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 /* 28*0957b409SSimon J. Gerraty * Hash some data. This is put as a separate function so that stack 29*0957b409SSimon J. Gerraty * allocation of the hash function context is done only for the duration 30*0957b409SSimon J. Gerraty * of the hash. 31*0957b409SSimon J. Gerraty */ 32*0957b409SSimon J. Gerraty static void 33*0957b409SSimon J. Gerraty hash_data(const br_hash_class *dig, void *dst, const void *src, size_t len) 34*0957b409SSimon J. Gerraty { 35*0957b409SSimon J. Gerraty br_hash_compat_context hc; 36*0957b409SSimon J. Gerraty 37*0957b409SSimon J. Gerraty hc.vtable = dig; 38*0957b409SSimon J. Gerraty dig->init(&hc.vtable); 39*0957b409SSimon J. Gerraty dig->update(&hc.vtable, src, len); 40*0957b409SSimon J. Gerraty dig->out(&hc.vtable, dst); 41*0957b409SSimon J. Gerraty } 42*0957b409SSimon J. Gerraty 43*0957b409SSimon J. Gerraty /* see inner.h */ 44*0957b409SSimon J. Gerraty size_t 45*0957b409SSimon J. Gerraty br_rsa_oaep_pad(const br_prng_class **rnd, const br_hash_class *dig, 46*0957b409SSimon J. Gerraty const void *label, size_t label_len, 47*0957b409SSimon J. Gerraty const br_rsa_public_key *pk, 48*0957b409SSimon J. Gerraty void *dst, size_t dst_max_len, 49*0957b409SSimon J. Gerraty const void *src, size_t src_len) 50*0957b409SSimon J. Gerraty { 51*0957b409SSimon J. Gerraty size_t k, hlen; 52*0957b409SSimon J. Gerraty unsigned char *buf; 53*0957b409SSimon J. Gerraty 54*0957b409SSimon J. Gerraty hlen = br_digest_size(dig); 55*0957b409SSimon J. Gerraty 56*0957b409SSimon J. Gerraty /* 57*0957b409SSimon J. Gerraty * Compute actual modulus length (in bytes). 58*0957b409SSimon J. Gerraty */ 59*0957b409SSimon J. Gerraty k = pk->nlen; 60*0957b409SSimon J. Gerraty while (k > 0 && pk->n[k - 1] == 0) { 61*0957b409SSimon J. Gerraty k --; 62*0957b409SSimon J. Gerraty } 63*0957b409SSimon J. Gerraty 64*0957b409SSimon J. Gerraty /* 65*0957b409SSimon J. Gerraty * An error is reported if: 66*0957b409SSimon J. Gerraty * - the modulus is too short; 67*0957b409SSimon J. Gerraty * - the source message length is too long; 68*0957b409SSimon J. Gerraty * - the destination buffer is too short. 69*0957b409SSimon J. Gerraty */ 70*0957b409SSimon J. Gerraty if (k < ((hlen << 1) + 2) 71*0957b409SSimon J. Gerraty || src_len > (k - (hlen << 1) - 2) 72*0957b409SSimon J. Gerraty || dst_max_len < k) 73*0957b409SSimon J. Gerraty { 74*0957b409SSimon J. Gerraty return 0; 75*0957b409SSimon J. Gerraty } 76*0957b409SSimon J. Gerraty 77*0957b409SSimon J. Gerraty /* 78*0957b409SSimon J. Gerraty * Apply padding. At this point, things cannot fail. 79*0957b409SSimon J. Gerraty */ 80*0957b409SSimon J. Gerraty buf = dst; 81*0957b409SSimon J. Gerraty 82*0957b409SSimon J. Gerraty /* 83*0957b409SSimon J. Gerraty * Assemble: DB = lHash || PS || 0x01 || M 84*0957b409SSimon J. Gerraty * We first place the source message M with memmove(), so that 85*0957b409SSimon J. Gerraty * overlaps between source and destination buffers are supported. 86*0957b409SSimon J. Gerraty */ 87*0957b409SSimon J. Gerraty memmove(buf + k - src_len, src, src_len); 88*0957b409SSimon J. Gerraty hash_data(dig, buf + 1 + hlen, label, label_len); 89*0957b409SSimon J. Gerraty memset(buf + 1 + (hlen << 1), 0, k - src_len - (hlen << 1) - 2); 90*0957b409SSimon J. Gerraty buf[k - src_len - 1] = 0x01; 91*0957b409SSimon J. Gerraty 92*0957b409SSimon J. Gerraty /* 93*0957b409SSimon J. Gerraty * Make the random seed. 94*0957b409SSimon J. Gerraty */ 95*0957b409SSimon J. Gerraty (*rnd)->generate(rnd, buf + 1, hlen); 96*0957b409SSimon J. Gerraty 97*0957b409SSimon J. Gerraty /* 98*0957b409SSimon J. Gerraty * Mask DB with the mask generated from the seed. 99*0957b409SSimon J. Gerraty */ 100*0957b409SSimon J. Gerraty br_mgf1_xor(buf + 1 + hlen, k - hlen - 1, dig, buf + 1, hlen); 101*0957b409SSimon J. Gerraty 102*0957b409SSimon J. Gerraty /* 103*0957b409SSimon J. Gerraty * Mask the seed with the mask generated from the masked DB. 104*0957b409SSimon J. Gerraty */ 105*0957b409SSimon J. Gerraty br_mgf1_xor(buf + 1, hlen, dig, buf + 1 + hlen, k - hlen - 1); 106*0957b409SSimon J. Gerraty 107*0957b409SSimon J. Gerraty /* 108*0957b409SSimon J. Gerraty * Padding result: EM = 0x00 || maskedSeed || maskedDB. 109*0957b409SSimon J. Gerraty */ 110*0957b409SSimon J. Gerraty buf[0] = 0x00; 111*0957b409SSimon J. Gerraty return k; 112*0957b409SSimon J. Gerraty } 113