[gssapi-openssh.git] / openssh / kex.c

/*
 * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "includes.h"
RCSID("$OpenBSD: kex.c,v 1.64 2005/07/25 11:59:39 markus Exp $");

#include <openssl/crypto.h>

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

#ifdef GSSAPI
#include "ssh-gss.h"
#endif

#define KEX_COOKIE_LEN	16

/* prototype */
static void kex_kexinit_finish(Kex *);
static void kex_choose_conf(Kex *);

/* put algorithm proposal into buffer */
static void
kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
{
	u_int i;

	buffer_clear(b);
	/*
	 * add a dummy cookie, the cookie will be overwritten by
	 * kex_send_kexinit(), each time a kexinit is set
	 */
	for (i = 0; i < KEX_COOKIE_LEN; i++)
		buffer_put_char(b, 0);
	for (i = 0; i < PROPOSAL_MAX; i++)
		buffer_put_cstring(b, proposal[i]);
	buffer_put_char(b, 0);			/* first_kex_packet_follows */
	buffer_put_int(b, 0);			/* uint32 reserved */
}

/* parse buffer and return algorithm proposal */
static char **
kex_buf2prop(Buffer *raw, int *first_kex_follows)
{
	Buffer b;
	int i;
	char **proposal;

	proposal = xmalloc(PROPOSAL_MAX * sizeof(char *));

	buffer_init(&b);
	buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
	/* skip cookie */
	for (i = 0; i < KEX_COOKIE_LEN; i++)
		buffer_get_char(&b);
	/* extract kex init proposal strings */
	for (i = 0; i < PROPOSAL_MAX; i++) {
		proposal[i] = buffer_get_string(&b,NULL);
		debug2("kex_parse_kexinit: %s", proposal[i]);
	}
	/* first kex follows / reserved */
	i = buffer_get_char(&b);
	if (first_kex_follows != NULL)
		*first_kex_follows = i;
	debug2("kex_parse_kexinit: first_kex_follows %d ", i);
	i = buffer_get_int(&b);
	debug2("kex_parse_kexinit: reserved %d ", i);
	buffer_free(&b);
	return proposal;
}

static void
kex_prop_free(char **proposal)
{
	u_int i;

	for (i = 0; i < PROPOSAL_MAX; i++)
		xfree(proposal[i]);
	xfree(proposal);
}

static void
kex_protocol_error(int type, u_int32_t seq, void *ctxt)
{
	error("Hm, kex protocol error: type %d seq %u", type, seq);
}

static void
kex_reset_dispatch(void)
{
	dispatch_range(SSH2_MSG_TRANSPORT_MIN,
	    SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
	dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
}

void
kex_finish(Kex *kex)
{
	kex_reset_dispatch();

	packet_start(SSH2_MSG_NEWKEYS);
	packet_send();
	/* packet_write_wait(); */
	debug("SSH2_MSG_NEWKEYS sent");

	debug("expecting SSH2_MSG_NEWKEYS");
	packet_read_expect(SSH2_MSG_NEWKEYS);
	packet_check_eom();
	debug("SSH2_MSG_NEWKEYS received");

	kex->done = 1;
	buffer_clear(&kex->peer);
	/* buffer_clear(&kex->my); */
	kex->flags &= ~KEX_INIT_SENT;
	xfree(kex->name);
	kex->name = NULL;
}

void
kex_send_kexinit(Kex *kex)
{
	u_int32_t rnd = 0;
	u_char *cookie;
	u_int i;

	if (kex == NULL) {
		error("kex_send_kexinit: no kex, cannot rekey");
		return;
	}
	if (kex->flags & KEX_INIT_SENT) {
		debug("KEX_INIT_SENT");
		return;
	}
	kex->done = 0;

	/* generate a random cookie */
	if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
		fatal("kex_send_kexinit: kex proposal too short");
	cookie = buffer_ptr(&kex->my);
	for (i = 0; i < KEX_COOKIE_LEN; i++) {
		if (i % 4 == 0)
			rnd = arc4random();
		cookie[i] = rnd;
		rnd >>= 8;
	}
	packet_start(SSH2_MSG_KEXINIT);
	packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
	packet_send();
	debug("SSH2_MSG_KEXINIT sent");
	kex->flags |= KEX_INIT_SENT;
}

void
kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
{
	char *ptr;
	u_int i, dlen;
	Kex *kex = (Kex *)ctxt;

	debug("SSH2_MSG_KEXINIT received");
	if (kex == NULL)
		fatal("kex_input_kexinit: no kex, cannot rekey");

	ptr = packet_get_raw(&dlen);
	buffer_append(&kex->peer, ptr, dlen);

	/* discard packet */
	for (i = 0; i < KEX_COOKIE_LEN; i++)
		packet_get_char();
	for (i = 0; i < PROPOSAL_MAX; i++)
		xfree(packet_get_string(NULL));
	(void) packet_get_char();
	(void) packet_get_int();
	packet_check_eom();

	kex_kexinit_finish(kex);
}

Kex *
kex_setup(char *proposal[PROPOSAL_MAX])
{
	Kex *kex;

	kex = xmalloc(sizeof(*kex));
	memset(kex, 0, sizeof(*kex));
	buffer_init(&kex->peer);
	buffer_init(&kex->my);
	kex_prop2buf(&kex->my, proposal);
	kex->done = 0;

	kex_send_kexinit(kex);					/* we start */
	kex_reset_dispatch();

	return kex;
}

static void
kex_kexinit_finish(Kex *kex)
{
	if (!(kex->flags & KEX_INIT_SENT))
		kex_send_kexinit(kex);

	kex_choose_conf(kex);

	if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
	    kex->kex[kex->kex_type] != NULL) {
		(kex->kex[kex->kex_type])(kex);
	} else {
		fatal("Unsupported key exchange %d", kex->kex_type);
	}
}

static void
choose_enc(Enc *enc, char *client, char *server)
{
	char *name = match_list(client, server, NULL);
	if (name == NULL)
		fatal("no matching cipher found: client %s server %s", client, server);
	if ((enc->cipher = cipher_by_name(name)) == NULL)
		fatal("matching cipher is not supported: %s", name);
	enc->name = name;
	enc->enabled = 0;
	enc->iv = NULL;
	enc->key = NULL;
	enc->key_len = cipher_keylen(enc->cipher);
	enc->block_size = cipher_blocksize(enc->cipher);
}
static void
choose_mac(Mac *mac, char *client, char *server)
{
	char *name = match_list(client, server, NULL);
	if (name == NULL)
		fatal("no matching mac found: client %s server %s", client, server);
	if (mac_init(mac, name) < 0)
		fatal("unsupported mac %s", name);
	/* truncate the key */
	if (datafellows & SSH_BUG_HMAC)
		mac->key_len = 16;
	mac->name = name;
	mac->key = NULL;
	mac->enabled = 0;
}
static void
choose_comp(Comp *comp, char *client, char *server)
{
	char *name = match_list(client, server, NULL);
	if (name == NULL)
		fatal("no matching comp found: client %s server %s", client, server);
	if (strcmp(name, "zlib@openssh.com") == 0) {
		comp->type = COMP_DELAYED;
	} else if (strcmp(name, "zlib") == 0) {
		comp->type = COMP_ZLIB;
	} else if (strcmp(name, "none") == 0) {
		comp->type = COMP_NONE;
	} else {
		fatal("unsupported comp %s", name);
	}
	comp->name = name;
}
static void
choose_kex(Kex *k, char *client, char *server)
{
	k->name = match_list(client, server, NULL);
	if (k->name == NULL)
		fatal("no kex alg");
	if (strcmp(k->name, KEX_DH1) == 0) {
		k->kex_type = KEX_DH_GRP1_SHA1;
	} else if (strcmp(k->name, KEX_DH14) == 0) {
		k->kex_type = KEX_DH_GRP14_SHA1;
	} else if (strcmp(k->name, KEX_DHGEX) == 0) {
		k->kex_type = KEX_DH_GEX_SHA1;
#ifdef GSSAPI
	} else if (strncmp(k->name, KEX_GSS_SHA1, sizeof(KEX_GSS_SHA1)-1) == 0) {
		k->kex_type = KEX_GSS_GRP1_SHA1;
#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 = xmalloc(sizeof(*newkeys));
		memset(newkeys, 0, sizeof(*newkeys));
		kex->newkeys[mode] = newkeys;
		ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
		nenc  = ctos ? PROPOSAL_ENC_ALGS_CTOS  : PROPOSAL_ENC_ALGS_STOC;
		nmac  = ctos ? PROPOSAL_MAC_ALGS_CTOS  : PROPOSAL_MAC_ALGS_STOC;
		ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
		choose_enc (&newkeys->enc,  cprop[nenc],  sprop[nenc]);
		choose_mac (&newkeys->mac,  cprop[nmac],  sprop[nmac]);
		choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
		debug("kex: %s %s %s %s",
		    ctos ? "client->server" : "server->client",
		    newkeys->enc.name,
		    newkeys->mac.name,
		    newkeys->comp.name);
	}
	choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
	choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
	    sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
	need = 0;
	for (mode = 0; mode < MODE_MAX; mode++) {
		newkeys = kex->newkeys[mode];
		if (need < newkeys->enc.key_len)
			need = newkeys->enc.key_len;
		if (need < newkeys->enc.block_size)
			need = newkeys->enc.block_size;
		if (need < newkeys->mac.key_len)
			need = newkeys->mac.key_len;
	}
	/* XXX need runden? */
	kex->we_need = need;

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

	kex_prop_free(my);
	kex_prop_free(peer);
}

static u_char *
derive_key(Kex *kex, int id, u_int need, u_char *hash, BIGNUM *shared_secret)
{
	Buffer b;
	const EVP_MD *evp_md = EVP_sha1();
	EVP_MD_CTX md;
	char c = id;
	u_int have;
	int mdsz = EVP_MD_size(evp_md);
	u_char *digest;

	if (mdsz < 0)
		fatal("derive_key: mdsz < 0");
	digest = xmalloc(roundup(need, mdsz));

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

	/* K1 = HASH(K || H || "A" || session_id) */
	EVP_DigestInit(&md, evp_md);
	if (!(datafellows & SSH_BUG_DERIVEKEY))
		EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
	EVP_DigestUpdate(&md, hash, mdsz);
	EVP_DigestUpdate(&md, &c, 1);
	EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
	EVP_DigestFinal(&md, digest, NULL);

	/*
	 * expand key:
	 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
	 * Key = K1 || K2 || ... || Kn
	 */
	for (have = mdsz; need > have; have += mdsz) {
		EVP_DigestInit(&md, evp_md);
		if (!(datafellows & SSH_BUG_DERIVEKEY))
			EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
		EVP_DigestUpdate(&md, hash, mdsz);
		EVP_DigestUpdate(&md, digest, have);
		EVP_DigestFinal(&md, digest + have, NULL);
	}
	buffer_free(&b);
#ifdef DEBUG_KEX
	fprintf(stderr, "key '%c'== ", c);
	dump_digest("key", digest, need);
#endif
	return digest;
}

Newkeys *current_keys[MODE_MAX];

#define NKEYS	6
void
kex_derive_keys(Kex *kex, u_char *hash, BIGNUM *shared_secret)
{
	u_char *keys[NKEYS];
	u_int i, mode, ctos;

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

	debug2("kex_derive_keys");
	for (mode = 0; mode < MODE_MAX; mode++) {
		current_keys[mode] = kex->newkeys[mode];
		kex->newkeys[mode] = NULL;
		ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
		current_keys[mode]->enc.iv  = keys[ctos ? 0 : 1];
		current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
		current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
	}
}

Newkeys *
kex_get_newkeys(int mode)
{
	Newkeys *ret;

	ret = current_keys[mode];
	current_keys[mode] = NULL;
	return ret;
}

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
3c0ef626	1	/*
	2	* Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
	3	*
	4	* Redistribution and use in source and binary forms, with or without
	5	* modification, are permitted provided that the following conditions
	6	* are met:
	7	* 1. Redistributions of source code must retain the above copyright
	8	* notice, this list of conditions and the following disclaimer.
	9	* 2. Redistributions in binary form must reproduce the above copyright
	10	* notice, this list of conditions and the following disclaimer in the
	11	* documentation and/or other materials provided with the distribution.
	12	*
	13	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
	14	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	15	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	16	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
	17	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	18	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	19	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	20	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	21	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	22	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	23	*/
	24
	25	#include "includes.h"
2ce0bfe4	26	RCSID("$OpenBSD: kex.c,v 1.64 2005/07/25 11:59:39 markus Exp $");
3c0ef626	27
	28	#include <openssl/crypto.h>
	29
	30	#include "ssh2.h"
	31	#include "xmalloc.h"
	32	#include "buffer.h"
	33	#include "bufaux.h"
	34	#include "packet.h"
	35	#include "compat.h"
	36	#include "cipher.h"
	37	#include "kex.h"
	38	#include "key.h"
	39	#include "log.h"
	40	#include "mac.h"
	41	#include "match.h"
	42	#include "dispatch.h"
350391c5	43	#include "monitor.h"
3c0ef626	44
5598e598	45	#ifdef GSSAPI
	46	#include "ssh-gss.h"
	47	#endif
	48
3c0ef626	49	#define KEX_COOKIE_LEN 16
	50
	51	/* prototype */
	52	static void kex_kexinit_finish(Kex *);
	53	static void kex_choose_conf(Kex *);
	54
	55	/* put algorithm proposal into buffer */
	56	static void
	57	kex_prop2buf(Buffer b, char proposal[PROPOSAL_MAX])
	58	{
2ce0bfe4	59	u_int i;
3c0ef626	60
3c0ef626	61	buffer_clear(b);
350391c5	62	/*
	63	* add a dummy cookie, the cookie will be overwritten by
	64	* kex_send_kexinit(), each time a kexinit is set
	65	*/
	66	for (i = 0; i < KEX_COOKIE_LEN; i++)
	67	buffer_put_char(b, 0);
3c0ef626	68	for (i = 0; i < PROPOSAL_MAX; i++)
	69	buffer_put_cstring(b, proposal[i]);
	70	buffer_put_char(b, 0); /* first_kex_packet_follows */
	71	buffer_put_int(b, 0); /* uint32 reserved */
	72	}
	73
	74	/* parse buffer and return algorithm proposal */
	75	static char **
8afc6a66	76	kex_buf2prop(Buffer raw, int first_kex_follows)
3c0ef626	77	{
	78	Buffer b;
	79	int i;
	80	char **proposal;
	81
	82	proposal = xmalloc(PROPOSAL_MAX * sizeof(char *));
	83
	84	buffer_init(&b);
	85	buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
	86	/* skip cookie */
	87	for (i = 0; i < KEX_COOKIE_LEN; i++)
	88	buffer_get_char(&b);
	89	/* extract kex init proposal strings */
	90	for (i = 0; i < PROPOSAL_MAX; i++) {
	91	proposal[i] = buffer_get_string(&b,NULL);
	92	debug2("kex_parse_kexinit: %s", proposal[i]);
	93	}
	94	/* first kex follows / reserved */
	95	i = buffer_get_char(&b);
8afc6a66	96	if (first_kex_follows != NULL)
8afc6a66	97	*first_kex_follows = i;
3c0ef626	98	debug2("kex_parse_kexinit: first_kex_follows %d ", i);
	99	i = buffer_get_int(&b);
	100	debug2("kex_parse_kexinit: reserved %d ", i);
	101	buffer_free(&b);
	102	return proposal;
	103	}
	104
	105	static void
	106	kex_prop_free(char **proposal)
	107	{
2ce0bfe4	108	u_int i;
3c0ef626	109
	110	for (i = 0; i < PROPOSAL_MAX; i++)
	111	xfree(proposal[i]);
	112	xfree(proposal);
	113	}
	114
	115	static void
e9702f7d	116	kex_protocol_error(int type, u_int32_t seq, void *ctxt)
3c0ef626	117	{
e9702f7d	118	error("Hm, kex protocol error: type %d seq %u", type, seq);
3c0ef626	119	}
	120
	121	static void
e9702f7d	122	kex_reset_dispatch(void)
3c0ef626	123	{
e9702f7d	124	dispatch_range(SSH2_MSG_TRANSPORT_MIN,
	125	SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
	126	dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
3c0ef626	127	}
	128
	129	void
	130	kex_finish(Kex *kex)
	131	{
e9702f7d	132	kex_reset_dispatch();
3c0ef626	133
	134	packet_start(SSH2_MSG_NEWKEYS);
	135	packet_send();
	136	/* packet_write_wait(); */
	137	debug("SSH2_MSG_NEWKEYS sent");
	138
8afc6a66	139	debug("expecting SSH2_MSG_NEWKEYS");
e9702f7d	140	packet_read_expect(SSH2_MSG_NEWKEYS);
e9702f7d	141	packet_check_eom();
3c0ef626	142	debug("SSH2_MSG_NEWKEYS received");
	143
	144	kex->done = 1;
	145	buffer_clear(&kex->peer);
	146	/* buffer_clear(&kex->my); */
	147	kex->flags &= ~KEX_INIT_SENT;
	148	xfree(kex->name);
	149	kex->name = NULL;
	150	}
	151
	152	void
	153	kex_send_kexinit(Kex *kex)
	154	{
7e82606e	155	u_int32_t rnd = 0;
350391c5	156	u_char *cookie;
2ce0bfe4	157	u_int i;
350391c5	158
3c0ef626	159	if (kex == NULL) {
	160	error("kex_send_kexinit: no kex, cannot rekey");
	161	return;
	162	}
	163	if (kex->flags & KEX_INIT_SENT) {
	164	debug("KEX_INIT_SENT");
	165	return;
	166	}
	167	kex->done = 0;
350391c5	168
	169	/* generate a random cookie */
	170	if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
	171	fatal("kex_send_kexinit: kex proposal too short");
	172	cookie = buffer_ptr(&kex->my);
	173	for (i = 0; i < KEX_COOKIE_LEN; i++) {
	174	if (i % 4 == 0)
7e82606e	175	rnd = arc4random();
	176	cookie[i] = rnd;
	177	rnd >>= 8;
350391c5	178	}
3c0ef626	179	packet_start(SSH2_MSG_KEXINIT);
	180	packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
	181	packet_send();
	182	debug("SSH2_MSG_KEXINIT sent");
	183	kex->flags \|= KEX_INIT_SENT;
	184	}
	185
	186	void
e9702f7d	187	kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
3c0ef626	188	{
3c0ef626	189	char *ptr;
2ce0bfe4	190	u_int i, dlen;
3c0ef626	191	Kex kex = (Kex )ctxt;
	192
	193	debug("SSH2_MSG_KEXINIT received");
	194	if (kex == NULL)
	195	fatal("kex_input_kexinit: no kex, cannot rekey");
	196
	197	ptr = packet_get_raw(&dlen);
	198	buffer_append(&kex->peer, ptr, dlen);
	199
	200	/* discard packet */
	201	for (i = 0; i < KEX_COOKIE_LEN; i++)
	202	packet_get_char();
	203	for (i = 0; i < PROPOSAL_MAX; i++)
	204	xfree(packet_get_string(NULL));
276b07a3	205	(void) packet_get_char();
276b07a3	206	(void) packet_get_int();
e9702f7d	207	packet_check_eom();
3c0ef626	208
	209	kex_kexinit_finish(kex);
	210	}
	211
	212	Kex *
	213	kex_setup(char *proposal[PROPOSAL_MAX])
	214	{
	215	Kex *kex;
	216
	217	kex = xmalloc(sizeof(*kex));
	218	memset(kex, 0, sizeof(*kex));
	219	buffer_init(&kex->peer);
	220	buffer_init(&kex->my);
	221	kex_prop2buf(&kex->my, proposal);
	222	kex->done = 0;
	223
	224	kex_send_kexinit(kex); /* we start */
e9702f7d	225	kex_reset_dispatch();
3c0ef626	226
	227	return kex;
	228	}
	229
	230	static void
	231	kex_kexinit_finish(Kex *kex)
	232	{
	233	if (!(kex->flags & KEX_INIT_SENT))
	234	kex_send_kexinit(kex);
	235
	236	kex_choose_conf(kex);
	237
8afc6a66	238	if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
	239	kex->kex[kex->kex_type] != NULL) {
	240	(kex->kex[kex->kex_type])(kex);
	241	} else {
3c0ef626	242	fatal("Unsupported key exchange %d", kex->kex_type);
	243	}
	244	}
	245
	246	static void
	247	choose_enc(Enc enc, char client, char *server)
	248	{
	249	char *name = match_list(client, server, NULL);
	250	if (name == NULL)
	251	fatal("no matching cipher found: client %s server %s", client, server);
e9702f7d	252	if ((enc->cipher = cipher_by_name(name)) == NULL)
3c0ef626	253	fatal("matching cipher is not supported: %s", name);
	254	enc->name = name;
	255	enc->enabled = 0;
	256	enc->iv = NULL;
	257	enc->key = NULL;
e9702f7d	258	enc->key_len = cipher_keylen(enc->cipher);
e9702f7d	259	enc->block_size = cipher_blocksize(enc->cipher);
3c0ef626	260	}
	261	static void
	262	choose_mac(Mac mac, char client, char *server)
	263	{
	264	char *name = match_list(client, server, NULL);
	265	if (name == NULL)
	266	fatal("no matching mac found: client %s server %s", client, server);
	267	if (mac_init(mac, name) < 0)
	268	fatal("unsupported mac %s", name);
	269	/* truncate the key */
	270	if (datafellows & SSH_BUG_HMAC)
	271	mac->key_len = 16;
	272	mac->name = name;
	273	mac->key = NULL;
	274	mac->enabled = 0;
	275	}
	276	static void
	277	choose_comp(Comp comp, char client, char *server)
	278	{
	279	char *name = match_list(client, server, NULL);
	280	if (name == NULL)
	281	fatal("no matching comp found: client %s server %s", client, server);
2ce0bfe4	282	if (strcmp(name, "zlib@openssh.com") == 0) {
	283	comp->type = COMP_DELAYED;
	284	} else if (strcmp(name, "zlib") == 0) {
	285	comp->type = COMP_ZLIB;
3c0ef626	286	} else if (strcmp(name, "none") == 0) {
2ce0bfe4	287	comp->type = COMP_NONE;
3c0ef626	288	} else {
	289	fatal("unsupported comp %s", name);
	290	}
	291	comp->name = name;
	292	}
	293	static void
	294	choose_kex(Kex k, char client, char *server)
	295	{
	296	k->name = match_list(client, server, NULL);
	297	if (k->name == NULL)
7cac2b65	298	fatal("no kex alg");
3c0ef626	299	if (strcmp(k->name, KEX_DH1) == 0) {
8afc6a66	300	k->kex_type = KEX_DH_GRP1_SHA1;
7e82606e	301	} else if (strcmp(k->name, KEX_DH14) == 0) {
7e82606e	302	k->kex_type = KEX_DH_GRP14_SHA1;
3c0ef626	303	} else if (strcmp(k->name, KEX_DHGEX) == 0) {
8afc6a66	304	k->kex_type = KEX_DH_GEX_SHA1;
5598e598	305	#ifdef GSSAPI
23987cb8	306	} else if (strncmp(k->name, KEX_GSS_SHA1, sizeof(KEX_GSS_SHA1)-1) == 0) {
8afc6a66	307	k->kex_type = KEX_GSS_GRP1_SHA1;
5598e598	308	#endif
3c0ef626	309	} else
	310	fatal("bad kex alg %s", k->name);
	311	}
	312	static void
	313	choose_hostkeyalg(Kex k, char client, char *server)
	314	{
	315	char *hostkeyalg = match_list(client, server, NULL);
	316	if (hostkeyalg == NULL)
	317	fatal("no hostkey alg");
	318	k->hostkey_type = key_type_from_name(hostkeyalg);
	319	if (k->hostkey_type == KEY_UNSPEC)
	320	fatal("bad hostkey alg '%s'", hostkeyalg);
	321	xfree(hostkeyalg);
	322	}
	323
540d72c3	324	static int
8afc6a66	325	proposals_match(char my[PROPOSAL_MAX], char peer[PROPOSAL_MAX])
	326	{
	327	static int check[] = {
	328	PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
	329	};
	330	int *idx;
	331	char *p;
	332
	333	for (idx = &check[0]; *idx != -1; idx++) {
	334	if ((p = strchr(my[*idx], ',')) != NULL)
	335	*p = '\0';
	336	if ((p = strchr(peer[*idx], ',')) != NULL)
	337	*p = '\0';
	338	if (strcmp(my[idx], peer[idx]) != 0) {
	339	debug2("proposal mismatch: my %s peer %s",
	340	my[idx], peer[idx]);
	341	return (0);
	342	}
	343	}
	344	debug2("proposals match");
	345	return (1);
	346	}
	347
3c0ef626	348	static void
	349	kex_choose_conf(Kex *kex)
	350	{
	351	Newkeys *newkeys;
	352	char my, peer;
	353	char cprop, sprop;
	354	int nenc, nmac, ncomp;
2ce0bfe4	355	u_int mode, ctos, need;
8afc6a66	356	int first_kex_follows, type;
3c0ef626	357
8afc6a66	358	my = kex_buf2prop(&kex->my, NULL);
8afc6a66	359	peer = kex_buf2prop(&kex->peer, &first_kex_follows);
3c0ef626	360
	361	if (kex->server) {
	362	cprop=peer;
	363	sprop=my;
	364	} else {
	365	cprop=my;
	366	sprop=peer;
	367	}
	368
	369	/* Algorithm Negotiation */
	370	for (mode = 0; mode < MODE_MAX; mode++) {
	371	newkeys = xmalloc(sizeof(*newkeys));
	372	memset(newkeys, 0, sizeof(*newkeys));
	373	kex->newkeys[mode] = newkeys;
	374	ctos = (!kex->server && mode == MODE_OUT) \|\| (kex->server && mode == MODE_IN);
	375	nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
	376	nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
	377	ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
	378	choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
	379	choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
	380	choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
	381	debug("kex: %s %s %s %s",
	382	ctos ? "client->server" : "server->client",
	383	newkeys->enc.name,
	384	newkeys->mac.name,
	385	newkeys->comp.name);
	386	}
	387	choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
	388	choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
	389	sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
	390	need = 0;
	391	for (mode = 0; mode < MODE_MAX; mode++) {
	392	newkeys = kex->newkeys[mode];
e9702f7d	393	if (need < newkeys->enc.key_len)
	394	need = newkeys->enc.key_len;
	395	if (need < newkeys->enc.block_size)
	396	need = newkeys->enc.block_size;
3c0ef626	397	if (need < newkeys->mac.key_len)
	398	need = newkeys->mac.key_len;
	399	}
	400	/* XXX need runden? */
	401	kex->we_need = need;
	402
8afc6a66	403	/* ignore the next message if the proposals do not match */
540d72c3	404	if (first_kex_follows && !proposals_match(my, peer) &&
2ce0bfe4	405	!(datafellows & SSH_BUG_FIRSTKEX)) {
8afc6a66	406	type = packet_read();
	407	debug2("skipping next packet (type %u)", type);
	408	}
	409
3c0ef626	410	kex_prop_free(my);
	411	kex_prop_free(peer);
	412	}
	413
	414	static u_char *
2ce0bfe4	415	derive_key(Kex kex, int id, u_int need, u_char hash, BIGNUM *shared_secret)
3c0ef626	416	{
3c0ef626	417	Buffer b;
e9702f7d	418	const EVP_MD *evp_md = EVP_sha1();
3c0ef626	419	EVP_MD_CTX md;
3c0ef626	420	char c = id;
2ce0bfe4	421	u_int have;
e9702f7d	422	int mdsz = EVP_MD_size(evp_md);
2ce0bfe4	423	u_char *digest;
	424
	425	if (mdsz < 0)
	426	fatal("derive_key: mdsz < 0");
	427	digest = xmalloc(roundup(need, mdsz));
3c0ef626	428
	429	buffer_init(&b);
	430	buffer_put_bignum2(&b, shared_secret);
	431
	432	/* K1 = HASH(K \|\| H \|\| "A" \|\| session_id) */
	433	EVP_DigestInit(&md, evp_md);
	434	if (!(datafellows & SSH_BUG_DERIVEKEY))
	435	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
	436	EVP_DigestUpdate(&md, hash, mdsz);
	437	EVP_DigestUpdate(&md, &c, 1);
	438	EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
	439	EVP_DigestFinal(&md, digest, NULL);
	440
	441	/*
	442	* expand key:
	443	* Kn = HASH(K \|\| H \|\| K1 \|\| K2 \|\| ... \|\| Kn-1)
	444	* Key = K1 \|\| K2 \|\| ... \|\| Kn
	445	*/
	446	for (have = mdsz; need > have; have += mdsz) {
	447	EVP_DigestInit(&md, evp_md);
	448	if (!(datafellows & SSH_BUG_DERIVEKEY))
	449	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
	450	EVP_DigestUpdate(&md, hash, mdsz);
	451	EVP_DigestUpdate(&md, digest, have);
	452	EVP_DigestFinal(&md, digest + have, NULL);
	453	}
	454	buffer_free(&b);
	455	#ifdef DEBUG_KEX
	456	fprintf(stderr, "key '%c'== ", c);
	457	dump_digest("key", digest, need);
	458	#endif
	459	return digest;
	460	}
	461
	462	Newkeys *current_keys[MODE_MAX];
	463
	464	#define NKEYS 6
	465	void
	466	kex_derive_keys(Kex kex, u_char hash, BIGNUM *shared_secret)
	467	{
	468	u_char *keys[NKEYS];
2ce0bfe4	469	u_int i, mode, ctos;
3c0ef626	470
	471	for (i = 0; i < NKEYS; i++)
	472	keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret);
	473
8afc6a66	474	debug2("kex_derive_keys");
3c0ef626	475	for (mode = 0; mode < MODE_MAX; mode++) {
	476	current_keys[mode] = kex->newkeys[mode];
	477	kex->newkeys[mode] = NULL;
	478	ctos = (!kex->server && mode == MODE_OUT) \|\| (kex->server && mode == MODE_IN);
	479	current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
	480	current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
	481	current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
	482	}
	483	}
	484
	485	Newkeys *
	486	kex_get_newkeys(int mode)
	487	{
	488	Newkeys *ret;
	489
	490	ret = current_keys[mode];
	491	current_keys[mode] = NULL;
	492	return ret;
	493	}
	494
7e82606e	495	void
	496	derive_ssh1_session_id(BIGNUM host_modulus, BIGNUM server_modulus,
	497	u_int8_t cookie[8], u_int8_t id[16])
	498	{
	499	const EVP_MD *evp_md = EVP_md5();
	500	EVP_MD_CTX md;
	501	u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE];
	502	int len;
	503
	504	EVP_DigestInit(&md, evp_md);
	505
	506	len = BN_num_bytes(host_modulus);
2ce0bfe4	507	if (len < (512 / 8) \|\| (u_int)len > sizeof(nbuf))
7e82606e	508	fatal("%s: bad host modulus (len %d)", __func__, len);
	509	BN_bn2bin(host_modulus, nbuf);
	510	EVP_DigestUpdate(&md, nbuf, len);
	511
	512	len = BN_num_bytes(server_modulus);
2ce0bfe4	513	if (len < (512 / 8) \|\| (u_int)len > sizeof(nbuf))
7e82606e	514	fatal("%s: bad server modulus (len %d)", __func__, len);
	515	BN_bn2bin(server_modulus, nbuf);
	516	EVP_DigestUpdate(&md, nbuf, len);
	517
	518	EVP_DigestUpdate(&md, cookie, 8);
	519
	520	EVP_DigestFinal(&md, obuf, NULL);
	521	memcpy(id, obuf, 16);
	522
	523	memset(nbuf, 0, sizeof(nbuf));
	524	memset(obuf, 0, sizeof(obuf));
	525	memset(&md, 0, sizeof(md));
	526	}
	527
3c0ef626	528	#if defined(DEBUG_KEX) \|\| defined(DEBUG_KEXDH)
	529	void
	530	dump_digest(char msg, u_char digest, int len)
	531	{
2ce0bfe4	532	u_int i;
3c0ef626	533
3c0ef626	534	fprintf(stderr, "%s\n", msg);
e9702f7d	535	for (i = 0; i< len; i++) {
3c0ef626	536	fprintf(stderr, "%02x", digest[i]);
	537	if (i%32 == 31)
	538	fprintf(stderr, "\n");
	539	else if (i%8 == 7)
	540	fprintf(stderr, " ");
	541	}
	542	fprintf(stderr, "\n");
	543	}
	544	#endif