Annotation of src/usr.bin/ssh/kex.c, Revision 1.183
1.183 ! djm 1: /* $OpenBSD: kex.c,v 1.182 2023/10/11 04:46:29 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"
1.176 dtucker 55: #include "myproposal.h"
1.102 markus 56:
57: #include "ssherr.h"
58: #include "sshbuf.h"
1.94 djm 59: #include "digest.h"
1.176 dtucker 60: #include "xmalloc.h"
1.48 provos 61:
1.35 itojun 62: /* prototype */
1.183 ! djm 63: static int kex_choose_conf(struct ssh *, uint32_t seq);
1.133 markus 64: static int kex_input_newkeys(int, u_int32_t, struct ssh *);
1.86 djm 65:
1.172 djm 66: static const char * const proposal_names[PROPOSAL_MAX] = {
1.110 djm 67: "KEX algorithms",
68: "host key algorithms",
69: "ciphers ctos",
70: "ciphers stoc",
71: "MACs ctos",
72: "MACs stoc",
73: "compression ctos",
74: "compression stoc",
75: "languages ctos",
76: "languages stoc",
77: };
78:
1.89 djm 79: struct kexalg {
80: char *name;
1.102 markus 81: u_int type;
1.89 djm 82: int ec_nid;
1.94 djm 83: int hash_alg;
1.89 djm 84: };
85: static const struct kexalg kexalgs[] = {
1.99 markus 86: #ifdef WITH_OPENSSL
1.94 djm 87: { KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },
1.118 djm 88: { KEX_DH14_SHA1, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 },
89: { KEX_DH14_SHA256, KEX_DH_GRP14_SHA256, 0, SSH_DIGEST_SHA256 },
90: { KEX_DH16_SHA512, KEX_DH_GRP16_SHA512, 0, SSH_DIGEST_SHA512 },
91: { KEX_DH18_SHA512, KEX_DH_GRP18_SHA512, 0, SSH_DIGEST_SHA512 },
1.94 djm 92: { KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 },
93: { KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 },
94: { KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2,
95: NID_X9_62_prime256v1, SSH_DIGEST_SHA256 },
96: { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1,
97: SSH_DIGEST_SHA384 },
98: { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1,
99: SSH_DIGEST_SHA512 },
1.99 markus 100: #endif
1.94 djm 101: { KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
1.124 djm 102: { KEX_CURVE25519_SHA256_OLD, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
1.163 djm 103: { KEX_SNTRUP761X25519_SHA512, KEX_KEM_SNTRUP761X25519_SHA512, 0,
1.147 djm 104: SSH_DIGEST_SHA512 },
1.155 dtucker 105: { NULL, 0, -1, -1},
1.89 djm 106: };
107:
108: char *
1.93 dtucker 109: kex_alg_list(char sep)
1.89 djm 110: {
1.102 markus 111: char *ret = NULL, *tmp;
1.89 djm 112: size_t nlen, rlen = 0;
113: const struct kexalg *k;
114:
115: for (k = kexalgs; k->name != NULL; k++) {
116: if (ret != NULL)
1.93 dtucker 117: ret[rlen++] = sep;
1.89 djm 118: nlen = strlen(k->name);
1.102 markus 119: if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
120: free(ret);
121: return NULL;
122: }
123: ret = tmp;
1.89 djm 124: memcpy(ret + rlen, k->name, nlen + 1);
125: rlen += nlen;
126: }
127: return ret;
128: }
129:
130: static const struct kexalg *
131: kex_alg_by_name(const char *name)
132: {
133: const struct kexalg *k;
134:
135: for (k = kexalgs; k->name != NULL; k++) {
136: if (strcmp(k->name, name) == 0)
137: return k;
138: }
139: return NULL;
140: }
141:
1.86 djm 142: /* Validate KEX method name list */
143: int
144: kex_names_valid(const char *names)
145: {
146: char *s, *cp, *p;
147:
148: if (names == NULL || strcmp(names, "") == 0)
149: return 0;
1.102 markus 150: if ((s = cp = strdup(names)) == NULL)
151: return 0;
1.86 djm 152: for ((p = strsep(&cp, ",")); p && *p != '\0';
153: (p = strsep(&cp, ","))) {
1.89 djm 154: if (kex_alg_by_name(p) == NULL) {
1.86 djm 155: error("Unsupported KEX algorithm \"%.100s\"", p);
1.91 djm 156: free(s);
1.86 djm 157: return 0;
158: }
159: }
160: debug3("kex names ok: [%s]", names);
1.91 djm 161: free(s);
1.86 djm 162: return 1;
1.109 djm 163: }
164:
1.183 ! djm 165: /* returns non-zero if proposal contains any algorithm from algs */
! 166: static int
! 167: has_any_alg(const char *proposal, const char *algs)
! 168: {
! 169: char *cp;
! 170:
! 171: if ((cp = match_list(proposal, algs, NULL)) == NULL)
! 172: return 0;
! 173: free(cp);
! 174: return 1;
! 175: }
! 176:
1.109 djm 177: /*
178: * Concatenate algorithm names, avoiding duplicates in the process.
179: * Caller must free returned string.
180: */
181: char *
182: kex_names_cat(const char *a, const char *b)
183: {
1.183 ! djm 184: char *ret = NULL, *tmp = NULL, *cp, *p;
1.109 djm 185: size_t len;
186:
187: if (a == NULL || *a == '\0')
1.138 djm 188: return strdup(b);
1.109 djm 189: if (b == NULL || *b == '\0')
190: return strdup(a);
191: if (strlen(b) > 1024*1024)
192: return NULL;
193: len = strlen(a) + strlen(b) + 2;
194: if ((tmp = cp = strdup(b)) == NULL ||
195: (ret = calloc(1, len)) == NULL) {
196: free(tmp);
197: return NULL;
198: }
199: strlcpy(ret, a, len);
200: for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) {
1.183 ! djm 201: if (has_any_alg(ret, p))
1.109 djm 202: continue; /* Algorithm already present */
203: if (strlcat(ret, ",", len) >= len ||
204: strlcat(ret, p, len) >= len) {
205: free(tmp);
206: free(ret);
207: return NULL; /* Shouldn't happen */
208: }
209: }
210: free(tmp);
211: return ret;
212: }
213:
214: /*
215: * Assemble a list of algorithms from a default list and a string from a
216: * configuration file. The user-provided string may begin with '+' to
1.154 naddy 217: * indicate that it should be appended to the default, '-' that the
218: * specified names should be removed, or '^' that they should be placed
219: * at the head.
1.109 djm 220: */
221: int
1.138 djm 222: kex_assemble_names(char **listp, const char *def, const char *all)
1.109 djm 223: {
1.138 djm 224: char *cp, *tmp, *patterns;
225: char *list = NULL, *ret = NULL, *matching = NULL, *opatterns = NULL;
226: int r = SSH_ERR_INTERNAL_ERROR;
227:
1.153 djm 228: if (listp == NULL || def == NULL || all == NULL)
229: return SSH_ERR_INVALID_ARGUMENT;
230:
231: if (*listp == NULL || **listp == '\0') {
1.138 djm 232: if ((*listp = strdup(def)) == NULL)
233: return SSH_ERR_ALLOC_FAIL;
234: return 0;
235: }
1.109 djm 236:
1.138 djm 237: list = *listp;
238: *listp = NULL;
239: if (*list == '+') {
240: /* Append names to default list */
241: if ((tmp = kex_names_cat(def, list + 1)) == NULL) {
242: r = SSH_ERR_ALLOC_FAIL;
243: goto fail;
244: }
245: free(list);
246: list = tmp;
247: } else if (*list == '-') {
248: /* Remove names from default list */
1.159 djm 249: if ((*listp = match_filter_denylist(def, list + 1)) == NULL) {
1.138 djm 250: r = SSH_ERR_ALLOC_FAIL;
251: goto fail;
252: }
253: free(list);
254: /* filtering has already been done */
1.109 djm 255: return 0;
1.154 naddy 256: } else if (*list == '^') {
257: /* Place names at head of default list */
258: if ((tmp = kex_names_cat(list + 1, def)) == NULL) {
259: r = SSH_ERR_ALLOC_FAIL;
260: goto fail;
261: }
262: free(list);
263: list = tmp;
1.138 djm 264: } else {
265: /* Explicit list, overrides default - just use "list" as is */
266: }
267:
268: /*
269: * The supplied names may be a pattern-list. For the -list case,
270: * the patterns are applied above. For the +list and explicit list
271: * cases we need to do it now.
272: */
273: ret = NULL;
274: if ((patterns = opatterns = strdup(list)) == NULL) {
275: r = SSH_ERR_ALLOC_FAIL;
276: goto fail;
277: }
278: /* Apply positive (i.e. non-negated) patterns from the list */
279: while ((cp = strsep(&patterns, ",")) != NULL) {
280: if (*cp == '!') {
281: /* negated matches are not supported here */
282: r = SSH_ERR_INVALID_ARGUMENT;
283: goto fail;
284: }
285: free(matching);
1.159 djm 286: if ((matching = match_filter_allowlist(all, cp)) == NULL) {
1.138 djm 287: r = SSH_ERR_ALLOC_FAIL;
288: goto fail;
289: }
290: if ((tmp = kex_names_cat(ret, matching)) == NULL) {
291: r = SSH_ERR_ALLOC_FAIL;
292: goto fail;
293: }
294: free(ret);
295: ret = tmp;
1.109 djm 296: }
1.138 djm 297: if (ret == NULL || *ret == '\0') {
298: /* An empty name-list is an error */
299: /* XXX better error code? */
300: r = SSH_ERR_INVALID_ARGUMENT;
301: goto fail;
1.109 djm 302: }
303:
1.138 djm 304: /* success */
305: *listp = ret;
306: ret = NULL;
307: r = 0;
308:
309: fail:
310: free(matching);
311: free(opatterns);
312: free(list);
313: free(ret);
314: return r;
1.176 dtucker 315: }
316:
317: /*
318: * Fill out a proposal array with dynamically allocated values, which may
319: * be modified as required for compatibility reasons.
320: * Any of the options may be NULL, in which case the default is used.
321: * Array contents must be freed by calling kex_proposal_free_entries.
322: */
323: void
324: kex_proposal_populate_entries(struct ssh *ssh, char *prop[PROPOSAL_MAX],
325: const char *kexalgos, const char *ciphers, const char *macs,
326: const char *comp, const char *hkalgs)
327: {
328: const char *defpropserver[PROPOSAL_MAX] = { KEX_SERVER };
329: const char *defpropclient[PROPOSAL_MAX] = { KEX_CLIENT };
330: const char **defprop = ssh->kex->server ? defpropserver : defpropclient;
331: u_int i;
1.183 ! djm 332: char *cp;
1.176 dtucker 333:
334: if (prop == NULL)
335: fatal_f("proposal missing");
336:
1.183 ! djm 337: /* Append EXT_INFO signalling to KexAlgorithms */
! 338: if (kexalgos == NULL)
! 339: kexalgos = defprop[PROPOSAL_KEX_ALGS];
! 340: if ((cp = kex_names_cat(kexalgos, ssh->kex->server ?
! 341: "kex-strict-s-v00@openssh.com" :
! 342: "ext-info-c,kex-strict-c-v00@openssh.com")) == NULL)
! 343: fatal_f("kex_names_cat");
! 344:
1.176 dtucker 345: for (i = 0; i < PROPOSAL_MAX; i++) {
346: switch(i) {
347: case PROPOSAL_KEX_ALGS:
1.183 ! djm 348: prop[i] = compat_kex_proposal(ssh, cp);
1.176 dtucker 349: break;
350: case PROPOSAL_ENC_ALGS_CTOS:
351: case PROPOSAL_ENC_ALGS_STOC:
352: prop[i] = xstrdup(ciphers ? ciphers : defprop[i]);
353: break;
354: case PROPOSAL_MAC_ALGS_CTOS:
355: case PROPOSAL_MAC_ALGS_STOC:
356: prop[i] = xstrdup(macs ? macs : defprop[i]);
357: break;
358: case PROPOSAL_COMP_ALGS_CTOS:
359: case PROPOSAL_COMP_ALGS_STOC:
360: prop[i] = xstrdup(comp ? comp : defprop[i]);
361: break;
362: case PROPOSAL_SERVER_HOST_KEY_ALGS:
363: prop[i] = xstrdup(hkalgs ? hkalgs : defprop[i]);
364: break;
365: default:
366: prop[i] = xstrdup(defprop[i]);
367: }
368: }
1.183 ! djm 369: free(cp);
1.176 dtucker 370: }
371:
372: void
373: kex_proposal_free_entries(char *prop[PROPOSAL_MAX])
374: {
375: u_int i;
376:
377: for (i = 0; i < PROPOSAL_MAX; i++)
378: free(prop[i]);
1.86 djm 379: }
1.26 markus 380:
381: /* put algorithm proposal into buffer */
1.102 markus 382: int
383: kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
1.1 markus 384: {
1.61 djm 385: u_int i;
1.102 markus 386: int r;
387:
388: sshbuf_reset(b);
1.26 markus 389:
1.49 markus 390: /*
391: * add a dummy cookie, the cookie will be overwritten by
392: * kex_send_kexinit(), each time a kexinit is set
393: */
1.102 markus 394: for (i = 0; i < KEX_COOKIE_LEN; i++) {
395: if ((r = sshbuf_put_u8(b, 0)) != 0)
396: return r;
397: }
398: for (i = 0; i < PROPOSAL_MAX; i++) {
399: if ((r = sshbuf_put_cstring(b, proposal[i])) != 0)
400: return r;
401: }
402: if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */
403: (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */
404: return r;
405: return 0;
1.1 markus 406: }
407:
1.26 markus 408: /* parse buffer and return algorithm proposal */
1.102 markus 409: int
410: kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp)
1.7 markus 411: {
1.102 markus 412: struct sshbuf *b = NULL;
413: u_char v;
1.78 djm 414: u_int i;
1.102 markus 415: char **proposal = NULL;
416: int r;
1.7 markus 417:
1.102 markus 418: *propp = NULL;
419: if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL)
420: return SSH_ERR_ALLOC_FAIL;
421: if ((b = sshbuf_fromb(raw)) == NULL) {
422: r = SSH_ERR_ALLOC_FAIL;
423: goto out;
424: }
1.152 djm 425: if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) { /* skip cookie */
1.160 djm 426: error_fr(r, "consume cookie");
1.102 markus 427: goto out;
1.152 djm 428: }
1.7 markus 429: /* extract kex init proposal strings */
430: for (i = 0; i < PROPOSAL_MAX; i++) {
1.152 djm 431: if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0) {
1.160 djm 432: error_fr(r, "parse proposal %u", i);
1.102 markus 433: goto out;
1.152 djm 434: }
1.110 djm 435: debug2("%s: %s", proposal_names[i], proposal[i]);
1.7 markus 436: }
1.26 markus 437: /* first kex follows / reserved */
1.115 djm 438: if ((r = sshbuf_get_u8(b, &v)) != 0 || /* first_kex_follows */
1.152 djm 439: (r = sshbuf_get_u32(b, &i)) != 0) { /* reserved */
1.160 djm 440: error_fr(r, "parse");
1.102 markus 441: goto out;
1.152 djm 442: }
1.53 markus 443: if (first_kex_follows != NULL)
1.115 djm 444: *first_kex_follows = v;
1.110 djm 445: debug2("first_kex_follows %d ", v);
446: debug2("reserved %u ", i);
1.102 markus 447: r = 0;
448: *propp = proposal;
449: out:
450: if (r != 0 && proposal != NULL)
451: kex_prop_free(proposal);
452: sshbuf_free(b);
453: return r;
1.1 markus 454: }
455:
1.102 markus 456: void
1.26 markus 457: kex_prop_free(char **proposal)
1.1 markus 458: {
1.61 djm 459: u_int i;
1.26 markus 460:
1.106 djm 461: if (proposal == NULL)
462: return;
1.26 markus 463: for (i = 0; i < PROPOSAL_MAX; i++)
1.91 djm 464: free(proposal[i]);
465: free(proposal);
1.1 markus 466: }
467:
1.167 djm 468: int
1.133 markus 469: kex_protocol_error(int type, u_int32_t seq, struct ssh *ssh)
1.1 markus 470: {
1.112 djm 471: int r;
472:
1.183 ! djm 473: /* If in strict mode, any unexpected message is an error */
! 474: if ((ssh->kex->flags & KEX_INITIAL) && ssh->kex->kex_strict) {
! 475: ssh_packet_disconnect(ssh, "strict KEX violation: "
! 476: "unexpected packet type %u (seqnr %u)", type, seq);
! 477: }
! 478: error_f("type %u seq %u", type, seq);
1.112 djm 479: if ((r = sshpkt_start(ssh, SSH2_MSG_UNIMPLEMENTED)) != 0 ||
480: (r = sshpkt_put_u32(ssh, seq)) != 0 ||
481: (r = sshpkt_send(ssh)) != 0)
482: return r;
1.101 markus 483: return 0;
1.26 markus 484: }
1.1 markus 485:
1.35 itojun 486: static void
1.102 markus 487: kex_reset_dispatch(struct ssh *ssh)
1.29 markus 488: {
1.102 markus 489: ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
1.42 markus 490: SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
1.29 markus 491: }
492:
1.113 markus 493: static int
494: kex_send_ext_info(struct ssh *ssh)
495: {
496: int r;
1.121 djm 497: char *algs;
1.113 markus 498:
1.151 djm 499: debug("Sending SSH2_MSG_EXT_INFO");
1.130 djm 500: if ((algs = sshkey_alg_list(0, 1, 1, ',')) == NULL)
1.121 djm 501: return SSH_ERR_ALLOC_FAIL;
1.137 djm 502: /* XXX filter algs list by allowed pubkey/hostbased types */
1.113 markus 503: if ((r = sshpkt_start(ssh, SSH2_MSG_EXT_INFO)) != 0 ||
1.181 djm 504: (r = sshpkt_put_u32(ssh, 3)) != 0 ||
1.113 markus 505: (r = sshpkt_put_cstring(ssh, "server-sig-algs")) != 0 ||
1.121 djm 506: (r = sshpkt_put_cstring(ssh, algs)) != 0 ||
1.170 djm 507: (r = sshpkt_put_cstring(ssh,
508: "publickey-hostbound@openssh.com")) != 0 ||
509: (r = sshpkt_put_cstring(ssh, "0")) != 0 ||
1.181 djm 510: (r = sshpkt_put_cstring(ssh, "ping@openssh.com")) != 0 ||
511: (r = sshpkt_put_cstring(ssh, "0")) != 0 ||
1.152 djm 512: (r = sshpkt_send(ssh)) != 0) {
1.160 djm 513: error_fr(r, "compose");
1.121 djm 514: goto out;
1.152 djm 515: }
1.121 djm 516: /* success */
517: r = 0;
518: out:
519: free(algs);
1.123 djm 520: return r;
1.113 markus 521: }
522:
1.102 markus 523: int
524: kex_send_newkeys(struct ssh *ssh)
1.26 markus 525: {
1.102 markus 526: int r;
1.28 markus 527:
1.102 markus 528: kex_reset_dispatch(ssh);
529: if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
530: (r = sshpkt_send(ssh)) != 0)
531: return r;
1.26 markus 532: debug("SSH2_MSG_NEWKEYS sent");
1.102 markus 533: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
1.151 djm 534: if (ssh->kex->ext_info_c && (ssh->kex->flags & KEX_INITIAL) != 0)
1.113 markus 535: if ((r = kex_send_ext_info(ssh)) != 0)
536: return r;
1.151 djm 537: debug("expecting SSH2_MSG_NEWKEYS");
1.102 markus 538: return 0;
539: }
540:
1.181 djm 541: /* Check whether an ext_info value contains the expected version string */
542: static int
543: kex_ext_info_check_ver(struct kex *kex, const char *name,
544: const u_char *val, size_t len, const char *want_ver, u_int flag)
545: {
546: if (memchr(val, '\0', len) != NULL) {
547: error("SSH2_MSG_EXT_INFO: %s value contains nul byte", name);
548: return SSH_ERR_INVALID_FORMAT;
549: }
550: debug_f("%s=<%s>", name, val);
551: if (strcmp(val, want_ver) == 0)
552: kex->flags |= flag;
553: else
554: debug_f("unsupported version of %s extension", name);
555: return 0;
556: }
557:
1.113 markus 558: int
1.133 markus 559: kex_input_ext_info(int type, u_int32_t seq, struct ssh *ssh)
1.113 markus 560: {
561: struct kex *kex = ssh->kex;
562: u_int32_t i, ninfo;
1.137 djm 563: char *name;
1.134 djm 564: u_char *val;
565: size_t vlen;
1.113 markus 566: int r;
567:
568: debug("SSH2_MSG_EXT_INFO received");
569: ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_protocol_error);
570: if ((r = sshpkt_get_u32(ssh, &ninfo)) != 0)
571: return r;
1.178 dtucker 572: if (ninfo >= 1024) {
573: error("SSH2_MSG_EXT_INFO with too many entries, expected "
574: "<=1024, received %u", ninfo);
1.183 ! djm 575: return dispatch_protocol_error(type, seq, ssh);
1.178 dtucker 576: }
1.113 markus 577: for (i = 0; i < ninfo; i++) {
578: if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0)
579: return r;
1.134 djm 580: if ((r = sshpkt_get_string(ssh, &val, &vlen)) != 0) {
1.113 markus 581: free(name);
582: return r;
583: }
584: if (strcmp(name, "server-sig-algs") == 0) {
1.134 djm 585: /* Ensure no \0 lurking in value */
586: if (memchr(val, '\0', vlen) != NULL) {
1.160 djm 587: error_f("nul byte in %s", name);
1.181 djm 588: free(name);
589: free(val);
1.134 djm 590: return SSH_ERR_INVALID_FORMAT;
591: }
1.160 djm 592: debug_f("%s=<%s>", name, val);
1.137 djm 593: kex->server_sig_algs = val;
594: val = NULL;
1.170 djm 595: } else if (strcmp(name,
596: "publickey-hostbound@openssh.com") == 0) {
1.181 djm 597: if ((r = kex_ext_info_check_ver(kex, name, val, vlen,
598: "0", KEX_HAS_PUBKEY_HOSTBOUND)) != 0) {
599: free(name);
600: free(val);
601: return r;
1.170 djm 602: }
1.181 djm 603: } else if (strcmp(name, "ping@openssh.com") == 0) {
604: if ((r = kex_ext_info_check_ver(kex, name, val, vlen,
605: "0", KEX_HAS_PING)) != 0) {
606: free(name);
607: free(val);
608: return r;
1.170 djm 609: }
1.134 djm 610: } else
1.160 djm 611: debug_f("%s (unrecognised)", name);
1.113 markus 612: free(name);
613: free(val);
614: }
615: return sshpkt_get_end(ssh);
616: }
617:
1.102 markus 618: static int
1.133 markus 619: kex_input_newkeys(int type, u_int32_t seq, struct ssh *ssh)
1.102 markus 620: {
621: struct kex *kex = ssh->kex;
622: int r;
1.19 stevesk 623:
1.26 markus 624: debug("SSH2_MSG_NEWKEYS received");
1.102 markus 625: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
1.131 markus 626: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.102 markus 627: if ((r = sshpkt_get_end(ssh)) != 0)
1.122 markus 628: return r;
629: if ((r = ssh_set_newkeys(ssh, MODE_IN)) != 0)
1.102 markus 630: return r;
1.30 markus 631: kex->done = 1;
1.142 djm 632: kex->flags &= ~KEX_INITIAL;
1.102 markus 633: sshbuf_reset(kex->peer);
634: /* sshbuf_reset(kex->my); */
1.26 markus 635: kex->flags &= ~KEX_INIT_SENT;
1.91 djm 636: free(kex->name);
1.32 markus 637: kex->name = NULL;
1.102 markus 638: return 0;
1.26 markus 639: }
1.1 markus 640:
1.102 markus 641: int
642: kex_send_kexinit(struct ssh *ssh)
1.26 markus 643: {
1.49 markus 644: u_char *cookie;
1.102 markus 645: struct kex *kex = ssh->kex;
646: int r;
1.49 markus 647:
1.152 djm 648: if (kex == NULL) {
1.161 djm 649: error_f("no kex");
1.102 markus 650: return SSH_ERR_INTERNAL_ERROR;
1.152 djm 651: }
1.102 markus 652: if (kex->flags & KEX_INIT_SENT)
653: return 0;
1.30 markus 654: kex->done = 0;
1.49 markus 655:
656: /* generate a random cookie */
1.152 djm 657: if (sshbuf_len(kex->my) < KEX_COOKIE_LEN) {
1.160 djm 658: error_f("bad kex length: %zu < %d",
1.152 djm 659: sshbuf_len(kex->my), KEX_COOKIE_LEN);
1.102 markus 660: return SSH_ERR_INVALID_FORMAT;
1.152 djm 661: }
662: if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL) {
1.160 djm 663: error_f("buffer error");
1.102 markus 664: return SSH_ERR_INTERNAL_ERROR;
1.152 djm 665: }
1.102 markus 666: arc4random_buf(cookie, KEX_COOKIE_LEN);
667:
668: if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
669: (r = sshpkt_putb(ssh, kex->my)) != 0 ||
1.152 djm 670: (r = sshpkt_send(ssh)) != 0) {
1.160 djm 671: error_fr(r, "compose reply");
1.102 markus 672: return r;
1.152 djm 673: }
1.26 markus 674: debug("SSH2_MSG_KEXINIT sent");
675: kex->flags |= KEX_INIT_SENT;
1.102 markus 676: return 0;
1.1 markus 677: }
678:
1.101 markus 679: int
1.133 markus 680: kex_input_kexinit(int type, u_int32_t seq, struct ssh *ssh)
1.11 provos 681: {
1.102 markus 682: struct kex *kex = ssh->kex;
683: const u_char *ptr;
1.100 markus 684: u_int i;
685: size_t dlen;
1.102 markus 686: int r;
1.11 provos 687:
1.26 markus 688: debug("SSH2_MSG_KEXINIT received");
1.152 djm 689: if (kex == NULL) {
1.161 djm 690: error_f("no kex");
1.152 djm 691: return SSH_ERR_INTERNAL_ERROR;
692: }
1.183 ! djm 693: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_protocol_error);
1.102 markus 694: ptr = sshpkt_ptr(ssh, &dlen);
695: if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
696: return r;
1.31 markus 697:
698: /* discard packet */
1.152 djm 699: for (i = 0; i < KEX_COOKIE_LEN; i++) {
700: if ((r = sshpkt_get_u8(ssh, NULL)) != 0) {
1.160 djm 701: error_fr(r, "discard cookie");
1.102 markus 702: return r;
1.152 djm 703: }
704: }
705: for (i = 0; i < PROPOSAL_MAX; i++) {
706: if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0) {
1.160 djm 707: error_fr(r, "discard proposal");
1.102 markus 708: return r;
1.152 djm 709: }
710: }
1.87 djm 711: /*
712: * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
713: * KEX method has the server move first, but a server might be using
714: * a custom method or one that we otherwise don't support. We should
715: * be prepared to remember first_kex_follows here so we can eat a
716: * packet later.
717: * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
718: * for cases where the server *doesn't* go first. I guess we should
719: * ignore it when it is set for these cases, which is what we do now.
720: */
1.102 markus 721: if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
722: (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
723: (r = sshpkt_get_end(ssh)) != 0)
724: return r;
725:
726: if (!(kex->flags & KEX_INIT_SENT))
727: if ((r = kex_send_kexinit(ssh)) != 0)
728: return r;
1.183 ! djm 729: if ((r = kex_choose_conf(ssh, seq)) != 0)
1.102 markus 730: return r;
1.19 stevesk 731:
1.102 markus 732: if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
733: return (kex->kex[kex->kex_type])(ssh);
734:
1.160 djm 735: error_f("unknown kex type %u", kex->kex_type);
1.102 markus 736: return SSH_ERR_INTERNAL_ERROR;
737: }
738:
1.143 djm 739: struct kex *
740: kex_new(void)
1.102 markus 741: {
742: struct kex *kex;
743:
1.143 djm 744: if ((kex = calloc(1, sizeof(*kex))) == NULL ||
745: (kex->peer = sshbuf_new()) == NULL ||
746: (kex->my = sshbuf_new()) == NULL ||
747: (kex->client_version = sshbuf_new()) == NULL ||
1.165 djm 748: (kex->server_version = sshbuf_new()) == NULL ||
749: (kex->session_id = sshbuf_new()) == NULL) {
1.143 djm 750: kex_free(kex);
751: return NULL;
1.102 markus 752: }
1.143 djm 753: return kex;
1.26 markus 754: }
1.11 provos 755:
1.100 markus 756: void
757: kex_free_newkeys(struct newkeys *newkeys)
758: {
759: if (newkeys == NULL)
760: return;
761: if (newkeys->enc.key) {
762: explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
763: free(newkeys->enc.key);
764: newkeys->enc.key = NULL;
765: }
766: if (newkeys->enc.iv) {
1.111 djm 767: explicit_bzero(newkeys->enc.iv, newkeys->enc.iv_len);
1.100 markus 768: free(newkeys->enc.iv);
769: newkeys->enc.iv = NULL;
770: }
771: free(newkeys->enc.name);
772: explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
773: free(newkeys->comp.name);
774: explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
775: mac_clear(&newkeys->mac);
776: if (newkeys->mac.key) {
777: explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
778: free(newkeys->mac.key);
779: newkeys->mac.key = NULL;
780: }
781: free(newkeys->mac.name);
782: explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
1.157 jsg 783: freezero(newkeys, sizeof(*newkeys));
1.100 markus 784: }
785:
1.102 markus 786: void
787: kex_free(struct kex *kex)
1.26 markus 788: {
1.102 markus 789: u_int mode;
1.11 provos 790:
1.143 djm 791: if (kex == NULL)
792: return;
793:
1.102 markus 794: #ifdef WITH_OPENSSL
1.136 jsing 795: DH_free(kex->dh);
796: EC_KEY_free(kex->ec_client_key);
1.102 markus 797: #endif
798: for (mode = 0; mode < MODE_MAX; mode++) {
799: kex_free_newkeys(kex->newkeys[mode]);
800: kex->newkeys[mode] = NULL;
1.100 markus 801: }
1.102 markus 802: sshbuf_free(kex->peer);
803: sshbuf_free(kex->my);
1.143 djm 804: sshbuf_free(kex->client_version);
805: sshbuf_free(kex->server_version);
1.149 djm 806: sshbuf_free(kex->client_pub);
1.165 djm 807: sshbuf_free(kex->session_id);
1.169 djm 808: sshbuf_free(kex->initial_sig);
809: sshkey_free(kex->initial_hostkey);
1.107 djm 810: free(kex->failed_choice);
1.113 markus 811: free(kex->hostkey_alg);
812: free(kex->name);
1.102 markus 813: free(kex);
1.11 provos 814: }
815:
1.102 markus 816: int
1.143 djm 817: kex_ready(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
818: {
819: int r;
820:
821: if ((r = kex_prop2buf(ssh->kex->my, proposal)) != 0)
822: return r;
823: ssh->kex->flags = KEX_INITIAL;
824: kex_reset_dispatch(ssh);
825: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
826: return 0;
827: }
828:
829: int
1.102 markus 830: kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
1.1 markus 831: {
1.102 markus 832: int r;
1.1 markus 833:
1.143 djm 834: if ((r = kex_ready(ssh, proposal)) != 0)
1.102 markus 835: return r;
836: if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
837: kex_free(ssh->kex);
838: ssh->kex = NULL;
839: return r;
1.1 markus 840: }
1.102 markus 841: return 0;
1.117 djm 842: }
843:
844: /*
845: * Request key re-exchange, returns 0 on success or a ssherr.h error
846: * code otherwise. Must not be called if KEX is incomplete or in-progress.
847: */
848: int
849: kex_start_rekex(struct ssh *ssh)
850: {
851: if (ssh->kex == NULL) {
1.160 djm 852: error_f("no kex");
1.117 djm 853: return SSH_ERR_INTERNAL_ERROR;
854: }
855: if (ssh->kex->done == 0) {
1.160 djm 856: error_f("requested twice");
1.117 djm 857: return SSH_ERR_INTERNAL_ERROR;
858: }
859: ssh->kex->done = 0;
860: return kex_send_kexinit(ssh);
1.1 markus 861: }
862:
1.102 markus 863: static int
864: choose_enc(struct sshenc *enc, char *client, char *server)
1.1 markus 865: {
1.23 markus 866: char *name = match_list(client, server, NULL);
1.102 markus 867:
1.1 markus 868: if (name == NULL)
1.102 markus 869: return SSH_ERR_NO_CIPHER_ALG_MATCH;
1.129 dtucker 870: if ((enc->cipher = cipher_by_name(name)) == NULL) {
1.160 djm 871: error_f("unsupported cipher %s", name);
1.129 dtucker 872: free(name);
1.102 markus 873: return SSH_ERR_INTERNAL_ERROR;
1.129 dtucker 874: }
1.1 markus 875: enc->name = name;
876: enc->enabled = 0;
877: enc->iv = NULL;
1.88 markus 878: enc->iv_len = cipher_ivlen(enc->cipher);
1.1 markus 879: enc->key = NULL;
1.45 markus 880: enc->key_len = cipher_keylen(enc->cipher);
881: enc->block_size = cipher_blocksize(enc->cipher);
1.102 markus 882: return 0;
1.1 markus 883: }
1.69 deraadt 884:
1.102 markus 885: static int
886: choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
1.1 markus 887: {
1.23 markus 888: char *name = match_list(client, server, NULL);
1.102 markus 889:
1.1 markus 890: if (name == NULL)
1.102 markus 891: return SSH_ERR_NO_MAC_ALG_MATCH;
1.129 dtucker 892: if (mac_setup(mac, name) < 0) {
1.160 djm 893: error_f("unsupported MAC %s", name);
1.129 dtucker 894: free(name);
1.102 markus 895: return SSH_ERR_INTERNAL_ERROR;
1.129 dtucker 896: }
1.1 markus 897: mac->name = name;
898: mac->key = NULL;
899: mac->enabled = 0;
1.102 markus 900: return 0;
1.1 markus 901: }
1.69 deraadt 902:
1.102 markus 903: static int
904: choose_comp(struct sshcomp *comp, char *client, char *server)
1.1 markus 905: {
1.23 markus 906: char *name = match_list(client, server, NULL);
1.102 markus 907:
1.1 markus 908: if (name == NULL)
1.102 markus 909: return SSH_ERR_NO_COMPRESS_ALG_MATCH;
1.156 dtucker 910: #ifdef WITH_ZLIB
1.64 markus 911: if (strcmp(name, "zlib@openssh.com") == 0) {
1.141 sf 912: comp->type = COMP_DELAYED;
913: } else if (strcmp(name, "zlib") == 0) {
1.140 sf 914: comp->type = COMP_ZLIB;
1.156 dtucker 915: } else
916: #endif /* WITH_ZLIB */
917: if (strcmp(name, "none") == 0) {
1.64 markus 918: comp->type = COMP_NONE;
1.1 markus 919: } else {
1.160 djm 920: error_f("unsupported compression scheme %s", name);
1.129 dtucker 921: free(name);
1.102 markus 922: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 923: }
924: comp->name = name;
1.102 markus 925: return 0;
1.1 markus 926: }
1.69 deraadt 927:
1.102 markus 928: static int
929: choose_kex(struct kex *k, char *client, char *server)
1.1 markus 930: {
1.89 djm 931: const struct kexalg *kexalg;
932:
1.23 markus 933: k->name = match_list(client, server, NULL);
1.102 markus 934:
1.110 djm 935: debug("kex: algorithm: %s", k->name ? k->name : "(no match)");
1.1 markus 936: if (k->name == NULL)
1.102 markus 937: return SSH_ERR_NO_KEX_ALG_MATCH;
1.152 djm 938: if ((kexalg = kex_alg_by_name(k->name)) == NULL) {
1.160 djm 939: error_f("unsupported KEX method %s", k->name);
1.102 markus 940: return SSH_ERR_INTERNAL_ERROR;
1.152 djm 941: }
1.89 djm 942: k->kex_type = kexalg->type;
1.94 djm 943: k->hash_alg = kexalg->hash_alg;
1.89 djm 944: k->ec_nid = kexalg->ec_nid;
1.102 markus 945: return 0;
1.1 markus 946: }
1.65 djm 947:
1.102 markus 948: static int
949: choose_hostkeyalg(struct kex *k, char *client, char *server)
1.1 markus 950: {
1.162 djm 951: free(k->hostkey_alg);
1.113 markus 952: k->hostkey_alg = match_list(client, server, NULL);
1.102 markus 953:
1.110 djm 954: debug("kex: host key algorithm: %s",
1.113 markus 955: k->hostkey_alg ? k->hostkey_alg : "(no match)");
956: if (k->hostkey_alg == NULL)
1.102 markus 957: return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
1.113 markus 958: k->hostkey_type = sshkey_type_from_name(k->hostkey_alg);
1.152 djm 959: if (k->hostkey_type == KEY_UNSPEC) {
1.160 djm 960: error_f("unsupported hostkey algorithm %s", k->hostkey_alg);
1.102 markus 961: return SSH_ERR_INTERNAL_ERROR;
1.152 djm 962: }
1.113 markus 963: k->hostkey_nid = sshkey_ecdsa_nid_from_name(k->hostkey_alg);
1.102 markus 964: return 0;
1.1 markus 965: }
966:
1.56 djm 967: static int
1.53 markus 968: proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
969: {
970: static int check[] = {
971: PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
972: };
973: int *idx;
974: char *p;
975:
976: for (idx = &check[0]; *idx != -1; idx++) {
977: if ((p = strchr(my[*idx], ',')) != NULL)
978: *p = '\0';
979: if ((p = strchr(peer[*idx], ',')) != NULL)
980: *p = '\0';
981: if (strcmp(my[*idx], peer[*idx]) != 0) {
982: debug2("proposal mismatch: my %s peer %s",
983: my[*idx], peer[*idx]);
984: return (0);
985: }
986: }
987: debug2("proposals match");
988: return (1);
989: }
990:
1.171 djm 991: static int
1.183 ! djm 992: kexalgs_contains(char **peer, const char *ext)
1.171 djm 993: {
1.183 ! djm 994: return has_any_alg(peer[PROPOSAL_KEX_ALGS], ext);
1.171 djm 995: }
996:
1.102 markus 997: static int
1.183 ! djm 998: kex_choose_conf(struct ssh *ssh, uint32_t seq)
1.1 markus 999: {
1.102 markus 1000: struct kex *kex = ssh->kex;
1001: struct newkeys *newkeys;
1002: char **my = NULL, **peer = NULL;
1.26 markus 1003: char **cprop, **sprop;
1.27 markus 1004: int nenc, nmac, ncomp;
1.96 dtucker 1005: u_int mode, ctos, need, dh_need, authlen;
1.102 markus 1006: int r, first_kex_follows;
1.1 markus 1007:
1.110 djm 1008: debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
1009: if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
1010: goto out;
1011: debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
1012: if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
1.102 markus 1013: goto out;
1.26 markus 1014:
1.27 markus 1015: if (kex->server) {
1.26 markus 1016: cprop=peer;
1017: sprop=my;
1018: } else {
1019: cprop=my;
1020: sprop=peer;
1.113 markus 1021: }
1022:
1.183 ! djm 1023: /* Check whether peer supports ext_info/kex_strict */
! 1024: if ((kex->flags & KEX_INITIAL) != 0) {
! 1025: if (kex->server) {
! 1026: kex->ext_info_c = kexalgs_contains(peer, "ext-info-c");
! 1027: kex->kex_strict = kexalgs_contains(peer,
! 1028: "kex-strict-c-v00@openssh.com");
! 1029: } else {
! 1030: kex->kex_strict = kexalgs_contains(peer,
! 1031: "kex-strict-s-v00@openssh.com");
! 1032: }
! 1033: if (kex->kex_strict) {
! 1034: debug3_f("will use strict KEX ordering");
! 1035: if (seq != 0)
! 1036: ssh_packet_disconnect(ssh,
! 1037: "strict KEX violation: "
! 1038: "KEXINIT was not the first packet");
! 1039: }
1.171 djm 1040: }
1041:
1042: /* Check whether client supports rsa-sha2 algorithms */
1043: if (kex->server && (kex->flags & KEX_INITIAL)) {
1044: if (has_any_alg(peer[PROPOSAL_SERVER_HOST_KEY_ALGS],
1045: "rsa-sha2-256,rsa-sha2-256-cert-v01@openssh.com"))
1046: kex->flags |= KEX_RSA_SHA2_256_SUPPORTED;
1047: if (has_any_alg(peer[PROPOSAL_SERVER_HOST_KEY_ALGS],
1048: "rsa-sha2-512,rsa-sha2-512-cert-v01@openssh.com"))
1049: kex->flags |= KEX_RSA_SHA2_512_SUPPORTED;
1.26 markus 1050: }
1.1 markus 1051:
1.30 markus 1052: /* Algorithm Negotiation */
1.110 djm 1053: if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
1054: sprop[PROPOSAL_KEX_ALGS])) != 0) {
1055: kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
1056: peer[PROPOSAL_KEX_ALGS] = NULL;
1057: goto out;
1058: }
1059: if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
1060: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
1061: kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
1062: peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
1063: goto out;
1064: }
1.1 markus 1065: for (mode = 0; mode < MODE_MAX; mode++) {
1.102 markus 1066: if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
1067: r = SSH_ERR_ALLOC_FAIL;
1068: goto out;
1069: }
1.30 markus 1070: kex->newkeys[mode] = newkeys;
1.78 djm 1071: ctos = (!kex->server && mode == MODE_OUT) ||
1072: (kex->server && mode == MODE_IN);
1.1 markus 1073: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
1074: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
1075: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.102 markus 1076: if ((r = choose_enc(&newkeys->enc, cprop[nenc],
1.107 djm 1077: sprop[nenc])) != 0) {
1078: kex->failed_choice = peer[nenc];
1079: peer[nenc] = NULL;
1.102 markus 1080: goto out;
1.107 djm 1081: }
1.102 markus 1082: authlen = cipher_authlen(newkeys->enc.cipher);
1.88 markus 1083: /* ignore mac for authenticated encryption */
1.102 markus 1084: if (authlen == 0 &&
1085: (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
1.107 djm 1086: sprop[nmac])) != 0) {
1087: kex->failed_choice = peer[nmac];
1088: peer[nmac] = NULL;
1.102 markus 1089: goto out;
1.107 djm 1090: }
1.102 markus 1091: if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
1.107 djm 1092: sprop[ncomp])) != 0) {
1093: kex->failed_choice = peer[ncomp];
1094: peer[ncomp] = NULL;
1.102 markus 1095: goto out;
1.107 djm 1096: }
1.110 djm 1097: debug("kex: %s cipher: %s MAC: %s compression: %s",
1.1 markus 1098: ctos ? "client->server" : "server->client",
1.27 markus 1099: newkeys->enc.name,
1.88 markus 1100: authlen == 0 ? newkeys->mac.name : "<implicit>",
1.27 markus 1101: newkeys->comp.name);
1.107 djm 1102: }
1.96 dtucker 1103: need = dh_need = 0;
1.1 markus 1104: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 1105: newkeys = kex->newkeys[mode];
1.120 deraadt 1106: need = MAXIMUM(need, newkeys->enc.key_len);
1107: need = MAXIMUM(need, newkeys->enc.block_size);
1108: need = MAXIMUM(need, newkeys->enc.iv_len);
1109: need = MAXIMUM(need, newkeys->mac.key_len);
1110: dh_need = MAXIMUM(dh_need, cipher_seclen(newkeys->enc.cipher));
1111: dh_need = MAXIMUM(dh_need, newkeys->enc.block_size);
1112: dh_need = MAXIMUM(dh_need, newkeys->enc.iv_len);
1113: dh_need = MAXIMUM(dh_need, newkeys->mac.key_len);
1.1 markus 1114: }
1.7 markus 1115: /* XXX need runden? */
1.27 markus 1116: kex->we_need = need;
1.96 dtucker 1117: kex->dh_need = dh_need;
1.53 markus 1118:
1119: /* ignore the next message if the proposals do not match */
1.135 djm 1120: if (first_kex_follows && !proposals_match(my, peer))
1.102 markus 1121: ssh->dispatch_skip_packets = 1;
1122: r = 0;
1123: out:
1.26 markus 1124: kex_prop_free(my);
1125: kex_prop_free(peer);
1.102 markus 1126: return r;
1.26 markus 1127: }
1128:
1.102 markus 1129: static int
1130: derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
1131: const struct sshbuf *shared_secret, u_char **keyp)
1.26 markus 1132: {
1.102 markus 1133: struct kex *kex = ssh->kex;
1134: struct ssh_digest_ctx *hashctx = NULL;
1.26 markus 1135: char c = id;
1.61 djm 1136: u_int have;
1.94 djm 1137: size_t mdsz;
1.61 djm 1138: u_char *digest;
1.102 markus 1139: int r;
1.62 djm 1140:
1.94 djm 1141: if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
1.102 markus 1142: return SSH_ERR_INVALID_ARGUMENT;
1.120 deraadt 1143: if ((digest = calloc(1, ROUNDUP(need, mdsz))) == NULL) {
1.102 markus 1144: r = SSH_ERR_ALLOC_FAIL;
1145: goto out;
1146: }
1.26 markus 1147:
1.30 markus 1148: /* K1 = HASH(K || H || "A" || session_id) */
1.102 markus 1149: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
1150: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 1151: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1152: ssh_digest_update(hashctx, &c, 1) != 0 ||
1.165 djm 1153: ssh_digest_update_buffer(hashctx, kex->session_id) != 0 ||
1.102 markus 1154: ssh_digest_final(hashctx, digest, mdsz) != 0) {
1155: r = SSH_ERR_LIBCRYPTO_ERROR;
1.160 djm 1156: error_f("KEX hash failed");
1.102 markus 1157: goto out;
1158: }
1.94 djm 1159: ssh_digest_free(hashctx);
1.102 markus 1160: hashctx = NULL;
1.26 markus 1161:
1.30 markus 1162: /*
1163: * expand key:
1164: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
1165: * Key = K1 || K2 || ... || Kn
1166: */
1.26 markus 1167: for (have = mdsz; need > have; have += mdsz) {
1.102 markus 1168: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
1169: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 1170: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1.102 markus 1171: ssh_digest_update(hashctx, digest, have) != 0 ||
1172: ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
1.160 djm 1173: error_f("KDF failed");
1.102 markus 1174: r = SSH_ERR_LIBCRYPTO_ERROR;
1175: goto out;
1176: }
1.94 djm 1177: ssh_digest_free(hashctx);
1.102 markus 1178: hashctx = NULL;
1.26 markus 1179: }
1180: #ifdef DEBUG_KEX
1181: fprintf(stderr, "key '%c'== ", c);
1182: dump_digest("key", digest, need);
1183: #endif
1.102 markus 1184: *keyp = digest;
1185: digest = NULL;
1186: r = 0;
1187: out:
1.114 mmcc 1188: free(digest);
1.102 markus 1189: ssh_digest_free(hashctx);
1190: return r;
1.1 markus 1191: }
1192:
1.23 markus 1193: #define NKEYS 6
1.102 markus 1194: int
1195: kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
1196: const struct sshbuf *shared_secret)
1.1 markus 1197: {
1.102 markus 1198: struct kex *kex = ssh->kex;
1.15 markus 1199: u_char *keys[NKEYS];
1.102 markus 1200: u_int i, j, mode, ctos;
1201: int r;
1.1 markus 1202:
1.144 djm 1203: /* save initial hash as session id */
1.165 djm 1204: if ((kex->flags & KEX_INITIAL) != 0) {
1.166 djm 1205: if (sshbuf_len(kex->session_id) != 0) {
1206: error_f("already have session ID at kex");
1207: return SSH_ERR_INTERNAL_ERROR;
1208: }
1.165 djm 1209: if ((r = sshbuf_put(kex->session_id, hash, hashlen)) != 0)
1210: return r;
1211: } else if (sshbuf_len(kex->session_id) == 0) {
1212: error_f("no session ID in rekex");
1.166 djm 1213: return SSH_ERR_INTERNAL_ERROR;
1.144 djm 1214: }
1.65 djm 1215: for (i = 0; i < NKEYS; i++) {
1.102 markus 1216: if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
1217: shared_secret, &keys[i])) != 0) {
1218: for (j = 0; j < i; j++)
1219: free(keys[j]);
1220: return r;
1221: }
1.65 djm 1222: }
1.1 markus 1223: for (mode = 0; mode < MODE_MAX; mode++) {
1.69 deraadt 1224: ctos = (!kex->server && mode == MODE_OUT) ||
1225: (kex->server && mode == MODE_IN);
1.100 markus 1226: kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
1227: kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
1228: kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
1.1 markus 1229: }
1.102 markus 1230: return 0;
1.95 djm 1231: }
1.57 djm 1232:
1.145 djm 1233: int
1.150 djm 1234: kex_load_hostkey(struct ssh *ssh, struct sshkey **prvp, struct sshkey **pubp)
1.145 djm 1235: {
1236: struct kex *kex = ssh->kex;
1237:
1238: *pubp = NULL;
1239: *prvp = NULL;
1240: if (kex->load_host_public_key == NULL ||
1.152 djm 1241: kex->load_host_private_key == NULL) {
1.160 djm 1242: error_f("missing hostkey loader");
1.145 djm 1243: return SSH_ERR_INVALID_ARGUMENT;
1.152 djm 1244: }
1.145 djm 1245: *pubp = kex->load_host_public_key(kex->hostkey_type,
1246: kex->hostkey_nid, ssh);
1247: *prvp = kex->load_host_private_key(kex->hostkey_type,
1248: kex->hostkey_nid, ssh);
1249: if (*pubp == NULL)
1250: return SSH_ERR_NO_HOSTKEY_LOADED;
1.146 djm 1251: return 0;
1252: }
1253:
1254: int
1255: kex_verify_host_key(struct ssh *ssh, struct sshkey *server_host_key)
1256: {
1257: struct kex *kex = ssh->kex;
1258:
1.152 djm 1259: if (kex->verify_host_key == NULL) {
1.160 djm 1260: error_f("missing hostkey verifier");
1.146 djm 1261: return SSH_ERR_INVALID_ARGUMENT;
1.152 djm 1262: }
1.146 djm 1263: if (server_host_key->type != kex->hostkey_type ||
1264: (kex->hostkey_type == KEY_ECDSA &&
1265: server_host_key->ecdsa_nid != kex->hostkey_nid))
1266: return SSH_ERR_KEY_TYPE_MISMATCH;
1267: if (kex->verify_host_key(server_host_key, ssh) == -1)
1268: return SSH_ERR_SIGNATURE_INVALID;
1.145 djm 1269: return 0;
1270: }
1.26 markus 1271:
1.84 djm 1272: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1.26 markus 1273: void
1.147 djm 1274: dump_digest(const char *msg, const u_char *digest, int len)
1.26 markus 1275: {
1276: fprintf(stderr, "%s\n", msg);
1.102 markus 1277: sshbuf_dump_data(digest, len, stderr);
1.26 markus 1278: }
1279: #endif
1.143 djm 1280:
1281: /*
1282: * Send a plaintext error message to the peer, suffixed by \r\n.
1283: * Only used during banner exchange, and there only for the server.
1284: */
1285: static void
1286: send_error(struct ssh *ssh, char *msg)
1287: {
1288: char *crnl = "\r\n";
1289:
1290: if (!ssh->kex->server)
1291: return;
1292:
1293: if (atomicio(vwrite, ssh_packet_get_connection_out(ssh),
1294: msg, strlen(msg)) != strlen(msg) ||
1295: atomicio(vwrite, ssh_packet_get_connection_out(ssh),
1296: crnl, strlen(crnl)) != strlen(crnl))
1.160 djm 1297: error_f("write: %.100s", strerror(errno));
1.143 djm 1298: }
1299:
1300: /*
1301: * Sends our identification string and waits for the peer's. Will block for
1302: * up to timeout_ms (or indefinitely if timeout_ms <= 0).
1303: * Returns on 0 success or a ssherr.h code on failure.
1304: */
1305: int
1306: kex_exchange_identification(struct ssh *ssh, int timeout_ms,
1307: const char *version_addendum)
1308: {
1.158 djm 1309: int remote_major, remote_minor, mismatch, oerrno = 0;
1.173 dtucker 1310: size_t len, n;
1.143 djm 1311: int r, expect_nl;
1312: u_char c;
1313: struct sshbuf *our_version = ssh->kex->server ?
1314: ssh->kex->server_version : ssh->kex->client_version;
1315: struct sshbuf *peer_version = ssh->kex->server ?
1316: ssh->kex->client_version : ssh->kex->server_version;
1317: char *our_version_string = NULL, *peer_version_string = NULL;
1318: char *cp, *remote_version = NULL;
1319:
1320: /* Prepare and send our banner */
1321: sshbuf_reset(our_version);
1322: if (version_addendum != NULL && *version_addendum == '\0')
1323: version_addendum = NULL;
1.182 djm 1324: if ((r = sshbuf_putf(our_version, "SSH-%d.%d-%s%s%s\r\n",
1.168 djm 1325: PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION,
1.143 djm 1326: version_addendum == NULL ? "" : " ",
1327: version_addendum == NULL ? "" : version_addendum)) != 0) {
1.158 djm 1328: oerrno = errno;
1.160 djm 1329: error_fr(r, "sshbuf_putf");
1.143 djm 1330: goto out;
1331: }
1332:
1333: if (atomicio(vwrite, ssh_packet_get_connection_out(ssh),
1334: sshbuf_mutable_ptr(our_version),
1335: sshbuf_len(our_version)) != sshbuf_len(our_version)) {
1.158 djm 1336: oerrno = errno;
1.160 djm 1337: debug_f("write: %.100s", strerror(errno));
1.143 djm 1338: r = SSH_ERR_SYSTEM_ERROR;
1339: goto out;
1340: }
1341: if ((r = sshbuf_consume_end(our_version, 2)) != 0) { /* trim \r\n */
1.158 djm 1342: oerrno = errno;
1.160 djm 1343: error_fr(r, "sshbuf_consume_end");
1.143 djm 1344: goto out;
1345: }
1346: our_version_string = sshbuf_dup_string(our_version);
1347: if (our_version_string == NULL) {
1.160 djm 1348: error_f("sshbuf_dup_string failed");
1.143 djm 1349: r = SSH_ERR_ALLOC_FAIL;
1350: goto out;
1351: }
1352: debug("Local version string %.100s", our_version_string);
1353:
1354: /* Read other side's version identification. */
1355: for (n = 0; ; n++) {
1356: if (n >= SSH_MAX_PRE_BANNER_LINES) {
1357: send_error(ssh, "No SSH identification string "
1358: "received.");
1.160 djm 1359: error_f("No SSH version received in first %u lines "
1360: "from server", SSH_MAX_PRE_BANNER_LINES);
1.143 djm 1361: r = SSH_ERR_INVALID_FORMAT;
1362: goto out;
1363: }
1364: sshbuf_reset(peer_version);
1365: expect_nl = 0;
1.173 dtucker 1366: for (;;) {
1.143 djm 1367: if (timeout_ms > 0) {
1368: r = waitrfd(ssh_packet_get_connection_in(ssh),
1.179 djm 1369: &timeout_ms, NULL);
1.143 djm 1370: if (r == -1 && errno == ETIMEDOUT) {
1371: send_error(ssh, "Timed out waiting "
1372: "for SSH identification string.");
1373: error("Connection timed out during "
1374: "banner exchange");
1375: r = SSH_ERR_CONN_TIMEOUT;
1376: goto out;
1377: } else if (r == -1) {
1.158 djm 1378: oerrno = errno;
1.160 djm 1379: error_f("%s", strerror(errno));
1.143 djm 1380: r = SSH_ERR_SYSTEM_ERROR;
1381: goto out;
1382: }
1383: }
1384:
1385: len = atomicio(read, ssh_packet_get_connection_in(ssh),
1386: &c, 1);
1387: if (len != 1 && errno == EPIPE) {
1.180 tobhe 1388: verbose_f("Connection closed by remote host");
1.143 djm 1389: r = SSH_ERR_CONN_CLOSED;
1390: goto out;
1391: } else if (len != 1) {
1.158 djm 1392: oerrno = errno;
1.160 djm 1393: error_f("read: %.100s", strerror(errno));
1.143 djm 1394: r = SSH_ERR_SYSTEM_ERROR;
1395: goto out;
1396: }
1397: if (c == '\r') {
1398: expect_nl = 1;
1399: continue;
1400: }
1401: if (c == '\n')
1402: break;
1403: if (c == '\0' || expect_nl) {
1.180 tobhe 1404: verbose_f("banner line contains invalid "
1.160 djm 1405: "characters");
1.143 djm 1406: goto invalid;
1407: }
1408: if ((r = sshbuf_put_u8(peer_version, c)) != 0) {
1.158 djm 1409: oerrno = errno;
1.160 djm 1410: error_fr(r, "sshbuf_put");
1.143 djm 1411: goto out;
1412: }
1413: if (sshbuf_len(peer_version) > SSH_MAX_BANNER_LEN) {
1.180 tobhe 1414: verbose_f("banner line too long");
1.143 djm 1415: goto invalid;
1416: }
1417: }
1418: /* Is this an actual protocol banner? */
1419: if (sshbuf_len(peer_version) > 4 &&
1420: memcmp(sshbuf_ptr(peer_version), "SSH-", 4) == 0)
1421: break;
1422: /* If not, then just log the line and continue */
1423: if ((cp = sshbuf_dup_string(peer_version)) == NULL) {
1.160 djm 1424: error_f("sshbuf_dup_string failed");
1.143 djm 1425: r = SSH_ERR_ALLOC_FAIL;
1426: goto out;
1427: }
1428: /* Do not accept lines before the SSH ident from a client */
1429: if (ssh->kex->server) {
1.180 tobhe 1430: verbose_f("client sent invalid protocol identifier "
1.160 djm 1431: "\"%.256s\"", cp);
1.143 djm 1432: free(cp);
1433: goto invalid;
1434: }
1.160 djm 1435: debug_f("banner line %zu: %s", n, cp);
1.143 djm 1436: free(cp);
1437: }
1438: peer_version_string = sshbuf_dup_string(peer_version);
1439: if (peer_version_string == NULL)
1.175 dtucker 1440: fatal_f("sshbuf_dup_string failed");
1.143 djm 1441: /* XXX must be same size for sscanf */
1442: if ((remote_version = calloc(1, sshbuf_len(peer_version))) == NULL) {
1.160 djm 1443: error_f("calloc failed");
1.143 djm 1444: r = SSH_ERR_ALLOC_FAIL;
1445: goto out;
1446: }
1447:
1448: /*
1449: * Check that the versions match. In future this might accept
1450: * several versions and set appropriate flags to handle them.
1451: */
1452: if (sscanf(peer_version_string, "SSH-%d.%d-%[^\n]\n",
1453: &remote_major, &remote_minor, remote_version) != 3) {
1454: error("Bad remote protocol version identification: '%.100s'",
1455: peer_version_string);
1456: invalid:
1457: send_error(ssh, "Invalid SSH identification string.");
1458: r = SSH_ERR_INVALID_FORMAT;
1459: goto out;
1460: }
1461: debug("Remote protocol version %d.%d, remote software version %.100s",
1462: remote_major, remote_minor, remote_version);
1.164 djm 1463: compat_banner(ssh, remote_version);
1.143 djm 1464:
1465: mismatch = 0;
1466: switch (remote_major) {
1467: case 2:
1468: break;
1469: case 1:
1470: if (remote_minor != 99)
1471: mismatch = 1;
1472: break;
1473: default:
1474: mismatch = 1;
1475: break;
1476: }
1477: if (mismatch) {
1478: error("Protocol major versions differ: %d vs. %d",
1479: PROTOCOL_MAJOR_2, remote_major);
1480: send_error(ssh, "Protocol major versions differ.");
1481: r = SSH_ERR_NO_PROTOCOL_VERSION;
1482: goto out;
1483: }
1484:
1485: if (ssh->kex->server && (ssh->compat & SSH_BUG_PROBE) != 0) {
1486: logit("probed from %s port %d with %s. Don't panic.",
1487: ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
1488: peer_version_string);
1489: r = SSH_ERR_CONN_CLOSED; /* XXX */
1490: goto out;
1491: }
1492: if (ssh->kex->server && (ssh->compat & SSH_BUG_SCANNER) != 0) {
1493: logit("scanned from %s port %d with %s. Don't panic.",
1494: ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
1495: peer_version_string);
1496: r = SSH_ERR_CONN_CLOSED; /* XXX */
1497: goto out;
1498: }
1499: /* success */
1500: r = 0;
1501: out:
1502: free(our_version_string);
1503: free(peer_version_string);
1504: free(remote_version);
1.158 djm 1505: if (r == SSH_ERR_SYSTEM_ERROR)
1506: errno = oerrno;
1.143 djm 1507: return r;
1508: }
1509:
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