fix: distrust incident certificates in Chromium and gRPC

tests/test_chromium_ca_policy.py

@@ -0,0 +1,41 @@
+"""The managed browser policy must distrust exactly the incident's eight keys."""
+
+import base64
+import hashlib
+import json
+from pathlib import Path
+import unittest
+
+from cryptography import x509
+from cryptography.hazmat.primitives import serialization
+
+
+ROOT = Path(__file__).resolve().parents[1]
+# Public incident inventory: impacted-intermediates.json, 2026-10-21.
+COMPROMISED_SPKIS = {
+    "43bffa19d6ef651451f6841e019931e96f6f2eaeff28ab4b6f1ce4576de2717b",
+    "49dd353dc2b919a3770645117d0e60c16115e7d1bc259eefe734b00ea434fe5f",
+    "5c0660a2b164910d8ff589c18e14552e9e0ec237dcefe2cb736d41a4811f81a0",
+    "63ecefee431d49523bc1136c4e72d0206a477086caf606cd5cf025686c109cf8",
+    "92c063d67e8f14db71d288e11266ffdaf69cbf115f7bab14f3bc2f68d25e0e30",
+    "e0254c7fcdc265e2f0f8a428dabb75ab4ae039b4872d62f5ee57f0877d5a8a41",
+    "ebed6475c2c2d80fcb199f3fe8dd6e6b3ce60b77eb15d4e42c3dec0c6f5b5105",
+    "ec4ffa1ad0ac88081314b7aaffef6a91f97cd57291bb5ba686c5415f5eb4f6b6",
+}
+
+
+class ChromiumCATrustTests(unittest.TestCase):
+    def test_policy_distrusts_each_compromised_key_without_adding_trust(self):
+        policy = json.loads((ROOT / "docker" / "chromium-emudhra.json").read_text())
+        self.assertEqual(set(policy), {"CADistrustedCertificates"})
+        self.assertEqual(len(policy["CADistrustedCertificates"]), 8)
+        keys = set()
+        for encoded in policy["CADistrustedCertificates"]:
+            certificate = x509.load_der_x509_certificate(base64.b64decode(encoded, validate=True))
+            self.assertTrue(certificate.extensions.get_extension_for_class(x509.BasicConstraints).value.ca)
+            self.assertNotEqual(certificate.subject, certificate.issuer)
+            public_key = certificate.public_key().public_bytes(
+                serialization.Encoding.DER, serialization.PublicFormat.SubjectPublicKeyInfo
+            )
+            keys.add(hashlib.sha256(public_key).hexdigest())
+        self.assertEqual(keys, COMPROMISED_SPKIS)