http_auth.py

"""
'How to do basic authentication on twisted web', from here:
http://twistedmatrix.com/pipermail/twisted-python/2009-August/020236.html
Original Copyright (c) 2008 Twisted Matrix Laboratories.  See LICENSE for details.

Which I modified to use Twisted's Application framework.

USAGE
-----
1) Make htpasswd file:
    $ htpasswd -c .htpassfile some_user #prompts for password

2) Run (tested using Twisted 8.2.0 / Python 2.5 / OS 10.6):
    $ twistd -ny http_auth.py

3) Open web browser to http://localhost:PORT
"""

import os
import sys
import crypt

from zope.interface import implements

from twisted.python import log
from twisted.application import internet, service
from twisted.web import server, resource, guard
from twisted.cred.portal import IRealm, Portal
from twisted.cred.checkers import FilePasswordDB


HTPASSFILE = os.path.expanduser("~/.htpassfile")
DOMAIN = "localhost"
PORT = 8000


class GuardedResource(resource.Resource):
    """
    A resource which is protected by guard and requires authentication in order
    to access.
    """
    def getChild(self, path, request):
        return self

    def render(self, request):
        # is served on root
        return "Authorized!"

class SimpleRealm(object):
    """
    A realm which gives out L{GuardedResource} instances for authenticated
    users.
    """
    implements(IRealm)
    # requestAvatar supplies the username, and checks against the corresponding password 
    def requestAvatar(self, avatarId, mind, *interfaces):
        if resource.IResource in interfaces:
            # somewhat confused here...
            return resource.IResource, GuardedResource(), lambda: None
        raise NotImplementedError()



# compare password, 
def cmp_pass(uname, password, storedpass):
   return crypt.crypt(password, storedpass[:2])

# checker  opens a file called htpasswd, and passing in the hash as defined by the method cmp_pass 
checkers = [FilePasswordDB(HTPASSFILE, hash=cmp_pass)]

# guard acts like middleware, forcing all incoming requests to 'yoursite.com' be checked the file defined in checkers
wrapper = guard.HTTPAuthSessionWrapper(Portal(SimpleRealm(), checkers), [guard.BasicCredentialFactory(DOMAIN)])

# serves the this as a resource on port 8080
application = service.Application('http-auth')
serviceCollection = service.IServiceCollection(application)
factory = server.Site(resource=wrapper)
internet.TCPServer(PORT, factory).setServiceParent(serviceCollection)