[cors] Access-Control-Allow-Origin wildcard subdomains, ports and protocols

I'm trying to enable CORS for all subdomains, ports and protocol.

For example, I want to be able to run an XHR request from http://sub.mywebsite.com:8080/ to https://www.mywebsite.com/*

Typically, I'd like to enable request from origins matching (and limited to):

//*.mywebsite.com:*/*

For Spring Boot I found this RegexCorsConfiguration which extends the official CorsConfiguration: https://github.com/looorent/spring-security-jwt/blob/master/src/main/java/be/looorent/security/jwt/RegexCorsConfiguration.java

The CORS spec is all-or-nothing. It only supports *, null or the exact protocol + domain + port: http://www.w3.org/TR/cors/#access-control-allow-origin-response-header

Your server will need to validate the origin header using the regex, and then you can echo the origin value in the Access-Control-Allow-Origin response header.

We were having similar issues with Font Awesome on a static "cookie-less" domain when reading fonts from the "cookie domain" (www.domain.tld) and this post was our hero. See here: How can I fix the 'Missing Cross-Origin Resource Sharing (CORS) Response Header' webfont issue?

For the copy/paste-r types (and to give some props) I pieced this together from all the contributions and added it to the top of the .htaccess file of the site root:

<IfModule mod_headers.c>
 <IfModule mod_rewrite.c>
    SetEnvIf Origin "http(s)?://(.+\.)?(othersite\.com|mywebsite\.com)(:\d{1,5})?$" CORS=$0
    Header set Access-Control-Allow-Origin "%{CORS}e" env=CORS
    Header merge  Vary "Origin"
 </IfModule>
</IfModule>

Super Secure, Super Elegant. Love it: You don't have to open up your servers bandwidth to resource thieves / hot-link-er types.

Props to:@Noyo @DaveRandom @pratap-koritala

(I tried to leave this as a comment to the accepted answer, but I can't do that yet)

in my case using angular

in my HTTP interceptor , i set

with Credentials: true.

in the header of the request

It looks like the original answer was for pre Apache 2.4. It did not work for me. Here's what I had to change to make it work in 2.4. This will work for any depth of subdomain of yourcompany.com.

SetEnvIf Host ^((?:.+\.)*yourcompany\.com?)$    CORS_ALLOW_ORIGIN=$1
Header append Access-Control-Allow-Origin  %{REQUEST_SCHEME}e://%{CORS_ALLOW_ORIGIN}e    env=CORS_ALLOW_ORIGIN
Header merge  Vary "Origin"

I'm answering this question, because the accepted answer can't do following

1. regex grouping is a performance hit, which is not necessary.
2. cannot match primary domain and it only works for sub domain.

For example: It won't send CORS headers for http://mywebsite.com while works for http://somedomain.mywebsite.com/

SetEnvIf Origin "http(s)?://(.+\.)?mywebsite\.com(:\d{1,5})?$" CORS=$0

Header set Access-Control-Allow-Origin "%{CORS}e" env=CORS
Header merge  Vary "Origin"

To enable for your site, you just put your site in place of "mywebsite.com" in the above Apache Configuration.

To allow Multiple sites:

SetEnvIf Origin "http(s)?://(.+\.)?(othersite\.com|mywebsite\.com)(:\d{1,5})?$" CORS=$0

Testing After deploying:

The following curl response should have the "Access-Control-Allow-Origin" header after the change.

curl -X GET -H "Origin: http://examplesite1.com" --verbose http://examplesite2.com/query

I needed a PHP-only solution, so just in case someone needs it as well. It takes an allowed input string like "*.example.com" and returns the request header server name, if the input matches.

function getCORSHeaderOrigin($allowed, $input)
{
    if ($allowed == '*') {
        return '*';
    }

    $allowed = preg_quote($allowed, '/');

    if (($wildcardPos = strpos($allowed, '*')) !== false) {
        $allowed = str_replace('*', '(.*)', $allowed);
    }

    $regexp = '/^' . $allowed . '$/';

    if (!preg_match($regexp, $input, $matches)) {
        return 'none';
    }

    return $input;
}

And here are the test cases for a phpunit data provider:

//    <description>                            <allowed>          <input>                   <expected>
array('Allow Subdomain',                       'www.example.com', 'www.example.com',        'www.example.com'),
array('Disallow wrong Subdomain',              'www.example.com', 'ws.example.com',         'none'),
array('Allow All',                             '*',               'ws.example.com',         '*'),
array('Allow Subdomain Wildcard',              '*.example.com',   'ws.example.com',         'ws.example.com'),
array('Disallow Wrong Subdomain no Wildcard',  '*.example.com',   'example.com',            'none'),
array('Allow Double Subdomain for Wildcard',   '*.example.com',   'a.b.example.com',        'a.b.example.com'),
array('Don\'t fall for incorrect position',    '*.example.com',   'a.example.com.evil.com', 'none'),
array('Allow Subdomain in the middle',         'a.*.example.com', 'a.bc.example.com',       'a.bc.example.com'),
array('Disallow wrong Subdomain',              'a.*.example.com', 'b.bc.example.com',       'none'),
array('Correctly handle dots in allowed',      'example.com',     'exampleXcom',            'none'),

EDIT: Use @Noyo's solution instead of this one. It's simpler, clearer and likely a lot more performant under load.

ORIGINAL ANSWER LEFT HERE FOR HISTORICAL PURPOSES ONLY!!

I did some playing around with this issue and came up with this reusable .htaccess (or httpd.conf) solution that works with Apache:

<IfModule mod_rewrite.c>
<IfModule mod_headers.c>
    # Define the root domain that is allowed
    SetEnvIf Origin .+ ACCESS_CONTROL_ROOT=yourdomain.com

    # Check that the Origin: matches the defined root domain and capture it in
    # an environment var if it does
    RewriteEngine On
    RewriteCond %{ENV:ACCESS_CONTROL_ROOT} !=""
    RewriteCond %{ENV:ACCESS_CONTROL_ORIGIN} =""
    RewriteCond %{ENV:ACCESS_CONTROL_ROOT}&%{HTTP:Origin} ^([^&]+)&(https?://(?:.+?\.)?\1(?::\d{1,5})?)$
    RewriteRule .* - [E=ACCESS_CONTROL_ORIGIN:%2]

    # Set the response header to the captured value if there was a match
    Header set Access-Control-Allow-Origin %{ACCESS_CONTROL_ORIGIN}e env=ACCESS_CONTROL_ORIGIN
</IfModule>
</IfModule>

Just set the ACCESS_CONTROL_ROOT variable at the top of the block to your root domain and it will echo the Origin: request header value back to the client in the Access-Control-Allow-Origin: response header value if it matches your domain.

Note also that you can use sub.mydomain.com as the ACCESS_CONTROL_ROOT and it will limit origins to sub.mydomain.com and *.sub.mydomain.com (i.e. it doesn't have to be the domain root). The elements that are allowed to vary (protocol, port) can be controlled by modifying the URI matching portion of the regex.

When setting Access-Control-Allow-Origin in .htaccess, only following worked:

SetEnvIf Origin "http(s)?://(.+\.)?domain\.com(:\d{1,5})?$" CRS=$0
Header always set Access-Control-Allow-Origin "%{CRS}e" env=CRS

I tried several other suggested keywords Header append, Header set, none worked as suggested in many answers on SO, though I have no idea if these keywords are outdated or not valid for nginx.

Here is my complete solution:

SetEnvIf Origin "http(s)?://(.+\.)?domain\.com(:\d{1,5})?$" CRS=$0
Header always set Access-Control-Allow-Origin "%{CRS}e" env=CRS
Header merge Vary "Origin"

Header always set Access-Control-Allow-Methods "GET, POST"
Header always set Access-Control-Allow-Headers: *

# Cached for a day
Header always set Access-Control-Max-Age: 86400

RewriteEngine On

# Respond with 200OK for OPTIONS
RewriteCond %{REQUEST_METHOD} OPTIONS
RewriteRule ^(.*)$ $1 [R=200,L]

I had to modify Lars' answer a bit, as an orphaned \ ended up in the regex, to only compare the actual host (not paying attention to the protocol or port) and I wanted to support localhost domain besides my production domain. Thus I changed the $allowed parameter to be an array.

function getCORSHeaderOrigin($allowed, $input)
{
    if ($allowed == '*') {
        return '*';
    }

    if (!is_array($allowed)) {
        $allowed = array($allowed);
    }

    foreach ($allowed as &$value) {
        $value = preg_quote($value, '/');

        if (($wildcardPos = strpos($value, '\*')) !== false) {
            $value = str_replace('\*', '(.*)', $value);
        }
    }

    $regexp = '/^(' . implode('|', $allowed) . ')$/';

    $inputHost = parse_url($input, PHP_URL_HOST);

    if ($inputHost === null || !preg_match($regexp, $inputHost, $matches)) {
        return 'none';
    }

    return $input;
}

Usage as follows:

if (isset($_SERVER['HTTP_ORIGIN'])) {
    header("Access-Control-Allow-Origin: " . getCORSHeaderOrigin(array("*.myproduction.com", "localhost"), $_SERVER['HTTP_ORIGIN']));
}