How to check if the request is an AJAX request with PHP
Example from an archived tutorial:
if(!empty($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest')
{
exit;
}
continue;
This checks if the
HTTP_X_REQUESTED_WITH
parameter is not empty and if it's equal toxmlhttprequest
, then it will exit from the script.
From PHP 7 with null coalescing operator it will be shorter:
$is_ajax = 'xmlhttprequest' == strtolower( $_SERVER['HTTP_X_REQUESTED_WITH'] ?? '' );
Set a session variable for every page on your site (actual pages not includes or rpcs) that contains the current page name, then in your Ajax call pass a nonce salted with the $_SERVER['SCRIPT_NAME'];
<?php
function create_nonce($optional_salt='')
{
return hash_hmac('sha256', session_id().$optional_salt, date("YmdG").'someSalt'.$_SERVER['REMOTE_ADDR']);
}
$_SESSION['current_page'] = $_SERVER['SCRIPT_NAME'];
?>
<form>
<input name="formNonce" id="formNonce" type="hidden" value="<?=create_nonce($_SERVER['SCRIPT_NAME']);?>">
<label class="form-group">
Login<br />
<input name="userName" id="userName" type="text" />
</label>
<label class="form-group">
Password<br />
<input name="userPassword" id="userPassword" type="password" />
</label>
<button type="button" class="btnLogin">Sign in</button>
</form>
<script type="text/javascript">
$("form.login button").on("click", function() {
authorize($("#userName").val(),$("#userPassword").val(),$("#formNonce").val());
});
function authorize (authUser, authPassword, authNonce) {
$.ajax({
type: "POST",
url: "/inc/rpc.php",
dataType: "json",
data: "userID="+authUser+"&password="+authPassword+"&nonce="+authNonce
})
.success(function( msg ) {
//some successful stuff
});
}
</script>
Then in the rpc you are calling test the nonce you passed, if it is good then odds are pretty great that your rpc was legitimately called:
<?php
function check_nonce($nonce, $optional_salt='')
{
$lasthour = date("G")-1<0 ? date('Ymd').'23' : date("YmdG")-1;
if (hash_hmac('sha256', session_id().$optional_salt, date("YmdG").'someSalt'.$_SERVER['REMOTE_ADDR']) == $nonce ||
hash_hmac('sha256', session_id().$optional_salt, $lasthour.'someSalt'.$_SERVER['REMOTE_ADDR']) == $nonce)
{
return true;
} else {
return false;
}
}
$ret = array();
header('Content-Type: application/json');
if (check_nonce($_POST['nonce'], $_SESSION['current_page']))
{
$ret['nonce_check'] = 'passed';
} else {
$ret['nonce_check'] = 'failed';
}
echo json_encode($ret);
exit;
?>
edit: FYI the way I have it set the nonce is only good for an hour and change, so if they have not refreshed the page doing the ajax call in the last hour or 2 the ajax request will fail.
There is no sure-fire way of knowing that a request was made via Ajax. You can never trust data coming from the client. You could use a couple of different methods but they can be easily overcome by spoofing.