[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 1.55 2003/04/01 10:31:26 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"
#include "monitor.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])
{
	int i;

	buffer_clear(b);
	/*
	 * add a dummy cookie, the cookie will be overwritten by
	 * kex_send_kexinit(), each time a kexinit is set
	 */
	for (i = 0; i < KEX_COOKIE_LEN; i++)
		buffer_put_char(b, 0);
	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, int *first_kex_follows)
{
	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);
	if (first_kex_follows != NULL)
		*first_kex_follows = i;
	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("expecting 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)
{
	u_int32_t rand = 0;
	u_char *cookie;
	int i;

	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;

	/* generate a random cookie */
	if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
		fatal("kex_send_kexinit: kex proposal too short");
	cookie = buffer_ptr(&kex->my);
	for (i = 0; i < KEX_COOKIE_LEN; i++) {
		if (i % 4 == 0)
			rand = arc4random();
		cookie[i] = rand;
		rand >>= 8;
	}
	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));
	(void) packet_get_char();
	(void) 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);

	if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
	    kex->kex[kex->kex_type] != NULL) {
		(kex->kex[kex->kex_type])(kex);
	} else {
		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 = KEX_DH_GRP1_SHA1;
	} else if (strcmp(k->name, KEX_DHGEX) == 0) {
		k->kex_type = KEX_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 int 
proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
{
	static int check[] = {
		PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
	};
	int *idx;
	char *p;

	for (idx = &check[0]; *idx != -1; idx++) {
		if ((p = strchr(my[*idx], ',')) != NULL)
			*p = '\0';
		if ((p = strchr(peer[*idx], ',')) != NULL)
			*p = '\0';
		if (strcmp(my[*idx], peer[*idx]) != 0) {
			debug2("proposal mismatch: my %s peer %s",
			    my[*idx], peer[*idx]);
			return (0);
		}
	}
	debug2("proposals match");
	return (1);
}

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;
	int first_kex_follows, type;

	my   = kex_buf2prop(&kex->my, NULL);
	peer = kex_buf2prop(&kex->peer, &first_kex_follows);

	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;

	/* ignore the next message if the proposals do not match */
	if (first_kex_follows && !proposals_match(my, peer) && 
	   !(datafellows & SSH_BUG_FIRSTKEX)) {
		type = packet_read();
		debug2("skipping next packet (type %u)", type);
	}

	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);

	debug2("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"
6a9b3198	26	RCSID("$OpenBSD: kex.c,v 1.55 2003/04/01 10:31:26 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"
700318f3	43	#include "monitor.h"
3c0ef626	44
	45	#define KEX_COOKIE_LEN 16
	46
	47	/* prototype */
	48	static void kex_kexinit_finish(Kex *);
	49	static void kex_choose_conf(Kex *);
	50
	51	/* put algorithm proposal into buffer */
	52	static void
	53	kex_prop2buf(Buffer b, char proposal[PROPOSAL_MAX])
	54	{
3c0ef626	55	int i;
	56
	57	buffer_clear(b);
700318f3	58	/*
	59	* add a dummy cookie, the cookie will be overwritten by
	60	* kex_send_kexinit(), each time a kexinit is set
	61	*/
	62	for (i = 0; i < KEX_COOKIE_LEN; i++)
	63	buffer_put_char(b, 0);
3c0ef626	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 **
6a9b3198	72	kex_buf2prop(Buffer raw, int first_kex_follows)
3c0ef626	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);
6a9b3198	92	if (first_kex_follows != NULL)
6a9b3198	93	*first_kex_follows = i;
3c0ef626	94	debug2("kex_parse_kexinit: first_kex_follows %d ", i);
	95	i = buffer_get_int(&b);
	96	debug2("kex_parse_kexinit: reserved %d ", i);
	97	buffer_free(&b);
	98	return proposal;
	99	}
	100
	101	static void
	102	kex_prop_free(char **proposal)
	103	{
	104	int i;
	105
	106	for (i = 0; i < PROPOSAL_MAX; i++)
	107	xfree(proposal[i]);
	108	xfree(proposal);
	109	}
	110
	111	static void
e9a17296	112	kex_protocol_error(int type, u_int32_t seq, void *ctxt)
3c0ef626	113	{
e9a17296	114	error("Hm, kex protocol error: type %d seq %u", type, seq);
3c0ef626	115	}
	116
	117	static void
e9a17296	118	kex_reset_dispatch(void)
3c0ef626	119	{
e9a17296	120	dispatch_range(SSH2_MSG_TRANSPORT_MIN,
	121	SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
	122	dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
3c0ef626	123	}
	124
	125	void
	126	kex_finish(Kex *kex)
	127	{
e9a17296	128	kex_reset_dispatch();
3c0ef626	129
	130	packet_start(SSH2_MSG_NEWKEYS);
	131	packet_send();
	132	/* packet_write_wait(); */
	133	debug("SSH2_MSG_NEWKEYS sent");
	134
6a9b3198	135	debug("expecting SSH2_MSG_NEWKEYS");
e9a17296	136	packet_read_expect(SSH2_MSG_NEWKEYS);
e9a17296	137	packet_check_eom();
3c0ef626	138	debug("SSH2_MSG_NEWKEYS received");
	139
	140	kex->done = 1;
	141	buffer_clear(&kex->peer);
	142	/* buffer_clear(&kex->my); */
	143	kex->flags &= ~KEX_INIT_SENT;
	144	xfree(kex->name);
	145	kex->name = NULL;
	146	}
	147
	148	void
	149	kex_send_kexinit(Kex *kex)
	150	{
700318f3	151	u_int32_t rand = 0;
	152	u_char *cookie;
	153	int i;
	154
3c0ef626	155	if (kex == NULL) {
	156	error("kex_send_kexinit: no kex, cannot rekey");
	157	return;
	158	}
	159	if (kex->flags & KEX_INIT_SENT) {
	160	debug("KEX_INIT_SENT");
	161	return;
	162	}
	163	kex->done = 0;
700318f3	164
	165	/* generate a random cookie */
	166	if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
	167	fatal("kex_send_kexinit: kex proposal too short");
	168	cookie = buffer_ptr(&kex->my);
	169	for (i = 0; i < KEX_COOKIE_LEN; i++) {
	170	if (i % 4 == 0)
	171	rand = arc4random();
	172	cookie[i] = rand;
	173	rand >>= 8;
	174	}
3c0ef626	175	packet_start(SSH2_MSG_KEXINIT);
	176	packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
	177	packet_send();
	178	debug("SSH2_MSG_KEXINIT sent");
	179	kex->flags \|= KEX_INIT_SENT;
	180	}
	181
	182	void
e9a17296	183	kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
3c0ef626	184	{
	185	char *ptr;
	186	int dlen;
	187	int i;
	188	Kex kex = (Kex )ctxt;
	189
	190	debug("SSH2_MSG_KEXINIT received");
	191	if (kex == NULL)
	192	fatal("kex_input_kexinit: no kex, cannot rekey");
	193
	194	ptr = packet_get_raw(&dlen);
	195	buffer_append(&kex->peer, ptr, dlen);
	196
	197	/* discard packet */
	198	for (i = 0; i < KEX_COOKIE_LEN; i++)
	199	packet_get_char();
	200	for (i = 0; i < PROPOSAL_MAX; i++)
	201	xfree(packet_get_string(NULL));
680cee3b	202	(void) packet_get_char();
680cee3b	203	(void) packet_get_int();
e9a17296	204	packet_check_eom();
3c0ef626	205
	206	kex_kexinit_finish(kex);
	207	}
	208
	209	Kex *
	210	kex_setup(char *proposal[PROPOSAL_MAX])
	211	{
	212	Kex *kex;
	213
	214	kex = xmalloc(sizeof(*kex));
	215	memset(kex, 0, sizeof(*kex));
	216	buffer_init(&kex->peer);
	217	buffer_init(&kex->my);
	218	kex_prop2buf(&kex->my, proposal);
	219	kex->done = 0;
	220
	221	kex_send_kexinit(kex); /* we start */
e9a17296	222	kex_reset_dispatch();
3c0ef626	223
	224	return kex;
	225	}
	226
	227	static void
	228	kex_kexinit_finish(Kex *kex)
	229	{
	230	if (!(kex->flags & KEX_INIT_SENT))
	231	kex_send_kexinit(kex);
	232
	233	kex_choose_conf(kex);
	234
6a9b3198	235	if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
	236	kex->kex[kex->kex_type] != NULL) {
	237	(kex->kex[kex->kex_type])(kex);
	238	} else {
3c0ef626	239	fatal("Unsupported key exchange %d", kex->kex_type);
	240	}
	241	}
	242
	243	static void
	244	choose_enc(Enc enc, char client, char *server)
	245	{
	246	char *name = match_list(client, server, NULL);
	247	if (name == NULL)
	248	fatal("no matching cipher found: client %s server %s", client, server);
e9a17296	249	if ((enc->cipher = cipher_by_name(name)) == NULL)
3c0ef626	250	fatal("matching cipher is not supported: %s", name);
	251	enc->name = name;
	252	enc->enabled = 0;
	253	enc->iv = NULL;
	254	enc->key = NULL;
e9a17296	255	enc->key_len = cipher_keylen(enc->cipher);
e9a17296	256	enc->block_size = cipher_blocksize(enc->cipher);
3c0ef626	257	}
	258	static void
	259	choose_mac(Mac mac, char client, char *server)
	260	{
	261	char *name = match_list(client, server, NULL);
	262	if (name == NULL)
	263	fatal("no matching mac found: client %s server %s", client, server);
	264	if (mac_init(mac, name) < 0)
	265	fatal("unsupported mac %s", name);
	266	/* truncate the key */
	267	if (datafellows & SSH_BUG_HMAC)
	268	mac->key_len = 16;
	269	mac->name = name;
	270	mac->key = NULL;
	271	mac->enabled = 0;
	272	}
	273	static void
	274	choose_comp(Comp comp, char client, char *server)
	275	{
	276	char *name = match_list(client, server, NULL);
	277	if (name == NULL)
	278	fatal("no matching comp found: client %s server %s", client, server);
	279	if (strcmp(name, "zlib") == 0) {
	280	comp->type = 1;
	281	} else if (strcmp(name, "none") == 0) {
	282	comp->type = 0;
	283	} else {
	284	fatal("unsupported comp %s", name);
	285	}
	286	comp->name = name;
	287	}
	288	static void
	289	choose_kex(Kex k, char client, char *server)
	290	{
	291	k->name = match_list(client, server, NULL);
	292	if (k->name == NULL)
	293	fatal("no kex alg");
	294	if (strcmp(k->name, KEX_DH1) == 0) {
6a9b3198	295	k->kex_type = KEX_DH_GRP1_SHA1;
3c0ef626	296	} else if (strcmp(k->name, KEX_DHGEX) == 0) {
6a9b3198	297	k->kex_type = KEX_DH_GEX_SHA1;
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
6a9b3198	313	static int
	314	proposals_match(char my[PROPOSAL_MAX], char peer[PROPOSAL_MAX])
	315	{
	316	static int check[] = {
	317	PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
	318	};
	319	int *idx;
	320	char *p;
	321
	322	for (idx = &check[0]; *idx != -1; idx++) {
	323	if ((p = strchr(my[*idx], ',')) != NULL)
	324	*p = '\0';
	325	if ((p = strchr(peer[*idx], ',')) != NULL)
	326	*p = '\0';
	327	if (strcmp(my[idx], peer[idx]) != 0) {
	328	debug2("proposal mismatch: my %s peer %s",
	329	my[idx], peer[idx]);
	330	return (0);
	331	}
	332	}
	333	debug2("proposals match");
	334	return (1);
	335	}
	336
3c0ef626	337	static void
	338	kex_choose_conf(Kex *kex)
	339	{
	340	Newkeys *newkeys;
	341	char my, peer;
	342	char cprop, sprop;
	343	int nenc, nmac, ncomp;
	344	int mode;
	345	int ctos; /* direction: if true client-to-server */
	346	int need;
6a9b3198	347	int first_kex_follows, type;
3c0ef626	348
6a9b3198	349	my = kex_buf2prop(&kex->my, NULL);
6a9b3198	350	peer = kex_buf2prop(&kex->peer, &first_kex_follows);
3c0ef626	351
	352	if (kex->server) {
	353	cprop=peer;
	354	sprop=my;
	355	} else {
	356	cprop=my;
	357	sprop=peer;
	358	}
	359
	360	/* Algorithm Negotiation */
	361	for (mode = 0; mode < MODE_MAX; mode++) {
	362	newkeys = xmalloc(sizeof(*newkeys));
	363	memset(newkeys, 0, sizeof(*newkeys));
	364	kex->newkeys[mode] = newkeys;
	365	ctos = (!kex->server && mode == MODE_OUT) \|\| (kex->server && mode == MODE_IN);
	366	nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
	367	nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
	368	ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
	369	choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
	370	choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
	371	choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
	372	debug("kex: %s %s %s %s",
	373	ctos ? "client->server" : "server->client",
	374	newkeys->enc.name,
	375	newkeys->mac.name,
	376	newkeys->comp.name);
	377	}
	378	choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
	379	choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
	380	sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
	381	need = 0;
	382	for (mode = 0; mode < MODE_MAX; mode++) {
	383	newkeys = kex->newkeys[mode];
e9a17296	384	if (need < newkeys->enc.key_len)
	385	need = newkeys->enc.key_len;
	386	if (need < newkeys->enc.block_size)
	387	need = newkeys->enc.block_size;
3c0ef626	388	if (need < newkeys->mac.key_len)
	389	need = newkeys->mac.key_len;
	390	}
	391	/* XXX need runden? */
	392	kex->we_need = need;
	393
6a9b3198	394	/* ignore the next message if the proposals do not match */
	395	if (first_kex_follows && !proposals_match(my, peer) &&
	396	!(datafellows & SSH_BUG_FIRSTKEX)) {
	397	type = packet_read();
	398	debug2("skipping next packet (type %u)", type);
	399	}
	400
3c0ef626	401	kex_prop_free(my);
	402	kex_prop_free(peer);
	403	}
	404
	405	static u_char *
	406	derive_key(Kex kex, int id, int need, u_char hash, BIGNUM *shared_secret)
	407	{
	408	Buffer b;
e9a17296	409	const EVP_MD *evp_md = EVP_sha1();
3c0ef626	410	EVP_MD_CTX md;
	411	char c = id;
	412	int have;
e9a17296	413	int mdsz = EVP_MD_size(evp_md);
3c0ef626	414	u_char *digest = xmalloc(roundup(need, mdsz));
	415
	416	buffer_init(&b);
	417	buffer_put_bignum2(&b, shared_secret);
	418
	419	/* K1 = HASH(K \|\| H \|\| "A" \|\| session_id) */
	420	EVP_DigestInit(&md, evp_md);
	421	if (!(datafellows & SSH_BUG_DERIVEKEY))
	422	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
	423	EVP_DigestUpdate(&md, hash, mdsz);
	424	EVP_DigestUpdate(&md, &c, 1);
	425	EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
	426	EVP_DigestFinal(&md, digest, NULL);
	427
	428	/*
	429	* expand key:
	430	* Kn = HASH(K \|\| H \|\| K1 \|\| K2 \|\| ... \|\| Kn-1)
	431	* Key = K1 \|\| K2 \|\| ... \|\| Kn
	432	*/
	433	for (have = mdsz; need > have; have += mdsz) {
	434	EVP_DigestInit(&md, evp_md);
	435	if (!(datafellows & SSH_BUG_DERIVEKEY))
	436	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
	437	EVP_DigestUpdate(&md, hash, mdsz);
	438	EVP_DigestUpdate(&md, digest, have);
	439	EVP_DigestFinal(&md, digest + have, NULL);
	440	}
	441	buffer_free(&b);
	442	#ifdef DEBUG_KEX
	443	fprintf(stderr, "key '%c'== ", c);
	444	dump_digest("key", digest, need);
	445	#endif
	446	return digest;
	447	}
	448
	449	Newkeys *current_keys[MODE_MAX];
	450
	451	#define NKEYS 6
	452	void
	453	kex_derive_keys(Kex kex, u_char hash, BIGNUM *shared_secret)
	454	{
	455	u_char *keys[NKEYS];
	456	int i, mode, ctos;
	457
	458	for (i = 0; i < NKEYS; i++)
	459	keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret);
	460
6a9b3198	461	debug2("kex_derive_keys");
3c0ef626	462	for (mode = 0; mode < MODE_MAX; mode++) {
	463	current_keys[mode] = kex->newkeys[mode];
	464	kex->newkeys[mode] = NULL;
	465	ctos = (!kex->server && mode == MODE_OUT) \|\| (kex->server && mode == MODE_IN);
	466	current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
	467	current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
	468	current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
	469	}
	470	}
	471
	472	Newkeys *
	473	kex_get_newkeys(int mode)
	474	{
	475	Newkeys *ret;
	476
	477	ret = current_keys[mode];
	478	current_keys[mode] = NULL;
	479	return ret;
	480	}
	481
	482	#if defined(DEBUG_KEX) \|\| defined(DEBUG_KEXDH)
	483	void
	484	dump_digest(char msg, u_char digest, int len)
	485	{
	486	int i;
	487
	488	fprintf(stderr, "%s\n", msg);
e9a17296	489	for (i = 0; i< len; i++) {
3c0ef626	490	fprintf(stderr, "%02x", digest[i]);
	491	if (i%32 == 31)
	492	fprintf(stderr, "\n");
	493	else if (i%8 == 7)
	494	fprintf(stderr, " ");
	495	}
	496	fprintf(stderr, "\n");
	497	}
	498	#endif