337 lines
12 KiB
Python
337 lines
12 KiB
Python
"""Basic SAML Processor"""
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import time
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import uuid
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from defusedxml import ElementTree
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from structlog import get_logger
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from passbook.providers.saml import exceptions, utils, xml_render
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MINUTES = 60
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HOURS = 60 * MINUTES
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def get_random_id():
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"""Random hex id"""
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# It is very important that these random IDs NOT start with a number.
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random_id = "_" + uuid.uuid4().hex
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return random_id
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def get_time_string(delta=0):
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"""Get Data formatted in SAML format"""
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return time.strftime("%Y-%m-%dT%H:%M:%SZ", time.gmtime(time.time() + delta))
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# Design note: I've tried to make this easy to sub-class and override
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# just the bits you need to override. I've made use of object properties,
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# so that your sub-classes have access to all information: use wisely.
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# Formatting note: These methods are alphabetized.
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# pylint: disable=too-many-instance-attributes
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class Processor:
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"""Base SAML 2.0 AuthnRequest to Response Processor.
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Sub-classes should provide Service Provider-specific functionality."""
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is_idp_initiated = False
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_audience = ""
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_assertion_params = None
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_assertion_xml = None
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_assertion_id = None
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_django_request = None
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_relay_state = None
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_request = None
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_request_id = None
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_request_xml = None
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_request_params = None
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_response_id = None
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_response_xml = None
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_response_params = None
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_saml_request = None
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_saml_response = None
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_session_index = None
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_subject = None
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_subject_format = "urn:oasis:names:tc:SAML:2.0:nameid-format:persistent"
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_system_params = {}
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@property
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def dotted_path(self):
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"""Return a dotted path to this class"""
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return "{module}.{class_name}".format(
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module=self.__module__, class_name=self.__class__.__name__
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)
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def __init__(self, remote):
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self.name = remote.name
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self._remote = remote
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self._logger = get_logger()
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self._system_params["ISSUER"] = self._remote.issuer
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self._logger.debug("processor configured")
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def _build_assertion(self):
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"""Builds _assertion_params."""
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self._determine_assertion_id()
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self._determine_audience()
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self._determine_subject()
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self._determine_session_index()
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self._assertion_params = {
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"ASSERTION_ID": self._assertion_id,
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"ASSERTION_SIGNATURE": "", # it's unsigned
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"AUDIENCE": self._audience,
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"AUTH_INSTANT": get_time_string(),
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"ISSUE_INSTANT": get_time_string(),
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"NOT_BEFORE": get_time_string(-1 * HOURS), # TODO: Make these settings.
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"NOT_ON_OR_AFTER": get_time_string(86400 * MINUTES),
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"SESSION_INDEX": self._session_index,
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"SESSION_NOT_ON_OR_AFTER": get_time_string(8 * HOURS),
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"SP_NAME_QUALIFIER": self._audience,
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"SUBJECT": self._subject,
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"SUBJECT_FORMAT": self._subject_format,
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}
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self._assertion_params.update(self._system_params)
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self._assertion_params.update(self._request_params)
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def _build_response(self):
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"""Builds _response_params."""
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self._determine_response_id()
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self._response_params = {
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"ASSERTION": self._assertion_xml,
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"ISSUE_INSTANT": get_time_string(),
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"RESPONSE_ID": self._response_id,
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"RESPONSE_SIGNATURE": "", # initially unsigned
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}
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self._response_params.update(self._system_params)
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self._response_params.update(self._request_params)
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def _decode_request(self):
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"""Decodes _request_xml from _saml_request."""
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self._request_xml = utils.decode_base64_and_inflate(self._saml_request).decode(
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"utf-8"
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)
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self._logger.debug("SAML request decoded")
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def _determine_assertion_id(self):
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"""Determines the _assertion_id."""
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self._assertion_id = get_random_id()
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def _determine_audience(self):
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"""Determines the _audience."""
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self._audience = self._remote.audience
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self._logger.info("determined audience")
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def _determine_response_id(self):
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"""Determines _response_id."""
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self._response_id = get_random_id()
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def _determine_session_index(self):
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self._session_index = self._django_request.session.session_key
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def _determine_subject(self):
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"""Determines _subject and _subject_type for Assertion Subject."""
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self._subject = self._django_request.user.email
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def _encode_response(self):
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"""Encodes _response_xml to _encoded_xml."""
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self._saml_response = utils.nice64(str.encode(self._response_xml))
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def _extract_saml_request(self):
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"""Retrieves the _saml_request AuthnRequest from the _django_request."""
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self._saml_request = self._django_request.session["SAMLRequest"]
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self._relay_state = self._django_request.session["RelayState"]
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def _format_assertion(self):
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"""Formats _assertion_params as _assertion_xml."""
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# https://commons.lbl.gov/display/IDMgmt/Attribute+Definitions
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self._assertion_params["ATTRIBUTES"] = [
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{
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"FriendlyName": "eduPersonPrincipalName",
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"Name": "urn:oid:1.3.6.1.4.1.5923.1.1.1.6",
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"Value": self._django_request.user.email,
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},
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{
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"FriendlyName": "cn",
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"Name": "urn:oid:2.5.4.3",
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"Value": self._django_request.user.name,
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},
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{
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"FriendlyName": "mail",
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"Name": "urn:oid:0.9.2342.19200300.100.1.3",
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"Value": self._django_request.user.email,
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},
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{
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"FriendlyName": "displayName",
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"Name": "urn:oid:2.16.840.1.113730.3.1.241",
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"Value": self._django_request.user.username,
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},
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{
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"FriendlyName": "uid",
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"Name": "urn:oid:0.9.2342.19200300.100.1.1",
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"Value": self._django_request.user.pk,
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},
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]
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from passbook.providers.saml.models import SAMLPropertyMapping
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for mapping in self._remote.property_mappings.all().select_subclasses():
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if isinstance(mapping, SAMLPropertyMapping):
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mapping_payload = {
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"Name": mapping.saml_name,
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"ValueArray": [],
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"FriendlyName": mapping.friendly_name,
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}
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for value in mapping.values:
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mapping_payload["ValueArray"].append(
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value.format(
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user=self._django_request.user, request=self._django_request
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)
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)
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self._assertion_params["ATTRIBUTES"].append(mapping_payload)
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self._assertion_xml = xml_render.get_assertion_xml(
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"saml/xml/assertions/generic.xml", self._assertion_params, signed=True
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)
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def _format_response(self):
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"""Formats _response_params as _response_xml."""
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assertion_id = self._assertion_params["ASSERTION_ID"]
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self._response_xml = xml_render.get_response_xml(
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self._response_params, saml_provider=self._remote, assertion_id=assertion_id
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)
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def _get_django_response_params(self):
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"""Returns a dictionary of parameters for the response template."""
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return {
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"acs_url": self._request_params["ACS_URL"],
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"saml_response": self._saml_response,
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"relay_state": self._relay_state,
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"autosubmit": self._remote.application.skip_authorization,
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}
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def _parse_request(self):
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"""Parses various parameters from _request_xml into _request_params."""
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# Minimal test to verify that it's not binarily encoded still:
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if not str(self._request_xml.strip()).startswith("<"):
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raise Exception(
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"RequestXML is not valid XML; "
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"it may need to be decoded or decompressed."
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)
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root = ElementTree.fromstring(self._request_xml)
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params = {}
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params["ACS_URL"] = root.attrib["AssertionConsumerServiceURL"]
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params["REQUEST_ID"] = root.attrib["ID"]
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params["DESTINATION"] = root.attrib.get("Destination", "")
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params["PROVIDER_NAME"] = root.attrib.get("ProviderName", "")
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self._request_params = params
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def _reset(self, django_request, sp_config=None):
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"""Initialize (and reset) object properties, so we don't risk carrying
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over anything from the last authentication.
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If provided, use sp_config throughout; otherwise, it will be set in
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_validate_request(). """
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self._assertion_params = sp_config
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self._assertion_xml = sp_config
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self._assertion_id = sp_config
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self._django_request = django_request
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self._relay_state = sp_config
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self._request = sp_config
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self._request_id = sp_config
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self._request_xml = sp_config
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self._request_params = sp_config
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self._response_id = sp_config
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self._response_xml = sp_config
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self._response_params = sp_config
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self._saml_request = sp_config
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self._saml_response = sp_config
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self._session_index = sp_config
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self._subject = sp_config
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self._subject_format = "urn:oasis:names:tc:SAML:2.0:nameid-format:persistent"
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self._system_params = {"ISSUER": self._remote.issuer}
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def _validate_request(self):
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"""
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Validates the SAML request against the SP configuration of this
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processor. Sub-classes should override this and raise a
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`CannotHandleAssertion` exception if the validation fails.
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Raises:
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CannotHandleAssertion: if the ACS URL specified in the SAML request
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doesn't match the one specified in the processor config.
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"""
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request_acs_url = self._request_params["ACS_URL"]
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if self._remote.acs_url != request_acs_url:
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msg = "couldn't find ACS url '{}' in SAML2IDP_REMOTES " "setting.".format(
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request_acs_url
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)
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self._logger.info(msg)
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raise exceptions.CannotHandleAssertion(msg)
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def _validate_user(self):
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"""Validates the User. Sub-classes should override this and
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throw an CannotHandleAssertion Exception if the validation does not succeed."""
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def can_handle(self, request):
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"""Returns true if this processor can handle this request."""
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self._reset(request)
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# Read the request.
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try:
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self._extract_saml_request()
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except Exception as exc:
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msg = "can't find SAML request in user session: %s" % exc
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self._logger.info(msg)
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raise exceptions.CannotHandleAssertion(msg)
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try:
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self._decode_request()
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except Exception as exc:
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msg = "can't decode SAML request: %s" % exc
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self._logger.info(msg)
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raise exceptions.CannotHandleAssertion(msg)
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try:
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self._parse_request()
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except Exception as exc:
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msg = "can't parse SAML request: %s" % exc
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self._logger.info(msg)
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raise exceptions.CannotHandleAssertion(msg)
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self._validate_request()
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return True
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def generate_response(self):
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"""Processes request and returns template variables suitable for a response."""
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# Build the assertion and response.
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# Only call can_handle if SP initiated Request, otherwise we have no Request
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if not self.is_idp_initiated:
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self.can_handle(self._django_request)
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self._validate_user()
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self._build_assertion()
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self._format_assertion()
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self._build_response()
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self._format_response()
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self._encode_response()
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# Return proper template params.
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return self._get_django_response_params()
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def init_deep_link(self, request, url):
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"""Initialize this Processor to make an IdP-initiated call to the SP's
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deep-linked URL."""
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self._reset(request)
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acs_url = self._remote.acs_url
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# NOTE: The following request params are made up. Some are blank,
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# because they comes over in the AuthnRequest, but we don't have an
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# AuthnRequest in this case:
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# - Destination: Should be this IdP's SSO endpoint URL. Not used in the response?
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# - ProviderName: According to the spec, this is optional.
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self._request_params = {
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"ACS_URL": acs_url,
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"DESTINATION": "",
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"PROVIDER_NAME": "",
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}
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self._relay_state = url
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