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cipher_sub.c

/*
 * Copyright (C) 2001, 2002, and 2003  Roy Keene
 *
 * 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; either version 2
 * of the License, or (at your option) any later version.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 *      email: dact@rkeene.org
 */

/*
      Encrypt data.
*/
#include "cipher_sub.h"
#include "parse.h"
#include "dact.h"
#include "ui.h"
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#ifdef HAVE_STRING_H
#include <string.h>
#endif
#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#include <fcntl.h>
#include <stdio.h>
#ifndef RANDOM_DEV
#ifdef TIME_WITH_SYS_TIME
#include <sys/time.h>
#include <time.h>
#else
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#else
#include <time.h>
#endif
#endif
#endif

#if defined(USE_MODULES) && defined(AS_MODULE)
#include "module.h"
uint32_t DC_NUM=1;
uint32_t DC_TYPE=DACT_MOD_TYPE_ENC;
void *DC_ALGO=cipher_sub;
char *DC_NAME="subst (MOD)";
#endif


int cipher_sub(const char *inblock, char *outblock, const int blksize, char *key, const int mode) {
      switch (mode) {
            case (DACT_MODE_CINIT+DACT_MODE_CDEC):
            case (DACT_MODE_CINIT+DACT_MODE_CENC):
            case DACT_MODE_CINIT:
                  return(cipher_sub_init(mode,key));
                  break;
            case DACT_MODE_CDEC:
                  return(cipher_sub_decrypt(inblock, outblock, blksize, key));
                  break;
            case DACT_MODE_CENC:
                  return(cipher_sub_encrypt(inblock, outblock, blksize, key));
                  break;
      }
      return(0);
}


int cipher_sub_init(const int mode, char *key) {
      return(cipher_sub_init_getkey(mode-DACT_MODE_CINIT,key));
}

int cipher_sub_init_getkey(const int mode, char *key) {
      char *fname;
      char keybuf[1024], *ptrbuf;
      int fd,x=257;

      fname=dact_ui_getuserinput("Key file: ",128,0);
      fd=open(fname, O_RDONLY);
      if (fd>=0) {
            x=read(fd, &keybuf, sizeof(keybuf));
            if (x==257) {
                  memcpy(key,keybuf,257); /* For backward compatability with DACT 0.8.1*/
            } else {
                  memcpy(key,ptrbuf=demime64(keybuf),257);
                  free(ptrbuf);
            }
            close(fd);
            return(257);
      }
      if (fd<0 && mode==DACT_MODE_CENC) {
            fd=open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0600);
            if (fd<0) { PERROR("open"); return(0); }
            memcpy(key,generatekey(),257);
            memcpy(keybuf, ptrbuf=mimes64(key,&x), 400);
            write(fd, keybuf, x);
            write(fd, "\n", 1);
            close(fd);
            free(ptrbuf);
            return(257);
      }
      return(-1);
}

int cipher_sub_encrypt(const unsigned char *inblk, unsigned char *outblk, int blksize, unsigned char *key) {
      int i,mod;
      static int keyoffset=0;

      mod=(int) key[0];
      for (i=0;i<blksize;i++) {
            if (!(i%mod)) {
                  keyoffset=((keyoffset+1)&0xff);
            }
            outblk[i]=key[((((int) inblk[i])+keyoffset)&0xff)+1];
      }
      return(blksize);
}

int cipher_sub_decrypt(const unsigned char *inblk, unsigned char *outblk, int blksize, unsigned char *key) {
      int i,mod,x;
      char reversekey[256];
      static int keyoffset=0;

      mod=(int) key[0];
      for (i=1;i<257;i++) reversekey[(int) key[i]]=(i-1);
      for (i=0;i<blksize;i++) {
            if (!(i%mod)) {
                  keyoffset=((keyoffset+1)&0xff);
                  for (x=0;x<256;x++) reversekey[(int) key[((x+keyoffset)&0xff)+1]]=x;
            }
            outblk[i]=reversekey[(int) inblk[i]];
      }
      return(blksize);
}

char *generatekey(void) {
      static char key[257];
      char used[256];
      int i,x;
#ifdef RANDOM_DEV
      unsigned char buff[1];
      int fd;
      fd=open(RANDOM_DEV, O_RDONLY);
      read(fd, buff, 1);
      if (buff[0]==0) buff[0]=3;
      key[0]=buff[0];
#else
      srand(time(NULL)+rand());
      key[0]=1+(int) (255.0*rand()/(RAND_MAX+1.0));
#endif
      for (i=0;i<256;i++) used[i]=0;
      for (i=1;i<257;i++) {
#ifdef RANDOM_DEV
            read(fd, buff, 1);
            x=buff[0];
#else
            srand(time(NULL)+rand());
            x=(int) (256.0*rand()/(RAND_MAX+1.0));
#endif
            if (used[x]==0) { key[i]=x; used[x]=1; } else { i--; }
      }
#ifdef RANDOM_DEV
      close(fd);
#endif
      return(key);
}

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