1 /* $OpenBSD: kex.c,v 1.131 2017/03/15 07:07:39 markus 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>
57 #if OPENSSL_VERSION_NUMBER >= 0x00907000L
58 # if defined(HAVE_EVP_SHA256)
59 # define evp_ssh_sha256 EVP_sha256
61 extern const EVP_MD *evp_ssh_sha256(void);
66 static int kex_choose_conf(struct ssh *);
67 static int kex_input_newkeys(int, u_int32_t, void *);
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 #endif /* HAVE_EVP_SHA256 || !WITH_OPENSSL */
118 kex_alg_list(char sep)
120 char *ret = NULL, *tmp;
121 size_t nlen, rlen = 0;
122 const struct kexalg *k;
124 for (k = kexalgs; k->name != NULL; k++) {
127 nlen = strlen(k->name);
128 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
133 memcpy(ret + rlen, k->name, nlen + 1);
139 static const struct kexalg *
140 kex_alg_by_name(const char *name)
142 const struct kexalg *k;
144 for (k = kexalgs; k->name != NULL; k++) {
145 if (strcmp(k->name, name) == 0)
151 /* Validate KEX method name list */
153 kex_names_valid(const char *names)
157 if (names == NULL || strcmp(names, "") == 0)
159 if ((s = cp = strdup(names)) == NULL)
161 for ((p = strsep(&cp, ",")); p && *p != '\0';
162 (p = strsep(&cp, ","))) {
163 if (kex_alg_by_name(p) == NULL) {
164 error("Unsupported KEX algorithm \"%.100s\"", p);
169 debug3("kex names ok: [%s]", names);
175 * Concatenate algorithm names, avoiding duplicates in the process.
176 * Caller must free returned string.
179 kex_names_cat(const char *a, const char *b)
181 char *ret = NULL, *tmp = NULL, *cp, *p, *m;
184 if (a == NULL || *a == '\0')
186 if (b == NULL || *b == '\0')
188 if (strlen(b) > 1024*1024)
190 len = strlen(a) + strlen(b) + 2;
191 if ((tmp = cp = strdup(b)) == NULL ||
192 (ret = calloc(1, len)) == NULL) {
196 strlcpy(ret, a, len);
197 for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) {
198 if ((m = match_list(ret, p, NULL)) != NULL) {
200 continue; /* Algorithm already present */
202 if (strlcat(ret, ",", len) >= len ||
203 strlcat(ret, p, len) >= len) {
206 return NULL; /* Shouldn't happen */
214 * Assemble a list of algorithms from a default list and a string from a
215 * configuration file. The user-provided string may begin with '+' to
216 * indicate that it should be appended to the default or '-' that the
217 * specified names should be removed.
220 kex_assemble_names(const char *def, char **list)
224 if (list == NULL || *list == NULL || **list == '\0') {
229 if ((ret = kex_names_cat(def, *list + 1)) == NULL)
230 return SSH_ERR_ALLOC_FAIL;
233 } else if (**list == '-') {
234 if ((ret = match_filter_list(def, *list + 1)) == NULL)
235 return SSH_ERR_ALLOC_FAIL;
243 /* put algorithm proposal into buffer */
245 kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
253 * add a dummy cookie, the cookie will be overwritten by
254 * kex_send_kexinit(), each time a kexinit is set
256 for (i = 0; i < KEX_COOKIE_LEN; i++) {
257 if ((r = sshbuf_put_u8(b, 0)) != 0)
260 for (i = 0; i < PROPOSAL_MAX; i++) {
261 if ((r = sshbuf_put_cstring(b, proposal[i])) != 0)
264 if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */
265 (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */
270 /* parse buffer and return algorithm proposal */
272 kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp)
274 struct sshbuf *b = NULL;
277 char **proposal = NULL;
281 if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL)
282 return SSH_ERR_ALLOC_FAIL;
283 if ((b = sshbuf_fromb(raw)) == NULL) {
284 r = SSH_ERR_ALLOC_FAIL;
287 if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */
289 /* extract kex init proposal strings */
290 for (i = 0; i < PROPOSAL_MAX; i++) {
291 if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0)
293 debug2("%s: %s", proposal_names[i], proposal[i]);
295 /* first kex follows / reserved */
296 if ((r = sshbuf_get_u8(b, &v)) != 0 || /* first_kex_follows */
297 (r = sshbuf_get_u32(b, &i)) != 0) /* reserved */
299 if (first_kex_follows != NULL)
300 *first_kex_follows = v;
301 debug2("first_kex_follows %d ", v);
302 debug2("reserved %u ", i);
306 if (r != 0 && proposal != NULL)
307 kex_prop_free(proposal);
313 kex_prop_free(char **proposal)
317 if (proposal == NULL)
319 for (i = 0; i < PROPOSAL_MAX; i++)
326 kex_protocol_error(int type, u_int32_t seq, void *ctxt)
328 struct ssh *ssh = active_state; /* XXX */
331 error("kex protocol error: type %d seq %u", type, seq);
332 if ((r = sshpkt_start(ssh, SSH2_MSG_UNIMPLEMENTED)) != 0 ||
333 (r = sshpkt_put_u32(ssh, seq)) != 0 ||
334 (r = sshpkt_send(ssh)) != 0)
340 kex_reset_dispatch(struct ssh *ssh)
342 ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
343 SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
347 kex_send_ext_info(struct ssh *ssh)
352 if ((algs = sshkey_alg_list(0, 1, 1, ',')) == NULL)
353 return SSH_ERR_ALLOC_FAIL;
354 if ((r = sshpkt_start(ssh, SSH2_MSG_EXT_INFO)) != 0 ||
355 (r = sshpkt_put_u32(ssh, 1)) != 0 ||
356 (r = sshpkt_put_cstring(ssh, "server-sig-algs")) != 0 ||
357 (r = sshpkt_put_cstring(ssh, algs)) != 0 ||
358 (r = sshpkt_send(ssh)) != 0)
368 kex_send_newkeys(struct ssh *ssh)
372 kex_reset_dispatch(ssh);
373 if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
374 (r = sshpkt_send(ssh)) != 0)
376 debug("SSH2_MSG_NEWKEYS sent");
377 debug("expecting SSH2_MSG_NEWKEYS");
378 ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
379 if (ssh->kex->ext_info_c)
380 if ((r = kex_send_ext_info(ssh)) != 0)
386 kex_input_ext_info(int type, u_int32_t seq, void *ctxt)
388 struct ssh *ssh = ctxt;
389 struct kex *kex = ssh->kex;
391 char *name, *val, *found;
394 debug("SSH2_MSG_EXT_INFO received");
395 ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_protocol_error);
396 if ((r = sshpkt_get_u32(ssh, &ninfo)) != 0)
398 for (i = 0; i < ninfo; i++) {
399 if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0)
401 if ((r = sshpkt_get_cstring(ssh, &val, NULL)) != 0) {
405 debug("%s: %s=<%s>", __func__, name, val);
406 if (strcmp(name, "server-sig-algs") == 0) {
407 found = match_list("rsa-sha2-256", val, NULL);
412 found = match_list("rsa-sha2-512", val, NULL);
421 return sshpkt_get_end(ssh);
425 kex_input_newkeys(int type, u_int32_t seq, void *ctxt)
427 struct ssh *ssh = ctxt;
428 struct kex *kex = ssh->kex;
431 debug("SSH2_MSG_NEWKEYS received");
432 ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
433 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
434 if ((r = sshpkt_get_end(ssh)) != 0)
436 if ((r = ssh_set_newkeys(ssh, MODE_IN)) != 0)
439 sshbuf_reset(kex->peer);
440 /* sshbuf_reset(kex->my); */
441 kex->flags &= ~KEX_INIT_SENT;
448 kex_send_kexinit(struct ssh *ssh)
451 struct kex *kex = ssh->kex;
455 return SSH_ERR_INTERNAL_ERROR;
456 if (kex->flags & KEX_INIT_SENT)
460 /* generate a random cookie */
461 if (sshbuf_len(kex->my) < KEX_COOKIE_LEN)
462 return SSH_ERR_INVALID_FORMAT;
463 if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL)
464 return SSH_ERR_INTERNAL_ERROR;
465 arc4random_buf(cookie, KEX_COOKIE_LEN);
467 if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
468 (r = sshpkt_putb(ssh, kex->my)) != 0 ||
469 (r = sshpkt_send(ssh)) != 0)
471 debug("SSH2_MSG_KEXINIT sent");
472 kex->flags |= KEX_INIT_SENT;
478 kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
480 struct ssh *ssh = ctxt;
481 struct kex *kex = ssh->kex;
487 debug("SSH2_MSG_KEXINIT received");
489 return SSH_ERR_INVALID_ARGUMENT;
491 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, NULL);
492 ptr = sshpkt_ptr(ssh, &dlen);
493 if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
497 for (i = 0; i < KEX_COOKIE_LEN; i++)
498 if ((r = sshpkt_get_u8(ssh, NULL)) != 0)
500 for (i = 0; i < PROPOSAL_MAX; i++)
501 if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0)
504 * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
505 * KEX method has the server move first, but a server might be using
506 * a custom method or one that we otherwise don't support. We should
507 * be prepared to remember first_kex_follows here so we can eat a
509 * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
510 * for cases where the server *doesn't* go first. I guess we should
511 * ignore it when it is set for these cases, which is what we do now.
513 if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
514 (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
515 (r = sshpkt_get_end(ssh)) != 0)
518 if (!(kex->flags & KEX_INIT_SENT))
519 if ((r = kex_send_kexinit(ssh)) != 0)
521 if ((r = kex_choose_conf(ssh)) != 0)
524 if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
525 return (kex->kex[kex->kex_type])(ssh);
527 return SSH_ERR_INTERNAL_ERROR;
531 kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp)
537 if ((kex = calloc(1, sizeof(*kex))) == NULL)
538 return SSH_ERR_ALLOC_FAIL;
539 if ((kex->peer = sshbuf_new()) == NULL ||
540 (kex->my = sshbuf_new()) == NULL) {
541 r = SSH_ERR_ALLOC_FAIL;
544 if ((r = kex_prop2buf(kex->my, proposal)) != 0)
547 kex_reset_dispatch(ssh);
548 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
558 kex_free_newkeys(struct newkeys *newkeys)
562 if (newkeys->enc.key) {
563 explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
564 free(newkeys->enc.key);
565 newkeys->enc.key = NULL;
567 if (newkeys->enc.iv) {
568 explicit_bzero(newkeys->enc.iv, newkeys->enc.iv_len);
569 free(newkeys->enc.iv);
570 newkeys->enc.iv = NULL;
572 free(newkeys->enc.name);
573 explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
574 free(newkeys->comp.name);
575 explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
576 mac_clear(&newkeys->mac);
577 if (newkeys->mac.key) {
578 explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
579 free(newkeys->mac.key);
580 newkeys->mac.key = NULL;
582 free(newkeys->mac.name);
583 explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
584 explicit_bzero(newkeys, sizeof(*newkeys));
589 kex_free(struct kex *kex)
596 #ifdef OPENSSL_HAS_ECC
597 if (kex->ec_client_key)
598 EC_KEY_free(kex->ec_client_key);
599 #endif /* OPENSSL_HAS_ECC */
600 #endif /* WITH_OPENSSL */
601 for (mode = 0; mode < MODE_MAX; mode++) {
602 kex_free_newkeys(kex->newkeys[mode]);
603 kex->newkeys[mode] = NULL;
605 sshbuf_free(kex->peer);
606 sshbuf_free(kex->my);
607 free(kex->session_id);
608 free(kex->client_version_string);
609 free(kex->server_version_string);
610 free(kex->failed_choice);
611 free(kex->hostkey_alg);
617 kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
621 if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0)
623 if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
632 * Request key re-exchange, returns 0 on success or a ssherr.h error
633 * code otherwise. Must not be called if KEX is incomplete or in-progress.
636 kex_start_rekex(struct ssh *ssh)
638 if (ssh->kex == NULL) {
639 error("%s: no kex", __func__);
640 return SSH_ERR_INTERNAL_ERROR;
642 if (ssh->kex->done == 0) {
643 error("%s: requested twice", __func__);
644 return SSH_ERR_INTERNAL_ERROR;
647 return kex_send_kexinit(ssh);
651 choose_enc(struct sshenc *enc, char *client, char *server)
653 char *name = match_list(client, server, NULL);
656 return SSH_ERR_NO_CIPHER_ALG_MATCH;
657 if ((enc->cipher = cipher_by_name(name)) == NULL) {
659 return SSH_ERR_INTERNAL_ERROR;
664 enc->iv_len = cipher_ivlen(enc->cipher);
666 enc->key_len = cipher_keylen(enc->cipher);
667 enc->block_size = cipher_blocksize(enc->cipher);
672 choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
674 char *name = match_list(client, server, NULL);
677 return SSH_ERR_NO_MAC_ALG_MATCH;
678 if (mac_setup(mac, name) < 0) {
680 return SSH_ERR_INTERNAL_ERROR;
682 /* truncate the key */
683 if (ssh->compat & SSH_BUG_HMAC)
692 choose_comp(struct sshcomp *comp, char *client, char *server)
694 char *name = match_list(client, server, NULL);
697 return SSH_ERR_NO_COMPRESS_ALG_MATCH;
698 if (strcmp(name, "zlib@openssh.com") == 0) {
699 comp->type = COMP_DELAYED;
700 } else if (strcmp(name, "zlib") == 0) {
701 comp->type = COMP_ZLIB;
702 } else if (strcmp(name, "none") == 0) {
703 comp->type = COMP_NONE;
706 return SSH_ERR_INTERNAL_ERROR;
713 choose_kex(struct kex *k, char *client, char *server)
715 const struct kexalg *kexalg;
717 k->name = match_list(client, server, NULL);
719 debug("kex: algorithm: %s", k->name ? k->name : "(no match)");
721 return SSH_ERR_NO_KEX_ALG_MATCH;
722 if ((kexalg = kex_alg_by_name(k->name)) == NULL)
723 return SSH_ERR_INTERNAL_ERROR;
724 k->kex_type = kexalg->type;
725 k->hash_alg = kexalg->hash_alg;
726 k->ec_nid = kexalg->ec_nid;
731 choose_hostkeyalg(struct kex *k, char *client, char *server)
733 k->hostkey_alg = match_list(client, server, NULL);
735 debug("kex: host key algorithm: %s",
736 k->hostkey_alg ? k->hostkey_alg : "(no match)");
737 if (k->hostkey_alg == NULL)
738 return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
739 k->hostkey_type = sshkey_type_from_name(k->hostkey_alg);
740 if (k->hostkey_type == KEY_UNSPEC)
741 return SSH_ERR_INTERNAL_ERROR;
742 k->hostkey_nid = sshkey_ecdsa_nid_from_name(k->hostkey_alg);
747 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
749 static int check[] = {
750 PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
755 for (idx = &check[0]; *idx != -1; idx++) {
756 if ((p = strchr(my[*idx], ',')) != NULL)
758 if ((p = strchr(peer[*idx], ',')) != NULL)
760 if (strcmp(my[*idx], peer[*idx]) != 0) {
761 debug2("proposal mismatch: my %s peer %s",
762 my[*idx], peer[*idx]);
766 debug2("proposals match");
771 kex_choose_conf(struct ssh *ssh)
773 struct kex *kex = ssh->kex;
774 struct newkeys *newkeys;
775 char **my = NULL, **peer = NULL;
776 char **cprop, **sprop;
777 int nenc, nmac, ncomp;
778 u_int mode, ctos, need, dh_need, authlen;
779 int r, first_kex_follows;
781 debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
782 if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
784 debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
785 if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
796 /* Check whether client supports ext_info_c */
800 ext = match_list("ext-info-c", peer[PROPOSAL_KEX_ALGS], NULL);
801 kex->ext_info_c = (ext != NULL);
805 /* Algorithm Negotiation */
806 if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
807 sprop[PROPOSAL_KEX_ALGS])) != 0) {
808 kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
809 peer[PROPOSAL_KEX_ALGS] = NULL;
812 if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
813 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
814 kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
815 peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
818 for (mode = 0; mode < MODE_MAX; mode++) {
819 if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
820 r = SSH_ERR_ALLOC_FAIL;
823 kex->newkeys[mode] = newkeys;
824 ctos = (!kex->server && mode == MODE_OUT) ||
825 (kex->server && mode == MODE_IN);
826 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
827 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
828 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
829 if ((r = choose_enc(&newkeys->enc, cprop[nenc],
830 sprop[nenc])) != 0) {
831 kex->failed_choice = peer[nenc];
835 authlen = cipher_authlen(newkeys->enc.cipher);
836 /* ignore mac for authenticated encryption */
838 (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
839 sprop[nmac])) != 0) {
840 kex->failed_choice = peer[nmac];
844 if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
845 sprop[ncomp])) != 0) {
846 kex->failed_choice = peer[ncomp];
850 debug("kex: %s cipher: %s MAC: %s compression: %s",
851 ctos ? "client->server" : "server->client",
853 authlen == 0 ? newkeys->mac.name : "<implicit>",
857 for (mode = 0; mode < MODE_MAX; mode++) {
858 newkeys = kex->newkeys[mode];
859 need = MAXIMUM(need, newkeys->enc.key_len);
860 need = MAXIMUM(need, newkeys->enc.block_size);
861 need = MAXIMUM(need, newkeys->enc.iv_len);
862 need = MAXIMUM(need, newkeys->mac.key_len);
863 dh_need = MAXIMUM(dh_need, cipher_seclen(newkeys->enc.cipher));
864 dh_need = MAXIMUM(dh_need, newkeys->enc.block_size);
865 dh_need = MAXIMUM(dh_need, newkeys->enc.iv_len);
866 dh_need = MAXIMUM(dh_need, newkeys->mac.key_len);
868 /* XXX need runden? */
870 kex->dh_need = dh_need;
872 /* ignore the next message if the proposals do not match */
873 if (first_kex_follows && !proposals_match(my, peer) &&
874 !(ssh->compat & SSH_BUG_FIRSTKEX))
875 ssh->dispatch_skip_packets = 1;
884 derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
885 const struct sshbuf *shared_secret, u_char **keyp)
887 struct kex *kex = ssh->kex;
888 struct ssh_digest_ctx *hashctx = NULL;
895 if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
896 return SSH_ERR_INVALID_ARGUMENT;
897 if ((digest = calloc(1, ROUNDUP(need, mdsz))) == NULL) {
898 r = SSH_ERR_ALLOC_FAIL;
902 /* K1 = HASH(K || H || "A" || session_id) */
903 if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
904 ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
905 ssh_digest_update(hashctx, hash, hashlen) != 0 ||
906 ssh_digest_update(hashctx, &c, 1) != 0 ||
907 ssh_digest_update(hashctx, kex->session_id,
908 kex->session_id_len) != 0 ||
909 ssh_digest_final(hashctx, digest, mdsz) != 0) {
910 r = SSH_ERR_LIBCRYPTO_ERROR;
913 ssh_digest_free(hashctx);
918 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
919 * Key = K1 || K2 || ... || Kn
921 for (have = mdsz; need > have; have += mdsz) {
922 if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
923 ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
924 ssh_digest_update(hashctx, hash, hashlen) != 0 ||
925 ssh_digest_update(hashctx, digest, have) != 0 ||
926 ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
927 r = SSH_ERR_LIBCRYPTO_ERROR;
930 ssh_digest_free(hashctx);
934 fprintf(stderr, "key '%c'== ", c);
935 dump_digest("key", digest, need);
942 ssh_digest_free(hashctx);
948 kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
949 const struct sshbuf *shared_secret)
951 struct kex *kex = ssh->kex;
953 u_int i, j, mode, ctos;
956 for (i = 0; i < NKEYS; i++) {
957 if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
958 shared_secret, &keys[i])) != 0) {
959 for (j = 0; j < i; j++)
964 for (mode = 0; mode < MODE_MAX; mode++) {
965 ctos = (!kex->server && mode == MODE_OUT) ||
966 (kex->server && mode == MODE_IN);
967 kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
968 kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
969 kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
976 kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen,
977 const BIGNUM *secret)
979 struct sshbuf *shared_secret;
982 if ((shared_secret = sshbuf_new()) == NULL)
983 return SSH_ERR_ALLOC_FAIL;
984 if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0)
985 r = kex_derive_keys(ssh, hash, hashlen, shared_secret);
986 sshbuf_free(shared_secret);
993 derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
994 u_int8_t cookie[8], u_int8_t id[16])
996 u_int8_t hbuf[2048], sbuf[2048], obuf[SSH_DIGEST_MAX_LENGTH];
997 struct ssh_digest_ctx *hashctx = NULL;
1001 hlen = BN_num_bytes(host_modulus);
1002 slen = BN_num_bytes(server_modulus);
1003 if (hlen < (512 / 8) || (u_int)hlen > sizeof(hbuf) ||
1004 slen < (512 / 8) || (u_int)slen > sizeof(sbuf))
1005 return SSH_ERR_KEY_BITS_MISMATCH;
1006 if (BN_bn2bin(host_modulus, hbuf) <= 0 ||
1007 BN_bn2bin(server_modulus, sbuf) <= 0) {
1008 r = SSH_ERR_LIBCRYPTO_ERROR;
1011 if ((hashctx = ssh_digest_start(SSH_DIGEST_MD5)) == NULL) {
1012 r = SSH_ERR_ALLOC_FAIL;
1015 if (ssh_digest_update(hashctx, hbuf, hlen) != 0 ||
1016 ssh_digest_update(hashctx, sbuf, slen) != 0 ||
1017 ssh_digest_update(hashctx, cookie, 8) != 0 ||
1018 ssh_digest_final(hashctx, obuf, sizeof(obuf)) != 0) {
1019 r = SSH_ERR_LIBCRYPTO_ERROR;
1022 memcpy(id, obuf, ssh_digest_bytes(SSH_DIGEST_MD5));
1025 ssh_digest_free(hashctx);
1026 explicit_bzero(hbuf, sizeof(hbuf));
1027 explicit_bzero(sbuf, sizeof(sbuf));
1028 explicit_bzero(obuf, sizeof(obuf));
1033 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
1035 dump_digest(char *msg, u_char *digest, int len)
1037 fprintf(stderr, "%s\n", msg);
1038 sshbuf_dump_data(digest, len, stderr);