swcipher.cpp

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/******************************************************************************
 *
 *  swcipher.cpp -  code for class 'SWCipher'- a driver class that
 *          provides cipher utilities
 *
 * $Id: swcipher.cpp 3755 2020-07-19 18:43:07Z scribe $
 *
 * Copyright 1999-2013 CrossWire Bible Society (http://www.crosswire.org)
 *  CrossWire Bible Society
 *  P. O. Box 2528
 *  Tempe, AZ  85280-2528
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation version 2.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 */


#include <stdlib.h>
#include <string.h>
#include <swcipher.h>
#include <map>

namespace {
    char lats[] = {
        'b', 'c', 'e', 'a', 'f', 'g', 'i', 'j', 'k', 'l',
        'h', 'm', 'p', 'q', 'B', 'r', 'H', 'o', 's', 't',
        'T', 'u', 'w', 'x', 'y', 'A', 'd', 'C', 'D', 'z',
        'E', 'F', 'I', 'J', 'K', 'G', 'L', 'N', 'O', '7',
        'P', 'Q', 'M', 'R', 'S', 'U', 'V', 'W', 'X', 'Y',
        '9', '0', '1', '2', 'Z', '3', '6', '4', 'n', '8',
        'v', '5'
    };
}

SWORD_NAMESPACE_START

/******************************************************************************
 * SWCipher Constructor - Initializes data for instance of SWCipher
 *
 */

SWCipher::SWCipher(unsigned char *key) {
    SWBuf cipherKey = personalize((const char *)key, false);
    master.initialize((unsigned char *)(const char *)cipherKey, cipherKey.size());
    buf = 0;
}


/******************************************************************************
 * SWCipher Destructor - Cleans up instance of SWCipher
 */

SWCipher::~SWCipher()
{
    if (buf)
        free(buf);
}


void SWCipher::setUncipheredBuf(const char *ibuf, unsigned long ilen) {
    if (ibuf) {
    
        if (buf)
            free(buf);

        if (!ilen) {
                len = strlen(buf);
            ilen = len + 1;
        }
        else len = ilen;

        buf = (char *) malloc(ilen);
        memcpy(buf, ibuf, ilen);
        cipher = false;
    }

    decode();
}

char *SWCipher::getUncipheredBuf() {

    decode();

    return buf;
}


void SWCipher::setCipheredBuf(unsigned long *ilen, const char *ibuf) {
    if (ibuf) {
    
        if (buf)
            free(buf);
            
        buf = (char *) malloc(*ilen+1);
        memcpy(buf, ibuf, *ilen);
        len = *ilen;
        cipher = true;
    }

    encode();

    *ilen = len;
}

char *SWCipher::getCipheredBuf(unsigned long *ilen) {

    encode();

    if (ilen) *ilen = len;

    return buf;
}


/******************************************************************************
 * SWCipher::encode - This function "encodes" the input stream into the
 *                      output stream.
 *                      The GetChars() and SendChars() functions are
 *                      used to separate this method from the actual
 *                      i/o.
 */

void SWCipher::encode(void)
{
    if (!cipher) {
        work = master;
        for (unsigned long i = 0; i < len; i++)
            buf[i] = work.encrypt(buf[i]);
        cipher = true;
    }
}


/******************************************************************************
 * SWCipher::decode - This function "decodes" the input stream into the
 *                      output stream.
 *                      The GetChars() and SendChars() functions are
 *                      used to separate this method from the actual
 *                      i/o.
 */

void SWCipher::decode(void)
{
    if (cipher) {
        work = master;
        unsigned long i;
        for (i = 0; i < len; i++)
            buf[i] = work.decrypt(buf[i]);
        buf[i] = 0;
        cipher = false;
    }
}


/******************************************************************************
 * SWCipher::setCipherKey   - setter for a new CipherKey
 *
 */

void SWCipher::setCipherKey(const char *ikey) {
    SWBuf cipherKey = personalize(ikey, false);
    master.initialize((unsigned char *)(const char *)cipherKey, cipherKey.size());
}


/******************************************************************************
 * SWCipher::personalize    - a simple personalization encoding
 *
 * encode - whether to encode or decode
 *
 */
SWBuf SWCipher::personalize(const SWBuf &buf, bool encode) {

    std::map<char, int> charHash;
    for (int i = 0; i < 62; ++i) charHash[lats[i]] = i;

    SWBuf segs[5];
    int segn = 0;
    for (unsigned int i = 0; i < buf.size() && segn < 5; ++i) {
        if (buf[i] == '-') ++segn;
        else segs[segn].append(buf[i]);
    }
    SWBuf result;
    SWBuf chkSum = segs[4];
    if (segs[4].size() < 5) segs[4].size(4);
    for (int i = 0; i < 4; ++i) {
        int csum = 0;
        for (unsigned int j = 0; j < segs[i].size() && j < segs[0].size(); ++j) {
            char hash = charHash[segs[i][j]];
            char obfusHash = charHash[segs[0][j%segs[0].size()]];
            if (encode) {
                obfusHash = hash - (i ? obfusHash : 0);
                if (obfusHash < 0) obfusHash = (62 + obfusHash);
            }
            else {
                obfusHash = hash + (i ? obfusHash : 0);
                obfusHash %= 62;
            }
            if (i) segs[i][j] = lats[(long)obfusHash];
            csum += (encode ? obfusHash : hash);
        }
        segs[4][i] = lats[csum%62];
        if (result.size()) result += "-";
        result += (!encode && !i ? "" : segs[i].c_str());
    }
    if (encode) {
        result += "-";
        result += segs[4];
    }
    return (!encode && chkSum != segs[4]) ? buf : result;
}

SWORD_NAMESPACE_END