crypto/des/cfb_enc.c

/*
 * Copyright 1995-2022 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
 */

/*
 * DES low level APIs are deprecated for public use, but still ok for internal
 * use.
 */
#include "internal/deprecated.h"

#include "internal/e_os.h"
#include "des_local.h"
#include <assert.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)
{
    register DES_LONG d0, d1, v0, v1;
    register unsigned long l = length;
    register int num = numbits / 8, n = (numbits + 7) / 8, i, rem =
        numbits % 8;
    DES_LONG ti[2];
    unsigned char *iv;
#ifndef L_ENDIAN
    unsigned char ovec[16];
#else
    unsigned int sh[4];
    unsigned char *ovec = (unsigned char *)sh;

    /* I kind of count that compiler optimizes away this assertion, */
    assert(sizeof(sh[0]) == 4); /* as this holds true for all, */
    /* but 16-bit platforms...      */

#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 {
#ifndef L_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);
#ifdef L_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 {
#ifndef L_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);
#ifdef L_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;
}