Annotation of src/usr.bin/ssh/kex.c, Revision 1.128
1.128 ! djm 1: /* $OpenBSD: kex.c,v 1.127 2016/10/10 19:28:48 markus 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 *);
55: static int kex_input_newkeys(int, u_int32_t, void *);
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: {
161: char *ret = NULL, *tmp = NULL, *cp, *p;
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, ","))) {
178: if (match_list(ret, p, NULL) != NULL)
179: continue; /* Algorithm already present */
180: if (strlcat(ret, ",", len) >= len ||
181: strlcat(ret, p, len) >= len) {
182: free(tmp);
183: free(ret);
184: return NULL; /* Shouldn't happen */
185: }
186: }
187: free(tmp);
188: return ret;
189: }
190:
191: /*
192: * Assemble a list of algorithms from a default list and a string from a
193: * configuration file. The user-provided string may begin with '+' to
1.128 ! djm 194: * indicate that it should be appended to the default or '-' that the
! 195: * specified names should be removed.
1.109 djm 196: */
197: int
198: kex_assemble_names(const char *def, char **list)
199: {
200: char *ret;
201:
202: if (list == NULL || *list == NULL || **list == '\0') {
203: *list = strdup(def);
204: return 0;
205: }
1.128 ! djm 206: if (**list == '+') {
! 207: if ((ret = kex_names_cat(def, *list + 1)) == NULL)
! 208: return SSH_ERR_ALLOC_FAIL;
! 209: free(*list);
! 210: *list = ret;
! 211: } else if (**list == '-') {
! 212: if ((ret = match_filter_list(def, *list + 1)) == NULL)
! 213: return SSH_ERR_ALLOC_FAIL;
! 214: free(*list);
! 215: *list = ret;
1.109 djm 216: }
217:
218: return 0;
1.86 djm 219: }
1.26 markus 220:
221: /* put algorithm proposal into buffer */
1.102 markus 222: int
223: kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
1.1 markus 224: {
1.61 djm 225: u_int i;
1.102 markus 226: int r;
227:
228: sshbuf_reset(b);
1.26 markus 229:
1.49 markus 230: /*
231: * add a dummy cookie, the cookie will be overwritten by
232: * kex_send_kexinit(), each time a kexinit is set
233: */
1.102 markus 234: for (i = 0; i < KEX_COOKIE_LEN; i++) {
235: if ((r = sshbuf_put_u8(b, 0)) != 0)
236: return r;
237: }
238: for (i = 0; i < PROPOSAL_MAX; i++) {
239: if ((r = sshbuf_put_cstring(b, proposal[i])) != 0)
240: return r;
241: }
242: if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */
243: (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */
244: return r;
245: return 0;
1.1 markus 246: }
247:
1.26 markus 248: /* parse buffer and return algorithm proposal */
1.102 markus 249: int
250: kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp)
1.7 markus 251: {
1.102 markus 252: struct sshbuf *b = NULL;
253: u_char v;
1.78 djm 254: u_int i;
1.102 markus 255: char **proposal = NULL;
256: int r;
1.7 markus 257:
1.102 markus 258: *propp = NULL;
259: if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL)
260: return SSH_ERR_ALLOC_FAIL;
261: if ((b = sshbuf_fromb(raw)) == NULL) {
262: r = SSH_ERR_ALLOC_FAIL;
263: goto out;
264: }
265: if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */
266: goto out;
1.7 markus 267: /* extract kex init proposal strings */
268: for (i = 0; i < PROPOSAL_MAX; i++) {
1.102 markus 269: if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0)
270: goto out;
1.110 djm 271: debug2("%s: %s", proposal_names[i], proposal[i]);
1.7 markus 272: }
1.26 markus 273: /* first kex follows / reserved */
1.115 djm 274: if ((r = sshbuf_get_u8(b, &v)) != 0 || /* first_kex_follows */
275: (r = sshbuf_get_u32(b, &i)) != 0) /* reserved */
1.102 markus 276: goto out;
1.53 markus 277: if (first_kex_follows != NULL)
1.115 djm 278: *first_kex_follows = v;
1.110 djm 279: debug2("first_kex_follows %d ", v);
280: debug2("reserved %u ", i);
1.102 markus 281: r = 0;
282: *propp = proposal;
283: out:
284: if (r != 0 && proposal != NULL)
285: kex_prop_free(proposal);
286: sshbuf_free(b);
287: return r;
1.1 markus 288: }
289:
1.102 markus 290: void
1.26 markus 291: kex_prop_free(char **proposal)
1.1 markus 292: {
1.61 djm 293: u_int i;
1.26 markus 294:
1.106 djm 295: if (proposal == NULL)
296: return;
1.26 markus 297: for (i = 0; i < PROPOSAL_MAX; i++)
1.91 djm 298: free(proposal[i]);
299: free(proposal);
1.1 markus 300: }
301:
1.78 djm 302: /* ARGSUSED */
1.101 markus 303: static int
1.41 markus 304: kex_protocol_error(int type, u_int32_t seq, void *ctxt)
1.1 markus 305: {
1.112 djm 306: struct ssh *ssh = active_state; /* XXX */
307: int r;
308:
309: error("kex protocol error: type %d seq %u", type, seq);
310: if ((r = sshpkt_start(ssh, SSH2_MSG_UNIMPLEMENTED)) != 0 ||
311: (r = sshpkt_put_u32(ssh, seq)) != 0 ||
312: (r = sshpkt_send(ssh)) != 0)
313: return r;
1.101 markus 314: return 0;
1.26 markus 315: }
1.1 markus 316:
1.35 itojun 317: static void
1.102 markus 318: kex_reset_dispatch(struct ssh *ssh)
1.29 markus 319: {
1.102 markus 320: ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
1.42 markus 321: SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
1.102 markus 322: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
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:
1.121 djm 331: if ((algs = sshkey_alg_list(0, 1, ',')) == NULL)
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
365: kex_input_ext_info(int type, u_int32_t seq, void *ctxt)
366: {
367: struct ssh *ssh = ctxt;
368: struct kex *kex = ssh->kex;
369: u_int32_t i, ninfo;
370: char *name, *val, *found;
371: int r;
372:
373: debug("SSH2_MSG_EXT_INFO received");
374: ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_protocol_error);
375: if ((r = sshpkt_get_u32(ssh, &ninfo)) != 0)
376: return r;
377: for (i = 0; i < ninfo; i++) {
378: if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0)
379: return r;
380: if ((r = sshpkt_get_cstring(ssh, &val, NULL)) != 0) {
381: free(name);
382: return r;
383: }
384: debug("%s: %s=<%s>", __func__, name, val);
385: if (strcmp(name, "server-sig-algs") == 0) {
386: found = match_list("rsa-sha2-256", val, NULL);
387: if (found) {
388: kex->rsa_sha2 = 256;
389: free(found);
390: }
391: found = match_list("rsa-sha2-512", val, NULL);
392: if (found) {
393: kex->rsa_sha2 = 512;
394: free(found);
395: }
396: }
397: free(name);
398: free(val);
399: }
400: return sshpkt_get_end(ssh);
401: }
402:
1.102 markus 403: static int
404: kex_input_newkeys(int type, u_int32_t seq, void *ctxt)
405: {
406: struct ssh *ssh = ctxt;
407: struct kex *kex = ssh->kex;
408: int r;
1.19 stevesk 409:
1.26 markus 410: debug("SSH2_MSG_NEWKEYS received");
1.102 markus 411: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
412: if ((r = sshpkt_get_end(ssh)) != 0)
1.122 markus 413: return r;
414: if ((r = ssh_set_newkeys(ssh, MODE_IN)) != 0)
1.102 markus 415: return r;
1.30 markus 416: kex->done = 1;
1.102 markus 417: sshbuf_reset(kex->peer);
418: /* sshbuf_reset(kex->my); */
1.26 markus 419: kex->flags &= ~KEX_INIT_SENT;
1.91 djm 420: free(kex->name);
1.32 markus 421: kex->name = NULL;
1.102 markus 422: return 0;
1.26 markus 423: }
1.1 markus 424:
1.102 markus 425: int
426: kex_send_kexinit(struct ssh *ssh)
1.26 markus 427: {
1.49 markus 428: u_char *cookie;
1.102 markus 429: struct kex *kex = ssh->kex;
430: int r;
1.49 markus 431:
1.102 markus 432: if (kex == NULL)
433: return SSH_ERR_INTERNAL_ERROR;
434: if (kex->flags & KEX_INIT_SENT)
435: return 0;
1.30 markus 436: kex->done = 0;
1.49 markus 437:
438: /* generate a random cookie */
1.102 markus 439: if (sshbuf_len(kex->my) < KEX_COOKIE_LEN)
440: return SSH_ERR_INVALID_FORMAT;
441: if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL)
442: return SSH_ERR_INTERNAL_ERROR;
443: arc4random_buf(cookie, KEX_COOKIE_LEN);
444:
445: if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
446: (r = sshpkt_putb(ssh, kex->my)) != 0 ||
447: (r = sshpkt_send(ssh)) != 0)
448: return r;
1.26 markus 449: debug("SSH2_MSG_KEXINIT sent");
450: kex->flags |= KEX_INIT_SENT;
1.102 markus 451: return 0;
1.1 markus 452: }
453:
1.78 djm 454: /* ARGSUSED */
1.101 markus 455: int
1.41 markus 456: kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
1.11 provos 457: {
1.102 markus 458: struct ssh *ssh = ctxt;
459: struct kex *kex = ssh->kex;
460: const u_char *ptr;
1.100 markus 461: u_int i;
462: size_t dlen;
1.102 markus 463: int r;
1.11 provos 464:
1.26 markus 465: debug("SSH2_MSG_KEXINIT received");
1.29 markus 466: if (kex == NULL)
1.102 markus 467: return SSH_ERR_INVALID_ARGUMENT;
1.11 provos 468:
1.127 markus 469: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, NULL);
1.102 markus 470: ptr = sshpkt_ptr(ssh, &dlen);
471: if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
472: return r;
1.31 markus 473:
474: /* discard packet */
475: for (i = 0; i < KEX_COOKIE_LEN; i++)
1.102 markus 476: if ((r = sshpkt_get_u8(ssh, NULL)) != 0)
477: return r;
1.31 markus 478: for (i = 0; i < PROPOSAL_MAX; i++)
1.102 markus 479: if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0)
480: return r;
1.87 djm 481: /*
482: * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
483: * KEX method has the server move first, but a server might be using
484: * a custom method or one that we otherwise don't support. We should
485: * be prepared to remember first_kex_follows here so we can eat a
486: * packet later.
487: * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
488: * for cases where the server *doesn't* go first. I guess we should
489: * ignore it when it is set for these cases, which is what we do now.
490: */
1.102 markus 491: if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
492: (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
493: (r = sshpkt_get_end(ssh)) != 0)
494: return r;
495:
496: if (!(kex->flags & KEX_INIT_SENT))
497: if ((r = kex_send_kexinit(ssh)) != 0)
498: return r;
499: if ((r = kex_choose_conf(ssh)) != 0)
500: return r;
1.19 stevesk 501:
1.102 markus 502: if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
503: return (kex->kex[kex->kex_type])(ssh);
504:
505: return SSH_ERR_INTERNAL_ERROR;
506: }
507:
508: int
509: kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp)
510: {
511: struct kex *kex;
512: int r;
513:
514: *kexp = NULL;
515: if ((kex = calloc(1, sizeof(*kex))) == NULL)
516: return SSH_ERR_ALLOC_FAIL;
517: if ((kex->peer = sshbuf_new()) == NULL ||
518: (kex->my = sshbuf_new()) == NULL) {
519: r = SSH_ERR_ALLOC_FAIL;
520: goto out;
521: }
522: if ((r = kex_prop2buf(kex->my, proposal)) != 0)
523: goto out;
524: kex->done = 0;
525: kex_reset_dispatch(ssh);
526: r = 0;
527: *kexp = kex;
528: out:
529: if (r != 0)
530: kex_free(kex);
531: return r;
1.26 markus 532: }
1.11 provos 533:
1.100 markus 534: void
535: kex_free_newkeys(struct newkeys *newkeys)
536: {
537: if (newkeys == NULL)
538: return;
539: if (newkeys->enc.key) {
540: explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
541: free(newkeys->enc.key);
542: newkeys->enc.key = NULL;
543: }
544: if (newkeys->enc.iv) {
1.111 djm 545: explicit_bzero(newkeys->enc.iv, newkeys->enc.iv_len);
1.100 markus 546: free(newkeys->enc.iv);
547: newkeys->enc.iv = NULL;
548: }
549: free(newkeys->enc.name);
550: explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
551: free(newkeys->comp.name);
552: explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
553: mac_clear(&newkeys->mac);
554: if (newkeys->mac.key) {
555: explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
556: free(newkeys->mac.key);
557: newkeys->mac.key = NULL;
558: }
559: free(newkeys->mac.name);
560: explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
561: explicit_bzero(newkeys, sizeof(*newkeys));
562: free(newkeys);
563: }
564:
1.102 markus 565: void
566: kex_free(struct kex *kex)
1.26 markus 567: {
1.102 markus 568: u_int mode;
1.11 provos 569:
1.102 markus 570: #ifdef WITH_OPENSSL
571: if (kex->dh)
572: DH_free(kex->dh);
573: if (kex->ec_client_key)
574: EC_KEY_free(kex->ec_client_key);
575: #endif
576: for (mode = 0; mode < MODE_MAX; mode++) {
577: kex_free_newkeys(kex->newkeys[mode]);
578: kex->newkeys[mode] = NULL;
1.100 markus 579: }
1.102 markus 580: sshbuf_free(kex->peer);
581: sshbuf_free(kex->my);
582: free(kex->session_id);
583: free(kex->client_version_string);
584: free(kex->server_version_string);
1.107 djm 585: free(kex->failed_choice);
1.113 markus 586: free(kex->hostkey_alg);
587: free(kex->name);
1.102 markus 588: free(kex);
1.11 provos 589: }
590:
1.102 markus 591: int
592: kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
1.1 markus 593: {
1.102 markus 594: int r;
1.1 markus 595:
1.102 markus 596: if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0)
597: return r;
598: if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
599: kex_free(ssh->kex);
600: ssh->kex = NULL;
601: return r;
1.1 markus 602: }
1.102 markus 603: return 0;
1.117 djm 604: }
605:
606: /*
607: * Request key re-exchange, returns 0 on success or a ssherr.h error
608: * code otherwise. Must not be called if KEX is incomplete or in-progress.
609: */
610: int
611: kex_start_rekex(struct ssh *ssh)
612: {
613: if (ssh->kex == NULL) {
614: error("%s: no kex", __func__);
615: return SSH_ERR_INTERNAL_ERROR;
616: }
617: if (ssh->kex->done == 0) {
618: error("%s: requested twice", __func__);
619: return SSH_ERR_INTERNAL_ERROR;
620: }
621: ssh->kex->done = 0;
622: return kex_send_kexinit(ssh);
1.1 markus 623: }
624:
1.102 markus 625: static int
626: choose_enc(struct sshenc *enc, char *client, char *server)
1.1 markus 627: {
1.23 markus 628: char *name = match_list(client, server, NULL);
1.102 markus 629:
1.1 markus 630: if (name == NULL)
1.102 markus 631: return SSH_ERR_NO_CIPHER_ALG_MATCH;
1.45 markus 632: if ((enc->cipher = cipher_by_name(name)) == NULL)
1.102 markus 633: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 634: enc->name = name;
635: enc->enabled = 0;
636: enc->iv = NULL;
1.88 markus 637: enc->iv_len = cipher_ivlen(enc->cipher);
1.1 markus 638: enc->key = NULL;
1.45 markus 639: enc->key_len = cipher_keylen(enc->cipher);
640: enc->block_size = cipher_blocksize(enc->cipher);
1.102 markus 641: return 0;
1.1 markus 642: }
1.69 deraadt 643:
1.102 markus 644: static int
645: choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
1.1 markus 646: {
1.23 markus 647: char *name = match_list(client, server, NULL);
1.102 markus 648:
1.1 markus 649: if (name == NULL)
1.102 markus 650: return SSH_ERR_NO_MAC_ALG_MATCH;
1.79 djm 651: if (mac_setup(mac, name) < 0)
1.102 markus 652: return SSH_ERR_INTERNAL_ERROR;
1.21 markus 653: /* truncate the key */
1.102 markus 654: if (ssh->compat & SSH_BUG_HMAC)
1.21 markus 655: mac->key_len = 16;
1.1 markus 656: mac->name = name;
657: mac->key = NULL;
658: mac->enabled = 0;
1.102 markus 659: return 0;
1.1 markus 660: }
1.69 deraadt 661:
1.102 markus 662: static int
663: choose_comp(struct sshcomp *comp, char *client, char *server)
1.1 markus 664: {
1.23 markus 665: char *name = match_list(client, server, NULL);
1.102 markus 666:
1.1 markus 667: if (name == NULL)
1.102 markus 668: return SSH_ERR_NO_COMPRESS_ALG_MATCH;
1.64 markus 669: if (strcmp(name, "zlib@openssh.com") == 0) {
670: comp->type = COMP_DELAYED;
1.126 djm 671: } else if (strcmp(name, "zlib") == 0) {
672: comp->type = COMP_ZLIB;
1.1 markus 673: } else if (strcmp(name, "none") == 0) {
1.64 markus 674: comp->type = COMP_NONE;
1.1 markus 675: } else {
1.102 markus 676: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 677: }
678: comp->name = name;
1.102 markus 679: return 0;
1.1 markus 680: }
1.69 deraadt 681:
1.102 markus 682: static int
683: choose_kex(struct kex *k, char *client, char *server)
1.1 markus 684: {
1.89 djm 685: const struct kexalg *kexalg;
686:
1.23 markus 687: k->name = match_list(client, server, NULL);
1.102 markus 688:
1.110 djm 689: debug("kex: algorithm: %s", k->name ? k->name : "(no match)");
1.1 markus 690: if (k->name == NULL)
1.102 markus 691: return SSH_ERR_NO_KEX_ALG_MATCH;
1.89 djm 692: if ((kexalg = kex_alg_by_name(k->name)) == NULL)
1.102 markus 693: return SSH_ERR_INTERNAL_ERROR;
1.89 djm 694: k->kex_type = kexalg->type;
1.94 djm 695: k->hash_alg = kexalg->hash_alg;
1.89 djm 696: k->ec_nid = kexalg->ec_nid;
1.102 markus 697: return 0;
1.1 markus 698: }
1.65 djm 699:
1.102 markus 700: static int
701: choose_hostkeyalg(struct kex *k, char *client, char *server)
1.1 markus 702: {
1.113 markus 703: k->hostkey_alg = match_list(client, server, NULL);
1.102 markus 704:
1.110 djm 705: debug("kex: host key algorithm: %s",
1.113 markus 706: k->hostkey_alg ? k->hostkey_alg : "(no match)");
707: if (k->hostkey_alg == NULL)
1.102 markus 708: return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
1.113 markus 709: k->hostkey_type = sshkey_type_from_name(k->hostkey_alg);
1.13 markus 710: if (k->hostkey_type == KEY_UNSPEC)
1.102 markus 711: return SSH_ERR_INTERNAL_ERROR;
1.113 markus 712: k->hostkey_nid = sshkey_ecdsa_nid_from_name(k->hostkey_alg);
1.102 markus 713: return 0;
1.1 markus 714: }
715:
1.56 djm 716: static int
1.53 markus 717: proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
718: {
719: static int check[] = {
720: PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
721: };
722: int *idx;
723: char *p;
724:
725: for (idx = &check[0]; *idx != -1; idx++) {
726: if ((p = strchr(my[*idx], ',')) != NULL)
727: *p = '\0';
728: if ((p = strchr(peer[*idx], ',')) != NULL)
729: *p = '\0';
730: if (strcmp(my[*idx], peer[*idx]) != 0) {
731: debug2("proposal mismatch: my %s peer %s",
732: my[*idx], peer[*idx]);
733: return (0);
734: }
735: }
736: debug2("proposals match");
737: return (1);
738: }
739:
1.102 markus 740: static int
741: kex_choose_conf(struct ssh *ssh)
1.1 markus 742: {
1.102 markus 743: struct kex *kex = ssh->kex;
744: struct newkeys *newkeys;
745: char **my = NULL, **peer = NULL;
1.26 markus 746: char **cprop, **sprop;
1.27 markus 747: int nenc, nmac, ncomp;
1.96 dtucker 748: u_int mode, ctos, need, dh_need, authlen;
1.102 markus 749: int r, first_kex_follows;
1.1 markus 750:
1.110 djm 751: debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
752: if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
753: goto out;
754: debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
755: if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
1.102 markus 756: goto out;
1.26 markus 757:
1.27 markus 758: if (kex->server) {
1.26 markus 759: cprop=peer;
760: sprop=my;
761: } else {
762: cprop=my;
763: sprop=peer;
1.113 markus 764: }
765:
766: /* Check whether client supports ext_info_c */
767: if (kex->server) {
768: char *ext;
769:
770: ext = match_list("ext-info-c", peer[PROPOSAL_KEX_ALGS], NULL);
1.119 markus 771: kex->ext_info_c = (ext != NULL);
772: free(ext);
1.26 markus 773: }
1.1 markus 774:
1.30 markus 775: /* Algorithm Negotiation */
1.110 djm 776: if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
777: sprop[PROPOSAL_KEX_ALGS])) != 0) {
778: kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
779: peer[PROPOSAL_KEX_ALGS] = NULL;
780: goto out;
781: }
782: if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
783: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
784: kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
785: peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
786: goto out;
787: }
1.1 markus 788: for (mode = 0; mode < MODE_MAX; mode++) {
1.102 markus 789: if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
790: r = SSH_ERR_ALLOC_FAIL;
791: goto out;
792: }
1.30 markus 793: kex->newkeys[mode] = newkeys;
1.78 djm 794: ctos = (!kex->server && mode == MODE_OUT) ||
795: (kex->server && mode == MODE_IN);
1.1 markus 796: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
797: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
798: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.102 markus 799: if ((r = choose_enc(&newkeys->enc, cprop[nenc],
1.107 djm 800: sprop[nenc])) != 0) {
801: kex->failed_choice = peer[nenc];
802: peer[nenc] = NULL;
1.102 markus 803: goto out;
1.107 djm 804: }
1.102 markus 805: authlen = cipher_authlen(newkeys->enc.cipher);
1.88 markus 806: /* ignore mac for authenticated encryption */
1.102 markus 807: if (authlen == 0 &&
808: (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
1.107 djm 809: sprop[nmac])) != 0) {
810: kex->failed_choice = peer[nmac];
811: peer[nmac] = NULL;
1.102 markus 812: goto out;
1.107 djm 813: }
1.102 markus 814: if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
1.107 djm 815: sprop[ncomp])) != 0) {
816: kex->failed_choice = peer[ncomp];
817: peer[ncomp] = NULL;
1.102 markus 818: goto out;
1.107 djm 819: }
1.110 djm 820: debug("kex: %s cipher: %s MAC: %s compression: %s",
1.1 markus 821: ctos ? "client->server" : "server->client",
1.27 markus 822: newkeys->enc.name,
1.88 markus 823: authlen == 0 ? newkeys->mac.name : "<implicit>",
1.27 markus 824: newkeys->comp.name);
1.107 djm 825: }
1.96 dtucker 826: need = dh_need = 0;
1.1 markus 827: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 828: newkeys = kex->newkeys[mode];
1.120 deraadt 829: need = MAXIMUM(need, newkeys->enc.key_len);
830: need = MAXIMUM(need, newkeys->enc.block_size);
831: need = MAXIMUM(need, newkeys->enc.iv_len);
832: need = MAXIMUM(need, newkeys->mac.key_len);
833: dh_need = MAXIMUM(dh_need, cipher_seclen(newkeys->enc.cipher));
834: dh_need = MAXIMUM(dh_need, newkeys->enc.block_size);
835: dh_need = MAXIMUM(dh_need, newkeys->enc.iv_len);
836: dh_need = MAXIMUM(dh_need, newkeys->mac.key_len);
1.1 markus 837: }
1.7 markus 838: /* XXX need runden? */
1.27 markus 839: kex->we_need = need;
1.96 dtucker 840: kex->dh_need = dh_need;
1.53 markus 841:
842: /* ignore the next message if the proposals do not match */
1.56 djm 843: if (first_kex_follows && !proposals_match(my, peer) &&
1.102 markus 844: !(ssh->compat & SSH_BUG_FIRSTKEX))
845: ssh->dispatch_skip_packets = 1;
846: r = 0;
847: out:
1.26 markus 848: kex_prop_free(my);
849: kex_prop_free(peer);
1.102 markus 850: return r;
1.26 markus 851: }
852:
1.102 markus 853: static int
854: derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
855: const struct sshbuf *shared_secret, u_char **keyp)
1.26 markus 856: {
1.102 markus 857: struct kex *kex = ssh->kex;
858: struct ssh_digest_ctx *hashctx = NULL;
1.26 markus 859: char c = id;
1.61 djm 860: u_int have;
1.94 djm 861: size_t mdsz;
1.61 djm 862: u_char *digest;
1.102 markus 863: int r;
1.62 djm 864:
1.94 djm 865: if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
1.102 markus 866: return SSH_ERR_INVALID_ARGUMENT;
1.120 deraadt 867: if ((digest = calloc(1, ROUNDUP(need, mdsz))) == NULL) {
1.102 markus 868: r = SSH_ERR_ALLOC_FAIL;
869: goto out;
870: }
1.26 markus 871:
1.30 markus 872: /* K1 = HASH(K || H || "A" || session_id) */
1.102 markus 873: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
874: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 875: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
876: ssh_digest_update(hashctx, &c, 1) != 0 ||
877: ssh_digest_update(hashctx, kex->session_id,
1.102 markus 878: kex->session_id_len) != 0 ||
879: ssh_digest_final(hashctx, digest, mdsz) != 0) {
880: r = SSH_ERR_LIBCRYPTO_ERROR;
881: goto out;
882: }
1.94 djm 883: ssh_digest_free(hashctx);
1.102 markus 884: hashctx = NULL;
1.26 markus 885:
1.30 markus 886: /*
887: * expand key:
888: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
889: * Key = K1 || K2 || ... || Kn
890: */
1.26 markus 891: for (have = mdsz; need > have; have += mdsz) {
1.102 markus 892: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
893: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 894: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1.102 markus 895: ssh_digest_update(hashctx, digest, have) != 0 ||
896: ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
897: r = SSH_ERR_LIBCRYPTO_ERROR;
898: goto out;
899: }
1.94 djm 900: ssh_digest_free(hashctx);
1.102 markus 901: hashctx = NULL;
1.26 markus 902: }
903: #ifdef DEBUG_KEX
904: fprintf(stderr, "key '%c'== ", c);
905: dump_digest("key", digest, need);
906: #endif
1.102 markus 907: *keyp = digest;
908: digest = NULL;
909: r = 0;
910: out:
1.114 mmcc 911: free(digest);
1.102 markus 912: ssh_digest_free(hashctx);
913: return r;
1.1 markus 914: }
915:
1.23 markus 916: #define NKEYS 6
1.102 markus 917: int
918: kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
919: const struct sshbuf *shared_secret)
1.1 markus 920: {
1.102 markus 921: struct kex *kex = ssh->kex;
1.15 markus 922: u_char *keys[NKEYS];
1.102 markus 923: u_int i, j, mode, ctos;
924: int r;
1.1 markus 925:
1.65 djm 926: for (i = 0; i < NKEYS; i++) {
1.102 markus 927: if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
928: shared_secret, &keys[i])) != 0) {
929: for (j = 0; j < i; j++)
930: free(keys[j]);
931: return r;
932: }
1.65 djm 933: }
1.1 markus 934: for (mode = 0; mode < MODE_MAX; mode++) {
1.69 deraadt 935: ctos = (!kex->server && mode == MODE_OUT) ||
936: (kex->server && mode == MODE_IN);
1.100 markus 937: kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
938: kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
939: kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
1.1 markus 940: }
1.102 markus 941: return 0;
1.95 djm 942: }
943:
1.99 markus 944: #ifdef WITH_OPENSSL
1.102 markus 945: int
946: kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen,
947: const BIGNUM *secret)
1.95 djm 948: {
1.102 markus 949: struct sshbuf *shared_secret;
950: int r;
1.95 djm 951:
1.102 markus 952: if ((shared_secret = sshbuf_new()) == NULL)
953: return SSH_ERR_ALLOC_FAIL;
954: if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0)
955: r = kex_derive_keys(ssh, hash, hashlen, shared_secret);
956: sshbuf_free(shared_secret);
957: return r;
1.27 markus 958: }
1.99 markus 959: #endif
1.57 djm 960:
1.99 markus 961: #ifdef WITH_SSH1
1.102 markus 962: int
1.57 djm 963: derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
964: u_int8_t cookie[8], u_int8_t id[16])
965: {
1.105 djm 966: u_int8_t hbuf[2048], sbuf[2048], obuf[SSH_DIGEST_MAX_LENGTH];
1.102 markus 967: struct ssh_digest_ctx *hashctx = NULL;
1.105 djm 968: size_t hlen, slen;
1.102 markus 969: int r;
1.57 djm 970:
1.105 djm 971: hlen = BN_num_bytes(host_modulus);
972: slen = BN_num_bytes(server_modulus);
973: if (hlen < (512 / 8) || (u_int)hlen > sizeof(hbuf) ||
974: slen < (512 / 8) || (u_int)slen > sizeof(sbuf))
1.102 markus 975: return SSH_ERR_KEY_BITS_MISMATCH;
1.105 djm 976: if (BN_bn2bin(host_modulus, hbuf) <= 0 ||
977: BN_bn2bin(server_modulus, sbuf) <= 0) {
978: r = SSH_ERR_LIBCRYPTO_ERROR;
979: goto out;
980: }
981: if ((hashctx = ssh_digest_start(SSH_DIGEST_MD5)) == NULL) {
982: r = SSH_ERR_ALLOC_FAIL;
983: goto out;
984: }
985: if (ssh_digest_update(hashctx, hbuf, hlen) != 0 ||
986: ssh_digest_update(hashctx, sbuf, slen) != 0 ||
1.102 markus 987: ssh_digest_update(hashctx, cookie, 8) != 0 ||
988: ssh_digest_final(hashctx, obuf, sizeof(obuf)) != 0) {
989: r = SSH_ERR_LIBCRYPTO_ERROR;
990: goto out;
991: }
1.94 djm 992: memcpy(id, obuf, ssh_digest_bytes(SSH_DIGEST_MD5));
1.102 markus 993: r = 0;
994: out:
995: ssh_digest_free(hashctx);
1.105 djm 996: explicit_bzero(hbuf, sizeof(hbuf));
997: explicit_bzero(sbuf, sizeof(sbuf));
1.98 djm 998: explicit_bzero(obuf, sizeof(obuf));
1.102 markus 999: return r;
1.1 markus 1000: }
1.99 markus 1001: #endif
1.26 markus 1002:
1.84 djm 1003: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1.26 markus 1004: void
1005: dump_digest(char *msg, u_char *digest, int len)
1006: {
1007: fprintf(stderr, "%s\n", msg);
1.102 markus 1008: sshbuf_dump_data(digest, len, stderr);
1.26 markus 1009: }
1010: #endif
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