Annotation of src/usr.bin/ssh/kex.c, Revision 1.117.2.1
1.117.2.1! markus 1: /* $OpenBSD: kex.c,v 1.117 2016/02/08 10:57:07 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"
1.102 markus 49:
50: #include "ssherr.h"
51: #include "sshbuf.h"
1.94 djm 52: #include "digest.h"
1.48 provos 53:
1.35 itojun 54: /* prototype */
1.102 markus 55: static int kex_choose_conf(struct ssh *);
56: static int kex_input_newkeys(int, u_int32_t, void *);
1.86 djm 57:
1.110 djm 58: static const char *proposal_names[PROPOSAL_MAX] = {
59: "KEX algorithms",
60: "host key algorithms",
61: "ciphers ctos",
62: "ciphers stoc",
63: "MACs ctos",
64: "MACs stoc",
65: "compression ctos",
66: "compression stoc",
67: "languages ctos",
68: "languages stoc",
69: };
70:
1.89 djm 71: struct kexalg {
72: char *name;
1.102 markus 73: u_int type;
1.89 djm 74: int ec_nid;
1.94 djm 75: int hash_alg;
1.89 djm 76: };
77: static const struct kexalg kexalgs[] = {
1.99 markus 78: #ifdef WITH_OPENSSL
1.94 djm 79: { KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },
80: { KEX_DH14, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 },
81: { KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 },
82: { KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 },
83: { KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2,
84: NID_X9_62_prime256v1, SSH_DIGEST_SHA256 },
85: { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1,
86: SSH_DIGEST_SHA384 },
87: { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1,
88: SSH_DIGEST_SHA512 },
1.99 markus 89: #endif
1.94 djm 90: { KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
91: { NULL, -1, -1, -1},
1.89 djm 92: };
93:
94: char *
1.93 dtucker 95: kex_alg_list(char sep)
1.89 djm 96: {
1.102 markus 97: char *ret = NULL, *tmp;
1.89 djm 98: size_t nlen, rlen = 0;
99: const struct kexalg *k;
100:
101: for (k = kexalgs; k->name != NULL; k++) {
102: if (ret != NULL)
1.93 dtucker 103: ret[rlen++] = sep;
1.89 djm 104: nlen = strlen(k->name);
1.102 markus 105: if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
106: free(ret);
107: return NULL;
108: }
109: ret = tmp;
1.89 djm 110: memcpy(ret + rlen, k->name, nlen + 1);
111: rlen += nlen;
112: }
113: return ret;
114: }
115:
116: static const struct kexalg *
117: kex_alg_by_name(const char *name)
118: {
119: const struct kexalg *k;
120:
121: for (k = kexalgs; k->name != NULL; k++) {
122: if (strcmp(k->name, name) == 0)
123: return k;
124: }
125: return NULL;
126: }
127:
1.86 djm 128: /* Validate KEX method name list */
129: int
130: kex_names_valid(const char *names)
131: {
132: char *s, *cp, *p;
133:
134: if (names == NULL || strcmp(names, "") == 0)
135: return 0;
1.102 markus 136: if ((s = cp = strdup(names)) == NULL)
137: return 0;
1.86 djm 138: for ((p = strsep(&cp, ",")); p && *p != '\0';
139: (p = strsep(&cp, ","))) {
1.89 djm 140: if (kex_alg_by_name(p) == NULL) {
1.86 djm 141: error("Unsupported KEX algorithm \"%.100s\"", p);
1.91 djm 142: free(s);
1.86 djm 143: return 0;
144: }
145: }
146: debug3("kex names ok: [%s]", names);
1.91 djm 147: free(s);
1.86 djm 148: return 1;
1.109 djm 149: }
150:
151: /*
152: * Concatenate algorithm names, avoiding duplicates in the process.
153: * Caller must free returned string.
154: */
155: char *
156: kex_names_cat(const char *a, const char *b)
157: {
158: char *ret = NULL, *tmp = NULL, *cp, *p;
159: size_t len;
160:
161: if (a == NULL || *a == '\0')
162: return NULL;
163: if (b == NULL || *b == '\0')
164: return strdup(a);
165: if (strlen(b) > 1024*1024)
166: return NULL;
167: len = strlen(a) + strlen(b) + 2;
168: if ((tmp = cp = strdup(b)) == NULL ||
169: (ret = calloc(1, len)) == NULL) {
170: free(tmp);
171: return NULL;
172: }
173: strlcpy(ret, a, len);
174: for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) {
175: if (match_list(ret, p, NULL) != NULL)
176: continue; /* Algorithm already present */
177: if (strlcat(ret, ",", len) >= len ||
178: strlcat(ret, p, len) >= len) {
179: free(tmp);
180: free(ret);
181: return NULL; /* Shouldn't happen */
182: }
183: }
184: free(tmp);
185: return ret;
186: }
187:
188: /*
189: * Assemble a list of algorithms from a default list and a string from a
190: * configuration file. The user-provided string may begin with '+' to
191: * indicate that it should be appended to the default.
192: */
193: int
194: kex_assemble_names(const char *def, char **list)
195: {
196: char *ret;
197:
198: if (list == NULL || *list == NULL || **list == '\0') {
199: *list = strdup(def);
200: return 0;
201: }
202: if (**list != '+') {
203: return 0;
204: }
205:
206: if ((ret = kex_names_cat(def, *list + 1)) == NULL)
207: return SSH_ERR_ALLOC_FAIL;
208: free(*list);
209: *list = ret;
210: return 0;
1.86 djm 211: }
1.26 markus 212:
213: /* put algorithm proposal into buffer */
1.102 markus 214: int
215: kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
1.1 markus 216: {
1.61 djm 217: u_int i;
1.102 markus 218: int r;
219:
220: sshbuf_reset(b);
1.26 markus 221:
1.49 markus 222: /*
223: * add a dummy cookie, the cookie will be overwritten by
224: * kex_send_kexinit(), each time a kexinit is set
225: */
1.102 markus 226: for (i = 0; i < KEX_COOKIE_LEN; i++) {
227: if ((r = sshbuf_put_u8(b, 0)) != 0)
228: return r;
229: }
230: for (i = 0; i < PROPOSAL_MAX; i++) {
231: if ((r = sshbuf_put_cstring(b, proposal[i])) != 0)
232: return r;
233: }
234: if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */
235: (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */
236: return r;
237: return 0;
1.1 markus 238: }
239:
1.26 markus 240: /* parse buffer and return algorithm proposal */
1.102 markus 241: int
242: kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp)
1.7 markus 243: {
1.102 markus 244: struct sshbuf *b = NULL;
245: u_char v;
1.78 djm 246: u_int i;
1.102 markus 247: char **proposal = NULL;
248: int r;
1.7 markus 249:
1.102 markus 250: *propp = NULL;
251: if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL)
252: return SSH_ERR_ALLOC_FAIL;
253: if ((b = sshbuf_fromb(raw)) == NULL) {
254: r = SSH_ERR_ALLOC_FAIL;
255: goto out;
256: }
257: if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */
258: goto out;
1.7 markus 259: /* extract kex init proposal strings */
260: for (i = 0; i < PROPOSAL_MAX; i++) {
1.102 markus 261: if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0)
262: goto out;
1.110 djm 263: debug2("%s: %s", proposal_names[i], proposal[i]);
1.7 markus 264: }
1.26 markus 265: /* first kex follows / reserved */
1.115 djm 266: if ((r = sshbuf_get_u8(b, &v)) != 0 || /* first_kex_follows */
267: (r = sshbuf_get_u32(b, &i)) != 0) /* reserved */
1.102 markus 268: goto out;
1.53 markus 269: if (first_kex_follows != NULL)
1.115 djm 270: *first_kex_follows = v;
1.110 djm 271: debug2("first_kex_follows %d ", v);
272: debug2("reserved %u ", i);
1.102 markus 273: r = 0;
274: *propp = proposal;
275: out:
276: if (r != 0 && proposal != NULL)
277: kex_prop_free(proposal);
278: sshbuf_free(b);
279: return r;
1.1 markus 280: }
281:
1.102 markus 282: void
1.26 markus 283: kex_prop_free(char **proposal)
1.1 markus 284: {
1.61 djm 285: u_int i;
1.26 markus 286:
1.106 djm 287: if (proposal == NULL)
288: return;
1.26 markus 289: for (i = 0; i < PROPOSAL_MAX; i++)
1.91 djm 290: free(proposal[i]);
291: free(proposal);
1.1 markus 292: }
293:
1.78 djm 294: /* ARGSUSED */
1.101 markus 295: static int
1.41 markus 296: kex_protocol_error(int type, u_int32_t seq, void *ctxt)
1.1 markus 297: {
1.112 djm 298: struct ssh *ssh = active_state; /* XXX */
299: int r;
300:
301: error("kex protocol error: type %d seq %u", type, seq);
302: if ((r = sshpkt_start(ssh, SSH2_MSG_UNIMPLEMENTED)) != 0 ||
303: (r = sshpkt_put_u32(ssh, seq)) != 0 ||
304: (r = sshpkt_send(ssh)) != 0)
305: return r;
1.101 markus 306: return 0;
1.26 markus 307: }
1.1 markus 308:
1.35 itojun 309: static void
1.102 markus 310: kex_reset_dispatch(struct ssh *ssh)
1.29 markus 311: {
1.102 markus 312: ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
1.42 markus 313: SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
1.102 markus 314: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.29 markus 315: }
316:
1.113 markus 317: static int
318: kex_send_ext_info(struct ssh *ssh)
319: {
320: int r;
321:
322: if ((r = sshpkt_start(ssh, SSH2_MSG_EXT_INFO)) != 0 ||
323: (r = sshpkt_put_u32(ssh, 1)) != 0 ||
324: (r = sshpkt_put_cstring(ssh, "server-sig-algs")) != 0 ||
325: (r = sshpkt_put_cstring(ssh, "rsa-sha2-256,rsa-sha2-512")) != 0 ||
326: (r = sshpkt_send(ssh)) != 0)
327: return r;
328: return 0;
329: }
330:
1.102 markus 331: int
332: kex_send_newkeys(struct ssh *ssh)
1.26 markus 333: {
1.102 markus 334: int r;
1.28 markus 335:
1.102 markus 336: kex_reset_dispatch(ssh);
337: if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
338: (r = sshpkt_send(ssh)) != 0)
339: return r;
1.26 markus 340: debug("SSH2_MSG_NEWKEYS sent");
1.102 markus 341: debug("expecting SSH2_MSG_NEWKEYS");
342: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
1.113 markus 343: if (ssh->kex->ext_info_c)
344: if ((r = kex_send_ext_info(ssh)) != 0)
345: return r;
1.102 markus 346: return 0;
347: }
348:
1.113 markus 349: int
350: kex_input_ext_info(int type, u_int32_t seq, void *ctxt)
351: {
352: struct ssh *ssh = ctxt;
353: struct kex *kex = ssh->kex;
354: u_int32_t i, ninfo;
355: char *name, *val, *found;
356: int r;
357:
358: debug("SSH2_MSG_EXT_INFO received");
359: ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_protocol_error);
360: if ((r = sshpkt_get_u32(ssh, &ninfo)) != 0)
361: return r;
362: for (i = 0; i < ninfo; i++) {
363: if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0)
364: return r;
365: if ((r = sshpkt_get_cstring(ssh, &val, NULL)) != 0) {
366: free(name);
367: return r;
368: }
369: debug("%s: %s=<%s>", __func__, name, val);
370: if (strcmp(name, "server-sig-algs") == 0) {
371: found = match_list("rsa-sha2-256", val, NULL);
372: if (found) {
373: kex->rsa_sha2 = 256;
374: free(found);
375: }
376: found = match_list("rsa-sha2-512", val, NULL);
377: if (found) {
378: kex->rsa_sha2 = 512;
379: free(found);
380: }
381: }
382: free(name);
383: free(val);
384: }
385: return sshpkt_get_end(ssh);
386: }
387:
1.102 markus 388: static int
389: kex_input_newkeys(int type, u_int32_t seq, void *ctxt)
390: {
391: struct ssh *ssh = ctxt;
392: struct kex *kex = ssh->kex;
393: int r;
1.19 stevesk 394:
1.26 markus 395: debug("SSH2_MSG_NEWKEYS received");
1.102 markus 396: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
397: if ((r = sshpkt_get_end(ssh)) != 0)
398: return r;
1.30 markus 399: kex->done = 1;
1.102 markus 400: sshbuf_reset(kex->peer);
401: /* sshbuf_reset(kex->my); */
1.26 markus 402: kex->flags &= ~KEX_INIT_SENT;
1.91 djm 403: free(kex->name);
1.32 markus 404: kex->name = NULL;
1.102 markus 405: return 0;
1.26 markus 406: }
1.1 markus 407:
1.102 markus 408: int
409: kex_send_kexinit(struct ssh *ssh)
1.26 markus 410: {
1.49 markus 411: u_char *cookie;
1.102 markus 412: struct kex *kex = ssh->kex;
413: int r;
1.49 markus 414:
1.102 markus 415: if (kex == NULL)
416: return SSH_ERR_INTERNAL_ERROR;
417: if (kex->flags & KEX_INIT_SENT)
418: return 0;
1.30 markus 419: kex->done = 0;
1.49 markus 420:
421: /* generate a random cookie */
1.102 markus 422: if (sshbuf_len(kex->my) < KEX_COOKIE_LEN)
423: return SSH_ERR_INVALID_FORMAT;
424: if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL)
425: return SSH_ERR_INTERNAL_ERROR;
426: arc4random_buf(cookie, KEX_COOKIE_LEN);
427:
428: if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
429: (r = sshpkt_putb(ssh, kex->my)) != 0 ||
430: (r = sshpkt_send(ssh)) != 0)
431: return r;
1.26 markus 432: debug("SSH2_MSG_KEXINIT sent");
433: kex->flags |= KEX_INIT_SENT;
1.102 markus 434: return 0;
1.1 markus 435: }
436:
1.78 djm 437: /* ARGSUSED */
1.101 markus 438: int
1.41 markus 439: kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
1.11 provos 440: {
1.102 markus 441: struct ssh *ssh = ctxt;
442: struct kex *kex = ssh->kex;
443: const u_char *ptr;
1.100 markus 444: u_int i;
445: size_t dlen;
1.102 markus 446: int r;
1.11 provos 447:
1.26 markus 448: debug("SSH2_MSG_KEXINIT received");
1.29 markus 449: if (kex == NULL)
1.102 markus 450: return SSH_ERR_INVALID_ARGUMENT;
1.11 provos 451:
1.117.2.1! markus 452: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, NULL);
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;
1.117 djm 587: }
588:
589: /*
590: * Request key re-exchange, returns 0 on success or a ssherr.h error
591: * code otherwise. Must not be called if KEX is incomplete or in-progress.
592: */
593: int
594: kex_start_rekex(struct ssh *ssh)
595: {
596: if (ssh->kex == NULL) {
597: error("%s: no kex", __func__);
598: return SSH_ERR_INTERNAL_ERROR;
599: }
600: if (ssh->kex->done == 0) {
601: error("%s: requested twice", __func__);
602: return SSH_ERR_INTERNAL_ERROR;
603: }
604: ssh->kex->done = 0;
605: return kex_send_kexinit(ssh);
1.1 markus 606: }
607:
1.102 markus 608: static int
609: choose_enc(struct sshenc *enc, 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_CIPHER_ALG_MATCH;
1.45 markus 615: if ((enc->cipher = cipher_by_name(name)) == NULL)
1.102 markus 616: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 617: enc->name = name;
618: enc->enabled = 0;
619: enc->iv = NULL;
1.88 markus 620: enc->iv_len = cipher_ivlen(enc->cipher);
1.1 markus 621: enc->key = NULL;
1.45 markus 622: enc->key_len = cipher_keylen(enc->cipher);
623: enc->block_size = cipher_blocksize(enc->cipher);
1.102 markus 624: return 0;
1.1 markus 625: }
1.69 deraadt 626:
1.102 markus 627: static int
628: choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
1.1 markus 629: {
1.23 markus 630: char *name = match_list(client, server, NULL);
1.102 markus 631:
1.1 markus 632: if (name == NULL)
1.102 markus 633: return SSH_ERR_NO_MAC_ALG_MATCH;
1.79 djm 634: if (mac_setup(mac, name) < 0)
1.102 markus 635: return SSH_ERR_INTERNAL_ERROR;
1.21 markus 636: /* truncate the key */
1.102 markus 637: if (ssh->compat & SSH_BUG_HMAC)
1.21 markus 638: mac->key_len = 16;
1.1 markus 639: mac->name = name;
640: mac->key = NULL;
641: mac->enabled = 0;
1.102 markus 642: return 0;
1.1 markus 643: }
1.69 deraadt 644:
1.102 markus 645: static int
646: choose_comp(struct sshcomp *comp, char *client, char *server)
1.1 markus 647: {
1.23 markus 648: char *name = match_list(client, server, NULL);
1.102 markus 649:
1.1 markus 650: if (name == NULL)
1.102 markus 651: return SSH_ERR_NO_COMPRESS_ALG_MATCH;
1.64 markus 652: if (strcmp(name, "zlib@openssh.com") == 0) {
653: comp->type = COMP_DELAYED;
654: } else if (strcmp(name, "zlib") == 0) {
655: comp->type = COMP_ZLIB;
1.1 markus 656: } else if (strcmp(name, "none") == 0) {
1.64 markus 657: comp->type = COMP_NONE;
1.1 markus 658: } else {
1.102 markus 659: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 660: }
661: comp->name = name;
1.102 markus 662: return 0;
1.1 markus 663: }
1.69 deraadt 664:
1.102 markus 665: static int
666: choose_kex(struct kex *k, char *client, char *server)
1.1 markus 667: {
1.89 djm 668: const struct kexalg *kexalg;
669:
1.23 markus 670: k->name = match_list(client, server, NULL);
1.102 markus 671:
1.110 djm 672: debug("kex: algorithm: %s", k->name ? k->name : "(no match)");
1.1 markus 673: if (k->name == NULL)
1.102 markus 674: return SSH_ERR_NO_KEX_ALG_MATCH;
1.89 djm 675: if ((kexalg = kex_alg_by_name(k->name)) == NULL)
1.102 markus 676: return SSH_ERR_INTERNAL_ERROR;
1.89 djm 677: k->kex_type = kexalg->type;
1.94 djm 678: k->hash_alg = kexalg->hash_alg;
1.89 djm 679: k->ec_nid = kexalg->ec_nid;
1.102 markus 680: return 0;
1.1 markus 681: }
1.65 djm 682:
1.102 markus 683: static int
684: choose_hostkeyalg(struct kex *k, char *client, char *server)
1.1 markus 685: {
1.113 markus 686: k->hostkey_alg = match_list(client, server, NULL);
1.102 markus 687:
1.110 djm 688: debug("kex: host key algorithm: %s",
1.113 markus 689: k->hostkey_alg ? k->hostkey_alg : "(no match)");
690: if (k->hostkey_alg == NULL)
1.102 markus 691: return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
1.113 markus 692: k->hostkey_type = sshkey_type_from_name(k->hostkey_alg);
1.13 markus 693: if (k->hostkey_type == KEY_UNSPEC)
1.102 markus 694: return SSH_ERR_INTERNAL_ERROR;
1.113 markus 695: k->hostkey_nid = sshkey_ecdsa_nid_from_name(k->hostkey_alg);
1.102 markus 696: return 0;
1.1 markus 697: }
698:
1.56 djm 699: static int
1.53 markus 700: proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
701: {
702: static int check[] = {
703: PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
704: };
705: int *idx;
706: char *p;
707:
708: for (idx = &check[0]; *idx != -1; idx++) {
709: if ((p = strchr(my[*idx], ',')) != NULL)
710: *p = '\0';
711: if ((p = strchr(peer[*idx], ',')) != NULL)
712: *p = '\0';
713: if (strcmp(my[*idx], peer[*idx]) != 0) {
714: debug2("proposal mismatch: my %s peer %s",
715: my[*idx], peer[*idx]);
716: return (0);
717: }
718: }
719: debug2("proposals match");
720: return (1);
721: }
722:
1.102 markus 723: static int
724: kex_choose_conf(struct ssh *ssh)
1.1 markus 725: {
1.102 markus 726: struct kex *kex = ssh->kex;
727: struct newkeys *newkeys;
728: char **my = NULL, **peer = NULL;
1.26 markus 729: char **cprop, **sprop;
1.27 markus 730: int nenc, nmac, ncomp;
1.96 dtucker 731: u_int mode, ctos, need, dh_need, authlen;
1.102 markus 732: int r, first_kex_follows;
1.1 markus 733:
1.110 djm 734: debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
735: if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
736: goto out;
737: debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
738: if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
1.102 markus 739: goto out;
1.26 markus 740:
1.27 markus 741: if (kex->server) {
1.26 markus 742: cprop=peer;
743: sprop=my;
744: } else {
745: cprop=my;
746: sprop=peer;
1.113 markus 747: }
748:
749: /* Check whether client supports ext_info_c */
750: if (kex->server) {
751: char *ext;
752:
753: ext = match_list("ext-info-c", peer[PROPOSAL_KEX_ALGS], NULL);
754: if (ext) {
755: kex->ext_info_c = 1;
756: free(ext);
1.82 andreas 757: }
1.26 markus 758: }
1.1 markus 759:
1.30 markus 760: /* Algorithm Negotiation */
1.110 djm 761: if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
762: sprop[PROPOSAL_KEX_ALGS])) != 0) {
763: kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
764: peer[PROPOSAL_KEX_ALGS] = NULL;
765: goto out;
766: }
767: if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
768: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
769: kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
770: peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
771: goto out;
772: }
1.1 markus 773: for (mode = 0; mode < MODE_MAX; mode++) {
1.102 markus 774: if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
775: r = SSH_ERR_ALLOC_FAIL;
776: goto out;
777: }
1.30 markus 778: kex->newkeys[mode] = newkeys;
1.78 djm 779: ctos = (!kex->server && mode == MODE_OUT) ||
780: (kex->server && mode == MODE_IN);
1.1 markus 781: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
782: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
783: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.102 markus 784: if ((r = choose_enc(&newkeys->enc, cprop[nenc],
1.107 djm 785: sprop[nenc])) != 0) {
786: kex->failed_choice = peer[nenc];
787: peer[nenc] = NULL;
1.102 markus 788: goto out;
1.107 djm 789: }
1.102 markus 790: authlen = cipher_authlen(newkeys->enc.cipher);
1.88 markus 791: /* ignore mac for authenticated encryption */
1.102 markus 792: if (authlen == 0 &&
793: (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
1.107 djm 794: sprop[nmac])) != 0) {
795: kex->failed_choice = peer[nmac];
796: peer[nmac] = NULL;
1.102 markus 797: goto out;
1.107 djm 798: }
1.102 markus 799: if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
1.107 djm 800: sprop[ncomp])) != 0) {
801: kex->failed_choice = peer[ncomp];
802: peer[ncomp] = NULL;
1.102 markus 803: goto out;
1.107 djm 804: }
1.110 djm 805: debug("kex: %s cipher: %s MAC: %s compression: %s",
1.1 markus 806: ctos ? "client->server" : "server->client",
1.27 markus 807: newkeys->enc.name,
1.88 markus 808: authlen == 0 ? newkeys->mac.name : "<implicit>",
1.27 markus 809: newkeys->comp.name);
1.107 djm 810: }
1.96 dtucker 811: need = dh_need = 0;
1.1 markus 812: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 813: newkeys = kex->newkeys[mode];
1.97 markus 814: need = MAX(need, newkeys->enc.key_len);
815: need = MAX(need, newkeys->enc.block_size);
816: need = MAX(need, newkeys->enc.iv_len);
817: need = MAX(need, newkeys->mac.key_len);
818: dh_need = MAX(dh_need, cipher_seclen(newkeys->enc.cipher));
819: dh_need = MAX(dh_need, newkeys->enc.block_size);
820: dh_need = MAX(dh_need, newkeys->enc.iv_len);
821: dh_need = MAX(dh_need, newkeys->mac.key_len);
1.1 markus 822: }
1.7 markus 823: /* XXX need runden? */
1.27 markus 824: kex->we_need = need;
1.96 dtucker 825: kex->dh_need = dh_need;
1.53 markus 826:
827: /* ignore the next message if the proposals do not match */
1.56 djm 828: if (first_kex_follows && !proposals_match(my, peer) &&
1.102 markus 829: !(ssh->compat & SSH_BUG_FIRSTKEX))
830: ssh->dispatch_skip_packets = 1;
831: r = 0;
832: out:
1.26 markus 833: kex_prop_free(my);
834: kex_prop_free(peer);
1.102 markus 835: return r;
1.26 markus 836: }
837:
1.102 markus 838: static int
839: derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
840: const struct sshbuf *shared_secret, u_char **keyp)
1.26 markus 841: {
1.102 markus 842: struct kex *kex = ssh->kex;
843: struct ssh_digest_ctx *hashctx = NULL;
1.26 markus 844: char c = id;
1.61 djm 845: u_int have;
1.94 djm 846: size_t mdsz;
1.61 djm 847: u_char *digest;
1.102 markus 848: int r;
1.62 djm 849:
1.94 djm 850: if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
1.102 markus 851: return SSH_ERR_INVALID_ARGUMENT;
852: if ((digest = calloc(1, roundup(need, mdsz))) == NULL) {
853: r = SSH_ERR_ALLOC_FAIL;
854: goto out;
855: }
1.26 markus 856:
1.30 markus 857: /* K1 = HASH(K || H || "A" || session_id) */
1.102 markus 858: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
859: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 860: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
861: ssh_digest_update(hashctx, &c, 1) != 0 ||
862: ssh_digest_update(hashctx, kex->session_id,
1.102 markus 863: kex->session_id_len) != 0 ||
864: ssh_digest_final(hashctx, digest, mdsz) != 0) {
865: r = SSH_ERR_LIBCRYPTO_ERROR;
866: goto out;
867: }
1.94 djm 868: ssh_digest_free(hashctx);
1.102 markus 869: hashctx = NULL;
1.26 markus 870:
1.30 markus 871: /*
872: * expand key:
873: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
874: * Key = K1 || K2 || ... || Kn
875: */
1.26 markus 876: for (have = mdsz; need > have; have += mdsz) {
1.102 markus 877: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
878: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 879: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1.102 markus 880: ssh_digest_update(hashctx, digest, have) != 0 ||
881: ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
882: r = SSH_ERR_LIBCRYPTO_ERROR;
883: goto out;
884: }
1.94 djm 885: ssh_digest_free(hashctx);
1.102 markus 886: hashctx = NULL;
1.26 markus 887: }
888: #ifdef DEBUG_KEX
889: fprintf(stderr, "key '%c'== ", c);
890: dump_digest("key", digest, need);
891: #endif
1.102 markus 892: *keyp = digest;
893: digest = NULL;
894: r = 0;
895: out:
1.114 mmcc 896: free(digest);
1.102 markus 897: ssh_digest_free(hashctx);
898: return r;
1.1 markus 899: }
900:
1.23 markus 901: #define NKEYS 6
1.102 markus 902: int
903: kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
904: const struct sshbuf *shared_secret)
1.1 markus 905: {
1.102 markus 906: struct kex *kex = ssh->kex;
1.15 markus 907: u_char *keys[NKEYS];
1.102 markus 908: u_int i, j, mode, ctos;
909: int r;
1.1 markus 910:
1.65 djm 911: for (i = 0; i < NKEYS; i++) {
1.102 markus 912: if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
913: shared_secret, &keys[i])) != 0) {
914: for (j = 0; j < i; j++)
915: free(keys[j]);
916: return r;
917: }
1.65 djm 918: }
1.1 markus 919: for (mode = 0; mode < MODE_MAX; mode++) {
1.69 deraadt 920: ctos = (!kex->server && mode == MODE_OUT) ||
921: (kex->server && mode == MODE_IN);
1.100 markus 922: kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
923: kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
924: kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
1.1 markus 925: }
1.102 markus 926: return 0;
1.95 djm 927: }
928:
1.99 markus 929: #ifdef WITH_OPENSSL
1.102 markus 930: int
931: kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen,
932: const BIGNUM *secret)
1.95 djm 933: {
1.102 markus 934: struct sshbuf *shared_secret;
935: int r;
1.95 djm 936:
1.102 markus 937: if ((shared_secret = sshbuf_new()) == NULL)
938: return SSH_ERR_ALLOC_FAIL;
939: if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0)
940: r = kex_derive_keys(ssh, hash, hashlen, shared_secret);
941: sshbuf_free(shared_secret);
942: return r;
1.27 markus 943: }
1.99 markus 944: #endif
1.57 djm 945:
1.99 markus 946: #ifdef WITH_SSH1
1.102 markus 947: int
1.57 djm 948: derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
949: u_int8_t cookie[8], u_int8_t id[16])
950: {
1.105 djm 951: u_int8_t hbuf[2048], sbuf[2048], obuf[SSH_DIGEST_MAX_LENGTH];
1.102 markus 952: struct ssh_digest_ctx *hashctx = NULL;
1.105 djm 953: size_t hlen, slen;
1.102 markus 954: int r;
1.57 djm 955:
1.105 djm 956: hlen = BN_num_bytes(host_modulus);
957: slen = BN_num_bytes(server_modulus);
958: if (hlen < (512 / 8) || (u_int)hlen > sizeof(hbuf) ||
959: slen < (512 / 8) || (u_int)slen > sizeof(sbuf))
1.102 markus 960: return SSH_ERR_KEY_BITS_MISMATCH;
1.105 djm 961: if (BN_bn2bin(host_modulus, hbuf) <= 0 ||
962: BN_bn2bin(server_modulus, sbuf) <= 0) {
963: r = SSH_ERR_LIBCRYPTO_ERROR;
964: goto out;
965: }
966: if ((hashctx = ssh_digest_start(SSH_DIGEST_MD5)) == NULL) {
967: r = SSH_ERR_ALLOC_FAIL;
968: goto out;
969: }
970: if (ssh_digest_update(hashctx, hbuf, hlen) != 0 ||
971: ssh_digest_update(hashctx, sbuf, slen) != 0 ||
1.102 markus 972: ssh_digest_update(hashctx, cookie, 8) != 0 ||
973: ssh_digest_final(hashctx, obuf, sizeof(obuf)) != 0) {
974: r = SSH_ERR_LIBCRYPTO_ERROR;
975: goto out;
976: }
1.94 djm 977: memcpy(id, obuf, ssh_digest_bytes(SSH_DIGEST_MD5));
1.102 markus 978: r = 0;
979: out:
980: ssh_digest_free(hashctx);
1.105 djm 981: explicit_bzero(hbuf, sizeof(hbuf));
982: explicit_bzero(sbuf, sizeof(sbuf));
1.98 djm 983: explicit_bzero(obuf, sizeof(obuf));
1.102 markus 984: return r;
1.1 markus 985: }
1.99 markus 986: #endif
1.26 markus 987:
1.84 djm 988: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1.26 markus 989: void
990: dump_digest(char *msg, u_char *digest, int len)
991: {
992: fprintf(stderr, "%s\n", msg);
1.102 markus 993: sshbuf_dump_data(digest, len, stderr);
1.26 markus 994: }
995: #endif
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