1 /* $OpenBSD: kex.c,v 1.141 2018/07/09 13:37:10 sf 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(char **listp, const char *def, const char *all)
214 char *cp, *tmp, *patterns;
215 char *list = NULL, *ret = NULL, *matching = NULL, *opatterns = NULL;
216 int r = SSH_ERR_INTERNAL_ERROR;
218 if (listp == NULL || *listp == NULL || **listp == '\0') {
219 if ((*listp = strdup(def)) == NULL)
220 return SSH_ERR_ALLOC_FAIL;
227 /* Append names to default list */
228 if ((tmp = kex_names_cat(def, list + 1)) == NULL) {
229 r = SSH_ERR_ALLOC_FAIL;
234 } else if (*list == '-') {
235 /* Remove names from default list */
236 if ((*listp = match_filter_blacklist(def, list + 1)) == NULL) {
237 r = SSH_ERR_ALLOC_FAIL;
241 /* filtering has already been done */
244 /* Explicit list, overrides default - just use "list" as is */
248 * The supplied names may be a pattern-list. For the -list case,
249 * the patterns are applied above. For the +list and explicit list
250 * cases we need to do it now.
253 if ((patterns = opatterns = strdup(list)) == NULL) {
254 r = SSH_ERR_ALLOC_FAIL;
257 /* Apply positive (i.e. non-negated) patterns from the list */
258 while ((cp = strsep(&patterns, ",")) != NULL) {
260 /* negated matches are not supported here */
261 r = SSH_ERR_INVALID_ARGUMENT;
265 if ((matching = match_filter_whitelist(all, cp)) == NULL) {
266 r = SSH_ERR_ALLOC_FAIL;
269 if ((tmp = kex_names_cat(ret, matching)) == NULL) {
270 r = SSH_ERR_ALLOC_FAIL;
276 if (ret == NULL || *ret == '\0') {
277 /* An empty name-list is an error */
278 /* XXX better error code? */
279 r = SSH_ERR_INVALID_ARGUMENT;
296 /* put algorithm proposal into buffer */
298 kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
306 * add a dummy cookie, the cookie will be overwritten by
307 * kex_send_kexinit(), each time a kexinit is set
309 for (i = 0; i < KEX_COOKIE_LEN; i++) {
310 if ((r = sshbuf_put_u8(b, 0)) != 0)
313 for (i = 0; i < PROPOSAL_MAX; i++) {
314 if ((r = sshbuf_put_cstring(b, proposal[i])) != 0)
317 if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */
318 (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */
323 /* parse buffer and return algorithm proposal */
325 kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp)
327 struct sshbuf *b = NULL;
330 char **proposal = NULL;
334 if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL)
335 return SSH_ERR_ALLOC_FAIL;
336 if ((b = sshbuf_fromb(raw)) == NULL) {
337 r = SSH_ERR_ALLOC_FAIL;
340 if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */
342 /* extract kex init proposal strings */
343 for (i = 0; i < PROPOSAL_MAX; i++) {
344 if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0)
346 debug2("%s: %s", proposal_names[i], proposal[i]);
348 /* first kex follows / reserved */
349 if ((r = sshbuf_get_u8(b, &v)) != 0 || /* first_kex_follows */
350 (r = sshbuf_get_u32(b, &i)) != 0) /* reserved */
352 if (first_kex_follows != NULL)
353 *first_kex_follows = v;
354 debug2("first_kex_follows %d ", v);
355 debug2("reserved %u ", i);
359 if (r != 0 && proposal != NULL)
360 kex_prop_free(proposal);
366 kex_prop_free(char **proposal)
370 if (proposal == NULL)
372 for (i = 0; i < PROPOSAL_MAX; i++)
379 kex_protocol_error(int type, u_int32_t seq, struct ssh *ssh)
383 error("kex protocol error: type %d seq %u", type, seq);
384 if ((r = sshpkt_start(ssh, SSH2_MSG_UNIMPLEMENTED)) != 0 ||
385 (r = sshpkt_put_u32(ssh, seq)) != 0 ||
386 (r = sshpkt_send(ssh)) != 0)
392 kex_reset_dispatch(struct ssh *ssh)
394 ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
395 SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
399 kex_send_ext_info(struct ssh *ssh)
404 if ((algs = sshkey_alg_list(0, 1, 1, ',')) == NULL)
405 return SSH_ERR_ALLOC_FAIL;
406 /* XXX filter algs list by allowed pubkey/hostbased types */
407 if ((r = sshpkt_start(ssh, SSH2_MSG_EXT_INFO)) != 0 ||
408 (r = sshpkt_put_u32(ssh, 1)) != 0 ||
409 (r = sshpkt_put_cstring(ssh, "server-sig-algs")) != 0 ||
410 (r = sshpkt_put_cstring(ssh, algs)) != 0 ||
411 (r = sshpkt_send(ssh)) != 0)
421 kex_send_newkeys(struct ssh *ssh)
425 kex_reset_dispatch(ssh);
426 if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
427 (r = sshpkt_send(ssh)) != 0)
429 debug("SSH2_MSG_NEWKEYS sent");
430 debug("expecting SSH2_MSG_NEWKEYS");
431 ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
432 if (ssh->kex->ext_info_c)
433 if ((r = kex_send_ext_info(ssh)) != 0)
439 kex_input_ext_info(int type, u_int32_t seq, struct ssh *ssh)
441 struct kex *kex = ssh->kex;
448 debug("SSH2_MSG_EXT_INFO received");
449 ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_protocol_error);
450 if ((r = sshpkt_get_u32(ssh, &ninfo)) != 0)
452 for (i = 0; i < ninfo; i++) {
453 if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0)
455 if ((r = sshpkt_get_string(ssh, &val, &vlen)) != 0) {
459 if (strcmp(name, "server-sig-algs") == 0) {
460 /* Ensure no \0 lurking in value */
461 if (memchr(val, '\0', vlen) != NULL) {
462 error("%s: nul byte in %s", __func__, name);
463 return SSH_ERR_INVALID_FORMAT;
465 debug("%s: %s=<%s>", __func__, name, val);
466 kex->server_sig_algs = val;
469 debug("%s: %s (unrecognised)", __func__, name);
473 return sshpkt_get_end(ssh);
477 kex_input_newkeys(int type, u_int32_t seq, struct ssh *ssh)
479 struct kex *kex = ssh->kex;
482 debug("SSH2_MSG_NEWKEYS received");
483 ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
484 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
485 if ((r = sshpkt_get_end(ssh)) != 0)
487 if ((r = ssh_set_newkeys(ssh, MODE_IN)) != 0)
490 sshbuf_reset(kex->peer);
491 /* sshbuf_reset(kex->my); */
492 kex->flags &= ~KEX_INIT_SENT;
499 kex_send_kexinit(struct ssh *ssh)
502 struct kex *kex = ssh->kex;
506 return SSH_ERR_INTERNAL_ERROR;
507 if (kex->flags & KEX_INIT_SENT)
511 /* generate a random cookie */
512 if (sshbuf_len(kex->my) < KEX_COOKIE_LEN)
513 return SSH_ERR_INVALID_FORMAT;
514 if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL)
515 return SSH_ERR_INTERNAL_ERROR;
516 arc4random_buf(cookie, KEX_COOKIE_LEN);
518 if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
519 (r = sshpkt_putb(ssh, kex->my)) != 0 ||
520 (r = sshpkt_send(ssh)) != 0)
522 debug("SSH2_MSG_KEXINIT sent");
523 kex->flags |= KEX_INIT_SENT;
529 kex_input_kexinit(int type, u_int32_t seq, struct ssh *ssh)
531 struct kex *kex = ssh->kex;
537 debug("SSH2_MSG_KEXINIT received");
539 return SSH_ERR_INVALID_ARGUMENT;
541 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, NULL);
542 ptr = sshpkt_ptr(ssh, &dlen);
543 if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
547 for (i = 0; i < KEX_COOKIE_LEN; i++)
548 if ((r = sshpkt_get_u8(ssh, NULL)) != 0)
550 for (i = 0; i < PROPOSAL_MAX; i++)
551 if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0)
554 * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
555 * KEX method has the server move first, but a server might be using
556 * a custom method or one that we otherwise don't support. We should
557 * be prepared to remember first_kex_follows here so we can eat a
559 * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
560 * for cases where the server *doesn't* go first. I guess we should
561 * ignore it when it is set for these cases, which is what we do now.
563 if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
564 (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
565 (r = sshpkt_get_end(ssh)) != 0)
568 if (!(kex->flags & KEX_INIT_SENT))
569 if ((r = kex_send_kexinit(ssh)) != 0)
571 if ((r = kex_choose_conf(ssh)) != 0)
574 if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
575 return (kex->kex[kex->kex_type])(ssh);
577 return SSH_ERR_INTERNAL_ERROR;
581 kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp)
587 if ((kex = calloc(1, sizeof(*kex))) == NULL)
588 return SSH_ERR_ALLOC_FAIL;
589 if ((kex->peer = sshbuf_new()) == NULL ||
590 (kex->my = sshbuf_new()) == NULL) {
591 r = SSH_ERR_ALLOC_FAIL;
594 if ((r = kex_prop2buf(kex->my, proposal)) != 0)
597 kex_reset_dispatch(ssh);
598 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
608 kex_free_newkeys(struct newkeys *newkeys)
612 if (newkeys->enc.key) {
613 explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
614 free(newkeys->enc.key);
615 newkeys->enc.key = NULL;
617 if (newkeys->enc.iv) {
618 explicit_bzero(newkeys->enc.iv, newkeys->enc.iv_len);
619 free(newkeys->enc.iv);
620 newkeys->enc.iv = NULL;
622 free(newkeys->enc.name);
623 explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
624 free(newkeys->comp.name);
625 explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
626 mac_clear(&newkeys->mac);
627 if (newkeys->mac.key) {
628 explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
629 free(newkeys->mac.key);
630 newkeys->mac.key = NULL;
632 free(newkeys->mac.name);
633 explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
634 explicit_bzero(newkeys, sizeof(*newkeys));
639 kex_free(struct kex *kex)
645 #ifdef OPENSSL_HAS_ECC
646 EC_KEY_free(kex->ec_client_key);
647 #endif /* OPENSSL_HAS_ECC */
648 #endif /* WITH_OPENSSL */
649 for (mode = 0; mode < MODE_MAX; mode++) {
650 kex_free_newkeys(kex->newkeys[mode]);
651 kex->newkeys[mode] = NULL;
653 sshbuf_free(kex->peer);
654 sshbuf_free(kex->my);
655 free(kex->session_id);
656 free(kex->client_version_string);
657 free(kex->server_version_string);
658 free(kex->failed_choice);
659 free(kex->hostkey_alg);
665 kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
669 if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0)
671 if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
680 * Request key re-exchange, returns 0 on success or a ssherr.h error
681 * code otherwise. Must not be called if KEX is incomplete or in-progress.
684 kex_start_rekex(struct ssh *ssh)
686 if (ssh->kex == NULL) {
687 error("%s: no kex", __func__);
688 return SSH_ERR_INTERNAL_ERROR;
690 if (ssh->kex->done == 0) {
691 error("%s: requested twice", __func__);
692 return SSH_ERR_INTERNAL_ERROR;
695 return kex_send_kexinit(ssh);
699 choose_enc(struct sshenc *enc, char *client, char *server)
701 char *name = match_list(client, server, NULL);
704 return SSH_ERR_NO_CIPHER_ALG_MATCH;
705 if ((enc->cipher = cipher_by_name(name)) == NULL) {
707 return SSH_ERR_INTERNAL_ERROR;
712 enc->iv_len = cipher_ivlen(enc->cipher);
714 enc->key_len = cipher_keylen(enc->cipher);
715 enc->block_size = cipher_blocksize(enc->cipher);
720 choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
722 char *name = match_list(client, server, NULL);
725 return SSH_ERR_NO_MAC_ALG_MATCH;
726 if (mac_setup(mac, name) < 0) {
728 return SSH_ERR_INTERNAL_ERROR;
737 choose_comp(struct sshcomp *comp, char *client, char *server)
739 char *name = match_list(client, server, NULL);
742 return SSH_ERR_NO_COMPRESS_ALG_MATCH;
743 if (strcmp(name, "zlib@openssh.com") == 0) {
744 comp->type = COMP_DELAYED;
745 } else if (strcmp(name, "zlib") == 0) {
746 comp->type = COMP_ZLIB;
747 } else if (strcmp(name, "none") == 0) {
748 comp->type = COMP_NONE;
751 return SSH_ERR_INTERNAL_ERROR;
758 choose_kex(struct kex *k, char *client, char *server)
760 const struct kexalg *kexalg;
762 k->name = match_list(client, server, NULL);
764 debug("kex: algorithm: %s", k->name ? k->name : "(no match)");
766 return SSH_ERR_NO_KEX_ALG_MATCH;
767 if ((kexalg = kex_alg_by_name(k->name)) == NULL)
768 return SSH_ERR_INTERNAL_ERROR;
769 k->kex_type = kexalg->type;
770 k->hash_alg = kexalg->hash_alg;
771 k->ec_nid = kexalg->ec_nid;
776 choose_hostkeyalg(struct kex *k, char *client, char *server)
778 k->hostkey_alg = match_list(client, server, NULL);
780 debug("kex: host key algorithm: %s",
781 k->hostkey_alg ? k->hostkey_alg : "(no match)");
782 if (k->hostkey_alg == NULL)
783 return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
784 k->hostkey_type = sshkey_type_from_name(k->hostkey_alg);
785 if (k->hostkey_type == KEY_UNSPEC)
786 return SSH_ERR_INTERNAL_ERROR;
787 k->hostkey_nid = sshkey_ecdsa_nid_from_name(k->hostkey_alg);
792 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
794 static int check[] = {
795 PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
800 for (idx = &check[0]; *idx != -1; idx++) {
801 if ((p = strchr(my[*idx], ',')) != NULL)
803 if ((p = strchr(peer[*idx], ',')) != NULL)
805 if (strcmp(my[*idx], peer[*idx]) != 0) {
806 debug2("proposal mismatch: my %s peer %s",
807 my[*idx], peer[*idx]);
811 debug2("proposals match");
816 kex_choose_conf(struct ssh *ssh)
818 struct kex *kex = ssh->kex;
819 struct newkeys *newkeys;
820 char **my = NULL, **peer = NULL;
821 char **cprop, **sprop;
822 int nenc, nmac, ncomp;
823 u_int mode, ctos, need, dh_need, authlen;
824 int r, first_kex_follows;
826 debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
827 if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
829 debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
830 if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
841 /* Check whether client supports ext_info_c */
845 ext = match_list("ext-info-c", peer[PROPOSAL_KEX_ALGS], NULL);
846 kex->ext_info_c = (ext != NULL);
850 /* Algorithm Negotiation */
851 if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
852 sprop[PROPOSAL_KEX_ALGS])) != 0) {
853 kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
854 peer[PROPOSAL_KEX_ALGS] = NULL;
857 if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
858 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
859 kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
860 peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
863 for (mode = 0; mode < MODE_MAX; mode++) {
864 if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
865 r = SSH_ERR_ALLOC_FAIL;
868 kex->newkeys[mode] = newkeys;
869 ctos = (!kex->server && mode == MODE_OUT) ||
870 (kex->server && mode == MODE_IN);
871 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
872 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
873 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
874 if ((r = choose_enc(&newkeys->enc, cprop[nenc],
875 sprop[nenc])) != 0) {
876 kex->failed_choice = peer[nenc];
880 authlen = cipher_authlen(newkeys->enc.cipher);
881 /* ignore mac for authenticated encryption */
883 (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
884 sprop[nmac])) != 0) {
885 kex->failed_choice = peer[nmac];
889 if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
890 sprop[ncomp])) != 0) {
891 kex->failed_choice = peer[ncomp];
895 debug("kex: %s cipher: %s MAC: %s compression: %s",
896 ctos ? "client->server" : "server->client",
898 authlen == 0 ? newkeys->mac.name : "<implicit>",
902 for (mode = 0; mode < MODE_MAX; mode++) {
903 newkeys = kex->newkeys[mode];
904 need = MAXIMUM(need, newkeys->enc.key_len);
905 need = MAXIMUM(need, newkeys->enc.block_size);
906 need = MAXIMUM(need, newkeys->enc.iv_len);
907 need = MAXIMUM(need, newkeys->mac.key_len);
908 dh_need = MAXIMUM(dh_need, cipher_seclen(newkeys->enc.cipher));
909 dh_need = MAXIMUM(dh_need, newkeys->enc.block_size);
910 dh_need = MAXIMUM(dh_need, newkeys->enc.iv_len);
911 dh_need = MAXIMUM(dh_need, newkeys->mac.key_len);
913 /* XXX need runden? */
915 kex->dh_need = dh_need;
917 /* ignore the next message if the proposals do not match */
918 if (first_kex_follows && !proposals_match(my, peer))
919 ssh->dispatch_skip_packets = 1;
928 derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
929 const struct sshbuf *shared_secret, u_char **keyp)
931 struct kex *kex = ssh->kex;
932 struct ssh_digest_ctx *hashctx = NULL;
939 if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
940 return SSH_ERR_INVALID_ARGUMENT;
941 if ((digest = calloc(1, ROUNDUP(need, mdsz))) == NULL) {
942 r = SSH_ERR_ALLOC_FAIL;
946 /* K1 = HASH(K || H || "A" || session_id) */
947 if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
948 ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
949 ssh_digest_update(hashctx, hash, hashlen) != 0 ||
950 ssh_digest_update(hashctx, &c, 1) != 0 ||
951 ssh_digest_update(hashctx, kex->session_id,
952 kex->session_id_len) != 0 ||
953 ssh_digest_final(hashctx, digest, mdsz) != 0) {
954 r = SSH_ERR_LIBCRYPTO_ERROR;
957 ssh_digest_free(hashctx);
962 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
963 * Key = K1 || K2 || ... || Kn
965 for (have = mdsz; need > have; have += mdsz) {
966 if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
967 ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
968 ssh_digest_update(hashctx, hash, hashlen) != 0 ||
969 ssh_digest_update(hashctx, digest, have) != 0 ||
970 ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
971 r = SSH_ERR_LIBCRYPTO_ERROR;
974 ssh_digest_free(hashctx);
978 fprintf(stderr, "key '%c'== ", c);
979 dump_digest("key", digest, need);
986 ssh_digest_free(hashctx);
992 kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
993 const struct sshbuf *shared_secret)
995 struct kex *kex = ssh->kex;
997 u_int i, j, mode, ctos;
1000 for (i = 0; i < NKEYS; i++) {
1001 if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
1002 shared_secret, &keys[i])) != 0) {
1003 for (j = 0; j < i; j++)
1008 for (mode = 0; mode < MODE_MAX; mode++) {
1009 ctos = (!kex->server && mode == MODE_OUT) ||
1010 (kex->server && mode == MODE_IN);
1011 kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
1012 kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
1013 kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
1020 kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen,
1021 const BIGNUM *secret)
1023 struct sshbuf *shared_secret;
1026 if ((shared_secret = sshbuf_new()) == NULL)
1027 return SSH_ERR_ALLOC_FAIL;
1028 if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0)
1029 r = kex_derive_keys(ssh, hash, hashlen, shared_secret);
1030 sshbuf_free(shared_secret);
1036 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1038 dump_digest(char *msg, u_char *digest, int len)
1040 fprintf(stderr, "%s\n", msg);
1041 sshbuf_dump_data(digest, len, stderr);