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/* Copyright (c) 2016, Google Inc.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
#include <openssl/base.h>
#include <assert.h>
#include <string.h>
#include "internal.h"
#include "../../internal.h"
// byte_reverse reverses the order of the bytes in |b->c|.
static void byte_reverse(polyval_block *b) {
const uint64_t t = CRYPTO_bswap8(b->u[0]);
b->u[0] = CRYPTO_bswap8(b->u[1]);
b->u[1] = t;
}
// reverse_and_mulX_ghash interprets the bytes |b->c| as a reversed element of
// the GHASH field, multiplies that by 'x' and serialises the result back into
// |b|, but with GHASH's backwards bit ordering.
static void reverse_and_mulX_ghash(polyval_block *b) {
uint64_t hi = b->u[0];
uint64_t lo = b->u[1];
const crypto_word_t carry = constant_time_eq_w(hi & 1, 1);
hi >>= 1;
hi |= lo << 63;
lo >>= 1;
lo ^= ((uint64_t) constant_time_select_w(carry, 0xe1, 0)) << 56;
b->u[0] = CRYPTO_bswap8(lo);
b->u[1] = CRYPTO_bswap8(hi);
}
// POLYVAL(H, X_1, ..., X_n) =
// ByteReverse(GHASH(mulX_GHASH(ByteReverse(H)), ByteReverse(X_1), ...,
// ByteReverse(X_n))).
//
// See https://tools.ietf.org/html/draft-irtf-cfrg-gcmsiv-02#appendix-A.
void CRYPTO_POLYVAL_init(struct polyval_ctx *ctx, const uint8_t key[16]) {
polyval_block H;
OPENSSL_memcpy(H.c, key, 16);
reverse_and_mulX_ghash(&H);
int is_avx;
CRYPTO_ghash_init(&ctx->gmult, &ctx->ghash, &ctx->H, ctx->Htable, &is_avx,
H.c);
OPENSSL_memset(&ctx->S, 0, sizeof(ctx->S));
}
void CRYPTO_POLYVAL_update_blocks(struct polyval_ctx *ctx, const uint8_t *in,
size_t in_len) {
assert((in_len & 15) == 0);
polyval_block reversed[32];
while (in_len > 0) {
size_t todo = in_len;
if (todo > sizeof(reversed)) {
todo = sizeof(reversed);
}
OPENSSL_memcpy(reversed, in, todo);
in += todo;
in_len -= todo;
size_t blocks = todo / sizeof(polyval_block);
for (size_t i = 0; i < blocks; i++) {
byte_reverse(&reversed[i]);
}
ctx->ghash(ctx->S.u, ctx->Htable, (const uint8_t *) reversed, todo);
}
}
void CRYPTO_POLYVAL_finish(const struct polyval_ctx *ctx, uint8_t out[16]) {
polyval_block S = ctx->S;
byte_reverse(&S);
OPENSSL_memcpy(out, &S.c, sizeof(polyval_block));
}
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