/*

  *  Copyright (C) 2007-2008 Sourcefire, Inc.
  *
  *  Authors: Alberto Wu, Michal 'GiM' Spadlinski

  *
  *  This program is free software; you can redistribute it and/or modify

  *  it under the terms of the GNU General Public License version 2 as
  *  published by the Free Software Foundation.

  *
  *  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., 51 Franklin Street, Fifth Floor, Boston,
  *  MA 02110-1301, USA.
  */
 
 #if HAVE_CONFIG_H
 #include "clamav-config.h"
 #endif
 
 #include "others.h"

 #include "execs.h"
 #include "pe.h"

 #include "packlibs.h"

 
 static int doubledl(char **scur, uint8_t *mydlptr, char *buffer, uint32_t buffersize)
 {
   unsigned char mydl = *mydlptr;
   unsigned char olddl = mydl;
 
   mydl*=2;
   if ( !(olddl & 0x7f)) {
     if ( *scur < buffer || *scur >= buffer+buffersize-1 )
       return -1;
     olddl = **scur;
     mydl = olddl*2+1;
     *scur=*scur + 1;
   }
   *mydlptr = mydl;
   return (olddl>>7)&1;
 }
 
 
 int cli_unfsg(char *source, char *dest, int ssize, int dsize, char **endsrc, char **enddst) {
   uint8_t mydl=0x80;
   uint32_t backbytes, backsize, oldback = 0;
   char *csrc = source, *cdst = dest;
   int oob, lostbit = 1;
 

   if (ssize<=0 || dsize<=0) return -1;

   *cdst++=*csrc++;
 
   while ( 1 ) {
     if ((oob=doubledl(&csrc, &mydl, source, ssize))) {
       if (oob == -1)
 	return -1;
       /* 164 */
       backsize = 0;
       if ((oob=doubledl(&csrc, &mydl, source, ssize))) {
 	if (oob == -1)
 	  return -1;
 	/* 16a */
 	backbytes = 0;
 	if ((oob=doubledl(&csrc, &mydl, source, ssize))) {
 	  if (oob == -1)
 	    return -1;
 	  /* 170 */
 	  lostbit = 1;
 	  backsize++;
 	  backbytes = 0x10;
 	  while ( backbytes < 0x100 ) {
 	    if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
 	      return -1;
 	    backbytes = backbytes*2+oob;
 	  }
 	  backbytes &= 0xff;
 	  if ( ! backbytes ) {
 	    if (cdst >= dest+dsize)
 	      return -1;
 	    *cdst++=0x00;
 	    continue;
 	  }
 	} else {
 	  /* 18f */
 	  if (csrc >= source+ssize)
 	    return -1;
 	  backbytes = *(unsigned char*)csrc;
 	  backsize = backsize * 2 + (backbytes & 1);
 	  backbytes = (backbytes & 0xff)>>1;
 	  csrc++;
 	  if (! backbytes)
 	    break;
 	  backsize+=2;
 	  oldback = backbytes;
 	  lostbit = 0;
 	}
       } else {
 	/* 180 */
 	backsize = 1;
 	do {
 	  if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
 	    return -1;
 	  backsize = backsize*2+oob;
 	  if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
 	    return -1;
 	} while (oob);
 
 	backsize = backsize - 1 - lostbit;
 	if (! backsize) {
 	  /* 18a */
 	  backsize = 1;
 	  do {
 	    if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
 	      return -1;
 	    backsize = backsize*2+oob;
 	    if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
 	      return -1;
 	  } while (oob);
 
 	  backbytes = oldback;
 	} else {
 	  /* 198 */
 	  if (csrc >= source+ssize)
 	    return -1;
 	  backbytes = *(unsigned char*)csrc;
 	  backbytes += (backsize-1)<<8;
 	  backsize = 1;
 	  csrc++;
 	  do {
 	    if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
 	      return -1;
 	    backsize = backsize*2+oob;
 	    if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
 	      return -1;
 	  } while (oob);
 
           if (backbytes >= 0x7d00)
             backsize++;
           if (backbytes >= 0x500)
             backsize++;
           if (backbytes <= 0x7f)
             backsize += 2;
 
 	  oldback = backbytes;
 	}
 	lostbit = 0;
       }
       if (!CLI_ISCONTAINED(dest, dsize, cdst, backsize) || !CLI_ISCONTAINED(dest, dsize, cdst-backbytes, backsize))
 	return -1;
       while(backsize--) {
 	*cdst=*(cdst-backbytes);
 	cdst++;
       }
 
     } else {
       /* 15d */
       if (cdst < dest || cdst >= dest+dsize || csrc < source || csrc >= source+ssize)
 	return -1;
       *cdst++=*csrc++;
       lostbit=1;
     }
   }
 
   if (endsrc) *endsrc = csrc;
   if (enddst) *enddst = cdst;
   return 0;
 }

 int unmew(char *source, char *dest, int ssize, int dsize, char **endsrc, char **enddst) {

   uint8_t mydl=0x80;
   uint32_t myeax_backbytes, myecx_backsize, oldback = 0;
   char *csrc = source, *cdst = dest;
   int oob, lostbit = 1;
 
   *cdst++=*csrc++;
 
   while ( 1 ) {
     if ((oob=doubledl(&csrc, &mydl, source, ssize))) {
       if (oob == -1)
 	return -1;
       /* 164 */
       myecx_backsize = 0;
       if ((oob=doubledl(&csrc, &mydl, source, ssize))) {
 	if (oob == -1)
 	  return -1;
 	/* 16a */
 	myeax_backbytes = 0;
 	if ((oob=doubledl(&csrc, &mydl, source, ssize))) {
 	  if (oob == -1)
 	    return -1;
 	  /* 170 */
 	  lostbit = 1;
 	  myecx_backsize++;
 	  myeax_backbytes = 0x10;
 	  while ( myeax_backbytes < 0x100 ) {
 	    if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
 	      return -1;
 	    myeax_backbytes = myeax_backbytes*2+oob;
 	  }
 	  myeax_backbytes &= 0xff;
 	  if ( ! myeax_backbytes ) {
 	    if (cdst >= dest+dsize)
 	      return -1;
 	    *cdst++=0x00;
 	    /*cli_dbgmsg("X%02x  ", *(cdst-1)&0xff);*/
 	    continue;
 	  }
 	} else {
 	  /* 18f */
 	  if (csrc >= source+ssize)
 	    return -1;
 	  myeax_backbytes = *(unsigned char*)csrc;
 	  myecx_backsize = myecx_backsize * 2 + (myeax_backbytes & 1);
 	  myeax_backbytes = (myeax_backbytes & 0xff)>>1;
 	  csrc++;
 	  if (! myeax_backbytes)
 	  {
 	    /* cli_dbgmsg("\nBREAK \n"); */
 	    break;
 	  }
 	  myecx_backsize+=2;
 	  oldback = myeax_backbytes;
 	  lostbit = 0;
 	}
       } else {
 	/* 180 */
 	myecx_backsize = 1;
 	do {
 	  if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
 	    return -1;
 	  myecx_backsize = myecx_backsize*2+oob;
 	  if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
 	    return -1;
 	} while (oob);
 
 	myecx_backsize = myecx_backsize - 1 - lostbit;
 	if (! myecx_backsize) {
 	  /* 18a */
 	  myecx_backsize = 1;
 	  do {
 	    if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
 	      return -1;
 	    myecx_backsize = myecx_backsize*2+oob;
 	    if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
 	      return -1;
 	  } while (oob);
 
 	  myeax_backbytes = oldback;
 	} else {
 	  /* 198 */
 	  if (csrc >= source+ssize)
 	    return -1;
 	  myeax_backbytes = *(unsigned char*)csrc;
 	  myeax_backbytes += (myecx_backsize-1)<<8;
 	  myecx_backsize = 1;
 	  csrc++;
 	  do {
 	    if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
 	      return -1;
 	    myecx_backsize = myecx_backsize*2+oob;
 	    if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
 	      return -1;
 	  } while (oob);
 
           if (myeax_backbytes >= 0x7d00)
             myecx_backsize++;
           if (myeax_backbytes >= 0x500)
             myecx_backsize++;
           if (myeax_backbytes <= 0x7f)
             myecx_backsize += 2;
 
 	  oldback = myeax_backbytes;
 	}
 	lostbit = 0;
       }
       if (!CLI_ISCONTAINED(dest, dsize, cdst, myecx_backsize) || !CLI_ISCONTAINED(dest, dsize, cdst-myeax_backbytes, myecx_backsize))
       {

 	cli_dbgmsg("MEW: rete: %p %d %p %d %d || %p %d %p %d %d\n", dest, dsize, cdst, myecx_backsize,

 			CLI_ISCONTAINED(dest, dsize, cdst, myecx_backsize),
 			dest, dsize, cdst-myeax_backbytes, myecx_backsize,
       			CLI_ISCONTAINED(dest, dsize, cdst-myeax_backbytes, myecx_backsize) );
 	return -1;
       }
       while(myecx_backsize--) {
 	*cdst=*(cdst-myeax_backbytes);
 	cdst++;
       }
 
     } else {
       /* 15d */
       if (cdst < dest || cdst >= dest+dsize || csrc < source || csrc >= source+ssize)
       {

 	cli_dbgmsg("MEW: retf %p %p+%08x=%p, %p %p+%08x=%p\n",

 			cdst, dest, dsize, dest+dsize, csrc, source, ssize, source+ssize);
 	return -1;
       }
       *cdst++=*csrc++;
       /* cli_dbgmsg("Z%02x  ", *(cdst-1)&0xff); */
       lostbit=1;
     }
   }
 
   *endsrc = csrc;
   *enddst = cdst;
   return 0;
 }