Annotation of src/usr.bin/ssh/kex.c, Revision 1.108
1.108 ! djm 1: /* $OpenBSD: kex.c,v 1.107 2015/07/29 04:43:06 djm Exp $ */
1.1 markus 2: /*
1.36 markus 3: * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
1.1 markus 4: *
5: * Redistribution and use in source and binary forms, with or without
6: * modification, are permitted provided that the following conditions
7: * are met:
8: * 1. Redistributions of source code must retain the above copyright
9: * notice, this list of conditions and the following disclaimer.
10: * 2. Redistributions in binary form must reproduce the above copyright
11: * notice, this list of conditions and the following disclaimer in the
12: * documentation and/or other materials provided with the distribution.
13: *
14: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24: */
25:
1.103 deraadt 26: #include <sys/param.h> /* MAX roundup */
1.18 markus 27:
1.76 deraadt 28: #include <signal.h>
1.75 stevesk 29: #include <stdio.h>
1.74 stevesk 30: #include <stdlib.h>
1.72 stevesk 31: #include <string.h>
1.1 markus 32:
1.99 markus 33: #ifdef WITH_OPENSSL
1.76 deraadt 34: #include <openssl/crypto.h>
1.99 markus 35: #endif
1.76 deraadt 36:
1.1 markus 37: #include "ssh2.h"
1.7 markus 38: #include "packet.h"
1.1 markus 39: #include "compat.h"
1.18 markus 40: #include "cipher.h"
1.102 markus 41: #include "sshkey.h"
1.1 markus 42: #include "kex.h"
1.18 markus 43: #include "log.h"
1.21 markus 44: #include "mac.h"
1.23 markus 45: #include "match.h"
1.102 markus 46: #include "misc.h"
1.26 markus 47: #include "dispatch.h"
1.48 provos 48: #include "monitor.h"
1.82 andreas 49: #include "roaming.h"
1.102 markus 50:
51: #include "ssherr.h"
52: #include "sshbuf.h"
1.94 djm 53: #include "digest.h"
1.48 provos 54:
1.35 itojun 55: /* prototype */
1.102 markus 56: static int kex_choose_conf(struct ssh *);
57: static int kex_input_newkeys(int, u_int32_t, void *);
1.86 djm 58:
1.89 djm 59: struct kexalg {
60: char *name;
1.102 markus 61: u_int type;
1.89 djm 62: int ec_nid;
1.94 djm 63: int hash_alg;
1.89 djm 64: };
65: static const struct kexalg kexalgs[] = {
1.99 markus 66: #ifdef WITH_OPENSSL
1.94 djm 67: { KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },
68: { KEX_DH14, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 },
69: { KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 },
70: { KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 },
71: { KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2,
72: NID_X9_62_prime256v1, SSH_DIGEST_SHA256 },
73: { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1,
74: SSH_DIGEST_SHA384 },
75: { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1,
76: SSH_DIGEST_SHA512 },
1.99 markus 77: #endif
1.94 djm 78: { KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
79: { NULL, -1, -1, -1},
1.89 djm 80: };
81:
82: char *
1.93 dtucker 83: kex_alg_list(char sep)
1.89 djm 84: {
1.102 markus 85: char *ret = NULL, *tmp;
1.89 djm 86: size_t nlen, rlen = 0;
87: const struct kexalg *k;
88:
89: for (k = kexalgs; k->name != NULL; k++) {
90: if (ret != NULL)
1.93 dtucker 91: ret[rlen++] = sep;
1.89 djm 92: nlen = strlen(k->name);
1.102 markus 93: if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
94: free(ret);
95: return NULL;
96: }
97: ret = tmp;
1.89 djm 98: memcpy(ret + rlen, k->name, nlen + 1);
99: rlen += nlen;
100: }
101: return ret;
102: }
103:
104: static const struct kexalg *
105: kex_alg_by_name(const char *name)
106: {
107: const struct kexalg *k;
108:
109: for (k = kexalgs; k->name != NULL; k++) {
110: if (strcmp(k->name, name) == 0)
111: return k;
112: }
113: return NULL;
114: }
115:
1.86 djm 116: /* Validate KEX method name list */
117: int
118: kex_names_valid(const char *names)
119: {
120: char *s, *cp, *p;
121:
122: if (names == NULL || strcmp(names, "") == 0)
123: return 0;
1.102 markus 124: if ((s = cp = strdup(names)) == NULL)
125: return 0;
1.86 djm 126: for ((p = strsep(&cp, ",")); p && *p != '\0';
127: (p = strsep(&cp, ","))) {
1.89 djm 128: if (kex_alg_by_name(p) == NULL) {
1.86 djm 129: error("Unsupported KEX algorithm \"%.100s\"", p);
1.91 djm 130: free(s);
1.86 djm 131: return 0;
132: }
133: }
134: debug3("kex names ok: [%s]", names);
1.91 djm 135: free(s);
1.86 djm 136: return 1;
137: }
1.26 markus 138:
139: /* put algorithm proposal into buffer */
1.102 markus 140: int
141: kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
1.1 markus 142: {
1.61 djm 143: u_int i;
1.102 markus 144: int r;
145:
146: sshbuf_reset(b);
1.26 markus 147:
1.49 markus 148: /*
149: * add a dummy cookie, the cookie will be overwritten by
150: * kex_send_kexinit(), each time a kexinit is set
151: */
1.102 markus 152: for (i = 0; i < KEX_COOKIE_LEN; i++) {
153: if ((r = sshbuf_put_u8(b, 0)) != 0)
154: return r;
155: }
156: for (i = 0; i < PROPOSAL_MAX; i++) {
157: if ((r = sshbuf_put_cstring(b, proposal[i])) != 0)
158: return r;
159: }
160: if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */
161: (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */
162: return r;
163: return 0;
1.1 markus 164: }
165:
1.26 markus 166: /* parse buffer and return algorithm proposal */
1.102 markus 167: int
168: kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp)
1.7 markus 169: {
1.102 markus 170: struct sshbuf *b = NULL;
171: u_char v;
1.78 djm 172: u_int i;
1.102 markus 173: char **proposal = NULL;
174: int r;
1.7 markus 175:
1.102 markus 176: *propp = NULL;
177: if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL)
178: return SSH_ERR_ALLOC_FAIL;
179: if ((b = sshbuf_fromb(raw)) == NULL) {
180: r = SSH_ERR_ALLOC_FAIL;
181: goto out;
182: }
183: if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */
184: goto out;
1.7 markus 185: /* extract kex init proposal strings */
186: for (i = 0; i < PROPOSAL_MAX; i++) {
1.102 markus 187: if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0)
188: goto out;
1.26 markus 189: debug2("kex_parse_kexinit: %s", proposal[i]);
1.7 markus 190: }
1.26 markus 191: /* first kex follows / reserved */
1.102 markus 192: if ((r = sshbuf_get_u8(b, &v)) != 0 ||
193: (r = sshbuf_get_u32(b, &i)) != 0)
194: goto out;
1.53 markus 195: if (first_kex_follows != NULL)
196: *first_kex_follows = i;
1.102 markus 197: debug2("kex_parse_kexinit: first_kex_follows %d ", v);
1.78 djm 198: debug2("kex_parse_kexinit: reserved %u ", i);
1.102 markus 199: r = 0;
200: *propp = proposal;
201: out:
202: if (r != 0 && proposal != NULL)
203: kex_prop_free(proposal);
204: sshbuf_free(b);
205: return r;
1.1 markus 206: }
207:
1.102 markus 208: void
1.26 markus 209: kex_prop_free(char **proposal)
1.1 markus 210: {
1.61 djm 211: u_int i;
1.26 markus 212:
1.106 djm 213: if (proposal == NULL)
214: return;
1.26 markus 215: for (i = 0; i < PROPOSAL_MAX; i++)
1.91 djm 216: free(proposal[i]);
217: free(proposal);
1.1 markus 218: }
219:
1.78 djm 220: /* ARGSUSED */
1.101 markus 221: static int
1.41 markus 222: kex_protocol_error(int type, u_int32_t seq, void *ctxt)
1.1 markus 223: {
1.41 markus 224: error("Hm, kex protocol error: type %d seq %u", type, seq);
1.101 markus 225: return 0;
1.26 markus 226: }
1.1 markus 227:
1.35 itojun 228: static void
1.102 markus 229: kex_reset_dispatch(struct ssh *ssh)
1.29 markus 230: {
1.102 markus 231: ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
1.42 markus 232: SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
1.102 markus 233: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.29 markus 234: }
235:
1.102 markus 236: int
237: kex_send_newkeys(struct ssh *ssh)
1.26 markus 238: {
1.102 markus 239: int r;
1.28 markus 240:
1.102 markus 241: kex_reset_dispatch(ssh);
242: if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
243: (r = sshpkt_send(ssh)) != 0)
244: return r;
1.26 markus 245: debug("SSH2_MSG_NEWKEYS sent");
1.102 markus 246: debug("expecting SSH2_MSG_NEWKEYS");
247: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
248: return 0;
249: }
250:
251: static int
252: kex_input_newkeys(int type, u_int32_t seq, void *ctxt)
253: {
254: struct ssh *ssh = ctxt;
255: struct kex *kex = ssh->kex;
256: int r;
1.19 stevesk 257:
1.26 markus 258: debug("SSH2_MSG_NEWKEYS received");
1.102 markus 259: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
260: if ((r = sshpkt_get_end(ssh)) != 0)
261: return r;
1.30 markus 262: kex->done = 1;
1.102 markus 263: sshbuf_reset(kex->peer);
264: /* sshbuf_reset(kex->my); */
1.26 markus 265: kex->flags &= ~KEX_INIT_SENT;
1.91 djm 266: free(kex->name);
1.32 markus 267: kex->name = NULL;
1.102 markus 268: return 0;
1.26 markus 269: }
1.1 markus 270:
1.102 markus 271: int
272: kex_send_kexinit(struct ssh *ssh)
1.26 markus 273: {
1.49 markus 274: u_char *cookie;
1.102 markus 275: struct kex *kex = ssh->kex;
276: int r;
1.49 markus 277:
1.102 markus 278: if (kex == NULL)
279: return SSH_ERR_INTERNAL_ERROR;
280: if (kex->flags & KEX_INIT_SENT)
281: return 0;
1.30 markus 282: kex->done = 0;
1.49 markus 283:
284: /* generate a random cookie */
1.102 markus 285: if (sshbuf_len(kex->my) < KEX_COOKIE_LEN)
286: return SSH_ERR_INVALID_FORMAT;
287: if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL)
288: return SSH_ERR_INTERNAL_ERROR;
289: arc4random_buf(cookie, KEX_COOKIE_LEN);
290:
291: if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
292: (r = sshpkt_putb(ssh, kex->my)) != 0 ||
293: (r = sshpkt_send(ssh)) != 0)
294: return r;
1.26 markus 295: debug("SSH2_MSG_KEXINIT sent");
296: kex->flags |= KEX_INIT_SENT;
1.102 markus 297: return 0;
1.1 markus 298: }
299:
1.78 djm 300: /* ARGSUSED */
1.101 markus 301: int
1.41 markus 302: kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
1.11 provos 303: {
1.102 markus 304: struct ssh *ssh = ctxt;
305: struct kex *kex = ssh->kex;
306: const u_char *ptr;
1.100 markus 307: u_int i;
308: size_t dlen;
1.102 markus 309: int r;
1.11 provos 310:
1.26 markus 311: debug("SSH2_MSG_KEXINIT received");
1.29 markus 312: if (kex == NULL)
1.102 markus 313: return SSH_ERR_INVALID_ARGUMENT;
1.11 provos 314:
1.102 markus 315: ptr = sshpkt_ptr(ssh, &dlen);
316: if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
317: return r;
1.31 markus 318:
319: /* discard packet */
320: for (i = 0; i < KEX_COOKIE_LEN; i++)
1.102 markus 321: if ((r = sshpkt_get_u8(ssh, NULL)) != 0)
322: return r;
1.31 markus 323: for (i = 0; i < PROPOSAL_MAX; i++)
1.102 markus 324: if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0)
325: return r;
1.87 djm 326: /*
327: * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
328: * KEX method has the server move first, but a server might be using
329: * a custom method or one that we otherwise don't support. We should
330: * be prepared to remember first_kex_follows here so we can eat a
331: * packet later.
332: * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
333: * for cases where the server *doesn't* go first. I guess we should
334: * ignore it when it is set for these cases, which is what we do now.
335: */
1.102 markus 336: if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
337: (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
338: (r = sshpkt_get_end(ssh)) != 0)
339: return r;
340:
341: if (!(kex->flags & KEX_INIT_SENT))
342: if ((r = kex_send_kexinit(ssh)) != 0)
343: return r;
344: if ((r = kex_choose_conf(ssh)) != 0)
345: return r;
1.19 stevesk 346:
1.102 markus 347: if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
348: return (kex->kex[kex->kex_type])(ssh);
349:
350: return SSH_ERR_INTERNAL_ERROR;
351: }
352:
353: int
354: kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp)
355: {
356: struct kex *kex;
357: int r;
358:
359: *kexp = NULL;
360: if ((kex = calloc(1, sizeof(*kex))) == NULL)
361: return SSH_ERR_ALLOC_FAIL;
362: if ((kex->peer = sshbuf_new()) == NULL ||
363: (kex->my = sshbuf_new()) == NULL) {
364: r = SSH_ERR_ALLOC_FAIL;
365: goto out;
366: }
367: if ((r = kex_prop2buf(kex->my, proposal)) != 0)
368: goto out;
369: kex->done = 0;
370: kex_reset_dispatch(ssh);
371: r = 0;
372: *kexp = kex;
373: out:
374: if (r != 0)
375: kex_free(kex);
376: return r;
1.26 markus 377: }
1.11 provos 378:
1.100 markus 379: void
380: kex_free_newkeys(struct newkeys *newkeys)
381: {
382: if (newkeys == NULL)
383: return;
384: if (newkeys->enc.key) {
385: explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
386: free(newkeys->enc.key);
387: newkeys->enc.key = NULL;
388: }
389: if (newkeys->enc.iv) {
390: explicit_bzero(newkeys->enc.iv, newkeys->enc.block_size);
391: free(newkeys->enc.iv);
392: newkeys->enc.iv = NULL;
393: }
394: free(newkeys->enc.name);
395: explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
396: free(newkeys->comp.name);
397: explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
398: mac_clear(&newkeys->mac);
399: if (newkeys->mac.key) {
400: explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
401: free(newkeys->mac.key);
402: newkeys->mac.key = NULL;
403: }
404: free(newkeys->mac.name);
405: explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
406: explicit_bzero(newkeys, sizeof(*newkeys));
407: free(newkeys);
408: }
409:
1.102 markus 410: void
411: kex_free(struct kex *kex)
1.26 markus 412: {
1.102 markus 413: u_int mode;
1.11 provos 414:
1.102 markus 415: #ifdef WITH_OPENSSL
416: if (kex->dh)
417: DH_free(kex->dh);
418: if (kex->ec_client_key)
419: EC_KEY_free(kex->ec_client_key);
420: #endif
421: for (mode = 0; mode < MODE_MAX; mode++) {
422: kex_free_newkeys(kex->newkeys[mode]);
423: kex->newkeys[mode] = NULL;
1.100 markus 424: }
1.102 markus 425: sshbuf_free(kex->peer);
426: sshbuf_free(kex->my);
427: free(kex->session_id);
428: free(kex->client_version_string);
429: free(kex->server_version_string);
1.107 djm 430: free(kex->failed_choice);
1.102 markus 431: free(kex);
1.11 provos 432: }
433:
1.102 markus 434: int
435: kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
1.1 markus 436: {
1.102 markus 437: int r;
1.1 markus 438:
1.102 markus 439: if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0)
440: return r;
441: if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
442: kex_free(ssh->kex);
443: ssh->kex = NULL;
444: return r;
1.1 markus 445: }
1.102 markus 446: return 0;
1.1 markus 447: }
448:
1.102 markus 449: static int
450: choose_enc(struct sshenc *enc, char *client, char *server)
1.1 markus 451: {
1.23 markus 452: char *name = match_list(client, server, NULL);
1.102 markus 453:
1.1 markus 454: if (name == NULL)
1.102 markus 455: return SSH_ERR_NO_CIPHER_ALG_MATCH;
1.45 markus 456: if ((enc->cipher = cipher_by_name(name)) == NULL)
1.102 markus 457: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 458: enc->name = name;
459: enc->enabled = 0;
460: enc->iv = NULL;
1.88 markus 461: enc->iv_len = cipher_ivlen(enc->cipher);
1.1 markus 462: enc->key = NULL;
1.45 markus 463: enc->key_len = cipher_keylen(enc->cipher);
464: enc->block_size = cipher_blocksize(enc->cipher);
1.102 markus 465: return 0;
1.1 markus 466: }
1.69 deraadt 467:
1.102 markus 468: static int
469: choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
1.1 markus 470: {
1.23 markus 471: char *name = match_list(client, server, NULL);
1.102 markus 472:
1.1 markus 473: if (name == NULL)
1.102 markus 474: return SSH_ERR_NO_MAC_ALG_MATCH;
1.79 djm 475: if (mac_setup(mac, name) < 0)
1.102 markus 476: return SSH_ERR_INTERNAL_ERROR;
1.21 markus 477: /* truncate the key */
1.102 markus 478: if (ssh->compat & SSH_BUG_HMAC)
1.21 markus 479: mac->key_len = 16;
1.1 markus 480: mac->name = name;
481: mac->key = NULL;
482: mac->enabled = 0;
1.102 markus 483: return 0;
1.1 markus 484: }
1.69 deraadt 485:
1.102 markus 486: static int
487: choose_comp(struct sshcomp *comp, char *client, char *server)
1.1 markus 488: {
1.23 markus 489: char *name = match_list(client, server, NULL);
1.102 markus 490:
1.1 markus 491: if (name == NULL)
1.102 markus 492: return SSH_ERR_NO_COMPRESS_ALG_MATCH;
1.64 markus 493: if (strcmp(name, "zlib@openssh.com") == 0) {
494: comp->type = COMP_DELAYED;
495: } else if (strcmp(name, "zlib") == 0) {
496: comp->type = COMP_ZLIB;
1.1 markus 497: } else if (strcmp(name, "none") == 0) {
1.64 markus 498: comp->type = COMP_NONE;
1.1 markus 499: } else {
1.102 markus 500: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 501: }
502: comp->name = name;
1.102 markus 503: return 0;
1.1 markus 504: }
1.69 deraadt 505:
1.102 markus 506: static int
507: choose_kex(struct kex *k, char *client, char *server)
1.1 markus 508: {
1.89 djm 509: const struct kexalg *kexalg;
510:
1.23 markus 511: k->name = match_list(client, server, NULL);
1.102 markus 512:
1.1 markus 513: if (k->name == NULL)
1.102 markus 514: return SSH_ERR_NO_KEX_ALG_MATCH;
1.89 djm 515: if ((kexalg = kex_alg_by_name(k->name)) == NULL)
1.102 markus 516: return SSH_ERR_INTERNAL_ERROR;
1.89 djm 517: k->kex_type = kexalg->type;
1.94 djm 518: k->hash_alg = kexalg->hash_alg;
1.89 djm 519: k->ec_nid = kexalg->ec_nid;
1.102 markus 520: return 0;
1.1 markus 521: }
1.65 djm 522:
1.102 markus 523: static int
524: choose_hostkeyalg(struct kex *k, char *client, char *server)
1.1 markus 525: {
1.23 markus 526: char *hostkeyalg = match_list(client, server, NULL);
1.102 markus 527:
1.13 markus 528: if (hostkeyalg == NULL)
1.102 markus 529: return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
530: k->hostkey_type = sshkey_type_from_name(hostkeyalg);
1.13 markus 531: if (k->hostkey_type == KEY_UNSPEC)
1.102 markus 532: return SSH_ERR_INTERNAL_ERROR;
1.104 djm 533: k->hostkey_nid = sshkey_ecdsa_nid_from_name(hostkeyalg);
1.91 djm 534: free(hostkeyalg);
1.102 markus 535: return 0;
1.1 markus 536: }
537:
1.56 djm 538: static int
1.53 markus 539: proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
540: {
541: static int check[] = {
542: PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
543: };
544: int *idx;
545: char *p;
546:
547: for (idx = &check[0]; *idx != -1; idx++) {
548: if ((p = strchr(my[*idx], ',')) != NULL)
549: *p = '\0';
550: if ((p = strchr(peer[*idx], ',')) != NULL)
551: *p = '\0';
552: if (strcmp(my[*idx], peer[*idx]) != 0) {
553: debug2("proposal mismatch: my %s peer %s",
554: my[*idx], peer[*idx]);
555: return (0);
556: }
557: }
558: debug2("proposals match");
559: return (1);
560: }
561:
1.102 markus 562: static int
563: kex_choose_conf(struct ssh *ssh)
1.1 markus 564: {
1.102 markus 565: struct kex *kex = ssh->kex;
566: struct newkeys *newkeys;
567: char **my = NULL, **peer = NULL;
1.26 markus 568: char **cprop, **sprop;
1.27 markus 569: int nenc, nmac, ncomp;
1.96 dtucker 570: u_int mode, ctos, need, dh_need, authlen;
1.102 markus 571: int r, first_kex_follows;
1.1 markus 572:
1.102 markus 573: if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0 ||
574: (r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
575: goto out;
1.26 markus 576:
1.27 markus 577: if (kex->server) {
1.26 markus 578: cprop=peer;
579: sprop=my;
580: } else {
581: cprop=my;
582: sprop=peer;
1.82 andreas 583: }
584:
585: /* Check whether server offers roaming */
586: if (!kex->server) {
1.102 markus 587: char *roaming = match_list(KEX_RESUME,
588: peer[PROPOSAL_KEX_ALGS], NULL);
589:
1.82 andreas 590: if (roaming) {
591: kex->roaming = 1;
1.91 djm 592: free(roaming);
1.82 andreas 593: }
1.26 markus 594: }
1.1 markus 595:
1.30 markus 596: /* Algorithm Negotiation */
1.1 markus 597: for (mode = 0; mode < MODE_MAX; mode++) {
1.102 markus 598: if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
599: r = SSH_ERR_ALLOC_FAIL;
600: goto out;
601: }
1.30 markus 602: kex->newkeys[mode] = newkeys;
1.78 djm 603: ctos = (!kex->server && mode == MODE_OUT) ||
604: (kex->server && mode == MODE_IN);
1.1 markus 605: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
606: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
607: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.102 markus 608: if ((r = choose_enc(&newkeys->enc, cprop[nenc],
1.107 djm 609: sprop[nenc])) != 0) {
610: kex->failed_choice = peer[nenc];
611: peer[nenc] = NULL;
1.102 markus 612: goto out;
1.107 djm 613: }
1.102 markus 614: authlen = cipher_authlen(newkeys->enc.cipher);
1.88 markus 615: /* ignore mac for authenticated encryption */
1.102 markus 616: if (authlen == 0 &&
617: (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
1.107 djm 618: sprop[nmac])) != 0) {
619: kex->failed_choice = peer[nmac];
620: peer[nmac] = NULL;
1.102 markus 621: goto out;
1.107 djm 622: }
1.102 markus 623: if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
1.107 djm 624: sprop[ncomp])) != 0) {
625: kex->failed_choice = peer[ncomp];
626: peer[ncomp] = NULL;
1.102 markus 627: goto out;
1.107 djm 628: }
1.2 markus 629: debug("kex: %s %s %s %s",
1.1 markus 630: ctos ? "client->server" : "server->client",
1.27 markus 631: newkeys->enc.name,
1.88 markus 632: authlen == 0 ? newkeys->mac.name : "<implicit>",
1.27 markus 633: newkeys->comp.name);
1.1 markus 634: }
1.102 markus 635: if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
1.107 djm 636: sprop[PROPOSAL_KEX_ALGS])) != 0) {
637: kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
638: peer[PROPOSAL_KEX_ALGS] = NULL;
1.102 markus 639: goto out;
1.107 djm 640: }
641: if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
642: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
1.108 ! djm 643: kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
! 644: peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
1.107 djm 645: goto out;
646: }
1.96 dtucker 647: need = dh_need = 0;
1.1 markus 648: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 649: newkeys = kex->newkeys[mode];
1.97 markus 650: need = MAX(need, newkeys->enc.key_len);
651: need = MAX(need, newkeys->enc.block_size);
652: need = MAX(need, newkeys->enc.iv_len);
653: need = MAX(need, newkeys->mac.key_len);
654: dh_need = MAX(dh_need, cipher_seclen(newkeys->enc.cipher));
655: dh_need = MAX(dh_need, newkeys->enc.block_size);
656: dh_need = MAX(dh_need, newkeys->enc.iv_len);
657: dh_need = MAX(dh_need, newkeys->mac.key_len);
1.1 markus 658: }
1.7 markus 659: /* XXX need runden? */
1.27 markus 660: kex->we_need = need;
1.96 dtucker 661: kex->dh_need = dh_need;
1.53 markus 662:
663: /* ignore the next message if the proposals do not match */
1.56 djm 664: if (first_kex_follows && !proposals_match(my, peer) &&
1.102 markus 665: !(ssh->compat & SSH_BUG_FIRSTKEX))
666: ssh->dispatch_skip_packets = 1;
667: r = 0;
668: out:
1.26 markus 669: kex_prop_free(my);
670: kex_prop_free(peer);
1.102 markus 671: return r;
1.26 markus 672: }
673:
1.102 markus 674: static int
675: derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
676: const struct sshbuf *shared_secret, u_char **keyp)
1.26 markus 677: {
1.102 markus 678: struct kex *kex = ssh->kex;
679: struct ssh_digest_ctx *hashctx = NULL;
1.26 markus 680: char c = id;
1.61 djm 681: u_int have;
1.94 djm 682: size_t mdsz;
1.61 djm 683: u_char *digest;
1.102 markus 684: int r;
1.62 djm 685:
1.94 djm 686: if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
1.102 markus 687: return SSH_ERR_INVALID_ARGUMENT;
688: if ((digest = calloc(1, roundup(need, mdsz))) == NULL) {
689: r = SSH_ERR_ALLOC_FAIL;
690: goto out;
691: }
1.26 markus 692:
1.30 markus 693: /* K1 = HASH(K || H || "A" || session_id) */
1.102 markus 694: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
695: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 696: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
697: ssh_digest_update(hashctx, &c, 1) != 0 ||
698: ssh_digest_update(hashctx, kex->session_id,
1.102 markus 699: kex->session_id_len) != 0 ||
700: ssh_digest_final(hashctx, digest, mdsz) != 0) {
701: r = SSH_ERR_LIBCRYPTO_ERROR;
702: goto out;
703: }
1.94 djm 704: ssh_digest_free(hashctx);
1.102 markus 705: hashctx = NULL;
1.26 markus 706:
1.30 markus 707: /*
708: * expand key:
709: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
710: * Key = K1 || K2 || ... || Kn
711: */
1.26 markus 712: for (have = mdsz; need > have; have += mdsz) {
1.102 markus 713: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
714: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 715: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1.102 markus 716: ssh_digest_update(hashctx, digest, have) != 0 ||
717: ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
718: r = SSH_ERR_LIBCRYPTO_ERROR;
719: goto out;
720: }
1.94 djm 721: ssh_digest_free(hashctx);
1.102 markus 722: hashctx = NULL;
1.26 markus 723: }
724: #ifdef DEBUG_KEX
725: fprintf(stderr, "key '%c'== ", c);
726: dump_digest("key", digest, need);
727: #endif
1.102 markus 728: *keyp = digest;
729: digest = NULL;
730: r = 0;
731: out:
732: if (digest)
733: free(digest);
734: ssh_digest_free(hashctx);
735: return r;
1.1 markus 736: }
737:
1.23 markus 738: #define NKEYS 6
1.102 markus 739: int
740: kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
741: const struct sshbuf *shared_secret)
1.1 markus 742: {
1.102 markus 743: struct kex *kex = ssh->kex;
1.15 markus 744: u_char *keys[NKEYS];
1.102 markus 745: u_int i, j, mode, ctos;
746: int r;
1.1 markus 747:
1.65 djm 748: for (i = 0; i < NKEYS; i++) {
1.102 markus 749: if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
750: shared_secret, &keys[i])) != 0) {
751: for (j = 0; j < i; j++)
752: free(keys[j]);
753: return r;
754: }
1.65 djm 755: }
1.1 markus 756: for (mode = 0; mode < MODE_MAX; mode++) {
1.69 deraadt 757: ctos = (!kex->server && mode == MODE_OUT) ||
758: (kex->server && mode == MODE_IN);
1.100 markus 759: kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
760: kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
761: kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
1.1 markus 762: }
1.102 markus 763: return 0;
1.95 djm 764: }
765:
1.99 markus 766: #ifdef WITH_OPENSSL
1.102 markus 767: int
768: kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen,
769: const BIGNUM *secret)
1.95 djm 770: {
1.102 markus 771: struct sshbuf *shared_secret;
772: int r;
1.95 djm 773:
1.102 markus 774: if ((shared_secret = sshbuf_new()) == NULL)
775: return SSH_ERR_ALLOC_FAIL;
776: if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0)
777: r = kex_derive_keys(ssh, hash, hashlen, shared_secret);
778: sshbuf_free(shared_secret);
779: return r;
1.27 markus 780: }
1.99 markus 781: #endif
1.57 djm 782:
1.99 markus 783: #ifdef WITH_SSH1
1.102 markus 784: int
1.57 djm 785: derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
786: u_int8_t cookie[8], u_int8_t id[16])
787: {
1.105 djm 788: u_int8_t hbuf[2048], sbuf[2048], obuf[SSH_DIGEST_MAX_LENGTH];
1.102 markus 789: struct ssh_digest_ctx *hashctx = NULL;
1.105 djm 790: size_t hlen, slen;
1.102 markus 791: int r;
1.57 djm 792:
1.105 djm 793: hlen = BN_num_bytes(host_modulus);
794: slen = BN_num_bytes(server_modulus);
795: if (hlen < (512 / 8) || (u_int)hlen > sizeof(hbuf) ||
796: slen < (512 / 8) || (u_int)slen > sizeof(sbuf))
1.102 markus 797: return SSH_ERR_KEY_BITS_MISMATCH;
1.105 djm 798: if (BN_bn2bin(host_modulus, hbuf) <= 0 ||
799: BN_bn2bin(server_modulus, sbuf) <= 0) {
800: r = SSH_ERR_LIBCRYPTO_ERROR;
801: goto out;
802: }
803: if ((hashctx = ssh_digest_start(SSH_DIGEST_MD5)) == NULL) {
804: r = SSH_ERR_ALLOC_FAIL;
805: goto out;
806: }
807: if (ssh_digest_update(hashctx, hbuf, hlen) != 0 ||
808: ssh_digest_update(hashctx, sbuf, slen) != 0 ||
1.102 markus 809: ssh_digest_update(hashctx, cookie, 8) != 0 ||
810: ssh_digest_final(hashctx, obuf, sizeof(obuf)) != 0) {
811: r = SSH_ERR_LIBCRYPTO_ERROR;
812: goto out;
813: }
1.94 djm 814: memcpy(id, obuf, ssh_digest_bytes(SSH_DIGEST_MD5));
1.102 markus 815: r = 0;
816: out:
817: ssh_digest_free(hashctx);
1.105 djm 818: explicit_bzero(hbuf, sizeof(hbuf));
819: explicit_bzero(sbuf, sizeof(sbuf));
1.98 djm 820: explicit_bzero(obuf, sizeof(obuf));
1.102 markus 821: return r;
1.1 markus 822: }
1.99 markus 823: #endif
1.26 markus 824:
1.84 djm 825: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1.26 markus 826: void
827: dump_digest(char *msg, u_char *digest, int len)
828: {
829: fprintf(stderr, "%s\n", msg);
1.102 markus 830: sshbuf_dump_data(digest, len, stderr);
1.26 markus 831: }
832: #endif
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