Specify Multiple Subdomains with Access Control Origin

Question

I am trying to allow access to every subdomain on my site in order to allow cross subdomain AJAX calls. Is there a way to specify all subdomains of a site like *.example.c

Answer 1

This was my challenge and solution:

1 - Backend PHP on api.example.com.

2 - Multiple JS front ends such as one.example.com, two.example.com etc.

3 - Cookies needed to be passed both ways.

4 - AJAX call from multiple front-ends to PHP backend on api.example.com

5 - In PHP, I do not prefer to use $_SERVER["HTTP_ORIGIN"], not always reliable/safe in my opinion (I had some browsers where HTTP-ORIGIN was always empty).

The normal way to do this in PHP with single front end domain is starting PHP code with:

header('Access-Control-Allow-Origin: https://one.example.com');  
header('Access-Control-Allow-Headers: Origin, Content-Type, X-Auth-Token');  
header('Access-Control-Allow-Credentials: true');  

And in JS on one.example.com domain:

jQuery.ajax({
    url: myURL,
    type: "POST",
    xhrFields: {withCredentials: true},
    dataType: "text",
    contentType: "text/xml; charset=\"utf-8\"",
    cache: false,
    headers: "",
    data: myCallJSONStr,
    success: function(myResponse) {.....}

However, this is not workable as I am using multiple subdomains to call my API domain.

And this solution will NOT work as I want to pass on cookies:

header('Access-Control-Allow-Origin: *');  

It conflicts with the pass on cookie setting on the JS site:

xhrFields: {withCredentials: true}

Here is what I did:

1 - use GET parameter to pass the Subdomain. 2 - Hardcode the Main domain in PHP so only (all) Subdomains are allowed.

This is the JS/JQuery AJAX part of my solution:

function getSubDomain(){
    
    let mySubDomain = "";
    
    let myDomain = window.location.host;
    let myArrayParts = myDomain.split(".");
    if (myArrayParts.length == 3){
        mySubDomain = myArrayParts[0];
    }
    
    return mySubDomain;
    
}

And in the AJAX call:

    let mySubDomain = getSubDomain();
    if (mySubDomain != ""){
        myURL += "?source=" + mySubDomain + "&end"; //use & instead of ? if URL already has GET parameters
    }
    
    jQuery.ajax({
        url: myURL,
        type: "POST",
        xhrFields: {withCredentials: true},
        dataType: "text",
        contentType: "text/xml; charset=\"utf-8\"",
        cache: false,
        headers: "",
        data: myCallJSONStr,
        success: function(myResponse) {.....}

Finally, the PHP part:

IMPORTANT, don't forget to set the cookies for all subdomains, in this case the domain for the cookie would be: .example.com (so with a dot in front of the main domain):

This solution allows me to call the API on api.example.com from any subdomains on example.com.

NB. for situation where there is only a single calling subdomain, I prefer using .htaccess for setting CORS instead of PHP. Here is an example of .htaccess (linux/apache) for only one.example.com calling api.example.com:

    Header set Access-Control-Allow-Origin "https://one.example.com"
    Header set Access-Control-Allow-Headers "Origin, Content-Type, X-Auth-Token"
    Header set Access-Control-Allow-Credentials "true"

And place this .htaccess in the root of api.example.com.