/* $OpenBSD: xts128.c,v 1.8 2021/11/09 18:40:21 bcook Exp $ */
/* ====================================================================
 * Copyright (c) 2011 The OpenSSL Project.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
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 *    distribution.
 *
 * 3. All advertising materials mentioning features or use of this
 *    software must display the following acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
 *
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    openssl-core@openssl.org.
 *
 * 5. Products derived from this software may not be called "OpenSSL"
 *    nor may "OpenSSL" appear in their names without prior written
 *    permission of the OpenSSL Project.
 *
 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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 * ====================================================================
 */

#include <openssl/crypto.h>
#include "modes_lcl.h"

#include <endian.h>
#include <string.h>

#ifndef MODES_DEBUG
# ifndef NDEBUG
#  define NDEBUG
# endif
#endif

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)
{
        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) {
#ifdef __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);
#ifdef __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 BYTE_ORDER == LITTLE_ENDIAN
                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 /* BIG_ENDIAN */
                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));
#endif
        }
        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 BYTE_ORDER == LITTLE_ENDIAN
                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));
#endif
#ifdef __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);
#ifdef __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;
}