Annotation of src/usr.bin/ssh/kex.c, Revision 1.142
1.142 ! djm 1: /* $OpenBSD: kex.c,v 1.141 2018/07/09 13:37:10 sf 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:
1.18 markus 26:
1.76 deraadt 27: #include <signal.h>
1.75 stevesk 28: #include <stdio.h>
1.74 stevesk 29: #include <stdlib.h>
1.72 stevesk 30: #include <string.h>
1.1 markus 31:
1.99 markus 32: #ifdef WITH_OPENSSL
1.76 deraadt 33: #include <openssl/crypto.h>
1.99 markus 34: #endif
1.76 deraadt 35:
1.1 markus 36: #include "ssh2.h"
1.7 markus 37: #include "packet.h"
1.1 markus 38: #include "compat.h"
1.18 markus 39: #include "cipher.h"
1.102 markus 40: #include "sshkey.h"
1.1 markus 41: #include "kex.h"
1.18 markus 42: #include "log.h"
1.21 markus 43: #include "mac.h"
1.23 markus 44: #include "match.h"
1.102 markus 45: #include "misc.h"
1.26 markus 46: #include "dispatch.h"
1.48 provos 47: #include "monitor.h"
1.102 markus 48:
49: #include "ssherr.h"
50: #include "sshbuf.h"
1.94 djm 51: #include "digest.h"
1.48 provos 52:
1.35 itojun 53: /* prototype */
1.102 markus 54: static int kex_choose_conf(struct ssh *);
1.133 markus 55: static int kex_input_newkeys(int, u_int32_t, struct ssh *);
1.86 djm 56:
1.110 djm 57: static const char *proposal_names[PROPOSAL_MAX] = {
58: "KEX algorithms",
59: "host key algorithms",
60: "ciphers ctos",
61: "ciphers stoc",
62: "MACs ctos",
63: "MACs stoc",
64: "compression ctos",
65: "compression stoc",
66: "languages ctos",
67: "languages stoc",
68: };
69:
1.89 djm 70: struct kexalg {
71: char *name;
1.102 markus 72: u_int type;
1.89 djm 73: int ec_nid;
1.94 djm 74: int hash_alg;
1.89 djm 75: };
76: static const struct kexalg kexalgs[] = {
1.99 markus 77: #ifdef WITH_OPENSSL
1.94 djm 78: { KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },
1.118 djm 79: { KEX_DH14_SHA1, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 },
80: { KEX_DH14_SHA256, KEX_DH_GRP14_SHA256, 0, SSH_DIGEST_SHA256 },
81: { KEX_DH16_SHA512, KEX_DH_GRP16_SHA512, 0, SSH_DIGEST_SHA512 },
82: { KEX_DH18_SHA512, KEX_DH_GRP18_SHA512, 0, SSH_DIGEST_SHA512 },
1.94 djm 83: { KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 },
84: { KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 },
85: { KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2,
86: NID_X9_62_prime256v1, SSH_DIGEST_SHA256 },
87: { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1,
88: SSH_DIGEST_SHA384 },
89: { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1,
90: SSH_DIGEST_SHA512 },
1.99 markus 91: #endif
1.94 djm 92: { KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
1.124 djm 93: { KEX_CURVE25519_SHA256_OLD, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
1.94 djm 94: { NULL, -1, -1, -1},
1.89 djm 95: };
96:
97: char *
1.93 dtucker 98: kex_alg_list(char sep)
1.89 djm 99: {
1.102 markus 100: char *ret = NULL, *tmp;
1.89 djm 101: size_t nlen, rlen = 0;
102: const struct kexalg *k;
103:
104: for (k = kexalgs; k->name != NULL; k++) {
105: if (ret != NULL)
1.93 dtucker 106: ret[rlen++] = sep;
1.89 djm 107: nlen = strlen(k->name);
1.102 markus 108: if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
109: free(ret);
110: return NULL;
111: }
112: ret = tmp;
1.89 djm 113: memcpy(ret + rlen, k->name, nlen + 1);
114: rlen += nlen;
115: }
116: return ret;
117: }
118:
119: static const struct kexalg *
120: kex_alg_by_name(const char *name)
121: {
122: const struct kexalg *k;
123:
124: for (k = kexalgs; k->name != NULL; k++) {
125: if (strcmp(k->name, name) == 0)
126: return k;
127: }
128: return NULL;
129: }
130:
1.86 djm 131: /* Validate KEX method name list */
132: int
133: kex_names_valid(const char *names)
134: {
135: char *s, *cp, *p;
136:
137: if (names == NULL || strcmp(names, "") == 0)
138: return 0;
1.102 markus 139: if ((s = cp = strdup(names)) == NULL)
140: return 0;
1.86 djm 141: for ((p = strsep(&cp, ",")); p && *p != '\0';
142: (p = strsep(&cp, ","))) {
1.89 djm 143: if (kex_alg_by_name(p) == NULL) {
1.86 djm 144: error("Unsupported KEX algorithm \"%.100s\"", p);
1.91 djm 145: free(s);
1.86 djm 146: return 0;
147: }
148: }
149: debug3("kex names ok: [%s]", names);
1.91 djm 150: free(s);
1.86 djm 151: return 1;
1.109 djm 152: }
153:
154: /*
155: * Concatenate algorithm names, avoiding duplicates in the process.
156: * Caller must free returned string.
157: */
158: char *
159: kex_names_cat(const char *a, const char *b)
160: {
1.129 dtucker 161: char *ret = NULL, *tmp = NULL, *cp, *p, *m;
1.109 djm 162: size_t len;
163:
164: if (a == NULL || *a == '\0')
1.138 djm 165: return strdup(b);
1.109 djm 166: if (b == NULL || *b == '\0')
167: return strdup(a);
168: if (strlen(b) > 1024*1024)
169: return NULL;
170: len = strlen(a) + strlen(b) + 2;
171: if ((tmp = cp = strdup(b)) == NULL ||
172: (ret = calloc(1, len)) == NULL) {
173: free(tmp);
174: return NULL;
175: }
176: strlcpy(ret, a, len);
177: for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) {
1.129 dtucker 178: if ((m = match_list(ret, p, NULL)) != NULL) {
179: free(m);
1.109 djm 180: continue; /* Algorithm already present */
1.129 dtucker 181: }
1.109 djm 182: if (strlcat(ret, ",", len) >= len ||
183: strlcat(ret, p, len) >= len) {
184: free(tmp);
185: free(ret);
186: return NULL; /* Shouldn't happen */
187: }
188: }
189: free(tmp);
190: return ret;
191: }
192:
193: /*
194: * Assemble a list of algorithms from a default list and a string from a
195: * configuration file. The user-provided string may begin with '+' to
1.128 djm 196: * indicate that it should be appended to the default or '-' that the
197: * specified names should be removed.
1.109 djm 198: */
199: int
1.138 djm 200: kex_assemble_names(char **listp, const char *def, const char *all)
1.109 djm 201: {
1.138 djm 202: char *cp, *tmp, *patterns;
203: char *list = NULL, *ret = NULL, *matching = NULL, *opatterns = NULL;
204: int r = SSH_ERR_INTERNAL_ERROR;
205:
206: if (listp == NULL || *listp == NULL || **listp == '\0') {
207: if ((*listp = strdup(def)) == NULL)
208: return SSH_ERR_ALLOC_FAIL;
209: return 0;
210: }
1.109 djm 211:
1.138 djm 212: list = *listp;
213: *listp = NULL;
214: if (*list == '+') {
215: /* Append names to default list */
216: if ((tmp = kex_names_cat(def, list + 1)) == NULL) {
217: r = SSH_ERR_ALLOC_FAIL;
218: goto fail;
219: }
220: free(list);
221: list = tmp;
222: } else if (*list == '-') {
223: /* Remove names from default list */
224: if ((*listp = match_filter_blacklist(def, list + 1)) == NULL) {
225: r = SSH_ERR_ALLOC_FAIL;
226: goto fail;
227: }
228: free(list);
229: /* filtering has already been done */
1.109 djm 230: return 0;
1.138 djm 231: } else {
232: /* Explicit list, overrides default - just use "list" as is */
233: }
234:
235: /*
236: * The supplied names may be a pattern-list. For the -list case,
237: * the patterns are applied above. For the +list and explicit list
238: * cases we need to do it now.
239: */
240: ret = NULL;
241: if ((patterns = opatterns = strdup(list)) == NULL) {
242: r = SSH_ERR_ALLOC_FAIL;
243: goto fail;
244: }
245: /* Apply positive (i.e. non-negated) patterns from the list */
246: while ((cp = strsep(&patterns, ",")) != NULL) {
247: if (*cp == '!') {
248: /* negated matches are not supported here */
249: r = SSH_ERR_INVALID_ARGUMENT;
250: goto fail;
251: }
252: free(matching);
253: if ((matching = match_filter_whitelist(all, cp)) == NULL) {
254: r = SSH_ERR_ALLOC_FAIL;
255: goto fail;
256: }
257: if ((tmp = kex_names_cat(ret, matching)) == NULL) {
258: r = SSH_ERR_ALLOC_FAIL;
259: goto fail;
260: }
261: free(ret);
262: ret = tmp;
1.109 djm 263: }
1.138 djm 264: if (ret == NULL || *ret == '\0') {
265: /* An empty name-list is an error */
266: /* XXX better error code? */
267: r = SSH_ERR_INVALID_ARGUMENT;
268: goto fail;
1.109 djm 269: }
270:
1.138 djm 271: /* success */
272: *listp = ret;
273: ret = NULL;
274: r = 0;
275:
276: fail:
277: free(matching);
278: free(opatterns);
279: free(list);
280: free(ret);
281: return r;
1.86 djm 282: }
1.26 markus 283:
284: /* put algorithm proposal into buffer */
1.102 markus 285: int
286: kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
1.1 markus 287: {
1.61 djm 288: u_int i;
1.102 markus 289: int r;
290:
291: sshbuf_reset(b);
1.26 markus 292:
1.49 markus 293: /*
294: * add a dummy cookie, the cookie will be overwritten by
295: * kex_send_kexinit(), each time a kexinit is set
296: */
1.102 markus 297: for (i = 0; i < KEX_COOKIE_LEN; i++) {
298: if ((r = sshbuf_put_u8(b, 0)) != 0)
299: return r;
300: }
301: for (i = 0; i < PROPOSAL_MAX; i++) {
302: if ((r = sshbuf_put_cstring(b, proposal[i])) != 0)
303: return r;
304: }
305: if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */
306: (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */
307: return r;
308: return 0;
1.1 markus 309: }
310:
1.26 markus 311: /* parse buffer and return algorithm proposal */
1.102 markus 312: int
313: kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp)
1.7 markus 314: {
1.102 markus 315: struct sshbuf *b = NULL;
316: u_char v;
1.78 djm 317: u_int i;
1.102 markus 318: char **proposal = NULL;
319: int r;
1.7 markus 320:
1.102 markus 321: *propp = NULL;
322: if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL)
323: return SSH_ERR_ALLOC_FAIL;
324: if ((b = sshbuf_fromb(raw)) == NULL) {
325: r = SSH_ERR_ALLOC_FAIL;
326: goto out;
327: }
328: if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */
329: goto out;
1.7 markus 330: /* extract kex init proposal strings */
331: for (i = 0; i < PROPOSAL_MAX; i++) {
1.102 markus 332: if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0)
333: goto out;
1.110 djm 334: debug2("%s: %s", proposal_names[i], proposal[i]);
1.7 markus 335: }
1.26 markus 336: /* first kex follows / reserved */
1.115 djm 337: if ((r = sshbuf_get_u8(b, &v)) != 0 || /* first_kex_follows */
338: (r = sshbuf_get_u32(b, &i)) != 0) /* reserved */
1.102 markus 339: goto out;
1.53 markus 340: if (first_kex_follows != NULL)
1.115 djm 341: *first_kex_follows = v;
1.110 djm 342: debug2("first_kex_follows %d ", v);
343: debug2("reserved %u ", i);
1.102 markus 344: r = 0;
345: *propp = proposal;
346: out:
347: if (r != 0 && proposal != NULL)
348: kex_prop_free(proposal);
349: sshbuf_free(b);
350: return r;
1.1 markus 351: }
352:
1.102 markus 353: void
1.26 markus 354: kex_prop_free(char **proposal)
1.1 markus 355: {
1.61 djm 356: u_int i;
1.26 markus 357:
1.106 djm 358: if (proposal == NULL)
359: return;
1.26 markus 360: for (i = 0; i < PROPOSAL_MAX; i++)
1.91 djm 361: free(proposal[i]);
362: free(proposal);
1.1 markus 363: }
364:
1.78 djm 365: /* ARGSUSED */
1.101 markus 366: static int
1.133 markus 367: kex_protocol_error(int type, u_int32_t seq, struct ssh *ssh)
1.1 markus 368: {
1.112 djm 369: int r;
370:
371: error("kex protocol error: type %d seq %u", type, seq);
372: if ((r = sshpkt_start(ssh, SSH2_MSG_UNIMPLEMENTED)) != 0 ||
373: (r = sshpkt_put_u32(ssh, seq)) != 0 ||
374: (r = sshpkt_send(ssh)) != 0)
375: return r;
1.101 markus 376: return 0;
1.26 markus 377: }
1.1 markus 378:
1.35 itojun 379: static void
1.102 markus 380: kex_reset_dispatch(struct ssh *ssh)
1.29 markus 381: {
1.102 markus 382: ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
1.42 markus 383: SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
1.29 markus 384: }
385:
1.113 markus 386: static int
387: kex_send_ext_info(struct ssh *ssh)
388: {
389: int r;
1.121 djm 390: char *algs;
1.113 markus 391:
1.130 djm 392: if ((algs = sshkey_alg_list(0, 1, 1, ',')) == NULL)
1.121 djm 393: return SSH_ERR_ALLOC_FAIL;
1.137 djm 394: /* XXX filter algs list by allowed pubkey/hostbased types */
1.113 markus 395: if ((r = sshpkt_start(ssh, SSH2_MSG_EXT_INFO)) != 0 ||
396: (r = sshpkt_put_u32(ssh, 1)) != 0 ||
397: (r = sshpkt_put_cstring(ssh, "server-sig-algs")) != 0 ||
1.121 djm 398: (r = sshpkt_put_cstring(ssh, algs)) != 0 ||
1.113 markus 399: (r = sshpkt_send(ssh)) != 0)
1.121 djm 400: goto out;
401: /* success */
402: r = 0;
403: out:
404: free(algs);
1.123 djm 405: return r;
1.113 markus 406: }
407:
1.102 markus 408: int
409: kex_send_newkeys(struct ssh *ssh)
1.26 markus 410: {
1.102 markus 411: int r;
1.28 markus 412:
1.102 markus 413: kex_reset_dispatch(ssh);
414: if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
415: (r = sshpkt_send(ssh)) != 0)
416: return r;
1.26 markus 417: debug("SSH2_MSG_NEWKEYS sent");
1.102 markus 418: debug("expecting SSH2_MSG_NEWKEYS");
419: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
1.113 markus 420: if (ssh->kex->ext_info_c)
421: if ((r = kex_send_ext_info(ssh)) != 0)
422: return r;
1.102 markus 423: return 0;
424: }
425:
1.113 markus 426: int
1.133 markus 427: kex_input_ext_info(int type, u_int32_t seq, struct ssh *ssh)
1.113 markus 428: {
429: struct kex *kex = ssh->kex;
430: u_int32_t i, ninfo;
1.137 djm 431: char *name;
1.134 djm 432: u_char *val;
433: size_t vlen;
1.113 markus 434: int r;
435:
436: debug("SSH2_MSG_EXT_INFO received");
437: ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_protocol_error);
438: if ((r = sshpkt_get_u32(ssh, &ninfo)) != 0)
439: return r;
440: for (i = 0; i < ninfo; i++) {
441: if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0)
442: return r;
1.134 djm 443: if ((r = sshpkt_get_string(ssh, &val, &vlen)) != 0) {
1.113 markus 444: free(name);
445: return r;
446: }
447: if (strcmp(name, "server-sig-algs") == 0) {
1.134 djm 448: /* Ensure no \0 lurking in value */
449: if (memchr(val, '\0', vlen) != NULL) {
450: error("%s: nul byte in %s", __func__, name);
451: return SSH_ERR_INVALID_FORMAT;
452: }
453: debug("%s: %s=<%s>", __func__, name, val);
1.137 djm 454: kex->server_sig_algs = val;
455: val = NULL;
1.134 djm 456: } else
457: debug("%s: %s (unrecognised)", __func__, name);
1.113 markus 458: free(name);
459: free(val);
460: }
461: return sshpkt_get_end(ssh);
462: }
463:
1.102 markus 464: static int
1.133 markus 465: kex_input_newkeys(int type, u_int32_t seq, struct ssh *ssh)
1.102 markus 466: {
467: struct kex *kex = ssh->kex;
468: int r;
1.19 stevesk 469:
1.26 markus 470: debug("SSH2_MSG_NEWKEYS received");
1.102 markus 471: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
1.131 markus 472: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.102 markus 473: if ((r = sshpkt_get_end(ssh)) != 0)
1.122 markus 474: return r;
475: if ((r = ssh_set_newkeys(ssh, MODE_IN)) != 0)
1.102 markus 476: return r;
1.30 markus 477: kex->done = 1;
1.142 ! djm 478: kex->flags &= ~KEX_INITIAL;
1.102 markus 479: sshbuf_reset(kex->peer);
480: /* sshbuf_reset(kex->my); */
1.26 markus 481: kex->flags &= ~KEX_INIT_SENT;
1.91 djm 482: free(kex->name);
1.32 markus 483: kex->name = NULL;
1.102 markus 484: return 0;
1.26 markus 485: }
1.1 markus 486:
1.102 markus 487: int
488: kex_send_kexinit(struct ssh *ssh)
1.26 markus 489: {
1.49 markus 490: u_char *cookie;
1.102 markus 491: struct kex *kex = ssh->kex;
492: int r;
1.49 markus 493:
1.102 markus 494: if (kex == NULL)
495: return SSH_ERR_INTERNAL_ERROR;
496: if (kex->flags & KEX_INIT_SENT)
497: return 0;
1.30 markus 498: kex->done = 0;
1.49 markus 499:
500: /* generate a random cookie */
1.102 markus 501: if (sshbuf_len(kex->my) < KEX_COOKIE_LEN)
502: return SSH_ERR_INVALID_FORMAT;
503: if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL)
504: return SSH_ERR_INTERNAL_ERROR;
505: arc4random_buf(cookie, KEX_COOKIE_LEN);
506:
507: if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
508: (r = sshpkt_putb(ssh, kex->my)) != 0 ||
509: (r = sshpkt_send(ssh)) != 0)
510: return r;
1.26 markus 511: debug("SSH2_MSG_KEXINIT sent");
512: kex->flags |= KEX_INIT_SENT;
1.102 markus 513: return 0;
1.1 markus 514: }
515:
1.78 djm 516: /* ARGSUSED */
1.101 markus 517: int
1.133 markus 518: kex_input_kexinit(int type, u_int32_t seq, struct ssh *ssh)
1.11 provos 519: {
1.102 markus 520: struct kex *kex = ssh->kex;
521: const u_char *ptr;
1.100 markus 522: u_int i;
523: size_t dlen;
1.102 markus 524: int r;
1.11 provos 525:
1.26 markus 526: debug("SSH2_MSG_KEXINIT received");
1.29 markus 527: if (kex == NULL)
1.102 markus 528: return SSH_ERR_INVALID_ARGUMENT;
1.11 provos 529:
1.127 markus 530: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, NULL);
1.102 markus 531: ptr = sshpkt_ptr(ssh, &dlen);
532: if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
533: return r;
1.31 markus 534:
535: /* discard packet */
536: for (i = 0; i < KEX_COOKIE_LEN; i++)
1.102 markus 537: if ((r = sshpkt_get_u8(ssh, NULL)) != 0)
538: return r;
1.31 markus 539: for (i = 0; i < PROPOSAL_MAX; i++)
1.102 markus 540: if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0)
541: return r;
1.87 djm 542: /*
543: * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
544: * KEX method has the server move first, but a server might be using
545: * a custom method or one that we otherwise don't support. We should
546: * be prepared to remember first_kex_follows here so we can eat a
547: * packet later.
548: * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
549: * for cases where the server *doesn't* go first. I guess we should
550: * ignore it when it is set for these cases, which is what we do now.
551: */
1.102 markus 552: if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
553: (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
554: (r = sshpkt_get_end(ssh)) != 0)
555: return r;
556:
557: if (!(kex->flags & KEX_INIT_SENT))
558: if ((r = kex_send_kexinit(ssh)) != 0)
559: return r;
560: if ((r = kex_choose_conf(ssh)) != 0)
561: return r;
1.19 stevesk 562:
1.102 markus 563: if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
564: return (kex->kex[kex->kex_type])(ssh);
565:
566: return SSH_ERR_INTERNAL_ERROR;
567: }
568:
569: int
570: kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp)
571: {
572: struct kex *kex;
573: int r;
574:
575: *kexp = NULL;
576: if ((kex = calloc(1, sizeof(*kex))) == NULL)
577: return SSH_ERR_ALLOC_FAIL;
578: if ((kex->peer = sshbuf_new()) == NULL ||
579: (kex->my = sshbuf_new()) == NULL) {
580: r = SSH_ERR_ALLOC_FAIL;
581: goto out;
582: }
583: if ((r = kex_prop2buf(kex->my, proposal)) != 0)
584: goto out;
585: kex->done = 0;
1.142 ! djm 586: kex->flags = KEX_INITIAL;
1.102 markus 587: kex_reset_dispatch(ssh);
1.131 markus 588: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.102 markus 589: r = 0;
590: *kexp = kex;
591: out:
592: if (r != 0)
593: kex_free(kex);
594: return r;
1.26 markus 595: }
1.11 provos 596:
1.100 markus 597: void
598: kex_free_newkeys(struct newkeys *newkeys)
599: {
600: if (newkeys == NULL)
601: return;
602: if (newkeys->enc.key) {
603: explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
604: free(newkeys->enc.key);
605: newkeys->enc.key = NULL;
606: }
607: if (newkeys->enc.iv) {
1.111 djm 608: explicit_bzero(newkeys->enc.iv, newkeys->enc.iv_len);
1.100 markus 609: free(newkeys->enc.iv);
610: newkeys->enc.iv = NULL;
611: }
612: free(newkeys->enc.name);
613: explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
614: free(newkeys->comp.name);
615: explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
616: mac_clear(&newkeys->mac);
617: if (newkeys->mac.key) {
618: explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
619: free(newkeys->mac.key);
620: newkeys->mac.key = NULL;
621: }
622: free(newkeys->mac.name);
623: explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
624: explicit_bzero(newkeys, sizeof(*newkeys));
625: free(newkeys);
626: }
627:
1.102 markus 628: void
629: kex_free(struct kex *kex)
1.26 markus 630: {
1.102 markus 631: u_int mode;
1.11 provos 632:
1.102 markus 633: #ifdef WITH_OPENSSL
1.136 jsing 634: DH_free(kex->dh);
635: EC_KEY_free(kex->ec_client_key);
1.102 markus 636: #endif
637: for (mode = 0; mode < MODE_MAX; mode++) {
638: kex_free_newkeys(kex->newkeys[mode]);
639: kex->newkeys[mode] = NULL;
1.100 markus 640: }
1.102 markus 641: sshbuf_free(kex->peer);
642: sshbuf_free(kex->my);
643: free(kex->session_id);
644: free(kex->client_version_string);
645: free(kex->server_version_string);
1.107 djm 646: free(kex->failed_choice);
1.113 markus 647: free(kex->hostkey_alg);
648: free(kex->name);
1.102 markus 649: free(kex);
1.11 provos 650: }
651:
1.102 markus 652: int
653: kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
1.1 markus 654: {
1.102 markus 655: int r;
1.1 markus 656:
1.102 markus 657: if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0)
658: return r;
659: if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
660: kex_free(ssh->kex);
661: ssh->kex = NULL;
662: return r;
1.1 markus 663: }
1.102 markus 664: return 0;
1.117 djm 665: }
666:
667: /*
668: * Request key re-exchange, returns 0 on success or a ssherr.h error
669: * code otherwise. Must not be called if KEX is incomplete or in-progress.
670: */
671: int
672: kex_start_rekex(struct ssh *ssh)
673: {
674: if (ssh->kex == NULL) {
675: error("%s: no kex", __func__);
676: return SSH_ERR_INTERNAL_ERROR;
677: }
678: if (ssh->kex->done == 0) {
679: error("%s: requested twice", __func__);
680: return SSH_ERR_INTERNAL_ERROR;
681: }
682: ssh->kex->done = 0;
683: return kex_send_kexinit(ssh);
1.1 markus 684: }
685:
1.102 markus 686: static int
687: choose_enc(struct sshenc *enc, char *client, char *server)
1.1 markus 688: {
1.23 markus 689: char *name = match_list(client, server, NULL);
1.102 markus 690:
1.1 markus 691: if (name == NULL)
1.102 markus 692: return SSH_ERR_NO_CIPHER_ALG_MATCH;
1.129 dtucker 693: if ((enc->cipher = cipher_by_name(name)) == NULL) {
694: free(name);
1.102 markus 695: return SSH_ERR_INTERNAL_ERROR;
1.129 dtucker 696: }
1.1 markus 697: enc->name = name;
698: enc->enabled = 0;
699: enc->iv = NULL;
1.88 markus 700: enc->iv_len = cipher_ivlen(enc->cipher);
1.1 markus 701: enc->key = NULL;
1.45 markus 702: enc->key_len = cipher_keylen(enc->cipher);
703: enc->block_size = cipher_blocksize(enc->cipher);
1.102 markus 704: return 0;
1.1 markus 705: }
1.69 deraadt 706:
1.102 markus 707: static int
708: choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
1.1 markus 709: {
1.23 markus 710: char *name = match_list(client, server, NULL);
1.102 markus 711:
1.1 markus 712: if (name == NULL)
1.102 markus 713: return SSH_ERR_NO_MAC_ALG_MATCH;
1.129 dtucker 714: if (mac_setup(mac, name) < 0) {
715: free(name);
1.102 markus 716: return SSH_ERR_INTERNAL_ERROR;
1.129 dtucker 717: }
1.1 markus 718: mac->name = name;
719: mac->key = NULL;
720: mac->enabled = 0;
1.102 markus 721: return 0;
1.1 markus 722: }
1.69 deraadt 723:
1.102 markus 724: static int
725: choose_comp(struct sshcomp *comp, char *client, char *server)
1.1 markus 726: {
1.23 markus 727: char *name = match_list(client, server, NULL);
1.102 markus 728:
1.1 markus 729: if (name == NULL)
1.102 markus 730: return SSH_ERR_NO_COMPRESS_ALG_MATCH;
1.64 markus 731: if (strcmp(name, "zlib@openssh.com") == 0) {
1.141 sf 732: comp->type = COMP_DELAYED;
733: } else if (strcmp(name, "zlib") == 0) {
1.140 sf 734: comp->type = COMP_ZLIB;
1.1 markus 735: } else if (strcmp(name, "none") == 0) {
1.64 markus 736: comp->type = COMP_NONE;
1.1 markus 737: } else {
1.129 dtucker 738: free(name);
1.102 markus 739: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 740: }
741: comp->name = name;
1.102 markus 742: return 0;
1.1 markus 743: }
1.69 deraadt 744:
1.102 markus 745: static int
746: choose_kex(struct kex *k, char *client, char *server)
1.1 markus 747: {
1.89 djm 748: const struct kexalg *kexalg;
749:
1.23 markus 750: k->name = match_list(client, server, NULL);
1.102 markus 751:
1.110 djm 752: debug("kex: algorithm: %s", k->name ? k->name : "(no match)");
1.1 markus 753: if (k->name == NULL)
1.102 markus 754: return SSH_ERR_NO_KEX_ALG_MATCH;
1.89 djm 755: if ((kexalg = kex_alg_by_name(k->name)) == NULL)
1.102 markus 756: return SSH_ERR_INTERNAL_ERROR;
1.89 djm 757: k->kex_type = kexalg->type;
1.94 djm 758: k->hash_alg = kexalg->hash_alg;
1.89 djm 759: k->ec_nid = kexalg->ec_nid;
1.102 markus 760: return 0;
1.1 markus 761: }
1.65 djm 762:
1.102 markus 763: static int
764: choose_hostkeyalg(struct kex *k, char *client, char *server)
1.1 markus 765: {
1.113 markus 766: k->hostkey_alg = match_list(client, server, NULL);
1.102 markus 767:
1.110 djm 768: debug("kex: host key algorithm: %s",
1.113 markus 769: k->hostkey_alg ? k->hostkey_alg : "(no match)");
770: if (k->hostkey_alg == NULL)
1.102 markus 771: return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
1.113 markus 772: k->hostkey_type = sshkey_type_from_name(k->hostkey_alg);
1.13 markus 773: if (k->hostkey_type == KEY_UNSPEC)
1.102 markus 774: return SSH_ERR_INTERNAL_ERROR;
1.113 markus 775: k->hostkey_nid = sshkey_ecdsa_nid_from_name(k->hostkey_alg);
1.102 markus 776: return 0;
1.1 markus 777: }
778:
1.56 djm 779: static int
1.53 markus 780: proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
781: {
782: static int check[] = {
783: PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
784: };
785: int *idx;
786: char *p;
787:
788: for (idx = &check[0]; *idx != -1; idx++) {
789: if ((p = strchr(my[*idx], ',')) != NULL)
790: *p = '\0';
791: if ((p = strchr(peer[*idx], ',')) != NULL)
792: *p = '\0';
793: if (strcmp(my[*idx], peer[*idx]) != 0) {
794: debug2("proposal mismatch: my %s peer %s",
795: my[*idx], peer[*idx]);
796: return (0);
797: }
798: }
799: debug2("proposals match");
800: return (1);
801: }
802:
1.102 markus 803: static int
804: kex_choose_conf(struct ssh *ssh)
1.1 markus 805: {
1.102 markus 806: struct kex *kex = ssh->kex;
807: struct newkeys *newkeys;
808: char **my = NULL, **peer = NULL;
1.26 markus 809: char **cprop, **sprop;
1.27 markus 810: int nenc, nmac, ncomp;
1.96 dtucker 811: u_int mode, ctos, need, dh_need, authlen;
1.102 markus 812: int r, first_kex_follows;
1.1 markus 813:
1.110 djm 814: debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
815: if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
816: goto out;
817: debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
818: if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
1.102 markus 819: goto out;
1.26 markus 820:
1.27 markus 821: if (kex->server) {
1.26 markus 822: cprop=peer;
823: sprop=my;
824: } else {
825: cprop=my;
826: sprop=peer;
1.113 markus 827: }
828:
829: /* Check whether client supports ext_info_c */
1.142 ! djm 830: if (kex->server && (kex->flags & KEX_INITIAL)) {
1.113 markus 831: char *ext;
832:
833: ext = match_list("ext-info-c", peer[PROPOSAL_KEX_ALGS], NULL);
1.119 markus 834: kex->ext_info_c = (ext != NULL);
835: free(ext);
1.26 markus 836: }
1.1 markus 837:
1.30 markus 838: /* Algorithm Negotiation */
1.110 djm 839: if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
840: sprop[PROPOSAL_KEX_ALGS])) != 0) {
841: kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
842: peer[PROPOSAL_KEX_ALGS] = NULL;
843: goto out;
844: }
845: if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
846: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
847: kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
848: peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
849: goto out;
850: }
1.1 markus 851: for (mode = 0; mode < MODE_MAX; mode++) {
1.102 markus 852: if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
853: r = SSH_ERR_ALLOC_FAIL;
854: goto out;
855: }
1.30 markus 856: kex->newkeys[mode] = newkeys;
1.78 djm 857: ctos = (!kex->server && mode == MODE_OUT) ||
858: (kex->server && mode == MODE_IN);
1.1 markus 859: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
860: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
861: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.102 markus 862: if ((r = choose_enc(&newkeys->enc, cprop[nenc],
1.107 djm 863: sprop[nenc])) != 0) {
864: kex->failed_choice = peer[nenc];
865: peer[nenc] = NULL;
1.102 markus 866: goto out;
1.107 djm 867: }
1.102 markus 868: authlen = cipher_authlen(newkeys->enc.cipher);
1.88 markus 869: /* ignore mac for authenticated encryption */
1.102 markus 870: if (authlen == 0 &&
871: (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
1.107 djm 872: sprop[nmac])) != 0) {
873: kex->failed_choice = peer[nmac];
874: peer[nmac] = NULL;
1.102 markus 875: goto out;
1.107 djm 876: }
1.102 markus 877: if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
1.107 djm 878: sprop[ncomp])) != 0) {
879: kex->failed_choice = peer[ncomp];
880: peer[ncomp] = NULL;
1.102 markus 881: goto out;
1.107 djm 882: }
1.110 djm 883: debug("kex: %s cipher: %s MAC: %s compression: %s",
1.1 markus 884: ctos ? "client->server" : "server->client",
1.27 markus 885: newkeys->enc.name,
1.88 markus 886: authlen == 0 ? newkeys->mac.name : "<implicit>",
1.27 markus 887: newkeys->comp.name);
1.107 djm 888: }
1.96 dtucker 889: need = dh_need = 0;
1.1 markus 890: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 891: newkeys = kex->newkeys[mode];
1.120 deraadt 892: need = MAXIMUM(need, newkeys->enc.key_len);
893: need = MAXIMUM(need, newkeys->enc.block_size);
894: need = MAXIMUM(need, newkeys->enc.iv_len);
895: need = MAXIMUM(need, newkeys->mac.key_len);
896: dh_need = MAXIMUM(dh_need, cipher_seclen(newkeys->enc.cipher));
897: dh_need = MAXIMUM(dh_need, newkeys->enc.block_size);
898: dh_need = MAXIMUM(dh_need, newkeys->enc.iv_len);
899: dh_need = MAXIMUM(dh_need, newkeys->mac.key_len);
1.1 markus 900: }
1.7 markus 901: /* XXX need runden? */
1.27 markus 902: kex->we_need = need;
1.96 dtucker 903: kex->dh_need = dh_need;
1.53 markus 904:
905: /* ignore the next message if the proposals do not match */
1.135 djm 906: if (first_kex_follows && !proposals_match(my, peer))
1.102 markus 907: ssh->dispatch_skip_packets = 1;
908: r = 0;
909: out:
1.26 markus 910: kex_prop_free(my);
911: kex_prop_free(peer);
1.102 markus 912: return r;
1.26 markus 913: }
914:
1.102 markus 915: static int
916: derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
917: const struct sshbuf *shared_secret, u_char **keyp)
1.26 markus 918: {
1.102 markus 919: struct kex *kex = ssh->kex;
920: struct ssh_digest_ctx *hashctx = NULL;
1.26 markus 921: char c = id;
1.61 djm 922: u_int have;
1.94 djm 923: size_t mdsz;
1.61 djm 924: u_char *digest;
1.102 markus 925: int r;
1.62 djm 926:
1.94 djm 927: if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
1.102 markus 928: return SSH_ERR_INVALID_ARGUMENT;
1.120 deraadt 929: if ((digest = calloc(1, ROUNDUP(need, mdsz))) == NULL) {
1.102 markus 930: r = SSH_ERR_ALLOC_FAIL;
931: goto out;
932: }
1.26 markus 933:
1.30 markus 934: /* K1 = HASH(K || H || "A" || session_id) */
1.102 markus 935: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
936: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 937: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
938: ssh_digest_update(hashctx, &c, 1) != 0 ||
939: ssh_digest_update(hashctx, kex->session_id,
1.102 markus 940: kex->session_id_len) != 0 ||
941: ssh_digest_final(hashctx, digest, mdsz) != 0) {
942: r = SSH_ERR_LIBCRYPTO_ERROR;
943: goto out;
944: }
1.94 djm 945: ssh_digest_free(hashctx);
1.102 markus 946: hashctx = NULL;
1.26 markus 947:
1.30 markus 948: /*
949: * expand key:
950: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
951: * Key = K1 || K2 || ... || Kn
952: */
1.26 markus 953: for (have = mdsz; need > have; have += mdsz) {
1.102 markus 954: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
955: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 956: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1.102 markus 957: ssh_digest_update(hashctx, digest, have) != 0 ||
958: ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
959: r = SSH_ERR_LIBCRYPTO_ERROR;
960: goto out;
961: }
1.94 djm 962: ssh_digest_free(hashctx);
1.102 markus 963: hashctx = NULL;
1.26 markus 964: }
965: #ifdef DEBUG_KEX
966: fprintf(stderr, "key '%c'== ", c);
967: dump_digest("key", digest, need);
968: #endif
1.102 markus 969: *keyp = digest;
970: digest = NULL;
971: r = 0;
972: out:
1.114 mmcc 973: free(digest);
1.102 markus 974: ssh_digest_free(hashctx);
975: return r;
1.1 markus 976: }
977:
1.23 markus 978: #define NKEYS 6
1.102 markus 979: int
980: kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
981: const struct sshbuf *shared_secret)
1.1 markus 982: {
1.102 markus 983: struct kex *kex = ssh->kex;
1.15 markus 984: u_char *keys[NKEYS];
1.102 markus 985: u_int i, j, mode, ctos;
986: int r;
1.1 markus 987:
1.65 djm 988: for (i = 0; i < NKEYS; i++) {
1.102 markus 989: if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
990: shared_secret, &keys[i])) != 0) {
991: for (j = 0; j < i; j++)
992: free(keys[j]);
993: return r;
994: }
1.65 djm 995: }
1.1 markus 996: for (mode = 0; mode < MODE_MAX; mode++) {
1.69 deraadt 997: ctos = (!kex->server && mode == MODE_OUT) ||
998: (kex->server && mode == MODE_IN);
1.100 markus 999: kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
1000: kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
1001: kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
1.1 markus 1002: }
1.102 markus 1003: return 0;
1.95 djm 1004: }
1005:
1.99 markus 1006: #ifdef WITH_OPENSSL
1.102 markus 1007: int
1008: kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen,
1009: const BIGNUM *secret)
1.95 djm 1010: {
1.102 markus 1011: struct sshbuf *shared_secret;
1012: int r;
1.95 djm 1013:
1.102 markus 1014: if ((shared_secret = sshbuf_new()) == NULL)
1015: return SSH_ERR_ALLOC_FAIL;
1016: if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0)
1017: r = kex_derive_keys(ssh, hash, hashlen, shared_secret);
1018: sshbuf_free(shared_secret);
1019: return r;
1.27 markus 1020: }
1.99 markus 1021: #endif
1.57 djm 1022:
1.26 markus 1023:
1.84 djm 1024: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1.26 markus 1025: void
1026: dump_digest(char *msg, u_char *digest, int len)
1027: {
1028: fprintf(stderr, "%s\n", msg);
1.102 markus 1029: sshbuf_dump_data(digest, len, stderr);
1.26 markus 1030: }
1031: #endif
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