Annotation of src/usr.bin/ssh/kex.c, Revision 1.127
1.127 ! markus 1: /* $OpenBSD: kex.c,v 1.126 2016/09/28 21:44:52 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 *);
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
194: * indicate that it should be appended to the default.
195: */
196: int
197: kex_assemble_names(const char *def, char **list)
198: {
199: char *ret;
200:
201: if (list == NULL || *list == NULL || **list == '\0') {
202: *list = strdup(def);
203: return 0;
204: }
205: if (**list != '+') {
206: return 0;
207: }
208:
209: if ((ret = kex_names_cat(def, *list + 1)) == NULL)
210: return SSH_ERR_ALLOC_FAIL;
211: free(*list);
212: *list = ret;
213: return 0;
1.86 djm 214: }
1.26 markus 215:
216: /* put algorithm proposal into buffer */
1.102 markus 217: int
218: kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
1.1 markus 219: {
1.61 djm 220: u_int i;
1.102 markus 221: int r;
222:
223: sshbuf_reset(b);
1.26 markus 224:
1.49 markus 225: /*
226: * add a dummy cookie, the cookie will be overwritten by
227: * kex_send_kexinit(), each time a kexinit is set
228: */
1.102 markus 229: for (i = 0; i < KEX_COOKIE_LEN; i++) {
230: if ((r = sshbuf_put_u8(b, 0)) != 0)
231: return r;
232: }
233: for (i = 0; i < PROPOSAL_MAX; i++) {
234: if ((r = sshbuf_put_cstring(b, proposal[i])) != 0)
235: return r;
236: }
237: if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */
238: (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */
239: return r;
240: return 0;
1.1 markus 241: }
242:
1.26 markus 243: /* parse buffer and return algorithm proposal */
1.102 markus 244: int
245: kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp)
1.7 markus 246: {
1.102 markus 247: struct sshbuf *b = NULL;
248: u_char v;
1.78 djm 249: u_int i;
1.102 markus 250: char **proposal = NULL;
251: int r;
1.7 markus 252:
1.102 markus 253: *propp = NULL;
254: if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL)
255: return SSH_ERR_ALLOC_FAIL;
256: if ((b = sshbuf_fromb(raw)) == NULL) {
257: r = SSH_ERR_ALLOC_FAIL;
258: goto out;
259: }
260: if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */
261: goto out;
1.7 markus 262: /* extract kex init proposal strings */
263: for (i = 0; i < PROPOSAL_MAX; i++) {
1.102 markus 264: if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0)
265: goto out;
1.110 djm 266: debug2("%s: %s", proposal_names[i], proposal[i]);
1.7 markus 267: }
1.26 markus 268: /* first kex follows / reserved */
1.115 djm 269: if ((r = sshbuf_get_u8(b, &v)) != 0 || /* first_kex_follows */
270: (r = sshbuf_get_u32(b, &i)) != 0) /* reserved */
1.102 markus 271: goto out;
1.53 markus 272: if (first_kex_follows != NULL)
1.115 djm 273: *first_kex_follows = v;
1.110 djm 274: debug2("first_kex_follows %d ", v);
275: debug2("reserved %u ", i);
1.102 markus 276: r = 0;
277: *propp = proposal;
278: out:
279: if (r != 0 && proposal != NULL)
280: kex_prop_free(proposal);
281: sshbuf_free(b);
282: return r;
1.1 markus 283: }
284:
1.102 markus 285: void
1.26 markus 286: kex_prop_free(char **proposal)
1.1 markus 287: {
1.61 djm 288: u_int i;
1.26 markus 289:
1.106 djm 290: if (proposal == NULL)
291: return;
1.26 markus 292: for (i = 0; i < PROPOSAL_MAX; i++)
1.91 djm 293: free(proposal[i]);
294: free(proposal);
1.1 markus 295: }
296:
1.78 djm 297: /* ARGSUSED */
1.101 markus 298: static int
1.41 markus 299: kex_protocol_error(int type, u_int32_t seq, void *ctxt)
1.1 markus 300: {
1.112 djm 301: struct ssh *ssh = active_state; /* XXX */
302: int r;
303:
304: error("kex protocol error: type %d seq %u", type, seq);
305: if ((r = sshpkt_start(ssh, SSH2_MSG_UNIMPLEMENTED)) != 0 ||
306: (r = sshpkt_put_u32(ssh, seq)) != 0 ||
307: (r = sshpkt_send(ssh)) != 0)
308: return r;
1.101 markus 309: return 0;
1.26 markus 310: }
1.1 markus 311:
1.35 itojun 312: static void
1.102 markus 313: kex_reset_dispatch(struct ssh *ssh)
1.29 markus 314: {
1.102 markus 315: ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
1.42 markus 316: SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
1.102 markus 317: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.29 markus 318: }
319:
1.113 markus 320: static int
321: kex_send_ext_info(struct ssh *ssh)
322: {
323: int r;
1.121 djm 324: char *algs;
1.113 markus 325:
1.121 djm 326: if ((algs = sshkey_alg_list(0, 1, ',')) == NULL)
327: return SSH_ERR_ALLOC_FAIL;
1.113 markus 328: if ((r = sshpkt_start(ssh, SSH2_MSG_EXT_INFO)) != 0 ||
329: (r = sshpkt_put_u32(ssh, 1)) != 0 ||
330: (r = sshpkt_put_cstring(ssh, "server-sig-algs")) != 0 ||
1.121 djm 331: (r = sshpkt_put_cstring(ssh, algs)) != 0 ||
1.113 markus 332: (r = sshpkt_send(ssh)) != 0)
1.121 djm 333: goto out;
334: /* success */
335: r = 0;
336: out:
337: free(algs);
1.123 djm 338: return r;
1.113 markus 339: }
340:
1.102 markus 341: int
342: kex_send_newkeys(struct ssh *ssh)
1.26 markus 343: {
1.102 markus 344: int r;
1.28 markus 345:
1.102 markus 346: kex_reset_dispatch(ssh);
347: if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
348: (r = sshpkt_send(ssh)) != 0)
349: return r;
1.26 markus 350: debug("SSH2_MSG_NEWKEYS sent");
1.102 markus 351: debug("expecting SSH2_MSG_NEWKEYS");
352: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
1.113 markus 353: if (ssh->kex->ext_info_c)
354: if ((r = kex_send_ext_info(ssh)) != 0)
355: return r;
1.102 markus 356: return 0;
357: }
358:
1.113 markus 359: int
360: kex_input_ext_info(int type, u_int32_t seq, void *ctxt)
361: {
362: struct ssh *ssh = ctxt;
363: struct kex *kex = ssh->kex;
364: u_int32_t i, ninfo;
365: char *name, *val, *found;
366: int r;
367:
368: debug("SSH2_MSG_EXT_INFO received");
369: ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_protocol_error);
370: if ((r = sshpkt_get_u32(ssh, &ninfo)) != 0)
371: return r;
372: for (i = 0; i < ninfo; i++) {
373: if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0)
374: return r;
375: if ((r = sshpkt_get_cstring(ssh, &val, NULL)) != 0) {
376: free(name);
377: return r;
378: }
379: debug("%s: %s=<%s>", __func__, name, val);
380: if (strcmp(name, "server-sig-algs") == 0) {
381: found = match_list("rsa-sha2-256", val, NULL);
382: if (found) {
383: kex->rsa_sha2 = 256;
384: free(found);
385: }
386: found = match_list("rsa-sha2-512", val, NULL);
387: if (found) {
388: kex->rsa_sha2 = 512;
389: free(found);
390: }
391: }
392: free(name);
393: free(val);
394: }
395: return sshpkt_get_end(ssh);
396: }
397:
1.102 markus 398: static int
399: kex_input_newkeys(int type, u_int32_t seq, void *ctxt)
400: {
401: struct ssh *ssh = ctxt;
402: struct kex *kex = ssh->kex;
403: int r;
1.19 stevesk 404:
1.26 markus 405: debug("SSH2_MSG_NEWKEYS received");
1.102 markus 406: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
407: if ((r = sshpkt_get_end(ssh)) != 0)
1.122 markus 408: return r;
409: if ((r = ssh_set_newkeys(ssh, MODE_IN)) != 0)
1.102 markus 410: return r;
1.30 markus 411: kex->done = 1;
1.102 markus 412: sshbuf_reset(kex->peer);
413: /* sshbuf_reset(kex->my); */
1.26 markus 414: kex->flags &= ~KEX_INIT_SENT;
1.91 djm 415: free(kex->name);
1.32 markus 416: kex->name = NULL;
1.102 markus 417: return 0;
1.26 markus 418: }
1.1 markus 419:
1.102 markus 420: int
421: kex_send_kexinit(struct ssh *ssh)
1.26 markus 422: {
1.49 markus 423: u_char *cookie;
1.102 markus 424: struct kex *kex = ssh->kex;
425: int r;
1.49 markus 426:
1.102 markus 427: if (kex == NULL)
428: return SSH_ERR_INTERNAL_ERROR;
429: if (kex->flags & KEX_INIT_SENT)
430: return 0;
1.30 markus 431: kex->done = 0;
1.49 markus 432:
433: /* generate a random cookie */
1.102 markus 434: if (sshbuf_len(kex->my) < KEX_COOKIE_LEN)
435: return SSH_ERR_INVALID_FORMAT;
436: if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL)
437: return SSH_ERR_INTERNAL_ERROR;
438: arc4random_buf(cookie, KEX_COOKIE_LEN);
439:
440: if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
441: (r = sshpkt_putb(ssh, kex->my)) != 0 ||
442: (r = sshpkt_send(ssh)) != 0)
443: return r;
1.26 markus 444: debug("SSH2_MSG_KEXINIT sent");
445: kex->flags |= KEX_INIT_SENT;
1.102 markus 446: return 0;
1.1 markus 447: }
448:
1.78 djm 449: /* ARGSUSED */
1.101 markus 450: int
1.41 markus 451: kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
1.11 provos 452: {
1.102 markus 453: struct ssh *ssh = ctxt;
454: struct kex *kex = ssh->kex;
455: const u_char *ptr;
1.100 markus 456: u_int i;
457: size_t dlen;
1.102 markus 458: int r;
1.11 provos 459:
1.26 markus 460: debug("SSH2_MSG_KEXINIT received");
1.29 markus 461: if (kex == NULL)
1.102 markus 462: return SSH_ERR_INVALID_ARGUMENT;
1.11 provos 463:
1.127 ! markus 464: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, NULL);
1.102 markus 465: ptr = sshpkt_ptr(ssh, &dlen);
466: if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
467: return r;
1.31 markus 468:
469: /* discard packet */
470: for (i = 0; i < KEX_COOKIE_LEN; i++)
1.102 markus 471: if ((r = sshpkt_get_u8(ssh, NULL)) != 0)
472: return r;
1.31 markus 473: for (i = 0; i < PROPOSAL_MAX; i++)
1.102 markus 474: if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0)
475: return r;
1.87 djm 476: /*
477: * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
478: * KEX method has the server move first, but a server might be using
479: * a custom method or one that we otherwise don't support. We should
480: * be prepared to remember first_kex_follows here so we can eat a
481: * packet later.
482: * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
483: * for cases where the server *doesn't* go first. I guess we should
484: * ignore it when it is set for these cases, which is what we do now.
485: */
1.102 markus 486: if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
487: (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
488: (r = sshpkt_get_end(ssh)) != 0)
489: return r;
490:
491: if (!(kex->flags & KEX_INIT_SENT))
492: if ((r = kex_send_kexinit(ssh)) != 0)
493: return r;
494: if ((r = kex_choose_conf(ssh)) != 0)
495: return r;
1.19 stevesk 496:
1.102 markus 497: if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
498: return (kex->kex[kex->kex_type])(ssh);
499:
500: return SSH_ERR_INTERNAL_ERROR;
501: }
502:
503: int
504: kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp)
505: {
506: struct kex *kex;
507: int r;
508:
509: *kexp = NULL;
510: if ((kex = calloc(1, sizeof(*kex))) == NULL)
511: return SSH_ERR_ALLOC_FAIL;
512: if ((kex->peer = sshbuf_new()) == NULL ||
513: (kex->my = sshbuf_new()) == NULL) {
514: r = SSH_ERR_ALLOC_FAIL;
515: goto out;
516: }
517: if ((r = kex_prop2buf(kex->my, proposal)) != 0)
518: goto out;
519: kex->done = 0;
520: kex_reset_dispatch(ssh);
521: r = 0;
522: *kexp = kex;
523: out:
524: if (r != 0)
525: kex_free(kex);
526: return r;
1.26 markus 527: }
1.11 provos 528:
1.100 markus 529: void
530: kex_free_newkeys(struct newkeys *newkeys)
531: {
532: if (newkeys == NULL)
533: return;
534: if (newkeys->enc.key) {
535: explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
536: free(newkeys->enc.key);
537: newkeys->enc.key = NULL;
538: }
539: if (newkeys->enc.iv) {
1.111 djm 540: explicit_bzero(newkeys->enc.iv, newkeys->enc.iv_len);
1.100 markus 541: free(newkeys->enc.iv);
542: newkeys->enc.iv = NULL;
543: }
544: free(newkeys->enc.name);
545: explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
546: free(newkeys->comp.name);
547: explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
548: mac_clear(&newkeys->mac);
549: if (newkeys->mac.key) {
550: explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
551: free(newkeys->mac.key);
552: newkeys->mac.key = NULL;
553: }
554: free(newkeys->mac.name);
555: explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
556: explicit_bzero(newkeys, sizeof(*newkeys));
557: free(newkeys);
558: }
559:
1.102 markus 560: void
561: kex_free(struct kex *kex)
1.26 markus 562: {
1.102 markus 563: u_int mode;
1.11 provos 564:
1.102 markus 565: #ifdef WITH_OPENSSL
566: if (kex->dh)
567: DH_free(kex->dh);
568: if (kex->ec_client_key)
569: EC_KEY_free(kex->ec_client_key);
570: #endif
571: for (mode = 0; mode < MODE_MAX; mode++) {
572: kex_free_newkeys(kex->newkeys[mode]);
573: kex->newkeys[mode] = NULL;
1.100 markus 574: }
1.102 markus 575: sshbuf_free(kex->peer);
576: sshbuf_free(kex->my);
577: free(kex->session_id);
578: free(kex->client_version_string);
579: free(kex->server_version_string);
1.107 djm 580: free(kex->failed_choice);
1.113 markus 581: free(kex->hostkey_alg);
582: free(kex->name);
1.102 markus 583: free(kex);
1.11 provos 584: }
585:
1.102 markus 586: int
587: kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
1.1 markus 588: {
1.102 markus 589: int r;
1.1 markus 590:
1.102 markus 591: if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0)
592: return r;
593: if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
594: kex_free(ssh->kex);
595: ssh->kex = NULL;
596: return r;
1.1 markus 597: }
1.102 markus 598: return 0;
1.117 djm 599: }
600:
601: /*
602: * Request key re-exchange, returns 0 on success or a ssherr.h error
603: * code otherwise. Must not be called if KEX is incomplete or in-progress.
604: */
605: int
606: kex_start_rekex(struct ssh *ssh)
607: {
608: if (ssh->kex == NULL) {
609: error("%s: no kex", __func__);
610: return SSH_ERR_INTERNAL_ERROR;
611: }
612: if (ssh->kex->done == 0) {
613: error("%s: requested twice", __func__);
614: return SSH_ERR_INTERNAL_ERROR;
615: }
616: ssh->kex->done = 0;
617: return kex_send_kexinit(ssh);
1.1 markus 618: }
619:
1.102 markus 620: static int
621: choose_enc(struct sshenc *enc, char *client, char *server)
1.1 markus 622: {
1.23 markus 623: char *name = match_list(client, server, NULL);
1.102 markus 624:
1.1 markus 625: if (name == NULL)
1.102 markus 626: return SSH_ERR_NO_CIPHER_ALG_MATCH;
1.45 markus 627: if ((enc->cipher = cipher_by_name(name)) == NULL)
1.102 markus 628: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 629: enc->name = name;
630: enc->enabled = 0;
631: enc->iv = NULL;
1.88 markus 632: enc->iv_len = cipher_ivlen(enc->cipher);
1.1 markus 633: enc->key = NULL;
1.45 markus 634: enc->key_len = cipher_keylen(enc->cipher);
635: enc->block_size = cipher_blocksize(enc->cipher);
1.102 markus 636: return 0;
1.1 markus 637: }
1.69 deraadt 638:
1.102 markus 639: static int
640: choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
1.1 markus 641: {
1.23 markus 642: char *name = match_list(client, server, NULL);
1.102 markus 643:
1.1 markus 644: if (name == NULL)
1.102 markus 645: return SSH_ERR_NO_MAC_ALG_MATCH;
1.79 djm 646: if (mac_setup(mac, name) < 0)
1.102 markus 647: return SSH_ERR_INTERNAL_ERROR;
1.21 markus 648: /* truncate the key */
1.102 markus 649: if (ssh->compat & SSH_BUG_HMAC)
1.21 markus 650: mac->key_len = 16;
1.1 markus 651: mac->name = name;
652: mac->key = NULL;
653: mac->enabled = 0;
1.102 markus 654: return 0;
1.1 markus 655: }
1.69 deraadt 656:
1.102 markus 657: static int
658: choose_comp(struct sshcomp *comp, char *client, char *server)
1.1 markus 659: {
1.23 markus 660: char *name = match_list(client, server, NULL);
1.102 markus 661:
1.1 markus 662: if (name == NULL)
1.102 markus 663: return SSH_ERR_NO_COMPRESS_ALG_MATCH;
1.64 markus 664: if (strcmp(name, "zlib@openssh.com") == 0) {
665: comp->type = COMP_DELAYED;
1.126 djm 666: } else if (strcmp(name, "zlib") == 0) {
667: comp->type = COMP_ZLIB;
1.1 markus 668: } else if (strcmp(name, "none") == 0) {
1.64 markus 669: comp->type = COMP_NONE;
1.1 markus 670: } else {
1.102 markus 671: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 672: }
673: comp->name = name;
1.102 markus 674: return 0;
1.1 markus 675: }
1.69 deraadt 676:
1.102 markus 677: static int
678: choose_kex(struct kex *k, char *client, char *server)
1.1 markus 679: {
1.89 djm 680: const struct kexalg *kexalg;
681:
1.23 markus 682: k->name = match_list(client, server, NULL);
1.102 markus 683:
1.110 djm 684: debug("kex: algorithm: %s", k->name ? k->name : "(no match)");
1.1 markus 685: if (k->name == NULL)
1.102 markus 686: return SSH_ERR_NO_KEX_ALG_MATCH;
1.89 djm 687: if ((kexalg = kex_alg_by_name(k->name)) == NULL)
1.102 markus 688: return SSH_ERR_INTERNAL_ERROR;
1.89 djm 689: k->kex_type = kexalg->type;
1.94 djm 690: k->hash_alg = kexalg->hash_alg;
1.89 djm 691: k->ec_nid = kexalg->ec_nid;
1.102 markus 692: return 0;
1.1 markus 693: }
1.65 djm 694:
1.102 markus 695: static int
696: choose_hostkeyalg(struct kex *k, char *client, char *server)
1.1 markus 697: {
1.113 markus 698: k->hostkey_alg = match_list(client, server, NULL);
1.102 markus 699:
1.110 djm 700: debug("kex: host key algorithm: %s",
1.113 markus 701: k->hostkey_alg ? k->hostkey_alg : "(no match)");
702: if (k->hostkey_alg == NULL)
1.102 markus 703: return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
1.113 markus 704: k->hostkey_type = sshkey_type_from_name(k->hostkey_alg);
1.13 markus 705: if (k->hostkey_type == KEY_UNSPEC)
1.102 markus 706: return SSH_ERR_INTERNAL_ERROR;
1.113 markus 707: k->hostkey_nid = sshkey_ecdsa_nid_from_name(k->hostkey_alg);
1.102 markus 708: return 0;
1.1 markus 709: }
710:
1.56 djm 711: static int
1.53 markus 712: proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
713: {
714: static int check[] = {
715: PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
716: };
717: int *idx;
718: char *p;
719:
720: for (idx = &check[0]; *idx != -1; idx++) {
721: if ((p = strchr(my[*idx], ',')) != NULL)
722: *p = '\0';
723: if ((p = strchr(peer[*idx], ',')) != NULL)
724: *p = '\0';
725: if (strcmp(my[*idx], peer[*idx]) != 0) {
726: debug2("proposal mismatch: my %s peer %s",
727: my[*idx], peer[*idx]);
728: return (0);
729: }
730: }
731: debug2("proposals match");
732: return (1);
733: }
734:
1.102 markus 735: static int
736: kex_choose_conf(struct ssh *ssh)
1.1 markus 737: {
1.102 markus 738: struct kex *kex = ssh->kex;
739: struct newkeys *newkeys;
740: char **my = NULL, **peer = NULL;
1.26 markus 741: char **cprop, **sprop;
1.27 markus 742: int nenc, nmac, ncomp;
1.96 dtucker 743: u_int mode, ctos, need, dh_need, authlen;
1.102 markus 744: int r, first_kex_follows;
1.1 markus 745:
1.110 djm 746: debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
747: if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
748: goto out;
749: debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
750: if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
1.102 markus 751: goto out;
1.26 markus 752:
1.27 markus 753: if (kex->server) {
1.26 markus 754: cprop=peer;
755: sprop=my;
756: } else {
757: cprop=my;
758: sprop=peer;
1.113 markus 759: }
760:
761: /* Check whether client supports ext_info_c */
762: if (kex->server) {
763: char *ext;
764:
765: ext = match_list("ext-info-c", peer[PROPOSAL_KEX_ALGS], NULL);
1.119 markus 766: kex->ext_info_c = (ext != NULL);
767: free(ext);
1.26 markus 768: }
1.1 markus 769:
1.30 markus 770: /* Algorithm Negotiation */
1.110 djm 771: if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
772: sprop[PROPOSAL_KEX_ALGS])) != 0) {
773: kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
774: peer[PROPOSAL_KEX_ALGS] = NULL;
775: goto out;
776: }
777: if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
778: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
779: kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
780: peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
781: goto out;
782: }
1.1 markus 783: for (mode = 0; mode < MODE_MAX; mode++) {
1.102 markus 784: if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
785: r = SSH_ERR_ALLOC_FAIL;
786: goto out;
787: }
1.30 markus 788: kex->newkeys[mode] = newkeys;
1.78 djm 789: ctos = (!kex->server && mode == MODE_OUT) ||
790: (kex->server && mode == MODE_IN);
1.1 markus 791: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
792: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
793: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.102 markus 794: if ((r = choose_enc(&newkeys->enc, cprop[nenc],
1.107 djm 795: sprop[nenc])) != 0) {
796: kex->failed_choice = peer[nenc];
797: peer[nenc] = NULL;
1.102 markus 798: goto out;
1.107 djm 799: }
1.102 markus 800: authlen = cipher_authlen(newkeys->enc.cipher);
1.88 markus 801: /* ignore mac for authenticated encryption */
1.102 markus 802: if (authlen == 0 &&
803: (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
1.107 djm 804: sprop[nmac])) != 0) {
805: kex->failed_choice = peer[nmac];
806: peer[nmac] = NULL;
1.102 markus 807: goto out;
1.107 djm 808: }
1.102 markus 809: if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
1.107 djm 810: sprop[ncomp])) != 0) {
811: kex->failed_choice = peer[ncomp];
812: peer[ncomp] = NULL;
1.102 markus 813: goto out;
1.107 djm 814: }
1.110 djm 815: debug("kex: %s cipher: %s MAC: %s compression: %s",
1.1 markus 816: ctos ? "client->server" : "server->client",
1.27 markus 817: newkeys->enc.name,
1.88 markus 818: authlen == 0 ? newkeys->mac.name : "<implicit>",
1.27 markus 819: newkeys->comp.name);
1.107 djm 820: }
1.96 dtucker 821: need = dh_need = 0;
1.1 markus 822: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 823: newkeys = kex->newkeys[mode];
1.120 deraadt 824: need = MAXIMUM(need, newkeys->enc.key_len);
825: need = MAXIMUM(need, newkeys->enc.block_size);
826: need = MAXIMUM(need, newkeys->enc.iv_len);
827: need = MAXIMUM(need, newkeys->mac.key_len);
828: dh_need = MAXIMUM(dh_need, cipher_seclen(newkeys->enc.cipher));
829: dh_need = MAXIMUM(dh_need, newkeys->enc.block_size);
830: dh_need = MAXIMUM(dh_need, newkeys->enc.iv_len);
831: dh_need = MAXIMUM(dh_need, newkeys->mac.key_len);
1.1 markus 832: }
1.7 markus 833: /* XXX need runden? */
1.27 markus 834: kex->we_need = need;
1.96 dtucker 835: kex->dh_need = dh_need;
1.53 markus 836:
837: /* ignore the next message if the proposals do not match */
1.56 djm 838: if (first_kex_follows && !proposals_match(my, peer) &&
1.102 markus 839: !(ssh->compat & SSH_BUG_FIRSTKEX))
840: ssh->dispatch_skip_packets = 1;
841: r = 0;
842: out:
1.26 markus 843: kex_prop_free(my);
844: kex_prop_free(peer);
1.102 markus 845: return r;
1.26 markus 846: }
847:
1.102 markus 848: static int
849: derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
850: const struct sshbuf *shared_secret, u_char **keyp)
1.26 markus 851: {
1.102 markus 852: struct kex *kex = ssh->kex;
853: struct ssh_digest_ctx *hashctx = NULL;
1.26 markus 854: char c = id;
1.61 djm 855: u_int have;
1.94 djm 856: size_t mdsz;
1.61 djm 857: u_char *digest;
1.102 markus 858: int r;
1.62 djm 859:
1.94 djm 860: if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
1.102 markus 861: return SSH_ERR_INVALID_ARGUMENT;
1.120 deraadt 862: if ((digest = calloc(1, ROUNDUP(need, mdsz))) == NULL) {
1.102 markus 863: r = SSH_ERR_ALLOC_FAIL;
864: goto out;
865: }
1.26 markus 866:
1.30 markus 867: /* K1 = HASH(K || H || "A" || session_id) */
1.102 markus 868: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
869: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 870: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
871: ssh_digest_update(hashctx, &c, 1) != 0 ||
872: ssh_digest_update(hashctx, kex->session_id,
1.102 markus 873: kex->session_id_len) != 0 ||
874: ssh_digest_final(hashctx, digest, mdsz) != 0) {
875: r = SSH_ERR_LIBCRYPTO_ERROR;
876: goto out;
877: }
1.94 djm 878: ssh_digest_free(hashctx);
1.102 markus 879: hashctx = NULL;
1.26 markus 880:
1.30 markus 881: /*
882: * expand key:
883: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
884: * Key = K1 || K2 || ... || Kn
885: */
1.26 markus 886: for (have = mdsz; need > have; have += mdsz) {
1.102 markus 887: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
888: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 889: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1.102 markus 890: ssh_digest_update(hashctx, digest, have) != 0 ||
891: ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
892: r = SSH_ERR_LIBCRYPTO_ERROR;
893: goto out;
894: }
1.94 djm 895: ssh_digest_free(hashctx);
1.102 markus 896: hashctx = NULL;
1.26 markus 897: }
898: #ifdef DEBUG_KEX
899: fprintf(stderr, "key '%c'== ", c);
900: dump_digest("key", digest, need);
901: #endif
1.102 markus 902: *keyp = digest;
903: digest = NULL;
904: r = 0;
905: out:
1.114 mmcc 906: free(digest);
1.102 markus 907: ssh_digest_free(hashctx);
908: return r;
1.1 markus 909: }
910:
1.23 markus 911: #define NKEYS 6
1.102 markus 912: int
913: kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
914: const struct sshbuf *shared_secret)
1.1 markus 915: {
1.102 markus 916: struct kex *kex = ssh->kex;
1.15 markus 917: u_char *keys[NKEYS];
1.102 markus 918: u_int i, j, mode, ctos;
919: int r;
1.1 markus 920:
1.65 djm 921: for (i = 0; i < NKEYS; i++) {
1.102 markus 922: if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
923: shared_secret, &keys[i])) != 0) {
924: for (j = 0; j < i; j++)
925: free(keys[j]);
926: return r;
927: }
1.65 djm 928: }
1.1 markus 929: for (mode = 0; mode < MODE_MAX; mode++) {
1.69 deraadt 930: ctos = (!kex->server && mode == MODE_OUT) ||
931: (kex->server && mode == MODE_IN);
1.100 markus 932: kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
933: kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
934: kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
1.1 markus 935: }
1.102 markus 936: return 0;
1.95 djm 937: }
938:
1.99 markus 939: #ifdef WITH_OPENSSL
1.102 markus 940: int
941: kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen,
942: const BIGNUM *secret)
1.95 djm 943: {
1.102 markus 944: struct sshbuf *shared_secret;
945: int r;
1.95 djm 946:
1.102 markus 947: if ((shared_secret = sshbuf_new()) == NULL)
948: return SSH_ERR_ALLOC_FAIL;
949: if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0)
950: r = kex_derive_keys(ssh, hash, hashlen, shared_secret);
951: sshbuf_free(shared_secret);
952: return r;
1.27 markus 953: }
1.99 markus 954: #endif
1.57 djm 955:
1.99 markus 956: #ifdef WITH_SSH1
1.102 markus 957: int
1.57 djm 958: derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
959: u_int8_t cookie[8], u_int8_t id[16])
960: {
1.105 djm 961: u_int8_t hbuf[2048], sbuf[2048], obuf[SSH_DIGEST_MAX_LENGTH];
1.102 markus 962: struct ssh_digest_ctx *hashctx = NULL;
1.105 djm 963: size_t hlen, slen;
1.102 markus 964: int r;
1.57 djm 965:
1.105 djm 966: hlen = BN_num_bytes(host_modulus);
967: slen = BN_num_bytes(server_modulus);
968: if (hlen < (512 / 8) || (u_int)hlen > sizeof(hbuf) ||
969: slen < (512 / 8) || (u_int)slen > sizeof(sbuf))
1.102 markus 970: return SSH_ERR_KEY_BITS_MISMATCH;
1.105 djm 971: if (BN_bn2bin(host_modulus, hbuf) <= 0 ||
972: BN_bn2bin(server_modulus, sbuf) <= 0) {
973: r = SSH_ERR_LIBCRYPTO_ERROR;
974: goto out;
975: }
976: if ((hashctx = ssh_digest_start(SSH_DIGEST_MD5)) == NULL) {
977: r = SSH_ERR_ALLOC_FAIL;
978: goto out;
979: }
980: if (ssh_digest_update(hashctx, hbuf, hlen) != 0 ||
981: ssh_digest_update(hashctx, sbuf, slen) != 0 ||
1.102 markus 982: ssh_digest_update(hashctx, cookie, 8) != 0 ||
983: ssh_digest_final(hashctx, obuf, sizeof(obuf)) != 0) {
984: r = SSH_ERR_LIBCRYPTO_ERROR;
985: goto out;
986: }
1.94 djm 987: memcpy(id, obuf, ssh_digest_bytes(SSH_DIGEST_MD5));
1.102 markus 988: r = 0;
989: out:
990: ssh_digest_free(hashctx);
1.105 djm 991: explicit_bzero(hbuf, sizeof(hbuf));
992: explicit_bzero(sbuf, sizeof(sbuf));
1.98 djm 993: explicit_bzero(obuf, sizeof(obuf));
1.102 markus 994: return r;
1.1 markus 995: }
1.99 markus 996: #endif
1.26 markus 997:
1.84 djm 998: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1.26 markus 999: void
1000: dump_digest(char *msg, u_char *digest, int len)
1001: {
1002: fprintf(stderr, "%s\n", msg);
1.102 markus 1003: sshbuf_dump_data(digest, len, stderr);
1.26 markus 1004: }
1005: #endif
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