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