Annotation of src/usr.bin/ssh/kex.c, Revision 1.144
1.144 ! djm 1: /* $OpenBSD: kex.c,v 1.143 2018/12/27 03:25:25 djm Exp $ */
1.1 markus 2: /*
1.36 markus 3: * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
1.1 markus 4: *
5: * Redistribution and use in source and binary forms, with or without
6: * modification, are permitted provided that the following conditions
7: * are met:
8: * 1. Redistributions of source code must retain the above copyright
9: * notice, this list of conditions and the following disclaimer.
10: * 2. Redistributions in binary form must reproduce the above copyright
11: * notice, this list of conditions and the following disclaimer in the
12: * documentation and/or other materials provided with the distribution.
13: *
14: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24: */
25:
1.18 markus 26:
1.143 djm 27: #include <sys/types.h>
28: #include <errno.h>
1.76 deraadt 29: #include <signal.h>
1.75 stevesk 30: #include <stdio.h>
1.74 stevesk 31: #include <stdlib.h>
1.72 stevesk 32: #include <string.h>
1.143 djm 33: #include <unistd.h>
34: #include <poll.h>
1.1 markus 35:
1.99 markus 36: #ifdef WITH_OPENSSL
1.76 deraadt 37: #include <openssl/crypto.h>
1.99 markus 38: #endif
1.76 deraadt 39:
1.143 djm 40: #include "ssh.h"
1.1 markus 41: #include "ssh2.h"
1.143 djm 42: #include "atomicio.h"
43: #include "version.h"
1.7 markus 44: #include "packet.h"
1.1 markus 45: #include "compat.h"
1.18 markus 46: #include "cipher.h"
1.102 markus 47: #include "sshkey.h"
1.1 markus 48: #include "kex.h"
1.18 markus 49: #include "log.h"
1.21 markus 50: #include "mac.h"
1.23 markus 51: #include "match.h"
1.102 markus 52: #include "misc.h"
1.26 markus 53: #include "dispatch.h"
1.48 provos 54: #include "monitor.h"
1.102 markus 55:
56: #include "ssherr.h"
57: #include "sshbuf.h"
1.94 djm 58: #include "digest.h"
1.48 provos 59:
1.35 itojun 60: /* prototype */
1.102 markus 61: static int kex_choose_conf(struct ssh *);
1.133 markus 62: static int kex_input_newkeys(int, u_int32_t, struct ssh *);
1.86 djm 63:
1.110 djm 64: static const char *proposal_names[PROPOSAL_MAX] = {
65: "KEX algorithms",
66: "host key algorithms",
67: "ciphers ctos",
68: "ciphers stoc",
69: "MACs ctos",
70: "MACs stoc",
71: "compression ctos",
72: "compression stoc",
73: "languages ctos",
74: "languages stoc",
75: };
76:
1.89 djm 77: struct kexalg {
78: char *name;
1.102 markus 79: u_int type;
1.89 djm 80: int ec_nid;
1.94 djm 81: int hash_alg;
1.89 djm 82: };
83: static const struct kexalg kexalgs[] = {
1.99 markus 84: #ifdef WITH_OPENSSL
1.94 djm 85: { KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },
1.118 djm 86: { KEX_DH14_SHA1, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 },
87: { KEX_DH14_SHA256, KEX_DH_GRP14_SHA256, 0, SSH_DIGEST_SHA256 },
88: { KEX_DH16_SHA512, KEX_DH_GRP16_SHA512, 0, SSH_DIGEST_SHA512 },
89: { KEX_DH18_SHA512, KEX_DH_GRP18_SHA512, 0, SSH_DIGEST_SHA512 },
1.94 djm 90: { KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 },
91: { KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 },
92: { KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2,
93: NID_X9_62_prime256v1, SSH_DIGEST_SHA256 },
94: { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1,
95: SSH_DIGEST_SHA384 },
96: { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1,
97: SSH_DIGEST_SHA512 },
1.99 markus 98: #endif
1.94 djm 99: { KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
1.124 djm 100: { KEX_CURVE25519_SHA256_OLD, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
1.94 djm 101: { NULL, -1, -1, -1},
1.89 djm 102: };
103:
104: char *
1.93 dtucker 105: kex_alg_list(char sep)
1.89 djm 106: {
1.102 markus 107: char *ret = NULL, *tmp;
1.89 djm 108: size_t nlen, rlen = 0;
109: const struct kexalg *k;
110:
111: for (k = kexalgs; k->name != NULL; k++) {
112: if (ret != NULL)
1.93 dtucker 113: ret[rlen++] = sep;
1.89 djm 114: nlen = strlen(k->name);
1.102 markus 115: if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
116: free(ret);
117: return NULL;
118: }
119: ret = tmp;
1.89 djm 120: memcpy(ret + rlen, k->name, nlen + 1);
121: rlen += nlen;
122: }
123: return ret;
124: }
125:
126: static const struct kexalg *
127: kex_alg_by_name(const char *name)
128: {
129: const struct kexalg *k;
130:
131: for (k = kexalgs; k->name != NULL; k++) {
132: if (strcmp(k->name, name) == 0)
133: return k;
134: }
135: return NULL;
136: }
137:
1.86 djm 138: /* Validate KEX method name list */
139: int
140: kex_names_valid(const char *names)
141: {
142: char *s, *cp, *p;
143:
144: if (names == NULL || strcmp(names, "") == 0)
145: return 0;
1.102 markus 146: if ((s = cp = strdup(names)) == NULL)
147: return 0;
1.86 djm 148: for ((p = strsep(&cp, ",")); p && *p != '\0';
149: (p = strsep(&cp, ","))) {
1.89 djm 150: if (kex_alg_by_name(p) == NULL) {
1.86 djm 151: error("Unsupported KEX algorithm \"%.100s\"", p);
1.91 djm 152: free(s);
1.86 djm 153: return 0;
154: }
155: }
156: debug3("kex names ok: [%s]", names);
1.91 djm 157: free(s);
1.86 djm 158: return 1;
1.109 djm 159: }
160:
161: /*
162: * Concatenate algorithm names, avoiding duplicates in the process.
163: * Caller must free returned string.
164: */
165: char *
166: kex_names_cat(const char *a, const char *b)
167: {
1.129 dtucker 168: char *ret = NULL, *tmp = NULL, *cp, *p, *m;
1.109 djm 169: size_t len;
170:
171: if (a == NULL || *a == '\0')
1.138 djm 172: return strdup(b);
1.109 djm 173: if (b == NULL || *b == '\0')
174: return strdup(a);
175: if (strlen(b) > 1024*1024)
176: return NULL;
177: len = strlen(a) + strlen(b) + 2;
178: if ((tmp = cp = strdup(b)) == NULL ||
179: (ret = calloc(1, len)) == NULL) {
180: free(tmp);
181: return NULL;
182: }
183: strlcpy(ret, a, len);
184: for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) {
1.129 dtucker 185: if ((m = match_list(ret, p, NULL)) != NULL) {
186: free(m);
1.109 djm 187: continue; /* Algorithm already present */
1.129 dtucker 188: }
1.109 djm 189: if (strlcat(ret, ",", len) >= len ||
190: strlcat(ret, p, len) >= len) {
191: free(tmp);
192: free(ret);
193: return NULL; /* Shouldn't happen */
194: }
195: }
196: free(tmp);
197: return ret;
198: }
199:
200: /*
201: * Assemble a list of algorithms from a default list and a string from a
202: * configuration file. The user-provided string may begin with '+' to
1.128 djm 203: * indicate that it should be appended to the default or '-' that the
204: * specified names should be removed.
1.109 djm 205: */
206: int
1.138 djm 207: kex_assemble_names(char **listp, const char *def, const char *all)
1.109 djm 208: {
1.138 djm 209: char *cp, *tmp, *patterns;
210: char *list = NULL, *ret = NULL, *matching = NULL, *opatterns = NULL;
211: int r = SSH_ERR_INTERNAL_ERROR;
212:
213: if (listp == NULL || *listp == NULL || **listp == '\0') {
214: if ((*listp = strdup(def)) == NULL)
215: return SSH_ERR_ALLOC_FAIL;
216: return 0;
217: }
1.109 djm 218:
1.138 djm 219: list = *listp;
220: *listp = NULL;
221: if (*list == '+') {
222: /* Append names to default list */
223: if ((tmp = kex_names_cat(def, list + 1)) == NULL) {
224: r = SSH_ERR_ALLOC_FAIL;
225: goto fail;
226: }
227: free(list);
228: list = tmp;
229: } else if (*list == '-') {
230: /* Remove names from default list */
231: if ((*listp = match_filter_blacklist(def, list + 1)) == NULL) {
232: r = SSH_ERR_ALLOC_FAIL;
233: goto fail;
234: }
235: free(list);
236: /* filtering has already been done */
1.109 djm 237: return 0;
1.138 djm 238: } else {
239: /* Explicit list, overrides default - just use "list" as is */
240: }
241:
242: /*
243: * The supplied names may be a pattern-list. For the -list case,
244: * the patterns are applied above. For the +list and explicit list
245: * cases we need to do it now.
246: */
247: ret = NULL;
248: if ((patterns = opatterns = strdup(list)) == NULL) {
249: r = SSH_ERR_ALLOC_FAIL;
250: goto fail;
251: }
252: /* Apply positive (i.e. non-negated) patterns from the list */
253: while ((cp = strsep(&patterns, ",")) != NULL) {
254: if (*cp == '!') {
255: /* negated matches are not supported here */
256: r = SSH_ERR_INVALID_ARGUMENT;
257: goto fail;
258: }
259: free(matching);
260: if ((matching = match_filter_whitelist(all, cp)) == NULL) {
261: r = SSH_ERR_ALLOC_FAIL;
262: goto fail;
263: }
264: if ((tmp = kex_names_cat(ret, matching)) == NULL) {
265: r = SSH_ERR_ALLOC_FAIL;
266: goto fail;
267: }
268: free(ret);
269: ret = tmp;
1.109 djm 270: }
1.138 djm 271: if (ret == NULL || *ret == '\0') {
272: /* An empty name-list is an error */
273: /* XXX better error code? */
274: r = SSH_ERR_INVALID_ARGUMENT;
275: goto fail;
1.109 djm 276: }
277:
1.138 djm 278: /* success */
279: *listp = ret;
280: ret = NULL;
281: r = 0;
282:
283: fail:
284: free(matching);
285: free(opatterns);
286: free(list);
287: free(ret);
288: return r;
1.86 djm 289: }
1.26 markus 290:
291: /* put algorithm proposal into buffer */
1.102 markus 292: int
293: kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
1.1 markus 294: {
1.61 djm 295: u_int i;
1.102 markus 296: int r;
297:
298: sshbuf_reset(b);
1.26 markus 299:
1.49 markus 300: /*
301: * add a dummy cookie, the cookie will be overwritten by
302: * kex_send_kexinit(), each time a kexinit is set
303: */
1.102 markus 304: for (i = 0; i < KEX_COOKIE_LEN; i++) {
305: if ((r = sshbuf_put_u8(b, 0)) != 0)
306: return r;
307: }
308: for (i = 0; i < PROPOSAL_MAX; i++) {
309: if ((r = sshbuf_put_cstring(b, proposal[i])) != 0)
310: return r;
311: }
312: if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */
313: (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */
314: return r;
315: return 0;
1.1 markus 316: }
317:
1.26 markus 318: /* parse buffer and return algorithm proposal */
1.102 markus 319: int
320: kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp)
1.7 markus 321: {
1.102 markus 322: struct sshbuf *b = NULL;
323: u_char v;
1.78 djm 324: u_int i;
1.102 markus 325: char **proposal = NULL;
326: int r;
1.7 markus 327:
1.102 markus 328: *propp = NULL;
329: if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL)
330: return SSH_ERR_ALLOC_FAIL;
331: if ((b = sshbuf_fromb(raw)) == NULL) {
332: r = SSH_ERR_ALLOC_FAIL;
333: goto out;
334: }
335: if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */
336: goto out;
1.7 markus 337: /* extract kex init proposal strings */
338: for (i = 0; i < PROPOSAL_MAX; i++) {
1.102 markus 339: if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0)
340: goto out;
1.110 djm 341: debug2("%s: %s", proposal_names[i], proposal[i]);
1.7 markus 342: }
1.26 markus 343: /* first kex follows / reserved */
1.115 djm 344: if ((r = sshbuf_get_u8(b, &v)) != 0 || /* first_kex_follows */
345: (r = sshbuf_get_u32(b, &i)) != 0) /* reserved */
1.102 markus 346: goto out;
1.53 markus 347: if (first_kex_follows != NULL)
1.115 djm 348: *first_kex_follows = v;
1.110 djm 349: debug2("first_kex_follows %d ", v);
350: debug2("reserved %u ", i);
1.102 markus 351: r = 0;
352: *propp = proposal;
353: out:
354: if (r != 0 && proposal != NULL)
355: kex_prop_free(proposal);
356: sshbuf_free(b);
357: return r;
1.1 markus 358: }
359:
1.102 markus 360: void
1.26 markus 361: kex_prop_free(char **proposal)
1.1 markus 362: {
1.61 djm 363: u_int i;
1.26 markus 364:
1.106 djm 365: if (proposal == NULL)
366: return;
1.26 markus 367: for (i = 0; i < PROPOSAL_MAX; i++)
1.91 djm 368: free(proposal[i]);
369: free(proposal);
1.1 markus 370: }
371:
1.78 djm 372: /* ARGSUSED */
1.101 markus 373: static int
1.133 markus 374: kex_protocol_error(int type, u_int32_t seq, struct ssh *ssh)
1.1 markus 375: {
1.112 djm 376: int r;
377:
378: error("kex protocol error: type %d seq %u", type, seq);
379: if ((r = sshpkt_start(ssh, SSH2_MSG_UNIMPLEMENTED)) != 0 ||
380: (r = sshpkt_put_u32(ssh, seq)) != 0 ||
381: (r = sshpkt_send(ssh)) != 0)
382: return r;
1.101 markus 383: return 0;
1.26 markus 384: }
1.1 markus 385:
1.35 itojun 386: static void
1.102 markus 387: kex_reset_dispatch(struct ssh *ssh)
1.29 markus 388: {
1.102 markus 389: ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
1.42 markus 390: SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
1.29 markus 391: }
392:
1.113 markus 393: static int
394: kex_send_ext_info(struct ssh *ssh)
395: {
396: int r;
1.121 djm 397: char *algs;
1.113 markus 398:
1.130 djm 399: if ((algs = sshkey_alg_list(0, 1, 1, ',')) == NULL)
1.121 djm 400: return SSH_ERR_ALLOC_FAIL;
1.137 djm 401: /* XXX filter algs list by allowed pubkey/hostbased types */
1.113 markus 402: if ((r = sshpkt_start(ssh, SSH2_MSG_EXT_INFO)) != 0 ||
403: (r = sshpkt_put_u32(ssh, 1)) != 0 ||
404: (r = sshpkt_put_cstring(ssh, "server-sig-algs")) != 0 ||
1.121 djm 405: (r = sshpkt_put_cstring(ssh, algs)) != 0 ||
1.113 markus 406: (r = sshpkt_send(ssh)) != 0)
1.121 djm 407: goto out;
408: /* success */
409: r = 0;
410: out:
411: free(algs);
1.123 djm 412: return r;
1.113 markus 413: }
414:
1.102 markus 415: int
416: kex_send_newkeys(struct ssh *ssh)
1.26 markus 417: {
1.102 markus 418: int r;
1.28 markus 419:
1.102 markus 420: kex_reset_dispatch(ssh);
421: if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
422: (r = sshpkt_send(ssh)) != 0)
423: return r;
1.26 markus 424: debug("SSH2_MSG_NEWKEYS sent");
1.102 markus 425: debug("expecting SSH2_MSG_NEWKEYS");
426: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
1.113 markus 427: if (ssh->kex->ext_info_c)
428: if ((r = kex_send_ext_info(ssh)) != 0)
429: return r;
1.102 markus 430: return 0;
431: }
432:
1.113 markus 433: int
1.133 markus 434: kex_input_ext_info(int type, u_int32_t seq, struct ssh *ssh)
1.113 markus 435: {
436: struct kex *kex = ssh->kex;
437: u_int32_t i, ninfo;
1.137 djm 438: char *name;
1.134 djm 439: u_char *val;
440: size_t vlen;
1.113 markus 441: int r;
442:
443: debug("SSH2_MSG_EXT_INFO received");
444: ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_protocol_error);
445: if ((r = sshpkt_get_u32(ssh, &ninfo)) != 0)
446: return r;
447: for (i = 0; i < ninfo; i++) {
448: if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0)
449: return r;
1.134 djm 450: if ((r = sshpkt_get_string(ssh, &val, &vlen)) != 0) {
1.113 markus 451: free(name);
452: return r;
453: }
454: if (strcmp(name, "server-sig-algs") == 0) {
1.134 djm 455: /* Ensure no \0 lurking in value */
456: if (memchr(val, '\0', vlen) != NULL) {
457: error("%s: nul byte in %s", __func__, name);
458: return SSH_ERR_INVALID_FORMAT;
459: }
460: debug("%s: %s=<%s>", __func__, name, val);
1.137 djm 461: kex->server_sig_algs = val;
462: val = NULL;
1.134 djm 463: } else
464: debug("%s: %s (unrecognised)", __func__, name);
1.113 markus 465: free(name);
466: free(val);
467: }
468: return sshpkt_get_end(ssh);
469: }
470:
1.102 markus 471: static int
1.133 markus 472: kex_input_newkeys(int type, u_int32_t seq, struct ssh *ssh)
1.102 markus 473: {
474: struct kex *kex = ssh->kex;
475: int r;
1.19 stevesk 476:
1.26 markus 477: debug("SSH2_MSG_NEWKEYS received");
1.102 markus 478: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
1.131 markus 479: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.102 markus 480: if ((r = sshpkt_get_end(ssh)) != 0)
1.122 markus 481: return r;
482: if ((r = ssh_set_newkeys(ssh, MODE_IN)) != 0)
1.102 markus 483: return r;
1.30 markus 484: kex->done = 1;
1.142 djm 485: kex->flags &= ~KEX_INITIAL;
1.102 markus 486: sshbuf_reset(kex->peer);
487: /* sshbuf_reset(kex->my); */
1.26 markus 488: kex->flags &= ~KEX_INIT_SENT;
1.91 djm 489: free(kex->name);
1.32 markus 490: kex->name = NULL;
1.102 markus 491: return 0;
1.26 markus 492: }
1.1 markus 493:
1.102 markus 494: int
495: kex_send_kexinit(struct ssh *ssh)
1.26 markus 496: {
1.49 markus 497: u_char *cookie;
1.102 markus 498: struct kex *kex = ssh->kex;
499: int r;
1.49 markus 500:
1.102 markus 501: if (kex == NULL)
502: return SSH_ERR_INTERNAL_ERROR;
503: if (kex->flags & KEX_INIT_SENT)
504: return 0;
1.30 markus 505: kex->done = 0;
1.49 markus 506:
507: /* generate a random cookie */
1.102 markus 508: if (sshbuf_len(kex->my) < KEX_COOKIE_LEN)
509: return SSH_ERR_INVALID_FORMAT;
510: if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL)
511: return SSH_ERR_INTERNAL_ERROR;
512: arc4random_buf(cookie, KEX_COOKIE_LEN);
513:
514: if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
515: (r = sshpkt_putb(ssh, kex->my)) != 0 ||
516: (r = sshpkt_send(ssh)) != 0)
517: return r;
1.26 markus 518: debug("SSH2_MSG_KEXINIT sent");
519: kex->flags |= KEX_INIT_SENT;
1.102 markus 520: return 0;
1.1 markus 521: }
522:
1.78 djm 523: /* ARGSUSED */
1.101 markus 524: int
1.133 markus 525: kex_input_kexinit(int type, u_int32_t seq, struct ssh *ssh)
1.11 provos 526: {
1.102 markus 527: struct kex *kex = ssh->kex;
528: const u_char *ptr;
1.100 markus 529: u_int i;
530: size_t dlen;
1.102 markus 531: int r;
1.11 provos 532:
1.26 markus 533: debug("SSH2_MSG_KEXINIT received");
1.29 markus 534: if (kex == NULL)
1.102 markus 535: return SSH_ERR_INVALID_ARGUMENT;
1.11 provos 536:
1.127 markus 537: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, NULL);
1.102 markus 538: ptr = sshpkt_ptr(ssh, &dlen);
539: if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
540: return r;
1.31 markus 541:
542: /* discard packet */
543: for (i = 0; i < KEX_COOKIE_LEN; i++)
1.102 markus 544: if ((r = sshpkt_get_u8(ssh, NULL)) != 0)
545: return r;
1.31 markus 546: for (i = 0; i < PROPOSAL_MAX; i++)
1.102 markus 547: if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0)
548: return r;
1.87 djm 549: /*
550: * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
551: * KEX method has the server move first, but a server might be using
552: * a custom method or one that we otherwise don't support. We should
553: * be prepared to remember first_kex_follows here so we can eat a
554: * packet later.
555: * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
556: * for cases where the server *doesn't* go first. I guess we should
557: * ignore it when it is set for these cases, which is what we do now.
558: */
1.102 markus 559: if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
560: (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
561: (r = sshpkt_get_end(ssh)) != 0)
562: return r;
563:
564: if (!(kex->flags & KEX_INIT_SENT))
565: if ((r = kex_send_kexinit(ssh)) != 0)
566: return r;
567: if ((r = kex_choose_conf(ssh)) != 0)
568: return r;
1.19 stevesk 569:
1.102 markus 570: if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
571: return (kex->kex[kex->kex_type])(ssh);
572:
573: return SSH_ERR_INTERNAL_ERROR;
574: }
575:
1.143 djm 576: struct kex *
577: kex_new(void)
1.102 markus 578: {
579: struct kex *kex;
580:
1.143 djm 581: if ((kex = calloc(1, sizeof(*kex))) == NULL ||
582: (kex->peer = sshbuf_new()) == NULL ||
583: (kex->my = sshbuf_new()) == NULL ||
584: (kex->client_version = sshbuf_new()) == NULL ||
585: (kex->server_version = sshbuf_new()) == NULL) {
586: kex_free(kex);
587: return NULL;
1.102 markus 588: }
1.143 djm 589: return kex;
1.26 markus 590: }
1.11 provos 591:
1.100 markus 592: void
593: kex_free_newkeys(struct newkeys *newkeys)
594: {
595: if (newkeys == NULL)
596: return;
597: if (newkeys->enc.key) {
598: explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
599: free(newkeys->enc.key);
600: newkeys->enc.key = NULL;
601: }
602: if (newkeys->enc.iv) {
1.111 djm 603: explicit_bzero(newkeys->enc.iv, newkeys->enc.iv_len);
1.100 markus 604: free(newkeys->enc.iv);
605: newkeys->enc.iv = NULL;
606: }
607: free(newkeys->enc.name);
608: explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
609: free(newkeys->comp.name);
610: explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
611: mac_clear(&newkeys->mac);
612: if (newkeys->mac.key) {
613: explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
614: free(newkeys->mac.key);
615: newkeys->mac.key = NULL;
616: }
617: free(newkeys->mac.name);
618: explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
619: explicit_bzero(newkeys, sizeof(*newkeys));
620: free(newkeys);
621: }
622:
1.102 markus 623: void
624: kex_free(struct kex *kex)
1.26 markus 625: {
1.102 markus 626: u_int mode;
1.11 provos 627:
1.143 djm 628: if (kex == NULL)
629: return;
630:
1.102 markus 631: #ifdef WITH_OPENSSL
1.136 jsing 632: DH_free(kex->dh);
633: EC_KEY_free(kex->ec_client_key);
1.102 markus 634: #endif
635: for (mode = 0; mode < MODE_MAX; mode++) {
636: kex_free_newkeys(kex->newkeys[mode]);
637: kex->newkeys[mode] = NULL;
1.100 markus 638: }
1.102 markus 639: sshbuf_free(kex->peer);
640: sshbuf_free(kex->my);
1.143 djm 641: sshbuf_free(kex->client_version);
642: sshbuf_free(kex->server_version);
1.102 markus 643: free(kex->session_id);
1.107 djm 644: free(kex->failed_choice);
1.113 markus 645: free(kex->hostkey_alg);
646: free(kex->name);
1.102 markus 647: free(kex);
1.11 provos 648: }
649:
1.102 markus 650: int
1.143 djm 651: kex_ready(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
652: {
653: int r;
654:
655: if ((r = kex_prop2buf(ssh->kex->my, proposal)) != 0)
656: return r;
657: ssh->kex->flags = KEX_INITIAL;
658: kex_reset_dispatch(ssh);
659: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
660: return 0;
661: }
662:
663: int
1.102 markus 664: kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
1.1 markus 665: {
1.102 markus 666: int r;
1.1 markus 667:
1.143 djm 668: if ((r = kex_ready(ssh, proposal)) != 0)
1.102 markus 669: return r;
670: if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
671: kex_free(ssh->kex);
672: ssh->kex = NULL;
673: return r;
1.1 markus 674: }
1.102 markus 675: return 0;
1.117 djm 676: }
677:
678: /*
679: * Request key re-exchange, returns 0 on success or a ssherr.h error
680: * code otherwise. Must not be called if KEX is incomplete or in-progress.
681: */
682: int
683: kex_start_rekex(struct ssh *ssh)
684: {
685: if (ssh->kex == NULL) {
686: error("%s: no kex", __func__);
687: return SSH_ERR_INTERNAL_ERROR;
688: }
689: if (ssh->kex->done == 0) {
690: error("%s: requested twice", __func__);
691: return SSH_ERR_INTERNAL_ERROR;
692: }
693: ssh->kex->done = 0;
694: return kex_send_kexinit(ssh);
1.1 markus 695: }
696:
1.102 markus 697: static int
698: choose_enc(struct sshenc *enc, char *client, char *server)
1.1 markus 699: {
1.23 markus 700: char *name = match_list(client, server, NULL);
1.102 markus 701:
1.1 markus 702: if (name == NULL)
1.102 markus 703: return SSH_ERR_NO_CIPHER_ALG_MATCH;
1.129 dtucker 704: if ((enc->cipher = cipher_by_name(name)) == NULL) {
705: free(name);
1.102 markus 706: return SSH_ERR_INTERNAL_ERROR;
1.129 dtucker 707: }
1.1 markus 708: enc->name = name;
709: enc->enabled = 0;
710: enc->iv = NULL;
1.88 markus 711: enc->iv_len = cipher_ivlen(enc->cipher);
1.1 markus 712: enc->key = NULL;
1.45 markus 713: enc->key_len = cipher_keylen(enc->cipher);
714: enc->block_size = cipher_blocksize(enc->cipher);
1.102 markus 715: return 0;
1.1 markus 716: }
1.69 deraadt 717:
1.102 markus 718: static int
719: choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
1.1 markus 720: {
1.23 markus 721: char *name = match_list(client, server, NULL);
1.102 markus 722:
1.1 markus 723: if (name == NULL)
1.102 markus 724: return SSH_ERR_NO_MAC_ALG_MATCH;
1.129 dtucker 725: if (mac_setup(mac, name) < 0) {
726: free(name);
1.102 markus 727: return SSH_ERR_INTERNAL_ERROR;
1.129 dtucker 728: }
1.1 markus 729: mac->name = name;
730: mac->key = NULL;
731: mac->enabled = 0;
1.102 markus 732: return 0;
1.1 markus 733: }
1.69 deraadt 734:
1.102 markus 735: static int
736: choose_comp(struct sshcomp *comp, char *client, char *server)
1.1 markus 737: {
1.23 markus 738: char *name = match_list(client, server, NULL);
1.102 markus 739:
1.1 markus 740: if (name == NULL)
1.102 markus 741: return SSH_ERR_NO_COMPRESS_ALG_MATCH;
1.64 markus 742: if (strcmp(name, "zlib@openssh.com") == 0) {
1.141 sf 743: comp->type = COMP_DELAYED;
744: } else if (strcmp(name, "zlib") == 0) {
1.140 sf 745: comp->type = COMP_ZLIB;
1.1 markus 746: } else if (strcmp(name, "none") == 0) {
1.64 markus 747: comp->type = COMP_NONE;
1.1 markus 748: } else {
1.129 dtucker 749: free(name);
1.102 markus 750: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 751: }
752: comp->name = name;
1.102 markus 753: return 0;
1.1 markus 754: }
1.69 deraadt 755:
1.102 markus 756: static int
757: choose_kex(struct kex *k, char *client, char *server)
1.1 markus 758: {
1.89 djm 759: const struct kexalg *kexalg;
760:
1.23 markus 761: k->name = match_list(client, server, NULL);
1.102 markus 762:
1.110 djm 763: debug("kex: algorithm: %s", k->name ? k->name : "(no match)");
1.1 markus 764: if (k->name == NULL)
1.102 markus 765: return SSH_ERR_NO_KEX_ALG_MATCH;
1.89 djm 766: if ((kexalg = kex_alg_by_name(k->name)) == NULL)
1.102 markus 767: return SSH_ERR_INTERNAL_ERROR;
1.89 djm 768: k->kex_type = kexalg->type;
1.94 djm 769: k->hash_alg = kexalg->hash_alg;
1.89 djm 770: k->ec_nid = kexalg->ec_nid;
1.102 markus 771: return 0;
1.1 markus 772: }
1.65 djm 773:
1.102 markus 774: static int
775: choose_hostkeyalg(struct kex *k, char *client, char *server)
1.1 markus 776: {
1.113 markus 777: k->hostkey_alg = match_list(client, server, NULL);
1.102 markus 778:
1.110 djm 779: debug("kex: host key algorithm: %s",
1.113 markus 780: k->hostkey_alg ? k->hostkey_alg : "(no match)");
781: if (k->hostkey_alg == NULL)
1.102 markus 782: return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
1.113 markus 783: k->hostkey_type = sshkey_type_from_name(k->hostkey_alg);
1.13 markus 784: if (k->hostkey_type == KEY_UNSPEC)
1.102 markus 785: return SSH_ERR_INTERNAL_ERROR;
1.113 markus 786: k->hostkey_nid = sshkey_ecdsa_nid_from_name(k->hostkey_alg);
1.102 markus 787: return 0;
1.1 markus 788: }
789:
1.56 djm 790: static int
1.53 markus 791: proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
792: {
793: static int check[] = {
794: PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
795: };
796: int *idx;
797: char *p;
798:
799: for (idx = &check[0]; *idx != -1; idx++) {
800: if ((p = strchr(my[*idx], ',')) != NULL)
801: *p = '\0';
802: if ((p = strchr(peer[*idx], ',')) != NULL)
803: *p = '\0';
804: if (strcmp(my[*idx], peer[*idx]) != 0) {
805: debug2("proposal mismatch: my %s peer %s",
806: my[*idx], peer[*idx]);
807: return (0);
808: }
809: }
810: debug2("proposals match");
811: return (1);
812: }
813:
1.102 markus 814: static int
815: kex_choose_conf(struct ssh *ssh)
1.1 markus 816: {
1.102 markus 817: struct kex *kex = ssh->kex;
818: struct newkeys *newkeys;
819: char **my = NULL, **peer = NULL;
1.26 markus 820: char **cprop, **sprop;
1.27 markus 821: int nenc, nmac, ncomp;
1.96 dtucker 822: u_int mode, ctos, need, dh_need, authlen;
1.102 markus 823: int r, first_kex_follows;
1.1 markus 824:
1.110 djm 825: debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
826: if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
827: goto out;
828: debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
829: if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
1.102 markus 830: goto out;
1.26 markus 831:
1.27 markus 832: if (kex->server) {
1.26 markus 833: cprop=peer;
834: sprop=my;
835: } else {
836: cprop=my;
837: sprop=peer;
1.113 markus 838: }
839:
840: /* Check whether client supports ext_info_c */
1.142 djm 841: if (kex->server && (kex->flags & KEX_INITIAL)) {
1.113 markus 842: char *ext;
843:
844: ext = match_list("ext-info-c", peer[PROPOSAL_KEX_ALGS], NULL);
1.119 markus 845: kex->ext_info_c = (ext != NULL);
846: free(ext);
1.26 markus 847: }
1.1 markus 848:
1.30 markus 849: /* Algorithm Negotiation */
1.110 djm 850: if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
851: sprop[PROPOSAL_KEX_ALGS])) != 0) {
852: kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
853: peer[PROPOSAL_KEX_ALGS] = NULL;
854: goto out;
855: }
856: if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
857: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
858: kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
859: peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
860: goto out;
861: }
1.1 markus 862: for (mode = 0; mode < MODE_MAX; mode++) {
1.102 markus 863: if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
864: r = SSH_ERR_ALLOC_FAIL;
865: goto out;
866: }
1.30 markus 867: kex->newkeys[mode] = newkeys;
1.78 djm 868: ctos = (!kex->server && mode == MODE_OUT) ||
869: (kex->server && mode == MODE_IN);
1.1 markus 870: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
871: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
872: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.102 markus 873: if ((r = choose_enc(&newkeys->enc, cprop[nenc],
1.107 djm 874: sprop[nenc])) != 0) {
875: kex->failed_choice = peer[nenc];
876: peer[nenc] = NULL;
1.102 markus 877: goto out;
1.107 djm 878: }
1.102 markus 879: authlen = cipher_authlen(newkeys->enc.cipher);
1.88 markus 880: /* ignore mac for authenticated encryption */
1.102 markus 881: if (authlen == 0 &&
882: (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
1.107 djm 883: sprop[nmac])) != 0) {
884: kex->failed_choice = peer[nmac];
885: peer[nmac] = NULL;
1.102 markus 886: goto out;
1.107 djm 887: }
1.102 markus 888: if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
1.107 djm 889: sprop[ncomp])) != 0) {
890: kex->failed_choice = peer[ncomp];
891: peer[ncomp] = NULL;
1.102 markus 892: goto out;
1.107 djm 893: }
1.110 djm 894: debug("kex: %s cipher: %s MAC: %s compression: %s",
1.1 markus 895: ctos ? "client->server" : "server->client",
1.27 markus 896: newkeys->enc.name,
1.88 markus 897: authlen == 0 ? newkeys->mac.name : "<implicit>",
1.27 markus 898: newkeys->comp.name);
1.107 djm 899: }
1.96 dtucker 900: need = dh_need = 0;
1.1 markus 901: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 902: newkeys = kex->newkeys[mode];
1.120 deraadt 903: need = MAXIMUM(need, newkeys->enc.key_len);
904: need = MAXIMUM(need, newkeys->enc.block_size);
905: need = MAXIMUM(need, newkeys->enc.iv_len);
906: need = MAXIMUM(need, newkeys->mac.key_len);
907: dh_need = MAXIMUM(dh_need, cipher_seclen(newkeys->enc.cipher));
908: dh_need = MAXIMUM(dh_need, newkeys->enc.block_size);
909: dh_need = MAXIMUM(dh_need, newkeys->enc.iv_len);
910: dh_need = MAXIMUM(dh_need, newkeys->mac.key_len);
1.1 markus 911: }
1.7 markus 912: /* XXX need runden? */
1.27 markus 913: kex->we_need = need;
1.96 dtucker 914: kex->dh_need = dh_need;
1.53 markus 915:
916: /* ignore the next message if the proposals do not match */
1.135 djm 917: if (first_kex_follows && !proposals_match(my, peer))
1.102 markus 918: ssh->dispatch_skip_packets = 1;
919: r = 0;
920: out:
1.26 markus 921: kex_prop_free(my);
922: kex_prop_free(peer);
1.102 markus 923: return r;
1.26 markus 924: }
925:
1.102 markus 926: static int
927: derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
928: const struct sshbuf *shared_secret, u_char **keyp)
1.26 markus 929: {
1.102 markus 930: struct kex *kex = ssh->kex;
931: struct ssh_digest_ctx *hashctx = NULL;
1.26 markus 932: char c = id;
1.61 djm 933: u_int have;
1.94 djm 934: size_t mdsz;
1.61 djm 935: u_char *digest;
1.102 markus 936: int r;
1.62 djm 937:
1.94 djm 938: if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
1.102 markus 939: return SSH_ERR_INVALID_ARGUMENT;
1.120 deraadt 940: if ((digest = calloc(1, ROUNDUP(need, mdsz))) == NULL) {
1.102 markus 941: r = SSH_ERR_ALLOC_FAIL;
942: goto out;
943: }
1.26 markus 944:
1.30 markus 945: /* K1 = HASH(K || H || "A" || session_id) */
1.102 markus 946: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
947: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 948: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
949: ssh_digest_update(hashctx, &c, 1) != 0 ||
950: ssh_digest_update(hashctx, kex->session_id,
1.102 markus 951: kex->session_id_len) != 0 ||
952: ssh_digest_final(hashctx, digest, mdsz) != 0) {
953: r = SSH_ERR_LIBCRYPTO_ERROR;
954: goto out;
955: }
1.94 djm 956: ssh_digest_free(hashctx);
1.102 markus 957: hashctx = NULL;
1.26 markus 958:
1.30 markus 959: /*
960: * expand key:
961: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
962: * Key = K1 || K2 || ... || Kn
963: */
1.26 markus 964: for (have = mdsz; need > have; have += mdsz) {
1.102 markus 965: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
966: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 967: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1.102 markus 968: ssh_digest_update(hashctx, digest, have) != 0 ||
969: ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
970: r = SSH_ERR_LIBCRYPTO_ERROR;
971: goto out;
972: }
1.94 djm 973: ssh_digest_free(hashctx);
1.102 markus 974: hashctx = NULL;
1.26 markus 975: }
976: #ifdef DEBUG_KEX
977: fprintf(stderr, "key '%c'== ", c);
978: dump_digest("key", digest, need);
979: #endif
1.102 markus 980: *keyp = digest;
981: digest = NULL;
982: r = 0;
983: out:
1.114 mmcc 984: free(digest);
1.102 markus 985: ssh_digest_free(hashctx);
986: return r;
1.1 markus 987: }
988:
1.23 markus 989: #define NKEYS 6
1.102 markus 990: int
991: kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
992: const struct sshbuf *shared_secret)
1.1 markus 993: {
1.102 markus 994: struct kex *kex = ssh->kex;
1.15 markus 995: u_char *keys[NKEYS];
1.102 markus 996: u_int i, j, mode, ctos;
997: int r;
1.1 markus 998:
1.144 ! djm 999: /* save initial hash as session id */
! 1000: if (kex->session_id == NULL) {
! 1001: kex->session_id_len = hashlen;
! 1002: kex->session_id = malloc(kex->session_id_len);
! 1003: if (kex->session_id == NULL)
! 1004: return SSH_ERR_ALLOC_FAIL;
! 1005: memcpy(kex->session_id, hash, kex->session_id_len);
! 1006: }
1.65 djm 1007: for (i = 0; i < NKEYS; i++) {
1.102 markus 1008: if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
1009: shared_secret, &keys[i])) != 0) {
1010: for (j = 0; j < i; j++)
1011: free(keys[j]);
1012: return r;
1013: }
1.65 djm 1014: }
1.1 markus 1015: for (mode = 0; mode < MODE_MAX; mode++) {
1.69 deraadt 1016: ctos = (!kex->server && mode == MODE_OUT) ||
1017: (kex->server && mode == MODE_IN);
1.100 markus 1018: kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
1019: kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
1020: kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
1.1 markus 1021: }
1.102 markus 1022: return 0;
1.95 djm 1023: }
1024:
1.99 markus 1025: #ifdef WITH_OPENSSL
1.102 markus 1026: int
1027: kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen,
1028: const BIGNUM *secret)
1.95 djm 1029: {
1.102 markus 1030: struct sshbuf *shared_secret;
1031: int r;
1.95 djm 1032:
1.102 markus 1033: if ((shared_secret = sshbuf_new()) == NULL)
1034: return SSH_ERR_ALLOC_FAIL;
1035: if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0)
1036: r = kex_derive_keys(ssh, hash, hashlen, shared_secret);
1037: sshbuf_free(shared_secret);
1038: return r;
1.27 markus 1039: }
1.99 markus 1040: #endif
1.57 djm 1041:
1.26 markus 1042:
1.84 djm 1043: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1.26 markus 1044: void
1045: dump_digest(char *msg, u_char *digest, int len)
1046: {
1047: fprintf(stderr, "%s\n", msg);
1.102 markus 1048: sshbuf_dump_data(digest, len, stderr);
1.26 markus 1049: }
1050: #endif
1.143 djm 1051:
1052: /*
1053: * Send a plaintext error message to the peer, suffixed by \r\n.
1054: * Only used during banner exchange, and there only for the server.
1055: */
1056: static void
1057: send_error(struct ssh *ssh, char *msg)
1058: {
1059: char *crnl = "\r\n";
1060:
1061: if (!ssh->kex->server)
1062: return;
1063:
1064: if (atomicio(vwrite, ssh_packet_get_connection_out(ssh),
1065: msg, strlen(msg)) != strlen(msg) ||
1066: atomicio(vwrite, ssh_packet_get_connection_out(ssh),
1067: crnl, strlen(crnl)) != strlen(crnl))
1068: error("%s: write: %.100s", __func__, strerror(errno));
1069: }
1070:
1071: /*
1072: * Sends our identification string and waits for the peer's. Will block for
1073: * up to timeout_ms (or indefinitely if timeout_ms <= 0).
1074: * Returns on 0 success or a ssherr.h code on failure.
1075: */
1076: int
1077: kex_exchange_identification(struct ssh *ssh, int timeout_ms,
1078: const char *version_addendum)
1079: {
1080: int remote_major, remote_minor, mismatch;
1081: size_t len, i, n;
1082: int r, expect_nl;
1083: u_char c;
1084: struct sshbuf *our_version = ssh->kex->server ?
1085: ssh->kex->server_version : ssh->kex->client_version;
1086: struct sshbuf *peer_version = ssh->kex->server ?
1087: ssh->kex->client_version : ssh->kex->server_version;
1088: char *our_version_string = NULL, *peer_version_string = NULL;
1089: char *cp, *remote_version = NULL;
1090:
1091: /* Prepare and send our banner */
1092: sshbuf_reset(our_version);
1093: if (version_addendum != NULL && *version_addendum == '\0')
1094: version_addendum = NULL;
1095: if ((r = sshbuf_putf(our_version, "SSH-%d.%d-%.100s%s%s\r\n",
1096: PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION,
1097: version_addendum == NULL ? "" : " ",
1098: version_addendum == NULL ? "" : version_addendum)) != 0) {
1099: error("%s: sshbuf_putf: %s", __func__, ssh_err(r));
1100: goto out;
1101: }
1102:
1103: if (atomicio(vwrite, ssh_packet_get_connection_out(ssh),
1104: sshbuf_mutable_ptr(our_version),
1105: sshbuf_len(our_version)) != sshbuf_len(our_version)) {
1106: error("%s: write: %.100s", __func__, strerror(errno));
1107: r = SSH_ERR_SYSTEM_ERROR;
1108: goto out;
1109: }
1110: if ((r = sshbuf_consume_end(our_version, 2)) != 0) { /* trim \r\n */
1111: error("%s: sshbuf_consume_end: %s", __func__, ssh_err(r));
1112: goto out;
1113: }
1114: our_version_string = sshbuf_dup_string(our_version);
1115: if (our_version_string == NULL) {
1116: error("%s: sshbuf_dup_string failed", __func__);
1117: r = SSH_ERR_ALLOC_FAIL;
1118: goto out;
1119: }
1120: debug("Local version string %.100s", our_version_string);
1121:
1122: /* Read other side's version identification. */
1123: for (n = 0; ; n++) {
1124: if (n >= SSH_MAX_PRE_BANNER_LINES) {
1125: send_error(ssh, "No SSH identification string "
1126: "received.");
1127: error("%s: No SSH version received in first %u lines "
1128: "from server", __func__, SSH_MAX_PRE_BANNER_LINES);
1129: r = SSH_ERR_INVALID_FORMAT;
1130: goto out;
1131: }
1132: sshbuf_reset(peer_version);
1133: expect_nl = 0;
1134: for (i = 0; ; i++) {
1135: if (timeout_ms > 0) {
1136: r = waitrfd(ssh_packet_get_connection_in(ssh),
1137: &timeout_ms);
1138: if (r == -1 && errno == ETIMEDOUT) {
1139: send_error(ssh, "Timed out waiting "
1140: "for SSH identification string.");
1141: error("Connection timed out during "
1142: "banner exchange");
1143: r = SSH_ERR_CONN_TIMEOUT;
1144: goto out;
1145: } else if (r == -1) {
1146: error("%s: %s",
1147: __func__, strerror(errno));
1148: r = SSH_ERR_SYSTEM_ERROR;
1149: goto out;
1150: }
1151: }
1152:
1153: len = atomicio(read, ssh_packet_get_connection_in(ssh),
1154: &c, 1);
1155: if (len != 1 && errno == EPIPE) {
1156: error("%s: Connection closed by remote host",
1157: __func__);
1158: r = SSH_ERR_CONN_CLOSED;
1159: goto out;
1160: } else if (len != 1) {
1161: error("%s: read: %.100s",
1162: __func__, strerror(errno));
1163: r = SSH_ERR_SYSTEM_ERROR;
1164: goto out;
1165: }
1166: if (c == '\r') {
1167: expect_nl = 1;
1168: continue;
1169: }
1170: if (c == '\n')
1171: break;
1172: if (c == '\0' || expect_nl) {
1173: error("%s: banner line contains invalid "
1174: "characters", __func__);
1175: goto invalid;
1176: }
1177: if ((r = sshbuf_put_u8(peer_version, c)) != 0) {
1178: error("%s: sshbuf_put: %s",
1179: __func__, ssh_err(r));
1180: goto out;
1181: }
1182: if (sshbuf_len(peer_version) > SSH_MAX_BANNER_LEN) {
1183: error("%s: banner line too long", __func__);
1184: goto invalid;
1185: }
1186: }
1187: /* Is this an actual protocol banner? */
1188: if (sshbuf_len(peer_version) > 4 &&
1189: memcmp(sshbuf_ptr(peer_version), "SSH-", 4) == 0)
1190: break;
1191: /* If not, then just log the line and continue */
1192: if ((cp = sshbuf_dup_string(peer_version)) == NULL) {
1193: error("%s: sshbuf_dup_string failed", __func__);
1194: r = SSH_ERR_ALLOC_FAIL;
1195: goto out;
1196: }
1197: /* Do not accept lines before the SSH ident from a client */
1198: if (ssh->kex->server) {
1199: error("%s: client sent invalid protocol identifier "
1200: "\"%.256s\"", __func__, cp);
1201: free(cp);
1202: goto invalid;
1203: }
1204: debug("%s: banner line %zu: %s", __func__, n, cp);
1205: free(cp);
1206: }
1207: peer_version_string = sshbuf_dup_string(peer_version);
1208: if (peer_version_string == NULL)
1209: error("%s: sshbuf_dup_string failed", __func__);
1210: /* XXX must be same size for sscanf */
1211: if ((remote_version = calloc(1, sshbuf_len(peer_version))) == NULL) {
1212: error("%s: calloc failed", __func__);
1213: r = SSH_ERR_ALLOC_FAIL;
1214: goto out;
1215: }
1216:
1217: /*
1218: * Check that the versions match. In future this might accept
1219: * several versions and set appropriate flags to handle them.
1220: */
1221: if (sscanf(peer_version_string, "SSH-%d.%d-%[^\n]\n",
1222: &remote_major, &remote_minor, remote_version) != 3) {
1223: error("Bad remote protocol version identification: '%.100s'",
1224: peer_version_string);
1225: invalid:
1226: send_error(ssh, "Invalid SSH identification string.");
1227: r = SSH_ERR_INVALID_FORMAT;
1228: goto out;
1229: }
1230: debug("Remote protocol version %d.%d, remote software version %.100s",
1231: remote_major, remote_minor, remote_version);
1232: ssh->compat = compat_datafellows(remote_version);
1233:
1234: mismatch = 0;
1235: switch (remote_major) {
1236: case 2:
1237: break;
1238: case 1:
1239: if (remote_minor != 99)
1240: mismatch = 1;
1241: break;
1242: default:
1243: mismatch = 1;
1244: break;
1245: }
1246: if (mismatch) {
1247: error("Protocol major versions differ: %d vs. %d",
1248: PROTOCOL_MAJOR_2, remote_major);
1249: send_error(ssh, "Protocol major versions differ.");
1250: r = SSH_ERR_NO_PROTOCOL_VERSION;
1251: goto out;
1252: }
1253:
1254: if (ssh->kex->server && (ssh->compat & SSH_BUG_PROBE) != 0) {
1255: logit("probed from %s port %d with %s. Don't panic.",
1256: ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
1257: peer_version_string);
1258: r = SSH_ERR_CONN_CLOSED; /* XXX */
1259: goto out;
1260: }
1261: if (ssh->kex->server && (ssh->compat & SSH_BUG_SCANNER) != 0) {
1262: logit("scanned from %s port %d with %s. Don't panic.",
1263: ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
1264: peer_version_string);
1265: r = SSH_ERR_CONN_CLOSED; /* XXX */
1266: goto out;
1267: }
1268: if ((ssh->compat & SSH_BUG_RSASIGMD5) != 0) {
1269: logit("Remote version \"%.100s\" uses unsafe RSA signature "
1270: "scheme; disabling use of RSA keys", remote_version);
1271: }
1272: /* success */
1273: r = 0;
1274: out:
1275: free(our_version_string);
1276: free(peer_version_string);
1277: free(remote_version);
1278: return r;
1279: }
1280:
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