Annotation of src/usr.bin/ssh/kex.c, Revision 1.141
1.141 ! sf 1: /* $OpenBSD: kex.c,v 1.140 2018/07/06 09:06:14 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;
1.102 markus 478: sshbuf_reset(kex->peer);
479: /* sshbuf_reset(kex->my); */
1.26 markus 480: kex->flags &= ~KEX_INIT_SENT;
1.91 djm 481: free(kex->name);
1.32 markus 482: kex->name = NULL;
1.102 markus 483: return 0;
1.26 markus 484: }
1.1 markus 485:
1.102 markus 486: int
487: kex_send_kexinit(struct ssh *ssh)
1.26 markus 488: {
1.49 markus 489: u_char *cookie;
1.102 markus 490: struct kex *kex = ssh->kex;
491: int r;
1.49 markus 492:
1.102 markus 493: if (kex == NULL)
494: return SSH_ERR_INTERNAL_ERROR;
495: if (kex->flags & KEX_INIT_SENT)
496: return 0;
1.30 markus 497: kex->done = 0;
1.49 markus 498:
499: /* generate a random cookie */
1.102 markus 500: if (sshbuf_len(kex->my) < KEX_COOKIE_LEN)
501: return SSH_ERR_INVALID_FORMAT;
502: if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL)
503: return SSH_ERR_INTERNAL_ERROR;
504: arc4random_buf(cookie, KEX_COOKIE_LEN);
505:
506: if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
507: (r = sshpkt_putb(ssh, kex->my)) != 0 ||
508: (r = sshpkt_send(ssh)) != 0)
509: return r;
1.26 markus 510: debug("SSH2_MSG_KEXINIT sent");
511: kex->flags |= KEX_INIT_SENT;
1.102 markus 512: return 0;
1.1 markus 513: }
514:
1.78 djm 515: /* ARGSUSED */
1.101 markus 516: int
1.133 markus 517: kex_input_kexinit(int type, u_int32_t seq, struct ssh *ssh)
1.11 provos 518: {
1.102 markus 519: struct kex *kex = ssh->kex;
520: const u_char *ptr;
1.100 markus 521: u_int i;
522: size_t dlen;
1.102 markus 523: int r;
1.11 provos 524:
1.26 markus 525: debug("SSH2_MSG_KEXINIT received");
1.29 markus 526: if (kex == NULL)
1.102 markus 527: return SSH_ERR_INVALID_ARGUMENT;
1.11 provos 528:
1.127 markus 529: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, NULL);
1.102 markus 530: ptr = sshpkt_ptr(ssh, &dlen);
531: if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
532: return r;
1.31 markus 533:
534: /* discard packet */
535: for (i = 0; i < KEX_COOKIE_LEN; i++)
1.102 markus 536: if ((r = sshpkt_get_u8(ssh, NULL)) != 0)
537: return r;
1.31 markus 538: for (i = 0; i < PROPOSAL_MAX; i++)
1.102 markus 539: if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0)
540: return r;
1.87 djm 541: /*
542: * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
543: * KEX method has the server move first, but a server might be using
544: * a custom method or one that we otherwise don't support. We should
545: * be prepared to remember first_kex_follows here so we can eat a
546: * packet later.
547: * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
548: * for cases where the server *doesn't* go first. I guess we should
549: * ignore it when it is set for these cases, which is what we do now.
550: */
1.102 markus 551: if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
552: (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
553: (r = sshpkt_get_end(ssh)) != 0)
554: return r;
555:
556: if (!(kex->flags & KEX_INIT_SENT))
557: if ((r = kex_send_kexinit(ssh)) != 0)
558: return r;
559: if ((r = kex_choose_conf(ssh)) != 0)
560: return r;
1.19 stevesk 561:
1.102 markus 562: if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
563: return (kex->kex[kex->kex_type])(ssh);
564:
565: return SSH_ERR_INTERNAL_ERROR;
566: }
567:
568: int
569: kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp)
570: {
571: struct kex *kex;
572: int r;
573:
574: *kexp = NULL;
575: if ((kex = calloc(1, sizeof(*kex))) == NULL)
576: return SSH_ERR_ALLOC_FAIL;
577: if ((kex->peer = sshbuf_new()) == NULL ||
578: (kex->my = sshbuf_new()) == NULL) {
579: r = SSH_ERR_ALLOC_FAIL;
580: goto out;
581: }
582: if ((r = kex_prop2buf(kex->my, proposal)) != 0)
583: goto out;
584: kex->done = 0;
585: kex_reset_dispatch(ssh);
1.131 markus 586: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.102 markus 587: r = 0;
588: *kexp = kex;
589: out:
590: if (r != 0)
591: kex_free(kex);
592: return r;
1.26 markus 593: }
1.11 provos 594:
1.100 markus 595: void
596: kex_free_newkeys(struct newkeys *newkeys)
597: {
598: if (newkeys == NULL)
599: return;
600: if (newkeys->enc.key) {
601: explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
602: free(newkeys->enc.key);
603: newkeys->enc.key = NULL;
604: }
605: if (newkeys->enc.iv) {
1.111 djm 606: explicit_bzero(newkeys->enc.iv, newkeys->enc.iv_len);
1.100 markus 607: free(newkeys->enc.iv);
608: newkeys->enc.iv = NULL;
609: }
610: free(newkeys->enc.name);
611: explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
612: free(newkeys->comp.name);
613: explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
614: mac_clear(&newkeys->mac);
615: if (newkeys->mac.key) {
616: explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
617: free(newkeys->mac.key);
618: newkeys->mac.key = NULL;
619: }
620: free(newkeys->mac.name);
621: explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
622: explicit_bzero(newkeys, sizeof(*newkeys));
623: free(newkeys);
624: }
625:
1.102 markus 626: void
627: kex_free(struct kex *kex)
1.26 markus 628: {
1.102 markus 629: u_int mode;
1.11 provos 630:
1.102 markus 631: #ifdef WITH_OPENSSL
1.136 jsing 632: DH_free(kex->dh);
633: EC_KEY_free(kex->ec_client_key);
1.102 markus 634: #endif
635: for (mode = 0; mode < MODE_MAX; mode++) {
636: kex_free_newkeys(kex->newkeys[mode]);
637: kex->newkeys[mode] = NULL;
1.100 markus 638: }
1.102 markus 639: sshbuf_free(kex->peer);
640: sshbuf_free(kex->my);
641: free(kex->session_id);
642: free(kex->client_version_string);
643: free(kex->server_version_string);
1.107 djm 644: free(kex->failed_choice);
1.113 markus 645: free(kex->hostkey_alg);
646: free(kex->name);
1.102 markus 647: free(kex);
1.11 provos 648: }
649:
1.102 markus 650: int
651: kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
1.1 markus 652: {
1.102 markus 653: int r;
1.1 markus 654:
1.102 markus 655: if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0)
656: return r;
657: if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
658: kex_free(ssh->kex);
659: ssh->kex = NULL;
660: return r;
1.1 markus 661: }
1.102 markus 662: return 0;
1.117 djm 663: }
664:
665: /*
666: * Request key re-exchange, returns 0 on success or a ssherr.h error
667: * code otherwise. Must not be called if KEX is incomplete or in-progress.
668: */
669: int
670: kex_start_rekex(struct ssh *ssh)
671: {
672: if (ssh->kex == NULL) {
673: error("%s: no kex", __func__);
674: return SSH_ERR_INTERNAL_ERROR;
675: }
676: if (ssh->kex->done == 0) {
677: error("%s: requested twice", __func__);
678: return SSH_ERR_INTERNAL_ERROR;
679: }
680: ssh->kex->done = 0;
681: return kex_send_kexinit(ssh);
1.1 markus 682: }
683:
1.102 markus 684: static int
685: choose_enc(struct sshenc *enc, char *client, char *server)
1.1 markus 686: {
1.23 markus 687: char *name = match_list(client, server, NULL);
1.102 markus 688:
1.1 markus 689: if (name == NULL)
1.102 markus 690: return SSH_ERR_NO_CIPHER_ALG_MATCH;
1.129 dtucker 691: if ((enc->cipher = cipher_by_name(name)) == NULL) {
692: free(name);
1.102 markus 693: return SSH_ERR_INTERNAL_ERROR;
1.129 dtucker 694: }
1.1 markus 695: enc->name = name;
696: enc->enabled = 0;
697: enc->iv = NULL;
1.88 markus 698: enc->iv_len = cipher_ivlen(enc->cipher);
1.1 markus 699: enc->key = NULL;
1.45 markus 700: enc->key_len = cipher_keylen(enc->cipher);
701: enc->block_size = cipher_blocksize(enc->cipher);
1.102 markus 702: return 0;
1.1 markus 703: }
1.69 deraadt 704:
1.102 markus 705: static int
706: choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
1.1 markus 707: {
1.23 markus 708: char *name = match_list(client, server, NULL);
1.102 markus 709:
1.1 markus 710: if (name == NULL)
1.102 markus 711: return SSH_ERR_NO_MAC_ALG_MATCH;
1.129 dtucker 712: if (mac_setup(mac, name) < 0) {
713: free(name);
1.102 markus 714: return SSH_ERR_INTERNAL_ERROR;
1.129 dtucker 715: }
1.1 markus 716: mac->name = name;
717: mac->key = NULL;
718: mac->enabled = 0;
1.102 markus 719: return 0;
1.1 markus 720: }
1.69 deraadt 721:
1.102 markus 722: static int
723: choose_comp(struct sshcomp *comp, char *client, char *server)
1.1 markus 724: {
1.23 markus 725: char *name = match_list(client, server, NULL);
1.102 markus 726:
1.1 markus 727: if (name == NULL)
1.102 markus 728: return SSH_ERR_NO_COMPRESS_ALG_MATCH;
1.64 markus 729: if (strcmp(name, "zlib@openssh.com") == 0) {
1.141 ! sf 730: comp->type = COMP_DELAYED;
! 731: } else if (strcmp(name, "zlib") == 0) {
1.140 sf 732: comp->type = COMP_ZLIB;
1.1 markus 733: } else if (strcmp(name, "none") == 0) {
1.64 markus 734: comp->type = COMP_NONE;
1.1 markus 735: } else {
1.129 dtucker 736: free(name);
1.102 markus 737: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 738: }
739: comp->name = name;
1.102 markus 740: return 0;
1.1 markus 741: }
1.69 deraadt 742:
1.102 markus 743: static int
744: choose_kex(struct kex *k, char *client, char *server)
1.1 markus 745: {
1.89 djm 746: const struct kexalg *kexalg;
747:
1.23 markus 748: k->name = match_list(client, server, NULL);
1.102 markus 749:
1.110 djm 750: debug("kex: algorithm: %s", k->name ? k->name : "(no match)");
1.1 markus 751: if (k->name == NULL)
1.102 markus 752: return SSH_ERR_NO_KEX_ALG_MATCH;
1.89 djm 753: if ((kexalg = kex_alg_by_name(k->name)) == NULL)
1.102 markus 754: return SSH_ERR_INTERNAL_ERROR;
1.89 djm 755: k->kex_type = kexalg->type;
1.94 djm 756: k->hash_alg = kexalg->hash_alg;
1.89 djm 757: k->ec_nid = kexalg->ec_nid;
1.102 markus 758: return 0;
1.1 markus 759: }
1.65 djm 760:
1.102 markus 761: static int
762: choose_hostkeyalg(struct kex *k, char *client, char *server)
1.1 markus 763: {
1.113 markus 764: k->hostkey_alg = match_list(client, server, NULL);
1.102 markus 765:
1.110 djm 766: debug("kex: host key algorithm: %s",
1.113 markus 767: k->hostkey_alg ? k->hostkey_alg : "(no match)");
768: if (k->hostkey_alg == NULL)
1.102 markus 769: return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
1.113 markus 770: k->hostkey_type = sshkey_type_from_name(k->hostkey_alg);
1.13 markus 771: if (k->hostkey_type == KEY_UNSPEC)
1.102 markus 772: return SSH_ERR_INTERNAL_ERROR;
1.113 markus 773: k->hostkey_nid = sshkey_ecdsa_nid_from_name(k->hostkey_alg);
1.102 markus 774: return 0;
1.1 markus 775: }
776:
1.56 djm 777: static int
1.53 markus 778: proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
779: {
780: static int check[] = {
781: PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
782: };
783: int *idx;
784: char *p;
785:
786: for (idx = &check[0]; *idx != -1; idx++) {
787: if ((p = strchr(my[*idx], ',')) != NULL)
788: *p = '\0';
789: if ((p = strchr(peer[*idx], ',')) != NULL)
790: *p = '\0';
791: if (strcmp(my[*idx], peer[*idx]) != 0) {
792: debug2("proposal mismatch: my %s peer %s",
793: my[*idx], peer[*idx]);
794: return (0);
795: }
796: }
797: debug2("proposals match");
798: return (1);
799: }
800:
1.102 markus 801: static int
802: kex_choose_conf(struct ssh *ssh)
1.1 markus 803: {
1.102 markus 804: struct kex *kex = ssh->kex;
805: struct newkeys *newkeys;
806: char **my = NULL, **peer = NULL;
1.26 markus 807: char **cprop, **sprop;
1.27 markus 808: int nenc, nmac, ncomp;
1.96 dtucker 809: u_int mode, ctos, need, dh_need, authlen;
1.102 markus 810: int r, first_kex_follows;
1.1 markus 811:
1.110 djm 812: debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
813: if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
814: goto out;
815: debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
816: if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
1.102 markus 817: goto out;
1.26 markus 818:
1.27 markus 819: if (kex->server) {
1.26 markus 820: cprop=peer;
821: sprop=my;
822: } else {
823: cprop=my;
824: sprop=peer;
1.113 markus 825: }
826:
827: /* Check whether client supports ext_info_c */
828: if (kex->server) {
829: char *ext;
830:
831: ext = match_list("ext-info-c", peer[PROPOSAL_KEX_ALGS], NULL);
1.119 markus 832: kex->ext_info_c = (ext != NULL);
833: free(ext);
1.26 markus 834: }
1.1 markus 835:
1.30 markus 836: /* Algorithm Negotiation */
1.110 djm 837: if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
838: sprop[PROPOSAL_KEX_ALGS])) != 0) {
839: kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
840: peer[PROPOSAL_KEX_ALGS] = NULL;
841: goto out;
842: }
843: if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
844: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
845: kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
846: peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
847: goto out;
848: }
1.1 markus 849: for (mode = 0; mode < MODE_MAX; mode++) {
1.102 markus 850: if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
851: r = SSH_ERR_ALLOC_FAIL;
852: goto out;
853: }
1.30 markus 854: kex->newkeys[mode] = newkeys;
1.78 djm 855: ctos = (!kex->server && mode == MODE_OUT) ||
856: (kex->server && mode == MODE_IN);
1.1 markus 857: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
858: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
859: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.102 markus 860: if ((r = choose_enc(&newkeys->enc, cprop[nenc],
1.107 djm 861: sprop[nenc])) != 0) {
862: kex->failed_choice = peer[nenc];
863: peer[nenc] = NULL;
1.102 markus 864: goto out;
1.107 djm 865: }
1.102 markus 866: authlen = cipher_authlen(newkeys->enc.cipher);
1.88 markus 867: /* ignore mac for authenticated encryption */
1.102 markus 868: if (authlen == 0 &&
869: (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
1.107 djm 870: sprop[nmac])) != 0) {
871: kex->failed_choice = peer[nmac];
872: peer[nmac] = NULL;
1.102 markus 873: goto out;
1.107 djm 874: }
1.102 markus 875: if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
1.107 djm 876: sprop[ncomp])) != 0) {
877: kex->failed_choice = peer[ncomp];
878: peer[ncomp] = NULL;
1.102 markus 879: goto out;
1.107 djm 880: }
1.110 djm 881: debug("kex: %s cipher: %s MAC: %s compression: %s",
1.1 markus 882: ctos ? "client->server" : "server->client",
1.27 markus 883: newkeys->enc.name,
1.88 markus 884: authlen == 0 ? newkeys->mac.name : "<implicit>",
1.27 markus 885: newkeys->comp.name);
1.107 djm 886: }
1.96 dtucker 887: need = dh_need = 0;
1.1 markus 888: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 889: newkeys = kex->newkeys[mode];
1.120 deraadt 890: need = MAXIMUM(need, newkeys->enc.key_len);
891: need = MAXIMUM(need, newkeys->enc.block_size);
892: need = MAXIMUM(need, newkeys->enc.iv_len);
893: need = MAXIMUM(need, newkeys->mac.key_len);
894: dh_need = MAXIMUM(dh_need, cipher_seclen(newkeys->enc.cipher));
895: dh_need = MAXIMUM(dh_need, newkeys->enc.block_size);
896: dh_need = MAXIMUM(dh_need, newkeys->enc.iv_len);
897: dh_need = MAXIMUM(dh_need, newkeys->mac.key_len);
1.1 markus 898: }
1.7 markus 899: /* XXX need runden? */
1.27 markus 900: kex->we_need = need;
1.96 dtucker 901: kex->dh_need = dh_need;
1.53 markus 902:
903: /* ignore the next message if the proposals do not match */
1.135 djm 904: if (first_kex_follows && !proposals_match(my, peer))
1.102 markus 905: ssh->dispatch_skip_packets = 1;
906: r = 0;
907: out:
1.26 markus 908: kex_prop_free(my);
909: kex_prop_free(peer);
1.102 markus 910: return r;
1.26 markus 911: }
912:
1.102 markus 913: static int
914: derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
915: const struct sshbuf *shared_secret, u_char **keyp)
1.26 markus 916: {
1.102 markus 917: struct kex *kex = ssh->kex;
918: struct ssh_digest_ctx *hashctx = NULL;
1.26 markus 919: char c = id;
1.61 djm 920: u_int have;
1.94 djm 921: size_t mdsz;
1.61 djm 922: u_char *digest;
1.102 markus 923: int r;
1.62 djm 924:
1.94 djm 925: if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
1.102 markus 926: return SSH_ERR_INVALID_ARGUMENT;
1.120 deraadt 927: if ((digest = calloc(1, ROUNDUP(need, mdsz))) == NULL) {
1.102 markus 928: r = SSH_ERR_ALLOC_FAIL;
929: goto out;
930: }
1.26 markus 931:
1.30 markus 932: /* K1 = HASH(K || H || "A" || session_id) */
1.102 markus 933: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
934: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 935: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
936: ssh_digest_update(hashctx, &c, 1) != 0 ||
937: ssh_digest_update(hashctx, kex->session_id,
1.102 markus 938: kex->session_id_len) != 0 ||
939: ssh_digest_final(hashctx, digest, mdsz) != 0) {
940: r = SSH_ERR_LIBCRYPTO_ERROR;
941: goto out;
942: }
1.94 djm 943: ssh_digest_free(hashctx);
1.102 markus 944: hashctx = NULL;
1.26 markus 945:
1.30 markus 946: /*
947: * expand key:
948: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
949: * Key = K1 || K2 || ... || Kn
950: */
1.26 markus 951: for (have = mdsz; need > have; have += mdsz) {
1.102 markus 952: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
953: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 954: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1.102 markus 955: ssh_digest_update(hashctx, digest, have) != 0 ||
956: ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
957: r = SSH_ERR_LIBCRYPTO_ERROR;
958: goto out;
959: }
1.94 djm 960: ssh_digest_free(hashctx);
1.102 markus 961: hashctx = NULL;
1.26 markus 962: }
963: #ifdef DEBUG_KEX
964: fprintf(stderr, "key '%c'== ", c);
965: dump_digest("key", digest, need);
966: #endif
1.102 markus 967: *keyp = digest;
968: digest = NULL;
969: r = 0;
970: out:
1.114 mmcc 971: free(digest);
1.102 markus 972: ssh_digest_free(hashctx);
973: return r;
1.1 markus 974: }
975:
1.23 markus 976: #define NKEYS 6
1.102 markus 977: int
978: kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
979: const struct sshbuf *shared_secret)
1.1 markus 980: {
1.102 markus 981: struct kex *kex = ssh->kex;
1.15 markus 982: u_char *keys[NKEYS];
1.102 markus 983: u_int i, j, mode, ctos;
984: int r;
1.1 markus 985:
1.65 djm 986: for (i = 0; i < NKEYS; i++) {
1.102 markus 987: if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
988: shared_secret, &keys[i])) != 0) {
989: for (j = 0; j < i; j++)
990: free(keys[j]);
991: return r;
992: }
1.65 djm 993: }
1.1 markus 994: for (mode = 0; mode < MODE_MAX; mode++) {
1.69 deraadt 995: ctos = (!kex->server && mode == MODE_OUT) ||
996: (kex->server && mode == MODE_IN);
1.100 markus 997: kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
998: kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
999: kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
1.1 markus 1000: }
1.102 markus 1001: return 0;
1.95 djm 1002: }
1003:
1.99 markus 1004: #ifdef WITH_OPENSSL
1.102 markus 1005: int
1006: kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen,
1007: const BIGNUM *secret)
1.95 djm 1008: {
1.102 markus 1009: struct sshbuf *shared_secret;
1010: int r;
1.95 djm 1011:
1.102 markus 1012: if ((shared_secret = sshbuf_new()) == NULL)
1013: return SSH_ERR_ALLOC_FAIL;
1014: if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0)
1015: r = kex_derive_keys(ssh, hash, hashlen, shared_secret);
1016: sshbuf_free(shared_secret);
1017: return r;
1.27 markus 1018: }
1.99 markus 1019: #endif
1.57 djm 1020:
1.26 markus 1021:
1.84 djm 1022: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1.26 markus 1023: void
1024: dump_digest(char *msg, u_char *digest, int len)
1025: {
1026: fprintf(stderr, "%s\n", msg);
1.102 markus 1027: sshbuf_dump_data(digest, len, stderr);
1.26 markus 1028: }
1029: #endif
![[BACK]](/icons/back.gif){kind=icon}
Return to kex.c CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / ssh