Annotation of src/usr.bin/ssh/kex.c, Revision 1.109
1.109 ! djm 1: /* $OpenBSD: kex.c,v 1.108 2015/07/29 08:34:54 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;
1.109 ! djm 137: }
! 138:
! 139: /*
! 140: * Concatenate algorithm names, avoiding duplicates in the process.
! 141: * Caller must free returned string.
! 142: */
! 143: char *
! 144: kex_names_cat(const char *a, const char *b)
! 145: {
! 146: char *ret = NULL, *tmp = NULL, *cp, *p;
! 147: size_t len;
! 148:
! 149: if (a == NULL || *a == '\0')
! 150: return NULL;
! 151: if (b == NULL || *b == '\0')
! 152: return strdup(a);
! 153: if (strlen(b) > 1024*1024)
! 154: return NULL;
! 155: len = strlen(a) + strlen(b) + 2;
! 156: if ((tmp = cp = strdup(b)) == NULL ||
! 157: (ret = calloc(1, len)) == NULL) {
! 158: free(tmp);
! 159: return NULL;
! 160: }
! 161: strlcpy(ret, a, len);
! 162: for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) {
! 163: if (match_list(ret, p, NULL) != NULL)
! 164: continue; /* Algorithm already present */
! 165: if (strlcat(ret, ",", len) >= len ||
! 166: strlcat(ret, p, len) >= len) {
! 167: free(tmp);
! 168: free(ret);
! 169: return NULL; /* Shouldn't happen */
! 170: }
! 171: }
! 172: free(tmp);
! 173: return ret;
! 174: }
! 175:
! 176: /*
! 177: * Assemble a list of algorithms from a default list and a string from a
! 178: * configuration file. The user-provided string may begin with '+' to
! 179: * indicate that it should be appended to the default.
! 180: */
! 181: int
! 182: kex_assemble_names(const char *def, char **list)
! 183: {
! 184: char *ret;
! 185:
! 186: if (list == NULL || *list == NULL || **list == '\0') {
! 187: *list = strdup(def);
! 188: return 0;
! 189: }
! 190: if (**list != '+') {
! 191: return 0;
! 192: }
! 193:
! 194: if ((ret = kex_names_cat(def, *list + 1)) == NULL)
! 195: return SSH_ERR_ALLOC_FAIL;
! 196: free(*list);
! 197: *list = ret;
! 198: return 0;
1.86 djm 199: }
1.26 markus 200:
201: /* put algorithm proposal into buffer */
1.102 markus 202: int
203: kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
1.1 markus 204: {
1.61 djm 205: u_int i;
1.102 markus 206: int r;
207:
208: sshbuf_reset(b);
1.26 markus 209:
1.49 markus 210: /*
211: * add a dummy cookie, the cookie will be overwritten by
212: * kex_send_kexinit(), each time a kexinit is set
213: */
1.102 markus 214: for (i = 0; i < KEX_COOKIE_LEN; i++) {
215: if ((r = sshbuf_put_u8(b, 0)) != 0)
216: return r;
217: }
218: for (i = 0; i < PROPOSAL_MAX; i++) {
219: if ((r = sshbuf_put_cstring(b, proposal[i])) != 0)
220: return r;
221: }
222: if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */
223: (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */
224: return r;
225: return 0;
1.1 markus 226: }
227:
1.26 markus 228: /* parse buffer and return algorithm proposal */
1.102 markus 229: int
230: kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp)
1.7 markus 231: {
1.102 markus 232: struct sshbuf *b = NULL;
233: u_char v;
1.78 djm 234: u_int i;
1.102 markus 235: char **proposal = NULL;
236: int r;
1.7 markus 237:
1.102 markus 238: *propp = NULL;
239: if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL)
240: return SSH_ERR_ALLOC_FAIL;
241: if ((b = sshbuf_fromb(raw)) == NULL) {
242: r = SSH_ERR_ALLOC_FAIL;
243: goto out;
244: }
245: if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */
246: goto out;
1.7 markus 247: /* extract kex init proposal strings */
248: for (i = 0; i < PROPOSAL_MAX; i++) {
1.102 markus 249: if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0)
250: goto out;
1.26 markus 251: debug2("kex_parse_kexinit: %s", proposal[i]);
1.7 markus 252: }
1.26 markus 253: /* first kex follows / reserved */
1.102 markus 254: if ((r = sshbuf_get_u8(b, &v)) != 0 ||
255: (r = sshbuf_get_u32(b, &i)) != 0)
256: goto out;
1.53 markus 257: if (first_kex_follows != NULL)
258: *first_kex_follows = i;
1.102 markus 259: debug2("kex_parse_kexinit: first_kex_follows %d ", v);
1.78 djm 260: debug2("kex_parse_kexinit: reserved %u ", i);
1.102 markus 261: r = 0;
262: *propp = proposal;
263: out:
264: if (r != 0 && proposal != NULL)
265: kex_prop_free(proposal);
266: sshbuf_free(b);
267: return r;
1.1 markus 268: }
269:
1.102 markus 270: void
1.26 markus 271: kex_prop_free(char **proposal)
1.1 markus 272: {
1.61 djm 273: u_int i;
1.26 markus 274:
1.106 djm 275: if (proposal == NULL)
276: return;
1.26 markus 277: for (i = 0; i < PROPOSAL_MAX; i++)
1.91 djm 278: free(proposal[i]);
279: free(proposal);
1.1 markus 280: }
281:
1.78 djm 282: /* ARGSUSED */
1.101 markus 283: static int
1.41 markus 284: kex_protocol_error(int type, u_int32_t seq, void *ctxt)
1.1 markus 285: {
1.41 markus 286: error("Hm, kex protocol error: type %d seq %u", type, seq);
1.101 markus 287: return 0;
1.26 markus 288: }
1.1 markus 289:
1.35 itojun 290: static void
1.102 markus 291: kex_reset_dispatch(struct ssh *ssh)
1.29 markus 292: {
1.102 markus 293: ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
1.42 markus 294: SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
1.102 markus 295: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.29 markus 296: }
297:
1.102 markus 298: int
299: kex_send_newkeys(struct ssh *ssh)
1.26 markus 300: {
1.102 markus 301: int r;
1.28 markus 302:
1.102 markus 303: kex_reset_dispatch(ssh);
304: if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
305: (r = sshpkt_send(ssh)) != 0)
306: return r;
1.26 markus 307: debug("SSH2_MSG_NEWKEYS sent");
1.102 markus 308: debug("expecting SSH2_MSG_NEWKEYS");
309: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
310: return 0;
311: }
312:
313: static int
314: kex_input_newkeys(int type, u_int32_t seq, void *ctxt)
315: {
316: struct ssh *ssh = ctxt;
317: struct kex *kex = ssh->kex;
318: int r;
1.19 stevesk 319:
1.26 markus 320: debug("SSH2_MSG_NEWKEYS received");
1.102 markus 321: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
322: if ((r = sshpkt_get_end(ssh)) != 0)
323: return r;
1.30 markus 324: kex->done = 1;
1.102 markus 325: sshbuf_reset(kex->peer);
326: /* sshbuf_reset(kex->my); */
1.26 markus 327: kex->flags &= ~KEX_INIT_SENT;
1.91 djm 328: free(kex->name);
1.32 markus 329: kex->name = NULL;
1.102 markus 330: return 0;
1.26 markus 331: }
1.1 markus 332:
1.102 markus 333: int
334: kex_send_kexinit(struct ssh *ssh)
1.26 markus 335: {
1.49 markus 336: u_char *cookie;
1.102 markus 337: struct kex *kex = ssh->kex;
338: int r;
1.49 markus 339:
1.102 markus 340: if (kex == NULL)
341: return SSH_ERR_INTERNAL_ERROR;
342: if (kex->flags & KEX_INIT_SENT)
343: return 0;
1.30 markus 344: kex->done = 0;
1.49 markus 345:
346: /* generate a random cookie */
1.102 markus 347: if (sshbuf_len(kex->my) < KEX_COOKIE_LEN)
348: return SSH_ERR_INVALID_FORMAT;
349: if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL)
350: return SSH_ERR_INTERNAL_ERROR;
351: arc4random_buf(cookie, KEX_COOKIE_LEN);
352:
353: if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
354: (r = sshpkt_putb(ssh, kex->my)) != 0 ||
355: (r = sshpkt_send(ssh)) != 0)
356: return r;
1.26 markus 357: debug("SSH2_MSG_KEXINIT sent");
358: kex->flags |= KEX_INIT_SENT;
1.102 markus 359: return 0;
1.1 markus 360: }
361:
1.78 djm 362: /* ARGSUSED */
1.101 markus 363: int
1.41 markus 364: kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
1.11 provos 365: {
1.102 markus 366: struct ssh *ssh = ctxt;
367: struct kex *kex = ssh->kex;
368: const u_char *ptr;
1.100 markus 369: u_int i;
370: size_t dlen;
1.102 markus 371: int r;
1.11 provos 372:
1.26 markus 373: debug("SSH2_MSG_KEXINIT received");
1.29 markus 374: if (kex == NULL)
1.102 markus 375: return SSH_ERR_INVALID_ARGUMENT;
1.11 provos 376:
1.102 markus 377: ptr = sshpkt_ptr(ssh, &dlen);
378: if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
379: return r;
1.31 markus 380:
381: /* discard packet */
382: for (i = 0; i < KEX_COOKIE_LEN; i++)
1.102 markus 383: if ((r = sshpkt_get_u8(ssh, NULL)) != 0)
384: return r;
1.31 markus 385: for (i = 0; i < PROPOSAL_MAX; i++)
1.102 markus 386: if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0)
387: return r;
1.87 djm 388: /*
389: * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
390: * KEX method has the server move first, but a server might be using
391: * a custom method or one that we otherwise don't support. We should
392: * be prepared to remember first_kex_follows here so we can eat a
393: * packet later.
394: * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
395: * for cases where the server *doesn't* go first. I guess we should
396: * ignore it when it is set for these cases, which is what we do now.
397: */
1.102 markus 398: if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
399: (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
400: (r = sshpkt_get_end(ssh)) != 0)
401: return r;
402:
403: if (!(kex->flags & KEX_INIT_SENT))
404: if ((r = kex_send_kexinit(ssh)) != 0)
405: return r;
406: if ((r = kex_choose_conf(ssh)) != 0)
407: return r;
1.19 stevesk 408:
1.102 markus 409: if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
410: return (kex->kex[kex->kex_type])(ssh);
411:
412: return SSH_ERR_INTERNAL_ERROR;
413: }
414:
415: int
416: kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp)
417: {
418: struct kex *kex;
419: int r;
420:
421: *kexp = NULL;
422: if ((kex = calloc(1, sizeof(*kex))) == NULL)
423: return SSH_ERR_ALLOC_FAIL;
424: if ((kex->peer = sshbuf_new()) == NULL ||
425: (kex->my = sshbuf_new()) == NULL) {
426: r = SSH_ERR_ALLOC_FAIL;
427: goto out;
428: }
429: if ((r = kex_prop2buf(kex->my, proposal)) != 0)
430: goto out;
431: kex->done = 0;
432: kex_reset_dispatch(ssh);
433: r = 0;
434: *kexp = kex;
435: out:
436: if (r != 0)
437: kex_free(kex);
438: return r;
1.26 markus 439: }
1.11 provos 440:
1.100 markus 441: void
442: kex_free_newkeys(struct newkeys *newkeys)
443: {
444: if (newkeys == NULL)
445: return;
446: if (newkeys->enc.key) {
447: explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
448: free(newkeys->enc.key);
449: newkeys->enc.key = NULL;
450: }
451: if (newkeys->enc.iv) {
452: explicit_bzero(newkeys->enc.iv, newkeys->enc.block_size);
453: free(newkeys->enc.iv);
454: newkeys->enc.iv = NULL;
455: }
456: free(newkeys->enc.name);
457: explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
458: free(newkeys->comp.name);
459: explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
460: mac_clear(&newkeys->mac);
461: if (newkeys->mac.key) {
462: explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
463: free(newkeys->mac.key);
464: newkeys->mac.key = NULL;
465: }
466: free(newkeys->mac.name);
467: explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
468: explicit_bzero(newkeys, sizeof(*newkeys));
469: free(newkeys);
470: }
471:
1.102 markus 472: void
473: kex_free(struct kex *kex)
1.26 markus 474: {
1.102 markus 475: u_int mode;
1.11 provos 476:
1.102 markus 477: #ifdef WITH_OPENSSL
478: if (kex->dh)
479: DH_free(kex->dh);
480: if (kex->ec_client_key)
481: EC_KEY_free(kex->ec_client_key);
482: #endif
483: for (mode = 0; mode < MODE_MAX; mode++) {
484: kex_free_newkeys(kex->newkeys[mode]);
485: kex->newkeys[mode] = NULL;
1.100 markus 486: }
1.102 markus 487: sshbuf_free(kex->peer);
488: sshbuf_free(kex->my);
489: free(kex->session_id);
490: free(kex->client_version_string);
491: free(kex->server_version_string);
1.107 djm 492: free(kex->failed_choice);
1.102 markus 493: free(kex);
1.11 provos 494: }
495:
1.102 markus 496: int
497: kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
1.1 markus 498: {
1.102 markus 499: int r;
1.1 markus 500:
1.102 markus 501: if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0)
502: return r;
503: if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
504: kex_free(ssh->kex);
505: ssh->kex = NULL;
506: return r;
1.1 markus 507: }
1.102 markus 508: return 0;
1.1 markus 509: }
510:
1.102 markus 511: static int
512: choose_enc(struct sshenc *enc, char *client, char *server)
1.1 markus 513: {
1.23 markus 514: char *name = match_list(client, server, NULL);
1.102 markus 515:
1.1 markus 516: if (name == NULL)
1.102 markus 517: return SSH_ERR_NO_CIPHER_ALG_MATCH;
1.45 markus 518: if ((enc->cipher = cipher_by_name(name)) == NULL)
1.102 markus 519: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 520: enc->name = name;
521: enc->enabled = 0;
522: enc->iv = NULL;
1.88 markus 523: enc->iv_len = cipher_ivlen(enc->cipher);
1.1 markus 524: enc->key = NULL;
1.45 markus 525: enc->key_len = cipher_keylen(enc->cipher);
526: enc->block_size = cipher_blocksize(enc->cipher);
1.102 markus 527: return 0;
1.1 markus 528: }
1.69 deraadt 529:
1.102 markus 530: static int
531: choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
1.1 markus 532: {
1.23 markus 533: char *name = match_list(client, server, NULL);
1.102 markus 534:
1.1 markus 535: if (name == NULL)
1.102 markus 536: return SSH_ERR_NO_MAC_ALG_MATCH;
1.79 djm 537: if (mac_setup(mac, name) < 0)
1.102 markus 538: return SSH_ERR_INTERNAL_ERROR;
1.21 markus 539: /* truncate the key */
1.102 markus 540: if (ssh->compat & SSH_BUG_HMAC)
1.21 markus 541: mac->key_len = 16;
1.1 markus 542: mac->name = name;
543: mac->key = NULL;
544: mac->enabled = 0;
1.102 markus 545: return 0;
1.1 markus 546: }
1.69 deraadt 547:
1.102 markus 548: static int
549: choose_comp(struct sshcomp *comp, char *client, char *server)
1.1 markus 550: {
1.23 markus 551: char *name = match_list(client, server, NULL);
1.102 markus 552:
1.1 markus 553: if (name == NULL)
1.102 markus 554: return SSH_ERR_NO_COMPRESS_ALG_MATCH;
1.64 markus 555: if (strcmp(name, "zlib@openssh.com") == 0) {
556: comp->type = COMP_DELAYED;
557: } else if (strcmp(name, "zlib") == 0) {
558: comp->type = COMP_ZLIB;
1.1 markus 559: } else if (strcmp(name, "none") == 0) {
1.64 markus 560: comp->type = COMP_NONE;
1.1 markus 561: } else {
1.102 markus 562: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 563: }
564: comp->name = name;
1.102 markus 565: return 0;
1.1 markus 566: }
1.69 deraadt 567:
1.102 markus 568: static int
569: choose_kex(struct kex *k, char *client, char *server)
1.1 markus 570: {
1.89 djm 571: const struct kexalg *kexalg;
572:
1.23 markus 573: k->name = match_list(client, server, NULL);
1.102 markus 574:
1.1 markus 575: if (k->name == NULL)
1.102 markus 576: return SSH_ERR_NO_KEX_ALG_MATCH;
1.89 djm 577: if ((kexalg = kex_alg_by_name(k->name)) == NULL)
1.102 markus 578: return SSH_ERR_INTERNAL_ERROR;
1.89 djm 579: k->kex_type = kexalg->type;
1.94 djm 580: k->hash_alg = kexalg->hash_alg;
1.89 djm 581: k->ec_nid = kexalg->ec_nid;
1.102 markus 582: return 0;
1.1 markus 583: }
1.65 djm 584:
1.102 markus 585: static int
586: choose_hostkeyalg(struct kex *k, char *client, char *server)
1.1 markus 587: {
1.23 markus 588: char *hostkeyalg = match_list(client, server, NULL);
1.102 markus 589:
1.13 markus 590: if (hostkeyalg == NULL)
1.102 markus 591: return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
592: k->hostkey_type = sshkey_type_from_name(hostkeyalg);
1.13 markus 593: if (k->hostkey_type == KEY_UNSPEC)
1.102 markus 594: return SSH_ERR_INTERNAL_ERROR;
1.104 djm 595: k->hostkey_nid = sshkey_ecdsa_nid_from_name(hostkeyalg);
1.91 djm 596: free(hostkeyalg);
1.102 markus 597: return 0;
1.1 markus 598: }
599:
1.56 djm 600: static int
1.53 markus 601: proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
602: {
603: static int check[] = {
604: PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
605: };
606: int *idx;
607: char *p;
608:
609: for (idx = &check[0]; *idx != -1; idx++) {
610: if ((p = strchr(my[*idx], ',')) != NULL)
611: *p = '\0';
612: if ((p = strchr(peer[*idx], ',')) != NULL)
613: *p = '\0';
614: if (strcmp(my[*idx], peer[*idx]) != 0) {
615: debug2("proposal mismatch: my %s peer %s",
616: my[*idx], peer[*idx]);
617: return (0);
618: }
619: }
620: debug2("proposals match");
621: return (1);
622: }
623:
1.102 markus 624: static int
625: kex_choose_conf(struct ssh *ssh)
1.1 markus 626: {
1.102 markus 627: struct kex *kex = ssh->kex;
628: struct newkeys *newkeys;
629: char **my = NULL, **peer = NULL;
1.26 markus 630: char **cprop, **sprop;
1.27 markus 631: int nenc, nmac, ncomp;
1.96 dtucker 632: u_int mode, ctos, need, dh_need, authlen;
1.102 markus 633: int r, first_kex_follows;
1.1 markus 634:
1.102 markus 635: if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0 ||
636: (r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
637: goto out;
1.26 markus 638:
1.27 markus 639: if (kex->server) {
1.26 markus 640: cprop=peer;
641: sprop=my;
642: } else {
643: cprop=my;
644: sprop=peer;
1.82 andreas 645: }
646:
647: /* Check whether server offers roaming */
648: if (!kex->server) {
1.102 markus 649: char *roaming = match_list(KEX_RESUME,
650: peer[PROPOSAL_KEX_ALGS], NULL);
651:
1.82 andreas 652: if (roaming) {
653: kex->roaming = 1;
1.91 djm 654: free(roaming);
1.82 andreas 655: }
1.26 markus 656: }
1.1 markus 657:
1.30 markus 658: /* Algorithm Negotiation */
1.1 markus 659: for (mode = 0; mode < MODE_MAX; mode++) {
1.102 markus 660: if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
661: r = SSH_ERR_ALLOC_FAIL;
662: goto out;
663: }
1.30 markus 664: kex->newkeys[mode] = newkeys;
1.78 djm 665: ctos = (!kex->server && mode == MODE_OUT) ||
666: (kex->server && mode == MODE_IN);
1.1 markus 667: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
668: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
669: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.102 markus 670: if ((r = choose_enc(&newkeys->enc, cprop[nenc],
1.107 djm 671: sprop[nenc])) != 0) {
672: kex->failed_choice = peer[nenc];
673: peer[nenc] = NULL;
1.102 markus 674: goto out;
1.107 djm 675: }
1.102 markus 676: authlen = cipher_authlen(newkeys->enc.cipher);
1.88 markus 677: /* ignore mac for authenticated encryption */
1.102 markus 678: if (authlen == 0 &&
679: (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
1.107 djm 680: sprop[nmac])) != 0) {
681: kex->failed_choice = peer[nmac];
682: peer[nmac] = NULL;
1.102 markus 683: goto out;
1.107 djm 684: }
1.102 markus 685: if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
1.107 djm 686: sprop[ncomp])) != 0) {
687: kex->failed_choice = peer[ncomp];
688: peer[ncomp] = NULL;
1.102 markus 689: goto out;
1.107 djm 690: }
1.2 markus 691: debug("kex: %s %s %s %s",
1.1 markus 692: ctos ? "client->server" : "server->client",
1.27 markus 693: newkeys->enc.name,
1.88 markus 694: authlen == 0 ? newkeys->mac.name : "<implicit>",
1.27 markus 695: newkeys->comp.name);
1.1 markus 696: }
1.102 markus 697: if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
1.107 djm 698: sprop[PROPOSAL_KEX_ALGS])) != 0) {
699: kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
700: peer[PROPOSAL_KEX_ALGS] = NULL;
1.102 markus 701: goto out;
1.107 djm 702: }
703: if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
704: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
1.108 djm 705: kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
706: peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
1.107 djm 707: goto out;
708: }
1.96 dtucker 709: need = dh_need = 0;
1.1 markus 710: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 711: newkeys = kex->newkeys[mode];
1.97 markus 712: need = MAX(need, newkeys->enc.key_len);
713: need = MAX(need, newkeys->enc.block_size);
714: need = MAX(need, newkeys->enc.iv_len);
715: need = MAX(need, newkeys->mac.key_len);
716: dh_need = MAX(dh_need, cipher_seclen(newkeys->enc.cipher));
717: dh_need = MAX(dh_need, newkeys->enc.block_size);
718: dh_need = MAX(dh_need, newkeys->enc.iv_len);
719: dh_need = MAX(dh_need, newkeys->mac.key_len);
1.1 markus 720: }
1.7 markus 721: /* XXX need runden? */
1.27 markus 722: kex->we_need = need;
1.96 dtucker 723: kex->dh_need = dh_need;
1.53 markus 724:
725: /* ignore the next message if the proposals do not match */
1.56 djm 726: if (first_kex_follows && !proposals_match(my, peer) &&
1.102 markus 727: !(ssh->compat & SSH_BUG_FIRSTKEX))
728: ssh->dispatch_skip_packets = 1;
729: r = 0;
730: out:
1.26 markus 731: kex_prop_free(my);
732: kex_prop_free(peer);
1.102 markus 733: return r;
1.26 markus 734: }
735:
1.102 markus 736: static int
737: derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
738: const struct sshbuf *shared_secret, u_char **keyp)
1.26 markus 739: {
1.102 markus 740: struct kex *kex = ssh->kex;
741: struct ssh_digest_ctx *hashctx = NULL;
1.26 markus 742: char c = id;
1.61 djm 743: u_int have;
1.94 djm 744: size_t mdsz;
1.61 djm 745: u_char *digest;
1.102 markus 746: int r;
1.62 djm 747:
1.94 djm 748: if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
1.102 markus 749: return SSH_ERR_INVALID_ARGUMENT;
750: if ((digest = calloc(1, roundup(need, mdsz))) == NULL) {
751: r = SSH_ERR_ALLOC_FAIL;
752: goto out;
753: }
1.26 markus 754:
1.30 markus 755: /* K1 = HASH(K || H || "A" || session_id) */
1.102 markus 756: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
757: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 758: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
759: ssh_digest_update(hashctx, &c, 1) != 0 ||
760: ssh_digest_update(hashctx, kex->session_id,
1.102 markus 761: kex->session_id_len) != 0 ||
762: ssh_digest_final(hashctx, digest, mdsz) != 0) {
763: r = SSH_ERR_LIBCRYPTO_ERROR;
764: goto out;
765: }
1.94 djm 766: ssh_digest_free(hashctx);
1.102 markus 767: hashctx = NULL;
1.26 markus 768:
1.30 markus 769: /*
770: * expand key:
771: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
772: * Key = K1 || K2 || ... || Kn
773: */
1.26 markus 774: for (have = mdsz; need > have; have += mdsz) {
1.102 markus 775: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
776: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 777: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1.102 markus 778: ssh_digest_update(hashctx, digest, have) != 0 ||
779: ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
780: r = SSH_ERR_LIBCRYPTO_ERROR;
781: goto out;
782: }
1.94 djm 783: ssh_digest_free(hashctx);
1.102 markus 784: hashctx = NULL;
1.26 markus 785: }
786: #ifdef DEBUG_KEX
787: fprintf(stderr, "key '%c'== ", c);
788: dump_digest("key", digest, need);
789: #endif
1.102 markus 790: *keyp = digest;
791: digest = NULL;
792: r = 0;
793: out:
794: if (digest)
795: free(digest);
796: ssh_digest_free(hashctx);
797: return r;
1.1 markus 798: }
799:
1.23 markus 800: #define NKEYS 6
1.102 markus 801: int
802: kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
803: const struct sshbuf *shared_secret)
1.1 markus 804: {
1.102 markus 805: struct kex *kex = ssh->kex;
1.15 markus 806: u_char *keys[NKEYS];
1.102 markus 807: u_int i, j, mode, ctos;
808: int r;
1.1 markus 809:
1.65 djm 810: for (i = 0; i < NKEYS; i++) {
1.102 markus 811: if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
812: shared_secret, &keys[i])) != 0) {
813: for (j = 0; j < i; j++)
814: free(keys[j]);
815: return r;
816: }
1.65 djm 817: }
1.1 markus 818: for (mode = 0; mode < MODE_MAX; mode++) {
1.69 deraadt 819: ctos = (!kex->server && mode == MODE_OUT) ||
820: (kex->server && mode == MODE_IN);
1.100 markus 821: kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
822: kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
823: kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
1.1 markus 824: }
1.102 markus 825: return 0;
1.95 djm 826: }
827:
1.99 markus 828: #ifdef WITH_OPENSSL
1.102 markus 829: int
830: kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen,
831: const BIGNUM *secret)
1.95 djm 832: {
1.102 markus 833: struct sshbuf *shared_secret;
834: int r;
1.95 djm 835:
1.102 markus 836: if ((shared_secret = sshbuf_new()) == NULL)
837: return SSH_ERR_ALLOC_FAIL;
838: if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0)
839: r = kex_derive_keys(ssh, hash, hashlen, shared_secret);
840: sshbuf_free(shared_secret);
841: return r;
1.27 markus 842: }
1.99 markus 843: #endif
1.57 djm 844:
1.99 markus 845: #ifdef WITH_SSH1
1.102 markus 846: int
1.57 djm 847: derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
848: u_int8_t cookie[8], u_int8_t id[16])
849: {
1.105 djm 850: u_int8_t hbuf[2048], sbuf[2048], obuf[SSH_DIGEST_MAX_LENGTH];
1.102 markus 851: struct ssh_digest_ctx *hashctx = NULL;
1.105 djm 852: size_t hlen, slen;
1.102 markus 853: int r;
1.57 djm 854:
1.105 djm 855: hlen = BN_num_bytes(host_modulus);
856: slen = BN_num_bytes(server_modulus);
857: if (hlen < (512 / 8) || (u_int)hlen > sizeof(hbuf) ||
858: slen < (512 / 8) || (u_int)slen > sizeof(sbuf))
1.102 markus 859: return SSH_ERR_KEY_BITS_MISMATCH;
1.105 djm 860: if (BN_bn2bin(host_modulus, hbuf) <= 0 ||
861: BN_bn2bin(server_modulus, sbuf) <= 0) {
862: r = SSH_ERR_LIBCRYPTO_ERROR;
863: goto out;
864: }
865: if ((hashctx = ssh_digest_start(SSH_DIGEST_MD5)) == NULL) {
866: r = SSH_ERR_ALLOC_FAIL;
867: goto out;
868: }
869: if (ssh_digest_update(hashctx, hbuf, hlen) != 0 ||
870: ssh_digest_update(hashctx, sbuf, slen) != 0 ||
1.102 markus 871: ssh_digest_update(hashctx, cookie, 8) != 0 ||
872: ssh_digest_final(hashctx, obuf, sizeof(obuf)) != 0) {
873: r = SSH_ERR_LIBCRYPTO_ERROR;
874: goto out;
875: }
1.94 djm 876: memcpy(id, obuf, ssh_digest_bytes(SSH_DIGEST_MD5));
1.102 markus 877: r = 0;
878: out:
879: ssh_digest_free(hashctx);
1.105 djm 880: explicit_bzero(hbuf, sizeof(hbuf));
881: explicit_bzero(sbuf, sizeof(sbuf));
1.98 djm 882: explicit_bzero(obuf, sizeof(obuf));
1.102 markus 883: return r;
1.1 markus 884: }
1.99 markus 885: #endif
1.26 markus 886:
1.84 djm 887: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1.26 markus 888: void
889: dump_digest(char *msg, u_char *digest, int len)
890: {
891: fprintf(stderr, "%s\n", msg);
1.102 markus 892: sshbuf_dump_data(digest, len, stderr);
1.26 markus 893: }
894: #endif
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