source: fedd/federation/skeleton_access.py @ ee950c2

#!/usr/local/bin/python

import os,sys
import re
import string
import copy
import pickle
import logging
import random

from util import *
from fedid import fedid, generate_fedid
from authorizer import authorizer, abac_authorizer
from service_error import service_error
from remote_service import xmlrpc_handler, soap_handler, service_caller

import topdl

from access import access_base

# Make log messages disappear if noone configures a fedd logger.  This is
# something of an incantation, but basically it creates a logger object
# registered to fedd.access if no other module above us has.  It's an extra
# belt for the suspenders.
class nullHandler(logging.Handler):
    def emit(self, record): pass

fl = logging.getLogger("fedd.access")
fl.addHandler(nullHandler())


# The plug-in itself.
class access(access_base):
    """
    This is a demonstration plug-in for fedd.  It responds to all the
    experiment_control requests and keeps internal state.  The allocations it
    makes are simple integers associated with each valid request.  It makes use
    of the general routines in access.access_base.

    Detailed comments in the code and info at 
    """

    @staticmethod 
    def parse_access_string(s):
        """
        Parse a parenthesized string from the access db by removing the parens.
        If the string isn't in parens, we just return it with whitespace
        trimmed in either case.
        """
        st = s.strip()
        if st.startswith("(") and st.endswith(")"): return st[1:-1]
        else: return st

    def __init__(self, config=None, auth=None):
        """
        Initializer.  Pulls parameters out of the ConfigParser's access
        section, and initializes simple internal state.  This version reads a
        maximum integer to assign from the configuration file, while most other
        configuration entries  are read by the base class.  

        An access database in the cannonical format is also read as well as a
        state database that is a hash of internal state.  Routines to
        manipulate these are in the base class, but specializations appear
        here.

        The access database maps users to a simple string.
        """

        # Calling the base initializer, which reads canonical configuration
        # information and initializes canonical members.
        access_base.__init__(self, config, auth)
        # Reading the maximum integer parameter from the configuration file
        self.maxint = config.getint("access", "maxint") or 5
        # The available integers
        self.available_ints = set(range(0,self.maxint))

        # authorization information
        self.auth_type = config.get('access', 'auth_type') \
                or 'abac'
        self.auth_dir = config.get('access', 'auth_dir')
        accessdb = config.get("access", "accessdb")
        # initialize the authorization system.  We make a call to
        # read the access database that maps from authorization information
        # into local information.  The local information is parsed by the
        # translator above.
        if self.auth_type == 'abac':
            #  Load the current authorization state
            self.auth = abac_authorizer(load=self.auth_dir)
            self.access = [ ]
            if accessdb:
                try:
                    self.read_access(accessdb, self.parse_access_string)
                except EnvironmentError, e:
                    self.log.error("Cannot read %s: %s" % \
                            (config.get("access", "accessdb"), e))
                    raise e
        else:
            raise service_error(service_error.internal, 
                    "Unknown auth_type: %s" % self.auth_type)

        # Clean the state
        self.state_lock.acquire()
        for k in self.state.keys():
            # Remove any allocated integers from the available ones
            if 'integer' in self.state[k]:
                self.available_ints.discard(self.state[k]['integer'])
        self.state_lock.release()

        # These dictionaries register the plug-in's local routines for handline
        # these four messages with the server code above.  There's a version
        # for SOAP and XMLRPC, depending on which interfaces the plugin
        # supports.  There's rarely a technical reason not to support one or
        # the other - the plugin code almost never deals with the transport -
        # but if a plug-in writer wanted to disable XMLRPC, they could leave
        # the self.xmlrpc_services dictionary empty.
        self.soap_services = {\
            'RequestAccess': soap_handler("RequestAccess", self.RequestAccess),
            'ReleaseAccess': soap_handler("ReleaseAccess", self.ReleaseAccess),
            'StartSegment': soap_handler("StartSegment", self.StartSegment),
            'TerminateSegment': soap_handler("TerminateSegment", 
                self.TerminateSegment),
            }
        self.xmlrpc_services =  {\
            'RequestAccess': xmlrpc_handler('RequestAccess',
                self.RequestAccess),
            'ReleaseAccess': xmlrpc_handler('ReleaseAccess',
                self.ReleaseAccess),
            'StartSegment': xmlrpc_handler("StartSegment", self.StartSegment),
            'TerminateSegment': xmlrpc_handler('TerminateSegment',
                self.TerminateSegment),
            }

    # RequestAccess and ReleaseAccess come from the base class

    def StartSegment(self, req, fid):
        """
        Start a segment.  In this simple skeleton, this means to parse the
        request and assign an unassigned integer to it.  We store the integer
        in the persistent state.
        """
        try:
            req = req['StartSegmentRequestBody']
            # Get the request topology.  If not present, a KeyError is thrown.
            topref = req['segmentdescription']['topdldescription']
            # The fedid of the allocation we're attaching resources to
            auth_attr = req['allocID']['fedid']
        except KeyError:
            raise service_error(server_error.req, "Badly formed request")

        # String version of the allocation ID for keying
        aid = "%s" % auth_attr
        # Authorization check
        access_ok, proof = self.auth.check_attribute(fid, auth_attr, 
                with_proof=True)
        if not access_ok:
            raise service_error(service_error.access, "Access denied", 
                    proof=proof)
        else:
            # See if this is a replay of an earlier succeeded StartSegment -
            # sometimes SSL kills 'em.  If so, replay the response rather than
            # redoing the allocation.
            self.state_lock.acquire()
            retval = self.state[aid].get('started', None)
            self.state_lock.release()
            if retval:
                self.log.warning(
                        "[StartSegment] Duplicate StartSegment for %s: " \
                                % aid + \
                        "replaying response")
                return retval

        certfile = "%s/%s.pem" % (self.certdir, aid)

        # Convert the topology into topdl data structures.  Again, the
        # skeletion doesn't do anything with it, but this is how one parses a
        # topology request.
        if topref: topo = topdl.Topology(**topref)
        else:
            raise service_error(service_error.req, 
                    "Request missing segmentdescription'")

        # The attributes of the request.  Not used by this plug-in, but that's
        # where they are.
        attrs = req.get('fedAttr', [])

        # Gather connection information.  Used to send messages to those
        # waiting.
        connInfo = req.get('connection', [])

        # Do the assignment,  A more complex plug-in would interface to the
        # facility here to create and configure the allocation.
        if len(self.available_ints) > 0:
            # NB: lock the data structure during allocation
            self.state_lock.acquire()
            assigned = random.choice([ i for i in self.available_ints])
            self.available_ints.discard(assigned)
            self.state[aid]['integer'] = assigned
            self.write_state()
            self.state_lock.release()
            self.log.debug("[StartSegment] Allocated %d to %s" \
                    % (assigned, aid))
        else:
            self.log.debug("[StartSegment] No remaining resources for %s" % aid)
            raise service_error(service_error.federant, "No available integers")

        # Save the information
        self.state_lock.acquire()
        # It's possible that the StartSegment call gets retried (!). 
        # if the 'started' key is in the allocation, we'll return it rather
        # than redo the setup.  The integer allocation was saved when we made
        # it.
        self.state[aid]['started'] = { 
                'allocID': req['allocID'],
                'allocationLog': "Allocatation complete",
                'segmentdescription': { 'topdldescription': topo.to_dict() },
                'proof': proof.to_dict(),
                }
        retval = copy.deepcopy(self.state[aid]['started'])
        self.write_state()
        self.state_lock.release()

        return retval

    def TerminateSegment(self, req, fid):
        """
        Remove the resources associated with th eallocation and stop the music.
        In this example, this simply means removing the integer we allocated.
        """
        # Gather the same access information as for Start Segment
        try:
            req = req['TerminateSegmentRequestBody']
        except KeyError:
            raise service_error(server_error.req, "Badly formed request")

        auth_attr = req['allocID']['fedid']
        aid = "%s" % auth_attr

        self.log.debug("Terminate request for %s" %aid)
        # Check authorization
        access_ok, proof = self.auth.check_attribute(fid, auth_attr, 
                with_proof=True)
        if not access_ok:
            raise service_error(service_error.access, "Access denied", 
                    proof=proof)

        # Authorized: remove the integer from the allocation.  A more complex
        # plug in would interface with the underlying facility to turn off the
        # experiment here.
        self.state_lock.acquire()
        if aid in self.state:
            assigned = self.state[aid].get('integer', None)
            self.available_ints.add(assigned)
            if 'integer' in self.state[aid]:
                del self.state[aid]['integer']
            self.write_state()
        self.state_lock.release()
   
        return { 'allocID': req['allocID'], 'proof': proof.to_dict() }