This doesn't seem to work for me ... I'm uisng nginx/1.0.5. For testing I replaced http://10.140.10.40 with *.

Thanks a lot. This saved my day :)

good example for config options

If only I could see this before wasting 5 hours of time... Thanks a lot for saving the rest of my day! :)

For me I hade to return 204 otherwise the browser would hang and then timeout on the option request:
add_header 'Access-Control-Max-Age' 1728000;
add_header 'Content-Type' 'text/plain charset=UTF-8';
add_header 'Content-Length' 0;

    return 204;
 }

Updated with 204 return for OPTIONS (mrdevin) and wildcard '*' for Access-Control-Allow-Origin (epicserve).

I've updated this in https://gist.github.com/4165271 to add a poor man's whitelist. I'm not really sure where having Access-Control-Allow-Origin as wildcard would cause too many issues, but some people may be extra conscious. We use a simple-ish regexp to match valid URLs. Please note that I haven't load tested this, so I don't know what kind of effect it'll have.

Thanks for this. I use:

add_header "Access-Control-Allow-Origin" $http_origin;

FWIW HTTP/1.1 RFC says response from OPTIONS is not cacheable. Doesn't that mean a browser must ignore your Access-Control-Max-Age header?

Thanks a lot!

From MDN:

Important note: when responding to a credentialed request, server must specify a domain, and cannot use wild carding.

I've confirmed that at least Firefox will block a request with cookies if the Access-Control-Allow-Origin is set to '*'.

This does not work for me

location / {
             add_header 'Access-Control-Allow-Origin' '*';
    add_header 'Access-Control-Allow-Credentials' 'true';
    add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
    add_header 'Access-Control-Allow-Headers' 'DNT,X-Mx-ReqToken,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type';

        root   share/nginx/html;
        proxy_pass         https://dddd.dd.com;
        proxy_set_header   Host dddd.dd.com;  

    }

You cannot use a wildcard Access-Control-Allow-Origin if you want to use xhrFields: {withCredentials:true} to send cookies/basicauth. In that case you must use the exact origin:

add_header "Access-Control-Allow-Origin" $http_origin;

When starting to use this Chrome will cache the earlier (CORS failed) requests. Reset the cache to get things working!

Place this in nginx.conf or server blocks?