[openssh.git] / kexdh.c

/*
 * Copyright (c) 2001 Markus Friedl.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "includes.h"
RCSID("$OpenBSD: kexdh.c,v 1.2 2001/04/03 23:32:12 markus Exp $");

#include <openssl/crypto.h>
#include <openssl/bn.h>

#include "xmalloc.h"
#include "buffer.h"
#include "bufaux.h"
#include "key.h"
#include "kex.h"
#include "log.h"
#include "packet.h"
#include "dh.h"
#include "ssh2.h"

u_char *
kex_dh_hash(
    char *client_version_string,
    char *server_version_string,
    char *ckexinit, int ckexinitlen,
    char *skexinit, int skexinitlen,
    char *serverhostkeyblob, int sbloblen,
    BIGNUM *client_dh_pub,
    BIGNUM *server_dh_pub,
    BIGNUM *shared_secret)
{
	Buffer b;
	static u_char digest[EVP_MAX_MD_SIZE];
	EVP_MD *evp_md = EVP_sha1();
	EVP_MD_CTX md;

	buffer_init(&b);
	buffer_put_string(&b, client_version_string, strlen(client_version_string));
	buffer_put_string(&b, server_version_string, strlen(server_version_string));

	/* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
	buffer_put_int(&b, ckexinitlen+1);
	buffer_put_char(&b, SSH2_MSG_KEXINIT);
	buffer_append(&b, ckexinit, ckexinitlen);
	buffer_put_int(&b, skexinitlen+1);
	buffer_put_char(&b, SSH2_MSG_KEXINIT);
	buffer_append(&b, skexinit, skexinitlen);

	buffer_put_string(&b, serverhostkeyblob, sbloblen);
	buffer_put_bignum2(&b, client_dh_pub);
	buffer_put_bignum2(&b, server_dh_pub);
	buffer_put_bignum2(&b, shared_secret);

#ifdef DEBUG_KEX
	buffer_dump(&b);
#endif
	EVP_DigestInit(&md, evp_md);
	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
	EVP_DigestFinal(&md, digest, NULL);

	buffer_free(&b);

#ifdef DEBUG_KEX
	dump_digest("hash", digest, evp_md->md_size);
#endif
	return digest;
}

/* client */

void
kexdh_client(Kex *kex)
{
	BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
	DH *dh;
	Key *server_host_key;
	char *server_host_key_blob = NULL, *signature = NULL;
	u_char *kbuf, *hash;
	u_int klen, kout, slen, sbloblen;
	int dlen, plen;

	/* generate and send 'e', client DH public key */
	dh = dh_new_group1();
	dh_gen_key(dh, kex->we_need * 8);
	packet_start(SSH2_MSG_KEXDH_INIT);
	packet_put_bignum2(dh->pub_key);
	packet_send();

	debug("sending SSH2_MSG_KEXDH_INIT");
#ifdef DEBUG_KEXDH
	DHparams_print_fp(stderr, dh);
	fprintf(stderr, "pub= ");
	BN_print_fp(stderr, dh->pub_key);
	fprintf(stderr, "\n");
#endif

	debug("expecting SSH2_MSG_KEXDH_REPLY");
	packet_read_expect(&plen, SSH2_MSG_KEXDH_REPLY);

	/* key, cert */
	server_host_key_blob = packet_get_string(&sbloblen);
	server_host_key = key_from_blob(server_host_key_blob, sbloblen);
	if (server_host_key == NULL)
		fatal("cannot decode server_host_key_blob");

	if (kex->check_host_key == NULL)
		fatal("cannot check server_host_key");
	kex->check_host_key(server_host_key);

	/* DH paramter f, server public DH key */
	dh_server_pub = BN_new();
	if (dh_server_pub == NULL)
		fatal("dh_server_pub == NULL");
	packet_get_bignum2(dh_server_pub, &dlen);

#ifdef DEBUG_KEXDH
	fprintf(stderr, "dh_server_pub= ");
	BN_print_fp(stderr, dh_server_pub);
	fprintf(stderr, "\n");
	debug("bits %d", BN_num_bits(dh_server_pub));
#endif

	/* signed H */
	signature = packet_get_string(&slen);
	packet_done();

	if (!dh_pub_is_valid(dh, dh_server_pub))
		packet_disconnect("bad server public DH value");

	klen = DH_size(dh);
	kbuf = xmalloc(klen);
	kout = DH_compute_key(kbuf, dh_server_pub, dh);
#ifdef DEBUG_KEXDH
	dump_digest("shared secret", kbuf, kout);
#endif
	shared_secret = BN_new();
	BN_bin2bn(kbuf, kout, shared_secret);
	memset(kbuf, 0, klen);
	xfree(kbuf);

	/* calc and verify H */
	hash = kex_dh_hash(
	    kex->client_version_string,
	    kex->server_version_string,
	    buffer_ptr(&kex->my), buffer_len(&kex->my),
	    buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	    server_host_key_blob, sbloblen,
	    dh->pub_key,
	    dh_server_pub,
	    shared_secret
	);
	xfree(server_host_key_blob);
	DH_free(dh);
	BN_free(dh_server_pub);

	if (key_verify(server_host_key, (u_char *)signature, slen, hash, 20) != 1)
		fatal("key_verify failed for server_host_key");
	key_free(server_host_key);
	xfree(signature);

	/* save session id */
	if (kex->session_id == NULL) {
		kex->session_id_len = 20;
		kex->session_id = xmalloc(kex->session_id_len);
		memcpy(kex->session_id, hash, kex->session_id_len);
	}

	kex_derive_keys(kex, hash, shared_secret);
	BN_clear_free(shared_secret);
	kex_send_newkeys();
}

/* server */

void
kexdh_server(Kex *kex)
{
	BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
	DH *dh;
	Key *server_host_key;
	u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
	u_int sbloblen, klen, kout;
	int dlen, slen, plen;

	/* generate server DH public key */
	dh = dh_new_group1();
	dh_gen_key(dh, kex->we_need * 8);

	debug("expecting SSH2_MSG_KEXDH_INIT");
	packet_read_expect(&plen, SSH2_MSG_KEXDH_INIT);

	if (kex->load_host_key == NULL)
		fatal("Cannot load hostkey");
	server_host_key = kex->load_host_key(kex->hostkey_type);
	if (server_host_key == NULL)
		fatal("Unsupported hostkey type %d", kex->hostkey_type);

	/* key, cert */
	dh_client_pub = BN_new();
	if (dh_client_pub == NULL)
		fatal("dh_client_pub == NULL");
	packet_get_bignum2(dh_client_pub, &dlen);

#ifdef DEBUG_KEXDH
	fprintf(stderr, "dh_client_pub= ");
	BN_print_fp(stderr, dh_client_pub);
	fprintf(stderr, "\n");
	debug("bits %d", BN_num_bits(dh_client_pub));
#endif

#ifdef DEBUG_KEXDH
	DHparams_print_fp(stderr, dh);
	fprintf(stderr, "pub= ");
	BN_print_fp(stderr, dh->pub_key);
	fprintf(stderr, "\n");
#endif
	if (!dh_pub_is_valid(dh, dh_client_pub))
		packet_disconnect("bad client public DH value");

	klen = DH_size(dh);
	kbuf = xmalloc(klen);
	kout = DH_compute_key(kbuf, dh_client_pub, dh);
#ifdef DEBUG_KEXDH
	dump_digest("shared secret", kbuf, kout);
#endif
	shared_secret = BN_new();
	BN_bin2bn(kbuf, kout, shared_secret);
	memset(kbuf, 0, klen);
	xfree(kbuf);

	key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);

	/* calc H */
	hash = kex_dh_hash(
	    kex->client_version_string,
	    kex->server_version_string,
	    buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	    buffer_ptr(&kex->my), buffer_len(&kex->my),
	    (char *)server_host_key_blob, sbloblen,
	    dh_client_pub,
	    dh->pub_key,
	    shared_secret
	);
	BN_free(dh_client_pub);

	/* save session id := H */
	/* XXX hashlen depends on KEX */
	if (kex->session_id == NULL) {
		kex->session_id_len = 20;
		kex->session_id = xmalloc(kex->session_id_len);
		memcpy(kex->session_id, hash, kex->session_id_len);
	}

	/* sign H */
	/* XXX hashlen depends on KEX */
	key_sign(server_host_key, &signature, &slen, hash, 20);

	/* destroy_sensitive_data(); */

	/* send server hostkey, DH pubkey 'f' and singed H */
	packet_start(SSH2_MSG_KEXDH_REPLY);
	packet_put_string((char *)server_host_key_blob, sbloblen);
	packet_put_bignum2(dh->pub_key);	/* f */
	packet_put_string((char *)signature, slen);
	packet_send();
	xfree(signature);
	xfree(server_host_key_blob);

	kex_derive_keys(kex, hash, shared_secret);
	BN_clear_free(shared_secret);
	kex_send_newkeys();

	/* have keys, free DH */
	DH_free(dh);
}

void
kexdh(Kex *kex)
{
	if (kex->server)
		kexdh_server(kex);
	else
		kexdh_client(kex);
}
Commit	Line	Data
0bc35151	1	/*
	2	* Copyright (c) 2001 Markus Friedl. All rights reserved.
	3	*
	4	* Redistribution and use in source and binary forms, with or without
	5	* modification, are permitted provided that the following conditions
	6	* are met:
	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.
	12	*
	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.
	23	*/
	24
	25	#include "includes.h"
	26	RCSID("$OpenBSD: kexdh.c,v 1.2 2001/04/03 23:32:12 markus Exp $");
	27
	28	#include <openssl/crypto.h>
	29	#include <openssl/bn.h>
	30
	31	#include "xmalloc.h"
	32	#include "buffer.h"
	33	#include "bufaux.h"
	34	#include "key.h"
	35	#include "kex.h"
	36	#include "log.h"
	37	#include "packet.h"
	38	#include "dh.h"
	39	#include "ssh2.h"
	40
	41	u_char *
	42	kex_dh_hash(
	43	char *client_version_string,
	44	char *server_version_string,
	45	char *ckexinit, int ckexinitlen,
	46	char *skexinit, int skexinitlen,
	47	char *serverhostkeyblob, int sbloblen,
	48	BIGNUM *client_dh_pub,
	49	BIGNUM *server_dh_pub,
	50	BIGNUM *shared_secret)
	51	{
	52	Buffer b;
	53	static u_char digest[EVP_MAX_MD_SIZE];
	54	EVP_MD *evp_md = EVP_sha1();
	55	EVP_MD_CTX md;
	56
	57	buffer_init(&b);
	58	buffer_put_string(&b, client_version_string, strlen(client_version_string));
	59	buffer_put_string(&b, server_version_string, strlen(server_version_string));
	60
	61	/* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
	62	buffer_put_int(&b, ckexinitlen+1);
	63	buffer_put_char(&b, SSH2_MSG_KEXINIT);
	64	buffer_append(&b, ckexinit, ckexinitlen);
65	buffer_put_int(&b, skexinitlen+1);
66	buffer_put_char(&b, SSH2_MSG_KEXINIT);
67	buffer_append(&b, skexinit, skexinitlen);
68
69	buffer_put_string(&b, serverhostkeyblob, sbloblen);
70	buffer_put_bignum2(&b, client_dh_pub);
71	buffer_put_bignum2(&b, server_dh_pub);
72	buffer_put_bignum2(&b, shared_secret);
73
74	#ifdef DEBUG_KEX
75	buffer_dump(&b);
76	#endif
77	EVP_DigestInit(&md, evp_md);
78	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
79	EVP_DigestFinal(&md, digest, NULL);
80
81	buffer_free(&b);
82
83	#ifdef DEBUG_KEX
84	dump_digest("hash", digest, evp_md->md_size);
85	#endif
86	return digest;
87	}
88
89	/* client */
90
91	void
92	kexdh_client(Kex *kex)
93	{
94	BIGNUM dh_server_pub = NULL, shared_secret = NULL;
95	DH *dh;
96	Key *server_host_key;
97	char server_host_key_blob = NULL, signature = NULL;
98	u_char kbuf, hash;
99	u_int klen, kout, slen, sbloblen;
100	int dlen, plen;
101
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);
107	packet_send();
108
109	debug("sending SSH2_MSG_KEXDH_INIT");
110	#ifdef DEBUG_KEXDH
111	DHparams_print_fp(stderr, dh);
112	fprintf(stderr, "pub= ");
113	BN_print_fp(stderr, dh->pub_key);
114	fprintf(stderr, "\n");
115	#endif
116
117	debug("expecting SSH2_MSG_KEXDH_REPLY");
118	packet_read_expect(&plen, SSH2_MSG_KEXDH_REPLY);
119
120	/* key, cert */
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
126	if (kex->check_host_key == NULL)
127	fatal("cannot check server_host_key");
128	kex->check_host_key(server_host_key);
129
130	/* DH paramter f, server public DH key */
131	dh_server_pub = BN_new();
132	if (dh_server_pub == NULL)
133	fatal("dh_server_pub == NULL");
134	packet_get_bignum2(dh_server_pub, &dlen);
135
136	#ifdef DEBUG_KEXDH
137	fprintf(stderr, "dh_server_pub= ");
138	BN_print_fp(stderr, dh_server_pub);
139	fprintf(stderr, "\n");
140	debug("bits %d", BN_num_bits(dh_server_pub));
141	#endif
142
143	/* signed H */
144	signature = packet_get_string(&slen);
145	packet_done();
146
147	if (!dh_pub_is_valid(dh, dh_server_pub))
148	packet_disconnect("bad server public DH value");
149
150	klen = DH_size(dh);
151	kbuf = xmalloc(klen);
152	kout = DH_compute_key(kbuf, dh_server_pub, dh);
153	#ifdef DEBUG_KEXDH
154	dump_digest("shared secret", kbuf, kout);
155	#endif
156	shared_secret = BN_new();
157	BN_bin2bn(kbuf, kout, shared_secret);
158	memset(kbuf, 0, klen);
159	xfree(kbuf);
160
161	/* calc and verify H */
162	hash = kex_dh_hash(
163	kex->client_version_string,
164	kex->server_version_string,
165	buffer_ptr(&kex->my), buffer_len(&kex->my),
166	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
167	server_host_key_blob, sbloblen,
168	dh->pub_key,
169	dh_server_pub,
170	shared_secret
171	);
172	xfree(server_host_key_blob);
173	DH_free(dh);
174	BN_free(dh_server_pub);
175
176	if (key_verify(server_host_key, (u_char *)signature, slen, hash, 20) != 1)
177	fatal("key_verify failed for server_host_key");
178	key_free(server_host_key);
179	xfree(signature);
180
181	/* save session id */
182	if (kex->session_id == NULL) {
183	kex->session_id_len = 20;
184	kex->session_id = xmalloc(kex->session_id_len);
185	memcpy(kex->session_id, hash, kex->session_id_len);
186	}
187
188	kex_derive_keys(kex, hash, shared_secret);
189	BN_clear_free(shared_secret);
190	kex_send_newkeys();
191	}
192
193	/* server */
194
195	void
196	kexdh_server(Kex *kex)
197	{
198	BIGNUM shared_secret = NULL, dh_client_pub = NULL;
199	DH *dh;
200	Key *server_host_key;
201	u_char kbuf, hash, signature = NULL, server_host_key_blob = NULL;
202	u_int sbloblen, klen, kout;
203	int dlen, slen, plen;
204
205	/* generate server DH public key */
206	dh = dh_new_group1();
207	dh_gen_key(dh, kex->we_need * 8);
208
209	debug("expecting SSH2_MSG_KEXDH_INIT");
210	packet_read_expect(&plen, SSH2_MSG_KEXDH_INIT);
211
212	if (kex->load_host_key == NULL)
213	fatal("Cannot load hostkey");
214	server_host_key = kex->load_host_key(kex->hostkey_type);
215	if (server_host_key == NULL)
216	fatal("Unsupported hostkey type %d", kex->hostkey_type);
217
218	/* key, cert */
219	dh_client_pub = BN_new();
220	if (dh_client_pub == NULL)
221	fatal("dh_client_pub == NULL");
222	packet_get_bignum2(dh_client_pub, &dlen);
223
224	#ifdef DEBUG_KEXDH
225	fprintf(stderr, "dh_client_pub= ");
226	BN_print_fp(stderr, dh_client_pub);
227	fprintf(stderr, "\n");
228	debug("bits %d", BN_num_bits(dh_client_pub));
229	#endif
230
231	#ifdef DEBUG_KEXDH
232	DHparams_print_fp(stderr, dh);
233	fprintf(stderr, "pub= ");
234	BN_print_fp(stderr, dh->pub_key);
235	fprintf(stderr, "\n");
236	#endif
237	if (!dh_pub_is_valid(dh, dh_client_pub))
238	packet_disconnect("bad client public DH value");
239
240	klen = DH_size(dh);
241	kbuf = xmalloc(klen);
242	kout = DH_compute_key(kbuf, dh_client_pub, dh);
243	#ifdef DEBUG_KEXDH
244	dump_digest("shared secret", kbuf, kout);
245	#endif
246	shared_secret = BN_new();
247	BN_bin2bn(kbuf, kout, shared_secret);
248	memset(kbuf, 0, klen);
249	xfree(kbuf);
250
251	key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
252
253	/* calc H */
254	hash = kex_dh_hash(
255	kex->client_version_string,
256	kex->server_version_string,
257	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
258	buffer_ptr(&kex->my), buffer_len(&kex->my),
259	(char *)server_host_key_blob, sbloblen,
260	dh_client_pub,
261	dh->pub_key,
262	shared_secret
263	);
264	BN_free(dh_client_pub);
265
266	/* save session id := H */
267	/* XXX hashlen depends on KEX */
268	if (kex->session_id == NULL) {
269	kex->session_id_len = 20;
270	kex->session_id = xmalloc(kex->session_id_len);
271	memcpy(kex->session_id, hash, kex->session_id_len);
272	}
273
274	/* sign H */
275	/* XXX hashlen depends on KEX */
276	key_sign(server_host_key, &signature, &slen, hash, 20);
277
278	/* destroy_sensitive_data(); */
279
280	/* send server hostkey, DH pubkey 'f' and singed H */
281	packet_start(SSH2_MSG_KEXDH_REPLY);
282	packet_put_string((char *)server_host_key_blob, sbloblen);
283	packet_put_bignum2(dh->pub_key); /* f */
284	packet_put_string((char *)signature, slen);
285	packet_send();
286	xfree(signature);
287	xfree(server_host_key_blob);
288
289	kex_derive_keys(kex, hash, shared_secret);
290	BN_clear_free(shared_secret);
291	kex_send_newkeys();
292
293	/* have keys, free DH */
294	DH_free(dh);
295	}
296
297	void
298	kexdh(Kex *kex)
299	{
300	if (kex->server)
301	kexdh_server(kex);
302	else
303	kexdh_client(kex);
304	}