1 /* $OpenBSD: kexdhc.c,v 1.18 2015/01/26 06:10:03 djm Exp $ */
2 /*
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"
27
28 #ifdef WITH_OPENSSL
29
30 #include <sys/types.h>
31
32 #include <openssl/dh.h>
33
34 #include <stdarg.h>
35 #include <stdio.h>
36 #include <string.h>
37 #include <signal.h>
38
39 #include "sshkey.h"
40 #include "cipher.h"
41 #include "digest.h"
42 #include "kex.h"
43 #include "log.h"
44 #include "packet.h"
45 #include "dh.h"
46 #include "ssh2.h"
47 #include "dispatch.h"
48 #include "compat.h"
49 #include "ssherr.h"
50 #include "sshbuf.h"
51
52 static int input_kex_dh(int, u_int32_t, void *);
53
54 int
kexdh_client(struct ssh * ssh)55 kexdh_client(struct ssh *ssh)
56 {
57 struct kex *kex = ssh->kex;
58 int r;
59
60 /* generate and send 'e', client DH public key */
61 switch (kex->kex_type) {
62 case KEX_DH_GRP1_SHA1:
63 kex->dh = dh_new_group1();
64 break;
65 case KEX_DH_GRP14_SHA1:
66 kex->dh = dh_new_group14();
67 break;
68 default:
69 r = SSH_ERR_INVALID_ARGUMENT;
70 goto out;
71 }
72 if (kex->dh == NULL) {
73 r = SSH_ERR_ALLOC_FAIL;
74 goto out;
75 }
76 debug("sending SSH2_MSG_KEXDH_INIT");
77 if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0 ||
78 (r = sshpkt_start(ssh, SSH2_MSG_KEXDH_INIT)) != 0 ||
79 (r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 ||
80 (r = sshpkt_send(ssh)) != 0)
81 goto out;
82 #ifdef DEBUG_KEXDH
83 DHparams_print_fp(stderr, kex->dh);
84 fprintf(stderr, "pub= ");
85 BN_print_fp(stderr, kex->dh->pub_key);
86 fprintf(stderr, "\n");
87 #endif
88 debug("expecting SSH2_MSG_KEXDH_REPLY");
89 ssh_dispatch_set(ssh, SSH2_MSG_KEXDH_REPLY, &input_kex_dh);
90 r = 0;
91 out:
92 return r;
93 }
94
95 static int
input_kex_dh(int type,u_int32_t seq,void * ctxt)96 input_kex_dh(int type, u_int32_t seq, void *ctxt)
97 {
98 struct ssh *ssh = ctxt;
99 struct kex *kex = ssh->kex;
100 BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
101 struct sshkey *server_host_key = NULL;
102 u_char *kbuf = NULL, *server_host_key_blob = NULL, *signature = NULL;
103 u_char hash[SSH_DIGEST_MAX_LENGTH];
104 size_t klen = 0, slen, sbloblen, hashlen;
105 int kout, r;
106
107 if (kex->verify_host_key == NULL) {
108 r = SSH_ERR_INVALID_ARGUMENT;
109 goto out;
110 }
111 /* key, cert */
112 if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
113 &sbloblen)) != 0 ||
114 (r = sshkey_from_blob(server_host_key_blob, sbloblen,
115 &server_host_key)) != 0)
116 goto out;
117 if (server_host_key->type != kex->hostkey_type ||
118 (kex->hostkey_type == KEY_ECDSA &&
119 server_host_key->ecdsa_nid != kex->hostkey_nid)) {
120 r = SSH_ERR_KEY_TYPE_MISMATCH;
121 goto out;
122 }
123 if (kex->verify_host_key(server_host_key, ssh) == -1) {
124 r = SSH_ERR_SIGNATURE_INVALID;
125 goto out;
126 }
127 /* DH parameter f, server public DH key */
128 if ((dh_server_pub = BN_new()) == NULL) {
129 r = SSH_ERR_ALLOC_FAIL;
130 goto out;
131 }
132 /* signed H */
133 if ((r = sshpkt_get_bignum2(ssh, dh_server_pub)) != 0 ||
134 (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
135 (r = sshpkt_get_end(ssh)) != 0)
136 goto out;
137 #ifdef DEBUG_KEXDH
138 fprintf(stderr, "dh_server_pub= ");
139 BN_print_fp(stderr, dh_server_pub);
140 fprintf(stderr, "\n");
141 debug("bits %d", BN_num_bits(dh_server_pub));
142 #endif
143 if (!dh_pub_is_valid(kex->dh, dh_server_pub)) {
144 sshpkt_disconnect(ssh, "bad server public DH value");
145 r = SSH_ERR_MESSAGE_INCOMPLETE;
146 goto out;
147 }
148
149 klen = DH_size(kex->dh);
150 if ((kbuf = malloc(klen)) == NULL ||
151 (shared_secret = BN_new()) == NULL) {
152 r = SSH_ERR_ALLOC_FAIL;
153 goto out;
154 }
155 if ((kout = DH_compute_key(kbuf, dh_server_pub, kex->dh)) < 0 ||
156 BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
157 r = SSH_ERR_LIBCRYPTO_ERROR;
158 goto out;
159 }
160 #ifdef DEBUG_KEXDH
161 dump_digest("shared secret", kbuf, kout);
162 #endif
163
164 /* calc and verify H */
165 hashlen = sizeof(hash);
166 if ((r = kex_dh_hash(
167 kex->client_version_string,
168 kex->server_version_string,
169 sshbuf_ptr(kex->my), sshbuf_len(kex->my),
170 sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
171 server_host_key_blob, sbloblen,
172 kex->dh->pub_key,
173 dh_server_pub,
174 shared_secret,
175 hash, &hashlen)) != 0)
176 goto out;
177
178 if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
179 ssh->compat)) != 0)
180 goto out;
181
182 /* save session id */
183 if (kex->session_id == NULL) {
184 kex->session_id_len = hashlen;
185 kex->session_id = malloc(kex->session_id_len);
186 if (kex->session_id == NULL) {
187 r = SSH_ERR_ALLOC_FAIL;
188 goto out;
189 }
190 memcpy(kex->session_id, hash, kex->session_id_len);
191 }
192
193 if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
194 r = kex_send_newkeys(ssh);
195 out:
196 explicit_bzero(hash, sizeof(hash));
197 DH_free(kex->dh);
198 kex->dh = NULL;
199 if (dh_server_pub)
200 BN_clear_free(dh_server_pub);
201 if (kbuf) {
202 explicit_bzero(kbuf, klen);
203 free(kbuf);
204 }
205 if (shared_secret)
206 BN_clear_free(shared_secret);
207 sshkey_free(server_host_key);
208 free(server_host_key_blob);
209 free(signature);
210 return r;
211 }
212 #endif /* WITH_OPENSSL */
213