DeprecationWarning: `datetime.datetime.utcnow()` is deprecated in Python 3.12+

[libre-man]

When running python-saml on Python 3.12, a DeprecationWarning is triggered during the authentication process. This occurs because datetime.datetime.utcnow() has been deprecated in favor of timezone-aware objects.

While this is currently only a warning, it is scheduled for removal in future Python versions and litters the logs of applications using this toolkit on modern Python environments.

Traceback / Warning:

  File ".../onelogin/saml2/auth.py", line 419, in login
    authn_request = self.authn_request_class(self._settings, force_authn, is_passive, set_nameid_policy, name_id_value_req)
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".../onelogin/saml2/authn_request.py", line 49, in __init__
    issue_instant = OneLogin_Saml2_Utils.parse_time_to_SAML(OneLogin_Saml2_Utils.now())
                                                           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".../onelogin/saml2/utils.py", line 428, in now
    return calendar.timegm(datetime.utcnow().utctimetuple())
                           ^^^^^^^^^^^^^^^^^
DeprecationWarning: datetime.datetime.utcnow() is deprecated and scheduled for removal in a future version. 
Use timezone-aware objects to represent datetimes in UTC: datetime.datetime.now(datetime.UTC).

Affected Code:

The issue is located in the now() static method of the OneLogin_Saml2_Utils class:

python-saml/src/onelogin/saml2/utils.py

Line 486 in 488a00d

return calendar.timegm(datetime.utcnow().utctimetuple())

Suggested Resolution:

Update the now() method to use a timezone-aware UTC datetime. For backwards compatibility with older Python 3 versions, datetime.now(timezone.utc) is the standard approach:

from datetime import datetime, timezone

# ...

@staticmethod
def now():
    return calendar.timegm(datetime.now(timezone.utc).utctimetuple())

Environment:

• Python Version: 3.12+
• Library: python-saml / python3-saml