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|.
25static 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.
34static 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
53void 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
64void 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
87void 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