Annotation of src/usr.bin/ssh/kex.c, Revision 1.113
1.113 ! markus 1: /* $OpenBSD: kex.c,v 1.112 2015/11/13 04:39:35 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:
1.110 djm 59: static const char *proposal_names[PROPOSAL_MAX] = {
60: "KEX algorithms",
61: "host key algorithms",
62: "ciphers ctos",
63: "ciphers stoc",
64: "MACs ctos",
65: "MACs stoc",
66: "compression ctos",
67: "compression stoc",
68: "languages ctos",
69: "languages stoc",
70: };
71:
1.89 djm 72: struct kexalg {
73: char *name;
1.102 markus 74: u_int type;
1.89 djm 75: int ec_nid;
1.94 djm 76: int hash_alg;
1.89 djm 77: };
78: static const struct kexalg kexalgs[] = {
1.99 markus 79: #ifdef WITH_OPENSSL
1.94 djm 80: { KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },
81: { KEX_DH14, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 },
82: { KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 },
83: { KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 },
84: { KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2,
85: NID_X9_62_prime256v1, SSH_DIGEST_SHA256 },
86: { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1,
87: SSH_DIGEST_SHA384 },
88: { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1,
89: SSH_DIGEST_SHA512 },
1.99 markus 90: #endif
1.94 djm 91: { KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
92: { NULL, -1, -1, -1},
1.89 djm 93: };
94:
95: char *
1.93 dtucker 96: kex_alg_list(char sep)
1.89 djm 97: {
1.102 markus 98: char *ret = NULL, *tmp;
1.89 djm 99: size_t nlen, rlen = 0;
100: const struct kexalg *k;
101:
102: for (k = kexalgs; k->name != NULL; k++) {
103: if (ret != NULL)
1.93 dtucker 104: ret[rlen++] = sep;
1.89 djm 105: nlen = strlen(k->name);
1.102 markus 106: if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
107: free(ret);
108: return NULL;
109: }
110: ret = tmp;
1.89 djm 111: memcpy(ret + rlen, k->name, nlen + 1);
112: rlen += nlen;
113: }
114: return ret;
115: }
116:
117: static const struct kexalg *
118: kex_alg_by_name(const char *name)
119: {
120: const struct kexalg *k;
121:
122: for (k = kexalgs; k->name != NULL; k++) {
123: if (strcmp(k->name, name) == 0)
124: return k;
125: }
126: return NULL;
127: }
128:
1.86 djm 129: /* Validate KEX method name list */
130: int
131: kex_names_valid(const char *names)
132: {
133: char *s, *cp, *p;
134:
135: if (names == NULL || strcmp(names, "") == 0)
136: return 0;
1.102 markus 137: if ((s = cp = strdup(names)) == NULL)
138: return 0;
1.86 djm 139: for ((p = strsep(&cp, ",")); p && *p != '\0';
140: (p = strsep(&cp, ","))) {
1.89 djm 141: if (kex_alg_by_name(p) == NULL) {
1.86 djm 142: error("Unsupported KEX algorithm \"%.100s\"", p);
1.91 djm 143: free(s);
1.86 djm 144: return 0;
145: }
146: }
147: debug3("kex names ok: [%s]", names);
1.91 djm 148: free(s);
1.86 djm 149: return 1;
1.109 djm 150: }
151:
152: /*
153: * Concatenate algorithm names, avoiding duplicates in the process.
154: * Caller must free returned string.
155: */
156: char *
157: kex_names_cat(const char *a, const char *b)
158: {
159: char *ret = NULL, *tmp = NULL, *cp, *p;
160: size_t len;
161:
162: if (a == NULL || *a == '\0')
163: return NULL;
164: if (b == NULL || *b == '\0')
165: return strdup(a);
166: if (strlen(b) > 1024*1024)
167: return NULL;
168: len = strlen(a) + strlen(b) + 2;
169: if ((tmp = cp = strdup(b)) == NULL ||
170: (ret = calloc(1, len)) == NULL) {
171: free(tmp);
172: return NULL;
173: }
174: strlcpy(ret, a, len);
175: for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) {
176: if (match_list(ret, p, NULL) != NULL)
177: continue; /* Algorithm already present */
178: if (strlcat(ret, ",", len) >= len ||
179: strlcat(ret, p, len) >= len) {
180: free(tmp);
181: free(ret);
182: return NULL; /* Shouldn't happen */
183: }
184: }
185: free(tmp);
186: return ret;
187: }
188:
189: /*
190: * Assemble a list of algorithms from a default list and a string from a
191: * configuration file. The user-provided string may begin with '+' to
192: * indicate that it should be appended to the default.
193: */
194: int
195: kex_assemble_names(const char *def, char **list)
196: {
197: char *ret;
198:
199: if (list == NULL || *list == NULL || **list == '\0') {
200: *list = strdup(def);
201: return 0;
202: }
203: if (**list != '+') {
204: return 0;
205: }
206:
207: if ((ret = kex_names_cat(def, *list + 1)) == NULL)
208: return SSH_ERR_ALLOC_FAIL;
209: free(*list);
210: *list = ret;
211: return 0;
1.86 djm 212: }
1.26 markus 213:
214: /* put algorithm proposal into buffer */
1.102 markus 215: int
216: kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
1.1 markus 217: {
1.61 djm 218: u_int i;
1.102 markus 219: int r;
220:
221: sshbuf_reset(b);
1.26 markus 222:
1.49 markus 223: /*
224: * add a dummy cookie, the cookie will be overwritten by
225: * kex_send_kexinit(), each time a kexinit is set
226: */
1.102 markus 227: for (i = 0; i < KEX_COOKIE_LEN; i++) {
228: if ((r = sshbuf_put_u8(b, 0)) != 0)
229: return r;
230: }
231: for (i = 0; i < PROPOSAL_MAX; i++) {
232: if ((r = sshbuf_put_cstring(b, proposal[i])) != 0)
233: return r;
234: }
235: if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */
236: (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */
237: return r;
238: return 0;
1.1 markus 239: }
240:
1.26 markus 241: /* parse buffer and return algorithm proposal */
1.102 markus 242: int
243: kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp)
1.7 markus 244: {
1.102 markus 245: struct sshbuf *b = NULL;
246: u_char v;
1.78 djm 247: u_int i;
1.102 markus 248: char **proposal = NULL;
249: int r;
1.7 markus 250:
1.102 markus 251: *propp = NULL;
252: if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL)
253: return SSH_ERR_ALLOC_FAIL;
254: if ((b = sshbuf_fromb(raw)) == NULL) {
255: r = SSH_ERR_ALLOC_FAIL;
256: goto out;
257: }
258: if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */
259: goto out;
1.7 markus 260: /* extract kex init proposal strings */
261: for (i = 0; i < PROPOSAL_MAX; i++) {
1.102 markus 262: if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0)
263: goto out;
1.110 djm 264: debug2("%s: %s", proposal_names[i], proposal[i]);
1.7 markus 265: }
1.26 markus 266: /* first kex follows / reserved */
1.102 markus 267: if ((r = sshbuf_get_u8(b, &v)) != 0 ||
268: (r = sshbuf_get_u32(b, &i)) != 0)
269: goto out;
1.53 markus 270: if (first_kex_follows != NULL)
271: *first_kex_follows = i;
1.110 djm 272: debug2("first_kex_follows %d ", v);
273: debug2("reserved %u ", i);
1.102 markus 274: r = 0;
275: *propp = proposal;
276: out:
277: if (r != 0 && proposal != NULL)
278: kex_prop_free(proposal);
279: sshbuf_free(b);
280: return r;
1.1 markus 281: }
282:
1.102 markus 283: void
1.26 markus 284: kex_prop_free(char **proposal)
1.1 markus 285: {
1.61 djm 286: u_int i;
1.26 markus 287:
1.106 djm 288: if (proposal == NULL)
289: return;
1.26 markus 290: for (i = 0; i < PROPOSAL_MAX; i++)
1.91 djm 291: free(proposal[i]);
292: free(proposal);
1.1 markus 293: }
294:
1.78 djm 295: /* ARGSUSED */
1.101 markus 296: static int
1.41 markus 297: kex_protocol_error(int type, u_int32_t seq, void *ctxt)
1.1 markus 298: {
1.112 djm 299: struct ssh *ssh = active_state; /* XXX */
300: int r;
301:
302: error("kex protocol error: type %d seq %u", type, seq);
303: if ((r = sshpkt_start(ssh, SSH2_MSG_UNIMPLEMENTED)) != 0 ||
304: (r = sshpkt_put_u32(ssh, seq)) != 0 ||
305: (r = sshpkt_send(ssh)) != 0)
306: return r;
1.101 markus 307: return 0;
1.26 markus 308: }
1.1 markus 309:
1.35 itojun 310: static void
1.102 markus 311: kex_reset_dispatch(struct ssh *ssh)
1.29 markus 312: {
1.102 markus 313: ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
1.42 markus 314: SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
1.102 markus 315: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.29 markus 316: }
317:
1.113 ! markus 318: static int
! 319: kex_send_ext_info(struct ssh *ssh)
! 320: {
! 321: int r;
! 322:
! 323: if ((r = sshpkt_start(ssh, SSH2_MSG_EXT_INFO)) != 0 ||
! 324: (r = sshpkt_put_u32(ssh, 1)) != 0 ||
! 325: (r = sshpkt_put_cstring(ssh, "server-sig-algs")) != 0 ||
! 326: (r = sshpkt_put_cstring(ssh, "rsa-sha2-256,rsa-sha2-512")) != 0 ||
! 327: (r = sshpkt_send(ssh)) != 0)
! 328: return r;
! 329: return 0;
! 330: }
! 331:
1.102 markus 332: int
333: kex_send_newkeys(struct ssh *ssh)
1.26 markus 334: {
1.102 markus 335: int r;
1.28 markus 336:
1.102 markus 337: kex_reset_dispatch(ssh);
338: if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
339: (r = sshpkt_send(ssh)) != 0)
340: return r;
1.26 markus 341: debug("SSH2_MSG_NEWKEYS sent");
1.102 markus 342: debug("expecting SSH2_MSG_NEWKEYS");
343: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
1.113 ! markus 344: if (ssh->kex->ext_info_c)
! 345: if ((r = kex_send_ext_info(ssh)) != 0)
! 346: return r;
1.102 markus 347: return 0;
348: }
349:
1.113 ! markus 350: int
! 351: kex_input_ext_info(int type, u_int32_t seq, void *ctxt)
! 352: {
! 353: struct ssh *ssh = ctxt;
! 354: struct kex *kex = ssh->kex;
! 355: u_int32_t i, ninfo;
! 356: char *name, *val, *found;
! 357: int r;
! 358:
! 359: debug("SSH2_MSG_EXT_INFO received");
! 360: ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_protocol_error);
! 361: if ((r = sshpkt_get_u32(ssh, &ninfo)) != 0)
! 362: return r;
! 363: for (i = 0; i < ninfo; i++) {
! 364: if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0)
! 365: return r;
! 366: if ((r = sshpkt_get_cstring(ssh, &val, NULL)) != 0) {
! 367: free(name);
! 368: return r;
! 369: }
! 370: debug("%s: %s=<%s>", __func__, name, val);
! 371: if (strcmp(name, "server-sig-algs") == 0) {
! 372: found = match_list("rsa-sha2-256", val, NULL);
! 373: if (found) {
! 374: kex->rsa_sha2 = 256;
! 375: free(found);
! 376: }
! 377: found = match_list("rsa-sha2-512", val, NULL);
! 378: if (found) {
! 379: kex->rsa_sha2 = 512;
! 380: free(found);
! 381: }
! 382: }
! 383: free(name);
! 384: free(val);
! 385: }
! 386: return sshpkt_get_end(ssh);
! 387: }
! 388:
1.102 markus 389: static int
390: kex_input_newkeys(int type, u_int32_t seq, void *ctxt)
391: {
392: struct ssh *ssh = ctxt;
393: struct kex *kex = ssh->kex;
394: int r;
1.19 stevesk 395:
1.26 markus 396: debug("SSH2_MSG_NEWKEYS received");
1.102 markus 397: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
398: if ((r = sshpkt_get_end(ssh)) != 0)
399: return r;
1.30 markus 400: kex->done = 1;
1.102 markus 401: sshbuf_reset(kex->peer);
402: /* sshbuf_reset(kex->my); */
1.26 markus 403: kex->flags &= ~KEX_INIT_SENT;
1.91 djm 404: free(kex->name);
1.32 markus 405: kex->name = NULL;
1.102 markus 406: return 0;
1.26 markus 407: }
1.1 markus 408:
1.102 markus 409: int
410: kex_send_kexinit(struct ssh *ssh)
1.26 markus 411: {
1.49 markus 412: u_char *cookie;
1.102 markus 413: struct kex *kex = ssh->kex;
414: int r;
1.49 markus 415:
1.102 markus 416: if (kex == NULL)
417: return SSH_ERR_INTERNAL_ERROR;
418: if (kex->flags & KEX_INIT_SENT)
419: return 0;
1.30 markus 420: kex->done = 0;
1.49 markus 421:
422: /* generate a random cookie */
1.102 markus 423: if (sshbuf_len(kex->my) < KEX_COOKIE_LEN)
424: return SSH_ERR_INVALID_FORMAT;
425: if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL)
426: return SSH_ERR_INTERNAL_ERROR;
427: arc4random_buf(cookie, KEX_COOKIE_LEN);
428:
429: if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
430: (r = sshpkt_putb(ssh, kex->my)) != 0 ||
431: (r = sshpkt_send(ssh)) != 0)
432: return r;
1.26 markus 433: debug("SSH2_MSG_KEXINIT sent");
434: kex->flags |= KEX_INIT_SENT;
1.102 markus 435: return 0;
1.1 markus 436: }
437:
1.78 djm 438: /* ARGSUSED */
1.101 markus 439: int
1.41 markus 440: kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
1.11 provos 441: {
1.102 markus 442: struct ssh *ssh = ctxt;
443: struct kex *kex = ssh->kex;
444: const u_char *ptr;
1.100 markus 445: u_int i;
446: size_t dlen;
1.102 markus 447: int r;
1.11 provos 448:
1.26 markus 449: debug("SSH2_MSG_KEXINIT received");
1.29 markus 450: if (kex == NULL)
1.102 markus 451: return SSH_ERR_INVALID_ARGUMENT;
1.11 provos 452:
1.102 markus 453: ptr = sshpkt_ptr(ssh, &dlen);
454: if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
455: return r;
1.31 markus 456:
457: /* discard packet */
458: for (i = 0; i < KEX_COOKIE_LEN; i++)
1.102 markus 459: if ((r = sshpkt_get_u8(ssh, NULL)) != 0)
460: return r;
1.31 markus 461: for (i = 0; i < PROPOSAL_MAX; i++)
1.102 markus 462: if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0)
463: return r;
1.87 djm 464: /*
465: * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
466: * KEX method has the server move first, but a server might be using
467: * a custom method or one that we otherwise don't support. We should
468: * be prepared to remember first_kex_follows here so we can eat a
469: * packet later.
470: * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
471: * for cases where the server *doesn't* go first. I guess we should
472: * ignore it when it is set for these cases, which is what we do now.
473: */
1.102 markus 474: if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
475: (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
476: (r = sshpkt_get_end(ssh)) != 0)
477: return r;
478:
479: if (!(kex->flags & KEX_INIT_SENT))
480: if ((r = kex_send_kexinit(ssh)) != 0)
481: return r;
482: if ((r = kex_choose_conf(ssh)) != 0)
483: return r;
1.19 stevesk 484:
1.102 markus 485: if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
486: return (kex->kex[kex->kex_type])(ssh);
487:
488: return SSH_ERR_INTERNAL_ERROR;
489: }
490:
491: int
492: kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp)
493: {
494: struct kex *kex;
495: int r;
496:
497: *kexp = NULL;
498: if ((kex = calloc(1, sizeof(*kex))) == NULL)
499: return SSH_ERR_ALLOC_FAIL;
500: if ((kex->peer = sshbuf_new()) == NULL ||
501: (kex->my = sshbuf_new()) == NULL) {
502: r = SSH_ERR_ALLOC_FAIL;
503: goto out;
504: }
505: if ((r = kex_prop2buf(kex->my, proposal)) != 0)
506: goto out;
507: kex->done = 0;
508: kex_reset_dispatch(ssh);
509: r = 0;
510: *kexp = kex;
511: out:
512: if (r != 0)
513: kex_free(kex);
514: return r;
1.26 markus 515: }
1.11 provos 516:
1.100 markus 517: void
518: kex_free_newkeys(struct newkeys *newkeys)
519: {
520: if (newkeys == NULL)
521: return;
522: if (newkeys->enc.key) {
523: explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
524: free(newkeys->enc.key);
525: newkeys->enc.key = NULL;
526: }
527: if (newkeys->enc.iv) {
1.111 djm 528: explicit_bzero(newkeys->enc.iv, newkeys->enc.iv_len);
1.100 markus 529: free(newkeys->enc.iv);
530: newkeys->enc.iv = NULL;
531: }
532: free(newkeys->enc.name);
533: explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
534: free(newkeys->comp.name);
535: explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
536: mac_clear(&newkeys->mac);
537: if (newkeys->mac.key) {
538: explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
539: free(newkeys->mac.key);
540: newkeys->mac.key = NULL;
541: }
542: free(newkeys->mac.name);
543: explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
544: explicit_bzero(newkeys, sizeof(*newkeys));
545: free(newkeys);
546: }
547:
1.102 markus 548: void
549: kex_free(struct kex *kex)
1.26 markus 550: {
1.102 markus 551: u_int mode;
1.11 provos 552:
1.102 markus 553: #ifdef WITH_OPENSSL
554: if (kex->dh)
555: DH_free(kex->dh);
556: if (kex->ec_client_key)
557: EC_KEY_free(kex->ec_client_key);
558: #endif
559: for (mode = 0; mode < MODE_MAX; mode++) {
560: kex_free_newkeys(kex->newkeys[mode]);
561: kex->newkeys[mode] = NULL;
1.100 markus 562: }
1.102 markus 563: sshbuf_free(kex->peer);
564: sshbuf_free(kex->my);
565: free(kex->session_id);
566: free(kex->client_version_string);
567: free(kex->server_version_string);
1.107 djm 568: free(kex->failed_choice);
1.113 ! markus 569: free(kex->hostkey_alg);
! 570: free(kex->name);
1.102 markus 571: free(kex);
1.11 provos 572: }
573:
1.102 markus 574: int
575: kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
1.1 markus 576: {
1.102 markus 577: int r;
1.1 markus 578:
1.102 markus 579: if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0)
580: return r;
581: if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
582: kex_free(ssh->kex);
583: ssh->kex = NULL;
584: return r;
1.1 markus 585: }
1.102 markus 586: return 0;
1.1 markus 587: }
588:
1.102 markus 589: static int
590: choose_enc(struct sshenc *enc, char *client, char *server)
1.1 markus 591: {
1.23 markus 592: char *name = match_list(client, server, NULL);
1.102 markus 593:
1.1 markus 594: if (name == NULL)
1.102 markus 595: return SSH_ERR_NO_CIPHER_ALG_MATCH;
1.45 markus 596: if ((enc->cipher = cipher_by_name(name)) == NULL)
1.102 markus 597: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 598: enc->name = name;
599: enc->enabled = 0;
600: enc->iv = NULL;
1.88 markus 601: enc->iv_len = cipher_ivlen(enc->cipher);
1.1 markus 602: enc->key = NULL;
1.45 markus 603: enc->key_len = cipher_keylen(enc->cipher);
604: enc->block_size = cipher_blocksize(enc->cipher);
1.102 markus 605: return 0;
1.1 markus 606: }
1.69 deraadt 607:
1.102 markus 608: static int
609: choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
1.1 markus 610: {
1.23 markus 611: char *name = match_list(client, server, NULL);
1.102 markus 612:
1.1 markus 613: if (name == NULL)
1.102 markus 614: return SSH_ERR_NO_MAC_ALG_MATCH;
1.79 djm 615: if (mac_setup(mac, name) < 0)
1.102 markus 616: return SSH_ERR_INTERNAL_ERROR;
1.21 markus 617: /* truncate the key */
1.102 markus 618: if (ssh->compat & SSH_BUG_HMAC)
1.21 markus 619: mac->key_len = 16;
1.1 markus 620: mac->name = name;
621: mac->key = NULL;
622: mac->enabled = 0;
1.102 markus 623: return 0;
1.1 markus 624: }
1.69 deraadt 625:
1.102 markus 626: static int
627: choose_comp(struct sshcomp *comp, char *client, char *server)
1.1 markus 628: {
1.23 markus 629: char *name = match_list(client, server, NULL);
1.102 markus 630:
1.1 markus 631: if (name == NULL)
1.102 markus 632: return SSH_ERR_NO_COMPRESS_ALG_MATCH;
1.64 markus 633: if (strcmp(name, "zlib@openssh.com") == 0) {
634: comp->type = COMP_DELAYED;
635: } else if (strcmp(name, "zlib") == 0) {
636: comp->type = COMP_ZLIB;
1.1 markus 637: } else if (strcmp(name, "none") == 0) {
1.64 markus 638: comp->type = COMP_NONE;
1.1 markus 639: } else {
1.102 markus 640: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 641: }
642: comp->name = name;
1.102 markus 643: return 0;
1.1 markus 644: }
1.69 deraadt 645:
1.102 markus 646: static int
647: choose_kex(struct kex *k, char *client, char *server)
1.1 markus 648: {
1.89 djm 649: const struct kexalg *kexalg;
650:
1.23 markus 651: k->name = match_list(client, server, NULL);
1.102 markus 652:
1.110 djm 653: debug("kex: algorithm: %s", k->name ? k->name : "(no match)");
1.1 markus 654: if (k->name == NULL)
1.102 markus 655: return SSH_ERR_NO_KEX_ALG_MATCH;
1.89 djm 656: if ((kexalg = kex_alg_by_name(k->name)) == NULL)
1.102 markus 657: return SSH_ERR_INTERNAL_ERROR;
1.89 djm 658: k->kex_type = kexalg->type;
1.94 djm 659: k->hash_alg = kexalg->hash_alg;
1.89 djm 660: k->ec_nid = kexalg->ec_nid;
1.102 markus 661: return 0;
1.1 markus 662: }
1.65 djm 663:
1.102 markus 664: static int
665: choose_hostkeyalg(struct kex *k, char *client, char *server)
1.1 markus 666: {
1.113 ! markus 667: k->hostkey_alg = match_list(client, server, NULL);
1.102 markus 668:
1.110 djm 669: debug("kex: host key algorithm: %s",
1.113 ! markus 670: k->hostkey_alg ? k->hostkey_alg : "(no match)");
! 671: if (k->hostkey_alg == NULL)
1.102 markus 672: return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
1.113 ! markus 673: k->hostkey_type = sshkey_type_from_name(k->hostkey_alg);
1.13 markus 674: if (k->hostkey_type == KEY_UNSPEC)
1.102 markus 675: return SSH_ERR_INTERNAL_ERROR;
1.113 ! markus 676: k->hostkey_nid = sshkey_ecdsa_nid_from_name(k->hostkey_alg);
1.102 markus 677: return 0;
1.1 markus 678: }
679:
1.56 djm 680: static int
1.53 markus 681: proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
682: {
683: static int check[] = {
684: PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
685: };
686: int *idx;
687: char *p;
688:
689: for (idx = &check[0]; *idx != -1; idx++) {
690: if ((p = strchr(my[*idx], ',')) != NULL)
691: *p = '\0';
692: if ((p = strchr(peer[*idx], ',')) != NULL)
693: *p = '\0';
694: if (strcmp(my[*idx], peer[*idx]) != 0) {
695: debug2("proposal mismatch: my %s peer %s",
696: my[*idx], peer[*idx]);
697: return (0);
698: }
699: }
700: debug2("proposals match");
701: return (1);
702: }
703:
1.102 markus 704: static int
705: kex_choose_conf(struct ssh *ssh)
1.1 markus 706: {
1.102 markus 707: struct kex *kex = ssh->kex;
708: struct newkeys *newkeys;
709: char **my = NULL, **peer = NULL;
1.26 markus 710: char **cprop, **sprop;
1.27 markus 711: int nenc, nmac, ncomp;
1.96 dtucker 712: u_int mode, ctos, need, dh_need, authlen;
1.102 markus 713: int r, first_kex_follows;
1.1 markus 714:
1.110 djm 715: debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
716: if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
717: goto out;
718: debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
719: if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
1.102 markus 720: goto out;
1.26 markus 721:
1.27 markus 722: if (kex->server) {
1.26 markus 723: cprop=peer;
724: sprop=my;
725: } else {
726: cprop=my;
727: sprop=peer;
1.82 andreas 728: }
729:
730: /* Check whether server offers roaming */
731: if (!kex->server) {
1.102 markus 732: char *roaming = match_list(KEX_RESUME,
733: peer[PROPOSAL_KEX_ALGS], NULL);
734:
1.82 andreas 735: if (roaming) {
736: kex->roaming = 1;
1.91 djm 737: free(roaming);
1.113 ! markus 738: }
! 739: }
! 740:
! 741: /* Check whether client supports ext_info_c */
! 742: if (kex->server) {
! 743: char *ext;
! 744:
! 745: ext = match_list("ext-info-c", peer[PROPOSAL_KEX_ALGS], NULL);
! 746: if (ext) {
! 747: kex->ext_info_c = 1;
! 748: free(ext);
1.82 andreas 749: }
1.26 markus 750: }
1.1 markus 751:
1.30 markus 752: /* Algorithm Negotiation */
1.110 djm 753: if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
754: sprop[PROPOSAL_KEX_ALGS])) != 0) {
755: kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
756: peer[PROPOSAL_KEX_ALGS] = NULL;
757: goto out;
758: }
759: if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
760: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
761: kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
762: peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
763: goto out;
764: }
1.1 markus 765: for (mode = 0; mode < MODE_MAX; mode++) {
1.102 markus 766: if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
767: r = SSH_ERR_ALLOC_FAIL;
768: goto out;
769: }
1.30 markus 770: kex->newkeys[mode] = newkeys;
1.78 djm 771: ctos = (!kex->server && mode == MODE_OUT) ||
772: (kex->server && mode == MODE_IN);
1.1 markus 773: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
774: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
775: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.102 markus 776: if ((r = choose_enc(&newkeys->enc, cprop[nenc],
1.107 djm 777: sprop[nenc])) != 0) {
778: kex->failed_choice = peer[nenc];
779: peer[nenc] = NULL;
1.102 markus 780: goto out;
1.107 djm 781: }
1.102 markus 782: authlen = cipher_authlen(newkeys->enc.cipher);
1.88 markus 783: /* ignore mac for authenticated encryption */
1.102 markus 784: if (authlen == 0 &&
785: (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
1.107 djm 786: sprop[nmac])) != 0) {
787: kex->failed_choice = peer[nmac];
788: peer[nmac] = NULL;
1.102 markus 789: goto out;
1.107 djm 790: }
1.102 markus 791: if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
1.107 djm 792: sprop[ncomp])) != 0) {
793: kex->failed_choice = peer[ncomp];
794: peer[ncomp] = NULL;
1.102 markus 795: goto out;
1.107 djm 796: }
1.110 djm 797: debug("kex: %s cipher: %s MAC: %s compression: %s",
1.1 markus 798: ctos ? "client->server" : "server->client",
1.27 markus 799: newkeys->enc.name,
1.88 markus 800: authlen == 0 ? newkeys->mac.name : "<implicit>",
1.27 markus 801: newkeys->comp.name);
1.107 djm 802: }
1.96 dtucker 803: need = dh_need = 0;
1.1 markus 804: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 805: newkeys = kex->newkeys[mode];
1.97 markus 806: need = MAX(need, newkeys->enc.key_len);
807: need = MAX(need, newkeys->enc.block_size);
808: need = MAX(need, newkeys->enc.iv_len);
809: need = MAX(need, newkeys->mac.key_len);
810: dh_need = MAX(dh_need, cipher_seclen(newkeys->enc.cipher));
811: dh_need = MAX(dh_need, newkeys->enc.block_size);
812: dh_need = MAX(dh_need, newkeys->enc.iv_len);
813: dh_need = MAX(dh_need, newkeys->mac.key_len);
1.1 markus 814: }
1.7 markus 815: /* XXX need runden? */
1.27 markus 816: kex->we_need = need;
1.96 dtucker 817: kex->dh_need = dh_need;
1.53 markus 818:
819: /* ignore the next message if the proposals do not match */
1.56 djm 820: if (first_kex_follows && !proposals_match(my, peer) &&
1.102 markus 821: !(ssh->compat & SSH_BUG_FIRSTKEX))
822: ssh->dispatch_skip_packets = 1;
823: r = 0;
824: out:
1.26 markus 825: kex_prop_free(my);
826: kex_prop_free(peer);
1.102 markus 827: return r;
1.26 markus 828: }
829:
1.102 markus 830: static int
831: derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
832: const struct sshbuf *shared_secret, u_char **keyp)
1.26 markus 833: {
1.102 markus 834: struct kex *kex = ssh->kex;
835: struct ssh_digest_ctx *hashctx = NULL;
1.26 markus 836: char c = id;
1.61 djm 837: u_int have;
1.94 djm 838: size_t mdsz;
1.61 djm 839: u_char *digest;
1.102 markus 840: int r;
1.62 djm 841:
1.94 djm 842: if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
1.102 markus 843: return SSH_ERR_INVALID_ARGUMENT;
844: if ((digest = calloc(1, roundup(need, mdsz))) == NULL) {
845: r = SSH_ERR_ALLOC_FAIL;
846: goto out;
847: }
1.26 markus 848:
1.30 markus 849: /* K1 = HASH(K || H || "A" || session_id) */
1.102 markus 850: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
851: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 852: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
853: ssh_digest_update(hashctx, &c, 1) != 0 ||
854: ssh_digest_update(hashctx, kex->session_id,
1.102 markus 855: kex->session_id_len) != 0 ||
856: ssh_digest_final(hashctx, digest, mdsz) != 0) {
857: r = SSH_ERR_LIBCRYPTO_ERROR;
858: goto out;
859: }
1.94 djm 860: ssh_digest_free(hashctx);
1.102 markus 861: hashctx = NULL;
1.26 markus 862:
1.30 markus 863: /*
864: * expand key:
865: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
866: * Key = K1 || K2 || ... || Kn
867: */
1.26 markus 868: for (have = mdsz; need > have; have += mdsz) {
1.102 markus 869: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
870: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 871: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1.102 markus 872: ssh_digest_update(hashctx, digest, have) != 0 ||
873: ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
874: r = SSH_ERR_LIBCRYPTO_ERROR;
875: goto out;
876: }
1.94 djm 877: ssh_digest_free(hashctx);
1.102 markus 878: hashctx = NULL;
1.26 markus 879: }
880: #ifdef DEBUG_KEX
881: fprintf(stderr, "key '%c'== ", c);
882: dump_digest("key", digest, need);
883: #endif
1.102 markus 884: *keyp = digest;
885: digest = NULL;
886: r = 0;
887: out:
888: if (digest)
889: free(digest);
890: ssh_digest_free(hashctx);
891: return r;
1.1 markus 892: }
893:
1.23 markus 894: #define NKEYS 6
1.102 markus 895: int
896: kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
897: const struct sshbuf *shared_secret)
1.1 markus 898: {
1.102 markus 899: struct kex *kex = ssh->kex;
1.15 markus 900: u_char *keys[NKEYS];
1.102 markus 901: u_int i, j, mode, ctos;
902: int r;
1.1 markus 903:
1.65 djm 904: for (i = 0; i < NKEYS; i++) {
1.102 markus 905: if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
906: shared_secret, &keys[i])) != 0) {
907: for (j = 0; j < i; j++)
908: free(keys[j]);
909: return r;
910: }
1.65 djm 911: }
1.1 markus 912: for (mode = 0; mode < MODE_MAX; mode++) {
1.69 deraadt 913: ctos = (!kex->server && mode == MODE_OUT) ||
914: (kex->server && mode == MODE_IN);
1.100 markus 915: kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
916: kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
917: kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
1.1 markus 918: }
1.102 markus 919: return 0;
1.95 djm 920: }
921:
1.99 markus 922: #ifdef WITH_OPENSSL
1.102 markus 923: int
924: kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen,
925: const BIGNUM *secret)
1.95 djm 926: {
1.102 markus 927: struct sshbuf *shared_secret;
928: int r;
1.95 djm 929:
1.102 markus 930: if ((shared_secret = sshbuf_new()) == NULL)
931: return SSH_ERR_ALLOC_FAIL;
932: if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0)
933: r = kex_derive_keys(ssh, hash, hashlen, shared_secret);
934: sshbuf_free(shared_secret);
935: return r;
1.27 markus 936: }
1.99 markus 937: #endif
1.57 djm 938:
1.99 markus 939: #ifdef WITH_SSH1
1.102 markus 940: int
1.57 djm 941: derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
942: u_int8_t cookie[8], u_int8_t id[16])
943: {
1.105 djm 944: u_int8_t hbuf[2048], sbuf[2048], obuf[SSH_DIGEST_MAX_LENGTH];
1.102 markus 945: struct ssh_digest_ctx *hashctx = NULL;
1.105 djm 946: size_t hlen, slen;
1.102 markus 947: int r;
1.57 djm 948:
1.105 djm 949: hlen = BN_num_bytes(host_modulus);
950: slen = BN_num_bytes(server_modulus);
951: if (hlen < (512 / 8) || (u_int)hlen > sizeof(hbuf) ||
952: slen < (512 / 8) || (u_int)slen > sizeof(sbuf))
1.102 markus 953: return SSH_ERR_KEY_BITS_MISMATCH;
1.105 djm 954: if (BN_bn2bin(host_modulus, hbuf) <= 0 ||
955: BN_bn2bin(server_modulus, sbuf) <= 0) {
956: r = SSH_ERR_LIBCRYPTO_ERROR;
957: goto out;
958: }
959: if ((hashctx = ssh_digest_start(SSH_DIGEST_MD5)) == NULL) {
960: r = SSH_ERR_ALLOC_FAIL;
961: goto out;
962: }
963: if (ssh_digest_update(hashctx, hbuf, hlen) != 0 ||
964: ssh_digest_update(hashctx, sbuf, slen) != 0 ||
1.102 markus 965: ssh_digest_update(hashctx, cookie, 8) != 0 ||
966: ssh_digest_final(hashctx, obuf, sizeof(obuf)) != 0) {
967: r = SSH_ERR_LIBCRYPTO_ERROR;
968: goto out;
969: }
1.94 djm 970: memcpy(id, obuf, ssh_digest_bytes(SSH_DIGEST_MD5));
1.102 markus 971: r = 0;
972: out:
973: ssh_digest_free(hashctx);
1.105 djm 974: explicit_bzero(hbuf, sizeof(hbuf));
975: explicit_bzero(sbuf, sizeof(sbuf));
1.98 djm 976: explicit_bzero(obuf, sizeof(obuf));
1.102 markus 977: return r;
1.1 markus 978: }
1.99 markus 979: #endif
1.26 markus 980:
1.84 djm 981: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1.26 markus 982: void
983: dump_digest(char *msg, u_char *digest, int len)
984: {
985: fprintf(stderr, "%s\n", msg);
1.102 markus 986: sshbuf_dump_data(digest, len, stderr);
1.26 markus 987: }
988: #endif
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