[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 1.9 2001/12/27 19:37:22 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"

static u_char *
kex_dh_hash(
    char *client_version_string,
    char *server_version_string,
    char *ckexinit, int ckexinitlen,
    char *skexinit, int skexinitlen,
    u_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_cstring(&b, client_version_string);
	buffer_put_cstring(&b, 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 */

static void
kexdh_client(Kex *kex)
{
	BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
	DH *dh;
	Key *server_host_key;
	u_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->verify_host_key == NULL)
		fatal("cannot verify server_host_key");
	if (kex->verify_host_key(server_host_key) == -1)
		fatal("server_host_key verification failed");

	/* DH paramter f, server public DH key */
	if ((dh_server_pub = BN_new()) == 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
	if ((shared_secret = BN_new()) == NULL)
		fatal("kexdh_client: BN_new failed");
	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);
	BN_clear_free(dh_server_pub);
	DH_free(dh);

	if (key_verify(server_host_key, 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_finish(kex);
}

/* server */

static 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 */
	if ((dh_client_pub = BN_new()) == 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
	if ((shared_secret = BN_new()) == NULL)
		fatal("kexdh_server: BN_new failed");
	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),
	    server_host_key_blob, sbloblen,
	    dh_client_pub,
	    dh->pub_key,
	    shared_secret
	);
	BN_clear_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(server_host_key_blob, sbloblen);
	packet_put_bignum2(dh->pub_key);	/* f */
	packet_put_string(signature, slen);
	packet_send();

	xfree(signature);
	xfree(server_host_key_blob);
	/* have keys, free DH */
	DH_free(dh);

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

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"
108d362e	26	RCSID("$OpenBSD: kexdh.c,v 1.9 2001/12/27 19:37:22 markus Exp $");
0bc35151	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
396c147e	41	static u_char *
0bc35151	42	kex_dh_hash(
	43	char *client_version_string,
	44	char *server_version_string,
	45	char *ckexinit, int ckexinitlen,
	46	char *skexinit, int skexinitlen,
cf54363d	47	u_char *serverhostkeyblob, int sbloblen,
0bc35151	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);
449c5ba5	58	buffer_put_cstring(&b, client_version_string);
449c5ba5	59	buffer_put_cstring(&b, server_version_string);
0bc35151	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
396c147e	91	static void
0bc35151	92	kexdh_client(Kex *kex)
	93	{
	94	BIGNUM dh_server_pub = NULL, shared_secret = NULL;
	95	DH *dh;
	96	Key *server_host_key;
cf54363d	97	u_char server_host_key_blob = NULL, signature = NULL;
0bc35151	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
f49bc4f7	126	if (kex->verify_host_key == NULL)
	127	fatal("cannot verify server_host_key");
	128	if (kex->verify_host_key(server_host_key) == -1)
	129	fatal("server_host_key verification failed");
0bc35151	130
0bc35151	131	/* DH paramter f, server public DH key */
b775c6f2	132	if ((dh_server_pub = BN_new()) == NULL)
0bc35151	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
b775c6f2	156	if ((shared_secret = BN_new()) == NULL)
b775c6f2	157	fatal("kexdh_client: BN_new failed");
0bc35151	158	BN_bin2bn(kbuf, kout, shared_secret);
	159	memset(kbuf, 0, klen);
	160	xfree(kbuf);
	161
	162	/* calc and verify H */
	163	hash = kex_dh_hash(
	164	kex->client_version_string,
	165	kex->server_version_string,
	166	buffer_ptr(&kex->my), buffer_len(&kex->my),
	167	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	168	server_host_key_blob, sbloblen,
	169	dh->pub_key,
	170	dh_server_pub,
	171	shared_secret
	172	);
	173	xfree(server_host_key_blob);
108d362e	174	BN_clear_free(dh_server_pub);
d8ee838b	175	DH_free(dh);
0bc35151	176
cf54363d	177	if (key_verify(server_host_key, signature, slen, hash, 20) != 1)
0bc35151	178	fatal("key_verify failed for server_host_key");
	179	key_free(server_host_key);
	180	xfree(signature);
	181
	182	/* save session id */
	183	if (kex->session_id == NULL) {
	184	kex->session_id_len = 20;
	185	kex->session_id = xmalloc(kex->session_id_len);
	186	memcpy(kex->session_id, hash, kex->session_id_len);
	187	}
	188
	189	kex_derive_keys(kex, hash, shared_secret);
	190	BN_clear_free(shared_secret);
d8ee838b	191	kex_finish(kex);
0bc35151	192	}
	193
	194	/* server */
	195
396c147e	196	static void
0bc35151	197	kexdh_server(Kex *kex)
	198	{
	199	BIGNUM shared_secret = NULL, dh_client_pub = NULL;
	200	DH *dh;
	201	Key *server_host_key;
	202	u_char kbuf, hash, signature = NULL, server_host_key_blob = NULL;
	203	u_int sbloblen, klen, kout;
	204	int dlen, slen, plen;
	205
	206	/* generate server DH public key */
	207	dh = dh_new_group1();
	208	dh_gen_key(dh, kex->we_need * 8);
	209
	210	debug("expecting SSH2_MSG_KEXDH_INIT");
	211	packet_read_expect(&plen, SSH2_MSG_KEXDH_INIT);
	212
	213	if (kex->load_host_key == NULL)
	214	fatal("Cannot load hostkey");
	215	server_host_key = kex->load_host_key(kex->hostkey_type);
	216	if (server_host_key == NULL)
	217	fatal("Unsupported hostkey type %d", kex->hostkey_type);
	218
	219	/* key, cert */
b775c6f2	220	if ((dh_client_pub = BN_new()) == NULL)
0bc35151	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
b775c6f2	246	if ((shared_secret = BN_new()) == NULL)
b775c6f2	247	fatal("kexdh_server: BN_new failed");
0bc35151	248	BN_bin2bn(kbuf, kout, shared_secret);
	249	memset(kbuf, 0, klen);
	250	xfree(kbuf);
	251
	252	key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
	253
	254	/* calc H */
	255	hash = kex_dh_hash(
	256	kex->client_version_string,
	257	kex->server_version_string,
	258	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	259	buffer_ptr(&kex->my), buffer_len(&kex->my),
cf54363d	260	server_host_key_blob, sbloblen,
0bc35151	261	dh_client_pub,
	262	dh->pub_key,
	263	shared_secret
	264	);
108d362e	265	BN_clear_free(dh_client_pub);
0bc35151	266
	267	/* save session id := H */
	268	/* XXX hashlen depends on KEX */
	269	if (kex->session_id == NULL) {
	270	kex->session_id_len = 20;
	271	kex->session_id = xmalloc(kex->session_id_len);
	272	memcpy(kex->session_id, hash, kex->session_id_len);
	273	}
	274
	275	/* sign H */
	276	/* XXX hashlen depends on KEX */
	277	key_sign(server_host_key, &signature, &slen, hash, 20);
	278
	279	/* destroy_sensitive_data(); */
	280
	281	/* send server hostkey, DH pubkey 'f' and singed H */
	282	packet_start(SSH2_MSG_KEXDH_REPLY);
cf54363d	283	packet_put_string(server_host_key_blob, sbloblen);
0bc35151	284	packet_put_bignum2(dh->pub_key); /* f */
cf54363d	285	packet_put_string(signature, slen);
0bc35151	286	packet_send();
d8ee838b	287
0bc35151	288	xfree(signature);
0bc35151	289	xfree(server_host_key_blob);
d8ee838b	290	/* have keys, free DH */
d8ee838b	291	DH_free(dh);
0bc35151	292
	293	kex_derive_keys(kex, hash, shared_secret);
	294	BN_clear_free(shared_secret);
d8ee838b	295	kex_finish(kex);
0bc35151	296	}
	297
	298	void
	299	kexdh(Kex *kex)
	300	{
	301	if (kex->server)
	302	kexdh_server(kex);
	303	else
	304	kexdh_client(kex);
	305	}