Annotation of src/usr.bin/ssh/kex.c, Revision 1.120
1.120 ! deraadt 1: /* $OpenBSD: kex.c,v 1.119 2016/09/06 09:14:05 markus 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 },
93: { NULL, -1, -1, -1},
1.89 djm 94: };
95:
96: char *
1.93 dtucker 97: kex_alg_list(char sep)
1.89 djm 98: {
1.102 markus 99: char *ret = NULL, *tmp;
1.89 djm 100: size_t nlen, rlen = 0;
101: const struct kexalg *k;
102:
103: for (k = kexalgs; k->name != NULL; k++) {
104: if (ret != NULL)
1.93 dtucker 105: ret[rlen++] = sep;
1.89 djm 106: nlen = strlen(k->name);
1.102 markus 107: if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
108: free(ret);
109: return NULL;
110: }
111: ret = tmp;
1.89 djm 112: memcpy(ret + rlen, k->name, nlen + 1);
113: rlen += nlen;
114: }
115: return ret;
116: }
117:
118: static const struct kexalg *
119: kex_alg_by_name(const char *name)
120: {
121: const struct kexalg *k;
122:
123: for (k = kexalgs; k->name != NULL; k++) {
124: if (strcmp(k->name, name) == 0)
125: return k;
126: }
127: return NULL;
128: }
129:
1.86 djm 130: /* Validate KEX method name list */
131: int
132: kex_names_valid(const char *names)
133: {
134: char *s, *cp, *p;
135:
136: if (names == NULL || strcmp(names, "") == 0)
137: return 0;
1.102 markus 138: if ((s = cp = strdup(names)) == NULL)
139: return 0;
1.86 djm 140: for ((p = strsep(&cp, ",")); p && *p != '\0';
141: (p = strsep(&cp, ","))) {
1.89 djm 142: if (kex_alg_by_name(p) == NULL) {
1.86 djm 143: error("Unsupported KEX algorithm \"%.100s\"", p);
1.91 djm 144: free(s);
1.86 djm 145: return 0;
146: }
147: }
148: debug3("kex names ok: [%s]", names);
1.91 djm 149: free(s);
1.86 djm 150: return 1;
1.109 djm 151: }
152:
153: /*
154: * Concatenate algorithm names, avoiding duplicates in the process.
155: * Caller must free returned string.
156: */
157: char *
158: kex_names_cat(const char *a, const char *b)
159: {
160: char *ret = NULL, *tmp = NULL, *cp, *p;
161: size_t len;
162:
163: if (a == NULL || *a == '\0')
164: return NULL;
165: if (b == NULL || *b == '\0')
166: return strdup(a);
167: if (strlen(b) > 1024*1024)
168: return NULL;
169: len = strlen(a) + strlen(b) + 2;
170: if ((tmp = cp = strdup(b)) == NULL ||
171: (ret = calloc(1, len)) == NULL) {
172: free(tmp);
173: return NULL;
174: }
175: strlcpy(ret, a, len);
176: for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) {
177: if (match_list(ret, p, NULL) != NULL)
178: continue; /* Algorithm already present */
179: if (strlcat(ret, ",", len) >= len ||
180: strlcat(ret, p, len) >= len) {
181: free(tmp);
182: free(ret);
183: return NULL; /* Shouldn't happen */
184: }
185: }
186: free(tmp);
187: return ret;
188: }
189:
190: /*
191: * Assemble a list of algorithms from a default list and a string from a
192: * configuration file. The user-provided string may begin with '+' to
193: * indicate that it should be appended to the default.
194: */
195: int
196: kex_assemble_names(const char *def, char **list)
197: {
198: char *ret;
199:
200: if (list == NULL || *list == NULL || **list == '\0') {
201: *list = strdup(def);
202: return 0;
203: }
204: if (**list != '+') {
205: return 0;
206: }
207:
208: if ((ret = kex_names_cat(def, *list + 1)) == NULL)
209: return SSH_ERR_ALLOC_FAIL;
210: free(*list);
211: *list = ret;
212: return 0;
1.86 djm 213: }
1.26 markus 214:
215: /* put algorithm proposal into buffer */
1.102 markus 216: int
217: kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
1.1 markus 218: {
1.61 djm 219: u_int i;
1.102 markus 220: int r;
221:
222: sshbuf_reset(b);
1.26 markus 223:
1.49 markus 224: /*
225: * add a dummy cookie, the cookie will be overwritten by
226: * kex_send_kexinit(), each time a kexinit is set
227: */
1.102 markus 228: for (i = 0; i < KEX_COOKIE_LEN; i++) {
229: if ((r = sshbuf_put_u8(b, 0)) != 0)
230: return r;
231: }
232: for (i = 0; i < PROPOSAL_MAX; i++) {
233: if ((r = sshbuf_put_cstring(b, proposal[i])) != 0)
234: return r;
235: }
236: if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */
237: (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */
238: return r;
239: return 0;
1.1 markus 240: }
241:
1.26 markus 242: /* parse buffer and return algorithm proposal */
1.102 markus 243: int
244: kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp)
1.7 markus 245: {
1.102 markus 246: struct sshbuf *b = NULL;
247: u_char v;
1.78 djm 248: u_int i;
1.102 markus 249: char **proposal = NULL;
250: int r;
1.7 markus 251:
1.102 markus 252: *propp = NULL;
253: if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL)
254: return SSH_ERR_ALLOC_FAIL;
255: if ((b = sshbuf_fromb(raw)) == NULL) {
256: r = SSH_ERR_ALLOC_FAIL;
257: goto out;
258: }
259: if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */
260: goto out;
1.7 markus 261: /* extract kex init proposal strings */
262: for (i = 0; i < PROPOSAL_MAX; i++) {
1.102 markus 263: if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0)
264: goto out;
1.110 djm 265: debug2("%s: %s", proposal_names[i], proposal[i]);
1.7 markus 266: }
1.26 markus 267: /* first kex follows / reserved */
1.115 djm 268: if ((r = sshbuf_get_u8(b, &v)) != 0 || /* first_kex_follows */
269: (r = sshbuf_get_u32(b, &i)) != 0) /* reserved */
1.102 markus 270: goto out;
1.53 markus 271: if (first_kex_follows != NULL)
1.115 djm 272: *first_kex_follows = v;
1.110 djm 273: debug2("first_kex_follows %d ", v);
274: debug2("reserved %u ", i);
1.102 markus 275: r = 0;
276: *propp = proposal;
277: out:
278: if (r != 0 && proposal != NULL)
279: kex_prop_free(proposal);
280: sshbuf_free(b);
281: return r;
1.1 markus 282: }
283:
1.102 markus 284: void
1.26 markus 285: kex_prop_free(char **proposal)
1.1 markus 286: {
1.61 djm 287: u_int i;
1.26 markus 288:
1.106 djm 289: if (proposal == NULL)
290: return;
1.26 markus 291: for (i = 0; i < PROPOSAL_MAX; i++)
1.91 djm 292: free(proposal[i]);
293: free(proposal);
1.1 markus 294: }
295:
1.78 djm 296: /* ARGSUSED */
1.101 markus 297: static int
1.41 markus 298: kex_protocol_error(int type, u_int32_t seq, void *ctxt)
1.1 markus 299: {
1.112 djm 300: struct ssh *ssh = active_state; /* XXX */
301: int r;
302:
303: error("kex protocol error: type %d seq %u", type, seq);
304: if ((r = sshpkt_start(ssh, SSH2_MSG_UNIMPLEMENTED)) != 0 ||
305: (r = sshpkt_put_u32(ssh, seq)) != 0 ||
306: (r = sshpkt_send(ssh)) != 0)
307: return r;
1.101 markus 308: return 0;
1.26 markus 309: }
1.1 markus 310:
1.35 itojun 311: static void
1.102 markus 312: kex_reset_dispatch(struct ssh *ssh)
1.29 markus 313: {
1.102 markus 314: ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
1.42 markus 315: SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
1.102 markus 316: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.29 markus 317: }
318:
1.113 markus 319: static int
320: kex_send_ext_info(struct ssh *ssh)
321: {
322: int r;
323:
324: if ((r = sshpkt_start(ssh, SSH2_MSG_EXT_INFO)) != 0 ||
325: (r = sshpkt_put_u32(ssh, 1)) != 0 ||
326: (r = sshpkt_put_cstring(ssh, "server-sig-algs")) != 0 ||
327: (r = sshpkt_put_cstring(ssh, "rsa-sha2-256,rsa-sha2-512")) != 0 ||
328: (r = sshpkt_send(ssh)) != 0)
329: return r;
330: return 0;
331: }
332:
1.102 markus 333: int
334: kex_send_newkeys(struct ssh *ssh)
1.26 markus 335: {
1.102 markus 336: int r;
1.28 markus 337:
1.102 markus 338: kex_reset_dispatch(ssh);
339: if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
340: (r = sshpkt_send(ssh)) != 0)
341: return r;
1.26 markus 342: debug("SSH2_MSG_NEWKEYS sent");
1.102 markus 343: debug("expecting SSH2_MSG_NEWKEYS");
344: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
1.113 markus 345: if (ssh->kex->ext_info_c)
346: if ((r = kex_send_ext_info(ssh)) != 0)
347: return r;
1.102 markus 348: return 0;
349: }
350:
1.113 markus 351: int
352: kex_input_ext_info(int type, u_int32_t seq, void *ctxt)
353: {
354: struct ssh *ssh = ctxt;
355: struct kex *kex = ssh->kex;
356: u_int32_t i, ninfo;
357: char *name, *val, *found;
358: int r;
359:
360: debug("SSH2_MSG_EXT_INFO received");
361: ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_protocol_error);
362: if ((r = sshpkt_get_u32(ssh, &ninfo)) != 0)
363: return r;
364: for (i = 0; i < ninfo; i++) {
365: if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0)
366: return r;
367: if ((r = sshpkt_get_cstring(ssh, &val, NULL)) != 0) {
368: free(name);
369: return r;
370: }
371: debug("%s: %s=<%s>", __func__, name, val);
372: if (strcmp(name, "server-sig-algs") == 0) {
373: found = match_list("rsa-sha2-256", val, NULL);
374: if (found) {
375: kex->rsa_sha2 = 256;
376: free(found);
377: }
378: found = match_list("rsa-sha2-512", val, NULL);
379: if (found) {
380: kex->rsa_sha2 = 512;
381: free(found);
382: }
383: }
384: free(name);
385: free(val);
386: }
387: return sshpkt_get_end(ssh);
388: }
389:
1.102 markus 390: static int
391: kex_input_newkeys(int type, u_int32_t seq, void *ctxt)
392: {
393: struct ssh *ssh = ctxt;
394: struct kex *kex = ssh->kex;
395: int r;
1.19 stevesk 396:
1.26 markus 397: debug("SSH2_MSG_NEWKEYS received");
1.102 markus 398: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
399: if ((r = sshpkt_get_end(ssh)) != 0)
400: return r;
1.30 markus 401: kex->done = 1;
1.102 markus 402: sshbuf_reset(kex->peer);
403: /* sshbuf_reset(kex->my); */
1.26 markus 404: kex->flags &= ~KEX_INIT_SENT;
1.91 djm 405: free(kex->name);
1.32 markus 406: kex->name = NULL;
1.102 markus 407: return 0;
1.26 markus 408: }
1.1 markus 409:
1.102 markus 410: int
411: kex_send_kexinit(struct ssh *ssh)
1.26 markus 412: {
1.49 markus 413: u_char *cookie;
1.102 markus 414: struct kex *kex = ssh->kex;
415: int r;
1.49 markus 416:
1.102 markus 417: if (kex == NULL)
418: return SSH_ERR_INTERNAL_ERROR;
419: if (kex->flags & KEX_INIT_SENT)
420: return 0;
1.30 markus 421: kex->done = 0;
1.49 markus 422:
423: /* generate a random cookie */
1.102 markus 424: if (sshbuf_len(kex->my) < KEX_COOKIE_LEN)
425: return SSH_ERR_INVALID_FORMAT;
426: if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL)
427: return SSH_ERR_INTERNAL_ERROR;
428: arc4random_buf(cookie, KEX_COOKIE_LEN);
429:
430: if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
431: (r = sshpkt_putb(ssh, kex->my)) != 0 ||
432: (r = sshpkt_send(ssh)) != 0)
433: return r;
1.26 markus 434: debug("SSH2_MSG_KEXINIT sent");
435: kex->flags |= KEX_INIT_SENT;
1.102 markus 436: return 0;
1.1 markus 437: }
438:
1.78 djm 439: /* ARGSUSED */
1.101 markus 440: int
1.41 markus 441: kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
1.11 provos 442: {
1.102 markus 443: struct ssh *ssh = ctxt;
444: struct kex *kex = ssh->kex;
445: const u_char *ptr;
1.100 markus 446: u_int i;
447: size_t dlen;
1.102 markus 448: int r;
1.11 provos 449:
1.26 markus 450: debug("SSH2_MSG_KEXINIT received");
1.29 markus 451: if (kex == NULL)
1.102 markus 452: return SSH_ERR_INVALID_ARGUMENT;
1.11 provos 453:
1.102 markus 454: ptr = sshpkt_ptr(ssh, &dlen);
455: if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
456: return r;
1.31 markus 457:
458: /* discard packet */
459: for (i = 0; i < KEX_COOKIE_LEN; i++)
1.102 markus 460: if ((r = sshpkt_get_u8(ssh, NULL)) != 0)
461: return r;
1.31 markus 462: for (i = 0; i < PROPOSAL_MAX; i++)
1.102 markus 463: if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0)
464: return r;
1.87 djm 465: /*
466: * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
467: * KEX method has the server move first, but a server might be using
468: * a custom method or one that we otherwise don't support. We should
469: * be prepared to remember first_kex_follows here so we can eat a
470: * packet later.
471: * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
472: * for cases where the server *doesn't* go first. I guess we should
473: * ignore it when it is set for these cases, which is what we do now.
474: */
1.102 markus 475: if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
476: (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
477: (r = sshpkt_get_end(ssh)) != 0)
478: return r;
479:
480: if (!(kex->flags & KEX_INIT_SENT))
481: if ((r = kex_send_kexinit(ssh)) != 0)
482: return r;
483: if ((r = kex_choose_conf(ssh)) != 0)
484: return r;
1.19 stevesk 485:
1.102 markus 486: if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
487: return (kex->kex[kex->kex_type])(ssh);
488:
489: return SSH_ERR_INTERNAL_ERROR;
490: }
491:
492: int
493: kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp)
494: {
495: struct kex *kex;
496: int r;
497:
498: *kexp = NULL;
499: if ((kex = calloc(1, sizeof(*kex))) == NULL)
500: return SSH_ERR_ALLOC_FAIL;
501: if ((kex->peer = sshbuf_new()) == NULL ||
502: (kex->my = sshbuf_new()) == NULL) {
503: r = SSH_ERR_ALLOC_FAIL;
504: goto out;
505: }
506: if ((r = kex_prop2buf(kex->my, proposal)) != 0)
507: goto out;
508: kex->done = 0;
509: kex_reset_dispatch(ssh);
510: r = 0;
511: *kexp = kex;
512: out:
513: if (r != 0)
514: kex_free(kex);
515: return r;
1.26 markus 516: }
1.11 provos 517:
1.100 markus 518: void
519: kex_free_newkeys(struct newkeys *newkeys)
520: {
521: if (newkeys == NULL)
522: return;
523: if (newkeys->enc.key) {
524: explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
525: free(newkeys->enc.key);
526: newkeys->enc.key = NULL;
527: }
528: if (newkeys->enc.iv) {
1.111 djm 529: explicit_bzero(newkeys->enc.iv, newkeys->enc.iv_len);
1.100 markus 530: free(newkeys->enc.iv);
531: newkeys->enc.iv = NULL;
532: }
533: free(newkeys->enc.name);
534: explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
535: free(newkeys->comp.name);
536: explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
537: mac_clear(&newkeys->mac);
538: if (newkeys->mac.key) {
539: explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
540: free(newkeys->mac.key);
541: newkeys->mac.key = NULL;
542: }
543: free(newkeys->mac.name);
544: explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
545: explicit_bzero(newkeys, sizeof(*newkeys));
546: free(newkeys);
547: }
548:
1.102 markus 549: void
550: kex_free(struct kex *kex)
1.26 markus 551: {
1.102 markus 552: u_int mode;
1.11 provos 553:
1.102 markus 554: #ifdef WITH_OPENSSL
555: if (kex->dh)
556: DH_free(kex->dh);
557: if (kex->ec_client_key)
558: EC_KEY_free(kex->ec_client_key);
559: #endif
560: for (mode = 0; mode < MODE_MAX; mode++) {
561: kex_free_newkeys(kex->newkeys[mode]);
562: kex->newkeys[mode] = NULL;
1.100 markus 563: }
1.102 markus 564: sshbuf_free(kex->peer);
565: sshbuf_free(kex->my);
566: free(kex->session_id);
567: free(kex->client_version_string);
568: free(kex->server_version_string);
1.107 djm 569: free(kex->failed_choice);
1.113 markus 570: free(kex->hostkey_alg);
571: free(kex->name);
1.102 markus 572: free(kex);
1.11 provos 573: }
574:
1.102 markus 575: int
576: kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
1.1 markus 577: {
1.102 markus 578: int r;
1.1 markus 579:
1.102 markus 580: if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0)
581: return r;
582: if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
583: kex_free(ssh->kex);
584: ssh->kex = NULL;
585: return r;
1.1 markus 586: }
1.102 markus 587: return 0;
1.117 djm 588: }
589:
590: /*
591: * Request key re-exchange, returns 0 on success or a ssherr.h error
592: * code otherwise. Must not be called if KEX is incomplete or in-progress.
593: */
594: int
595: kex_start_rekex(struct ssh *ssh)
596: {
597: if (ssh->kex == NULL) {
598: error("%s: no kex", __func__);
599: return SSH_ERR_INTERNAL_ERROR;
600: }
601: if (ssh->kex->done == 0) {
602: error("%s: requested twice", __func__);
603: return SSH_ERR_INTERNAL_ERROR;
604: }
605: ssh->kex->done = 0;
606: return kex_send_kexinit(ssh);
1.1 markus 607: }
608:
1.102 markus 609: static int
610: choose_enc(struct sshenc *enc, char *client, char *server)
1.1 markus 611: {
1.23 markus 612: char *name = match_list(client, server, NULL);
1.102 markus 613:
1.1 markus 614: if (name == NULL)
1.102 markus 615: return SSH_ERR_NO_CIPHER_ALG_MATCH;
1.45 markus 616: if ((enc->cipher = cipher_by_name(name)) == NULL)
1.102 markus 617: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 618: enc->name = name;
619: enc->enabled = 0;
620: enc->iv = NULL;
1.88 markus 621: enc->iv_len = cipher_ivlen(enc->cipher);
1.1 markus 622: enc->key = NULL;
1.45 markus 623: enc->key_len = cipher_keylen(enc->cipher);
624: enc->block_size = cipher_blocksize(enc->cipher);
1.102 markus 625: return 0;
1.1 markus 626: }
1.69 deraadt 627:
1.102 markus 628: static int
629: choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
1.1 markus 630: {
1.23 markus 631: char *name = match_list(client, server, NULL);
1.102 markus 632:
1.1 markus 633: if (name == NULL)
1.102 markus 634: return SSH_ERR_NO_MAC_ALG_MATCH;
1.79 djm 635: if (mac_setup(mac, name) < 0)
1.102 markus 636: return SSH_ERR_INTERNAL_ERROR;
1.21 markus 637: /* truncate the key */
1.102 markus 638: if (ssh->compat & SSH_BUG_HMAC)
1.21 markus 639: mac->key_len = 16;
1.1 markus 640: mac->name = name;
641: mac->key = NULL;
642: mac->enabled = 0;
1.102 markus 643: return 0;
1.1 markus 644: }
1.69 deraadt 645:
1.102 markus 646: static int
647: choose_comp(struct sshcomp *comp, char *client, char *server)
1.1 markus 648: {
1.23 markus 649: char *name = match_list(client, server, NULL);
1.102 markus 650:
1.1 markus 651: if (name == NULL)
1.102 markus 652: return SSH_ERR_NO_COMPRESS_ALG_MATCH;
1.64 markus 653: if (strcmp(name, "zlib@openssh.com") == 0) {
654: comp->type = COMP_DELAYED;
655: } else if (strcmp(name, "zlib") == 0) {
656: comp->type = COMP_ZLIB;
1.1 markus 657: } else if (strcmp(name, "none") == 0) {
1.64 markus 658: comp->type = COMP_NONE;
1.1 markus 659: } else {
1.102 markus 660: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 661: }
662: comp->name = name;
1.102 markus 663: return 0;
1.1 markus 664: }
1.69 deraadt 665:
1.102 markus 666: static int
667: choose_kex(struct kex *k, char *client, char *server)
1.1 markus 668: {
1.89 djm 669: const struct kexalg *kexalg;
670:
1.23 markus 671: k->name = match_list(client, server, NULL);
1.102 markus 672:
1.110 djm 673: debug("kex: algorithm: %s", k->name ? k->name : "(no match)");
1.1 markus 674: if (k->name == NULL)
1.102 markus 675: return SSH_ERR_NO_KEX_ALG_MATCH;
1.89 djm 676: if ((kexalg = kex_alg_by_name(k->name)) == NULL)
1.102 markus 677: return SSH_ERR_INTERNAL_ERROR;
1.89 djm 678: k->kex_type = kexalg->type;
1.94 djm 679: k->hash_alg = kexalg->hash_alg;
1.89 djm 680: k->ec_nid = kexalg->ec_nid;
1.102 markus 681: return 0;
1.1 markus 682: }
1.65 djm 683:
1.102 markus 684: static int
685: choose_hostkeyalg(struct kex *k, char *client, char *server)
1.1 markus 686: {
1.113 markus 687: k->hostkey_alg = match_list(client, server, NULL);
1.102 markus 688:
1.110 djm 689: debug("kex: host key algorithm: %s",
1.113 markus 690: k->hostkey_alg ? k->hostkey_alg : "(no match)");
691: if (k->hostkey_alg == NULL)
1.102 markus 692: return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
1.113 markus 693: k->hostkey_type = sshkey_type_from_name(k->hostkey_alg);
1.13 markus 694: if (k->hostkey_type == KEY_UNSPEC)
1.102 markus 695: return SSH_ERR_INTERNAL_ERROR;
1.113 markus 696: k->hostkey_nid = sshkey_ecdsa_nid_from_name(k->hostkey_alg);
1.102 markus 697: return 0;
1.1 markus 698: }
699:
1.56 djm 700: static int
1.53 markus 701: proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
702: {
703: static int check[] = {
704: PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
705: };
706: int *idx;
707: char *p;
708:
709: for (idx = &check[0]; *idx != -1; idx++) {
710: if ((p = strchr(my[*idx], ',')) != NULL)
711: *p = '\0';
712: if ((p = strchr(peer[*idx], ',')) != NULL)
713: *p = '\0';
714: if (strcmp(my[*idx], peer[*idx]) != 0) {
715: debug2("proposal mismatch: my %s peer %s",
716: my[*idx], peer[*idx]);
717: return (0);
718: }
719: }
720: debug2("proposals match");
721: return (1);
722: }
723:
1.102 markus 724: static int
725: kex_choose_conf(struct ssh *ssh)
1.1 markus 726: {
1.102 markus 727: struct kex *kex = ssh->kex;
728: struct newkeys *newkeys;
729: char **my = NULL, **peer = NULL;
1.26 markus 730: char **cprop, **sprop;
1.27 markus 731: int nenc, nmac, ncomp;
1.96 dtucker 732: u_int mode, ctos, need, dh_need, authlen;
1.102 markus 733: int r, first_kex_follows;
1.1 markus 734:
1.110 djm 735: debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
736: if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
737: goto out;
738: debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
739: if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
1.102 markus 740: goto out;
1.26 markus 741:
1.27 markus 742: if (kex->server) {
1.26 markus 743: cprop=peer;
744: sprop=my;
745: } else {
746: cprop=my;
747: sprop=peer;
1.113 markus 748: }
749:
750: /* Check whether client supports ext_info_c */
751: if (kex->server) {
752: char *ext;
753:
754: ext = match_list("ext-info-c", peer[PROPOSAL_KEX_ALGS], NULL);
1.119 markus 755: kex->ext_info_c = (ext != NULL);
756: free(ext);
1.26 markus 757: }
1.1 markus 758:
1.30 markus 759: /* Algorithm Negotiation */
1.110 djm 760: if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
761: sprop[PROPOSAL_KEX_ALGS])) != 0) {
762: kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
763: peer[PROPOSAL_KEX_ALGS] = NULL;
764: goto out;
765: }
766: if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
767: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
768: kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
769: peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
770: goto out;
771: }
1.1 markus 772: for (mode = 0; mode < MODE_MAX; mode++) {
1.102 markus 773: if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
774: r = SSH_ERR_ALLOC_FAIL;
775: goto out;
776: }
1.30 markus 777: kex->newkeys[mode] = newkeys;
1.78 djm 778: ctos = (!kex->server && mode == MODE_OUT) ||
779: (kex->server && mode == MODE_IN);
1.1 markus 780: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
781: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
782: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.102 markus 783: if ((r = choose_enc(&newkeys->enc, cprop[nenc],
1.107 djm 784: sprop[nenc])) != 0) {
785: kex->failed_choice = peer[nenc];
786: peer[nenc] = NULL;
1.102 markus 787: goto out;
1.107 djm 788: }
1.102 markus 789: authlen = cipher_authlen(newkeys->enc.cipher);
1.88 markus 790: /* ignore mac for authenticated encryption */
1.102 markus 791: if (authlen == 0 &&
792: (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
1.107 djm 793: sprop[nmac])) != 0) {
794: kex->failed_choice = peer[nmac];
795: peer[nmac] = NULL;
1.102 markus 796: goto out;
1.107 djm 797: }
1.102 markus 798: if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
1.107 djm 799: sprop[ncomp])) != 0) {
800: kex->failed_choice = peer[ncomp];
801: peer[ncomp] = NULL;
1.102 markus 802: goto out;
1.107 djm 803: }
1.110 djm 804: debug("kex: %s cipher: %s MAC: %s compression: %s",
1.1 markus 805: ctos ? "client->server" : "server->client",
1.27 markus 806: newkeys->enc.name,
1.88 markus 807: authlen == 0 ? newkeys->mac.name : "<implicit>",
1.27 markus 808: newkeys->comp.name);
1.107 djm 809: }
1.96 dtucker 810: need = dh_need = 0;
1.1 markus 811: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 812: newkeys = kex->newkeys[mode];
1.120 ! deraadt 813: need = MAXIMUM(need, newkeys->enc.key_len);
! 814: need = MAXIMUM(need, newkeys->enc.block_size);
! 815: need = MAXIMUM(need, newkeys->enc.iv_len);
! 816: need = MAXIMUM(need, newkeys->mac.key_len);
! 817: dh_need = MAXIMUM(dh_need, cipher_seclen(newkeys->enc.cipher));
! 818: dh_need = MAXIMUM(dh_need, newkeys->enc.block_size);
! 819: dh_need = MAXIMUM(dh_need, newkeys->enc.iv_len);
! 820: dh_need = MAXIMUM(dh_need, newkeys->mac.key_len);
1.1 markus 821: }
1.7 markus 822: /* XXX need runden? */
1.27 markus 823: kex->we_need = need;
1.96 dtucker 824: kex->dh_need = dh_need;
1.53 markus 825:
826: /* ignore the next message if the proposals do not match */
1.56 djm 827: if (first_kex_follows && !proposals_match(my, peer) &&
1.102 markus 828: !(ssh->compat & SSH_BUG_FIRSTKEX))
829: ssh->dispatch_skip_packets = 1;
830: r = 0;
831: out:
1.26 markus 832: kex_prop_free(my);
833: kex_prop_free(peer);
1.102 markus 834: return r;
1.26 markus 835: }
836:
1.102 markus 837: static int
838: derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
839: const struct sshbuf *shared_secret, u_char **keyp)
1.26 markus 840: {
1.102 markus 841: struct kex *kex = ssh->kex;
842: struct ssh_digest_ctx *hashctx = NULL;
1.26 markus 843: char c = id;
1.61 djm 844: u_int have;
1.94 djm 845: size_t mdsz;
1.61 djm 846: u_char *digest;
1.102 markus 847: int r;
1.62 djm 848:
1.94 djm 849: if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
1.102 markus 850: return SSH_ERR_INVALID_ARGUMENT;
1.120 ! deraadt 851: if ((digest = calloc(1, ROUNDUP(need, mdsz))) == NULL) {
1.102 markus 852: r = SSH_ERR_ALLOC_FAIL;
853: goto out;
854: }
1.26 markus 855:
1.30 markus 856: /* K1 = HASH(K || H || "A" || session_id) */
1.102 markus 857: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
858: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 859: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
860: ssh_digest_update(hashctx, &c, 1) != 0 ||
861: ssh_digest_update(hashctx, kex->session_id,
1.102 markus 862: kex->session_id_len) != 0 ||
863: ssh_digest_final(hashctx, digest, mdsz) != 0) {
864: r = SSH_ERR_LIBCRYPTO_ERROR;
865: goto out;
866: }
1.94 djm 867: ssh_digest_free(hashctx);
1.102 markus 868: hashctx = NULL;
1.26 markus 869:
1.30 markus 870: /*
871: * expand key:
872: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
873: * Key = K1 || K2 || ... || Kn
874: */
1.26 markus 875: for (have = mdsz; need > have; have += mdsz) {
1.102 markus 876: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
877: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 878: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1.102 markus 879: ssh_digest_update(hashctx, digest, have) != 0 ||
880: ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
881: r = SSH_ERR_LIBCRYPTO_ERROR;
882: goto out;
883: }
1.94 djm 884: ssh_digest_free(hashctx);
1.102 markus 885: hashctx = NULL;
1.26 markus 886: }
887: #ifdef DEBUG_KEX
888: fprintf(stderr, "key '%c'== ", c);
889: dump_digest("key", digest, need);
890: #endif
1.102 markus 891: *keyp = digest;
892: digest = NULL;
893: r = 0;
894: out:
1.114 mmcc 895: free(digest);
1.102 markus 896: ssh_digest_free(hashctx);
897: return r;
1.1 markus 898: }
899:
1.23 markus 900: #define NKEYS 6
1.102 markus 901: int
902: kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
903: const struct sshbuf *shared_secret)
1.1 markus 904: {
1.102 markus 905: struct kex *kex = ssh->kex;
1.15 markus 906: u_char *keys[NKEYS];
1.102 markus 907: u_int i, j, mode, ctos;
908: int r;
1.1 markus 909:
1.65 djm 910: for (i = 0; i < NKEYS; i++) {
1.102 markus 911: if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
912: shared_secret, &keys[i])) != 0) {
913: for (j = 0; j < i; j++)
914: free(keys[j]);
915: return r;
916: }
1.65 djm 917: }
1.1 markus 918: for (mode = 0; mode < MODE_MAX; mode++) {
1.69 deraadt 919: ctos = (!kex->server && mode == MODE_OUT) ||
920: (kex->server && mode == MODE_IN);
1.100 markus 921: kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
922: kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
923: kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
1.1 markus 924: }
1.102 markus 925: return 0;
1.95 djm 926: }
927:
1.99 markus 928: #ifdef WITH_OPENSSL
1.102 markus 929: int
930: kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen,
931: const BIGNUM *secret)
1.95 djm 932: {
1.102 markus 933: struct sshbuf *shared_secret;
934: int r;
1.95 djm 935:
1.102 markus 936: if ((shared_secret = sshbuf_new()) == NULL)
937: return SSH_ERR_ALLOC_FAIL;
938: if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0)
939: r = kex_derive_keys(ssh, hash, hashlen, shared_secret);
940: sshbuf_free(shared_secret);
941: return r;
1.27 markus 942: }
1.99 markus 943: #endif
1.57 djm 944:
1.99 markus 945: #ifdef WITH_SSH1
1.102 markus 946: int
1.57 djm 947: derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
948: u_int8_t cookie[8], u_int8_t id[16])
949: {
1.105 djm 950: u_int8_t hbuf[2048], sbuf[2048], obuf[SSH_DIGEST_MAX_LENGTH];
1.102 markus 951: struct ssh_digest_ctx *hashctx = NULL;
1.105 djm 952: size_t hlen, slen;
1.102 markus 953: int r;
1.57 djm 954:
1.105 djm 955: hlen = BN_num_bytes(host_modulus);
956: slen = BN_num_bytes(server_modulus);
957: if (hlen < (512 / 8) || (u_int)hlen > sizeof(hbuf) ||
958: slen < (512 / 8) || (u_int)slen > sizeof(sbuf))
1.102 markus 959: return SSH_ERR_KEY_BITS_MISMATCH;
1.105 djm 960: if (BN_bn2bin(host_modulus, hbuf) <= 0 ||
961: BN_bn2bin(server_modulus, sbuf) <= 0) {
962: r = SSH_ERR_LIBCRYPTO_ERROR;
963: goto out;
964: }
965: if ((hashctx = ssh_digest_start(SSH_DIGEST_MD5)) == NULL) {
966: r = SSH_ERR_ALLOC_FAIL;
967: goto out;
968: }
969: if (ssh_digest_update(hashctx, hbuf, hlen) != 0 ||
970: ssh_digest_update(hashctx, sbuf, slen) != 0 ||
1.102 markus 971: ssh_digest_update(hashctx, cookie, 8) != 0 ||
972: ssh_digest_final(hashctx, obuf, sizeof(obuf)) != 0) {
973: r = SSH_ERR_LIBCRYPTO_ERROR;
974: goto out;
975: }
1.94 djm 976: memcpy(id, obuf, ssh_digest_bytes(SSH_DIGEST_MD5));
1.102 markus 977: r = 0;
978: out:
979: ssh_digest_free(hashctx);
1.105 djm 980: explicit_bzero(hbuf, sizeof(hbuf));
981: explicit_bzero(sbuf, sizeof(sbuf));
1.98 djm 982: explicit_bzero(obuf, sizeof(obuf));
1.102 markus 983: return r;
1.1 markus 984: }
1.99 markus 985: #endif
1.26 markus 986:
1.84 djm 987: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1.26 markus 988: void
989: dump_digest(char *msg, u_char *digest, int len)
990: {
991: fprintf(stderr, "%s\n", msg);
1.102 markus 992: sshbuf_dump_data(digest, len, stderr);
1.26 markus 993: }
994: #endif
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