Annotation of src/usr.bin/ssh/kex.c, Revision 1.136
1.136 ! jsing 1: /* $OpenBSD: kex.c,v 1.135 2018/01/23 05:27:21 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:
1.18 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')
165: return NULL;
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
200: kex_assemble_names(const char *def, char **list)
201: {
202: char *ret;
203:
204: if (list == NULL || *list == NULL || **list == '\0') {
205: *list = strdup(def);
206: return 0;
207: }
1.128 djm 208: if (**list == '+') {
209: if ((ret = kex_names_cat(def, *list + 1)) == NULL)
210: return SSH_ERR_ALLOC_FAIL;
211: free(*list);
212: *list = ret;
213: } else if (**list == '-') {
214: if ((ret = match_filter_list(def, *list + 1)) == NULL)
215: return SSH_ERR_ALLOC_FAIL;
216: free(*list);
217: *list = ret;
1.109 djm 218: }
219:
220: return 0;
1.86 djm 221: }
1.26 markus 222:
223: /* put algorithm proposal into buffer */
1.102 markus 224: int
225: kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
1.1 markus 226: {
1.61 djm 227: u_int i;
1.102 markus 228: int r;
229:
230: sshbuf_reset(b);
1.26 markus 231:
1.49 markus 232: /*
233: * add a dummy cookie, the cookie will be overwritten by
234: * kex_send_kexinit(), each time a kexinit is set
235: */
1.102 markus 236: for (i = 0; i < KEX_COOKIE_LEN; i++) {
237: if ((r = sshbuf_put_u8(b, 0)) != 0)
238: return r;
239: }
240: for (i = 0; i < PROPOSAL_MAX; i++) {
241: if ((r = sshbuf_put_cstring(b, proposal[i])) != 0)
242: return r;
243: }
244: if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */
245: (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */
246: return r;
247: return 0;
1.1 markus 248: }
249:
1.26 markus 250: /* parse buffer and return algorithm proposal */
1.102 markus 251: int
252: kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp)
1.7 markus 253: {
1.102 markus 254: struct sshbuf *b = NULL;
255: u_char v;
1.78 djm 256: u_int i;
1.102 markus 257: char **proposal = NULL;
258: int r;
1.7 markus 259:
1.102 markus 260: *propp = NULL;
261: if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL)
262: return SSH_ERR_ALLOC_FAIL;
263: if ((b = sshbuf_fromb(raw)) == NULL) {
264: r = SSH_ERR_ALLOC_FAIL;
265: goto out;
266: }
267: if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */
268: goto out;
1.7 markus 269: /* extract kex init proposal strings */
270: for (i = 0; i < PROPOSAL_MAX; i++) {
1.102 markus 271: if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0)
272: goto out;
1.110 djm 273: debug2("%s: %s", proposal_names[i], proposal[i]);
1.7 markus 274: }
1.26 markus 275: /* first kex follows / reserved */
1.115 djm 276: if ((r = sshbuf_get_u8(b, &v)) != 0 || /* first_kex_follows */
277: (r = sshbuf_get_u32(b, &i)) != 0) /* reserved */
1.102 markus 278: goto out;
1.53 markus 279: if (first_kex_follows != NULL)
1.115 djm 280: *first_kex_follows = v;
1.110 djm 281: debug2("first_kex_follows %d ", v);
282: debug2("reserved %u ", i);
1.102 markus 283: r = 0;
284: *propp = proposal;
285: out:
286: if (r != 0 && proposal != NULL)
287: kex_prop_free(proposal);
288: sshbuf_free(b);
289: return r;
1.1 markus 290: }
291:
1.102 markus 292: void
1.26 markus 293: kex_prop_free(char **proposal)
1.1 markus 294: {
1.61 djm 295: u_int i;
1.26 markus 296:
1.106 djm 297: if (proposal == NULL)
298: return;
1.26 markus 299: for (i = 0; i < PROPOSAL_MAX; i++)
1.91 djm 300: free(proposal[i]);
301: free(proposal);
1.1 markus 302: }
303:
1.78 djm 304: /* ARGSUSED */
1.101 markus 305: static int
1.133 markus 306: kex_protocol_error(int type, u_int32_t seq, struct ssh *ssh)
1.1 markus 307: {
1.112 djm 308: int r;
309:
310: error("kex protocol error: type %d seq %u", type, seq);
311: if ((r = sshpkt_start(ssh, SSH2_MSG_UNIMPLEMENTED)) != 0 ||
312: (r = sshpkt_put_u32(ssh, seq)) != 0 ||
313: (r = sshpkt_send(ssh)) != 0)
314: return r;
1.101 markus 315: return 0;
1.26 markus 316: }
1.1 markus 317:
1.35 itojun 318: static void
1.102 markus 319: kex_reset_dispatch(struct ssh *ssh)
1.29 markus 320: {
1.102 markus 321: ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
1.42 markus 322: SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
1.29 markus 323: }
324:
1.113 markus 325: static int
326: kex_send_ext_info(struct ssh *ssh)
327: {
328: int r;
1.121 djm 329: char *algs;
1.113 markus 330:
1.130 djm 331: if ((algs = sshkey_alg_list(0, 1, 1, ',')) == NULL)
1.121 djm 332: return SSH_ERR_ALLOC_FAIL;
1.113 markus 333: if ((r = sshpkt_start(ssh, SSH2_MSG_EXT_INFO)) != 0 ||
334: (r = sshpkt_put_u32(ssh, 1)) != 0 ||
335: (r = sshpkt_put_cstring(ssh, "server-sig-algs")) != 0 ||
1.121 djm 336: (r = sshpkt_put_cstring(ssh, algs)) != 0 ||
1.113 markus 337: (r = sshpkt_send(ssh)) != 0)
1.121 djm 338: goto out;
339: /* success */
340: r = 0;
341: out:
342: free(algs);
1.123 djm 343: return r;
1.113 markus 344: }
345:
1.102 markus 346: int
347: kex_send_newkeys(struct ssh *ssh)
1.26 markus 348: {
1.102 markus 349: int r;
1.28 markus 350:
1.102 markus 351: kex_reset_dispatch(ssh);
352: if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
353: (r = sshpkt_send(ssh)) != 0)
354: return r;
1.26 markus 355: debug("SSH2_MSG_NEWKEYS sent");
1.102 markus 356: debug("expecting SSH2_MSG_NEWKEYS");
357: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
1.113 markus 358: if (ssh->kex->ext_info_c)
359: if ((r = kex_send_ext_info(ssh)) != 0)
360: return r;
1.102 markus 361: return 0;
362: }
363:
1.113 markus 364: int
1.133 markus 365: kex_input_ext_info(int type, u_int32_t seq, struct ssh *ssh)
1.113 markus 366: {
367: struct kex *kex = ssh->kex;
368: u_int32_t i, ninfo;
1.134 djm 369: char *name, *found;
370: u_char *val;
371: size_t vlen;
1.113 markus 372: int r;
373:
374: debug("SSH2_MSG_EXT_INFO received");
375: ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_protocol_error);
376: if ((r = sshpkt_get_u32(ssh, &ninfo)) != 0)
377: return r;
378: for (i = 0; i < ninfo; i++) {
379: if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0)
380: return r;
1.134 djm 381: if ((r = sshpkt_get_string(ssh, &val, &vlen)) != 0) {
1.113 markus 382: free(name);
383: return r;
384: }
385: if (strcmp(name, "server-sig-algs") == 0) {
1.134 djm 386: /* Ensure no \0 lurking in value */
387: if (memchr(val, '\0', vlen) != NULL) {
388: error("%s: nul byte in %s", __func__, name);
389: return SSH_ERR_INVALID_FORMAT;
390: }
391: debug("%s: %s=<%s>", __func__, name, val);
1.113 markus 392: found = match_list("rsa-sha2-256", val, NULL);
393: if (found) {
394: kex->rsa_sha2 = 256;
395: free(found);
396: }
397: found = match_list("rsa-sha2-512", val, NULL);
398: if (found) {
399: kex->rsa_sha2 = 512;
400: free(found);
401: }
1.134 djm 402: } else
403: debug("%s: %s (unrecognised)", __func__, name);
1.113 markus 404: free(name);
405: free(val);
406: }
407: return sshpkt_get_end(ssh);
408: }
409:
1.102 markus 410: static int
1.133 markus 411: kex_input_newkeys(int type, u_int32_t seq, struct ssh *ssh)
1.102 markus 412: {
413: struct kex *kex = ssh->kex;
414: int r;
1.19 stevesk 415:
1.26 markus 416: debug("SSH2_MSG_NEWKEYS received");
1.102 markus 417: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
1.131 markus 418: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.102 markus 419: if ((r = sshpkt_get_end(ssh)) != 0)
1.122 markus 420: return r;
421: if ((r = ssh_set_newkeys(ssh, MODE_IN)) != 0)
1.102 markus 422: return r;
1.30 markus 423: kex->done = 1;
1.102 markus 424: sshbuf_reset(kex->peer);
425: /* sshbuf_reset(kex->my); */
1.26 markus 426: kex->flags &= ~KEX_INIT_SENT;
1.91 djm 427: free(kex->name);
1.32 markus 428: kex->name = NULL;
1.102 markus 429: return 0;
1.26 markus 430: }
1.1 markus 431:
1.102 markus 432: int
433: kex_send_kexinit(struct ssh *ssh)
1.26 markus 434: {
1.49 markus 435: u_char *cookie;
1.102 markus 436: struct kex *kex = ssh->kex;
437: int r;
1.49 markus 438:
1.102 markus 439: if (kex == NULL)
440: return SSH_ERR_INTERNAL_ERROR;
441: if (kex->flags & KEX_INIT_SENT)
442: return 0;
1.30 markus 443: kex->done = 0;
1.49 markus 444:
445: /* generate a random cookie */
1.102 markus 446: if (sshbuf_len(kex->my) < KEX_COOKIE_LEN)
447: return SSH_ERR_INVALID_FORMAT;
448: if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL)
449: return SSH_ERR_INTERNAL_ERROR;
450: arc4random_buf(cookie, KEX_COOKIE_LEN);
451:
452: if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
453: (r = sshpkt_putb(ssh, kex->my)) != 0 ||
454: (r = sshpkt_send(ssh)) != 0)
455: return r;
1.26 markus 456: debug("SSH2_MSG_KEXINIT sent");
457: kex->flags |= KEX_INIT_SENT;
1.102 markus 458: return 0;
1.1 markus 459: }
460:
1.78 djm 461: /* ARGSUSED */
1.101 markus 462: int
1.133 markus 463: kex_input_kexinit(int type, u_int32_t seq, struct ssh *ssh)
1.11 provos 464: {
1.102 markus 465: struct kex *kex = ssh->kex;
466: const u_char *ptr;
1.100 markus 467: u_int i;
468: size_t dlen;
1.102 markus 469: int r;
1.11 provos 470:
1.26 markus 471: debug("SSH2_MSG_KEXINIT received");
1.29 markus 472: if (kex == NULL)
1.102 markus 473: return SSH_ERR_INVALID_ARGUMENT;
1.11 provos 474:
1.127 markus 475: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, NULL);
1.102 markus 476: ptr = sshpkt_ptr(ssh, &dlen);
477: if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
478: return r;
1.31 markus 479:
480: /* discard packet */
481: for (i = 0; i < KEX_COOKIE_LEN; i++)
1.102 markus 482: if ((r = sshpkt_get_u8(ssh, NULL)) != 0)
483: return r;
1.31 markus 484: for (i = 0; i < PROPOSAL_MAX; i++)
1.102 markus 485: if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0)
486: return r;
1.87 djm 487: /*
488: * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
489: * KEX method has the server move first, but a server might be using
490: * a custom method or one that we otherwise don't support. We should
491: * be prepared to remember first_kex_follows here so we can eat a
492: * packet later.
493: * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
494: * for cases where the server *doesn't* go first. I guess we should
495: * ignore it when it is set for these cases, which is what we do now.
496: */
1.102 markus 497: if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
498: (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
499: (r = sshpkt_get_end(ssh)) != 0)
500: return r;
501:
502: if (!(kex->flags & KEX_INIT_SENT))
503: if ((r = kex_send_kexinit(ssh)) != 0)
504: return r;
505: if ((r = kex_choose_conf(ssh)) != 0)
506: return r;
1.19 stevesk 507:
1.102 markus 508: if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
509: return (kex->kex[kex->kex_type])(ssh);
510:
511: return SSH_ERR_INTERNAL_ERROR;
512: }
513:
514: int
515: kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp)
516: {
517: struct kex *kex;
518: int r;
519:
520: *kexp = NULL;
521: if ((kex = calloc(1, sizeof(*kex))) == NULL)
522: return SSH_ERR_ALLOC_FAIL;
523: if ((kex->peer = sshbuf_new()) == NULL ||
524: (kex->my = sshbuf_new()) == NULL) {
525: r = SSH_ERR_ALLOC_FAIL;
526: goto out;
527: }
528: if ((r = kex_prop2buf(kex->my, proposal)) != 0)
529: goto out;
530: kex->done = 0;
531: kex_reset_dispatch(ssh);
1.131 markus 532: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.102 markus 533: r = 0;
534: *kexp = kex;
535: out:
536: if (r != 0)
537: kex_free(kex);
538: return r;
1.26 markus 539: }
1.11 provos 540:
1.100 markus 541: void
542: kex_free_newkeys(struct newkeys *newkeys)
543: {
544: if (newkeys == NULL)
545: return;
546: if (newkeys->enc.key) {
547: explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
548: free(newkeys->enc.key);
549: newkeys->enc.key = NULL;
550: }
551: if (newkeys->enc.iv) {
1.111 djm 552: explicit_bzero(newkeys->enc.iv, newkeys->enc.iv_len);
1.100 markus 553: free(newkeys->enc.iv);
554: newkeys->enc.iv = NULL;
555: }
556: free(newkeys->enc.name);
557: explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
558: free(newkeys->comp.name);
559: explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
560: mac_clear(&newkeys->mac);
561: if (newkeys->mac.key) {
562: explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
563: free(newkeys->mac.key);
564: newkeys->mac.key = NULL;
565: }
566: free(newkeys->mac.name);
567: explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
568: explicit_bzero(newkeys, sizeof(*newkeys));
569: free(newkeys);
570: }
571:
1.102 markus 572: void
573: kex_free(struct kex *kex)
1.26 markus 574: {
1.102 markus 575: u_int mode;
1.11 provos 576:
1.102 markus 577: #ifdef WITH_OPENSSL
1.136 ! jsing 578: DH_free(kex->dh);
! 579: EC_KEY_free(kex->ec_client_key);
1.102 markus 580: #endif
581: for (mode = 0; mode < MODE_MAX; mode++) {
582: kex_free_newkeys(kex->newkeys[mode]);
583: kex->newkeys[mode] = NULL;
1.100 markus 584: }
1.102 markus 585: sshbuf_free(kex->peer);
586: sshbuf_free(kex->my);
587: free(kex->session_id);
588: free(kex->client_version_string);
589: free(kex->server_version_string);
1.107 djm 590: free(kex->failed_choice);
1.113 markus 591: free(kex->hostkey_alg);
592: free(kex->name);
1.102 markus 593: free(kex);
1.11 provos 594: }
595:
1.102 markus 596: int
597: kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
1.1 markus 598: {
1.102 markus 599: int r;
1.1 markus 600:
1.102 markus 601: if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0)
602: return r;
603: if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
604: kex_free(ssh->kex);
605: ssh->kex = NULL;
606: return r;
1.1 markus 607: }
1.102 markus 608: return 0;
1.117 djm 609: }
610:
611: /*
612: * Request key re-exchange, returns 0 on success or a ssherr.h error
613: * code otherwise. Must not be called if KEX is incomplete or in-progress.
614: */
615: int
616: kex_start_rekex(struct ssh *ssh)
617: {
618: if (ssh->kex == NULL) {
619: error("%s: no kex", __func__);
620: return SSH_ERR_INTERNAL_ERROR;
621: }
622: if (ssh->kex->done == 0) {
623: error("%s: requested twice", __func__);
624: return SSH_ERR_INTERNAL_ERROR;
625: }
626: ssh->kex->done = 0;
627: return kex_send_kexinit(ssh);
1.1 markus 628: }
629:
1.102 markus 630: static int
631: choose_enc(struct sshenc *enc, char *client, char *server)
1.1 markus 632: {
1.23 markus 633: char *name = match_list(client, server, NULL);
1.102 markus 634:
1.1 markus 635: if (name == NULL)
1.102 markus 636: return SSH_ERR_NO_CIPHER_ALG_MATCH;
1.129 dtucker 637: if ((enc->cipher = cipher_by_name(name)) == NULL) {
638: free(name);
1.102 markus 639: return SSH_ERR_INTERNAL_ERROR;
1.129 dtucker 640: }
1.1 markus 641: enc->name = name;
642: enc->enabled = 0;
643: enc->iv = NULL;
1.88 markus 644: enc->iv_len = cipher_ivlen(enc->cipher);
1.1 markus 645: enc->key = NULL;
1.45 markus 646: enc->key_len = cipher_keylen(enc->cipher);
647: enc->block_size = cipher_blocksize(enc->cipher);
1.102 markus 648: return 0;
1.1 markus 649: }
1.69 deraadt 650:
1.102 markus 651: static int
652: choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
1.1 markus 653: {
1.23 markus 654: char *name = match_list(client, server, NULL);
1.102 markus 655:
1.1 markus 656: if (name == NULL)
1.102 markus 657: return SSH_ERR_NO_MAC_ALG_MATCH;
1.129 dtucker 658: if (mac_setup(mac, name) < 0) {
659: free(name);
1.102 markus 660: return SSH_ERR_INTERNAL_ERROR;
1.129 dtucker 661: }
1.1 markus 662: mac->name = name;
663: mac->key = NULL;
664: mac->enabled = 0;
1.102 markus 665: return 0;
1.1 markus 666: }
1.69 deraadt 667:
1.102 markus 668: static int
669: choose_comp(struct sshcomp *comp, char *client, char *server)
1.1 markus 670: {
1.23 markus 671: char *name = match_list(client, server, NULL);
1.102 markus 672:
1.1 markus 673: if (name == NULL)
1.102 markus 674: return SSH_ERR_NO_COMPRESS_ALG_MATCH;
1.64 markus 675: if (strcmp(name, "zlib@openssh.com") == 0) {
676: comp->type = COMP_DELAYED;
1.126 djm 677: } else if (strcmp(name, "zlib") == 0) {
678: comp->type = COMP_ZLIB;
1.1 markus 679: } else if (strcmp(name, "none") == 0) {
1.64 markus 680: comp->type = COMP_NONE;
1.1 markus 681: } else {
1.129 dtucker 682: free(name);
1.102 markus 683: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 684: }
685: comp->name = name;
1.102 markus 686: return 0;
1.1 markus 687: }
1.69 deraadt 688:
1.102 markus 689: static int
690: choose_kex(struct kex *k, char *client, char *server)
1.1 markus 691: {
1.89 djm 692: const struct kexalg *kexalg;
693:
1.23 markus 694: k->name = match_list(client, server, NULL);
1.102 markus 695:
1.110 djm 696: debug("kex: algorithm: %s", k->name ? k->name : "(no match)");
1.1 markus 697: if (k->name == NULL)
1.102 markus 698: return SSH_ERR_NO_KEX_ALG_MATCH;
1.89 djm 699: if ((kexalg = kex_alg_by_name(k->name)) == NULL)
1.102 markus 700: return SSH_ERR_INTERNAL_ERROR;
1.89 djm 701: k->kex_type = kexalg->type;
1.94 djm 702: k->hash_alg = kexalg->hash_alg;
1.89 djm 703: k->ec_nid = kexalg->ec_nid;
1.102 markus 704: return 0;
1.1 markus 705: }
1.65 djm 706:
1.102 markus 707: static int
708: choose_hostkeyalg(struct kex *k, char *client, char *server)
1.1 markus 709: {
1.113 markus 710: k->hostkey_alg = match_list(client, server, NULL);
1.102 markus 711:
1.110 djm 712: debug("kex: host key algorithm: %s",
1.113 markus 713: k->hostkey_alg ? k->hostkey_alg : "(no match)");
714: if (k->hostkey_alg == NULL)
1.102 markus 715: return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
1.113 markus 716: k->hostkey_type = sshkey_type_from_name(k->hostkey_alg);
1.13 markus 717: if (k->hostkey_type == KEY_UNSPEC)
1.102 markus 718: return SSH_ERR_INTERNAL_ERROR;
1.113 markus 719: k->hostkey_nid = sshkey_ecdsa_nid_from_name(k->hostkey_alg);
1.102 markus 720: return 0;
1.1 markus 721: }
722:
1.56 djm 723: static int
1.53 markus 724: proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
725: {
726: static int check[] = {
727: PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
728: };
729: int *idx;
730: char *p;
731:
732: for (idx = &check[0]; *idx != -1; idx++) {
733: if ((p = strchr(my[*idx], ',')) != NULL)
734: *p = '\0';
735: if ((p = strchr(peer[*idx], ',')) != NULL)
736: *p = '\0';
737: if (strcmp(my[*idx], peer[*idx]) != 0) {
738: debug2("proposal mismatch: my %s peer %s",
739: my[*idx], peer[*idx]);
740: return (0);
741: }
742: }
743: debug2("proposals match");
744: return (1);
745: }
746:
1.102 markus 747: static int
748: kex_choose_conf(struct ssh *ssh)
1.1 markus 749: {
1.102 markus 750: struct kex *kex = ssh->kex;
751: struct newkeys *newkeys;
752: char **my = NULL, **peer = NULL;
1.26 markus 753: char **cprop, **sprop;
1.27 markus 754: int nenc, nmac, ncomp;
1.96 dtucker 755: u_int mode, ctos, need, dh_need, authlen;
1.102 markus 756: int r, first_kex_follows;
1.1 markus 757:
1.110 djm 758: debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
759: if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
760: goto out;
761: debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
762: if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
1.102 markus 763: goto out;
1.26 markus 764:
1.27 markus 765: if (kex->server) {
1.26 markus 766: cprop=peer;
767: sprop=my;
768: } else {
769: cprop=my;
770: sprop=peer;
1.113 markus 771: }
772:
773: /* Check whether client supports ext_info_c */
774: if (kex->server) {
775: char *ext;
776:
777: ext = match_list("ext-info-c", peer[PROPOSAL_KEX_ALGS], NULL);
1.119 markus 778: kex->ext_info_c = (ext != NULL);
779: free(ext);
1.26 markus 780: }
1.1 markus 781:
1.30 markus 782: /* Algorithm Negotiation */
1.110 djm 783: if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
784: sprop[PROPOSAL_KEX_ALGS])) != 0) {
785: kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
786: peer[PROPOSAL_KEX_ALGS] = NULL;
787: goto out;
788: }
789: if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
790: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
791: kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
792: peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
793: goto out;
794: }
1.1 markus 795: for (mode = 0; mode < MODE_MAX; mode++) {
1.102 markus 796: if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
797: r = SSH_ERR_ALLOC_FAIL;
798: goto out;
799: }
1.30 markus 800: kex->newkeys[mode] = newkeys;
1.78 djm 801: ctos = (!kex->server && mode == MODE_OUT) ||
802: (kex->server && mode == MODE_IN);
1.1 markus 803: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
804: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
805: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.102 markus 806: if ((r = choose_enc(&newkeys->enc, cprop[nenc],
1.107 djm 807: sprop[nenc])) != 0) {
808: kex->failed_choice = peer[nenc];
809: peer[nenc] = NULL;
1.102 markus 810: goto out;
1.107 djm 811: }
1.102 markus 812: authlen = cipher_authlen(newkeys->enc.cipher);
1.88 markus 813: /* ignore mac for authenticated encryption */
1.102 markus 814: if (authlen == 0 &&
815: (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
1.107 djm 816: sprop[nmac])) != 0) {
817: kex->failed_choice = peer[nmac];
818: peer[nmac] = NULL;
1.102 markus 819: goto out;
1.107 djm 820: }
1.102 markus 821: if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
1.107 djm 822: sprop[ncomp])) != 0) {
823: kex->failed_choice = peer[ncomp];
824: peer[ncomp] = NULL;
1.102 markus 825: goto out;
1.107 djm 826: }
1.110 djm 827: debug("kex: %s cipher: %s MAC: %s compression: %s",
1.1 markus 828: ctos ? "client->server" : "server->client",
1.27 markus 829: newkeys->enc.name,
1.88 markus 830: authlen == 0 ? newkeys->mac.name : "<implicit>",
1.27 markus 831: newkeys->comp.name);
1.107 djm 832: }
1.96 dtucker 833: need = dh_need = 0;
1.1 markus 834: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 835: newkeys = kex->newkeys[mode];
1.120 deraadt 836: need = MAXIMUM(need, newkeys->enc.key_len);
837: need = MAXIMUM(need, newkeys->enc.block_size);
838: need = MAXIMUM(need, newkeys->enc.iv_len);
839: need = MAXIMUM(need, newkeys->mac.key_len);
840: dh_need = MAXIMUM(dh_need, cipher_seclen(newkeys->enc.cipher));
841: dh_need = MAXIMUM(dh_need, newkeys->enc.block_size);
842: dh_need = MAXIMUM(dh_need, newkeys->enc.iv_len);
843: dh_need = MAXIMUM(dh_need, newkeys->mac.key_len);
1.1 markus 844: }
1.7 markus 845: /* XXX need runden? */
1.27 markus 846: kex->we_need = need;
1.96 dtucker 847: kex->dh_need = dh_need;
1.53 markus 848:
849: /* ignore the next message if the proposals do not match */
1.135 djm 850: if (first_kex_follows && !proposals_match(my, peer))
1.102 markus 851: ssh->dispatch_skip_packets = 1;
852: r = 0;
853: out:
1.26 markus 854: kex_prop_free(my);
855: kex_prop_free(peer);
1.102 markus 856: return r;
1.26 markus 857: }
858:
1.102 markus 859: static int
860: derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
861: const struct sshbuf *shared_secret, u_char **keyp)
1.26 markus 862: {
1.102 markus 863: struct kex *kex = ssh->kex;
864: struct ssh_digest_ctx *hashctx = NULL;
1.26 markus 865: char c = id;
1.61 djm 866: u_int have;
1.94 djm 867: size_t mdsz;
1.61 djm 868: u_char *digest;
1.102 markus 869: int r;
1.62 djm 870:
1.94 djm 871: if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
1.102 markus 872: return SSH_ERR_INVALID_ARGUMENT;
1.120 deraadt 873: if ((digest = calloc(1, ROUNDUP(need, mdsz))) == NULL) {
1.102 markus 874: r = SSH_ERR_ALLOC_FAIL;
875: goto out;
876: }
1.26 markus 877:
1.30 markus 878: /* K1 = HASH(K || H || "A" || session_id) */
1.102 markus 879: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
880: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 881: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
882: ssh_digest_update(hashctx, &c, 1) != 0 ||
883: ssh_digest_update(hashctx, kex->session_id,
1.102 markus 884: kex->session_id_len) != 0 ||
885: ssh_digest_final(hashctx, digest, mdsz) != 0) {
886: r = SSH_ERR_LIBCRYPTO_ERROR;
887: goto out;
888: }
1.94 djm 889: ssh_digest_free(hashctx);
1.102 markus 890: hashctx = NULL;
1.26 markus 891:
1.30 markus 892: /*
893: * expand key:
894: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
895: * Key = K1 || K2 || ... || Kn
896: */
1.26 markus 897: for (have = mdsz; need > have; have += mdsz) {
1.102 markus 898: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
899: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 900: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1.102 markus 901: ssh_digest_update(hashctx, digest, have) != 0 ||
902: ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
903: r = SSH_ERR_LIBCRYPTO_ERROR;
904: goto out;
905: }
1.94 djm 906: ssh_digest_free(hashctx);
1.102 markus 907: hashctx = NULL;
1.26 markus 908: }
909: #ifdef DEBUG_KEX
910: fprintf(stderr, "key '%c'== ", c);
911: dump_digest("key", digest, need);
912: #endif
1.102 markus 913: *keyp = digest;
914: digest = NULL;
915: r = 0;
916: out:
1.114 mmcc 917: free(digest);
1.102 markus 918: ssh_digest_free(hashctx);
919: return r;
1.1 markus 920: }
921:
1.23 markus 922: #define NKEYS 6
1.102 markus 923: int
924: kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
925: const struct sshbuf *shared_secret)
1.1 markus 926: {
1.102 markus 927: struct kex *kex = ssh->kex;
1.15 markus 928: u_char *keys[NKEYS];
1.102 markus 929: u_int i, j, mode, ctos;
930: int r;
1.1 markus 931:
1.65 djm 932: for (i = 0; i < NKEYS; i++) {
1.102 markus 933: if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
934: shared_secret, &keys[i])) != 0) {
935: for (j = 0; j < i; j++)
936: free(keys[j]);
937: return r;
938: }
1.65 djm 939: }
1.1 markus 940: for (mode = 0; mode < MODE_MAX; mode++) {
1.69 deraadt 941: ctos = (!kex->server && mode == MODE_OUT) ||
942: (kex->server && mode == MODE_IN);
1.100 markus 943: kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
944: kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
945: kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
1.1 markus 946: }
1.102 markus 947: return 0;
1.95 djm 948: }
949:
1.99 markus 950: #ifdef WITH_OPENSSL
1.102 markus 951: int
952: kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen,
953: const BIGNUM *secret)
1.95 djm 954: {
1.102 markus 955: struct sshbuf *shared_secret;
956: int r;
1.95 djm 957:
1.102 markus 958: if ((shared_secret = sshbuf_new()) == NULL)
959: return SSH_ERR_ALLOC_FAIL;
960: if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0)
961: r = kex_derive_keys(ssh, hash, hashlen, shared_secret);
962: sshbuf_free(shared_secret);
963: return r;
1.27 markus 964: }
1.99 markus 965: #endif
1.57 djm 966:
1.26 markus 967:
1.84 djm 968: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1.26 markus 969: void
970: dump_digest(char *msg, u_char *digest, int len)
971: {
972: fprintf(stderr, "%s\n", msg);
1.102 markus 973: sshbuf_dump_data(digest, len, stderr);
1.26 markus 974: }
975: #endif
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