session.py

Mod_python is an Apache module that embeds the Python interpreter within the server. With mod_python

 # vim: set sw=4 expandtab :
 #
 # Copyright 2004 Apache Software Foundation 
 # 
 # Licensed under the Apache License, Version 2.0 (the "License"); you
 # may not use this file except in compliance with the License.  You
 # may obtain a copy of the License at
 #
 #      http://www.apache.org/licenses/LICENSE-2.0
 #
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 # implied.  See the License for the specific language governing
 # permissions and limitations under the License.
 #
 # Originally developed by Gregory Trubetskoy.
 #
 # $Id: Session.py 472053 2006-11-07 10:11:01Z grahamd $

import apache, Cookie
import _apache

import os
import stat
import time
import anydbm, whichdb
import random
import md5
import cPickle, cStringIO
import tempfile
import traceback
import re

COOKIE_NAME="pysid"
DFT_TIMEOUT=30*60 # 30 min
DFT_LOCK = True
CLEANUP_CHANCE=1000 # cleanups have 1 in CLEANUP_CHANCE chance

tempdir = tempfile.gettempdir()

def _init_rnd():
    """ initialize random number generators
    this is key in multithreaded env, see
    python docs for random """

    # query max number of threads

    
    if _apache.mpm_query(apache.AP_MPMQ_IS_THREADED):
        gennum = _apache.mpm_query(apache.AP_MPMQ_MAX_SPARE_THREADS)
    else:
        gennum = 10

    # make generators
    # this bit is from Python lib reference
    g = random.Random(time.time())
    result = [g]
    for i in range(gennum - 1):
        laststate = g.getstate()
        g = random.Random()
        g.setstate(laststate)
        g.jumpahead(1000000)
        result.append(g)

    return result

rnd_gens = _init_rnd()
rnd_iter = iter(rnd_gens)

def _get_generator():
    # get rnd_iter.next(), or start over
    # if we reached the end of it
    global rnd_iter
    try:
        return rnd_iter.next()
    except StopIteration:
        # the small potential for two threads doing this
        # seems does not warrant use of a lock
        rnd_iter = iter(rnd_gens)
        return rnd_iter.next()

def _new_sid(req):
    # Make a number based on current time, pid, remote ip
    # and two random ints, then hash with md5. This should
    # be fairly unique and very difficult to guess.
    #
    # WARNING
    # The current implementation of _new_sid returns an
    # md5 hexdigest string. To avoid a possible directory traversal
    # attack in FileSession the sid is validated using
    # the _check_sid() method and the compiled regex
    # validate_sid_re. The sid will be accepted only if len(sid) == 32
    # and it only contains the characters 0-9 and a-f. 
    #
    # If you change this implementation of _new_sid, make sure to also
    # change the validation scheme, as well as the test_Session_illegal_sid()
    # unit test in test/test.py.
    # /WARNING

    t = long(time.time()*10000)
    pid = os.getpid()
    g = _get_generator()
    rnd1 = g.randint(0, 999999999)
    rnd2 = g.randint(0, 999999999)
    ip = req.connection.remote_ip

    return md5.new("%d%d%d%d%s" % (t, pid, rnd1, rnd2, ip)).hexdigest()
    
validate_sid_re = re.compile('[0-9a-f]{32}$')

def _check_sid(sid):
    ## Check the validity of the session id
    # # The sid must be 32 characters long, and consisting of the characters
    # 0-9 and a-f.
    # 
    # The sid may be passed in a cookie from the client and as such
    # should not be trusted. This is particularly important in
    # FileSession, where the session filename is derived from the sid.
    # A sid containing '/' or '.' characters could result in a directory
    # traversal attack
    
    return not not validate_sid_re.match(sid)

class BaseSession(dict):

    def __init__(self, req, sid=None, secret=None, lock=1,
                 timeout=0):

        self._req, self._sid, self._secret = req, sid, secret
        self._lock = lock
        self._new = 1
        self._created = 0
        self._accessed = 0
        self._timeout = 0
        self._locked = 0
        self._invalid = 0
        
        dict.__init__(self)

        config = req.get_options()
        if config.has_key("mod_python.session.cookie_name"):
            session_cookie_name = config.get("mod_python.session.cookie_name", COOKIE_NAME)
        else:
            # For backwards compatability with versions
            # of mod_python prior to 3.3.
            session_cookie_name = config.get("session_cookie_name", COOKIE_NAME)

        if not self._sid:
            # check to see if cookie exists
            if secret:  
                cookie = Cookie.get_cookie(req, session_cookie_name,
                                           Class=Cookie.SignedCookie,
                                           secret=self._secret,
                                           mismatch=Cookie.Cookie.IGNORE)
            else:
                cookie = Cookie.get_cookie(req, session_cookie_name)

            if cookie:
                self._sid = cookie.value

        if self._sid:
            if not _check_sid(self._sid):
                if sid:
                    # Supplied explicitly by user of the class,
                    # raise an exception and make the user code
                    # deal with it.
                    raise ValueError("Invalid Session ID: sid=%s" % sid)
                else:
                    # Derived from the cookie sent by browser,
                    # wipe it out so it gets replaced with a
                    # correct value.
                    self._sid = None

        self.init_lock()

        if self._sid:
            # attempt to load ourselves
            self.lock()
            if self.load():
                self._new = 0

        if self._new:
            # make a new session
            if self._sid: self.unlock() # unlock old sid
            self._sid = _new_sid(self._req)
            self.lock()                 # lock new sid
            Cookie.add_cookie(self._req, self.make_cookie())
            self._created = time.time()
            if timeout:
                self._timeout = timeout
            else:
                self._timeout = DFT_TIMEOUT

        self._accessed = time.time()

        # need cleanup?
        if random.randint(1, CLEANUP_CHANCE) == 1:
            self.cleanup()

    def make_cookie(self):
        config = self._req.get_options()
        if config.has_key("mod_python.session.cookie_name"):
            session_cookie_name = config.get("mod_python.session.cookie_name", COOKIE_NAME)
        else:
            # For backwards compatability with versions
            # of mod_python prior to 3.3.
            session_cookie_name = config.get("session_cookie_name", COOKIE_NAME)

        if self._secret:
            c = Cookie.SignedCookie(session_cookie_name, self._sid,
                                    secret=self._secret)
        else:
            c = Cookie.Cookie(session_cookie_name, self._sid)

        if config.has_key("mod_python.session.application_domain"): 
            c.domain = config["mod_python.session.application_domain"] 
        if config.has_key("mod_python.session.application_path"):
            c.path = config["mod_python.session.application_path"]
        elif config.has_key("ApplicationPath"):
            # For backwards compatability with versions
            # of mod_python prior to 3.3.
            c.path = config["ApplicationPath"]
        else:
            # the path where *Handler directive was specified
            dirpath = self._req.hlist.directory 
            if dirpath:
                docroot = self._req.document_root()
                c.path = dirpath[len(docroot):]
            else:
                c.path = '/'

            # Sometimes there is no path, e.g. when Location
            # is used. When Alias or UserDir are used, then
            # the path wouldn't match the URI. In those cases
            # just default to '/'
            if not c.path or not self._req.uri.startswith(c.path):
                c.path = '/'

        return c

    def invalidate(self):
        c = self.make_cookie()
        c.expires = 0
        Cookie.add_cookie(self._req, c)
        self.delete()
        self._invalid = 1

    def load(self):
        dict = self.do_load()
        if dict == None:
            return 0

        if (time.time() - dict["_accessed"]) > dict["_timeout"]:
            return 0

        self._created  = dict["_created"]
        self._accessed = dict["_accessed"]
        self._timeout  = dict["_timeout"]
        self.update(dict["_data"])
        return 1

    def save(self):
        if not self._invalid:
            dict = {"_data"    : self.copy(), 
                    "_created" : self._created, 
                    "_accessed": self._accessed, 
                    "_timeout" : self._timeout}
            self.do_save(dict)

    def delete(self):
        self.do_delete()
        self.clear()

    def init_lock(self):
        pass
            
    def lock(self):
        if self._lock:
            _apache._global_lock(self._req.server, self._sid)
            self._locked = 1
            self._req.register_cleanup(unlock_session_cleanup, self)

    def unlock(self):
        if self._lock and self._locked:
            _apache._global_unlock(self._req.server, self._sid)
            self._locked = 0
            
    def is_new(self):
        return not not self._new

    def id(self):
        return self._sid

    def created(self):
        return self._created

    def last_accessed(self):
        return self._accessed

    def timeout(self):
        return self._timeout

    def set_timeout(self, secs):
        self._timeout = secs

    def cleanup(self):
        self.do_cleanup()

    def __del__(self):
        self.unlock()

def unlock_session_cleanup(sess):
    sess.unlock()

###########################################################################
## DbmSession

def dbm_cleanup(data):
    dbm, server = data
    _apache._global_lock(server, None, 0)
    db = anydbm.open(dbm, 'c')
    try:
        old = []
        s = db.first()
        while 1:
            key, val = s
            dict = cPickle.loads(val)
            try:
                if (time.time() - dict["_accessed"]) > dict["_timeout"]:
                    old.append(key)
            except KeyError:
                old.append(key)
            try:
                s = db.next()
            except KeyError: break

        for key in old:
            try:
                del db[key]
            except: pass
    finally:
        db.close()
        _apache._global_unlock(server, None, 0)

class DbmSession(BaseSession):

    def __init__(self, req, dbm=None, sid=0, secret=None, dbmtype=anydbm,
                 timeout=0, lock=1):

        if not dbm:
            opts = req.get_options()
            if opts.has_key("mod_python.dbm_session.database_filename"):
                dbm = opts["mod_python.dbm_session.database_filename"]
            elif opts.has_key("session_dbm"):
                # For backwards compatability with versions
                # of mod_python prior to 3.3.
                dbm = opts["session_dbm"]
            elif opts.has_key("mod_python.dbm_session.database_directory"):
                dbm = os.path.join(opts.get('mod_python.dbm_session.database_directory', tempdir), 'mp_sess.dbm')
            elif opts.has_key("mod_python.session.database_directory"):
                dbm = os.path.join(opts.get('mod_python.session.database_directory', tempdir), 'mp_sess.dbm')
            else:
                # For backwards compatability with versions
                # of mod_python prior to 3.3.
                dbm = os.path.join(opts.get('session_directory', tempdir), 'mp_sess.dbm')

        self._dbmfile = dbm
        self._dbmtype = dbmtype

        BaseSession.__init__(self, req, sid=sid, secret=secret,
                             timeout=timeout, lock=lock)

    def _set_dbm_type(self):
        module = whichdb.whichdb(self._dbmfile)
        if module:
            self._dbmtype = __import__(module)
        
    def _get_dbm(self):
        result = self._dbmtype.open(self._dbmfile, 'c', stat.S_IRUSR | stat.S_IWUSR | stat.S_IRGRP)
        if self._dbmtype is anydbm:
            self._set_dbm_type()
        return result

    def do_cleanup(self):
        data = [self._dbmfile, self._req.server]
        self._req.register_cleanup(dbm_cleanup, data)
        self._req.log_error("DbmSession: registered database cleanup.",
                            apache.APLOG_NOTICE)

    def do_load(self):
        _apache._global_lock(self._req.server, None, 0)
        dbm = self._get_dbm()
        try:
            if dbm.has_key(self._sid):
                return cPickle.loads(dbm[self._sid])
            else:
                return None
        finally:
            dbm.close()
            _apache._global_unlock(self._req.server, None, 0)

    def do_save(self, dict):
        _apache._global_lock(self._req.server, None, 0)
        dbm = self._get_dbm()
        try:
            dbm[self._sid] = cPickle.dumps(dict)
        finally:
            dbm.close()
            _apache._global_unlock(self._req.server, None, 0)