1 /* $OpenBSD: kexdhc.c,v 1.19 2016/05/02 10:26:04 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 case KEX_DH_GRP14_SHA256:
67 kex->dh = dh_new_group14();
68 break;
69 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;
75 default:
76 r = SSH_ERR_INVALID_ARGUMENT;
77 goto out;
78 }
79 if (kex->dh == NULL) {
80 r = SSH_ERR_ALLOC_FAIL;
81 goto out;
82 }
83 debug("sending SSH2_MSG_KEXDH_INIT");
84 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;
89 #ifdef DEBUG_KEXDH
90 DHparams_print_fp(stderr, kex->dh);
91 fprintf(stderr, "pub= ");
92 BN_print_fp(stderr, kex->dh->pub_key);
93 fprintf(stderr, "\n");
94 #endif
95 debug("expecting SSH2_MSG_KEXDH_REPLY");
96 ssh_dispatch_set(ssh, SSH2_MSG_KEXDH_REPLY, &input_kex_dh);
97 r = 0;
98 out:
99 return r;
100 }
101
102 static int
input_kex_dh(int type,u_int32_t seq,void * ctxt)103 input_kex_dh(int type, u_int32_t seq, void *ctxt)
104 {
105 struct ssh *ssh = ctxt;
106 struct kex *kex = ssh->kex;
107 BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
108 struct sshkey *server_host_key = NULL;
109 u_char *kbuf = NULL, *server_host_key_blob = NULL, *signature = NULL;
110 u_char hash[SSH_DIGEST_MAX_LENGTH];
111 size_t klen = 0, slen, sbloblen, hashlen;
112 int kout, r;
113
114 if (kex->verify_host_key == NULL) {
115 r = SSH_ERR_INVALID_ARGUMENT;
116 goto out;
117 }
118 /* key, cert */
119 if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
120 &sbloblen)) != 0 ||
121 (r = sshkey_from_blob(server_host_key_blob, sbloblen,
122 &server_host_key)) != 0)
123 goto out;
124 if (server_host_key->type != kex->hostkey_type ||
125 (kex->hostkey_type == KEY_ECDSA &&
126 server_host_key->ecdsa_nid != kex->hostkey_nid)) {
127 r = SSH_ERR_KEY_TYPE_MISMATCH;
128 goto out;
129 }
130 if (kex->verify_host_key(server_host_key, ssh) == -1) {
131 r = SSH_ERR_SIGNATURE_INVALID;
132 goto out;
133 }
134 /* DH parameter f, server public DH key */
135 if ((dh_server_pub = BN_new()) == NULL) {
136 r = SSH_ERR_ALLOC_FAIL;
137 goto out;
138 }
139 /* signed H */
140 if ((r = sshpkt_get_bignum2(ssh, dh_server_pub)) != 0 ||
141 (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
142 (r = sshpkt_get_end(ssh)) != 0)
143 goto out;
144 #ifdef DEBUG_KEXDH
145 fprintf(stderr, "dh_server_pub= ");
146 BN_print_fp(stderr, dh_server_pub);
147 fprintf(stderr, "\n");
148 debug("bits %d", BN_num_bits(dh_server_pub));
149 #endif
150 if (!dh_pub_is_valid(kex->dh, dh_server_pub)) {
151 sshpkt_disconnect(ssh, "bad server public DH value");
152 r = SSH_ERR_MESSAGE_INCOMPLETE;
153 goto out;
154 }
155
156 klen = DH_size(kex->dh);
157 if ((kbuf = malloc(klen)) == NULL ||
158 (shared_secret = BN_new()) == NULL) {
159 r = SSH_ERR_ALLOC_FAIL;
160 goto out;
161 }
162 if ((kout = DH_compute_key(kbuf, dh_server_pub, kex->dh)) < 0 ||
163 BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
164 r = SSH_ERR_LIBCRYPTO_ERROR;
165 goto out;
166 }
167 #ifdef DEBUG_KEXDH
168 dump_digest("shared secret", kbuf, kout);
169 #endif
170
171 /* calc and verify H */
172 hashlen = sizeof(hash);
173 if ((r = kex_dh_hash(
174 kex->hash_alg,
175 kex->client_version_string,
176 kex->server_version_string,
177 sshbuf_ptr(kex->my), sshbuf_len(kex->my),
178 sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
179 server_host_key_blob, sbloblen,
180 kex->dh->pub_key,
181 dh_server_pub,
182 shared_secret,
183 hash, &hashlen)) != 0)
184 goto out;
185
186 if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
187 ssh->compat)) != 0)
188 goto out;
189
190 /* save session id */
191 if (kex->session_id == NULL) {
192 kex->session_id_len = hashlen;
193 kex->session_id = malloc(kex->session_id_len);
194 if (kex->session_id == NULL) {
195 r = SSH_ERR_ALLOC_FAIL;
196 goto out;
197 }
198 memcpy(kex->session_id, hash, kex->session_id_len);
199 }
200
201 if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
202 r = kex_send_newkeys(ssh);
203 out:
204 explicit_bzero(hash, sizeof(hash));
205 DH_free(kex->dh);
206 kex->dh = NULL;
207 if (dh_server_pub)
208 BN_clear_free(dh_server_pub);
209 if (kbuf) {
210 explicit_bzero(kbuf, klen);
211 free(kbuf);
212 }
213 if (shared_secret)
214 BN_clear_free(shared_secret);
215 sshkey_free(server_host_key);
216 free(server_host_key_blob);
217 free(signature);
218 return r;
219 }
220 #endif /* WITH_OPENSSL */
221