all: Use utils.timestamp2datetime .

datetime.datetime.fromtimestamp applies timezones, which is unintended.
Fixes a time drift on revoked certificates.

caucase/ca.py

@@ -760,9 +760,7 @@ class CertificateAuthority(object):
         revoked_certificates=[
           x509.RevokedCertificateBuilder(
             serial_number=x['serial'],
-            revocation_date=datetime.datetime.fromtimestamp(
-              x['revocation_date'],
-            ),
+            revocation_date=utils.timestamp2datetime(x['revocation_date']),
           ).build(_cryptography_backend)
           for x in self._storage.getRevocationList()
         ],

caucase/http.py

@@ -809,7 +809,7 @@ def main(
     backup_period = datetime.timedelta(args.backup_period, 0)
     try:
       next_backup = max(
-        datetime.datetime.utcfromtimestamp(os.stat(x).st_ctime)
+        utils.timestamp2datetime(os.stat(x).st_ctime)
         for x in glob.iglob(
           os.path.join(args.backup_directory, '*' + BACKUP_SUFFIX),
         )

caucase/utils.py

@@ -553,6 +553,12 @@ def datetime2timestamp(value):
   """
   return int((value - EPOCH).total_seconds())
 
+def timestamp2datetime(value):
+  """
+  Convert given unix timestamp into a datetime.
+  """
+  return EPOCH + datetime.timedelta(0, value)
+
 def timestamp2IMFfixdate(value):
   """
   Convert a timestamp into an IMF-fixdate string following RFC7231.