path: root/src/saml2/entity.py

import base64
from binascii import hexlify
import logging
from hashlib import sha1
import requests
from saml2.metadata import ENDPOINTS
from saml2.profile import paos, ecp
from saml2.soap import parse_soap_enveloped_saml_artifact_resolve
from saml2.soap import class_instances_from_soap_enveloped_saml_thingies
from saml2.soap import open_soap_envelope

from saml2 import samlp
from saml2 import SamlBase
from saml2 import SAMLError
from saml2 import saml
from saml2 import response as saml_response
from saml2 import BINDING_URI
from saml2 import BINDING_HTTP_ARTIFACT
from saml2 import BINDING_PAOS
from saml2 import request as saml_request
from saml2 import soap
from saml2 import element_to_extension_element
from saml2 import extension_elements_to_elements

from saml2.saml import NameID
from saml2.saml import Issuer
from saml2.saml import NAMEID_FORMAT_ENTITY
from saml2.response import LogoutResponse
from saml2.response import UnsolicitedResponse
from saml2.time_util import instant
from saml2.s_utils import sid
from saml2.s_utils import UnravelError
from saml2.s_utils import error_status_factory
from saml2.s_utils import rndstr
from saml2.s_utils import success_status_factory
from saml2.s_utils import decode_base64_and_inflate
from saml2.s_utils import UnsupportedBinding
from saml2.samlp import AuthnRequest
from saml2.samlp import AuthzDecisionQuery
from saml2.samlp import AuthnQuery
from saml2.samlp import AssertionIDRequest
from saml2.samlp import ManageNameIDRequest
from saml2.samlp import NameIDMappingRequest
from saml2.samlp import artifact_resolve_from_string
from saml2.samlp import ArtifactResolve
from saml2.samlp import ArtifactResponse
from saml2.samlp import Artifact
from saml2.samlp import LogoutRequest
from saml2.samlp import AttributeQuery
from saml2.mdstore import destinations
from saml2 import BINDING_HTTP_POST
from saml2 import BINDING_HTTP_REDIRECT
from saml2 import BINDING_SOAP
from saml2 import VERSION
from saml2 import class_name
from saml2.config import config_factory
from saml2.httpbase import HTTPBase
from saml2.sigver import security_context
from saml2.sigver import response_factory
from saml2.sigver import SigverError
from saml2.sigver import CryptoBackendXmlSec1
from saml2.sigver import make_temp
from saml2.sigver import pre_encryption_part
from saml2.sigver import pre_signature_part
from saml2.sigver import signed_instance_factory
from saml2.virtual_org import VirtualOrg

logger = logging.getLogger(__name__)

__author__ = 'rolandh'

ARTIFACT_TYPECODE = '\x00\x04'

SERVICE2MESSAGE = {
    "single_sign_on_service": AuthnRequest,
    "attribute_service": AttributeQuery,
    "authz_service": AuthzDecisionQuery,
    "assertion_id_request_service": AssertionIDRequest,
    "authn_query_service": AuthnQuery,
    "manage_name_id_service": ManageNameIDRequest,
    "name_id_mapping_service": NameIDMappingRequest,
    "artifact_resolve_service": ArtifactResolve,
    "single_logout_service": LogoutRequest
}


def create_artifact(entity_id, message_handle, endpoint_index=0):
    """
    SAML_artifact   := B64(TypeCode EndpointIndex RemainingArtifact)
    TypeCode        := Byte1Byte2
    EndpointIndex   := Byte1Byte2

    RemainingArtifact := SourceID MessageHandle
    SourceID          := 20-byte_sequence
    MessageHandle     := 20-byte_sequence

    :param entity_id:
    :param message_handle:
    :param endpoint_index:
    :return:
    """
    sourceid = sha1(entity_id)

    ter = "%s%.2x%s%s" % (ARTIFACT_TYPECODE, endpoint_index,
                          sourceid.digest(), message_handle)
    return base64.b64encode(ter)


class Entity(HTTPBase):
    def __init__(self, entity_type, config=None, config_file="",
                 virtual_organization=""):
        self.entity_type = entity_type
        self.users = None

        if config:
            self.config = config
        elif config_file:
            self.config = config_factory(entity_type, config_file)
        else:
            raise SAMLError("Missing configuration")

        for item in ["cert_file", "key_file", "ca_certs"]:
            _val = getattr(self.config, item, None)
            if not _val:
                continue

            if _val.startswith("http"):
                r = requests.request("GET", _val)
                if r.status_code == 200:
                    _, filename = make_temp(r.text, ".pem", False)
                    setattr(self.config, item, filename)
                else:
                    raise Exception(
                        "Could not fetch certificate from %s" % _val)

        HTTPBase.__init__(self, self.config.verify_ssl_cert,
                          self.config.ca_certs, self.config.key_file,
                          self.config.cert_file)

        if self.config.vorg:
            for vo in self.config.vorg.values():
                vo.sp = self

        self.metadata = self.config.metadata
        self.config.setup_logger()
        self.debug = self.config.debug
        self.seed = rndstr(32)

        self.sec = security_context(self.config)

        if virtual_organization:
            if isinstance(virtual_organization, basestring):
                self.vorg = self.config.vorg[virtual_organization]
            elif isinstance(virtual_organization, VirtualOrg):
                self.vorg = virtual_organization
        else:
            self.vorg = None

        self.artifact = {}
        if self.metadata:
            self.sourceid = self.metadata.construct_source_id()
        else:
            self.sourceid = {}

    def _issuer(self, entityid=None):
        """ Return an Issuer instance """
        if entityid:
            if isinstance(entityid, Issuer):
                return entityid
            else:
                return Issuer(text=entityid, format=NAMEID_FORMAT_ENTITY)
        else:
            return Issuer(text=self.config.entityid,
                          format=NAMEID_FORMAT_ENTITY)

    def apply_binding(self, binding, msg_str, destination="", relay_state="",
                      response=False, sign=False, **kwargs):
        """
        Construct the necessary HTTP arguments dependent on Binding

        :param binding: Which binding to use
        :param msg_str: The return message as a string (XML) if the message is
            to be signed it MUST contain the signature element.
        :param destination: Where to send the message
        :param relay_state: Relay_state if provided
        :param response: Which type of message this is
        :param kwargs: response type specific arguments
        :return: A dictionary
        """
        # unless if BINDING_HTTP_ARTIFACT
        if response:
            typ = "SAMLResponse"
        else:
            typ = "SAMLRequest"

        if binding == BINDING_HTTP_POST:
            logger.info("HTTP POST")
            info = self.use_http_form_post(msg_str, destination,
                                           relay_state, typ)
            info["url"] = destination
            info["method"] = "GET"
        elif binding == BINDING_HTTP_REDIRECT:
            logger.info("HTTP REDIRECT")
            info = self.use_http_get(msg_str, destination, relay_state, typ)
            info["url"] = str(destination)
            info["method"] = "GET"
        elif binding == BINDING_SOAP or binding == BINDING_PAOS:
            info = self.use_soap(msg_str, destination, sign=sign, **kwargs)
        elif binding == BINDING_URI:
            info = self.use_http_uri(msg_str, typ, destination)
        elif binding == BINDING_HTTP_ARTIFACT:
            if response:
                info = self.use_http_artifact(msg_str, destination, relay_state)
                info["method"] = "GET"
                info["status"] = 302
            else:
                info = self.use_http_artifact(msg_str, destination, relay_state)
        else:
            raise SAMLError("Unknown binding type: %s" % binding)

        return info

    def pick_binding(self, service, bindings=None, descr_type="", request=None,
                     entity_id=""):
        if request and not entity_id:
            entity_id = request.issuer.text.strip()

        sfunc = getattr(self.metadata, service)

        if bindings is None:
            if request and request.protocol_binding:
                bindings = [request.protocol_binding]
            else:
                bindings = self.config.preferred_binding[service]

        if not descr_type:
            if self.entity_type == "sp":
                descr_type = "idpsso"
            else:
                descr_type = "spsso"

        _url = _index = None
        if request:
            try:
                _url = getattr(request, "%s_url" % service)
            except AttributeError:
                _url = None
                try:
                    _index = getattr(request, "%s_index" % service)
                except AttributeError:
                    pass

        for binding in bindings:
            try:
                srvs = sfunc(entity_id, binding, descr_type)
                if srvs:
                    if _url:
                        for srv in srvs:
                            if srv["location"] == _url:
                                return binding, _url
                    elif _index:
                        for srv in srvs:
                            if srv["index"] == _index:
                                return binding, srv["location"]
                    else:
                        return binding, destinations(srvs)[0]
            except UnsupportedBinding:
                pass

        logger.error("Failed to find consumer URL: %s, %s, %s" % (entity_id,
                                                                  bindings,
                                                                  descr_type))
        #logger.error("Bindings: %s" % bindings)
        #logger.error("Entities: %s" % self.metadata)

        raise SAMLError("Unkown entity or unsupported bindings")

    def message_args(self, message_id=0):
        if not message_id:
            message_id = sid(self.seed)

        return {"id": message_id, "version": VERSION,
                "issue_instant": instant(), "issuer": self._issuer()}

    def response_args(self, message, bindings=None, descr_type=""):
        """

        :param message: The message to which a reply is constructed
        :param bindings: Which bindings can be used.
        :param descr_type: Type of descriptor (spssp, idpsso, )
        :return: Dictionary
        """
        info = {"in_response_to": message.id}

        if isinstance(message, AuthnRequest):
            rsrv = "assertion_consumer_service"
            descr_type = "spsso"
            info["sp_entity_id"] = message.issuer.text
            info["name_id_policy"] = message.name_id_policy
        elif isinstance(message, LogoutRequest):
            rsrv = "single_logout_service"
        elif isinstance(message, AttributeQuery):
            info["sp_entity_id"] = message.issuer.text
            rsrv = "attribute_consuming_service"
            descr_type = "spsso"
        elif isinstance(message, ManageNameIDRequest):
            rsrv = "manage_name_id_service"
        # The once below are solely SOAP so no return destination needed
        elif isinstance(message, AssertionIDRequest):
            rsrv = ""
        elif isinstance(message, ArtifactResolve):
            rsrv = ""
        elif isinstance(message, AssertionIDRequest):
            rsrv = ""
        elif isinstance(message, NameIDMappingRequest):
            rsrv = ""
        else:
            raise SAMLError("No support for this type of query")

        if bindings == [BINDING_SOAP]:
            info["binding"] = BINDING_SOAP
            info["destination"] = ""
            return info

        if rsrv:
            if not descr_type:
                if self.entity_type == "sp":
                    descr_type = "idpsso"
                else:
                    descr_type = "spsso"

            binding, destination = self.pick_binding(rsrv, bindings,
                                                     descr_type=descr_type,
                                                     request=message)
            info["binding"] = binding
            info["destination"] = destination

        return info

    @staticmethod
    def unravel(txt, binding, msgtype="response"):
        """
        Will unpack the received text. Depending on the context the original
         response may have been transformed before transmission.
        :param txt:
        :param binding:
        :param msgtype:
        :return:
        """
        #logger.debug("unravel '%s'" % txt)
        if binding not in [BINDING_HTTP_REDIRECT, BINDING_HTTP_POST,
                           BINDING_SOAP, BINDING_URI, BINDING_HTTP_ARTIFACT,
                           None]:
            raise ValueError("Don't know how to handle '%s'" % binding)
        else:
            try:
                if binding == BINDING_HTTP_REDIRECT:
                    xmlstr = decode_base64_and_inflate(txt)
                elif binding == BINDING_HTTP_POST:
                    xmlstr = base64.b64decode(txt)
                elif binding == BINDING_SOAP:
                    func = getattr(soap,
                                   "parse_soap_enveloped_saml_%s" % msgtype)
                    xmlstr = func(txt)
                elif binding == BINDING_HTTP_ARTIFACT:
                    xmlstr = base64.b64decode(txt)
                else:
                    xmlstr = txt
            except Exception:
                raise UnravelError()

        return xmlstr

    @staticmethod
    def parse_soap_message(text):
        """

        :param text: The SOAP message
        :return: A dictionary with two keys "body" and "header"
        """
        return class_instances_from_soap_enveloped_saml_thingies(text, [paos,
                                                                        ecp,
                                                                        samlp])

    @staticmethod
    def unpack_soap_message(text):
        """
        Picks out the parts of the SOAP message, body and headers apart
        :param text: The SOAP message
        :return: A dictionary with two keys "body"/"header"
        """
        return open_soap_envelope(text)

# --------------------------------------------------------------------------

    def sign(self, msg, mid=None, to_sign=None, sign_prepare=False):
        if msg.signature is None:
            msg.signature = pre_signature_part(msg.id, self.sec.my_cert, 1)

        if sign_prepare:
            return msg

        if mid is None:
            mid = msg.id

        try:
            to_sign += [(class_name(msg), mid)]
        except (AttributeError, TypeError):
            to_sign = [(class_name(msg), mid)]

        logger.info("REQUEST: %s" % msg)
        return signed_instance_factory(msg, self.sec, to_sign)

    def _message(self, request_cls, destination=None, message_id=0,
                 consent=None, extensions=None, sign=False, sign_prepare=False,
                 **kwargs):
        """
        Some parameters appear in all requests so simplify by doing
        it in one place

        :param request_cls: The specific request type
        :param destination: The recipient
        :param message_id: A message identifier
        :param consent: Whether the principal have given her consent
        :param extensions: Possible extensions
        :param sign: Whether the request should be signed or not.
        :param sign_prepare: Whether the signature should be prepared or not.
        :param kwargs: Key word arguments specific to one request type
        :return: A tuple containing the request ID and an instance of the
            request_cls
        """
        if not message_id:
            message_id = sid(self.seed)

        for key, val in self.message_args(message_id).items():
            if key not in kwargs:
                kwargs[key] = val

        req = request_cls(**kwargs)
        reqid = req.id

        if destination:
            req.destination = destination

        if consent:
            req.consent = "true"

        if extensions:
            req.extensions = extensions

        if sign:
            return reqid, self.sign(req, sign_prepare=sign_prepare)
        else:
            logger.info("REQUEST: %s" % req)
            return reqid, req

    @staticmethod
    def _filter_args(instance, extensions=None, **kwargs):
        args = {}
        if extensions is None:
            extensions = []

        allowed_attributes = instance.keys()
        for key, val in kwargs.items():
            if key in allowed_attributes:
                args[key] = val
            elif isinstance(val, SamlBase):
                # extension elements allowed ?
                extensions.append(element_to_extension_element(val))

        return args, extensions

    def _add_info(self, msg, **kwargs):
        """
        Add information to a SAML message. If the attribute is not part of
        what's defined in the SAML standard add it as an extension.

        :param msg:
        :param kwargs:
        :return:
        """

        args, extensions = self._filter_args(msg, **kwargs)
        for key, val in args.items():
            setattr(msg, key, val)

        if extensions:
            if msg.extension_elements:
                msg.extension_elements.extend(extensions)
            else:
                msg.extension_elements = extensions

    def _response(self, in_response_to, consumer_url=None, status=None,
                  issuer=None, sign=False, to_sign=None,
                  encrypt_assertion=False, encrypt_cert=None, **kwargs):
        """ Create a Response.

        :param in_response_to: The session identifier of the request
        :param consumer_url: The URL which should receive the response
        :param status: The status of the response
        :param issuer: The issuer of the response
        :param sign: Whether the response should be signed or not
        :param to_sign: If there are other parts to sign
        :param kwargs: Extra key word arguments
        :return: A Response instance
        """

        if not status:
            status = success_status_factory()

        _issuer = self._issuer(issuer)

        response = response_factory(issuer=_issuer,
                                    in_response_to=in_response_to,
                                    status=status)

        if consumer_url:
            response.destination = consumer_url

        self._add_info(response, **kwargs)

        if not sign and to_sign and not encrypt_assertion:
            return signed_instance_factory(response, self.sec, to_sign)

        if encrypt_assertion:
            sign_class = [(class_name(response), response.id)]
            if sign:
                response.signature = pre_signature_part(response.id,
                                                        self.sec.my_cert, 1)
            cbxs = CryptoBackendXmlSec1(self.config.xmlsec_binary)
            _, cert_file = make_temp("%s" % encrypt_cert, decode=False)
            response = cbxs.encrypt_assertion(response, cert_file,
                                              pre_encryption_part())
                                              # template(response.assertion.id))
            if sign:
                return signed_instance_factory(response, self.sec, sign_class)
            else:
                return response

        if sign:
            return self.sign(response, to_sign=to_sign)
        else:
            return response

    def _status_response(self, response_class, issuer, status, sign=False,
                         **kwargs):
        """ Create a StatusResponse.

        :param response_class: Which subclass of StatusResponse that should be
            used
        :param issuer: The issuer of the response message
        :param status: The return status of the response operation
        :param sign: Whether the response should be signed or not
        :param kwargs: Extra arguments to the response class
        :return: Class instance or string representation of the instance
        """

        mid = sid()

        for key in ["binding"]:
            try:
                del kwargs[key]
            except KeyError:
                pass

        if not status:
            status = success_status_factory()

        response = response_class(issuer=issuer, id=mid, version=VERSION,
                                  issue_instant=instant(),
                                  status=status, **kwargs)

        if sign:
            return self.sign(response, mid)
        else:
            return response

    # ------------------------------------------------------------------------

    @staticmethod
    def srv2typ(service):
        for typ in ["aa", "pdp", "aq"]:
            if service in ENDPOINTS[typ]:
                if typ == "aa":
                    return "attribute_authority"
                elif typ == "aq":
                    return "authn_authority"
                else:
                    return typ

    def _parse_request(self, enc_request, request_cls, service, binding):
        """Parse a Request

        :param enc_request: The request in its transport format
        :param request_cls: The type of requests I expect
        :param service:
        :param binding: Which binding that was used to transport the message
            to this entity.
        :return: A request instance
        """

        _log_info = logger.info
        _log_debug = logger.debug

        # The addresses I should receive messages like this on
        receiver_addresses = self.config.endpoint(service, binding,
                                                  self.entity_type)
        if not receiver_addresses and self.entity_type == "idp":
            for typ in ["aa", "aq", "pdp"]:
                receiver_addresses = self.config.endpoint(service, binding, typ)
                if receiver_addresses:
                    break

        _log_info("receiver addresses: %s" % receiver_addresses)
        _log_info("Binding: %s" % binding)

        try:
            timeslack = self.config.accepted_time_diff
            if not timeslack:
                timeslack = 0
        except AttributeError:
            timeslack = 0

        _request = request_cls(self.sec, receiver_addresses,
                               self.config.attribute_converters,
                               timeslack=timeslack)

        xmlstr = self.unravel(enc_request, binding, request_cls.msgtype)
        must = self.config.getattr("want_authn_requests_signed", "idp")
        only_valid_cert = self.config.getattr(
            "want_authn_requests_only_with_valid_cert", "idp")
        if only_valid_cert is None:
            only_valid_cert = False
        if only_valid_cert:
            must = True
        _request = _request.loads(xmlstr, binding, origdoc=enc_request, must=must,
                                  only_valid_cert=only_valid_cert)

        _log_debug("Loaded request")

        if _request:
            _request = _request.verify()
            _log_debug("Verified request")

        if not _request:
            return None
        else:
            return _request

    # ------------------------------------------------------------------------

    def create_error_response(self, in_response_to, destination, info,
                              sign=False, issuer=None, **kwargs):
        """ Create a error response.

        :param in_response_to: The identifier of the message this is a response
            to.
        :param destination: The intended recipient of this message
        :param info: Either an Exception instance or a 2-tuple consisting of
            error code and descriptive text
        :param sign: Whether the response should be signed or not
        :param issuer: The issuer of the response
        :param kwargs: To capture key,value pairs I don't care about
        :return: A response instance
        """
        status = error_status_factory(info)

        return self._response(in_response_to, destination, status, issuer,
                              sign)

    # ------------------------------------------------------------------------

    def create_logout_request(self, destination, issuer_entity_id,
                              subject_id=None, name_id=None,
                              reason=None, expire=None, message_id=0,
                              consent=None, extensions=None, sign=False):
        """ Constructs a LogoutRequest

        :param destination: Destination of the request
        :param issuer_entity_id: The entity ID of the IdP the request is
            target at.
        :param subject_id: The identifier of the subject
        :param name_id: A NameID instance identifying the subject
        :param reason: An indication of the reason for the logout, in the
            form of a URI reference.
        :param expire: The time at which the request expires,
            after which the recipient may discard the message.
        :param message_id: Request identifier
        :param consent: Whether the principal have given her consent
        :param extensions: Possible extensions
        :param sign: Whether the query should be signed or not.
        :return: A LogoutRequest instance
        """

        if subject_id:
            if self.entity_type == "idp":
                name_id = NameID(text=self.users.get_entityid(subject_id,
                                                              issuer_entity_id,
                                                              False))
            else:
                name_id = NameID(text=subject_id)

        if not name_id:
            raise SAMLError("Missing subject identification")

        return self._message(LogoutRequest, destination, message_id,
                             consent, extensions, sign, name_id=name_id,
                             reason=reason, not_on_or_after=expire,
                             issuer=self._issuer())

    def create_logout_response(self, request, bindings=None, status=None,
                               sign=False, issuer=None):
        """ Create a LogoutResponse.

        :param request: The request this is a response to
        :param bindings: Which bindings that can be used for the response
            If None the preferred bindings are gathered from the configuration
        :param status: The return status of the response operation
            If None the operation is regarded as a Success.
        :param issuer: The issuer of the message
        :return: HTTP args
        """

        rinfo = self.response_args(request, bindings)

        if not issuer:
            issuer = self._issuer()

        response = self._status_response(samlp.LogoutResponse, issuer, status,
                                         sign, **rinfo)

        logger.info("Response: %s" % (response,))

        return response

    def create_artifact_resolve(self, artifact, destination, sessid,
                                consent=None, extensions=None, sign=False):
        """
        Create a ArtifactResolve request

        :param artifact:
        :param destination:
        :param sessid: session id
        :param consent:
        :param extensions:
        :param sign:
        :return: The request message
        """

        artifact = Artifact(text=artifact)

        return self._message(ArtifactResolve, destination, sessid,
                             consent, extensions, sign, artifact=artifact)

    def create_artifact_response(self, request, artifact, bindings=None,
                                 status=None, sign=False, issuer=None):
        """
        Create an ArtifactResponse
        :return:
        """

        rinfo = self.response_args(request, bindings)
        response = self._status_response(ArtifactResponse, issuer, status,
                                         sign=sign, **rinfo)

        msg = element_to_extension_element(self.artifact[artifact])
        response.extension_elements = [msg]

        logger.info("Response: %s" % (response,))

        return response

    def create_manage_name_id_request(self, destination, message_id=0,
                                      consent=None, extensions=None, sign=False,
                                      name_id=None, new_id=None,
                                      encrypted_id=None, new_encrypted_id=None,
                                      terminate=None):
        """

        :param destination:
        :param message_id:
        :param consent:
        :param extensions:
        :param sign:
        :param name_id:
        :param new_id:
        :param encrypted_id:
        :param new_encrypted_id:
        :param terminate:
        :return:
        """
        kwargs = self.message_args(message_id)

        if name_id:
            kwargs["name_id"] = name_id
        elif encrypted_id:
            kwargs["encrypted_id"] = encrypted_id
        else:
            raise AttributeError(
                "One of NameID or EncryptedNameID has to be provided")

        if new_id:
            kwargs["new_id"] = new_id
        elif new_encrypted_id:
            kwargs["new_encrypted_id"] = new_encrypted_id
        elif terminate:
            kwargs["terminate"] = terminate
        else:
            raise AttributeError(
                "One of NewID, NewEncryptedNameID or Terminate has to be provided")

        return self._message(ManageNameIDRequest, destination, consent=consent,
                             extensions=extensions, sign=sign, **kwargs)

    def parse_manage_name_id_request(self, xmlstr, binding=BINDING_SOAP):
        """ Deal with a LogoutRequest

        :param xmlstr: The response as a xml string
        :param binding: What type of binding this message came through.
        :return: None if the reply doesn't contain a valid SAML LogoutResponse,
            otherwise the reponse if the logout was successful and None if it
            was not.
        """

        return self._parse_request(xmlstr, saml_request.ManageNameIDRequest,
                                   "manage_name_id_service", binding)

    def create_manage_name_id_response(self, request, bindings=None,
                                       status=None, sign=False, issuer=None,
                                       **kwargs):

        rinfo = self.response_args(request, bindings)

        response = self._status_response(samlp.ManageNameIDResponse, issuer,
                                         status, sign, **rinfo)

        logger.info("Response: %s" % (response,))

        return response

    def parse_manage_name_id_request_response(self, string,
                                              binding=BINDING_SOAP):
        return self._parse_response(string, saml_response.ManageNameIDResponse,
                                    "manage_name_id_service", binding,
                                    asynchop=False)

    # ------------------------------------------------------------------------

    def _parse_response(self, xmlstr, response_cls, service, binding,
                        outstanding_certs=None, **kwargs):
        """ Deal with a Response

        :param xmlstr: The response as a xml string
        :param response_cls: What type of response it is
        :param binding: What type of binding this message came through.
        :param outstanding_certs: Certificates that belongs to me that the
                IdP may have used to encrypt a response/assertion/..
        :param kwargs: Extra key word arguments
        :return: None if the reply doesn't contain a valid SAML Response,
            otherwise the response.
        """

        response = None

        if self.config.accepted_time_diff:
            kwargs["timeslack"] = self.config.accepted_time_diff

        if "asynchop" not in kwargs:
            if binding in [BINDING_SOAP, BINDING_PAOS]:
                kwargs["asynchop"] = False
            else:
                kwargs["asynchop"] = True

        if xmlstr:
            if "return_addrs" not in kwargs:
                if binding in [BINDING_HTTP_REDIRECT, BINDING_HTTP_POST]:
                    try:
                        # expected return address
                        kwargs["return_addrs"] = self.config.endpoint(
                            service, binding=binding)
                    except Exception:
                        logger.info("Not supposed to handle this!")
                        return None

            try:
                response = response_cls(self.sec, **kwargs)
            except Exception, exc:
                logger.info("%s" % exc)
                raise

            xmlstr = self.unravel(xmlstr, binding, response_cls.msgtype)
            origxml = xmlstr
            if not xmlstr:  # Not a valid reponse
                return None

            try:
                response = response.loads(xmlstr, False, origxml=origxml)
            except SigverError, err:
                logger.error("Signature Error: %s" % err)
                raise
            except UnsolicitedResponse:
                logger.error("Unsolicited response")
                raise
            except Exception, err:
                if "not well-formed" in "%s" % err:
                    logger.error("Not well-formed XML")
                    raise

            logger.debug("XMLSTR: %s" % xmlstr)

            if response:
                if outstanding_certs:
                    _, key_file = make_temp(
                        "%s" % outstanding_certs[
                            response.in_response_to]["key"], decode=False)
                else:
                    key_file = ""
                response = response.verify(key_file)

            if not response:
                return None

            #logger.debug(response)

        return response

    # ------------------------------------------------------------------------

    def parse_logout_request_response(self, xmlstr, binding=BINDING_SOAP):
        return self._parse_response(xmlstr, LogoutResponse,
                                    "single_logout_service", binding)

    # ------------------------------------------------------------------------

    def parse_logout_request(self, xmlstr, binding=BINDING_SOAP):
        """ Deal with a LogoutRequest

        :param xmlstr: The response as a xml string
        :param binding: What type of binding this message came through.
        :return: None if the reply doesn't contain a valid SAML LogoutResponse,
            otherwise the reponse if the logout was successful and None if it
            was not.
        """

        return self._parse_request(xmlstr, saml_request.LogoutRequest,
                                   "single_logout_service", binding)

    def use_artifact(self, message, endpoint_index=0):
        """

        :param message:
        :param endpoint_index:
        :return:
        """
        message_handle = sha1("%s" % message)
        message_handle.update(rndstr())
        mhd = message_handle.digest()
        saml_art = create_artifact(self.config.entityid, mhd, endpoint_index)
        self.artifact[saml_art] = message
        return saml_art

    def artifact2destination(self, artifact, descriptor):
        """
        Translate an artifact into a receiver location

        :param artifact: The Base64 encoded SAML artifact
        :return:
        """

        _art = base64.b64decode(artifact)

        assert _art[:2] == ARTIFACT_TYPECODE

        try:
            endpoint_index = str(int(_art[2:4]))
        except ValueError:
            endpoint_index = str(int(hexlify(_art[2:4])))
        entity = self.sourceid[_art[4:24]]

        destination = None
        for desc in entity["%s_descriptor" % descriptor]:
            for srv in desc["artifact_resolution_service"]:
                if srv["index"] == endpoint_index:
                    destination = srv["location"]
                    break

        return destination

    def artifact2message(self, artifact, descriptor):
        """

        :param artifact: The Base64 encoded SAML artifact as sent over the net
        :param descriptor: The type of entity on the other side
        :return: A SAML message (request/response)
        """

        destination = self.artifact2destination(artifact, descriptor)

        if not destination:
            raise SAMLError("Missing endpoint location")

        _sid = sid()
        mid, msg = self.create_artifact_resolve(artifact, destination, _sid)
        return self.send_using_soap(msg, destination)

    def parse_artifact_resolve(self, txt, **kwargs):
        """
        Always done over SOAP

        :param txt: The SOAP enveloped ArtifactResolve
        :param kwargs:
        :return: An ArtifactResolve instance
        """

        _resp = parse_soap_enveloped_saml_artifact_resolve(txt)
        return artifact_resolve_from_string(_resp)

    def parse_artifact_resolve_response(self, xmlstr):
        kwargs = {"entity_id": self.config.entityid,
                  "attribute_converters": self.config.attribute_converters}

        resp = self._parse_response(xmlstr, saml_response.ArtifactResponse,
                                    "artifact_resolve", BINDING_SOAP,
                                    **kwargs)
        # should just be one
        elems = extension_elements_to_elements(resp.response.extension_elements,
                                               [samlp, saml])
        return elems[0]