1 /* Copyright (c) 2016, Google Inc. 2 * 3 * Permission to use, copy, modify, and/or distribute this software for any 4 * purpose with or without fee is hereby granted, provided that the above 5 * copyright notice and this permission notice appear in all copies. 6 * 7 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 8 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 9 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY 10 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 11 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION 12 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN 13 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ 14 15 #include <openssl/base.h> 16 17 #include <assert.h> 18 #include <string.h> 19 20 #include "internal.h" 21 #include "../../internal.h" 22 23 24 // byte_reverse reverses the order of the bytes in |b->c|. 25 static void byte_reverse(polyval_block *b) { 26 const uint64_t t = CRYPTO_bswap8(b->u[0]); 27 b->u[0] = CRYPTO_bswap8(b->u[1]); 28 b->u[1] = t; 29 } 30 31 // reverse_and_mulX_ghash interprets the bytes |b->c| as a reversed element of 32 // the GHASH field, multiplies that by 'x' and serialises the result back into 33 // |b|, but with GHASH's backwards bit ordering. 34 static void reverse_and_mulX_ghash(polyval_block *b) { 35 uint64_t hi = b->u[0]; 36 uint64_t lo = b->u[1]; 37 const crypto_word_t carry = constant_time_eq_w(hi & 1, 1); 38 hi >>= 1; 39 hi |= lo << 63; 40 lo >>= 1; 41 lo ^= ((uint64_t) constant_time_select_w(carry, 0xe1, 0)) << 56; 42 43 b->u[0] = CRYPTO_bswap8(lo); 44 b->u[1] = CRYPTO_bswap8(hi); 45 } 46 47 // POLYVAL(H, X_1, ..., X_n) = 48 // ByteReverse(GHASH(mulX_GHASH(ByteReverse(H)), ByteReverse(X_1), ..., 49 // ByteReverse(X_n))). 50 // 51 // See https://tools.ietf.org/html/draft-irtf-cfrg-gcmsiv-02#appendix-A. 52 53 void CRYPTO_POLYVAL_init(struct polyval_ctx *ctx, const uint8_t key[16]) { 54 polyval_block H; 55 OPENSSL_memcpy(H.c, key, 16); 56 reverse_and_mulX_ghash(&H); 57 58 int is_avx; 59 CRYPTO_ghash_init(&ctx->gmult, &ctx->ghash, &ctx->H, ctx->Htable, &is_avx, 60 H.c); 61 OPENSSL_memset(&ctx->S, 0, sizeof(ctx->S)); 62 } 63 64 void CRYPTO_POLYVAL_update_blocks(struct polyval_ctx *ctx, const uint8_t *in, 65 size_t in_len) { 66 assert((in_len & 15) == 0); 67 polyval_block reversed[32]; 68 69 while (in_len > 0) { 70 size_t todo = in_len; 71 if (todo > sizeof(reversed)) { 72 todo = sizeof(reversed); 73 } 74 OPENSSL_memcpy(reversed, in, todo); 75 in += todo; 76 in_len -= todo; 77 78 size_t blocks = todo / sizeof(polyval_block); 79 for (size_t i = 0; i < blocks; i++) { 80 byte_reverse(&reversed[i]); 81 } 82 83 ctx->ghash(ctx->S.u, ctx->Htable, (const uint8_t *) reversed, todo); 84 } 85 } 86 87 void CRYPTO_POLYVAL_finish(const struct polyval_ctx *ctx, uint8_t out[16]) { 88 polyval_block S = ctx->S; 89 byte_reverse(&S); 90 OPENSSL_memcpy(out, &S.c, sizeof(polyval_block)); 91 } 92
