Simple shellcode executor for Linux(-like) systems.

executor.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>

void* alloc_mem(size_t size) {
  void *ptr = mmap(0, size, PROT_READ | PROT_WRITE | PROT_EXEC,
    MAP_PRIVATE | MAP_ANONYMOUS, -1 ,0);
  if(ptr == MAP_FAILED)
    return NULL;
  return ptr;
}

FILE* open_file(char *path) {
  FILE* ptr = fopen(path, "rb");
  return ptr;
}

size_t get_size(FILE *file) {
  fseek(file, 0L, SEEK_END);
  size_t size = ftell(file);
  rewind(file);
  return size;
}

int main(int argc, char** argv) {
  if(argc < 2) {
    puts("Usage: executor [file]");
    return 1;
  }

  FILE *file = open_file(argv[1]);
  if(file == NULL) {
    puts("Can not open file.");
    return 2;
  }
  size_t fs = get_size(file);

  void *mem = alloc_mem(fs);
  if(mem == NULL) {
    puts("Can not allocate memory.");
    return 3;
  }

  fread(mem, fs, 1, file);
  fclose(file);

  ((void (*)())mem)();
  return 0;
}