Here’s an example of an nginx server config allowing CORS from any subdomain of yoursweetdomain. Even if the server returns a successful response, the browser. Specifically, the browser disallows the request. And it’s really this setting that, when set to true, enables most CORS attacks. The Access-Control-Allow-Credentials policy is set with a value of true or false. Now let’s take a look at the Access-Control-Allow-Credentials policy. If the response doesnt include the Access-Control-Allow-Origin header, the cross-origin request fails. HTTP/1.1 200 OK Access-Control-Allow-Origin: null. But what if you want to allow *.? It turns out that’s not supported by the spec, but you can, with some trickery, make it happen. If AllowAnyOrigin is called, the Access-Control-Allow-Origin:, the wildcard value, is returned. From MDN: 'Attempting to use the wildcard with credentials will result in an error.'. But with Access-Control-Allow-Origin: you don't get credentials. You are allowed to use a blanket wildcard, but if you’re allowing cookie sharing, you’re even more restricted in that you need to specify exact domains and wildcards are not allowed. 1 It looks like your are requiring credentials - or why you should use Access-Control-Allow-Credentials: true then. For simple cases where disabling CORS checking means (almost) no harm, the standard allows the wildcard. I find it a very good compromise between security and convenience. But in this case is not allowed for the Access-Control-Allow-Origin.

As far as it being safe, note the comment from Jules in this post about CORS. In this case, the browser checks if the response contains Access-Control-Allow-Credentials: true. The domains that may hit your server must be specified in your configuration. Response should only have the accepted headers in Access-Control-Allow-Headers, dont use wildcard. Simply put, it lets you be on one domain, and perform XMLHttpRequests to another, which is normally not allowed due to the Same Origin Policy. Access-Control-Allow-Origin is a CORS header. The credentials mode of an XMLHttpRequest is controlled by the withCredentials attribute. Origin ' localhost:12345 ' is therefore not allowed access.

You can read up in lengthy detail on it’s features here. A wildcard '' cannot be used in the 'Access-Control-Allow-Origin' header when the credentials flag is true. This was originally posted on the SHIFT developers blog.įirst off - what is CORS? CORS is a means of allowing cross site requests. CORS With Wildcard Subdomains Using Nginx

Access control allow origin wildcard