xts128.c
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/*
* Copyright 2011-2016 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include <openssl/crypto.h>
#include "modes_lcl.h"
#include <string.h>
int CRYPTO_xts128_encrypt(const XTS128_CONTEXT *ctx,
const unsigned char iv[16],
const unsigned char *inp, unsigned char *out,
size_t len, int enc)
{
const union {
long one;
char little;
} is_endian = {
1
};
union {
u64 u[2];
u32 d[4];
u8 c[16];
} tweak, scratch;
unsigned int i;
if (len < 16)
return -1;
memcpy(tweak.c, iv, 16);
(*ctx->block2) (tweak.c, tweak.c, ctx->key2);
if (!enc && (len % 16))
len -= 16;
while (len >= 16) {
#if defined(STRICT_ALIGNMENT)
memcpy(scratch.c, inp, 16);
scratch.u[0] ^= tweak.u[0];
scratch.u[1] ^= tweak.u[1];
#else
scratch.u[0] = ((u64 *)inp)[0] ^ tweak.u[0];
scratch.u[1] = ((u64 *)inp)[1] ^ tweak.u[1];
#endif
(*ctx->block1) (scratch.c, scratch.c, ctx->key1);
#if defined(STRICT_ALIGNMENT)
scratch.u[0] ^= tweak.u[0];
scratch.u[1] ^= tweak.u[1];
memcpy(out, scratch.c, 16);
#else
((u64 *)out)[0] = scratch.u[0] ^= tweak.u[0];
((u64 *)out)[1] = scratch.u[1] ^= tweak.u[1];
#endif
inp += 16;
out += 16;
len -= 16;
if (len == 0)
return 0;
if (is_endian.little) {
unsigned int carry, res;
res = 0x87 & (((int)tweak.d[3]) >> 31);
carry = (unsigned int)(tweak.u[0] >> 63);
tweak.u[0] = (tweak.u[0] << 1) ^ res;
tweak.u[1] = (tweak.u[1] << 1) | carry;
} else {
size_t c;
for (c = 0, i = 0; i < 16; ++i) {
/*
* + substitutes for |, because c is 1 bit
*/
c += ((size_t)tweak.c[i]) << 1;
tweak.c[i] = (u8)c;
c = c >> 8;
}
tweak.c[0] ^= (u8)(0x87 & (0 - c));
}
}
if (enc) {
for (i = 0; i < len; ++i) {
u8 c = inp[i];
out[i] = scratch.c[i];
scratch.c[i] = c;
}
scratch.u[0] ^= tweak.u[0];
scratch.u[1] ^= tweak.u[1];
(*ctx->block1) (scratch.c, scratch.c, ctx->key1);
scratch.u[0] ^= tweak.u[0];
scratch.u[1] ^= tweak.u[1];
memcpy(out - 16, scratch.c, 16);
} else {
union {
u64 u[2];
u8 c[16];
} tweak1;
if (is_endian.little) {
unsigned int carry, res;
res = 0x87 & (((int)tweak.d[3]) >> 31);
carry = (unsigned int)(tweak.u[0] >> 63);
tweak1.u[0] = (tweak.u[0] << 1) ^ res;
tweak1.u[1] = (tweak.u[1] << 1) | carry;
} else {
size_t c;
for (c = 0, i = 0; i < 16; ++i) {
/*
* + substitutes for |, because c is 1 bit
*/
c += ((size_t)tweak.c[i]) << 1;
tweak1.c[i] = (u8)c;
c = c >> 8;
}
tweak1.c[0] ^= (u8)(0x87 & (0 - c));
}
#if defined(STRICT_ALIGNMENT)
memcpy(scratch.c, inp, 16);
scratch.u[0] ^= tweak1.u[0];
scratch.u[1] ^= tweak1.u[1];
#else
scratch.u[0] = ((u64 *)inp)[0] ^ tweak1.u[0];
scratch.u[1] = ((u64 *)inp)[1] ^ tweak1.u[1];
#endif
(*ctx->block1) (scratch.c, scratch.c, ctx->key1);
scratch.u[0] ^= tweak1.u[0];
scratch.u[1] ^= tweak1.u[1];
for (i = 0; i < len; ++i) {
u8 c = inp[16 + i];
out[16 + i] = scratch.c[i];
scratch.c[i] = c;
}
scratch.u[0] ^= tweak.u[0];
scratch.u[1] ^= tweak.u[1];
(*ctx->block1) (scratch.c, scratch.c, ctx->key1);
#if defined(STRICT_ALIGNMENT)
scratch.u[0] ^= tweak.u[0];
scratch.u[1] ^= tweak.u[1];
memcpy(out, scratch.c, 16);
#else
((u64 *)out)[0] = scratch.u[0] ^ tweak.u[0];
((u64 *)out)[1] = scratch.u[1] ^ tweak.u[1];
#endif
}
return 0;
}