[openssh.git] / 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 1.66 2006/03/07 09:07:40 djm 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

#ifdef HAVE_EVP_SHA256
# define evp_ssh_sha256 EVP_sha256
#else /* HAVE_EVP_SHA256 */
extern const EVP_MD *evp_ssh_sha256(void);
#endif /* HAVE_EVP_SHA256 */

/* 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_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)
{
	u_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 rnd = 0;
	u_char *cookie;
	u_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)
			rnd = arc4random();
		cookie[i] = rnd;
		rnd >>= 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;
	u_int i, dlen;
	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@openssh.com") == 0) {
		comp->type = COMP_DELAYED;
	} else if (strcmp(name, "zlib") == 0) {
		comp->type = COMP_ZLIB;
	} else if (strcmp(name, "none") == 0) {
		comp->type = COMP_NONE;
	} 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;
		k->evp_md = EVP_sha1();
	} else if (strcmp(k->name, KEX_DH14) == 0) {
		k->kex_type = KEX_DH_GRP14_SHA1;
		k->evp_md = EVP_sha1();
	} else if (strcmp(k->name, KEX_DHGEX_SHA1) == 0) {
		k->kex_type = KEX_DH_GEX_SHA1;
		k->evp_md = EVP_sha1();
	} else if (strcmp(k->name, KEX_DHGEX_SHA256) == 0) {
		k->kex_type = KEX_DH_GEX_SHA256;
		k->evp_md = evp_ssh_sha256();
	} 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;
	u_int mode, ctos, 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, u_int need, u_char *hash, u_int hashlen,
    BIGNUM *shared_secret)
{
	Buffer b;
	EVP_MD_CTX md;
	char c = id;
	u_int have;
	int mdsz;
	u_char *digest;

	if ((mdsz = EVP_MD_size(kex->evp_md)) <= 0)
		fatal("bad kex md size %d", mdsz);
 	digest = xmalloc(roundup(need, mdsz));

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

	/* K1 = HASH(K || H || "A" || session_id) */
	EVP_DigestInit(&md, kex->evp_md);
	if (!(datafellows & SSH_BUG_DERIVEKEY))
		EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
	EVP_DigestUpdate(&md, hash, hashlen);
	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, kex->evp_md);
		if (!(datafellows & SSH_BUG_DERIVEKEY))
			EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
		EVP_DigestUpdate(&md, hash, hashlen);
		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, u_int hashlen, BIGNUM *shared_secret)
{
	u_char *keys[NKEYS];
	u_int i, mode, ctos;

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

void
derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
    u_int8_t cookie[8], u_int8_t id[16])
{
	const EVP_MD *evp_md = EVP_md5();
	EVP_MD_CTX md;
	u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE];
	int len;

	EVP_DigestInit(&md, evp_md);

	len = BN_num_bytes(host_modulus);
	if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
		fatal("%s: bad host modulus (len %d)", __func__, len);
	BN_bn2bin(host_modulus, nbuf);
	EVP_DigestUpdate(&md, nbuf, len);

	len = BN_num_bytes(server_modulus);
	if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
		fatal("%s: bad server modulus (len %d)", __func__, len);
	BN_bn2bin(server_modulus, nbuf);
	EVP_DigestUpdate(&md, nbuf, len);

	EVP_DigestUpdate(&md, cookie, 8);

	EVP_DigestFinal(&md, obuf, NULL);
	memcpy(id, obuf, 16);

	memset(nbuf, 0, sizeof(nbuf));
	memset(obuf, 0, sizeof(obuf));
	memset(&md, 0, sizeof(md));
}

#if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
void
dump_digest(char *msg, u_char *digest, int len)
{
	u_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
4f8c6159	1	/*
a96070d4	2	* Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
4f8c6159	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.
4f8c6159	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"
2ff8003a	26	RCSID("$OpenBSD: kex.c,v 1.66 2006/03/07 09:07:40 djm Exp $");
4f8c6159	27
4f8c6159	28	#include <openssl/crypto.h>
4f8c6159	29
42f11eb2	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"
4f8c6159	37	#include "kex.h"
fa08c86b	38	#include "key.h"
42f11eb2	39	#include "log.h"
b2552997	40	#include "mac.h"
cab80f75	41	#include "match.h"
a5c9ffdb	42	#include "dispatch.h"
1853d1ef	43	#include "monitor.h"
4f8c6159	44
71276795	45	#define KEX_COOKIE_LEN 16
71276795	46
13ff27b7	47	#ifdef HAVE_EVP_SHA256
	48	# define evp_ssh_sha256 EVP_sha256
	49	#else /* HAVE_EVP_SHA256 */
2ff8003a	50	extern const EVP_MD *evp_ssh_sha256(void);
13ff27b7	51	#endif /* HAVE_EVP_SHA256 */
2ff8003a	52
396c147e	53	/* prototype */
	54	static void kex_kexinit_finish(Kex *);
	55	static void kex_choose_conf(Kex *);
a5c9ffdb	56
a5c9ffdb	57	/* put algorithm proposal into buffer */
396c147e	58	static void
a5c9ffdb	59	kex_prop2buf(Buffer b, char proposal[PROPOSAL_MAX])
4f8c6159	60	{
2ceb8101	61	u_int i;
a5c9ffdb	62
a5c9ffdb	63	buffer_clear(b);
76bf34f1	64	/*
	65	* add a dummy cookie, the cookie will be overwritten by
	66	* kex_send_kexinit(), each time a kexinit is set
	67	*/
	68	for (i = 0; i < KEX_COOKIE_LEN; i++)
	69	buffer_put_char(b, 0);
4f8c6159	70	for (i = 0; i < PROPOSAL_MAX; i++)
a5c9ffdb	71	buffer_put_cstring(b, proposal[i]);
	72	buffer_put_char(b, 0); /* first_kex_packet_follows */
	73	buffer_put_int(b, 0); /* uint32 reserved */
4f8c6159	74	}
4f8c6159	75
a5c9ffdb	76	/* parse buffer and return algorithm proposal */
396c147e	77	static char **
eed8e583	78	kex_buf2prop(Buffer raw, int first_kex_follows)
71276795	79	{
a5c9ffdb	80	Buffer b;
71276795	81	int i;
a5c9ffdb	82	char **proposal;
71276795	83
a5c9ffdb	84	proposal = xmalloc(PROPOSAL_MAX * sizeof(char *));
	85
	86	buffer_init(&b);
	87	buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
71276795	88	/* skip cookie */
71276795	89	for (i = 0; i < KEX_COOKIE_LEN; i++)
a5c9ffdb	90	buffer_get_char(&b);
71276795	91	/* extract kex init proposal strings */
71276795	92	for (i = 0; i < PROPOSAL_MAX; i++) {
a5c9ffdb	93	proposal[i] = buffer_get_string(&b,NULL);
a5c9ffdb	94	debug2("kex_parse_kexinit: %s", proposal[i]);
71276795	95	}
a5c9ffdb	96	/* first kex follows / reserved */
a5c9ffdb	97	i = buffer_get_char(&b);
eed8e583	98	if (first_kex_follows != NULL)
eed8e583	99	*first_kex_follows = i;
a5c9ffdb	100	debug2("kex_parse_kexinit: first_kex_follows %d ", i);
	101	i = buffer_get_int(&b);
	102	debug2("kex_parse_kexinit: reserved %d ", i);
	103	buffer_free(&b);
	104	return proposal;
71276795	105	}
71276795	106
396c147e	107	static void
a5c9ffdb	108	kex_prop_free(char **proposal)
4f8c6159	109	{
2ceb8101	110	u_int i;
a5c9ffdb	111
	112	for (i = 0; i < PROPOSAL_MAX; i++)
	113	xfree(proposal[i]);
	114	xfree(proposal);
4f8c6159	115	}
4f8c6159	116
396c147e	117	static void
7819b5c3	118	kex_protocol_error(int type, u_int32_t seq, void *ctxt)
4f8c6159	119	{
7819b5c3	120	error("Hm, kex protocol error: type %d seq %u", type, seq);
a5c9ffdb	121	}
4f8c6159	122
396c147e	123	static void
9d726f16	124	kex_reset_dispatch(void)
7a37c112	125	{
6367063f	126	dispatch_range(SSH2_MSG_TRANSPORT_MIN,
6367063f	127	SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
9d726f16	128	dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
7a37c112	129	}
7a37c112	130
a5c9ffdb	131	void
d8ee838b	132	kex_finish(Kex *kex)
a5c9ffdb	133	{
9d726f16	134	kex_reset_dispatch();
d8ee838b	135
a5c9ffdb	136	packet_start(SSH2_MSG_NEWKEYS);
	137	packet_send();
	138	/* packet_write_wait(); */
	139	debug("SSH2_MSG_NEWKEYS sent");
4f8c6159	140
a77673cc	141	debug("expecting SSH2_MSG_NEWKEYS");
54a5250f	142	packet_read_expect(SSH2_MSG_NEWKEYS);
b967d870	143	packet_check_eom();
a5c9ffdb	144	debug("SSH2_MSG_NEWKEYS received");
a7ca6275	145
c422989b	146	kex->done = 1;
a5c9ffdb	147	buffer_clear(&kex->peer);
d1ac6175	148	/* buffer_clear(&kex->my); */
a5c9ffdb	149	kex->flags &= ~KEX_INIT_SENT;
a7ca6275	150	xfree(kex->name);
a7ca6275	151	kex->name = NULL;
4f8c6159	152	}
4f8c6159	153
a5c9ffdb	154	void
a5c9ffdb	155	kex_send_kexinit(Kex *kex)
94ec8c6b	156	{
ca75d7de	157	u_int32_t rnd = 0;
76bf34f1	158	u_char *cookie;
2ceb8101	159	u_int i;
76bf34f1	160
7a37c112	161	if (kex == NULL) {
	162	error("kex_send_kexinit: no kex, cannot rekey");
	163	return;
	164	}
d8ee838b	165	if (kex->flags & KEX_INIT_SENT) {
	166	debug("KEX_INIT_SENT");
	167	return;
	168	}
c422989b	169	kex->done = 0;
76bf34f1	170
	171	/* generate a random cookie */
	172	if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
	173	fatal("kex_send_kexinit: kex proposal too short");
	174	cookie = buffer_ptr(&kex->my);
	175	for (i = 0; i < KEX_COOKIE_LEN; i++) {
	176	if (i % 4 == 0)
ca75d7de	177	rnd = arc4random();
	178	cookie[i] = rnd;
	179	rnd >>= 8;
76bf34f1	180	}
a5c9ffdb	181	packet_start(SSH2_MSG_KEXINIT);
	182	packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
	183	packet_send();
	184	debug("SSH2_MSG_KEXINIT sent");
	185	kex->flags \|= KEX_INIT_SENT;
	186	}
2b87da3b	187
a5c9ffdb	188	void
7819b5c3	189	kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
a5c9ffdb	190	{
a5c9ffdb	191	char *ptr;
2ceb8101	192	u_int i, dlen;
a5c9ffdb	193	Kex kex = (Kex )ctxt;
94ec8c6b	194
a5c9ffdb	195	debug("SSH2_MSG_KEXINIT received");
7a37c112	196	if (kex == NULL)
7a37c112	197	fatal("kex_input_kexinit: no kex, cannot rekey");
94ec8c6b	198
a5c9ffdb	199	ptr = packet_get_raw(&dlen);
a5c9ffdb	200	buffer_append(&kex->peer, ptr, dlen);
94ec8c6b	201
bbb4cc1b	202	/* discard packet */
	203	for (i = 0; i < KEX_COOKIE_LEN; i++)
	204	packet_get_char();
	205	for (i = 0; i < PROPOSAL_MAX; i++)
	206	xfree(packet_get_string(NULL));
1169c3df	207	(void) packet_get_char();
1169c3df	208	(void) packet_get_int();
95500969	209	packet_check_eom();
bbb4cc1b	210
a5c9ffdb	211	kex_kexinit_finish(kex);
94ec8c6b	212	}
94ec8c6b	213
a5c9ffdb	214	Kex *
d8ee838b	215	kex_setup(char *proposal[PROPOSAL_MAX])
4f8c6159	216	{
a5c9ffdb	217	Kex *kex;
4f8c6159	218
a5c9ffdb	219	kex = xmalloc(sizeof(*kex));
	220	memset(kex, 0, sizeof(*kex));
	221	buffer_init(&kex->peer);
	222	buffer_init(&kex->my);
	223	kex_prop2buf(&kex->my, proposal);
c422989b	224	kex->done = 0;
a5c9ffdb	225
a5c9ffdb	226	kex_send_kexinit(kex); /* we start */
9d726f16	227	kex_reset_dispatch();
7a37c112	228
a5c9ffdb	229	return kex;
a5c9ffdb	230	}
4f8c6159	231
396c147e	232	static void
a5c9ffdb	233	kex_kexinit_finish(Kex *kex)
	234	{
	235	if (!(kex->flags & KEX_INIT_SENT))
	236	kex_send_kexinit(kex);
	237
	238	kex_choose_conf(kex);
	239
98a58eda	240	if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
	241	kex->kex[kex->kex_type] != NULL) {
	242	(kex->kex[kex->kex_type])(kex);
	243	} else {
a5c9ffdb	244	fatal("Unsupported key exchange %d", kex->kex_type);
4f8c6159	245	}
4f8c6159	246	}
4f8c6159	247
396c147e	248	static void
4f8c6159	249	choose_enc(Enc enc, char client, char *server)
4f8c6159	250	{
cab80f75	251	char *name = match_list(client, server, NULL);
4f8c6159	252	if (name == NULL)
4f8c6159	253	fatal("no matching cipher found: client %s server %s", client, server);
3ee832e5	254	if ((enc->cipher = cipher_by_name(name)) == NULL)
94ec8c6b	255	fatal("matching cipher is not supported: %s", name);
4f8c6159	256	enc->name = name;
	257	enc->enabled = 0;
	258	enc->iv = NULL;
	259	enc->key = NULL;
3ee832e5	260	enc->key_len = cipher_keylen(enc->cipher);
3ee832e5	261	enc->block_size = cipher_blocksize(enc->cipher);
4f8c6159	262	}
396c147e	263	static void
4f8c6159	264	choose_mac(Mac mac, char client, char *server)
4f8c6159	265	{
cab80f75	266	char *name = match_list(client, server, NULL);
4f8c6159	267	if (name == NULL)
4f8c6159	268	fatal("no matching mac found: client %s server %s", client, server);
b2552997	269	if (mac_init(mac, name) < 0)
4f8c6159	270	fatal("unsupported mac %s", name);
b2552997	271	/* truncate the key */
	272	if (datafellows & SSH_BUG_HMAC)
	273	mac->key_len = 16;
4f8c6159	274	mac->name = name;
4f8c6159	275	mac->key = NULL;
	276	mac->enabled = 0;
	277	}
396c147e	278	static void
4f8c6159	279	choose_comp(Comp comp, char client, char *server)
4f8c6159	280	{
cab80f75	281	char *name = match_list(client, server, NULL);
4f8c6159	282	if (name == NULL)
4f8c6159	283	fatal("no matching comp found: client %s server %s", client, server);
07200973	284	if (strcmp(name, "zlib@openssh.com") == 0) {
	285	comp->type = COMP_DELAYED;
	286	} else if (strcmp(name, "zlib") == 0) {
	287	comp->type = COMP_ZLIB;
4f8c6159	288	} else if (strcmp(name, "none") == 0) {
07200973	289	comp->type = COMP_NONE;
4f8c6159	290	} else {
	291	fatal("unsupported comp %s", name);
	292	}
	293	comp->name = name;
	294	}
396c147e	295	static void
4f8c6159	296	choose_kex(Kex k, char client, char *server)
4f8c6159	297	{
cab80f75	298	k->name = match_list(client, server, NULL);
4f8c6159	299	if (k->name == NULL)
4f8c6159	300	fatal("no kex alg");
94ec8c6b	301	if (strcmp(k->name, KEX_DH1) == 0) {
98a58eda	302	k->kex_type = KEX_DH_GRP1_SHA1;
47e5dc72	303	k->evp_md = EVP_sha1();
41e5bd9a	304	} else if (strcmp(k->name, KEX_DH14) == 0) {
41e5bd9a	305	k->kex_type = KEX_DH_GRP14_SHA1;
47e5dc72	306	k->evp_md = EVP_sha1();
47e5dc72	307	} else if (strcmp(k->name, KEX_DHGEX_SHA1) == 0) {
98a58eda	308	k->kex_type = KEX_DH_GEX_SHA1;
47e5dc72	309	k->evp_md = EVP_sha1();
2ff8003a	310	} else if (strcmp(k->name, KEX_DHGEX_SHA256) == 0) {
	311	k->kex_type = KEX_DH_GEX_SHA256;
	312	k->evp_md = evp_ssh_sha256();
94ec8c6b	313	} else
4f8c6159	314	fatal("bad kex alg %s", k->name);
4f8c6159	315	}
47e5dc72	316
396c147e	317	static void
4f8c6159	318	choose_hostkeyalg(Kex k, char client, char *server)
4f8c6159	319	{
cab80f75	320	char *hostkeyalg = match_list(client, server, NULL);
fa08c86b	321	if (hostkeyalg == NULL)
4f8c6159	322	fatal("no hostkey alg");
fa08c86b	323	k->hostkey_type = key_type_from_name(hostkeyalg);
	324	if (k->hostkey_type == KEY_UNSPEC)
	325	fatal("bad hostkey alg '%s'", hostkeyalg);
eea39c02	326	xfree(hostkeyalg);
4f8c6159	327	}
4f8c6159	328
aff51935	329	static int
eed8e583	330	proposals_match(char my[PROPOSAL_MAX], char peer[PROPOSAL_MAX])
	331	{
	332	static int check[] = {
	333	PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
	334	};
	335	int *idx;
	336	char *p;
	337
	338	for (idx = &check[0]; *idx != -1; idx++) {
	339	if ((p = strchr(my[*idx], ',')) != NULL)
	340	*p = '\0';
	341	if ((p = strchr(peer[*idx], ',')) != NULL)
	342	*p = '\0';
	343	if (strcmp(my[idx], peer[idx]) != 0) {
	344	debug2("proposal mismatch: my %s peer %s",
	345	my[idx], peer[idx]);
	346	return (0);
	347	}
	348	}
	349	debug2("proposals match");
	350	return (1);
	351	}
	352
396c147e	353	static void
d1ac6175	354	kex_choose_conf(Kex *kex)
4f8c6159	355	{
d1ac6175	356	Newkeys *newkeys;
a5c9ffdb	357	char my, peer;
a5c9ffdb	358	char cprop, sprop;
d1ac6175	359	int nenc, nmac, ncomp;
2ceb8101	360	u_int mode, ctos, need;
eed8e583	361	int first_kex_follows, type;
4f8c6159	362
eed8e583	363	my = kex_buf2prop(&kex->my, NULL);
eed8e583	364	peer = kex_buf2prop(&kex->peer, &first_kex_follows);
a5c9ffdb	365
d1ac6175	366	if (kex->server) {
a5c9ffdb	367	cprop=peer;
	368	sprop=my;
	369	} else {
	370	cprop=my;
	371	sprop=peer;
	372	}
4f8c6159	373
c422989b	374	/* Algorithm Negotiation */
4f8c6159	375	for (mode = 0; mode < MODE_MAX; mode++) {
d1ac6175	376	newkeys = xmalloc(sizeof(*newkeys));
d1ac6175	377	memset(newkeys, 0, sizeof(*newkeys));
c422989b	378	kex->newkeys[mode] = newkeys;
d1ac6175	379	ctos = (!kex->server && mode == MODE_OUT) \|\| (kex->server && mode == MODE_IN);
4f8c6159	380	nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
	381	nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
	382	ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
d1ac6175	383	choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
	384	choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
	385	choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
4f8c6159	386	debug("kex: %s %s %s %s",
4f8c6159	387	ctos ? "client->server" : "server->client",
d1ac6175	388	newkeys->enc.name,
	389	newkeys->mac.name,
	390	newkeys->comp.name);
4f8c6159	391	}
d1ac6175	392	choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
d1ac6175	393	choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
4f8c6159	394	sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
4f8c6159	395	need = 0;
4f8c6159	396	for (mode = 0; mode < MODE_MAX; mode++) {
c422989b	397	newkeys = kex->newkeys[mode];
3ee832e5	398	if (need < newkeys->enc.key_len)
	399	need = newkeys->enc.key_len;
	400	if (need < newkeys->enc.block_size)
	401	need = newkeys->enc.block_size;
d1ac6175	402	if (need < newkeys->mac.key_len)
d1ac6175	403	need = newkeys->mac.key_len;
4f8c6159	404	}
71276795	405	/* XXX need runden? */
d1ac6175	406	kex->we_need = need;
a5c9ffdb	407
eed8e583	408	/* ignore the next message if the proposals do not match */
aff51935	409	if (first_kex_follows && !proposals_match(my, peer) &&
4e2e5cfd	410	!(datafellows & SSH_BUG_FIRSTKEX)) {
eed8e583	411	type = packet_read();
	412	debug2("skipping next packet (type %u)", type);
	413	}
	414
a5c9ffdb	415	kex_prop_free(my);
a5c9ffdb	416	kex_prop_free(peer);
a5c9ffdb	417	}
a5c9ffdb	418
396c147e	419	static u_char *
47e5dc72	420	derive_key(Kex kex, int id, u_int need, u_char hash, u_int hashlen,
47e5dc72	421	BIGNUM *shared_secret)
a5c9ffdb	422	{
a5c9ffdb	423	Buffer b;
a5c9ffdb	424	EVP_MD_CTX md;
a5c9ffdb	425	char c = id;
2ceb8101	426	u_int have;
47e5dc72	427	int mdsz;
2ceb8101	428	u_char *digest;
56964485	429
47e5dc72	430	if ((mdsz = EVP_MD_size(kex->evp_md)) <= 0)
	431	fatal("bad kex md size %d", mdsz);
	432	digest = xmalloc(roundup(need, mdsz));
a5c9ffdb	433
	434	buffer_init(&b);
	435	buffer_put_bignum2(&b, shared_secret);
	436
c422989b	437	/* K1 = HASH(K \|\| H \|\| "A" \|\| session_id) */
47e5dc72	438	EVP_DigestInit(&md, kex->evp_md);
eef7adcb	439	if (!(datafellows & SSH_BUG_DERIVEKEY))
eef7adcb	440	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
47e5dc72	441	EVP_DigestUpdate(&md, hash, hashlen);
c422989b	442	EVP_DigestUpdate(&md, &c, 1);
d1ac6175	443	EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
a5c9ffdb	444	EVP_DigestFinal(&md, digest, NULL);
a5c9ffdb	445
c422989b	446	/*
	447	* expand key:
	448	* Kn = HASH(K \|\| H \|\| K1 \|\| K2 \|\| ... \|\| Kn-1)
	449	* Key = K1 \|\| K2 \|\| ... \|\| Kn
	450	*/
a5c9ffdb	451	for (have = mdsz; need > have; have += mdsz) {
47e5dc72	452	EVP_DigestInit(&md, kex->evp_md);
eef7adcb	453	if (!(datafellows & SSH_BUG_DERIVEKEY))
eef7adcb	454	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
47e5dc72	455	EVP_DigestUpdate(&md, hash, hashlen);
a5c9ffdb	456	EVP_DigestUpdate(&md, digest, have);
	457	EVP_DigestFinal(&md, digest + have, NULL);
	458	}
	459	buffer_free(&b);
	460	#ifdef DEBUG_KEX
	461	fprintf(stderr, "key '%c'== ", c);
	462	dump_digest("key", digest, need);
	463	#endif
	464	return digest;
4f8c6159	465	}
4f8c6159	466
c422989b	467	Newkeys *current_keys[MODE_MAX];
d1ac6175	468
cab80f75	469	#define NKEYS 6
a5c9ffdb	470	void
47e5dc72	471	kex_derive_keys(Kex kex, u_char hash, u_int hashlen, BIGNUM *shared_secret)
4f8c6159	472	{
1e3b8b07	473	u_char *keys[NKEYS];
2ceb8101	474	u_int i, mode, ctos;
4f8c6159	475
47e5dc72	476	for (i = 0; i < NKEYS; i++) {
	477	keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, hashlen,
	478	shared_secret);
	479	}
4f8c6159	480
a77673cc	481	debug2("kex_derive_keys");
4f8c6159	482	for (mode = 0; mode < MODE_MAX; mode++) {
c422989b	483	current_keys[mode] = kex->newkeys[mode];
c422989b	484	kex->newkeys[mode] = NULL;
d1ac6175	485	ctos = (!kex->server && mode == MODE_OUT) \|\| (kex->server && mode == MODE_IN);
c422989b	486	current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
	487	current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
	488	current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
4f8c6159	489	}
4f8c6159	490	}
a5c9ffdb	491
d1ac6175	492	Newkeys *
	493	kex_get_newkeys(int mode)
	494	{
c422989b	495	Newkeys *ret;
	496
	497	ret = current_keys[mode];
	498	current_keys[mode] = NULL;
	499	return ret;
d1ac6175	500	}
d1ac6175	501
8bbf1fa6	502	void
	503	derive_ssh1_session_id(BIGNUM host_modulus, BIGNUM server_modulus,
	504	u_int8_t cookie[8], u_int8_t id[16])
	505	{
	506	const EVP_MD *evp_md = EVP_md5();
	507	EVP_MD_CTX md;
	508	u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE];
	509	int len;
	510
	511	EVP_DigestInit(&md, evp_md);
	512
	513	len = BN_num_bytes(host_modulus);
2ceb8101	514	if (len < (512 / 8) \|\| (u_int)len > sizeof(nbuf))
8bbf1fa6	515	fatal("%s: bad host modulus (len %d)", __func__, len);
	516	BN_bn2bin(host_modulus, nbuf);
	517	EVP_DigestUpdate(&md, nbuf, len);
	518
	519	len = BN_num_bytes(server_modulus);
2ceb8101	520	if (len < (512 / 8) \|\| (u_int)len > sizeof(nbuf))
8bbf1fa6	521	fatal("%s: bad server modulus (len %d)", __func__, len);
	522	BN_bn2bin(server_modulus, nbuf);
	523	EVP_DigestUpdate(&md, nbuf, len);
	524
	525	EVP_DigestUpdate(&md, cookie, 8);
	526
59657003	527	EVP_DigestFinal(&md, obuf, NULL);
8bbf1fa6	528	memcpy(id, obuf, 16);
	529
	530	memset(nbuf, 0, sizeof(nbuf));
	531	memset(obuf, 0, sizeof(obuf));
	532	memset(&md, 0, sizeof(md));
	533	}
	534
a5c9ffdb	535	#if defined(DEBUG_KEX) \|\| defined(DEBUG_KEXDH)
	536	void
	537	dump_digest(char msg, u_char digest, int len)
	538	{
2ceb8101	539	u_int i;
a5c9ffdb	540
a5c9ffdb	541	fprintf(stderr, "%s\n", msg);
6aacefa7	542	for (i = 0; i< len; i++) {
a5c9ffdb	543	fprintf(stderr, "%02x", digest[i]);
	544	if (i%32 == 31)
	545	fprintf(stderr, "\n");
	546	else if (i%8 == 7)
	547	fprintf(stderr, " ");
	548	}
	549	fprintf(stderr, "\n");
	550	}
	551	#endif