[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"

#ifdef GSSAPI
#include "ssh-gss.h"
#endif

#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;
#ifdef GSSAPI
	case GSS_GRP1_SHA1:
		kexgss(kex);
		break;
#endif
	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 key exchange algorithm");
	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;
#ifdef GSSAPI
	} else if (strncmp(k->name, KEX_GSS_SHA1, sizeof(KEX_GSS_SHA1)-1) == 0) {
		k->kex_type = GSS_GRP1_SHA1;
#endif
	} 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"
e9702f7d	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
5598e598	44	#ifdef GSSAPI
	45	#include "ssh-gss.h"
	46	#endif
	47
3c0ef626	48	#define KEX_COOKIE_LEN 16
	49
	50	/* prototype */
	51	static void kex_kexinit_finish(Kex *);
	52	static void kex_choose_conf(Kex *);
	53
	54	/* put algorithm proposal into buffer */
	55	static void
	56	kex_prop2buf(Buffer b, char proposal[PROPOSAL_MAX])
	57	{
	58	u_int32_t rand = 0;
	59	int i;
	60
	61	buffer_clear(b);
	62	for (i = 0; i < KEX_COOKIE_LEN; i++) {
	63	if (i % 4 == 0)
	64	rand = arc4random();
	65	buffer_put_char(b, rand & 0xff);
	66	rand >>= 8;
	67	}
	68	for (i = 0; i < PROPOSAL_MAX; i++)
	69	buffer_put_cstring(b, proposal[i]);
	70	buffer_put_char(b, 0); /* first_kex_packet_follows */
	71	buffer_put_int(b, 0); /* uint32 reserved */
	72	}
	73
	74	/* parse buffer and return algorithm proposal */
	75	static char **
	76	kex_buf2prop(Buffer *raw)
	77	{
	78	Buffer b;
	79	int i;
	80	char **proposal;
	81
	82	proposal = xmalloc(PROPOSAL_MAX * sizeof(char *));
	83
	84	buffer_init(&b);
	85	buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
	86	/* skip cookie */
	87	for (i = 0; i < KEX_COOKIE_LEN; i++)
	88	buffer_get_char(&b);
	89	/* extract kex init proposal strings */
	90	for (i = 0; i < PROPOSAL_MAX; i++) {
	91	proposal[i] = buffer_get_string(&b,NULL);
	92	debug2("kex_parse_kexinit: %s", proposal[i]);
	93	}
	94	/* first kex follows / reserved */
	95	i = buffer_get_char(&b);
	96	debug2("kex_parse_kexinit: first_kex_follows %d ", i);
	97	i = buffer_get_int(&b);
	98	debug2("kex_parse_kexinit: reserved %d ", i);
	99	buffer_free(&b);
	100	return proposal;
	101	}
	102
	103	static void
	104	kex_prop_free(char **proposal)
	105	{
	106	int i;
	107
	108	for (i = 0; i < PROPOSAL_MAX; i++)
	109	xfree(proposal[i]);
	110	xfree(proposal);
	111	}
112
113	static void
e9702f7d	114	kex_protocol_error(int type, u_int32_t seq, void *ctxt)
3c0ef626	115	{
e9702f7d	116	error("Hm, kex protocol error: type %d seq %u", type, seq);
3c0ef626	117	}
	118
	119	static void
e9702f7d	120	kex_reset_dispatch(void)
3c0ef626	121	{
e9702f7d	122	dispatch_range(SSH2_MSG_TRANSPORT_MIN,
	123	SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
	124	dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
3c0ef626	125	}
	126
	127	void
	128	kex_finish(Kex *kex)
	129	{
e9702f7d	130	kex_reset_dispatch();
3c0ef626	131
	132	packet_start(SSH2_MSG_NEWKEYS);
	133	packet_send();
	134	/* packet_write_wait(); */
	135	debug("SSH2_MSG_NEWKEYS sent");
	136
	137	debug("waiting for SSH2_MSG_NEWKEYS");
e9702f7d	138	packet_read_expect(SSH2_MSG_NEWKEYS);
e9702f7d	139	packet_check_eom();
3c0ef626	140	debug("SSH2_MSG_NEWKEYS received");
	141
	142	kex->done = 1;
	143	buffer_clear(&kex->peer);
	144	/* buffer_clear(&kex->my); */
	145	kex->flags &= ~KEX_INIT_SENT;
	146	xfree(kex->name);
	147	kex->name = NULL;
	148	}
	149
	150	void
	151	kex_send_kexinit(Kex *kex)
	152	{
	153	if (kex == NULL) {
	154	error("kex_send_kexinit: no kex, cannot rekey");
	155	return;
	156	}
	157	if (kex->flags & KEX_INIT_SENT) {
	158	debug("KEX_INIT_SENT");
	159	return;
	160	}
	161	kex->done = 0;
	162	packet_start(SSH2_MSG_KEXINIT);
	163	packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
	164	packet_send();
	165	debug("SSH2_MSG_KEXINIT sent");
	166	kex->flags \|= KEX_INIT_SENT;
	167	}
	168
	169	void
e9702f7d	170	kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
3c0ef626	171	{
	172	char *ptr;
	173	int dlen;
	174	int i;
	175	Kex kex = (Kex )ctxt;
	176
	177	debug("SSH2_MSG_KEXINIT received");
	178	if (kex == NULL)
	179	fatal("kex_input_kexinit: no kex, cannot rekey");
	180
	181	ptr = packet_get_raw(&dlen);
	182	buffer_append(&kex->peer, ptr, dlen);
	183
	184	/* discard packet */
	185	for (i = 0; i < KEX_COOKIE_LEN; i++)
	186	packet_get_char();
	187	for (i = 0; i < PROPOSAL_MAX; i++)
	188	xfree(packet_get_string(NULL));
	189	packet_get_char();
	190	packet_get_int();
e9702f7d	191	packet_check_eom();
3c0ef626	192
	193	kex_kexinit_finish(kex);
	194	}
	195
	196	Kex *
	197	kex_setup(char *proposal[PROPOSAL_MAX])
	198	{
	199	Kex *kex;
	200
	201	kex = xmalloc(sizeof(*kex));
	202	memset(kex, 0, sizeof(*kex));
	203	buffer_init(&kex->peer);
	204	buffer_init(&kex->my);
	205	kex_prop2buf(&kex->my, proposal);
	206	kex->done = 0;
	207
	208	kex_send_kexinit(kex); /* we start */
e9702f7d	209	kex_reset_dispatch();
3c0ef626	210
	211	return kex;
	212	}
	213
	214	static void
	215	kex_kexinit_finish(Kex *kex)
	216	{
	217	if (!(kex->flags & KEX_INIT_SENT))
	218	kex_send_kexinit(kex);
	219
	220	kex_choose_conf(kex);
	221
e9702f7d	222	switch (kex->kex_type) {
3c0ef626	223	case DH_GRP1_SHA1:
	224	kexdh(kex);
	225	break;
	226	case DH_GEX_SHA1:
	227	kexgex(kex);
	228	break;
5598e598	229	#ifdef GSSAPI
	230	case GSS_GRP1_SHA1:
	231	kexgss(kex);
	232	break;
	233	#endif
3c0ef626	234	default:
	235	fatal("Unsupported key exchange %d", kex->kex_type);
	236	}
	237	}
	238
	239	static void
	240	choose_enc(Enc enc, char client, char *server)
	241	{
	242	char *name = match_list(client, server, NULL);
	243	if (name == NULL)
	244	fatal("no matching cipher found: client %s server %s", client, server);
e9702f7d	245	if ((enc->cipher = cipher_by_name(name)) == NULL)
3c0ef626	246	fatal("matching cipher is not supported: %s", name);
	247	enc->name = name;
	248	enc->enabled = 0;
	249	enc->iv = NULL;
	250	enc->key = NULL;
e9702f7d	251	enc->key_len = cipher_keylen(enc->cipher);
e9702f7d	252	enc->block_size = cipher_blocksize(enc->cipher);
3c0ef626	253	}
	254	static void
	255	choose_mac(Mac mac, char client, char *server)
	256	{
	257	char *name = match_list(client, server, NULL);
	258	if (name == NULL)
	259	fatal("no matching mac found: client %s server %s", client, server);
	260	if (mac_init(mac, name) < 0)
	261	fatal("unsupported mac %s", name);
	262	/* truncate the key */
	263	if (datafellows & SSH_BUG_HMAC)
	264	mac->key_len = 16;
	265	mac->name = name;
	266	mac->key = NULL;
	267	mac->enabled = 0;
	268	}
	269	static void
	270	choose_comp(Comp comp, char client, char *server)
	271	{
	272	char *name = match_list(client, server, NULL);
	273	if (name == NULL)
	274	fatal("no matching comp found: client %s server %s", client, server);
	275	if (strcmp(name, "zlib") == 0) {
	276	comp->type = 1;
	277	} else if (strcmp(name, "none") == 0) {
	278	comp->type = 0;
	279	} else {
	280	fatal("unsupported comp %s", name);
	281	}
	282	comp->name = name;
	283	}
	284	static void
	285	choose_kex(Kex k, char client, char *server)
	286	{
	287	k->name = match_list(client, server, NULL);
	288	if (k->name == NULL)
5598e598	289	fatal("No key exchange algorithm");
3c0ef626	290	if (strcmp(k->name, KEX_DH1) == 0) {
	291	k->kex_type = DH_GRP1_SHA1;
	292	} else if (strcmp(k->name, KEX_DHGEX) == 0) {
	293	k->kex_type = DH_GEX_SHA1;
5598e598	294	#ifdef GSSAPI
	295	} else if (strncmp(k->name, KEX_GSS_SHA1, sizeof(KEX_GSS_SHA1)-1) == 0) {
	296	k->kex_type = GSS_GRP1_SHA1;
	297	#endif
3c0ef626	298	} else
	299	fatal("bad kex alg %s", k->name);
	300	}
	301	static void
	302	choose_hostkeyalg(Kex k, char client, char *server)
	303	{
	304	char *hostkeyalg = match_list(client, server, NULL);
	305	if (hostkeyalg == NULL)
	306	fatal("no hostkey alg");
	307	k->hostkey_type = key_type_from_name(hostkeyalg);
	308	if (k->hostkey_type == KEY_UNSPEC)
	309	fatal("bad hostkey alg '%s'", hostkeyalg);
	310	xfree(hostkeyalg);
	311	}
	312
	313	static void
	314	kex_choose_conf(Kex *kex)
	315	{
	316	Newkeys *newkeys;
	317	char my, peer;
	318	char cprop, sprop;
	319	int nenc, nmac, ncomp;
	320	int mode;
	321	int ctos; /* direction: if true client-to-server */
	322	int need;
	323
	324	my = kex_buf2prop(&kex->my);
	325	peer = kex_buf2prop(&kex->peer);
	326
	327	if (kex->server) {
	328	cprop=peer;
	329	sprop=my;
	330	} else {
	331	cprop=my;
	332	sprop=peer;
	333	}
	334
	335	/* Algorithm Negotiation */
	336	for (mode = 0; mode < MODE_MAX; mode++) {
	337	newkeys = xmalloc(sizeof(*newkeys));
	338	memset(newkeys, 0, sizeof(*newkeys));
	339	kex->newkeys[mode] = newkeys;
	340	ctos = (!kex->server && mode == MODE_OUT) \|\| (kex->server && mode == MODE_IN);
	341	nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
	342	nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
	343	ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
	344	choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
	345	choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
	346	choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
	347	debug("kex: %s %s %s %s",
	348	ctos ? "client->server" : "server->client",
	349	newkeys->enc.name,
	350	newkeys->mac.name,
	351	newkeys->comp.name);
	352	}
	353	choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
	354	choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
	355	sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
	356	need = 0;
	357	for (mode = 0; mode < MODE_MAX; mode++) {
	358	newkeys = kex->newkeys[mode];
e9702f7d	359	if (need < newkeys->enc.key_len)
	360	need = newkeys->enc.key_len;
	361	if (need < newkeys->enc.block_size)
	362	need = newkeys->enc.block_size;
3c0ef626	363	if (need < newkeys->mac.key_len)
	364	need = newkeys->mac.key_len;
	365	}
	366	/* XXX need runden? */
	367	kex->we_need = need;
	368
	369	kex_prop_free(my);
	370	kex_prop_free(peer);
	371	}
	372
	373	static u_char *
	374	derive_key(Kex kex, int id, int need, u_char hash, BIGNUM *shared_secret)
	375	{
	376	Buffer b;
e9702f7d	377	const EVP_MD *evp_md = EVP_sha1();
3c0ef626	378	EVP_MD_CTX md;
	379	char c = id;
	380	int have;
e9702f7d	381	int mdsz = EVP_MD_size(evp_md);
3c0ef626	382	u_char *digest = xmalloc(roundup(need, mdsz));
	383
	384	buffer_init(&b);
	385	buffer_put_bignum2(&b, shared_secret);
	386
	387	/* K1 = HASH(K \|\| H \|\| "A" \|\| session_id) */
	388	EVP_DigestInit(&md, evp_md);
	389	if (!(datafellows & SSH_BUG_DERIVEKEY))
	390	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
	391	EVP_DigestUpdate(&md, hash, mdsz);
	392	EVP_DigestUpdate(&md, &c, 1);
	393	EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
	394	EVP_DigestFinal(&md, digest, NULL);
	395
	396	/*
	397	* expand key:
	398	* Kn = HASH(K \|\| H \|\| K1 \|\| K2 \|\| ... \|\| Kn-1)
	399	* Key = K1 \|\| K2 \|\| ... \|\| Kn
	400	*/
	401	for (have = mdsz; need > have; have += mdsz) {
	402	EVP_DigestInit(&md, evp_md);
	403	if (!(datafellows & SSH_BUG_DERIVEKEY))
	404	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
	405	EVP_DigestUpdate(&md, hash, mdsz);
	406	EVP_DigestUpdate(&md, digest, have);
	407	EVP_DigestFinal(&md, digest + have, NULL);
	408	}
	409	buffer_free(&b);
	410	#ifdef DEBUG_KEX
	411	fprintf(stderr, "key '%c'== ", c);
	412	dump_digest("key", digest, need);
	413	#endif
	414	return digest;
	415	}
	416
	417	Newkeys *current_keys[MODE_MAX];
	418
	419	#define NKEYS 6
	420	void
	421	kex_derive_keys(Kex kex, u_char hash, BIGNUM *shared_secret)
	422	{
	423	u_char *keys[NKEYS];
	424	int i, mode, ctos;
	425
	426	for (i = 0; i < NKEYS; i++)
	427	keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret);
	428
	429	debug("kex_derive_keys");
	430	for (mode = 0; mode < MODE_MAX; mode++) {
	431	current_keys[mode] = kex->newkeys[mode];
	432	kex->newkeys[mode] = NULL;
	433	ctos = (!kex->server && mode == MODE_OUT) \|\| (kex->server && mode == MODE_IN);
	434	current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
	435	current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
	436	current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
	437	}
	438	}
	439
	440	Newkeys *
	441	kex_get_newkeys(int mode)
	442	{
	443	Newkeys *ret;
	444
	445	ret = current_keys[mode];
446	current_keys[mode] = NULL;
447	return ret;
448	}
449
450	#if defined(DEBUG_KEX) \|\| defined(DEBUG_KEXDH)
451	void
452	dump_digest(char msg, u_char digest, int len)
453	{
454	int i;
455
456	fprintf(stderr, "%s\n", msg);
e9702f7d	457	for (i = 0; i< len; i++) {
3c0ef626	458	fprintf(stderr, "%02x", digest[i]);
	459	if (i%32 == 31)
	460	fprintf(stderr, "\n");
	461	else if (i%8 == 7)
	462	fprintf(stderr, " ");
	463	}
	464	fprintf(stderr, "\n");
	465	}
	466	#endif