243 lines
9.9 KiB
Python
243 lines
9.9 KiB
Python
"""SAML Assertion generator"""
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from hashlib import sha256
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from types import GeneratorType
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from django.http import HttpRequest
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from lxml import etree # nosec
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from lxml.etree import Element, SubElement # nosec
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from signxml import XMLSigner, XMLVerifier, strip_pem_header
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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.lib.utils.time import timedelta_from_string
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from passbook.providers.saml.models import SAMLPropertyMapping, SAMLProvider
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from passbook.providers.saml.processors.request_parser import AuthNRequest
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from passbook.providers.saml.utils import get_random_id
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from passbook.providers.saml.utils.time import get_time_string
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from passbook.sources.saml.exceptions import UnsupportedNameIDFormat
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from passbook.sources.saml.processors.constants import (
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NS_MAP,
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NS_SAML_ASSERTION,
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NS_SAML_PROTOCOL,
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NS_SIGNATURE,
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SAML_NAME_ID_FORMAT_EMAIL,
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SAML_NAME_ID_FORMAT_PERSISTENT,
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SAML_NAME_ID_FORMAT_TRANSIENT,
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SAML_NAME_ID_FORMAT_X509,
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)
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LOGGER = get_logger()
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class AssertionProcessor:
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"""Generate a SAML Response from an AuthNRequest"""
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provider: SAMLProvider
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http_request: HttpRequest
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auth_n_request: AuthNRequest
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_issue_instant: str
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_assertion_id: str
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_valid_not_before: str
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_valid_not_on_or_after: str
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def __init__(
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self, provider: SAMLProvider, request: HttpRequest, auth_n_request: AuthNRequest
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):
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self.provider = provider
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self.http_request = request
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self.auth_n_request = auth_n_request
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self._issue_instant = get_time_string()
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self._assertion_id = get_random_id()
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self._valid_not_before = get_time_string(
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timedelta_from_string(self.provider.assertion_valid_not_before)
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)
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self._valid_not_on_or_after = get_time_string(
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timedelta_from_string(self.provider.assertion_valid_not_on_or_after)
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)
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def get_attributes(self) -> Element:
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"""Get AttributeStatement Element with Attributes from Property Mappings."""
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# https://commons.lbl.gov/display/IDMgmt/Attribute+Definitions
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attribute_statement = Element(f"{{{NS_SAML_ASSERTION}}}AttributeStatement")
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for mapping in self.provider.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.provider,
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)
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if value is None:
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continue
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attribute = Element(f"{{{NS_SAML_ASSERTION}}}Attribute")
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attribute.attrib["FriendlyName"] = mapping.friendly_name
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attribute.attrib["Name"] = mapping.saml_name
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if not isinstance(value, (list, GeneratorType)):
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value = [value]
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for value_item in value:
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attribute_value = SubElement(
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attribute, f"{{{NS_SAML_ASSERTION}}}AttributeValue"
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)
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if not isinstance(value_item, str):
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value_item = str(value_item)
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attribute_value.text = value_item
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attribute_statement.append(attribute)
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except PropertyMappingExpressionException as exc:
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LOGGER.warning(exc)
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continue
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return attribute_statement
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def get_issuer(self) -> Element:
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"""Get Issuer Element"""
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issuer = Element(f"{{{NS_SAML_ASSERTION}}}Issuer", nsmap=NS_MAP)
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issuer.text = self.provider.issuer
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return issuer
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def get_assertion_auth_n_statement(self) -> Element:
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"""Generate AuthnStatement with AuthnContext and ContextClassRef Elements."""
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auth_n_statement = Element(f"{{{NS_SAML_ASSERTION}}}AuthnStatement")
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auth_n_statement.attrib["AuthnInstant"] = self._valid_not_before
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auth_n_statement.attrib["SessionIndex"] = self._assertion_id
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auth_n_context = SubElement(
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auth_n_statement, f"{{{NS_SAML_ASSERTION}}}AuthnContext"
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)
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auth_n_context_class_ref = SubElement(
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auth_n_context, f"{{{NS_SAML_ASSERTION}}}AuthnContextClassRef"
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)
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auth_n_context_class_ref.text = (
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"urn:oasis:names:tc:SAML:2.0:ac:classes:PasswordProtectedTransport"
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)
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return auth_n_statement
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def get_assertion_conditions(self) -> Element:
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"""Generate Conditions with AudienceRestriction and Audience Elements."""
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conditions = Element(f"{{{NS_SAML_ASSERTION}}}Conditions")
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conditions.attrib["NotBefore"] = self._valid_not_before
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conditions.attrib["NotOnOrAfter"] = self._valid_not_on_or_after
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audience_restriction = SubElement(
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conditions, f"{{{NS_SAML_ASSERTION}}}AudienceRestriction"
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)
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audience = SubElement(audience_restriction, f"{{{NS_SAML_ASSERTION}}}Audience")
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audience.text = self.provider.audience
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return conditions
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def get_name_id(self) -> Element:
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"""Get NameID Element"""
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name_id = Element(f"{{{NS_SAML_ASSERTION}}}NameID")
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name_id.attrib["Format"] = self.auth_n_request.name_id_policy
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if name_id.attrib["Format"] == SAML_NAME_ID_FORMAT_EMAIL:
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name_id.text = self.http_request.user.email
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return name_id
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if name_id.attrib["Format"] == SAML_NAME_ID_FORMAT_PERSISTENT:
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name_id.text = self.http_request.user.username
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return name_id
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if name_id.attrib["Format"] == SAML_NAME_ID_FORMAT_X509:
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# This attribute is statically set by the LDAP source
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name_id.text = self.http_request.user.attributes.get(
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"distinguishedName", ""
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)
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return name_id
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if name_id.attrib["Format"] == SAML_NAME_ID_FORMAT_TRANSIENT:
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# This attribute is statically set by the LDAP source
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session_key: str = self.http_request.user.session.session_key
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name_id.text = sha256(session_key.encode()).hexdigest()
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return name_id
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raise UnsupportedNameIDFormat(
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f"Assertion contains NameID with unsupported format {name_id.attrib['Format']}."
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)
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def get_assertion_subject(self) -> Element:
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"""Generate Subject Element with NameID and SubjectConfirmation Objects"""
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subject = Element(f"{{{NS_SAML_ASSERTION}}}Subject")
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subject.append(self.get_name_id())
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subject_confirmation = SubElement(
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subject, f"{{{NS_SAML_ASSERTION}}}SubjectConfirmation"
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)
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subject_confirmation.attrib["Method"] = "urn:oasis:names:tc:SAML:2.0:cm:bearer"
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subject_confirmation_data = SubElement(
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subject_confirmation, f"{{{NS_SAML_ASSERTION}}}SubjectConfirmationData"
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)
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if self.auth_n_request.id:
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subject_confirmation_data.attrib["InResponseTo"] = self.auth_n_request.id
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subject_confirmation_data.attrib["NotOnOrAfter"] = self._valid_not_on_or_after
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subject_confirmation_data.attrib["Recipient"] = self.provider.acs_url
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return subject
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def get_assertion(self) -> Element:
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"""Generate Main Assertion Element"""
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assertion = Element(f"{{{NS_SAML_ASSERTION}}}Assertion", nsmap=NS_MAP)
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assertion.attrib["Version"] = "2.0"
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assertion.attrib["ID"] = self._assertion_id
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assertion.attrib["IssueInstant"] = self._issue_instant
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assertion.append(self.get_issuer())
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if self.provider.signing_kp:
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# We need a placeholder signature as SAML requires the signature to be between
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# Issuer and subject
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signature_placeholder = SubElement(
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assertion, f"{{{NS_SIGNATURE}}}Signature", nsmap=NS_MAP
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)
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signature_placeholder.attrib["Id"] = "placeholder"
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assertion.append(self.get_assertion_subject())
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assertion.append(self.get_assertion_conditions())
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assertion.append(self.get_assertion_auth_n_statement())
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assertion.append(self.get_attributes())
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return assertion
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def get_response(self) -> Element:
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"""Generate Root response element"""
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response = Element(f"{{{NS_SAML_PROTOCOL}}}Response", nsmap=NS_MAP)
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response.attrib["Version"] = "2.0"
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response.attrib["IssueInstant"] = self._issue_instant
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response.attrib["Destination"] = self.provider.acs_url
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response.attrib["ID"] = get_random_id()
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if self.auth_n_request.id:
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response.attrib["InResponseTo"] = self.auth_n_request.id
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response.append(self.get_issuer())
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status = SubElement(response, f"{{{NS_SAML_PROTOCOL}}}Status")
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status_code = SubElement(status, f"{{{NS_SAML_PROTOCOL}}}StatusCode")
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status_code.attrib["Value"] = "urn:oasis:names:tc:SAML:2.0:status:Success"
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response.append(self.get_assertion())
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return response
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def build_response(self) -> str:
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"""Build string XML Response and sign if signing is enabled."""
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root_response = self.get_response()
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if self.provider.signing_kp:
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signer = XMLSigner(
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c14n_algorithm="http://www.w3.org/2001/10/xml-exc-c14n#",
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signature_algorithm=self.provider.signature_algorithm,
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digest_algorithm=self.provider.digest_algorithm,
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)
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x509_data = strip_pem_header(
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self.provider.signing_kp.certificate_data
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).replace("\n", "")
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signed = signer.sign(
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root_response,
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key=self.provider.signing_kp.private_key,
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cert=[x509_data],
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reference_uri=self._assertion_id,
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)
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XMLVerifier().verify(signed, x509_cert=x509_data)
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return etree.tostring(signed).decode("utf-8") # nosec
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return etree.tostring(root_response).decode("utf-8") # nosec
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