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djm@openbsd.org04c7e282017-12-18 02:25:15 +00001/* $OpenBSD: kexdhc.c,v 1.21 2017/12/18 02:25:15 djm Exp $ */
Damien Miller8e7fb332003-02-24 12:03:03 +11002/*
3 * Copyright (c) 2001 Markus Friedl. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#include "includes.h"
Damien Miller8e7fb332003-02-24 12:03:03 +110027
Damien Miller72ef7c12015-01-15 02:21:31 +110028#ifdef WITH_OPENSSL
29
Damien Millerd7834352006-08-05 12:39:39 +100030#include <sys/types.h>
31
Damien Miller4499f4c2010-11-20 15:15:49 +110032#include <openssl/dh.h>
33
Damien Millerded319c2006-09-01 15:38:36 +100034#include <stdarg.h>
Damien Millera7a73ee2006-08-05 11:37:59 +100035#include <stdio.h>
Damien Millere3476ed2006-07-24 14:13:33 +100036#include <string.h>
Damien Millerd7834352006-08-05 12:39:39 +100037#include <signal.h>
Damien Millere3476ed2006-07-24 14:13:33 +100038
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000039#include "sshkey.h"
Damien Millerd7834352006-08-05 12:39:39 +100040#include "cipher.h"
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000041#include "digest.h"
Damien Miller8e7fb332003-02-24 12:03:03 +110042#include "kex.h"
43#include "log.h"
44#include "packet.h"
45#include "dh.h"
46#include "ssh2.h"
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000047#include "dispatch.h"
48#include "compat.h"
49#include "ssherr.h"
50#include "sshbuf.h"
Damien Miller8e7fb332003-02-24 12:03:03 +110051
markus@openbsd.org2ae666a2017-05-30 14:23:52 +000052static int input_kex_dh(int, u_int32_t, struct ssh *);
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000053
54int
55kexdh_client(struct ssh *ssh)
Damien Miller8e7fb332003-02-24 12:03:03 +110056{
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000057 struct kex *kex = ssh->kex;
58 int r;
Damien Miller8e7fb332003-02-24 12:03:03 +110059
60 /* generate and send 'e', client DH public key */
Damien Millerf675fc42004-06-15 10:30:09 +100061 switch (kex->kex_type) {
62 case KEX_DH_GRP1_SHA1:
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000063 kex->dh = dh_new_group1();
Damien Millerf675fc42004-06-15 10:30:09 +100064 break;
65 case KEX_DH_GRP14_SHA1:
djm@openbsd.org0e8eeec2016-05-02 10:26:04 +000066 case KEX_DH_GRP14_SHA256:
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000067 kex->dh = dh_new_group14();
Damien Millerf675fc42004-06-15 10:30:09 +100068 break;
djm@openbsd.org0e8eeec2016-05-02 10:26:04 +000069 case KEX_DH_GRP16_SHA512:
70 kex->dh = dh_new_group16();
71 break;
72 case KEX_DH_GRP18_SHA512:
73 kex->dh = dh_new_group18();
74 break;
Damien Millerf675fc42004-06-15 10:30:09 +100075 default:
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000076 r = SSH_ERR_INVALID_ARGUMENT;
77 goto out;
Damien Millerf675fc42004-06-15 10:30:09 +100078 }
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000079 if (kex->dh == NULL) {
80 r = SSH_ERR_ALLOC_FAIL;
81 goto out;
82 }
Damien Miller8e7fb332003-02-24 12:03:03 +110083 debug("sending SSH2_MSG_KEXDH_INIT");
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000084 if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0 ||
85 (r = sshpkt_start(ssh, SSH2_MSG_KEXDH_INIT)) != 0 ||
86 (r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 ||
87 (r = sshpkt_send(ssh)) != 0)
88 goto out;
Damien Miller8e7fb332003-02-24 12:03:03 +110089#ifdef DEBUG_KEXDH
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000090 DHparams_print_fp(stderr, kex->dh);
Damien Miller8e7fb332003-02-24 12:03:03 +110091 fprintf(stderr, "pub= ");
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000092 BN_print_fp(stderr, kex->dh->pub_key);
Damien Miller8e7fb332003-02-24 12:03:03 +110093 fprintf(stderr, "\n");
94#endif
Damien Miller8e7fb332003-02-24 12:03:03 +110095 debug("expecting SSH2_MSG_KEXDH_REPLY");
markus@openbsd.org57d10cb2015-01-19 20:16:15 +000096 ssh_dispatch_set(ssh, SSH2_MSG_KEXDH_REPLY, &input_kex_dh);
97 r = 0;
98 out:
99 return r;
100}
Damien Miller8e7fb332003-02-24 12:03:03 +1100101
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000102static int
markus@openbsd.org2ae666a2017-05-30 14:23:52 +0000103input_kex_dh(int type, u_int32_t seq, struct ssh *ssh)
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000104{
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000105 struct kex *kex = ssh->kex;
106 BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
107 struct sshkey *server_host_key = NULL;
108 u_char *kbuf = NULL, *server_host_key_blob = NULL, *signature = NULL;
109 u_char hash[SSH_DIGEST_MAX_LENGTH];
110 size_t klen = 0, slen, sbloblen, hashlen;
111 int kout, r;
112
113 if (kex->verify_host_key == NULL) {
114 r = SSH_ERR_INVALID_ARGUMENT;
115 goto out;
116 }
Damien Miller8e7fb332003-02-24 12:03:03 +1100117 /* key, cert */
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000118 if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
119 &sbloblen)) != 0 ||
120 (r = sshkey_from_blob(server_host_key_blob, sbloblen,
121 &server_host_key)) != 0)
122 goto out;
djm@openbsd.org5104db72015-01-26 06:10:03 +0000123 if (server_host_key->type != kex->hostkey_type ||
124 (kex->hostkey_type == KEY_ECDSA &&
125 server_host_key->ecdsa_nid != kex->hostkey_nid)) {
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000126 r = SSH_ERR_KEY_TYPE_MISMATCH;
127 goto out;
128 }
129 if (kex->verify_host_key(server_host_key, ssh) == -1) {
130 r = SSH_ERR_SIGNATURE_INVALID;
131 goto out;
132 }
Damien Millerad6b14d2006-06-13 13:00:41 +1000133 /* DH parameter f, server public DH key */
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000134 if ((dh_server_pub = BN_new()) == NULL) {
135 r = SSH_ERR_ALLOC_FAIL;
136 goto out;
137 }
138 /* signed H */
139 if ((r = sshpkt_get_bignum2(ssh, dh_server_pub)) != 0 ||
140 (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
141 (r = sshpkt_get_end(ssh)) != 0)
142 goto out;
Damien Miller8e7fb332003-02-24 12:03:03 +1100143#ifdef DEBUG_KEXDH
144 fprintf(stderr, "dh_server_pub= ");
145 BN_print_fp(stderr, dh_server_pub);
146 fprintf(stderr, "\n");
147 debug("bits %d", BN_num_bits(dh_server_pub));
148#endif
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000149 if (!dh_pub_is_valid(kex->dh, dh_server_pub)) {
150 sshpkt_disconnect(ssh, "bad server public DH value");
151 r = SSH_ERR_MESSAGE_INCOMPLETE;
152 goto out;
153 }
Damien Miller8e7fb332003-02-24 12:03:03 +1100154
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000155 klen = DH_size(kex->dh);
156 if ((kbuf = malloc(klen)) == NULL ||
157 (shared_secret = BN_new()) == NULL) {
158 r = SSH_ERR_ALLOC_FAIL;
159 goto out;
160 }
161 if ((kout = DH_compute_key(kbuf, dh_server_pub, kex->dh)) < 0 ||
162 BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
163 r = SSH_ERR_LIBCRYPTO_ERROR;
164 goto out;
165 }
Damien Miller8e7fb332003-02-24 12:03:03 +1100166#ifdef DEBUG_KEXDH
167 dump_digest("shared secret", kbuf, kout);
168#endif
Damien Miller8e7fb332003-02-24 12:03:03 +1100169
170 /* calc and verify H */
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000171 hashlen = sizeof(hash);
172 if ((r = kex_dh_hash(
djm@openbsd.org0e8eeec2016-05-02 10:26:04 +0000173 kex->hash_alg,
Damien Miller8e7fb332003-02-24 12:03:03 +1100174 kex->client_version_string,
175 kex->server_version_string,
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000176 sshbuf_ptr(kex->my), sshbuf_len(kex->my),
177 sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
Damien Miller8e7fb332003-02-24 12:03:03 +1100178 server_host_key_blob, sbloblen,
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000179 kex->dh->pub_key,
Damien Miller8e7fb332003-02-24 12:03:03 +1100180 dh_server_pub,
Damien Miller19bb3a52005-11-05 15:19:35 +1100181 shared_secret,
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000182 hash, &hashlen)) != 0)
183 goto out;
Damien Miller8e7fb332003-02-24 12:03:03 +1100184
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000185 if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
djm@openbsd.org04c7e282017-12-18 02:25:15 +0000186 kex->hostkey_alg, ssh->compat)) != 0)
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000187 goto out;
Damien Miller8e7fb332003-02-24 12:03:03 +1100188
189 /* save session id */
190 if (kex->session_id == NULL) {
Damien Miller19bb3a52005-11-05 15:19:35 +1100191 kex->session_id_len = hashlen;
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000192 kex->session_id = malloc(kex->session_id_len);
193 if (kex->session_id == NULL) {
194 r = SSH_ERR_ALLOC_FAIL;
195 goto out;
196 }
Damien Miller8e7fb332003-02-24 12:03:03 +1100197 memcpy(kex->session_id, hash, kex->session_id_len);
198 }
199
markus@openbsd.org57d10cb2015-01-19 20:16:15 +0000200 if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
201 r = kex_send_newkeys(ssh);
202 out:
203 explicit_bzero(hash, sizeof(hash));
204 DH_free(kex->dh);
205 kex->dh = NULL;
206 if (dh_server_pub)
207 BN_clear_free(dh_server_pub);
208 if (kbuf) {
209 explicit_bzero(kbuf, klen);
210 free(kbuf);
211 }
212 if (shared_secret)
213 BN_clear_free(shared_secret);
214 sshkey_free(server_host_key);
215 free(server_host_key_blob);
216 free(signature);
217 return r;
Damien Miller8e7fb332003-02-24 12:03:03 +1100218}
Damien Miller72ef7c12015-01-15 02:21:31 +1100219#endif /* WITH_OPENSSL */