kexgexs.c - platform/external/openssh - Gitiles

 /* $OpenBSD: kexgexs.c,v 1.17 2014/01/09 23:20:00 djm Exp $ */
 /*
  * Copyright (c) 2000 Niels Provos.  All rights reserved.
  * Copyright (c) 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 <stdarg.h>
 #include <stdio.h>
 #include <string.h>
 #include <signal.h>

 #include <openssl/dh.h>

 #include "xmalloc.h"
 #include "buffer.h"
 #include "key.h"
 #include "cipher.h"
 #include "kex.h"
 #include "log.h"
 #include "packet.h"
 #include "dh.h"
 #include "ssh2.h"
 #include "compat.h"
 #ifdef GSSAPI
 #include "ssh-gss.h"
 #endif
 #include "monitor_wrap.h"

 void
 kexgex_server(Kex *kex)
 {
 	BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
 	Key *server_host_public, *server_host_private;
 	DH *dh;
 	u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
 	u_int sbloblen, klen, slen, hashlen;
 	int omin = -1, min = -1, omax = -1, max = -1, onbits = -1, nbits = -1;
 	int type, kout;

 	if (kex->load_host_public_key == NULL ||
 	    kex->load_host_private_key == NULL)
 		fatal("Cannot load hostkey");
 	server_host_public = kex->load_host_public_key(kex->hostkey_type);
 	if (server_host_public == NULL)
 		fatal("Unsupported hostkey type %d", kex->hostkey_type);
 	server_host_private = kex->load_host_private_key(kex->hostkey_type);

 	type = packet_read();
 	switch (type) {
 	case SSH2_MSG_KEX_DH_GEX_REQUEST:
 		debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
 		omin = min = packet_get_int();
 		onbits = nbits = packet_get_int();
 		omax = max = packet_get_int();
 		min = MAX(DH_GRP_MIN, min);
 		max = MIN(DH_GRP_MAX, max);
 		nbits = MAX(DH_GRP_MIN, nbits);
 		nbits = MIN(DH_GRP_MAX, nbits);
 		break;
 	case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
 		debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
 		onbits = nbits = packet_get_int();
 		/* unused for old GEX */
 		omin = min = DH_GRP_MIN;
 		omax = max = DH_GRP_MAX;
 		break;
 	default:
 		fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
 	}
 	packet_check_eom();

 	if (omax < omin || onbits < omin || omax < onbits)
 		fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
 		    omin, onbits, omax);

 	/* Contact privileged parent */
 	dh = PRIVSEP(choose_dh(min, nbits, max));
 	if (dh == NULL)
 		packet_disconnect("Protocol error: no matching DH grp found");

 	debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
 	packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
 	packet_put_bignum2(dh->p);
 	packet_put_bignum2(dh->g);
 	packet_send();

 	/* flush */
 	packet_write_wait();

 	/* Compute our exchange value in parallel with the client */
 	dh_gen_key(dh, kex->we_need * 8);

 	debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
 	packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);

 	/* key, cert */
 	if ((dh_client_pub = BN_new()) == NULL)
 		fatal("dh_client_pub == NULL");
 	packet_get_bignum2(dh_client_pub);
 	packet_check_eom();

 #ifdef DEBUG_KEXDH
 	fprintf(stderr, "dh_client_pub= ");
 	BN_print_fp(stderr, dh_client_pub);
 	fprintf(stderr, "\n");
 	debug("bits %d", BN_num_bits(dh_client_pub));
 #endif

 #ifdef DEBUG_KEXDH
 	DHparams_print_fp(stderr, dh);
 	fprintf(stderr, "pub= ");
 	BN_print_fp(stderr, dh->pub_key);
 	fprintf(stderr, "\n");
 #endif
 	if (!dh_pub_is_valid(dh, dh_client_pub))
 		packet_disconnect("bad client public DH value");

 	klen = DH_size(dh);
 	kbuf = xmalloc(klen);
 	if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0)
 		fatal("DH_compute_key: failed");
 #ifdef DEBUG_KEXDH
 	dump_digest("shared secret", kbuf, kout);
 #endif
 	if ((shared_secret = BN_new()) == NULL)
 		fatal("kexgex_server: BN_new failed");
 	if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
 		fatal("kexgex_server: BN_bin2bn failed");
 	memset(kbuf, 0, klen);
 	free(kbuf);

 	key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);

 	if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
 		omin = min = omax = max = -1;

 	/* calc H */
 	kexgex_hash(
 	    kex->hash_alg,
 	    kex->client_version_string,
 	    kex->server_version_string,
 	    buffer_ptr(&kex->peer), buffer_len(&kex->peer),
 	    buffer_ptr(&kex->my), buffer_len(&kex->my),
 	    server_host_key_blob, sbloblen,
 	    omin, onbits, omax,
 	    dh->p, dh->g,
 	    dh_client_pub,
 	    dh->pub_key,
 	    shared_secret,
 	    &hash, &hashlen
 	);
 	BN_clear_free(dh_client_pub);

 	/* save session id := H */
 	if (kex->session_id == NULL) {
 		kex->session_id_len = hashlen;
 		kex->session_id = xmalloc(kex->session_id_len);
 		memcpy(kex->session_id, hash, kex->session_id_len);
 	}

 	/* sign H */
 	kex->sign(server_host_private, server_host_public, &signature, &slen,
 	    hash, hashlen);

 	/* destroy_sensitive_data(); */

 	/* send server hostkey, DH pubkey 'f' and singed H */
 	debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
 	packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
 	packet_put_string(server_host_key_blob, sbloblen);
 	packet_put_bignum2(dh->pub_key);	/* f */
 	packet_put_string(signature, slen);
 	packet_send();

 	free(signature);
 	free(server_host_key_blob);
 	/* have keys, free DH */
 	DH_free(dh);

 	kex_derive_keys(kex, hash, hashlen, shared_secret);
 	BN_clear_free(shared_secret);

 	kex_finish(kex);
 }
	/* $OpenBSD: kexgexs.c,v 1.17 2014/01/09 23:20:00 djm Exp $ */
	/*
	* Copyright (c) 2000 Niels Provos. All rights reserved.
	* Copyright (c) 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 <stdarg.h>
	#include <stdio.h>
	#include <string.h>
	#include <signal.h>

	#include <openssl/dh.h>

	#include "xmalloc.h"
	#include "buffer.h"
	#include "key.h"
	#include "cipher.h"
	#include "kex.h"
	#include "log.h"
	#include "packet.h"
	#include "dh.h"
	#include "ssh2.h"
	#include "compat.h"
	#ifdef GSSAPI
	#include "ssh-gss.h"
	#endif
	#include "monitor_wrap.h"

	void
	kexgex_server(Kex *kex)
	{
	BIGNUM shared_secret = NULL, dh_client_pub = NULL;
	Key server_host_public, server_host_private;
	DH *dh;
	u_char kbuf, hash, signature = NULL, server_host_key_blob = NULL;
	u_int sbloblen, klen, slen, hashlen;
	int omin = -1, min = -1, omax = -1, max = -1, onbits = -1, nbits = -1;
	int type, kout;

	if (kex->load_host_public_key == NULL \|\|
	kex->load_host_private_key == NULL)
	fatal("Cannot load hostkey");
	server_host_public = kex->load_host_public_key(kex->hostkey_type);
	if (server_host_public == NULL)
	fatal("Unsupported hostkey type %d", kex->hostkey_type);
	server_host_private = kex->load_host_private_key(kex->hostkey_type);

	type = packet_read();
	switch (type) {
	case SSH2_MSG_KEX_DH_GEX_REQUEST:
	debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
	omin = min = packet_get_int();
	onbits = nbits = packet_get_int();
	omax = max = packet_get_int();
	min = MAX(DH_GRP_MIN, min);
	max = MIN(DH_GRP_MAX, max);
	nbits = MAX(DH_GRP_MIN, nbits);
	nbits = MIN(DH_GRP_MAX, nbits);
	break;
	case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
	debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
	onbits = nbits = packet_get_int();
	/* unused for old GEX */
	omin = min = DH_GRP_MIN;
	omax = max = DH_GRP_MAX;
	break;
	default:
	fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
	}
	packet_check_eom();

	if (omax < omin \|\| onbits < omin \|\| omax < onbits)
	fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
	omin, onbits, omax);

	/* Contact privileged parent */
	dh = PRIVSEP(choose_dh(min, nbits, max));
	if (dh == NULL)
	packet_disconnect("Protocol error: no matching DH grp found");

	debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
	packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
	packet_put_bignum2(dh->p);
	packet_put_bignum2(dh->g);
	packet_send();

	/* flush */
	packet_write_wait();

	/* Compute our exchange value in parallel with the client */
	dh_gen_key(dh, kex->we_need * 8);

	debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
	packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);

	/* key, cert */
	if ((dh_client_pub = BN_new()) == NULL)
	fatal("dh_client_pub == NULL");
	packet_get_bignum2(dh_client_pub);
	packet_check_eom();

	#ifdef DEBUG_KEXDH
	fprintf(stderr, "dh_client_pub= ");
	BN_print_fp(stderr, dh_client_pub);
	fprintf(stderr, "\n");
	debug("bits %d", BN_num_bits(dh_client_pub));
	#endif

	#ifdef DEBUG_KEXDH
	DHparams_print_fp(stderr, dh);
	fprintf(stderr, "pub= ");
	BN_print_fp(stderr, dh->pub_key);
	fprintf(stderr, "\n");
	#endif
	if (!dh_pub_is_valid(dh, dh_client_pub))
	packet_disconnect("bad client public DH value");

	klen = DH_size(dh);
	kbuf = xmalloc(klen);
	if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0)
	fatal("DH_compute_key: failed");
	#ifdef DEBUG_KEXDH
	dump_digest("shared secret", kbuf, kout);
	#endif
	if ((shared_secret = BN_new()) == NULL)
	fatal("kexgex_server: BN_new failed");
	if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
	fatal("kexgex_server: BN_bin2bn failed");
	memset(kbuf, 0, klen);
	free(kbuf);

	key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);

	if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
	omin = min = omax = max = -1;

	/* calc H */
	kexgex_hash(
	kex->hash_alg,
	kex->client_version_string,
	kex->server_version_string,
	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	buffer_ptr(&kex->my), buffer_len(&kex->my),
	server_host_key_blob, sbloblen,
	omin, onbits, omax,
	dh->p, dh->g,
	dh_client_pub,
	dh->pub_key,
	shared_secret,
	&hash, &hashlen
	);
	BN_clear_free(dh_client_pub);

	/* save session id := H */
	if (kex->session_id == NULL) {
	kex->session_id_len = hashlen;
	kex->session_id = xmalloc(kex->session_id_len);
	memcpy(kex->session_id, hash, kex->session_id_len);
	}

	/* sign H */
	kex->sign(server_host_private, server_host_public, &signature, &slen,
	hash, hashlen);

	/* destroy_sensitive_data(); */

	/* send server hostkey, DH pubkey 'f' and singed H */
	debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
	packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
	packet_put_string(server_host_key_blob, sbloblen);
	packet_put_bignum2(dh->pub_key); /* f */
	packet_put_string(signature, slen);
	packet_send();

	free(signature);
	free(server_host_key_blob);
	/* have keys, free DH */
	DH_free(dh);

	kex_derive_keys(kex, hash, hashlen, shared_secret);
	BN_clear_free(shared_secret);

	kex_finish(kex);
	}