fix: distrust incident certificates in Chromium and gRPC

tests/test_ca_trust.py

@@ -7,6 +7,7 @@ import os
 from pathlib import Path
 import ssl
 import tempfile
+from types import SimpleNamespace
 import unittest
 from unittest.mock import patch
 
@@ -107,6 +108,41 @@ class CATrustTests(unittest.TestCase):
             self.assertEqual(result, 1)
             self.assertIn("AAA Certificate Services", errors.getvalue())
 
+    def test_grpc_bundled_roots_are_checked_without_an_override(self):
+        with tempfile.TemporaryDirectory() as temporary:
+            package = Path(temporary) / "grpc"
+            bundle = package / "_cython" / "_credentials" / "roots.pem"
+            bundle.parent.mkdir(parents=True)
+            bundle.write_bytes((self.fixtures / "emsign-g3.pem").read_bytes())
+            errors = io.StringIO()
+            with patch.dict(os.environ, {"GRPC_DEFAULT_SSL_ROOTS_FILE_PATH": ""}), patch.object(
+                checker.importlib.util, "find_spec", return_value=SimpleNamespace(origin=str(package / "__init__.py"))
+            ), contextlib.redirect_stderr(errors):
+                self.assertEqual(checker.main(["--grpc"]), 1)
+            self.assertIn("emSign ECC Root CA - G3", errors.getvalue())
+
+    def test_grpc_explicit_clean_store_replaces_the_independent_bundle(self):
+        with patch.dict(os.environ, {"GRPC_DEFAULT_SSL_ROOTS_FILE_PATH": str(self.fixtures / "emsign-g1.pem")}), patch.object(
+            checker.importlib.util, "find_spec", side_effect=AssertionError("must use the explicit store")
+        ), contextlib.redirect_stdout(io.StringIO()):
+            self.assertEqual(checker.main(["--grpc"]), 0)
+
+    def test_grpc_invalid_override_does_not_fall_back_silently(self):
+        with tempfile.TemporaryDirectory() as temporary:
+            for name, content in (("empty.pem", ""), ("malformed.pem", "not a certificate"), ("affected.pem", PUBLIC_CERTIFICATES["aaa.pem"])):
+                bundle = Path(temporary) / name
+                bundle.write_text(content)
+                with self.subTest(name=name), patch.dict(os.environ, {"GRPC_DEFAULT_SSL_ROOTS_FILE_PATH": str(bundle)}), contextlib.redirect_stderr(io.StringIO()):
+                    self.assertEqual(checker.main(["--grpc"]), 1)
+            with patch.dict(os.environ, {"GRPC_DEFAULT_SSL_ROOTS_FILE_PATH": str(Path(temporary) / "missing.pem")}), contextlib.redirect_stderr(io.StringIO()):
+                self.assertEqual(checker.main(["--grpc"]), 1)
+
+    def test_grpc_check_reports_a_missing_installation(self):
+        with patch.dict(os.environ, {"GRPC_DEFAULT_SSL_ROOTS_FILE_PATH": ""}), patch.object(
+            checker.importlib.util, "find_spec", return_value=None
+        ), contextlib.redirect_stderr(io.StringIO()):
+            self.assertEqual(checker.main(["--grpc"]), 1)
+
 
 # Public Mozilla CA certificates; provenance: tests/fixtures/ca-trust/README.md.
 PUBLIC_CERTIFICATES = {

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)