Annotation of src/usr.bin/ssh/kex.c, Revision 1.126
1.126 ! djm 1: /* $OpenBSD: kex.c,v 1.125 2016/09/28 20:32:42 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:
1.102 markus 464: ptr = sshpkt_ptr(ssh, &dlen);
465: if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
466: return r;
1.31 markus 467:
468: /* discard packet */
469: for (i = 0; i < KEX_COOKIE_LEN; i++)
1.102 markus 470: if ((r = sshpkt_get_u8(ssh, NULL)) != 0)
471: return r;
1.31 markus 472: for (i = 0; i < PROPOSAL_MAX; i++)
1.102 markus 473: if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0)
474: return r;
1.87 djm 475: /*
476: * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
477: * KEX method has the server move first, but a server might be using
478: * a custom method or one that we otherwise don't support. We should
479: * be prepared to remember first_kex_follows here so we can eat a
480: * packet later.
481: * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
482: * for cases where the server *doesn't* go first. I guess we should
483: * ignore it when it is set for these cases, which is what we do now.
484: */
1.102 markus 485: if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
486: (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
487: (r = sshpkt_get_end(ssh)) != 0)
488: return r;
489:
490: if (!(kex->flags & KEX_INIT_SENT))
491: if ((r = kex_send_kexinit(ssh)) != 0)
492: return r;
493: if ((r = kex_choose_conf(ssh)) != 0)
494: return r;
1.19 stevesk 495:
1.102 markus 496: if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
497: return (kex->kex[kex->kex_type])(ssh);
498:
499: return SSH_ERR_INTERNAL_ERROR;
500: }
501:
502: int
503: kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp)
504: {
505: struct kex *kex;
506: int r;
507:
508: *kexp = NULL;
509: if ((kex = calloc(1, sizeof(*kex))) == NULL)
510: return SSH_ERR_ALLOC_FAIL;
511: if ((kex->peer = sshbuf_new()) == NULL ||
512: (kex->my = sshbuf_new()) == NULL) {
513: r = SSH_ERR_ALLOC_FAIL;
514: goto out;
515: }
516: if ((r = kex_prop2buf(kex->my, proposal)) != 0)
517: goto out;
518: kex->done = 0;
519: kex_reset_dispatch(ssh);
520: r = 0;
521: *kexp = kex;
522: out:
523: if (r != 0)
524: kex_free(kex);
525: return r;
1.26 markus 526: }
1.11 provos 527:
1.100 markus 528: void
529: kex_free_newkeys(struct newkeys *newkeys)
530: {
531: if (newkeys == NULL)
532: return;
533: if (newkeys->enc.key) {
534: explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
535: free(newkeys->enc.key);
536: newkeys->enc.key = NULL;
537: }
538: if (newkeys->enc.iv) {
1.111 djm 539: explicit_bzero(newkeys->enc.iv, newkeys->enc.iv_len);
1.100 markus 540: free(newkeys->enc.iv);
541: newkeys->enc.iv = NULL;
542: }
543: free(newkeys->enc.name);
544: explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
545: free(newkeys->comp.name);
546: explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
547: mac_clear(&newkeys->mac);
548: if (newkeys->mac.key) {
549: explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
550: free(newkeys->mac.key);
551: newkeys->mac.key = NULL;
552: }
553: free(newkeys->mac.name);
554: explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
555: explicit_bzero(newkeys, sizeof(*newkeys));
556: free(newkeys);
557: }
558:
1.102 markus 559: void
560: kex_free(struct kex *kex)
1.26 markus 561: {
1.102 markus 562: u_int mode;
1.11 provos 563:
1.102 markus 564: #ifdef WITH_OPENSSL
565: if (kex->dh)
566: DH_free(kex->dh);
567: if (kex->ec_client_key)
568: EC_KEY_free(kex->ec_client_key);
569: #endif
570: for (mode = 0; mode < MODE_MAX; mode++) {
571: kex_free_newkeys(kex->newkeys[mode]);
572: kex->newkeys[mode] = NULL;
1.100 markus 573: }
1.102 markus 574: sshbuf_free(kex->peer);
575: sshbuf_free(kex->my);
576: free(kex->session_id);
577: free(kex->client_version_string);
578: free(kex->server_version_string);
1.107 djm 579: free(kex->failed_choice);
1.113 markus 580: free(kex->hostkey_alg);
581: free(kex->name);
1.102 markus 582: free(kex);
1.11 provos 583: }
584:
1.102 markus 585: int
586: kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
1.1 markus 587: {
1.102 markus 588: int r;
1.1 markus 589:
1.102 markus 590: if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0)
591: return r;
592: if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
593: kex_free(ssh->kex);
594: ssh->kex = NULL;
595: return r;
1.1 markus 596: }
1.102 markus 597: return 0;
1.117 djm 598: }
599:
600: /*
601: * Request key re-exchange, returns 0 on success or a ssherr.h error
602: * code otherwise. Must not be called if KEX is incomplete or in-progress.
603: */
604: int
605: kex_start_rekex(struct ssh *ssh)
606: {
607: if (ssh->kex == NULL) {
608: error("%s: no kex", __func__);
609: return SSH_ERR_INTERNAL_ERROR;
610: }
611: if (ssh->kex->done == 0) {
612: error("%s: requested twice", __func__);
613: return SSH_ERR_INTERNAL_ERROR;
614: }
615: ssh->kex->done = 0;
616: return kex_send_kexinit(ssh);
1.1 markus 617: }
618:
1.102 markus 619: static int
620: choose_enc(struct sshenc *enc, char *client, char *server)
1.1 markus 621: {
1.23 markus 622: char *name = match_list(client, server, NULL);
1.102 markus 623:
1.1 markus 624: if (name == NULL)
1.102 markus 625: return SSH_ERR_NO_CIPHER_ALG_MATCH;
1.45 markus 626: if ((enc->cipher = cipher_by_name(name)) == NULL)
1.102 markus 627: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 628: enc->name = name;
629: enc->enabled = 0;
630: enc->iv = NULL;
1.88 markus 631: enc->iv_len = cipher_ivlen(enc->cipher);
1.1 markus 632: enc->key = NULL;
1.45 markus 633: enc->key_len = cipher_keylen(enc->cipher);
634: enc->block_size = cipher_blocksize(enc->cipher);
1.102 markus 635: return 0;
1.1 markus 636: }
1.69 deraadt 637:
1.102 markus 638: static int
639: choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
1.1 markus 640: {
1.23 markus 641: char *name = match_list(client, server, NULL);
1.102 markus 642:
1.1 markus 643: if (name == NULL)
1.102 markus 644: return SSH_ERR_NO_MAC_ALG_MATCH;
1.79 djm 645: if (mac_setup(mac, name) < 0)
1.102 markus 646: return SSH_ERR_INTERNAL_ERROR;
1.21 markus 647: /* truncate the key */
1.102 markus 648: if (ssh->compat & SSH_BUG_HMAC)
1.21 markus 649: mac->key_len = 16;
1.1 markus 650: mac->name = name;
651: mac->key = NULL;
652: mac->enabled = 0;
1.102 markus 653: return 0;
1.1 markus 654: }
1.69 deraadt 655:
1.102 markus 656: static int
657: choose_comp(struct sshcomp *comp, char *client, char *server)
1.1 markus 658: {
1.23 markus 659: char *name = match_list(client, server, NULL);
1.102 markus 660:
1.1 markus 661: if (name == NULL)
1.102 markus 662: return SSH_ERR_NO_COMPRESS_ALG_MATCH;
1.64 markus 663: if (strcmp(name, "zlib@openssh.com") == 0) {
664: comp->type = COMP_DELAYED;
1.126 ! djm 665: } else if (strcmp(name, "zlib") == 0) {
! 666: comp->type = COMP_ZLIB;
1.1 markus 667: } else if (strcmp(name, "none") == 0) {
1.64 markus 668: comp->type = COMP_NONE;
1.1 markus 669: } else {
1.102 markus 670: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 671: }
672: comp->name = name;
1.102 markus 673: return 0;
1.1 markus 674: }
1.69 deraadt 675:
1.102 markus 676: static int
677: choose_kex(struct kex *k, char *client, char *server)
1.1 markus 678: {
1.89 djm 679: const struct kexalg *kexalg;
680:
1.23 markus 681: k->name = match_list(client, server, NULL);
1.102 markus 682:
1.110 djm 683: debug("kex: algorithm: %s", k->name ? k->name : "(no match)");
1.1 markus 684: if (k->name == NULL)
1.102 markus 685: return SSH_ERR_NO_KEX_ALG_MATCH;
1.89 djm 686: if ((kexalg = kex_alg_by_name(k->name)) == NULL)
1.102 markus 687: return SSH_ERR_INTERNAL_ERROR;
1.89 djm 688: k->kex_type = kexalg->type;
1.94 djm 689: k->hash_alg = kexalg->hash_alg;
1.89 djm 690: k->ec_nid = kexalg->ec_nid;
1.102 markus 691: return 0;
1.1 markus 692: }
1.65 djm 693:
1.102 markus 694: static int
695: choose_hostkeyalg(struct kex *k, char *client, char *server)
1.1 markus 696: {
1.113 markus 697: k->hostkey_alg = match_list(client, server, NULL);
1.102 markus 698:
1.110 djm 699: debug("kex: host key algorithm: %s",
1.113 markus 700: k->hostkey_alg ? k->hostkey_alg : "(no match)");
701: if (k->hostkey_alg == NULL)
1.102 markus 702: return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
1.113 markus 703: k->hostkey_type = sshkey_type_from_name(k->hostkey_alg);
1.13 markus 704: if (k->hostkey_type == KEY_UNSPEC)
1.102 markus 705: return SSH_ERR_INTERNAL_ERROR;
1.113 markus 706: k->hostkey_nid = sshkey_ecdsa_nid_from_name(k->hostkey_alg);
1.102 markus 707: return 0;
1.1 markus 708: }
709:
1.56 djm 710: static int
1.53 markus 711: proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
712: {
713: static int check[] = {
714: PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
715: };
716: int *idx;
717: char *p;
718:
719: for (idx = &check[0]; *idx != -1; idx++) {
720: if ((p = strchr(my[*idx], ',')) != NULL)
721: *p = '\0';
722: if ((p = strchr(peer[*idx], ',')) != NULL)
723: *p = '\0';
724: if (strcmp(my[*idx], peer[*idx]) != 0) {
725: debug2("proposal mismatch: my %s peer %s",
726: my[*idx], peer[*idx]);
727: return (0);
728: }
729: }
730: debug2("proposals match");
731: return (1);
732: }
733:
1.102 markus 734: static int
735: kex_choose_conf(struct ssh *ssh)
1.1 markus 736: {
1.102 markus 737: struct kex *kex = ssh->kex;
738: struct newkeys *newkeys;
739: char **my = NULL, **peer = NULL;
1.26 markus 740: char **cprop, **sprop;
1.27 markus 741: int nenc, nmac, ncomp;
1.96 dtucker 742: u_int mode, ctos, need, dh_need, authlen;
1.102 markus 743: int r, first_kex_follows;
1.1 markus 744:
1.110 djm 745: debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
746: if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
747: goto out;
748: debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
749: if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
1.102 markus 750: goto out;
1.26 markus 751:
1.27 markus 752: if (kex->server) {
1.26 markus 753: cprop=peer;
754: sprop=my;
755: } else {
756: cprop=my;
757: sprop=peer;
1.113 markus 758: }
759:
760: /* Check whether client supports ext_info_c */
761: if (kex->server) {
762: char *ext;
763:
764: ext = match_list("ext-info-c", peer[PROPOSAL_KEX_ALGS], NULL);
1.119 markus 765: kex->ext_info_c = (ext != NULL);
766: free(ext);
1.26 markus 767: }
1.1 markus 768:
1.30 markus 769: /* Algorithm Negotiation */
1.110 djm 770: if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
771: sprop[PROPOSAL_KEX_ALGS])) != 0) {
772: kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
773: peer[PROPOSAL_KEX_ALGS] = NULL;
774: goto out;
775: }
776: if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
777: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
778: kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
779: peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
780: goto out;
781: }
1.1 markus 782: for (mode = 0; mode < MODE_MAX; mode++) {
1.102 markus 783: if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
784: r = SSH_ERR_ALLOC_FAIL;
785: goto out;
786: }
1.30 markus 787: kex->newkeys[mode] = newkeys;
1.78 djm 788: ctos = (!kex->server && mode == MODE_OUT) ||
789: (kex->server && mode == MODE_IN);
1.1 markus 790: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
791: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
792: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.102 markus 793: if ((r = choose_enc(&newkeys->enc, cprop[nenc],
1.107 djm 794: sprop[nenc])) != 0) {
795: kex->failed_choice = peer[nenc];
796: peer[nenc] = NULL;
1.102 markus 797: goto out;
1.107 djm 798: }
1.102 markus 799: authlen = cipher_authlen(newkeys->enc.cipher);
1.88 markus 800: /* ignore mac for authenticated encryption */
1.102 markus 801: if (authlen == 0 &&
802: (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
1.107 djm 803: sprop[nmac])) != 0) {
804: kex->failed_choice = peer[nmac];
805: peer[nmac] = NULL;
1.102 markus 806: goto out;
1.107 djm 807: }
1.102 markus 808: if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
1.107 djm 809: sprop[ncomp])) != 0) {
810: kex->failed_choice = peer[ncomp];
811: peer[ncomp] = NULL;
1.102 markus 812: goto out;
1.107 djm 813: }
1.110 djm 814: debug("kex: %s cipher: %s MAC: %s compression: %s",
1.1 markus 815: ctos ? "client->server" : "server->client",
1.27 markus 816: newkeys->enc.name,
1.88 markus 817: authlen == 0 ? newkeys->mac.name : "<implicit>",
1.27 markus 818: newkeys->comp.name);
1.107 djm 819: }
1.96 dtucker 820: need = dh_need = 0;
1.1 markus 821: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 822: newkeys = kex->newkeys[mode];
1.120 deraadt 823: need = MAXIMUM(need, newkeys->enc.key_len);
824: need = MAXIMUM(need, newkeys->enc.block_size);
825: need = MAXIMUM(need, newkeys->enc.iv_len);
826: need = MAXIMUM(need, newkeys->mac.key_len);
827: dh_need = MAXIMUM(dh_need, cipher_seclen(newkeys->enc.cipher));
828: dh_need = MAXIMUM(dh_need, newkeys->enc.block_size);
829: dh_need = MAXIMUM(dh_need, newkeys->enc.iv_len);
830: dh_need = MAXIMUM(dh_need, newkeys->mac.key_len);
1.1 markus 831: }
1.7 markus 832: /* XXX need runden? */
1.27 markus 833: kex->we_need = need;
1.96 dtucker 834: kex->dh_need = dh_need;
1.53 markus 835:
836: /* ignore the next message if the proposals do not match */
1.56 djm 837: if (first_kex_follows && !proposals_match(my, peer) &&
1.102 markus 838: !(ssh->compat & SSH_BUG_FIRSTKEX))
839: ssh->dispatch_skip_packets = 1;
840: r = 0;
841: out:
1.26 markus 842: kex_prop_free(my);
843: kex_prop_free(peer);
1.102 markus 844: return r;
1.26 markus 845: }
846:
1.102 markus 847: static int
848: derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
849: const struct sshbuf *shared_secret, u_char **keyp)
1.26 markus 850: {
1.102 markus 851: struct kex *kex = ssh->kex;
852: struct ssh_digest_ctx *hashctx = NULL;
1.26 markus 853: char c = id;
1.61 djm 854: u_int have;
1.94 djm 855: size_t mdsz;
1.61 djm 856: u_char *digest;
1.102 markus 857: int r;
1.62 djm 858:
1.94 djm 859: if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
1.102 markus 860: return SSH_ERR_INVALID_ARGUMENT;
1.120 deraadt 861: if ((digest = calloc(1, ROUNDUP(need, mdsz))) == NULL) {
1.102 markus 862: r = SSH_ERR_ALLOC_FAIL;
863: goto out;
864: }
1.26 markus 865:
1.30 markus 866: /* K1 = HASH(K || H || "A" || session_id) */
1.102 markus 867: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
868: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 869: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
870: ssh_digest_update(hashctx, &c, 1) != 0 ||
871: ssh_digest_update(hashctx, kex->session_id,
1.102 markus 872: kex->session_id_len) != 0 ||
873: ssh_digest_final(hashctx, digest, mdsz) != 0) {
874: r = SSH_ERR_LIBCRYPTO_ERROR;
875: goto out;
876: }
1.94 djm 877: ssh_digest_free(hashctx);
1.102 markus 878: hashctx = NULL;
1.26 markus 879:
1.30 markus 880: /*
881: * expand key:
882: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
883: * Key = K1 || K2 || ... || Kn
884: */
1.26 markus 885: for (have = mdsz; need > have; have += mdsz) {
1.102 markus 886: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
887: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 888: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1.102 markus 889: ssh_digest_update(hashctx, digest, have) != 0 ||
890: ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
891: r = SSH_ERR_LIBCRYPTO_ERROR;
892: goto out;
893: }
1.94 djm 894: ssh_digest_free(hashctx);
1.102 markus 895: hashctx = NULL;
1.26 markus 896: }
897: #ifdef DEBUG_KEX
898: fprintf(stderr, "key '%c'== ", c);
899: dump_digest("key", digest, need);
900: #endif
1.102 markus 901: *keyp = digest;
902: digest = NULL;
903: r = 0;
904: out:
1.114 mmcc 905: free(digest);
1.102 markus 906: ssh_digest_free(hashctx);
907: return r;
1.1 markus 908: }
909:
1.23 markus 910: #define NKEYS 6
1.102 markus 911: int
912: kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
913: const struct sshbuf *shared_secret)
1.1 markus 914: {
1.102 markus 915: struct kex *kex = ssh->kex;
1.15 markus 916: u_char *keys[NKEYS];
1.102 markus 917: u_int i, j, mode, ctos;
918: int r;
1.1 markus 919:
1.65 djm 920: for (i = 0; i < NKEYS; i++) {
1.102 markus 921: if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
922: shared_secret, &keys[i])) != 0) {
923: for (j = 0; j < i; j++)
924: free(keys[j]);
925: return r;
926: }
1.65 djm 927: }
1.1 markus 928: for (mode = 0; mode < MODE_MAX; mode++) {
1.69 deraadt 929: ctos = (!kex->server && mode == MODE_OUT) ||
930: (kex->server && mode == MODE_IN);
1.100 markus 931: kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
932: kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
933: kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
1.1 markus 934: }
1.102 markus 935: return 0;
1.95 djm 936: }
937:
1.99 markus 938: #ifdef WITH_OPENSSL
1.102 markus 939: int
940: kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen,
941: const BIGNUM *secret)
1.95 djm 942: {
1.102 markus 943: struct sshbuf *shared_secret;
944: int r;
1.95 djm 945:
1.102 markus 946: if ((shared_secret = sshbuf_new()) == NULL)
947: return SSH_ERR_ALLOC_FAIL;
948: if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0)
949: r = kex_derive_keys(ssh, hash, hashlen, shared_secret);
950: sshbuf_free(shared_secret);
951: return r;
1.27 markus 952: }
1.99 markus 953: #endif
1.57 djm 954:
1.99 markus 955: #ifdef WITH_SSH1
1.102 markus 956: int
1.57 djm 957: derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
958: u_int8_t cookie[8], u_int8_t id[16])
959: {
1.105 djm 960: u_int8_t hbuf[2048], sbuf[2048], obuf[SSH_DIGEST_MAX_LENGTH];
1.102 markus 961: struct ssh_digest_ctx *hashctx = NULL;
1.105 djm 962: size_t hlen, slen;
1.102 markus 963: int r;
1.57 djm 964:
1.105 djm 965: hlen = BN_num_bytes(host_modulus);
966: slen = BN_num_bytes(server_modulus);
967: if (hlen < (512 / 8) || (u_int)hlen > sizeof(hbuf) ||
968: slen < (512 / 8) || (u_int)slen > sizeof(sbuf))
1.102 markus 969: return SSH_ERR_KEY_BITS_MISMATCH;
1.105 djm 970: if (BN_bn2bin(host_modulus, hbuf) <= 0 ||
971: BN_bn2bin(server_modulus, sbuf) <= 0) {
972: r = SSH_ERR_LIBCRYPTO_ERROR;
973: goto out;
974: }
975: if ((hashctx = ssh_digest_start(SSH_DIGEST_MD5)) == NULL) {
976: r = SSH_ERR_ALLOC_FAIL;
977: goto out;
978: }
979: if (ssh_digest_update(hashctx, hbuf, hlen) != 0 ||
980: ssh_digest_update(hashctx, sbuf, slen) != 0 ||
1.102 markus 981: ssh_digest_update(hashctx, cookie, 8) != 0 ||
982: ssh_digest_final(hashctx, obuf, sizeof(obuf)) != 0) {
983: r = SSH_ERR_LIBCRYPTO_ERROR;
984: goto out;
985: }
1.94 djm 986: memcpy(id, obuf, ssh_digest_bytes(SSH_DIGEST_MD5));
1.102 markus 987: r = 0;
988: out:
989: ssh_digest_free(hashctx);
1.105 djm 990: explicit_bzero(hbuf, sizeof(hbuf));
991: explicit_bzero(sbuf, sizeof(sbuf));
1.98 djm 992: explicit_bzero(obuf, sizeof(obuf));
1.102 markus 993: return r;
1.1 markus 994: }
1.99 markus 995: #endif
1.26 markus 996:
1.84 djm 997: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1.26 markus 998: void
999: dump_digest(char *msg, u_char *digest, int len)
1000: {
1001: fprintf(stderr, "%s\n", msg);
1.102 markus 1002: sshbuf_dump_data(digest, len, stderr);
1.26 markus 1003: }
1004: #endif
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