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ech_ossl.c
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1 /* crypto/ecdh/ech_ossl.c */
2 /* ====================================================================
3  * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
4  *
5  * The Elliptic Curve Public-Key Crypto Library (ECC Code) included
6  * herein is developed by SUN MICROSYSTEMS, INC., and is contributed
7  * to the OpenSSL project.
8  *
9  * The ECC Code is licensed pursuant to the OpenSSL open source
10  * license provided below.
11  *
12  * The ECDH software is originally written by Douglas Stebila of
13  * Sun Microsystems Laboratories.
14  *
15  */
16 /* ====================================================================
17  * Copyright (c) 1998-2003 The OpenSSL Project. All rights reserved.
18  *
19  * Redistribution and use in source and binary forms, with or without
20  * modification, are permitted provided that the following conditions
21  * are met:
22  *
23  * 1. Redistributions of source code must retain the above copyright
24  * notice, this list of conditions and the following disclaimer.
25  *
26  * 2. Redistributions in binary form must reproduce the above copyright
27  * notice, this list of conditions and the following disclaimer in
28  * the documentation and/or other materials provided with the
29  * distribution.
30  *
31  * 3. All advertising materials mentioning features or use of this
32  * software must display the following acknowledgment:
33  * "This product includes software developed by the OpenSSL Project
34  * for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
35  *
36  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
37  * endorse or promote products derived from this software without
38  * prior written permission. For written permission, please contact
39  * [email protected].
40  *
41  * 5. Products derived from this software may not be called "OpenSSL"
42  * nor may "OpenSSL" appear in their names without prior written
43  * permission of the OpenSSL Project.
44  *
45  * 6. Redistributions of any form whatsoever must retain the following
46  * acknowledgment:
47  * "This product includes software developed by the OpenSSL Project
48  * for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
49  *
50  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
51  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
52  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
53  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
54  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
55  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
56  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
57  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
58  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
59  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
60  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
61  * OF THE POSSIBILITY OF SUCH DAMAGE.
62  * ====================================================================
63  *
64  * This product includes cryptographic software written by Eric Young
65  * ([email protected]). This product includes software written by Tim
66  * Hudson ([email protected]).
67  *
68  */
69 
70 
71 #include <string.h>
72 #include <limits.h>
73 
74 #include "cryptlib.h"
75 
76 #include "ech_locl.h"
77 #include <openssl/err.h>
78 #include <openssl/sha.h>
79 #include <openssl/obj_mac.h>
80 #include <openssl/bn.h>
81 
82 static int ecdh_compute_key(void *out, size_t len, const EC_POINT *pub_key,
83  EC_KEY *ecdh,
84  void *(*KDF)(const void *in, size_t inlen, void *out, size_t *outlen));
85 
86 static ECDH_METHOD openssl_ecdh_meth = {
87  "OpenSSL ECDH method",
88  ecdh_compute_key,
89 #if 0
90  NULL, /* init */
91  NULL, /* finish */
92 #endif
93  0, /* flags */
94  NULL /* app_data */
95 };
96 
97 const ECDH_METHOD *ECDH_OpenSSL(void)
98  {
99  return &openssl_ecdh_meth;
100  }
101 
102 
103 /* This implementation is based on the following primitives in the IEEE 1363 standard:
104  * - ECKAS-DH1
105  * - ECSVDP-DH
106  * Finally an optional KDF is applied.
107  */
108 static int ecdh_compute_key(void *out, size_t outlen, const EC_POINT *pub_key,
109  EC_KEY *ecdh,
110  void *(*KDF)(const void *in, size_t inlen, void *out, size_t *outlen))
111  {
112  BN_CTX *ctx;
113  EC_POINT *tmp=NULL;
114  BIGNUM *x=NULL, *y=NULL;
115  const BIGNUM *priv_key;
116  const EC_GROUP* group;
117  int ret= -1;
118  size_t buflen, len;
119  unsigned char *buf=NULL;
120 
121  if (outlen > INT_MAX)
122  {
123  ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ERR_R_MALLOC_FAILURE); /* sort of, anyway */
124  return -1;
125  }
126 
127  if ((ctx = BN_CTX_new()) == NULL) goto err;
128  BN_CTX_start(ctx);
129  x = BN_CTX_get(ctx);
130  y = BN_CTX_get(ctx);
131 
132  priv_key = EC_KEY_get0_private_key(ecdh);
133  if (priv_key == NULL)
134  {
135  ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ECDH_R_NO_PRIVATE_VALUE);
136  goto err;
137  }
138 
139  group = EC_KEY_get0_group(ecdh);
140  if ((tmp=EC_POINT_new(group)) == NULL)
141  {
142  ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ERR_R_MALLOC_FAILURE);
143  goto err;
144  }
145 
146  if (!EC_POINT_mul(group, tmp, NULL, pub_key, priv_key, ctx))
147  {
148  ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ECDH_R_POINT_ARITHMETIC_FAILURE);
149  goto err;
150  }
151 
152  if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) == NID_X9_62_prime_field)
153  {
154  if (!EC_POINT_get_affine_coordinates_GFp(group, tmp, x, y, ctx))
155  {
156  ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ECDH_R_POINT_ARITHMETIC_FAILURE);
157  goto err;
158  }
159  }
160 #ifndef OPENSSL_NO_EC2M
161  else
162  {
163  if (!EC_POINT_get_affine_coordinates_GF2m(group, tmp, x, y, ctx))
164  {
165  ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ECDH_R_POINT_ARITHMETIC_FAILURE);
166  goto err;
167  }
168  }
169 #endif
170 
171  buflen = (EC_GROUP_get_degree(group) + 7)/8;
172  len = BN_num_bytes(x);
173  if (len > buflen)
174  {
175  ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ERR_R_INTERNAL_ERROR);
176  goto err;
177  }
178  if ((buf = OPENSSL_malloc(buflen)) == NULL)
179  {
180  ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ERR_R_MALLOC_FAILURE);
181  goto err;
182  }
183 
184  memset(buf, 0, buflen - len);
185  if (len != (size_t)BN_bn2bin(x, buf + buflen - len))
186  {
187  ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ERR_R_BN_LIB);
188  goto err;
189  }
190 
191  if (KDF != 0)
192  {
193  if (KDF(buf, buflen, out, &outlen) == NULL)
194  {
195  ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ECDH_R_KDF_FAILED);
196  goto err;
197  }
198  ret = outlen;
199  }
200  else
201  {
202  /* no KDF, just copy as much as we can */
203  if (outlen > buflen)
204  outlen = buflen;
205  memcpy(out, buf, outlen);
206  ret = outlen;
207  }
208 
209 err:
210  if (tmp) EC_POINT_free(tmp);
211  if (ctx) BN_CTX_end(ctx);
212  if (ctx) BN_CTX_free(ctx);
213  if (buf) OPENSSL_free(buf);
214  return(ret);
215  }
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