forksand-it-manual/source/resources/apps/ansible-debian-mail/roles/mikegleasonjr.firewall/README.md

Ansible Firewall Role
=========

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After I found out `UFW` was too limited in terms of functionalities, I tried several firewall roles out there but none satisfied the requirements I had:

- Support virtually all iptables rules from the start
- Allow granular rules addition/overriding for specific hosts
- Easily inject variables in the rules
- Allow rules ordering
- Simplicity (not having to learn how role variables would generate the rules)
- Persistence (reload the rules at boot)

This role is an attempt to solve these requirements.

It supports **ipv4** and **ipv6*** on Debian and RedHat distributions.

*ipv6 support was brought up thanks to [@maloddon](https://github.com/maloddon). It is currently in early stages and knowledgable people should review the [default rules](https://github.com/mikegleasonjr/ansible-role-firewall/blob/master/defaults/main.yml). ipv6 rules are not configured by default. If you which to use them, don't forget to set `firewall_v6_configure` to `true`.

Requirements
------------

* Ansible 2.2.1.0
* `iptables` (installed by default on all official Debian and RedHat distributions)

Installation
------------

`$ ansible-galaxy install mikegleasonjr.firewall`

Role Variables
--------------

`defaults/main.yml`:

```
firewall_v4_configure: true
firewall_v6_configure: false

firewall_v4_default_rules:
  001 default policies:
    - -P INPUT ACCEPT
    - -P OUTPUT ACCEPT
    - -P FORWARD DROP
  002 allow loopback:
    - -A INPUT -i lo -s 127.0.0.0/8 -d 127.0.0.0/8 -j ACCEPT
  003 allow ping replies:
    - -A INPUT -p icmp --icmp-type echo-request -j ACCEPT
    - -A OUTPUT -p icmp --icmp-type echo-reply -j ACCEPT
  100 allow established related:
    - -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
  200 allow ssh:
    - -A INPUT -p tcp --dport ssh -j ACCEPT
  999 drop everything:
    - -P INPUT DROP
firewall_v4_group_rules: {}
firewall_v4_host_rules: {}

firewall_v6_default_rules:
  001 default policies:
    - -P INPUT ACCEPT
    - -P OUTPUT ACCEPT
    - -P FORWARD DROP
  002 allow loopback:
    - -A INPUT -i lo -s ::1/128 -d ::1/128 -j ACCEPT
  003 allow ping replies:
    - -A INPUT -p icmpv6 --icmpv6-type echo-request -j ACCEPT
    - -A OUTPUT -p icmpv6 --icmpv6-type echo-reply -j ACCEPT
  100 allow established related:
    - -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
  200 allow ssh:
    - -A INPUT -p tcp --dport ssh -j ACCEPT
  999 drop everything:
    - -P INPUT DROP
firewall_v6_group_rules: {}
firewall_v6_host_rules: {}

```

The keys to the `*_rules` dictionaries (`001 default policies`, `002 allow loopback`, ...) can be anything. They are only used for rules **ordering** and **overriding**. On rules generation, the keys are sorted alphabetically. That's why I chose here the 001s and 999s.

Those defaults will generate the following script to be executed on the host (for ipv4):

```
#!/bin/sh
# Ansible managed: <redacted>

# flush rules & delete user-defined chains
iptables -F
iptables -X
iptables -t raw -F
iptables -t raw -X
iptables -t nat -F
iptables -t nat -X
iptables -t mangle -F
iptables -t mangle -X

# 001 default policies
iptables -P INPUT ACCEPT
iptables -P OUTPUT ACCEPT
iptables -P FORWARD DROP

# 002 allow loopback
iptables -A INPUT -i lo -s 127.0.0.0/8 -d 127.0.0.0/8 -j ACCEPT

# 003 allow ping replies
iptables -A INPUT -p icmp --icmp-type echo-request -j ACCEPT
iptables -A OUTPUT -p icmp --icmp-type echo-reply -j ACCEPT

# 100 allow established related
iptables -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT

# 200 allow ssh
iptables -A INPUT -p tcp --dport ssh -j ACCEPT

# 999 drop everything
iptables -P INPUT DROP
```

As you can see, you have complete control over the rules syntax.

`$ iptables -L -n` on the host then shows...

```
Chain INPUT (policy DROP)
target     prot opt source               destination
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0
ACCEPT     icmp --  0.0.0.0/0            0.0.0.0/0            icmptype 8
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0            ctstate RELATED,ESTABLISHED
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0            tcp dpt:22

Chain FORWARD (policy DROP)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination
ACCEPT     icmp --  0.0.0.0/0            0.0.0.0/0            icmptype 0
```

Now that takes care of the default rules. What about overriding?

You can change the rules for specific hosts and groups instead of re-defining everything. Rules in `firewall_v4_host_rules` will be merged with `firewall_v4_group_rules`, and then the result will be merged back with the defaults. Same thing for ipv6.

This allows 3 levels of rules definition and overriding. I simply chose the names to match how the variable precedence works in Ansible (`all` -> `group` -> `host`). See the example playbook below to see rules overriding in action.

Example Playbook (ipv4)
----------------

```
- hosts: all
  roles:
    - mikegleasonjr.firewall
```

in `group_vars/all.yml` you could define the default rules for all your hosts:

```
firewall_v4_default_rules:
  001 default policies:
    - -P INPUT ACCEPT
    - -P OUTPUT ACCEPT
    - -P FORWARD DROP
  002 allow loopback:
    - -A INPUT -i lo -j ACCEPT
  003 allow ping replies:
    - -A INPUT -p icmp --icmp-type echo-request -j ACCEPT
    - -A OUTPUT -p icmp --icmp-type echo-reply -j ACCEPT
  100 allow established related:
    - -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
  200 allow ssh limiting brute force:
    - -I INPUT -p tcp -d {{ hostvars[inventory_hostname]['ansible_eth1']['ipv4']['address'] }} --dport 22 -m state --state NEW -m recent --set
    - -I INPUT -p tcp -d {{ hostvars[inventory_hostname]['ansible_eth1']['ipv4']['address'] }} --dport 22 -m state --state NEW -m recent --update --seconds 60 --hitcount 4 -j DROP
  999 drop everything:
    - -P INPUT DROP
```

in `group_vars/webservers.yml` you would open up port 80:

```
firewall_v4_group_rules:
  400 allow web traffic:
    - -A INPUT -p tcp --dport http -j ACCEPT
```

in `host_vars/secureweb.yml` you would want to open https as well and remove ssh logins:

```
firewall_v4_host_rules:
  400 allow web traffic:
    - -A INPUT -p tcp --dport http -j ACCEPT    # need to redefine this one as well because the whole key is overwritten
    - -A INPUT -p tcp --dport https -j ACCEPT
  200 allow ssh limiting brute force: []
```

To "delete" rules, you just assign an empty list to an existing dictionary key.

To summarize, rules in `firewall_v4_host_rules` will overwrite rules in `firewall_v4_group_rules`, and then rules in `firewall_v4_group_rules` will overwrite rules in `firewall_v4_default_rules`.

You can play with the rules and see the generated script on the host at the following location: `/etc/iptables.v4.generated` and `/etc/iptables.v6.generated`.

Dependencies
------------

none

License
-------

BSD

Contributing
-------

A vagrant environment has been provided to test the role on different distributions. Add your tests in `tests.yml` and...

```
$ vagrant up
$ vagrant provision
```

Author Information
------------------

Mike Gleason jr Couturier (mikegleasonjr@gmail.com)

Other roles from the same author:

- [swap](https://github.com/mikegleasonjr/ansible-role-swap)