servnest/inc/auth.php

<?php

function hashPassword($password) {
	return password_hash($password, ALGO_PASSWORD, OPTIONS_PASSWORD);
}

function checkPassword($username, $password) {
	$username2[0] = $username;

	$db = new PDO('sqlite:' . DB_PATH);

	$op = $db->prepare('SELECT username, password FROM users WHERE username = ?');
	$op->execute($username2);

	$dbPassword = $op->fetch()['password'];

	return password_verify($password, $dbPassword);
}

function outdatedPasswordHash($username) {
	$username2[0] = $username;

	$db = new PDO('sqlite:' . DB_PATH);

	$op = $db->prepare('SELECT username, password FROM users WHERE username = ?');
	$op->execute($username2);

	$dbPassword = $op->fetch()['password'];

	return password_needs_rehash($dbPassword, ALGO_PASSWORD, OPTIONS_PASSWORD);
}

function changePassword($username, $password) {
	$password = hashPassword($password);

	$db = new PDO('sqlite:' . DB_PATH);

	$stmt = $db->prepare("UPDATE users SET password = :password WHERE username = :username");

	$stmt->bindParam(':username', $username);
	$stmt->bindParam(':password', $password);

	$stmt->execute();
}

function antiCSRF() {

	if (!isset($_SERVER['HTTP_SEC_FETCH_SITE']) AND !isset($_SERVER['HTTP_ORIGIN']))
		exit("ERROR: Browser sent neither Sec-Fetch-Site nor Origin HTTP headers, so anti-CSRF verification can't be done.");

	if (isset($_SERVER['HTTP_ORIGIN']) AND $_SERVER['HTTP_ORIGIN'] !== ORIGIN)
		exit("ERROR: Anti-CSRF verification failed");

	if (isset($_SERVER['HTTP_SEC_FETCH_SITE']) AND $_SERVER['HTTP_SEC_FETCH_SITE'] !== "same-origin")
		exit("ERROR: Anti-CSRF verification failed");

}