Graham Knop > Plack-Middleware-CrossOrigin-0.007 > Plack::Middleware::CrossOrigin

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Module Version: 0.007   Source   Latest Release: Plack-Middleware-CrossOrigin-0.009

NAME ^

Plack::Middleware::CrossOrigin - Adds headers to allow Cross-Origin Resource Sharing

VERSION ^

version 0.007

SYNOPSIS ^

    # Allow any WebDAV or standard HTTP request from any location.
    builder {
        enable 'CrossOrigin', origins => '*';
        $app;
    };
    
    # Allow GET and POST requests from any location, cache results for 30 days.
    builder {
        enable 'CrossOrigin',
            origins => '*', methods => ['GET', 'POST'], max_age => 60*60*24*30;
        $app;
    };

DESCRIPTION ^

Adds Cross Origin Request Sharing headers used by modern browsers to allow XMLHttpRequest to work across domains. This module will also help protect against CSRF attacks in some browsers.

This module attempts to fully conform to the CORS spec, while allowing additional flexibility in the values specified for the of the headers.

CORS REQUESTS IN BRIEF ^

There are two types of CORS requests. Simple requests, and preflighted requests.

Simple Requests

A simple request is one that could be generated by a standard HTML form. Either a GET or POST request, with no additional headers. For these requests, the server processes the request as normal, and attaches the correct CORS headers in the response. The browser then decides based on those headers whether to allow the client script access to the response.

Preflighted Requests

If additional headers are specified, or a method other than GET or POST is used, the request must be preflighted. This means that the browser will first send a special request to the server to check if access is allowed. If the server allows it by responding with the correct headers, the actual request is then performed.

CSRF Protection ^

Some browsers will also provide same headers with cross domain POST requests from HTML forms. These requests will also be checked against the allowed origins and rejected before they reach the rest of your Plack application.

CONFIGURATION ^

origins

A list of allowed origins. Origins should be formatted as a URL scheme and host, with no path information. (http://www.example.com) '*' can be specified to allow access from any location. Must be specified for this middleware to have any effect. This will be matched against the Origin request header, and will control the Access-Control-Allow-Origin response header. If the origin does not match, the request is aborted.

headers

A list of allowed request headers. '*' can be specified to allow any headers. Controls the Access-Control-Allow-Headers response header. Includes a set of headers by default to simplify working with WebDAV and AJAX frameworks:

  • Cache-Control
  • Depth
  • If-Modified-Since
  • User-Agent
  • X-File-Name
  • X-File-Size
  • X-Prototype-Version
  • X-Requested-With
methods

A list of allowed methods. '*' can be specified to allow any methods. Controls the Access-Control-Allow-Methods response header. Defaults to all of the standard HTTP and WebDAV methods.

max_age

The max length in seconds to cache the response data for. Controls the Access-Control-Max-Age response header. If not specified, the web browser will decide how long to use.

expose_headers

A list of allowed headers to expose to the client. '*' can be specified to allow the browser to see all of the response headers. Controls the Access-Control-Expose-Headers response header.

credentials

Whether the resource will be allowed with user credentials (cookies, HTTP authentication, and client-side SSL certificates) supplied. Controls the Access-Control-Allow-Credentials response header.

continue_on_failure

Normally, simple requests with an Origin that hasn't been allowed will be stopped before they continue to the main app. If this option is set, the request will be allowed to continue, but no CORS headers will be added to the response. This matches how non-allowed requests would be handled if this module was not used at all.

This disabled the CSRF protection and is not recommended. It could be needed for applications that need to allow cross-origin HTML form POSTs without whitelisting domains.

BROWSER SUPPORT ^

Different browsers have different levels of support for CORS headers.

Gecko (Firefox, Seamonkey)

Initially supported in Gecko 1.9.1 (Firefox 3.5). Supports the complete CORS spec for XMLHttpRequests.

Does not yet provide the Origin header for CSRF protection (Bugzilla #446344).

WebKit (Safari, Google Chrome)

Initially supported in Safari 4 and Chrome 3. The expose_headers feature is currently unsupported (WebKit bug #41210). The current release of Safari has a bug in its handling of preflighted GET requests (WebKit bug #50773) which has been fixed in WebKit v534.19 and Chrome 11. This module uses the Referer header to work around the issue when possible.

Also provides the Origin header for CSRF protection starting with WebKit v528.5 (Chrome 2, Safari 4).

Internet Explorer

Initially supported in IE8. Not supported with the standard XMLHttpRequest object. A separate object, XDomainRequest, must be used. Only GET and POST methods are allowed. No extra headers can be added to the request. Neither the status code or any headers aside from Content-Type can be retrieved from the response.

Opera

Not supported in any version of Opera.

SEE ALSO ^

CORS Resources

CSRF Resources

Related Technologies

AUTHOR ^

Graham Knop <haarg@haarg.org>

COPYRIGHT AND LICENSE ^

This software is copyright (c) 2011 by Graham Knop.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

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