[gssapi-openssh.git] / openssh / kex.c

/*
 * Copyright (c) 2000, 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: kex.c,v 1.47 2002/02/28 15:46:33 markus Exp $");

#include <openssl/crypto.h>

#include "ssh2.h"
#include "xmalloc.h"
#include "buffer.h"
#include "bufaux.h"
#include "packet.h"
#include "compat.h"
#include "cipher.h"
#include "kex.h"
#include "key.h"
#include "log.h"
#include "mac.h"
#include "match.h"
#include "dispatch.h"

#define KEX_COOKIE_LEN	16

/* prototype */
static void kex_kexinit_finish(Kex *);
static void kex_choose_conf(Kex *);

/* put algorithm proposal into buffer */
static void
kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
{
	u_int32_t rand = 0;
	int i;

	buffer_clear(b);
	for (i = 0; i < KEX_COOKIE_LEN; i++) {
		if (i % 4 == 0)
			rand = arc4random();
		buffer_put_char(b, rand & 0xff);
		rand >>= 8;
	}
	for (i = 0; i < PROPOSAL_MAX; i++)
		buffer_put_cstring(b, proposal[i]);
	buffer_put_char(b, 0);			/* first_kex_packet_follows */
	buffer_put_int(b, 0);			/* uint32 reserved */
}

/* parse buffer and return algorithm proposal */
static char **
kex_buf2prop(Buffer *raw)
{
	Buffer b;
	int i;
	char **proposal;

	proposal = xmalloc(PROPOSAL_MAX * sizeof(char *));

	buffer_init(&b);
	buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
	/* skip cookie */
	for (i = 0; i < KEX_COOKIE_LEN; i++)
		buffer_get_char(&b);
	/* extract kex init proposal strings */
	for (i = 0; i < PROPOSAL_MAX; i++) {
		proposal[i] = buffer_get_string(&b,NULL);
		debug2("kex_parse_kexinit: %s", proposal[i]);
	}
	/* first kex follows / reserved */
	i = buffer_get_char(&b);
	debug2("kex_parse_kexinit: first_kex_follows %d ", i);
	i = buffer_get_int(&b);
	debug2("kex_parse_kexinit: reserved %d ", i);
	buffer_free(&b);
	return proposal;
}

static void
kex_prop_free(char **proposal)
{
	int i;

	for (i = 0; i < PROPOSAL_MAX; i++)
		xfree(proposal[i]);
	xfree(proposal);
}

static void
kex_protocol_error(int type, u_int32_t seq, void *ctxt)
{
	error("Hm, kex protocol error: type %d seq %u", type, seq);
}

static void
kex_reset_dispatch(void)
{
	dispatch_range(SSH2_MSG_TRANSPORT_MIN,
	    SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
	dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
}

void
kex_finish(Kex *kex)
{
	kex_reset_dispatch();

	packet_start(SSH2_MSG_NEWKEYS);
	packet_send();
	/* packet_write_wait(); */
	debug("SSH2_MSG_NEWKEYS sent");

	debug("waiting for SSH2_MSG_NEWKEYS");
	packet_read_expect(SSH2_MSG_NEWKEYS);
	packet_check_eom();
	debug("SSH2_MSG_NEWKEYS received");

	kex->done = 1;
	buffer_clear(&kex->peer);
	/* buffer_clear(&kex->my); */
	kex->flags &= ~KEX_INIT_SENT;
	xfree(kex->name);
	kex->name = NULL;
}

void
kex_send_kexinit(Kex *kex)
{
	if (kex == NULL) {
		error("kex_send_kexinit: no kex, cannot rekey");
		return;
	}
	if (kex->flags & KEX_INIT_SENT) {
		debug("KEX_INIT_SENT");
		return;
	}
	kex->done = 0;
	packet_start(SSH2_MSG_KEXINIT);
	packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
	packet_send();
	debug("SSH2_MSG_KEXINIT sent");
	kex->flags |= KEX_INIT_SENT;
}

void
kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
{
	char *ptr;
	int dlen;
	int i;
	Kex *kex = (Kex *)ctxt;

	debug("SSH2_MSG_KEXINIT received");
	if (kex == NULL)
		fatal("kex_input_kexinit: no kex, cannot rekey");

	ptr = packet_get_raw(&dlen);
	buffer_append(&kex->peer, ptr, dlen);

	/* discard packet */
	for (i = 0; i < KEX_COOKIE_LEN; i++)
		packet_get_char();
	for (i = 0; i < PROPOSAL_MAX; i++)
		xfree(packet_get_string(NULL));
	packet_get_char();
	packet_get_int();
	packet_check_eom();

	kex_kexinit_finish(kex);
}

Kex *
kex_setup(char *proposal[PROPOSAL_MAX])
{
	Kex *kex;

	kex = xmalloc(sizeof(*kex));
	memset(kex, 0, sizeof(*kex));
	buffer_init(&kex->peer);
	buffer_init(&kex->my);
	kex_prop2buf(&kex->my, proposal);
	kex->done = 0;

	kex_send_kexinit(kex);					/* we start */
	kex_reset_dispatch();

	return kex;
}

static void
kex_kexinit_finish(Kex *kex)
{
	if (!(kex->flags & KEX_INIT_SENT))
		kex_send_kexinit(kex);

	kex_choose_conf(kex);

	switch (kex->kex_type) {
	case DH_GRP1_SHA1:
		kexdh(kex);
		break;
	case DH_GEX_SHA1:
		kexgex(kex);
		break;
	default:
		fatal("Unsupported key exchange %d", kex->kex_type);
	}
}

static void
choose_enc(Enc *enc, char *client, char *server)
{
	char *name = match_list(client, server, NULL);
	if (name == NULL)
		fatal("no matching cipher found: client %s server %s", client, server);
	if ((enc->cipher = cipher_by_name(name)) == NULL)
		fatal("matching cipher is not supported: %s", name);
	enc->name = name;
	enc->enabled = 0;
	enc->iv = NULL;
	enc->key = NULL;
	enc->key_len = cipher_keylen(enc->cipher);
	enc->block_size = cipher_blocksize(enc->cipher);
}
static void
choose_mac(Mac *mac, char *client, char *server)
{
	char *name = match_list(client, server, NULL);
	if (name == NULL)
		fatal("no matching mac found: client %s server %s", client, server);
	if (mac_init(mac, name) < 0)
		fatal("unsupported mac %s", name);
	/* truncate the key */
	if (datafellows & SSH_BUG_HMAC)
		mac->key_len = 16;
	mac->name = name;
	mac->key = NULL;
	mac->enabled = 0;
}
static void
choose_comp(Comp *comp, char *client, char *server)
{
	char *name = match_list(client, server, NULL);
	if (name == NULL)
		fatal("no matching comp found: client %s server %s", client, server);
	if (strcmp(name, "zlib") == 0) {
		comp->type = 1;
	} else if (strcmp(name, "none") == 0) {
		comp->type = 0;
	} else {
		fatal("unsupported comp %s", name);
	}
	comp->name = name;
}
static void
choose_kex(Kex *k, char *client, char *server)
{
	k->name = match_list(client, server, NULL);
	if (k->name == NULL)
		fatal("no kex alg");
	if (strcmp(k->name, KEX_DH1) == 0) {
		k->kex_type = DH_GRP1_SHA1;
	} else if (strcmp(k->name, KEX_DHGEX) == 0) {
		k->kex_type = DH_GEX_SHA1;
	} else
		fatal("bad kex alg %s", k->name);
}
static void
choose_hostkeyalg(Kex *k, char *client, char *server)
{
	char *hostkeyalg = match_list(client, server, NULL);
	if (hostkeyalg == NULL)
		fatal("no hostkey alg");
	k->hostkey_type = key_type_from_name(hostkeyalg);
	if (k->hostkey_type == KEY_UNSPEC)
		fatal("bad hostkey alg '%s'", hostkeyalg);
	xfree(hostkeyalg);
}

static void
kex_choose_conf(Kex *kex)
{
	Newkeys *newkeys;
	char **my, **peer;
	char **cprop, **sprop;
	int nenc, nmac, ncomp;
	int mode;
	int ctos;				/* direction: if true client-to-server */
	int need;

	my   = kex_buf2prop(&kex->my);
	peer = kex_buf2prop(&kex->peer);

	if (kex->server) {
		cprop=peer;
		sprop=my;
	} else {
		cprop=my;
		sprop=peer;
	}

	/* Algorithm Negotiation */
	for (mode = 0; mode < MODE_MAX; mode++) {
		newkeys = xmalloc(sizeof(*newkeys));
		memset(newkeys, 0, sizeof(*newkeys));
		kex->newkeys[mode] = newkeys;
		ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
		nenc  = ctos ? PROPOSAL_ENC_ALGS_CTOS  : PROPOSAL_ENC_ALGS_STOC;
		nmac  = ctos ? PROPOSAL_MAC_ALGS_CTOS  : PROPOSAL_MAC_ALGS_STOC;
		ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
		choose_enc (&newkeys->enc,  cprop[nenc],  sprop[nenc]);
		choose_mac (&newkeys->mac,  cprop[nmac],  sprop[nmac]);
		choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
		debug("kex: %s %s %s %s",
		    ctos ? "client->server" : "server->client",
		    newkeys->enc.name,
		    newkeys->mac.name,
		    newkeys->comp.name);
	}
	choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
	choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
	    sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
	need = 0;
	for (mode = 0; mode < MODE_MAX; mode++) {
		newkeys = kex->newkeys[mode];
		if (need < newkeys->enc.key_len)
			need = newkeys->enc.key_len;
		if (need < newkeys->enc.block_size)
			need = newkeys->enc.block_size;
		if (need < newkeys->mac.key_len)
			need = newkeys->mac.key_len;
	}
	/* XXX need runden? */
	kex->we_need = need;

	kex_prop_free(my);
	kex_prop_free(peer);
}

static u_char *
derive_key(Kex *kex, int id, int need, u_char *hash, BIGNUM *shared_secret)
{
	Buffer b;
	const EVP_MD *evp_md = EVP_sha1();
	EVP_MD_CTX md;
	char c = id;
	int have;
	int mdsz = EVP_MD_size(evp_md);
	u_char *digest = xmalloc(roundup(need, mdsz));

	buffer_init(&b);
	buffer_put_bignum2(&b, shared_secret);

	/* K1 = HASH(K || H || "A" || session_id) */
	EVP_DigestInit(&md, evp_md);
	if (!(datafellows & SSH_BUG_DERIVEKEY))
		EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
	EVP_DigestUpdate(&md, hash, mdsz);
	EVP_DigestUpdate(&md, &c, 1);
	EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
	EVP_DigestFinal(&md, digest, NULL);

	/*
	 * expand key:
	 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
	 * Key = K1 || K2 || ... || Kn
	 */
	for (have = mdsz; need > have; have += mdsz) {
		EVP_DigestInit(&md, evp_md);
		if (!(datafellows & SSH_BUG_DERIVEKEY))
			EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
		EVP_DigestUpdate(&md, hash, mdsz);
		EVP_DigestUpdate(&md, digest, have);
		EVP_DigestFinal(&md, digest + have, NULL);
	}
	buffer_free(&b);
#ifdef DEBUG_KEX
	fprintf(stderr, "key '%c'== ", c);
	dump_digest("key", digest, need);
#endif
	return digest;
}

Newkeys *current_keys[MODE_MAX];

#define NKEYS	6
void
kex_derive_keys(Kex *kex, u_char *hash, BIGNUM *shared_secret)
{
	u_char *keys[NKEYS];
	int i, mode, ctos;

	for (i = 0; i < NKEYS; i++)
		keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret);

	debug("kex_derive_keys");
	for (mode = 0; mode < MODE_MAX; mode++) {
		current_keys[mode] = kex->newkeys[mode];
		kex->newkeys[mode] = NULL;
		ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
		current_keys[mode]->enc.iv  = keys[ctos ? 0 : 1];
		current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
		current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
	}
}

Newkeys *
kex_get_newkeys(int mode)
{
	Newkeys *ret;

	ret = current_keys[mode];
	current_keys[mode] = NULL;
	return ret;
}

#if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
void
dump_digest(char *msg, u_char *digest, int len)
{
	int i;

	fprintf(stderr, "%s\n", msg);
	for (i = 0; i< len; i++) {
		fprintf(stderr, "%02x", digest[i]);
		if (i%32 == 31)
			fprintf(stderr, "\n");
		else if (i%8 == 7)
			fprintf(stderr, " ");
	}
	fprintf(stderr, "\n");
}
#endif
Commit	Line	Data
3c0ef626	1	/*
	2	* Copyright (c) 2000, 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"
e9a17296	26	RCSID("$OpenBSD: kex.c,v 1.47 2002/02/28 15:46:33 markus Exp $");
3c0ef626	27
	28	#include <openssl/crypto.h>
	29
	30	#include "ssh2.h"
	31	#include "xmalloc.h"
	32	#include "buffer.h"
	33	#include "bufaux.h"
	34	#include "packet.h"
	35	#include "compat.h"
	36	#include "cipher.h"
	37	#include "kex.h"
	38	#include "key.h"
	39	#include "log.h"
	40	#include "mac.h"
	41	#include "match.h"
	42	#include "dispatch.h"
	43
	44	#define KEX_COOKIE_LEN 16
	45
	46	/* prototype */
	47	static void kex_kexinit_finish(Kex *);
	48	static void kex_choose_conf(Kex *);
	49
	50	/* put algorithm proposal into buffer */
	51	static void
	52	kex_prop2buf(Buffer b, char proposal[PROPOSAL_MAX])
	53	{
	54	u_int32_t rand = 0;
	55	int i;
	56
	57	buffer_clear(b);
	58	for (i = 0; i < KEX_COOKIE_LEN; i++) {
	59	if (i % 4 == 0)
	60	rand = arc4random();
	61	buffer_put_char(b, rand & 0xff);
	62	rand >>= 8;
	63	}
	64	for (i = 0; i < PROPOSAL_MAX; i++)
	65	buffer_put_cstring(b, proposal[i]);
	66	buffer_put_char(b, 0); /* first_kex_packet_follows */
	67	buffer_put_int(b, 0); /* uint32 reserved */
	68	}
	69
	70	/* parse buffer and return algorithm proposal */
	71	static char **
	72	kex_buf2prop(Buffer *raw)
	73	{
	74	Buffer b;
	75	int i;
	76	char **proposal;
	77
	78	proposal = xmalloc(PROPOSAL_MAX * sizeof(char *));
	79
	80	buffer_init(&b);
	81	buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
	82	/* skip cookie */
	83	for (i = 0; i < KEX_COOKIE_LEN; i++)
	84	buffer_get_char(&b);
	85	/* extract kex init proposal strings */
	86	for (i = 0; i < PROPOSAL_MAX; i++) {
	87	proposal[i] = buffer_get_string(&b,NULL);
	88	debug2("kex_parse_kexinit: %s", proposal[i]);
	89	}
	90	/* first kex follows / reserved */
91	i = buffer_get_char(&b);
92	debug2("kex_parse_kexinit: first_kex_follows %d ", i);
93	i = buffer_get_int(&b);
94	debug2("kex_parse_kexinit: reserved %d ", i);
95	buffer_free(&b);
96	return proposal;
97	}
98
99	static void
100	kex_prop_free(char **proposal)
101	{
102	int i;
103
104	for (i = 0; i < PROPOSAL_MAX; i++)
105	xfree(proposal[i]);
106	xfree(proposal);
107	}
108
109	static void
e9a17296	110	kex_protocol_error(int type, u_int32_t seq, void *ctxt)
3c0ef626	111	{
e9a17296	112	error("Hm, kex protocol error: type %d seq %u", type, seq);
3c0ef626	113	}
	114
	115	static void
e9a17296	116	kex_reset_dispatch(void)
3c0ef626	117	{
e9a17296	118	dispatch_range(SSH2_MSG_TRANSPORT_MIN,
	119	SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
	120	dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
3c0ef626	121	}
	122
	123	void
	124	kex_finish(Kex *kex)
	125	{
e9a17296	126	kex_reset_dispatch();
3c0ef626	127
	128	packet_start(SSH2_MSG_NEWKEYS);
	129	packet_send();
	130	/* packet_write_wait(); */
	131	debug("SSH2_MSG_NEWKEYS sent");
	132
	133	debug("waiting for SSH2_MSG_NEWKEYS");
e9a17296	134	packet_read_expect(SSH2_MSG_NEWKEYS);
e9a17296	135	packet_check_eom();
3c0ef626	136	debug("SSH2_MSG_NEWKEYS received");
	137
	138	kex->done = 1;
	139	buffer_clear(&kex->peer);
	140	/* buffer_clear(&kex->my); */
	141	kex->flags &= ~KEX_INIT_SENT;
	142	xfree(kex->name);
	143	kex->name = NULL;
	144	}
	145
	146	void
	147	kex_send_kexinit(Kex *kex)
	148	{
	149	if (kex == NULL) {
	150	error("kex_send_kexinit: no kex, cannot rekey");
	151	return;
	152	}
	153	if (kex->flags & KEX_INIT_SENT) {
	154	debug("KEX_INIT_SENT");
	155	return;
	156	}
	157	kex->done = 0;
	158	packet_start(SSH2_MSG_KEXINIT);
	159	packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
	160	packet_send();
	161	debug("SSH2_MSG_KEXINIT sent");
	162	kex->flags \|= KEX_INIT_SENT;
	163	}
	164
	165	void
e9a17296	166	kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
3c0ef626	167	{
	168	char *ptr;
	169	int dlen;
	170	int i;
	171	Kex kex = (Kex )ctxt;
	172
	173	debug("SSH2_MSG_KEXINIT received");
	174	if (kex == NULL)
	175	fatal("kex_input_kexinit: no kex, cannot rekey");
	176
	177	ptr = packet_get_raw(&dlen);
	178	buffer_append(&kex->peer, ptr, dlen);
	179
	180	/* discard packet */
	181	for (i = 0; i < KEX_COOKIE_LEN; i++)
	182	packet_get_char();
	183	for (i = 0; i < PROPOSAL_MAX; i++)
	184	xfree(packet_get_string(NULL));
	185	packet_get_char();
	186	packet_get_int();
e9a17296	187	packet_check_eom();
3c0ef626	188
	189	kex_kexinit_finish(kex);
	190	}
	191
	192	Kex *
	193	kex_setup(char *proposal[PROPOSAL_MAX])
	194	{
	195	Kex *kex;
	196
	197	kex = xmalloc(sizeof(*kex));
	198	memset(kex, 0, sizeof(*kex));
	199	buffer_init(&kex->peer);
	200	buffer_init(&kex->my);
	201	kex_prop2buf(&kex->my, proposal);
	202	kex->done = 0;
	203
	204	kex_send_kexinit(kex); /* we start */
e9a17296	205	kex_reset_dispatch();
3c0ef626	206
	207	return kex;
	208	}
	209
	210	static void
	211	kex_kexinit_finish(Kex *kex)
	212	{
	213	if (!(kex->flags & KEX_INIT_SENT))
	214	kex_send_kexinit(kex);
	215
	216	kex_choose_conf(kex);
	217
e9a17296	218	switch (kex->kex_type) {
3c0ef626	219	case DH_GRP1_SHA1:
	220	kexdh(kex);
	221	break;
	222	case DH_GEX_SHA1:
	223	kexgex(kex);
	224	break;
	225	default:
	226	fatal("Unsupported key exchange %d", kex->kex_type);
	227	}
	228	}
	229
	230	static void
	231	choose_enc(Enc enc, char client, char *server)
	232	{
	233	char *name = match_list(client, server, NULL);
	234	if (name == NULL)
	235	fatal("no matching cipher found: client %s server %s", client, server);
e9a17296	236	if ((enc->cipher = cipher_by_name(name)) == NULL)
3c0ef626	237	fatal("matching cipher is not supported: %s", name);
	238	enc->name = name;
	239	enc->enabled = 0;
	240	enc->iv = NULL;
	241	enc->key = NULL;
e9a17296	242	enc->key_len = cipher_keylen(enc->cipher);
e9a17296	243	enc->block_size = cipher_blocksize(enc->cipher);
3c0ef626	244	}
	245	static void
	246	choose_mac(Mac mac, char client, char *server)
	247	{
	248	char *name = match_list(client, server, NULL);
	249	if (name == NULL)
	250	fatal("no matching mac found: client %s server %s", client, server);
	251	if (mac_init(mac, name) < 0)
	252	fatal("unsupported mac %s", name);
	253	/* truncate the key */
	254	if (datafellows & SSH_BUG_HMAC)
	255	mac->key_len = 16;
	256	mac->name = name;
	257	mac->key = NULL;
	258	mac->enabled = 0;
	259	}
	260	static void
	261	choose_comp(Comp comp, char client, char *server)
	262	{
	263	char *name = match_list(client, server, NULL);
	264	if (name == NULL)
	265	fatal("no matching comp found: client %s server %s", client, server);
	266	if (strcmp(name, "zlib") == 0) {
	267	comp->type = 1;
	268	} else if (strcmp(name, "none") == 0) {
	269	comp->type = 0;
	270	} else {
	271	fatal("unsupported comp %s", name);
	272	}
	273	comp->name = name;
	274	}
	275	static void
	276	choose_kex(Kex k, char client, char *server)
	277	{
	278	k->name = match_list(client, server, NULL);
	279	if (k->name == NULL)
	280	fatal("no kex alg");
	281	if (strcmp(k->name, KEX_DH1) == 0) {
	282	k->kex_type = DH_GRP1_SHA1;
	283	} else if (strcmp(k->name, KEX_DHGEX) == 0) {
	284	k->kex_type = DH_GEX_SHA1;
	285	} else
	286	fatal("bad kex alg %s", k->name);
	287	}
	288	static void
	289	choose_hostkeyalg(Kex k, char client, char *server)
	290	{
	291	char *hostkeyalg = match_list(client, server, NULL);
	292	if (hostkeyalg == NULL)
	293	fatal("no hostkey alg");
	294	k->hostkey_type = key_type_from_name(hostkeyalg);
	295	if (k->hostkey_type == KEY_UNSPEC)
	296	fatal("bad hostkey alg '%s'", hostkeyalg);
	297	xfree(hostkeyalg);
	298	}
	299
	300	static void
	301	kex_choose_conf(Kex *kex)
	302	{
	303	Newkeys *newkeys;
	304	char my, peer;
	305	char cprop, sprop;
	306	int nenc, nmac, ncomp;
	307	int mode;
308	int ctos; /* direction: if true client-to-server */
309	int need;
310
311	my = kex_buf2prop(&kex->my);
312	peer = kex_buf2prop(&kex->peer);
313
314	if (kex->server) {
315	cprop=peer;
316	sprop=my;
317	} else {
318	cprop=my;
319	sprop=peer;
320	}
321
322	/* Algorithm Negotiation */
323	for (mode = 0; mode < MODE_MAX; mode++) {
324	newkeys = xmalloc(sizeof(*newkeys));
325	memset(newkeys, 0, sizeof(*newkeys));
326	kex->newkeys[mode] = newkeys;
327	ctos = (!kex->server && mode == MODE_OUT) \|\| (kex->server && mode == MODE_IN);
328	nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
329	nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
330	ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
331	choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
332	choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
333	choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
334	debug("kex: %s %s %s %s",
335	ctos ? "client->server" : "server->client",
336	newkeys->enc.name,
337	newkeys->mac.name,
338	newkeys->comp.name);
339	}
340	choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
341	choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
342	sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
343	need = 0;
344	for (mode = 0; mode < MODE_MAX; mode++) {
345	newkeys = kex->newkeys[mode];
e9a17296	346	if (need < newkeys->enc.key_len)
	347	need = newkeys->enc.key_len;
	348	if (need < newkeys->enc.block_size)
	349	need = newkeys->enc.block_size;
3c0ef626	350	if (need < newkeys->mac.key_len)
	351	need = newkeys->mac.key_len;
	352	}
	353	/* XXX need runden? */
	354	kex->we_need = need;
	355
	356	kex_prop_free(my);
	357	kex_prop_free(peer);
	358	}
	359
	360	static u_char *
	361	derive_key(Kex kex, int id, int need, u_char hash, BIGNUM *shared_secret)
	362	{
	363	Buffer b;
e9a17296	364	const EVP_MD *evp_md = EVP_sha1();
3c0ef626	365	EVP_MD_CTX md;
	366	char c = id;
	367	int have;
e9a17296	368	int mdsz = EVP_MD_size(evp_md);
3c0ef626	369	u_char *digest = xmalloc(roundup(need, mdsz));
	370
	371	buffer_init(&b);
	372	buffer_put_bignum2(&b, shared_secret);
	373
	374	/* K1 = HASH(K \|\| H \|\| "A" \|\| session_id) */
	375	EVP_DigestInit(&md, evp_md);
	376	if (!(datafellows & SSH_BUG_DERIVEKEY))
	377	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
	378	EVP_DigestUpdate(&md, hash, mdsz);
	379	EVP_DigestUpdate(&md, &c, 1);
	380	EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
	381	EVP_DigestFinal(&md, digest, NULL);
	382
	383	/*
	384	* expand key:
	385	* Kn = HASH(K \|\| H \|\| K1 \|\| K2 \|\| ... \|\| Kn-1)
	386	* Key = K1 \|\| K2 \|\| ... \|\| Kn
	387	*/
	388	for (have = mdsz; need > have; have += mdsz) {
	389	EVP_DigestInit(&md, evp_md);
	390	if (!(datafellows & SSH_BUG_DERIVEKEY))
	391	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
	392	EVP_DigestUpdate(&md, hash, mdsz);
	393	EVP_DigestUpdate(&md, digest, have);
	394	EVP_DigestFinal(&md, digest + have, NULL);
	395	}
	396	buffer_free(&b);
	397	#ifdef DEBUG_KEX
	398	fprintf(stderr, "key '%c'== ", c);
	399	dump_digest("key", digest, need);
	400	#endif
	401	return digest;
	402	}
	403
	404	Newkeys *current_keys[MODE_MAX];
	405
	406	#define NKEYS 6
	407	void
	408	kex_derive_keys(Kex kex, u_char hash, BIGNUM *shared_secret)
	409	{
	410	u_char *keys[NKEYS];
	411	int i, mode, ctos;
	412
	413	for (i = 0; i < NKEYS; i++)
	414	keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret);
	415
	416	debug("kex_derive_keys");
	417	for (mode = 0; mode < MODE_MAX; mode++) {
	418	current_keys[mode] = kex->newkeys[mode];
	419	kex->newkeys[mode] = NULL;
	420	ctos = (!kex->server && mode == MODE_OUT) \|\| (kex->server && mode == MODE_IN);
	421	current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
	422	current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
	423	current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
	424	}
	425	}
	426
	427	Newkeys *
	428	kex_get_newkeys(int mode)
	429	{
	430	Newkeys *ret;
	431
	432	ret = current_keys[mode];
433	current_keys[mode] = NULL;
434	return ret;
435	}
436
437	#if defined(DEBUG_KEX) \|\| defined(DEBUG_KEXDH)
438	void
439	dump_digest(char msg, u_char digest, int len)
440	{
441	int i;
442
443	fprintf(stderr, "%s\n", msg);
e9a17296	444	for (i = 0; i< len; i++) {
3c0ef626	445	fprintf(stderr, "%02x", digest[i]);
	446	if (i%32 == 31)
	447	fprintf(stderr, "\n");
	448	else if (i%8 == 7)
	449	fprintf(stderr, " ");
	450	}
	451	fprintf(stderr, "\n");
	452	}
	453	#endif