/*

 * Copyright 2022 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the Apache License 2.0 (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 <string.h>

#include <openssl/crypto.h>

#include "internal/endian.h"

#include "crypto/modes.h"

#ifndef STRICT_ALIGNMENT

# ifdef __GNUC__

typedef u64 u64_a1 __attribute((__aligned__(1)));

# else

typedef u64 u64_a1;

# endif

#endif

int ossl_crypto_xts128gb_encrypt(const XTS128_CONTEXT *ctx,

                                 const unsigned char iv[16],

                                 const unsigned char *inp, unsigned char *out,

                                 size_t len, int enc)

{

    DECLARE_IS_ENDIAN;

    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_a1 *)inp)[0] ^ tweak.u[0];

        scratch.u[1] = ((u64_a1 *)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_a1 *)out)[0] = scratch.u[0] ^= tweak.u[0];

        ((u64_a1 *)out)[1] = scratch.u[1] ^= tweak.u[1];

#endif

        inp += 16;

        out += 16;

        len -= 16;

        if (len == 0)

            return 0;

        if (IS_LITTLE_ENDIAN) {

            u8 res;

            u64 hi, lo;

#ifdef BSWAP8

            hi = BSWAP8(tweak.u[0]);

            lo = BSWAP8(tweak.u[1]);

#else

            u8 *p = tweak.c;

            hi = (u64)GETU32(p) << 32 | GETU32(p + 4);

            lo = (u64)GETU32(p + 8) << 32 | GETU32(p + 12);

#endif

            res = (u8)lo & 1;

            tweak.u[0] = (lo >> 1) | (hi << 63);

            tweak.u[1] = hi >> 1;

            if (res)

                tweak.c[15] ^= 0xe1;

#ifdef BSWAP8

            hi = BSWAP8(tweak.u[0]);

            lo = BSWAP8(tweak.u[1]);

#else

            p = tweak.c;

            hi = (u64)GETU32(p) << 32 | GETU32(p + 4);

            lo = (u64)GETU32(p + 8) << 32 | GETU32(p + 12);

#endif

            tweak.u[0] = lo;

            tweak.u[1] = hi;

        } else {

            u8 carry, res;

            carry = 0;

            for (i = 0; i < 16; ++i) {

                res = (tweak.c[i] << 7) & 0x80;

                tweak.c[i] = ((tweak.c[i] >> 1) + carry) & 0xff;

                carry = res;

            }

            if (res)

                tweak.c[0] ^= 0xe1;

        }

    }

    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_LITTLE_ENDIAN) {

            u8 res;

            u64 hi, lo;

#ifdef BSWAP8

            hi = BSWAP8(tweak.u[0]);

            lo = BSWAP8(tweak.u[1]);

#else

            u8 *p = tweak.c;

            hi = (u64)GETU32(p) << 32 | GETU32(p + 4);

            lo = (u64)GETU32(p + 8) << 32 | GETU32(p + 12);

#endif

            res = (u8)lo & 1;

            tweak1.u[0] = (lo >> 1) | (hi << 63);

            tweak1.u[1] = hi >> 1;

            if (res)

                tweak1.c[15] ^= 0xe1;

#ifdef BSWAP8

            hi = BSWAP8(tweak1.u[0]);

            lo = BSWAP8(tweak1.u[1]);

#else

            p = tweak1.c;

            hi = (u64)GETU32(p) << 32 | GETU32(p + 4);

            lo = (u64)GETU32(p + 8) << 32 | GETU32(p + 12);

#endif

            tweak1.u[0] = lo;

            tweak1.u[1] = hi;

        } else {

            u8 carry, res;

            carry = 0;

            for (i = 0; i < 16; ++i) {

                res = (tweak.c[i] << 7) & 0x80;

                tweak1.c[i] = ((tweak.c[i] >> 1) + carry) & 0xff;

                carry = res;

            }

            if (res)

                tweak1.c[0] ^= 0xe1;

        }

#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_a1 *)inp)[0] ^ tweak1.u[0];

        scratch.u[1] = ((u64_a1 *)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_a1 *)out)[0] = scratch.u[0] ^ tweak.u[0];

        ((u64_a1 *)out)[1] = scratch.u[1] ^ tweak.u[1];

#endif

    }

    return 0;

}