Annotation of src/usr.bin/ssh/kex.c, Revision 1.178.4.1
1.178.4.1! bluhm 1: /* $OpenBSD: kex.c,v 1.178 2023/03/12 10:40:39 dtucker 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 */
1.178.4.1! bluhm 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:
1.178.4.1! bluhm 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: {
1.178.4.1! bluhm 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, ","))) {
1.178.4.1! bluhm 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;
1.178.4.1! bluhm 332: char *cp;
1.176 dtucker 333:
334: if (prop == NULL)
335: fatal_f("proposal missing");
336:
1.178.4.1! bluhm 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:
1.178.4.1! bluhm 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: }
1.178.4.1! bluhm 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:
1.178.4.1! bluhm 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 ||
1.170 djm 504: (r = sshpkt_put_u32(ssh, 2)) != 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 ||
1.152 djm 510: (r = sshpkt_send(ssh)) != 0) {
1.160 djm 511: error_fr(r, "compose");
1.121 djm 512: goto out;
1.152 djm 513: }
1.121 djm 514: /* success */
515: r = 0;
516: out:
517: free(algs);
1.123 djm 518: return r;
1.113 markus 519: }
520:
1.102 markus 521: int
522: kex_send_newkeys(struct ssh *ssh)
1.26 markus 523: {
1.102 markus 524: int r;
1.28 markus 525:
1.102 markus 526: kex_reset_dispatch(ssh);
527: if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
528: (r = sshpkt_send(ssh)) != 0)
529: return r;
1.26 markus 530: debug("SSH2_MSG_NEWKEYS sent");
1.102 markus 531: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
1.151 djm 532: if (ssh->kex->ext_info_c && (ssh->kex->flags & KEX_INITIAL) != 0)
1.113 markus 533: if ((r = kex_send_ext_info(ssh)) != 0)
534: return r;
1.151 djm 535: debug("expecting SSH2_MSG_NEWKEYS");
1.102 markus 536: return 0;
537: }
538:
1.113 markus 539: int
1.133 markus 540: kex_input_ext_info(int type, u_int32_t seq, struct ssh *ssh)
1.113 markus 541: {
542: struct kex *kex = ssh->kex;
543: u_int32_t i, ninfo;
1.137 djm 544: char *name;
1.134 djm 545: u_char *val;
546: size_t vlen;
1.113 markus 547: int r;
548:
549: debug("SSH2_MSG_EXT_INFO received");
550: ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_protocol_error);
551: if ((r = sshpkt_get_u32(ssh, &ninfo)) != 0)
552: return r;
1.178 dtucker 553: if (ninfo >= 1024) {
554: error("SSH2_MSG_EXT_INFO with too many entries, expected "
555: "<=1024, received %u", ninfo);
1.178.4.1! bluhm 556: return dispatch_protocol_error(type, seq, ssh);
1.178 dtucker 557: }
1.113 markus 558: for (i = 0; i < ninfo; i++) {
559: if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0)
560: return r;
1.134 djm 561: if ((r = sshpkt_get_string(ssh, &val, &vlen)) != 0) {
1.113 markus 562: free(name);
563: return r;
564: }
565: if (strcmp(name, "server-sig-algs") == 0) {
1.134 djm 566: /* Ensure no \0 lurking in value */
567: if (memchr(val, '\0', vlen) != NULL) {
1.160 djm 568: error_f("nul byte in %s", name);
1.134 djm 569: return SSH_ERR_INVALID_FORMAT;
570: }
1.160 djm 571: debug_f("%s=<%s>", name, val);
1.137 djm 572: kex->server_sig_algs = val;
573: val = NULL;
1.170 djm 574: } else if (strcmp(name,
575: "publickey-hostbound@openssh.com") == 0) {
576: /* XXX refactor */
577: /* Ensure no \0 lurking in value */
578: if (memchr(val, '\0', vlen) != NULL) {
579: error_f("nul byte in %s", name);
580: return SSH_ERR_INVALID_FORMAT;
581: }
582: debug_f("%s=<%s>", name, val);
583: if (strcmp(val, "0") == 0)
584: kex->flags |= KEX_HAS_PUBKEY_HOSTBOUND;
585: else {
586: debug_f("unsupported version of %s extension",
587: name);
588: }
1.134 djm 589: } else
1.160 djm 590: debug_f("%s (unrecognised)", name);
1.113 markus 591: free(name);
592: free(val);
593: }
594: return sshpkt_get_end(ssh);
595: }
596:
1.102 markus 597: static int
1.133 markus 598: kex_input_newkeys(int type, u_int32_t seq, struct ssh *ssh)
1.102 markus 599: {
600: struct kex *kex = ssh->kex;
601: int r;
1.19 stevesk 602:
1.26 markus 603: debug("SSH2_MSG_NEWKEYS received");
1.102 markus 604: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
1.131 markus 605: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.102 markus 606: if ((r = sshpkt_get_end(ssh)) != 0)
1.122 markus 607: return r;
608: if ((r = ssh_set_newkeys(ssh, MODE_IN)) != 0)
1.102 markus 609: return r;
1.30 markus 610: kex->done = 1;
1.142 djm 611: kex->flags &= ~KEX_INITIAL;
1.102 markus 612: sshbuf_reset(kex->peer);
613: /* sshbuf_reset(kex->my); */
1.26 markus 614: kex->flags &= ~KEX_INIT_SENT;
1.91 djm 615: free(kex->name);
1.32 markus 616: kex->name = NULL;
1.102 markus 617: return 0;
1.26 markus 618: }
1.1 markus 619:
1.102 markus 620: int
621: kex_send_kexinit(struct ssh *ssh)
1.26 markus 622: {
1.49 markus 623: u_char *cookie;
1.102 markus 624: struct kex *kex = ssh->kex;
625: int r;
1.49 markus 626:
1.152 djm 627: if (kex == NULL) {
1.161 djm 628: error_f("no kex");
1.102 markus 629: return SSH_ERR_INTERNAL_ERROR;
1.152 djm 630: }
1.102 markus 631: if (kex->flags & KEX_INIT_SENT)
632: return 0;
1.30 markus 633: kex->done = 0;
1.49 markus 634:
635: /* generate a random cookie */
1.152 djm 636: if (sshbuf_len(kex->my) < KEX_COOKIE_LEN) {
1.160 djm 637: error_f("bad kex length: %zu < %d",
1.152 djm 638: sshbuf_len(kex->my), KEX_COOKIE_LEN);
1.102 markus 639: return SSH_ERR_INVALID_FORMAT;
1.152 djm 640: }
641: if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL) {
1.160 djm 642: error_f("buffer error");
1.102 markus 643: return SSH_ERR_INTERNAL_ERROR;
1.152 djm 644: }
1.102 markus 645: arc4random_buf(cookie, KEX_COOKIE_LEN);
646:
647: if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
648: (r = sshpkt_putb(ssh, kex->my)) != 0 ||
1.152 djm 649: (r = sshpkt_send(ssh)) != 0) {
1.160 djm 650: error_fr(r, "compose reply");
1.102 markus 651: return r;
1.152 djm 652: }
1.26 markus 653: debug("SSH2_MSG_KEXINIT sent");
654: kex->flags |= KEX_INIT_SENT;
1.102 markus 655: return 0;
1.1 markus 656: }
657:
1.101 markus 658: int
1.133 markus 659: kex_input_kexinit(int type, u_int32_t seq, struct ssh *ssh)
1.11 provos 660: {
1.102 markus 661: struct kex *kex = ssh->kex;
662: const u_char *ptr;
1.100 markus 663: u_int i;
664: size_t dlen;
1.102 markus 665: int r;
1.11 provos 666:
1.26 markus 667: debug("SSH2_MSG_KEXINIT received");
1.152 djm 668: if (kex == NULL) {
1.161 djm 669: error_f("no kex");
1.152 djm 670: return SSH_ERR_INTERNAL_ERROR;
671: }
1.178.4.1! bluhm 672: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_protocol_error);
1.102 markus 673: ptr = sshpkt_ptr(ssh, &dlen);
674: if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
675: return r;
1.31 markus 676:
677: /* discard packet */
1.152 djm 678: for (i = 0; i < KEX_COOKIE_LEN; i++) {
679: if ((r = sshpkt_get_u8(ssh, NULL)) != 0) {
1.160 djm 680: error_fr(r, "discard cookie");
1.102 markus 681: return r;
1.152 djm 682: }
683: }
684: for (i = 0; i < PROPOSAL_MAX; i++) {
685: if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0) {
1.160 djm 686: error_fr(r, "discard proposal");
1.102 markus 687: return r;
1.152 djm 688: }
689: }
1.87 djm 690: /*
691: * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
692: * KEX method has the server move first, but a server might be using
693: * a custom method or one that we otherwise don't support. We should
694: * be prepared to remember first_kex_follows here so we can eat a
695: * packet later.
696: * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
697: * for cases where the server *doesn't* go first. I guess we should
698: * ignore it when it is set for these cases, which is what we do now.
699: */
1.102 markus 700: if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
701: (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
702: (r = sshpkt_get_end(ssh)) != 0)
703: return r;
704:
705: if (!(kex->flags & KEX_INIT_SENT))
706: if ((r = kex_send_kexinit(ssh)) != 0)
707: return r;
1.178.4.1! bluhm 708: if ((r = kex_choose_conf(ssh, seq)) != 0)
1.102 markus 709: return r;
1.19 stevesk 710:
1.102 markus 711: if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
712: return (kex->kex[kex->kex_type])(ssh);
713:
1.160 djm 714: error_f("unknown kex type %u", kex->kex_type);
1.102 markus 715: return SSH_ERR_INTERNAL_ERROR;
716: }
717:
1.143 djm 718: struct kex *
719: kex_new(void)
1.102 markus 720: {
721: struct kex *kex;
722:
1.143 djm 723: if ((kex = calloc(1, sizeof(*kex))) == NULL ||
724: (kex->peer = sshbuf_new()) == NULL ||
725: (kex->my = sshbuf_new()) == NULL ||
726: (kex->client_version = sshbuf_new()) == NULL ||
1.165 djm 727: (kex->server_version = sshbuf_new()) == NULL ||
728: (kex->session_id = sshbuf_new()) == NULL) {
1.143 djm 729: kex_free(kex);
730: return NULL;
1.102 markus 731: }
1.143 djm 732: return kex;
1.26 markus 733: }
1.11 provos 734:
1.100 markus 735: void
736: kex_free_newkeys(struct newkeys *newkeys)
737: {
738: if (newkeys == NULL)
739: return;
740: if (newkeys->enc.key) {
741: explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
742: free(newkeys->enc.key);
743: newkeys->enc.key = NULL;
744: }
745: if (newkeys->enc.iv) {
1.111 djm 746: explicit_bzero(newkeys->enc.iv, newkeys->enc.iv_len);
1.100 markus 747: free(newkeys->enc.iv);
748: newkeys->enc.iv = NULL;
749: }
750: free(newkeys->enc.name);
751: explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
752: free(newkeys->comp.name);
753: explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
754: mac_clear(&newkeys->mac);
755: if (newkeys->mac.key) {
756: explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
757: free(newkeys->mac.key);
758: newkeys->mac.key = NULL;
759: }
760: free(newkeys->mac.name);
761: explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
1.157 jsg 762: freezero(newkeys, sizeof(*newkeys));
1.100 markus 763: }
764:
1.102 markus 765: void
766: kex_free(struct kex *kex)
1.26 markus 767: {
1.102 markus 768: u_int mode;
1.11 provos 769:
1.143 djm 770: if (kex == NULL)
771: return;
772:
1.102 markus 773: #ifdef WITH_OPENSSL
1.136 jsing 774: DH_free(kex->dh);
775: EC_KEY_free(kex->ec_client_key);
1.102 markus 776: #endif
777: for (mode = 0; mode < MODE_MAX; mode++) {
778: kex_free_newkeys(kex->newkeys[mode]);
779: kex->newkeys[mode] = NULL;
1.100 markus 780: }
1.102 markus 781: sshbuf_free(kex->peer);
782: sshbuf_free(kex->my);
1.143 djm 783: sshbuf_free(kex->client_version);
784: sshbuf_free(kex->server_version);
1.149 djm 785: sshbuf_free(kex->client_pub);
1.165 djm 786: sshbuf_free(kex->session_id);
1.169 djm 787: sshbuf_free(kex->initial_sig);
788: sshkey_free(kex->initial_hostkey);
1.107 djm 789: free(kex->failed_choice);
1.113 markus 790: free(kex->hostkey_alg);
791: free(kex->name);
1.102 markus 792: free(kex);
1.11 provos 793: }
794:
1.102 markus 795: int
1.143 djm 796: kex_ready(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
797: {
798: int r;
799:
800: if ((r = kex_prop2buf(ssh->kex->my, proposal)) != 0)
801: return r;
802: ssh->kex->flags = KEX_INITIAL;
803: kex_reset_dispatch(ssh);
804: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
805: return 0;
806: }
807:
808: int
1.102 markus 809: kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
1.1 markus 810: {
1.102 markus 811: int r;
1.1 markus 812:
1.143 djm 813: if ((r = kex_ready(ssh, proposal)) != 0)
1.102 markus 814: return r;
815: if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
816: kex_free(ssh->kex);
817: ssh->kex = NULL;
818: return r;
1.1 markus 819: }
1.102 markus 820: return 0;
1.117 djm 821: }
822:
823: /*
824: * Request key re-exchange, returns 0 on success or a ssherr.h error
825: * code otherwise. Must not be called if KEX is incomplete or in-progress.
826: */
827: int
828: kex_start_rekex(struct ssh *ssh)
829: {
830: if (ssh->kex == NULL) {
1.160 djm 831: error_f("no kex");
1.117 djm 832: return SSH_ERR_INTERNAL_ERROR;
833: }
834: if (ssh->kex->done == 0) {
1.160 djm 835: error_f("requested twice");
1.117 djm 836: return SSH_ERR_INTERNAL_ERROR;
837: }
838: ssh->kex->done = 0;
839: return kex_send_kexinit(ssh);
1.1 markus 840: }
841:
1.102 markus 842: static int
843: choose_enc(struct sshenc *enc, char *client, char *server)
1.1 markus 844: {
1.23 markus 845: char *name = match_list(client, server, NULL);
1.102 markus 846:
1.1 markus 847: if (name == NULL)
1.102 markus 848: return SSH_ERR_NO_CIPHER_ALG_MATCH;
1.129 dtucker 849: if ((enc->cipher = cipher_by_name(name)) == NULL) {
1.160 djm 850: error_f("unsupported cipher %s", name);
1.129 dtucker 851: free(name);
1.102 markus 852: return SSH_ERR_INTERNAL_ERROR;
1.129 dtucker 853: }
1.1 markus 854: enc->name = name;
855: enc->enabled = 0;
856: enc->iv = NULL;
1.88 markus 857: enc->iv_len = cipher_ivlen(enc->cipher);
1.1 markus 858: enc->key = NULL;
1.45 markus 859: enc->key_len = cipher_keylen(enc->cipher);
860: enc->block_size = cipher_blocksize(enc->cipher);
1.102 markus 861: return 0;
1.1 markus 862: }
1.69 deraadt 863:
1.102 markus 864: static int
865: choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
1.1 markus 866: {
1.23 markus 867: char *name = match_list(client, server, NULL);
1.102 markus 868:
1.1 markus 869: if (name == NULL)
1.102 markus 870: return SSH_ERR_NO_MAC_ALG_MATCH;
1.129 dtucker 871: if (mac_setup(mac, name) < 0) {
1.160 djm 872: error_f("unsupported MAC %s", name);
1.129 dtucker 873: free(name);
1.102 markus 874: return SSH_ERR_INTERNAL_ERROR;
1.129 dtucker 875: }
1.1 markus 876: mac->name = name;
877: mac->key = NULL;
878: mac->enabled = 0;
1.102 markus 879: return 0;
1.1 markus 880: }
1.69 deraadt 881:
1.102 markus 882: static int
883: choose_comp(struct sshcomp *comp, char *client, char *server)
1.1 markus 884: {
1.23 markus 885: char *name = match_list(client, server, NULL);
1.102 markus 886:
1.1 markus 887: if (name == NULL)
1.102 markus 888: return SSH_ERR_NO_COMPRESS_ALG_MATCH;
1.156 dtucker 889: #ifdef WITH_ZLIB
1.64 markus 890: if (strcmp(name, "zlib@openssh.com") == 0) {
1.141 sf 891: comp->type = COMP_DELAYED;
892: } else if (strcmp(name, "zlib") == 0) {
1.140 sf 893: comp->type = COMP_ZLIB;
1.156 dtucker 894: } else
895: #endif /* WITH_ZLIB */
896: if (strcmp(name, "none") == 0) {
1.64 markus 897: comp->type = COMP_NONE;
1.1 markus 898: } else {
1.160 djm 899: error_f("unsupported compression scheme %s", name);
1.129 dtucker 900: free(name);
1.102 markus 901: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 902: }
903: comp->name = name;
1.102 markus 904: return 0;
1.1 markus 905: }
1.69 deraadt 906:
1.102 markus 907: static int
908: choose_kex(struct kex *k, char *client, char *server)
1.1 markus 909: {
1.89 djm 910: const struct kexalg *kexalg;
911:
1.23 markus 912: k->name = match_list(client, server, NULL);
1.102 markus 913:
1.110 djm 914: debug("kex: algorithm: %s", k->name ? k->name : "(no match)");
1.1 markus 915: if (k->name == NULL)
1.102 markus 916: return SSH_ERR_NO_KEX_ALG_MATCH;
1.152 djm 917: if ((kexalg = kex_alg_by_name(k->name)) == NULL) {
1.160 djm 918: error_f("unsupported KEX method %s", k->name);
1.102 markus 919: return SSH_ERR_INTERNAL_ERROR;
1.152 djm 920: }
1.89 djm 921: k->kex_type = kexalg->type;
1.94 djm 922: k->hash_alg = kexalg->hash_alg;
1.89 djm 923: k->ec_nid = kexalg->ec_nid;
1.102 markus 924: return 0;
1.1 markus 925: }
1.65 djm 926:
1.102 markus 927: static int
928: choose_hostkeyalg(struct kex *k, char *client, char *server)
1.1 markus 929: {
1.162 djm 930: free(k->hostkey_alg);
1.113 markus 931: k->hostkey_alg = match_list(client, server, NULL);
1.102 markus 932:
1.110 djm 933: debug("kex: host key algorithm: %s",
1.113 markus 934: k->hostkey_alg ? k->hostkey_alg : "(no match)");
935: if (k->hostkey_alg == NULL)
1.102 markus 936: return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
1.113 markus 937: k->hostkey_type = sshkey_type_from_name(k->hostkey_alg);
1.152 djm 938: if (k->hostkey_type == KEY_UNSPEC) {
1.160 djm 939: error_f("unsupported hostkey algorithm %s", k->hostkey_alg);
1.102 markus 940: return SSH_ERR_INTERNAL_ERROR;
1.152 djm 941: }
1.113 markus 942: k->hostkey_nid = sshkey_ecdsa_nid_from_name(k->hostkey_alg);
1.102 markus 943: return 0;
1.1 markus 944: }
945:
1.56 djm 946: static int
1.53 markus 947: proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
948: {
949: static int check[] = {
950: PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
951: };
952: int *idx;
953: char *p;
954:
955: for (idx = &check[0]; *idx != -1; idx++) {
956: if ((p = strchr(my[*idx], ',')) != NULL)
957: *p = '\0';
958: if ((p = strchr(peer[*idx], ',')) != NULL)
959: *p = '\0';
960: if (strcmp(my[*idx], peer[*idx]) != 0) {
961: debug2("proposal mismatch: my %s peer %s",
962: my[*idx], peer[*idx]);
963: return (0);
964: }
965: }
966: debug2("proposals match");
967: return (1);
968: }
969:
1.171 djm 970: static int
1.178.4.1! bluhm 971: kexalgs_contains(char **peer, const char *ext)
1.171 djm 972: {
1.178.4.1! bluhm 973: return has_any_alg(peer[PROPOSAL_KEX_ALGS], ext);
1.171 djm 974: }
975:
1.102 markus 976: static int
1.178.4.1! bluhm 977: kex_choose_conf(struct ssh *ssh, uint32_t seq)
1.1 markus 978: {
1.102 markus 979: struct kex *kex = ssh->kex;
980: struct newkeys *newkeys;
981: char **my = NULL, **peer = NULL;
1.26 markus 982: char **cprop, **sprop;
1.27 markus 983: int nenc, nmac, ncomp;
1.96 dtucker 984: u_int mode, ctos, need, dh_need, authlen;
1.102 markus 985: int r, first_kex_follows;
1.1 markus 986:
1.110 djm 987: debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
988: if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
989: goto out;
990: debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
991: if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
1.102 markus 992: goto out;
1.26 markus 993:
1.27 markus 994: if (kex->server) {
1.26 markus 995: cprop=peer;
996: sprop=my;
997: } else {
998: cprop=my;
999: sprop=peer;
1.113 markus 1000: }
1001:
1.178.4.1! bluhm 1002: /* Check whether peer supports ext_info/kex_strict */
! 1003: if ((kex->flags & KEX_INITIAL) != 0) {
! 1004: if (kex->server) {
! 1005: kex->ext_info_c = kexalgs_contains(peer, "ext-info-c");
! 1006: kex->kex_strict = kexalgs_contains(peer,
! 1007: "kex-strict-c-v00@openssh.com");
! 1008: } else {
! 1009: kex->kex_strict = kexalgs_contains(peer,
! 1010: "kex-strict-s-v00@openssh.com");
! 1011: }
! 1012: if (kex->kex_strict) {
! 1013: debug3_f("will use strict KEX ordering");
! 1014: if (seq != 0)
! 1015: ssh_packet_disconnect(ssh,
! 1016: "strict KEX violation: "
! 1017: "KEXINIT was not the first packet");
! 1018: }
1.171 djm 1019: }
1020:
1021: /* Check whether client supports rsa-sha2 algorithms */
1022: if (kex->server && (kex->flags & KEX_INITIAL)) {
1023: if (has_any_alg(peer[PROPOSAL_SERVER_HOST_KEY_ALGS],
1024: "rsa-sha2-256,rsa-sha2-256-cert-v01@openssh.com"))
1025: kex->flags |= KEX_RSA_SHA2_256_SUPPORTED;
1026: if (has_any_alg(peer[PROPOSAL_SERVER_HOST_KEY_ALGS],
1027: "rsa-sha2-512,rsa-sha2-512-cert-v01@openssh.com"))
1028: kex->flags |= KEX_RSA_SHA2_512_SUPPORTED;
1.26 markus 1029: }
1.1 markus 1030:
1.30 markus 1031: /* Algorithm Negotiation */
1.110 djm 1032: if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
1033: sprop[PROPOSAL_KEX_ALGS])) != 0) {
1034: kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
1035: peer[PROPOSAL_KEX_ALGS] = NULL;
1036: goto out;
1037: }
1038: if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
1039: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
1040: kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
1041: peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
1042: goto out;
1043: }
1.1 markus 1044: for (mode = 0; mode < MODE_MAX; mode++) {
1.102 markus 1045: if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
1046: r = SSH_ERR_ALLOC_FAIL;
1047: goto out;
1048: }
1.30 markus 1049: kex->newkeys[mode] = newkeys;
1.78 djm 1050: ctos = (!kex->server && mode == MODE_OUT) ||
1051: (kex->server && mode == MODE_IN);
1.1 markus 1052: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
1053: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
1054: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.102 markus 1055: if ((r = choose_enc(&newkeys->enc, cprop[nenc],
1.107 djm 1056: sprop[nenc])) != 0) {
1057: kex->failed_choice = peer[nenc];
1058: peer[nenc] = NULL;
1.102 markus 1059: goto out;
1.107 djm 1060: }
1.102 markus 1061: authlen = cipher_authlen(newkeys->enc.cipher);
1.88 markus 1062: /* ignore mac for authenticated encryption */
1.102 markus 1063: if (authlen == 0 &&
1064: (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
1.107 djm 1065: sprop[nmac])) != 0) {
1066: kex->failed_choice = peer[nmac];
1067: peer[nmac] = NULL;
1.102 markus 1068: goto out;
1.107 djm 1069: }
1.102 markus 1070: if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
1.107 djm 1071: sprop[ncomp])) != 0) {
1072: kex->failed_choice = peer[ncomp];
1073: peer[ncomp] = NULL;
1.102 markus 1074: goto out;
1.107 djm 1075: }
1.110 djm 1076: debug("kex: %s cipher: %s MAC: %s compression: %s",
1.1 markus 1077: ctos ? "client->server" : "server->client",
1.27 markus 1078: newkeys->enc.name,
1.88 markus 1079: authlen == 0 ? newkeys->mac.name : "<implicit>",
1.27 markus 1080: newkeys->comp.name);
1.107 djm 1081: }
1.96 dtucker 1082: need = dh_need = 0;
1.1 markus 1083: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 1084: newkeys = kex->newkeys[mode];
1.120 deraadt 1085: need = MAXIMUM(need, newkeys->enc.key_len);
1086: need = MAXIMUM(need, newkeys->enc.block_size);
1087: need = MAXIMUM(need, newkeys->enc.iv_len);
1088: need = MAXIMUM(need, newkeys->mac.key_len);
1089: dh_need = MAXIMUM(dh_need, cipher_seclen(newkeys->enc.cipher));
1090: dh_need = MAXIMUM(dh_need, newkeys->enc.block_size);
1091: dh_need = MAXIMUM(dh_need, newkeys->enc.iv_len);
1092: dh_need = MAXIMUM(dh_need, newkeys->mac.key_len);
1.1 markus 1093: }
1.7 markus 1094: /* XXX need runden? */
1.27 markus 1095: kex->we_need = need;
1.96 dtucker 1096: kex->dh_need = dh_need;
1.53 markus 1097:
1098: /* ignore the next message if the proposals do not match */
1.135 djm 1099: if (first_kex_follows && !proposals_match(my, peer))
1.102 markus 1100: ssh->dispatch_skip_packets = 1;
1101: r = 0;
1102: out:
1.26 markus 1103: kex_prop_free(my);
1104: kex_prop_free(peer);
1.102 markus 1105: return r;
1.26 markus 1106: }
1107:
1.102 markus 1108: static int
1109: derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
1110: const struct sshbuf *shared_secret, u_char **keyp)
1.26 markus 1111: {
1.102 markus 1112: struct kex *kex = ssh->kex;
1113: struct ssh_digest_ctx *hashctx = NULL;
1.26 markus 1114: char c = id;
1.61 djm 1115: u_int have;
1.94 djm 1116: size_t mdsz;
1.61 djm 1117: u_char *digest;
1.102 markus 1118: int r;
1.62 djm 1119:
1.94 djm 1120: if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
1.102 markus 1121: return SSH_ERR_INVALID_ARGUMENT;
1.120 deraadt 1122: if ((digest = calloc(1, ROUNDUP(need, mdsz))) == NULL) {
1.102 markus 1123: r = SSH_ERR_ALLOC_FAIL;
1124: goto out;
1125: }
1.26 markus 1126:
1.30 markus 1127: /* K1 = HASH(K || H || "A" || session_id) */
1.102 markus 1128: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
1129: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 1130: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1131: ssh_digest_update(hashctx, &c, 1) != 0 ||
1.165 djm 1132: ssh_digest_update_buffer(hashctx, kex->session_id) != 0 ||
1.102 markus 1133: ssh_digest_final(hashctx, digest, mdsz) != 0) {
1134: r = SSH_ERR_LIBCRYPTO_ERROR;
1.160 djm 1135: error_f("KEX hash failed");
1.102 markus 1136: goto out;
1137: }
1.94 djm 1138: ssh_digest_free(hashctx);
1.102 markus 1139: hashctx = NULL;
1.26 markus 1140:
1.30 markus 1141: /*
1142: * expand key:
1143: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
1144: * Key = K1 || K2 || ... || Kn
1145: */
1.26 markus 1146: for (have = mdsz; need > have; have += mdsz) {
1.102 markus 1147: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
1148: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 1149: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1.102 markus 1150: ssh_digest_update(hashctx, digest, have) != 0 ||
1151: ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
1.160 djm 1152: error_f("KDF failed");
1.102 markus 1153: r = SSH_ERR_LIBCRYPTO_ERROR;
1154: goto out;
1155: }
1.94 djm 1156: ssh_digest_free(hashctx);
1.102 markus 1157: hashctx = NULL;
1.26 markus 1158: }
1159: #ifdef DEBUG_KEX
1160: fprintf(stderr, "key '%c'== ", c);
1161: dump_digest("key", digest, need);
1162: #endif
1.102 markus 1163: *keyp = digest;
1164: digest = NULL;
1165: r = 0;
1166: out:
1.114 mmcc 1167: free(digest);
1.102 markus 1168: ssh_digest_free(hashctx);
1169: return r;
1.1 markus 1170: }
1171:
1.23 markus 1172: #define NKEYS 6
1.102 markus 1173: int
1174: kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
1175: const struct sshbuf *shared_secret)
1.1 markus 1176: {
1.102 markus 1177: struct kex *kex = ssh->kex;
1.15 markus 1178: u_char *keys[NKEYS];
1.102 markus 1179: u_int i, j, mode, ctos;
1180: int r;
1.1 markus 1181:
1.144 djm 1182: /* save initial hash as session id */
1.165 djm 1183: if ((kex->flags & KEX_INITIAL) != 0) {
1.166 djm 1184: if (sshbuf_len(kex->session_id) != 0) {
1185: error_f("already have session ID at kex");
1186: return SSH_ERR_INTERNAL_ERROR;
1187: }
1.165 djm 1188: if ((r = sshbuf_put(kex->session_id, hash, hashlen)) != 0)
1189: return r;
1190: } else if (sshbuf_len(kex->session_id) == 0) {
1191: error_f("no session ID in rekex");
1.166 djm 1192: return SSH_ERR_INTERNAL_ERROR;
1.144 djm 1193: }
1.65 djm 1194: for (i = 0; i < NKEYS; i++) {
1.102 markus 1195: if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
1196: shared_secret, &keys[i])) != 0) {
1197: for (j = 0; j < i; j++)
1198: free(keys[j]);
1199: return r;
1200: }
1.65 djm 1201: }
1.1 markus 1202: for (mode = 0; mode < MODE_MAX; mode++) {
1.69 deraadt 1203: ctos = (!kex->server && mode == MODE_OUT) ||
1204: (kex->server && mode == MODE_IN);
1.100 markus 1205: kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
1206: kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
1207: kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
1.1 markus 1208: }
1.102 markus 1209: return 0;
1.95 djm 1210: }
1.57 djm 1211:
1.145 djm 1212: int
1.150 djm 1213: kex_load_hostkey(struct ssh *ssh, struct sshkey **prvp, struct sshkey **pubp)
1.145 djm 1214: {
1215: struct kex *kex = ssh->kex;
1216:
1217: *pubp = NULL;
1218: *prvp = NULL;
1219: if (kex->load_host_public_key == NULL ||
1.152 djm 1220: kex->load_host_private_key == NULL) {
1.160 djm 1221: error_f("missing hostkey loader");
1.145 djm 1222: return SSH_ERR_INVALID_ARGUMENT;
1.152 djm 1223: }
1.145 djm 1224: *pubp = kex->load_host_public_key(kex->hostkey_type,
1225: kex->hostkey_nid, ssh);
1226: *prvp = kex->load_host_private_key(kex->hostkey_type,
1227: kex->hostkey_nid, ssh);
1228: if (*pubp == NULL)
1229: return SSH_ERR_NO_HOSTKEY_LOADED;
1.146 djm 1230: return 0;
1231: }
1232:
1233: int
1234: kex_verify_host_key(struct ssh *ssh, struct sshkey *server_host_key)
1235: {
1236: struct kex *kex = ssh->kex;
1237:
1.152 djm 1238: if (kex->verify_host_key == NULL) {
1.160 djm 1239: error_f("missing hostkey verifier");
1.146 djm 1240: return SSH_ERR_INVALID_ARGUMENT;
1.152 djm 1241: }
1.146 djm 1242: if (server_host_key->type != kex->hostkey_type ||
1243: (kex->hostkey_type == KEY_ECDSA &&
1244: server_host_key->ecdsa_nid != kex->hostkey_nid))
1245: return SSH_ERR_KEY_TYPE_MISMATCH;
1246: if (kex->verify_host_key(server_host_key, ssh) == -1)
1247: return SSH_ERR_SIGNATURE_INVALID;
1.145 djm 1248: return 0;
1249: }
1.26 markus 1250:
1.84 djm 1251: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1.26 markus 1252: void
1.147 djm 1253: dump_digest(const char *msg, const u_char *digest, int len)
1.26 markus 1254: {
1255: fprintf(stderr, "%s\n", msg);
1.102 markus 1256: sshbuf_dump_data(digest, len, stderr);
1.26 markus 1257: }
1258: #endif
1.143 djm 1259:
1260: /*
1261: * Send a plaintext error message to the peer, suffixed by \r\n.
1262: * Only used during banner exchange, and there only for the server.
1263: */
1264: static void
1265: send_error(struct ssh *ssh, char *msg)
1266: {
1267: char *crnl = "\r\n";
1268:
1269: if (!ssh->kex->server)
1270: return;
1271:
1272: if (atomicio(vwrite, ssh_packet_get_connection_out(ssh),
1273: msg, strlen(msg)) != strlen(msg) ||
1274: atomicio(vwrite, ssh_packet_get_connection_out(ssh),
1275: crnl, strlen(crnl)) != strlen(crnl))
1.160 djm 1276: error_f("write: %.100s", strerror(errno));
1.143 djm 1277: }
1278:
1279: /*
1280: * Sends our identification string and waits for the peer's. Will block for
1281: * up to timeout_ms (or indefinitely if timeout_ms <= 0).
1282: * Returns on 0 success or a ssherr.h code on failure.
1283: */
1284: int
1285: kex_exchange_identification(struct ssh *ssh, int timeout_ms,
1286: const char *version_addendum)
1287: {
1.158 djm 1288: int remote_major, remote_minor, mismatch, oerrno = 0;
1.173 dtucker 1289: size_t len, n;
1.143 djm 1290: int r, expect_nl;
1291: u_char c;
1292: struct sshbuf *our_version = ssh->kex->server ?
1293: ssh->kex->server_version : ssh->kex->client_version;
1294: struct sshbuf *peer_version = ssh->kex->server ?
1295: ssh->kex->client_version : ssh->kex->server_version;
1296: char *our_version_string = NULL, *peer_version_string = NULL;
1297: char *cp, *remote_version = NULL;
1298:
1299: /* Prepare and send our banner */
1300: sshbuf_reset(our_version);
1301: if (version_addendum != NULL && *version_addendum == '\0')
1302: version_addendum = NULL;
1303: if ((r = sshbuf_putf(our_version, "SSH-%d.%d-%.100s%s%s\r\n",
1.168 djm 1304: PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION,
1.143 djm 1305: version_addendum == NULL ? "" : " ",
1306: version_addendum == NULL ? "" : version_addendum)) != 0) {
1.158 djm 1307: oerrno = errno;
1.160 djm 1308: error_fr(r, "sshbuf_putf");
1.143 djm 1309: goto out;
1310: }
1311:
1312: if (atomicio(vwrite, ssh_packet_get_connection_out(ssh),
1313: sshbuf_mutable_ptr(our_version),
1314: sshbuf_len(our_version)) != sshbuf_len(our_version)) {
1.158 djm 1315: oerrno = errno;
1.160 djm 1316: debug_f("write: %.100s", strerror(errno));
1.143 djm 1317: r = SSH_ERR_SYSTEM_ERROR;
1318: goto out;
1319: }
1320: if ((r = sshbuf_consume_end(our_version, 2)) != 0) { /* trim \r\n */
1.158 djm 1321: oerrno = errno;
1.160 djm 1322: error_fr(r, "sshbuf_consume_end");
1.143 djm 1323: goto out;
1324: }
1325: our_version_string = sshbuf_dup_string(our_version);
1326: if (our_version_string == NULL) {
1.160 djm 1327: error_f("sshbuf_dup_string failed");
1.143 djm 1328: r = SSH_ERR_ALLOC_FAIL;
1329: goto out;
1330: }
1331: debug("Local version string %.100s", our_version_string);
1332:
1333: /* Read other side's version identification. */
1334: for (n = 0; ; n++) {
1335: if (n >= SSH_MAX_PRE_BANNER_LINES) {
1336: send_error(ssh, "No SSH identification string "
1337: "received.");
1.160 djm 1338: error_f("No SSH version received in first %u lines "
1339: "from server", SSH_MAX_PRE_BANNER_LINES);
1.143 djm 1340: r = SSH_ERR_INVALID_FORMAT;
1341: goto out;
1342: }
1343: sshbuf_reset(peer_version);
1344: expect_nl = 0;
1.173 dtucker 1345: for (;;) {
1.143 djm 1346: if (timeout_ms > 0) {
1347: r = waitrfd(ssh_packet_get_connection_in(ssh),
1348: &timeout_ms);
1349: if (r == -1 && errno == ETIMEDOUT) {
1350: send_error(ssh, "Timed out waiting "
1351: "for SSH identification string.");
1352: error("Connection timed out during "
1353: "banner exchange");
1354: r = SSH_ERR_CONN_TIMEOUT;
1355: goto out;
1356: } else if (r == -1) {
1.158 djm 1357: oerrno = errno;
1.160 djm 1358: error_f("%s", strerror(errno));
1.143 djm 1359: r = SSH_ERR_SYSTEM_ERROR;
1360: goto out;
1361: }
1362: }
1363:
1364: len = atomicio(read, ssh_packet_get_connection_in(ssh),
1365: &c, 1);
1366: if (len != 1 && errno == EPIPE) {
1.160 djm 1367: error_f("Connection closed by remote host");
1.143 djm 1368: r = SSH_ERR_CONN_CLOSED;
1369: goto out;
1370: } else if (len != 1) {
1.158 djm 1371: oerrno = errno;
1.160 djm 1372: error_f("read: %.100s", strerror(errno));
1.143 djm 1373: r = SSH_ERR_SYSTEM_ERROR;
1374: goto out;
1375: }
1376: if (c == '\r') {
1377: expect_nl = 1;
1378: continue;
1379: }
1380: if (c == '\n')
1381: break;
1382: if (c == '\0' || expect_nl) {
1.160 djm 1383: error_f("banner line contains invalid "
1384: "characters");
1.143 djm 1385: goto invalid;
1386: }
1387: if ((r = sshbuf_put_u8(peer_version, c)) != 0) {
1.158 djm 1388: oerrno = errno;
1.160 djm 1389: error_fr(r, "sshbuf_put");
1.143 djm 1390: goto out;
1391: }
1392: if (sshbuf_len(peer_version) > SSH_MAX_BANNER_LEN) {
1.160 djm 1393: error_f("banner line too long");
1.143 djm 1394: goto invalid;
1395: }
1396: }
1397: /* Is this an actual protocol banner? */
1398: if (sshbuf_len(peer_version) > 4 &&
1399: memcmp(sshbuf_ptr(peer_version), "SSH-", 4) == 0)
1400: break;
1401: /* If not, then just log the line and continue */
1402: if ((cp = sshbuf_dup_string(peer_version)) == NULL) {
1.160 djm 1403: error_f("sshbuf_dup_string failed");
1.143 djm 1404: r = SSH_ERR_ALLOC_FAIL;
1405: goto out;
1406: }
1407: /* Do not accept lines before the SSH ident from a client */
1408: if (ssh->kex->server) {
1.160 djm 1409: error_f("client sent invalid protocol identifier "
1410: "\"%.256s\"", cp);
1.143 djm 1411: free(cp);
1412: goto invalid;
1413: }
1.160 djm 1414: debug_f("banner line %zu: %s", n, cp);
1.143 djm 1415: free(cp);
1416: }
1417: peer_version_string = sshbuf_dup_string(peer_version);
1418: if (peer_version_string == NULL)
1.175 dtucker 1419: fatal_f("sshbuf_dup_string failed");
1.143 djm 1420: /* XXX must be same size for sscanf */
1421: if ((remote_version = calloc(1, sshbuf_len(peer_version))) == NULL) {
1.160 djm 1422: error_f("calloc failed");
1.143 djm 1423: r = SSH_ERR_ALLOC_FAIL;
1424: goto out;
1425: }
1426:
1427: /*
1428: * Check that the versions match. In future this might accept
1429: * several versions and set appropriate flags to handle them.
1430: */
1431: if (sscanf(peer_version_string, "SSH-%d.%d-%[^\n]\n",
1432: &remote_major, &remote_minor, remote_version) != 3) {
1433: error("Bad remote protocol version identification: '%.100s'",
1434: peer_version_string);
1435: invalid:
1436: send_error(ssh, "Invalid SSH identification string.");
1437: r = SSH_ERR_INVALID_FORMAT;
1438: goto out;
1439: }
1440: debug("Remote protocol version %d.%d, remote software version %.100s",
1441: remote_major, remote_minor, remote_version);
1.164 djm 1442: compat_banner(ssh, remote_version);
1.143 djm 1443:
1444: mismatch = 0;
1445: switch (remote_major) {
1446: case 2:
1447: break;
1448: case 1:
1449: if (remote_minor != 99)
1450: mismatch = 1;
1451: break;
1452: default:
1453: mismatch = 1;
1454: break;
1455: }
1456: if (mismatch) {
1457: error("Protocol major versions differ: %d vs. %d",
1458: PROTOCOL_MAJOR_2, remote_major);
1459: send_error(ssh, "Protocol major versions differ.");
1460: r = SSH_ERR_NO_PROTOCOL_VERSION;
1461: goto out;
1462: }
1463:
1464: if (ssh->kex->server && (ssh->compat & SSH_BUG_PROBE) != 0) {
1465: logit("probed from %s port %d with %s. Don't panic.",
1466: ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
1467: peer_version_string);
1468: r = SSH_ERR_CONN_CLOSED; /* XXX */
1469: goto out;
1470: }
1471: if (ssh->kex->server && (ssh->compat & SSH_BUG_SCANNER) != 0) {
1472: logit("scanned from %s port %d with %s. Don't panic.",
1473: ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
1474: peer_version_string);
1475: r = SSH_ERR_CONN_CLOSED; /* XXX */
1476: goto out;
1477: }
1478: /* success */
1479: r = 0;
1480: out:
1481: free(our_version_string);
1482: free(peer_version_string);
1483: free(remote_version);
1.158 djm 1484: if (r == SSH_ERR_SYSTEM_ERROR)
1485: errno = oerrno;
1.143 djm 1486: return r;
1487: }
1488:
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