Any WSGI middleware to make HTTP redirect on specific status code?

Question

I'm using Pylons and want to add some middleware to it so that it catches 401 status codes and makes HTTP Redirect (302) to Signin page.

I know there is built-in StatusCodeRedirect in Pylons that acts in a similar fashion, but it does not produce HTTP redirect, and rather redirects internally (this is what I do not want).

Is there any existing middleware to add, or any generic middleware that can be easily modified to make HTTP redirects on specific status codes?

Answer 1

This should get you pretty close i didn't test it though but it's loosely based on something I wrote that I am using so tweak as necessary.

from webob.dec import wsgify


class Catch401AndRedirect(object):
    """
    responds to 401 redirects to signin page
    """

    def __init__(self, app, signin_url):
        self._app = app
        self._signin_url = signin_url

    @wsgify
    def __call__(self, request):

        response = request.get_response(self._app)

        if response.status_int == 401:
            response.headers["Location"] = self._signin_url
            response.status_int = 302
        else:
            return response

edit: forgot to mention this solution requires webob, but since you are using pylons already, you have that dependency.

Answer 2

You can use a complete authentication & authorization library for Pylons. The two most popular are: AuthKit and repoze.who. They already implement what you want to do.

If you don't want to use an existing library, you can write a custom middleware. It is simply a Python callable f(environ, start_response) which processes request data kept in environ. Look into config/environment.py.

Answer 3

Finally. I've implemented my own middleware class that uses *call_wsgi_application* helper function of pylons.util

from pylons.util import call_wsgi_application

class StatusCodeHTTPRedirect(object):

    def __init__(self, wsgi_app, codes, redirect_to):
        self.app = wsgi_app
        # Transform codes to str for comparison
        self.codes = tuple([str(x) for x in codes])
        self.redirect_to = redirect_to

    def __call__(self, environ, start_response):
        status, headers, app_iter, exc_info = call_wsgi_application(self.app,
            environ, catch_exc_info=True)

        if status[:3] in self.codes:
            start_response('302 Found', [('Location', self.redirect_to)])
            return []

        start_response(status, headers, exc_info)
        return app_iter

Hope this will help someone