241 lines
9.4 KiB
Python
241 lines
9.4 KiB
Python
"""Basic SAML Processor"""
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from typing import TYPE_CHECKING, Dict, List, Union
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from cryptography.exceptions import InvalidSignature
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from defusedxml import ElementTree
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from django.http import HttpRequest
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from signxml import XMLVerifier
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from structlog import get_logger
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from passbook.core.exceptions import PropertyMappingExpressionException
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from passbook.providers.saml.exceptions import CannotHandleAssertion
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from passbook.providers.saml.processors.types import SAMLResponseParams
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from passbook.providers.saml.utils import get_random_id
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from passbook.providers.saml.utils.encoding import decode_base64_and_inflate, nice64
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from passbook.providers.saml.utils.time import get_time_string, timedelta_from_string
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from passbook.providers.saml.utils.xml_render import get_assertion_xml, get_response_xml
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if TYPE_CHECKING:
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from passbook.providers.saml.models import SAMLProvider
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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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_remote: "SAMLProvider"
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_http_request: HttpRequest
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_assertion_xml: str
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_response_xml: str
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_saml_response: str
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_relay_state: str
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_saml_request: str
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_assertion_params: Dict[str, Union[str, List[Dict[str, str]]]]
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_request_params: Dict[str, str]
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_response_params: Dict[str, str]
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@property
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def subject_format(self) -> str:
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"""Get subject Format"""
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return "urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress"
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def __init__(self, remote: "SAMLProvider"):
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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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def _build_assertion(self):
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"""Builds _assertion_params."""
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self._assertion_params = {
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"ASSERTION_ID": get_random_id(),
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"ASSERTION_SIGNATURE": "", # it's unsigned
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"AUDIENCE": self._remote.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(
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timedelta_from_string(self._remote.assertion_valid_not_before)
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),
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"NOT_ON_OR_AFTER": get_time_string(
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timedelta_from_string(self._remote.assertion_valid_not_on_or_after)
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),
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"SESSION_INDEX": self._http_request.session.session_key,
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"SESSION_NOT_ON_OR_AFTER": get_time_string(
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timedelta_from_string(self._remote.session_valid_not_on_or_after)
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),
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"SP_NAME_QUALIFIER": self._remote.audience,
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"SUBJECT": self._http_request.user.email,
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"SUBJECT_FORMAT": self.subject_format,
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"ISSUER": self._remote.issuer,
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}
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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._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": get_random_id(),
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"RESPONSE_SIGNATURE": "", # initially unsigned
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"ISSUER": self._remote.issuer,
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}
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self._response_params.update(self._request_params)
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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 = 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 _http_request."""
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self._saml_request = self._http_request.session["SAMLRequest"]
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self._relay_state = self._http_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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attributes = []
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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 not isinstance(mapping, SAMLPropertyMapping):
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continue
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try:
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mapping: SAMLPropertyMapping
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value = mapping.evaluate(
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user=self._http_request.user,
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request=self._http_request,
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provider=self._remote,
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)
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mapping_payload = {
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"Name": mapping.saml_name,
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"FriendlyName": mapping.friendly_name,
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}
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# Normal values and arrays need different dict keys as they are handeled
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# differently in the template
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if isinstance(value, list):
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mapping_payload["ValueArray"] = value
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else:
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mapping_payload["Value"] = value
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attributes.append(mapping_payload)
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except PropertyMappingExpressionException as exc:
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self._logger.warning(exc)
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continue
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self._assertion_params["ATTRIBUTES"] = attributes
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self._assertion_xml = 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 = 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_saml_response_params(self) -> SAMLResponseParams:
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"""Returns a dictionary of parameters for the response template."""
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return SAMLResponseParams(
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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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)
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def _decode_and_parse_request(self):
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"""Parses various parameters from _request_xml into _request_params."""
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decoded_xml = decode_base64_and_inflate(self._saml_request)
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if self._remote.require_signing and self._remote.signing_kp:
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self._logger.debug("Verifying Request signature")
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try:
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XMLVerifier().verify(
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decoded_xml, x509_cert=self._remote.signing_kp.certificate_data
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)
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except InvalidSignature as exc:
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raise CannotHandleAssertion("Failed to verify signature") from exc
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root = ElementTree.fromstring(decoded_xml)
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params = {}
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params["ACS_URL"] = root.attrib.get(
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"AssertionConsumerServiceURL", self._remote.acs_url
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)
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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 _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 = (
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f"ACS URL of {request_acs_url} doesn't match Provider "
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f"ACS URL of {self._remote.acs_url}."
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)
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self._logger.info(msg)
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raise CannotHandleAssertion(msg)
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def can_handle(self, request: HttpRequest) -> bool:
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"""Returns true if this processor can handle this request."""
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self._http_request = 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 KeyError:
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raise CannotHandleAssertion("Couldn't find SAML request in user session")
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try:
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self._decode_and_parse_request()
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except Exception as exc:
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raise CannotHandleAssertion(f"Couldn't parse SAML request: {exc}") from exc
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self._validate_request()
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return True
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def generate_response(self) -> SAMLResponseParams:
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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._http_request)
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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_saml_response_params()
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def init_deep_link(self, request: HttpRequest):
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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._http_request = 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 = ""
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