authentication.py

import binascii
from codecs import utf_8_decode
from codecs import utf_8_encode
import hashlib
import base64
import datetime
import re
import time as time_mod
import warnings

from zope.interface import implementer

from webob.cookies import CookieProfile

from pyramid.compat import (
    long,
    text_type,
    binary_type,
    url_unquote,
    url_quote,
    bytes_,
    ascii_native_,
    native_,
    )

from pyramid.interfaces import (
    IAuthenticationPolicy,
    IDebugLogger,
    )

from pyramid.security import (
    Authenticated,
    Everyone,
    )

from pyramid.util import strings_differ

VALID_TOKEN = re.compile(r"^[A-Za-z][A-Za-z0-9+_-]*$")

class CallbackAuthenticationPolicy(object):
    """ Abstract class """

    debug = False
    callback = None

    def _log(self, msg, methodname, request):
        logger = request.registry.queryUtility(IDebugLogger)
        if logger:
            cls = self.__class__
            classname = cls.__module__ + '.' + cls.__name__
            methodname = classname + '.' + methodname
            logger.debug(methodname + ': ' + msg)

    def _clean_principal(self, princid):
        if princid in (Authenticated, Everyone):
            princid = None
        return princid

    def authenticated_userid(self, request):
        """ Return the authenticated userid or ``None``.

        If no callback is registered, this will be the same as
        ``unauthenticated_userid``.

        If a ``callback`` is registered, this will return the userid if
        and only if the callback returns a value that is not ``None``.

        """
        debug = self.debug
        userid = self.unauthenticated_userid(request)
        if userid is None:
            debug and self._log(
                'call to unauthenticated_userid returned None; returning None',
                'authenticated_userid',
                request)
            return None
        if self._clean_principal(userid) is None:
            debug and self._log(
                ('use of userid %r is disallowed by any built-in Pyramid '
                 'security policy, returning None' % userid),
                'authenticated_userid' ,
                request)
            return None
            
        if self.callback is None:
            debug and self._log(
                'there was no groupfinder callback; returning %r' % (userid,),
                'authenticated_userid',
                request)
            return userid
        callback_ok = self.callback(userid, request)
        if callback_ok is not None: # is not None!
            debug and self._log(
                'groupfinder callback returned %r; returning %r' % (
                    callback_ok, userid),
                'authenticated_userid',
                request
                )
            return userid
        debug and self._log(
            'groupfinder callback returned None; returning None',
            'authenticated_userid',
            request
            )

    def effective_principals(self, request):
        """ A list of effective principals derived from request.

        This will return a list of principals including, at least,
        :data:`pyramid.security.Everyone`. If there is no authenticated
        userid, or the ``callback`` returns ``None``, this will be the
        only principal:

        .. code-block:: python

            return [Everyone]

        If the ``callback`` does not return ``None`` and an authenticated
        userid is found, then the principals will include
        :data:`pyramid.security.Authenticated`, the ``authenticated_userid``
        and the list of principals returned by the ``callback``:

        .. code-block:: python

            extra_principals = callback(userid, request)
            return [Everyone, Authenticated, userid] + extra_principals

        """
        debug = self.debug
        effective_principals = [Everyone]
        userid = self.unauthenticated_userid(request)

        if userid is None:
            debug and self._log(
                'unauthenticated_userid returned %r; returning %r' % (
                    userid, effective_principals),
                'effective_principals',
                request
                )
            return effective_principals

        if self._clean_principal(userid) is None:
            debug and self._log(
                ('unauthenticated_userid returned disallowed %r; returning %r '
                 'as if it was None' % (userid, effective_principals)),
                'effective_principals',
                request
                )
            return effective_principals
            
        if self.callback is None:
            debug and self._log(
                'groupfinder callback is None, so groups is []',
                'effective_principals',
                request)
            groups = []
        else:
            groups = self.callback(userid, request)
            debug and self._log(
                'groupfinder callback returned %r as groups' % (groups,),
                'effective_principals',
                request)

        if groups is None: # is None!
            debug and self._log(
                'returning effective principals: %r' % (
                    effective_principals,),
                'effective_principals',
                request
                )
            return effective_principals

        effective_principals.append(Authenticated)
        effective_principals.append(userid)
        effective_principals.extend(groups)

        debug and self._log(
            'returning effective principals: %r' % (
                effective_principals,),
            'effective_principals',
            request
             )
        return effective_principals

@implementer(IAuthenticationPolicy)
class RepozeWho1AuthenticationPolicy(CallbackAuthenticationPolicy):
    """ A :app:`Pyramid` :term:`authentication policy` which
    obtains data from the :mod:`repoze.who` 1.X WSGI 'API' (the
    ``repoze.who.identity`` key in the WSGI environment).

    Constructor Arguments

    ``identifier_name``

       Default: ``auth_tkt``.  The :mod:`repoze.who` plugin name that
       performs remember/forget.  Optional.

    ``callback``

        Default: ``None``.  A callback passed the :mod:`repoze.who` identity
        and the :term:`request`, expected to return ``None`` if the user
        represented by the identity doesn't exist or a sequence of principal
        identifiers (possibly empty) representing groups if the user does
        exist.  If ``callback`` is None, the userid will be assumed to exist
        with no group principals.

    Objects of this class implement the interface described by
    :class:`pyramid.interfaces.IAuthenticationPolicy`.
    """

    def __init__(self, identifier_name='auth_tkt', callback=None):
        self.identifier_name = identifier_name
        self.callback = callback

    def _get_identity(self, request):
        return request.environ.get('repoze.who.identity')

    def _get_identifier(self, request):
        plugins = request.environ.get('repoze.who.plugins')
        if plugins is None:
            return None
        identifier = plugins[self.identifier_name]
        return identifier

    def authenticated_userid(self, request):
        """ Return the authenticated userid or ``None``.

        If no callback is registered, this will be the same as
        ``unauthenticated_userid``.

        If a ``callback`` is registered, this will return the userid if
        and only if the callback returns a value that is not ``None``.

        """
        identity = self._get_identity(request)

        if identity is None:
            self.debug and self._log(
                'repoze.who identity is None, returning None',
                'authenticated_userid',
                request)
            return None

        userid = identity['repoze.who.userid']

        if userid is None:
            self.debug and self._log(
                'repoze.who.userid is None, returning None' % userid,
                'authenticated_userid',
                request)
            return None
            
        if self._clean_principal(userid) is None:
            self.debug and self._log(
                ('use of userid %r is disallowed by any built-in Pyramid '
                 'security policy, returning None' % userid),
                'authenticated_userid',
                request)
            return None

        if self.callback is None:
            return userid

        if self.callback(identity, request) is not None: # is not None!
            return userid

    def unauthenticated_userid(self, request):
        """ Return the ``repoze.who.userid`` key from the detected identity."""
        identity = self._get_identity(request)
        if identity is None:
            return None
        return identity['repoze.who.userid']

    def effective_principals(self, request):
        """ A list of effective principals derived from the identity.

        This will return a list of principals including, at least,
        :data:`pyramid.security.Everyone`. If there is no identity, or
        the ``callback`` returns ``None``, this will be the only principal.

        If the ``callback`` does not return ``None`` and an identity is
        found, then the principals will include
        :data:`pyramid.security.Authenticated`, the ``authenticated_userid``
        and the list of principals returned by the ``callback``.

        """
        effective_principals = [Everyone]
        identity = self._get_identity(request)

        if identity is None:
            self.debug and self._log(
                ('repoze.who identity was None; returning %r' %
                 effective_principals),
                'effective_principals',
                request
                )
            return effective_principals

        if self.callback is None:
            groups = []
        else:
            groups = self.callback(identity, request)

        if groups is None: # is None!
            self.debug and self._log(
                ('security policy groups callback returned None; returning %r' %
                 effective_principals),
                'effective_principals',
                request
                )
            return effective_principals

        userid = identity['repoze.who.userid']

        if userid is None:
            self.debug and self._log(
                ('repoze.who.userid was None; returning %r' %
                 effective_principals),
                'effective_principals',
                request
                )
            return effective_principals

        if self._clean_principal(userid) is None:
            self.debug and self._log(
                ('unauthenticated_userid returned disallowed %r; returning %r '
                 'as if it was None' % (userid, effective_principals)),
                'effective_principals',
                request
                )
            return effective_principals

        effective_principals.append(Authenticated)
        effective_principals.append(userid)
        effective_principals.extend(groups)
        return effective_principals

    def remember(self, request, principal, **kw):
        """ Store the ``principal`` as ``repoze.who.userid``."""
        identifier = self._get_identifier(request)
        if identifier is None:
            return []
        environ = request.environ
        identity = {'repoze.who.userid':principal}
        return identifier.remember(environ, identity)

    def forget(self, request):
        """ Forget the current authenticated user.

        Return headers that, if included in a response, will delete the
        cookie responsible for tracking the current user.

        """
        identifier = self._get_identifier(request)
        if identifier is None:
            return []
        identity = self._get_identity(request)
        return identifier.forget(request.environ, identity)

@implementer(IAuthenticationPolicy)
class RemoteUserAuthenticationPolicy(CallbackAuthenticationPolicy):
    """ A :app:`Pyramid` :term:`authentication policy` which
    obtains data from the ``REMOTE_USER`` WSGI environment variable.

    Constructor Arguments

    ``environ_key``

        Default: ``REMOTE_USER``.  The key in the WSGI environ which
        provides the userid.

    ``callback``

        Default: ``None``.  A callback passed the userid and the request,
        expected to return None if the userid doesn't exist or a sequence of
        principal identifiers (possibly empty) representing groups if the
        user does exist.  If ``callback`` is None, the userid will be assumed
        to exist with no group principals.

    ``debug``

        Default: ``False``.  If ``debug`` is ``True``, log messages to the
        Pyramid debug logger about the results of various authentication
        steps.  The output from debugging is useful for reporting to maillist
        or IRC channels when asking for support.

    Objects of this class implement the interface described by
    :class:`pyramid.interfaces.IAuthenticationPolicy`.
    """

    def __init__(self, environ_key='REMOTE_USER', callback=None, debug=False):
        self.environ_key = environ_key
        self.callback = callback
        self.debug = debug

    def unauthenticated_userid(self, request):
        """ The ``REMOTE_USER`` value found within the ``environ``."""
        return request.environ.get(self.environ_key)

    def remember(self, request, principal, **kw):
        """ A no-op. The ``REMOTE_USER`` does not provide a protocol for
        remembering the user. This will be application-specific and can
        be done somewhere else or in a subclass."""
        return []

    def forget(self, request):
        """ A no-op. The ``REMOTE_USER`` does not provide a protocol for
        forgetting the user. This will be application-specific and can
        be done somewhere else or in a subclass."""
        return []

_marker = object()

@implementer(IAuthenticationPolicy)
class AuthTktAuthenticationPolicy(CallbackAuthenticationPolicy):
    """A :app:`Pyramid` :term:`authentication policy` which
    obtains data from a Pyramid "auth ticket" cookie.

    .. warning::

       The default hash algorithm used in this policy is MD5 and has known
       hash collision vulnerabilities. The risk of an exploit is low.
       However, for improved authentication security, use
       ``hashalg='sha512'``.

    Constructor Arguments

    ``secret``

       The secret (a string) used for auth_tkt cookie signing.  This value
       should be unique across all values provided to Pyramid for various
       subsystem secrets (see :ref:`admonishment_against_secret_sharing`).
       Required.

    ``callback``

       Default: ``None``.  A callback passed the userid and the
       request, expected to return ``None`` if the userid doesn't
       exist or a sequence of principal identifiers (possibly empty) if
       the user does exist.  If ``callback`` is ``None``, the userid
       will be assumed to exist with no principals.  Optional.

    ``cookie_name``

       Default: ``auth_tkt``.  The cookie name used
       (string).  Optional.

    ``secure``

       Default: ``False``.  Only send the cookie back over a secure
       conn.  Optional.

    ``include_ip``

       Default: ``False``.  Make the requesting IP address part of
       the authentication data in the cookie.  Optional.

       For IPv6 this option is not recommended. The ``mod_auth_tkt``
       specification does not specify how to handle IPv6 addresses, so using
       this option in combination with IPv6 addresses may cause an
       incompatible cookie. It ties the authentication ticket to that
       individual's IPv6 address.

    ``timeout``

       Default: ``None``.  Maximum number of seconds which a newly
       issued ticket will be considered valid.  After this amount of
       time, the ticket will expire (effectively logging the user
       out).  If this value is ``None``, the ticket never expires.
       Optional.

    ``reissue_time``

       Default: ``None``.  If this parameter is set, it represents the number
       of seconds that must pass before an authentication token cookie is
       automatically reissued as the result of a request which requires
       authentication.  The duration is measured as the number of seconds
       since the last auth_tkt cookie was issued and 'now'.  If this value is
       ``0``, a new ticket cookie will be reissued on every request which
       requires authentication.

       A good rule of thumb: if you want auto-expired cookies based on
       inactivity: set the ``timeout`` value to 1200 (20 mins) and set the
       ``reissue_time`` value to perhaps a tenth of the ``timeout`` value
       (120 or 2 mins).  It's nonsensical to set the ``timeout`` value lower
       than the ``reissue_time`` value, as the ticket will never be reissued
       if so.  However, such a configuration is not explicitly prevented.

       Optional.

    ``max_age``

       Default: ``None``.  The max age of the auth_tkt cookie, in
       seconds.  This differs from ``timeout`` inasmuch as ``timeout``
       represents the lifetime of the ticket contained in the cookie,
       while this value represents the lifetime of the cookie itself.
       When this value is set, the cookie's ``Max-Age`` and
       ``Expires`` settings will be set, allowing the auth_tkt cookie
       to last between browser sessions.  It is typically nonsensical
       to set this to a value that is lower than ``timeout`` or
       ``reissue_time``, although it is not explicitly prevented.
       Optional.

    ``path``

       Default: ``/``. The path for which the auth_tkt cookie is valid.
       May be desirable if the application only serves part of a domain.
       Optional.

    ``http_only``

       Default: ``False``. Hide cookie from JavaScript by setting the
       HttpOnly flag. Not honored by all browsers.
       Optional.

    ``wild_domain``

       Default: ``True``. An auth_tkt cookie will be generated for the
       wildcard domain. If your site is hosted as ``example.com`` this
       will make the cookie available for sites underneath ``example.com``
       such as ``www.example.com``.
       Optional.

    ``parent_domain``

       Default: ``False``. An auth_tkt cookie will be generated for the
       parent domain of the current site. For example if your site is
       hosted under ``www.example.com`` a cookie will be generated for
       ``.example.com``. This can be useful if you have multiple sites
       sharing the same domain. This option supercedes the ``wild_domain``
       option.
       Optional.

       This option is available as of :app:`Pyramid` 1.5.

    ``domain``

       Default: ``None``. If provided the auth_tkt cookie will only be
       set for this domain. This option is not compatible with ``wild_domain``
       and ``parent_domain``.
       Optional.

       This option is available as of :app:`Pyramid` 1.5.

    ``hashalg``

       Default: ``md5`` (the literal string).

       Any hash algorithm supported by Python's ``hashlib.new()`` function
       can be used as the ``hashalg``.

       Cookies generated by different instances of AuthTktAuthenticationPolicy
       using different ``hashalg`` options are not compatible. Switching the
       ``hashalg`` will imply that all existing users with a valid cookie will
       be required to re-login.

       A warning is emitted at startup if an explicit ``hashalg`` is not
       passed.  This is for backwards compatibility reasons.

       This option is available as of :app:`Pyramid` 1.4.

       Optional.

       .. note::

          ``md5`` is the default for backwards compatibility reasons. However,
          if you don't specify ``md5`` as the hashalg explicitly, a warning is
          issued at application startup time.  An explicit value of ``sha512``
          is recommended for improved security, and ``sha512`` will become the
          default in a future Pyramid version.

    ``debug``

        Default: ``False``.  If ``debug`` is ``True``, log messages to the
        Pyramid debug logger about the results of various authentication
        steps.  The output from debugging is useful for reporting to maillist
        or IRC channels when asking for support.

    Objects of this class implement the interface described by
    :class:`pyramid.interfaces.IAuthenticationPolicy`.
    """

    def __init__(self,
                 secret,
                 callback=None,
                 cookie_name='auth_tkt',
                 secure=False,
                 include_ip=False,
                 timeout=None,
                 reissue_time=None,
                 max_age=None,
                 path="/",
                 http_only=False,
                 wild_domain=True,
                 debug=False,
                 hashalg=_marker,
                 parent_domain=False,
                 domain=None,
                 ):
        if hashalg is _marker:
            hashalg = 'md5'
            warnings.warn(
                'The MD5 hash function used by default by the '
                'AuthTktAuthenticationPolicy is known to be '
                'susceptible to collision attacks.  It is the current default '
                'for backwards compatibility reasons, but we recommend that '
                'you use the SHA512 algorithm instead for improved security.  '
                'Pass ``hashalg=\'sha512\'`` to the '
                'AuthTktAuthenticationPolicy constructor to do so.\n\nNote '
                'that a change to the hash algorithms will invalidate existing '
                'auth tkt cookies set by your application.  If backwards '
                'compatibility of existing auth tkt cookies is of greater '
                'concern than the risk posed by the potential for a hash '
                'collision, you\'ll want to continue using MD5 explicitly.  '
                'To do so, pass ``hashalg=\'md5\'`` in your application to '
                'the AuthTktAuthenticationPolicy constructor.   When you do so '
                'this warning will not be emitted again.  The default '
                'algorithm used in this policy will change in the future, so '
                'setting an explicit hashalg will futureproof your '
                'application.',
                DeprecationWarning,
                stacklevel=2
                )
        self.cookie = AuthTktCookieHelper(
            secret,
            cookie_name=cookie_name,
            secure=secure,
            include_ip=include_ip,
            timeout=timeout,
            reissue_time=reissue_time,
            max_age=max_age,
            http_only=http_only,
            path=path,
            wild_domain=wild_domain,
            hashalg=hashalg,
            parent_domain=parent_domain,
            domain=domain,
            )
        self.callback = callback
        self.debug = debug

    def unauthenticated_userid(self, request):
        """ The userid key within the auth_tkt cookie."""
        result = self.cookie.identify(request)
        if result:
            return result['userid']

    def remember(self, request, principal, **kw):
        """ Accepts the following kw args: ``max_age=<int-seconds>,
        ``tokens=<sequence-of-ascii-strings>``.

        Return a list of headers which will set appropriate cookies on
        the response.

        """
        return self.cookie.remember(request, principal, **kw)

    def forget(self, request):
        """ A list of headers which will delete appropriate cookies."""
        return self.cookie.forget(request)

def b64encode(v):
    return base64.b64encode(bytes_(v)).strip().replace(b'\n', b'')

def b64decode(v):
    return base64.b64decode(bytes_(v))

# this class licensed under the MIT license (stolen from Paste)
class AuthTicket(object):
    """
    This class represents an authentication token.  You must pass in
    the shared secret, the userid, and the IP address.  Optionally you
    can include tokens (a list of strings, representing role names),
    'user_data', which is arbitrary data available for your own use in
    later scripts.  Lastly, you can override the cookie name and
    timestamp.

    Once you provide all the arguments, use .cookie_value() to
    generate the appropriate authentication ticket.

    Usage::

        token = AuthTicket('sharedsecret', 'username',
            os.environ['REMOTE_ADDR'], tokens=['admin'])
        val = token.cookie_value()

    """

    def __init__(self, secret, userid, ip, tokens=(), user_data='',
                 time=None, cookie_name='auth_tkt', secure=False,
                 hashalg='md5'):
        self.secret = secret
        self.userid = userid
        self.ip = ip
        self.tokens = ','.join(tokens)
        self.user_data = user_data
        if time is None:
            self.time = time_mod.time()
        else:
            self.time = time
        self.cookie_name = cookie_name
        self.secure = secure
        self.hashalg = hashalg

    def digest(self):
        return calculate_digest(
            self.ip, self.time, self.secret, self.userid, self.tokens,
            self.user_data, self.hashalg)

    def cookie_value(self):
        v = '%s%08x%s!' % (self.digest(), int(self.time),
                           url_quote(self.userid))
        if self.tokens:
            v += self.tokens + '!'
        v += self.user_data
        return v

# this class licensed under the MIT license (stolen from Paste)
class BadTicket(Exception):
    """
    Exception raised when a ticket can't be parsed.  If we get far enough to
    determine what the expected digest should have been, expected is set.
    This should not be shown by default, but can be useful for debugging.
    """
    def __init__(self, msg, expected=None):
        self.expected = expected
        Exception.__init__(self, msg)

# this function licensed under the MIT license (stolen from Paste)
def parse_ticket(secret, ticket, ip, hashalg='md5'):
    """
    Parse the ticket, returning (timestamp, userid, tokens, user_data).

    If the ticket cannot be parsed, a ``BadTicket`` exception will be raised
    with an explanation.
    """
    ticket = ticket.strip('"')
    digest_size = hashlib.new(hashalg).digest_size * 2
    digest = ticket[:digest_size]
    try:
        timestamp = int(ticket[digest_size:digest_size + 8], 16)
    except ValueError as e:
        raise BadTicket('Timestamp is not a hex integer: %s' % e)
    try:
        userid, data = ticket[digest_size + 8:].split('!', 1)
    except ValueError:
        raise BadTicket('userid is not followed by !')
    userid = url_unquote(userid)
    if '!' in data:
        tokens, user_data = data.split('!', 1)
    else: # pragma: no cover (never generated)
        # @@: Is this the right order?
        tokens = ''
        user_data = data

    expected = calculate_digest(ip, timestamp, secret,
                                userid, tokens, user_data, hashalg)

    # Avoid timing attacks (see
    # http://seb.dbzteam.org/crypto/python-oauth-timing-hmac.pdf)
    if strings_differ(expected, digest):
        raise BadTicket('Digest signature is not correct',
                        expected=(expected, digest))

    tokens = tokens.split(',')

    return (timestamp, userid, tokens, user_data)

# this function licensed under the MIT license (stolen from Paste)
def calculate_digest(ip, timestamp, secret, userid, tokens, user_data,
                     hashalg='md5'):
    secret = bytes_(secret, 'utf-8')
    userid = bytes_(userid, 'utf-8')
    tokens = bytes_(tokens, 'utf-8')
    user_data = bytes_(user_data, 'utf-8')
    hash_obj = hashlib.new(hashalg)

    # Check to see if this is an IPv6 address
    if ':' in ip:
        ip_timestamp = ip + str(int(timestamp))
        ip_timestamp = bytes_(ip_timestamp)
    else:
        # encode_ip_timestamp not required, left in for backwards compatibility
        ip_timestamp = encode_ip_timestamp(ip, timestamp)

    hash_obj.update(ip_timestamp + secret + userid + b'\0' +
            tokens + b'\0' + user_data)
    digest = hash_obj.hexdigest()
    hash_obj2 = hashlib.new(hashalg)
    hash_obj2.update(bytes_(digest) + secret)
    return hash_obj2.hexdigest()

# this function licensed under the MIT license (stolen from Paste)
def encode_ip_timestamp(ip, timestamp):
    ip_chars = ''.join(map(chr, map(int, ip.split('.'))))
    t = int(timestamp)
    ts = ((t & 0xff000000) >> 24,
          (t & 0xff0000) >> 16,
          (t & 0xff00) >> 8,
          t & 0xff)
    ts_chars = ''.join(map(chr, ts))
    return bytes_(ip_chars + ts_chars)

class AuthTktCookieHelper(object):
    """
    A helper class for use in third-party authentication policy
    implementations.  See
    :class:`pyramid.authentication.AuthTktAuthenticationPolicy` for the
    meanings of the constructor arguments.
    """
    parse_ticket = staticmethod(parse_ticket) # for tests
    AuthTicket = AuthTicket # for tests
    BadTicket = BadTicket # for tests
    now = None # for tests

    userid_type_decoders = {
        'int':int,
        'unicode':lambda x: utf_8_decode(x)[0], # bw compat for old cookies
        'b64unicode': lambda x: utf_8_decode(b64decode(x))[0],
        'b64str': lambda x: b64decode(x),
        }

    userid_type_encoders = {
        int: ('int', str),
        long: ('int', str),
        text_type: ('b64unicode', lambda x: b64encode(utf_8_encode(x)[0])),
        binary_type: ('b64str', lambda x: b64encode(x)),
        }

    def __init__(self, secret, cookie_name='auth_tkt', secure=False,
                 include_ip=False, timeout=None, reissue_time=None,
                 max_age=None, http_only=False, path="/", wild_domain=True,
                 hashalg='md5', parent_domain=False, domain=None):

        serializer = _SimpleSerializer()
            
        self.cookie_profile = CookieProfile(
            cookie_name = cookie_name,
            secure = secure,
            max_age = max_age,
            httponly = http_only,
            path = path,
            serializer=serializer
            )

        self.secret = secret
        self.cookie_name = cookie_name
        self.secure = secure
        self.include_ip = include_ip
        self.timeout = timeout
        self.reissue_time = reissue_time
        self.max_age = max_age
        self.wild_domain = wild_domain
        self.parent_domain = parent_domain
        self.domain = domain
        self.hashalg = hashalg

    def _get_cookies(self, request, value, max_age=None):
        cur_domain = request.domain

        domains = []
        if self.domain:
            domains.append(self.domain)
        else:
            if self.parent_domain and cur_domain.count('.') > 1:
                domains.append('.' + cur_domain.split('.', 1)[1])
            else:
                domains.append(None)
                domains.append(cur_domain)
                if self.wild_domain:
                    domains.append('.' + cur_domain)

        profile = self.cookie_profile(request)

        kw = {}
        kw['domains'] = domains
        if max_age is not None:
            kw['max_age'] = max_age
            
        headers = profile.get_headers(value, **kw)
        return headers

    def identify(self, request):
        """ Return a dictionary with authentication information, or ``None``
        if no valid auth_tkt is attached to ``request``"""
        environ = request.environ
        cookie = request.cookies.get(self.cookie_name)

        if cookie is None:
            return None

        if self.include_ip:
            remote_addr = environ['REMOTE_ADDR']
        else:
            remote_addr = '0.0.0.0'

        try:
            timestamp, userid, tokens, user_data = self.parse_ticket(
                self.secret, cookie, remote_addr, self.hashalg)
        except self.BadTicket:
            return None

        now = self.now # service tests

        if now is None:
            now = time_mod.time()

        if self.timeout and ( (timestamp + self.timeout) < now ):
            # the auth_tkt data has expired
            return None

        userid_typename = 'userid_type:'
        user_data_info = user_data.split('|')
        for datum in filter(None, user_data_info):
            if datum.startswith(userid_typename):
                userid_type = datum[len(userid_typename):]
                decoder = self.userid_type_decoders.get(userid_type)
                if decoder:
                    userid = decoder(userid)

        reissue = self.reissue_time is not None

        if reissue and not hasattr(request, '_authtkt_reissued'):
            if ( (now - timestamp) > self.reissue_time ):
                # work around https://github.com/Pylons/pyramid/issues#issue/108
                tokens = list(filter(None, tokens))
                headers = self.remember(request, userid, max_age=self.max_age,
                                        tokens=tokens)
                def reissue_authtkt(request, response):
                    if not hasattr(request, '_authtkt_reissue_revoked'):
                        for k, v in headers:
                            response.headerlist.append((k, v))
                request.add_response_callback(reissue_authtkt)
                request._authtkt_reissued = True

        environ['REMOTE_USER_TOKENS'] = tokens
        environ['REMOTE_USER_DATA'] = user_data
        environ['AUTH_TYPE'] = 'cookie'

        identity = {}
        identity['timestamp'] = timestamp
        identity['userid'] = userid
        identity['tokens'] = tokens
        identity['userdata'] = user_data
        return identity

    def forget(self, request):
        """ Return a set of expires Set-Cookie headers, which will destroy
        any existing auth_tkt cookie when attached to a response"""
        request._authtkt_reissue_revoked = True
        return self._get_cookies(request, None)

    def remember(self, request, userid, max_age=None, tokens=()):
        """ Return a set of Set-Cookie headers; when set into a response,
        these headers will represent a valid authentication ticket.

        ``max_age``
          The max age of the auth_tkt cookie, in seconds.  When this value is
          set, the cookie's ``Max-Age`` and ``Expires`` settings will be set,
          allowing the auth_tkt cookie to last between browser sessions.  If
          this value is ``None``, the ``max_age`` value provided to the
          helper itself will be used as the ``max_age`` value.  Default:
          ``None``.

        ``tokens``
          A sequence of strings that will be placed into the auth_tkt tokens
          field.  Each string in the sequence must be of the Python ``str``
          type and must match the regex ``^[A-Za-z][A-Za-z0-9+_-]*$``.
          Tokens are available in the returned identity when an auth_tkt is
          found in the request and unpacked.  Default: ``()``.
        """
        if max_age is None:
            max_age = self.max_age

        environ = request.environ

        if self.include_ip:
            remote_addr = environ['REMOTE_ADDR']
        else:
            remote_addr = '0.0.0.0'

        user_data = ''

        encoding_data = self.userid_type_encoders.get(type(userid))

        if encoding_data:
            encoding, encoder = encoding_data
            userid = encoder(userid)
            user_data = 'userid_type:%s' % encoding

        new_tokens = []
        for token in tokens:
            if isinstance(token, text_type):
                try:
                    token = ascii_native_(token)
                except UnicodeEncodeError:
                    raise ValueError("Invalid token %r" % (token,))
            if not (isinstance(token, str) and VALID_TOKEN.match(token)):
                raise ValueError("Invalid token %r" % (token,))
            new_tokens.append(token)
        tokens = tuple(new_tokens)

        if hasattr(request, '_authtkt_reissued'):
            request._authtkt_reissue_revoked = True

        ticket = self.AuthTicket(
            self.secret,
            userid,
            remote_addr,
            tokens=tokens,
            user_data=user_data,
            cookie_name=self.cookie_name,
            secure=self.secure,
            hashalg=self.hashalg
            )

        cookie_value = ticket.cookie_value()
        return self._get_cookies(request, cookie_value, max_age)

@implementer(IAuthenticationPolicy)
class SessionAuthenticationPolicy(CallbackAuthenticationPolicy):
    """ A :app:`Pyramid` authentication policy which gets its data from the
    configured :term:`session`.  For this authentication policy to work, you
    will have to follow the instructions in the :ref:`sessions_chapter` to
    configure a :term:`session factory`.

    Constructor Arguments

    ``prefix``

       A prefix used when storing the authentication parameters in the
       session. Defaults to 'auth.'. Optional.

    ``callback``

       Default: ``None``.  A callback passed the userid and the
       request, expected to return ``None`` if the userid doesn't
       exist or a sequence of principal identifiers (possibly empty) if
       the user does exist.  If ``callback`` is ``None``, the userid
       will be assumed to exist with no principals.  Optional.

    ``debug``

        Default: ``False``.  If ``debug`` is ``True``, log messages to the
        Pyramid debug logger about the results of various authentication
        steps.  The output from debugging is useful for reporting to maillist
        or IRC channels when asking for support.

    """

    def __init__(self, prefix='auth.', callback=None, debug=False):
        self.callback = callback
        self.prefix = prefix or ''
        self.userid_key = prefix + 'userid'
        self.debug = debug

    def remember(self, request, principal, **kw):
        """ Store a principal in the session."""
        request.session[self.userid_key] = principal
        return []

    def forget(self, request):
        """ Remove the stored principal from the session."""
        if self.userid_key in request.session:
            del request.session[self.userid_key]
        return []

    def unauthenticated_userid(self, request):
        return request.session.get(self.userid_key)


@implementer(IAuthenticationPolicy)
class BasicAuthAuthenticationPolicy(CallbackAuthenticationPolicy):
    """ A :app:`Pyramid` authentication policy which uses HTTP standard basic
    authentication protocol to authenticate users.  To use this policy you will
    need to provide a callback which checks the supplied user credentials
    against your source of login data.

    Constructor Arguments

    ``check``

       A callback function passed a username, password and request, in that
       order as positional arguments.  Expected to return ``None`` if the
       userid doesn't exist or a sequence of principal identifiers (possibly
       empty) if the user does exist.

    ``realm``

       Default: ``"Realm"``.  The Basic Auth Realm string.  Usually displayed to
       the user by the browser in the login dialog.

    ``debug``

        Default: ``False``.  If ``debug`` is ``True``, log messages to the
        Pyramid debug logger about the results of various authentication
        steps.  The output from debugging is useful for reporting to maillist
        or IRC channels when asking for support.

    **Issuing a challenge**

    Regular browsers will not send username/password credentials unless they
    first receive a challenge from the server.  The following recipe will
    register a view that will send a Basic Auth challenge to the user whenever
    there is an attempt to call a view which results in a Forbidden response::

        from pyramid.httpexceptions import HTTPUnauthorized
        from pyramid.security import forget
        from pyramid.view import forbidden_view_config

        @forbidden_view_config()
        def basic_challenge(request):
            response = HTTPUnauthorized()
            response.headers.update(forget(request))
            return response
    """
    def __init__(self, check, realm='Realm', debug=False):
        self.check = check
        self.realm = realm
        self.debug = debug

    def unauthenticated_userid(self, request):
        """ The userid parsed from the ``Authorization`` request header."""
        credentials = self._get_credentials(request)
        if credentials:
            return credentials[0]

    def remember(self, request, principal, **kw):
        """ A no-op. Basic authentication does not provide a protocol for
        remembering the user. Credentials are sent on every request.

        """
        return []

    def forget(self, request):
        """ Returns challenge headers. This should be attached to a response
        to indicate that credentials are required."""
        return [('WWW-Authenticate', 'Basic realm="%s"' % self.realm)]

    def callback(self, username, request):
        # Username arg is ignored.  Unfortunately _get_credentials winds up
        # getting called twice when authenticated_userid is called.  Avoiding
        # that, however, winds up duplicating logic from the superclass.
        credentials = self._get_credentials(request)
        if credentials:
            username, password = credentials
            return self.check(username, password, request)

    def _get_credentials(self, request):
        authorization = request.headers.get('Authorization')
        if not authorization:
            return None
        try:
            authmeth, auth = authorization.split(' ', 1)
        except ValueError: # not enough values to unpack
            return None
        if authmeth.lower() != 'basic':
            return None

        try:
            authbytes = b64decode(auth.strip())
        except (TypeError, binascii.Error): # can't decode
            return None

        # try utf-8 first, then latin-1; see discussion in
        # https://github.com/Pylons/pyramid/issues/898
        try:
            auth = authbytes.decode('utf-8')
        except UnicodeDecodeError:
            auth = authbytes.decode('latin-1')

        try:
            username, password = auth.split(':', 1)
        except ValueError: # not enough values to unpack
            return None
        return username, password

class _SimpleSerializer(object):
    def loads(self, bstruct):
        return native_(bstruct)

    def dumps(self, appstruct):
        return bytes_(appstruct)