1 /* $OpenBSD: kexdhs.c,v 1.22 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 <stdarg.h>
33 #include <string.h>
34 #include <signal.h>
35
36 #include <openssl/dh.h>
37
38 #include "sshkey.h"
39 #include "cipher.h"
40 #include "digest.h"
41 #include "kex.h"
42 #include "log.h"
43 #include "packet.h"
44 #include "dh.h"
45 #include "ssh2.h"
46
47 #include "dispatch.h"
48 #include "compat.h"
49 #include "ssherr.h"
50 #include "sshbuf.h"
51
52 static int input_kex_dh_init(int, u_int32_t, void *);
53
54 int
kexdh_server(struct ssh * ssh)55 kexdh_server(struct ssh *ssh)
56 {
57 struct kex *kex = ssh->kex;
58 int r;
59
60 /* generate server 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 if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
77 goto out;
78
79 debug("expecting SSH2_MSG_KEXDH_INIT");
80 ssh_dispatch_set(ssh, SSH2_MSG_KEXDH_INIT, &input_kex_dh_init);
81 r = 0;
82 out:
83 return r;
84 }
85
86 int
input_kex_dh_init(int type,u_int32_t seq,void * ctxt)87 input_kex_dh_init(int type, u_int32_t seq, void *ctxt)
88 {
89 struct ssh *ssh = ctxt;
90 struct kex *kex = ssh->kex;
91 BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
92 struct sshkey *server_host_public, *server_host_private;
93 u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL;
94 u_char hash[SSH_DIGEST_MAX_LENGTH];
95 size_t sbloblen, slen;
96 size_t klen = 0, hashlen;
97 int kout, r;
98
99 if (kex->load_host_public_key == NULL ||
100 kex->load_host_private_key == NULL) {
101 r = SSH_ERR_INVALID_ARGUMENT;
102 goto out;
103 }
104 server_host_public = kex->load_host_public_key(kex->hostkey_type,
105 kex->hostkey_nid, ssh);
106 server_host_private = kex->load_host_private_key(kex->hostkey_type,
107 kex->hostkey_nid, ssh);
108 if (server_host_public == NULL) {
109 r = SSH_ERR_NO_HOSTKEY_LOADED;
110 goto out;
111 }
112
113 /* key, cert */
114 if ((dh_client_pub = BN_new()) == NULL) {
115 r = SSH_ERR_ALLOC_FAIL;
116 goto out;
117 }
118 if ((r = sshpkt_get_bignum2(ssh, dh_client_pub)) != 0 ||
119 (r = sshpkt_get_end(ssh)) != 0)
120 goto out;
121
122 #ifdef DEBUG_KEXDH
123 fprintf(stderr, "dh_client_pub= ");
124 BN_print_fp(stderr, dh_client_pub);
125 fprintf(stderr, "\n");
126 debug("bits %d", BN_num_bits(dh_client_pub));
127 #endif
128
129 #ifdef DEBUG_KEXDH
130 DHparams_print_fp(stderr, kex->dh);
131 fprintf(stderr, "pub= ");
132 BN_print_fp(stderr, kex->dh->pub_key);
133 fprintf(stderr, "\n");
134 #endif
135 if (!dh_pub_is_valid(kex->dh, dh_client_pub)) {
136 sshpkt_disconnect(ssh, "bad client public DH value");
137 r = SSH_ERR_MESSAGE_INCOMPLETE;
138 goto out;
139 }
140
141 klen = DH_size(kex->dh);
142 if ((kbuf = malloc(klen)) == NULL ||
143 (shared_secret = BN_new()) == NULL) {
144 r = SSH_ERR_ALLOC_FAIL;
145 goto out;
146 }
147 if ((kout = DH_compute_key(kbuf, dh_client_pub, kex->dh)) < 0 ||
148 BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
149 r = SSH_ERR_LIBCRYPTO_ERROR;
150 goto out;
151 }
152 #ifdef DEBUG_KEXDH
153 dump_digest("shared secret", kbuf, kout);
154 #endif
155 if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
156 &sbloblen)) != 0)
157 goto out;
158 /* calc H */
159 hashlen = sizeof(hash);
160 if ((r = kex_dh_hash(
161 kex->client_version_string,
162 kex->server_version_string,
163 sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
164 sshbuf_ptr(kex->my), sshbuf_len(kex->my),
165 server_host_key_blob, sbloblen,
166 dh_client_pub,
167 kex->dh->pub_key,
168 shared_secret,
169 hash, &hashlen)) != 0)
170 goto out;
171
172 /* save session id := H */
173 if (kex->session_id == NULL) {
174 kex->session_id_len = hashlen;
175 kex->session_id = malloc(kex->session_id_len);
176 if (kex->session_id == NULL) {
177 r = SSH_ERR_ALLOC_FAIL;
178 goto out;
179 }
180 memcpy(kex->session_id, hash, kex->session_id_len);
181 }
182
183 /* sign H */
184 if ((r = kex->sign(server_host_private, server_host_public,
185 &signature, &slen, hash, hashlen, ssh->compat)) < 0)
186 goto out;
187
188 /* destroy_sensitive_data(); */
189
190 /* send server hostkey, DH pubkey 'f' and singed H */
191 if ((r = sshpkt_start(ssh, SSH2_MSG_KEXDH_REPLY)) != 0 ||
192 (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
193 (r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 || /* f */
194 (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
195 (r = sshpkt_send(ssh)) != 0)
196 goto out;
197
198 if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
199 r = kex_send_newkeys(ssh);
200 out:
201 explicit_bzero(hash, sizeof(hash));
202 DH_free(kex->dh);
203 kex->dh = NULL;
204 if (dh_client_pub)
205 BN_clear_free(dh_client_pub);
206 if (kbuf) {
207 explicit_bzero(kbuf, klen);
208 free(kbuf);
209 }
210 if (shared_secret)
211 BN_clear_free(shared_secret);
212 free(server_host_key_blob);
213 free(signature);
214 return r;
215 }
216 #endif /* WITH_OPENSSL */
217