cfb128.c

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/* ====================================================================
 * 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
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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/)"
 *
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 *    prior written permission. For written permission, please contact
 *    [email protected].
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 * 5. Products derived from this software may not be called "OpenSSL"
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 * 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
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#include <openssl/crypto.h>
#include "modes_lcl.h"
#include <string.h>

#ifndef MODES_DEBUG
# ifndef NDEBUG
#  define NDEBUG
# endif
#endif
#include <assert.h>

/* The input and output encrypted as though 128bit cfb 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_cfb128_encrypt(const unsigned char *in, unsigned char *out,
            size_t len, const void *key,
            unsigned char ivec[16], int *num,
            int enc, block128_f block)
{
    unsigned int n;
    size_t l = 0;

    assert(in && out && key && ivec && num);

    n = *num;

    if (enc) {
#if !defined(OPENSSL_SMALL_FOOTPRINT)
    if (16%sizeof(size_t) == 0) do {    /* always true actually */
        while (n && len) {
            *(out++) = ivec[n] ^= *(in++);
            --len;
            n = (n+1) % 16;
        }
#if defined(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*)(ivec+n) ^= *(size_t*)(in+n);
            }
            len -= 16;
            out += 16;
            in  += 16;
            n = 0;
        }
        if (len) {
            (*block)(ivec, ivec, key);
            while (len--) {
                out[n] = ivec[n] ^= in[n];
                ++n;
            }
        }
        *num = n;
        return;
    } while (0);
    /* the rest would be commonly eliminated by x86* compiler */
#endif
    while (l<len) {
        if (n == 0) {
            (*block)(ivec, ivec, key);
        }
        out[l] = ivec[n] ^= in[l];
        ++l;
        n = (n+1) % 16;
    }
    *num = n;
    } else {
#if !defined(OPENSSL_SMALL_FOOTPRINT)
    if (16%sizeof(size_t) == 0) do {    /* always true actually */
        while (n && len) {
            unsigned char c;
            *(out++) = ivec[n] ^ (c = *(in++)); ivec[n] = c;
            --len;
            n = (n+1) % 16;
        }
#if defined(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 t = *(size_t*)(in+n);
                *(size_t*)(out+n) = *(size_t*)(ivec+n) ^ t;
                *(size_t*)(ivec+n) = t;
            }
            len -= 16;
            out += 16;
            in  += 16;
            n = 0;
        }
        if (len) {
            (*block)(ivec, ivec, key);
            while (len--) {
                unsigned char c;
                out[n] = ivec[n] ^ (c = in[n]); ivec[n] = c;
                ++n;
            }
        }
        *num = n;
        return;
    } while (0);
    /* the rest would be commonly eliminated by x86* compiler */
#endif
    while (l<len) {
        unsigned char c;
        if (n == 0) {
            (*block)(ivec, ivec, key);
        }
        out[l] = ivec[n] ^ (c = in[l]); ivec[n] = c;
        ++l;
        n = (n+1) % 16;
    }
    *num=n;
    }
}

/* This expects a single block of size nbits for both in and out. Note that
   it corrupts any extra bits in the last byte of out */
static void cfbr_encrypt_block(const unsigned char *in,unsigned char *out,
                int nbits,const void *key,
                unsigned char ivec[16],int enc,
                block128_f block)
{
    int n,rem,num;
    unsigned char ovec[16*2 + 1];  /* +1 because we dererefence (but don't use) one byte off the end */

    if (nbits<=0 || nbits>128) return;

    /* fill in the first half of the new IV with the current IV */
    memcpy(ovec,ivec,16);
    /* construct the new IV */
    (*block)(ivec,ivec,key);
    num = (nbits+7)/8;
    if (enc)    /* encrypt the input */
        for(n=0 ; n < num ; ++n)
        out[n] = (ovec[16+n] = in[n] ^ ivec[n]);
    else        /* decrypt the input */
        for(n=0 ; n < num ; ++n)
        out[n] = (ovec[16+n] = in[n]) ^ ivec[n];
    /* shift ovec left... */
    rem = nbits%8;
    num = nbits/8;
    if(rem==0)
        memcpy(ivec,ovec+num,16);
    else
        for(n=0 ; n < 16 ; ++n)
        ivec[n] = ovec[n+num]<<rem | ovec[n+num+1]>>(8-rem);

    /* it is not necessary to cleanse ovec, since the IV is not secret */
}

/* N.B. This expects the input to be packed, MS bit first */
void CRYPTO_cfb128_1_encrypt(const unsigned char *in, unsigned char *out,
            size_t bits, const void *key,
            unsigned char ivec[16], int *num,
            int enc, block128_f block)
{
    size_t n;
    unsigned char c[1],d[1];

    assert(in && out && key && ivec && num);
    assert(*num == 0);

    for(n=0 ; n<bits ; ++n)
    {
    c[0]=(in[n/8]&(1 << (7-n%8))) ? 0x80 : 0;
    cfbr_encrypt_block(c,d,1,key,ivec,enc,block);
    out[n/8]=(out[n/8]&~(1 << (unsigned int)(7-n%8))) |
         ((d[0]&0x80) >> (unsigned int)(n%8));
    }
}

void CRYPTO_cfb128_8_encrypt(const unsigned char *in, unsigned char *out,
            size_t length, const void *key,
            unsigned char ivec[16], int *num,
            int enc, block128_f block)
{
    size_t n;

    assert(in && out && key && ivec && num);
    assert(*num == 0);

    for(n=0 ; n<length ; ++n)
    cfbr_encrypt_block(&in[n],&out[n],8,key,ivec,enc,block);
}