2 * Copyright (c) 2001 Markus Friedl. All rights reserved.
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 RCSID("$OpenBSD: kexdh.c,v 1.18 2002/03/18 17:50:31 provos Exp $");
28 #include <openssl/crypto.h>
29 #include <openssl/bn.h>
40 #include "monitor_wrap.h"
44 char *client_version_string,
45 char *server_version_string,
46 char *ckexinit, int ckexinitlen,
47 char *skexinit, int skexinitlen,
48 u_char *serverhostkeyblob, int sbloblen,
49 BIGNUM *client_dh_pub,
50 BIGNUM *server_dh_pub,
51 BIGNUM *shared_secret)
54 static u_char digest[EVP_MAX_MD_SIZE];
55 const EVP_MD *evp_md = EVP_sha1();
59 buffer_put_cstring(&b, client_version_string);
60 buffer_put_cstring(&b, server_version_string);
62 /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
63 buffer_put_int(&b, ckexinitlen+1);
64 buffer_put_char(&b, SSH2_MSG_KEXINIT);
65 buffer_append(&b, ckexinit, ckexinitlen);
66 buffer_put_int(&b, skexinitlen+1);
67 buffer_put_char(&b, SSH2_MSG_KEXINIT);
68 buffer_append(&b, skexinit, skexinitlen);
70 buffer_put_string(&b, serverhostkeyblob, sbloblen);
71 buffer_put_bignum2(&b, client_dh_pub);
72 buffer_put_bignum2(&b, server_dh_pub);
73 buffer_put_bignum2(&b, shared_secret);
78 EVP_DigestInit(&md, evp_md);
79 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
80 EVP_DigestFinal(&md, digest, NULL);
85 dump_digest("hash", digest, EVP_MD_size(evp_md));
93 kexdh_client(Kex *kex)
95 BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
98 u_char *server_host_key_blob = NULL, *signature = NULL;
100 u_int klen, kout, slen, sbloblen;
102 /* generate and send 'e', client DH public key */
103 dh = dh_new_group1();
104 dh_gen_key(dh, kex->we_need * 8);
105 packet_start(SSH2_MSG_KEXDH_INIT);
106 packet_put_bignum2(dh->pub_key);
109 debug("sending SSH2_MSG_KEXDH_INIT");
111 DHparams_print_fp(stderr, dh);
112 fprintf(stderr, "pub= ");
113 BN_print_fp(stderr, dh->pub_key);
114 fprintf(stderr, "\n");
117 debug("expecting SSH2_MSG_KEXDH_REPLY");
118 packet_read_expect(SSH2_MSG_KEXDH_REPLY);
121 server_host_key_blob = packet_get_string(&sbloblen);
122 server_host_key = key_from_blob(server_host_key_blob, sbloblen);
123 if (server_host_key == NULL)
124 fatal("cannot decode server_host_key_blob");
125 if (server_host_key->type != kex->hostkey_type)
126 fatal("type mismatch for decoded server_host_key_blob");
127 if (kex->verify_host_key == NULL)
128 fatal("cannot verify server_host_key");
129 if (kex->verify_host_key(server_host_key) == -1)
130 fatal("server_host_key verification failed");
132 /* DH paramter f, server public DH key */
133 if ((dh_server_pub = BN_new()) == NULL)
134 fatal("dh_server_pub == NULL");
135 packet_get_bignum2(dh_server_pub);
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));
145 signature = packet_get_string(&slen);
148 if (!dh_pub_is_valid(dh, dh_server_pub))
149 packet_disconnect("bad server public DH value");
152 kbuf = xmalloc(klen);
153 kout = DH_compute_key(kbuf, dh_server_pub, dh);
155 dump_digest("shared secret", kbuf, kout);
157 if ((shared_secret = BN_new()) == NULL)
158 fatal("kexdh_client: BN_new failed");
159 BN_bin2bn(kbuf, kout, shared_secret);
160 memset(kbuf, 0, klen);
163 /* calc and verify H */
165 kex->client_version_string,
166 kex->server_version_string,
167 buffer_ptr(&kex->my), buffer_len(&kex->my),
168 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
169 server_host_key_blob, sbloblen,
174 xfree(server_host_key_blob);
175 BN_clear_free(dh_server_pub);
178 if (key_verify(server_host_key, signature, slen, hash, 20) != 1)
179 fatal("key_verify failed for server_host_key");
180 key_free(server_host_key);
183 /* save session id */
184 if (kex->session_id == NULL) {
185 kex->session_id_len = 20;
186 kex->session_id = xmalloc(kex->session_id_len);
187 memcpy(kex->session_id, hash, kex->session_id_len);
190 kex_derive_keys(kex, hash, shared_secret);
191 BN_clear_free(shared_secret);
198 kexdh_server(Kex *kex)
200 BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
202 Key *server_host_key;
203 u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
204 u_int sbloblen, klen, kout;
207 /* generate server DH public key */
208 dh = dh_new_group1();
209 dh_gen_key(dh, kex->we_need * 8);
211 debug("expecting SSH2_MSG_KEXDH_INIT");
212 packet_read_expect(SSH2_MSG_KEXDH_INIT);
214 if (kex->load_host_key == NULL)
215 fatal("Cannot load hostkey");
216 server_host_key = kex->load_host_key(kex->hostkey_type);
217 if (server_host_key == NULL)
218 fatal("Unsupported hostkey type %d", kex->hostkey_type);
221 if ((dh_client_pub = BN_new()) == NULL)
222 fatal("dh_client_pub == NULL");
223 packet_get_bignum2(dh_client_pub);
227 fprintf(stderr, "dh_client_pub= ");
228 BN_print_fp(stderr, dh_client_pub);
229 fprintf(stderr, "\n");
230 debug("bits %d", BN_num_bits(dh_client_pub));
234 DHparams_print_fp(stderr, dh);
235 fprintf(stderr, "pub= ");
236 BN_print_fp(stderr, dh->pub_key);
237 fprintf(stderr, "\n");
239 if (!dh_pub_is_valid(dh, dh_client_pub))
240 packet_disconnect("bad client public DH value");
243 kbuf = xmalloc(klen);
244 kout = DH_compute_key(kbuf, dh_client_pub, dh);
246 dump_digest("shared secret", kbuf, kout);
248 if ((shared_secret = BN_new()) == NULL)
249 fatal("kexdh_server: BN_new failed");
250 BN_bin2bn(kbuf, kout, shared_secret);
251 memset(kbuf, 0, klen);
254 key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
258 kex->client_version_string,
259 kex->server_version_string,
260 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
261 buffer_ptr(&kex->my), buffer_len(&kex->my),
262 server_host_key_blob, sbloblen,
267 BN_clear_free(dh_client_pub);
269 /* save session id := H */
270 /* XXX hashlen depends on KEX */
271 if (kex->session_id == NULL) {
272 kex->session_id_len = 20;
273 kex->session_id = xmalloc(kex->session_id_len);
274 memcpy(kex->session_id, hash, kex->session_id_len);
278 /* XXX hashlen depends on KEX */
279 PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, 20));
281 /* destroy_sensitive_data(); */
283 /* send server hostkey, DH pubkey 'f' and singed H */
284 packet_start(SSH2_MSG_KEXDH_REPLY);
285 packet_put_string(server_host_key_blob, sbloblen);
286 packet_put_bignum2(dh->pub_key); /* f */
287 packet_put_string(signature, slen);
291 xfree(server_host_key_blob);
292 /* have keys, free DH */
295 kex_derive_keys(kex, hash, shared_secret);
296 BN_clear_free(shared_secret);