Send notifications to the Slack from fail2ban

jail.local

...

action_with_slack_notification = %(banaction)s[name=%(__name__)s, port="%(port)s"]
                                 slack[name=%(__name__)s]

action = %(action_with_slack_notification)s

...

slack.conf

[Definition]

actioncheck=
actionstart =
actionstop =
actionban = /bin/bash /etc/fail2ban/slack_notify.sh "Banned _country_ <ip> in the jail <name> after <failures> attempts" "<ip>" > /dev/null 2>&1
actionunban = /bin/bash /etc/fail2ban/slack_notify.sh "Unbanned _country_ <ip> in the jail <name>" "<ip>" > /dev/null 2>&1

slack_notify.sh

#!/bin/bash

# message first command argument
MESSAGE=$1
HOOK_URL=https://hooks.slack.com/services/<your hook url>
HOST=$(hostname)

CHANNEL="#alerts"
USERNAME="fail2ban"
ICON=":cop:"

# ip second command argument
IP=$2
# lets find out from what country we have our hacker
COUNTRY=$(curl ipinfo.io/${IP}/country)
# converting country to lover case. I love you bash script =\
COUNTRY=$(echo "$COUNTRY" | tr -s  '[:upper:]'  '[:lower:]')
# slack emoji
COUNTRY=":flag-$COUNTRY:"

# replace _country_ template to the country emoji
MESSAGE="${MESSAGE/_country_/$COUNTRY}"

curl -X POST --data-urlencode "payload={\"channel\": \"${CHANNEL}\", \"username\": \"${USERNAME}\", \"text\": \"[${HOST}] ${MESSAGE}\", \"icon_emoji\": \"${ICON}\"}" ${HOOK_URL}

exit 0