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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|. */
byte_reverse(polyval_block * b)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. */
reverse_and_mulX_ghash(polyval_block * b)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 
CRYPTO_POLYVAL_init(struct polyval_ctx * ctx,const uint8_t key[16])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 
CRYPTO_POLYVAL_update_blocks(struct polyval_ctx * ctx,const uint8_t * in,size_t in_len)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 
CRYPTO_POLYVAL_finish(const struct polyval_ctx * ctx,uint8_t out[16])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