1*0957b409SSimon J. Gerraty /*
2*0957b409SSimon J. Gerraty * Copyright (c) 2016 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_rsa.h */
28*0957b409SSimon J. Gerraty uint32_t
br_rsa_i32_public(unsigned char * x,size_t xlen,const br_rsa_public_key * pk)29*0957b409SSimon J. Gerraty br_rsa_i32_public(unsigned char *x, size_t xlen,
30*0957b409SSimon J. Gerraty const br_rsa_public_key *pk)
31*0957b409SSimon J. Gerraty {
32*0957b409SSimon J. Gerraty const unsigned char *n;
33*0957b409SSimon J. Gerraty size_t nlen;
34*0957b409SSimon J. Gerraty uint32_t m[1 + (BR_MAX_RSA_SIZE >> 5)];
35*0957b409SSimon J. Gerraty uint32_t a[1 + (BR_MAX_RSA_SIZE >> 5)];
36*0957b409SSimon J. Gerraty uint32_t t1[1 + (BR_MAX_RSA_SIZE >> 5)];
37*0957b409SSimon J. Gerraty uint32_t t2[1 + (BR_MAX_RSA_SIZE >> 5)];
38*0957b409SSimon J. Gerraty uint32_t m0i, r;
39*0957b409SSimon J. Gerraty
40*0957b409SSimon J. Gerraty /*
41*0957b409SSimon J. Gerraty * Get the actual length of the modulus, and see if it fits within
42*0957b409SSimon J. Gerraty * our stack buffer. We also check that the length of x[] is valid.
43*0957b409SSimon J. Gerraty */
44*0957b409SSimon J. Gerraty n = pk->n;
45*0957b409SSimon J. Gerraty nlen = pk->nlen;
46*0957b409SSimon J. Gerraty while (nlen > 0 && *n == 0) {
47*0957b409SSimon J. Gerraty n ++;
48*0957b409SSimon J. Gerraty nlen --;
49*0957b409SSimon J. Gerraty }
50*0957b409SSimon J. Gerraty if (nlen == 0 || nlen > (BR_MAX_RSA_SIZE >> 3) || xlen != nlen) {
51*0957b409SSimon J. Gerraty return 0;
52*0957b409SSimon J. Gerraty }
53*0957b409SSimon J. Gerraty br_i32_decode(m, n, nlen);
54*0957b409SSimon J. Gerraty m0i = br_i32_ninv32(m[1]);
55*0957b409SSimon J. Gerraty
56*0957b409SSimon J. Gerraty /*
57*0957b409SSimon J. Gerraty * Note: if m[] is even, then m0i == 0. Otherwise, m0i must be
58*0957b409SSimon J. Gerraty * an odd integer.
59*0957b409SSimon J. Gerraty */
60*0957b409SSimon J. Gerraty r = m0i & 1;
61*0957b409SSimon J. Gerraty
62*0957b409SSimon J. Gerraty /*
63*0957b409SSimon J. Gerraty * Decode x[] into a[]; we also check that its value is proper.
64*0957b409SSimon J. Gerraty */
65*0957b409SSimon J. Gerraty r &= br_i32_decode_mod(a, x, xlen, m);
66*0957b409SSimon J. Gerraty
67*0957b409SSimon J. Gerraty /*
68*0957b409SSimon J. Gerraty * Compute the modular exponentiation.
69*0957b409SSimon J. Gerraty */
70*0957b409SSimon J. Gerraty br_i32_modpow(a, pk->e, pk->elen, m, m0i, t1, t2);
71*0957b409SSimon J. Gerraty
72*0957b409SSimon J. Gerraty /*
73*0957b409SSimon J. Gerraty * Encode the result.
74*0957b409SSimon J. Gerraty */
75*0957b409SSimon J. Gerraty br_i32_encode(x, xlen, a);
76*0957b409SSimon J. Gerraty return r;
77*0957b409SSimon J. Gerraty }
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