[BR]: PY_SSIZE_T_CLEAN macro must be defined for '#' formats" with python3

[saheerskt]

I'm trying to run the python3-fail2ban component built by yocto, but I'm encountering an error related to the PY_SSIZE_T_CLEAN macro. The error message is PY_SSIZE_T_CLEAN macro must be defined for '#' formats.

I have no issues with python dependent fail2ban, issues observed only with python3

I've looked into the issue and found that in the Python 3.10 C-API documentation https://docs.python.org/3.10/c-api/arg.html#arg-parsing, it's mentioned that,

Note: For all # variants of formats (s#, y#, etc.), the macro PY_SSIZE_T_CLEAN must be defined before including Python.h. On Python 3.9 and older, the type of the length argument is [Py_ssize_t](https://docs.python.org/3.10/c-api/intro.html#c.Py_ssize_t) if the PY_SSIZE_T_CLEAN macro is defined, or int otherwise.

1. I tried to resolve this issue by defining the PY_SSIZE_T_CLEAN macro before including Python.h. But the issue was not resolved, patch snippet here,

+#ifndef PY_SSIZE_T_CLEAN
+#define PY_SSIZE_T_CLEAN 1
+#endif
#include "Python.h"

2. Also included CFLAGS += "PY_SSIZE_T_CLEAN " in the python3-fail2ban component. No impact on observation

Environment:

• Fail2Ban version : python3-fail2ban 0.11.2
• OS, including release name/version : Linux built by yocto kirkstone (Yocto Project 4.0)
• Python dependency: python3 3.10.12 [no issues with python dependency. We use only python3 in this setup]
• No additional patches or changes
• No other customization

The issue:

Steps to reproduce

1. Created a jail /etc/fail2ban/jail.local with the below data,

[sshd]
enabled = yes
port    = ssh
backend = systemd

2. restarted fail2ban services: sudo systemctl restart fail2ban.service
3. Checking the log : cat /var/log/fail2ban.log

Expected behavior

No error expected here, so sshd jail not working

Relevant parts of /var/log/fail2ban.log file:

fail2ban-server[11527]: fail2ban [11527]: ERROR NOK: ("PY_SSIZE_T_CLEAN macro must be defined for '#' formats",)

[sebres]

no issues with python dependency

I don't think so, vice versa it looks like it may be one...
Because of usage of systemd backend (which requires journal.Reader from python-systemd module) I believe it is systemd/python-systemd#107 (seems to be already fixed and a fixed version published on pypi, but probably did not reach your distro/python installation).
To check whether it is really abovementioned issue, try this... here is (successful) output with 3.11 on Debian 12:

$ fail2ban-python --version
Python 3.11.2
$ fail2ban-python -c 'from systemd import journal; print("v:", journal.__version__); j = journal.Reader(); j.add_match(_SYSTEMD_UNIT="sshd"); print("OK")'
v: 235
OK

If you see the error, try to upgrade systemd-python package, e. g. using pip (pip3), like:

pip3 install --upgrade systemd-python
#or
fail2ban-python -m pip install --upgrade systemd-python

or contact your Python installation or OS distribution maintainers.

Thus I'll close it here as 3rd party issue.

[saheerskt]

This fix helped me to resolve this issue