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/* $OpenBSD: gmac.c,v 1.10 2017/05/02 11:44:32 mikeb Exp $ */
/*
* Copyright (c) 2010 Mike Belopuhov
*
* Permission to use, copy, modify, and 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.
*/
/*
* This code implements the Message Authentication part of the
* Galois/Counter Mode (as being described in the RFC 4543) using
* the AES cipher. FIPS SP 800-38D describes the algorithm details.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <crypto/aes.h>
#include <crypto/gmac.h>
void ghash_gfmul(uint32_t *, uint32_t *, uint32_t *);
void ghash_update_mi(GHASH_CTX *, uint8_t *, size_t);
/* Allow overriding with optimized MD function */
void (*ghash_update)(GHASH_CTX *, uint8_t *, size_t) = ghash_update_mi;
/* Computes a block multiplication in the GF(2^128) */
void
ghash_gfmul(uint32_t *X, uint32_t *Y, uint32_t *product)
{
uint32_t v[4];
uint32_t z[4] = { 0, 0, 0, 0};
uint8_t *x = (uint8_t *)X;
uint32_t mask;
int i;
v[0] = betoh32(Y[0]);
v[1] = betoh32(Y[1]);
v[2] = betoh32(Y[2]);
v[3] = betoh32(Y[3]);
for (i = 0; i < GMAC_BLOCK_LEN * 8; i++) {
/* update Z */
mask = !!(x[i >> 3] & (1 << (~i & 7)));
mask = ~(mask - 1);
z[0] ^= v[0] & mask;
z[1] ^= v[1] & mask;
z[2] ^= v[2] & mask;
z[3] ^= v[3] & mask;
/* update V */
mask = ~((v[3] & 1) - 1);
v[3] = (v[2] << 31) | (v[3] >> 1);
v[2] = (v[1] << 31) | (v[2] >> 1);
v[1] = (v[0] << 31) | (v[1] >> 1);
v[0] = (v[0] >> 1) ^ (0xe1000000 & mask);
}
product[0] = htobe32(z[0]);
product[1] = htobe32(z[1]);
product[2] = htobe32(z[2]);
product[3] = htobe32(z[3]);
}
void
ghash_update_mi(GHASH_CTX *ctx, uint8_t *X, size_t len)
{
uint32_t *x = (uint32_t *)X;
uint32_t *s = (uint32_t *)ctx->S;
uint32_t *y = (uint32_t *)ctx->Z;
int i;
for (i = 0; i < len / GMAC_BLOCK_LEN; i++) {
s[0] = y[0] ^ x[0];
s[1] = y[1] ^ x[1];
s[2] = y[2] ^ x[2];
s[3] = y[3] ^ x[3];
ghash_gfmul((uint32_t *)ctx->S, (uint32_t *)ctx->H,
(uint32_t *)ctx->S);
y = s;
x += 4;
}
bcopy(ctx->S, ctx->Z, GMAC_BLOCK_LEN);
}
#define AESCTR_NONCESIZE 4
void
AES_GMAC_Init(void *xctx)
{
AES_GMAC_CTX *ctx = xctx;
bzero(ctx->ghash.H, GMAC_BLOCK_LEN);
bzero(ctx->ghash.S, GMAC_BLOCK_LEN);
bzero(ctx->ghash.Z, GMAC_BLOCK_LEN);
bzero(ctx->J, GMAC_BLOCK_LEN);
}
void
AES_GMAC_Setkey(void *xctx, const uint8_t *key, uint16_t klen)
{
AES_GMAC_CTX *ctx = xctx;
AES_Setkey(&ctx->K, key, klen - AESCTR_NONCESIZE);
/* copy out salt to the counter block */
bcopy(key + klen - AESCTR_NONCESIZE, ctx->J, AESCTR_NONCESIZE);
/* prepare a hash subkey */
AES_Encrypt(&ctx->K, ctx->ghash.H, ctx->ghash.H);
}
void
AES_GMAC_Reinit(void *xctx, const uint8_t *iv, uint16_t ivlen)
{
AES_GMAC_CTX *ctx = xctx;
/* copy out IV to the counter block */
bcopy(iv, ctx->J + AESCTR_NONCESIZE, ivlen);
}
int
AES_GMAC_Update(void *xctx, const uint8_t *data, uint16_t len)
{
AES_GMAC_CTX *ctx = xctx;
uint32_t blk[4] = { 0, 0, 0, 0 };
int plen;
if (len > 0) {
plen = len % GMAC_BLOCK_LEN;
if (len >= GMAC_BLOCK_LEN)
(*ghash_update)(&ctx->ghash, (uint8_t *)data,
len - plen);
if (plen) {
memcpy((uint8_t *)blk, (uint8_t *)data + (len - plen),
plen);
(*ghash_update)(&ctx->ghash, (uint8_t *)blk,
GMAC_BLOCK_LEN);
}
}
return (0);
}
void
AES_GMAC_Final(uint8_t digest[GMAC_DIGEST_LEN], void *xctx)
{
AES_GMAC_CTX *ctx = xctx;
uint8_t keystream[GMAC_BLOCK_LEN];
int i;
/* do one round of GCTR */
ctx->J[GMAC_BLOCK_LEN - 1] = 1;
AES_Encrypt(&ctx->K, ctx->J, keystream);
for (i = 0; i < GMAC_DIGEST_LEN; i++)
digest[i] = ctx->ghash.S[i] ^ keystream[i];
explicit_bzero(keystream, sizeof(keystream));
}
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