/*

 * 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;

}