1*0957b409SSimon J. Gerraty /*
2*0957b409SSimon J. Gerraty * Copyright (c) 2018 Thomas Pornin <pornin@bolet.org>
3*0957b409SSimon J. Gerraty *
4*0957b409SSimon J. Gerraty * Permission is hereby granted, free of charge, to any person obtaining
5*0957b409SSimon J. Gerraty * a copy of this software and associated documentation files (the
6*0957b409SSimon J. Gerraty * "Software"), to deal in the Software without restriction, including
7*0957b409SSimon J. Gerraty * without limitation the rights to use, copy, modify, merge, publish,
8*0957b409SSimon J. Gerraty * distribute, sublicense, and/or sell copies of the Software, and to
9*0957b409SSimon J. Gerraty * permit persons to whom the Software is furnished to do so, subject to
10*0957b409SSimon J. Gerraty * the following conditions:
11*0957b409SSimon J. Gerraty *
12*0957b409SSimon J. Gerraty * The above copyright notice and this permission notice shall be
13*0957b409SSimon J. Gerraty * included in all copies or substantial portions of the Software.
14*0957b409SSimon J. Gerraty *
15*0957b409SSimon J. Gerraty * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16*0957b409SSimon J. Gerraty * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17*0957b409SSimon J. Gerraty * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
18*0957b409SSimon J. Gerraty * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
19*0957b409SSimon J. Gerraty * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
20*0957b409SSimon J. Gerraty * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
21*0957b409SSimon J. Gerraty * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
22*0957b409SSimon J. Gerraty * SOFTWARE.
23*0957b409SSimon J. Gerraty */
24*0957b409SSimon J. Gerraty
25*0957b409SSimon J. Gerraty #include "inner.h"
26*0957b409SSimon J. Gerraty
27*0957b409SSimon J. Gerraty /* see bearssl_ec.h */
28*0957b409SSimon J. Gerraty size_t
br_ec_keygen(const br_prng_class ** rng_ctx,const br_ec_impl * impl,br_ec_private_key * sk,void * kbuf,int curve)29*0957b409SSimon J. Gerraty br_ec_keygen(const br_prng_class **rng_ctx,
30*0957b409SSimon J. Gerraty const br_ec_impl *impl, br_ec_private_key *sk,
31*0957b409SSimon J. Gerraty void *kbuf, int curve)
32*0957b409SSimon J. Gerraty {
33*0957b409SSimon J. Gerraty const unsigned char *order;
34*0957b409SSimon J. Gerraty unsigned char *buf;
35*0957b409SSimon J. Gerraty size_t len;
36*0957b409SSimon J. Gerraty unsigned mask;
37*0957b409SSimon J. Gerraty
38*0957b409SSimon J. Gerraty if (curve < 0 || curve >= 32
39*0957b409SSimon J. Gerraty || ((impl->supported_curves >> curve) & 1) == 0)
40*0957b409SSimon J. Gerraty {
41*0957b409SSimon J. Gerraty return 0;
42*0957b409SSimon J. Gerraty }
43*0957b409SSimon J. Gerraty order = impl->order(curve, &len);
44*0957b409SSimon J. Gerraty while (len > 0 && *order == 0) {
45*0957b409SSimon J. Gerraty order ++;
46*0957b409SSimon J. Gerraty len --;
47*0957b409SSimon J. Gerraty }
48*0957b409SSimon J. Gerraty if (kbuf == NULL || len == 0) {
49*0957b409SSimon J. Gerraty return len;
50*0957b409SSimon J. Gerraty }
51*0957b409SSimon J. Gerraty mask = order[0];
52*0957b409SSimon J. Gerraty mask |= (mask >> 1);
53*0957b409SSimon J. Gerraty mask |= (mask >> 2);
54*0957b409SSimon J. Gerraty mask |= (mask >> 4);
55*0957b409SSimon J. Gerraty
56*0957b409SSimon J. Gerraty /*
57*0957b409SSimon J. Gerraty * We generate sequences of random bits of the right size, until
58*0957b409SSimon J. Gerraty * the value is strictly lower than the curve order (we also
59*0957b409SSimon J. Gerraty * check for all-zero values, which are invalid).
60*0957b409SSimon J. Gerraty */
61*0957b409SSimon J. Gerraty buf = kbuf;
62*0957b409SSimon J. Gerraty for (;;) {
63*0957b409SSimon J. Gerraty size_t u;
64*0957b409SSimon J. Gerraty unsigned cc, zz;
65*0957b409SSimon J. Gerraty
66*0957b409SSimon J. Gerraty (*rng_ctx)->generate(rng_ctx, buf, len);
67*0957b409SSimon J. Gerraty buf[0] &= mask;
68*0957b409SSimon J. Gerraty cc = 0;
69*0957b409SSimon J. Gerraty u = len;
70*0957b409SSimon J. Gerraty zz = 0;
71*0957b409SSimon J. Gerraty while (u -- > 0) {
72*0957b409SSimon J. Gerraty cc = ((unsigned)(buf[u] - order[u] - cc) >> 8) & 1;
73*0957b409SSimon J. Gerraty zz |= buf[u];
74*0957b409SSimon J. Gerraty }
75*0957b409SSimon J. Gerraty if (cc != 0 && zz != 0) {
76*0957b409SSimon J. Gerraty break;
77*0957b409SSimon J. Gerraty }
78*0957b409SSimon J. Gerraty }
79*0957b409SSimon J. Gerraty
80*0957b409SSimon J. Gerraty if (sk != NULL) {
81*0957b409SSimon J. Gerraty sk->curve = curve;
82*0957b409SSimon J. Gerraty sk->x = buf;
83*0957b409SSimon J. Gerraty sk->xlen = len;
84*0957b409SSimon J. Gerraty }
85*0957b409SSimon J. Gerraty return len;
86*0957b409SSimon J. Gerraty }
87