dist: Copy fail2ban configuration from wiki

dist/README.md

@@ -15,3 +15,10 @@ the system to a bare minimum. Subset of these options makes it impossible for
 privileged authentication helper binaries to gain required permissions, so you
 may have to disable it when using system account-based authentication with
 maddy running as a unprivilieged user.
+
+## fail2ban configuration
+
+Configuration files for use with fail2ban. Assume either `backend = systemd` specified
+in system-wide configuration or log file written to /var/log/maddy/maddy.log.
+
+See https://github.com/foxcpp/maddy/wiki/fail2ban-configuration for details.

dist/fail2ban/filter.d/maddy

@@ -0,0 +1,2 @@
+[Definition]
+failregex = authentication failed for (.+) \(from <HOST>:[0-9]+\)

dist/fail2ban/jail.d/maddy

@@ -0,0 +1,5 @@
+[maddy]
+enabled  = true
+port     = 143,993,587,465,25
+filter   = maddy
+logpath  = /var/log/maddy/maddy.log