Annotation of src/usr.bin/ssh/kex.c, Revision 1.186
1.186 ! djm 1: /* $OpenBSD: kex.c,v 1.185 2024/01/08 00:34:33 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:
1.176 dtucker 79: /*
80: * Fill out a proposal array with dynamically allocated values, which may
81: * be modified as required for compatibility reasons.
82: * Any of the options may be NULL, in which case the default is used.
83: * Array contents must be freed by calling kex_proposal_free_entries.
84: */
85: void
86: kex_proposal_populate_entries(struct ssh *ssh, char *prop[PROPOSAL_MAX],
87: const char *kexalgos, const char *ciphers, const char *macs,
88: const char *comp, const char *hkalgs)
89: {
90: const char *defpropserver[PROPOSAL_MAX] = { KEX_SERVER };
91: const char *defpropclient[PROPOSAL_MAX] = { KEX_CLIENT };
92: const char **defprop = ssh->kex->server ? defpropserver : defpropclient;
93: u_int i;
1.183 djm 94: char *cp;
1.176 dtucker 95:
96: if (prop == NULL)
97: fatal_f("proposal missing");
98:
1.183 djm 99: /* Append EXT_INFO signalling to KexAlgorithms */
100: if (kexalgos == NULL)
101: kexalgos = defprop[PROPOSAL_KEX_ALGS];
102: if ((cp = kex_names_cat(kexalgos, ssh->kex->server ?
1.184 djm 103: "ext-info-s,kex-strict-s-v00@openssh.com" :
1.183 djm 104: "ext-info-c,kex-strict-c-v00@openssh.com")) == NULL)
105: fatal_f("kex_names_cat");
106:
1.176 dtucker 107: for (i = 0; i < PROPOSAL_MAX; i++) {
108: switch(i) {
109: case PROPOSAL_KEX_ALGS:
1.183 djm 110: prop[i] = compat_kex_proposal(ssh, cp);
1.176 dtucker 111: break;
112: case PROPOSAL_ENC_ALGS_CTOS:
113: case PROPOSAL_ENC_ALGS_STOC:
114: prop[i] = xstrdup(ciphers ? ciphers : defprop[i]);
115: break;
116: case PROPOSAL_MAC_ALGS_CTOS:
117: case PROPOSAL_MAC_ALGS_STOC:
118: prop[i] = xstrdup(macs ? macs : defprop[i]);
119: break;
120: case PROPOSAL_COMP_ALGS_CTOS:
121: case PROPOSAL_COMP_ALGS_STOC:
122: prop[i] = xstrdup(comp ? comp : defprop[i]);
123: break;
124: case PROPOSAL_SERVER_HOST_KEY_ALGS:
125: prop[i] = xstrdup(hkalgs ? hkalgs : defprop[i]);
126: break;
127: default:
128: prop[i] = xstrdup(defprop[i]);
129: }
130: }
1.183 djm 131: free(cp);
1.176 dtucker 132: }
133:
134: void
135: kex_proposal_free_entries(char *prop[PROPOSAL_MAX])
136: {
137: u_int i;
138:
139: for (i = 0; i < PROPOSAL_MAX; i++)
140: free(prop[i]);
1.86 djm 141: }
1.26 markus 142:
143: /* put algorithm proposal into buffer */
1.102 markus 144: int
145: kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
1.1 markus 146: {
1.61 djm 147: u_int i;
1.102 markus 148: int r;
149:
150: sshbuf_reset(b);
1.26 markus 151:
1.49 markus 152: /*
153: * add a dummy cookie, the cookie will be overwritten by
154: * kex_send_kexinit(), each time a kexinit is set
155: */
1.102 markus 156: for (i = 0; i < KEX_COOKIE_LEN; i++) {
157: if ((r = sshbuf_put_u8(b, 0)) != 0)
158: return r;
159: }
160: for (i = 0; i < PROPOSAL_MAX; i++) {
161: if ((r = sshbuf_put_cstring(b, proposal[i])) != 0)
162: return r;
163: }
164: if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */
165: (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */
166: return r;
167: return 0;
1.1 markus 168: }
169:
1.26 markus 170: /* parse buffer and return algorithm proposal */
1.102 markus 171: int
172: kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp)
1.7 markus 173: {
1.102 markus 174: struct sshbuf *b = NULL;
175: u_char v;
1.78 djm 176: u_int i;
1.102 markus 177: char **proposal = NULL;
178: int r;
1.7 markus 179:
1.102 markus 180: *propp = NULL;
181: if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL)
182: return SSH_ERR_ALLOC_FAIL;
183: if ((b = sshbuf_fromb(raw)) == NULL) {
184: r = SSH_ERR_ALLOC_FAIL;
185: goto out;
186: }
1.152 djm 187: if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) { /* skip cookie */
1.160 djm 188: error_fr(r, "consume cookie");
1.102 markus 189: goto out;
1.152 djm 190: }
1.7 markus 191: /* extract kex init proposal strings */
192: for (i = 0; i < PROPOSAL_MAX; i++) {
1.152 djm 193: if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0) {
1.160 djm 194: error_fr(r, "parse proposal %u", i);
1.102 markus 195: goto out;
1.152 djm 196: }
1.110 djm 197: debug2("%s: %s", proposal_names[i], proposal[i]);
1.7 markus 198: }
1.26 markus 199: /* first kex follows / reserved */
1.115 djm 200: if ((r = sshbuf_get_u8(b, &v)) != 0 || /* first_kex_follows */
1.152 djm 201: (r = sshbuf_get_u32(b, &i)) != 0) { /* reserved */
1.160 djm 202: error_fr(r, "parse");
1.102 markus 203: goto out;
1.152 djm 204: }
1.53 markus 205: if (first_kex_follows != NULL)
1.115 djm 206: *first_kex_follows = v;
1.110 djm 207: debug2("first_kex_follows %d ", v);
208: debug2("reserved %u ", i);
1.102 markus 209: r = 0;
210: *propp = proposal;
211: out:
212: if (r != 0 && proposal != NULL)
213: kex_prop_free(proposal);
214: sshbuf_free(b);
215: return r;
1.1 markus 216: }
217:
1.102 markus 218: void
1.26 markus 219: kex_prop_free(char **proposal)
1.1 markus 220: {
1.61 djm 221: u_int i;
1.26 markus 222:
1.106 djm 223: if (proposal == NULL)
224: return;
1.26 markus 225: for (i = 0; i < PROPOSAL_MAX; i++)
1.91 djm 226: free(proposal[i]);
227: free(proposal);
1.1 markus 228: }
229:
1.167 djm 230: int
1.133 markus 231: kex_protocol_error(int type, u_int32_t seq, struct ssh *ssh)
1.1 markus 232: {
1.112 djm 233: int r;
234:
1.183 djm 235: /* If in strict mode, any unexpected message is an error */
236: if ((ssh->kex->flags & KEX_INITIAL) && ssh->kex->kex_strict) {
237: ssh_packet_disconnect(ssh, "strict KEX violation: "
238: "unexpected packet type %u (seqnr %u)", type, seq);
239: }
240: error_f("type %u seq %u", type, seq);
1.112 djm 241: if ((r = sshpkt_start(ssh, SSH2_MSG_UNIMPLEMENTED)) != 0 ||
242: (r = sshpkt_put_u32(ssh, seq)) != 0 ||
243: (r = sshpkt_send(ssh)) != 0)
244: return r;
1.101 markus 245: return 0;
1.26 markus 246: }
1.1 markus 247:
1.35 itojun 248: static void
1.102 markus 249: kex_reset_dispatch(struct ssh *ssh)
1.29 markus 250: {
1.102 markus 251: ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
1.42 markus 252: SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
1.29 markus 253: }
254:
1.184 djm 255: void
256: kex_set_server_sig_algs(struct ssh *ssh, const char *allowed_algs)
257: {
258: char *alg, *oalgs, *algs, *sigalgs;
259: const char *sigalg;
260:
261: /*
262: * NB. allowed algorithms may contain certificate algorithms that
263: * map to a specific plain signature type, e.g.
264: * rsa-sha2-512-cert-v01@openssh.com => rsa-sha2-512
265: * We need to be careful here to match these, retain the mapping
266: * and only add each signature algorithm once.
267: */
268: if ((sigalgs = sshkey_alg_list(0, 1, 1, ',')) == NULL)
269: fatal_f("sshkey_alg_list failed");
270: oalgs = algs = xstrdup(allowed_algs);
271: free(ssh->kex->server_sig_algs);
272: ssh->kex->server_sig_algs = NULL;
273: for ((alg = strsep(&algs, ",")); alg != NULL && *alg != '\0';
274: (alg = strsep(&algs, ","))) {
275: if ((sigalg = sshkey_sigalg_by_name(alg)) == NULL)
276: continue;
1.186 ! djm 277: if (!kex_has_any_alg(sigalg, sigalgs))
1.184 djm 278: continue;
279: /* Don't add an algorithm twice. */
280: if (ssh->kex->server_sig_algs != NULL &&
1.186 ! djm 281: kex_has_any_alg(sigalg, ssh->kex->server_sig_algs))
1.184 djm 282: continue;
283: xextendf(&ssh->kex->server_sig_algs, ",", "%s", sigalg);
284: }
285: free(oalgs);
286: free(sigalgs);
287: if (ssh->kex->server_sig_algs == NULL)
288: ssh->kex->server_sig_algs = xstrdup("");
289: }
290:
1.113 markus 291: static int
1.184 djm 292: kex_compose_ext_info_server(struct ssh *ssh, struct sshbuf *m)
1.113 markus 293: {
294: int r;
295:
1.184 djm 296: if (ssh->kex->server_sig_algs == NULL &&
297: (ssh->kex->server_sig_algs = sshkey_alg_list(0, 1, 1, ',')) == NULL)
1.121 djm 298: return SSH_ERR_ALLOC_FAIL;
1.184 djm 299: if ((r = sshbuf_put_u32(m, 3)) != 0 ||
300: (r = sshbuf_put_cstring(m, "server-sig-algs")) != 0 ||
301: (r = sshbuf_put_cstring(m, ssh->kex->server_sig_algs)) != 0 ||
302: (r = sshbuf_put_cstring(m,
1.170 djm 303: "publickey-hostbound@openssh.com")) != 0 ||
1.184 djm 304: (r = sshbuf_put_cstring(m, "0")) != 0 ||
305: (r = sshbuf_put_cstring(m, "ping@openssh.com")) != 0 ||
306: (r = sshbuf_put_cstring(m, "0")) != 0) {
307: error_fr(r, "compose");
308: return r;
309: }
310: return 0;
311: }
312:
313: static int
314: kex_compose_ext_info_client(struct ssh *ssh, struct sshbuf *m)
315: {
316: int r;
317:
318: if ((r = sshbuf_put_u32(m, 1)) != 0 ||
319: (r = sshbuf_put_cstring(m, "ext-info-in-auth@openssh.com")) != 0 ||
320: (r = sshbuf_put_cstring(m, "0")) != 0) {
1.160 djm 321: error_fr(r, "compose");
1.121 djm 322: goto out;
1.152 djm 323: }
1.121 djm 324: /* success */
325: r = 0;
326: out:
1.123 djm 327: return r;
1.113 markus 328: }
329:
1.184 djm 330: static int
331: kex_maybe_send_ext_info(struct ssh *ssh)
332: {
333: int r;
334: struct sshbuf *m = NULL;
335:
336: if ((ssh->kex->flags & KEX_INITIAL) == 0)
337: return 0;
338: if (!ssh->kex->ext_info_c && !ssh->kex->ext_info_s)
339: return 0;
340:
341: /* Compose EXT_INFO packet. */
342: if ((m = sshbuf_new()) == NULL)
343: fatal_f("sshbuf_new failed");
344: if (ssh->kex->ext_info_c &&
345: (r = kex_compose_ext_info_server(ssh, m)) != 0)
346: goto fail;
347: if (ssh->kex->ext_info_s &&
348: (r = kex_compose_ext_info_client(ssh, m)) != 0)
349: goto fail;
350:
351: /* Send the actual KEX_INFO packet */
352: debug("Sending SSH2_MSG_EXT_INFO");
353: if ((r = sshpkt_start(ssh, SSH2_MSG_EXT_INFO)) != 0 ||
354: (r = sshpkt_putb(ssh, m)) != 0 ||
355: (r = sshpkt_send(ssh)) != 0) {
356: error_f("send EXT_INFO");
357: goto fail;
358: }
359:
360: r = 0;
361:
362: fail:
363: sshbuf_free(m);
364: return r;
365: }
366:
367: int
368: kex_server_update_ext_info(struct ssh *ssh)
369: {
370: int r;
371:
372: if ((ssh->kex->flags & KEX_HAS_EXT_INFO_IN_AUTH) == 0)
373: return 0;
374:
375: debug_f("Sending SSH2_MSG_EXT_INFO");
376: if ((r = sshpkt_start(ssh, SSH2_MSG_EXT_INFO)) != 0 ||
377: (r = sshpkt_put_u32(ssh, 1)) != 0 ||
378: (r = sshpkt_put_cstring(ssh, "server-sig-algs")) != 0 ||
379: (r = sshpkt_put_cstring(ssh, ssh->kex->server_sig_algs)) != 0 ||
380: (r = sshpkt_send(ssh)) != 0) {
381: error_f("send EXT_INFO");
382: return r;
383: }
384: return 0;
385: }
386:
1.102 markus 387: int
388: kex_send_newkeys(struct ssh *ssh)
1.26 markus 389: {
1.102 markus 390: int r;
1.28 markus 391:
1.102 markus 392: kex_reset_dispatch(ssh);
393: if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
394: (r = sshpkt_send(ssh)) != 0)
395: return r;
1.26 markus 396: debug("SSH2_MSG_NEWKEYS sent");
1.102 markus 397: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
1.184 djm 398: if ((r = kex_maybe_send_ext_info(ssh)) != 0)
399: return r;
1.151 djm 400: debug("expecting SSH2_MSG_NEWKEYS");
1.102 markus 401: return 0;
402: }
403:
1.181 djm 404: /* Check whether an ext_info value contains the expected version string */
405: static int
406: kex_ext_info_check_ver(struct kex *kex, const char *name,
407: const u_char *val, size_t len, const char *want_ver, u_int flag)
408: {
409: if (memchr(val, '\0', len) != NULL) {
410: error("SSH2_MSG_EXT_INFO: %s value contains nul byte", name);
411: return SSH_ERR_INVALID_FORMAT;
412: }
413: debug_f("%s=<%s>", name, val);
414: if (strcmp(val, want_ver) == 0)
415: kex->flags |= flag;
416: else
417: debug_f("unsupported version of %s extension", name);
418: return 0;
419: }
420:
1.184 djm 421: static int
422: kex_ext_info_client_parse(struct ssh *ssh, const char *name,
423: const u_char *value, size_t vlen)
424: {
425: int r;
426:
427: /* NB. some messages are only accepted in the initial EXT_INFO */
428: if (strcmp(name, "server-sig-algs") == 0) {
429: /* Ensure no \0 lurking in value */
430: if (memchr(value, '\0', vlen) != NULL) {
431: error_f("nul byte in %s", name);
432: return SSH_ERR_INVALID_FORMAT;
433: }
434: debug_f("%s=<%s>", name, value);
435: free(ssh->kex->server_sig_algs);
436: ssh->kex->server_sig_algs = xstrdup((const char *)value);
437: } else if (ssh->kex->ext_info_received == 1 &&
438: strcmp(name, "publickey-hostbound@openssh.com") == 0) {
439: if ((r = kex_ext_info_check_ver(ssh->kex, name, value, vlen,
440: "0", KEX_HAS_PUBKEY_HOSTBOUND)) != 0) {
441: return r;
442: }
443: } else if (ssh->kex->ext_info_received == 1 &&
444: strcmp(name, "ping@openssh.com") == 0) {
445: if ((r = kex_ext_info_check_ver(ssh->kex, name, value, vlen,
446: "0", KEX_HAS_PING)) != 0) {
447: return r;
448: }
449: } else
450: debug_f("%s (unrecognised)", name);
451:
452: return 0;
453: }
454:
455: static int
456: kex_ext_info_server_parse(struct ssh *ssh, const char *name,
457: const u_char *value, size_t vlen)
458: {
459: int r;
460:
461: if (strcmp(name, "ext-info-in-auth@openssh.com") == 0) {
462: if ((r = kex_ext_info_check_ver(ssh->kex, name, value, vlen,
463: "0", KEX_HAS_EXT_INFO_IN_AUTH)) != 0) {
464: return r;
465: }
466: } else
467: debug_f("%s (unrecognised)", name);
468: return 0;
469: }
470:
1.113 markus 471: int
1.133 markus 472: kex_input_ext_info(int type, u_int32_t seq, struct ssh *ssh)
1.113 markus 473: {
474: struct kex *kex = ssh->kex;
1.184 djm 475: const int max_ext_info = kex->server ? 1 : 2;
1.113 markus 476: u_int32_t i, ninfo;
1.137 djm 477: char *name;
1.134 djm 478: u_char *val;
479: size_t vlen;
1.113 markus 480: int r;
481:
482: debug("SSH2_MSG_EXT_INFO received");
1.184 djm 483: if (++kex->ext_info_received > max_ext_info) {
484: error("too many SSH2_MSG_EXT_INFO messages sent by peer");
485: return dispatch_protocol_error(type, seq, ssh);
486: }
1.113 markus 487: ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_protocol_error);
488: if ((r = sshpkt_get_u32(ssh, &ninfo)) != 0)
489: return r;
1.178 dtucker 490: if (ninfo >= 1024) {
491: error("SSH2_MSG_EXT_INFO with too many entries, expected "
492: "<=1024, received %u", ninfo);
1.183 djm 493: return dispatch_protocol_error(type, seq, ssh);
1.178 dtucker 494: }
1.113 markus 495: for (i = 0; i < ninfo; i++) {
496: if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0)
497: return r;
1.134 djm 498: if ((r = sshpkt_get_string(ssh, &val, &vlen)) != 0) {
1.113 markus 499: free(name);
500: return r;
501: }
1.184 djm 502: debug3_f("extension %s", name);
503: if (kex->server) {
504: if ((r = kex_ext_info_server_parse(ssh, name,
505: val, vlen)) != 0)
1.181 djm 506: return r;
1.184 djm 507: } else {
508: if ((r = kex_ext_info_client_parse(ssh, name,
509: val, vlen)) != 0)
1.181 djm 510: return r;
1.184 djm 511: }
1.113 markus 512: free(name);
513: free(val);
514: }
515: return sshpkt_get_end(ssh);
516: }
517:
1.102 markus 518: static int
1.133 markus 519: kex_input_newkeys(int type, u_int32_t seq, struct ssh *ssh)
1.102 markus 520: {
521: struct kex *kex = ssh->kex;
1.185 djm 522: int r, initial = (kex->flags & KEX_INITIAL) != 0;
523: char *cp, **prop;
1.19 stevesk 524:
1.26 markus 525: debug("SSH2_MSG_NEWKEYS received");
1.185 djm 526: if (kex->ext_info_c && initial)
1.184 djm 527: ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_input_ext_info);
1.102 markus 528: ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
1.131 markus 529: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
1.102 markus 530: if ((r = sshpkt_get_end(ssh)) != 0)
1.122 markus 531: return r;
532: if ((r = ssh_set_newkeys(ssh, MODE_IN)) != 0)
1.102 markus 533: return r;
1.185 djm 534: if (initial) {
535: /* Remove initial KEX signalling from proposal for rekeying */
536: if ((r = kex_buf2prop(kex->my, NULL, &prop)) != 0)
537: return r;
538: if ((cp = match_filter_denylist(prop[PROPOSAL_KEX_ALGS],
539: kex->server ?
540: "ext-info-s,kex-strict-s-v00@openssh.com" :
541: "ext-info-c,kex-strict-c-v00@openssh.com")) == NULL) {
542: error_f("match_filter_denylist failed");
543: goto fail;
544: }
545: free(prop[PROPOSAL_KEX_ALGS]);
546: prop[PROPOSAL_KEX_ALGS] = cp;
547: if ((r = kex_prop2buf(ssh->kex->my, prop)) != 0) {
548: error_f("kex_prop2buf failed");
549: fail:
550: kex_proposal_free_entries(prop);
551: free(prop);
552: return SSH_ERR_INTERNAL_ERROR;
553: }
554: kex_proposal_free_entries(prop);
555: free(prop);
556: }
1.30 markus 557: kex->done = 1;
1.142 djm 558: kex->flags &= ~KEX_INITIAL;
1.102 markus 559: sshbuf_reset(kex->peer);
1.26 markus 560: kex->flags &= ~KEX_INIT_SENT;
1.91 djm 561: free(kex->name);
1.32 markus 562: kex->name = NULL;
1.102 markus 563: return 0;
1.26 markus 564: }
1.1 markus 565:
1.102 markus 566: int
567: kex_send_kexinit(struct ssh *ssh)
1.26 markus 568: {
1.49 markus 569: u_char *cookie;
1.102 markus 570: struct kex *kex = ssh->kex;
571: int r;
1.49 markus 572:
1.152 djm 573: if (kex == NULL) {
1.161 djm 574: error_f("no kex");
1.102 markus 575: return SSH_ERR_INTERNAL_ERROR;
1.152 djm 576: }
1.102 markus 577: if (kex->flags & KEX_INIT_SENT)
578: return 0;
1.30 markus 579: kex->done = 0;
1.49 markus 580:
581: /* generate a random cookie */
1.152 djm 582: if (sshbuf_len(kex->my) < KEX_COOKIE_LEN) {
1.160 djm 583: error_f("bad kex length: %zu < %d",
1.152 djm 584: sshbuf_len(kex->my), KEX_COOKIE_LEN);
1.102 markus 585: return SSH_ERR_INVALID_FORMAT;
1.152 djm 586: }
587: if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL) {
1.160 djm 588: error_f("buffer error");
1.102 markus 589: return SSH_ERR_INTERNAL_ERROR;
1.152 djm 590: }
1.102 markus 591: arc4random_buf(cookie, KEX_COOKIE_LEN);
592:
593: if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
594: (r = sshpkt_putb(ssh, kex->my)) != 0 ||
1.152 djm 595: (r = sshpkt_send(ssh)) != 0) {
1.160 djm 596: error_fr(r, "compose reply");
1.102 markus 597: return r;
1.152 djm 598: }
1.26 markus 599: debug("SSH2_MSG_KEXINIT sent");
600: kex->flags |= KEX_INIT_SENT;
1.102 markus 601: return 0;
1.1 markus 602: }
603:
1.101 markus 604: int
1.133 markus 605: kex_input_kexinit(int type, u_int32_t seq, struct ssh *ssh)
1.11 provos 606: {
1.102 markus 607: struct kex *kex = ssh->kex;
608: const u_char *ptr;
1.100 markus 609: u_int i;
610: size_t dlen;
1.102 markus 611: int r;
1.11 provos 612:
1.26 markus 613: debug("SSH2_MSG_KEXINIT received");
1.152 djm 614: if (kex == NULL) {
1.161 djm 615: error_f("no kex");
1.152 djm 616: return SSH_ERR_INTERNAL_ERROR;
617: }
1.183 djm 618: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_protocol_error);
1.102 markus 619: ptr = sshpkt_ptr(ssh, &dlen);
620: if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
621: return r;
1.31 markus 622:
623: /* discard packet */
1.152 djm 624: for (i = 0; i < KEX_COOKIE_LEN; i++) {
625: if ((r = sshpkt_get_u8(ssh, NULL)) != 0) {
1.160 djm 626: error_fr(r, "discard cookie");
1.102 markus 627: return r;
1.152 djm 628: }
629: }
630: for (i = 0; i < PROPOSAL_MAX; i++) {
631: if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0) {
1.160 djm 632: error_fr(r, "discard proposal");
1.102 markus 633: return r;
1.152 djm 634: }
635: }
1.87 djm 636: /*
637: * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
638: * KEX method has the server move first, but a server might be using
639: * a custom method or one that we otherwise don't support. We should
640: * be prepared to remember first_kex_follows here so we can eat a
641: * packet later.
642: * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
643: * for cases where the server *doesn't* go first. I guess we should
644: * ignore it when it is set for these cases, which is what we do now.
645: */
1.102 markus 646: if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
647: (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
648: (r = sshpkt_get_end(ssh)) != 0)
649: return r;
650:
651: if (!(kex->flags & KEX_INIT_SENT))
652: if ((r = kex_send_kexinit(ssh)) != 0)
653: return r;
1.183 djm 654: if ((r = kex_choose_conf(ssh, seq)) != 0)
1.102 markus 655: return r;
1.19 stevesk 656:
1.102 markus 657: if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
658: return (kex->kex[kex->kex_type])(ssh);
659:
1.160 djm 660: error_f("unknown kex type %u", kex->kex_type);
1.102 markus 661: return SSH_ERR_INTERNAL_ERROR;
662: }
663:
1.143 djm 664: struct kex *
665: kex_new(void)
1.102 markus 666: {
667: struct kex *kex;
668:
1.143 djm 669: if ((kex = calloc(1, sizeof(*kex))) == NULL ||
670: (kex->peer = sshbuf_new()) == NULL ||
671: (kex->my = sshbuf_new()) == NULL ||
672: (kex->client_version = sshbuf_new()) == NULL ||
1.165 djm 673: (kex->server_version = sshbuf_new()) == NULL ||
674: (kex->session_id = sshbuf_new()) == NULL) {
1.143 djm 675: kex_free(kex);
676: return NULL;
1.102 markus 677: }
1.143 djm 678: return kex;
1.26 markus 679: }
1.11 provos 680:
1.100 markus 681: void
682: kex_free_newkeys(struct newkeys *newkeys)
683: {
684: if (newkeys == NULL)
685: return;
686: if (newkeys->enc.key) {
687: explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
688: free(newkeys->enc.key);
689: newkeys->enc.key = NULL;
690: }
691: if (newkeys->enc.iv) {
1.111 djm 692: explicit_bzero(newkeys->enc.iv, newkeys->enc.iv_len);
1.100 markus 693: free(newkeys->enc.iv);
694: newkeys->enc.iv = NULL;
695: }
696: free(newkeys->enc.name);
697: explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
698: free(newkeys->comp.name);
699: explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
700: mac_clear(&newkeys->mac);
701: if (newkeys->mac.key) {
702: explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
703: free(newkeys->mac.key);
704: newkeys->mac.key = NULL;
705: }
706: free(newkeys->mac.name);
707: explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
1.157 jsg 708: freezero(newkeys, sizeof(*newkeys));
1.100 markus 709: }
710:
1.102 markus 711: void
712: kex_free(struct kex *kex)
1.26 markus 713: {
1.102 markus 714: u_int mode;
1.11 provos 715:
1.143 djm 716: if (kex == NULL)
717: return;
718:
1.102 markus 719: #ifdef WITH_OPENSSL
1.136 jsing 720: DH_free(kex->dh);
721: EC_KEY_free(kex->ec_client_key);
1.102 markus 722: #endif
723: for (mode = 0; mode < MODE_MAX; mode++) {
724: kex_free_newkeys(kex->newkeys[mode]);
725: kex->newkeys[mode] = NULL;
1.100 markus 726: }
1.102 markus 727: sshbuf_free(kex->peer);
728: sshbuf_free(kex->my);
1.143 djm 729: sshbuf_free(kex->client_version);
730: sshbuf_free(kex->server_version);
1.149 djm 731: sshbuf_free(kex->client_pub);
1.165 djm 732: sshbuf_free(kex->session_id);
1.169 djm 733: sshbuf_free(kex->initial_sig);
734: sshkey_free(kex->initial_hostkey);
1.107 djm 735: free(kex->failed_choice);
1.113 markus 736: free(kex->hostkey_alg);
737: free(kex->name);
1.102 markus 738: free(kex);
1.11 provos 739: }
740:
1.102 markus 741: int
1.143 djm 742: kex_ready(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
743: {
744: int r;
745:
746: if ((r = kex_prop2buf(ssh->kex->my, proposal)) != 0)
747: return r;
748: ssh->kex->flags = KEX_INITIAL;
749: kex_reset_dispatch(ssh);
750: ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
751: return 0;
752: }
753:
754: int
1.102 markus 755: kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
1.1 markus 756: {
1.102 markus 757: int r;
1.1 markus 758:
1.143 djm 759: if ((r = kex_ready(ssh, proposal)) != 0)
1.102 markus 760: return r;
761: if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
762: kex_free(ssh->kex);
763: ssh->kex = NULL;
764: return r;
1.1 markus 765: }
1.102 markus 766: return 0;
1.117 djm 767: }
768:
769: /*
770: * Request key re-exchange, returns 0 on success or a ssherr.h error
771: * code otherwise. Must not be called if KEX is incomplete or in-progress.
772: */
773: int
774: kex_start_rekex(struct ssh *ssh)
775: {
776: if (ssh->kex == NULL) {
1.160 djm 777: error_f("no kex");
1.117 djm 778: return SSH_ERR_INTERNAL_ERROR;
779: }
780: if (ssh->kex->done == 0) {
1.160 djm 781: error_f("requested twice");
1.117 djm 782: return SSH_ERR_INTERNAL_ERROR;
783: }
784: ssh->kex->done = 0;
785: return kex_send_kexinit(ssh);
1.1 markus 786: }
787:
1.102 markus 788: static int
789: choose_enc(struct sshenc *enc, char *client, char *server)
1.1 markus 790: {
1.23 markus 791: char *name = match_list(client, server, NULL);
1.102 markus 792:
1.1 markus 793: if (name == NULL)
1.102 markus 794: return SSH_ERR_NO_CIPHER_ALG_MATCH;
1.129 dtucker 795: if ((enc->cipher = cipher_by_name(name)) == NULL) {
1.160 djm 796: error_f("unsupported cipher %s", name);
1.129 dtucker 797: free(name);
1.102 markus 798: return SSH_ERR_INTERNAL_ERROR;
1.129 dtucker 799: }
1.1 markus 800: enc->name = name;
801: enc->enabled = 0;
802: enc->iv = NULL;
1.88 markus 803: enc->iv_len = cipher_ivlen(enc->cipher);
1.1 markus 804: enc->key = NULL;
1.45 markus 805: enc->key_len = cipher_keylen(enc->cipher);
806: enc->block_size = cipher_blocksize(enc->cipher);
1.102 markus 807: return 0;
1.1 markus 808: }
1.69 deraadt 809:
1.102 markus 810: static int
811: choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
1.1 markus 812: {
1.23 markus 813: char *name = match_list(client, server, NULL);
1.102 markus 814:
1.1 markus 815: if (name == NULL)
1.102 markus 816: return SSH_ERR_NO_MAC_ALG_MATCH;
1.129 dtucker 817: if (mac_setup(mac, name) < 0) {
1.160 djm 818: error_f("unsupported MAC %s", name);
1.129 dtucker 819: free(name);
1.102 markus 820: return SSH_ERR_INTERNAL_ERROR;
1.129 dtucker 821: }
1.1 markus 822: mac->name = name;
823: mac->key = NULL;
824: mac->enabled = 0;
1.102 markus 825: return 0;
1.1 markus 826: }
1.69 deraadt 827:
1.102 markus 828: static int
829: choose_comp(struct sshcomp *comp, char *client, char *server)
1.1 markus 830: {
1.23 markus 831: char *name = match_list(client, server, NULL);
1.102 markus 832:
1.1 markus 833: if (name == NULL)
1.102 markus 834: return SSH_ERR_NO_COMPRESS_ALG_MATCH;
1.156 dtucker 835: #ifdef WITH_ZLIB
1.64 markus 836: if (strcmp(name, "zlib@openssh.com") == 0) {
1.141 sf 837: comp->type = COMP_DELAYED;
838: } else if (strcmp(name, "zlib") == 0) {
1.140 sf 839: comp->type = COMP_ZLIB;
1.156 dtucker 840: } else
841: #endif /* WITH_ZLIB */
842: if (strcmp(name, "none") == 0) {
1.64 markus 843: comp->type = COMP_NONE;
1.1 markus 844: } else {
1.160 djm 845: error_f("unsupported compression scheme %s", name);
1.129 dtucker 846: free(name);
1.102 markus 847: return SSH_ERR_INTERNAL_ERROR;
1.1 markus 848: }
849: comp->name = name;
1.102 markus 850: return 0;
1.1 markus 851: }
1.69 deraadt 852:
1.102 markus 853: static int
854: choose_kex(struct kex *k, char *client, char *server)
1.1 markus 855: {
1.23 markus 856: k->name = match_list(client, server, NULL);
1.102 markus 857:
1.110 djm 858: debug("kex: algorithm: %s", k->name ? k->name : "(no match)");
1.1 markus 859: if (k->name == NULL)
1.102 markus 860: return SSH_ERR_NO_KEX_ALG_MATCH;
1.186 ! djm 861: if (!kex_name_valid(k->name)) {
1.160 djm 862: error_f("unsupported KEX method %s", k->name);
1.102 markus 863: return SSH_ERR_INTERNAL_ERROR;
1.152 djm 864: }
1.186 ! djm 865: k->kex_type = kex_type_from_name(k->name);
! 866: k->hash_alg = kex_hash_from_name(k->name);
! 867: k->ec_nid = kex_nid_from_name(k->name);
1.102 markus 868: return 0;
1.1 markus 869: }
1.65 djm 870:
1.102 markus 871: static int
872: choose_hostkeyalg(struct kex *k, char *client, char *server)
1.1 markus 873: {
1.162 djm 874: free(k->hostkey_alg);
1.113 markus 875: k->hostkey_alg = match_list(client, server, NULL);
1.102 markus 876:
1.110 djm 877: debug("kex: host key algorithm: %s",
1.113 markus 878: k->hostkey_alg ? k->hostkey_alg : "(no match)");
879: if (k->hostkey_alg == NULL)
1.102 markus 880: return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
1.113 markus 881: k->hostkey_type = sshkey_type_from_name(k->hostkey_alg);
1.152 djm 882: if (k->hostkey_type == KEY_UNSPEC) {
1.160 djm 883: error_f("unsupported hostkey algorithm %s", k->hostkey_alg);
1.102 markus 884: return SSH_ERR_INTERNAL_ERROR;
1.152 djm 885: }
1.113 markus 886: k->hostkey_nid = sshkey_ecdsa_nid_from_name(k->hostkey_alg);
1.102 markus 887: return 0;
1.1 markus 888: }
889:
1.56 djm 890: static int
1.53 markus 891: proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
892: {
893: static int check[] = {
894: PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
895: };
896: int *idx;
897: char *p;
898:
899: for (idx = &check[0]; *idx != -1; idx++) {
900: if ((p = strchr(my[*idx], ',')) != NULL)
901: *p = '\0';
902: if ((p = strchr(peer[*idx], ',')) != NULL)
903: *p = '\0';
904: if (strcmp(my[*idx], peer[*idx]) != 0) {
905: debug2("proposal mismatch: my %s peer %s",
906: my[*idx], peer[*idx]);
907: return (0);
908: }
909: }
910: debug2("proposals match");
911: return (1);
912: }
913:
1.171 djm 914: static int
1.183 djm 915: kexalgs_contains(char **peer, const char *ext)
1.171 djm 916: {
1.186 ! djm 917: return kex_has_any_alg(peer[PROPOSAL_KEX_ALGS], ext);
1.171 djm 918: }
919:
1.102 markus 920: static int
1.183 djm 921: kex_choose_conf(struct ssh *ssh, uint32_t seq)
1.1 markus 922: {
1.102 markus 923: struct kex *kex = ssh->kex;
924: struct newkeys *newkeys;
925: char **my = NULL, **peer = NULL;
1.26 markus 926: char **cprop, **sprop;
1.27 markus 927: int nenc, nmac, ncomp;
1.96 dtucker 928: u_int mode, ctos, need, dh_need, authlen;
1.102 markus 929: int r, first_kex_follows;
1.1 markus 930:
1.110 djm 931: debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
932: if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
933: goto out;
934: debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
935: if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
1.102 markus 936: goto out;
1.26 markus 937:
1.27 markus 938: if (kex->server) {
1.26 markus 939: cprop=peer;
940: sprop=my;
941: } else {
942: cprop=my;
943: sprop=peer;
1.113 markus 944: }
945:
1.183 djm 946: /* Check whether peer supports ext_info/kex_strict */
947: if ((kex->flags & KEX_INITIAL) != 0) {
948: if (kex->server) {
949: kex->ext_info_c = kexalgs_contains(peer, "ext-info-c");
950: kex->kex_strict = kexalgs_contains(peer,
951: "kex-strict-c-v00@openssh.com");
952: } else {
1.184 djm 953: kex->ext_info_s = kexalgs_contains(peer, "ext-info-s");
1.183 djm 954: kex->kex_strict = kexalgs_contains(peer,
955: "kex-strict-s-v00@openssh.com");
956: }
957: if (kex->kex_strict) {
958: debug3_f("will use strict KEX ordering");
959: if (seq != 0)
960: ssh_packet_disconnect(ssh,
961: "strict KEX violation: "
962: "KEXINIT was not the first packet");
963: }
1.171 djm 964: }
965:
966: /* Check whether client supports rsa-sha2 algorithms */
967: if (kex->server && (kex->flags & KEX_INITIAL)) {
1.186 ! djm 968: if (kex_has_any_alg(peer[PROPOSAL_SERVER_HOST_KEY_ALGS],
1.171 djm 969: "rsa-sha2-256,rsa-sha2-256-cert-v01@openssh.com"))
970: kex->flags |= KEX_RSA_SHA2_256_SUPPORTED;
1.186 ! djm 971: if (kex_has_any_alg(peer[PROPOSAL_SERVER_HOST_KEY_ALGS],
1.171 djm 972: "rsa-sha2-512,rsa-sha2-512-cert-v01@openssh.com"))
973: kex->flags |= KEX_RSA_SHA2_512_SUPPORTED;
1.26 markus 974: }
1.1 markus 975:
1.30 markus 976: /* Algorithm Negotiation */
1.110 djm 977: if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
978: sprop[PROPOSAL_KEX_ALGS])) != 0) {
979: kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
980: peer[PROPOSAL_KEX_ALGS] = NULL;
981: goto out;
982: }
983: if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
984: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
985: kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
986: peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
987: goto out;
988: }
1.1 markus 989: for (mode = 0; mode < MODE_MAX; mode++) {
1.102 markus 990: if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
991: r = SSH_ERR_ALLOC_FAIL;
992: goto out;
993: }
1.30 markus 994: kex->newkeys[mode] = newkeys;
1.78 djm 995: ctos = (!kex->server && mode == MODE_OUT) ||
996: (kex->server && mode == MODE_IN);
1.1 markus 997: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
998: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
999: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.102 markus 1000: if ((r = choose_enc(&newkeys->enc, cprop[nenc],
1.107 djm 1001: sprop[nenc])) != 0) {
1002: kex->failed_choice = peer[nenc];
1003: peer[nenc] = NULL;
1.102 markus 1004: goto out;
1.107 djm 1005: }
1.102 markus 1006: authlen = cipher_authlen(newkeys->enc.cipher);
1.88 markus 1007: /* ignore mac for authenticated encryption */
1.102 markus 1008: if (authlen == 0 &&
1009: (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
1.107 djm 1010: sprop[nmac])) != 0) {
1011: kex->failed_choice = peer[nmac];
1012: peer[nmac] = NULL;
1.102 markus 1013: goto out;
1.107 djm 1014: }
1.102 markus 1015: if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
1.107 djm 1016: sprop[ncomp])) != 0) {
1017: kex->failed_choice = peer[ncomp];
1018: peer[ncomp] = NULL;
1.102 markus 1019: goto out;
1.107 djm 1020: }
1.110 djm 1021: debug("kex: %s cipher: %s MAC: %s compression: %s",
1.1 markus 1022: ctos ? "client->server" : "server->client",
1.27 markus 1023: newkeys->enc.name,
1.88 markus 1024: authlen == 0 ? newkeys->mac.name : "<implicit>",
1.27 markus 1025: newkeys->comp.name);
1.107 djm 1026: }
1.96 dtucker 1027: need = dh_need = 0;
1.1 markus 1028: for (mode = 0; mode < MODE_MAX; mode++) {
1.30 markus 1029: newkeys = kex->newkeys[mode];
1.120 deraadt 1030: need = MAXIMUM(need, newkeys->enc.key_len);
1031: need = MAXIMUM(need, newkeys->enc.block_size);
1032: need = MAXIMUM(need, newkeys->enc.iv_len);
1033: need = MAXIMUM(need, newkeys->mac.key_len);
1034: dh_need = MAXIMUM(dh_need, cipher_seclen(newkeys->enc.cipher));
1035: dh_need = MAXIMUM(dh_need, newkeys->enc.block_size);
1036: dh_need = MAXIMUM(dh_need, newkeys->enc.iv_len);
1037: dh_need = MAXIMUM(dh_need, newkeys->mac.key_len);
1.1 markus 1038: }
1.7 markus 1039: /* XXX need runden? */
1.27 markus 1040: kex->we_need = need;
1.96 dtucker 1041: kex->dh_need = dh_need;
1.53 markus 1042:
1043: /* ignore the next message if the proposals do not match */
1.135 djm 1044: if (first_kex_follows && !proposals_match(my, peer))
1.102 markus 1045: ssh->dispatch_skip_packets = 1;
1046: r = 0;
1047: out:
1.26 markus 1048: kex_prop_free(my);
1049: kex_prop_free(peer);
1.102 markus 1050: return r;
1.26 markus 1051: }
1052:
1.102 markus 1053: static int
1054: derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
1055: const struct sshbuf *shared_secret, u_char **keyp)
1.26 markus 1056: {
1.102 markus 1057: struct kex *kex = ssh->kex;
1058: struct ssh_digest_ctx *hashctx = NULL;
1.26 markus 1059: char c = id;
1.61 djm 1060: u_int have;
1.94 djm 1061: size_t mdsz;
1.61 djm 1062: u_char *digest;
1.102 markus 1063: int r;
1.62 djm 1064:
1.94 djm 1065: if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
1.102 markus 1066: return SSH_ERR_INVALID_ARGUMENT;
1.120 deraadt 1067: if ((digest = calloc(1, ROUNDUP(need, mdsz))) == NULL) {
1.102 markus 1068: r = SSH_ERR_ALLOC_FAIL;
1069: goto out;
1070: }
1.26 markus 1071:
1.30 markus 1072: /* K1 = HASH(K || H || "A" || session_id) */
1.102 markus 1073: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
1074: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 1075: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1076: ssh_digest_update(hashctx, &c, 1) != 0 ||
1.165 djm 1077: ssh_digest_update_buffer(hashctx, kex->session_id) != 0 ||
1.102 markus 1078: ssh_digest_final(hashctx, digest, mdsz) != 0) {
1079: r = SSH_ERR_LIBCRYPTO_ERROR;
1.160 djm 1080: error_f("KEX hash failed");
1.102 markus 1081: goto out;
1082: }
1.94 djm 1083: ssh_digest_free(hashctx);
1.102 markus 1084: hashctx = NULL;
1.26 markus 1085:
1.30 markus 1086: /*
1087: * expand key:
1088: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
1089: * Key = K1 || K2 || ... || Kn
1090: */
1.26 markus 1091: for (have = mdsz; need > have; have += mdsz) {
1.102 markus 1092: if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
1093: ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1.94 djm 1094: ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1.102 markus 1095: ssh_digest_update(hashctx, digest, have) != 0 ||
1096: ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
1.160 djm 1097: error_f("KDF failed");
1.102 markus 1098: r = SSH_ERR_LIBCRYPTO_ERROR;
1099: goto out;
1100: }
1.94 djm 1101: ssh_digest_free(hashctx);
1.102 markus 1102: hashctx = NULL;
1.26 markus 1103: }
1104: #ifdef DEBUG_KEX
1105: fprintf(stderr, "key '%c'== ", c);
1106: dump_digest("key", digest, need);
1107: #endif
1.102 markus 1108: *keyp = digest;
1109: digest = NULL;
1110: r = 0;
1111: out:
1.114 mmcc 1112: free(digest);
1.102 markus 1113: ssh_digest_free(hashctx);
1114: return r;
1.1 markus 1115: }
1116:
1.23 markus 1117: #define NKEYS 6
1.102 markus 1118: int
1119: kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
1120: const struct sshbuf *shared_secret)
1.1 markus 1121: {
1.102 markus 1122: struct kex *kex = ssh->kex;
1.15 markus 1123: u_char *keys[NKEYS];
1.102 markus 1124: u_int i, j, mode, ctos;
1125: int r;
1.1 markus 1126:
1.144 djm 1127: /* save initial hash as session id */
1.165 djm 1128: if ((kex->flags & KEX_INITIAL) != 0) {
1.166 djm 1129: if (sshbuf_len(kex->session_id) != 0) {
1130: error_f("already have session ID at kex");
1131: return SSH_ERR_INTERNAL_ERROR;
1132: }
1.165 djm 1133: if ((r = sshbuf_put(kex->session_id, hash, hashlen)) != 0)
1134: return r;
1135: } else if (sshbuf_len(kex->session_id) == 0) {
1136: error_f("no session ID in rekex");
1.166 djm 1137: return SSH_ERR_INTERNAL_ERROR;
1.144 djm 1138: }
1.65 djm 1139: for (i = 0; i < NKEYS; i++) {
1.102 markus 1140: if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
1141: shared_secret, &keys[i])) != 0) {
1142: for (j = 0; j < i; j++)
1143: free(keys[j]);
1144: return r;
1145: }
1.65 djm 1146: }
1.1 markus 1147: for (mode = 0; mode < MODE_MAX; mode++) {
1.69 deraadt 1148: ctos = (!kex->server && mode == MODE_OUT) ||
1149: (kex->server && mode == MODE_IN);
1.100 markus 1150: kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
1151: kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
1152: kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
1.1 markus 1153: }
1.102 markus 1154: return 0;
1.95 djm 1155: }
1.57 djm 1156:
1.145 djm 1157: int
1.150 djm 1158: kex_load_hostkey(struct ssh *ssh, struct sshkey **prvp, struct sshkey **pubp)
1.145 djm 1159: {
1160: struct kex *kex = ssh->kex;
1161:
1162: *pubp = NULL;
1163: *prvp = NULL;
1164: if (kex->load_host_public_key == NULL ||
1.152 djm 1165: kex->load_host_private_key == NULL) {
1.160 djm 1166: error_f("missing hostkey loader");
1.145 djm 1167: return SSH_ERR_INVALID_ARGUMENT;
1.152 djm 1168: }
1.145 djm 1169: *pubp = kex->load_host_public_key(kex->hostkey_type,
1170: kex->hostkey_nid, ssh);
1171: *prvp = kex->load_host_private_key(kex->hostkey_type,
1172: kex->hostkey_nid, ssh);
1173: if (*pubp == NULL)
1174: return SSH_ERR_NO_HOSTKEY_LOADED;
1.146 djm 1175: return 0;
1176: }
1177:
1178: int
1179: kex_verify_host_key(struct ssh *ssh, struct sshkey *server_host_key)
1180: {
1181: struct kex *kex = ssh->kex;
1182:
1.152 djm 1183: if (kex->verify_host_key == NULL) {
1.160 djm 1184: error_f("missing hostkey verifier");
1.146 djm 1185: return SSH_ERR_INVALID_ARGUMENT;
1.152 djm 1186: }
1.146 djm 1187: if (server_host_key->type != kex->hostkey_type ||
1188: (kex->hostkey_type == KEY_ECDSA &&
1189: server_host_key->ecdsa_nid != kex->hostkey_nid))
1190: return SSH_ERR_KEY_TYPE_MISMATCH;
1191: if (kex->verify_host_key(server_host_key, ssh) == -1)
1192: return SSH_ERR_SIGNATURE_INVALID;
1.145 djm 1193: return 0;
1194: }
1.26 markus 1195:
1.84 djm 1196: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1.26 markus 1197: void
1.147 djm 1198: dump_digest(const char *msg, const u_char *digest, int len)
1.26 markus 1199: {
1200: fprintf(stderr, "%s\n", msg);
1.102 markus 1201: sshbuf_dump_data(digest, len, stderr);
1.26 markus 1202: }
1203: #endif
1.143 djm 1204:
1205: /*
1206: * Send a plaintext error message to the peer, suffixed by \r\n.
1207: * Only used during banner exchange, and there only for the server.
1208: */
1209: static void
1210: send_error(struct ssh *ssh, char *msg)
1211: {
1212: char *crnl = "\r\n";
1213:
1214: if (!ssh->kex->server)
1215: return;
1216:
1217: if (atomicio(vwrite, ssh_packet_get_connection_out(ssh),
1218: msg, strlen(msg)) != strlen(msg) ||
1219: atomicio(vwrite, ssh_packet_get_connection_out(ssh),
1220: crnl, strlen(crnl)) != strlen(crnl))
1.160 djm 1221: error_f("write: %.100s", strerror(errno));
1.143 djm 1222: }
1223:
1224: /*
1225: * Sends our identification string and waits for the peer's. Will block for
1226: * up to timeout_ms (or indefinitely if timeout_ms <= 0).
1227: * Returns on 0 success or a ssherr.h code on failure.
1228: */
1229: int
1230: kex_exchange_identification(struct ssh *ssh, int timeout_ms,
1231: const char *version_addendum)
1232: {
1.158 djm 1233: int remote_major, remote_minor, mismatch, oerrno = 0;
1.173 dtucker 1234: size_t len, n;
1.143 djm 1235: int r, expect_nl;
1236: u_char c;
1237: struct sshbuf *our_version = ssh->kex->server ?
1238: ssh->kex->server_version : ssh->kex->client_version;
1239: struct sshbuf *peer_version = ssh->kex->server ?
1240: ssh->kex->client_version : ssh->kex->server_version;
1241: char *our_version_string = NULL, *peer_version_string = NULL;
1242: char *cp, *remote_version = NULL;
1243:
1244: /* Prepare and send our banner */
1245: sshbuf_reset(our_version);
1246: if (version_addendum != NULL && *version_addendum == '\0')
1247: version_addendum = NULL;
1.182 djm 1248: if ((r = sshbuf_putf(our_version, "SSH-%d.%d-%s%s%s\r\n",
1.168 djm 1249: PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION,
1.143 djm 1250: version_addendum == NULL ? "" : " ",
1251: version_addendum == NULL ? "" : version_addendum)) != 0) {
1.158 djm 1252: oerrno = errno;
1.160 djm 1253: error_fr(r, "sshbuf_putf");
1.143 djm 1254: goto out;
1255: }
1256:
1257: if (atomicio(vwrite, ssh_packet_get_connection_out(ssh),
1258: sshbuf_mutable_ptr(our_version),
1259: sshbuf_len(our_version)) != sshbuf_len(our_version)) {
1.158 djm 1260: oerrno = errno;
1.160 djm 1261: debug_f("write: %.100s", strerror(errno));
1.143 djm 1262: r = SSH_ERR_SYSTEM_ERROR;
1263: goto out;
1264: }
1265: if ((r = sshbuf_consume_end(our_version, 2)) != 0) { /* trim \r\n */
1.158 djm 1266: oerrno = errno;
1.160 djm 1267: error_fr(r, "sshbuf_consume_end");
1.143 djm 1268: goto out;
1269: }
1270: our_version_string = sshbuf_dup_string(our_version);
1271: if (our_version_string == NULL) {
1.160 djm 1272: error_f("sshbuf_dup_string failed");
1.143 djm 1273: r = SSH_ERR_ALLOC_FAIL;
1274: goto out;
1275: }
1276: debug("Local version string %.100s", our_version_string);
1277:
1278: /* Read other side's version identification. */
1279: for (n = 0; ; n++) {
1280: if (n >= SSH_MAX_PRE_BANNER_LINES) {
1281: send_error(ssh, "No SSH identification string "
1282: "received.");
1.160 djm 1283: error_f("No SSH version received in first %u lines "
1284: "from server", SSH_MAX_PRE_BANNER_LINES);
1.143 djm 1285: r = SSH_ERR_INVALID_FORMAT;
1286: goto out;
1287: }
1288: sshbuf_reset(peer_version);
1289: expect_nl = 0;
1.173 dtucker 1290: for (;;) {
1.143 djm 1291: if (timeout_ms > 0) {
1292: r = waitrfd(ssh_packet_get_connection_in(ssh),
1.179 djm 1293: &timeout_ms, NULL);
1.143 djm 1294: if (r == -1 && errno == ETIMEDOUT) {
1295: send_error(ssh, "Timed out waiting "
1296: "for SSH identification string.");
1297: error("Connection timed out during "
1298: "banner exchange");
1299: r = SSH_ERR_CONN_TIMEOUT;
1300: goto out;
1301: } else if (r == -1) {
1.158 djm 1302: oerrno = errno;
1.160 djm 1303: error_f("%s", strerror(errno));
1.143 djm 1304: r = SSH_ERR_SYSTEM_ERROR;
1305: goto out;
1306: }
1307: }
1308:
1309: len = atomicio(read, ssh_packet_get_connection_in(ssh),
1310: &c, 1);
1311: if (len != 1 && errno == EPIPE) {
1.180 tobhe 1312: verbose_f("Connection closed by remote host");
1.143 djm 1313: r = SSH_ERR_CONN_CLOSED;
1314: goto out;
1315: } else if (len != 1) {
1.158 djm 1316: oerrno = errno;
1.160 djm 1317: error_f("read: %.100s", strerror(errno));
1.143 djm 1318: r = SSH_ERR_SYSTEM_ERROR;
1319: goto out;
1320: }
1321: if (c == '\r') {
1322: expect_nl = 1;
1323: continue;
1324: }
1325: if (c == '\n')
1326: break;
1327: if (c == '\0' || expect_nl) {
1.180 tobhe 1328: verbose_f("banner line contains invalid "
1.160 djm 1329: "characters");
1.143 djm 1330: goto invalid;
1331: }
1332: if ((r = sshbuf_put_u8(peer_version, c)) != 0) {
1.158 djm 1333: oerrno = errno;
1.160 djm 1334: error_fr(r, "sshbuf_put");
1.143 djm 1335: goto out;
1336: }
1337: if (sshbuf_len(peer_version) > SSH_MAX_BANNER_LEN) {
1.180 tobhe 1338: verbose_f("banner line too long");
1.143 djm 1339: goto invalid;
1340: }
1341: }
1342: /* Is this an actual protocol banner? */
1343: if (sshbuf_len(peer_version) > 4 &&
1344: memcmp(sshbuf_ptr(peer_version), "SSH-", 4) == 0)
1345: break;
1346: /* If not, then just log the line and continue */
1347: if ((cp = sshbuf_dup_string(peer_version)) == 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: /* Do not accept lines before the SSH ident from a client */
1353: if (ssh->kex->server) {
1.180 tobhe 1354: verbose_f("client sent invalid protocol identifier "
1.160 djm 1355: "\"%.256s\"", cp);
1.143 djm 1356: free(cp);
1357: goto invalid;
1358: }
1.160 djm 1359: debug_f("banner line %zu: %s", n, cp);
1.143 djm 1360: free(cp);
1361: }
1362: peer_version_string = sshbuf_dup_string(peer_version);
1363: if (peer_version_string == NULL)
1.175 dtucker 1364: fatal_f("sshbuf_dup_string failed");
1.143 djm 1365: /* XXX must be same size for sscanf */
1366: if ((remote_version = calloc(1, sshbuf_len(peer_version))) == NULL) {
1.160 djm 1367: error_f("calloc failed");
1.143 djm 1368: r = SSH_ERR_ALLOC_FAIL;
1369: goto out;
1370: }
1371:
1372: /*
1373: * Check that the versions match. In future this might accept
1374: * several versions and set appropriate flags to handle them.
1375: */
1376: if (sscanf(peer_version_string, "SSH-%d.%d-%[^\n]\n",
1377: &remote_major, &remote_minor, remote_version) != 3) {
1378: error("Bad remote protocol version identification: '%.100s'",
1379: peer_version_string);
1380: invalid:
1381: send_error(ssh, "Invalid SSH identification string.");
1382: r = SSH_ERR_INVALID_FORMAT;
1383: goto out;
1384: }
1385: debug("Remote protocol version %d.%d, remote software version %.100s",
1386: remote_major, remote_minor, remote_version);
1.164 djm 1387: compat_banner(ssh, remote_version);
1.143 djm 1388:
1389: mismatch = 0;
1390: switch (remote_major) {
1391: case 2:
1392: break;
1393: case 1:
1394: if (remote_minor != 99)
1395: mismatch = 1;
1396: break;
1397: default:
1398: mismatch = 1;
1399: break;
1400: }
1401: if (mismatch) {
1402: error("Protocol major versions differ: %d vs. %d",
1403: PROTOCOL_MAJOR_2, remote_major);
1404: send_error(ssh, "Protocol major versions differ.");
1405: r = SSH_ERR_NO_PROTOCOL_VERSION;
1406: goto out;
1407: }
1408:
1409: if (ssh->kex->server && (ssh->compat & SSH_BUG_PROBE) != 0) {
1410: logit("probed from %s port %d with %s. Don't panic.",
1411: ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
1412: peer_version_string);
1413: r = SSH_ERR_CONN_CLOSED; /* XXX */
1414: goto out;
1415: }
1416: if (ssh->kex->server && (ssh->compat & SSH_BUG_SCANNER) != 0) {
1417: logit("scanned from %s port %d with %s. Don't panic.",
1418: ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
1419: peer_version_string);
1420: r = SSH_ERR_CONN_CLOSED; /* XXX */
1421: goto out;
1422: }
1423: /* success */
1424: r = 0;
1425: out:
1426: free(our_version_string);
1427: free(peer_version_string);
1428: free(remote_version);
1.158 djm 1429: if (r == SSH_ERR_SYSTEM_ERROR)
1430: errno = oerrno;
1.143 djm 1431: return r;
1432: }
1433:
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