providers/saml: fix invalid SAML Response when assertion and response…

… are signed (cherry-pick #12611) (#12613)

providers/saml: fix invalid SAML Response when assertion and response are signed (#12611)

* providers/saml: fix invalid SAML Response when assertion and response are signed



* validate against schema too



---------

Signed-off-by: Jens Langhammer <[email protected]>
Co-authored-by: Jens L. <[email protected]>

authentik/providers/saml/processors/assertion.py

@@ -256,7 +256,7 @@ def get_assertion(self) -> Element:
         assertion.attrib["IssueInstant"] = self._issue_instant
         assertion.append(self.get_issuer())
 
-        if self.provider.signing_kp:
+        if self.provider.signing_kp and self.provider.sign_assertion:
             sign_algorithm_transform = SIGN_ALGORITHM_TRANSFORM_MAP.get(
                 self.provider.signature_algorithm, xmlsec.constants.TransformRsaSha1
             )
@@ -295,6 +295,18 @@ def get_response(self) -> Element:
 
         response.append(self.get_issuer())
 
+        if self.provider.signing_kp and self.provider.sign_response:
+            sign_algorithm_transform = SIGN_ALGORITHM_TRANSFORM_MAP.get(
+                self.provider.signature_algorithm, xmlsec.constants.TransformRsaSha1
+            )
+            signature = xmlsec.template.create(
+                response,
+                xmlsec.constants.TransformExclC14N,
+                sign_algorithm_transform,
+                ns=xmlsec.constants.DSigNs,
+            )
+            response.append(signature)
+
         status = SubElement(response, f"{{{NS_SAML_PROTOCOL}}}Status")
         status_code = SubElement(status, f"{{{NS_SAML_PROTOCOL}}}StatusCode")
         status_code.attrib["Value"] = "urn:oasis:names:tc:SAML:2.0:status:Success"

authentik/providers/saml/tests/test_auth_n_request.py

@@ -2,21 +2,25 @@
 
 from base64 import b64encode
 
+from defusedxml.lxml import fromstring
 from django.http.request import QueryDict
 from django.test import TestCase
+from lxml import etree  # nosec
 
 from authentik.blueprints.tests import apply_blueprint
 from authentik.core.tests.utils import create_test_admin_user, create_test_cert, create_test_flow
 from authentik.crypto.models import CertificateKeyPair
 from authentik.events.models import Event, EventAction
 from authentik.lib.generators import generate_id
 from authentik.lib.tests.utils import get_request
+from authentik.lib.xml import lxml_from_string
 from authentik.providers.saml.models import SAMLPropertyMapping, SAMLProvider
 from authentik.providers.saml.processors.assertion import AssertionProcessor
 from authentik.providers.saml.processors.authn_request_parser import AuthNRequestParser
 from authentik.sources.saml.exceptions import MismatchedRequestID
 from authentik.sources.saml.models import SAMLSource
 from authentik.sources.saml.processors.constants import (
+    NS_MAP,
     SAML_BINDING_REDIRECT,
     SAML_NAME_ID_FORMAT_EMAIL,
     SAML_NAME_ID_FORMAT_UNSPECIFIED,
@@ -185,6 +189,19 @@ def test_request_signed_both(self):
         self.assertEqual(response.count(response_proc._assertion_id), 2)
         self.assertEqual(response.count(response_proc._response_id), 2)
 
+        schema = etree.XMLSchema(
+            etree.parse("schemas/saml-schema-protocol-2.0.xsd", parser=etree.XMLParser())  # nosec
+        )
+        self.assertTrue(schema.validate(lxml_from_string(response)))
+
+        response_xml = fromstring(response)
+        self.assertEqual(
+            len(response_xml.xpath("//saml:Assertion/ds:Signature", namespaces=NS_MAP)), 1
+        )
+        self.assertEqual(
+            len(response_xml.xpath("//samlp:Response/ds:Signature", namespaces=NS_MAP)), 1
+        )
+
         # Now parse the response (source)
         http_request.POST = QueryDict(mutable=True)
         http_request.POST["SAMLResponse"] = b64encode(response.encode()).decode()