##############################################################################
#
# Copyright (c) 2004 Zope Corporation and Contributors.
# All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.0 (ZPL).  A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE.
#
##############################################################################
"""Session implementation using cookies

$Id: http.py 99330 2009-04-20 20:28:50Z hannosch $
"""
import hmac
import logging
import random
import re
import string
import time
from cStringIO import StringIO
try:
    from hashlib import sha1
except ImportError:
    # Python 2.4
    import sha as sha1
try:
    from email.utils import formatdate
except ImportError:
    # Python 2.4
    from email.Utils import formatdate

import zope.location
from persistent import Persistent
from zope import schema, component
from zope.interface import implements
from zope.publisher.interfaces.http import IHTTPRequest
from zope.publisher.interfaces.http import IHTTPApplicationRequest
from zope.i18nmessageid import ZopeMessageFactory as _
from zope.session.interfaces import IClientIdManager
from zope.schema.fieldproperty import FieldProperty

__docformat__ = 'restructuredtext'

cookieSafeTrans = string.maketrans("+/", "-.")

logger = logging.getLogger()

def digestEncode(s):
    """Encode SHA digest for cookie."""
    return s.encode("base64")[:-2].translate(cookieSafeTrans)

class MissingClientIdException(Exception):
    """No ClientId found in Request"""

class ICookieClientIdManager(IClientIdManager):
    """Manages sessions using a cookie"""

    namespace = schema.TextLine(
            title=_('Cookie Name'),
            description=_(
                "Name of cookie used to maintain state. "
                "Must be unique to the site domain name, and only contain "
                "ASCII letters, digits and '_'"
                ),
            required=True,
            min_length=1,
            max_length=30,
            constraint=re.compile("^[\d\w_]+$").search,
            )

    cookieLifetime = schema.Int(
            title=_('Cookie Lifetime'),
            description=_(
                "Number of seconds until the browser expires the cookie. "
                "Leave blank expire the cookie when the browser is quit. "
                "Set to 0 to never expire. "
                ),
            min=0,
            required=False,
            default=None,
            missing_value=None,
            )

    thirdparty = schema.Bool(
            title=_('Third party cookie'),
            description=_(
                "Is a third party issuing the identification cookie? "
                "Servers like Apache or Nginx have capabilities to issue "
                "identification cookies too. If Third party cookies are "
                "beeing used, Zope will never send a cookie back, just check "
                "for them."
                ),
            required=False,
            default=False,
            )

    domain = schema.TextLine(
            title=_('Effective domain'),
            description=_(
                "An identification cookie can be restricted to a specific domain "
                "using this option. This option sets the ``domain`` attribute "
                "for the cookie header. It is useful for setting one "
                "identification cookie for multiple subdomains. So if this "
                "option is set to ``.example.org``, the cookie will be available "
                "for subdomains like ``yourname.example.org``. "
                "Note that if you set this option to some domain, the identification "
                "cookie won't be available for other domains, so, for example "
                "you won't be able to login using the SessionCredentials plugin "
                "via another domain."
                ),
            required=False,
            )

    secure = schema.Bool(
        title=_('Request Secure communication'),
        required=False,
        default=False,
        )

    postOnly = schema.Bool(
        title=_('Only set cookie on POST requests'),
        required=False,
        default=False,
        )

class CookieClientIdManager(zope.location.Location, Persistent):
    """Session utility implemented using cookies."""

    implements(IClientIdManager, ICookieClientIdManager)

    thirdparty = FieldProperty(ICookieClientIdManager['thirdparty'])
    cookieLifetime = FieldProperty(ICookieClientIdManager['cookieLifetime'])
    secure = FieldProperty(ICookieClientIdManager['secure'])
    postOnly = FieldProperty(ICookieClientIdManager['postOnly'])
    domain = FieldProperty(ICookieClientIdManager['domain'])

    def __init__(self):
        self.namespace = "zope3_cs_%x" % (int(time.time()) - 1000000000)
        self.secret = "%.20f" % random.random()

    def getClientId(self, request):
        """Get the client id

        This creates one if necessary:

          >>> from zope.publisher.http import HTTPRequest
          >>> request = HTTPRequest(StringIO(''), {})
          >>> bim = CookieClientIdManager()
          >>> id = bim.getClientId(request)
          >>> id == bim.getClientId(request)
          True

        The id is retained accross requests:

          >>> request2 = HTTPRequest(StringIO(''), {})
          >>> request2._cookies = dict(
          ...   [(name, cookie['value'])
          ...    for (name, cookie) in request.response._cookies.items()
          ...   ])
          >>> id == bim.getClientId(request2)
          True
          >>> bool(id)
          True

        Note that the return value of this function is a string, not
        an IClientId. This is because this method is used to implement
        the IClientId Adapter.

          >>> type(id) == type('')
          True

        We don't set the client id unless we need to, so, for example,
        the second response doesn't have cookies set:

          >>> request2.response._cookies
          {}

        An exception to this is if the cookieLifetime is set to a
        non-zero integer value, in which case we do set it on every
        request, regardless of when it was last set:
        
          >>> bim.cookieLifetime = 3600 # one hour
          >>> id == bim.getClientId(request2)
          True

          >>> bool(request2.response._cookies)
          True

        If the postOnly attribute is set to a true value, then cookies
        will only be set on POST requests.

          >>> bim.postOnly = True
          >>> request = HTTPRequest(StringIO(''), {})
          >>> bim.getClientId(request)
          Traceback (most recent call last):
          ...
          MissingClientIdException

          >>> print request.response.getCookie(bim.namespace)
          None
        
          >>> request = HTTPRequest(StringIO(''), {'REQUEST_METHOD': 'POST'})
          >>> id = bim.getClientId(request)
          >>> id == bim.getClientId(request)
          True
          
          >>> request.response.getCookie(bim.namespace) is not None
          True

          >>> bim.postOnly = False

        It's also possible to use third-party cookies. E.g. Apache `mod_uid`
        or Nginx `ngx_http_userid_module` are able to issue user tracking
        cookies in front of Zope. In case thirdparty is activated Zope may
        not set a cookie.

          >>> bim.thirdparty = True
          >>> request = HTTPRequest(StringIO(''), {})
          >>> bim.getClientId(request)
          Traceback (most recent call last):
          ...
          MissingClientIdException

          >>> print request.response.getCookie(bim.namespace)
          None

        """
        sid = self.getRequestId(request)
        if sid is None:
            if (self.thirdparty
                or
                (self.postOnly and not (request.method == 'POST'))
                ):
                raise MissingClientIdException
            else:
                sid = self.generateUniqueId()
                self.setRequestId(request, sid)
        elif (not self.thirdparty) and self.cookieLifetime:
            # If we have a finite cookie lifetime, then set the cookie
            # on each request to avoid losing it.
            self.setRequestId(request, sid)

        return sid

    def generateUniqueId(self):
        """Generate a new, random, unique id.

          >>> bim = CookieClientIdManager()
          >>> id1 = bim.generateUniqueId()
          >>> id2 = bim.generateUniqueId()
          >>> id1 != id2
          True

        """
        data = "%.20f%.20f%.20f" % (random.random(), time.time(), time.clock())
        # BBB code for Python 2.4, inspired by the fallback in hmac
        if hasattr(sha1, '__call__'):
            digest = sha1(data).digest()
        else:
            digest = sha1.new(data).digest()
        s = digestEncode(digest)
        # we store a HMAC of the random value together with it, which makes
        # our session ids unforgeable.
        mac = hmac.new(s, self.secret, digestmod=sha1).digest()
        return s + digestEncode(mac)

    def getRequestId(self, request):
        """Return the browser id encoded in request as a string

        Return None if an id is not set.

        For example:

          >>> from zope.publisher.http import HTTPRequest
          >>> request = HTTPRequest(StringIO(''), {}, None)
          >>> bim = CookieClientIdManager()

        Because no cookie has been set, we get no id:

          >>> bim.getRequestId(request) is None
          True

        We can set an id:

          >>> id1 = bim.generateUniqueId()
          >>> bim.setRequestId(request, id1)

        And get it back:

          >>> bim.getRequestId(request) == id1
          True

        When we set the request id, we also set a response cookie.  We
        can simulate getting this cookie back in a subsequent request:

          >>> request2 = HTTPRequest(StringIO(''), {}, None)
          >>> request2._cookies = dict(
          ...   [(name, cookie['value'])
          ...    for (name, cookie) in request.response._cookies.items()
          ...   ])

        And we get the same id back from the new request:

          >>> bim.getRequestId(request) == bim.getRequestId(request2)
          True

        Test a corner case where Python 2.6 hmac module does not allow
        unicode as input:

          >>> id_uni = unicode(bim.generateUniqueId())
          >>> bim.setRequestId(request, id_uni)
          >>> bim.getRequestId(request) == id_uni
          True
        
        If another server is managing the ClientId cookies (Apache, Nginx)
        we're returning their value without checking:

          >>> bim.namespace = 'uid'
          >>> bim.thirdparty = True
          >>> request3 = HTTPRequest(StringIO(''), {}, None)
          >>> request3._cookies = {'uid': 'AQAAf0Y4gjgAAAQ3AwMEAg=='}
          >>> bim.getRequestId(request3)
          'AQAAf0Y4gjgAAAQ3AwMEAg=='
        
        """
        response_cookie = request.response.getCookie(self.namespace)
        if response_cookie:
            sid = response_cookie['value']
        else:
            request = IHTTPApplicationRequest(request)
            sid = request.getCookies().get(self.namespace, None)
        if self.thirdparty:
            return sid
        else:
            
            # If there is an id set on the response, use that but
            # don't trust it.  We need to check the response in case
            # there has already been a new session created during the
            # course of this request.

            if sid is None or len(sid) != 54:
                return None
            s, mac = sid[:27], sid[27:]
            
            # call encode() on value s a workaround a bug where the hmac
            # module only accepts str() types in Python 2.6
            if (digestEncode(hmac.new(
                    s.encode(), self.secret, digestmod=sha1
                ).digest()) != mac):
                return None
            else:
                return sid

    def setRequestId(self, request, id):
        """Set cookie with id on request.

        This sets the response cookie:

        See the examples in getRequestId.

        Note that the id is checked for validity. Setting an
        invalid value is silently ignored:

            >>> from zope.publisher.http import HTTPRequest
            >>> request = HTTPRequest(StringIO(''), {}, None)
            >>> bim = CookieClientIdManager()
            >>> bim.getRequestId(request)
            >>> bim.setRequestId(request, 'invalid id')
            >>> bim.getRequestId(request)

        For now, the cookie path is the application URL:

            >>> cookie = request.response.getCookie(bim.namespace)
            >>> cookie['path'] == request.getApplicationURL(path_only=True)
            True

        By default, session cookies don't expire:

            >>> cookie.has_key('expires')
            False

        Expiry time of 0 means never (well - close enough)

            >>> bim.cookieLifetime = 0
            >>> request = HTTPRequest(StringIO(''), {}, None)
            >>> bid = bim.getClientId(request)
            >>> cookie = request.response.getCookie(bim.namespace)
            >>> cookie['expires']
            'Tue, 19 Jan 2038 00:00:00 GMT'

        A non-zero value means to expire after than number of seconds:

            >>> bim.cookieLifetime = 3600
            >>> request = HTTPRequest(StringIO(''), {}, None)
            >>> bid = bim.getClientId(request)
            >>> cookie = request.response.getCookie(bim.namespace)
            >>> import rfc822
            >>> expires = time.mktime(rfc822.parsedate(cookie['expires']))
            >>> expires > time.mktime(time.gmtime()) + 55*60
            True

        If another server in front of Zope (Apache, Nginx) is managing the
        cookies we won't set any ClientId cookies:

          >>> request = HTTPRequest(StringIO(''), {}, None)
          >>> bim.thirdparty = True
          >>> bim.setRequestId(request, '1234')
          >>> cookie = request.response.getCookie(bim.namespace)
          >>> cookie

        If the secure attribute is set to a true value, then the
        secure cookie option is included.
        
          >>> bim.thirdparty = False
          >>> bim.cookieLifetime = None
          >>> request = HTTPRequest(StringIO(''), {}, None)
          >>> bim.secure = True
          >>> bim.setRequestId(request, '1234')
          >>> print request.response.getCookie(bim.namespace)
          {'path': '/', 'secure': True, 'value': '1234'}

        If the domain is specified, it will be set as a cookie attribute.

          >>> bim.domain = u'.example.org'
          >>> bim.setRequestId(request, '1234')
          >>> print request.response.getCookie(bim.namespace)
          {'path': '/', 'domain': u'.example.org', 'secure': True, 'value': '1234'}

        When the cookie is set, cache headers are added to the
        response to try to prevent the cookie header from being cached:

          >>> request.response.getHeader('Cache-Control')
          'no-cache="Set-Cookie,Set-Cookie2"'
          >>> request.response.getHeader('Pragma')
          'no-cache'
          >>> request.response.getHeader('Expires')
          'Mon, 26 Jul 1997 05:00:00 GMT'

        """
        # TODO: Currently, the path is the ApplicationURL. This is reasonable,
        #     and will be adequate for most purposes.
        #     A better path to use would be that of the folder that contains
        #     the site manager this service is registered within. However,
        #     that would be expensive to look up on each request, and would
        #     have to be altered to take virtual hosting into account.
        #     Seeing as this utility instance has a unique namespace for its
        #     cookie, using ApplicationURL shouldn't be a problem.

        if self.thirdparty:
            logger.warning('ClientIdManager is using thirdparty cookies, '
                'ignoring setIdRequest call')
            return

        response = request.response
        options = {}
        if self.cookieLifetime is not None:
            if self.cookieLifetime:
                expires = formatdate(time.time() + self.cookieLifetime,
                                     localtime=False, usegmt=True)
            else:
                expires = 'Tue, 19 Jan 2038 00:00:00 GMT'

            options['expires'] = expires

        if self.secure:
            options['secure'] = True

        if self.domain:
            options['domain'] = self.domain

        response.setCookie(
            self.namespace, id,
            path=request.getApplicationURL(path_only=True),
            **options)

        response.setHeader('Cache-Control', 'no-cache="Set-Cookie,Set-Cookie2"')
        response.setHeader('Pragma', 'no-cache')
        response.setHeader('Expires', 'Mon, 26 Jul 1997 05:00:00 GMT')

def notifyVirtualHostChanged(event):
    """Adjust cookie paths when IVirtualHostRequest information changes.

    Given an event, this method should call a CookieClientIdManager's
    setRequestId if a cookie is present in the response for that manager. To
    demonstrate we create a dummy manager object and event:

        >>> class DummyManager(object):
        ...     implements(ICookieClientIdManager)
        ...     namespace = 'foo'
        ...     thirdparty = False
        ...     request_id = None
        ...     def setRequestId(self, request, id):
        ...         self.request_id = id
        ...
        >>> manager = DummyManager()
        >>> component.provideUtility(manager, IClientIdManager)
        >>> from zope.publisher.http import HTTPRequest
        >>> class DummyEvent (object):
        ...     request = HTTPRequest(StringIO(''), {}, None)
        >>> event = DummyEvent()

    With no cookies present, the manager should not be called:

        >>> notifyVirtualHostChanged(event)
        >>> manager.request_id is None
        True

    However, when a cookie *has* been set, the manager is called so it can
    update the cookie if need be:

        >>> event.request.response.setCookie('foo', 'bar')
        >>> notifyVirtualHostChanged(event)
        >>> manager.request_id
        'bar'

    If a server in front of Zope manages the ClientIds (Apache, Nginx), we
    don't need to take care about the cookies

        >>> manager2 = DummyManager()
        >>> manager2.thirdparty = True
        >>> event2 = DummyEvent()

    However, when a cookie *has* been set, the manager is called so it can
    update the cookie if need be:

        >>> event2.request.response.setCookie('foo2', 'bar2')
        >>> notifyVirtualHostChanged(event2)
        >>> id = manager2.request_id
        >>> id is None
        True

    Cleanup of the utility registration:

        >>> import zope.component.testing
        >>> zope.component.testing.tearDown()

    """
    # the event sends us a IHTTPApplicationRequest, but we need a
    # IHTTPRequest for the response attribute, and so does the cookie-
    # manager.
    request = IHTTPRequest(event.request, None)
    if event.request is None:
        return
    for name, manager in component.getUtilitiesFor(IClientIdManager):
        if manager and ICookieClientIdManager.providedBy(manager):
            # Third party ClientId Managers need no modification at all
            if not manager.thirdparty:
                cookie = request.response.getCookie(manager.namespace)
                if cookie:
                    manager.setRequestId(request, cookie['value'])
