[openssh.git] / kex.c

/* $OpenBSD: kex.c,v 1.71 2006/03/25 13:17:02 djm 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 <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

#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
c1cb7bae	1	/* $OpenBSD: kex.c,v 1.71 2006/03/25 13:17:02 djm 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
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
30baf904	47	#if OPENSSL_VERSION_NUMBER >= 0x00907000L
30baf904	48	# if defined(HAVE_EVP_SHA256)
13ff27b7	49	# define evp_ssh_sha256 EVP_sha256
30baf904	50	# else
2ff8003a	51	extern const EVP_MD *evp_ssh_sha256(void);
30baf904	52	# endif
b1f0c612	53	#endif
2ff8003a	54
396c147e	55	/* prototype */
	56	static void kex_kexinit_finish(Kex *);
	57	static void kex_choose_conf(Kex *);
a5c9ffdb	58
a5c9ffdb	59	/* put algorithm proposal into buffer */
396c147e	60	static void
a5c9ffdb	61	kex_prop2buf(Buffer b, char proposal[PROPOSAL_MAX])
4f8c6159	62	{
2ceb8101	63	u_int i;
a5c9ffdb	64
a5c9ffdb	65	buffer_clear(b);
76bf34f1	66	/*
	67	* add a dummy cookie, the cookie will be overwritten by
	68	* kex_send_kexinit(), each time a kexinit is set
	69	*/
	70	for (i = 0; i < KEX_COOKIE_LEN; i++)
	71	buffer_put_char(b, 0);
4f8c6159	72	for (i = 0; i < PROPOSAL_MAX; i++)
a5c9ffdb	73	buffer_put_cstring(b, proposal[i]);
	74	buffer_put_char(b, 0); /* first_kex_packet_follows */
	75	buffer_put_int(b, 0); /* uint32 reserved */
4f8c6159	76	}
4f8c6159	77
a5c9ffdb	78	/* parse buffer and return algorithm proposal */
396c147e	79	static char **
eed8e583	80	kex_buf2prop(Buffer raw, int first_kex_follows)
71276795	81	{
a5c9ffdb	82	Buffer b;
71276795	83	int i;
a5c9ffdb	84	char **proposal;
71276795	85
52e3daed	86	proposal = xcalloc(PROPOSAL_MAX, sizeof(char *));
a5c9ffdb	87
	88	buffer_init(&b);
	89	buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
71276795	90	/* skip cookie */
71276795	91	for (i = 0; i < KEX_COOKIE_LEN; i++)
a5c9ffdb	92	buffer_get_char(&b);
71276795	93	/* extract kex init proposal strings */
71276795	94	for (i = 0; i < PROPOSAL_MAX; i++) {
a5c9ffdb	95	proposal[i] = buffer_get_string(&b,NULL);
a5c9ffdb	96	debug2("kex_parse_kexinit: %s", proposal[i]);
71276795	97	}
a5c9ffdb	98	/* first kex follows / reserved */
a5c9ffdb	99	i = buffer_get_char(&b);
eed8e583	100	if (first_kex_follows != NULL)
eed8e583	101	*first_kex_follows = i;
a5c9ffdb	102	debug2("kex_parse_kexinit: first_kex_follows %d ", i);
	103	i = buffer_get_int(&b);
	104	debug2("kex_parse_kexinit: reserved %d ", i);
	105	buffer_free(&b);
	106	return proposal;
71276795	107	}
71276795	108
396c147e	109	static void
a5c9ffdb	110	kex_prop_free(char **proposal)
4f8c6159	111	{
2ceb8101	112	u_int i;
a5c9ffdb	113
	114	for (i = 0; i < PROPOSAL_MAX; i++)
	115	xfree(proposal[i]);
	116	xfree(proposal);
4f8c6159	117	}
4f8c6159	118
396c147e	119	static void
7819b5c3	120	kex_protocol_error(int type, u_int32_t seq, void *ctxt)
4f8c6159	121	{
7819b5c3	122	error("Hm, kex protocol error: type %d seq %u", type, seq);
a5c9ffdb	123	}
4f8c6159	124
396c147e	125	static void
9d726f16	126	kex_reset_dispatch(void)
7a37c112	127	{
6367063f	128	dispatch_range(SSH2_MSG_TRANSPORT_MIN,
6367063f	129	SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
9d726f16	130	dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
7a37c112	131	}
7a37c112	132
a5c9ffdb	133	void
d8ee838b	134	kex_finish(Kex *kex)
a5c9ffdb	135	{
9d726f16	136	kex_reset_dispatch();
d8ee838b	137
a5c9ffdb	138	packet_start(SSH2_MSG_NEWKEYS);
	139	packet_send();
	140	/* packet_write_wait(); */
	141	debug("SSH2_MSG_NEWKEYS sent");
4f8c6159	142
a77673cc	143	debug("expecting SSH2_MSG_NEWKEYS");
54a5250f	144	packet_read_expect(SSH2_MSG_NEWKEYS);
b967d870	145	packet_check_eom();
a5c9ffdb	146	debug("SSH2_MSG_NEWKEYS received");
a7ca6275	147
c422989b	148	kex->done = 1;
a5c9ffdb	149	buffer_clear(&kex->peer);
d1ac6175	150	/* buffer_clear(&kex->my); */
a5c9ffdb	151	kex->flags &= ~KEX_INIT_SENT;
a7ca6275	152	xfree(kex->name);
a7ca6275	153	kex->name = NULL;
4f8c6159	154	}
4f8c6159	155
a5c9ffdb	156	void
a5c9ffdb	157	kex_send_kexinit(Kex *kex)
94ec8c6b	158	{
ca75d7de	159	u_int32_t rnd = 0;
76bf34f1	160	u_char *cookie;
2ceb8101	161	u_int i;
76bf34f1	162
7a37c112	163	if (kex == NULL) {
	164	error("kex_send_kexinit: no kex, cannot rekey");
	165	return;
	166	}
d8ee838b	167	if (kex->flags & KEX_INIT_SENT) {
	168	debug("KEX_INIT_SENT");
	169	return;
	170	}
c422989b	171	kex->done = 0;
76bf34f1	172
	173	/* generate a random cookie */
	174	if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
	175	fatal("kex_send_kexinit: kex proposal too short");
	176	cookie = buffer_ptr(&kex->my);
	177	for (i = 0; i < KEX_COOKIE_LEN; i++) {
	178	if (i % 4 == 0)
ca75d7de	179	rnd = arc4random();
	180	cookie[i] = rnd;
	181	rnd >>= 8;
76bf34f1	182	}
a5c9ffdb	183	packet_start(SSH2_MSG_KEXINIT);
	184	packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
	185	packet_send();
	186	debug("SSH2_MSG_KEXINIT sent");
	187	kex->flags \|= KEX_INIT_SENT;
	188	}
2b87da3b	189
a5c9ffdb	190	void
7819b5c3	191	kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
a5c9ffdb	192	{
a5c9ffdb	193	char *ptr;
2ceb8101	194	u_int i, dlen;
a5c9ffdb	195	Kex kex = (Kex )ctxt;
94ec8c6b	196
a5c9ffdb	197	debug("SSH2_MSG_KEXINIT received");
7a37c112	198	if (kex == NULL)
7a37c112	199	fatal("kex_input_kexinit: no kex, cannot rekey");
94ec8c6b	200
a5c9ffdb	201	ptr = packet_get_raw(&dlen);
a5c9ffdb	202	buffer_append(&kex->peer, ptr, dlen);
94ec8c6b	203
bbb4cc1b	204	/* discard packet */
	205	for (i = 0; i < KEX_COOKIE_LEN; i++)
	206	packet_get_char();
	207	for (i = 0; i < PROPOSAL_MAX; i++)
	208	xfree(packet_get_string(NULL));
1169c3df	209	(void) packet_get_char();
1169c3df	210	(void) packet_get_int();
95500969	211	packet_check_eom();
bbb4cc1b	212
a5c9ffdb	213	kex_kexinit_finish(kex);
94ec8c6b	214	}
94ec8c6b	215
a5c9ffdb	216	Kex *
d8ee838b	217	kex_setup(char *proposal[PROPOSAL_MAX])
4f8c6159	218	{
a5c9ffdb	219	Kex *kex;
4f8c6159	220
52e3daed	221	kex = xcalloc(1, sizeof(*kex));
a5c9ffdb	222	buffer_init(&kex->peer);
	223	buffer_init(&kex->my);
	224	kex_prop2buf(&kex->my, proposal);
c422989b	225	kex->done = 0;
a5c9ffdb	226
a5c9ffdb	227	kex_send_kexinit(kex); /* we start */
9d726f16	228	kex_reset_dispatch();
7a37c112	229
a5c9ffdb	230	return kex;
a5c9ffdb	231	}
4f8c6159	232
396c147e	233	static void
a5c9ffdb	234	kex_kexinit_finish(Kex *kex)
	235	{
	236	if (!(kex->flags & KEX_INIT_SENT))
	237	kex_send_kexinit(kex);
	238
	239	kex_choose_conf(kex);
	240
98a58eda	241	if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
	242	kex->kex[kex->kex_type] != NULL) {
	243	(kex->kex[kex->kex_type])(kex);
	244	} else {
a5c9ffdb	245	fatal("Unsupported key exchange %d", kex->kex_type);
4f8c6159	246	}
4f8c6159	247	}
4f8c6159	248
396c147e	249	static void
4f8c6159	250	choose_enc(Enc enc, char client, char *server)
4f8c6159	251	{
cab80f75	252	char *name = match_list(client, server, NULL);
4f8c6159	253	if (name == NULL)
4f8c6159	254	fatal("no matching cipher found: client %s server %s", client, server);
3ee832e5	255	if ((enc->cipher = cipher_by_name(name)) == NULL)
94ec8c6b	256	fatal("matching cipher is not supported: %s", name);
4f8c6159	257	enc->name = name;
	258	enc->enabled = 0;
	259	enc->iv = NULL;
	260	enc->key = NULL;
3ee832e5	261	enc->key_len = cipher_keylen(enc->cipher);
3ee832e5	262	enc->block_size = cipher_blocksize(enc->cipher);
4f8c6159	263	}
a7137f6b	264
396c147e	265	static void
4f8c6159	266	choose_mac(Mac mac, char client, char *server)
4f8c6159	267	{
cab80f75	268	char *name = match_list(client, server, NULL);
4f8c6159	269	if (name == NULL)
4f8c6159	270	fatal("no matching mac found: client %s server %s", client, server);
b2552997	271	if (mac_init(mac, name) < 0)
4f8c6159	272	fatal("unsupported mac %s", name);
b2552997	273	/* truncate the key */
	274	if (datafellows & SSH_BUG_HMAC)
	275	mac->key_len = 16;
4f8c6159	276	mac->name = name;
4f8c6159	277	mac->key = NULL;
	278	mac->enabled = 0;
	279	}
a7137f6b	280
396c147e	281	static void
4f8c6159	282	choose_comp(Comp comp, char client, char *server)
4f8c6159	283	{
cab80f75	284	char *name = match_list(client, server, NULL);
4f8c6159	285	if (name == NULL)
4f8c6159	286	fatal("no matching comp found: client %s server %s", client, server);
07200973	287	if (strcmp(name, "zlib@openssh.com") == 0) {
	288	comp->type = COMP_DELAYED;
	289	} else if (strcmp(name, "zlib") == 0) {
	290	comp->type = COMP_ZLIB;
4f8c6159	291	} else if (strcmp(name, "none") == 0) {
07200973	292	comp->type = COMP_NONE;
4f8c6159	293	} else {
	294	fatal("unsupported comp %s", name);
	295	}
	296	comp->name = name;
	297	}
a7137f6b	298
396c147e	299	static void
4f8c6159	300	choose_kex(Kex k, char client, char *server)
4f8c6159	301	{
cab80f75	302	k->name = match_list(client, server, NULL);
4f8c6159	303	if (k->name == NULL)
4f8c6159	304	fatal("no kex alg");
94ec8c6b	305	if (strcmp(k->name, KEX_DH1) == 0) {
98a58eda	306	k->kex_type = KEX_DH_GRP1_SHA1;
47e5dc72	307	k->evp_md = EVP_sha1();
41e5bd9a	308	} else if (strcmp(k->name, KEX_DH14) == 0) {
41e5bd9a	309	k->kex_type = KEX_DH_GRP14_SHA1;
47e5dc72	310	k->evp_md = EVP_sha1();
47e5dc72	311	} else if (strcmp(k->name, KEX_DHGEX_SHA1) == 0) {
98a58eda	312	k->kex_type = KEX_DH_GEX_SHA1;
47e5dc72	313	k->evp_md = EVP_sha1();
30baf904	314	#if OPENSSL_VERSION_NUMBER >= 0x00907000L
2ff8003a	315	} else if (strcmp(k->name, KEX_DHGEX_SHA256) == 0) {
	316	k->kex_type = KEX_DH_GEX_SHA256;
	317	k->evp_md = evp_ssh_sha256();
30baf904	318	#endif
94ec8c6b	319	} else
4f8c6159	320	fatal("bad kex alg %s", k->name);
4f8c6159	321	}
47e5dc72	322
396c147e	323	static void
4f8c6159	324	choose_hostkeyalg(Kex k, char client, char *server)
4f8c6159	325	{
cab80f75	326	char *hostkeyalg = match_list(client, server, NULL);
fa08c86b	327	if (hostkeyalg == NULL)
4f8c6159	328	fatal("no hostkey alg");
fa08c86b	329	k->hostkey_type = key_type_from_name(hostkeyalg);
	330	if (k->hostkey_type == KEY_UNSPEC)
	331	fatal("bad hostkey alg '%s'", hostkeyalg);
eea39c02	332	xfree(hostkeyalg);
4f8c6159	333	}
4f8c6159	334
aff51935	335	static int
eed8e583	336	proposals_match(char my[PROPOSAL_MAX], char peer[PROPOSAL_MAX])
	337	{
	338	static int check[] = {
	339	PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
	340	};
	341	int *idx;
	342	char *p;
	343
	344	for (idx = &check[0]; *idx != -1; idx++) {
	345	if ((p = strchr(my[*idx], ',')) != NULL)
	346	*p = '\0';
	347	if ((p = strchr(peer[*idx], ',')) != NULL)
	348	*p = '\0';
	349	if (strcmp(my[idx], peer[idx]) != 0) {
	350	debug2("proposal mismatch: my %s peer %s",
	351	my[idx], peer[idx]);
	352	return (0);
	353	}
	354	}
	355	debug2("proposals match");
	356	return (1);
	357	}
	358
396c147e	359	static void
d1ac6175	360	kex_choose_conf(Kex *kex)
4f8c6159	361	{
d1ac6175	362	Newkeys *newkeys;
a5c9ffdb	363	char my, peer;
a5c9ffdb	364	char cprop, sprop;
d1ac6175	365	int nenc, nmac, ncomp;
2ceb8101	366	u_int mode, ctos, need;
eed8e583	367	int first_kex_follows, type;
4f8c6159	368
eed8e583	369	my = kex_buf2prop(&kex->my, NULL);
eed8e583	370	peer = kex_buf2prop(&kex->peer, &first_kex_follows);
a5c9ffdb	371
d1ac6175	372	if (kex->server) {
a5c9ffdb	373	cprop=peer;
	374	sprop=my;
	375	} else {
	376	cprop=my;
	377	sprop=peer;
	378	}
4f8c6159	379
c422989b	380	/* Algorithm Negotiation */
4f8c6159	381	for (mode = 0; mode < MODE_MAX; mode++) {
52e3daed	382	newkeys = xcalloc(1, sizeof(*newkeys));
c422989b	383	kex->newkeys[mode] = newkeys;
d1ac6175	384	ctos = (!kex->server && mode == MODE_OUT) \|\| (kex->server && mode == MODE_IN);
4f8c6159	385	nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
	386	nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
	387	ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
d1ac6175	388	choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
	389	choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
	390	choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
4f8c6159	391	debug("kex: %s %s %s %s",
4f8c6159	392	ctos ? "client->server" : "server->client",
d1ac6175	393	newkeys->enc.name,
	394	newkeys->mac.name,
	395	newkeys->comp.name);
4f8c6159	396	}
d1ac6175	397	choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
d1ac6175	398	choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
4f8c6159	399	sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
4f8c6159	400	need = 0;
4f8c6159	401	for (mode = 0; mode < MODE_MAX; mode++) {
c422989b	402	newkeys = kex->newkeys[mode];
3ee832e5	403	if (need < newkeys->enc.key_len)
	404	need = newkeys->enc.key_len;
	405	if (need < newkeys->enc.block_size)
	406	need = newkeys->enc.block_size;
d1ac6175	407	if (need < newkeys->mac.key_len)
d1ac6175	408	need = newkeys->mac.key_len;
4f8c6159	409	}
71276795	410	/* XXX need runden? */
d1ac6175	411	kex->we_need = need;
a5c9ffdb	412
eed8e583	413	/* ignore the next message if the proposals do not match */
aff51935	414	if (first_kex_follows && !proposals_match(my, peer) &&
4e2e5cfd	415	!(datafellows & SSH_BUG_FIRSTKEX)) {
eed8e583	416	type = packet_read();
	417	debug2("skipping next packet (type %u)", type);
	418	}
	419
a5c9ffdb	420	kex_prop_free(my);
a5c9ffdb	421	kex_prop_free(peer);
a5c9ffdb	422	}
a5c9ffdb	423
396c147e	424	static u_char *
47e5dc72	425	derive_key(Kex kex, int id, u_int need, u_char hash, u_int hashlen,
47e5dc72	426	BIGNUM *shared_secret)
a5c9ffdb	427	{
a5c9ffdb	428	Buffer b;
a5c9ffdb	429	EVP_MD_CTX md;
a5c9ffdb	430	char c = id;
2ceb8101	431	u_int have;
47e5dc72	432	int mdsz;
2ceb8101	433	u_char *digest;
56964485	434
47e5dc72	435	if ((mdsz = EVP_MD_size(kex->evp_md)) <= 0)
47e5dc72	436	fatal("bad kex md size %d", mdsz);
b4bbf172	437	digest = xmalloc(roundup(need, mdsz));
a5c9ffdb	438
	439	buffer_init(&b);
	440	buffer_put_bignum2(&b, shared_secret);
	441
c422989b	442	/* K1 = HASH(K \|\| H \|\| "A" \|\| session_id) */
47e5dc72	443	EVP_DigestInit(&md, kex->evp_md);
eef7adcb	444	if (!(datafellows & SSH_BUG_DERIVEKEY))
eef7adcb	445	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
47e5dc72	446	EVP_DigestUpdate(&md, hash, hashlen);
c422989b	447	EVP_DigestUpdate(&md, &c, 1);
d1ac6175	448	EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
a5c9ffdb	449	EVP_DigestFinal(&md, digest, NULL);
a5c9ffdb	450
c422989b	451	/*
	452	* expand key:
	453	* Kn = HASH(K \|\| H \|\| K1 \|\| K2 \|\| ... \|\| Kn-1)
	454	* Key = K1 \|\| K2 \|\| ... \|\| Kn
	455	*/
a5c9ffdb	456	for (have = mdsz; need > have; have += mdsz) {
47e5dc72	457	EVP_DigestInit(&md, kex->evp_md);
eef7adcb	458	if (!(datafellows & SSH_BUG_DERIVEKEY))
eef7adcb	459	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
47e5dc72	460	EVP_DigestUpdate(&md, hash, hashlen);
a5c9ffdb	461	EVP_DigestUpdate(&md, digest, have);
	462	EVP_DigestFinal(&md, digest + have, NULL);
	463	}
	464	buffer_free(&b);
	465	#ifdef DEBUG_KEX
	466	fprintf(stderr, "key '%c'== ", c);
	467	dump_digest("key", digest, need);
	468	#endif
	469	return digest;
4f8c6159	470	}
4f8c6159	471
c422989b	472	Newkeys *current_keys[MODE_MAX];
d1ac6175	473
cab80f75	474	#define NKEYS 6
a5c9ffdb	475	void
47e5dc72	476	kex_derive_keys(Kex kex, u_char hash, u_int hashlen, BIGNUM *shared_secret)
4f8c6159	477	{
1e3b8b07	478	u_char *keys[NKEYS];
2ceb8101	479	u_int i, mode, ctos;
4f8c6159	480
47e5dc72	481	for (i = 0; i < NKEYS; i++) {
	482	keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, hashlen,
	483	shared_secret);
	484	}
4f8c6159	485
a77673cc	486	debug2("kex_derive_keys");
4f8c6159	487	for (mode = 0; mode < MODE_MAX; mode++) {
c422989b	488	current_keys[mode] = kex->newkeys[mode];
c422989b	489	kex->newkeys[mode] = NULL;
a7137f6b	490	ctos = (!kex->server && mode == MODE_OUT) \|\|
a7137f6b	491	(kex->server && mode == MODE_IN);
c422989b	492	current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
	493	current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
	494	current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
4f8c6159	495	}
4f8c6159	496	}
a5c9ffdb	497
d1ac6175	498	Newkeys *
	499	kex_get_newkeys(int mode)
	500	{
c422989b	501	Newkeys *ret;
	502
	503	ret = current_keys[mode];
	504	current_keys[mode] = NULL;
	505	return ret;
d1ac6175	506	}
d1ac6175	507
8bbf1fa6	508	void
	509	derive_ssh1_session_id(BIGNUM host_modulus, BIGNUM server_modulus,
	510	u_int8_t cookie[8], u_int8_t id[16])
	511	{
	512	const EVP_MD *evp_md = EVP_md5();
	513	EVP_MD_CTX md;
	514	u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE];
	515	int len;
	516
	517	EVP_DigestInit(&md, evp_md);
	518
	519	len = BN_num_bytes(host_modulus);
2ceb8101	520	if (len < (512 / 8) \|\| (u_int)len > sizeof(nbuf))
8bbf1fa6	521	fatal("%s: bad host modulus (len %d)", __func__, len);
	522	BN_bn2bin(host_modulus, nbuf);
	523	EVP_DigestUpdate(&md, nbuf, len);
	524
	525	len = BN_num_bytes(server_modulus);
2ceb8101	526	if (len < (512 / 8) \|\| (u_int)len > sizeof(nbuf))
8bbf1fa6	527	fatal("%s: bad server modulus (len %d)", __func__, len);
	528	BN_bn2bin(server_modulus, nbuf);
	529	EVP_DigestUpdate(&md, nbuf, len);
	530
	531	EVP_DigestUpdate(&md, cookie, 8);
	532
59657003	533	EVP_DigestFinal(&md, obuf, NULL);
8bbf1fa6	534	memcpy(id, obuf, 16);
	535
	536	memset(nbuf, 0, sizeof(nbuf));
	537	memset(obuf, 0, sizeof(obuf));
	538	memset(&md, 0, sizeof(md));
	539	}
	540
a5c9ffdb	541	#if defined(DEBUG_KEX) \|\| defined(DEBUG_KEXDH)
	542	void
	543	dump_digest(char msg, u_char digest, int len)
	544	{
2ceb8101	545	u_int i;
a5c9ffdb	546
a5c9ffdb	547	fprintf(stderr, "%s\n", msg);
6aacefa7	548	for (i = 0; i< len; i++) {
a5c9ffdb	549	fprintf(stderr, "%02x", digest[i]);
	550	if (i%32 == 31)
	551	fprintf(stderr, "\n");
	552	else if (i%8 == 7)
	553	fprintf(stderr, " ");
	554	}
	555	fprintf(stderr, "\n");
	556	}
	557	#endif