/*
  *  Copyright (C) 2005 aCaB <acab@clamav.net>
  *
  *  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., 51 Franklin Street, Fifth Floor, Boston,
  *  MA 02110-1301, USA.

  */
 
 /*
 ** spin.c
 ** 
 ** 19/07/2k5 - Finally started coding something
 ** 21/07/2k5 - Works, started clearing the mess
 ** 31/07/2k5 - Porting to libclamav
 */
 
 /*
 ** Unpacks pespin v1.1
 **
 ** Funny thing to reverse
 **
 ** [ A big fat thank to christoph for not letting me give up ]
 */
 
 
 /*
 ** TODO ( a fat one ):
 **
 ** OEP restore and unhijacking
 ** code redir handling (at least near OEP)
 ** passwd protection (didn't really look at it)
 **
 ** All this stuff really needs a way better emu and a hell of unlaming
 ** ATM not worth the effort... and pespin v1.3 is out :@
 **
 */
 
 
 #if HAVE_CONFIG_H
 #include "clamav-config.h"
 #endif
 
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <unistd.h>
 #include <string.h>
 
 #include "cltypes.h"
 #include "pe.h"
 #include "rebuildpe.h"
 #include "others.h"

 #include "spin.h"

 #define EC32(x) le32_to_host(x) /* Convert little endian to host */

 static char exec86(uint8_t aelle, uint8_t cielle, char *curremu) {
   int len = 0;
   while (len <0x24) {
     uint8_t opcode = curremu[len], support;
     len++;

     switch (opcode) {
       case 0xeb:

         len++;

       case 0x0a:

         len++;

       case 0x90:
       case 0xf8:
       case 0xf9:
         break;
 
       case 0x02: /* add al, cl */
         aelle+=cielle;

 	len++;

         break;
       case 0x2a: /* sub al, cl */
         aelle-=cielle;

 	len++;

         break;
       case 0x04: /* add al, ?? */

         aelle+=curremu[len];
 	len++;

         break;
       case 0x2c: /* sub al, ?? */

         aelle-=curremu[len];
 	len++;

         break;
       case 0x32: /* xor al, cl */
         aelle^=cielle;

 	len++;

         break;
       case 0x34: /* xor al, ?? */

         aelle^=curremu[len];
 	len++;

         break;
 
       case 0xfe: /* inc/dec al */

         if ( curremu[len] == '\xc0' ) aelle++;

 	else aelle--;

         len++;

         break;
 
       case 0xc0: /* ror/rol al, ?? */

 	support = curremu[len];
         len++;
         if ( support == 0xc0 ) ROL(aelle, curremu[len]);
         else ROR(aelle, curremu[len]);
         len++;

         break;
 
       default:
         cli_dbgmsg("Bogus opcode %x\n", opcode);
     }
   }

   if ( len!=0x24 || curremu[len]!='\xaa' )

     cli_dbgmsg("spin: bad emucode\n"); /* FIXME: I should really give up here */

   return aelle;
 }
 
 
 static int doubledl(char **scur, uint8_t *mydlptr, char *buffer, int 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;
 }
 
 
 static int unfsg(char *source, char *dest, int ssize, int dsize) {
   uint8_t mydl=0x80;
   uint32_t backbytes, backsize, oldback = 0;
   char *csrc = source, *cdst = dest;
   int oob, lostbit = 1;
 
   /* I assume buffers size is >0 - No checking! */
   *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 {
 	    /* repne movsb - FIXME dont remove for now */
 	  }
 	} 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 ((backsize > (uint32_t)(dest + dsize - cdst)) || (backbytes > (uint32_t)(cdst - dest)))

 	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;
     }
   }
 
   return 0;
 }
 
 
 static uint32_t summit (char *src, int size) 
 {
   uint32_t eax=0xffffffff, ebx=0xffffffff;
   int i;
 
   while(size) {
     eax ^= *src++<<8 & 0xff00;
     eax = eax>>3 & 0x1fffffff;
     for (i=0; i<4; i++) {
       uint32_t swap;
       eax ^= ebx>>8 & 0xff;
       eax += 0x7801a108;
       eax ^= ebx;
       ROR(eax, ebx&0xff);
       swap = eax;
       eax = ebx;
       ebx = swap;
     }
     size--; 
   }
   return ebx;
 }
 
 
 int unspin(char *src, int ssize, struct pe_image_section_hdr *sections, int sectcnt, uint32_t nep, int desc) {
   char *curr, *emu, *ep, *spinned;
   char **sects;
   int blobsz=0, j;
   uint32_t key32, bitmap, bitman;
   uint32_t len;
   uint8_t key8;
 
   cli_dbgmsg("in unspin\n");
 
   if ( (spinned = (char *) cli_malloc(EC32(sections[sectcnt].SizeOfRawData))) == NULL )
     return 1;
 
   memcpy(spinned, src + EC32(sections[sectcnt].PointerToRawData), EC32(sections[sectcnt].SizeOfRawData)); 
   ep = spinned + nep - sections[sectcnt].VirtualAddress;
 

   curr = ep+0xdb; /* HELP: as a general rule, can i do char* math or should use monsters like "&ep[0xdb]" instead? */

   if ( *curr != '\xbb' ) {
     free(spinned);
     cli_dbgmsg("spin: Not spinned or bad version\n");
     return 1;
   }
   
   key8 = (uint8_t)*++curr;
   curr+=4;
   if ( *curr != '\xb9' ) {
     free(spinned);
     cli_dbgmsg("spin: Not spinned or bad version\n");
     return 1;
   }
 
   if ( (len = cli_readint32(curr+1)) != 0x11fe ) {
     free(spinned);
     cli_dbgmsg("spin: Not spinned or bad version\n");
     return 1;
   }
 
   cli_dbgmsg("spin: Key8 is %x, Len is %x\n", key8, len);
 

   if ( (uint32_t)(ep - spinned) >= EC32(sections[sectcnt].SizeOfRawData) - len - 0x1fe5 ) {

     free(spinned);
     cli_dbgmsg("spin: len out of bounds, giving up\n");

     return 1; /* Outta bounds - HELP: i suppose i should check for wraps.. not sure though */

   }
 

 
   if ( ep[0x1e0]!='\xb8' )
     cli_dbgmsg("spin: prolly not spinned, expect failure\n");
   
   if ( (cli_readint32(ep+0x1e1) & 0x00200000) )
     cli_dbgmsg("spin: password protected, expect failure\n");
 
 

   curr = ep+0x1fe5+len-1;
   while ( len-- ) {
     *curr=(*curr)^(key8--);
     curr--;
   }
 
   curr = ep+0x26eb;
   key32 = cli_readint32(curr);
   if ( (len = cli_readint32(curr+5)) != 0x5a0) {
     free(spinned);
     cli_dbgmsg("spin: Not spinned or bad version\n");

     return 1;

   }
 

   curr = ep+0x2d5; /* 0x2d5+5a0 < 0x3217 - still within bounds (checked by caller) */

   cli_dbgmsg("spin: Key is %x, Len is %x\n", key32, len);
 
   while ( len-- ) {
     if ( key32 & 1 ) {
       key32 = key32>>1&0x7fffffff;
       key32 ^= 0x8c328834;
     } else {
       key32 = key32>>1 & 0x7fffffff;
     }
     *curr = *curr ^ (key32 & 0xff);
     curr++;
   }
 

   len = ssize - cli_readint32(ep+0x429); /* sub size, value */
   if ( len >= (uint32_t)ssize ) {

     free(spinned);
     cli_dbgmsg("spin: crc out of bounds, giving up\n");

     return 1; /* We wrapped */

   }
   key32 = cli_readint32(ep+0x3217) - summit(src,len);
 
   memcpy(src + EC32(sections[sectcnt].PointerToRawData), spinned, EC32(sections[sectcnt].SizeOfRawData)); 

   free(spinned); /* done CRC'ing - can have a dirty buffer now */
   ep = src + nep + sections[sectcnt].PointerToRawData - sections[sectcnt].VirtualAddress; /* Fix the helper */

 
   bitmap = cli_readint32(ep+0x3207);

   cli_dbgmsg("spin: Key32 is %x - XORbitmap is %x\n", key32, bitmap);
   
   cli_dbgmsg("spin: Decrypting sects (xor)\n");

   for (j=0; j<sectcnt; j++) {

     if (bitmap&1) {
       uint32_t size = EC32(sections[j].SizeOfRawData);
       char *ptr = src + EC32(sections[j].PointerToRawData);
       uint32_t keydup = key32;
       

       if ( EC32(sections[j].PointerToRawData) + size >=  (uint32_t)ssize ) {

 	cli_dbgmsg("spin: sect %d out of file, giving up\n", j);

 	return 1; /* sect outta bounds - HELP: i suppose i should check for wraps.. not sure though */

       }
 
       while (size--) {
 	if (! (keydup & 1)) {
 	  keydup = keydup>>1&0x7fffffff; /* HELP: clear sign bit for unsigned values too? */
 	  keydup ^= 0xed43af31;
 	} else {
 	  keydup = keydup>>1 & 0x7fffffff; /* HELP: clear sign bit for unsigned values too? */
 	}
 	*ptr = *ptr ^ (keydup & 0xff);
 	ptr++;
       }

     } 
     bitmap = bitmap >>1 & 0x7fffffff; /* HELP: clear sign bit for unsigned values too? */

   }

   cli_dbgmsg("spin: done\n");
 

   curr = ep+0x644; /* 0x28d3+0x180 < 0x3217 - still within bounds (checked by caller) */

   if ( (len = cli_readint32(curr)) != 0x180) {
     cli_dbgmsg("spin: Not spinned or bad version\n");
     return 1;
   }
 
   key32 = cli_readint32(curr+0x0c);
   cli_dbgmsg("spin: Key is %x, Len is %x\n", key32, len);
   curr = ep+0x28d3;
 
   while ( len-- ) {
     if ( key32 & 1 ) {
       key32 = key32>>1&0x7fffffff;
       key32 ^= 0xed43af32;
     } else {
       key32 = key32>>1 & 0x7fffffff;
     }
     *curr = *curr ^ (key32 & 0xff);
     curr++;
   }
 
 
   curr = ep+0x28dd;
   if ( (len = cli_readint32(curr)) != 0x1a1 ) {
     cli_dbgmsg("spin: Not spinned or bad version\n");
     return 1;
   }
 
   cli_dbgmsg("spin: POLY1 len is %x\n", len);

   curr+=0xf; /* POLY1 */
   emu = ep+0x6d4; /* Still within bounds */

 
   while (len) {

     *emu=exec86(*emu, len-- & 0xff, curr); /* unlame POLY1 */

     emu++;
   }
 

   bitmap = cli_readint32(ep+0x6f1);

   cli_dbgmsg("spin: POLYbitmap is %x - decrypting sects (poly)\n", bitmap);

   curr = ep+0x755;
 
   for (j=0; j<sectcnt; j++) {
     if (bitmap&1) {

       uint32_t notthesamelen = EC32(sections[j].SizeOfRawData);

 
       emu = src + EC32(sections[j].PointerToRawData);
 

       if ( emu < src || EC32(sections[j].PointerToRawData) + notthesamelen >= (uint32_t)ssize) { /* HELP: Is this enough for me to be within bounds? */

 	cli_dbgmsg("spin: code to exec is out of file?\n");
 	return 1;
       }
 

       while (notthesamelen) {
         *emu=exec86(*emu, notthesamelen-- & 0xff, curr);

         emu++;
       }
     }

       bitmap = bitmap >>1 & 0x7fffffff;

   }

   
   cli_dbgmsg("spin: done\n");

 
   bitmap = cli_readint32(ep+0x3061);
   bitman = bitmap;
   cli_dbgmsg("spin: Compression bitmap is %x\n", bitmap);
   if ( (sects= (char **) cli_malloc(sectcnt*sizeof(char *))) == NULL )
     return 1;
 
   len = 0;
   for (j=0; j<sectcnt; j++) {
     if (bitmap&1) {

        if ( (sects[j] = (char *) cli_malloc(EC32(sections[j].VirtualSize)) ) == NULL ) { /* FIXME: use "static" maxmalloc @4380b6 instead??? */

 	 cli_dbgmsg("spin: malloc(%d) failed\n", EC32(sections[j].VirtualSize));

 	 len = 1;
 	 break;
        }
        blobsz+=EC32(sections[j].VirtualSize);
        memset(sects[j], 0, EC32(sections[j].VirtualSize));
        cli_dbgmsg("spin: Growing sect%d: was %x will be %x\n", j, EC32(sections[j].SizeOfRawData), EC32(sections[j].VirtualSize));

        if ( unfsg(src + EC32(sections[j].PointerToRawData), sects[j], EC32(sections[j].SizeOfRawData), EC32(sections[j].VirtualSize)) == -1 ) {
 	 len++;
          cli_dbgmsg("spin: Unpack failure\n");
        }

        /* sections[j].rsz = sections[j].vsz; FIXME: can't hack the caller, gotta find a better way! */

     } else {
       blobsz+=EC32(sections[j].SizeOfRawData);
       sects[j] = src + EC32(sections[j].PointerToRawData);
       cli_dbgmsg("spin: Not growing sect%d\n", j);
     }
     bitmap = bitmap >>1 & 0x7fffffff;
   }

   
   cli_dbgmsg("spin: decompression complete\n");
  

   if ( len ) {
     int t;

     for (t=0 ; t<j ; t++) {

       if (bitman&1)
 	free(sects[t]);

       bitman = bitman >>1 & 0x7fffffff;
     }

     free(sects);
     return 1;
   }
 
 
   key32 = cli_readint32(ep+0x2fee);
   if (key32) {
     /*    len = cli_readint32(ep+0x2fc8); -- Using vsizes instead */
 
     for (j=0; j<sectcnt; j++) {

       if (EC32(sections[j].VirtualAddress) <= key32 && EC32(sections[j].VirtualAddress)+EC32(sections[j].SizeOfRawData) > key32) /* HELP: wraps? */

 	break;
     }
 

     if (j!=sectcnt && ((bitman & (1<<j)) == 0)) { /* FIXME: not really sure either the res sect is lamed or just compressed, but this'll save some major headakes */

       cli_dbgmsg("spin: Resources (sect%d) appear to be compressed\n\tuncompressed offset %x, len %x\n\tcompressed offset %x, len %x\n", j, EC32(sections[j].VirtualAddress), key32 - EC32(sections[j].VirtualAddress), key32, EC32(sections[j].VirtualSize) - (key32 - EC32(sections[j].VirtualAddress)));

 
       if ( (curr=(char *)cli_malloc(EC32(sections[j].VirtualSize))) != NULL ) {

 	memcpy(curr, src + EC32(sections[j].PointerToRawData), key32 - EC32(sections[j].VirtualAddress)); /* Uncompressed part */
 	memset(curr + key32 - EC32(sections[j].VirtualAddress), 0, EC32(sections[j].VirtualSize) - (key32 - EC32(sections[j].VirtualAddress))); /* bzero */
 	if ( unfsg(src + EC32(sections[j].PointerToRawData) + key32 - EC32(sections[j].VirtualAddress), curr + key32 - EC32(sections[j].VirtualAddress), EC32(sections[j].SizeOfRawData) - (key32 - EC32(sections[j].VirtualAddress)), EC32(sections[j].VirtualSize) - (key32 - EC32(sections[j].VirtualAddress))) ) { /* HELP: i can't read my own line - hope's ok :( */

       
 	  free(curr);
 	  cli_dbgmsg("spin: Failed to grow resources, continuing anyway\n");
 	  blobsz+=EC32(sections[j].SizeOfRawData);
 	} else {

 	  sects[j]=curr; /* FIXME: bitman check above should save me from leaks */

 	  bitman|=1<<j;
 	  cli_dbgmsg("spin: Resources grown\n");
 	  blobsz+=EC32(sections[j].VirtualSize);
 	}
       } else {

 	/* HELP: malloc failed but i'm too deep into this crap to worry... what to do next? */

 	blobsz+=EC32(sections[j].SizeOfRawData);
       }
     } else {
       cli_dbgmsg("spin: No res?!\n");
     }
   }
   
 

   bitmap=bitman; /* save as a free() bitmap */

 
   if ( (ep = (char *) cli_malloc(blobsz)) != NULL ) {
     struct SECTION *rebhlp;
     if ( (rebhlp = (struct SECTION *) cli_malloc(sizeof(struct SECTION)*(sectcnt))) != NULL ) {
       char *to = ep;
       int retval = 0;
 
       for (j = 0; j < sectcnt; j++) {
 	rebhlp[j].raw = (j>0)*(rebhlp[j-1].raw + rebhlp[j-1].rsz);
 	rebhlp[j].rsz = (bitmap &1) ? EC32(sections[j].VirtualSize) : EC32(sections[j].SizeOfRawData);
 	rebhlp[j].rva = EC32(sections[j].VirtualAddress);
 	rebhlp[j].vsz = EC32(sections[j].VirtualSize);
 
 	memcpy(to, sects[j], rebhlp[j].rsz);
 	to+=rebhlp[j].rsz;
 	if ( bitmap & 1 ) free(sects[j]);
 	bitmap = bitmap >>1 & 0x7fffffff;
       }
 

       if ( (to = rebuildpe(ep, rebhlp, sectcnt, 0x400000, 0x1000, 0, 0))) { /* HELP: should i bother fixing those values? the rebuilt exe is completely broken anyway. */
 	if (cli_writen(desc, to, 0x148+0x80+0x28*j+rebhlp[j-1].raw+rebhlp[j-1].rsz)==-1) {
 	  cli_dbgmsg("spin: Cannot write unpacked file\n");
 	  retval = 1;
 	}

 	free(to);
       } else {
 	cli_dbgmsg("spin: Cannot write unpacked file\n");
 	retval = 1;
       }
       free(rebhlp);
       free(ep);
       free(sects);
       return retval;
     }
     free(ep);
   }
 
   cli_dbgmsg ("spin: free bitmap is %x\n", bitman);
   for (j=0; j<sectcnt; j++) {
     if (bitmap&1) free(sects[j]);
     bitman = bitman >>1 & 0x7fffffff;
   }
   free(sects);

   return 1; /* :( */

 }