1 /* $OpenBSD: kex.c,v 1.136 2018/02/07 02:06:50 jsing 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.
36 #include <openssl/crypto.h>
37 #include <openssl/dh.h>
58 static int kex_choose_conf(struct ssh *);
59 static int kex_input_newkeys(int, u_int32_t, struct ssh *);
61 static const char *proposal_names[PROPOSAL_MAX] = {
63 "host key algorithms",
80 static const struct kexalg kexalgs[] = {
82 { KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },
83 { KEX_DH14_SHA1, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 },
84 { KEX_DH14_SHA256, KEX_DH_GRP14_SHA256, 0, SSH_DIGEST_SHA256 },
85 { KEX_DH16_SHA512, KEX_DH_GRP16_SHA512, 0, SSH_DIGEST_SHA512 },
86 { KEX_DH18_SHA512, KEX_DH_GRP18_SHA512, 0, SSH_DIGEST_SHA512 },
87 { KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 },
88 #ifdef HAVE_EVP_SHA256
89 { KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 },
90 #endif /* HAVE_EVP_SHA256 */
91 #ifdef OPENSSL_HAS_ECC
92 { KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2,
93 NID_X9_62_prime256v1, SSH_DIGEST_SHA256 },
94 { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1,
96 # ifdef OPENSSL_HAS_NISTP521
97 { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1,
99 # endif /* OPENSSL_HAS_NISTP521 */
100 #endif /* OPENSSL_HAS_ECC */
101 #endif /* WITH_OPENSSL */
102 #if defined(HAVE_EVP_SHA256) || !defined(WITH_OPENSSL)
103 { KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
104 { KEX_CURVE25519_SHA256_OLD, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
105 #endif /* HAVE_EVP_SHA256 || !WITH_OPENSSL */
110 kex_alg_list(char sep)
112 char *ret = NULL, *tmp;
113 size_t nlen, rlen = 0;
114 const struct kexalg *k;
116 for (k = kexalgs; k->name != NULL; k++) {
119 nlen = strlen(k->name);
120 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
125 memcpy(ret + rlen, k->name, nlen + 1);
131 static const struct kexalg *
132 kex_alg_by_name(const char *name)
134 const struct kexalg *k;
136 for (k = kexalgs; k->name != NULL; k++) {
137 if (strcmp(k->name, name) == 0)
143 /* Validate KEX method name list */
145 kex_names_valid(const char *names)
149 if (names == NULL || strcmp(names, "") == 0)
151 if ((s = cp = strdup(names)) == NULL)
153 for ((p = strsep(&cp, ",")); p && *p != '\0';
154 (p = strsep(&cp, ","))) {
155 if (kex_alg_by_name(p) == NULL) {
156 error("Unsupported KEX algorithm \"%.100s\"", p);
161 debug3("kex names ok: [%s]", names);
167 * Concatenate algorithm names, avoiding duplicates in the process.
168 * Caller must free returned string.
171 kex_names_cat(const char *a, const char *b)
173 char *ret = NULL, *tmp = NULL, *cp, *p, *m;
176 if (a == NULL || *a == '\0')
178 if (b == NULL || *b == '\0')
180 if (strlen(b) > 1024*1024)
182 len = strlen(a) + strlen(b) + 2;
183 if ((tmp = cp = strdup(b)) == NULL ||
184 (ret = calloc(1, len)) == NULL) {
188 strlcpy(ret, a, len);
189 for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) {
190 if ((m = match_list(ret, p, NULL)) != NULL) {
192 continue; /* Algorithm already present */
194 if (strlcat(ret, ",", len) >= len ||
195 strlcat(ret, p, len) >= len) {
198 return NULL; /* Shouldn't happen */
206 * Assemble a list of algorithms from a default list and a string from a
207 * configuration file. The user-provided string may begin with '+' to
208 * indicate that it should be appended to the default or '-' that the
209 * specified names should be removed.
212 kex_assemble_names(const char *def, char **list)
216 if (list == NULL || *list == NULL || **list == '\0') {
221 if ((ret = kex_names_cat(def, *list + 1)) == NULL)
222 return SSH_ERR_ALLOC_FAIL;
225 } else if (**list == '-') {
226 if ((ret = match_filter_list(def, *list + 1)) == NULL)
227 return SSH_ERR_ALLOC_FAIL;
235 /* put algorithm proposal into buffer */
237 kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
245 * add a dummy cookie, the cookie will be overwritten by
246 * kex_send_kexinit(), each time a kexinit is set
248 for (i = 0; i < KEX_COOKIE_LEN; i++) {
249 if ((r = sshbuf_put_u8(b, 0)) != 0)
252 for (i = 0; i < PROPOSAL_MAX; i++) {
253 if ((r = sshbuf_put_cstring(b, proposal[i])) != 0)
256 if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */
257 (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */
262 /* parse buffer and return algorithm proposal */
264 kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp)
266 struct sshbuf *b = NULL;
269 char **proposal = NULL;
273 if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL)
274 return SSH_ERR_ALLOC_FAIL;
275 if ((b = sshbuf_fromb(raw)) == NULL) {
276 r = SSH_ERR_ALLOC_FAIL;
279 if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */
281 /* extract kex init proposal strings */
282 for (i = 0; i < PROPOSAL_MAX; i++) {
283 if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0)
285 debug2("%s: %s", proposal_names[i], proposal[i]);
287 /* first kex follows / reserved */
288 if ((r = sshbuf_get_u8(b, &v)) != 0 || /* first_kex_follows */
289 (r = sshbuf_get_u32(b, &i)) != 0) /* reserved */
291 if (first_kex_follows != NULL)
292 *first_kex_follows = v;
293 debug2("first_kex_follows %d ", v);
294 debug2("reserved %u ", i);
298 if (r != 0 && proposal != NULL)
299 kex_prop_free(proposal);
305 kex_prop_free(char **proposal)
309 if (proposal == NULL)
311 for (i = 0; i < PROPOSAL_MAX; i++)
318 kex_protocol_error(int type, u_int32_t seq, struct ssh *ssh)
322 error("kex protocol error: type %d seq %u", type, seq);
323 if ((r = sshpkt_start(ssh, SSH2_MSG_UNIMPLEMENTED)) != 0 ||
324 (r = sshpkt_put_u32(ssh, seq)) != 0 ||
325 (r = sshpkt_send(ssh)) != 0)
331 kex_reset_dispatch(struct ssh *ssh)
333 ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
334 SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
338 kex_send_ext_info(struct ssh *ssh)
343 if ((algs = sshkey_alg_list(0, 1, 1, ',')) == NULL)
344 return SSH_ERR_ALLOC_FAIL;
345 if ((r = sshpkt_start(ssh, SSH2_MSG_EXT_INFO)) != 0 ||
346 (r = sshpkt_put_u32(ssh, 1)) != 0 ||
347 (r = sshpkt_put_cstring(ssh, "server-sig-algs")) != 0 ||
348 (r = sshpkt_put_cstring(ssh, algs)) != 0 ||
349 (r = sshpkt_send(ssh)) != 0)
359 kex_send_newkeys(struct ssh *ssh)
363 kex_reset_dispatch(ssh);
364 if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
365 (r = sshpkt_send(ssh)) != 0)
367 debug("SSH2_MSG_NEWKEYS sent");
368 debug("expecting SSH2_MSG_NEWKEYS");
369 ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
370 if (ssh->kex->ext_info_c)
371 if ((r = kex_send_ext_info(ssh)) != 0)
377 kex_input_ext_info(int type, u_int32_t seq, struct ssh *ssh)
379 struct kex *kex = ssh->kex;
386 debug("SSH2_MSG_EXT_INFO received");
387 ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_protocol_error);
388 if ((r = sshpkt_get_u32(ssh, &ninfo)) != 0)
390 for (i = 0; i < ninfo; i++) {
391 if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0)
393 if ((r = sshpkt_get_string(ssh, &val, &vlen)) != 0) {
397 if (strcmp(name, "server-sig-algs") == 0) {
398 /* Ensure no \0 lurking in value */
399 if (memchr(val, '\0', vlen) != NULL) {
400 error("%s: nul byte in %s", __func__, name);
401 return SSH_ERR_INVALID_FORMAT;
403 debug("%s: %s=<%s>", __func__, name, val);
404 found = match_list("rsa-sha2-256", val, NULL);
409 found = match_list("rsa-sha2-512", val, NULL);
415 debug("%s: %s (unrecognised)", __func__, name);
419 return sshpkt_get_end(ssh);
423 kex_input_newkeys(int type, u_int32_t seq, struct ssh *ssh)
425 struct kex *kex = ssh->kex;
428 debug("SSH2_MSG_NEWKEYS received");
429 ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
430 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
431 if ((r = sshpkt_get_end(ssh)) != 0)
433 if ((r = ssh_set_newkeys(ssh, MODE_IN)) != 0)
436 sshbuf_reset(kex->peer);
437 /* sshbuf_reset(kex->my); */
438 kex->flags &= ~KEX_INIT_SENT;
445 kex_send_kexinit(struct ssh *ssh)
448 struct kex *kex = ssh->kex;
452 return SSH_ERR_INTERNAL_ERROR;
453 if (kex->flags & KEX_INIT_SENT)
457 /* generate a random cookie */
458 if (sshbuf_len(kex->my) < KEX_COOKIE_LEN)
459 return SSH_ERR_INVALID_FORMAT;
460 if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL)
461 return SSH_ERR_INTERNAL_ERROR;
462 arc4random_buf(cookie, KEX_COOKIE_LEN);
464 if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
465 (r = sshpkt_putb(ssh, kex->my)) != 0 ||
466 (r = sshpkt_send(ssh)) != 0)
468 debug("SSH2_MSG_KEXINIT sent");
469 kex->flags |= KEX_INIT_SENT;
475 kex_input_kexinit(int type, u_int32_t seq, struct ssh *ssh)
477 struct kex *kex = ssh->kex;
483 debug("SSH2_MSG_KEXINIT received");
485 return SSH_ERR_INVALID_ARGUMENT;
487 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, NULL);
488 ptr = sshpkt_ptr(ssh, &dlen);
489 if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
493 for (i = 0; i < KEX_COOKIE_LEN; i++)
494 if ((r = sshpkt_get_u8(ssh, NULL)) != 0)
496 for (i = 0; i < PROPOSAL_MAX; i++)
497 if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0)
500 * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
501 * KEX method has the server move first, but a server might be using
502 * a custom method or one that we otherwise don't support. We should
503 * be prepared to remember first_kex_follows here so we can eat a
505 * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
506 * for cases where the server *doesn't* go first. I guess we should
507 * ignore it when it is set for these cases, which is what we do now.
509 if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
510 (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
511 (r = sshpkt_get_end(ssh)) != 0)
514 if (!(kex->flags & KEX_INIT_SENT))
515 if ((r = kex_send_kexinit(ssh)) != 0)
517 if ((r = kex_choose_conf(ssh)) != 0)
520 if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
521 return (kex->kex[kex->kex_type])(ssh);
523 return SSH_ERR_INTERNAL_ERROR;
527 kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp)
533 if ((kex = calloc(1, sizeof(*kex))) == NULL)
534 return SSH_ERR_ALLOC_FAIL;
535 if ((kex->peer = sshbuf_new()) == NULL ||
536 (kex->my = sshbuf_new()) == NULL) {
537 r = SSH_ERR_ALLOC_FAIL;
540 if ((r = kex_prop2buf(kex->my, proposal)) != 0)
543 kex_reset_dispatch(ssh);
544 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
554 kex_free_newkeys(struct newkeys *newkeys)
558 if (newkeys->enc.key) {
559 explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
560 free(newkeys->enc.key);
561 newkeys->enc.key = NULL;
563 if (newkeys->enc.iv) {
564 explicit_bzero(newkeys->enc.iv, newkeys->enc.iv_len);
565 free(newkeys->enc.iv);
566 newkeys->enc.iv = NULL;
568 free(newkeys->enc.name);
569 explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
570 free(newkeys->comp.name);
571 explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
572 mac_clear(&newkeys->mac);
573 if (newkeys->mac.key) {
574 explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
575 free(newkeys->mac.key);
576 newkeys->mac.key = NULL;
578 free(newkeys->mac.name);
579 explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
580 explicit_bzero(newkeys, sizeof(*newkeys));
585 kex_free(struct kex *kex)
591 #ifdef OPENSSL_HAS_ECC
592 EC_KEY_free(kex->ec_client_key);
593 #endif /* OPENSSL_HAS_ECC */
594 #endif /* WITH_OPENSSL */
595 for (mode = 0; mode < MODE_MAX; mode++) {
596 kex_free_newkeys(kex->newkeys[mode]);
597 kex->newkeys[mode] = NULL;
599 sshbuf_free(kex->peer);
600 sshbuf_free(kex->my);
601 free(kex->session_id);
602 free(kex->client_version_string);
603 free(kex->server_version_string);
604 free(kex->failed_choice);
605 free(kex->hostkey_alg);
611 kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
615 if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0)
617 if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
626 * Request key re-exchange, returns 0 on success or a ssherr.h error
627 * code otherwise. Must not be called if KEX is incomplete or in-progress.
630 kex_start_rekex(struct ssh *ssh)
632 if (ssh->kex == NULL) {
633 error("%s: no kex", __func__);
634 return SSH_ERR_INTERNAL_ERROR;
636 if (ssh->kex->done == 0) {
637 error("%s: requested twice", __func__);
638 return SSH_ERR_INTERNAL_ERROR;
641 return kex_send_kexinit(ssh);
645 choose_enc(struct sshenc *enc, char *client, char *server)
647 char *name = match_list(client, server, NULL);
650 return SSH_ERR_NO_CIPHER_ALG_MATCH;
651 if ((enc->cipher = cipher_by_name(name)) == NULL) {
653 return SSH_ERR_INTERNAL_ERROR;
658 enc->iv_len = cipher_ivlen(enc->cipher);
660 enc->key_len = cipher_keylen(enc->cipher);
661 enc->block_size = cipher_blocksize(enc->cipher);
666 choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
668 char *name = match_list(client, server, NULL);
671 return SSH_ERR_NO_MAC_ALG_MATCH;
672 if (mac_setup(mac, name) < 0) {
674 return SSH_ERR_INTERNAL_ERROR;
683 choose_comp(struct sshcomp *comp, char *client, char *server)
685 char *name = match_list(client, server, NULL);
688 return SSH_ERR_NO_COMPRESS_ALG_MATCH;
689 if (strcmp(name, "zlib@openssh.com") == 0) {
690 comp->type = COMP_DELAYED;
691 } else if (strcmp(name, "zlib") == 0) {
692 comp->type = COMP_ZLIB;
693 } else if (strcmp(name, "none") == 0) {
694 comp->type = COMP_NONE;
697 return SSH_ERR_INTERNAL_ERROR;
704 choose_kex(struct kex *k, char *client, char *server)
706 const struct kexalg *kexalg;
708 k->name = match_list(client, server, NULL);
710 debug("kex: algorithm: %s", k->name ? k->name : "(no match)");
712 return SSH_ERR_NO_KEX_ALG_MATCH;
713 if ((kexalg = kex_alg_by_name(k->name)) == NULL)
714 return SSH_ERR_INTERNAL_ERROR;
715 k->kex_type = kexalg->type;
716 k->hash_alg = kexalg->hash_alg;
717 k->ec_nid = kexalg->ec_nid;
722 choose_hostkeyalg(struct kex *k, char *client, char *server)
724 k->hostkey_alg = match_list(client, server, NULL);
726 debug("kex: host key algorithm: %s",
727 k->hostkey_alg ? k->hostkey_alg : "(no match)");
728 if (k->hostkey_alg == NULL)
729 return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
730 k->hostkey_type = sshkey_type_from_name(k->hostkey_alg);
731 if (k->hostkey_type == KEY_UNSPEC)
732 return SSH_ERR_INTERNAL_ERROR;
733 k->hostkey_nid = sshkey_ecdsa_nid_from_name(k->hostkey_alg);
738 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
740 static int check[] = {
741 PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
746 for (idx = &check[0]; *idx != -1; idx++) {
747 if ((p = strchr(my[*idx], ',')) != NULL)
749 if ((p = strchr(peer[*idx], ',')) != NULL)
751 if (strcmp(my[*idx], peer[*idx]) != 0) {
752 debug2("proposal mismatch: my %s peer %s",
753 my[*idx], peer[*idx]);
757 debug2("proposals match");
762 kex_choose_conf(struct ssh *ssh)
764 struct kex *kex = ssh->kex;
765 struct newkeys *newkeys;
766 char **my = NULL, **peer = NULL;
767 char **cprop, **sprop;
768 int nenc, nmac, ncomp;
769 u_int mode, ctos, need, dh_need, authlen;
770 int r, first_kex_follows;
772 debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
773 if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
775 debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
776 if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
787 /* Check whether client supports ext_info_c */
791 ext = match_list("ext-info-c", peer[PROPOSAL_KEX_ALGS], NULL);
792 kex->ext_info_c = (ext != NULL);
796 /* Algorithm Negotiation */
797 if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
798 sprop[PROPOSAL_KEX_ALGS])) != 0) {
799 kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
800 peer[PROPOSAL_KEX_ALGS] = NULL;
803 if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
804 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
805 kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
806 peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
809 for (mode = 0; mode < MODE_MAX; mode++) {
810 if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
811 r = SSH_ERR_ALLOC_FAIL;
814 kex->newkeys[mode] = newkeys;
815 ctos = (!kex->server && mode == MODE_OUT) ||
816 (kex->server && mode == MODE_IN);
817 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
818 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
819 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
820 if ((r = choose_enc(&newkeys->enc, cprop[nenc],
821 sprop[nenc])) != 0) {
822 kex->failed_choice = peer[nenc];
826 authlen = cipher_authlen(newkeys->enc.cipher);
827 /* ignore mac for authenticated encryption */
829 (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
830 sprop[nmac])) != 0) {
831 kex->failed_choice = peer[nmac];
835 if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
836 sprop[ncomp])) != 0) {
837 kex->failed_choice = peer[ncomp];
841 debug("kex: %s cipher: %s MAC: %s compression: %s",
842 ctos ? "client->server" : "server->client",
844 authlen == 0 ? newkeys->mac.name : "<implicit>",
848 for (mode = 0; mode < MODE_MAX; mode++) {
849 newkeys = kex->newkeys[mode];
850 need = MAXIMUM(need, newkeys->enc.key_len);
851 need = MAXIMUM(need, newkeys->enc.block_size);
852 need = MAXIMUM(need, newkeys->enc.iv_len);
853 need = MAXIMUM(need, newkeys->mac.key_len);
854 dh_need = MAXIMUM(dh_need, cipher_seclen(newkeys->enc.cipher));
855 dh_need = MAXIMUM(dh_need, newkeys->enc.block_size);
856 dh_need = MAXIMUM(dh_need, newkeys->enc.iv_len);
857 dh_need = MAXIMUM(dh_need, newkeys->mac.key_len);
859 /* XXX need runden? */
861 kex->dh_need = dh_need;
863 /* ignore the next message if the proposals do not match */
864 if (first_kex_follows && !proposals_match(my, peer))
865 ssh->dispatch_skip_packets = 1;
874 derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
875 const struct sshbuf *shared_secret, u_char **keyp)
877 struct kex *kex = ssh->kex;
878 struct ssh_digest_ctx *hashctx = NULL;
885 if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
886 return SSH_ERR_INVALID_ARGUMENT;
887 if ((digest = calloc(1, ROUNDUP(need, mdsz))) == NULL) {
888 r = SSH_ERR_ALLOC_FAIL;
892 /* K1 = HASH(K || H || "A" || session_id) */
893 if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
894 ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
895 ssh_digest_update(hashctx, hash, hashlen) != 0 ||
896 ssh_digest_update(hashctx, &c, 1) != 0 ||
897 ssh_digest_update(hashctx, kex->session_id,
898 kex->session_id_len) != 0 ||
899 ssh_digest_final(hashctx, digest, mdsz) != 0) {
900 r = SSH_ERR_LIBCRYPTO_ERROR;
903 ssh_digest_free(hashctx);
908 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
909 * Key = K1 || K2 || ... || Kn
911 for (have = mdsz; need > have; have += mdsz) {
912 if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
913 ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
914 ssh_digest_update(hashctx, hash, hashlen) != 0 ||
915 ssh_digest_update(hashctx, digest, have) != 0 ||
916 ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
917 r = SSH_ERR_LIBCRYPTO_ERROR;
920 ssh_digest_free(hashctx);
924 fprintf(stderr, "key '%c'== ", c);
925 dump_digest("key", digest, need);
932 ssh_digest_free(hashctx);
938 kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
939 const struct sshbuf *shared_secret)
941 struct kex *kex = ssh->kex;
943 u_int i, j, mode, ctos;
946 for (i = 0; i < NKEYS; i++) {
947 if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
948 shared_secret, &keys[i])) != 0) {
949 for (j = 0; j < i; j++)
954 for (mode = 0; mode < MODE_MAX; mode++) {
955 ctos = (!kex->server && mode == MODE_OUT) ||
956 (kex->server && mode == MODE_IN);
957 kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
958 kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
959 kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
966 kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen,
967 const BIGNUM *secret)
969 struct sshbuf *shared_secret;
972 if ((shared_secret = sshbuf_new()) == NULL)
973 return SSH_ERR_ALLOC_FAIL;
974 if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0)
975 r = kex_derive_keys(ssh, hash, hashlen, shared_secret);
976 sshbuf_free(shared_secret);
982 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
984 dump_digest(char *msg, u_char *digest, int len)
986 fprintf(stderr, "%s\n", msg);
987 sshbuf_dump_data(digest, len, stderr);