Annotation of src/usr.bin/ssh/kex.c, Revision 1.13
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"
1.13 ! markus 26: RCSID("$OpenBSD: kex.c,v 1.12 2000/10/11 20:27:23 markus Exp $");
1.1 markus 27:
28: #include "ssh.h"
29: #include "ssh2.h"
30: #include "xmalloc.h"
31: #include "buffer.h"
32: #include "bufaux.h"
1.7 markus 33: #include "packet.h"
1.1 markus 34: #include "compat.h"
35:
1.4 markus 36: #include <openssl/bn.h>
37: #include <openssl/dh.h>
1.1 markus 38:
1.4 markus 39: #include <openssl/crypto.h>
40: #include <openssl/bio.h>
41: #include <openssl/bn.h>
42: #include <openssl/dh.h>
43: #include <openssl/pem.h>
1.1 markus 44:
45: #include "kex.h"
1.13 ! markus 46: #include "key.h"
1.1 markus 47:
1.7 markus 48: #define KEX_COOKIE_LEN 16
49:
1.1 markus 50: Buffer *
51: kex_init(char *myproposal[PROPOSAL_MAX])
52: {
1.7 markus 53: int first_kex_packet_follows = 0;
54: unsigned char cookie[KEX_COOKIE_LEN];
1.1 markus 55: u_int32_t rand = 0;
56: int i;
57: Buffer *ki = xmalloc(sizeof(*ki));
1.7 markus 58: for (i = 0; i < KEX_COOKIE_LEN; i++) {
1.1 markus 59: if (i % 4 == 0)
60: rand = arc4random();
61: cookie[i] = rand & 0xff;
62: rand >>= 8;
63: }
64: buffer_init(ki);
65: buffer_append(ki, (char *)cookie, sizeof cookie);
66: for (i = 0; i < PROPOSAL_MAX; i++)
67: buffer_put_cstring(ki, myproposal[i]);
1.7 markus 68: buffer_put_char(ki, first_kex_packet_follows);
69: buffer_put_int(ki, 0); /* uint32 reserved */
1.1 markus 70: return ki;
71: }
72:
1.7 markus 73: /* send kexinit, parse and save reply */
74: void
75: kex_exchange_kexinit(
76: Buffer *my_kexinit, Buffer *peer_kexint,
77: char *peer_proposal[PROPOSAL_MAX])
78: {
79: int i;
80: char *ptr;
81: int plen;
82:
83: debug("send KEXINIT");
84: packet_start(SSH2_MSG_KEXINIT);
85: packet_put_raw(buffer_ptr(my_kexinit), buffer_len(my_kexinit));
86: packet_send();
87: packet_write_wait();
88: debug("done");
89:
90: /*
91: * read and save raw KEXINIT payload in buffer. this is used during
92: * computation of the session_id and the session keys.
93: */
94: debug("wait KEXINIT");
95: packet_read_expect(&plen, SSH2_MSG_KEXINIT);
96: ptr = packet_get_raw(&plen);
97: buffer_append(peer_kexint, ptr, plen);
98:
99: /* parse packet and save algorithm proposal */
100: /* skip cookie */
101: for (i = 0; i < KEX_COOKIE_LEN; i++)
102: packet_get_char();
103: /* extract kex init proposal strings */
104: for (i = 0; i < PROPOSAL_MAX; i++) {
105: peer_proposal[i] = packet_get_string(NULL);
106: debug("got kexinit: %s", peer_proposal[i]);
107: }
108: /* first kex follow / reserved */
109: i = packet_get_char();
110: debug("first kex follow: %d ", i);
111: i = packet_get_int();
112: debug("reserved: %d ", i);
113: packet_done();
114: debug("done");
115: }
116:
1.1 markus 117: /* diffie-hellman-group1-sha1 */
118:
1.3 markus 119: int
120: dh_pub_is_valid(DH *dh, BIGNUM *dh_pub)
121: {
122: int i;
123: int n = BN_num_bits(dh_pub);
124: int bits_set = 0;
125:
126: if (dh_pub->neg) {
127: log("invalid public DH value: negativ");
128: return 0;
129: }
130: for (i = 0; i <= n; i++)
131: if (BN_is_bit_set(dh_pub, i))
132: bits_set++;
133: debug("bits set: %d/%d", bits_set, BN_num_bits(dh->p));
134:
135: /* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial */
136: if (bits_set > 1 && (BN_cmp(dh_pub, dh->p) == -1))
137: return 1;
138: log("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p));
139: return 0;
140: }
141:
1.1 markus 142: DH *
1.11 provos 143: dh_gen_key(DH *dh)
144: {
145: int tries = 0;
146:
147: do {
148: if (DH_generate_key(dh) == 0)
149: fatal("DH_generate_key");
150: if (tries++ > 10)
151: fatal("dh_new_group1: too many bad keys: giving up");
152: } while (!dh_pub_is_valid(dh, dh->pub_key));
153: return dh;
154: }
155:
156: DH *
157: dh_new_group_asc(const char *gen, const char *modulus)
158: {
159: DH *dh;
160: int ret;
161:
162: dh = DH_new();
163: if (dh == NULL)
164: fatal("DH_new");
165:
166: if ((ret = BN_hex2bn(&dh->p, modulus)) < 0)
167: fatal("BN_hex2bn p");
168: if ((ret = BN_hex2bn(&dh->g, gen)) < 0)
169: fatal("BN_hex2bn g");
170:
171: return (dh_gen_key(dh));
172: }
173:
174: DH *
175: dh_new_group(BIGNUM *gen, BIGNUM *modulus)
176: {
177: DH *dh;
178:
179: dh = DH_new();
180: if (dh == NULL)
181: fatal("DH_new");
182: dh->p = modulus;
183: dh->g = gen;
184:
185: return (dh_gen_key(dh));
186: }
187:
188: DH *
1.3 markus 189: dh_new_group1()
1.1 markus 190: {
1.11 provos 191: static char *gen = "2", *group1 =
1.1 markus 192: "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
193: "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
194: "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
195: "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
196: "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE65381"
197: "FFFFFFFF" "FFFFFFFF";
1.11 provos 198:
199: return (dh_new_group_asc(gen, group1));
1.1 markus 200: }
201:
202: void
203: dump_digest(unsigned char *digest, int len)
204: {
205: int i;
1.5 markus 206: for (i = 0; i< len; i++){
207: fprintf(stderr, "%02x", digest[i]);
1.1 markus 208: if(i%2!=0)
209: fprintf(stderr, " ");
210: }
1.5 markus 211: fprintf(stderr, "\n");
1.1 markus 212: }
213:
214: unsigned char *
215: kex_hash(
216: char *client_version_string,
217: char *server_version_string,
218: char *ckexinit, int ckexinitlen,
219: char *skexinit, int skexinitlen,
220: char *serverhostkeyblob, int sbloblen,
221: BIGNUM *client_dh_pub,
222: BIGNUM *server_dh_pub,
223: BIGNUM *shared_secret)
224: {
225: Buffer b;
226: static unsigned char digest[EVP_MAX_MD_SIZE];
227: EVP_MD *evp_md = EVP_sha1();
228: EVP_MD_CTX md;
229:
230: buffer_init(&b);
231: buffer_put_string(&b, client_version_string, strlen(client_version_string));
232: buffer_put_string(&b, server_version_string, strlen(server_version_string));
233:
234: /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
235: buffer_put_int(&b, ckexinitlen+1);
236: buffer_put_char(&b, SSH2_MSG_KEXINIT);
237: buffer_append(&b, ckexinit, ckexinitlen);
238: buffer_put_int(&b, skexinitlen+1);
239: buffer_put_char(&b, SSH2_MSG_KEXINIT);
240: buffer_append(&b, skexinit, skexinitlen);
241:
242: buffer_put_string(&b, serverhostkeyblob, sbloblen);
243: buffer_put_bignum2(&b, client_dh_pub);
244: buffer_put_bignum2(&b, server_dh_pub);
245: buffer_put_bignum2(&b, shared_secret);
246:
247: #ifdef DEBUG_KEX
248: buffer_dump(&b);
249: #endif
250:
251: EVP_DigestInit(&md, evp_md);
252: EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
253: EVP_DigestFinal(&md, digest, NULL);
254:
255: buffer_free(&b);
256:
257: #ifdef DEBUG_KEX
1.5 markus 258: dump_digest(digest, evp_md->md_size);
1.1 markus 259: #endif
260: return digest;
261: }
262:
263: unsigned char *
1.11 provos 264: kex_hash_gex(
265: char *client_version_string,
266: char *server_version_string,
267: char *ckexinit, int ckexinitlen,
268: char *skexinit, int skexinitlen,
269: char *serverhostkeyblob, int sbloblen,
270: int minbits, BIGNUM *prime, BIGNUM *gen,
271: BIGNUM *client_dh_pub,
272: BIGNUM *server_dh_pub,
273: BIGNUM *shared_secret)
274: {
275: Buffer b;
276: static unsigned char digest[EVP_MAX_MD_SIZE];
277: EVP_MD *evp_md = EVP_sha1();
278: EVP_MD_CTX md;
279:
280: buffer_init(&b);
281: buffer_put_string(&b, client_version_string, strlen(client_version_string));
282: buffer_put_string(&b, server_version_string, strlen(server_version_string));
283:
284: /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
285: buffer_put_int(&b, ckexinitlen+1);
286: buffer_put_char(&b, SSH2_MSG_KEXINIT);
287: buffer_append(&b, ckexinit, ckexinitlen);
288: buffer_put_int(&b, skexinitlen+1);
289: buffer_put_char(&b, SSH2_MSG_KEXINIT);
290: buffer_append(&b, skexinit, skexinitlen);
291:
292: buffer_put_string(&b, serverhostkeyblob, sbloblen);
293: buffer_put_int(&b, minbits);
294: buffer_put_bignum2(&b, prime);
295: buffer_put_bignum2(&b, gen);
296: buffer_put_bignum2(&b, client_dh_pub);
297: buffer_put_bignum2(&b, server_dh_pub);
298: buffer_put_bignum2(&b, shared_secret);
299:
300: #ifdef DEBUG_KEX
301: buffer_dump(&b);
302: #endif
303:
304: EVP_DigestInit(&md, evp_md);
305: EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
306: EVP_DigestFinal(&md, digest, NULL);
307:
308: buffer_free(&b);
309:
310: #ifdef DEBUG_KEX
311: dump_digest(digest, evp_md->md_size);
312: #endif
313: return digest;
314: }
315:
316: unsigned char *
1.1 markus 317: derive_key(int id, int need, char unsigned *hash, BIGNUM *shared_secret)
318: {
319: Buffer b;
320: EVP_MD *evp_md = EVP_sha1();
321: EVP_MD_CTX md;
322: char c = id;
323: int have;
324: int mdsz = evp_md->md_size;
325: unsigned char *digest = xmalloc(((need+mdsz-1)/mdsz)*mdsz);
326:
327: buffer_init(&b);
328: buffer_put_bignum2(&b, shared_secret);
329:
330: EVP_DigestInit(&md, evp_md);
331: EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b)); /* shared_secret K */
332: EVP_DigestUpdate(&md, hash, mdsz); /* transport-06 */
333: EVP_DigestUpdate(&md, &c, 1); /* key id */
334: EVP_DigestUpdate(&md, hash, mdsz); /* session id */
335: EVP_DigestFinal(&md, digest, NULL);
336:
337: /* expand */
338: for (have = mdsz; need > have; have += mdsz) {
339: EVP_DigestInit(&md, evp_md);
340: EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
341: EVP_DigestUpdate(&md, hash, mdsz);
342: EVP_DigestUpdate(&md, digest, have);
343: EVP_DigestFinal(&md, digest + have, NULL);
344: }
345: buffer_free(&b);
346: #ifdef DEBUG_KEX
347: fprintf(stderr, "Digest '%c'== ", c);
348: dump_digest(digest, need);
349: #endif
350: return digest;
351: }
352:
353: #define NKEYS 6
354:
355: #define MAX_PROP 20
356: #define SEP ","
357:
358: char *
359: get_match(char *client, char *server)
360: {
361: char *sproposals[MAX_PROP];
1.9 ho 362: char *c, *s, *p, *ret, *cp, *sp;
1.1 markus 363: int i, j, nproposals;
364:
1.9 ho 365: c = cp = xstrdup(client);
366: s = sp = xstrdup(server);
1.7 markus 367:
1.9 ho 368: for ((p = strsep(&sp, SEP)), i=0; p && *p != '\0';
369: (p = strsep(&sp, SEP)), i++) {
1.1 markus 370: if (i < MAX_PROP)
371: sproposals[i] = p;
372: else
373: break;
374: }
375: nproposals = i;
376:
1.9 ho 377: for ((p = strsep(&cp, SEP)), i=0; p && *p != '\0';
378: (p = strsep(&cp, SEP)), i++) {
1.7 markus 379: for (j = 0; j < nproposals; j++) {
380: if (strcmp(p, sproposals[j]) == 0) {
381: ret = xstrdup(p);
382: xfree(c);
383: xfree(s);
384: return ret;
385: }
386: }
1.1 markus 387: }
1.7 markus 388: xfree(c);
389: xfree(s);
1.1 markus 390: return NULL;
391: }
392: void
393: choose_enc(Enc *enc, char *client, char *server)
394: {
395: char *name = get_match(client, server);
396: if (name == NULL)
397: fatal("no matching cipher found: client %s server %s", client, server);
1.12 markus 398: enc->cipher = cipher_by_name(name);
399: if (enc->cipher == NULL)
400: fatal("matching cipher is not supported: %s", name);
1.1 markus 401: enc->name = name;
402: enc->enabled = 0;
403: enc->iv = NULL;
404: enc->key = NULL;
405: }
406: void
407: choose_mac(Mac *mac, char *client, char *server)
408: {
409: char *name = get_match(client, server);
410: if (name == NULL)
411: fatal("no matching mac found: client %s server %s", client, server);
412: if (strcmp(name, "hmac-md5") == 0) {
413: mac->md = EVP_md5();
414: } else if (strcmp(name, "hmac-sha1") == 0) {
415: mac->md = EVP_sha1();
416: } else if (strcmp(name, "hmac-ripemd160@openssh.com") == 0) {
417: mac->md = EVP_ripemd160();
418: } else {
419: fatal("unsupported mac %s", name);
420: }
421: mac->name = name;
422: mac->mac_len = mac->md->md_size;
1.6 markus 423: mac->key_len = (datafellows & SSH_BUG_HMAC) ? 16 : mac->mac_len;
1.1 markus 424: mac->key = NULL;
425: mac->enabled = 0;
426: }
427: void
428: choose_comp(Comp *comp, char *client, char *server)
429: {
430: char *name = get_match(client, server);
431: if (name == NULL)
432: fatal("no matching comp found: client %s server %s", client, server);
433: if (strcmp(name, "zlib") == 0) {
434: comp->type = 1;
435: } else if (strcmp(name, "none") == 0) {
436: comp->type = 0;
437: } else {
438: fatal("unsupported comp %s", name);
439: }
440: comp->name = name;
441: }
442: void
443: choose_kex(Kex *k, char *client, char *server)
444: {
445: k->name = get_match(client, server);
446: if (k->name == NULL)
447: fatal("no kex alg");
1.11 provos 448: if (strcmp(k->name, KEX_DH1) == 0) {
449: k->kex_type = DH_GRP1_SHA1;
450: } else if (strcmp(k->name, KEX_DHGEX) == 0) {
451: k->kex_type = DH_GEX_SHA1;
452: } else
1.1 markus 453: fatal("bad kex alg %s", k->name);
454: }
455: void
456: choose_hostkeyalg(Kex *k, char *client, char *server)
457: {
1.13 ! markus 458: char *hostkeyalg = get_match(client, server);
! 459: if (hostkeyalg == NULL)
1.1 markus 460: fatal("no hostkey alg");
1.13 ! markus 461: k->hostkey_type = key_type_from_name(hostkeyalg);
! 462: if (k->hostkey_type == KEY_UNSPEC)
! 463: fatal("bad hostkey alg '%s'", hostkeyalg);
1.1 markus 464: }
465:
466: Kex *
467: kex_choose_conf(char *cprop[PROPOSAL_MAX], char *sprop[PROPOSAL_MAX], int server)
468: {
469: int mode;
470: int ctos; /* direction: if true client-to-server */
471: int need;
472: Kex *k;
473:
474: k = xmalloc(sizeof(*k));
475: memset(k, 0, sizeof(*k));
476: k->server = server;
477:
478: for (mode = 0; mode < MODE_MAX; mode++) {
479: int nenc, nmac, ncomp;
480: ctos = (!k->server && mode == MODE_OUT) || (k->server && mode == MODE_IN);
481: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
482: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
483: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
484: choose_enc (&k->enc [mode], cprop[nenc], sprop[nenc]);
485: choose_mac (&k->mac [mode], cprop[nmac], sprop[nmac]);
486: choose_comp(&k->comp[mode], cprop[ncomp], sprop[ncomp]);
1.2 markus 487: debug("kex: %s %s %s %s",
1.1 markus 488: ctos ? "client->server" : "server->client",
489: k->enc[mode].name,
490: k->mac[mode].name,
491: k->comp[mode].name);
492: }
493: choose_kex(k, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
494: choose_hostkeyalg(k, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
495: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
496: need = 0;
497: for (mode = 0; mode < MODE_MAX; mode++) {
1.12 markus 498: if (need < k->enc[mode].cipher->key_len)
499: need = k->enc[mode].cipher->key_len;
500: if (need < k->enc[mode].cipher->block_size)
501: need = k->enc[mode].cipher->block_size;
1.1 markus 502: if (need < k->mac[mode].key_len)
503: need = k->mac[mode].key_len;
504: }
1.7 markus 505: /* XXX need runden? */
1.1 markus 506: k->we_need = need;
507: return k;
508: }
509:
510: int
511: kex_derive_keys(Kex *k, unsigned char *hash, BIGNUM *shared_secret)
512: {
513: int i;
514: int mode;
515: int ctos;
516: unsigned char *keys[NKEYS];
517:
518: for (i = 0; i < NKEYS; i++)
519: keys[i] = derive_key('A'+i, k->we_need, hash, shared_secret);
520:
521: for (mode = 0; mode < MODE_MAX; mode++) {
522: ctos = (!k->server && mode == MODE_OUT) || (k->server && mode == MODE_IN);
523: k->enc[mode].iv = keys[ctos ? 0 : 1];
524: k->enc[mode].key = keys[ctos ? 2 : 3];
525: k->mac[mode].key = keys[ctos ? 4 : 5];
526: }
527: return 0;
528: }
![[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