authentication.py

"""
   Copyright 2010 Daniel Graziotin <daniel.graziotin@acm.org>

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
"""

from server.models import Person
from django.contrib.auth.models import AnonymousUser
from django.http import HttpResponse

class HttpBasicAuthentication(object):
    """
    A slighty modified version of piston.authentication.HttpBasicAuthentication
    
    Basic HTTP authenticater. Synopsis:
    
    Authentication handlers must implement two methods:
     - `is_authenticated`: Will be called when checking for
        authentication. Receives a `request` object, please
        set your `User` object on `request.user`, otherwise
        return False (or something that evaluates to False.)
     - `challenge`: In cases where `is_authenticated` returns
        False, the result of this method will be returned.
        This will usually be a `HttpResponse` object with
        some kind of challenge headers and 401 code on it.
    """
    def __init__(self):
        self.realm = 'Dycapo Server API'
        
    def authenticate(self,username,password):
         # checks that the username is valid
        try:
            user = Person.objects.get(username=username)
        except Person.DoesNotExist:
            return None

        # verifies that the password is valid for the user
        if user.check_password(password):
            return user
        else:
            return None

    def is_authenticated(self, request):
        auth_string = request.META.get('HTTP_AUTHORIZATION', None)

        if not auth_string:
            return False
            
        try:
            (authmeth, auth) = auth_string.split(" ", 1)

            if not authmeth.lower() == 'basic':
                return False

            auth = auth.strip().decode('base64')
            (username, password) = auth.split(':', 1)
        except (ValueError, binascii.Error):
            return False
        
        request.user = self.authenticate(username=username, password=password) \
            or AnonymousUser()
        
        request.META['REMOTE_USER'] = request.user.username
                
        return not request.user in (False, None, AnonymousUser())
        
    def challenge(self):
        resp = HttpResponse("Authorization Required")
        resp['WWW-Authenticate'] = 'Basic realm="%s"' % self.realm
        resp.status_code = 401
        return resp

    def __repr__(self):
        return u'<HTTPBasic: realm=%s>' % self.realm