1/* ====================================================================
2 * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
3 *
4 * The Elliptic Curve Public-Key Crypto Library (ECC Code) included
5 * herein is developed by SUN MICROSYSTEMS, INC., and is contributed
6 * to the OpenSSL project.
7 *
8 * The ECC Code is licensed pursuant to the OpenSSL open source
9 * license provided below.
10 *
11 * The ECDH software is originally written by Douglas Stebila of
12 * Sun Microsystems Laboratories.
13 *
14 */
15/* ====================================================================
16 * Copyright (c) 2000-2002 The OpenSSL Project.  All rights reserved.
17 *
18 * Redistribution and use in source and binary forms, with or without
19 * modification, are permitted provided that the following conditions
20 * are met:
21 *
22 * 1. Redistributions of source code must retain the above copyright
23 *    notice, this list of conditions and the following disclaimer.
24 *
25 * 2. Redistributions in binary form must reproduce the above copyright
26 *    notice, this list of conditions and the following disclaimer in
27 *    the documentation and/or other materials provided with the
28 *    distribution.
29 *
30 * 3. All advertising materials mentioning features or use of this
31 *    software must display the following acknowledgment:
32 *    "This product includes software developed by the OpenSSL Project
33 *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
34 *
35 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
36 *    endorse or promote products derived from this software without
37 *    prior written permission. For written permission, please contact
38 *    licensing@OpenSSL.org.
39 *
40 * 5. Products derived from this software may not be called "OpenSSL"
41 *    nor may "OpenSSL" appear in their names without prior written
42 *    permission of the OpenSSL Project.
43 *
44 * 6. Redistributions of any form whatsoever must retain the following
45 *    acknowledgment:
46 *    "This product includes software developed by the OpenSSL Project
47 *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
48 *
49 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
50 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
51 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
52 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
53 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
54 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
55 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
56 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
57 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
58 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
59 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
60 * OF THE POSSIBILITY OF SUCH DAMAGE.
61 * ====================================================================
62 *
63 * This product includes cryptographic software written by Eric Young
64 * (eay@cryptsoft.com).  This product includes software written by Tim
65 * Hudson (tjh@cryptsoft.com). */
66
67#include <openssl/ecdh.h>
68
69#include <limits.h>
70#include <string.h>
71
72#include <openssl/bn.h>
73#include <openssl/digest.h>
74#include <openssl/err.h>
75#include <openssl/mem.h>
76
77#include "../internal.h"
78
79
80int ECDH_compute_key(void *out, size_t outlen, const EC_POINT *pub_key,
81                     const EC_KEY *priv_key,
82                     void *(*kdf)(const void *in, size_t inlen, void *out,
83                                  size_t *outlen)) {
84  const BIGNUM *const priv = EC_KEY_get0_private_key(priv_key);
85  if (priv == NULL) {
86    OPENSSL_PUT_ERROR(ECDH, ECDH_R_NO_PRIVATE_VALUE);
87    return -1;
88  }
89
90  BN_CTX *ctx = BN_CTX_new();
91  if (ctx == NULL) {
92    return -1;
93  }
94  BN_CTX_start(ctx);
95
96  int ret = -1;
97  size_t buflen = 0;
98  uint8_t *buf = NULL;
99
100  const EC_GROUP *const group = EC_KEY_get0_group(priv_key);
101  EC_POINT *tmp = EC_POINT_new(group);
102  if (tmp == NULL) {
103    OPENSSL_PUT_ERROR(ECDH, ERR_R_MALLOC_FAILURE);
104    goto err;
105  }
106
107  if (!EC_POINT_mul(group, tmp, NULL, pub_key, priv, ctx)) {
108    OPENSSL_PUT_ERROR(ECDH, ECDH_R_POINT_ARITHMETIC_FAILURE);
109    goto err;
110  }
111
112  BIGNUM *x = BN_CTX_get(ctx);
113  if (!x) {
114    OPENSSL_PUT_ERROR(ECDH, ERR_R_MALLOC_FAILURE);
115    goto err;
116  }
117
118  if (!EC_POINT_get_affine_coordinates_GFp(group, tmp, x, NULL, ctx)) {
119    OPENSSL_PUT_ERROR(ECDH, ECDH_R_POINT_ARITHMETIC_FAILURE);
120    goto err;
121  }
122
123  buflen = (EC_GROUP_get_degree(group) + 7) / 8;
124  buf = OPENSSL_malloc(buflen);
125  if (buf == NULL) {
126    OPENSSL_PUT_ERROR(ECDH, ERR_R_MALLOC_FAILURE);
127    goto err;
128  }
129
130  if (!BN_bn2bin_padded(buf, buflen, x)) {
131    OPENSSL_PUT_ERROR(ECDH, ERR_R_INTERNAL_ERROR);
132    goto err;
133  }
134
135  if (kdf != NULL) {
136    if (kdf(buf, buflen, out, &outlen) == NULL) {
137      OPENSSL_PUT_ERROR(ECDH, ECDH_R_KDF_FAILED);
138      goto err;
139    }
140  } else {
141    /* no KDF, just copy as much as we can */
142    if (buflen < outlen) {
143      outlen = buflen;
144    }
145    OPENSSL_memcpy(out, buf, outlen);
146  }
147
148  if (outlen > INT_MAX) {
149    OPENSSL_PUT_ERROR(ECDH, ERR_R_OVERFLOW);
150    goto err;
151  }
152
153  ret = (int)outlen;
154
155err:
156  OPENSSL_free(buf);
157  EC_POINT_free(tmp);
158  BN_CTX_end(ctx);
159  BN_CTX_free(ctx);
160  return ret;
161}
162