Configuring Cross-Domain Access with Multiple Origin Domains

Cross-domain access is a crucial aspect of web development, allowing different domains to communicate with each other. However, by default, web browsers enforce same-origin policy, which restricts this communication for security reasons. To overcome this restriction, the Access-Control-Allow-Origin header is used.

The Access-Control-Allow-Origin header specifies which domains are allowed to access resources from a particular domain. In many cases, developers want to allow multiple domains to access their resources. Unfortunately, simply listing multiple domains separated by commas in the Access-Control-Allow-Origin header does not work.

To allow multiple origin domains, you need to implement a dynamic solution that checks the Origin header of incoming requests and sets the Access-Control-Allow-Origin header accordingly. Here are some ways to achieve this:

Using Apache .htaccess

You can use the SetEnvIf directive in your .htaccess file to check the Origin header and set an environment variable. Then, you can use the Header directive to add the Access-Control-Allow-Origin header with the value of the Origin header.

<FilesMatch "\.(ttf|otf|eot|woff|woff2)$">
    <IfModule mod_headers.c>
        SetEnvIf Origin "http(s)?://(www\.)?(example\.com|otherdomain\.example)$" AccessControlAllowOrigin=$0
        Header add Access-Control-Allow-Origin %{AccessControlAllowOrigin}e env=AccessControlAllowOrigin
        Header merge Vary Origin
    </IfModule>
</FilesMatch>

Using PHP

In PHP, you can check the HTTP_ORIGIN server variable and set the Access-Control-Allow-Origin header using the header() function.

$http_origin = $_SERVER['HTTP_ORIGIN'];

if ($http_origin == "http://www.example.com" || $http_origin == "http://www.otherdomain.com") {
    header("Access-Control-Allow-Origin: $http_origin");
}

Using Nginx

In Nginx, you can use the if statement to check the $http_origin variable and add the Access-Control-Allow-Origin header using the add_header directive.

location /fonts {
    if ($http_origin ~ "example.org$") {
        add_header "Access-Control-Allow-Origin" $http_origin;
    }
}

Best Practices

When allowing multiple origin domains, make sure to follow these best practices:

• Only allow specific domains that need access to your resources.
• Use a secure protocol (HTTPS) for communication between domains.
• Regularly review and update the list of allowed domains.

In conclusion, configuring cross-domain access with multiple origin domains requires a dynamic solution that checks the Origin header and sets the Access-Control-Allow-Origin header accordingly. By using Apache .htaccess, PHP, or Nginx, you can implement this solution and ensure secure communication between different domains.