Actually, we do want to run fail2ban on all hosts because the sshd
monitoring via systemd is nice. At the very least it reduces spam
from failed logins in our systemd journal.
We can only run fail2ban when we have logs to monitor. When a host
is running Caddy we don't have logs, so fail2ban doesn't have any-
thing to monitor out of the box. For now I will restrict the task
to hosts running nginx.
According the the Debian docs for third-party repositories we must
create this manually on distros before Debian 12 and Ubuntu 22.04.
This is due to changes in apt-secure and the deprecation of apt-key.
See: https://wiki.debian.org/DebianRepository/UseThirdParty
I changed these yesterday when editing the truthy values, but acco-
rding to ansible-link we can just rely on them being true or false
without comparing.
According to Ansible we can use yes, true, True, "or any quoted st-
ring" for a boolean true, but ansible-lint wants us to use either
true or false.
See: https://chronicler.tech/red-hat-ansible-yes-no-and/
This comes from the AbuseIPDB with a confidence level of 95%. I use
the following command to download and sort the IPs:
$ curl -G https://api.abuseipdb.com/api/v2/blacklist -d \
confidenceMinimum=95 -H "Key: $ABUSEIPDB_API_KEY" \
-H "Accept: text/plain" | sort | sed -e '/:/w /tmp/ipv6.txt' \
-e '/:/d' > /tmp/ipv4.txt
I manually add the XML formatting to each file and run them through
tidy:
$ tidy -xml -utf8 -m -iq -w 0 roles/common/files/abusers-ipv4.xml
$ tidy -xml -utf8 -m -iq -w 0 roles/common/files/abusers-ipv6.xml
Then I formatted the nftables files manually. Meh...
This comes from the AbuseIPDB with a confidence level of 95%. I use
the following command to download and sort the IPs:
$ curl -G https://api.abuseipdb.com/api/v2/blacklist -d \
confidenceMinimum=95 -H "Key: $ABUSEIPDB_API_KEY" \
-H "Accept: text/plain" | sort | sed -e '/:/w /tmp/ipv6.txt' \
-e '/:/d' > /tmp/ipv4.txt
I manually add the XML formatting to each file and run them through
tidy:
$ tidy -xml -utf8 -m -iq -w 0 roles/common/files/abusers-ipv4.xml
$ tidy -xml -utf8 -m -iq -w 0 roles/common/files/abusers-ipv6.xml
Then I formatted the nftables files manually. Meh...
This seems to be automatically selected, but on some other servers
I notice it is not. I will set it here explicitly so fail2ban does
not fall back to the inefficient "polling" or incorrect "systemd"
backends.
This comes from the AbuseIPDB with a confidence level of 95%. I use
the following command to download and sort the IPs:
$ curl -G https://api.abuseipdb.com/api/v2/blacklist -d \
confidenceMinimum=95 -H "Key: $ABUSEIPDB_API_KEY" \
-H "Accept: text/plain" | sort | sed -e '/:/w /tmp/ipv6.txt' \
-e '/:/d' > /tmp/ipv4.txt
I manually add the XML formatting to each file and run them through
tidy:
$ tidy -xml -utf8 -m -iq -w 0 roles/common/files/abusers-ipv4.xml
$ tidy -xml -utf8 -m -iq -w 0 roles/common/files/abusers-ipv6.xml
Then I created the nftables files manually. Meh...
This comes from the AbuseIPDB with a confidence level of 95%. I use
the following command to download and sort the IPs:
$ curl -G https://api.abuseipdb.com/api/v2/blacklist -d \
confidenceMinimum=95 -H "Key: $ABUSEIPDB_API_KEY" \
-H "Accept: text/plain" | sort | sed -e '/:/w /tmp/ipv6.txt' \
-e '/:/d' > /tmp/ipv4.txt
I manually add the XML formatting to each file and run them through
tidy:
$ tidy -xml -utf8 -m -iq -w 0 roles/common/files/abusers-ipv4.xml
$ tidy -xml -utf8 -m -iq -w 0 roles/common/files/abusers-ipv6.xml
The WeakDH team showed (in 2015) that Diffie-Hellman key exchange
with prime number groups of 1024 bits or less were weaker than we
previously thought, and well within the reach of nation states. They
recommended (in 2015) using 2048-bit or higher prime groups.
The SSH audit project recommends that we should use 3072-bit now.
See: https://weakdh.org/
See: https://github.com/jtesta/ssh-audit/
We should always restart fail2ban after updating the firewall. Also
note that the order of execution of handlers depends on how they are
defined in the handler config, not on the order they are listed in
the task's notify statement.
See: https://docs.ansible.com/ansible/latest/user_guide/playbooks_handlers.html
