: newkeys = kex->newkeys[mode];
349: if (need < newkeys->enc.cipher->key_len)
350: need = newkeys->enc.cipher->key_len;
351: if (need < newkeys->enc.cipher->block_size)
352: need = newkeys->enc.cipher->block_size;
353: if (need < newkeys->mac.key_len)
354: need = newkeys->mac.key_len;
1.1 markus 355: }
1.7 markus 356: /* XXX need runden? */
1.12.2.4 jason 357: kex->we_need = need;
358:
359: kex_prop_free(my);
360: kex_prop_free(peer);
1.1 markus 361: }
362:
1.12.2.5! miod 363: static u_char *
1.12.2.4 jason 364: derive_key(Kex *kex, int id, int need, u_char *hash, BIGNUM *shared_secret)
365: {
366: Buffer b;
367: EVP_MD *evp_md = EVP_sha1();
368: EVP_MD_CTX md;
369: char c = id;
370: int have;
371: int mdsz = evp_md->md_size;
372: u_char *digest = xmalloc(roundup(need, mdsz));
373:
374: buffer_init(&b);
375: buffer_put_bignum2(&b, shared_secret);
376:
377: /* K1 = HASH(K || H || "A" || session_id) */
378: EVP_DigestInit(&md, evp_md);
1.12.2.5! miod 379: if (!(datafellows & SSH_BUG_DERIVEKEY))
! 380: EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
1.12.2.4 jason 381: EVP_DigestUpdate(&md, hash, mdsz);
382: EVP_DigestUpdate(&md, &c, 1);
383: EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
384: EVP_DigestFinal(&md, digest, NULL);
385:
386: /*
387: * expand key:
388: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
389: * Key = K1 || K2 || ... || Kn
390: */
391: for (have = mdsz; need > have; have += mdsz) {
392: EVP_DigestInit(&md, evp_md);
1.12.2.5! miod 393: if (!(datafellows & SSH_BUG_DERIVEKEY))
! 394: EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
1.12.2.4 jason 395: EVP_DigestUpdate(&md, hash, mdsz);
396: EVP_DigestUpdate(&md, digest, have);
397: EVP_DigestFinal(&md, digest + have, NULL);
398: }
399: buffer_free(&b);
400: #ifdef DEBUG_KEX
401: fprintf(stderr, "key '%c'== ", c);
402: dump_digest("key", digest, need);
403: #endif
404: return digest;
405: }
406:
407: Newkeys *current_keys[MODE_MAX];
408:
1.12.2.3 jason 409: #define NKEYS 6
1.12.2.4 jason 410: void
411: kex_derive_keys(Kex *kex, u_char *hash, BIGNUM *shared_secret)
1.1 markus 412: {
1.12.2.1 jason 413: u_char *keys[NKEYS];
1.12.2.4 jason 414: int i, mode, ctos;
1.1 markus 415:
416: for (i = 0; i < NKEYS; i++)
1.12.2.4 jason 417: keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret);
1.1 markus 418:
1.12.2.4 jason 419: debug("kex_derive_keys");
1.1 markus 420: for (mode = 0; mode < MODE_MAX; mode++) {
1.12.2.4 jason 421: current_keys[mode] = kex->newkeys[mode];
422: kex->newkeys[mode] = NULL;
423: ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
424: current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
425: current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
426: current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
427: }
428: }
429:
430: Newkeys *
431: kex_get_newkeys(int mode)
432: {
433: Newkeys *ret;
434:
435: ret = current_keys[mode];
436: current_keys[mode] = NULL;
437: return ret;
438: }
439:
440: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
441: void
442: dump_digest(char *msg, u_char *digest, int len)
443: {
444: int i;
445:
446: fprintf(stderr, "%s\n", msg);
447: for (i = 0; i< len; i++){
448: fprintf(stderr, "%02x", digest[i]);
449: if (i%32 == 31)
450: fprintf(stderr, "\n");
451: else if (i%8 == 7)
452: fprintf(stderr, " ");
1.1 markus 453: }
1.12.2.4 jason 454: fprintf(stderr, "\n");
1.1 markus 455: }
1.12.2.4 jason 456: #endif
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