Use timezone aware comparisons for cert validity (#50)

* Use timezone aware comparisons for cert validity

* Ran format

* Switch to backward compatible timezone.utc

* make format

---------

Co-authored-by: Alex Cottner <acottner@mozilla.com>

Author: leplatrem

src/autograph_utils/__init__.py

@@ -332,15 +332,15 @@ async def verify_x5u(self, url):
 
         now = _now()
         for cert in certs:
-            if cert.not_valid_before > cert.not_valid_after:
+            if cert.not_valid_before_utc > cert.not_valid_after_utc:
                 raise BadCertificate(
-                    f"not_before ({cert.not_valid_before}) after "
-                    f"not_after ({cert.not_valid_after})"
+                    f"not_before ({cert.not_valid_before_utc}) after "
+                    f"not_after ({cert.not_valid_after_utc})"
                 )
-            if now < cert.not_valid_before:
-                raise CertificateNotYetValid(cert.not_valid_before)
-            if now > cert.not_valid_after:
-                raise CertificateExpired(cert.not_valid_after)
+            if now < cert.not_valid_before_utc:
+                raise CertificateNotYetValid(cert.not_valid_before_utc)
+            if now > cert.not_valid_after_utc:
+                raise CertificateExpired(cert.not_valid_after_utc)
 
         # Verify chain of trust.
         chain = certs[::-1]

tests/test_autograph_utils.py

@@ -5,6 +5,7 @@
 
 import datetime
 import os.path
+from datetime import timezone
 from unittest import mock
 
 import aiohttp
@@ -89,7 +90,7 @@ def cache():
 def now_fixed():
     with mock.patch("autograph_utils._now") as m:
         # A common static time used in a lot of tests.
-        m.return_value = datetime.datetime(2019, 10, 23, 16, 16)
+        m.return_value = datetime.datetime(2019, 10, 23, 16, 16, tzinfo=timezone.utc)
         # Yield the mock so someone can change the time if they want
         yield m
 
@@ -107,8 +108,8 @@ def mock_cert(real_cert):
     """
 
     mock_cert = mock.MagicMock(wraps=real_cert)
-    mock_cert.not_valid_before = real_cert.not_valid_before
-    mock_cert.not_valid_after = real_cert.not_valid_after
+    mock_cert.not_valid_before_utc = real_cert.not_valid_before_utc
+    mock_cert.not_valid_after_utc = real_cert.not_valid_after_utc
     mock_cert.signature = real_cert.signature
     mock_cert.tbs_certificate_bytes = real_cert.tbs_certificate_bytes
     mock_cert.signature_hash_algorithm = real_cert.signature_hash_algorithm
@@ -180,21 +181,21 @@ async def test_verify_signature_bad_numbers(aiohttp_session, mock_with_x5u, cach
 
 
 async def test_verify_x5u_expired(aiohttp_session, mock_with_x5u, cache, now_fixed):
-    now_fixed.return_value = datetime.datetime(2022, 10, 23, 16, 16, 16)
+    now_fixed.return_value = datetime.datetime(2022, 10, 23, 16, 16, 16, tzinfo=timezone.utc)
     s = SignatureVerifier(aiohttp_session, cache, DEV_ROOT_HASH)
     with pytest.raises(autograph_utils.CertificateExpired) as excinfo:
         await s.verify(SIGNED_DATA, SAMPLE_SIGNATURE, FAKE_CERT_URL)
 
-    assert excinfo.value.detail == "Certificate expired on 2021-07-05 21:57:15"
+    assert excinfo.value.detail == "Certificate expired on 2021-07-05 21:57:15+00:00"
 
 
 async def test_verify_x5u_too_soon(aiohttp_session, mock_with_x5u, cache, now_fixed):
-    now_fixed.return_value = datetime.datetime(2010, 10, 23, 16, 16, 16)
+    now_fixed.return_value = datetime.datetime(2010, 10, 23, 16, 16, 16, tzinfo=timezone.utc)
     s = SignatureVerifier(aiohttp_session, cache, DEV_ROOT_HASH)
     with pytest.raises(autograph_utils.CertificateNotYetValid) as excinfo:
         await s.verify(SIGNED_DATA, SAMPLE_SIGNATURE, FAKE_CERT_URL)
 
-    assert excinfo.value.detail == "Certificate is not valid until 2016-07-06 21:57:15"
+    assert excinfo.value.detail == "Certificate is not valid until 2016-07-06 21:57:15+00:00"
 
 
 async def test_verify_x5u_screwy_dates(aiohttp_session, mock_with_x5u, cache, now_fixed):
@@ -204,16 +205,16 @@ async def test_verify_x5u_screwy_dates(aiohttp_session, mock_with_x5u, cache, no
         CERT_LIST[0], backend=default_backend()
     )
     bad_cert = mock_cert(leaf_cert)
-    bad_cert.not_valid_before = leaf_cert.not_valid_after
-    bad_cert.not_valid_after = leaf_cert.not_valid_before
+    bad_cert.not_valid_before_utc = leaf_cert.not_valid_after_utc
+    bad_cert.not_valid_after_utc = leaf_cert.not_valid_before_utc
     with mock.patch("autograph_utils.x509.load_pem_x509_certificate") as x509:
         x509.return_value = bad_cert
         with pytest.raises(autograph_utils.BadCertificate) as excinfo:
             await s.verify(SIGNED_DATA, SAMPLE_SIGNATURE, FAKE_CERT_URL)
 
     assert excinfo.value.detail == (
-        "Bad certificate: not_before (2021-07-05 21:57:15) "
-        "after not_after (2016-07-06 21:57:15)"
+        "Bad certificate: not_before (2021-07-05 21:57:15+00:00) "
+        "after not_after (2016-07-06 21:57:15+00:00)"
     )