enterprise/stages/mtls: improve certificate validation (#14582)

* improve certificate validation Signed-off-by: Jens Langhammer <jens@goauthentik.io> * fix fingerprint sha1 Signed-off-by: Jens Langhammer <jens@goauthentik.io> * new cert with fixed attributes Signed-off-by: Jens Langhammer <jens@goauthentik.io> * add sc amr support Signed-off-by: Jens Langhammer <jens@goauthentik.io> --------- Signed-off-by: Jens Langhammer <jens@goauthentik.io>
2025-05-20 14:15:32 +02:00
parent 73a3f29001
commit abaf8d9544
5 changed files with 80 additions and 46 deletions
--- a/authentik/enterprise/stages/mtls/stage.py
+++ b/authentik/enterprise/stages/mtls/stage.py
@ -3,7 +3,14 @@ from urllib.parse import unquote_plus

 from cryptography.exceptions import InvalidSignature
 from cryptography.hazmat.primitives import hashes
-from cryptography.x509 import Certificate, NameOID, ObjectIdentifier, load_pem_x509_certificate
+from cryptography.x509 import (
+    Certificate,
+    NameOID,
+    ObjectIdentifier,
+    UnsupportedGeneralNameType,
+    load_pem_x509_certificate,
+)
+from cryptography.x509.verification import PolicyBuilder, Store, VerificationError
 from django.utils.translation import gettext_lazy as _

 from authentik.brands.models import Brand
@ -102,15 +109,21 @@ class MTLSStageView(ChallengeStageView):
        return None

    def validate_cert(self, authorities: list[CertificateKeyPair], certs: list[Certificate]):
+        authorities_cert = [x.certificate for x in authorities]
        for _cert in certs:
-            for ca in authorities:
            try:
-                    _cert.verify_directly_issued_by(ca.certificate)
-                    return _cert
-                except (InvalidSignature, TypeError, ValueError) as exc:
-                    self.logger.warning(
-                        "Discarding cert not issued by authority", cert=_cert, authority=ca, exc=exc
+                PolicyBuilder().store(Store(authorities_cert)).build_client_verifier().verify(
+                    _cert, []
                )
+                return _cert
+            except (
+                InvalidSignature,
+                TypeError,
+                ValueError,
+                VerificationError,
+                UnsupportedGeneralNameType,
+            ) as exc:
+                self.logger.warning("Discarding invalid certificate", cert=_cert, exc=exc)
                continue
        return None

@ -141,7 +154,9 @@ class MTLSStageView(ChallengeStageView):
            "subject": cert.subject.rfc4514_string(),
            "issuer": cert.issuer.rfc4514_string(),
            "fingerprint_sha256": hexlify(cert.fingerprint(hashes.SHA256()), ":").decode("utf-8"),
-            "fingerprint_sha1": hexlify(cert.fingerprint(hashes.SHA256()), ":").decode("utf-8"),
+            "fingerprint_sha1": hexlify(cert.fingerprint(hashes.SHA1()), ":").decode(  # nosec
+                "utf-8"
+            ),
        }

    def auth_user(self, user: User, cert: Certificate):
--- a/authentik/enterprise/stages/mtls/tests/fixtures/cert_client.pem
+++ b/authentik/enterprise/stages/mtls/tests/fixtures/cert_client.pem
@ -1,30 +1,31 @@
 -----BEGIN CERTIFICATE-----
-MIIFOzCCAyOgAwIBAgIUbnIMy+Ewi5RvK7OBDxWMCk7wi08wDQYJKoZIhvcNAQEL
+MIIFWTCCA0GgAwIBAgIUDEnKCSmIXG/akySGes7bhOGrN/8wDQYJKoZIhvcNAQEL
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+nQe4JNS+u5e2VDEBWUxt8NTpu6eShDN0iIEHtxA=
 -----END CERTIFICATE-----
--- a/authentik/enterprise/stages/mtls/tests/test_stage.py
+++ b/authentik/enterprise/stages/mtls/tests/test_stage.py
@ -5,7 +5,12 @@ from django.urls import reverse
 from guardian.shortcuts import assign_perm

 from authentik.core.models import User
-from authentik.core.tests.utils import create_test_brand, create_test_flow, create_test_user
+from authentik.core.tests.utils import (
+    create_test_brand,
+    create_test_cert,
+    create_test_flow,
+    create_test_user,
+)
 from authentik.crypto.models import CertificateKeyPair
 from authentik.enterprise.stages.mtls.models import (
    CertAttributes,
@ -127,6 +132,18 @@ class MTLSStageTests(FlowTestCase):
            self.assertEqual(res.status_code, 200)
            self.assertStageResponse(res, self.flow, component="ak-stage-access-denied")

+    def test_invalid_cert(self):
+        """Test invalid certificate"""
+        cert = create_test_cert()
+        with self.assertFlowFinishes() as plan:
+            res = self.client.get(
+                reverse("authentik_api:flow-executor", kwargs={"flow_slug": self.flow.slug}),
+                headers={"X-Forwarded-TLS-Client-Cert": quote_plus(cert.certificate_data)},
+            )
+            self.assertEqual(res.status_code, 200)
+            self.assertStageResponse(res, self.flow, component="ak-stage-access-denied")
+        self.assertNotIn(PLAN_CONTEXT_PENDING_USER, plan().context)
+
    def test_auth_no_user(self):
        """Test auth with no user"""
        User.objects.filter(username="client").delete()
@ -200,14 +217,12 @@ class MTLSStageTests(FlowTestCase):
        self.assertEqual(
            plan().context[PLAN_CONTEXT_CERTIFICATE],
            {
-                "fingerprint_sha1": (
-                    "08:d4:a4:79:25:ca:c3:51:28:88:bb:30:c2:96:c3:44:5a:eb:18:07:84:ca:b4:75:27:74:61:19:8a:6a:af:fc"
-                ),
+                "fingerprint_sha1": "52:39:ca:1e:3a:1f:78:3a:9f:26:3b:c2:84:99:48:68:99:99:81:8a",
                "fingerprint_sha256": (
-                    "08:d4:a4:79:25:ca:c3:51:28:88:bb:30:c2:96:c3:44:5a:eb:18:07:84:ca:b4:75:27:74:61:19:8a:6a:af:fc"
+                    "c1:07:8b:7c:e9:02:57:87:1e:92:e5:81:83:21:bc:92:c7:47:65:e3:97:fb:05:97:6f:36:9e:b5:31:77:98:b7"
                ),
                "issuer": "OU=Self-signed,O=authentik,CN=authentik Test CA",
-                "serial_number": "630532384467334865093173111400266136879266564943",
+                "serial_number": "70153443448884702681996102271549704759327537151",
                "subject": "CN=client",
            },
        )
--- a/authentik/providers/oauth2/constants.py
+++ b/authentik/providers/oauth2/constants.py
@ -50,3 +50,4 @@ AMR_PASSWORD = "pwd"  # nosec
 AMR_MFA = "mfa"
 AMR_OTP = "otp"
 AMR_WEBAUTHN = "user"
+AMR_SMART_CARD = "sc"
--- a/authentik/providers/oauth2/id_token.py
+++ b/authentik/providers/oauth2/id_token.py
@ -16,6 +16,7 @@ from authentik.providers.oauth2.constants import (
    ACR_AUTHENTIK_DEFAULT,
    AMR_MFA,
    AMR_PASSWORD,
+    AMR_SMART_CARD,
    AMR_WEBAUTHN,
 )
 from authentik.stages.password.stage import PLAN_CONTEXT_METHOD, PLAN_CONTEXT_METHOD_ARGS
@ -139,8 +140,9 @@ class IDToken:
                amr.append(AMR_PASSWORD)
            if method == "auth_webauthn_pwl":
                amr.append(AMR_WEBAUTHN)
+            if "certificate" in method_args:
+                amr.append(AMR_SMART_CARD)
            if "mfa_devices" in method_args:
-                if len(amr) > 0:
                amr.append(AMR_MFA)
            if amr:
                id_token.amr = amr