CC masker

This is a lightweight tool intended to be used as a filter with Rsyslog.
It spawns a singlethreaded process and accepts log messages through stdin.
Rsyslog will spawn more processes as needed, and expects to receive messages in the same order.
If the message contains a PAN number, it returns the message with a masked PAN in a JSON key named "msg".
Otherwise, an empty JSON is returned.

For more information regarding the plugin nature of this tool:
https://github.com/rsyslog/rsyslog/blob/master/plugins/external/INTERFACE.md#external-message-modification-modules
https://github.com/rsyslog/rsyslog/blob/master/plugins/external/messagemod/anon_cc_nbrs/anon_cc_nbrs.py

How to use

Add the following to your rsyslog config and restart the process. More information here https://www.rsyslog.com/doc/master/configuration/modules/mmexternal.html

module(load="mmexternal")
action(type="mmexternal" binary="/path/to/ccmasker")

Feedback

This has been a learning excercise, constructive feedback is always appreciated.

False positives and rewrite

Filtering for PAN data without context is a process prone to false positives.
Further steps to reduce false positives were required and it was a tricky process due to variable length of matches.

Python version

Wrote an equivalent python script for comparison and it is actually faster ¯_(ツ)_/¯
A test with 748mb of real logs

timing ccmasker written in go (1.16)

real    0m34,526s
user    0m40,160s
sys     0m1,600s

timing ccmasker written in python (3.9)

real    0m28,051s
user    0m31,487s
sys     0m1,303s

TODO

• experiment with benchmarks