#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <dlfcn.h>
#include <limits.h>

enum {
    SIZE10  =  10,
    SIZE100 = 100,
    SIZE128 = 128
};

/* Use white list */
static const char *libX_safe_folder[] = {
  "/usr/",
  "/usr/lib",
  "/lib"
};

/* Return the index if the input is in the white list */
int identified_safe_libX_folder(const char* path)
{
  for (int i = 0; i < sizeof(libX_safe_folder) / sizeof(libX_safe_folder[0]); i ++)
    {
      if (strcmp(path, libX_safe_folder[i]) == 0)
      return i;
    }
  return -1;    
}

/* Function to sanitize a string */
char *sanitize_str(char* s, size_t n) {
  /* strlen is used here as a kind of firewall for tainted string errors */
  if (strlen(s) > 0 && strlen(s) < n)
    return s;
  else
    return NULL;
}

void* taintedpathlib(char* userpath) {
  void* libhandle = NULL;
  const char *const checked_userpath = sanitize_str(userpath, SIZE128);
  if (checked_userpath != NULL) {
    int index = identified_safe_libX_folder(checked_userpath);
    if (index > 0) {
      char lib[SIZE128] = "";
      strncpy(lib, libX_safe_folder[index], SIZE128);
      strcat(lib, "/libX.so");
      libhandle = dlopen(lib, RTLD_LAZY);    
    }
  }
  return libhandle;
}