Annotation of src/usr.bin/ssh/kex.c, Revision 1.110
1.110 ! djm 1: /* $OpenBSD: kex.c,v 1.109 2015/07/30 00:01:34 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: {
1.41 markus 299: error("Hm, kex protocol error: type %d seq %u", type, seq);
1.101 markus 300: return 0;
1.26 markus 301: }
1.1 markus 302:
1.35 itojun 303: static void
1.102 markus 304: kex_reset_dispatch(struct ssh *ssh)
1.29 markus 305: {
1.102 markus 306: ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
1.42 markus 307: SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
1.102 markus 308: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.29 markus 309: }
310:
1.102 markus 311: int
312: kex_send_newkeys(struct ssh *ssh)
1.26 markus 313: {
1.102 markus 314: int r;
1.28 markus 315:
1.102 markus 316: kex_reset_dispatch(ssh);
317: if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
318: (r = sshpkt_send(ssh)) != 0)
319: return r;
1.26 markus 320: debug("SSH2_MSG_NEWKEYS sent");
1.102 markus 321: debug("expecting SSH2_MSG_NEWKEYS");
322: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
323: return 0;
324: }
325:
326: static int
327: kex_input_newkeys(int type, u_int32_t seq, void *ctxt)
328: {
329: struct ssh *ssh = ctxt;
330: struct kex *kex = ssh->kex;
331: int r;
1.19 stevesk 332:
1.26 markus 333: debug("SSH2_MSG_NEWKEYS received");
1.102 markus 334: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
335: if ((r = sshpkt_get_end(ssh)) != 0)
336: return r;
1.30 markus 337: kex->done = 1;
1.102 markus 338: sshbuf_reset(kex->peer);
339: /* sshbuf_reset(kex->my); */
1.26 markus 340: kex->flags &= ~KEX_INIT_SENT;
1.91 djm 341: free(kex->name);
1.32 markus 342: kex->name = NULL;
1.102 markus 343: return 0;
1.26 markus 344: }
1.1 markus 345:
1.102 markus 346: int
347: kex_send_kexinit(struct ssh *ssh)
1.26 markus 348: {
1.49 markus 349: u_char *cookie;
1.102 markus 350: struct kex *kex = ssh->kex;
351: int r;
1.49 markus 352:
1.102 markus 353: if (kex == NULL)
354: return SSH_ERR_INTERNAL_ERROR;
355: if (kex->flags & KEX_INIT_SENT)
356: return 0;
1.30 markus 357: kex->done = 0;
1.49 markus 358:
359: /* generate a random cookie */
1.102 markus 360: if (sshbuf_len(kex->my) < KEX_COOKIE_LEN)
361: return SSH_ERR_INVALID_FORMAT;
362: if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL)
363: return SSH_ERR_INTERNAL_ERROR;
364: arc4random_buf(cookie, KEX_COOKIE_LEN);
365:
366: if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
367: (r = sshpkt_putb(ssh, kex->my)) != 0 ||
368: (r = sshpkt_send(ssh)) != 0)
369: return r;
1.26 markus 370: debug("SSH2_MSG_KEXINIT sent");
371: kex->flags |= KEX_INIT_SENT;
1.102 markus 372: return 0;
1.1 markus 373: }
374:
1.78 djm 375: /* ARGSUSED */
1.101 markus 376: int
1.41 markus 377: kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
1.11 provos 378: {
1.102 markus 379: struct ssh *ssh = ctxt;
380: struct kex *kex = ssh->kex;
381: const u_char *ptr;
1.100 markus 382: u_int i;
383: size_t dlen;
1.102 markus 384: int r;
1.11 provos 385:
1.26 markus 386: debug("SSH2_MSG_KEXINIT received");
1.29 markus 387: if (kex == NULL)
1.102 markus 388: return SSH_ERR_INVALID_ARGUMENT;
1.11 provos 389:
1.102 markus 390: ptr = sshpkt_ptr(ssh, &dlen);
391: if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
392: return r;
1.31 markus 393:
394: /* discard packet */
395: for (i = 0; i < KEX_COOKIE_LEN; i++)
1.102 markus 396: if ((r = sshpkt_get_u8(ssh, NULL)) != 0)
397: return r;
1.31 markus 398: for (i = 0; i < PROPOSAL_MAX; i++)
1.102 markus 399: if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0)
400: return r;
1.87 djm 401: /*
402: * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
403: * KEX method has the server move first, but a server might be using
404: * a custom method or one that we otherwise don't support. We should
405: * be prepared to remember first_kex_follows here so we can eat a
406: * packet later.
407: * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
408: * for cases where the server *doesn't* go first. I guess we should
409: * ignore it when it is set for these cases, which is what we do now.
410: */
1.102 markus 411: if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
412: (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
413: (r = sshpkt_get_end(ssh)) != 0)
414: return r;
415:
416: if (!(kex->flags & KEX_INIT_SENT))
417: if ((r = kex_send_kexinit(ssh)) != 0)
418: return r;
419: if ((r = kex_choose_conf(ssh)) != 0)
420: return r;
1.19 stevesk 421:
1.102 markus 422: if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
423: return (kex->kex[kex->kex_type])(ssh);
424:
425: return SSH_ERR_INTERNAL_ERROR;
426: }
427:
428: int
429: kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp)
430: {
431: struct kex *kex;
432: int r;
433:
434: *kexp = NULL;
435: if ((kex = calloc(1, sizeof(*kex))) == NULL)
436: return SSH_ERR_ALLOC_FAIL;
437: if ((kex->peer = sshbuf_new()) == NULL ||
438: (kex->my = sshbuf_new()) == NULL) {
439: r = SSH_ERR_ALLOC_FAIL;
440: goto out;
441: }
442: if ((r = kex_prop2buf(kex->my, proposal)) != 0)
443: goto out;
444: kex->done = 0;
445: kex_reset_dispatch(ssh);
446: r = 0;
447: *kexp = kex;
448: out:
449: if (r != 0)
450: kex_free(kex);
451: return r;
1.26 markus 452: }
1.11 provos 453:
1.100 markus 454: void
455: kex_free_newkeys(struct newkeys *newkeys)
456: {
457: if (newkeys == NULL)
458: return;
459: if (newkeys->enc.key) {
460: explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
461: free(newkeys->enc.key);
462: newkeys->enc.key = NULL;
463: }
464: if (newkeys->enc.iv) {
465: explicit_bzero(newkeys->enc.iv, newkeys->enc.block_size);
466: free(newkeys->enc.iv);
467: newkeys->enc.iv = NULL;
468: }
469: free(newkeys->enc.name);
470: explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
471: free(newkeys->comp.name);
472: explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
473: mac_clear(&newkeys->mac);
474: if (newkeys->mac.key) {
475: explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
476: free(newkeys->mac.key);
477: newkeys->mac.key = NULL;
478: }
479: free(newkeys->mac.name);
480: explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
481: explicit_bzero(newkeys, sizeof(*newkeys));
482: free(newkeys);
483: }
484:
1.102 markus 485: void
486: kex_free(struct kex *kex)
1.26 markus 487: {
1.102 markus 488: u_int mode;
1.11 provos 489:
1.102 markus 490: #ifdef WITH_OPENSSL
491: if (kex->dh)
492: DH_free(kex->dh);
493: if (kex->ec_client_key)
494: EC_KEY_free(kex->ec_client_key);
495: #endif
496: for (mode = 0; mode < MODE_MAX; mode++) {
497: kex_free_newkeys(kex->newkeys[mode]);
498: kex->newkeys[mode] = NULL;
1.100 markus 499: }
1.102 markus 500: sshbuf_free(kex->peer);
501: sshbuf_free(kex->my);
502: free(kex->session_id);
503: free(kex->client_version_string);
504: free(kex->server_version_string);
1.107 djm 505: free(kex->failed_choice);
1.102 markus 506: free(kex);
1.11 provos 507: }
508:
1.102 markus 509: int
510: kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
1.1 markus 511: {
1.102 markus 512: int r;
1.1 markus 513:
1.102 markus 514: if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0)
515: return r;
516: if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
517: kex_free(ssh->kex);
518: ssh->kex = NULL;
519: return r;
1.1 markus 520: }
1.102 markus 521: return 0;
1.1 markus 522: }
523:
1.102 markus 524: static int
525: choose_enc(struct sshenc *enc, char *client, char *server)
1.1 markus 526: {
1.23 markus 527: char *name = match_list(client, server, NULL);
1.102 markus 528:
1.1 markus 529: if (name == NULL)
1.102 markus 530: return SSH_ERR_NO_CIPHER_ALG_MATCH;
1.45 markus 531: if ((enc->cipher = cipher_by_name(name)) == NULL)
1.102 markus 532: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 533: enc->name = name;
534: enc->enabled = 0;
535: enc->iv = NULL;
1.88 markus 536: enc->iv_len = cipher_ivlen(enc->cipher);
1.1 markus 537: enc->key = NULL;
1.45 markus 538: enc->key_len = cipher_keylen(enc->cipher);
539: enc->block_size = cipher_blocksize(enc->cipher);
1.102 markus 540: return 0;
1.1 markus 541: }
1.69 deraadt 542:
1.102 markus 543: static int
544: choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
1.1 markus 545: {
1.23 markus 546: char *name = match_list(client, server, NULL);
1.102 markus 547:
1.1 markus 548: if (name == NULL)
1.102 markus 549: return SSH_ERR_NO_MAC_ALG_MATCH;
1.79 djm 550: if (mac_setup(mac, name) < 0)
1.102 markus 551: return SSH_ERR_INTERNAL_ERROR;
1.21 markus 552: /* truncate the key */
1.102 markus 553: if (ssh->compat & SSH_BUG_HMAC)
1.21 markus 554: mac->key_len = 16;
1.1 markus 555: mac->name = name;
556: mac->key = NULL;
557: mac->enabled = 0;
1.102 markus 558: return 0;
1.1 markus 559: }
1.69 deraadt 560:
1.102 markus 561: static int
562: choose_comp(struct sshcomp *comp, char *client, char *server)
1.1 markus 563: {
1.23 markus 564: char *name = match_list(client, server, NULL);
1.102 markus 565:
1.1 markus 566: if (name == NULL)
1.102 markus 567: return SSH_ERR_NO_COMPRESS_ALG_MATCH;
1.64 markus 568: if (strcmp(name, "zlib@openssh.com") == 0) {
569: comp->type = COMP_DELAYED;
570: } else if (strcmp(name, "zlib") == 0) {
571: comp->type = COMP_ZLIB;
1.1 markus 572: } else if (strcmp(name, "none") == 0) {
1.64 markus 573: comp->type = COMP_NONE;
1.1 markus 574: } else {
1.102 markus 575: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 576: }
577: comp->name = name;
1.102 markus 578: return 0;
1.1 markus 579: }
1.69 deraadt 580:
1.102 markus 581: static int
582: choose_kex(struct kex *k, char *client, char *server)
1.1 markus 583: {
1.89 djm 584: const struct kexalg *kexalg;
585:
1.23 markus 586: k->name = match_list(client, server, NULL);
1.102 markus 587:
1.110 ! djm 588: debug("kex: algorithm: %s", k->name ? k->name : "(no match)");
1.1 markus 589: if (k->name == NULL)
1.102 markus 590: return SSH_ERR_NO_KEX_ALG_MATCH;
1.89 djm 591: if ((kexalg = kex_alg_by_name(k->name)) == NULL)
1.102 markus 592: return SSH_ERR_INTERNAL_ERROR;
1.89 djm 593: k->kex_type = kexalg->type;
1.94 djm 594: k->hash_alg = kexalg->hash_alg;
1.89 djm 595: k->ec_nid = kexalg->ec_nid;
1.102 markus 596: return 0;
1.1 markus 597: }
1.65 djm 598:
1.102 markus 599: static int
600: choose_hostkeyalg(struct kex *k, char *client, char *server)
1.1 markus 601: {
1.23 markus 602: char *hostkeyalg = match_list(client, server, NULL);
1.102 markus 603:
1.110 ! djm 604: debug("kex: host key algorithm: %s",
! 605: hostkeyalg ? hostkeyalg : "(no match)");
1.13 markus 606: if (hostkeyalg == NULL)
1.102 markus 607: return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
608: k->hostkey_type = sshkey_type_from_name(hostkeyalg);
1.13 markus 609: if (k->hostkey_type == KEY_UNSPEC)
1.102 markus 610: return SSH_ERR_INTERNAL_ERROR;
1.104 djm 611: k->hostkey_nid = sshkey_ecdsa_nid_from_name(hostkeyalg);
1.91 djm 612: free(hostkeyalg);
1.102 markus 613: return 0;
1.1 markus 614: }
615:
1.56 djm 616: static int
1.53 markus 617: proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
618: {
619: static int check[] = {
620: PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
621: };
622: int *idx;
623: char *p;
624:
625: for (idx = &check[0]; *idx != -1; idx++) {
626: if ((p = strchr(my[*idx], ',')) != NULL)
627: *p = '\0';
628: if ((p = strchr(peer[*idx], ',')) != NULL)
629: *p = '\0';
630: if (strcmp(my[*idx], peer[*idx]) != 0) {
631: debug2("proposal mismatch: my %s peer %s",
632: my[*idx], peer[*idx]);
633: return (0);
634: }
635: }
636: debug2("proposals match");
637: return (1);
638: }
639:
1.102 markus 640: static int
641: kex_choose_conf(struct ssh *ssh)
1.1 markus 642: {
1.102 markus 643: struct kex *kex = ssh->kex;
644: struct newkeys *newkeys;
645: char **my = NULL, **peer = NULL;
1.26 markus 646: char **cprop, **sprop;
1.27 markus 647: int nenc, nmac, ncomp;
1.96 dtucker 648: u_int mode, ctos, need, dh_need, authlen;
1.102 markus 649: int r, first_kex_follows;
1.1 markus 650:
1.110 ! djm 651: debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
! 652: if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
! 653: goto out;
! 654: debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
! 655: if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
1.102 markus 656: goto out;
1.26 markus 657:
1.27 markus 658: if (kex->server) {
1.26 markus 659: cprop=peer;
660: sprop=my;
661: } else {
662: cprop=my;
663: sprop=peer;
1.82 andreas 664: }
665:
666: /* Check whether server offers roaming */
667: if (!kex->server) {
1.102 markus 668: char *roaming = match_list(KEX_RESUME,
669: peer[PROPOSAL_KEX_ALGS], NULL);
670:
1.82 andreas 671: if (roaming) {
672: kex->roaming = 1;
1.91 djm 673: free(roaming);
1.82 andreas 674: }
1.26 markus 675: }
1.1 markus 676:
1.30 markus 677: /* Algorithm Negotiation */
1.110 ! djm 678: if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
! 679: sprop[PROPOSAL_KEX_ALGS])) != 0) {
! 680: kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
! 681: peer[PROPOSAL_KEX_ALGS] = NULL;
! 682: goto out;
! 683: }
! 684: if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
! 685: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
! 686: kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
! 687: peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
! 688: goto out;
! 689: }
1.1 markus 690: for (mode = 0; mode < MODE_MAX; mode++) {
1.102 markus 691: if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
692: r = SSH_ERR_ALLOC_FAIL;
693: goto out;
694: }
1.30 markus 695: kex->newkeys[mode] = newkeys;
1.78 djm 696: ctos = (!kex->server && mode == MODE_OUT) ||
697: (kex->server && mode == MODE_IN);
1.1 markus 698: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
699: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
700: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.102 markus 701: if ((r = choose_enc(&newkeys->enc, cprop[nenc],
1.107 djm 702: sprop[nenc])) != 0) {
703: kex->failed_choice = peer[nenc];
704: peer[nenc] = NULL;
1.102 markus 705: goto out;
1.107 djm 706: }
1.102 markus 707: authlen = cipher_authlen(newkeys->enc.cipher);
1.88 markus 708: /* ignore mac for authenticated encryption */
1.102 markus 709: if (authlen == 0 &&
710: (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
1.107 djm 711: sprop[nmac])) != 0) {
712: kex->failed_choice = peer[nmac];
713: peer[nmac] = NULL;
1.102 markus 714: goto out;
1.107 djm 715: }
1.102 markus 716: if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
1.107 djm 717: sprop[ncomp])) != 0) {
718: kex->failed_choice = peer[ncomp];
719: peer[ncomp] = NULL;
1.102 markus 720: goto out;
1.107 djm 721: }
1.110 ! djm 722: debug("kex: %s cipher: %s MAC: %s compression: %s",
1.1 markus 723: ctos ? "client->server" : "server->client",
1.27 markus 724: newkeys->enc.name,
1.88 markus 725: authlen == 0 ? newkeys->mac.name : "<implicit>",
1.27 markus 726: newkeys->comp.name);
1.107 djm 727: }
1.96 dtucker 728: need = dh_need = 0;
1.1 markus 729: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 730: newkeys = kex->newkeys[mode];
1.97 markus 731: need = MAX(need, newkeys->enc.key_len);
732: need = MAX(need, newkeys->enc.block_size);
733: need = MAX(need, newkeys->enc.iv_len);
734: need = MAX(need, newkeys->mac.key_len);
735: dh_need = MAX(dh_need, cipher_seclen(newkeys->enc.cipher));
736: dh_need = MAX(dh_need, newkeys->enc.block_size);
737: dh_need = MAX(dh_need, newkeys->enc.iv_len);
738: dh_need = MAX(dh_need, newkeys->mac.key_len);
1.1 markus 739: }
1.7 markus 740: /* XXX need runden? */
1.27 markus 741: kex->we_need = need;
1.96 dtucker 742: kex->dh_need = dh_need;
1.53 markus 743:
744: /* ignore the next message if the proposals do not match */
1.56 djm 745: if (first_kex_follows && !proposals_match(my, peer) &&
1.102 markus 746: !(ssh->compat & SSH_BUG_FIRSTKEX))
747: ssh->dispatch_skip_packets = 1;
748: r = 0;
749: out:
1.26 markus 750: kex_prop_free(my);
751: kex_prop_free(peer);
1.102 markus 752: return r;
1.26 markus 753: }
754:
1.102 markus 755: static int
756: derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
757: const struct sshbuf *shared_secret, u_char **keyp)
1.26 markus 758: {
1.102 markus 759: struct kex *kex = ssh->kex;
760: struct ssh_digest_ctx *hashctx = NULL;
1.26 markus 761: char c = id;
1.61 djm 762: u_int have;
1.94 djm 763: size_t mdsz;
1.61 djm 764: u_char *digest;
1.102 markus 765: int r;
1.62 djm 766:
1.94 djm 767: if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
1.102 markus 768: return SSH_ERR_INVALID_ARGUMENT;
769: if ((digest = calloc(1, roundup(need, mdsz))) == NULL) {
770: r = SSH_ERR_ALLOC_FAIL;
771: goto out;
772: }
1.26 markus 773:
1.30 markus 774: /* K1 = HASH(K || H || "A" || session_id) */
1.102 markus 775: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
776: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 777: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
778: ssh_digest_update(hashctx, &c, 1) != 0 ||
779: ssh_digest_update(hashctx, kex->session_id,
1.102 markus 780: kex->session_id_len) != 0 ||
781: ssh_digest_final(hashctx, digest, mdsz) != 0) {
782: r = SSH_ERR_LIBCRYPTO_ERROR;
783: goto out;
784: }
1.94 djm 785: ssh_digest_free(hashctx);
1.102 markus 786: hashctx = NULL;
1.26 markus 787:
1.30 markus 788: /*
789: * expand key:
790: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
791: * Key = K1 || K2 || ... || Kn
792: */
1.26 markus 793: for (have = mdsz; need > have; have += mdsz) {
1.102 markus 794: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
795: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 796: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1.102 markus 797: ssh_digest_update(hashctx, digest, have) != 0 ||
798: ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
799: r = SSH_ERR_LIBCRYPTO_ERROR;
800: goto out;
801: }
1.94 djm 802: ssh_digest_free(hashctx);
1.102 markus 803: hashctx = NULL;
1.26 markus 804: }
805: #ifdef DEBUG_KEX
806: fprintf(stderr, "key '%c'== ", c);
807: dump_digest("key", digest, need);
808: #endif
1.102 markus 809: *keyp = digest;
810: digest = NULL;
811: r = 0;
812: out:
813: if (digest)
814: free(digest);
815: ssh_digest_free(hashctx);
816: return r;
1.1 markus 817: }
818:
1.23 markus 819: #define NKEYS 6
1.102 markus 820: int
821: kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
822: const struct sshbuf *shared_secret)
1.1 markus 823: {
1.102 markus 824: struct kex *kex = ssh->kex;
1.15 markus 825: u_char *keys[NKEYS];
1.102 markus 826: u_int i, j, mode, ctos;
827: int r;
1.1 markus 828:
1.65 djm 829: for (i = 0; i < NKEYS; i++) {
1.102 markus 830: if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
831: shared_secret, &keys[i])) != 0) {
832: for (j = 0; j < i; j++)
833: free(keys[j]);
834: return r;
835: }
1.65 djm 836: }
1.1 markus 837: for (mode = 0; mode < MODE_MAX; mode++) {
1.69 deraadt 838: ctos = (!kex->server && mode == MODE_OUT) ||
839: (kex->server && mode == MODE_IN);
1.100 markus 840: kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
841: kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
842: kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
1.1 markus 843: }
1.102 markus 844: return 0;
1.95 djm 845: }
846:
1.99 markus 847: #ifdef WITH_OPENSSL
1.102 markus 848: int
849: kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen,
850: const BIGNUM *secret)
1.95 djm 851: {
1.102 markus 852: struct sshbuf *shared_secret;
853: int r;
1.95 djm 854:
1.102 markus 855: if ((shared_secret = sshbuf_new()) == NULL)
856: return SSH_ERR_ALLOC_FAIL;
857: if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0)
858: r = kex_derive_keys(ssh, hash, hashlen, shared_secret);
859: sshbuf_free(shared_secret);
860: return r;
1.27 markus 861: }
1.99 markus 862: #endif
1.57 djm 863:
1.99 markus 864: #ifdef WITH_SSH1
1.102 markus 865: int
1.57 djm 866: derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
867: u_int8_t cookie[8], u_int8_t id[16])
868: {
1.105 djm 869: u_int8_t hbuf[2048], sbuf[2048], obuf[SSH_DIGEST_MAX_LENGTH];
1.102 markus 870: struct ssh_digest_ctx *hashctx = NULL;
1.105 djm 871: size_t hlen, slen;
1.102 markus 872: int r;
1.57 djm 873:
1.105 djm 874: hlen = BN_num_bytes(host_modulus);
875: slen = BN_num_bytes(server_modulus);
876: if (hlen < (512 / 8) || (u_int)hlen > sizeof(hbuf) ||
877: slen < (512 / 8) || (u_int)slen > sizeof(sbuf))
1.102 markus 878: return SSH_ERR_KEY_BITS_MISMATCH;
1.105 djm 879: if (BN_bn2bin(host_modulus, hbuf) <= 0 ||
880: BN_bn2bin(server_modulus, sbuf) <= 0) {
881: r = SSH_ERR_LIBCRYPTO_ERROR;
882: goto out;
883: }
884: if ((hashctx = ssh_digest_start(SSH_DIGEST_MD5)) == NULL) {
885: r = SSH_ERR_ALLOC_FAIL;
886: goto out;
887: }
888: if (ssh_digest_update(hashctx, hbuf, hlen) != 0 ||
889: ssh_digest_update(hashctx, sbuf, slen) != 0 ||
1.102 markus 890: ssh_digest_update(hashctx, cookie, 8) != 0 ||
891: ssh_digest_final(hashctx, obuf, sizeof(obuf)) != 0) {
892: r = SSH_ERR_LIBCRYPTO_ERROR;
893: goto out;
894: }
1.94 djm 895: memcpy(id, obuf, ssh_digest_bytes(SSH_DIGEST_MD5));
1.102 markus 896: r = 0;
897: out:
898: ssh_digest_free(hashctx);
1.105 djm 899: explicit_bzero(hbuf, sizeof(hbuf));
900: explicit_bzero(sbuf, sizeof(sbuf));
1.98 djm 901: explicit_bzero(obuf, sizeof(obuf));
1.102 markus 902: return r;
1.1 markus 903: }
1.99 markus 904: #endif
1.26 markus 905:
1.84 djm 906: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1.26 markus 907: void
908: dump_digest(char *msg, u_char *digest, int len)
909: {
910: fprintf(stderr, "%s\n", msg);
1.102 markus 911: sshbuf_dump_data(digest, len, stderr);
1.26 markus 912: }
913: #endif
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