/*
 * 
 *[elfrip.c - By PoWeR_PoRK of netric (http://www.netric.org)]
 * Tiny cat-like utility for ripping the code section out
 * of an elf executable image.
 *
 * compile with "gcc elfrip.c -o elfrip"
 * do a "./elfrip -h" for help with usage
 *
 * Made for scripting shellcode production sequences more
 * easily. Used for nasm generated code, not tested with gas
 * generated code but should work just as well (well, gas sucks
 * so it might not ;))
 *
 */
 
#include <stdio.h>

#define voffset 0x08048000

char usage[] =
"Usage: ./elfrip [-h][-i <inputelffile>]\n"
"cat like utility for ripping the code segment out of nasm generated elfs.\n"
"Example: ./elfrip -i shellcode.elf > shellcode.bin\n"
"This rips the code section of the elf image shellcode.elf into shellcode.bin\n\n"

"-h                See this usage overview.\n"
"-i <inputelffile> Set for rip and set the path of the source elf image to rip from.\n";

int main(int argc, char **argv[])
{
  char elfpath[41];
  int count = 0;
  unsigned int vaddr = 0;
  unsigned int phdroffset = 0;
  unsigned int codesize = 0;
  FILE * elffile;

  if(argc <= 1){
    printf("%s", &usage);
    exit(0);
  }else if(argc > 1){
    if(!strncmp(argv[1], "-h", 2)){
      printf("%s", &usage);
      exit(0);
    }else if(argc == 3){
    }else{
      printf("%s", &usage);
      exit(0);
    }
  }else{
    printf("%s", &usage);
  }
  
  elffile = fopen((char *)argv[2], "r");
  if(elffile == NULL){
    perror("Error:Opening of file failed (typo?)");
    exit(1);
  }

  fseek(elffile, 24, SEEK_SET);
   fread(&vaddr, 1, 4, elffile);
   fread(&phdroffset, 1, 4, elffile);

  fseek(elffile, phdroffset+16, SEEK_SET);
   fread(&codesize, 1, 4, elffile);
  
  fseek(elffile, (vaddr - voffset), SEEK_SET);
  if((codesize - (vaddr - voffset)) < 0){
    perror("Error: Code segment size mixup, "
     "prolly just a big assed gcc generated elf, use nasm instead");
    exit(1);
  }

  for(count = 0; count < (codesize - (vaddr - voffset));count++){
    if(feof(elffile) == 0){
      putchar(fgetc(elffile));
    }else{
      perror("Error: EOF encountered during elf load, prolly not an elf "
       "(either a gnome or just a particularly small person)");
      exit(1);
    }
  }

  return 0;
}