File isn't closing and read access violation exception in C? - c

Question

I'm making kind of an antivirus as a part of a project I got. I need to find if a binary file includes a certain string anywhere in it. What I'm trying to do is add 7 chars to an array, because i know the virus signature is 7 chars long, then compare to the string and if they are equal, means the file is infected. But, it doesn't work. it says "Exception thrown: read access violation.
currStr was 0x1110113.". Also, whenever I try to free arrays or free files, the program crashed. Any help would be appreciated.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <dirent.h>
#define ARR_SIZE 250
void Search_in_File(char* dir, char* str)
{
FILE *fp;
DIR *folder;
char currFilePath[ARR_SIZE] = { 0 };
struct dirent *entry;
int files = 0;
char ch = 0;
char* virusStr;
char* currStr;
char* buffer;
int fSize = 0;
int index = 0;
folder = opendir(dir); //Opening the folder
if (folder == NULL)
{
perror("Unable to read directory");
return(1);
}
virusStr = (char*)malloc(sizeof(char) * ARR_SIZE);
strcpy(virusStr, str); // Getting the virus detection string
while ((entry = readdir(folder))) // Reading each file in the folder
{
if ((entry->d_name)[0] != '.') //Making sure that we will go over valid files only
{
strcpy(currFilePath, dir); //Coppy the folder name into the file path
files++;
printf("File %3d: %s\n",
files,
entry->d_name
);
strcat(currFilePath, "/"); //Add slash so we can add the filename and get full path
strcat(currFilePath, entry->d_name); // Adding file name after the slash
fp = fopen(currFilePath, "rb"); //Opening the file with the full path
if (fp == NULL)
{
printf("Error opening file!\n");
}
fseek(fp, 0, SEEK_END);
fSize = ftell(fp);
fseek(fp, 0, SEEK_SET);
buffer = (char*)malloc(fSize + 1);
fread(buffer, sizeof(char), fSize, fp); // Reading the file content into a string
currStr = (char*)malloc(sizeof(char) * strlen(str) + 1); //Memory for the checking string
printf("%d", strlen(currStr));
printf("%p", &currStr);
for (index; index < fSize; index++)
{
printf("%c", buffer[index]);
if (buffer[index] != EOF)
{
//Error happens here
strcat(currStr[index], buffer[index]); // Adding the current char to the current string
// Checking if we have a string the same length as the virus signature
if ((index % strlen(virusStr)) == 0)
{
if (strcmp(currStr, virusStr) == 0) // Checking if we have the same string
{
printf("%s - Infected!", entry->d_name);
break;
}
}
}
currStr = '\0'; // Reset the current string
}
index = 0;
currFilePath[0] = '\0'; // Resetting the file path in order to get the new one
}
}
closedir(folder);
//fclose(fp); //Doesnt Work - ????
//free(virusStr); //Doesnt Work - ????
//free(currStr);//Doesnt Work - ????
//free(buffer);//Doesnt Work - ????
}