text: import base64
  import hmac
  import time
  import uuid
  
  from django.conf import settings
  from django.contrib.auth import authenticate
  from django.core.exceptions import ImproperlyConfigured
  from django.middleware.csrf import _sanitize_token, constant_time_compare
  from django.utils.http import same_origin
  from django.utils.translation import ugettext as _
  from tastypie.http import HttpUnauthorized
  
  try:
      from hashlib import sha1
  except ImportError:
      import sha
      sha1 = sha.sha
  
  try:
      import python_digest
  except ImportError:
      python_digest = None
  
  try:
      import oauth2
  except ImportError:
      oauth2 = None
  
  try:
      import oauth_provider
  except ImportError:
      oauth_provider = None
  
  
  class Authentication(object):
      """
      A simple base class to establish the protocol for auth.
  
      By default, this indicates the user is always authenticated.
      """
      def __init__(self, require_active=True):
          self.require_active = require_active
  
      def is_authenticated(self, request, **kwargs):
          """
          Identifies if the user is authenticated to continue or not.
  
          Should return either ``True`` if allowed, ``False`` if not or an
          ``HttpResponse`` if you need something custom.
          """
          return True
  
      def get_identifier(self, request):
          """
          Provides a unique string identifier for the requestor.
  
          This implementation returns a combination of IP address and hostname.
          """
          return "%s_%s" % (request.META.get('REMOTE_ADDR', 'noaddr'), request.META.get('REMOTE_HOST', 'nohost'))
  
      def check_active(self, user):
          """
          Ensures the user has an active account.
  
          Optimized for the ``django.contrib.auth.models.User`` case.
          """
          if not self.require_active:
              # Ignore & move on.
              return True
  
          return user.is_active
  
  
  class BasicAuthentication(Authentication):
      """
      Handles HTTP Basic auth against a specific auth backend if provided,
      or against all configured authentication backends using the
      ``authenticate`` method from ``django.contrib.auth``.
  
      Optional keyword arguments:
  
      ``backend``
          If specified, use a specific ``django.contrib.auth`` backend instead
          of checking all backends specified in the ``AUTHENTICATION_BACKENDS``
          setting.
      ``realm``
          The realm to use in the ``HttpUnauthorized`` response.  Default:
          ``django-tastypie``.
      """
      def __init__(self, backend=None, realm='django-tastypie', **kwargs):
          super(BasicAuthentication, self).__init__(**kwargs)
          self.backend = backend
          self.realm = realm
  
      def _unauthorized(self):
          response = HttpUnauthorized()
          # FIXME: Sanitize realm.
          response['WWW-Authenticate'] = 'Basic Realm="%s"' % self.realm
          return response
  
      def is_authenticated(self, request, **kwargs):
          """
          Checks a user's basic auth credentials against the current
          Django auth backend.
  
          Should return either ``True`` if allowed, ``False`` if not or an
          ``HttpResponse`` if you need something custom.
          """
          if not request.META.get('HTTP_AUTHORIZATION'):
              return self._unauthorized()
  
          try:
              (auth_type, data) = request.META['HTTP_AUTHORIZATION'].split()
              if auth_type.lower() != 'basic':
                  return self._unauthorized()
              user_pass = base64.b64decode(data)
          except:
              return self._unauthorized()
  
          bits = user_pass.split(':', 1)
  
          if len(bits) != 2:
              return self._unauthorized()
  
          if self.backend:
              user = self.backend.authenticate(username=bits[0], password=bits[1])
          else:
              user = authenticate(username=bits[0], password=bits[1])
  
          if user is None:
              return self._unauthorized()
  
          if not self.check_active(user):
              return False
  
          request.user = user
          return True
  
      def get_identifier(self, request):
          """
          Provides a unique string identifier for the requestor.
  
          This implementation returns the user's basic auth username.
          """
          return request.META.get('REMOTE_USER', 'nouser')
  
  
  class ApiKeyAuthentication(Authentication):
      """
      Handles API key auth, in which a user provides a username & API key.
  
      Uses the ``ApiKey`` model that ships with tastypie. If you wish to use
      a different model, override the ``get_key`` method to perform the key check
      as suits your needs.
      """
      def _unauthorized(self):
          return HttpUnauthorized()
  
      def extract_credentials(self, request):
          if request.META.get('HTTP_AUTHORIZATION') and request.META['HTTP_AUTHORIZATION'].lower().startswith('apikey '):
              (auth_type, data) = request.META['HTTP_AUTHORIZATION'].split()
  
              if auth_type.lower() != 'apikey':
                  raise ValueError("Incorrect authorization header.")
  
              username, api_key = data.split(':', 1)
          else:
              username = request.GET.get('username') or request.POST.get('username')
              api_key = request.GET.get('api_key') or request.POST.get('api_key')
  
          return username, api_key
  
      def is_authenticated(self, request, **kwargs):
          """
          Finds the user and checks their API key.
  
          Should return either ``True`` if allowed, ``False`` if not or an
          ``HttpResponse`` if you need something custom.
          """
          from django.contrib.auth.models import User
  
          try:
              username, api_key = self.extract_credentials(request)
          except ValueError:
              return self._unauthorized()
  
          if not username or not api_key:
              return self._unauthorized()
  
          try:
              user = User.objects.get(username=username)
          except (User.DoesNotExist, User.MultipleObjectsReturned):
              return self._unauthorized()
  
          if not self.check_active(user):
              return False
  
          key_auth_check = self.get_key(user, api_key)
          if key_auth_check and not isinstance(key_auth_check, HttpUnauthorized):
              request.user = user
  
          return key_auth_check
  
      def get_key(self, user, api_key):
          """
          Attempts to find the API key for the user. Uses ``ApiKey`` by default
          but can be overridden.
          """
          from tastypie.models import ApiKey
  
          try:
              ApiKey.objects.get(user=user, key=api_key)
          except ApiKey.DoesNotExist:
              return self._unauthorized()
  
          return True
  
      def get_identifier(self, request):
          """
          Provides a unique string identifier for the requestor.
  
          This implementation returns the user's username.
          """
          username, api_key = self.extract_credentials(request)
          return username or 'nouser'
  
  
  class SessionAuthentication(Authentication):
      """
      An authentication mechanism that piggy-backs on Django sessions.
  
      This is useful when the API is talking to Javascript on the same site.
      Relies on the user being logged in through the standard Django login
      setup.
  
      Requires a valid CSRF token.
      """
      def is_authenticated(self, request, **kwargs):
          """
          Checks to make sure the user is logged in & has a Django session.
          """
          # Cargo-culted from Django 1.3/1.4's ``django/middleware/csrf.py``.
          # We can't just use what's there, since the return values will be
          # wrong.
          # We also can't risk accessing ``request.POST``, which will break with
          # the serialized bodies.
          if request.method in ('GET', 'HEAD', 'OPTIONS', 'TRACE'):
              return request.user.is_authenticated()
  
          if getattr(request, '_dont_enforce_csrf_checks', False):
              return request.user.is_authenticated()
  
          csrf_token = _sanitize_token(request.COOKIES.get(settings.CSRF_COOKIE_NAME, ''))
  
          if request.is_secure():
              referer = request.META.get('HTTP_REFERER')
  
              if referer is None:
                  return False
  
              good_referer = 'https://%s/' % request.get_host()
  
              if not same_origin(referer, good_referer):
                  return False
  
          request_csrf_token = request.META.get('HTTP_X_CSRFTOKEN', '')
  
          if not constant_time_compare(request_csrf_token, csrf_token):
              return False
  
          return request.user.is_authenticated()
  
      def get_identifier(self, request):
          """
          Provides a unique string identifier for the requestor.
  
          This implementation returns the user's username.
          """
          return request.user.username
  
  
  class DigestAuthentication(Authentication):
      """
      Handles HTTP Digest auth against a specific auth backend if provided,
      or against all configured authentication backends using the
      ``authenticate`` method from ``django.contrib.auth``. However, instead of
      the user's password, their API key should be used.
  
      Optional keyword arguments:
  
      ``backend``
          If specified, use a specific ``django.contrib.auth`` backend instead
          of checking all backends specified in the ``AUTHENTICATION_BACKENDS``
          setting.
      ``realm``
          The realm to use in the ``HttpUnauthorized`` response.  Default:
          ``django-tastypie``.
      """
      def __init__(self, backend=None, realm='django-tastypie', **kwargs):
          super(DigestAuthentication, self).__init__(**kwargs)
          self.backend = backend
          self.realm = realm
  
          if python_digest is None:
              raise ImproperlyConfigured("The 'python_digest' package could not be imported. It is required for use with the 'DigestAuthentication' class.")
  
      def _unauthorized(self):
          response = HttpUnauthorized()
          new_uuid = uuid.uuid4()
          opaque = hmac.new(str(new_uuid), digestmod=sha1).hexdigest()
          response['WWW-Authenticate'] = python_digest.build_digest_challenge(time.time(), getattr(settings, 'SECRET_KEY', ''), self.realm, opaque, False)
          return response
  
      def is_authenticated(self, request, **kwargs):
          """
          Finds the user and checks their API key.
  
          Should return either ``True`` if allowed, ``False`` if not or an
          ``HttpResponse`` if you need something custom.
          """
          if not request.META.get('HTTP_AUTHORIZATION'):
              return self._unauthorized()
  
          try:
              (auth_type, data) = request.META['HTTP_AUTHORIZATION'].split(' ', 1)
  
              if auth_type.lower() != 'digest':
                  return self._unauthorized()
          except:
              return self._unauthorized()
  
          digest_response = python_digest.parse_digest_credentials(request.META['HTTP_AUTHORIZATION'])
  
          # FIXME: Should the nonce be per-user?
          if not python_digest.validate_nonce(digest_response.nonce, getattr(settings, 'SECRET_KEY', '')):
              return self._unauthorized()
  
          user = self.get_user(digest_response.username)
          api_key = self.get_key(user)
  
          if user is False or api_key is False:
              return self._unauthorized()
  
          expected = python_digest.calculate_request_digest(
              request.method,
              python_digest.calculate_partial_digest(digest_response.username, self.realm, api_key),
              digest_response)
  
          if not digest_response.response == expected:
              return self._unauthorized()
  
          if not self.check_active(user):
              return False
  
          request.user = user
          return True
  
      def get_user(self, username):
          from django.contrib.auth.models import User
  
          try:
              user = User.objects.get(username=username)
          except (User.DoesNotExist, User.MultipleObjectsReturned):
              return False
  
          return user
  
      def get_key(self, user):
          """
          Attempts to find the API key for the user. Uses ``ApiKey`` by default
          but can be overridden.
  
          Note that this behaves differently than the ``ApiKeyAuthentication``
          method of the same name.
          """
          from tastypie.models import ApiKey
  
          try:
              key = ApiKey.objects.get(user=user)
          except ApiKey.DoesNotExist:
              return False
  
          return key.key
  
      def get_identifier(self, request):
          """
          Provides a unique string identifier for the requestor.
  
          This implementation returns the user's username.
          """
          if hasattr(request, 'user'):
              if hasattr(request.user, 'username'):
                  return request.user.username
  
          return 'nouser'
  
  
  class OAuthAuthentication(Authentication):
      """
      Handles OAuth, which checks a user's credentials against a separate service.
      Currently verifies against OAuth 1.0a services.
  
      This does *NOT* provide OAuth authentication in your API, strictly
      consumption.
      """
      def __init__(self, **kwargs):
          super(OAuthAuthentication, self).__init__(**kwargs)
  
          if oauth2 is None:
              raise ImproperlyConfigured("The 'python-oauth2' package could not be imported. It is required for use with the 'OAuthAuthentication' class.")
  
          if oauth_provider is None:
              raise ImproperlyConfigured("The 'django-oauth-plus' package could not be imported. It is required for use with the 'OAuthAuthentication' class.")
  
      def is_authenticated(self, request, **kwargs):
          from oauth_provider.store import store, InvalidTokenError
  
          if self.is_valid_request(request):
              oauth_request = oauth_provider.utils.get_oauth_request(request)
              consumer = store.get_consumer(request, oauth_request, oauth_request.get_parameter('oauth_consumer_key'))
  
              try:
                  token = store.get_access_token(request, oauth_request, consumer, oauth_request.get_parameter('oauth_token'))
              except oauth_provider.store.InvalidTokenError:
                  return oauth_provider.utils.send_oauth_error(oauth2.Error(_('Invalid access token: %s') % oauth_request.get_parameter('oauth_token')))
  
              try:
                  self.validate_token(request, consumer, token)
              except oauth2.Error, e:
                  return oauth_provider.utils.send_oauth_error(e)
  
              if consumer and token:
                  if not self.check_active(token.user):
                      return False
  
                  request.user = token.user
                  return True
  
              return oauth_provider.utils.send_oauth_error(oauth2.Error(_('You are not allowed to access this resource.')))
  
          return oauth_provider.utils.send_oauth_error(oauth2.Error(_('Invalid request parameters.')))
  
      def is_in(self, params):
          """
          Checks to ensure that all the OAuth parameter names are in the
          provided ``params``.
          """
          from oauth_provider.consts import OAUTH_PARAMETERS_NAMES
  
          for param_name in OAUTH_PARAMETERS_NAMES:
              if param_name not in params:
                  return False
  
          return True
  
      def is_valid_request(self, request):
          """
          Checks whether the required parameters are either in the HTTP
          ``Authorization`` header sent by some clients (the preferred method
          according to OAuth spec) or fall back to ``GET/POST``.
          """
          auth_params = request.META.get("HTTP_AUTHORIZATION", [])
          return self.is_in(auth_params) or self.is_in(request.REQUEST)
  
      def validate_token(self, request, consumer, token):
          oauth_server, oauth_request = oauth_provider.utils.initialize_server_request(request)
          return oauth_server.verify_request(oauth_request, consumer, token)
  
  
  class MultiAuthentication(object):
      """
      An authentication backend that tries a number of backends in order.
      """
      def __init__(self, *backends, **kwargs):
          super(MultiAuthentication, self).__init__(**kwargs)
          self.backends = backends
  
      def is_authenticated(self, request, **kwargs):
          """
          Identifies if the user is authenticated to continue or not.
  
          Should return either ``True`` if allowed, ``False`` if not or an
          ``HttpResponse`` if you need something custom.
          """
          unauthorized = False
  
          for backend in self.backends:
              check = backend.is_authenticated(request, **kwargs)
  
              if check:
                  if isinstance(check, HttpUnauthorized):
                      unauthorized = unauthorized or check
                  else:
                      request._authentication_backend = backend
                      return check
  
          return unauthorized
  
      def get_identifier(self, request):
          """
          Provides a unique string identifier for the requestor.
  
          This implementation returns a combination of IP address and hostname.
          """
          try:
              return request._authentication_backend.get_identifier(request)
          except AttributeError:
              return 'nouser'
  