[openssh.git] / kexgex.c

/*
 * Copyright (c) 2000 Niels Provos.  All rights reserved.
 * 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: kexgex.c,v 1.22 2002/03/24 17:27:03 stevesk Exp $");

#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"
#include "compat.h"
#include "monitor_wrap.h"

static u_char *
kexgex_hash(
    char *client_version_string,
    char *server_version_string,
    char *ckexinit, int ckexinitlen,
    char *skexinit, int skexinitlen,
    u_char *serverhostkeyblob, int sbloblen,
    int min, int wantbits, int max, BIGNUM *prime, BIGNUM *gen,
    BIGNUM *client_dh_pub,
    BIGNUM *server_dh_pub,
    BIGNUM *shared_secret)
{
	Buffer b;
	static u_char digest[EVP_MAX_MD_SIZE];
	const 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);
	if (min == -1 || max == -1)
		buffer_put_int(&b, wantbits);
	else {
		buffer_put_int(&b, min);
		buffer_put_int(&b, wantbits);
		buffer_put_int(&b, max);
	}
	buffer_put_bignum2(&b, prime);
	buffer_put_bignum2(&b, gen);
	buffer_put_bignum2(&b, client_dh_pub);
	buffer_put_bignum2(&b, server_dh_pub);
	buffer_put_bignum2(&b, shared_secret);

#ifdef DEBUG_KEXDH
	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_KEXDH
	dump_digest("hash", digest, EVP_MD_size(evp_md));
#endif
	return digest;
}

/* client */

static void
kexgex_client(Kex *kex)
{
	BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
	BIGNUM *p = NULL, *g = NULL;
	Key *server_host_key;
	u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
	u_int klen, kout, slen, sbloblen;
	int min, max, nbits;
	DH *dh;

	nbits = dh_estimate(kex->we_need * 8);

	if (datafellows & SSH_OLD_DHGEX) {
		debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD sent");

		/* Old GEX request */
		packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
		packet_put_int(nbits);
		min = DH_GRP_MIN;
		max = DH_GRP_MAX;
	} else {
		debug("SSH2_MSG_KEX_DH_GEX_REQUEST sent");

		/* New GEX request */
		min = DH_GRP_MIN;
		max = DH_GRP_MAX;
		packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
		packet_put_int(min);
		packet_put_int(nbits);
		packet_put_int(max);
	}
#ifdef DEBUG_KEXDH
	fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
	    min, nbits, max);
#endif
	packet_send();

	debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
	packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP);

	if ((p = BN_new()) == NULL)
		fatal("BN_new");
	packet_get_bignum2(p);
	if ((g = BN_new()) == NULL)
		fatal("BN_new");
	packet_get_bignum2(g);
	packet_check_eom();

	if (BN_num_bits(p) < min || BN_num_bits(p) > max)
		fatal("DH_GEX group out of range: %d !< %d !< %d",
		    min, BN_num_bits(p), max);

	dh = dh_new_group(g, p);
	dh_gen_key(dh, kex->we_need * 8);

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

	debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
	/* generate and send 'e', client DH public key */
	packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
	packet_put_bignum2(dh->pub_key);
	packet_send();

	debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
	packet_read_expect(SSH2_MSG_KEX_DH_GEX_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 (server_host_key->type != kex->hostkey_type)
		fatal("type mismatch for decoded 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);

#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_check_eom();

	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("kexgex_client: BN_new failed");
	BN_bin2bn(kbuf, kout, shared_secret);
	memset(kbuf, 0, klen);
	xfree(kbuf);

	if (datafellows & SSH_OLD_DHGEX)
		min = max = -1;

	/* calc and verify H */
	hash = kexgex_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,
	    min, nbits, max,
	    dh->p, dh->g,
	    dh->pub_key,
	    dh_server_pub,
	    shared_secret
	);
	/* have keys, free DH */
	DH_free(dh);
	xfree(server_host_key_blob);
	BN_clear_free(dh_server_pub);

	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
kexgex_server(Kex *kex)
{
	BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
	Key *server_host_key;
	DH *dh;
	u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
	u_int sbloblen, klen, kout, slen;
	int min = -1, max = -1, nbits = -1, type;

	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);

	type = packet_read();
	switch (type) {
	case SSH2_MSG_KEX_DH_GEX_REQUEST:
		debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
		min = packet_get_int();
		nbits = packet_get_int();
		max = packet_get_int();
		min = MAX(DH_GRP_MIN, min);
		max = MIN(DH_GRP_MAX, max);
		break;
	case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
		debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
		nbits = packet_get_int();
		min = DH_GRP_MIN;
		max = DH_GRP_MAX;
		/* unused for old GEX */
		break;
	default:
		fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
	}
	packet_check_eom();

	if (max < min || nbits < min || max < nbits)
		fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
		    min, nbits, max);

	/* Contact privileged parent */
	dh = PRIVSEP(choose_dh(min, nbits, max));
	if (dh == NULL)
		packet_disconnect("Protocol error: no matching DH grp found");

	debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
	packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
	packet_put_bignum2(dh->p);
	packet_put_bignum2(dh->g);
	packet_send();

	/* flush */
	packet_write_wait();

	/* Compute our exchange value in parallel with the client */
	dh_gen_key(dh, kex->we_need * 8);

	debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
	packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);

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

#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("kexgex_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);

	if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
		min = max = -1;

	/* calc H */			/* XXX depends on 'kex' */
	hash = kexgex_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,
	    min, nbits, max,
	    dh->p, dh->g,
	    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 */
	PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, 20));

	/* destroy_sensitive_data(); */

	/* send server hostkey, DH pubkey 'f' and singed H */
	debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
	packet_start(SSH2_MSG_KEX_DH_GEX_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
kexgex(Kex *kex)
{
	if (kex->server)
		kexgex_server(kex);
	else
		kexgex_client(kex);
}
Commit	Line	Data
0bc35151	1	/*
	2	* Copyright (c) 2000 Niels Provos. All rights reserved.
	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"
5b0d7dc1	27	RCSID("$OpenBSD: kexgex.c,v 1.22 2002/03/24 17:27:03 stevesk Exp $");
0bc35151	28
	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	#include "compat.h"
1853d1ef	41	#include "monitor_wrap.h"
0bc35151	42
396c147e	43	static u_char *
0bc35151	44	kexgex_hash(
	45	char *client_version_string,
	46	char *server_version_string,
	47	char *ckexinit, int ckexinitlen,
	48	char *skexinit, int skexinitlen,
cf54363d	49	u_char *serverhostkeyblob, int sbloblen,
0bc35151	50	int min, int wantbits, int max, BIGNUM prime, BIGNUM gen,
	51	BIGNUM *client_dh_pub,
	52	BIGNUM *server_dh_pub,
	53	BIGNUM *shared_secret)
	54	{
	55	Buffer b;
	56	static u_char digest[EVP_MAX_MD_SIZE];
714954dc	57	const EVP_MD *evp_md = EVP_sha1();
0bc35151	58	EVP_MD_CTX md;
	59
	60	buffer_init(&b);
449c5ba5	61	buffer_put_cstring(&b, client_version_string);
449c5ba5	62	buffer_put_cstring(&b, server_version_string);
0bc35151	63
	64	/* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
	65	buffer_put_int(&b, ckexinitlen+1);
	66	buffer_put_char(&b, SSH2_MSG_KEXINIT);
	67	buffer_append(&b, ckexinit, ckexinitlen);
	68	buffer_put_int(&b, skexinitlen+1);
	69	buffer_put_char(&b, SSH2_MSG_KEXINIT);
	70	buffer_append(&b, skexinit, skexinitlen);
	71
	72	buffer_put_string(&b, serverhostkeyblob, sbloblen);
cd332296	73	if (min == -1 \|\| max == -1)
0bc35151	74	buffer_put_int(&b, wantbits);
	75	else {
	76	buffer_put_int(&b, min);
	77	buffer_put_int(&b, wantbits);
	78	buffer_put_int(&b, max);
	79	}
	80	buffer_put_bignum2(&b, prime);
	81	buffer_put_bignum2(&b, gen);
	82	buffer_put_bignum2(&b, client_dh_pub);
	83	buffer_put_bignum2(&b, server_dh_pub);
	84	buffer_put_bignum2(&b, shared_secret);
	85
	86	#ifdef DEBUG_KEXDH
	87	buffer_dump(&b);
	88	#endif
	89	EVP_DigestInit(&md, evp_md);
	90	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
	91	EVP_DigestFinal(&md, digest, NULL);
	92
	93	buffer_free(&b);
	94
	95	#ifdef DEBUG_KEXDH
a209a158	96	dump_digest("hash", digest, EVP_MD_size(evp_md));
0bc35151	97	#endif
	98	return digest;
	99	}
	100
	101	/* client */
	102
396c147e	103	static void
0bc35151	104	kexgex_client(Kex *kex)
	105	{
	106	BIGNUM dh_server_pub = NULL, shared_secret = NULL;
	107	BIGNUM p = NULL, g = NULL;
	108	Key *server_host_key;
	109	u_char kbuf, hash, signature = NULL, server_host_key_blob = NULL;
	110	u_int klen, kout, slen, sbloblen;
54a5250f	111	int min, max, nbits;
0bc35151	112	DH *dh;
	113
	114	nbits = dh_estimate(kex->we_need * 8);
	115
	116	if (datafellows & SSH_OLD_DHGEX) {
	117	debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD sent");
	118
	119	/* Old GEX request */
	120	packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
	121	packet_put_int(nbits);
	122	min = DH_GRP_MIN;
	123	max = DH_GRP_MAX;
	124	} else {
	125	debug("SSH2_MSG_KEX_DH_GEX_REQUEST sent");
	126
	127	/* New GEX request */
	128	min = DH_GRP_MIN;
	129	max = DH_GRP_MAX;
	130	packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
	131	packet_put_int(min);
	132	packet_put_int(nbits);
	133	packet_put_int(max);
	134	}
	135	#ifdef DEBUG_KEXDH
	136	fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
	137	min, nbits, max);
	138	#endif
	139	packet_send();
	140
	141	debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
54a5250f	142	packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP);
0bc35151	143
	144	if ((p = BN_new()) == NULL)
	145	fatal("BN_new");
20b279e6	146	packet_get_bignum2(p);
0bc35151	147	if ((g = BN_new()) == NULL)
0bc35151	148	fatal("BN_new");
20b279e6	149	packet_get_bignum2(g);
95500969	150	packet_check_eom();
0bc35151	151
	152	if (BN_num_bits(p) < min \|\| BN_num_bits(p) > max)
	153	fatal("DH_GEX group out of range: %d !< %d !< %d",
	154	min, BN_num_bits(p), max);
	155
	156	dh = dh_new_group(g, p);
	157	dh_gen_key(dh, kex->we_need * 8);
	158
	159	#ifdef DEBUG_KEXDH
	160	DHparams_print_fp(stderr, dh);
	161	fprintf(stderr, "pub= ");
	162	BN_print_fp(stderr, dh->pub_key);
	163	fprintf(stderr, "\n");
	164	#endif
	165
	166	debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
	167	/* generate and send 'e', client DH public key */
	168	packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
	169	packet_put_bignum2(dh->pub_key);
	170	packet_send();
	171
	172	debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
54a5250f	173	packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY);
0bc35151	174
	175	/* key, cert */
	176	server_host_key_blob = packet_get_string(&sbloblen);
	177	server_host_key = key_from_blob(server_host_key_blob, sbloblen);
	178	if (server_host_key == NULL)
	179	fatal("cannot decode server_host_key_blob");
215ced77	180	if (server_host_key->type != kex->hostkey_type)
215ced77	181	fatal("type mismatch for decoded server_host_key_blob");
f49bc4f7	182	if (kex->verify_host_key == NULL)
	183	fatal("cannot verify server_host_key");
	184	if (kex->verify_host_key(server_host_key) == -1)
	185	fatal("server_host_key verification failed");
0bc35151	186
0bc35151	187	/* DH paramter f, server public DH key */
b775c6f2	188	if ((dh_server_pub = BN_new()) == NULL)
0bc35151	189	fatal("dh_server_pub == NULL");
20b279e6	190	packet_get_bignum2(dh_server_pub);
0bc35151	191
	192	#ifdef DEBUG_KEXDH
	193	fprintf(stderr, "dh_server_pub= ");
	194	BN_print_fp(stderr, dh_server_pub);
	195	fprintf(stderr, "\n");
	196	debug("bits %d", BN_num_bits(dh_server_pub));
	197	#endif
	198
	199	/* signed H */
	200	signature = packet_get_string(&slen);
95500969	201	packet_check_eom();
0bc35151	202
	203	if (!dh_pub_is_valid(dh, dh_server_pub))
	204	packet_disconnect("bad server public DH value");
	205
	206	klen = DH_size(dh);
	207	kbuf = xmalloc(klen);
	208	kout = DH_compute_key(kbuf, dh_server_pub, dh);
	209	#ifdef DEBUG_KEXDH
cd332296	210	dump_digest("shared secret", kbuf, kout);
0bc35151	211	#endif
b775c6f2	212	if ((shared_secret = BN_new()) == NULL)
b775c6f2	213	fatal("kexgex_client: BN_new failed");
0bc35151	214	BN_bin2bn(kbuf, kout, shared_secret);
	215	memset(kbuf, 0, klen);
	216	xfree(kbuf);
	217
	218	if (datafellows & SSH_OLD_DHGEX)
	219	min = max = -1;
	220
	221	/* calc and verify H */
	222	hash = kexgex_hash(
	223	kex->client_version_string,
	224	kex->server_version_string,
	225	buffer_ptr(&kex->my), buffer_len(&kex->my),
	226	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	227	server_host_key_blob, sbloblen,
	228	min, nbits, max,
	229	dh->p, dh->g,
	230	dh->pub_key,
	231	dh_server_pub,
	232	shared_secret
	233	);
d8ee838b	234	/* have keys, free DH */
d8ee838b	235	DH_free(dh);
0bc35151	236	xfree(server_host_key_blob);
108d362e	237	BN_clear_free(dh_server_pub);
0bc35151	238
cf54363d	239	if (key_verify(server_host_key, signature, slen, hash, 20) != 1)
0bc35151	240	fatal("key_verify failed for server_host_key");
	241	key_free(server_host_key);
	242	xfree(signature);
	243
	244	/* save session id */
	245	if (kex->session_id == NULL) {
	246	kex->session_id_len = 20;
	247	kex->session_id = xmalloc(kex->session_id_len);
	248	memcpy(kex->session_id, hash, kex->session_id_len);
	249	}
0bc35151	250	kex_derive_keys(kex, hash, shared_secret);
	251	BN_clear_free(shared_secret);
	252
d8ee838b	253	kex_finish(kex);
0bc35151	254	}
	255
	256	/* server */
	257
396c147e	258	static void
0bc35151	259	kexgex_server(Kex *kex)
	260	{
	261	BIGNUM shared_secret = NULL, dh_client_pub = NULL;
	262	Key *server_host_key;
5b0d7dc1	263	DH *dh;
0bc35151	264	u_char kbuf, hash, signature = NULL, server_host_key_blob = NULL;
c66f9d0e	265	u_int sbloblen, klen, kout, slen;
c66f9d0e	266	int min = -1, max = -1, nbits = -1, type;
0bc35151	267
	268	if (kex->load_host_key == NULL)
	269	fatal("Cannot load hostkey");
	270	server_host_key = kex->load_host_key(kex->hostkey_type);
	271	if (server_host_key == NULL)
	272	fatal("Unsupported hostkey type %d", kex->hostkey_type);
	273
54a5250f	274	type = packet_read();
6aacefa7	275	switch (type) {
0bc35151	276	case SSH2_MSG_KEX_DH_GEX_REQUEST:
	277	debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
	278	min = packet_get_int();
	279	nbits = packet_get_int();
	280	max = packet_get_int();
	281	min = MAX(DH_GRP_MIN, min);
	282	max = MIN(DH_GRP_MAX, max);
	283	break;
	284	case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
	285	debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
	286	nbits = packet_get_int();
	287	min = DH_GRP_MIN;
	288	max = DH_GRP_MAX;
	289	/* unused for old GEX */
	290	break;
	291	default:
bbb4cc1b	292	fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
0bc35151	293	}
95500969	294	packet_check_eom();
0bc35151	295
	296	if (max < min \|\| nbits < min \|\| max < nbits)
	297	fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
	298	min, nbits, max);
	299
1853d1ef	300	/* Contact privileged parent */
1853d1ef	301	dh = PRIVSEP(choose_dh(min, nbits, max));
0bc35151	302	if (dh == NULL)
	303	packet_disconnect("Protocol error: no matching DH grp found");
	304
	305	debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
	306	packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
	307	packet_put_bignum2(dh->p);
	308	packet_put_bignum2(dh->g);
	309	packet_send();
	310
	311	/* flush */
	312	packet_write_wait();
	313
	314	/* Compute our exchange value in parallel with the client */
	315	dh_gen_key(dh, kex->we_need * 8);
	316
	317	debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
54a5250f	318	packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);
0bc35151	319
0bc35151	320	/* key, cert */
b775c6f2	321	if ((dh_client_pub = BN_new()) == NULL)
0bc35151	322	fatal("dh_client_pub == NULL");
20b279e6	323	packet_get_bignum2(dh_client_pub);
b967d870	324	packet_check_eom();
0bc35151	325
	326	#ifdef DEBUG_KEXDH
	327	fprintf(stderr, "dh_client_pub= ");
	328	BN_print_fp(stderr, dh_client_pub);
	329	fprintf(stderr, "\n");
	330	debug("bits %d", BN_num_bits(dh_client_pub));
	331	#endif
	332
	333	#ifdef DEBUG_KEXDH
	334	DHparams_print_fp(stderr, dh);
	335	fprintf(stderr, "pub= ");
	336	BN_print_fp(stderr, dh->pub_key);
	337	fprintf(stderr, "\n");
	338	#endif
	339	if (!dh_pub_is_valid(dh, dh_client_pub))
	340	packet_disconnect("bad client public DH value");
	341
	342	klen = DH_size(dh);
	343	kbuf = xmalloc(klen);
	344	kout = DH_compute_key(kbuf, dh_client_pub, dh);
	345	#ifdef DEBUG_KEXDH
cd332296	346	dump_digest("shared secret", kbuf, kout);
0bc35151	347	#endif
b775c6f2	348	if ((shared_secret = BN_new()) == NULL)
b775c6f2	349	fatal("kexgex_server: BN_new failed");
0bc35151	350	BN_bin2bn(kbuf, kout, shared_secret);
	351	memset(kbuf, 0, klen);
	352	xfree(kbuf);
	353
	354	key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
	355
	356	if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
	357	min = max = -1;
	358
	359	/* calc H / / XXX depends on 'kex' */
	360	hash = kexgex_hash(
	361	kex->client_version_string,
	362	kex->server_version_string,
	363	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	364	buffer_ptr(&kex->my), buffer_len(&kex->my),
cf54363d	365	server_host_key_blob, sbloblen,
0bc35151	366	min, nbits, max,
	367	dh->p, dh->g,
	368	dh_client_pub,
	369	dh->pub_key,
	370	shared_secret
	371	);
108d362e	372	BN_clear_free(dh_client_pub);
0bc35151	373
	374	/* save session id := H */
	375	/* XXX hashlen depends on KEX */
	376	if (kex->session_id == NULL) {
	377	kex->session_id_len = 20;
	378	kex->session_id = xmalloc(kex->session_id_len);
	379	memcpy(kex->session_id, hash, kex->session_id_len);
	380	}
	381
	382	/* sign H */
	383	/* XXX hashlen depends on KEX */
1853d1ef	384	PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, 20));
0bc35151	385
	386	/* destroy_sensitive_data(); */
	387
	388	/* send server hostkey, DH pubkey 'f' and singed H */
	389	debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
	390	packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
cf54363d	391	packet_put_string(server_host_key_blob, sbloblen);
0bc35151	392	packet_put_bignum2(dh->pub_key); /* f */
cf54363d	393	packet_put_string(signature, slen);
0bc35151	394	packet_send();
1853d1ef	395
0bc35151	396	xfree(signature);
0bc35151	397	xfree(server_host_key_blob);
d8ee838b	398	/* have keys, free DH */
d8ee838b	399	DH_free(dh);
0bc35151	400
	401	kex_derive_keys(kex, hash, shared_secret);
	402	BN_clear_free(shared_secret);
	403
d8ee838b	404	kex_finish(kex);
0bc35151	405	}
	406
	407	void
	408	kexgex(Kex *kex)
	409	{
	410	if (kex->server)
	411	kexgex_server(kex);
	412	else
	413	kexgex_client(kex);
	414	}