Annotation of src/usr.bin/ssh/kex.c, Revision 1.29
1.1 markus 1: /*
2: * Copyright (c) 2000 Markus Friedl. All rights reserved.
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"
1.29 ! markus 26: RCSID("$OpenBSD: kex.c,v 1.28 2001/04/04 09:48:34 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:
1.26 markus 46: void kex_kexinit_finish(Kex *kex);
47: void kex_choose_conf(Kex *k);
48:
49: /* put algorithm proposal into buffer */
50: void
51: kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
1.1 markus 52: {
53: u_int32_t rand = 0;
54: int i;
1.26 markus 55:
56: buffer_clear(b);
1.7 markus 57: for (i = 0; i < KEX_COOKIE_LEN; i++) {
1.1 markus 58: if (i % 4 == 0)
59: rand = arc4random();
1.26 markus 60: buffer_put_char(b, rand & 0xff);
1.1 markus 61: rand >>= 8;
62: }
63: for (i = 0; i < PROPOSAL_MAX; i++)
1.26 markus 64: buffer_put_cstring(b, proposal[i]);
65: buffer_put_char(b, 0); /* first_kex_packet_follows */
66: buffer_put_int(b, 0); /* uint32 reserved */
1.1 markus 67: }
68:
1.26 markus 69: /* parse buffer and return algorithm proposal */
70: char **
71: kex_buf2prop(Buffer *raw)
1.7 markus 72: {
1.26 markus 73: Buffer b;
1.7 markus 74: int i;
1.26 markus 75: char **proposal;
1.7 markus 76:
1.26 markus 77: proposal = xmalloc(PROPOSAL_MAX * sizeof(char *));
1.7 markus 78:
1.26 markus 79: buffer_init(&b);
80: buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
1.7 markus 81: /* skip cookie */
82: for (i = 0; i < KEX_COOKIE_LEN; i++)
1.26 markus 83: buffer_get_char(&b);
1.7 markus 84: /* extract kex init proposal strings */
85: for (i = 0; i < PROPOSAL_MAX; i++) {
1.26 markus 86: proposal[i] = buffer_get_string(&b,NULL);
87: debug2("kex_parse_kexinit: %s", proposal[i]);
1.7 markus 88: }
1.26 markus 89: /* first kex follows / reserved */
90: i = buffer_get_char(&b);
91: debug2("kex_parse_kexinit: first_kex_follows %d ", i);
92: i = buffer_get_int(&b);
93: debug2("kex_parse_kexinit: reserved %d ", i);
94: buffer_free(&b);
95: return proposal;
1.1 markus 96: }
97:
98: void
1.26 markus 99: kex_prop_free(char **proposal)
1.1 markus 100: {
101: int i;
1.26 markus 102:
103: for (i = 0; i < PROPOSAL_MAX; i++)
104: xfree(proposal[i]);
105: xfree(proposal);
1.1 markus 106: }
107:
1.26 markus 108: void
109: kex_protocol_error(int type, int plen, void *ctxt)
1.1 markus 110: {
1.26 markus 111: error("Hm, kex protocol error: type %d plen %d", type, plen);
112: }
1.1 markus 113:
1.26 markus 114: void
1.29 ! markus 115: kex_clear_dispatch(void)
! 116: {
! 117: int i;
! 118:
! 119: /* Numbers 30-49 are used for kex packets */
! 120: for (i = 30; i <= 49; i++)
! 121: dispatch_set(i, &kex_protocol_error);
! 122: }
! 123:
! 124: void
1.28 markus 125: kex_finish(Kex *kex)
1.26 markus 126: {
1.29 ! markus 127: int plen;
! 128:
! 129: kex_clear_dispatch();
1.28 markus 130:
1.26 markus 131: packet_start(SSH2_MSG_NEWKEYS);
132: packet_send();
133: /* packet_write_wait(); */
134: debug("SSH2_MSG_NEWKEYS sent");
1.19 stevesk 135:
1.28 markus 136: debug("waiting for SSH2_MSG_NEWKEYS");
137: packet_read_expect(&plen, SSH2_MSG_NEWKEYS);
1.26 markus 138: debug("SSH2_MSG_NEWKEYS received");
139: kex->newkeys = 1;
140: buffer_clear(&kex->peer);
1.27 markus 141: /* buffer_clear(&kex->my); */
1.26 markus 142: kex->flags &= ~KEX_INIT_SENT;
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: }
1.26 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
164: kex_input_kexinit(int type, int plen, void *ctxt)
1.11 provos 165: {
1.26 markus 166: char *ptr;
167: int dlen;
168: Kex *kex = (Kex *)ctxt;
1.11 provos 169:
1.26 markus 170: debug("SSH2_MSG_KEXINIT received");
1.29 ! markus 171: if (kex == NULL)
! 172: fatal("kex_input_kexinit: no kex, cannot rekey");
1.11 provos 173:
1.26 markus 174: ptr = packet_get_raw(&dlen);
175: buffer_append(&kex->peer, ptr, dlen);
1.19 stevesk 176:
1.26 markus 177: kex_kexinit_finish(kex);
178: }
1.11 provos 179:
1.26 markus 180: Kex *
1.28 markus 181: kex_setup(char *proposal[PROPOSAL_MAX])
1.26 markus 182: {
183: Kex *kex;
1.11 provos 184:
1.26 markus 185: kex = xmalloc(sizeof(*kex));
186: memset(kex, 0, sizeof(*kex));
187: buffer_init(&kex->peer);
188: buffer_init(&kex->my);
189: kex_prop2buf(&kex->my, proposal);
190: kex->newkeys = 0;
191:
192: kex_send_kexinit(kex); /* we start */
1.29 ! markus 193: kex_clear_dispatch();
! 194: dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.26 markus 195:
196: return kex;
1.11 provos 197: }
198:
1.26 markus 199: void
200: kex_kexinit_finish(Kex *kex)
1.1 markus 201: {
1.26 markus 202: if (!(kex->flags & KEX_INIT_SENT))
203: kex_send_kexinit(kex);
1.1 markus 204:
1.26 markus 205: kex_choose_conf(kex);
1.1 markus 206:
1.26 markus 207: switch(kex->kex_type) {
208: case DH_GRP1_SHA1:
209: kexdh(kex);
210: break;
211: case DH_GEX_SHA1:
212: kexgex(kex);
213: break;
214: default:
215: fatal("Unsupported key exchange %d", kex->kex_type);
1.1 markus 216: }
217: }
218:
219: void
220: choose_enc(Enc *enc, char *client, char *server)
221: {
1.23 markus 222: char *name = match_list(client, server, NULL);
1.1 markus 223: if (name == NULL)
224: fatal("no matching cipher found: client %s server %s", client, server);
1.12 markus 225: enc->cipher = cipher_by_name(name);
226: if (enc->cipher == NULL)
227: fatal("matching cipher is not supported: %s", name);
1.1 markus 228: enc->name = name;
229: enc->enabled = 0;
230: enc->iv = NULL;
231: enc->key = NULL;
232: }
233: void
234: choose_mac(Mac *mac, char *client, char *server)
235: {
1.23 markus 236: char *name = match_list(client, server, NULL);
1.1 markus 237: if (name == NULL)
238: fatal("no matching mac found: client %s server %s", client, server);
1.21 markus 239: if (mac_init(mac, name) < 0)
1.1 markus 240: fatal("unsupported mac %s", name);
1.21 markus 241: /* truncate the key */
242: if (datafellows & SSH_BUG_HMAC)
243: mac->key_len = 16;
1.1 markus 244: mac->name = name;
245: mac->key = NULL;
246: mac->enabled = 0;
247: }
248: void
249: choose_comp(Comp *comp, char *client, char *server)
250: {
1.23 markus 251: char *name = match_list(client, server, NULL);
1.1 markus 252: if (name == NULL)
253: fatal("no matching comp found: client %s server %s", client, server);
254: if (strcmp(name, "zlib") == 0) {
255: comp->type = 1;
256: } else if (strcmp(name, "none") == 0) {
257: comp->type = 0;
258: } else {
259: fatal("unsupported comp %s", name);
260: }
261: comp->name = name;
262: }
263: void
264: choose_kex(Kex *k, char *client, char *server)
265: {
1.23 markus 266: k->name = match_list(client, server, NULL);
1.1 markus 267: if (k->name == NULL)
268: fatal("no kex alg");
1.11 provos 269: if (strcmp(k->name, KEX_DH1) == 0) {
270: k->kex_type = DH_GRP1_SHA1;
271: } else if (strcmp(k->name, KEX_DHGEX) == 0) {
272: k->kex_type = DH_GEX_SHA1;
273: } else
1.1 markus 274: fatal("bad kex alg %s", k->name);
275: }
276: void
277: choose_hostkeyalg(Kex *k, char *client, char *server)
278: {
1.23 markus 279: char *hostkeyalg = match_list(client, server, NULL);
1.13 markus 280: if (hostkeyalg == NULL)
1.1 markus 281: fatal("no hostkey alg");
1.13 markus 282: k->hostkey_type = key_type_from_name(hostkeyalg);
283: if (k->hostkey_type == KEY_UNSPEC)
284: fatal("bad hostkey alg '%s'", hostkeyalg);
1.17 markus 285: xfree(hostkeyalg);
1.1 markus 286: }
287:
1.26 markus 288: void
1.27 markus 289: kex_choose_conf(Kex *kex)
1.1 markus 290: {
1.27 markus 291: Newkeys *newkeys;
1.26 markus 292: char **my, **peer;
293: char **cprop, **sprop;
1.27 markus 294: int nenc, nmac, ncomp;
1.1 markus 295: int mode;
296: int ctos; /* direction: if true client-to-server */
297: int need;
298:
1.27 markus 299: my = kex_buf2prop(&kex->my);
300: peer = kex_buf2prop(&kex->peer);
1.26 markus 301:
1.27 markus 302: if (kex->server) {
1.26 markus 303: cprop=peer;
304: sprop=my;
305: } else {
306: cprop=my;
307: sprop=peer;
308: }
1.1 markus 309:
310: for (mode = 0; mode < MODE_MAX; mode++) {
1.27 markus 311: newkeys = xmalloc(sizeof(*newkeys));
312: memset(newkeys, 0, sizeof(*newkeys));
313: kex->keys[mode] = newkeys;
314: ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
1.1 markus 315: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
316: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
317: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.27 markus 318: choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
319: choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
320: choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
1.2 markus 321: debug("kex: %s %s %s %s",
1.1 markus 322: ctos ? "client->server" : "server->client",
1.27 markus 323: newkeys->enc.name,
324: newkeys->mac.name,
325: newkeys->comp.name);
1.1 markus 326: }
1.27 markus 327: choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
328: choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
1.1 markus 329: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
330: need = 0;
331: for (mode = 0; mode < MODE_MAX; mode++) {
1.27 markus 332: newkeys = kex->keys[mode];
333: if (need < newkeys->enc.cipher->key_len)
334: need = newkeys->enc.cipher->key_len;
335: if (need < newkeys->enc.cipher->block_size)
336: need = newkeys->enc.cipher->block_size;
337: if (need < newkeys->mac.key_len)
338: need = newkeys->mac.key_len;
1.1 markus 339: }
1.7 markus 340: /* XXX need runden? */
1.27 markus 341: kex->we_need = need;
1.26 markus 342:
343: kex_prop_free(my);
344: kex_prop_free(peer);
345: }
346:
347: u_char *
1.27 markus 348: derive_key(Kex *kex, int id, int need, u_char *hash, BIGNUM *shared_secret)
1.26 markus 349: {
350: Buffer b;
351: EVP_MD *evp_md = EVP_sha1();
352: EVP_MD_CTX md;
353: char c = id;
354: int have;
355: int mdsz = evp_md->md_size;
356: u_char *digest = xmalloc(((need+mdsz-1)/mdsz)*mdsz);
357:
358: buffer_init(&b);
359: buffer_put_bignum2(&b, shared_secret);
360:
361: EVP_DigestInit(&md, evp_md);
362: EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b)); /* shared_secret K */
363: EVP_DigestUpdate(&md, hash, mdsz); /* transport-06 */
364: EVP_DigestUpdate(&md, &c, 1); /* key id */
1.27 markus 365: EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
1.26 markus 366: EVP_DigestFinal(&md, digest, NULL);
367:
368: /* expand */
369: for (have = mdsz; need > have; have += mdsz) {
370: EVP_DigestInit(&md, evp_md);
371: EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
372: EVP_DigestUpdate(&md, hash, mdsz);
373: EVP_DigestUpdate(&md, digest, have);
374: EVP_DigestFinal(&md, digest + have, NULL);
375: }
376: buffer_free(&b);
377: #ifdef DEBUG_KEX
378: fprintf(stderr, "key '%c'== ", c);
379: dump_digest("key", digest, need);
380: #endif
381: return digest;
1.1 markus 382: }
383:
1.27 markus 384: Newkeys *x_newkeys[MODE_MAX];
385:
1.23 markus 386: #define NKEYS 6
1.26 markus 387: void
1.27 markus 388: kex_derive_keys(Kex *kex, u_char *hash, BIGNUM *shared_secret)
1.1 markus 389: {
1.27 markus 390: Newkeys *newkeys;
1.15 markus 391: u_char *keys[NKEYS];
1.27 markus 392: int i, mode, ctos;
1.1 markus 393:
394: for (i = 0; i < NKEYS; i++)
1.27 markus 395: keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret);
1.1 markus 396:
1.27 markus 397: debug("kex_derive_keys");
1.1 markus 398: for (mode = 0; mode < MODE_MAX; mode++) {
1.27 markus 399: newkeys = kex->keys[mode];
400: ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
401: newkeys->enc.iv = keys[ctos ? 0 : 1];
402: newkeys->enc.key = keys[ctos ? 2 : 3];
403: newkeys->mac.key = keys[ctos ? 4 : 5];
404: x_newkeys[mode] = newkeys;
1.1 markus 405: }
1.27 markus 406: }
407:
408: Newkeys *
409: kex_get_newkeys(int mode)
410: {
411: return x_newkeys[mode];
1.1 markus 412: }
1.26 markus 413:
414: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
415: void
416: dump_digest(char *msg, u_char *digest, int len)
417: {
418: int i;
419:
420: fprintf(stderr, "%s\n", msg);
421: for (i = 0; i< len; i++){
422: fprintf(stderr, "%02x", digest[i]);
423: if (i%32 == 31)
424: fprintf(stderr, "\n");
425: else if (i%8 == 7)
426: fprintf(stderr, " ");
427: }
428: fprintf(stderr, "\n");
429: }
430: #endif
![[BACK]](/icons/back.gif){kind=icon}
Return to kex.c CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / ssh