Annotation of src/usr.bin/ssh/kex.c, Revision 1.151
1.151 ! djm 1: /* $OpenBSD: kex.c,v 1.150 2019/01/21 12:08:13 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 },
1.147 djm 101: { KEX_SNTRUP4591761X25519_SHA512, KEX_KEM_SNTRUP4591761X25519_SHA512, 0,
102: SSH_DIGEST_SHA512 },
1.94 djm 103: { NULL, -1, -1, -1},
1.89 djm 104: };
105:
106: char *
1.93 dtucker 107: kex_alg_list(char sep)
1.89 djm 108: {
1.102 markus 109: char *ret = NULL, *tmp;
1.89 djm 110: size_t nlen, rlen = 0;
111: const struct kexalg *k;
112:
113: for (k = kexalgs; k->name != NULL; k++) {
114: if (ret != NULL)
1.93 dtucker 115: ret[rlen++] = sep;
1.89 djm 116: nlen = strlen(k->name);
1.102 markus 117: if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
118: free(ret);
119: return NULL;
120: }
121: ret = tmp;
1.89 djm 122: memcpy(ret + rlen, k->name, nlen + 1);
123: rlen += nlen;
124: }
125: return ret;
126: }
127:
128: static const struct kexalg *
129: kex_alg_by_name(const char *name)
130: {
131: const struct kexalg *k;
132:
133: for (k = kexalgs; k->name != NULL; k++) {
134: if (strcmp(k->name, name) == 0)
135: return k;
136: }
137: return NULL;
138: }
139:
1.86 djm 140: /* Validate KEX method name list */
141: int
142: kex_names_valid(const char *names)
143: {
144: char *s, *cp, *p;
145:
146: if (names == NULL || strcmp(names, "") == 0)
147: return 0;
1.102 markus 148: if ((s = cp = strdup(names)) == NULL)
149: return 0;
1.86 djm 150: for ((p = strsep(&cp, ",")); p && *p != '\0';
151: (p = strsep(&cp, ","))) {
1.89 djm 152: if (kex_alg_by_name(p) == NULL) {
1.86 djm 153: error("Unsupported KEX algorithm \"%.100s\"", p);
1.91 djm 154: free(s);
1.86 djm 155: return 0;
156: }
157: }
158: debug3("kex names ok: [%s]", names);
1.91 djm 159: free(s);
1.86 djm 160: return 1;
1.109 djm 161: }
162:
163: /*
164: * Concatenate algorithm names, avoiding duplicates in the process.
165: * Caller must free returned string.
166: */
167: char *
168: kex_names_cat(const char *a, const char *b)
169: {
1.129 dtucker 170: char *ret = NULL, *tmp = NULL, *cp, *p, *m;
1.109 djm 171: size_t len;
172:
173: if (a == NULL || *a == '\0')
1.138 djm 174: return strdup(b);
1.109 djm 175: if (b == NULL || *b == '\0')
176: return strdup(a);
177: if (strlen(b) > 1024*1024)
178: return NULL;
179: len = strlen(a) + strlen(b) + 2;
180: if ((tmp = cp = strdup(b)) == NULL ||
181: (ret = calloc(1, len)) == NULL) {
182: free(tmp);
183: return NULL;
184: }
185: strlcpy(ret, a, len);
186: for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) {
1.129 dtucker 187: if ((m = match_list(ret, p, NULL)) != NULL) {
188: free(m);
1.109 djm 189: continue; /* Algorithm already present */
1.129 dtucker 190: }
1.109 djm 191: if (strlcat(ret, ",", len) >= len ||
192: strlcat(ret, p, len) >= len) {
193: free(tmp);
194: free(ret);
195: return NULL; /* Shouldn't happen */
196: }
197: }
198: free(tmp);
199: return ret;
200: }
201:
202: /*
203: * Assemble a list of algorithms from a default list and a string from a
204: * configuration file. The user-provided string may begin with '+' to
1.128 djm 205: * indicate that it should be appended to the default or '-' that the
206: * specified names should be removed.
1.109 djm 207: */
208: int
1.138 djm 209: kex_assemble_names(char **listp, const char *def, const char *all)
1.109 djm 210: {
1.138 djm 211: char *cp, *tmp, *patterns;
212: char *list = NULL, *ret = NULL, *matching = NULL, *opatterns = NULL;
213: int r = SSH_ERR_INTERNAL_ERROR;
214:
215: if (listp == NULL || *listp == NULL || **listp == '\0') {
216: if ((*listp = strdup(def)) == NULL)
217: return SSH_ERR_ALLOC_FAIL;
218: return 0;
219: }
1.109 djm 220:
1.138 djm 221: list = *listp;
222: *listp = NULL;
223: if (*list == '+') {
224: /* Append names to default list */
225: if ((tmp = kex_names_cat(def, list + 1)) == NULL) {
226: r = SSH_ERR_ALLOC_FAIL;
227: goto fail;
228: }
229: free(list);
230: list = tmp;
231: } else if (*list == '-') {
232: /* Remove names from default list */
233: if ((*listp = match_filter_blacklist(def, list + 1)) == NULL) {
234: r = SSH_ERR_ALLOC_FAIL;
235: goto fail;
236: }
237: free(list);
238: /* filtering has already been done */
1.109 djm 239: return 0;
1.138 djm 240: } else {
241: /* Explicit list, overrides default - just use "list" as is */
242: }
243:
244: /*
245: * The supplied names may be a pattern-list. For the -list case,
246: * the patterns are applied above. For the +list and explicit list
247: * cases we need to do it now.
248: */
249: ret = NULL;
250: if ((patterns = opatterns = strdup(list)) == NULL) {
251: r = SSH_ERR_ALLOC_FAIL;
252: goto fail;
253: }
254: /* Apply positive (i.e. non-negated) patterns from the list */
255: while ((cp = strsep(&patterns, ",")) != NULL) {
256: if (*cp == '!') {
257: /* negated matches are not supported here */
258: r = SSH_ERR_INVALID_ARGUMENT;
259: goto fail;
260: }
261: free(matching);
262: if ((matching = match_filter_whitelist(all, cp)) == NULL) {
263: r = SSH_ERR_ALLOC_FAIL;
264: goto fail;
265: }
266: if ((tmp = kex_names_cat(ret, matching)) == NULL) {
267: r = SSH_ERR_ALLOC_FAIL;
268: goto fail;
269: }
270: free(ret);
271: ret = tmp;
1.109 djm 272: }
1.138 djm 273: if (ret == NULL || *ret == '\0') {
274: /* An empty name-list is an error */
275: /* XXX better error code? */
276: r = SSH_ERR_INVALID_ARGUMENT;
277: goto fail;
1.109 djm 278: }
279:
1.138 djm 280: /* success */
281: *listp = ret;
282: ret = NULL;
283: r = 0;
284:
285: fail:
286: free(matching);
287: free(opatterns);
288: free(list);
289: free(ret);
290: return r;
1.86 djm 291: }
1.26 markus 292:
293: /* put algorithm proposal into buffer */
1.102 markus 294: int
295: kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
1.1 markus 296: {
1.61 djm 297: u_int i;
1.102 markus 298: int r;
299:
300: sshbuf_reset(b);
1.26 markus 301:
1.49 markus 302: /*
303: * add a dummy cookie, the cookie will be overwritten by
304: * kex_send_kexinit(), each time a kexinit is set
305: */
1.102 markus 306: for (i = 0; i < KEX_COOKIE_LEN; i++) {
307: if ((r = sshbuf_put_u8(b, 0)) != 0)
308: return r;
309: }
310: for (i = 0; i < PROPOSAL_MAX; i++) {
311: if ((r = sshbuf_put_cstring(b, proposal[i])) != 0)
312: return r;
313: }
314: if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */
315: (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */
316: return r;
317: return 0;
1.1 markus 318: }
319:
1.26 markus 320: /* parse buffer and return algorithm proposal */
1.102 markus 321: int
322: kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp)
1.7 markus 323: {
1.102 markus 324: struct sshbuf *b = NULL;
325: u_char v;
1.78 djm 326: u_int i;
1.102 markus 327: char **proposal = NULL;
328: int r;
1.7 markus 329:
1.102 markus 330: *propp = NULL;
331: if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL)
332: return SSH_ERR_ALLOC_FAIL;
333: if ((b = sshbuf_fromb(raw)) == NULL) {
334: r = SSH_ERR_ALLOC_FAIL;
335: goto out;
336: }
337: if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */
338: goto out;
1.7 markus 339: /* extract kex init proposal strings */
340: for (i = 0; i < PROPOSAL_MAX; i++) {
1.102 markus 341: if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0)
342: goto out;
1.110 djm 343: debug2("%s: %s", proposal_names[i], proposal[i]);
1.7 markus 344: }
1.26 markus 345: /* first kex follows / reserved */
1.115 djm 346: if ((r = sshbuf_get_u8(b, &v)) != 0 || /* first_kex_follows */
347: (r = sshbuf_get_u32(b, &i)) != 0) /* reserved */
1.102 markus 348: goto out;
1.53 markus 349: if (first_kex_follows != NULL)
1.115 djm 350: *first_kex_follows = v;
1.110 djm 351: debug2("first_kex_follows %d ", v);
352: debug2("reserved %u ", i);
1.102 markus 353: r = 0;
354: *propp = proposal;
355: out:
356: if (r != 0 && proposal != NULL)
357: kex_prop_free(proposal);
358: sshbuf_free(b);
359: return r;
1.1 markus 360: }
361:
1.102 markus 362: void
1.26 markus 363: kex_prop_free(char **proposal)
1.1 markus 364: {
1.61 djm 365: u_int i;
1.26 markus 366:
1.106 djm 367: if (proposal == NULL)
368: return;
1.26 markus 369: for (i = 0; i < PROPOSAL_MAX; i++)
1.91 djm 370: free(proposal[i]);
371: free(proposal);
1.1 markus 372: }
373:
1.78 djm 374: /* ARGSUSED */
1.101 markus 375: static int
1.133 markus 376: kex_protocol_error(int type, u_int32_t seq, struct ssh *ssh)
1.1 markus 377: {
1.112 djm 378: int r;
379:
380: error("kex protocol error: type %d seq %u", type, seq);
381: if ((r = sshpkt_start(ssh, SSH2_MSG_UNIMPLEMENTED)) != 0 ||
382: (r = sshpkt_put_u32(ssh, seq)) != 0 ||
383: (r = sshpkt_send(ssh)) != 0)
384: return r;
1.101 markus 385: return 0;
1.26 markus 386: }
1.1 markus 387:
1.35 itojun 388: static void
1.102 markus 389: kex_reset_dispatch(struct ssh *ssh)
1.29 markus 390: {
1.102 markus 391: ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
1.42 markus 392: SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
1.29 markus 393: }
394:
1.113 markus 395: static int
396: kex_send_ext_info(struct ssh *ssh)
397: {
398: int r;
1.121 djm 399: char *algs;
1.113 markus 400:
1.151 ! djm 401: debug("Sending SSH2_MSG_EXT_INFO");
1.130 djm 402: if ((algs = sshkey_alg_list(0, 1, 1, ',')) == NULL)
1.121 djm 403: return SSH_ERR_ALLOC_FAIL;
1.137 djm 404: /* XXX filter algs list by allowed pubkey/hostbased types */
1.113 markus 405: if ((r = sshpkt_start(ssh, SSH2_MSG_EXT_INFO)) != 0 ||
406: (r = sshpkt_put_u32(ssh, 1)) != 0 ||
407: (r = sshpkt_put_cstring(ssh, "server-sig-algs")) != 0 ||
1.121 djm 408: (r = sshpkt_put_cstring(ssh, algs)) != 0 ||
1.113 markus 409: (r = sshpkt_send(ssh)) != 0)
1.121 djm 410: goto out;
411: /* success */
412: r = 0;
413: out:
414: free(algs);
1.123 djm 415: return r;
1.113 markus 416: }
417:
1.102 markus 418: int
419: kex_send_newkeys(struct ssh *ssh)
1.26 markus 420: {
1.102 markus 421: int r;
1.28 markus 422:
1.102 markus 423: kex_reset_dispatch(ssh);
424: if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
425: (r = sshpkt_send(ssh)) != 0)
426: return r;
1.26 markus 427: debug("SSH2_MSG_NEWKEYS sent");
1.102 markus 428: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
1.151 ! djm 429: if (ssh->kex->ext_info_c && (ssh->kex->flags & KEX_INITIAL) != 0)
1.113 markus 430: if ((r = kex_send_ext_info(ssh)) != 0)
431: return r;
1.151 ! djm 432: debug("expecting SSH2_MSG_NEWKEYS");
1.102 markus 433: return 0;
434: }
435:
1.113 markus 436: int
1.133 markus 437: kex_input_ext_info(int type, u_int32_t seq, struct ssh *ssh)
1.113 markus 438: {
439: struct kex *kex = ssh->kex;
440: u_int32_t i, ninfo;
1.137 djm 441: char *name;
1.134 djm 442: u_char *val;
443: size_t vlen;
1.113 markus 444: int r;
445:
446: debug("SSH2_MSG_EXT_INFO received");
447: ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_protocol_error);
448: if ((r = sshpkt_get_u32(ssh, &ninfo)) != 0)
449: return r;
450: for (i = 0; i < ninfo; i++) {
451: if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0)
452: return r;
1.134 djm 453: if ((r = sshpkt_get_string(ssh, &val, &vlen)) != 0) {
1.113 markus 454: free(name);
455: return r;
456: }
457: if (strcmp(name, "server-sig-algs") == 0) {
1.134 djm 458: /* Ensure no \0 lurking in value */
459: if (memchr(val, '\0', vlen) != NULL) {
460: error("%s: nul byte in %s", __func__, name);
461: return SSH_ERR_INVALID_FORMAT;
462: }
463: debug("%s: %s=<%s>", __func__, name, val);
1.137 djm 464: kex->server_sig_algs = val;
465: val = NULL;
1.134 djm 466: } else
467: debug("%s: %s (unrecognised)", __func__, name);
1.113 markus 468: free(name);
469: free(val);
470: }
471: return sshpkt_get_end(ssh);
472: }
473:
1.102 markus 474: static int
1.133 markus 475: kex_input_newkeys(int type, u_int32_t seq, struct ssh *ssh)
1.102 markus 476: {
477: struct kex *kex = ssh->kex;
478: int r;
1.19 stevesk 479:
1.26 markus 480: debug("SSH2_MSG_NEWKEYS received");
1.102 markus 481: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
1.131 markus 482: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.102 markus 483: if ((r = sshpkt_get_end(ssh)) != 0)
1.122 markus 484: return r;
485: if ((r = ssh_set_newkeys(ssh, MODE_IN)) != 0)
1.102 markus 486: return r;
1.30 markus 487: kex->done = 1;
1.142 djm 488: kex->flags &= ~KEX_INITIAL;
1.102 markus 489: sshbuf_reset(kex->peer);
490: /* sshbuf_reset(kex->my); */
1.26 markus 491: kex->flags &= ~KEX_INIT_SENT;
1.91 djm 492: free(kex->name);
1.32 markus 493: kex->name = NULL;
1.102 markus 494: return 0;
1.26 markus 495: }
1.1 markus 496:
1.102 markus 497: int
498: kex_send_kexinit(struct ssh *ssh)
1.26 markus 499: {
1.49 markus 500: u_char *cookie;
1.102 markus 501: struct kex *kex = ssh->kex;
502: int r;
1.49 markus 503:
1.102 markus 504: if (kex == NULL)
505: return SSH_ERR_INTERNAL_ERROR;
506: if (kex->flags & KEX_INIT_SENT)
507: return 0;
1.30 markus 508: kex->done = 0;
1.49 markus 509:
510: /* generate a random cookie */
1.102 markus 511: if (sshbuf_len(kex->my) < KEX_COOKIE_LEN)
512: return SSH_ERR_INVALID_FORMAT;
513: if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL)
514: return SSH_ERR_INTERNAL_ERROR;
515: arc4random_buf(cookie, KEX_COOKIE_LEN);
516:
517: if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
518: (r = sshpkt_putb(ssh, kex->my)) != 0 ||
519: (r = sshpkt_send(ssh)) != 0)
520: return r;
1.26 markus 521: debug("SSH2_MSG_KEXINIT sent");
522: kex->flags |= KEX_INIT_SENT;
1.102 markus 523: return 0;
1.1 markus 524: }
525:
1.78 djm 526: /* ARGSUSED */
1.101 markus 527: int
1.133 markus 528: kex_input_kexinit(int type, u_int32_t seq, struct ssh *ssh)
1.11 provos 529: {
1.102 markus 530: struct kex *kex = ssh->kex;
531: const u_char *ptr;
1.100 markus 532: u_int i;
533: size_t dlen;
1.102 markus 534: int r;
1.11 provos 535:
1.26 markus 536: debug("SSH2_MSG_KEXINIT received");
1.29 markus 537: if (kex == NULL)
1.102 markus 538: return SSH_ERR_INVALID_ARGUMENT;
1.11 provos 539:
1.127 markus 540: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, NULL);
1.102 markus 541: ptr = sshpkt_ptr(ssh, &dlen);
542: if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
543: return r;
1.31 markus 544:
545: /* discard packet */
546: for (i = 0; i < KEX_COOKIE_LEN; i++)
1.102 markus 547: if ((r = sshpkt_get_u8(ssh, NULL)) != 0)
548: return r;
1.31 markus 549: for (i = 0; i < PROPOSAL_MAX; i++)
1.102 markus 550: if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0)
551: return r;
1.87 djm 552: /*
553: * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
554: * KEX method has the server move first, but a server might be using
555: * a custom method or one that we otherwise don't support. We should
556: * be prepared to remember first_kex_follows here so we can eat a
557: * packet later.
558: * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
559: * for cases where the server *doesn't* go first. I guess we should
560: * ignore it when it is set for these cases, which is what we do now.
561: */
1.102 markus 562: if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
563: (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
564: (r = sshpkt_get_end(ssh)) != 0)
565: return r;
566:
567: if (!(kex->flags & KEX_INIT_SENT))
568: if ((r = kex_send_kexinit(ssh)) != 0)
569: return r;
570: if ((r = kex_choose_conf(ssh)) != 0)
571: return r;
1.19 stevesk 572:
1.102 markus 573: if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
574: return (kex->kex[kex->kex_type])(ssh);
575:
576: return SSH_ERR_INTERNAL_ERROR;
577: }
578:
1.143 djm 579: struct kex *
580: kex_new(void)
1.102 markus 581: {
582: struct kex *kex;
583:
1.143 djm 584: if ((kex = calloc(1, sizeof(*kex))) == NULL ||
585: (kex->peer = sshbuf_new()) == NULL ||
586: (kex->my = sshbuf_new()) == NULL ||
587: (kex->client_version = sshbuf_new()) == NULL ||
588: (kex->server_version = sshbuf_new()) == NULL) {
589: kex_free(kex);
590: return NULL;
1.102 markus 591: }
1.143 djm 592: return kex;
1.26 markus 593: }
1.11 provos 594:
1.100 markus 595: void
596: kex_free_newkeys(struct newkeys *newkeys)
597: {
598: if (newkeys == NULL)
599: return;
600: if (newkeys->enc.key) {
601: explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
602: free(newkeys->enc.key);
603: newkeys->enc.key = NULL;
604: }
605: if (newkeys->enc.iv) {
1.111 djm 606: explicit_bzero(newkeys->enc.iv, newkeys->enc.iv_len);
1.100 markus 607: free(newkeys->enc.iv);
608: newkeys->enc.iv = NULL;
609: }
610: free(newkeys->enc.name);
611: explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
612: free(newkeys->comp.name);
613: explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
614: mac_clear(&newkeys->mac);
615: if (newkeys->mac.key) {
616: explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
617: free(newkeys->mac.key);
618: newkeys->mac.key = NULL;
619: }
620: free(newkeys->mac.name);
621: explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
622: explicit_bzero(newkeys, sizeof(*newkeys));
623: free(newkeys);
624: }
625:
1.102 markus 626: void
627: kex_free(struct kex *kex)
1.26 markus 628: {
1.102 markus 629: u_int mode;
1.11 provos 630:
1.143 djm 631: if (kex == NULL)
632: return;
633:
1.102 markus 634: #ifdef WITH_OPENSSL
1.136 jsing 635: DH_free(kex->dh);
636: EC_KEY_free(kex->ec_client_key);
1.102 markus 637: #endif
638: for (mode = 0; mode < MODE_MAX; mode++) {
639: kex_free_newkeys(kex->newkeys[mode]);
640: kex->newkeys[mode] = NULL;
1.100 markus 641: }
1.102 markus 642: sshbuf_free(kex->peer);
643: sshbuf_free(kex->my);
1.143 djm 644: sshbuf_free(kex->client_version);
645: sshbuf_free(kex->server_version);
1.149 djm 646: sshbuf_free(kex->client_pub);
1.102 markus 647: free(kex->session_id);
1.107 djm 648: free(kex->failed_choice);
1.113 markus 649: free(kex->hostkey_alg);
650: free(kex->name);
1.102 markus 651: free(kex);
1.11 provos 652: }
653:
1.102 markus 654: int
1.143 djm 655: kex_ready(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
656: {
657: int r;
658:
659: if ((r = kex_prop2buf(ssh->kex->my, proposal)) != 0)
660: return r;
661: ssh->kex->flags = KEX_INITIAL;
662: kex_reset_dispatch(ssh);
663: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
664: return 0;
665: }
666:
667: int
1.102 markus 668: kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
1.1 markus 669: {
1.102 markus 670: int r;
1.1 markus 671:
1.143 djm 672: if ((r = kex_ready(ssh, proposal)) != 0)
1.102 markus 673: return r;
674: if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
675: kex_free(ssh->kex);
676: ssh->kex = NULL;
677: return r;
1.1 markus 678: }
1.102 markus 679: return 0;
1.117 djm 680: }
681:
682: /*
683: * Request key re-exchange, returns 0 on success or a ssherr.h error
684: * code otherwise. Must not be called if KEX is incomplete or in-progress.
685: */
686: int
687: kex_start_rekex(struct ssh *ssh)
688: {
689: if (ssh->kex == NULL) {
690: error("%s: no kex", __func__);
691: return SSH_ERR_INTERNAL_ERROR;
692: }
693: if (ssh->kex->done == 0) {
694: error("%s: requested twice", __func__);
695: return SSH_ERR_INTERNAL_ERROR;
696: }
697: ssh->kex->done = 0;
698: return kex_send_kexinit(ssh);
1.1 markus 699: }
700:
1.102 markus 701: static int
702: choose_enc(struct sshenc *enc, char *client, char *server)
1.1 markus 703: {
1.23 markus 704: char *name = match_list(client, server, NULL);
1.102 markus 705:
1.1 markus 706: if (name == NULL)
1.102 markus 707: return SSH_ERR_NO_CIPHER_ALG_MATCH;
1.129 dtucker 708: if ((enc->cipher = cipher_by_name(name)) == NULL) {
709: free(name);
1.102 markus 710: return SSH_ERR_INTERNAL_ERROR;
1.129 dtucker 711: }
1.1 markus 712: enc->name = name;
713: enc->enabled = 0;
714: enc->iv = NULL;
1.88 markus 715: enc->iv_len = cipher_ivlen(enc->cipher);
1.1 markus 716: enc->key = NULL;
1.45 markus 717: enc->key_len = cipher_keylen(enc->cipher);
718: enc->block_size = cipher_blocksize(enc->cipher);
1.102 markus 719: return 0;
1.1 markus 720: }
1.69 deraadt 721:
1.102 markus 722: static int
723: choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
1.1 markus 724: {
1.23 markus 725: char *name = match_list(client, server, NULL);
1.102 markus 726:
1.1 markus 727: if (name == NULL)
1.102 markus 728: return SSH_ERR_NO_MAC_ALG_MATCH;
1.129 dtucker 729: if (mac_setup(mac, name) < 0) {
730: free(name);
1.102 markus 731: return SSH_ERR_INTERNAL_ERROR;
1.129 dtucker 732: }
1.1 markus 733: mac->name = name;
734: mac->key = NULL;
735: mac->enabled = 0;
1.102 markus 736: return 0;
1.1 markus 737: }
1.69 deraadt 738:
1.102 markus 739: static int
740: choose_comp(struct sshcomp *comp, char *client, char *server)
1.1 markus 741: {
1.23 markus 742: char *name = match_list(client, server, NULL);
1.102 markus 743:
1.1 markus 744: if (name == NULL)
1.102 markus 745: return SSH_ERR_NO_COMPRESS_ALG_MATCH;
1.64 markus 746: if (strcmp(name, "zlib@openssh.com") == 0) {
1.141 sf 747: comp->type = COMP_DELAYED;
748: } else if (strcmp(name, "zlib") == 0) {
1.140 sf 749: comp->type = COMP_ZLIB;
1.1 markus 750: } else if (strcmp(name, "none") == 0) {
1.64 markus 751: comp->type = COMP_NONE;
1.1 markus 752: } else {
1.129 dtucker 753: free(name);
1.102 markus 754: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 755: }
756: comp->name = name;
1.102 markus 757: return 0;
1.1 markus 758: }
1.69 deraadt 759:
1.102 markus 760: static int
761: choose_kex(struct kex *k, char *client, char *server)
1.1 markus 762: {
1.89 djm 763: const struct kexalg *kexalg;
764:
1.23 markus 765: k->name = match_list(client, server, NULL);
1.102 markus 766:
1.110 djm 767: debug("kex: algorithm: %s", k->name ? k->name : "(no match)");
1.1 markus 768: if (k->name == NULL)
1.102 markus 769: return SSH_ERR_NO_KEX_ALG_MATCH;
1.89 djm 770: if ((kexalg = kex_alg_by_name(k->name)) == NULL)
1.102 markus 771: return SSH_ERR_INTERNAL_ERROR;
1.89 djm 772: k->kex_type = kexalg->type;
1.94 djm 773: k->hash_alg = kexalg->hash_alg;
1.89 djm 774: k->ec_nid = kexalg->ec_nid;
1.102 markus 775: return 0;
1.1 markus 776: }
1.65 djm 777:
1.102 markus 778: static int
779: choose_hostkeyalg(struct kex *k, char *client, char *server)
1.1 markus 780: {
1.113 markus 781: k->hostkey_alg = match_list(client, server, NULL);
1.102 markus 782:
1.110 djm 783: debug("kex: host key algorithm: %s",
1.113 markus 784: k->hostkey_alg ? k->hostkey_alg : "(no match)");
785: if (k->hostkey_alg == NULL)
1.102 markus 786: return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
1.113 markus 787: k->hostkey_type = sshkey_type_from_name(k->hostkey_alg);
1.13 markus 788: if (k->hostkey_type == KEY_UNSPEC)
1.102 markus 789: return SSH_ERR_INTERNAL_ERROR;
1.113 markus 790: k->hostkey_nid = sshkey_ecdsa_nid_from_name(k->hostkey_alg);
1.102 markus 791: return 0;
1.1 markus 792: }
793:
1.56 djm 794: static int
1.53 markus 795: proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
796: {
797: static int check[] = {
798: PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
799: };
800: int *idx;
801: char *p;
802:
803: for (idx = &check[0]; *idx != -1; idx++) {
804: if ((p = strchr(my[*idx], ',')) != NULL)
805: *p = '\0';
806: if ((p = strchr(peer[*idx], ',')) != NULL)
807: *p = '\0';
808: if (strcmp(my[*idx], peer[*idx]) != 0) {
809: debug2("proposal mismatch: my %s peer %s",
810: my[*idx], peer[*idx]);
811: return (0);
812: }
813: }
814: debug2("proposals match");
815: return (1);
816: }
817:
1.102 markus 818: static int
819: kex_choose_conf(struct ssh *ssh)
1.1 markus 820: {
1.102 markus 821: struct kex *kex = ssh->kex;
822: struct newkeys *newkeys;
823: char **my = NULL, **peer = NULL;
1.26 markus 824: char **cprop, **sprop;
1.27 markus 825: int nenc, nmac, ncomp;
1.96 dtucker 826: u_int mode, ctos, need, dh_need, authlen;
1.102 markus 827: int r, first_kex_follows;
1.1 markus 828:
1.110 djm 829: debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
830: if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
831: goto out;
832: debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
833: if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
1.102 markus 834: goto out;
1.26 markus 835:
1.27 markus 836: if (kex->server) {
1.26 markus 837: cprop=peer;
838: sprop=my;
839: } else {
840: cprop=my;
841: sprop=peer;
1.113 markus 842: }
843:
844: /* Check whether client supports ext_info_c */
1.142 djm 845: if (kex->server && (kex->flags & KEX_INITIAL)) {
1.113 markus 846: char *ext;
847:
848: ext = match_list("ext-info-c", peer[PROPOSAL_KEX_ALGS], NULL);
1.119 markus 849: kex->ext_info_c = (ext != NULL);
850: free(ext);
1.26 markus 851: }
1.1 markus 852:
1.30 markus 853: /* Algorithm Negotiation */
1.110 djm 854: if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
855: sprop[PROPOSAL_KEX_ALGS])) != 0) {
856: kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
857: peer[PROPOSAL_KEX_ALGS] = NULL;
858: goto out;
859: }
860: if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
861: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
862: kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
863: peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
864: goto out;
865: }
1.1 markus 866: for (mode = 0; mode < MODE_MAX; mode++) {
1.102 markus 867: if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
868: r = SSH_ERR_ALLOC_FAIL;
869: goto out;
870: }
1.30 markus 871: kex->newkeys[mode] = newkeys;
1.78 djm 872: ctos = (!kex->server && mode == MODE_OUT) ||
873: (kex->server && mode == MODE_IN);
1.1 markus 874: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
875: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
876: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.102 markus 877: if ((r = choose_enc(&newkeys->enc, cprop[nenc],
1.107 djm 878: sprop[nenc])) != 0) {
879: kex->failed_choice = peer[nenc];
880: peer[nenc] = NULL;
1.102 markus 881: goto out;
1.107 djm 882: }
1.102 markus 883: authlen = cipher_authlen(newkeys->enc.cipher);
1.88 markus 884: /* ignore mac for authenticated encryption */
1.102 markus 885: if (authlen == 0 &&
886: (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
1.107 djm 887: sprop[nmac])) != 0) {
888: kex->failed_choice = peer[nmac];
889: peer[nmac] = NULL;
1.102 markus 890: goto out;
1.107 djm 891: }
1.102 markus 892: if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
1.107 djm 893: sprop[ncomp])) != 0) {
894: kex->failed_choice = peer[ncomp];
895: peer[ncomp] = NULL;
1.102 markus 896: goto out;
1.107 djm 897: }
1.110 djm 898: debug("kex: %s cipher: %s MAC: %s compression: %s",
1.1 markus 899: ctos ? "client->server" : "server->client",
1.27 markus 900: newkeys->enc.name,
1.88 markus 901: authlen == 0 ? newkeys->mac.name : "<implicit>",
1.27 markus 902: newkeys->comp.name);
1.107 djm 903: }
1.96 dtucker 904: need = dh_need = 0;
1.1 markus 905: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 906: newkeys = kex->newkeys[mode];
1.120 deraadt 907: need = MAXIMUM(need, newkeys->enc.key_len);
908: need = MAXIMUM(need, newkeys->enc.block_size);
909: need = MAXIMUM(need, newkeys->enc.iv_len);
910: need = MAXIMUM(need, newkeys->mac.key_len);
911: dh_need = MAXIMUM(dh_need, cipher_seclen(newkeys->enc.cipher));
912: dh_need = MAXIMUM(dh_need, newkeys->enc.block_size);
913: dh_need = MAXIMUM(dh_need, newkeys->enc.iv_len);
914: dh_need = MAXIMUM(dh_need, newkeys->mac.key_len);
1.1 markus 915: }
1.7 markus 916: /* XXX need runden? */
1.27 markus 917: kex->we_need = need;
1.96 dtucker 918: kex->dh_need = dh_need;
1.53 markus 919:
920: /* ignore the next message if the proposals do not match */
1.135 djm 921: if (first_kex_follows && !proposals_match(my, peer))
1.102 markus 922: ssh->dispatch_skip_packets = 1;
923: r = 0;
924: out:
1.26 markus 925: kex_prop_free(my);
926: kex_prop_free(peer);
1.102 markus 927: return r;
1.26 markus 928: }
929:
1.102 markus 930: static int
931: derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
932: const struct sshbuf *shared_secret, u_char **keyp)
1.26 markus 933: {
1.102 markus 934: struct kex *kex = ssh->kex;
935: struct ssh_digest_ctx *hashctx = NULL;
1.26 markus 936: char c = id;
1.61 djm 937: u_int have;
1.94 djm 938: size_t mdsz;
1.61 djm 939: u_char *digest;
1.102 markus 940: int r;
1.62 djm 941:
1.94 djm 942: if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
1.102 markus 943: return SSH_ERR_INVALID_ARGUMENT;
1.120 deraadt 944: if ((digest = calloc(1, ROUNDUP(need, mdsz))) == NULL) {
1.102 markus 945: r = SSH_ERR_ALLOC_FAIL;
946: goto out;
947: }
1.26 markus 948:
1.30 markus 949: /* K1 = HASH(K || H || "A" || session_id) */
1.102 markus 950: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
951: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 952: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
953: ssh_digest_update(hashctx, &c, 1) != 0 ||
954: ssh_digest_update(hashctx, kex->session_id,
1.102 markus 955: kex->session_id_len) != 0 ||
956: ssh_digest_final(hashctx, digest, mdsz) != 0) {
957: r = SSH_ERR_LIBCRYPTO_ERROR;
958: goto out;
959: }
1.94 djm 960: ssh_digest_free(hashctx);
1.102 markus 961: hashctx = NULL;
1.26 markus 962:
1.30 markus 963: /*
964: * expand key:
965: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
966: * Key = K1 || K2 || ... || Kn
967: */
1.26 markus 968: for (have = mdsz; need > have; have += mdsz) {
1.102 markus 969: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
970: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 971: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1.102 markus 972: ssh_digest_update(hashctx, digest, have) != 0 ||
973: ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
974: r = SSH_ERR_LIBCRYPTO_ERROR;
975: goto out;
976: }
1.94 djm 977: ssh_digest_free(hashctx);
1.102 markus 978: hashctx = NULL;
1.26 markus 979: }
980: #ifdef DEBUG_KEX
981: fprintf(stderr, "key '%c'== ", c);
982: dump_digest("key", digest, need);
983: #endif
1.102 markus 984: *keyp = digest;
985: digest = NULL;
986: r = 0;
987: out:
1.114 mmcc 988: free(digest);
1.102 markus 989: ssh_digest_free(hashctx);
990: return r;
1.1 markus 991: }
992:
1.23 markus 993: #define NKEYS 6
1.102 markus 994: int
995: kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
996: const struct sshbuf *shared_secret)
1.1 markus 997: {
1.102 markus 998: struct kex *kex = ssh->kex;
1.15 markus 999: u_char *keys[NKEYS];
1.102 markus 1000: u_int i, j, mode, ctos;
1001: int r;
1.1 markus 1002:
1.144 djm 1003: /* save initial hash as session id */
1004: if (kex->session_id == NULL) {
1005: kex->session_id_len = hashlen;
1006: kex->session_id = malloc(kex->session_id_len);
1007: if (kex->session_id == NULL)
1008: return SSH_ERR_ALLOC_FAIL;
1009: memcpy(kex->session_id, hash, kex->session_id_len);
1010: }
1.65 djm 1011: for (i = 0; i < NKEYS; i++) {
1.102 markus 1012: if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
1013: shared_secret, &keys[i])) != 0) {
1014: for (j = 0; j < i; j++)
1015: free(keys[j]);
1016: return r;
1017: }
1.65 djm 1018: }
1.1 markus 1019: for (mode = 0; mode < MODE_MAX; mode++) {
1.69 deraadt 1020: ctos = (!kex->server && mode == MODE_OUT) ||
1021: (kex->server && mode == MODE_IN);
1.100 markus 1022: kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
1023: kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
1024: kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
1.1 markus 1025: }
1.102 markus 1026: return 0;
1.95 djm 1027: }
1.57 djm 1028:
1.145 djm 1029: int
1.150 djm 1030: kex_load_hostkey(struct ssh *ssh, struct sshkey **prvp, struct sshkey **pubp)
1.145 djm 1031: {
1032: struct kex *kex = ssh->kex;
1033:
1034: *pubp = NULL;
1035: *prvp = NULL;
1036: if (kex->load_host_public_key == NULL ||
1037: kex->load_host_private_key == NULL)
1038: return SSH_ERR_INVALID_ARGUMENT;
1039: *pubp = kex->load_host_public_key(kex->hostkey_type,
1040: kex->hostkey_nid, ssh);
1041: *prvp = kex->load_host_private_key(kex->hostkey_type,
1042: kex->hostkey_nid, ssh);
1043: if (*pubp == NULL)
1044: return SSH_ERR_NO_HOSTKEY_LOADED;
1.146 djm 1045: return 0;
1046: }
1047:
1048: int
1049: kex_verify_host_key(struct ssh *ssh, struct sshkey *server_host_key)
1050: {
1051: struct kex *kex = ssh->kex;
1052:
1053: if (kex->verify_host_key == NULL)
1054: return SSH_ERR_INVALID_ARGUMENT;
1055: if (server_host_key->type != kex->hostkey_type ||
1056: (kex->hostkey_type == KEY_ECDSA &&
1057: server_host_key->ecdsa_nid != kex->hostkey_nid))
1058: return SSH_ERR_KEY_TYPE_MISMATCH;
1059: if (kex->verify_host_key(server_host_key, ssh) == -1)
1060: return SSH_ERR_SIGNATURE_INVALID;
1.145 djm 1061: return 0;
1062: }
1.26 markus 1063:
1.84 djm 1064: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1.26 markus 1065: void
1.147 djm 1066: dump_digest(const char *msg, const u_char *digest, int len)
1.26 markus 1067: {
1068: fprintf(stderr, "%s\n", msg);
1.102 markus 1069: sshbuf_dump_data(digest, len, stderr);
1.26 markus 1070: }
1071: #endif
1.143 djm 1072:
1073: /*
1074: * Send a plaintext error message to the peer, suffixed by \r\n.
1075: * Only used during banner exchange, and there only for the server.
1076: */
1077: static void
1078: send_error(struct ssh *ssh, char *msg)
1079: {
1080: char *crnl = "\r\n";
1081:
1082: if (!ssh->kex->server)
1083: return;
1084:
1085: if (atomicio(vwrite, ssh_packet_get_connection_out(ssh),
1086: msg, strlen(msg)) != strlen(msg) ||
1087: atomicio(vwrite, ssh_packet_get_connection_out(ssh),
1088: crnl, strlen(crnl)) != strlen(crnl))
1089: error("%s: write: %.100s", __func__, strerror(errno));
1090: }
1091:
1092: /*
1093: * Sends our identification string and waits for the peer's. Will block for
1094: * up to timeout_ms (or indefinitely if timeout_ms <= 0).
1095: * Returns on 0 success or a ssherr.h code on failure.
1096: */
1097: int
1098: kex_exchange_identification(struct ssh *ssh, int timeout_ms,
1099: const char *version_addendum)
1100: {
1101: int remote_major, remote_minor, mismatch;
1102: size_t len, i, n;
1103: int r, expect_nl;
1104: u_char c;
1105: struct sshbuf *our_version = ssh->kex->server ?
1106: ssh->kex->server_version : ssh->kex->client_version;
1107: struct sshbuf *peer_version = ssh->kex->server ?
1108: ssh->kex->client_version : ssh->kex->server_version;
1109: char *our_version_string = NULL, *peer_version_string = NULL;
1110: char *cp, *remote_version = NULL;
1111:
1112: /* Prepare and send our banner */
1113: sshbuf_reset(our_version);
1114: if (version_addendum != NULL && *version_addendum == '\0')
1115: version_addendum = NULL;
1116: if ((r = sshbuf_putf(our_version, "SSH-%d.%d-%.100s%s%s\r\n",
1117: PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION,
1118: version_addendum == NULL ? "" : " ",
1119: version_addendum == NULL ? "" : version_addendum)) != 0) {
1120: error("%s: sshbuf_putf: %s", __func__, ssh_err(r));
1121: goto out;
1122: }
1123:
1124: if (atomicio(vwrite, ssh_packet_get_connection_out(ssh),
1125: sshbuf_mutable_ptr(our_version),
1126: sshbuf_len(our_version)) != sshbuf_len(our_version)) {
1127: error("%s: write: %.100s", __func__, strerror(errno));
1128: r = SSH_ERR_SYSTEM_ERROR;
1129: goto out;
1130: }
1131: if ((r = sshbuf_consume_end(our_version, 2)) != 0) { /* trim \r\n */
1132: error("%s: sshbuf_consume_end: %s", __func__, ssh_err(r));
1133: goto out;
1134: }
1135: our_version_string = sshbuf_dup_string(our_version);
1136: if (our_version_string == NULL) {
1137: error("%s: sshbuf_dup_string failed", __func__);
1138: r = SSH_ERR_ALLOC_FAIL;
1139: goto out;
1140: }
1141: debug("Local version string %.100s", our_version_string);
1142:
1143: /* Read other side's version identification. */
1144: for (n = 0; ; n++) {
1145: if (n >= SSH_MAX_PRE_BANNER_LINES) {
1146: send_error(ssh, "No SSH identification string "
1147: "received.");
1148: error("%s: No SSH version received in first %u lines "
1149: "from server", __func__, SSH_MAX_PRE_BANNER_LINES);
1150: r = SSH_ERR_INVALID_FORMAT;
1151: goto out;
1152: }
1153: sshbuf_reset(peer_version);
1154: expect_nl = 0;
1155: for (i = 0; ; i++) {
1156: if (timeout_ms > 0) {
1157: r = waitrfd(ssh_packet_get_connection_in(ssh),
1158: &timeout_ms);
1159: if (r == -1 && errno == ETIMEDOUT) {
1160: send_error(ssh, "Timed out waiting "
1161: "for SSH identification string.");
1162: error("Connection timed out during "
1163: "banner exchange");
1164: r = SSH_ERR_CONN_TIMEOUT;
1165: goto out;
1166: } else if (r == -1) {
1167: error("%s: %s",
1168: __func__, strerror(errno));
1169: r = SSH_ERR_SYSTEM_ERROR;
1170: goto out;
1171: }
1172: }
1173:
1174: len = atomicio(read, ssh_packet_get_connection_in(ssh),
1175: &c, 1);
1176: if (len != 1 && errno == EPIPE) {
1177: error("%s: Connection closed by remote host",
1178: __func__);
1179: r = SSH_ERR_CONN_CLOSED;
1180: goto out;
1181: } else if (len != 1) {
1182: error("%s: read: %.100s",
1183: __func__, strerror(errno));
1184: r = SSH_ERR_SYSTEM_ERROR;
1185: goto out;
1186: }
1187: if (c == '\r') {
1188: expect_nl = 1;
1189: continue;
1190: }
1191: if (c == '\n')
1192: break;
1193: if (c == '\0' || expect_nl) {
1194: error("%s: banner line contains invalid "
1195: "characters", __func__);
1196: goto invalid;
1197: }
1198: if ((r = sshbuf_put_u8(peer_version, c)) != 0) {
1199: error("%s: sshbuf_put: %s",
1200: __func__, ssh_err(r));
1201: goto out;
1202: }
1203: if (sshbuf_len(peer_version) > SSH_MAX_BANNER_LEN) {
1204: error("%s: banner line too long", __func__);
1205: goto invalid;
1206: }
1207: }
1208: /* Is this an actual protocol banner? */
1209: if (sshbuf_len(peer_version) > 4 &&
1210: memcmp(sshbuf_ptr(peer_version), "SSH-", 4) == 0)
1211: break;
1212: /* If not, then just log the line and continue */
1213: if ((cp = sshbuf_dup_string(peer_version)) == NULL) {
1214: error("%s: sshbuf_dup_string failed", __func__);
1215: r = SSH_ERR_ALLOC_FAIL;
1216: goto out;
1217: }
1218: /* Do not accept lines before the SSH ident from a client */
1219: if (ssh->kex->server) {
1220: error("%s: client sent invalid protocol identifier "
1221: "\"%.256s\"", __func__, cp);
1222: free(cp);
1223: goto invalid;
1224: }
1225: debug("%s: banner line %zu: %s", __func__, n, cp);
1226: free(cp);
1227: }
1228: peer_version_string = sshbuf_dup_string(peer_version);
1229: if (peer_version_string == NULL)
1230: error("%s: sshbuf_dup_string failed", __func__);
1231: /* XXX must be same size for sscanf */
1232: if ((remote_version = calloc(1, sshbuf_len(peer_version))) == NULL) {
1233: error("%s: calloc failed", __func__);
1234: r = SSH_ERR_ALLOC_FAIL;
1235: goto out;
1236: }
1237:
1238: /*
1239: * Check that the versions match. In future this might accept
1240: * several versions and set appropriate flags to handle them.
1241: */
1242: if (sscanf(peer_version_string, "SSH-%d.%d-%[^\n]\n",
1243: &remote_major, &remote_minor, remote_version) != 3) {
1244: error("Bad remote protocol version identification: '%.100s'",
1245: peer_version_string);
1246: invalid:
1247: send_error(ssh, "Invalid SSH identification string.");
1248: r = SSH_ERR_INVALID_FORMAT;
1249: goto out;
1250: }
1251: debug("Remote protocol version %d.%d, remote software version %.100s",
1252: remote_major, remote_minor, remote_version);
1253: ssh->compat = compat_datafellows(remote_version);
1254:
1255: mismatch = 0;
1256: switch (remote_major) {
1257: case 2:
1258: break;
1259: case 1:
1260: if (remote_minor != 99)
1261: mismatch = 1;
1262: break;
1263: default:
1264: mismatch = 1;
1265: break;
1266: }
1267: if (mismatch) {
1268: error("Protocol major versions differ: %d vs. %d",
1269: PROTOCOL_MAJOR_2, remote_major);
1270: send_error(ssh, "Protocol major versions differ.");
1271: r = SSH_ERR_NO_PROTOCOL_VERSION;
1272: goto out;
1273: }
1274:
1275: if (ssh->kex->server && (ssh->compat & SSH_BUG_PROBE) != 0) {
1276: logit("probed from %s port %d with %s. Don't panic.",
1277: ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
1278: peer_version_string);
1279: r = SSH_ERR_CONN_CLOSED; /* XXX */
1280: goto out;
1281: }
1282: if (ssh->kex->server && (ssh->compat & SSH_BUG_SCANNER) != 0) {
1283: logit("scanned from %s port %d with %s. Don't panic.",
1284: ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
1285: peer_version_string);
1286: r = SSH_ERR_CONN_CLOSED; /* XXX */
1287: goto out;
1288: }
1289: if ((ssh->compat & SSH_BUG_RSASIGMD5) != 0) {
1290: logit("Remote version \"%.100s\" uses unsafe RSA signature "
1291: "scheme; disabling use of RSA keys", remote_version);
1292: }
1293: /* success */
1294: r = 0;
1295: out:
1296: free(our_version_string);
1297: free(peer_version_string);
1298: free(remote_version);
1299: return r;
1300: }
1301:
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