kexgexs.c - third_party/openssh-portable - Git at Google

 /* $OpenBSD: kexgexs.c,v 1.33 2018/04/10 00:10:49 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"

 #ifdef WITH_OPENSSL


 #include <stdarg.h>
 #include <stdio.h>
 #include <string.h>
 #include <signal.h>

 #include <openssl/dh.h>

 #include "sshkey.h"
 #include "cipher.h"
 #include "digest.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"
 #include "dispatch.h"
 #include "ssherr.h"
 #include "sshbuf.h"
 #include "misc.h"

 static int input_kex_dh_gex_request(int, u_int32_t, struct ssh *);
 static int input_kex_dh_gex_init(int, u_int32_t, struct ssh *);

 int
 kexgex_server(struct ssh *ssh)
 {
 	ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST,
 	    &input_kex_dh_gex_request);
 	debug("expecting SSH2_MSG_KEX_DH_GEX_REQUEST");
 	return 0;
 }

 static int
 input_kex_dh_gex_request(int type, u_int32_t seq, struct ssh *ssh)
 {
 	struct kex *kex = ssh->kex;
 	int r;
 	u_int min = 0, max = 0, nbits = 0;

 	debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
 	if ((r = sshpkt_get_u32(ssh, &min)) != 0 ||
 	    (r = sshpkt_get_u32(ssh, &nbits)) != 0 ||
 	    (r = sshpkt_get_u32(ssh, &max)) != 0 ||
 	    (r = sshpkt_get_end(ssh)) != 0)
 		goto out;
 	kex->nbits = nbits;
 	kex->min = min;
 	kex->max = max;
 	min = MAXIMUM(DH_GRP_MIN, min);
 	max = MINIMUM(DH_GRP_MAX, max);
 	nbits = MAXIMUM(DH_GRP_MIN, nbits);
 	nbits = MINIMUM(DH_GRP_MAX, nbits);

 	if (kex->max < kex->min || kex->nbits < kex->min ||
 	    kex->max < kex->nbits || kex->max < DH_GRP_MIN) {
 		r = SSH_ERR_DH_GEX_OUT_OF_RANGE;
 		goto out;
 	}

 	/* Contact privileged parent */
 	kex->dh = PRIVSEP(choose_dh(min, nbits, max));
 	if (kex->dh == NULL) {
 		sshpkt_disconnect(ssh, "no matching DH grp found");
 		r = SSH_ERR_ALLOC_FAIL;
 		goto out;
 	}
 	debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
 	if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_GROUP)) != 0 ||
 	    (r = sshpkt_put_bignum2(ssh, kex->dh->p)) != 0 ||
 	    (r = sshpkt_put_bignum2(ssh, kex->dh->g)) != 0 ||
 	    (r = sshpkt_send(ssh)) != 0)
 		goto out;

 	/* Compute our exchange value in parallel with the client */
 	if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
 		goto out;

 	debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
 	ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_INIT, &input_kex_dh_gex_init);
 	r = 0;
  out:
 	return r;
 }

 static int
 input_kex_dh_gex_init(int type, u_int32_t seq, struct ssh *ssh)
 {
 	struct kex *kex = ssh->kex;
 	BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
 	struct sshkey *server_host_public, *server_host_private;
 	u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL;
 	u_char hash[SSH_DIGEST_MAX_LENGTH];
 	size_t sbloblen, slen;
 	size_t klen = 0, hashlen;
 	int kout, r;

 	if (kex->load_host_public_key == NULL ||
 	    kex->load_host_private_key == NULL) {
 		r = SSH_ERR_INVALID_ARGUMENT;
 		goto out;
 	}
 	server_host_public = kex->load_host_public_key(kex->hostkey_type,
 	    kex->hostkey_nid, ssh);
 	server_host_private = kex->load_host_private_key(kex->hostkey_type,
 	    kex->hostkey_nid, ssh);
 	if (server_host_public == NULL) {
 		r = SSH_ERR_NO_HOSTKEY_LOADED;
 		goto out;
 	}

 	/* key, cert */
 	if ((dh_client_pub = BN_new()) == NULL) {
 		r = SSH_ERR_ALLOC_FAIL;
 		goto out;
 	}
 	if ((r = sshpkt_get_bignum2(ssh, dh_client_pub)) != 0 ||
 	    (r = sshpkt_get_end(ssh)) != 0)
 		goto out;

 #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, kex->dh);
 	fprintf(stderr, "pub= ");
 	BN_print_fp(stderr, kex->dh->pub_key);
 	fprintf(stderr, "\n");
 #endif
 	if (!dh_pub_is_valid(kex->dh, dh_client_pub)) {
 		sshpkt_disconnect(ssh, "bad client public DH value");
 		r = SSH_ERR_MESSAGE_INCOMPLETE;
 		goto out;
 	}

 	klen = DH_size(kex->dh);
 	if ((kbuf = malloc(klen)) == NULL ||
 	    (shared_secret = BN_new()) == NULL) {
 		r = SSH_ERR_ALLOC_FAIL;
 		goto out;
 	}
 	if ((kout = DH_compute_key(kbuf, dh_client_pub, kex->dh)) < 0 ||
 	    BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
 		r = SSH_ERR_LIBCRYPTO_ERROR;
 		goto out;
 	}
 #ifdef DEBUG_KEXDH
 	dump_digest("shared secret", kbuf, kout);
 #endif
 	if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
 	    &sbloblen)) != 0)
 		goto out;
 	/* calc H */
 	hashlen = sizeof(hash);
 	if ((r = kexgex_hash(
 	    kex->hash_alg,
 	    kex->client_version_string,
 	    kex->server_version_string,
 	    sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
 	    sshbuf_ptr(kex->my), sshbuf_len(kex->my),
 	    server_host_key_blob, sbloblen,
 	    kex->min, kex->nbits, kex->max,
 	    kex->dh->p, kex->dh->g,
 	    dh_client_pub,
 	    kex->dh->pub_key,
 	    shared_secret,
 	    hash, &hashlen)) != 0)
 		goto out;

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

 	/* sign H */
 	if ((r = kex->sign(server_host_private, server_host_public, &signature,
 	     &slen, hash, hashlen, kex->hostkey_alg, ssh->compat)) < 0)
 		goto out;

 	/* destroy_sensitive_data(); */

 	/* send server hostkey, DH pubkey 'f' and signed H */
 	if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REPLY)) != 0 ||
 	    (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
 	    (r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 ||     /* f */
 	    (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
 	    (r = sshpkt_send(ssh)) != 0)
 		goto out;

 	if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
 		r = kex_send_newkeys(ssh);
  out:
 	DH_free(kex->dh);
 	kex->dh = NULL;
 	BN_clear_free(dh_client_pub);
 	if (kbuf) {
 		explicit_bzero(kbuf, klen);
 		free(kbuf);
 	}
 	BN_clear_free(shared_secret);
 	free(server_host_key_blob);
 	free(signature);
 	return r;
 }
 #endif /* WITH_OPENSSL */
	/* $OpenBSD: kexgexs.c,v 1.33 2018/04/10 00:10:49 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"

	#ifdef WITH_OPENSSL


	#include <stdarg.h>
	#include <stdio.h>
	#include <string.h>
	#include <signal.h>

	#include <openssl/dh.h>

	#include "sshkey.h"
	#include "cipher.h"
	#include "digest.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"
	#include "dispatch.h"
	#include "ssherr.h"
	#include "sshbuf.h"
	#include "misc.h"

	static int input_kex_dh_gex_request(int, u_int32_t, struct ssh *);
	static int input_kex_dh_gex_init(int, u_int32_t, struct ssh *);

	int
	kexgex_server(struct ssh *ssh)
	{
	ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST,
	&input_kex_dh_gex_request);
	debug("expecting SSH2_MSG_KEX_DH_GEX_REQUEST");
	return 0;
	}

	static int
	input_kex_dh_gex_request(int type, u_int32_t seq, struct ssh *ssh)
	{
	struct kex *kex = ssh->kex;
	int r;
	u_int min = 0, max = 0, nbits = 0;

	debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
	if ((r = sshpkt_get_u32(ssh, &min)) != 0 \|\|
	(r = sshpkt_get_u32(ssh, &nbits)) != 0 \|\|
	(r = sshpkt_get_u32(ssh, &max)) != 0 \|\|
	(r = sshpkt_get_end(ssh)) != 0)
	goto out;
	kex->nbits = nbits;
	kex->min = min;
	kex->max = max;
	min = MAXIMUM(DH_GRP_MIN, min);
	max = MINIMUM(DH_GRP_MAX, max);
	nbits = MAXIMUM(DH_GRP_MIN, nbits);
	nbits = MINIMUM(DH_GRP_MAX, nbits);

	if (kex->max < kex->min \|\| kex->nbits < kex->min \|\|
	kex->max < kex->nbits \|\| kex->max < DH_GRP_MIN) {
	r = SSH_ERR_DH_GEX_OUT_OF_RANGE;
	goto out;
	}

	/* Contact privileged parent */
	kex->dh = PRIVSEP(choose_dh(min, nbits, max));
	if (kex->dh == NULL) {
	sshpkt_disconnect(ssh, "no matching DH grp found");
	r = SSH_ERR_ALLOC_FAIL;
	goto out;
	}
	debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
	if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_GROUP)) != 0 \|\|
	(r = sshpkt_put_bignum2(ssh, kex->dh->p)) != 0 \|\|
	(r = sshpkt_put_bignum2(ssh, kex->dh->g)) != 0 \|\|
	(r = sshpkt_send(ssh)) != 0)
	goto out;

	/* Compute our exchange value in parallel with the client */
	if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
	goto out;

	debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
	ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_INIT, &input_kex_dh_gex_init);
	r = 0;
	out:
	return r;
	}

	static int
	input_kex_dh_gex_init(int type, u_int32_t seq, struct ssh *ssh)
	{
	struct kex *kex = ssh->kex;
	BIGNUM shared_secret = NULL, dh_client_pub = NULL;
	struct sshkey server_host_public, server_host_private;
	u_char kbuf = NULL, signature = NULL, *server_host_key_blob = NULL;
	u_char hash[SSH_DIGEST_MAX_LENGTH];
	size_t sbloblen, slen;
	size_t klen = 0, hashlen;
	int kout, r;

	if (kex->load_host_public_key == NULL \|\|
	kex->load_host_private_key == NULL) {
	r = SSH_ERR_INVALID_ARGUMENT;
	goto out;
	}
	server_host_public = kex->load_host_public_key(kex->hostkey_type,
	kex->hostkey_nid, ssh);
	server_host_private = kex->load_host_private_key(kex->hostkey_type,
	kex->hostkey_nid, ssh);
	if (server_host_public == NULL) {
	r = SSH_ERR_NO_HOSTKEY_LOADED;
	goto out;
	}

	/* key, cert */
	if ((dh_client_pub = BN_new()) == NULL) {
	r = SSH_ERR_ALLOC_FAIL;
	goto out;
	}
	if ((r = sshpkt_get_bignum2(ssh, dh_client_pub)) != 0 \|\|
	(r = sshpkt_get_end(ssh)) != 0)
	goto out;

	#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, kex->dh);
	fprintf(stderr, "pub= ");
	BN_print_fp(stderr, kex->dh->pub_key);
	fprintf(stderr, "\n");
	#endif
	if (!dh_pub_is_valid(kex->dh, dh_client_pub)) {
	sshpkt_disconnect(ssh, "bad client public DH value");
	r = SSH_ERR_MESSAGE_INCOMPLETE;
	goto out;
	}

	klen = DH_size(kex->dh);
	if ((kbuf = malloc(klen)) == NULL \|\|
	(shared_secret = BN_new()) == NULL) {
	r = SSH_ERR_ALLOC_FAIL;
	goto out;
	}
	if ((kout = DH_compute_key(kbuf, dh_client_pub, kex->dh)) < 0 \|\|
	BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
	r = SSH_ERR_LIBCRYPTO_ERROR;
	goto out;
	}
	#ifdef DEBUG_KEXDH
	dump_digest("shared secret", kbuf, kout);
	#endif
	if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
	&sbloblen)) != 0)
	goto out;
	/* calc H */
	hashlen = sizeof(hash);
	if ((r = kexgex_hash(
	kex->hash_alg,
	kex->client_version_string,
	kex->server_version_string,
	sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
	sshbuf_ptr(kex->my), sshbuf_len(kex->my),
	server_host_key_blob, sbloblen,
	kex->min, kex->nbits, kex->max,
	kex->dh->p, kex->dh->g,
	dh_client_pub,
	kex->dh->pub_key,
	shared_secret,
	hash, &hashlen)) != 0)
	goto out;

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

	/* sign H */
	if ((r = kex->sign(server_host_private, server_host_public, &signature,
	&slen, hash, hashlen, kex->hostkey_alg, ssh->compat)) < 0)
	goto out;

	/* destroy_sensitive_data(); */

	/* send server hostkey, DH pubkey 'f' and signed H */
	if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REPLY)) != 0 \|\|
	(r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 \|\|
	(r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 \|\| /* f */
	(r = sshpkt_put_string(ssh, signature, slen)) != 0 \|\|
	(r = sshpkt_send(ssh)) != 0)
	goto out;

	if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
	r = kex_send_newkeys(ssh);
	out:
	DH_free(kex->dh);
	kex->dh = NULL;
	BN_clear_free(dh_client_pub);
	if (kbuf) {
	explicit_bzero(kbuf, klen);
	free(kbuf);
	}
	BN_clear_free(shared_secret);
	free(server_host_key_blob);
	free(signature);
	return r;
	}
	#endif /* WITH_OPENSSL */