[openssh.git] / kexgexs.c

/* $OpenBSD: kexgexs.c,v 1.12 2009/06/21 07:37:15 dtucker Exp $ */
/*
 * 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"

#include <sys/param.h>

#include <stdarg.h>
#include <stdio.h>
#include <string.h>
#include <signal.h>

#include "xmalloc.h"
#include "buffer.h"
#include "key.h"
#include "cipher.h"
#include "kex.h"
#include "log.h"
#include "packet.h"
#include "dh.h"
#include "ssh2.h"
#include "compat.h"
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
#include "monitor_wrap.h"

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, slen, hashlen;
	int omin = -1, min = -1, omax = -1, max = -1, onbits = -1, nbits = -1;
	int type, kout;

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

	if (omax < omin || onbits < omin || omax < onbits)
		fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
		    omin, onbits, omax);

	/* 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);
	if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0)
		fatal("DH_compute_key: failed");
#ifdef DEBUG_KEXDH
	dump_digest("shared secret", kbuf, kout);
#endif
	if ((shared_secret = BN_new()) == NULL)
		fatal("kexgex_server: BN_new failed");
	if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
		fatal("kexgex_server: BN_bin2bn failed");
	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)
		omin = min = omax = max = -1;

	/* calc H */
	kexgex_hash(
	    kex->evp_md,
	    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,
	    omin, onbits, omax,
	    dh->p, dh->g,
	    dh_client_pub,
	    dh->pub_key,
	    shared_secret,
	    &hash, &hashlen
	);
	BN_clear_free(dh_client_pub);

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

	/* sign H */
	if (PRIVSEP(key_sign(server_host_key, &signature, &slen, hash,
	    hashlen)) < 0)
		fatal("kexgex_server: key_sign failed");

	/* 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, hashlen, shared_secret);
	BN_clear_free(shared_secret);

	kex_finish(kex);
}
Commit	Line	Data
bec09968	1	/* $OpenBSD: kexgexs.c,v 1.12 2009/06/21 07:37:15 dtucker Exp $ */
98a58eda	2	/*
	3	* Copyright (c) 2000 Niels Provos. All rights reserved.
	4	* Copyright (c) 2001 Markus Friedl. All rights reserved.
	5	*
	6	* Redistribution and use in source and binary forms, with or without
	7	* modification, are permitted provided that the following conditions
	8	* are met:
	9	* 1. Redistributions of source code must retain the above copyright
	10	* notice, this list of conditions and the following disclaimer.
	11	* 2. Redistributions in binary form must reproduce the above copyright
	12	* notice, this list of conditions and the following disclaimer in the
	13	* documentation and/or other materials provided with the distribution.
	14	*
	15	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
	16	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	17	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	18	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
	19	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	20	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	21	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	22	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	23	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	24	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	25	*/
	26
	27	#include "includes.h"
98a58eda	28
536c14e8	29	#include <sys/param.h>
536c14e8	30
24436b92	31	#include <stdarg.h>
cf851879	32	#include <stdio.h>
00146caa	33	#include <string.h>
31652869	34	#include <signal.h>
00146caa	35
98a58eda	36	#include "xmalloc.h"
31652869	37	#include "buffer.h"
98a58eda	38	#include "key.h"
31652869	39	#include "cipher.h"
98a58eda	40	#include "kex.h"
	41	#include "log.h"
	42	#include "packet.h"
	43	#include "dh.h"
	44	#include "ssh2.h"
	45	#include "compat.h"
31652869	46	#ifdef GSSAPI
	47	#include "ssh-gss.h"
	48	#endif
98a58eda	49	#include "monitor_wrap.h"
	50
	51	void
	52	kexgex_server(Kex *kex)
	53	{
	54	BIGNUM shared_secret = NULL, dh_client_pub = NULL;
	55	Key *server_host_key;
	56	DH *dh;
	57	u_char kbuf, hash, signature = NULL, server_host_key_blob = NULL;
8e8b473c	58	u_int sbloblen, klen, slen, hashlen;
546202d0	59	int omin = -1, min = -1, omax = -1, max = -1, onbits = -1, nbits = -1;
546202d0	60	int type, kout;
98a58eda	61
	62	if (kex->load_host_key == NULL)
	63	fatal("Cannot load hostkey");
	64	server_host_key = kex->load_host_key(kex->hostkey_type);
	65	if (server_host_key == NULL)
	66	fatal("Unsupported hostkey type %d", kex->hostkey_type);
	67
	68	type = packet_read();
	69	switch (type) {
	70	case SSH2_MSG_KEX_DH_GEX_REQUEST:
	71	debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
546202d0	72	omin = min = packet_get_int();
	73	onbits = nbits = packet_get_int();
	74	omax = max = packet_get_int();
98a58eda	75	min = MAX(DH_GRP_MIN, min);
98a58eda	76	max = MIN(DH_GRP_MAX, max);
546202d0	77	nbits = MAX(DH_GRP_MIN, nbits);
546202d0	78	nbits = MIN(DH_GRP_MAX, nbits);
98a58eda	79	break;
	80	case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
	81	debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
546202d0	82	onbits = nbits = packet_get_int();
98a58eda	83	/* unused for old GEX */
546202d0	84	omin = min = DH_GRP_MIN;
546202d0	85	omax = max = DH_GRP_MAX;
98a58eda	86	break;
	87	default:
	88	fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
	89	}
	90	packet_check_eom();
	91
546202d0	92	if (omax < omin \|\| onbits < omin \|\| omax < onbits)
98a58eda	93	fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
546202d0	94	omin, onbits, omax);
98a58eda	95
	96	/* Contact privileged parent */
	97	dh = PRIVSEP(choose_dh(min, nbits, max));
	98	if (dh == NULL)
	99	packet_disconnect("Protocol error: no matching DH grp found");
	100
	101	debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
	102	packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
	103	packet_put_bignum2(dh->p);
	104	packet_put_bignum2(dh->g);
	105	packet_send();
	106
	107	/* flush */
	108	packet_write_wait();
	109
	110	/* Compute our exchange value in parallel with the client */
	111	dh_gen_key(dh, kex->we_need * 8);
	112
	113	debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
	114	packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);
	115
	116	/* key, cert */
	117	if ((dh_client_pub = BN_new()) == NULL)
	118	fatal("dh_client_pub == NULL");
	119	packet_get_bignum2(dh_client_pub);
	120	packet_check_eom();
	121
	122	#ifdef DEBUG_KEXDH
	123	fprintf(stderr, "dh_client_pub= ");
	124	BN_print_fp(stderr, dh_client_pub);
	125	fprintf(stderr, "\n");
	126	debug("bits %d", BN_num_bits(dh_client_pub));
	127	#endif
	128
	129	#ifdef DEBUG_KEXDH
	130	DHparams_print_fp(stderr, dh);
	131	fprintf(stderr, "pub= ");
	132	BN_print_fp(stderr, dh->pub_key);
	133	fprintf(stderr, "\n");
	134	#endif
	135	if (!dh_pub_is_valid(dh, dh_client_pub))
	136	packet_disconnect("bad client public DH value");
	137
	138	klen = DH_size(dh);
	139	kbuf = xmalloc(klen);
8e8b473c	140	if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0)
8e8b473c	141	fatal("DH_compute_key: failed");
98a58eda	142	#ifdef DEBUG_KEXDH
	143	dump_digest("shared secret", kbuf, kout);
	144	#endif
	145	if ((shared_secret = BN_new()) == NULL)
	146	fatal("kexgex_server: BN_new failed");
e516451d	147	if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
e516451d	148	fatal("kexgex_server: BN_bin2bn failed");
98a58eda	149	memset(kbuf, 0, klen);
	150	xfree(kbuf);
	151
	152	key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
	153
	154	if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
546202d0	155	omin = min = omax = max = -1;
98a58eda	156
47e5dc72	157	/* calc H */
	158	kexgex_hash(
	159	kex->evp_md,
98a58eda	160	kex->client_version_string,
	161	kex->server_version_string,
	162	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	163	buffer_ptr(&kex->my), buffer_len(&kex->my),
	164	server_host_key_blob, sbloblen,
546202d0	165	omin, onbits, omax,
98a58eda	166	dh->p, dh->g,
	167	dh_client_pub,
	168	dh->pub_key,
47e5dc72	169	shared_secret,
47e5dc72	170	&hash, &hashlen
98a58eda	171	);
	172	BN_clear_free(dh_client_pub);
	173
	174	/* save session id := H */
98a58eda	175	if (kex->session_id == NULL) {
47e5dc72	176	kex->session_id_len = hashlen;
98a58eda	177	kex->session_id = xmalloc(kex->session_id_len);
	178	memcpy(kex->session_id, hash, kex->session_id_len);
	179	}
	180
	181	/* sign H */
bec09968	182	if (PRIVSEP(key_sign(server_host_key, &signature, &slen, hash,
	183	hashlen)) < 0)
	184	fatal("kexgex_server: key_sign failed");
98a58eda	185
	186	/* destroy_sensitive_data(); */
	187
	188	/* send server hostkey, DH pubkey 'f' and singed H */
	189	debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
	190	packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
	191	packet_put_string(server_host_key_blob, sbloblen);
	192	packet_put_bignum2(dh->pub_key); /* f */
	193	packet_put_string(signature, slen);
	194	packet_send();
	195
	196	xfree(signature);
	197	xfree(server_host_key_blob);
	198	/* have keys, free DH */
	199	DH_free(dh);
	200
47e5dc72	201	kex_derive_keys(kex, hash, hashlen, shared_secret);
98a58eda	202	BN_clear_free(shared_secret);
	203
	204	kex_finish(kex);
	205	}