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 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/
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
We have to force these because they are not updated on the host like
the other lists (API limit of five requests per day!). We update the
list periodically here in git.
For now I am still manually updating this, as we can only hit their
API five times per day, so it is not possible to have each host get
the list themselves every day with our one API key.
This adds Abuse.sh's list of IPs using blacklisted SSL certificates
to nftables. These IPs are high confidence indicators of compromise
and we should not route them. The list is updated daily by a systemd
timer.
See: https://sslbl.abuse.ch/blacklist/
We should only try to start the nftables service after we finish
copying all the config files just in case there is some unclean
state in one of them. On a first run this shouldn't matter, but
after nftables and some abuse list update scripts have run this
can happen (mostly in testing!).
cron-apt updates the system against the security-only databases at
night so many packages are "missing" unless you run apt update. We
need to update the cache on all apt tasks actually because I might
be running them by their tag and they currently only get updated at
the beginning of the playbook.
This configures the recommended DROP, EDROP, and DROPv6 lists from
Spamhaus as ipsets in firewalld. First we copy an empty placeholder
ipset to seed firewalld, then we use a shell script to download the
real lists and activate them. The same shell script is run daily as
a service (update-spamhaus-lists.service) by a systemd timer.
I am strictly avoiding any direct ipset commands here because I want
to make sure that this works on older hosts where ipsets is used as
well as newer hosts that have moved to nftables such as Ubuntu 20.04.
So far I have tested this on Ubuntu 16.04, 18.04, and 20.04, but ev-
entually I need to abstract the tasks and run them on CentOS 7+ as
well.
See: https://www.spamhaus.org/drop/
The nftables backend should be more performant and flexible. I had
been planning to use it on Ubuntu 18.04 and Debian 10 as well, but
there were issues with the specific versions used in those distros.
See: https://firewalld.org/2018/07/nftables-backend
We never used this simple firewall utility and in at least one case
a user on the server tried to use it and messed up the rules I had
set via firewalld.
This is active banning of IPs that are brute forcing login attempts
to SSH, versus the passive banning of 10,000 abusive IPs from the
abuseipdb.com blacklist. For now I am banning IPs that fail to log
in successfully more than twelve times in a one-hour period, but
these settings might change, and I can override them at the group
and host level if needed.
Currently this works for CentOS 7, Ubuntu 16.04, and Ubuntu 18.04,
with minor differences in the systemd configuration due to older
versions on some distributions.
You can see the status of the jail like this:
# fail2ban-client status sshd
Status for the jail: sshd
|- Filter
| |- Currently failed: 0
| |- Total failed: 0
| `- Journal matches: _SYSTEMD_UNIT=sshd.service + _COMM=sshd
`- Actions
|- Currently banned: 1
|- Total banned: 1
`- Banned IP list: 106.13.112.20
You can unban IPs like this:
# fail2ban-client set sshd unbanip 106.13.112.20
This uses the ipsets feature of the Linux kernel to create lists of
IPs (though could be MACs, IP:port, etc) that we can block via the
existing firewalld zone we are already using. In my testing it works
on CentOS 7, Ubuntu 16.04, and Ubuntu 18.04.
The list of abusive IPs currently comes from HPC's systemd journal,
where I filtered for hosts that had attempted and failed to log in
over 100 times. The list is formatted with tidy, for example:
$ tidy -xml -iq -m -w 0 roles/common/files/abusers-ipv4.xml
See: https://firewalld.org/2015/12/ipset-support
After reörganizing for dynamic includes these tags will never be reached
because the children of dynamic includes do not inherit tags from their
parents as they did with static imports.
Use dynamic includes instead of static imports when you are running
tasks conditionally or using variable interpolation. The down side
is that you need to then tag the parent task as well as all child
tasks, as tags only apply to children of statically imported tasks.
Ansible 2.4 and 2.5 are moving away from specialized loop functions
and the old syntax will eventually be deprecated and removed. I did
not change the with_fileglob loops because I'm not sure about their
syntax yet.
See: https://docs.ansible.com/ansible/latest/user_guide/playbooks_loops.html
You should only use the "shell" module when you need shell functions
like flow control and redirects. Also, the "command" module is safer
because it is not affected by the user's environment.
