/*

  *  Copyright (C) 2013-2019 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
  *  Copyright (C) 2007-2013 Sourcefire, Inc.

  *
  *  Authors: Alberto Wu

  *
  *  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.

  */
 
 /*
 ** petitep.c
 ** 
 ** 09/07/2k4 - Dumped and reversed
 ** 10/07/2k4 - Very 1st approach
 ** 10/07/2k4 - PE stuff and main loop
 ** 11/07/2k4 - Porting finished, tracking my bugs...
 ** 12/07/2k4 - ARRRRRGHHH :D
 ** 14/07/2k4 - Code cleaned
 ** 15/07/2k4 - Securing && ClamAV porting
 ** 21/07/2k4 - Unmangled imports now supported
 ** 22/07/2k4 - Unstripped .relocs now supported
 **
 */
 
 /*
 ** Unpacks a buffer containing a petite 2.2 compressed
 ** file. Doesn't perform Import Table unmangling. Doesn't
 ** fixup call/jumps. Tries to "guess" the original sections
 ** structure and entrypoint.
 **
 ** Lotta phanx to Micky for patiently bearing my screams :P
 ** Greets to Ian Luck: the SEH MOVSB thingy almost got me :O
 ** TODO: Cope with level 0 and older petite versions.
 */
 
 
 #if HAVE_CONFIG_H
 #include "clamav-config.h"
 #endif
 
 #include <stdlib.h>
 #include <string.h>
 

 #include "clamav.h"

 #include "rebuildpe.h"

 #include "execs.h"

 #include "others.h"

 #include "petite.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 petite_inflate2x_1to9(char *buf, uint32_t minrva, uint32_t bufsz, struct cli_exe_section *sections, unsigned int sectcount, uint32_t Imagebase, uint32_t pep, int desc, int version, uint32_t ResRva, uint32_t ResSize)

 {
   char *adjbuf = buf - minrva;
   char *packed = NULL;
   uint32_t thisrva=0, bottom = 0, enc_ep=0, irva=0, workdone=0, grown=0x355, skew=0x35;
   int j = 0, oob, mangled = 0, check4resources=0;

   struct cli_exe_section *usects = NULL;

   void *tmpsct = NULL;

 
   /*
     -] The real thing [-
   */
 
   /* NOTE: (435063->4350a5) Petite kernel32!imports and error strings */
 
   /* Here we adjust the start of packed blob, the size of petite code,
    * the difference in size if relocs were stripped
    * See below...
    */
 
   if ( version == 2 )

     packed = adjbuf + sections[sectcount-1].rva + 0x1b8;

   if ( version == 1 ) {

     packed = adjbuf + sections[sectcount-1].rva + 0x178;

     grown=0x323;    /* My name is Harry potter */
     skew=0x34;
   }
 
   while (1) {
     char *ssrc, *ddst;
     uint32_t size, srva;

     int backbytes, oldback, addsize;
     unsigned int backsize;

     if ( ! CLI_ISCONTAINED(buf, bufsz, packed, 4)) {

       if (usects)
 	free(usects);

       return 1;

     }

     srva = cli_readint32(packed);
 
     if (! srva) {
       /* WERE DONE !!! :D */
       int t, upd = 1;
 
       if ( j <= 0 ) /* Some non petite compressed files will get here */

 	return 1;

     
       /* Select * from sections order by rva asc; */
       while ( upd ) {
 	upd = 0;
 	for (t = 0; t < j-1 ; t++) {
 	  uint32_t trva, trsz, tvsz;
 

 	  if ( usects[t].rva <= usects[t+1].rva )

 	    continue;
 	  trva = usects[t].rva;
 	  trsz = usects[t].rsz;
 	  tvsz = usects[t].vsz;
 	  usects[t].rva = usects[t+1].rva;
 	  usects[t].rsz = usects[t+1].rsz;
 	  usects[t].vsz = usects[t+1].vsz;
 	  usects[t+1].rva = trva;
 	  usects[t+1].rsz = trsz;
 	  usects[t+1].vsz = tvsz;
 	  upd = 1;
 	}
       }
 
       /* Computes virtualsize... we try to guess, actually :O */
       for (t = 0; t < j-1 ; t++) {
 	if ( usects[t].vsz != usects[t+1].rva - usects[t].rva )
 	  usects[t].vsz = usects[t+1].rva - usects[t].rva;
       }

       /*
        * Our encryption is pathetic and out software is lame but
        * we need to claim it's unbreakable.
        * So why dont we just mangle the imports and encrypt the EP?!
        */
 
       /* Decrypts old entrypoint if we got enough clues */
       if (enc_ep) {
 	uint32_t virtaddr = pep + 5 + Imagebase, tmpep;
 	int rndm = 0, dummy = 1;

 	char *thunk = adjbuf+irva;
 	char *imports;

 
 	if ( version == 2 ) { /* 2.2 onley */
 

 	  while ( dummy && CLI_ISCONTAINED(buf, bufsz, thunk, 4) ) {

 	    uint32_t api;

 	    if (! cli_readint32(thunk)) {

 	      workdone = 1;
 	      break;
 	    }
 

 	    imports = adjbuf + cli_readint32(thunk);
 	    thunk+=4;

 	    dummy = 0;
 

 	    while ( CLI_ISCONTAINED(buf, bufsz, imports, 4)) {
 	      dummy = 0;

 	      imports+=4;
 	      if ( ! (api = cli_readint32(imports-4)) ) {

 		dummy  = 1;
 		break;
 	      }
 	      if ( (api != (api | 0x80000000)) && mangled && --rndm < 0) {
 		api = virtaddr;
 		virtaddr +=5; /* EB + 1 double */
 		rndm = virtaddr & 7;
 	      } else {
 		api = 0xbff01337; /* KERNEL32!leet */
 	      }

 	      if (sections[sectcount-1].rva+Imagebase < api )

 		enc_ep--;
 	      if ( api < virtaddr )
 		enc_ep--;
 	      tmpep = (enc_ep & 0xfffffff8)>>3 & 0x1fffffff;
 	      enc_ep = (enc_ep & 7)<<29 | tmpep;
 	    }
 	  }
 	} else 
 	  workdone = 1;
 	enc_ep = pep+5+enc_ep;

 	if ( workdone == 1 ) {

 	  cli_dbgmsg("Petite: Old EP: %x\n", enc_ep);

 	} else {
 	  enc_ep = usects[0].rva;
 	  cli_dbgmsg("Petite: In troubles while attempting to decrypt old EP, using bogus %x\n", enc_ep);
 	}

       }
 
       /* Let's compact data */

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

 	usects[t].raw = (t>0)?(usects[t-1].raw + usects[t-1].rsz):0;

 	if (usects[t].rsz != 0) {

 	  if(CLI_ISCONTAINED(buf, bufsz, buf + usects[t].raw, usects[t].rsz)) {
 	    memmove(buf + usects[t].raw, adjbuf + usects[t].rva, usects[t].rsz);
 	  } else {
 	    cli_dbgmsg("Petite: Skipping section %d, Raw: %x, RSize:%x\n", t, usects[t].raw, usects[t].rsz);
 	    usects[t].raw = t>0 ? usects[t-1].raw : 0;
 	    usects[t].rsz = 0;
 	  }

 	}

       }
 
       /* Showtime!!! */
       cli_dbgmsg("Petite: Sections dump:\n");
       for (t = 0; t < j ; t++)

 	cli_dbgmsg("Petite: .SECT%d RVA:%x VSize:%x ROffset: %x, RSize:%x\n", t, usects[t].rva, usects[t].vsz, usects[t].raw, usects[t].rsz);

       if (! cli_rebuildpe(buf, usects, j, Imagebase, enc_ep, ResRva, ResSize, desc)) {

 	cli_dbgmsg("Petite: Rebuilding failed\n");

 	free(usects);
 	return 1;
       }

       free(usects);

       return 0;

     }
 
 
     size = srva & 0x7fffffff;
     if ( srva != size ) { /* Test and clear bit 31 */
       check4resources=0;
       /*
 	Enumerates each petite data section
 	I should get here once ot twice:
 	- 1 time for the resource section (if present)
 	- 1 time for the all_the_rest section
       */
 

       if ( ! CLI_ISCONTAINED(buf, bufsz, packed+4, 8) ) {

 	if (usects)
 	  free(usects);

 	return 1;

       }

       /* Save the end of current packed section for later use */
       bottom = cli_readint32(packed+8) + 4;
       ssrc = adjbuf + cli_readint32(packed+4) - (size-1)*4;
       ddst = adjbuf + cli_readint32(packed+8) - (size-1)*4;
 

       if ( !CLI_ISCONTAINED(buf, bufsz, ssrc, size*4) || !CLI_ISCONTAINED(buf, bufsz, ddst, size*4) ) {

 	if (usects)
 	  free(usects);

 	return 1;

       }

 
       /* Copy packed data to the end of the current packed section */
       memmove(ddst, ssrc, size*4);
       packed += 0x0c;
     } else {
       uint32_t check1, check2;
       uint8_t mydl = 0;
       uint8_t goback;

       unsigned int q;

       /* Unpack each original section in turn */

       if ( ! CLI_ISCONTAINED(buf, bufsz, packed+4, 8)) {

 	if (usects)
 	  free(usects);

 	return 1;

       }

 
       size = cli_readint32(packed+4); /* How many bytes to unpack */

       thisrva=cli_readint32(packed+8); /* RVA of the original section */

       packed += 0x10;
 

       if ( j >= 96 ) {

 	cli_dbgmsg("Petite: maximum number of sections exceeded, giving up.\n");
 	free(usects);

 	return 1;

       }

       /* Alloc 1 more struct */

       if ( ! (tmpsct = cli_realloc(usects, sizeof(struct cli_exe_section) * (j+1))) ) {

 	if (usects)
 	  free(usects);

 	return 1;

       }

       usects = (struct cli_exe_section *) tmpsct;

       /* Save section spex for later rebuilding */
       usects[j].rva = thisrva;
       usects[j].rsz = size;
       if ( (int)(bottom - thisrva) >0 )
 	usects[j].vsz = bottom - thisrva;
       else
 	usects[j].vsz = size;
       usects[j].raw = 0; /* Cheaper than memset */
 
       if (!size) { /* That's a ghost section! reloc any1? :P */
 	j++;
 	continue;
       }
 
       ssrc = adjbuf + srva;
       ddst = adjbuf + thisrva;
 
       /* Last petite section (unpacked 1st) could contain unpacked data
        * (eg the icon): let's fix the rva
        */
 

       for ( q = 0 ; q < sectcount ; q++ ) {
 	if(!CLI_ISCONTAINED(sections[q].rva, sections[q].vsz, usects[j].rva, usects[j].vsz))
 	  continue;
 	if (!check4resources) {

 	  usects[j].rva = sections[q].rva;
 	  usects[j].rsz = thisrva - sections[q].rva + size;

 	}

 	break;
       }
       if (q == sectcount) {
 	free(usects);
 	return 1;

       }
 
       /* Increase count of unpacked sections */
       j++;
 
 
       /* Setup some crap for later checks */
       if ( size < 0x10000 ) {
 	check1 = 0x0FFFFC060;
 	check2 = 0x0FFFFFC60;
 	goback = 5;
       } else if ( size < 0x40000 ) {
 	check1 = 0x0FFFF8180;
 	check2 = 0x0FFFFF980;
 	goback = 7;
       } else {
 	check1 = 0x0FFFF8300;
 	check2 = 0x0FFFFFB00;
 	goback = 8;
       }
 
       /*
        * NOTE: on last loop we get esi=edi=ImageBase (which is not writeable)
        * The movsb on the next line causes the iat_rebuild_and_decrypt_oldEP()
        * func to get called instead... ehehe very smart ;)
        */
 

       if ( !CLI_ISCONTAINED(buf, bufsz, ssrc, 1) || !CLI_ISCONTAINED(buf, bufsz, ddst, 1)) {

 	free(usects);

 	return 1;

       }

 
       size--;
       *ddst++=*ssrc++; /* eheh u C gurus gotta luv these monsters :P */
       backbytes=0;
       oldback = 0;
 
       /* No surprises here... NRV any1??? ;) */
       while (size > 0) {
 	oob = doubledl(&ssrc, &mydl, buf, bufsz);

 	if ( oob == -1 ) {
 	  free(usects);

 	  return 1;

 	}

 	if (!oob) {

 	  if ( !CLI_ISCONTAINED(buf, bufsz, ssrc, 1) || !CLI_ISCONTAINED(buf, bufsz, ddst, 1) ) {

 	    free(usects);

 	    return 1;

 	  }

 	  *ddst++ = (char)((*ssrc++)^(size & 0xff));
 	  size--;
 	} else {
 	  addsize = 0;
 	  backbytes++;
 	  while (1) {

 	    if ( (oob = doubledl(&ssrc, &mydl, buf, bufsz)) == -1 ) {
 	      free(usects);

 	      return 1;

 	    }

 	    if (backbytes >= INT_MAX / 2) {
 		    free(usects);
 		    cli_dbgmsg("Petite: probably invalid file\n");
 		    return 1;
 	    }

 	    backbytes = backbytes*2 + oob;

 	    if ( (oob = doubledl(&ssrc, &mydl, buf, bufsz)) == -1 ) {
 	      free(usects);

 	      return 1;

 	    }

 	    if (!oob)
 	      break;
 	  }
 	  backbytes -= 3;
 	  if ( backbytes >= 0 ) {
 	    backsize = goback;
 	    do {

 	      if ( (oob = doubledl(&ssrc, &mydl, buf, bufsz)) == -1 ) {
 		free(usects);

 		return 1;

 	      }

 	      if (backbytes >= INT_MAX / 2) {
 		      free(usects);
 		      cli_dbgmsg("Petite: probably invalid file\n");
 		      return 1;
 	      }

 	      backbytes = backbytes*2 + oob;
 	      backsize--;
 	    } while (backsize);
 	    backbytes^=0xffffffff;

 	    addsize += 1 + ( backbytes < (int) check2 ) + ( backbytes < (int) check1 );

 	    oldback = backbytes;
 	  } else {
 	    backsize = backbytes+1;
 	    backbytes = oldback;
 	  }
 

 	  if ( (oob = doubledl(&ssrc, &mydl, buf, bufsz)) == -1 ) {
 	    free(usects);

 	    return 1;

 	  }

 	  backsize = backsize*2 + oob;

 	  if ( (oob = doubledl(&ssrc, &mydl, buf, bufsz)) == -1 ) {
 	    free(usects);

 	    return 1;

 	  }

 	  backsize = backsize*2 + oob;
 	  if (!backsize) {
 	    backsize++;
 	    while (1) {

 	      if ( (oob = doubledl(&ssrc, &mydl, buf, bufsz)) == -1 ) {
 		free(usects);

 		return 1;

 	      }

 	      backsize = backsize*2 + oob;

 	      if ( (oob = doubledl(&ssrc, &mydl, buf, bufsz)) == -1 ) {
 		free(usects);

 		return 1;

 	      }

 	      if (!oob)
 		break;
 	    }
 	    backsize+=2;
 	  }
 	  backsize+=addsize;
 	  size-=backsize;

 	  if(!CLI_ISCONTAINED(buf, bufsz, ddst, backsize) || !CLI_ISCONTAINED(buf, bufsz, ddst+backbytes, backsize)) {

 	    free(usects);

 	    return 1;

 	  }

 	  while(backsize--) {
 	    *ddst=*(ddst+backbytes);
 	    ddst++;
 	  }
 	  backbytes=0;
 	  backsize=0;
 	} /* else */
       } /* while(ebx) */
 
       /* Any lame petite code here? If so let's strip it
        * We've done version adjustments already, see above
        */
 

       if ( j ) {
 	int strippetite=0;
 	uint32_t reloc;
 	
 	/* LONG MAGIC = 33C05E64 8B188B1B 8D63D65D */
 	if ( usects[j-1].rsz > grown && 
 	     CLI_ISCONTAINED(buf, bufsz, ddst-grown+5+0x4f, 8) &&
 	     cli_readint32(ddst-grown+5+0x4f) == 0x645ec033 &&
 	     cli_readint32(ddst-grown+5+0x4f+4) == 0x1b8b188b
 	     ) {
 	  reloc = 0;
 	  strippetite = 1;
 	}
 	if ( !strippetite && 
 	     usects[j-1].rsz > grown+skew &&
 	     CLI_ISCONTAINED(buf, bufsz, ddst-grown+5+0x4f-skew, 8) &&

 	      cli_readint32(ddst-grown+5+0x4f-skew) == 0x645ec033 &&

 	     cli_readint32(ddst-grown+5+0x4f+4-skew) == 0x1b8b188b
 	     ) {
 	  reloc = skew; /* If the original exe had a .reloc were skewed */
 	  strippetite = 1;
 	}
 	
 	if (strippetite && CLI_ISCONTAINED(buf, bufsz, ddst-grown+0x0f-8-reloc, 8)) {

 	  uint32_t test1, test2;
 	  
 	  /* REMINDER: DON'T BPX IN HERE U DUMBASS!!!!!!!!!!!!!!!!!!!!!!!! */
 	  test1 = cli_readint32(ddst-grown+0x0f-8-reloc)^0x9d6661aa;
 	  test2 = cli_readint32(ddst-grown+0x0f-4-reloc)^0xe908c483;

 	  cli_dbgmsg("Petite: Found petite code in sect%d(%x). Let's strip it.\n", j-1, usects[j-1].rva);

 	  if (test1 == test2 && CLI_ISCONTAINED(buf, bufsz, ddst-grown+0x0f-reloc, 0x1c0-0x0f+4)) {

 	    irva = cli_readint32(ddst-grown+0x121-reloc);
 	    enc_ep = cli_readint32(ddst-grown+0x0f-reloc)^test1;

 	    mangled = ((uint32_t) cli_readint32(ddst-grown+0x1c0-reloc) != 0x90909090); /* FIXME: Magic's too short??? */

 	    cli_dbgmsg("Petite: Encrypted EP: %x | Array of imports: %x\n",enc_ep, irva);
 	  }
 	  usects[j-1].rsz -= grown+reloc;

     	}
       }

       check4resources++;
     } /* outer else */
   } /* while true */
 }