<?php
/**
 * @file security.php
 * @date 2018-01-18
 * @author Go Namhyeon <gnh1201@gmail.com>
 * @brief Security module for VSPF
 */

if(!function_exists("check_token_abuse")) {
	function check_token_abuse($_post_token, $_sess_token) {
		$abuse = false;
		
		$_check_token = $_post_token . $_sess_token;
		if(empty($_check_token) || $_post_token != $_sess_token) {
			$abuse = true;
		}
		
		return $abuse;
	}
}

if(!function_exists("make_random_id")) {
	function make_random_id($length = 10) {
		$characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
		$charactersLength = strlen($characters);
		$randomString = '';
		for ($i = 0; $i < $length; $i++) {
			$randomString .= $characters[rand(0, $charactersLength - 1)];
		}
		return $randomString;
	}
}

if(!function_exists("set_session")) {
	function set_session($session_name, $value) {
		if(PHP_VERSION < '5.3.0') {
			session_register($session_name);
		}
		$$session_name = $_SESSION["$session_name"] = $value;
	}
}

if(!function_exists("get_session")) {
	function get_session($session_name) {
		$session_value = "";
		if(!array_key_empty($session_name, $_SESSION)) {
			$session_value = $_SESSION[$session_name];
		}
		return $session_value;
	}
}

if(!function_exists("set_session_token")) {
	function set_session_token() {
		$random_id = make_random_id(10);
		set_session("random_id", $random_id);

		return $random_id;
	}
}

if(!function_exists("get_session_token")) {
	function get_session_token() {
		return get_session("random_id");
	}
}

if(!function_exists("check_token_abuse_by_requests")) {
	function check_token_abuse_by_requests($name) {
		global $requests;
		return check_token_abuse($requests['_POST'][$name], get_session($name));
	}
}

if(!function_exists("check_login_session")) {
	function check_login_session($ss_key, $config) {
		$flag = false;

		$session_name = sha1($ss_key);
		$session_file = $config['session_dir'] . '/' . $session_name;
		$session_stored_key = "";

		if(file_exists($session_file)) {
			$fh = fopen($session_file, 'r');
			if($session_stored_key = fread($fh, filesize($session_file))) {
				$flag = ($session_stored_key == $ss_key) ? true : false;
			}
		}

		return $flag;
	}
}

if(!function_exists("store_login_session")) {
	function store_login_session($ss_key, $config) {
		$flag = false;

		$session_name = sha1($ss_key);
		$session_file = $config['session_dir'] . '/' . $session_name;

		if(is_writable($session_file)) {
			$fh = fopen($session_file, 'w');
			if($fh) {
				if(fwrite($fh, $session_name)) {
					$flag = check_login_session($ss_key, $config);
				}
				@chmod($session_file, 600);
			}
		}

		return $flag;
	}
}

if(!function_exists("process_safe_login")) {
	function process_safe_login($user_name) {
		global $config;

		$flag = false;
		$ss_key = get_session("ss_key");
		if(!empty($ss_key)) {
			$flag = check_login_session($ss_key, $config);
		}

		if($flag == false) {
			$ss_key = make_random_id(10);
			
			set_session("ss_user_name", $user_name);
			set_session("ss_key", $ss_key);	

			$flag = store_login_session($ss_key, $config);
		}

		return $flag;
	}
}

if(!function_exists("check_empty_fields")) {
	function check_empty_fields($no_empty_fields, $method_get=true) {
		global $requests;

		$errors = array();
		$check_data = $method_get ? $requests['_GET'] : $requests['_POST'];

		foreach($no_empty_fields as $fieldname) {
			if(array_key_empty($fieldname, $check_data)) {
				$errors[] = array(
					"fieldname" => $fieldname,
					"message"   => "{$fieldname} 항목은 공백일 수 없습니다."
				);
			}
		}

		return $errors;
	}
}