1 /* $OpenBSD: kex.c,v 1.168 2021/04/03 06:18:40 djm Exp $ */
3 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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.
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.
28 #include <sys/types.h>
41 #include <openssl/crypto.h>
42 #include <openssl/dh.h>
66 static int kex_choose_conf(struct ssh *);
67 static int kex_input_newkeys(int, u_int32_t, struct ssh *);
69 static const char *proposal_names[PROPOSAL_MAX] = {
71 "host key algorithms",
88 static const struct kexalg kexalgs[] = {
90 { KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },
91 { KEX_DH14_SHA1, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 },
92 { KEX_DH14_SHA256, KEX_DH_GRP14_SHA256, 0, SSH_DIGEST_SHA256 },
93 { KEX_DH16_SHA512, KEX_DH_GRP16_SHA512, 0, SSH_DIGEST_SHA512 },
94 { KEX_DH18_SHA512, KEX_DH_GRP18_SHA512, 0, SSH_DIGEST_SHA512 },
95 { KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 },
96 #ifdef HAVE_EVP_SHA256
97 { KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 },
98 #endif /* HAVE_EVP_SHA256 */
99 #ifdef OPENSSL_HAS_ECC
100 { KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2,
101 NID_X9_62_prime256v1, SSH_DIGEST_SHA256 },
102 { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1,
104 # ifdef OPENSSL_HAS_NISTP521
105 { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1,
107 # endif /* OPENSSL_HAS_NISTP521 */
108 #endif /* OPENSSL_HAS_ECC */
109 #endif /* WITH_OPENSSL */
110 #if defined(HAVE_EVP_SHA256) || !defined(WITH_OPENSSL)
111 { KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
112 { KEX_CURVE25519_SHA256_OLD, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
113 #ifdef USE_SNTRUP761X25519
114 { KEX_SNTRUP761X25519_SHA512, KEX_KEM_SNTRUP761X25519_SHA512, 0,
117 #endif /* HAVE_EVP_SHA256 || !WITH_OPENSSL */
122 kex_alg_list(char sep)
124 char *ret = NULL, *tmp;
125 size_t nlen, rlen = 0;
126 const struct kexalg *k;
128 for (k = kexalgs; k->name != NULL; k++) {
131 nlen = strlen(k->name);
132 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
137 memcpy(ret + rlen, k->name, nlen + 1);
143 static const struct kexalg *
144 kex_alg_by_name(const char *name)
146 const struct kexalg *k;
148 for (k = kexalgs; k->name != NULL; k++) {
149 if (strcmp(k->name, name) == 0)
155 /* Validate KEX method name list */
157 kex_names_valid(const char *names)
161 if (names == NULL || strcmp(names, "") == 0)
163 if ((s = cp = strdup(names)) == NULL)
165 for ((p = strsep(&cp, ",")); p && *p != '\0';
166 (p = strsep(&cp, ","))) {
167 if (kex_alg_by_name(p) == NULL) {
168 error("Unsupported KEX algorithm \"%.100s\"", p);
173 debug3("kex names ok: [%s]", names);
179 * Concatenate algorithm names, avoiding duplicates in the process.
180 * Caller must free returned string.
183 kex_names_cat(const char *a, const char *b)
185 char *ret = NULL, *tmp = NULL, *cp, *p, *m;
188 if (a == NULL || *a == '\0')
190 if (b == NULL || *b == '\0')
192 if (strlen(b) > 1024*1024)
194 len = strlen(a) + strlen(b) + 2;
195 if ((tmp = cp = strdup(b)) == NULL ||
196 (ret = calloc(1, len)) == NULL) {
200 strlcpy(ret, a, len);
201 for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) {
202 if ((m = match_list(ret, p, NULL)) != NULL) {
204 continue; /* Algorithm already present */
206 if (strlcat(ret, ",", len) >= len ||
207 strlcat(ret, p, len) >= len) {
210 return NULL; /* Shouldn't happen */
218 * Assemble a list of algorithms from a default list and a string from a
219 * configuration file. The user-provided string may begin with '+' to
220 * indicate that it should be appended to the default, '-' that the
221 * specified names should be removed, or '^' that they should be placed
225 kex_assemble_names(char **listp, const char *def, const char *all)
227 char *cp, *tmp, *patterns;
228 char *list = NULL, *ret = NULL, *matching = NULL, *opatterns = NULL;
229 int r = SSH_ERR_INTERNAL_ERROR;
231 if (listp == NULL || def == NULL || all == NULL)
232 return SSH_ERR_INVALID_ARGUMENT;
234 if (*listp == NULL || **listp == '\0') {
235 if ((*listp = strdup(def)) == NULL)
236 return SSH_ERR_ALLOC_FAIL;
243 /* Append names to default list */
244 if ((tmp = kex_names_cat(def, list + 1)) == NULL) {
245 r = SSH_ERR_ALLOC_FAIL;
250 } else if (*list == '-') {
251 /* Remove names from default list */
252 if ((*listp = match_filter_denylist(def, list + 1)) == NULL) {
253 r = SSH_ERR_ALLOC_FAIL;
257 /* filtering has already been done */
259 } else if (*list == '^') {
260 /* Place names at head of default list */
261 if ((tmp = kex_names_cat(list + 1, def)) == NULL) {
262 r = SSH_ERR_ALLOC_FAIL;
268 /* Explicit list, overrides default - just use "list" as is */
272 * The supplied names may be a pattern-list. For the -list case,
273 * the patterns are applied above. For the +list and explicit list
274 * cases we need to do it now.
277 if ((patterns = opatterns = strdup(list)) == NULL) {
278 r = SSH_ERR_ALLOC_FAIL;
281 /* Apply positive (i.e. non-negated) patterns from the list */
282 while ((cp = strsep(&patterns, ",")) != NULL) {
284 /* negated matches are not supported here */
285 r = SSH_ERR_INVALID_ARGUMENT;
289 if ((matching = match_filter_allowlist(all, cp)) == NULL) {
290 r = SSH_ERR_ALLOC_FAIL;
293 if ((tmp = kex_names_cat(ret, matching)) == NULL) {
294 r = SSH_ERR_ALLOC_FAIL;
300 if (ret == NULL || *ret == '\0') {
301 /* An empty name-list is an error */
302 /* XXX better error code? */
303 r = SSH_ERR_INVALID_ARGUMENT;
320 /* put algorithm proposal into buffer */
322 kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
330 * add a dummy cookie, the cookie will be overwritten by
331 * kex_send_kexinit(), each time a kexinit is set
333 for (i = 0; i < KEX_COOKIE_LEN; i++) {
334 if ((r = sshbuf_put_u8(b, 0)) != 0)
337 for (i = 0; i < PROPOSAL_MAX; i++) {
338 if ((r = sshbuf_put_cstring(b, proposal[i])) != 0)
341 if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */
342 (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */
347 /* parse buffer and return algorithm proposal */
349 kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp)
351 struct sshbuf *b = NULL;
354 char **proposal = NULL;
358 if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL)
359 return SSH_ERR_ALLOC_FAIL;
360 if ((b = sshbuf_fromb(raw)) == NULL) {
361 r = SSH_ERR_ALLOC_FAIL;
364 if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) { /* skip cookie */
365 error_fr(r, "consume cookie");
368 /* extract kex init proposal strings */
369 for (i = 0; i < PROPOSAL_MAX; i++) {
370 if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0) {
371 error_fr(r, "parse proposal %u", i);
374 debug2("%s: %s", proposal_names[i], proposal[i]);
376 /* first kex follows / reserved */
377 if ((r = sshbuf_get_u8(b, &v)) != 0 || /* first_kex_follows */
378 (r = sshbuf_get_u32(b, &i)) != 0) { /* reserved */
379 error_fr(r, "parse");
382 if (first_kex_follows != NULL)
383 *first_kex_follows = v;
384 debug2("first_kex_follows %d ", v);
385 debug2("reserved %u ", i);
389 if (r != 0 && proposal != NULL)
390 kex_prop_free(proposal);
396 kex_prop_free(char **proposal)
400 if (proposal == NULL)
402 for (i = 0; i < PROPOSAL_MAX; i++)
409 kex_protocol_error(int type, u_int32_t seq, struct ssh *ssh)
413 error("kex protocol error: type %d seq %u", type, seq);
414 if ((r = sshpkt_start(ssh, SSH2_MSG_UNIMPLEMENTED)) != 0 ||
415 (r = sshpkt_put_u32(ssh, seq)) != 0 ||
416 (r = sshpkt_send(ssh)) != 0)
422 kex_reset_dispatch(struct ssh *ssh)
424 ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
425 SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
429 kex_send_ext_info(struct ssh *ssh)
434 debug("Sending SSH2_MSG_EXT_INFO");
435 if ((algs = sshkey_alg_list(0, 1, 1, ',')) == NULL)
436 return SSH_ERR_ALLOC_FAIL;
437 /* XXX filter algs list by allowed pubkey/hostbased types */
438 if ((r = sshpkt_start(ssh, SSH2_MSG_EXT_INFO)) != 0 ||
439 (r = sshpkt_put_u32(ssh, 1)) != 0 ||
440 (r = sshpkt_put_cstring(ssh, "server-sig-algs")) != 0 ||
441 (r = sshpkt_put_cstring(ssh, algs)) != 0 ||
442 (r = sshpkt_send(ssh)) != 0) {
443 error_fr(r, "compose");
454 kex_send_newkeys(struct ssh *ssh)
458 kex_reset_dispatch(ssh);
459 if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
460 (r = sshpkt_send(ssh)) != 0)
462 debug("SSH2_MSG_NEWKEYS sent");
463 ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
464 if (ssh->kex->ext_info_c && (ssh->kex->flags & KEX_INITIAL) != 0)
465 if ((r = kex_send_ext_info(ssh)) != 0)
467 debug("expecting SSH2_MSG_NEWKEYS");
472 kex_input_ext_info(int type, u_int32_t seq, struct ssh *ssh)
474 struct kex *kex = ssh->kex;
481 debug("SSH2_MSG_EXT_INFO received");
482 ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_protocol_error);
483 if ((r = sshpkt_get_u32(ssh, &ninfo)) != 0)
485 for (i = 0; i < ninfo; i++) {
486 if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0)
488 if ((r = sshpkt_get_string(ssh, &val, &vlen)) != 0) {
492 if (strcmp(name, "server-sig-algs") == 0) {
493 /* Ensure no \0 lurking in value */
494 if (memchr(val, '\0', vlen) != NULL) {
495 error_f("nul byte in %s", name);
496 return SSH_ERR_INVALID_FORMAT;
498 debug_f("%s=<%s>", name, val);
499 kex->server_sig_algs = val;
502 debug_f("%s (unrecognised)", name);
506 return sshpkt_get_end(ssh);
510 kex_input_newkeys(int type, u_int32_t seq, struct ssh *ssh)
512 struct kex *kex = ssh->kex;
515 debug("SSH2_MSG_NEWKEYS received");
516 ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
517 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
518 if ((r = sshpkt_get_end(ssh)) != 0)
520 if ((r = ssh_set_newkeys(ssh, MODE_IN)) != 0)
523 kex->flags &= ~KEX_INITIAL;
524 sshbuf_reset(kex->peer);
525 /* sshbuf_reset(kex->my); */
526 kex->flags &= ~KEX_INIT_SENT;
533 kex_send_kexinit(struct ssh *ssh)
536 struct kex *kex = ssh->kex;
541 return SSH_ERR_INTERNAL_ERROR;
543 if (kex->flags & KEX_INIT_SENT)
547 /* generate a random cookie */
548 if (sshbuf_len(kex->my) < KEX_COOKIE_LEN) {
549 error_f("bad kex length: %zu < %d",
550 sshbuf_len(kex->my), KEX_COOKIE_LEN);
551 return SSH_ERR_INVALID_FORMAT;
553 if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL) {
554 error_f("buffer error");
555 return SSH_ERR_INTERNAL_ERROR;
557 arc4random_buf(cookie, KEX_COOKIE_LEN);
559 if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
560 (r = sshpkt_putb(ssh, kex->my)) != 0 ||
561 (r = sshpkt_send(ssh)) != 0) {
562 error_fr(r, "compose reply");
565 debug("SSH2_MSG_KEXINIT sent");
566 kex->flags |= KEX_INIT_SENT;
572 kex_input_kexinit(int type, u_int32_t seq, struct ssh *ssh)
574 struct kex *kex = ssh->kex;
580 debug("SSH2_MSG_KEXINIT received");
583 return SSH_ERR_INTERNAL_ERROR;
585 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, NULL);
586 ptr = sshpkt_ptr(ssh, &dlen);
587 if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
591 for (i = 0; i < KEX_COOKIE_LEN; i++) {
592 if ((r = sshpkt_get_u8(ssh, NULL)) != 0) {
593 error_fr(r, "discard cookie");
597 for (i = 0; i < PROPOSAL_MAX; i++) {
598 if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0) {
599 error_fr(r, "discard proposal");
604 * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
605 * KEX method has the server move first, but a server might be using
606 * a custom method or one that we otherwise don't support. We should
607 * be prepared to remember first_kex_follows here so we can eat a
609 * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
610 * for cases where the server *doesn't* go first. I guess we should
611 * ignore it when it is set for these cases, which is what we do now.
613 if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
614 (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
615 (r = sshpkt_get_end(ssh)) != 0)
618 if (!(kex->flags & KEX_INIT_SENT))
619 if ((r = kex_send_kexinit(ssh)) != 0)
621 if ((r = kex_choose_conf(ssh)) != 0)
624 if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
625 return (kex->kex[kex->kex_type])(ssh);
627 error_f("unknown kex type %u", kex->kex_type);
628 return SSH_ERR_INTERNAL_ERROR;
636 if ((kex = calloc(1, sizeof(*kex))) == NULL ||
637 (kex->peer = sshbuf_new()) == NULL ||
638 (kex->my = sshbuf_new()) == NULL ||
639 (kex->client_version = sshbuf_new()) == NULL ||
640 (kex->server_version = sshbuf_new()) == NULL ||
641 (kex->session_id = sshbuf_new()) == NULL) {
649 kex_free_newkeys(struct newkeys *newkeys)
653 if (newkeys->enc.key) {
654 explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
655 free(newkeys->enc.key);
656 newkeys->enc.key = NULL;
658 if (newkeys->enc.iv) {
659 explicit_bzero(newkeys->enc.iv, newkeys->enc.iv_len);
660 free(newkeys->enc.iv);
661 newkeys->enc.iv = NULL;
663 free(newkeys->enc.name);
664 explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
665 free(newkeys->comp.name);
666 explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
667 mac_clear(&newkeys->mac);
668 if (newkeys->mac.key) {
669 explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
670 free(newkeys->mac.key);
671 newkeys->mac.key = NULL;
673 free(newkeys->mac.name);
674 explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
675 freezero(newkeys, sizeof(*newkeys));
679 kex_free(struct kex *kex)
688 #ifdef OPENSSL_HAS_ECC
689 EC_KEY_free(kex->ec_client_key);
690 #endif /* OPENSSL_HAS_ECC */
691 #endif /* WITH_OPENSSL */
692 for (mode = 0; mode < MODE_MAX; mode++) {
693 kex_free_newkeys(kex->newkeys[mode]);
694 kex->newkeys[mode] = NULL;
696 sshbuf_free(kex->peer);
697 sshbuf_free(kex->my);
698 sshbuf_free(kex->client_version);
699 sshbuf_free(kex->server_version);
700 sshbuf_free(kex->client_pub);
701 sshbuf_free(kex->session_id);
702 free(kex->failed_choice);
703 free(kex->hostkey_alg);
709 kex_ready(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
713 if ((r = kex_prop2buf(ssh->kex->my, proposal)) != 0)
715 ssh->kex->flags = KEX_INITIAL;
716 kex_reset_dispatch(ssh);
717 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
722 kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
726 if ((r = kex_ready(ssh, proposal)) != 0)
728 if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
737 * Request key re-exchange, returns 0 on success or a ssherr.h error
738 * code otherwise. Must not be called if KEX is incomplete or in-progress.
741 kex_start_rekex(struct ssh *ssh)
743 if (ssh->kex == NULL) {
745 return SSH_ERR_INTERNAL_ERROR;
747 if (ssh->kex->done == 0) {
748 error_f("requested twice");
749 return SSH_ERR_INTERNAL_ERROR;
752 return kex_send_kexinit(ssh);
756 choose_enc(struct sshenc *enc, char *client, char *server)
758 char *name = match_list(client, server, NULL);
761 return SSH_ERR_NO_CIPHER_ALG_MATCH;
762 if ((enc->cipher = cipher_by_name(name)) == NULL) {
763 error_f("unsupported cipher %s", name);
765 return SSH_ERR_INTERNAL_ERROR;
770 enc->iv_len = cipher_ivlen(enc->cipher);
772 enc->key_len = cipher_keylen(enc->cipher);
773 enc->block_size = cipher_blocksize(enc->cipher);
778 choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
780 char *name = match_list(client, server, NULL);
783 return SSH_ERR_NO_MAC_ALG_MATCH;
784 if (mac_setup(mac, name) < 0) {
785 error_f("unsupported MAC %s", name);
787 return SSH_ERR_INTERNAL_ERROR;
796 choose_comp(struct sshcomp *comp, char *client, char *server)
798 char *name = match_list(client, server, NULL);
801 return SSH_ERR_NO_COMPRESS_ALG_MATCH;
803 if (strcmp(name, "zlib@openssh.com") == 0) {
804 comp->type = COMP_DELAYED;
805 } else if (strcmp(name, "zlib") == 0) {
806 comp->type = COMP_ZLIB;
808 #endif /* WITH_ZLIB */
809 if (strcmp(name, "none") == 0) {
810 comp->type = COMP_NONE;
812 error_f("unsupported compression scheme %s", name);
814 return SSH_ERR_INTERNAL_ERROR;
821 choose_kex(struct kex *k, char *client, char *server)
823 const struct kexalg *kexalg;
825 k->name = match_list(client, server, NULL);
827 debug("kex: algorithm: %s", k->name ? k->name : "(no match)");
829 return SSH_ERR_NO_KEX_ALG_MATCH;
830 if ((kexalg = kex_alg_by_name(k->name)) == NULL) {
831 error_f("unsupported KEX method %s", k->name);
832 return SSH_ERR_INTERNAL_ERROR;
834 k->kex_type = kexalg->type;
835 k->hash_alg = kexalg->hash_alg;
836 k->ec_nid = kexalg->ec_nid;
841 choose_hostkeyalg(struct kex *k, char *client, char *server)
843 free(k->hostkey_alg);
844 k->hostkey_alg = match_list(client, server, NULL);
846 debug("kex: host key algorithm: %s",
847 k->hostkey_alg ? k->hostkey_alg : "(no match)");
848 if (k->hostkey_alg == NULL)
849 return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
850 k->hostkey_type = sshkey_type_from_name(k->hostkey_alg);
851 if (k->hostkey_type == KEY_UNSPEC) {
852 error_f("unsupported hostkey algorithm %s", k->hostkey_alg);
853 return SSH_ERR_INTERNAL_ERROR;
855 k->hostkey_nid = sshkey_ecdsa_nid_from_name(k->hostkey_alg);
860 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
862 static int check[] = {
863 PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
868 for (idx = &check[0]; *idx != -1; idx++) {
869 if ((p = strchr(my[*idx], ',')) != NULL)
871 if ((p = strchr(peer[*idx], ',')) != NULL)
873 if (strcmp(my[*idx], peer[*idx]) != 0) {
874 debug2("proposal mismatch: my %s peer %s",
875 my[*idx], peer[*idx]);
879 debug2("proposals match");
884 kex_choose_conf(struct ssh *ssh)
886 struct kex *kex = ssh->kex;
887 struct newkeys *newkeys;
888 char **my = NULL, **peer = NULL;
889 char **cprop, **sprop;
890 int nenc, nmac, ncomp;
891 u_int mode, ctos, need, dh_need, authlen;
892 int r, first_kex_follows;
894 debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
895 if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
897 debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
898 if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
909 /* Check whether client supports ext_info_c */
910 if (kex->server && (kex->flags & KEX_INITIAL)) {
913 ext = match_list("ext-info-c", peer[PROPOSAL_KEX_ALGS], NULL);
914 kex->ext_info_c = (ext != NULL);
918 /* Algorithm Negotiation */
919 if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
920 sprop[PROPOSAL_KEX_ALGS])) != 0) {
921 kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
922 peer[PROPOSAL_KEX_ALGS] = NULL;
925 if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
926 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
927 kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
928 peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
931 for (mode = 0; mode < MODE_MAX; mode++) {
932 if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
933 r = SSH_ERR_ALLOC_FAIL;
936 kex->newkeys[mode] = newkeys;
937 ctos = (!kex->server && mode == MODE_OUT) ||
938 (kex->server && mode == MODE_IN);
939 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
940 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
941 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
942 if ((r = choose_enc(&newkeys->enc, cprop[nenc],
943 sprop[nenc])) != 0) {
944 kex->failed_choice = peer[nenc];
948 authlen = cipher_authlen(newkeys->enc.cipher);
949 /* ignore mac for authenticated encryption */
951 (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
952 sprop[nmac])) != 0) {
953 kex->failed_choice = peer[nmac];
957 if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
958 sprop[ncomp])) != 0) {
959 kex->failed_choice = peer[ncomp];
963 debug("kex: %s cipher: %s MAC: %s compression: %s",
964 ctos ? "client->server" : "server->client",
966 authlen == 0 ? newkeys->mac.name : "<implicit>",
970 for (mode = 0; mode < MODE_MAX; mode++) {
971 newkeys = kex->newkeys[mode];
972 need = MAXIMUM(need, newkeys->enc.key_len);
973 need = MAXIMUM(need, newkeys->enc.block_size);
974 need = MAXIMUM(need, newkeys->enc.iv_len);
975 need = MAXIMUM(need, newkeys->mac.key_len);
976 dh_need = MAXIMUM(dh_need, cipher_seclen(newkeys->enc.cipher));
977 dh_need = MAXIMUM(dh_need, newkeys->enc.block_size);
978 dh_need = MAXIMUM(dh_need, newkeys->enc.iv_len);
979 dh_need = MAXIMUM(dh_need, newkeys->mac.key_len);
981 /* XXX need runden? */
983 kex->dh_need = dh_need;
985 /* ignore the next message if the proposals do not match */
986 if (first_kex_follows && !proposals_match(my, peer))
987 ssh->dispatch_skip_packets = 1;
996 derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
997 const struct sshbuf *shared_secret, u_char **keyp)
999 struct kex *kex = ssh->kex;
1000 struct ssh_digest_ctx *hashctx = NULL;
1007 if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
1008 return SSH_ERR_INVALID_ARGUMENT;
1009 if ((digest = calloc(1, ROUNDUP(need, mdsz))) == NULL) {
1010 r = SSH_ERR_ALLOC_FAIL;
1014 /* K1 = HASH(K || H || "A" || session_id) */
1015 if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
1016 ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1017 ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1018 ssh_digest_update(hashctx, &c, 1) != 0 ||
1019 ssh_digest_update_buffer(hashctx, kex->session_id) != 0 ||
1020 ssh_digest_final(hashctx, digest, mdsz) != 0) {
1021 r = SSH_ERR_LIBCRYPTO_ERROR;
1022 error_f("KEX hash failed");
1025 ssh_digest_free(hashctx);
1030 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
1031 * Key = K1 || K2 || ... || Kn
1033 for (have = mdsz; need > have; have += mdsz) {
1034 if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
1035 ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
1036 ssh_digest_update(hashctx, hash, hashlen) != 0 ||
1037 ssh_digest_update(hashctx, digest, have) != 0 ||
1038 ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
1039 error_f("KDF failed");
1040 r = SSH_ERR_LIBCRYPTO_ERROR;
1043 ssh_digest_free(hashctx);
1047 fprintf(stderr, "key '%c'== ", c);
1048 dump_digest("key", digest, need);
1055 ssh_digest_free(hashctx);
1061 kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
1062 const struct sshbuf *shared_secret)
1064 struct kex *kex = ssh->kex;
1065 u_char *keys[NKEYS];
1066 u_int i, j, mode, ctos;
1069 /* save initial hash as session id */
1070 if ((kex->flags & KEX_INITIAL) != 0) {
1071 if (sshbuf_len(kex->session_id) != 0) {
1072 error_f("already have session ID at kex");
1073 return SSH_ERR_INTERNAL_ERROR;
1075 if ((r = sshbuf_put(kex->session_id, hash, hashlen)) != 0)
1077 } else if (sshbuf_len(kex->session_id) == 0) {
1078 error_f("no session ID in rekex");
1079 return SSH_ERR_INTERNAL_ERROR;
1081 for (i = 0; i < NKEYS; i++) {
1082 if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
1083 shared_secret, &keys[i])) != 0) {
1084 for (j = 0; j < i; j++)
1089 for (mode = 0; mode < MODE_MAX; mode++) {
1090 ctos = (!kex->server && mode == MODE_OUT) ||
1091 (kex->server && mode == MODE_IN);
1092 kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
1093 kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
1094 kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
1100 kex_load_hostkey(struct ssh *ssh, struct sshkey **prvp, struct sshkey **pubp)
1102 struct kex *kex = ssh->kex;
1106 if (kex->load_host_public_key == NULL ||
1107 kex->load_host_private_key == NULL) {
1108 error_f("missing hostkey loader");
1109 return SSH_ERR_INVALID_ARGUMENT;
1111 *pubp = kex->load_host_public_key(kex->hostkey_type,
1112 kex->hostkey_nid, ssh);
1113 *prvp = kex->load_host_private_key(kex->hostkey_type,
1114 kex->hostkey_nid, ssh);
1116 return SSH_ERR_NO_HOSTKEY_LOADED;
1121 kex_verify_host_key(struct ssh *ssh, struct sshkey *server_host_key)
1123 struct kex *kex = ssh->kex;
1125 if (kex->verify_host_key == NULL) {
1126 error_f("missing hostkey verifier");
1127 return SSH_ERR_INVALID_ARGUMENT;
1129 if (server_host_key->type != kex->hostkey_type ||
1130 (kex->hostkey_type == KEY_ECDSA &&
1131 server_host_key->ecdsa_nid != kex->hostkey_nid))
1132 return SSH_ERR_KEY_TYPE_MISMATCH;
1133 if (kex->verify_host_key(server_host_key, ssh) == -1)
1134 return SSH_ERR_SIGNATURE_INVALID;
1138 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1140 dump_digest(const char *msg, const u_char *digest, int len)
1142 fprintf(stderr, "%s\n", msg);
1143 sshbuf_dump_data(digest, len, stderr);
1148 * Send a plaintext error message to the peer, suffixed by \r\n.
1149 * Only used during banner exchange, and there only for the server.
1152 send_error(struct ssh *ssh, char *msg)
1154 char *crnl = "\r\n";
1156 if (!ssh->kex->server)
1159 if (atomicio(vwrite, ssh_packet_get_connection_out(ssh),
1160 msg, strlen(msg)) != strlen(msg) ||
1161 atomicio(vwrite, ssh_packet_get_connection_out(ssh),
1162 crnl, strlen(crnl)) != strlen(crnl))
1163 error_f("write: %.100s", strerror(errno));
1167 * Sends our identification string and waits for the peer's. Will block for
1168 * up to timeout_ms (or indefinitely if timeout_ms <= 0).
1169 * Returns on 0 success or a ssherr.h code on failure.
1172 kex_exchange_identification(struct ssh *ssh, int timeout_ms,
1173 const char *version_addendum)
1175 int remote_major, remote_minor, mismatch, oerrno = 0;
1179 struct sshbuf *our_version = ssh->kex->server ?
1180 ssh->kex->server_version : ssh->kex->client_version;
1181 struct sshbuf *peer_version = ssh->kex->server ?
1182 ssh->kex->client_version : ssh->kex->server_version;
1183 char *our_version_string = NULL, *peer_version_string = NULL;
1184 char *cp, *remote_version = NULL;
1186 /* Prepare and send our banner */
1187 sshbuf_reset(our_version);
1188 if (version_addendum != NULL && *version_addendum == '\0')
1189 version_addendum = NULL;
1190 if ((r = sshbuf_putf(our_version, "SSH-%d.%d-%.100s%s%s\r\n",
1191 PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION,
1192 version_addendum == NULL ? "" : " ",
1193 version_addendum == NULL ? "" : version_addendum)) != 0) {
1195 error_fr(r, "sshbuf_putf");
1199 if (atomicio(vwrite, ssh_packet_get_connection_out(ssh),
1200 sshbuf_mutable_ptr(our_version),
1201 sshbuf_len(our_version)) != sshbuf_len(our_version)) {
1203 debug_f("write: %.100s", strerror(errno));
1204 r = SSH_ERR_SYSTEM_ERROR;
1207 if ((r = sshbuf_consume_end(our_version, 2)) != 0) { /* trim \r\n */
1209 error_fr(r, "sshbuf_consume_end");
1212 our_version_string = sshbuf_dup_string(our_version);
1213 if (our_version_string == NULL) {
1214 error_f("sshbuf_dup_string failed");
1215 r = SSH_ERR_ALLOC_FAIL;
1218 debug("Local version string %.100s", our_version_string);
1220 /* Read other side's version identification. */
1221 for (n = 0; ; n++) {
1222 if (n >= SSH_MAX_PRE_BANNER_LINES) {
1223 send_error(ssh, "No SSH identification string "
1225 error_f("No SSH version received in first %u lines "
1226 "from server", SSH_MAX_PRE_BANNER_LINES);
1227 r = SSH_ERR_INVALID_FORMAT;
1230 sshbuf_reset(peer_version);
1232 for (i = 0; ; i++) {
1233 if (timeout_ms > 0) {
1234 r = waitrfd(ssh_packet_get_connection_in(ssh),
1236 if (r == -1 && errno == ETIMEDOUT) {
1237 send_error(ssh, "Timed out waiting "
1238 "for SSH identification string.");
1239 error("Connection timed out during "
1241 r = SSH_ERR_CONN_TIMEOUT;
1243 } else if (r == -1) {
1245 error_f("%s", strerror(errno));
1246 r = SSH_ERR_SYSTEM_ERROR;
1251 len = atomicio(read, ssh_packet_get_connection_in(ssh),
1253 if (len != 1 && errno == EPIPE) {
1254 error_f("Connection closed by remote host");
1255 r = SSH_ERR_CONN_CLOSED;
1257 } else if (len != 1) {
1259 error_f("read: %.100s", strerror(errno));
1260 r = SSH_ERR_SYSTEM_ERROR;
1269 if (c == '\0' || expect_nl) {
1270 error_f("banner line contains invalid "
1274 if ((r = sshbuf_put_u8(peer_version, c)) != 0) {
1276 error_fr(r, "sshbuf_put");
1279 if (sshbuf_len(peer_version) > SSH_MAX_BANNER_LEN) {
1280 error_f("banner line too long");
1284 /* Is this an actual protocol banner? */
1285 if (sshbuf_len(peer_version) > 4 &&
1286 memcmp(sshbuf_ptr(peer_version), "SSH-", 4) == 0)
1288 /* If not, then just log the line and continue */
1289 if ((cp = sshbuf_dup_string(peer_version)) == NULL) {
1290 error_f("sshbuf_dup_string failed");
1291 r = SSH_ERR_ALLOC_FAIL;
1294 /* Do not accept lines before the SSH ident from a client */
1295 if (ssh->kex->server) {
1296 error_f("client sent invalid protocol identifier "
1301 debug_f("banner line %zu: %s", n, cp);
1304 peer_version_string = sshbuf_dup_string(peer_version);
1305 if (peer_version_string == NULL)
1306 error_f("sshbuf_dup_string failed");
1307 /* XXX must be same size for sscanf */
1308 if ((remote_version = calloc(1, sshbuf_len(peer_version))) == NULL) {
1309 error_f("calloc failed");
1310 r = SSH_ERR_ALLOC_FAIL;
1315 * Check that the versions match. In future this might accept
1316 * several versions and set appropriate flags to handle them.
1318 if (sscanf(peer_version_string, "SSH-%d.%d-%[^\n]\n",
1319 &remote_major, &remote_minor, remote_version) != 3) {
1320 error("Bad remote protocol version identification: '%.100s'",
1321 peer_version_string);
1323 send_error(ssh, "Invalid SSH identification string.");
1324 r = SSH_ERR_INVALID_FORMAT;
1327 debug("Remote protocol version %d.%d, remote software version %.100s",
1328 remote_major, remote_minor, remote_version);
1329 compat_banner(ssh, remote_version);
1332 switch (remote_major) {
1336 if (remote_minor != 99)
1344 error("Protocol major versions differ: %d vs. %d",
1345 PROTOCOL_MAJOR_2, remote_major);
1346 send_error(ssh, "Protocol major versions differ.");
1347 r = SSH_ERR_NO_PROTOCOL_VERSION;
1351 if (ssh->kex->server && (ssh->compat & SSH_BUG_PROBE) != 0) {
1352 logit("probed from %s port %d with %s. Don't panic.",
1353 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
1354 peer_version_string);
1355 r = SSH_ERR_CONN_CLOSED; /* XXX */
1358 if (ssh->kex->server && (ssh->compat & SSH_BUG_SCANNER) != 0) {
1359 logit("scanned from %s port %d with %s. Don't panic.",
1360 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
1361 peer_version_string);
1362 r = SSH_ERR_CONN_CLOSED; /* XXX */
1365 if ((ssh->compat & SSH_BUG_RSASIGMD5) != 0) {
1366 logit("Remote version \"%.100s\" uses unsafe RSA signature "
1367 "scheme; disabling use of RSA keys", remote_version);
1372 free(our_version_string);
1373 free(peer_version_string);
1374 free(remote_version);
1375 if (r == SSH_ERR_SYSTEM_ERROR)