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_rsa.h */ 28*0957b409SSimon J. Gerraty size_t 29*0957b409SSimon J. Gerraty br_rsa_i15_compute_modulus(void *n, const br_rsa_private_key *sk) 30*0957b409SSimon J. Gerraty { 31*0957b409SSimon J. Gerraty uint16_t tmp[2 * ((BR_MAX_RSA_SIZE + 14) / 15) + 5]; 32*0957b409SSimon J. Gerraty uint16_t *t, *p, *q; 33*0957b409SSimon J. Gerraty const unsigned char *pbuf, *qbuf; 34*0957b409SSimon J. Gerraty size_t nlen, plen, qlen, tlen; 35*0957b409SSimon J. Gerraty 36*0957b409SSimon J. Gerraty /* 37*0957b409SSimon J. Gerraty * Compute actual byte and lengths for p and q. 38*0957b409SSimon J. Gerraty */ 39*0957b409SSimon J. Gerraty pbuf = sk->p; 40*0957b409SSimon J. Gerraty plen = sk->plen; 41*0957b409SSimon J. Gerraty while (plen > 0 && *pbuf == 0) { 42*0957b409SSimon J. Gerraty pbuf ++; 43*0957b409SSimon J. Gerraty plen --; 44*0957b409SSimon J. Gerraty } 45*0957b409SSimon J. Gerraty qbuf = sk->q; 46*0957b409SSimon J. Gerraty qlen = sk->qlen; 47*0957b409SSimon J. Gerraty while (qlen > 0 && *qbuf == 0) { 48*0957b409SSimon J. Gerraty qbuf ++; 49*0957b409SSimon J. Gerraty qlen --; 50*0957b409SSimon J. Gerraty } 51*0957b409SSimon J. Gerraty 52*0957b409SSimon J. Gerraty t = tmp; 53*0957b409SSimon J. Gerraty tlen = (sizeof tmp) / (sizeof tmp[0]); 54*0957b409SSimon J. Gerraty 55*0957b409SSimon J. Gerraty /* 56*0957b409SSimon J. Gerraty * Decode p. 57*0957b409SSimon J. Gerraty */ 58*0957b409SSimon J. Gerraty if ((15 * tlen) < (plen << 3) + 15) { 59*0957b409SSimon J. Gerraty return 0; 60*0957b409SSimon J. Gerraty } 61*0957b409SSimon J. Gerraty br_i15_decode(t, pbuf, plen); 62*0957b409SSimon J. Gerraty p = t; 63*0957b409SSimon J. Gerraty plen = (p[0] + 31) >> 4; 64*0957b409SSimon J. Gerraty t += plen; 65*0957b409SSimon J. Gerraty tlen -= plen; 66*0957b409SSimon J. Gerraty 67*0957b409SSimon J. Gerraty /* 68*0957b409SSimon J. Gerraty * Decode q. 69*0957b409SSimon J. Gerraty */ 70*0957b409SSimon J. Gerraty if ((15 * tlen) < (qlen << 3) + 15) { 71*0957b409SSimon J. Gerraty return 0; 72*0957b409SSimon J. Gerraty } 73*0957b409SSimon J. Gerraty br_i15_decode(t, qbuf, qlen); 74*0957b409SSimon J. Gerraty q = t; 75*0957b409SSimon J. Gerraty qlen = (q[0] + 31) >> 4; 76*0957b409SSimon J. Gerraty t += qlen; 77*0957b409SSimon J. Gerraty tlen -= qlen; 78*0957b409SSimon J. Gerraty 79*0957b409SSimon J. Gerraty /* 80*0957b409SSimon J. Gerraty * Computation can proceed only if we have enough room for the 81*0957b409SSimon J. Gerraty * modulus. 82*0957b409SSimon J. Gerraty */ 83*0957b409SSimon J. Gerraty if (tlen < (plen + qlen + 1)) { 84*0957b409SSimon J. Gerraty return 0; 85*0957b409SSimon J. Gerraty } 86*0957b409SSimon J. Gerraty 87*0957b409SSimon J. Gerraty /* 88*0957b409SSimon J. Gerraty * Private key already contains the modulus bit length, from which 89*0957b409SSimon J. Gerraty * we can infer the output length. Even if n is NULL, we still had 90*0957b409SSimon J. Gerraty * to decode p and q to make sure that the product can be computed. 91*0957b409SSimon J. Gerraty */ 92*0957b409SSimon J. Gerraty nlen = (sk->n_bitlen + 7) >> 3; 93*0957b409SSimon J. Gerraty if (n != NULL) { 94*0957b409SSimon J. Gerraty br_i15_zero(t, p[0]); 95*0957b409SSimon J. Gerraty br_i15_mulacc(t, p, q); 96*0957b409SSimon J. Gerraty br_i15_encode(n, nlen, t); 97*0957b409SSimon J. Gerraty } 98*0957b409SSimon J. Gerraty return nlen; 99*0957b409SSimon J. Gerraty } 100