findjmp

/*
 Findjmp.c
 written by Ryan Permeh - ryan at eeye - Summarily modified by I2S-LaB.com
 http://www.eeye.com

 Findjmp2.c (pop/pop/ret scanner, logging to file)
 version by A.D - class101 at hat-squad
 http://class101.org, http://www.hat-squad.com


 This finds useful jump points in a dll. Once you overflow a buffer, by
 looking in the various registers, it is likely that you will find a
 reference to your code. This program will find addresses suitible to
 overwrite eip that will return to your code.

 It should be easy to modify this to search for other good jump points,
 or specific code patterns within a dll.

 It currently supports looking for:
   1. jmp reg

   2. call reg

   3. push reg
      ret
 All three options result in the same thing, EIP being set to reg.

 It also supports the following registers:
  EAX
  EBX
  ECX
  EDX
  ESI
  EDI
  ESP
  EBP
*/

#include <iostream.h>
#include <fstream.h>
#include <Windows.h>
#include <stdio.h>

FILE *fplog;

void usage();
void sep();
void iok(BYTE *curpos, char *reg);
void iok2(BYTE *curpos, char *reg);
void ook(BYTE *curpos, char *reg);
void ook2(BYTE *curpos, char *reg);

DWORD GetRegNum( char *reg );
void findjmp( char *dll, char *reg );

 //This finds useful jump points in a dll. Once you overflow a buffer, by
 //looking in the various registers, it is likely that you will find a
 //reference to your code. This program will find addresses of suitible
 //addresses of eip that will return to your code.

int main( int argc, char **argv )
{
 if( argc <= 2 )
  usage();

 else
 {
  char dll[512], //holder for the dll to look in
  reg[512]; // holder for the register

  if ((fplog =fopen("findjmp.txt","r"))==NULL){
   fplog =fopen("findjmp.txt","w");}
  else fplog =fopen("findjmp.txt","a");
  strncpy( dll, argv[1], 512 );
  strncpy( reg, argv[2], 512 );
  findjmp( dll, reg );
 }
 return 0;
}

 //This prints the usage information.

void usage()
{
 printf("\nFindjmp, Eeye, I2S-LaB\nFindjmp2, Hat-Squad\nFindJmp DLL registre\nEx: findjmp KERNEL32.DLL esp"\
     "\nCurrently supported registre are: EAX, EBX, ECX, EDX, ESI, EDI, ESP, EBP\n" );
}

 //findjmp is the workhorse. it loads the requested dll, and searches for
 //the specific patterns for jmp reg, push reg ret, and call reg

void findjmp( char *dll,char *reg )
{
    char reg1[]="eax";char reg2[]="ebx";
    char reg3[]="ecx";char reg4[]="edx";
 char reg5[]="esi";char reg6[]="edi";
    char reg7[]="esp";char reg8[]="ebp";

 BYTE jmppat[8][2]={ { 0xFF, 0xE0 }, { 0xFF, 0xE3 }, { 0xFF, 0xE1 }, { 0xFF, 0xE2 },
       { 0xFF, 0xE6 }, { 0xFF, 0xE7 }, { 0xFF, 0xE4 }, { 0xFF, 0xE5 } }; // patterns for jmp ops

 BYTE callpat[8][2]={ { 0xFF, 0xD0 }, { 0xFF, 0xD3 }, { 0xFF, 0xD1 }, { 0xFF, 0xD2},
       { 0xFF, 0xD6 }, { 0xFF, 0xD7 }, { 0xFF, 0xD4 }, { 0xFF, 0xD5 } }; // patterns for call ops

 BYTE pushretpat[8][2]={ { 0x50, 0xC3 }, { 0x53, 0xC3 }, { 0x51, 0xC3 }, { 0x52, 0xC3 },
       { 0x56, 0xC3 }, { 0x57, 0xC3 }, { 0x54, 0xC3 }, { 0x55, 0xC3 } }; // patterns for pushret ops

 BYTE poppat[8][1]={ { 0x58 }, { 0x5B }, { 0x59 }, { 0x5A }, // patterns for pop,pop,ret
     { 0x5E }, { 0x5F }, { 0x5C }, { 0x5D },};

 BYTE retn[1][1]={ 0xC3 }; // pattern for pop,pop,ret

 BYTE retnbis[1][1]={ 0xC2 }; // pattern for pop,pop,ret


 HMODULE loadedDLL; //base pointer for the loaded DLL

 BYTE *curpos; //current position within the DLL
 BYTE *curpos2; //subposition pop,pop,ret

 DWORD regnum=GetRegNum(reg); // decimal representation of passed register
 DWORD regnum1=GetRegNum(reg1);DWORD regnum2=GetRegNum(reg2);
 DWORD regnum3=GetRegNum(reg3);DWORD regnum4=GetRegNum(reg4);
 DWORD regnum5=GetRegNum(reg5);DWORD regnum6=GetRegNum(reg6);
 DWORD regnum7=GetRegNum(reg7);DWORD regnum8=GetRegNum(reg8);

 DWORD numaddr=0; //accumulator for addresses

 if( regnum == -1 ) //check if register is useable
 { //it didn't load, time to bail
  printf( "There was a problem understanding the register.\n"\
   "Please check that it isa correct IA32 register name\n"\
   "Currently supported are:\n "\
   "EAX, EBX, ECX, EDX, ESI, EDI, ESP, EBP\n"\
   );

  exit(-1);
 }

 if( (loadedDLL=LoadLibraryA(dll)) == NULL) // check if DLL loaded correctly
 { //it didn't load, time to bail
  printf( "There was a problem Loading the requested DLL.\n"\
    "Please check that it is in your path and readable\n" );
  exit(-1);
 }
 else
 {
  sep();
  fprintf(fplog,"Findjmp, Eeye, I2S-LaB\nFindjmp2, Hat-Squad\n");
  printf("\nFindjmp, Eeye, I2S-LaB\nFindjmp2, Hat-Squad\n");
  printf( "Scanning %s for code useable with the %s register\n", dll, reg ); //we loaded the dll correctly, time to scan it
  fprintf(fplog,"Scanning %s for code useable with the %s register\n", dll, reg ); //we loaded the dll correctly, time to scan it
  sep();
  curpos=(BYTE*)loadedDLL; //set curpos at start of DLL
  curpos2=(BYTE*)loadedDLL; //pop,pop,ret subscan.

  __try
  {
   while(1)
   {
    Sleep(1/10);
    if( !memcmp( curpos, jmppat[regnum], 2) ) //check for jmp match
    {
     printf( "0x%X\tjmp %s\n", curpos, reg ); // we have a jmp match
     fprintf(fplog,"0x%X\tjmp %s\n", curpos, reg ); // we have a jmp match
     numaddr++;
    }
    else if( !memcmp( curpos, callpat[regnum],2) ) //check for call match

    {
     printf( "0x%X\tcall %s\n", curpos, reg ); // we have a call match
     fprintf(fplog,"0x%X\tcall %s\n", curpos, reg );
     numaddr++;
    }
    else if( !memcmp(curpos,pushretpat[regnum], 2) ) //check for push/ret match
    {
     printf( "0x%X\tpush %s - ret\n", curpos, reg ); // we have a pushret match
     fprintf(fplog,"0x%X\tpush %s - ret\n", curpos, reg ); // we have a jmp match
     numaddr++;
    }
    else if( !memcmp(curpos,poppat[regnum], 1) ) //check for pop/pop/ret match
    {
     curpos2++;
     if( !memcmp(curpos2,poppat[regnum1], 1) )
     {
      curpos2++;
      if( !memcmp(curpos2,retn, 1) )
      {
       iok(curpos, reg); // we have a popopret match
       ook(curpos, reg); // we have a popopret match
       numaddr++;
      }
      if( !memcmp(curpos2,retnbis, 1) )
      {
       iok2(curpos, reg); // we have a popopret match
       ook2(curpos, reg); // we have a popopret match
       numaddr++;
      }
      curpos2--;curpos2--;goto loop;
     }
     if( !memcmp(curpos2,poppat[regnum2], 1) )
     {
      curpos2++;
      if( !memcmp(curpos2,retn, 1) )
      {
       iok(curpos, reg); // we have a popopret match
       ook(curpos, reg); // we have a popopret match
       numaddr++;
      }
      if( !memcmp(curpos2,retnbis, 1) )
      {
       iok2(curpos, reg); // we have a popopret match
       ook2(curpos, reg); // we have a popopret match
       numaddr++;
      }
      curpos2--;curpos2--;goto loop;
     }
     if( !memcmp(curpos2,poppat[regnum3], 1) )
     {
      curpos2++;
      if( !memcmp(curpos2,retn, 1) )
      {
       iok(curpos, reg); // we have a popopret match
       ook(curpos, reg); // we have a popopret match
       numaddr++;
      }
      if( !memcmp(curpos2,retnbis, 1) )
      {
       iok2(curpos, reg); // we have a popopret match
       ook2(curpos, reg); // we have a popopret match
       numaddr++;
      }
      curpos2--;curpos2--;goto loop;
     }
     if( !memcmp(curpos2,poppat[regnum4], 1) )
     {
      curpos2++;
      if( !memcmp(curpos2,retn, 1) )
      {
       iok(curpos, reg); // we have a popopret match
       ook(curpos, reg); // we have a popopret match
       numaddr++;
      }
      if( !memcmp(curpos2,retnbis, 1) )
      {
       iok2(curpos, reg); // we have a popopret match
       ook2(curpos, reg); // we have a popopret match
       numaddr++;
      }
      curpos2--;curpos2--;goto loop;
     }
     if( !memcmp(curpos2,poppat[regnum5], 1) )
     {
      curpos2++;
      if( !memcmp(curpos2,retn, 1) )
      {
       iok(curpos, reg); // we have a popopret match
       ook(curpos, reg); // we have a popopret match
       numaddr++;
      }
      if( !memcmp(curpos2,retnbis, 1) )
      {
       iok2(curpos, reg); // we have a popopret match
       ook2(curpos, reg); // we have a popopret match
       numaddr++;
      }
      curpos2--;curpos2--;goto loop;
     }
     if( !memcmp(curpos2,poppat[regnum6], 1) )
     {
      curpos2++;
      if( !memcmp(curpos2,retn, 1) )
      {
       iok(curpos, reg); // we have a popopret match
       ook(curpos, reg); // we have a popopret match
       numaddr++;
      }
      if( !memcmp(curpos2,retnbis, 1) )
      {
       iok2(curpos, reg); // we have a popopret match
       ook2(curpos, reg); // we have a popopret match
       numaddr++;
      }
      curpos2--;curpos2--;goto loop;
     }
     if( !memcmp(curpos2,poppat[regnum7], 1) )
     {
      curpos2++;
      if( !memcmp(curpos2,retn, 1) )
      {
       iok(curpos, reg); // we have a popopret match
       ook(curpos, reg); // we have a popopret match
       numaddr++;
      }
      if( !memcmp(curpos2,retnbis, 1) )
      {
       iok2(curpos, reg); // we have a popopret match
       ook2(curpos, reg); // we have a popopret match
       numaddr++;
      }
      curpos2--;curpos2--;goto loop;
     }
     if( !memcmp(curpos2,poppat[regnum8], 1) )
     {
      curpos2++;
      if( !memcmp(curpos2,retn, 1) )
      {
       iok(curpos, reg); // we have a popopret match
       ook(curpos, reg); // we have a popopret match
       numaddr++;
      }
      if( !memcmp(curpos2,retnbis, 1) )
      {
       iok2(curpos, reg); // we have a popopret match
       ook2(curpos, reg); // we have a popopret match
       numaddr++;
      }
      curpos2--;curpos2--;goto loop;
     }
     curpos2--;
    }
loop:
    curpos++;
    curpos2++;
   }
  }
  __except(1)
  {
   sep();
   fprintf( fplog,"Finished Scanning %s for code useable with the %s register\n", dll, reg );
   printf( "Finished Scanning %s for code useable with the %s register\n", dll, reg );
   printf( "Found %d usable addresses\n", numaddr );
   fprintf( fplog,"Found %d usable addresses\n", numaddr );sep();fprintf( fplog,"\n\n\n");
  }
 }

}


DWORD GetRegNum( char *reg )
{
 DWORD ret=-1;
 if( !stricmp( reg, "eax") )
 {
  ret=0;
 }
 else if( !stricmp( reg, "ebx") )
 {
  ret=1;
 }
 else if( !stricmp( reg, "ecx") )
 {
  ret=2;
 }
 else if( !stricmp( reg, "edx") )
 {
  ret=3;
 }
 else if( !stricmp( reg, "esi") )
 {
  ret=4;
 }
 else if( !stricmp( reg, "edi") )
 {
  ret=5;
 }
 else if( !stricmp( reg, "esp") )
 {
  ret=6;
 }
 else if( !stricmp( reg, "ebp") )
 {
  ret=7;
 }

 return ret; //return our decimal register number
}

void sep()
{
 fprintf(fplog,"----------------------------------------------------------------------------\n");
}

void iok(BYTE *curpos, char *reg)
{
 printf( "0x%X\tpop %s - pop - ret\n", curpos, reg ); // we have a popopret match
}

void iok2(BYTE *curpos, char *reg)
{
 printf( "0x%X\tpop %s - pop - retbis\n", curpos, reg ); // we have a popopret match
}

void ook(BYTE *curpos, char *reg)
{
 fprintf(fplog,"0x%X\tpop %s - pop - ret\n", curpos, reg ); // we have a jmp match
}

void ook2(BYTE *curpos, char *reg)
{
 fprintf(fplog,"0x%X\tpop %s - pop - retbis\n", curpos, reg ); // we have a jmp match
}