/* $OpenBSD: ofb128.c,v 1.10 2025/04/23 10:09:08 jsing Exp $ */
/* ====================================================================
 * Copyright (c) 2008 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
 *    the documentation and/or other materials provided with the
 *    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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 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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 * ====================================================================
 *
 */

#include <string.h>

#include <openssl/crypto.h>

#include "modes_local.h"

/* The input and output encrypted as though 128bit ofb mode is being
 * used.  The extra state information to record how much of the
 * 128bit block we have used is contained in *num;
 */
void
CRYPTO_ofb128_encrypt(const unsigned char *in, unsigned char *out,
    size_t len, const void *key,
    unsigned char ivec[16], int *num,
    block128_f block)
{
        unsigned int n;
        size_t l = 0;

        n = *num;

        if (16 % sizeof(size_t) == 0)
                do { /* always true actually */
                        while (n && len) {
                                *(out++) = *(in++) ^ ivec[n];
                                --len;
                                n = (n + 1) % 16;
                        }
#ifdef __STRICT_ALIGNMENT
                        if (((size_t)in|(size_t)out|(size_t)ivec) %
                            sizeof(size_t) != 0)
                                break;
#endif
                        while (len >= 16) {
                                (*block)(ivec, ivec, key);
                                for (; n < 16; n += sizeof(size_t))
                                        *(size_t *)(out + n) =
                                            *(size_t *)(in + n) ^ *(size_t *)(ivec +
                                            n);
                                len -= 16;
                                out += 16;
                                in += 16;
                                n = 0;
                        }
                        if (len) {
                                (*block)(ivec, ivec, key);
                                while (len--) {
                                        out[n] = in[n] ^ ivec[n];
                                        ++n;
                                }
                        }
                        *num = n;
                        return;
                } while (0);
        /* the rest would be commonly eliminated by x86* compiler */
        while (l < len) {
                if (n == 0) {
                        (*block)(ivec, ivec, key);
                }
                out[l] = in[l] ^ ivec[n];
                ++l;
                n = (n + 1) % 16;
        }

        *num = n;
}
LCRYPTO_ALIAS(CRYPTO_ofb128_encrypt);