Harden Kubernetes lab CA profile [skip ci]

docs/KUBERNETES_TEST_LAB.md

@@ -187,7 +187,9 @@ digest and by the existing GovOPlaN signature policy. It deploys PostgreSQL,
 Redis, single-node Garage and GreenMail on the state VM. The API, WebUI, workers
 and scheduler run in K3s from digest-pinned release images. A private lab CA
 protects both ingress and S3; backend pods receive only the CA Secret and keep
-TLS verification enabled.
+TLS verification enabled. The CA profile carries critical `CA:TRUE` and
+`keyCertSign,cRLSign` constraints. `deploy` and `update` rotate older lab CAs
+that do not satisfy that profile and reissue the ingress/S3 certificate.
 
 The final output identifies two local files below `state_directory`:
 
@@ -206,7 +208,8 @@ sudo update-ca-certificates
 ```
 
 Review mappings before adding them to `/etc/hosts`; the lifecycle does not edit
-the workstation's trust or resolver configuration.
+the workstation's trust or resolver configuration. Reinstall `pki/ca.crt` in
+the client trust store after an automatic CA rotation.
 
 ### Enroll the first administrator
 

tests/test_kubernetes_lab.py

@@ -1,9 +1,11 @@
 from __future__ import annotations
 
 from contextlib import redirect_stdout
+from dataclasses import replace
 import io
 import json
 from pathlib import Path
+import shutil
 import stat
 import subprocess
 import sys
@@ -24,6 +26,7 @@ from govoplan_lab.lifecycle import (  # noqa: E402
     LabOperationError,
     _assert_domain_owned,
     _domain_description,
+    _ensure_certificates,
     _render_kubectl_wrapper,
     destroy,
 )
@@ -234,6 +237,37 @@ class KubernetesLabTests(unittest.TestCase):
 
             self.assertEqual(0o600, stat.S_IMODE(path.stat().st_mode))
 
+    @unittest.skipUnless(shutil.which("openssl"), "openssl is required")
+    def test_generated_lab_ca_passes_strict_chain_validation(self) -> None:
+        with tempfile.TemporaryDirectory(prefix="govoplan-lab-pki-") as directory:
+            config = replace(
+                load_config(REHEARSAL_CONFIG),
+                state_directory=Path(directory),
+            )
+            _ensure_certificates(config, CommandRunner(config))
+            ca_certificate = config.state_directory / "pki" / "ca.crt"
+            server_certificate = config.state_directory / "pki" / "server.crt"
+
+            result = subprocess.run(
+                [
+                    "openssl",
+                    "verify",
+                    "-x509_strict",
+                    "-CAfile",
+                    str(ca_certificate),
+                    str(server_certificate),
+                ],
+                stdout=subprocess.PIPE,
+                stderr=subprocess.PIPE,
+                check=False,
+            )
+
+            self.assertEqual(
+                0,
+                result.returncode,
+                (result.stdout + result.stderr).decode(errors="replace"),
+            )
+
 
 if __name__ == "__main__":
     unittest.main()

tools/lab/govoplan_lab/lifecycle.py

@@ -857,6 +857,7 @@ def _ensure_certificates(config: LabConfig, runner: CommandRunner) -> None:
     ca_valid = (
         ca_key.is_file()
         and ca_cert.is_file()
+        and _ca_key_usage_is_valid(runner, ca_cert)
         and runner.run(
             [
                 "openssl",
@@ -900,6 +901,10 @@ def _ensure_certificates(config: LabConfig, runner: CommandRunner) -> None:
                 str(ca_key),
                 "-subj",
                 f"/CN={config.name} private lab CA",
+                "-addext",
+                "basicConstraints=critical,CA:TRUE",
+                "-addext",
+                "keyUsage=critical,keyCertSign,cRLSign",
                 "-out",
                 str(ca_cert),
             ],
@@ -988,6 +993,28 @@ def _ensure_certificates(config: LabConfig, runner: CommandRunner) -> None:
     write_private(config.state_directory / "hosts", render_hosts(config))
 
 
+def _ca_key_usage_is_valid(runner: CommandRunner, certificate: Path) -> bool:
+    result = runner.run(
+        [
+            "openssl",
+            "x509",
+            "-in",
+            str(certificate),
+            "-noout",
+            "-ext",
+            "keyUsage",
+        ],
+        capture=True,
+        check=False,
+    )
+    output = result.stdout.decode("utf-8", errors="replace")
+    return (
+        result.returncode == 0
+        and "Certificate Sign" in output
+        and "CRL Sign" in output
+    )
+
+
 def _deploy_state_services(
     config: LabConfig,
     runner: CommandRunner,