/* $OpenBSD: cfb_enc.c,v 1.16 2023/07/08 07:11:07 beck Exp $ */
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young (eay@cryptsoft.com).
 * The implementation was written so as to conform with Netscapes SSL.
 *
 * This library is free for commercial and non-commercial use as long as
 * the following conditions are aheared to.  The following conditions
 * apply to all code found in this distribution, be it the RC4, RSA,
 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
 * included with this distribution is covered by the same copyright terms
 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
 *
 * Copyright remains Eric Young's, and as such any Copyright notices in
 * the code are not to be removed.
 * If this package is used in a product, Eric Young should be given attribution
 * as the author of the parts of the library used.
 * This can be in the form of a textual message at program startup or
 * in documentation (online or textual) provided with the package.
 *
 * 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 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 acknowledgement:
 *    "This product includes cryptographic software written by
 *     Eric Young (eay@cryptsoft.com)"
 *    The word 'cryptographic' can be left out if the rouines from the library
 *    being used are not cryptographic related :-).
 * 4. If you include any Windows specific code (or a derivative thereof) from
 *    the apps directory (application code) you must include an acknowledgement:
 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
 *
 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
 * ANY EXPRESS 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 AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * The licence and distribution terms for any publically available version or
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
 * copied and put under another distribution licence
 * [including the GNU Public Licence.]
 */

#include "des_local.h"
#include <endian.h>

/* The input and output are loaded in multiples of 8 bits.
 * What this means is that if you hame numbits=12 and length=2
 * the first 12 bits will be retrieved from the first byte and half
 * the second.  The second 12 bits will come from the 3rd and half the 4th
 * byte.
 */
/* Until Aug 1 2003 this function did not correctly implement CFB-r, so it
 * will not be compatible with any encryption prior to that date. Ben. */
void
DES_cfb_encrypt(const unsigned char *in, unsigned char *out, int numbits,
    long length, DES_key_schedule *schedule, DES_cblock *ivec,
    int enc)
{
	DES_LONG d0, d1, v0, v1;
	unsigned long l = length;
	int num = numbits/8, n = (numbits + 7)/8, i, rem = numbits % 8;
	DES_LONG ti[2];
	unsigned char *iv;
#if BYTE_ORDER != LITTLE_ENDIAN
	unsigned char ovec[16];
#else
	unsigned int sh[4];
	unsigned char *ovec = (unsigned char *)sh;
#endif

	if (numbits <= 0 || numbits > 64)
		return;
	iv = &(*ivec)[0];
	c2l(iv, v0);
	c2l(iv, v1);
	if (enc) {
		while (l >= (unsigned long)n) {
			l -= n;
			ti[0] = v0;
			ti[1] = v1;
			DES_encrypt1((DES_LONG *)ti, schedule, DES_ENCRYPT);
			c2ln(in, d0, d1, n);
			in += n;
			d0 ^= ti[0];
			d1 ^= ti[1];
			l2cn(d0, d1, out, n);
			out += n;
			/* 30-08-94 - eay - changed because l>>32 and
			 * l<<32 are bad under gcc :-( */
			if (numbits == 32) {
				v0 = v1;
				v1 = d0;
			} else if (numbits == 64) {
				v0 = d0;
				v1 = d1;
			} else {
#if BYTE_ORDER != LITTLE_ENDIAN
				iv = &ovec[0];
				l2c(v0, iv);
				l2c(v1, iv);
				l2c(d0, iv);
				l2c(d1, iv);
#else
				sh[0] = v0, sh[1] = v1, sh[2] = d0, sh[3] = d1;
#endif
				if (rem == 0)
					memmove(ovec, ovec + num, 8);
				else
					for (i = 0; i < 8; ++i)
						ovec[i] = ovec[i + num] << rem |
						    ovec[i + num + 1] >> (8 -
						    rem);
#if BYTE_ORDER == LITTLE_ENDIAN
				v0 = sh[0], v1 = sh[1];
#else
				iv = &ovec[0];
				c2l(iv, v0);
				c2l(iv, v1);
#endif
			}
		}
	} else {
		while (l >= (unsigned long)n) {
			l -= n;
			ti[0] = v0;
			ti[1] = v1;
			DES_encrypt1((DES_LONG *)ti, schedule, DES_ENCRYPT);
			c2ln(in, d0, d1, n);
			in += n;
			/* 30-08-94 - eay - changed because l>>32 and
			 * l<<32 are bad under gcc :-( */
			if (numbits == 32) {
				v0 = v1;
				v1 = d0;
			} else if (numbits == 64) {
				v0 = d0;
				v1 = d1;
			} else {
#if BYTE_ORDER != LITTLE_ENDIAN
				iv = &ovec[0];
				l2c(v0, iv);
				l2c(v1, iv);
				l2c(d0, iv);
				l2c(d1, iv);
#else
				sh[0] = v0, sh[1] = v1, sh[2] = d0, sh[3] = d1;
#endif
				if (rem == 0)
					memmove(ovec, ovec + num, 8);
				else
					for (i = 0; i < 8; ++i)
						ovec[i] = ovec[i + num] << rem |
						    ovec[i + num + 1] >> (8 -
						    rem);
#if BYTE_ORDER == LITTLE_ENDIAN
				v0 = sh[0], v1 = sh[1];
#else
				iv = &ovec[0];
				c2l(iv, v0);
				c2l(iv, v1);
#endif
			}
			d0 ^= ti[0];
			d1 ^= ti[1];
			l2cn(d0, d1, out, n);
			out += n;
		}
	}
	iv = &(*ivec)[0];
	l2c(v0, iv);
	l2c(v1, iv);
	v0 = v1 = d0 = d1 = ti[0] = ti[1] = 0;
}
