IABSD.fr/src/lib/libssl/ssl_kex.c

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• Author : jsing
  Date : 2020-04-18 14:07:56
  Hash : 501dd9a5
  Message : Expose the peer ephemeral public key used for TLSv1.3 key exchange. SSL_get_server_tmp_key() provides the peer ephemeral public key used for key exchange. In the case of TLSv1.3 this is essentially the peer public key from the key share used for TLSv1.3 key exchange, hence make it availaable via SSL_get_server_tmp_key(). ok inoguchi@ tb@

• lib/libssl/ssl_kex.c

• /* $OpenBSD: ssl_kex.c,v 1.2 2020/04/18 14:07:56 jsing Exp $ */
  /*
   * Copyright (c) 2020 Joel Sing <jsing@openbsd.org>
   *
   * Permission to use, copy, modify, and distribute this software for any
   * purpose with or without fee is hereby granted, provided that the above
   * copyright notice and this permission notice appear in all copies.
   *
   * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
   * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
   * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   */
  
  #include <stdlib.h>
  
  #include <openssl/ec.h>
  #include <openssl/ecdh.h>
  #include <openssl/evp.h>
  #include <openssl/objects.h>
  
  #include "bytestring.h"
  
  int
  ssl_kex_dummy_ecdhe_x25519(EVP_PKEY *pkey)
  {
  	EC_GROUP *group = NULL;
  	EC_POINT *point = NULL;
  	EC_KEY *ec_key = NULL;
  	BIGNUM *order = NULL;
  	int ret = 0;
  
  	/* Fudge up an EC_KEY that looks like X25519... */
  	if ((group = EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1)) == NULL)
  		goto err;
  	if ((point = EC_POINT_new(group)) == NULL)
  		goto err;
  	if ((order = BN_new()) == NULL)
  		goto err;
  	if (!BN_set_bit(order, 252))
  		goto err;
  	if (!EC_GROUP_set_generator(group, point, order, NULL))
  		goto err;
  	EC_GROUP_set_curve_name(group, NID_X25519);
  	if ((ec_key = EC_KEY_new()) == NULL)
  		goto err;
  	if (!EC_KEY_set_group(ec_key, group))
  		goto err;
  	if (!EVP_PKEY_set1_EC_KEY(pkey, ec_key))
  		goto err;
  
  	ret = 1;
  
   err:
  	EC_GROUP_free(group);
  	EC_POINT_free(point);
  	EC_KEY_free(ec_key);
  	BN_free(order);
  
  	return ret;
  }
  
  int
  ssl_kex_generate_ecdhe_ecp(EC_KEY *ecdh, int nid)
  {
  	EC_GROUP *group;
  	int ret = 0;
  
  	if ((group = EC_GROUP_new_by_curve_name(nid)) == NULL)
  		goto err;
  
  	if (!EC_KEY_set_group(ecdh, group))
  		goto err;
  	if (!EC_KEY_generate_key(ecdh))
  		goto err;
  
  	ret = 1;
  
   err:
  	EC_GROUP_free(group);
  
  	return ret;
  }
  
  int
  ssl_kex_public_ecdhe_ecp(EC_KEY *ecdh, CBB *cbb)
  {
  	const EC_GROUP *group;
  	const EC_POINT *point;
  	uint8_t *ecp;
  	size_t ecp_len;
  	int ret = 0;
  
  	if ((group = EC_KEY_get0_group(ecdh)) == NULL)
  		goto err;
  	if ((point = EC_KEY_get0_public_key(ecdh)) == NULL)
  		goto err;
  
  	if ((ecp_len = EC_POINT_point2oct(group, point,
  	    POINT_CONVERSION_UNCOMPRESSED, NULL, 0, NULL)) == 0)
  		goto err;
  	if (!CBB_add_space(cbb, &ecp, ecp_len))
  		goto err;
  	if ((EC_POINT_point2oct(group, point, POINT_CONVERSION_UNCOMPRESSED,
  	    ecp, ecp_len, NULL)) == 0)
  		goto err;
  
  	ret = 1;
  
   err:
  	return ret;
  }
  
  int
  ssl_kex_peer_public_ecdhe_ecp(EC_KEY *ecdh, int nid, CBS *cbs)
  {
  	EC_GROUP *group = NULL;
  	EC_POINT *point = NULL;
  	int ret = 0;
  
  	if ((group = EC_GROUP_new_by_curve_name(nid)) == NULL)
  		goto err;
  
  	if (!EC_KEY_set_group(ecdh, group))
  		goto err;
  
  	if ((point = EC_POINT_new(group)) == NULL)
  		goto err;
  	if (EC_POINT_oct2point(group, point, CBS_data(cbs), CBS_len(cbs),
  	    NULL) == 0)
  		goto err;
  	if (!EC_KEY_set_public_key(ecdh, point))
  		goto err;
  
  	ret = 1;
  
   err:
  	EC_GROUP_free(group);
  	EC_POINT_free(point);
  
  	return ret;
  }
  
  int
  ssl_kex_derive_ecdhe_ecp(EC_KEY *ecdh, EC_KEY *ecdh_peer,
      uint8_t **shared_key, size_t *shared_key_len)
  {
  	const EC_POINT *point;
  	uint8_t *sk = NULL;
  	int sk_len = 0;
  	int ret = 0;
  
  	if (!EC_GROUP_check(EC_KEY_get0_group(ecdh), NULL))
  		goto err;
  	if (!EC_GROUP_check(EC_KEY_get0_group(ecdh_peer), NULL))
  		goto err;
  
  	if ((point = EC_KEY_get0_public_key(ecdh_peer)) == NULL)
  		goto err;
  
  	if ((sk_len = ECDH_size(ecdh)) <= 0)
  		goto err;
  	if ((sk = calloc(1, sk_len)) == NULL)
  		goto err;
  
  	if (ECDH_compute_key(sk, sk_len, point, ecdh, NULL) <= 0)
  		goto err;
  
  	*shared_key = sk;
  	*shared_key_len = sk_len;
  	sk = NULL;
  
  	ret = 1;
  
   err:
  	freezero(sk, sk_len);
  
  	return ret;
  }