1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
|
/*
* Copyright 2016 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include <string.h>
#include <openssl/err.h>
#include <openssl/rand.h>
#include "ec_lcl.h"
/* Length of Curve 25519 keys */
#define EC_X25519_KEYLEN 32
/* Group degree and order bits */
#define EC_X25519_BITS 253
/* Copy Curve25519 public key buffer, allocating is necessary */
static int x25519_init_public(EC_POINT *pub, const void *src)
{
if (pub->custom_data == NULL) {
pub->custom_data = OPENSSL_malloc(EC_X25519_KEYLEN);
if (pub->custom_data == NULL)
return 0;
}
if (src != NULL)
memcpy(pub->custom_data, src, EC_X25519_KEYLEN);
return 1;
}
/* Copy Curve25519 private key buffer, allocating is necessary */
static int x25519_init_private(EC_KEY *dst, const void *src)
{
if (dst->custom_data == NULL) {
dst->custom_data = OPENSSL_secure_malloc(EC_X25519_KEYLEN);
if (dst->custom_data == NULL)
return 0;
}
if (src != NULL)
memcpy(dst->custom_data, src, EC_X25519_KEYLEN);
return 1;
}
static int x25519_group_init(EC_GROUP *grp)
{
return 1;
}
static int x25519_group_copy(EC_GROUP *dst, const EC_GROUP *src)
{
return 1;
}
static int x25519_group_get_degree(const EC_GROUP *src)
{
return EC_X25519_BITS;
}
static int x25519_group_order_bits(const EC_GROUP *src)
{
return EC_X25519_BITS;
}
static int x25519_set_private(EC_KEY *eckey, const BIGNUM *priv_key)
{
if (BN_num_bytes(priv_key) > EC_X25519_KEYLEN)
return 0;
if (x25519_init_private(eckey, NULL))
return 0;
/* Convert BIGNUM form private key to internal format */
if (BN_bn2lebinpad(priv_key, eckey->custom_data, EC_X25519_KEYLEN)
!= EC_X25519_KEYLEN)
return 0;
return 1;
}
static int x25519_keycheck(const EC_KEY *eckey)
{
const char *pubkey;
if (eckey->pub_key == NULL)
return 0;
pubkey = eckey->pub_key->custom_data;
if (pubkey == NULL)
return 0;
if (eckey->custom_data != NULL) {
uint8_t tmp[EC_X25519_KEYLEN];
/* Check eckey->priv_key exists and matches eckey->custom_data */
if (eckey->priv_key == NULL)
return 0;
if (BN_bn2lebinpad(eckey->priv_key, tmp, EC_X25519_KEYLEN)
!= EC_X25519_KEYLEN
|| CRYPTO_memcmp(tmp, eckey->custom_data,
EC_X25519_KEYLEN) != 0) {
OPENSSL_cleanse(tmp, EC_X25519_KEYLEN);
return 0;
}
X25519_public_from_private(tmp, eckey->custom_data);
if (CRYPTO_memcmp(pubkey, tmp, EC_X25519_KEYLEN) == 0)
return 1;
return 0;
} else {
return 1;
}
}
static int x25519_keygenpub(EC_KEY *eckey)
{
X25519_public_from_private(eckey->pub_key->custom_data,
eckey->custom_data);
return 1;
}
static int x25519_keygen(EC_KEY *eckey)
{
unsigned char *key;
if (x25519_init_private(eckey, NULL) == 0)
return 0;
key = eckey->custom_data;
if (RAND_bytes(key, EC_X25519_KEYLEN) <= 0)
return 0;
key[0] &= 248;
key[31] &= 127;
key[31] |= 64;
/*
* Although the private key is kept as an array in eckey->custom_data
* Set eckey->priv_key too so existing code which uses
* EC_KEY_get0_private_key() still works.
*/
if (eckey->priv_key == NULL)
eckey->priv_key = BN_secure_new();
if (eckey->priv_key == NULL)
return 0;
if (BN_lebin2bn(eckey->custom_data, EC_X25519_KEYLEN, eckey->priv_key) ==
NULL)
return 0;
if (eckey->pub_key == NULL)
eckey->pub_key = EC_POINT_new(eckey->group);
if (eckey->pub_key == NULL)
return 0;
return x25519_keygenpub(eckey);
}
static void x25519_keyfinish(EC_KEY *eckey)
{
OPENSSL_secure_free(eckey->custom_data);
eckey->custom_data = NULL;
}
static int x25519_keycopy(EC_KEY *dest, const EC_KEY *src)
{
if (src->custom_data == NULL)
return 0;
return x25519_init_private(dest, src->custom_data);
}
static int x25519_oct2priv(EC_KEY *eckey, unsigned char *buf, size_t len)
{
if (len != EC_X25519_KEYLEN)
return 0;
if (x25519_init_private(eckey, buf) == 0)
return 0;
/*
* Although the private key is kept as an array in eckey->custom_data
* Set eckey->priv_key too so existing code which uses
* EC_KEY_get0_private_key() still works.
*/
if (eckey->priv_key == NULL)
eckey->priv_key = BN_secure_new();
if (eckey->priv_key == NULL)
return 0;
if (BN_lebin2bn(buf, EC_X25519_KEYLEN, eckey->priv_key) == NULL)
return 0;
return 1;
}
static size_t x25519_priv2oct(const EC_KEY *eckey,
unsigned char *buf, size_t len)
{
size_t keylen = EC_X25519_KEYLEN;
if (eckey->custom_data == NULL)
return 0;
if (buf != NULL) {
if (len < keylen)
return 0;
memcpy(buf, eckey->custom_data, keylen);
}
return keylen;
}
static int x25519_point_init(EC_POINT *pt)
{
return x25519_init_public(pt, NULL);
}
static void x25519_point_finish(EC_POINT *pt)
{
OPENSSL_free(pt->custom_data);
pt->custom_data = NULL;
}
static void x25519_point_clear_finish(EC_POINT *pt)
{
OPENSSL_clear_free(pt->custom_data, EC_X25519_KEYLEN);
pt->custom_data = NULL;
}
static int x25519_point_copy(EC_POINT *dst, const EC_POINT *src)
{
memcpy(dst->custom_data, src->custom_data, EC_X25519_KEYLEN);
return 1;
}
static size_t x25519_point2oct(const EC_GROUP *grp, const EC_POINT *pt,
point_conversion_form_t form,
unsigned char *buf, size_t len, BN_CTX *ctx)
{
if (buf != NULL) {
if (len < EC_X25519_KEYLEN)
return 0;
memcpy(buf, pt->custom_data, EC_X25519_KEYLEN);
}
return EC_X25519_KEYLEN;
}
static int x25519_oct2point(const EC_GROUP *grp, EC_POINT *pt,
const unsigned char *buf, size_t len, BN_CTX *ctx)
{
unsigned char *pubkey = pt->custom_data;
if (len != EC_X25519_KEYLEN)
return 0;
memcpy(pubkey, buf, EC_X25519_KEYLEN);
/* Mask off MSB */
pubkey[EC_X25519_KEYLEN - 1] &= 0x7F;
return 1;
}
static int x25519_point_cmp(const EC_GROUP *group, const EC_POINT *a,
const EC_POINT *b, BN_CTX *ctx)
{
/* Shouldn't happen as initialised to non-zero */
if (a->custom_data == NULL || b->custom_data == NULL)
return -1;
if (CRYPTO_memcmp(a->custom_data, b->custom_data, EC_X25519_KEYLEN) == 0)
return 0;
return 1;
}
static int x25519_compute_key(unsigned char **psec, size_t *pseclen,
const EC_POINT *pub_key, const EC_KEY *ecdh)
{
unsigned char *key;
int ret = -1;
if (ecdh->custom_data == NULL)
return -1;
key = OPENSSL_malloc(EC_X25519_KEYLEN);
if (key == NULL)
return 0;
if (X25519(key, ecdh->custom_data, pub_key->custom_data) == 0)
goto err;
*psec = key;
*pseclen = EC_X25519_KEYLEN;
return 1;
err:
OPENSSL_clear_free(key, EC_X25519_KEYLEN);
return ret;
}
const EC_METHOD *ec_x25519_meth(void)
{
static const EC_METHOD ret = {
EC_FLAGS_CUSTOM_CURVE | EC_FLAGS_NO_SIGN,
NID_undef,
x25519_group_init, /* group_init */
0, /* group_finish */
0, /* group_clear_finish */
x25519_group_copy, /* group_copy */
0, /* group_set_curve */
0, /* group_get_curve */
x25519_group_get_degree,
x25519_group_order_bits,
0, /* group_check_discriminant */
x25519_point_init,
x25519_point_finish,
x25519_point_clear_finish,
x25519_point_copy,
0, /* point_set_to_infinity */
0, /* set_Jprojective_coordinates_GFp */
0, /* get_Jprojective_coordinates_GFp */
0, /* point_set_affine_coordinates */
0, /* point_get_affine_coordinates */
0, /* point_set_compressed_coordinates */
x25519_point2oct,
x25519_oct2point,
0, /* simple_add */
0, /* simple_dbl */
0, /* simple_invert */
0, /* simple_is_at_infinity */
0, /* simple_is_on_curve */
x25519_point_cmp,
0, /* simple_make_affine */
0, /* simple_points_make_affine */
0, /* points_mul */
0, /* precompute_mult */
0, /* have_precompute_mult */
0, /* field_mul */
0, /* field_sqr */
0, /* field_div */
0, /* field_encode */
0, /* field_decode */
0, /* field_set_to_one */
x25519_priv2oct,
x25519_oct2priv,
x25519_set_private,
x25519_keygen,
x25519_keycheck,
x25519_keygenpub,
x25519_keycopy,
x25519_keyfinish,
x25519_compute_key
};
return &ret;
}
|