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/* $OpenBSD: xform.c,v 1.16 2001/08/28 12:20:43 ben Exp $ */
/*-
* The authors of this code are John Ioannidis (ji@tla.org),
* Angelos D. Keromytis (kermit@csd.uch.gr),
* Niels Provos (provos@physnet.uni-hamburg.de) and
* Damien Miller (djm@mindrot.org).
*
* This code was written by John Ioannidis for BSD/OS in Athens, Greece,
* in November 1995.
*
* Ported to OpenBSD and NetBSD, with additional transforms, in December 1996,
* by Angelos D. Keromytis.
*
* Additional transforms and features in 1997 and 1998 by Angelos D. Keromytis
* and Niels Provos.
*
* Additional features in 1999 by Angelos D. Keromytis.
*
* AES XTS implementation in 2008 by Damien Miller
*
* Copyright (C) 1995, 1996, 1997, 1998, 1999 by John Ioannidis,
* Angelos D. Keromytis and Niels Provos.
*
* Copyright (C) 2001, Angelos D. Keromytis.
*
* Copyright (C) 2008, Damien Miller
* Copyright (c) 2014 The FreeBSD Foundation
* All rights reserved.
*
* Portions of this software were developed by John-Mark Gurney
* under sponsorship of the FreeBSD Foundation and
* Rubicon Communications, LLC (Netgate).
*
* Permission to use, copy, and modify this software with or without fee
* is hereby granted, provided that this entire notice is included in
* all copies of any software which is or includes a copy or
* modification of this software.
* You may use this code under the GNU public license if you so wish. Please
* contribute changes back to the authors under this freer than GPL license
* so that we may further the use of strong encryption without limitations to
* all.
*
* THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR
* IMPLIED WARRANTY. IN PARTICULAR, NONE OF THE AUTHORS MAKES ANY
* REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE
* MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR
* PURPOSE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <opencrypto/xform_enc.h>
static int aes_xts_setkey(u_int8_t **, u_int8_t *, int);
static void aes_xts_encrypt(caddr_t, u_int8_t *);
static void aes_xts_decrypt(caddr_t, u_int8_t *);
static void aes_xts_zerokey(u_int8_t **);
static void aes_xts_reinit(caddr_t, u_int8_t *);
/* Encryption instances */
struct enc_xform enc_xform_aes_xts = {
CRYPTO_AES_XTS, "AES-XTS",
AES_BLOCK_LEN, AES_XTS_IV_LEN, AES_XTS_MIN_KEY, AES_XTS_MAX_KEY,
aes_xts_encrypt,
aes_xts_decrypt,
aes_xts_setkey,
aes_xts_zerokey,
aes_xts_reinit
};
/*
* Encryption wrapper routines.
*/
static void
aes_xts_reinit(caddr_t key, u_int8_t *iv)
{
struct aes_xts_ctx *ctx = (struct aes_xts_ctx *)key;
u_int64_t blocknum;
u_int i;
/*
* Prepare tweak as E_k2(IV). IV is specified as LE representation
* of a 64-bit block number which we allow to be passed in directly.
*/
bcopy(iv, &blocknum, AES_XTS_IVSIZE);
for (i = 0; i < AES_XTS_IVSIZE; i++) {
ctx->tweak[i] = blocknum & 0xff;
blocknum >>= 8;
}
/* Last 64 bits of IV are always zero */
bzero(ctx->tweak + AES_XTS_IVSIZE, AES_XTS_IVSIZE);
rijndael_encrypt(&ctx->key2, ctx->tweak, ctx->tweak);
}
static void
aes_xts_crypt(struct aes_xts_ctx *ctx, u_int8_t *data, u_int do_encrypt)
{
u_int8_t block[AES_XTS_BLOCKSIZE];
u_int i, carry_in, carry_out;
for (i = 0; i < AES_XTS_BLOCKSIZE; i++)
block[i] = data[i] ^ ctx->tweak[i];
if (do_encrypt)
rijndael_encrypt(&ctx->key1, block, data);
else
rijndael_decrypt(&ctx->key1, block, data);
for (i = 0; i < AES_XTS_BLOCKSIZE; i++)
data[i] ^= ctx->tweak[i];
/* Exponentiate tweak */
carry_in = 0;
for (i = 0; i < AES_XTS_BLOCKSIZE; i++) {
carry_out = ctx->tweak[i] & 0x80;
ctx->tweak[i] = (ctx->tweak[i] << 1) | (carry_in ? 1 : 0);
carry_in = carry_out;
}
if (carry_in)
ctx->tweak[0] ^= AES_XTS_ALPHA;
bzero(block, sizeof(block));
}
static void
aes_xts_encrypt(caddr_t key, u_int8_t *data)
{
aes_xts_crypt((struct aes_xts_ctx *)key, data, 1);
}
static void
aes_xts_decrypt(caddr_t key, u_int8_t *data)
{
aes_xts_crypt((struct aes_xts_ctx *)key, data, 0);
}
static int
aes_xts_setkey(u_int8_t **sched, u_int8_t *key, int len)
{
struct aes_xts_ctx *ctx;
if (len != 32 && len != 64)
return EINVAL;
*sched = KMALLOC(sizeof(struct aes_xts_ctx), M_CRYPTO_DATA,
M_NOWAIT | M_ZERO);
if (*sched == NULL)
return ENOMEM;
ctx = (struct aes_xts_ctx *)*sched;
rijndael_set_key(&ctx->key1, key, len * 4);
rijndael_set_key(&ctx->key2, key + (len / 2), len * 4);
return 0;
}
static void
aes_xts_zerokey(u_int8_t **sched)
{
bzero(*sched, sizeof(struct aes_xts_ctx));
KFREE(*sched, M_CRYPTO_DATA);
*sched = NULL;
}
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