[openssh.git] / kex.c

/* $OpenBSD: kex.c,v 1.74 2006/07/26 13:57:17 stevesk Exp $ */
/*
 * 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"

#include <sys/param.h>

#include <openssl/crypto.h>

#include <stdlib.h>
#include <string.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

#if OPENSSL_VERSION_NUMBER >= 0x00907000L
# if defined(HAVE_EVP_SHA256)
# define evp_ssh_sha256 EVP_sha256
# else
extern const EVP_MD *evp_ssh_sha256(void);
# endif
#endif

/* 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 = xcalloc(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 = xcalloc(1, 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();
#if OPENSSL_VERSION_NUMBER >= 0x00907000L
	} else if (strcmp(k->name, KEX_DHGEX_SHA256) == 0) {
		k->kex_type = KEX_DH_GEX_SHA256;
		k->evp_md = evp_ssh_sha256();
#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 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 = xcalloc(1, 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
ffa517a8	1	/* $OpenBSD: kex.c,v 1.74 2006/07/26 13:57:17 stevesk Exp $ */
4f8c6159	2	/*
a96070d4	3	* Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
4f8c6159	4	*
	5	* Redistribution and use in source and binary forms, with or without
	6	* modification, are permitted provided that the following conditions
	7	* are met:
	8	* 1. Redistributions of source code must retain the above copyright
	9	* notice, this list of conditions and the following disclaimer.
	10	* 2. Redistributions in binary form must reproduce the above copyright
	11	* notice, this list of conditions and the following disclaimer in the
	12	* documentation and/or other materials provided with the distribution.
4f8c6159	13	*
	14	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
	15	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	16	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	17	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
	18	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	19	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	20	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	21	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	22	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	23	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	24	*/
	25
	26	#include "includes.h"
4f8c6159	27
536c14e8	28	#include <sys/param.h>
536c14e8	29
4f8c6159	30	#include <openssl/crypto.h>
4f8c6159	31
ffa517a8	32	#include <stdlib.h>
00146caa	33	#include <string.h>
00146caa	34
42f11eb2	35	#include "ssh2.h"
	36	#include "xmalloc.h"
	37	#include "buffer.h"
	38	#include "bufaux.h"
	39	#include "packet.h"
	40	#include "compat.h"
	41	#include "cipher.h"
4f8c6159	42	#include "kex.h"
fa08c86b	43	#include "key.h"
42f11eb2	44	#include "log.h"
b2552997	45	#include "mac.h"
cab80f75	46	#include "match.h"
a5c9ffdb	47	#include "dispatch.h"
1853d1ef	48	#include "monitor.h"
4f8c6159	49
71276795	50	#define KEX_COOKIE_LEN 16
71276795	51
30baf904	52	#if OPENSSL_VERSION_NUMBER >= 0x00907000L
30baf904	53	# if defined(HAVE_EVP_SHA256)
13ff27b7	54	# define evp_ssh_sha256 EVP_sha256
30baf904	55	# else
2ff8003a	56	extern const EVP_MD *evp_ssh_sha256(void);
30baf904	57	# endif
b1f0c612	58	#endif
2ff8003a	59
396c147e	60	/* prototype */
	61	static void kex_kexinit_finish(Kex *);
	62	static void kex_choose_conf(Kex *);
a5c9ffdb	63
a5c9ffdb	64	/* put algorithm proposal into buffer */
396c147e	65	static void
a5c9ffdb	66	kex_prop2buf(Buffer b, char proposal[PROPOSAL_MAX])
4f8c6159	67	{
2ceb8101	68	u_int i;
a5c9ffdb	69
a5c9ffdb	70	buffer_clear(b);
76bf34f1	71	/*
	72	* add a dummy cookie, the cookie will be overwritten by
	73	* kex_send_kexinit(), each time a kexinit is set
	74	*/
	75	for (i = 0; i < KEX_COOKIE_LEN; i++)
	76	buffer_put_char(b, 0);
4f8c6159	77	for (i = 0; i < PROPOSAL_MAX; i++)
a5c9ffdb	78	buffer_put_cstring(b, proposal[i]);
	79	buffer_put_char(b, 0); /* first_kex_packet_follows */
	80	buffer_put_int(b, 0); /* uint32 reserved */
4f8c6159	81	}
4f8c6159	82
a5c9ffdb	83	/* parse buffer and return algorithm proposal */
396c147e	84	static char **
eed8e583	85	kex_buf2prop(Buffer raw, int first_kex_follows)
71276795	86	{
a5c9ffdb	87	Buffer b;
71276795	88	int i;
a5c9ffdb	89	char **proposal;
71276795	90
52e3daed	91	proposal = xcalloc(PROPOSAL_MAX, sizeof(char *));
a5c9ffdb	92
	93	buffer_init(&b);
	94	buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
71276795	95	/* skip cookie */
71276795	96	for (i = 0; i < KEX_COOKIE_LEN; i++)
a5c9ffdb	97	buffer_get_char(&b);
71276795	98	/* extract kex init proposal strings */
71276795	99	for (i = 0; i < PROPOSAL_MAX; i++) {
a5c9ffdb	100	proposal[i] = buffer_get_string(&b,NULL);
a5c9ffdb	101	debug2("kex_parse_kexinit: %s", proposal[i]);
71276795	102	}
a5c9ffdb	103	/* first kex follows / reserved */
a5c9ffdb	104	i = buffer_get_char(&b);
eed8e583	105	if (first_kex_follows != NULL)
eed8e583	106	*first_kex_follows = i;
a5c9ffdb	107	debug2("kex_parse_kexinit: first_kex_follows %d ", i);
	108	i = buffer_get_int(&b);
	109	debug2("kex_parse_kexinit: reserved %d ", i);
	110	buffer_free(&b);
	111	return proposal;
71276795	112	}
71276795	113
396c147e	114	static void
a5c9ffdb	115	kex_prop_free(char **proposal)
4f8c6159	116	{
2ceb8101	117	u_int i;
a5c9ffdb	118
	119	for (i = 0; i < PROPOSAL_MAX; i++)
	120	xfree(proposal[i]);
	121	xfree(proposal);
4f8c6159	122	}
4f8c6159	123
396c147e	124	static void
7819b5c3	125	kex_protocol_error(int type, u_int32_t seq, void *ctxt)
4f8c6159	126	{
7819b5c3	127	error("Hm, kex protocol error: type %d seq %u", type, seq);
a5c9ffdb	128	}
4f8c6159	129
396c147e	130	static void
9d726f16	131	kex_reset_dispatch(void)
7a37c112	132	{
6367063f	133	dispatch_range(SSH2_MSG_TRANSPORT_MIN,
6367063f	134	SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
9d726f16	135	dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
7a37c112	136	}
7a37c112	137
a5c9ffdb	138	void
d8ee838b	139	kex_finish(Kex *kex)
a5c9ffdb	140	{
9d726f16	141	kex_reset_dispatch();
d8ee838b	142
a5c9ffdb	143	packet_start(SSH2_MSG_NEWKEYS);
	144	packet_send();
	145	/* packet_write_wait(); */
	146	debug("SSH2_MSG_NEWKEYS sent");
4f8c6159	147
a77673cc	148	debug("expecting SSH2_MSG_NEWKEYS");
54a5250f	149	packet_read_expect(SSH2_MSG_NEWKEYS);
b967d870	150	packet_check_eom();
a5c9ffdb	151	debug("SSH2_MSG_NEWKEYS received");
a7ca6275	152
c422989b	153	kex->done = 1;
a5c9ffdb	154	buffer_clear(&kex->peer);
d1ac6175	155	/* buffer_clear(&kex->my); */
a5c9ffdb	156	kex->flags &= ~KEX_INIT_SENT;
a7ca6275	157	xfree(kex->name);
a7ca6275	158	kex->name = NULL;
4f8c6159	159	}
4f8c6159	160
a5c9ffdb	161	void
a5c9ffdb	162	kex_send_kexinit(Kex *kex)
94ec8c6b	163	{
ca75d7de	164	u_int32_t rnd = 0;
76bf34f1	165	u_char *cookie;
2ceb8101	166	u_int i;
76bf34f1	167
7a37c112	168	if (kex == NULL) {
	169	error("kex_send_kexinit: no kex, cannot rekey");
	170	return;
	171	}
d8ee838b	172	if (kex->flags & KEX_INIT_SENT) {
	173	debug("KEX_INIT_SENT");
	174	return;
	175	}
c422989b	176	kex->done = 0;
76bf34f1	177
	178	/* generate a random cookie */
	179	if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
	180	fatal("kex_send_kexinit: kex proposal too short");
	181	cookie = buffer_ptr(&kex->my);
	182	for (i = 0; i < KEX_COOKIE_LEN; i++) {
	183	if (i % 4 == 0)
ca75d7de	184	rnd = arc4random();
	185	cookie[i] = rnd;
	186	rnd >>= 8;
76bf34f1	187	}
a5c9ffdb	188	packet_start(SSH2_MSG_KEXINIT);
	189	packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
	190	packet_send();
	191	debug("SSH2_MSG_KEXINIT sent");
	192	kex->flags \|= KEX_INIT_SENT;
	193	}
2b87da3b	194
a5c9ffdb	195	void
7819b5c3	196	kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
a5c9ffdb	197	{
a5c9ffdb	198	char *ptr;
2ceb8101	199	u_int i, dlen;
a5c9ffdb	200	Kex kex = (Kex )ctxt;
94ec8c6b	201
a5c9ffdb	202	debug("SSH2_MSG_KEXINIT received");
7a37c112	203	if (kex == NULL)
7a37c112	204	fatal("kex_input_kexinit: no kex, cannot rekey");
94ec8c6b	205
a5c9ffdb	206	ptr = packet_get_raw(&dlen);
a5c9ffdb	207	buffer_append(&kex->peer, ptr, dlen);
94ec8c6b	208
bbb4cc1b	209	/* discard packet */
	210	for (i = 0; i < KEX_COOKIE_LEN; i++)
	211	packet_get_char();
	212	for (i = 0; i < PROPOSAL_MAX; i++)
	213	xfree(packet_get_string(NULL));
1169c3df	214	(void) packet_get_char();
1169c3df	215	(void) packet_get_int();
95500969	216	packet_check_eom();
bbb4cc1b	217
a5c9ffdb	218	kex_kexinit_finish(kex);
94ec8c6b	219	}
94ec8c6b	220
a5c9ffdb	221	Kex *
d8ee838b	222	kex_setup(char *proposal[PROPOSAL_MAX])
4f8c6159	223	{
a5c9ffdb	224	Kex *kex;
4f8c6159	225
52e3daed	226	kex = xcalloc(1, sizeof(*kex));
a5c9ffdb	227	buffer_init(&kex->peer);
	228	buffer_init(&kex->my);
	229	kex_prop2buf(&kex->my, proposal);
c422989b	230	kex->done = 0;
a5c9ffdb	231
a5c9ffdb	232	kex_send_kexinit(kex); /* we start */
9d726f16	233	kex_reset_dispatch();
7a37c112	234
a5c9ffdb	235	return kex;
a5c9ffdb	236	}
4f8c6159	237
396c147e	238	static void
a5c9ffdb	239	kex_kexinit_finish(Kex *kex)
	240	{
	241	if (!(kex->flags & KEX_INIT_SENT))
	242	kex_send_kexinit(kex);
	243
	244	kex_choose_conf(kex);
	245
98a58eda	246	if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
	247	kex->kex[kex->kex_type] != NULL) {
	248	(kex->kex[kex->kex_type])(kex);
	249	} else {
a5c9ffdb	250	fatal("Unsupported key exchange %d", kex->kex_type);
4f8c6159	251	}
4f8c6159	252	}
4f8c6159	253
396c147e	254	static void
4f8c6159	255	choose_enc(Enc enc, char client, char *server)
4f8c6159	256	{
cab80f75	257	char *name = match_list(client, server, NULL);
4f8c6159	258	if (name == NULL)
4f8c6159	259	fatal("no matching cipher found: client %s server %s", client, server);
3ee832e5	260	if ((enc->cipher = cipher_by_name(name)) == NULL)
94ec8c6b	261	fatal("matching cipher is not supported: %s", name);
4f8c6159	262	enc->name = name;
	263	enc->enabled = 0;
	264	enc->iv = NULL;
	265	enc->key = NULL;
3ee832e5	266	enc->key_len = cipher_keylen(enc->cipher);
3ee832e5	267	enc->block_size = cipher_blocksize(enc->cipher);
4f8c6159	268	}
a7137f6b	269
396c147e	270	static void
4f8c6159	271	choose_mac(Mac mac, char client, char *server)
4f8c6159	272	{
cab80f75	273	char *name = match_list(client, server, NULL);
4f8c6159	274	if (name == NULL)
4f8c6159	275	fatal("no matching mac found: client %s server %s", client, server);
b2552997	276	if (mac_init(mac, name) < 0)
4f8c6159	277	fatal("unsupported mac %s", name);
b2552997	278	/* truncate the key */
	279	if (datafellows & SSH_BUG_HMAC)
	280	mac->key_len = 16;
4f8c6159	281	mac->name = name;
4f8c6159	282	mac->key = NULL;
	283	mac->enabled = 0;
	284	}
a7137f6b	285
396c147e	286	static void
4f8c6159	287	choose_comp(Comp comp, char client, char *server)
4f8c6159	288	{
cab80f75	289	char *name = match_list(client, server, NULL);
4f8c6159	290	if (name == NULL)
4f8c6159	291	fatal("no matching comp found: client %s server %s", client, server);
07200973	292	if (strcmp(name, "zlib@openssh.com") == 0) {
	293	comp->type = COMP_DELAYED;
	294	} else if (strcmp(name, "zlib") == 0) {
	295	comp->type = COMP_ZLIB;
4f8c6159	296	} else if (strcmp(name, "none") == 0) {
07200973	297	comp->type = COMP_NONE;
4f8c6159	298	} else {
	299	fatal("unsupported comp %s", name);
	300	}
	301	comp->name = name;
	302	}
a7137f6b	303
396c147e	304	static void
4f8c6159	305	choose_kex(Kex k, char client, char *server)
4f8c6159	306	{
cab80f75	307	k->name = match_list(client, server, NULL);
4f8c6159	308	if (k->name == NULL)
4f8c6159	309	fatal("no kex alg");
94ec8c6b	310	if (strcmp(k->name, KEX_DH1) == 0) {
98a58eda	311	k->kex_type = KEX_DH_GRP1_SHA1;
47e5dc72	312	k->evp_md = EVP_sha1();
41e5bd9a	313	} else if (strcmp(k->name, KEX_DH14) == 0) {
41e5bd9a	314	k->kex_type = KEX_DH_GRP14_SHA1;
47e5dc72	315	k->evp_md = EVP_sha1();
47e5dc72	316	} else if (strcmp(k->name, KEX_DHGEX_SHA1) == 0) {
98a58eda	317	k->kex_type = KEX_DH_GEX_SHA1;
47e5dc72	318	k->evp_md = EVP_sha1();
30baf904	319	#if OPENSSL_VERSION_NUMBER >= 0x00907000L
2ff8003a	320	} else if (strcmp(k->name, KEX_DHGEX_SHA256) == 0) {
	321	k->kex_type = KEX_DH_GEX_SHA256;
	322	k->evp_md = evp_ssh_sha256();
30baf904	323	#endif
94ec8c6b	324	} else
4f8c6159	325	fatal("bad kex alg %s", k->name);
4f8c6159	326	}
47e5dc72	327
396c147e	328	static void
4f8c6159	329	choose_hostkeyalg(Kex k, char client, char *server)
4f8c6159	330	{
cab80f75	331	char *hostkeyalg = match_list(client, server, NULL);
fa08c86b	332	if (hostkeyalg == NULL)
4f8c6159	333	fatal("no hostkey alg");
fa08c86b	334	k->hostkey_type = key_type_from_name(hostkeyalg);
	335	if (k->hostkey_type == KEY_UNSPEC)
	336	fatal("bad hostkey alg '%s'", hostkeyalg);
eea39c02	337	xfree(hostkeyalg);
4f8c6159	338	}
4f8c6159	339
aff51935	340	static int
eed8e583	341	proposals_match(char my[PROPOSAL_MAX], char peer[PROPOSAL_MAX])
	342	{
	343	static int check[] = {
	344	PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
	345	};
	346	int *idx;
	347	char *p;
	348
	349	for (idx = &check[0]; *idx != -1; idx++) {
	350	if ((p = strchr(my[*idx], ',')) != NULL)
	351	*p = '\0';
	352	if ((p = strchr(peer[*idx], ',')) != NULL)
	353	*p = '\0';
	354	if (strcmp(my[idx], peer[idx]) != 0) {
	355	debug2("proposal mismatch: my %s peer %s",
	356	my[idx], peer[idx]);
	357	return (0);
	358	}
	359	}
	360	debug2("proposals match");
	361	return (1);
	362	}
	363
396c147e	364	static void
d1ac6175	365	kex_choose_conf(Kex *kex)
4f8c6159	366	{
d1ac6175	367	Newkeys *newkeys;
a5c9ffdb	368	char my, peer;
a5c9ffdb	369	char cprop, sprop;
d1ac6175	370	int nenc, nmac, ncomp;
2ceb8101	371	u_int mode, ctos, need;
eed8e583	372	int first_kex_follows, type;
4f8c6159	373
eed8e583	374	my = kex_buf2prop(&kex->my, NULL);
eed8e583	375	peer = kex_buf2prop(&kex->peer, &first_kex_follows);
a5c9ffdb	376
d1ac6175	377	if (kex->server) {
a5c9ffdb	378	cprop=peer;
	379	sprop=my;
	380	} else {
	381	cprop=my;
	382	sprop=peer;
	383	}
4f8c6159	384
c422989b	385	/* Algorithm Negotiation */
4f8c6159	386	for (mode = 0; mode < MODE_MAX; mode++) {
52e3daed	387	newkeys = xcalloc(1, sizeof(*newkeys));
c422989b	388	kex->newkeys[mode] = newkeys;
d1ac6175	389	ctos = (!kex->server && mode == MODE_OUT) \|\| (kex->server && mode == MODE_IN);
4f8c6159	390	nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
	391	nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
	392	ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
d1ac6175	393	choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
	394	choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
	395	choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
4f8c6159	396	debug("kex: %s %s %s %s",
4f8c6159	397	ctos ? "client->server" : "server->client",
d1ac6175	398	newkeys->enc.name,
	399	newkeys->mac.name,
	400	newkeys->comp.name);
4f8c6159	401	}
d1ac6175	402	choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
d1ac6175	403	choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
4f8c6159	404	sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
4f8c6159	405	need = 0;
4f8c6159	406	for (mode = 0; mode < MODE_MAX; mode++) {
c422989b	407	newkeys = kex->newkeys[mode];
3ee832e5	408	if (need < newkeys->enc.key_len)
	409	need = newkeys->enc.key_len;
	410	if (need < newkeys->enc.block_size)
	411	need = newkeys->enc.block_size;
d1ac6175	412	if (need < newkeys->mac.key_len)
d1ac6175	413	need = newkeys->mac.key_len;
4f8c6159	414	}
71276795	415	/* XXX need runden? */
d1ac6175	416	kex->we_need = need;
a5c9ffdb	417
eed8e583	418	/* ignore the next message if the proposals do not match */
aff51935	419	if (first_kex_follows && !proposals_match(my, peer) &&
4e2e5cfd	420	!(datafellows & SSH_BUG_FIRSTKEX)) {
eed8e583	421	type = packet_read();
	422	debug2("skipping next packet (type %u)", type);
	423	}
	424
a5c9ffdb	425	kex_prop_free(my);
a5c9ffdb	426	kex_prop_free(peer);
a5c9ffdb	427	}
a5c9ffdb	428
396c147e	429	static u_char *
47e5dc72	430	derive_key(Kex kex, int id, u_int need, u_char hash, u_int hashlen,
47e5dc72	431	BIGNUM *shared_secret)
a5c9ffdb	432	{
a5c9ffdb	433	Buffer b;
a5c9ffdb	434	EVP_MD_CTX md;
a5c9ffdb	435	char c = id;
2ceb8101	436	u_int have;
47e5dc72	437	int mdsz;
2ceb8101	438	u_char *digest;
56964485	439
47e5dc72	440	if ((mdsz = EVP_MD_size(kex->evp_md)) <= 0)
47e5dc72	441	fatal("bad kex md size %d", mdsz);
b4bbf172	442	digest = xmalloc(roundup(need, mdsz));
a5c9ffdb	443
	444	buffer_init(&b);
	445	buffer_put_bignum2(&b, shared_secret);
	446
c422989b	447	/* K1 = HASH(K \|\| H \|\| "A" \|\| session_id) */
47e5dc72	448	EVP_DigestInit(&md, kex->evp_md);
eef7adcb	449	if (!(datafellows & SSH_BUG_DERIVEKEY))
eef7adcb	450	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
47e5dc72	451	EVP_DigestUpdate(&md, hash, hashlen);
c422989b	452	EVP_DigestUpdate(&md, &c, 1);
d1ac6175	453	EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
a5c9ffdb	454	EVP_DigestFinal(&md, digest, NULL);
a5c9ffdb	455
c422989b	456	/*
	457	* expand key:
	458	* Kn = HASH(K \|\| H \|\| K1 \|\| K2 \|\| ... \|\| Kn-1)
	459	* Key = K1 \|\| K2 \|\| ... \|\| Kn
	460	*/
a5c9ffdb	461	for (have = mdsz; need > have; have += mdsz) {
47e5dc72	462	EVP_DigestInit(&md, kex->evp_md);
eef7adcb	463	if (!(datafellows & SSH_BUG_DERIVEKEY))
eef7adcb	464	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
47e5dc72	465	EVP_DigestUpdate(&md, hash, hashlen);
a5c9ffdb	466	EVP_DigestUpdate(&md, digest, have);
	467	EVP_DigestFinal(&md, digest + have, NULL);
	468	}
	469	buffer_free(&b);
	470	#ifdef DEBUG_KEX
	471	fprintf(stderr, "key '%c'== ", c);
	472	dump_digest("key", digest, need);
	473	#endif
	474	return digest;
4f8c6159	475	}
4f8c6159	476
c422989b	477	Newkeys *current_keys[MODE_MAX];
d1ac6175	478
cab80f75	479	#define NKEYS 6
a5c9ffdb	480	void
47e5dc72	481	kex_derive_keys(Kex kex, u_char hash, u_int hashlen, BIGNUM *shared_secret)
4f8c6159	482	{
1e3b8b07	483	u_char *keys[NKEYS];
2ceb8101	484	u_int i, mode, ctos;
4f8c6159	485
47e5dc72	486	for (i = 0; i < NKEYS; i++) {
	487	keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, hashlen,
	488	shared_secret);
	489	}
4f8c6159	490
a77673cc	491	debug2("kex_derive_keys");
4f8c6159	492	for (mode = 0; mode < MODE_MAX; mode++) {
c422989b	493	current_keys[mode] = kex->newkeys[mode];
c422989b	494	kex->newkeys[mode] = NULL;
a7137f6b	495	ctos = (!kex->server && mode == MODE_OUT) \|\|
a7137f6b	496	(kex->server && mode == MODE_IN);
c422989b	497	current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
	498	current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
	499	current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
4f8c6159	500	}
4f8c6159	501	}
a5c9ffdb	502
d1ac6175	503	Newkeys *
	504	kex_get_newkeys(int mode)
	505	{
c422989b	506	Newkeys *ret;
	507
	508	ret = current_keys[mode];
	509	current_keys[mode] = NULL;
	510	return ret;
d1ac6175	511	}
d1ac6175	512
8bbf1fa6	513	void
	514	derive_ssh1_session_id(BIGNUM host_modulus, BIGNUM server_modulus,
	515	u_int8_t cookie[8], u_int8_t id[16])
	516	{
	517	const EVP_MD *evp_md = EVP_md5();
	518	EVP_MD_CTX md;
	519	u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE];
	520	int len;
	521
	522	EVP_DigestInit(&md, evp_md);
	523
	524	len = BN_num_bytes(host_modulus);
2ceb8101	525	if (len < (512 / 8) \|\| (u_int)len > sizeof(nbuf))
8bbf1fa6	526	fatal("%s: bad host modulus (len %d)", __func__, len);
	527	BN_bn2bin(host_modulus, nbuf);
	528	EVP_DigestUpdate(&md, nbuf, len);
	529
	530	len = BN_num_bytes(server_modulus);
2ceb8101	531	if (len < (512 / 8) \|\| (u_int)len > sizeof(nbuf))
8bbf1fa6	532	fatal("%s: bad server modulus (len %d)", __func__, len);
	533	BN_bn2bin(server_modulus, nbuf);
	534	EVP_DigestUpdate(&md, nbuf, len);
	535
	536	EVP_DigestUpdate(&md, cookie, 8);
	537
59657003	538	EVP_DigestFinal(&md, obuf, NULL);
8bbf1fa6	539	memcpy(id, obuf, 16);
	540
	541	memset(nbuf, 0, sizeof(nbuf));
	542	memset(obuf, 0, sizeof(obuf));
	543	memset(&md, 0, sizeof(md));
	544	}
	545
a5c9ffdb	546	#if defined(DEBUG_KEX) \|\| defined(DEBUG_KEXDH)
	547	void
	548	dump_digest(char msg, u_char digest, int len)
	549	{
2ceb8101	550	u_int i;
a5c9ffdb	551
a5c9ffdb	552	fprintf(stderr, "%s\n", msg);
6aacefa7	553	for (i = 0; i< len; i++) {
a5c9ffdb	554	fprintf(stderr, "%02x", digest[i]);
	555	if (i%32 == 31)
	556	fprintf(stderr, "\n");
	557	else if (i%8 == 7)
	558	fprintf(stderr, " ");
	559	}
	560	fprintf(stderr, "\n");
	561	}
	562	#endif