Compliant client side session cookie behavior

In summary this patch does:

* Follow the defined rules for cookies when:

  - receiving a cookie (process the attributes)

  - storing a cookie (store cookie + attributes)

  - sending a cookie

    + validate the cookie domain against the request URL

    + validate the cookie path against the request URL

    + validate the cookie expiration

    + if valid then send only the cookie, no attribtues

* Modifies how a request URL is stored during a XMLRPC
  request/response sequence.

* Refactors a bit of the request/response logic to allow for making
  the decision whether to send a session cookie instead of full
  Kerberous auth easier.

* The server now includes expiration information in the session cookie
  it sends to the client. The server always had the information
  available to prevent using an expired session cookie. Now that
  expiration timestamp is returned to the client as well and now the
  client will not send an expired session cookie back to the server.

* Adds a new module and unit test for cookies (see below)

Formerly we were always returning the session cookie no matter what
the domain or path was in the URL. We were also sending the cookie
attributes which are for the client only (used to determine if to
return a cookie). The attributes are not meant to be sent to the
server and the previous behavior was a protocol violation. We also
were not checking the cookie expiration.

Cookie library issues:

We need a library to create, parse, manipulate and format cookies both
in a client context and a server context. Core Python has two cookie
libraries, Cookie.py and cookielib.py. Why did we add a new cookie
module instead of using either of these two core Python libaries?

Cookie.py is designed for server side generation but can be used to
parse cookies on the client. It's the library we were using in the
server. However when I tried to use it in the client I discovered it
has some serious bugs. There are 7 defined cookie elements, it fails
to correctly parse 3 of the 7 elements which makes it unusable because
we depend on those elements. Since Cookie.py was designed for server
side cookie processing it's not hard to understand how fails to
correctly parse a cookie because that's a client side need. (Cookie.py
also has an awkward baroque API and is missing some useful
functionality we would have to build on top of it).

cookielib.py is designed for client side. It's fully featured and obeys
all the RFC's. It would be great to use however it's tightly coupled
with another core library, urllib2.py. The http request and response
objects must be urllib2 objects. But we don't use urllib2, rather we use
httplib because xmlrpclib uses httplib. I don't see a reason why a
cookie library should be so tightly coupled to a protocol library, but
it is and that means we can't use it (I tried to just pick some isolated
entrypoints for our use but I kept hitting interaction/dependency problems).

I decided to solve the cookie library problems by writing a minimal
cookie library that does what we need and no more than that. It is a
new module in ipapython shared by both client and server and comes
with a new unit test. The module has plenty of documentation, no need
to repeat it here.

Request URL issues:

We also had problems in rpc.py whereby information from the request
which is needed when we process the response is not available. Most
important was the requesting URL. It turns out that the way the class
and object relationships are structured it's impossible to get this
information. Someone else must have run into the same issue because
there was a routine called reconstruct_url() which attempted to
recreate the request URL from other available
information. Unfortunately reconstruct_url() was not callable from
inside the response handler. So I decided to store the information in
the thread context and when the request is received extract it from
the thread context. It's perhaps not an ideal solution but we do
similar things elsewhere so at least it's consistent. I removed the
reconstruct_url() function because the exact information is now in the
context and trying to apply heuristics to recreate the url is probably
not robust.

Ticket https://fedorahosted.org/freeipa/ticket/3022

1 files changed, 699 insertions, 0 deletions

diff --git a/ipapython/cookie.py b/ipapython/cookie.py
new file mode 100644
index 000000000..b45cb2b11
--- /dev/null
+++ b/ipapython/cookie.py
@@ -0,0 +1,699 @@
+# Authors:
+#   John Dennis <jdennis@redhat.com>
+#
+# Copyright (C) 2012  Red Hat
+# see file 'COPYING' for use and warranty information
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import re
+import time
+import datetime
+from urllib2 import urlparse
+from calendar import timegm
+from ipapython.ipa_log_manager import log_mgr
+
+'''
+Core Python has two cookie libraries, Cookie.py targeted to server
+side and cookielib.py targeted to client side. So why this module and
+not use the standard libraries?
+
+Cookie.py has some serious bugs, it cannot correctly parse the
+HttpOnly, Secure, and Expires cookie attributes (more of a client side
+need and not what it was designed for). Since we utilize those
+attributes that makes Cookie.py a non-starter. Plus it's API awkard
+and limited (we would have to build more on top of it).
+
+The Cookie.py bug reports are:
+
+http://bugs.python.org/issue3073
+http://bugs.python.org/issue16611
+
+cookielib.py has a lot of good featuress, a nice API and covers all
+the relevant RFC's as well as actual practice in the field. However
+cookielib.py is tighly integrated with urllib2 and it's not possible
+to use most of the features of cookielib without simultaneously using
+urllib2. Unfortunataely we only use httplib because of our dependency
+on xmlrpclib. Without urllib2 cookielib is a non-starter.
+
+This module is a minimal implementation of Netscape cookies which
+works equally well on either the client or server side. It's API is
+easy to use with cookie attributes as class properties which can be
+read or set easily. The Cookie object automatically converts Expires
+and Max-Age attributes into datetime objects for easy time
+comparision. Cookies in strings can easily be parsed, including
+multiple cookies in the HTTP_COOKIE envionment variable.
+
+The cookie RFC is silent on any escaping requirements for cookie
+contents as such this module does not provide any automated support
+escaping and unescapin.
+
+'''
+
+#-------------------------------------------------------------------------------
+
+# FIXME: The use of properties for the attributes timestamp, expires
+# and max_age produce a pylint error which is a false positive, this
+# is a known bug in pylint (http://www.logilab.org/ticket/89092,
+# http://www.logilab.org/ticket/89786) after the pylint bug is fixed
+# the disables for E0202 should be removed.
+
+class Cookie(object):
+    '''
+    A Cookie object has the following attributes:
+
+        key
+            The name of the cookie
+        value
+            The value of the cookie
+
+    A Cookie also supports these predefined optional attributes. If an
+    optional attribute is not set on the cookie it's value is None.
+
+        domain
+            Restrict cookie usage to this domain
+        path
+            Restrict cookie usage to this path or below
+        expires
+            Cookie is invalid after this UTC timestamp
+        max_age
+            Cookie is invalid this many seconds in the future.
+            Has precedence over the expires attribute.
+        secure
+            Cookie should only be returned on secure (i.e. SSL/TLS)
+            connections.
+        httponly
+            Cookie is intended only for HTTP communication, it can
+            never be utilized in any other context (e.g. browser
+            Javascript).
+
+    See the documentation of get_expiration() for an explanation of
+    how the expires and max-age attributes interact as well as the
+    role of the timestamp attribute. Expiration values are stored as
+    datetime objects for easy manipulation and comparision.
+
+    There are two ways to instantiate a Cookie object. Either directly
+    via the constructor or by calling the class function parse() which
+    returns a list of Cookie objects found in a string.
+
+    To create a cookie to sent to a client:
+
+    Example:
+
+    cookie = Cookie('session', session_id,
+                    domain=my_domain, path=mypath,
+                    httpOnly=True, secure=True, expires=expiration)
+    headers.append(('Set-Cookie', str(cookie)))
+
+
+    To receive cookies from a request:
+
+    Example:
+
+    cookies = Cookie.parse(response.getheader('Set-Cookie'), request_url)
+
+    '''
+
+    class Expired(ValueError):
+        pass
+
+    class URLMismatch(ValueError):
+        pass
+
+    # regexp to split fields at a semi-colon
+    field_re = re.compile(r';\s*')
+
+    # regexp to locate a key/value pair
+    kv_pair_re = re.compile(r'^\s*([a-zA-Z0-9\!\#\$\%\&\'\*\+\-\.\^\_\`\|\~]+)\s*=\s*(.*?)\s*$', re.IGNORECASE)
+
+    # Reserved attribute names, maps from lower case protocol name to
+    # object attribute name
+    attrs = {'domain'   : 'domain',
+             'path'     : 'path',
+             'max-age'  : 'max_age',
+             'expires'  : 'expires',
+             'secure'   : 'secure',
+             'httponly' : 'httponly'}
+
+    @classmethod
+    def datetime_to_time(cls, dt):
+        '''
+        Timestamps (timestamp & expires) are stored as datetime
+        objects in UTC.  It's non-obvious how to convert a naive UTC
+        datetime into a unix time value (seconds since the epoch
+        UTC). That functionality is oddly missing from the datetime
+        and time modules. This utility provides that missing
+        functionality.
+        '''
+        # Use timegm from the calendar module
+        return timegm(dt.utctimetuple())
+
+    @classmethod
+    def datetime_to_string(cls, dt=None):
+        '''
+        Given a datetime object in UTC generate RFC 1123 date string.
+        '''
+
+        # Try to verify dt is specified as UTC. If utcoffset is not
+        # available we'll just have to assume the caller is using the
+        # correct timezone.
+        utcoffset = dt.utcoffset()
+        if utcoffset is not None and utcoffset.total_seconds() != 0.0:
+            raise ValueError("timezone is not UTC")
+
+        # At this point we've validated as much as possible the
+        # timezone is UTC or GMT but we can't use the %Z timezone
+        # format specifier because the timezone in the string must be
+        # 'GMT', not something equivalent to GMT, so hardcode the GMT
+        # timezone string into the format.
+
+        return datetime.datetime.strftime(dt, '%a, %d %b %Y %H:%M:%S GMT')
+
+    @classmethod
+    def parse_datetime(cls, s):
+        '''
+        Parse a RFC 822, RFC 1123 date string, return a datetime aware object in UTC.
+        Accommodates some non-standard formats found in the wild.
+        '''
+
+        formats = ['%a, %d %b %Y %H:%M:%S',
+                   '%a, %d-%b-%Y %H:%M:%S',
+                   '%a, %d-%b-%y %H:%M:%S',
+                   '%a, %d %b %y %H:%M:%S',
+                   ]
+        s = s.strip()
+
+        # strptime does not read the time zone and generate a tzinfo
+        # object to insert in the datetime object so there is little point
+        # in specifying a %Z format, instead verify GMT is specified and
+        # generate the datetime object as if it were UTC.
+
+        if not s.endswith(' GMT'):
+            raise ValueError("http date string '%s' does not end with GMT time zone" % s)
+        s = s[:-4]
+
+        dt = None
+        for format in formats:
+            try:
+                dt = datetime.datetime(*(time.strptime(s, format)[0:6]))
+                break
+            except Exception:
+                continue
+
+        if dt is None:
+            raise ValueError("unable to parse expires datetime '%s'" % s)
+
+        return dt
+
+    @classmethod
+    def normalize_url_path(cls, url_path):
+        '''
+        Given a URL path, possibly empty, return a path consisting
+        only of directory components. The URL path must end with a
+        trailing slash for the last path element to be considered a
+        directory. Also the URL path must begin with a slash. Empty
+        input returns '/'.
+
+        Examples:
+
+        ''          -> '/'
+        '/'         -> '/'
+        'foo'       -> '/'
+        'foo/'      -> '/'
+        '/foo       -> '/'
+        '/foo/'     -> '/foo'
+        '/foo/bar'  -> '/foo'
+        '/foo/bar/' -> '/foo/bar'
+        '''
+        url_path = url_path.lower()
+
+        if not url_path:
+            return '/'
+
+        if not url_path.startswith('/'):
+            return '/'
+
+        if url_path.count('/') <= 1:
+            return'/'
+
+        return url_path[:url_path.rindex('/')]
+
+
+    @classmethod
+    def parse(cls, cookie_string, request_url=None):
+        '''
+        Given a string containing one or more cookies (the
+        HTTP_COOKIES environment variable typically contains multiple
+        cookies) parse the string and return a list of Cookie objects
+        found in the string.
+        '''
+
+        # Our list of returned cookies
+        cookies = []
+
+        # Split the input string at semi-colon boundaries, we call this a
+        # field. A field may either be a single keyword or a key=value
+        # pair.
+        fields = Cookie.field_re.split(cookie_string)
+
+        # The input string may have multiple cookies inside it. This is
+        # common when the string comes from a HTTP_COOKIE environment
+        # variable. All the cookies will be contenated, separated by a
+        # semi-colon. Semi-colons are also the separator between
+        # attributes in a cookie.
+        #
+        # To distinguish between two adjacent cookies in a string we
+        # have to locate the key=value pair at the start of a
+        # cookie. Unfortunately cookies have attributes that also look
+        # like key/value pairs, the only way to distinguish a cookie
+        # attribute from a cookie is the fact the attribute names are
+        # reserved. A cookie attribute may either be a key/value pair
+        # or a single key (e.g. HttpOnly). As we scan the cookie we
+        # first identify the key=value (cookie name, cookie
+        # value). Then we continue scanning, if a bare key or
+        # key/value pair follows and is a known reserved keyword than
+        # that's an attribute belonging to the current cookie. As soon
+        # as we see a key/value pair whose key is not reserved we know
+        # we've found a new cookie. Bare keys (no value) can never
+        # start a new cookie.
+
+        # Iterate over all the fields and emit a new cookie whenever the
+        # next field is not a known attribute.
+        cookie = None
+        for field in fields:
+            match = Cookie.kv_pair_re.search(field)
+            if match:
+                key = match.group(1)
+                value = match.group(2)
+                # Double quoted value?
+                if value[0] == '"':
+                    if value[-1] == '"':
+                        value = value[1:-1]
+                    else:
+                        raise ValueError("unterminated quote in '%s'" % value)
+                kv_pair = True
+            else:
+                key = field
+                value = True        # True because bare keys are boolean flags
+                kv_pair = False
+
+            is_attribute = key.lower() in Cookie.attrs
+
+            # First cookie found, create new cookie object
+            if cookie is None and kv_pair and not is_attribute:
+                cookie = Cookie(key, value)
+
+            # If start of new cookie then flush previous cookie and create
+            # a new one (it's a new cookie because it's a key/value pair
+            # whose key is not a reserved keyword).
+            elif cookie and kv_pair and not is_attribute:
+                if request_url is not None:
+                    cookie.normalize(request_url)
+                cookies.append(cookie)
+                cookie = Cookie(key, value)
+
+            # If it's a reserved keyword add that as an attribute to the
+            # current cookie being scanned.
+            elif cookie and is_attribute:
+                cookie.__set_attr(key, value)
+            # If we've found a non-empty single token that's not a
+            # reserved keyword it's an error. An empty token can occur
+            # when there are two adjacent semi-colons (i.e. "; ;").
+            # We don't consider empty tokens an error.
+            elif key:
+                raise ValueError("unknown cookie token '%s'" % key)
+
+        # Flush out final cookie
+        if cookie:
+            if request_url is not None:
+                cookie.normalize(request_url)
+            cookies.append(cookie)
+
+        return cookies
+
+    @classmethod
+    def get_named_cookie_from_string(cls, cookie_string, cookie_name, request_url=None):
+        '''
+        A cookie string may contain multiple cookies, parse the cookie
+        string and return the last cookie in the string matching the
+        cookie name or None if not found.
+
+        This is basically a utility wrapper around the parse() class
+        method which iterates over what parse() returns looking for
+        the specific cookie.
+
+        When cookie_name appears more than once the last instance is
+        returned rather than the first because the ordering sequence
+        makes the last instance the current value.
+        '''
+
+        target_cookie = None
+
+        cookies = cls.parse(cookie_string)
+        for cookie in cookies:
+            if cookie.key == cookie_name:
+                target_cookie = cookie
+
+        if request_url is not None:
+            target_cookie.normalize(request_url)
+        return target_cookie
+
+
+    def __init__(self, key, value, domain=None, path=None, max_age=None, expires=None,
+                 secure=None, httponly=None, timestamp=None):
+
+        log_mgr.get_logger(self, True)
+
+        self.key = key
+        self.value = value
+        self.domain = domain
+        self.path = path
+        self.max_age = max_age
+        self.expires = expires
+        self.secure = secure
+        self.httponly = httponly
+        self.timestamp = timestamp
+
+    @property
+    def timestamp(self):        #pylint: disable=E0202
+        '''
+        The UTC moment at which cookie was received for purposes of
+        computing the expiration given a Max-Age offset. The
+        expiration will be timestamp + max_age. The timestamp value
+        will aways be a datetime object.
+
+        By default the timestamp will be the moment the Cookie object
+        is created as this often corresponds to the moment the cookie
+        is received (the intent of the Max-Age attribute). But becuase
+        it's sometimes desirable to force a specific moment for
+        purposes of computing the expiration from the Max-Age the
+        Cookie timestamp can be updated.
+
+        Setting a value of None causes the timestamp to be set to the
+        current UTC time (now). You may also assign with a numeric
+        UNIX timestamp (seconds since the epoch UTC) or a formatted time
+        sting, in all cases the value will be converted to a datetime
+        object.
+        '''
+        return self._timestamp
+
+    @timestamp.setter
+    def timestamp(self, value): #pylint: disable=E0202
+        if value is None:
+            self._timestamp = None
+        elif isinstance(value, datetime.datetime):
+            self._timestamp = value
+        elif isinstance(value, (int, long, float)):
+            self._timestamp = datetime.datetime.utcfromtimestamp(value)
+        elif isinstance(value, basestring):
+            self._timestamp = Cookie.parse_datetime(value)
+        else:
+            raise TypeError('value must be datetime, int, long, float, basestring or None, not %s' % \
+                            value.__class__.__name__)
+
+    @property
+    def expires(self):          #pylint: disable=E0202
+        '''
+        The expiration timestamp (in UTC) as a datetime object for the
+        cookie, or None if not set.
+
+        You may assign a value of None, a datetime object, a numeric
+        UNIX timestamp (seconds since the epoch UTC) or formatted time
+        string (the latter two will be converted to a datetime object.
+        '''
+        return self._expires
+
+    @expires.setter
+    def expires(self, value):   #pylint: disable=E0202
+        if value is None:
+            self._expires = None
+        elif isinstance(value, datetime.datetime):
+            self._expires = value
+        elif isinstance(value, (int, long, float)):
+            self._expires = datetime.datetime.utcfromtimestamp(value)
+        elif isinstance(value, basestring):
+            self._expires = Cookie.parse_datetime(value)
+        else:
+            raise TypeError('value must be datetime, int, long, float, basestring or None, not %s' % \
+                            value.__class__.__name__)
+
+    @property
+    def max_age(self):          #pylint: disable=E0202
+        '''
+        The lifetime duration of the cookie. Computed as an offset
+        from the cookie's timestamp.
+        '''
+        return self._max_age
+
+    @max_age.setter
+    def max_age(self, value):   #pylint: disable=E0202
+        if value is None:
+            self._max_age = None
+        else:
+            try:
+                self._max_age = int(value)
+            except Exception:
+                raise ValueError("Max-Age value '%s' not convertable to integer" % value)
+
+    def __set_attr(self, name, value):
+        '''
+        Sets one of the predefined cookie attributes.
+        '''
+        attr_name = Cookie.attrs.get(name.lower(), None)
+        if attr_name is None:
+            raise ValueError("unknown cookie attribute '%s'" % name)
+        setattr(self, attr_name, value)
+
+    def __str__(self):
+        components = []
+
+        components.append("%s=%s" % (self.key, self.value))
+
+        if self.domain is not None:
+            components.append("Domain=%s" % self.domain)
+
+        if self.path is not None:
+            components.append("Path=%s" % self.path)
+
+        if self.max_age is not None:
+            components.append("Max-Age=%s" % self.max_age)
+
+        if self.expires is not None:
+            components.append("Expires=%s" % Cookie.datetime_to_string(self.expires))
+
+        if self.secure:
+            components.append("Secure")
+
+        if self.httponly:
+            components.append("HttpOnly")
+
+        return '; '.join(components)
+
+    def get_expiration(self):
+        '''
+        Return the effective expiration of the cookie as a datetime
+        object or None if no expiration is defined. Expiration may be
+        defined either by the "Expires" timestamp attribute or the
+        "Max-Age" duration attribute. If both are set "Max-Age" takes
+        precedence. If neither is set the cookie has no expiration and
+        None will be returned.
+
+        "Max-Age" specifies the number of seconds in the future from when the
+        cookie is received until it expires. Effectively it means
+        adding "Max-Age" seconds to a timestamp to arrive at an
+        expiration. By default the timestamp used to mark the arrival
+        of the cookie is set to the moment the cookie object is
+        created. However sometimes it is desirable to adjust the
+        received timestamp to something other than the moment of
+        object creation, therefore you can explicitly set the arrival
+        timestamp used in the "Max-Age" calculation.
+
+        "Expires" specifies an explicit timestamp.
+
+        If "Max-Age" is set a datetime object is returned which is the
+        sum of the arrival timestamp and "Max-Age".
+
+        If "Expires" is set a datetime object is returned matching the
+        timestamp specified as the "Expires" value.
+
+        If neither is set None is returned.
+        '''
+
+        if self.max_age is not None:
+            return self.timestamp + datetime.timedelta(seconds=self.max_age)
+
+        if self.expires is not None:
+            return self.expires
+
+        return None
+
+    def normalize_expiration(self):
+        '''
+        An expiration may be specified either with an explicit
+        timestamp in the "Expires" attribute or via an offset
+        specified witht the "Max-Age" attribute. The "Max-Age"
+        attribute has precedence over "Expires" if both are
+        specified.
+
+        This method normalizes the expiration of the cookie such that
+        only a "Expires" attribute remains after consideration of the
+        "Max-Age" attribute. This is useful when storing the cookie
+        for future reference.
+        '''
+
+        self.expires = self.get_expiration()
+        self.max_age = None
+        return self.expires
+
+    def set_defaults_from_url(self, url):
+        '''
+        If cookie domain and path attributes are not specified then
+        they assume defaults from the request url the cookie was
+        received from.
+        '''
+
+        scheme, domain, path, params, query, fragment = urlparse.urlparse(url)
+
+        if self.domain is None:
+            self.domain = domain.lower()
+
+        if self.path is None:
+            self.path = self.normalize_url_path(path)
+
+
+    def normalize(self, url):
+        '''
+        Missing cookie attributes will receive default values derived
+        from the request URL. The expiration value is normalized.
+        '''
+
+        self.set_defaults_from_url(url)
+        self.normalize_expiration()
+
+    def http_cookie(self):
+        '''
+        Return a string with just the key and value (no attributes).
+        This is appropriate for including in a HTTP Cookie header.
+        '''
+        return '%s=%s;' % (self.key, self.value)
+
+    def http_return_ok(self, url):
+        '''
+        Tests to see if a cookie should be returned when a request is
+        sent to a specific URL.
+
+        * The request url's host must match the cookie's doman
+          otherwise raises Cookie.URLMismatch.
+
+        * The path in the request url must contain the cookie's path
+          otherwise raises Cookie.URLMismatch.
+
+        * If the cookie defines an expiration date then the current
+          time must be less or equal to the cookie's expiration
+          timestamp. Will raise Cookie.Expired if a defined expiration
+          is not valid.
+
+        If the test fails Cookie.Expired or Cookie.URLMismatch will be raised,
+        otherwise True is returned.
+
+        '''
+
+        def domain_valid(url_domain, cookie_domain):
+            '''
+            Compute domain component and perform test per
+            RFC 6265, Section 5.1.3. "Domain Matching"
+            '''
+            # FIXME: At the moment we can't import from ipalib at the
+            # module level because of a dependency loop (cycle) in the
+            # import. Our module layout needs to be refactored.
+            from ipalib.util import validate_domain_name
+            try:
+                validate_domain_name(url_domain)
+            except Exception, e:
+                return False
+
+            if cookie_domain is None:
+                return True
+
+            url_domain = url_domain.lower()
+            cookie_domain = cookie_domain.lower()
+
+            if url_domain == cookie_domain:
+                return True
+
+            if url_domain.endswith(cookie_domain):
+                if cookie_domain.startswith('.'):
+                    return True
+
+            return False
+
+        def path_valid(url_path, cookie_path):
+            '''
+            Compute path component and perform test per
+            RFC 6265, Section 5.1.4. "Paths and Path-Match"
+            '''
+
+            if cookie_path is None:
+                return True
+
+            cookie_path = cookie_path.lower()
+            request_path = self.normalize_url_path(url_path)
+
+            if cookie_path == request_path:
+                return True
+
+            if cookie_path and request_path.startswith(cookie_path):
+                if cookie_path.endswith('/'):
+                    return True
+
+                tail = request_path[len(cookie_path):]
+                if tail.startswith('/'):
+                    return True
+
+            return False
+
+        cookie_name = self.key
+
+        url_scheme, url_domain, url_path, url_params, url_query, url_fragment = urlparse.urlparse(url)
+
+        cookie_expiration = self.get_expiration()
+        if cookie_expiration is not None:
+            now = datetime.datetime.utcnow()
+            if cookie_expiration < now:
+                raise Cookie.Expired("cookie named '%s'; expired at %s'" % \
+                                     (cookie_name,
+                                      self.datetime_to_string(cookie_expiration)))
+
+        if not domain_valid(url_domain, self.domain):
+            raise Cookie.URLMismatch("cookie named '%s'; it's domain '%s' does not match URL domain '%s'" % \
+                                  (cookie_name, self.domain, url_domain))
+
+        if not path_valid(url_path, self.path):
+            raise Cookie.URLMismatch("cookie named '%s'; it's path '%s' does not contain the URL path '%s'" % \
+                                  (cookie_name, self.path, url_path))
+
+        url_scheme = url_scheme.lower()
+
+        if self.httponly:
+            if url_scheme not in ('http', 'https'):
+                raise Cookie.URLMismatch("cookie named '%s'; is restricted to HTTP but it's URL scheme is '%s'" % \
+                                         (cookie_name, url_scheme))
+
+        if self.secure:
+            if url_scheme not in ('https',):
+                raise Cookie.URLMismatch("cookie named '%s'; is restricted to secure transport but it's URL scheme is '%s'" % \
+                                         (cookie_name, url_scheme))
+
+
+        return True