[openssh.git] / kex.c

/* $OpenBSD: kex.c,v 1.82 2009/10/24 11:13:54 andreas 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 <signal.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <openssl/crypto.h>

#include "xmalloc.h"
#include "ssh2.h"
#include "buffer.h"
#include "packet.h"
#include "compat.h"
#include "cipher.h"
#include "key.h"
#include "kex.h"
#include "log.h"
#include "mac.h"
#include "match.h"
#include "dispatch.h"
#include "monitor.h"
#include "roaming.h"

#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;
	u_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 %u ", 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);
}

/* ARGSUSED */
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;
}

/* ARGSUSED */
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_setup(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("Unable to negotiate a key exchange method");
	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;
	}

	/* Check whether server offers roaming */
	if (!kex->server) {
		char *roaming;
		roaming = match_list(KEX_RESUME, peer[PROPOSAL_KEX_ALGS], NULL);
		if (roaming) {
			kex->roaming = 1;
			xfree(roaming);
		}
	}

	/* 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
d8b0d145	1	/* $OpenBSD: kex.c,v 1.82 2009/10/24 11:13:54 andreas 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
31652869	30	#include <signal.h>
24436b92	31	#include <stdarg.h>
cf851879	32	#include <stdio.h>
ffa517a8	33	#include <stdlib.h>
00146caa	34	#include <string.h>
00146caa	35
31652869	36	#include <openssl/crypto.h>
31652869	37
42f11eb2	38	#include "xmalloc.h"
31652869	39	#include "ssh2.h"
42f11eb2	40	#include "buffer.h"
42f11eb2	41	#include "packet.h"
	42	#include "compat.h"
	43	#include "cipher.h"
fa08c86b	44	#include "key.h"
31652869	45	#include "kex.h"
42f11eb2	46	#include "log.h"
b2552997	47	#include "mac.h"
cab80f75	48	#include "match.h"
a5c9ffdb	49	#include "dispatch.h"
1853d1ef	50	#include "monitor.h"
d8b0d145	51	#include "roaming.h"
4f8c6159	52
30baf904	53	#if OPENSSL_VERSION_NUMBER >= 0x00907000L
30baf904	54	# if defined(HAVE_EVP_SHA256)
13ff27b7	55	# define evp_ssh_sha256 EVP_sha256
30baf904	56	# else
2ff8003a	57	extern const EVP_MD *evp_ssh_sha256(void);
30baf904	58	# endif
b1f0c612	59	#endif
2ff8003a	60
396c147e	61	/* prototype */
	62	static void kex_kexinit_finish(Kex *);
	63	static void kex_choose_conf(Kex *);
a5c9ffdb	64
a5c9ffdb	65	/* put algorithm proposal into buffer */
396c147e	66	static void
a5c9ffdb	67	kex_prop2buf(Buffer b, char proposal[PROPOSAL_MAX])
4f8c6159	68	{
2ceb8101	69	u_int i;
a5c9ffdb	70
a5c9ffdb	71	buffer_clear(b);
76bf34f1	72	/*
	73	* add a dummy cookie, the cookie will be overwritten by
	74	* kex_send_kexinit(), each time a kexinit is set
	75	*/
	76	for (i = 0; i < KEX_COOKIE_LEN; i++)
	77	buffer_put_char(b, 0);
4f8c6159	78	for (i = 0; i < PROPOSAL_MAX; i++)
a5c9ffdb	79	buffer_put_cstring(b, proposal[i]);
	80	buffer_put_char(b, 0); /* first_kex_packet_follows */
	81	buffer_put_int(b, 0); /* uint32 reserved */
4f8c6159	82	}
4f8c6159	83
a5c9ffdb	84	/* parse buffer and return algorithm proposal */
396c147e	85	static char **
eed8e583	86	kex_buf2prop(Buffer raw, int first_kex_follows)
71276795	87	{
a5c9ffdb	88	Buffer b;
68525040	89	u_int i;
a5c9ffdb	90	char **proposal;
71276795	91
52e3daed	92	proposal = xcalloc(PROPOSAL_MAX, sizeof(char *));
a5c9ffdb	93
	94	buffer_init(&b);
	95	buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
71276795	96	/* skip cookie */
71276795	97	for (i = 0; i < KEX_COOKIE_LEN; i++)
a5c9ffdb	98	buffer_get_char(&b);
71276795	99	/* extract kex init proposal strings */
71276795	100	for (i = 0; i < PROPOSAL_MAX; i++) {
a5c9ffdb	101	proposal[i] = buffer_get_string(&b,NULL);
a5c9ffdb	102	debug2("kex_parse_kexinit: %s", proposal[i]);
71276795	103	}
a5c9ffdb	104	/* first kex follows / reserved */
a5c9ffdb	105	i = buffer_get_char(&b);
eed8e583	106	if (first_kex_follows != NULL)
eed8e583	107	*first_kex_follows = i;
a5c9ffdb	108	debug2("kex_parse_kexinit: first_kex_follows %d ", i);
a5c9ffdb	109	i = buffer_get_int(&b);
68525040	110	debug2("kex_parse_kexinit: reserved %u ", i);
a5c9ffdb	111	buffer_free(&b);
a5c9ffdb	112	return proposal;
71276795	113	}
71276795	114
396c147e	115	static void
a5c9ffdb	116	kex_prop_free(char **proposal)
4f8c6159	117	{
2ceb8101	118	u_int i;
a5c9ffdb	119
	120	for (i = 0; i < PROPOSAL_MAX; i++)
	121	xfree(proposal[i]);
	122	xfree(proposal);
4f8c6159	123	}
4f8c6159	124
68525040	125	/* ARGSUSED */
396c147e	126	static void
7819b5c3	127	kex_protocol_error(int type, u_int32_t seq, void *ctxt)
4f8c6159	128	{
7819b5c3	129	error("Hm, kex protocol error: type %d seq %u", type, seq);
a5c9ffdb	130	}
4f8c6159	131
396c147e	132	static void
9d726f16	133	kex_reset_dispatch(void)
7a37c112	134	{
6367063f	135	dispatch_range(SSH2_MSG_TRANSPORT_MIN,
6367063f	136	SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
9d726f16	137	dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
7a37c112	138	}
7a37c112	139
a5c9ffdb	140	void
d8ee838b	141	kex_finish(Kex *kex)
a5c9ffdb	142	{
9d726f16	143	kex_reset_dispatch();
d8ee838b	144
a5c9ffdb	145	packet_start(SSH2_MSG_NEWKEYS);
	146	packet_send();
	147	/* packet_write_wait(); */
	148	debug("SSH2_MSG_NEWKEYS sent");
4f8c6159	149
a77673cc	150	debug("expecting SSH2_MSG_NEWKEYS");
54a5250f	151	packet_read_expect(SSH2_MSG_NEWKEYS);
b967d870	152	packet_check_eom();
a5c9ffdb	153	debug("SSH2_MSG_NEWKEYS received");
a7ca6275	154
c422989b	155	kex->done = 1;
a5c9ffdb	156	buffer_clear(&kex->peer);
d1ac6175	157	/* buffer_clear(&kex->my); */
a5c9ffdb	158	kex->flags &= ~KEX_INIT_SENT;
a7ca6275	159	xfree(kex->name);
a7ca6275	160	kex->name = NULL;
4f8c6159	161	}
4f8c6159	162
a5c9ffdb	163	void
a5c9ffdb	164	kex_send_kexinit(Kex *kex)
94ec8c6b	165	{
ca75d7de	166	u_int32_t rnd = 0;
76bf34f1	167	u_char *cookie;
2ceb8101	168	u_int i;
76bf34f1	169
7a37c112	170	if (kex == NULL) {
	171	error("kex_send_kexinit: no kex, cannot rekey");
	172	return;
	173	}
d8ee838b	174	if (kex->flags & KEX_INIT_SENT) {
	175	debug("KEX_INIT_SENT");
	176	return;
	177	}
c422989b	178	kex->done = 0;
76bf34f1	179
	180	/* generate a random cookie */
	181	if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
	182	fatal("kex_send_kexinit: kex proposal too short");
	183	cookie = buffer_ptr(&kex->my);
	184	for (i = 0; i < KEX_COOKIE_LEN; i++) {
	185	if (i % 4 == 0)
ca75d7de	186	rnd = arc4random();
	187	cookie[i] = rnd;
	188	rnd >>= 8;
76bf34f1	189	}
a5c9ffdb	190	packet_start(SSH2_MSG_KEXINIT);
	191	packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
	192	packet_send();
	193	debug("SSH2_MSG_KEXINIT sent");
	194	kex->flags \|= KEX_INIT_SENT;
	195	}
2b87da3b	196
68525040	197	/* ARGSUSED */
a5c9ffdb	198	void
7819b5c3	199	kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
a5c9ffdb	200	{
a5c9ffdb	201	char *ptr;
2ceb8101	202	u_int i, dlen;
a5c9ffdb	203	Kex kex = (Kex )ctxt;
94ec8c6b	204
a5c9ffdb	205	debug("SSH2_MSG_KEXINIT received");
7a37c112	206	if (kex == NULL)
7a37c112	207	fatal("kex_input_kexinit: no kex, cannot rekey");
94ec8c6b	208
a5c9ffdb	209	ptr = packet_get_raw(&dlen);
a5c9ffdb	210	buffer_append(&kex->peer, ptr, dlen);
94ec8c6b	211
bbb4cc1b	212	/* discard packet */
	213	for (i = 0; i < KEX_COOKIE_LEN; i++)
	214	packet_get_char();
	215	for (i = 0; i < PROPOSAL_MAX; i++)
	216	xfree(packet_get_string(NULL));
1169c3df	217	(void) packet_get_char();
1169c3df	218	(void) packet_get_int();
95500969	219	packet_check_eom();
bbb4cc1b	220
a5c9ffdb	221	kex_kexinit_finish(kex);
94ec8c6b	222	}
94ec8c6b	223
a5c9ffdb	224	Kex *
d8ee838b	225	kex_setup(char *proposal[PROPOSAL_MAX])
4f8c6159	226	{
a5c9ffdb	227	Kex *kex;
4f8c6159	228
52e3daed	229	kex = xcalloc(1, sizeof(*kex));
a5c9ffdb	230	buffer_init(&kex->peer);
	231	buffer_init(&kex->my);
	232	kex_prop2buf(&kex->my, proposal);
c422989b	233	kex->done = 0;
a5c9ffdb	234
a5c9ffdb	235	kex_send_kexinit(kex); /* we start */
9d726f16	236	kex_reset_dispatch();
7a37c112	237
a5c9ffdb	238	return kex;
a5c9ffdb	239	}
4f8c6159	240
396c147e	241	static void
a5c9ffdb	242	kex_kexinit_finish(Kex *kex)
	243	{
	244	if (!(kex->flags & KEX_INIT_SENT))
	245	kex_send_kexinit(kex);
	246
	247	kex_choose_conf(kex);
	248
98a58eda	249	if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
	250	kex->kex[kex->kex_type] != NULL) {
	251	(kex->kex[kex->kex_type])(kex);
	252	} else {
a5c9ffdb	253	fatal("Unsupported key exchange %d", kex->kex_type);
4f8c6159	254	}
4f8c6159	255	}
4f8c6159	256
396c147e	257	static void
4f8c6159	258	choose_enc(Enc enc, char client, char *server)
4f8c6159	259	{
cab80f75	260	char *name = match_list(client, server, NULL);
4f8c6159	261	if (name == NULL)
68525040	262	fatal("no matching cipher found: client %s server %s",
68525040	263	client, server);
3ee832e5	264	if ((enc->cipher = cipher_by_name(name)) == NULL)
94ec8c6b	265	fatal("matching cipher is not supported: %s", name);
4f8c6159	266	enc->name = name;
	267	enc->enabled = 0;
	268	enc->iv = NULL;
	269	enc->key = NULL;
3ee832e5	270	enc->key_len = cipher_keylen(enc->cipher);
3ee832e5	271	enc->block_size = cipher_blocksize(enc->cipher);
4f8c6159	272	}
a7137f6b	273
396c147e	274	static void
4f8c6159	275	choose_mac(Mac mac, char client, char *server)
4f8c6159	276	{
cab80f75	277	char *name = match_list(client, server, NULL);
4f8c6159	278	if (name == NULL)
68525040	279	fatal("no matching mac found: client %s server %s",
68525040	280	client, server);
a3de8da1	281	if (mac_setup(mac, name) < 0)
4f8c6159	282	fatal("unsupported mac %s", name);
b2552997	283	/* truncate the key */
	284	if (datafellows & SSH_BUG_HMAC)
	285	mac->key_len = 16;
4f8c6159	286	mac->name = name;
4f8c6159	287	mac->key = NULL;
	288	mac->enabled = 0;
	289	}
a7137f6b	290
396c147e	291	static void
4f8c6159	292	choose_comp(Comp comp, char client, char *server)
4f8c6159	293	{
cab80f75	294	char *name = match_list(client, server, NULL);
4f8c6159	295	if (name == NULL)
4f8c6159	296	fatal("no matching comp found: client %s server %s", client, server);
07200973	297	if (strcmp(name, "zlib@openssh.com") == 0) {
	298	comp->type = COMP_DELAYED;
	299	} else if (strcmp(name, "zlib") == 0) {
	300	comp->type = COMP_ZLIB;
4f8c6159	301	} else if (strcmp(name, "none") == 0) {
07200973	302	comp->type = COMP_NONE;
4f8c6159	303	} else {
	304	fatal("unsupported comp %s", name);
	305	}
	306	comp->name = name;
	307	}
a7137f6b	308
396c147e	309	static void
4f8c6159	310	choose_kex(Kex k, char client, char *server)
4f8c6159	311	{
cab80f75	312	k->name = match_list(client, server, NULL);
4f8c6159	313	if (k->name == NULL)
68525040	314	fatal("Unable to negotiate a key exchange method");
94ec8c6b	315	if (strcmp(k->name, KEX_DH1) == 0) {
98a58eda	316	k->kex_type = KEX_DH_GRP1_SHA1;
47e5dc72	317	k->evp_md = EVP_sha1();
41e5bd9a	318	} else if (strcmp(k->name, KEX_DH14) == 0) {
41e5bd9a	319	k->kex_type = KEX_DH_GRP14_SHA1;
47e5dc72	320	k->evp_md = EVP_sha1();
47e5dc72	321	} else if (strcmp(k->name, KEX_DHGEX_SHA1) == 0) {
98a58eda	322	k->kex_type = KEX_DH_GEX_SHA1;
47e5dc72	323	k->evp_md = EVP_sha1();
30baf904	324	#if OPENSSL_VERSION_NUMBER >= 0x00907000L
2ff8003a	325	} else if (strcmp(k->name, KEX_DHGEX_SHA256) == 0) {
	326	k->kex_type = KEX_DH_GEX_SHA256;
	327	k->evp_md = evp_ssh_sha256();
30baf904	328	#endif
94ec8c6b	329	} else
4f8c6159	330	fatal("bad kex alg %s", k->name);
4f8c6159	331	}
47e5dc72	332
396c147e	333	static void
4f8c6159	334	choose_hostkeyalg(Kex k, char client, char *server)
4f8c6159	335	{
cab80f75	336	char *hostkeyalg = match_list(client, server, NULL);
fa08c86b	337	if (hostkeyalg == NULL)
4f8c6159	338	fatal("no hostkey alg");
fa08c86b	339	k->hostkey_type = key_type_from_name(hostkeyalg);
	340	if (k->hostkey_type == KEY_UNSPEC)
	341	fatal("bad hostkey alg '%s'", hostkeyalg);
eea39c02	342	xfree(hostkeyalg);
4f8c6159	343	}
4f8c6159	344
aff51935	345	static int
eed8e583	346	proposals_match(char my[PROPOSAL_MAX], char peer[PROPOSAL_MAX])
	347	{
	348	static int check[] = {
	349	PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
	350	};
	351	int *idx;
	352	char *p;
	353
	354	for (idx = &check[0]; *idx != -1; idx++) {
	355	if ((p = strchr(my[*idx], ',')) != NULL)
	356	*p = '\0';
	357	if ((p = strchr(peer[*idx], ',')) != NULL)
	358	*p = '\0';
	359	if (strcmp(my[idx], peer[idx]) != 0) {
	360	debug2("proposal mismatch: my %s peer %s",
	361	my[idx], peer[idx]);
	362	return (0);
	363	}
	364	}
	365	debug2("proposals match");
	366	return (1);
	367	}
	368
396c147e	369	static void
d1ac6175	370	kex_choose_conf(Kex *kex)
4f8c6159	371	{
d1ac6175	372	Newkeys *newkeys;
a5c9ffdb	373	char my, peer;
a5c9ffdb	374	char cprop, sprop;
d1ac6175	375	int nenc, nmac, ncomp;
2ceb8101	376	u_int mode, ctos, need;
eed8e583	377	int first_kex_follows, type;
4f8c6159	378
eed8e583	379	my = kex_buf2prop(&kex->my, NULL);
eed8e583	380	peer = kex_buf2prop(&kex->peer, &first_kex_follows);
a5c9ffdb	381
d1ac6175	382	if (kex->server) {
a5c9ffdb	383	cprop=peer;
	384	sprop=my;
	385	} else {
	386	cprop=my;
	387	sprop=peer;
	388	}
4f8c6159	389
d8b0d145	390	/* Check whether server offers roaming */
	391	if (!kex->server) {
	392	char *roaming;
	393	roaming = match_list(KEX_RESUME, peer[PROPOSAL_KEX_ALGS], NULL);
	394	if (roaming) {
	395	kex->roaming = 1;
	396	xfree(roaming);
	397	}
	398	}
	399
c422989b	400	/* Algorithm Negotiation */
4f8c6159	401	for (mode = 0; mode < MODE_MAX; mode++) {
52e3daed	402	newkeys = xcalloc(1, sizeof(*newkeys));
c422989b	403	kex->newkeys[mode] = newkeys;
68525040	404	ctos = (!kex->server && mode == MODE_OUT) \|\|
68525040	405	(kex->server && mode == MODE_IN);
4f8c6159	406	nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
	407	nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
	408	ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
d1ac6175	409	choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
	410	choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
	411	choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
4f8c6159	412	debug("kex: %s %s %s %s",
4f8c6159	413	ctos ? "client->server" : "server->client",
d1ac6175	414	newkeys->enc.name,
	415	newkeys->mac.name,
	416	newkeys->comp.name);
4f8c6159	417	}
d1ac6175	418	choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
d1ac6175	419	choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
4f8c6159	420	sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
4f8c6159	421	need = 0;
4f8c6159	422	for (mode = 0; mode < MODE_MAX; mode++) {
c422989b	423	newkeys = kex->newkeys[mode];
3ee832e5	424	if (need < newkeys->enc.key_len)
	425	need = newkeys->enc.key_len;
	426	if (need < newkeys->enc.block_size)
	427	need = newkeys->enc.block_size;
d1ac6175	428	if (need < newkeys->mac.key_len)
d1ac6175	429	need = newkeys->mac.key_len;
4f8c6159	430	}
71276795	431	/* XXX need runden? */
d1ac6175	432	kex->we_need = need;
a5c9ffdb	433
eed8e583	434	/* ignore the next message if the proposals do not match */
aff51935	435	if (first_kex_follows && !proposals_match(my, peer) &&
4e2e5cfd	436	!(datafellows & SSH_BUG_FIRSTKEX)) {
eed8e583	437	type = packet_read();
	438	debug2("skipping next packet (type %u)", type);
	439	}
	440
a5c9ffdb	441	kex_prop_free(my);
a5c9ffdb	442	kex_prop_free(peer);
a5c9ffdb	443	}
a5c9ffdb	444
396c147e	445	static u_char *
47e5dc72	446	derive_key(Kex kex, int id, u_int need, u_char hash, u_int hashlen,
47e5dc72	447	BIGNUM *shared_secret)
a5c9ffdb	448	{
a5c9ffdb	449	Buffer b;
a5c9ffdb	450	EVP_MD_CTX md;
a5c9ffdb	451	char c = id;
2ceb8101	452	u_int have;
47e5dc72	453	int mdsz;
2ceb8101	454	u_char *digest;
56964485	455
47e5dc72	456	if ((mdsz = EVP_MD_size(kex->evp_md)) <= 0)
47e5dc72	457	fatal("bad kex md size %d", mdsz);
b4bbf172	458	digest = xmalloc(roundup(need, mdsz));
a5c9ffdb	459
	460	buffer_init(&b);
	461	buffer_put_bignum2(&b, shared_secret);
	462
c422989b	463	/* K1 = HASH(K \|\| H \|\| "A" \|\| session_id) */
47e5dc72	464	EVP_DigestInit(&md, kex->evp_md);
eef7adcb	465	if (!(datafellows & SSH_BUG_DERIVEKEY))
eef7adcb	466	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
47e5dc72	467	EVP_DigestUpdate(&md, hash, hashlen);
c422989b	468	EVP_DigestUpdate(&md, &c, 1);
d1ac6175	469	EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
a5c9ffdb	470	EVP_DigestFinal(&md, digest, NULL);
a5c9ffdb	471
c422989b	472	/*
	473	* expand key:
	474	* Kn = HASH(K \|\| H \|\| K1 \|\| K2 \|\| ... \|\| Kn-1)
	475	* Key = K1 \|\| K2 \|\| ... \|\| Kn
	476	*/
a5c9ffdb	477	for (have = mdsz; need > have; have += mdsz) {
47e5dc72	478	EVP_DigestInit(&md, kex->evp_md);
eef7adcb	479	if (!(datafellows & SSH_BUG_DERIVEKEY))
eef7adcb	480	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
47e5dc72	481	EVP_DigestUpdate(&md, hash, hashlen);
a5c9ffdb	482	EVP_DigestUpdate(&md, digest, have);
	483	EVP_DigestFinal(&md, digest + have, NULL);
	484	}
	485	buffer_free(&b);
	486	#ifdef DEBUG_KEX
	487	fprintf(stderr, "key '%c'== ", c);
	488	dump_digest("key", digest, need);
	489	#endif
	490	return digest;
4f8c6159	491	}
4f8c6159	492
c422989b	493	Newkeys *current_keys[MODE_MAX];
d1ac6175	494
cab80f75	495	#define NKEYS 6
a5c9ffdb	496	void
47e5dc72	497	kex_derive_keys(Kex kex, u_char hash, u_int hashlen, BIGNUM *shared_secret)
4f8c6159	498	{
1e3b8b07	499	u_char *keys[NKEYS];
2ceb8101	500	u_int i, mode, ctos;
4f8c6159	501
47e5dc72	502	for (i = 0; i < NKEYS; i++) {
	503	keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, hashlen,
	504	shared_secret);
	505	}
4f8c6159	506
a77673cc	507	debug2("kex_derive_keys");
4f8c6159	508	for (mode = 0; mode < MODE_MAX; mode++) {
c422989b	509	current_keys[mode] = kex->newkeys[mode];
c422989b	510	kex->newkeys[mode] = NULL;
a7137f6b	511	ctos = (!kex->server && mode == MODE_OUT) \|\|
a7137f6b	512	(kex->server && mode == MODE_IN);
c422989b	513	current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
	514	current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
	515	current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
4f8c6159	516	}
4f8c6159	517	}
a5c9ffdb	518
d1ac6175	519	Newkeys *
	520	kex_get_newkeys(int mode)
	521	{
c422989b	522	Newkeys *ret;
	523
	524	ret = current_keys[mode];
	525	current_keys[mode] = NULL;
	526	return ret;
d1ac6175	527	}
d1ac6175	528
8bbf1fa6	529	void
	530	derive_ssh1_session_id(BIGNUM host_modulus, BIGNUM server_modulus,
	531	u_int8_t cookie[8], u_int8_t id[16])
	532	{
	533	const EVP_MD *evp_md = EVP_md5();
	534	EVP_MD_CTX md;
	535	u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE];
	536	int len;
	537
	538	EVP_DigestInit(&md, evp_md);
	539
	540	len = BN_num_bytes(host_modulus);
2ceb8101	541	if (len < (512 / 8) \|\| (u_int)len > sizeof(nbuf))
8bbf1fa6	542	fatal("%s: bad host modulus (len %d)", __func__, len);
	543	BN_bn2bin(host_modulus, nbuf);
	544	EVP_DigestUpdate(&md, nbuf, len);
	545
	546	len = BN_num_bytes(server_modulus);
2ceb8101	547	if (len < (512 / 8) \|\| (u_int)len > sizeof(nbuf))
8bbf1fa6	548	fatal("%s: bad server modulus (len %d)", __func__, len);
	549	BN_bn2bin(server_modulus, nbuf);
	550	EVP_DigestUpdate(&md, nbuf, len);
	551
	552	EVP_DigestUpdate(&md, cookie, 8);
	553
59657003	554	EVP_DigestFinal(&md, obuf, NULL);
8bbf1fa6	555	memcpy(id, obuf, 16);
	556
	557	memset(nbuf, 0, sizeof(nbuf));
	558	memset(obuf, 0, sizeof(obuf));
	559	memset(&md, 0, sizeof(md));
	560	}
	561
a5c9ffdb	562	#if defined(DEBUG_KEX) \|\| defined(DEBUG_KEXDH)
	563	void
	564	dump_digest(char msg, u_char digest, int len)
	565	{
2ceb8101	566	u_int i;
a5c9ffdb	567
a5c9ffdb	568	fprintf(stderr, "%s\n", msg);
803c4226	569	for (i = 0; i < len; i++) {
a5c9ffdb	570	fprintf(stderr, "%02x", digest[i]);
	571	if (i%32 == 31)
	572	fprintf(stderr, "\n");
	573	else if (i%8 == 7)
	574	fprintf(stderr, " ");
	575	}
	576	fprintf(stderr, "\n");
	577	}
	578	#endif