Annotation of src/usr.bin/ssh/kex.c, Revision 1.112
1.112 ! djm 1: /* $OpenBSD: kex.c,v 1.111 2015/10/13 00:21:27 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:
1.103 deraadt 26: #include <sys/param.h> /* MAX roundup */
1.18 markus 27:
1.76 deraadt 28: #include <signal.h>
1.75 stevesk 29: #include <stdio.h>
1.74 stevesk 30: #include <stdlib.h>
1.72 stevesk 31: #include <string.h>
1.1 markus 32:
1.99 markus 33: #ifdef WITH_OPENSSL
1.76 deraadt 34: #include <openssl/crypto.h>
1.99 markus 35: #endif
1.76 deraadt 36:
1.1 markus 37: #include "ssh2.h"
1.7 markus 38: #include "packet.h"
1.1 markus 39: #include "compat.h"
1.18 markus 40: #include "cipher.h"
1.102 markus 41: #include "sshkey.h"
1.1 markus 42: #include "kex.h"
1.18 markus 43: #include "log.h"
1.21 markus 44: #include "mac.h"
1.23 markus 45: #include "match.h"
1.102 markus 46: #include "misc.h"
1.26 markus 47: #include "dispatch.h"
1.48 provos 48: #include "monitor.h"
1.82 andreas 49: #include "roaming.h"
1.102 markus 50:
51: #include "ssherr.h"
52: #include "sshbuf.h"
1.94 djm 53: #include "digest.h"
1.48 provos 54:
1.35 itojun 55: /* prototype */
1.102 markus 56: static int kex_choose_conf(struct ssh *);
57: static int kex_input_newkeys(int, u_int32_t, void *);
1.86 djm 58:
1.110 djm 59: static const char *proposal_names[PROPOSAL_MAX] = {
60: "KEX algorithms",
61: "host key algorithms",
62: "ciphers ctos",
63: "ciphers stoc",
64: "MACs ctos",
65: "MACs stoc",
66: "compression ctos",
67: "compression stoc",
68: "languages ctos",
69: "languages stoc",
70: };
71:
1.89 djm 72: struct kexalg {
73: char *name;
1.102 markus 74: u_int type;
1.89 djm 75: int ec_nid;
1.94 djm 76: int hash_alg;
1.89 djm 77: };
78: static const struct kexalg kexalgs[] = {
1.99 markus 79: #ifdef WITH_OPENSSL
1.94 djm 80: { KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },
81: { KEX_DH14, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 },
82: { KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 },
83: { KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 },
84: { KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2,
85: NID_X9_62_prime256v1, SSH_DIGEST_SHA256 },
86: { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1,
87: SSH_DIGEST_SHA384 },
88: { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1,
89: SSH_DIGEST_SHA512 },
1.99 markus 90: #endif
1.94 djm 91: { KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
92: { NULL, -1, -1, -1},
1.89 djm 93: };
94:
95: char *
1.93 dtucker 96: kex_alg_list(char sep)
1.89 djm 97: {
1.102 markus 98: char *ret = NULL, *tmp;
1.89 djm 99: size_t nlen, rlen = 0;
100: const struct kexalg *k;
101:
102: for (k = kexalgs; k->name != NULL; k++) {
103: if (ret != NULL)
1.93 dtucker 104: ret[rlen++] = sep;
1.89 djm 105: nlen = strlen(k->name);
1.102 markus 106: if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
107: free(ret);
108: return NULL;
109: }
110: ret = tmp;
1.89 djm 111: memcpy(ret + rlen, k->name, nlen + 1);
112: rlen += nlen;
113: }
114: return ret;
115: }
116:
117: static const struct kexalg *
118: kex_alg_by_name(const char *name)
119: {
120: const struct kexalg *k;
121:
122: for (k = kexalgs; k->name != NULL; k++) {
123: if (strcmp(k->name, name) == 0)
124: return k;
125: }
126: return NULL;
127: }
128:
1.86 djm 129: /* Validate KEX method name list */
130: int
131: kex_names_valid(const char *names)
132: {
133: char *s, *cp, *p;
134:
135: if (names == NULL || strcmp(names, "") == 0)
136: return 0;
1.102 markus 137: if ((s = cp = strdup(names)) == NULL)
138: return 0;
1.86 djm 139: for ((p = strsep(&cp, ",")); p && *p != '\0';
140: (p = strsep(&cp, ","))) {
1.89 djm 141: if (kex_alg_by_name(p) == NULL) {
1.86 djm 142: error("Unsupported KEX algorithm \"%.100s\"", p);
1.91 djm 143: free(s);
1.86 djm 144: return 0;
145: }
146: }
147: debug3("kex names ok: [%s]", names);
1.91 djm 148: free(s);
1.86 djm 149: return 1;
1.109 djm 150: }
151:
152: /*
153: * Concatenate algorithm names, avoiding duplicates in the process.
154: * Caller must free returned string.
155: */
156: char *
157: kex_names_cat(const char *a, const char *b)
158: {
159: char *ret = NULL, *tmp = NULL, *cp, *p;
160: size_t len;
161:
162: if (a == NULL || *a == '\0')
163: return NULL;
164: if (b == NULL || *b == '\0')
165: return strdup(a);
166: if (strlen(b) > 1024*1024)
167: return NULL;
168: len = strlen(a) + strlen(b) + 2;
169: if ((tmp = cp = strdup(b)) == NULL ||
170: (ret = calloc(1, len)) == NULL) {
171: free(tmp);
172: return NULL;
173: }
174: strlcpy(ret, a, len);
175: for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) {
176: if (match_list(ret, p, NULL) != NULL)
177: continue; /* Algorithm already present */
178: if (strlcat(ret, ",", len) >= len ||
179: strlcat(ret, p, len) >= len) {
180: free(tmp);
181: free(ret);
182: return NULL; /* Shouldn't happen */
183: }
184: }
185: free(tmp);
186: return ret;
187: }
188:
189: /*
190: * Assemble a list of algorithms from a default list and a string from a
191: * configuration file. The user-provided string may begin with '+' to
192: * indicate that it should be appended to the default.
193: */
194: int
195: kex_assemble_names(const char *def, char **list)
196: {
197: char *ret;
198:
199: if (list == NULL || *list == NULL || **list == '\0') {
200: *list = strdup(def);
201: return 0;
202: }
203: if (**list != '+') {
204: return 0;
205: }
206:
207: if ((ret = kex_names_cat(def, *list + 1)) == NULL)
208: return SSH_ERR_ALLOC_FAIL;
209: free(*list);
210: *list = ret;
211: return 0;
1.86 djm 212: }
1.26 markus 213:
214: /* put algorithm proposal into buffer */
1.102 markus 215: int
216: kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
1.1 markus 217: {
1.61 djm 218: u_int i;
1.102 markus 219: int r;
220:
221: sshbuf_reset(b);
1.26 markus 222:
1.49 markus 223: /*
224: * add a dummy cookie, the cookie will be overwritten by
225: * kex_send_kexinit(), each time a kexinit is set
226: */
1.102 markus 227: for (i = 0; i < KEX_COOKIE_LEN; i++) {
228: if ((r = sshbuf_put_u8(b, 0)) != 0)
229: return r;
230: }
231: for (i = 0; i < PROPOSAL_MAX; i++) {
232: if ((r = sshbuf_put_cstring(b, proposal[i])) != 0)
233: return r;
234: }
235: if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */
236: (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */
237: return r;
238: return 0;
1.1 markus 239: }
240:
1.26 markus 241: /* parse buffer and return algorithm proposal */
1.102 markus 242: int
243: kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp)
1.7 markus 244: {
1.102 markus 245: struct sshbuf *b = NULL;
246: u_char v;
1.78 djm 247: u_int i;
1.102 markus 248: char **proposal = NULL;
249: int r;
1.7 markus 250:
1.102 markus 251: *propp = NULL;
252: if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL)
253: return SSH_ERR_ALLOC_FAIL;
254: if ((b = sshbuf_fromb(raw)) == NULL) {
255: r = SSH_ERR_ALLOC_FAIL;
256: goto out;
257: }
258: if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */
259: goto out;
1.7 markus 260: /* extract kex init proposal strings */
261: for (i = 0; i < PROPOSAL_MAX; i++) {
1.102 markus 262: if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0)
263: goto out;
1.110 djm 264: debug2("%s: %s", proposal_names[i], proposal[i]);
1.7 markus 265: }
1.26 markus 266: /* first kex follows / reserved */
1.102 markus 267: if ((r = sshbuf_get_u8(b, &v)) != 0 ||
268: (r = sshbuf_get_u32(b, &i)) != 0)
269: goto out;
1.53 markus 270: if (first_kex_follows != NULL)
271: *first_kex_follows = i;
1.110 djm 272: debug2("first_kex_follows %d ", v);
273: debug2("reserved %u ", i);
1.102 markus 274: r = 0;
275: *propp = proposal;
276: out:
277: if (r != 0 && proposal != NULL)
278: kex_prop_free(proposal);
279: sshbuf_free(b);
280: return r;
1.1 markus 281: }
282:
1.102 markus 283: void
1.26 markus 284: kex_prop_free(char **proposal)
1.1 markus 285: {
1.61 djm 286: u_int i;
1.26 markus 287:
1.106 djm 288: if (proposal == NULL)
289: return;
1.26 markus 290: for (i = 0; i < PROPOSAL_MAX; i++)
1.91 djm 291: free(proposal[i]);
292: free(proposal);
1.1 markus 293: }
294:
1.78 djm 295: /* ARGSUSED */
1.101 markus 296: static int
1.41 markus 297: kex_protocol_error(int type, u_int32_t seq, void *ctxt)
1.1 markus 298: {
1.112 ! djm 299: struct ssh *ssh = active_state; /* XXX */
! 300: int r;
! 301:
! 302: error("kex protocol error: type %d seq %u", type, seq);
! 303: if ((r = sshpkt_start(ssh, SSH2_MSG_UNIMPLEMENTED)) != 0 ||
! 304: (r = sshpkt_put_u32(ssh, seq)) != 0 ||
! 305: (r = sshpkt_send(ssh)) != 0)
! 306: return r;
1.101 markus 307: return 0;
1.26 markus 308: }
1.1 markus 309:
1.35 itojun 310: static void
1.102 markus 311: kex_reset_dispatch(struct ssh *ssh)
1.29 markus 312: {
1.102 markus 313: ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
1.42 markus 314: SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
1.102 markus 315: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.29 markus 316: }
317:
1.102 markus 318: int
319: kex_send_newkeys(struct ssh *ssh)
1.26 markus 320: {
1.102 markus 321: int r;
1.28 markus 322:
1.102 markus 323: kex_reset_dispatch(ssh);
324: if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
325: (r = sshpkt_send(ssh)) != 0)
326: return r;
1.26 markus 327: debug("SSH2_MSG_NEWKEYS sent");
1.102 markus 328: debug("expecting SSH2_MSG_NEWKEYS");
329: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
330: return 0;
331: }
332:
333: static int
334: kex_input_newkeys(int type, u_int32_t seq, void *ctxt)
335: {
336: struct ssh *ssh = ctxt;
337: struct kex *kex = ssh->kex;
338: int r;
1.19 stevesk 339:
1.26 markus 340: debug("SSH2_MSG_NEWKEYS received");
1.102 markus 341: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
342: if ((r = sshpkt_get_end(ssh)) != 0)
343: return r;
1.30 markus 344: kex->done = 1;
1.102 markus 345: sshbuf_reset(kex->peer);
346: /* sshbuf_reset(kex->my); */
1.26 markus 347: kex->flags &= ~KEX_INIT_SENT;
1.91 djm 348: free(kex->name);
1.32 markus 349: kex->name = NULL;
1.102 markus 350: return 0;
1.26 markus 351: }
1.1 markus 352:
1.102 markus 353: int
354: kex_send_kexinit(struct ssh *ssh)
1.26 markus 355: {
1.49 markus 356: u_char *cookie;
1.102 markus 357: struct kex *kex = ssh->kex;
358: int r;
1.49 markus 359:
1.102 markus 360: if (kex == NULL)
361: return SSH_ERR_INTERNAL_ERROR;
362: if (kex->flags & KEX_INIT_SENT)
363: return 0;
1.30 markus 364: kex->done = 0;
1.49 markus 365:
366: /* generate a random cookie */
1.102 markus 367: if (sshbuf_len(kex->my) < KEX_COOKIE_LEN)
368: return SSH_ERR_INVALID_FORMAT;
369: if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL)
370: return SSH_ERR_INTERNAL_ERROR;
371: arc4random_buf(cookie, KEX_COOKIE_LEN);
372:
373: if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
374: (r = sshpkt_putb(ssh, kex->my)) != 0 ||
375: (r = sshpkt_send(ssh)) != 0)
376: return r;
1.26 markus 377: debug("SSH2_MSG_KEXINIT sent");
378: kex->flags |= KEX_INIT_SENT;
1.102 markus 379: return 0;
1.1 markus 380: }
381:
1.78 djm 382: /* ARGSUSED */
1.101 markus 383: int
1.41 markus 384: kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
1.11 provos 385: {
1.102 markus 386: struct ssh *ssh = ctxt;
387: struct kex *kex = ssh->kex;
388: const u_char *ptr;
1.100 markus 389: u_int i;
390: size_t dlen;
1.102 markus 391: int r;
1.11 provos 392:
1.26 markus 393: debug("SSH2_MSG_KEXINIT received");
1.29 markus 394: if (kex == NULL)
1.102 markus 395: return SSH_ERR_INVALID_ARGUMENT;
1.11 provos 396:
1.102 markus 397: ptr = sshpkt_ptr(ssh, &dlen);
398: if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
399: return r;
1.31 markus 400:
401: /* discard packet */
402: for (i = 0; i < KEX_COOKIE_LEN; i++)
1.102 markus 403: if ((r = sshpkt_get_u8(ssh, NULL)) != 0)
404: return r;
1.31 markus 405: for (i = 0; i < PROPOSAL_MAX; i++)
1.102 markus 406: if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0)
407: return r;
1.87 djm 408: /*
409: * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
410: * KEX method has the server move first, but a server might be using
411: * a custom method or one that we otherwise don't support. We should
412: * be prepared to remember first_kex_follows here so we can eat a
413: * packet later.
414: * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
415: * for cases where the server *doesn't* go first. I guess we should
416: * ignore it when it is set for these cases, which is what we do now.
417: */
1.102 markus 418: if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
419: (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
420: (r = sshpkt_get_end(ssh)) != 0)
421: return r;
422:
423: if (!(kex->flags & KEX_INIT_SENT))
424: if ((r = kex_send_kexinit(ssh)) != 0)
425: return r;
426: if ((r = kex_choose_conf(ssh)) != 0)
427: return r;
1.19 stevesk 428:
1.102 markus 429: if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
430: return (kex->kex[kex->kex_type])(ssh);
431:
432: return SSH_ERR_INTERNAL_ERROR;
433: }
434:
435: int
436: kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp)
437: {
438: struct kex *kex;
439: int r;
440:
441: *kexp = NULL;
442: if ((kex = calloc(1, sizeof(*kex))) == NULL)
443: return SSH_ERR_ALLOC_FAIL;
444: if ((kex->peer = sshbuf_new()) == NULL ||
445: (kex->my = sshbuf_new()) == NULL) {
446: r = SSH_ERR_ALLOC_FAIL;
447: goto out;
448: }
449: if ((r = kex_prop2buf(kex->my, proposal)) != 0)
450: goto out;
451: kex->done = 0;
452: kex_reset_dispatch(ssh);
453: r = 0;
454: *kexp = kex;
455: out:
456: if (r != 0)
457: kex_free(kex);
458: return r;
1.26 markus 459: }
1.11 provos 460:
1.100 markus 461: void
462: kex_free_newkeys(struct newkeys *newkeys)
463: {
464: if (newkeys == NULL)
465: return;
466: if (newkeys->enc.key) {
467: explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
468: free(newkeys->enc.key);
469: newkeys->enc.key = NULL;
470: }
471: if (newkeys->enc.iv) {
1.111 djm 472: explicit_bzero(newkeys->enc.iv, newkeys->enc.iv_len);
1.100 markus 473: free(newkeys->enc.iv);
474: newkeys->enc.iv = NULL;
475: }
476: free(newkeys->enc.name);
477: explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
478: free(newkeys->comp.name);
479: explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
480: mac_clear(&newkeys->mac);
481: if (newkeys->mac.key) {
482: explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
483: free(newkeys->mac.key);
484: newkeys->mac.key = NULL;
485: }
486: free(newkeys->mac.name);
487: explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
488: explicit_bzero(newkeys, sizeof(*newkeys));
489: free(newkeys);
490: }
491:
1.102 markus 492: void
493: kex_free(struct kex *kex)
1.26 markus 494: {
1.102 markus 495: u_int mode;
1.11 provos 496:
1.102 markus 497: #ifdef WITH_OPENSSL
498: if (kex->dh)
499: DH_free(kex->dh);
500: if (kex->ec_client_key)
501: EC_KEY_free(kex->ec_client_key);
502: #endif
503: for (mode = 0; mode < MODE_MAX; mode++) {
504: kex_free_newkeys(kex->newkeys[mode]);
505: kex->newkeys[mode] = NULL;
1.100 markus 506: }
1.102 markus 507: sshbuf_free(kex->peer);
508: sshbuf_free(kex->my);
509: free(kex->session_id);
510: free(kex->client_version_string);
511: free(kex->server_version_string);
1.107 djm 512: free(kex->failed_choice);
1.102 markus 513: free(kex);
1.11 provos 514: }
515:
1.102 markus 516: int
517: kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
1.1 markus 518: {
1.102 markus 519: int r;
1.1 markus 520:
1.102 markus 521: if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0)
522: return r;
523: if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
524: kex_free(ssh->kex);
525: ssh->kex = NULL;
526: return r;
1.1 markus 527: }
1.102 markus 528: return 0;
1.1 markus 529: }
530:
1.102 markus 531: static int
532: choose_enc(struct sshenc *enc, char *client, char *server)
1.1 markus 533: {
1.23 markus 534: char *name = match_list(client, server, NULL);
1.102 markus 535:
1.1 markus 536: if (name == NULL)
1.102 markus 537: return SSH_ERR_NO_CIPHER_ALG_MATCH;
1.45 markus 538: if ((enc->cipher = cipher_by_name(name)) == NULL)
1.102 markus 539: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 540: enc->name = name;
541: enc->enabled = 0;
542: enc->iv = NULL;
1.88 markus 543: enc->iv_len = cipher_ivlen(enc->cipher);
1.1 markus 544: enc->key = NULL;
1.45 markus 545: enc->key_len = cipher_keylen(enc->cipher);
546: enc->block_size = cipher_blocksize(enc->cipher);
1.102 markus 547: return 0;
1.1 markus 548: }
1.69 deraadt 549:
1.102 markus 550: static int
551: choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
1.1 markus 552: {
1.23 markus 553: char *name = match_list(client, server, NULL);
1.102 markus 554:
1.1 markus 555: if (name == NULL)
1.102 markus 556: return SSH_ERR_NO_MAC_ALG_MATCH;
1.79 djm 557: if (mac_setup(mac, name) < 0)
1.102 markus 558: return SSH_ERR_INTERNAL_ERROR;
1.21 markus 559: /* truncate the key */
1.102 markus 560: if (ssh->compat & SSH_BUG_HMAC)
1.21 markus 561: mac->key_len = 16;
1.1 markus 562: mac->name = name;
563: mac->key = NULL;
564: mac->enabled = 0;
1.102 markus 565: return 0;
1.1 markus 566: }
1.69 deraadt 567:
1.102 markus 568: static int
569: choose_comp(struct sshcomp *comp, char *client, char *server)
1.1 markus 570: {
1.23 markus 571: char *name = match_list(client, server, NULL);
1.102 markus 572:
1.1 markus 573: if (name == NULL)
1.102 markus 574: return SSH_ERR_NO_COMPRESS_ALG_MATCH;
1.64 markus 575: if (strcmp(name, "zlib@openssh.com") == 0) {
576: comp->type = COMP_DELAYED;
577: } else if (strcmp(name, "zlib") == 0) {
578: comp->type = COMP_ZLIB;
1.1 markus 579: } else if (strcmp(name, "none") == 0) {
1.64 markus 580: comp->type = COMP_NONE;
1.1 markus 581: } else {
1.102 markus 582: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 583: }
584: comp->name = name;
1.102 markus 585: return 0;
1.1 markus 586: }
1.69 deraadt 587:
1.102 markus 588: static int
589: choose_kex(struct kex *k, char *client, char *server)
1.1 markus 590: {
1.89 djm 591: const struct kexalg *kexalg;
592:
1.23 markus 593: k->name = match_list(client, server, NULL);
1.102 markus 594:
1.110 djm 595: debug("kex: algorithm: %s", k->name ? k->name : "(no match)");
1.1 markus 596: if (k->name == NULL)
1.102 markus 597: return SSH_ERR_NO_KEX_ALG_MATCH;
1.89 djm 598: if ((kexalg = kex_alg_by_name(k->name)) == NULL)
1.102 markus 599: return SSH_ERR_INTERNAL_ERROR;
1.89 djm 600: k->kex_type = kexalg->type;
1.94 djm 601: k->hash_alg = kexalg->hash_alg;
1.89 djm 602: k->ec_nid = kexalg->ec_nid;
1.102 markus 603: return 0;
1.1 markus 604: }
1.65 djm 605:
1.102 markus 606: static int
607: choose_hostkeyalg(struct kex *k, char *client, char *server)
1.1 markus 608: {
1.23 markus 609: char *hostkeyalg = match_list(client, server, NULL);
1.102 markus 610:
1.110 djm 611: debug("kex: host key algorithm: %s",
612: hostkeyalg ? hostkeyalg : "(no match)");
1.13 markus 613: if (hostkeyalg == NULL)
1.102 markus 614: return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
615: k->hostkey_type = sshkey_type_from_name(hostkeyalg);
1.13 markus 616: if (k->hostkey_type == KEY_UNSPEC)
1.102 markus 617: return SSH_ERR_INTERNAL_ERROR;
1.104 djm 618: k->hostkey_nid = sshkey_ecdsa_nid_from_name(hostkeyalg);
1.91 djm 619: free(hostkeyalg);
1.102 markus 620: return 0;
1.1 markus 621: }
622:
1.56 djm 623: static int
1.53 markus 624: proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
625: {
626: static int check[] = {
627: PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
628: };
629: int *idx;
630: char *p;
631:
632: for (idx = &check[0]; *idx != -1; idx++) {
633: if ((p = strchr(my[*idx], ',')) != NULL)
634: *p = '\0';
635: if ((p = strchr(peer[*idx], ',')) != NULL)
636: *p = '\0';
637: if (strcmp(my[*idx], peer[*idx]) != 0) {
638: debug2("proposal mismatch: my %s peer %s",
639: my[*idx], peer[*idx]);
640: return (0);
641: }
642: }
643: debug2("proposals match");
644: return (1);
645: }
646:
1.102 markus 647: static int
648: kex_choose_conf(struct ssh *ssh)
1.1 markus 649: {
1.102 markus 650: struct kex *kex = ssh->kex;
651: struct newkeys *newkeys;
652: char **my = NULL, **peer = NULL;
1.26 markus 653: char **cprop, **sprop;
1.27 markus 654: int nenc, nmac, ncomp;
1.96 dtucker 655: u_int mode, ctos, need, dh_need, authlen;
1.102 markus 656: int r, first_kex_follows;
1.1 markus 657:
1.110 djm 658: debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
659: if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
660: goto out;
661: debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
662: if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
1.102 markus 663: goto out;
1.26 markus 664:
1.27 markus 665: if (kex->server) {
1.26 markus 666: cprop=peer;
667: sprop=my;
668: } else {
669: cprop=my;
670: sprop=peer;
1.82 andreas 671: }
672:
673: /* Check whether server offers roaming */
674: if (!kex->server) {
1.102 markus 675: char *roaming = match_list(KEX_RESUME,
676: peer[PROPOSAL_KEX_ALGS], NULL);
677:
1.82 andreas 678: if (roaming) {
679: kex->roaming = 1;
1.91 djm 680: free(roaming);
1.82 andreas 681: }
1.26 markus 682: }
1.1 markus 683:
1.30 markus 684: /* Algorithm Negotiation */
1.110 djm 685: if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
686: sprop[PROPOSAL_KEX_ALGS])) != 0) {
687: kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
688: peer[PROPOSAL_KEX_ALGS] = NULL;
689: goto out;
690: }
691: if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
692: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
693: kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
694: peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
695: goto out;
696: }
1.1 markus 697: for (mode = 0; mode < MODE_MAX; mode++) {
1.102 markus 698: if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
699: r = SSH_ERR_ALLOC_FAIL;
700: goto out;
701: }
1.30 markus 702: kex->newkeys[mode] = newkeys;
1.78 djm 703: ctos = (!kex->server && mode == MODE_OUT) ||
704: (kex->server && mode == MODE_IN);
1.1 markus 705: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
706: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
707: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.102 markus 708: if ((r = choose_enc(&newkeys->enc, cprop[nenc],
1.107 djm 709: sprop[nenc])) != 0) {
710: kex->failed_choice = peer[nenc];
711: peer[nenc] = NULL;
1.102 markus 712: goto out;
1.107 djm 713: }
1.102 markus 714: authlen = cipher_authlen(newkeys->enc.cipher);
1.88 markus 715: /* ignore mac for authenticated encryption */
1.102 markus 716: if (authlen == 0 &&
717: (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
1.107 djm 718: sprop[nmac])) != 0) {
719: kex->failed_choice = peer[nmac];
720: peer[nmac] = NULL;
1.102 markus 721: goto out;
1.107 djm 722: }
1.102 markus 723: if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
1.107 djm 724: sprop[ncomp])) != 0) {
725: kex->failed_choice = peer[ncomp];
726: peer[ncomp] = NULL;
1.102 markus 727: goto out;
1.107 djm 728: }
1.110 djm 729: debug("kex: %s cipher: %s MAC: %s compression: %s",
1.1 markus 730: ctos ? "client->server" : "server->client",
1.27 markus 731: newkeys->enc.name,
1.88 markus 732: authlen == 0 ? newkeys->mac.name : "<implicit>",
1.27 markus 733: newkeys->comp.name);
1.107 djm 734: }
1.96 dtucker 735: need = dh_need = 0;
1.1 markus 736: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 737: newkeys = kex->newkeys[mode];
1.97 markus 738: need = MAX(need, newkeys->enc.key_len);
739: need = MAX(need, newkeys->enc.block_size);
740: need = MAX(need, newkeys->enc.iv_len);
741: need = MAX(need, newkeys->mac.key_len);
742: dh_need = MAX(dh_need, cipher_seclen(newkeys->enc.cipher));
743: dh_need = MAX(dh_need, newkeys->enc.block_size);
744: dh_need = MAX(dh_need, newkeys->enc.iv_len);
745: dh_need = MAX(dh_need, newkeys->mac.key_len);
1.1 markus 746: }
1.7 markus 747: /* XXX need runden? */
1.27 markus 748: kex->we_need = need;
1.96 dtucker 749: kex->dh_need = dh_need;
1.53 markus 750:
751: /* ignore the next message if the proposals do not match */
1.56 djm 752: if (first_kex_follows && !proposals_match(my, peer) &&
1.102 markus 753: !(ssh->compat & SSH_BUG_FIRSTKEX))
754: ssh->dispatch_skip_packets = 1;
755: r = 0;
756: out:
1.26 markus 757: kex_prop_free(my);
758: kex_prop_free(peer);
1.102 markus 759: return r;
1.26 markus 760: }
761:
1.102 markus 762: static int
763: derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
764: const struct sshbuf *shared_secret, u_char **keyp)
1.26 markus 765: {
1.102 markus 766: struct kex *kex = ssh->kex;
767: struct ssh_digest_ctx *hashctx = NULL;
1.26 markus 768: char c = id;
1.61 djm 769: u_int have;
1.94 djm 770: size_t mdsz;
1.61 djm 771: u_char *digest;
1.102 markus 772: int r;
1.62 djm 773:
1.94 djm 774: if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
1.102 markus 775: return SSH_ERR_INVALID_ARGUMENT;
776: if ((digest = calloc(1, roundup(need, mdsz))) == NULL) {
777: r = SSH_ERR_ALLOC_FAIL;
778: goto out;
779: }
1.26 markus 780:
1.30 markus 781: /* K1 = HASH(K || H || "A" || session_id) */
1.102 markus 782: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
783: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 784: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
785: ssh_digest_update(hashctx, &c, 1) != 0 ||
786: ssh_digest_update(hashctx, kex->session_id,
1.102 markus 787: kex->session_id_len) != 0 ||
788: ssh_digest_final(hashctx, digest, mdsz) != 0) {
789: r = SSH_ERR_LIBCRYPTO_ERROR;
790: goto out;
791: }
1.94 djm 792: ssh_digest_free(hashctx);
1.102 markus 793: hashctx = NULL;
1.26 markus 794:
1.30 markus 795: /*
796: * expand key:
797: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
798: * Key = K1 || K2 || ... || Kn
799: */
1.26 markus 800: for (have = mdsz; need > have; have += mdsz) {
1.102 markus 801: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
802: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 803: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1.102 markus 804: ssh_digest_update(hashctx, digest, have) != 0 ||
805: ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
806: r = SSH_ERR_LIBCRYPTO_ERROR;
807: goto out;
808: }
1.94 djm 809: ssh_digest_free(hashctx);
1.102 markus 810: hashctx = NULL;
1.26 markus 811: }
812: #ifdef DEBUG_KEX
813: fprintf(stderr, "key '%c'== ", c);
814: dump_digest("key", digest, need);
815: #endif
1.102 markus 816: *keyp = digest;
817: digest = NULL;
818: r = 0;
819: out:
820: if (digest)
821: free(digest);
822: ssh_digest_free(hashctx);
823: return r;
1.1 markus 824: }
825:
1.23 markus 826: #define NKEYS 6
1.102 markus 827: int
828: kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
829: const struct sshbuf *shared_secret)
1.1 markus 830: {
1.102 markus 831: struct kex *kex = ssh->kex;
1.15 markus 832: u_char *keys[NKEYS];
1.102 markus 833: u_int i, j, mode, ctos;
834: int r;
1.1 markus 835:
1.65 djm 836: for (i = 0; i < NKEYS; i++) {
1.102 markus 837: if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
838: shared_secret, &keys[i])) != 0) {
839: for (j = 0; j < i; j++)
840: free(keys[j]);
841: return r;
842: }
1.65 djm 843: }
1.1 markus 844: for (mode = 0; mode < MODE_MAX; mode++) {
1.69 deraadt 845: ctos = (!kex->server && mode == MODE_OUT) ||
846: (kex->server && mode == MODE_IN);
1.100 markus 847: kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
848: kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
849: kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
1.1 markus 850: }
1.102 markus 851: return 0;
1.95 djm 852: }
853:
1.99 markus 854: #ifdef WITH_OPENSSL
1.102 markus 855: int
856: kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen,
857: const BIGNUM *secret)
1.95 djm 858: {
1.102 markus 859: struct sshbuf *shared_secret;
860: int r;
1.95 djm 861:
1.102 markus 862: if ((shared_secret = sshbuf_new()) == NULL)
863: return SSH_ERR_ALLOC_FAIL;
864: if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0)
865: r = kex_derive_keys(ssh, hash, hashlen, shared_secret);
866: sshbuf_free(shared_secret);
867: return r;
1.27 markus 868: }
1.99 markus 869: #endif
1.57 djm 870:
1.99 markus 871: #ifdef WITH_SSH1
1.102 markus 872: int
1.57 djm 873: derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
874: u_int8_t cookie[8], u_int8_t id[16])
875: {
1.105 djm 876: u_int8_t hbuf[2048], sbuf[2048], obuf[SSH_DIGEST_MAX_LENGTH];
1.102 markus 877: struct ssh_digest_ctx *hashctx = NULL;
1.105 djm 878: size_t hlen, slen;
1.102 markus 879: int r;
1.57 djm 880:
1.105 djm 881: hlen = BN_num_bytes(host_modulus);
882: slen = BN_num_bytes(server_modulus);
883: if (hlen < (512 / 8) || (u_int)hlen > sizeof(hbuf) ||
884: slen < (512 / 8) || (u_int)slen > sizeof(sbuf))
1.102 markus 885: return SSH_ERR_KEY_BITS_MISMATCH;
1.105 djm 886: if (BN_bn2bin(host_modulus, hbuf) <= 0 ||
887: BN_bn2bin(server_modulus, sbuf) <= 0) {
888: r = SSH_ERR_LIBCRYPTO_ERROR;
889: goto out;
890: }
891: if ((hashctx = ssh_digest_start(SSH_DIGEST_MD5)) == NULL) {
892: r = SSH_ERR_ALLOC_FAIL;
893: goto out;
894: }
895: if (ssh_digest_update(hashctx, hbuf, hlen) != 0 ||
896: ssh_digest_update(hashctx, sbuf, slen) != 0 ||
1.102 markus 897: ssh_digest_update(hashctx, cookie, 8) != 0 ||
898: ssh_digest_final(hashctx, obuf, sizeof(obuf)) != 0) {
899: r = SSH_ERR_LIBCRYPTO_ERROR;
900: goto out;
901: }
1.94 djm 902: memcpy(id, obuf, ssh_digest_bytes(SSH_DIGEST_MD5));
1.102 markus 903: r = 0;
904: out:
905: ssh_digest_free(hashctx);
1.105 djm 906: explicit_bzero(hbuf, sizeof(hbuf));
907: explicit_bzero(sbuf, sizeof(sbuf));
1.98 djm 908: explicit_bzero(obuf, sizeof(obuf));
1.102 markus 909: return r;
1.1 markus 910: }
1.99 markus 911: #endif
1.26 markus 912:
1.84 djm 913: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1.26 markus 914: void
915: dump_digest(char *msg, u_char *digest, int len)
916: {
917: fprintf(stderr, "%s\n", msg);
1.102 markus 918: sshbuf_dump_data(digest, len, stderr);
1.26 markus 919: }
920: #endif
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