path: root/kex.c

/* $OpenBSD: kex.c,v 1.137 2018/07/03 11:39:54 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 <signal.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#ifdef WITH_OPENSSL
#include <openssl/crypto.h>
#include <openssl/dh.h>
#endif

#include "ssh2.h"
#include "packet.h"
#include "compat.h"
#include "cipher.h"
#include "sshkey.h"
#include "kex.h"
#include "log.h"
#include "mac.h"
#include "match.h"
#include "misc.h"
#include "dispatch.h"
#include "monitor.h"

#include "ssherr.h"
#include "sshbuf.h"
#include "digest.h"

/* prototype */
static int kex_choose_conf(struct ssh *);
static int kex_input_newkeys(int, u_int32_t, struct ssh *);

static const char *proposal_names[PROPOSAL_MAX] = {
	"KEX algorithms",
	"host key algorithms",
	"ciphers ctos",
	"ciphers stoc",
	"MACs ctos",
	"MACs stoc",
	"compression ctos",
	"compression stoc",
	"languages ctos",
	"languages stoc",
};

struct kexalg {
	char *name;
	u_int type;
	int ec_nid;
	int hash_alg;
};
static const struct kexalg kexalgs[] = {
#ifdef WITH_OPENSSL
	{ KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },
	{ KEX_DH14_SHA1, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 },
	{ KEX_DH14_SHA256, KEX_DH_GRP14_SHA256, 0, SSH_DIGEST_SHA256 },
	{ KEX_DH16_SHA512, KEX_DH_GRP16_SHA512, 0, SSH_DIGEST_SHA512 },
	{ KEX_DH18_SHA512, KEX_DH_GRP18_SHA512, 0, SSH_DIGEST_SHA512 },
	{ KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 },
#ifdef HAVE_EVP_SHA256
	{ KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 },
#endif /* HAVE_EVP_SHA256 */
#ifdef OPENSSL_HAS_ECC
	{ KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2,
	    NID_X9_62_prime256v1, SSH_DIGEST_SHA256 },
	{ KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1,
	    SSH_DIGEST_SHA384 },
# ifdef OPENSSL_HAS_NISTP521
	{ KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1,
	    SSH_DIGEST_SHA512 },
# endif /* OPENSSL_HAS_NISTP521 */
#endif /* OPENSSL_HAS_ECC */
#endif /* WITH_OPENSSL */
#if defined(HAVE_EVP_SHA256) || !defined(WITH_OPENSSL)
	{ KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
	{ KEX_CURVE25519_SHA256_OLD, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
#endif /* HAVE_EVP_SHA256 || !WITH_OPENSSL */
	{ NULL, -1, -1, -1},
};

char *
kex_alg_list(char sep)
{
	char *ret = NULL, *tmp;
	size_t nlen, rlen = 0;
	const struct kexalg *k;

	for (k = kexalgs; k->name != NULL; k++) {
		if (ret != NULL)
			ret[rlen++] = sep;
		nlen = strlen(k->name);
		if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
			free(ret);
			return NULL;
		}
		ret = tmp;
		memcpy(ret + rlen, k->name, nlen + 1);
		rlen += nlen;
	}
	return ret;
}

static const struct kexalg *
kex_alg_by_name(const char *name)
{
	const struct kexalg *k;

	for (k = kexalgs; k->name != NULL; k++) {
		if (strcmp(k->name, name) == 0)
			return k;
	}
	return NULL;
}

/* Validate KEX method name list */
int
kex_names_valid(const char *names)
{
	char *s, *cp, *p;