Annotation of src/usr.bin/ssh/kex.c, Revision 1.105
1.105 ! djm 1: /* $OpenBSD: kex.c,v 1.104 2015/01/26 06:10:03 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:
1.89 djm 59: struct kexalg {
60: char *name;
1.102 markus 61: u_int type;
1.89 djm 62: int ec_nid;
1.94 djm 63: int hash_alg;
1.89 djm 64: };
65: static const struct kexalg kexalgs[] = {
1.99 markus 66: #ifdef WITH_OPENSSL
1.94 djm 67: { KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },
68: { KEX_DH14, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 },
69: { KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 },
70: { KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 },
71: { KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2,
72: NID_X9_62_prime256v1, SSH_DIGEST_SHA256 },
73: { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1,
74: SSH_DIGEST_SHA384 },
75: { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1,
76: SSH_DIGEST_SHA512 },
1.99 markus 77: #endif
1.94 djm 78: { KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
79: { NULL, -1, -1, -1},
1.89 djm 80: };
81:
82: char *
1.93 dtucker 83: kex_alg_list(char sep)
1.89 djm 84: {
1.102 markus 85: char *ret = NULL, *tmp;
1.89 djm 86: size_t nlen, rlen = 0;
87: const struct kexalg *k;
88:
89: for (k = kexalgs; k->name != NULL; k++) {
90: if (ret != NULL)
1.93 dtucker 91: ret[rlen++] = sep;
1.89 djm 92: nlen = strlen(k->name);
1.102 markus 93: if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
94: free(ret);
95: return NULL;
96: }
97: ret = tmp;
1.89 djm 98: memcpy(ret + rlen, k->name, nlen + 1);
99: rlen += nlen;
100: }
101: return ret;
102: }
103:
104: static const struct kexalg *
105: kex_alg_by_name(const char *name)
106: {
107: const struct kexalg *k;
108:
109: for (k = kexalgs; k->name != NULL; k++) {
110: if (strcmp(k->name, name) == 0)
111: return k;
112: }
113: return NULL;
114: }
115:
1.86 djm 116: /* Validate KEX method name list */
117: int
118: kex_names_valid(const char *names)
119: {
120: char *s, *cp, *p;
121:
122: if (names == NULL || strcmp(names, "") == 0)
123: return 0;
1.102 markus 124: if ((s = cp = strdup(names)) == NULL)
125: return 0;
1.86 djm 126: for ((p = strsep(&cp, ",")); p && *p != '\0';
127: (p = strsep(&cp, ","))) {
1.89 djm 128: if (kex_alg_by_name(p) == NULL) {
1.86 djm 129: error("Unsupported KEX algorithm \"%.100s\"", p);
1.91 djm 130: free(s);
1.86 djm 131: return 0;
132: }
133: }
134: debug3("kex names ok: [%s]", names);
1.91 djm 135: free(s);
1.86 djm 136: return 1;
137: }
1.26 markus 138:
139: /* put algorithm proposal into buffer */
1.102 markus 140: int
141: kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
1.1 markus 142: {
1.61 djm 143: u_int i;
1.102 markus 144: int r;
145:
146: sshbuf_reset(b);
1.26 markus 147:
1.49 markus 148: /*
149: * add a dummy cookie, the cookie will be overwritten by
150: * kex_send_kexinit(), each time a kexinit is set
151: */
1.102 markus 152: for (i = 0; i < KEX_COOKIE_LEN; i++) {
153: if ((r = sshbuf_put_u8(b, 0)) != 0)
154: return r;
155: }
156: for (i = 0; i < PROPOSAL_MAX; i++) {
157: if ((r = sshbuf_put_cstring(b, proposal[i])) != 0)
158: return r;
159: }
160: if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */
161: (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */
162: return r;
163: return 0;
1.1 markus 164: }
165:
1.26 markus 166: /* parse buffer and return algorithm proposal */
1.102 markus 167: int
168: kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp)
1.7 markus 169: {
1.102 markus 170: struct sshbuf *b = NULL;
171: u_char v;
1.78 djm 172: u_int i;
1.102 markus 173: char **proposal = NULL;
174: int r;
1.7 markus 175:
1.102 markus 176: *propp = NULL;
177: if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL)
178: return SSH_ERR_ALLOC_FAIL;
179: if ((b = sshbuf_fromb(raw)) == NULL) {
180: r = SSH_ERR_ALLOC_FAIL;
181: goto out;
182: }
183: if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */
184: goto out;
1.7 markus 185: /* extract kex init proposal strings */
186: for (i = 0; i < PROPOSAL_MAX; i++) {
1.102 markus 187: if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0)
188: goto out;
1.26 markus 189: debug2("kex_parse_kexinit: %s", proposal[i]);
1.7 markus 190: }
1.26 markus 191: /* first kex follows / reserved */
1.102 markus 192: if ((r = sshbuf_get_u8(b, &v)) != 0 ||
193: (r = sshbuf_get_u32(b, &i)) != 0)
194: goto out;
1.53 markus 195: if (first_kex_follows != NULL)
196: *first_kex_follows = i;
1.102 markus 197: debug2("kex_parse_kexinit: first_kex_follows %d ", v);
1.78 djm 198: debug2("kex_parse_kexinit: reserved %u ", i);
1.102 markus 199: r = 0;
200: *propp = proposal;
201: out:
202: if (r != 0 && proposal != NULL)
203: kex_prop_free(proposal);
204: sshbuf_free(b);
205: return r;
1.1 markus 206: }
207:
1.102 markus 208: void
1.26 markus 209: kex_prop_free(char **proposal)
1.1 markus 210: {
1.61 djm 211: u_int i;
1.26 markus 212:
213: for (i = 0; i < PROPOSAL_MAX; i++)
1.91 djm 214: free(proposal[i]);
215: free(proposal);
1.1 markus 216: }
217:
1.78 djm 218: /* ARGSUSED */
1.101 markus 219: static int
1.41 markus 220: kex_protocol_error(int type, u_int32_t seq, void *ctxt)
1.1 markus 221: {
1.41 markus 222: error("Hm, kex protocol error: type %d seq %u", type, seq);
1.101 markus 223: return 0;
1.26 markus 224: }
1.1 markus 225:
1.35 itojun 226: static void
1.102 markus 227: kex_reset_dispatch(struct ssh *ssh)
1.29 markus 228: {
1.102 markus 229: ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
1.42 markus 230: SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
1.102 markus 231: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.29 markus 232: }
233:
1.102 markus 234: int
235: kex_send_newkeys(struct ssh *ssh)
1.26 markus 236: {
1.102 markus 237: int r;
1.28 markus 238:
1.102 markus 239: kex_reset_dispatch(ssh);
240: if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
241: (r = sshpkt_send(ssh)) != 0)
242: return r;
1.26 markus 243: debug("SSH2_MSG_NEWKEYS sent");
1.102 markus 244: debug("expecting SSH2_MSG_NEWKEYS");
245: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
246: return 0;
247: }
248:
249: static int
250: kex_input_newkeys(int type, u_int32_t seq, void *ctxt)
251: {
252: struct ssh *ssh = ctxt;
253: struct kex *kex = ssh->kex;
254: int r;
1.19 stevesk 255:
1.26 markus 256: debug("SSH2_MSG_NEWKEYS received");
1.102 markus 257: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
258: if ((r = sshpkt_get_end(ssh)) != 0)
259: return r;
1.30 markus 260: kex->done = 1;
1.102 markus 261: sshbuf_reset(kex->peer);
262: /* sshbuf_reset(kex->my); */
1.26 markus 263: kex->flags &= ~KEX_INIT_SENT;
1.91 djm 264: free(kex->name);
1.32 markus 265: kex->name = NULL;
1.102 markus 266: return 0;
1.26 markus 267: }
1.1 markus 268:
1.102 markus 269: int
270: kex_send_kexinit(struct ssh *ssh)
1.26 markus 271: {
1.49 markus 272: u_char *cookie;
1.102 markus 273: struct kex *kex = ssh->kex;
274: int r;
1.49 markus 275:
1.102 markus 276: if (kex == NULL)
277: return SSH_ERR_INTERNAL_ERROR;
278: if (kex->flags & KEX_INIT_SENT)
279: return 0;
1.30 markus 280: kex->done = 0;
1.49 markus 281:
282: /* generate a random cookie */
1.102 markus 283: if (sshbuf_len(kex->my) < KEX_COOKIE_LEN)
284: return SSH_ERR_INVALID_FORMAT;
285: if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL)
286: return SSH_ERR_INTERNAL_ERROR;
287: arc4random_buf(cookie, KEX_COOKIE_LEN);
288:
289: if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
290: (r = sshpkt_putb(ssh, kex->my)) != 0 ||
291: (r = sshpkt_send(ssh)) != 0)
292: return r;
1.26 markus 293: debug("SSH2_MSG_KEXINIT sent");
294: kex->flags |= KEX_INIT_SENT;
1.102 markus 295: return 0;
1.1 markus 296: }
297:
1.78 djm 298: /* ARGSUSED */
1.101 markus 299: int
1.41 markus 300: kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
1.11 provos 301: {
1.102 markus 302: struct ssh *ssh = ctxt;
303: struct kex *kex = ssh->kex;
304: const u_char *ptr;
1.100 markus 305: u_int i;
306: size_t dlen;
1.102 markus 307: int r;
1.11 provos 308:
1.26 markus 309: debug("SSH2_MSG_KEXINIT received");
1.29 markus 310: if (kex == NULL)
1.102 markus 311: return SSH_ERR_INVALID_ARGUMENT;
1.11 provos 312:
1.102 markus 313: ptr = sshpkt_ptr(ssh, &dlen);
314: if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
315: return r;
1.31 markus 316:
317: /* discard packet */
318: for (i = 0; i < KEX_COOKIE_LEN; i++)
1.102 markus 319: if ((r = sshpkt_get_u8(ssh, NULL)) != 0)
320: return r;
1.31 markus 321: for (i = 0; i < PROPOSAL_MAX; i++)
1.102 markus 322: if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0)
323: return r;
1.87 djm 324: /*
325: * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
326: * KEX method has the server move first, but a server might be using
327: * a custom method or one that we otherwise don't support. We should
328: * be prepared to remember first_kex_follows here so we can eat a
329: * packet later.
330: * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
331: * for cases where the server *doesn't* go first. I guess we should
332: * ignore it when it is set for these cases, which is what we do now.
333: */
1.102 markus 334: if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
335: (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
336: (r = sshpkt_get_end(ssh)) != 0)
337: return r;
338:
339: if (!(kex->flags & KEX_INIT_SENT))
340: if ((r = kex_send_kexinit(ssh)) != 0)
341: return r;
342: if ((r = kex_choose_conf(ssh)) != 0)
343: return r;
1.19 stevesk 344:
1.102 markus 345: if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
346: return (kex->kex[kex->kex_type])(ssh);
347:
348: return SSH_ERR_INTERNAL_ERROR;
349: }
350:
351: int
352: kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp)
353: {
354: struct kex *kex;
355: int r;
356:
357: *kexp = NULL;
358: if ((kex = calloc(1, sizeof(*kex))) == NULL)
359: return SSH_ERR_ALLOC_FAIL;
360: if ((kex->peer = sshbuf_new()) == NULL ||
361: (kex->my = sshbuf_new()) == NULL) {
362: r = SSH_ERR_ALLOC_FAIL;
363: goto out;
364: }
365: if ((r = kex_prop2buf(kex->my, proposal)) != 0)
366: goto out;
367: kex->done = 0;
368: kex_reset_dispatch(ssh);
369: r = 0;
370: *kexp = kex;
371: out:
372: if (r != 0)
373: kex_free(kex);
374: return r;
1.26 markus 375: }
1.11 provos 376:
1.100 markus 377: void
378: kex_free_newkeys(struct newkeys *newkeys)
379: {
380: if (newkeys == NULL)
381: return;
382: if (newkeys->enc.key) {
383: explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
384: free(newkeys->enc.key);
385: newkeys->enc.key = NULL;
386: }
387: if (newkeys->enc.iv) {
388: explicit_bzero(newkeys->enc.iv, newkeys->enc.block_size);
389: free(newkeys->enc.iv);
390: newkeys->enc.iv = NULL;
391: }
392: free(newkeys->enc.name);
393: explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
394: free(newkeys->comp.name);
395: explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
396: mac_clear(&newkeys->mac);
397: if (newkeys->mac.key) {
398: explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
399: free(newkeys->mac.key);
400: newkeys->mac.key = NULL;
401: }
402: free(newkeys->mac.name);
403: explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
404: explicit_bzero(newkeys, sizeof(*newkeys));
405: free(newkeys);
406: }
407:
1.102 markus 408: void
409: kex_free(struct kex *kex)
1.26 markus 410: {
1.102 markus 411: u_int mode;
1.11 provos 412:
1.102 markus 413: #ifdef WITH_OPENSSL
414: if (kex->dh)
415: DH_free(kex->dh);
416: if (kex->ec_client_key)
417: EC_KEY_free(kex->ec_client_key);
418: #endif
419: for (mode = 0; mode < MODE_MAX; mode++) {
420: kex_free_newkeys(kex->newkeys[mode]);
421: kex->newkeys[mode] = NULL;
1.100 markus 422: }
1.102 markus 423: sshbuf_free(kex->peer);
424: sshbuf_free(kex->my);
425: free(kex->session_id);
426: free(kex->client_version_string);
427: free(kex->server_version_string);
428: free(kex);
1.11 provos 429: }
430:
1.102 markus 431: int
432: kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
1.1 markus 433: {
1.102 markus 434: int r;
1.1 markus 435:
1.102 markus 436: if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0)
437: return r;
438: if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
439: kex_free(ssh->kex);
440: ssh->kex = NULL;
441: return r;
1.1 markus 442: }
1.102 markus 443: return 0;
1.1 markus 444: }
445:
1.102 markus 446: static int
447: choose_enc(struct sshenc *enc, char *client, char *server)
1.1 markus 448: {
1.23 markus 449: char *name = match_list(client, server, NULL);
1.102 markus 450:
1.1 markus 451: if (name == NULL)
1.102 markus 452: return SSH_ERR_NO_CIPHER_ALG_MATCH;
1.45 markus 453: if ((enc->cipher = cipher_by_name(name)) == NULL)
1.102 markus 454: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 455: enc->name = name;
456: enc->enabled = 0;
457: enc->iv = NULL;
1.88 markus 458: enc->iv_len = cipher_ivlen(enc->cipher);
1.1 markus 459: enc->key = NULL;
1.45 markus 460: enc->key_len = cipher_keylen(enc->cipher);
461: enc->block_size = cipher_blocksize(enc->cipher);
1.102 markus 462: return 0;
1.1 markus 463: }
1.69 deraadt 464:
1.102 markus 465: static int
466: choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
1.1 markus 467: {
1.23 markus 468: char *name = match_list(client, server, NULL);
1.102 markus 469:
1.1 markus 470: if (name == NULL)
1.102 markus 471: return SSH_ERR_NO_MAC_ALG_MATCH;
1.79 djm 472: if (mac_setup(mac, name) < 0)
1.102 markus 473: return SSH_ERR_INTERNAL_ERROR;
1.21 markus 474: /* truncate the key */
1.102 markus 475: if (ssh->compat & SSH_BUG_HMAC)
1.21 markus 476: mac->key_len = 16;
1.1 markus 477: mac->name = name;
478: mac->key = NULL;
479: mac->enabled = 0;
1.102 markus 480: return 0;
1.1 markus 481: }
1.69 deraadt 482:
1.102 markus 483: static int
484: choose_comp(struct sshcomp *comp, char *client, char *server)
1.1 markus 485: {
1.23 markus 486: char *name = match_list(client, server, NULL);
1.102 markus 487:
1.1 markus 488: if (name == NULL)
1.102 markus 489: return SSH_ERR_NO_COMPRESS_ALG_MATCH;
1.64 markus 490: if (strcmp(name, "zlib@openssh.com") == 0) {
491: comp->type = COMP_DELAYED;
492: } else if (strcmp(name, "zlib") == 0) {
493: comp->type = COMP_ZLIB;
1.1 markus 494: } else if (strcmp(name, "none") == 0) {
1.64 markus 495: comp->type = COMP_NONE;
1.1 markus 496: } else {
1.102 markus 497: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 498: }
499: comp->name = name;
1.102 markus 500: return 0;
1.1 markus 501: }
1.69 deraadt 502:
1.102 markus 503: static int
504: choose_kex(struct kex *k, char *client, char *server)
1.1 markus 505: {
1.89 djm 506: const struct kexalg *kexalg;
507:
1.23 markus 508: k->name = match_list(client, server, NULL);
1.102 markus 509:
1.1 markus 510: if (k->name == NULL)
1.102 markus 511: return SSH_ERR_NO_KEX_ALG_MATCH;
1.89 djm 512: if ((kexalg = kex_alg_by_name(k->name)) == NULL)
1.102 markus 513: return SSH_ERR_INTERNAL_ERROR;
1.89 djm 514: k->kex_type = kexalg->type;
1.94 djm 515: k->hash_alg = kexalg->hash_alg;
1.89 djm 516: k->ec_nid = kexalg->ec_nid;
1.102 markus 517: return 0;
1.1 markus 518: }
1.65 djm 519:
1.102 markus 520: static int
521: choose_hostkeyalg(struct kex *k, char *client, char *server)
1.1 markus 522: {
1.23 markus 523: char *hostkeyalg = match_list(client, server, NULL);
1.102 markus 524:
1.13 markus 525: if (hostkeyalg == NULL)
1.102 markus 526: return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
527: k->hostkey_type = sshkey_type_from_name(hostkeyalg);
1.13 markus 528: if (k->hostkey_type == KEY_UNSPEC)
1.102 markus 529: return SSH_ERR_INTERNAL_ERROR;
1.104 djm 530: k->hostkey_nid = sshkey_ecdsa_nid_from_name(hostkeyalg);
1.91 djm 531: free(hostkeyalg);
1.102 markus 532: return 0;
1.1 markus 533: }
534:
1.56 djm 535: static int
1.53 markus 536: proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
537: {
538: static int check[] = {
539: PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
540: };
541: int *idx;
542: char *p;
543:
544: for (idx = &check[0]; *idx != -1; idx++) {
545: if ((p = strchr(my[*idx], ',')) != NULL)
546: *p = '\0';
547: if ((p = strchr(peer[*idx], ',')) != NULL)
548: *p = '\0';
549: if (strcmp(my[*idx], peer[*idx]) != 0) {
550: debug2("proposal mismatch: my %s peer %s",
551: my[*idx], peer[*idx]);
552: return (0);
553: }
554: }
555: debug2("proposals match");
556: return (1);
557: }
558:
1.102 markus 559: static int
560: kex_choose_conf(struct ssh *ssh)
1.1 markus 561: {
1.102 markus 562: struct kex *kex = ssh->kex;
563: struct newkeys *newkeys;
564: char **my = NULL, **peer = NULL;
1.26 markus 565: char **cprop, **sprop;
1.27 markus 566: int nenc, nmac, ncomp;
1.96 dtucker 567: u_int mode, ctos, need, dh_need, authlen;
1.102 markus 568: int r, first_kex_follows;
1.1 markus 569:
1.102 markus 570: if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0 ||
571: (r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
572: goto out;
1.26 markus 573:
1.27 markus 574: if (kex->server) {
1.26 markus 575: cprop=peer;
576: sprop=my;
577: } else {
578: cprop=my;
579: sprop=peer;
1.82 andreas 580: }
581:
582: /* Check whether server offers roaming */
583: if (!kex->server) {
1.102 markus 584: char *roaming = match_list(KEX_RESUME,
585: peer[PROPOSAL_KEX_ALGS], NULL);
586:
1.82 andreas 587: if (roaming) {
588: kex->roaming = 1;
1.91 djm 589: free(roaming);
1.82 andreas 590: }
1.26 markus 591: }
1.1 markus 592:
1.30 markus 593: /* Algorithm Negotiation */
1.1 markus 594: for (mode = 0; mode < MODE_MAX; mode++) {
1.102 markus 595: if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
596: r = SSH_ERR_ALLOC_FAIL;
597: goto out;
598: }
1.30 markus 599: kex->newkeys[mode] = newkeys;
1.78 djm 600: ctos = (!kex->server && mode == MODE_OUT) ||
601: (kex->server && mode == MODE_IN);
1.1 markus 602: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
603: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
604: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.102 markus 605: if ((r = choose_enc(&newkeys->enc, cprop[nenc],
606: sprop[nenc])) != 0)
607: goto out;
608: authlen = cipher_authlen(newkeys->enc.cipher);
1.88 markus 609: /* ignore mac for authenticated encryption */
1.102 markus 610: if (authlen == 0 &&
611: (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
612: sprop[nmac])) != 0)
613: goto out;
614: if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
615: sprop[ncomp])) != 0)
616: goto out;
1.2 markus 617: debug("kex: %s %s %s %s",
1.1 markus 618: ctos ? "client->server" : "server->client",
1.27 markus 619: newkeys->enc.name,
1.88 markus 620: authlen == 0 ? newkeys->mac.name : "<implicit>",
1.27 markus 621: newkeys->comp.name);
1.1 markus 622: }
1.102 markus 623: if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
624: sprop[PROPOSAL_KEX_ALGS])) != 0 ||
625: (r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
626: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0)
627: goto out;
1.96 dtucker 628: need = dh_need = 0;
1.1 markus 629: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 630: newkeys = kex->newkeys[mode];
1.97 markus 631: need = MAX(need, newkeys->enc.key_len);
632: need = MAX(need, newkeys->enc.block_size);
633: need = MAX(need, newkeys->enc.iv_len);
634: need = MAX(need, newkeys->mac.key_len);
635: dh_need = MAX(dh_need, cipher_seclen(newkeys->enc.cipher));
636: dh_need = MAX(dh_need, newkeys->enc.block_size);
637: dh_need = MAX(dh_need, newkeys->enc.iv_len);
638: dh_need = MAX(dh_need, newkeys->mac.key_len);
1.1 markus 639: }
1.7 markus 640: /* XXX need runden? */
1.27 markus 641: kex->we_need = need;
1.96 dtucker 642: kex->dh_need = dh_need;
1.53 markus 643:
644: /* ignore the next message if the proposals do not match */
1.56 djm 645: if (first_kex_follows && !proposals_match(my, peer) &&
1.102 markus 646: !(ssh->compat & SSH_BUG_FIRSTKEX))
647: ssh->dispatch_skip_packets = 1;
648: r = 0;
649: out:
1.26 markus 650: kex_prop_free(my);
651: kex_prop_free(peer);
1.102 markus 652: return r;
1.26 markus 653: }
654:
1.102 markus 655: static int
656: derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
657: const struct sshbuf *shared_secret, u_char **keyp)
1.26 markus 658: {
1.102 markus 659: struct kex *kex = ssh->kex;
660: struct ssh_digest_ctx *hashctx = NULL;
1.26 markus 661: char c = id;
1.61 djm 662: u_int have;
1.94 djm 663: size_t mdsz;
1.61 djm 664: u_char *digest;
1.102 markus 665: int r;
1.62 djm 666:
1.94 djm 667: if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
1.102 markus 668: return SSH_ERR_INVALID_ARGUMENT;
669: if ((digest = calloc(1, roundup(need, mdsz))) == NULL) {
670: r = SSH_ERR_ALLOC_FAIL;
671: goto out;
672: }
1.26 markus 673:
1.30 markus 674: /* K1 = HASH(K || H || "A" || session_id) */
1.102 markus 675: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
676: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 677: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
678: ssh_digest_update(hashctx, &c, 1) != 0 ||
679: ssh_digest_update(hashctx, kex->session_id,
1.102 markus 680: kex->session_id_len) != 0 ||
681: ssh_digest_final(hashctx, digest, mdsz) != 0) {
682: r = SSH_ERR_LIBCRYPTO_ERROR;
683: goto out;
684: }
1.94 djm 685: ssh_digest_free(hashctx);
1.102 markus 686: hashctx = NULL;
1.26 markus 687:
1.30 markus 688: /*
689: * expand key:
690: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
691: * Key = K1 || K2 || ... || Kn
692: */
1.26 markus 693: for (have = mdsz; need > have; have += mdsz) {
1.102 markus 694: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
695: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 696: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1.102 markus 697: ssh_digest_update(hashctx, digest, have) != 0 ||
698: ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
699: r = SSH_ERR_LIBCRYPTO_ERROR;
700: goto out;
701: }
1.94 djm 702: ssh_digest_free(hashctx);
1.102 markus 703: hashctx = NULL;
1.26 markus 704: }
705: #ifdef DEBUG_KEX
706: fprintf(stderr, "key '%c'== ", c);
707: dump_digest("key", digest, need);
708: #endif
1.102 markus 709: *keyp = digest;
710: digest = NULL;
711: r = 0;
712: out:
713: if (digest)
714: free(digest);
715: ssh_digest_free(hashctx);
716: return r;
1.1 markus 717: }
718:
1.23 markus 719: #define NKEYS 6
1.102 markus 720: int
721: kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
722: const struct sshbuf *shared_secret)
1.1 markus 723: {
1.102 markus 724: struct kex *kex = ssh->kex;
1.15 markus 725: u_char *keys[NKEYS];
1.102 markus 726: u_int i, j, mode, ctos;
727: int r;
1.1 markus 728:
1.65 djm 729: for (i = 0; i < NKEYS; i++) {
1.102 markus 730: if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
731: shared_secret, &keys[i])) != 0) {
732: for (j = 0; j < i; j++)
733: free(keys[j]);
734: return r;
735: }
1.65 djm 736: }
1.1 markus 737: for (mode = 0; mode < MODE_MAX; mode++) {
1.69 deraadt 738: ctos = (!kex->server && mode == MODE_OUT) ||
739: (kex->server && mode == MODE_IN);
1.100 markus 740: kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
741: kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
742: kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
1.1 markus 743: }
1.102 markus 744: return 0;
1.95 djm 745: }
746:
1.99 markus 747: #ifdef WITH_OPENSSL
1.102 markus 748: int
749: kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen,
750: const BIGNUM *secret)
1.95 djm 751: {
1.102 markus 752: struct sshbuf *shared_secret;
753: int r;
1.95 djm 754:
1.102 markus 755: if ((shared_secret = sshbuf_new()) == NULL)
756: return SSH_ERR_ALLOC_FAIL;
757: if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0)
758: r = kex_derive_keys(ssh, hash, hashlen, shared_secret);
759: sshbuf_free(shared_secret);
760: return r;
1.27 markus 761: }
1.99 markus 762: #endif
1.57 djm 763:
1.99 markus 764: #ifdef WITH_SSH1
1.102 markus 765: int
1.57 djm 766: derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
767: u_int8_t cookie[8], u_int8_t id[16])
768: {
1.105 ! djm 769: u_int8_t hbuf[2048], sbuf[2048], obuf[SSH_DIGEST_MAX_LENGTH];
1.102 markus 770: struct ssh_digest_ctx *hashctx = NULL;
1.105 ! djm 771: size_t hlen, slen;
1.102 markus 772: int r;
1.57 djm 773:
1.105 ! djm 774: hlen = BN_num_bytes(host_modulus);
! 775: slen = BN_num_bytes(server_modulus);
! 776: if (hlen < (512 / 8) || (u_int)hlen > sizeof(hbuf) ||
! 777: slen < (512 / 8) || (u_int)slen > sizeof(sbuf))
1.102 markus 778: return SSH_ERR_KEY_BITS_MISMATCH;
1.105 ! djm 779: if (BN_bn2bin(host_modulus, hbuf) <= 0 ||
! 780: BN_bn2bin(server_modulus, sbuf) <= 0) {
! 781: r = SSH_ERR_LIBCRYPTO_ERROR;
! 782: goto out;
! 783: }
! 784: if ((hashctx = ssh_digest_start(SSH_DIGEST_MD5)) == NULL) {
! 785: r = SSH_ERR_ALLOC_FAIL;
! 786: goto out;
! 787: }
! 788: if (ssh_digest_update(hashctx, hbuf, hlen) != 0 ||
! 789: ssh_digest_update(hashctx, sbuf, slen) != 0 ||
1.102 markus 790: ssh_digest_update(hashctx, cookie, 8) != 0 ||
791: ssh_digest_final(hashctx, obuf, sizeof(obuf)) != 0) {
792: r = SSH_ERR_LIBCRYPTO_ERROR;
793: goto out;
794: }
1.94 djm 795: memcpy(id, obuf, ssh_digest_bytes(SSH_DIGEST_MD5));
1.102 markus 796: r = 0;
797: out:
798: ssh_digest_free(hashctx);
1.105 ! djm 799: explicit_bzero(hbuf, sizeof(hbuf));
! 800: explicit_bzero(sbuf, sizeof(sbuf));
1.98 djm 801: explicit_bzero(obuf, sizeof(obuf));
1.102 markus 802: return r;
1.1 markus 803: }
1.99 markus 804: #endif
1.26 markus 805:
1.84 djm 806: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1.26 markus 807: void
808: dump_digest(char *msg, u_char *digest, int len)
809: {
810: fprintf(stderr, "%s\n", msg);
1.102 markus 811: sshbuf_dump_data(digest, len, stderr);
1.26 markus 812: }
813: #endif
![[BACK]](/icons/back.gif){kind=icon}
Return to kex.c CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / ssh