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Ansible role: pf

MIT licensed Galaxy Role

DEPRECATION NOTICE

This role is being deprecated in favor of ansible-collection-mac.

Collection on Galaxy: drew1kun.mac

Description

Description

Ansible role for hardening configuration of pf firewall for MacOS.

Tutorial used

PF Anchors

The role will create the following pf anchors:

  • sshd anchor (<prefix>.sshd.rules) with bruteforce protection table and rules
  • emerging-treats open ruleset anchor (<prefix>.eto.rules) with table of known attackers' IPs and rules for blocking them
  • custom anchors <prefix>.rdr.rules and <prefix>.rdr.rules with rules specified in defaults/main.yml

Those anchors will be loaded in custom /etc/pf.<prefix>.conf configuration file.

NOTE: The system default /etc/pf.conf on MacOS can be overwritten during system updates, therefore custom /etc/pf.<prefix>.conf will be created and /etc/pf.conf may be included in that custom config.

Launchd jobs

On MacOS the following Launchd jobs will be created:

  • job for Enabling pf on boot. This is done by creating custom Library/LaunchDaemon/<>.pf.plist running /usr/local/bin/firewall.sh script for correct pf enabling on MacOS, therefore no SIP disabling is required
  • job for clearing the ssh_bruteforce table once a day at 10:00pm.
  • job for automated download of ETOpen ruleset once a day at 10:05pm.

Requirements

Reminder: Ansible uses ssh so make sure the pf configuration does not block ssh For example:

pass in log proto tcp to any port ssh flags S/SA keep state

Otherwise you may end up having ssh connection blocked

Role Variables

OS-Agnostic:

Variables Description Default
pf_ssh_bruteforce_protect Enable ssh bruteforce protection yes
pf_emerging_threats_protect Enable ETOpen Ruleset configuration yes
pf_macros Macros variables for pf configuration see defaults/main.yml
pf_tables pf configuration tables see defaults/main.yml
pf_options pf configuration options see defaults/main.yml
pf_normalization pf configuration normalization rules see defaults/main.yml
pf_queueing pf configuration queueing see defaults/main.yml
pf_translation Redirect rules for port forwarding and NAT see defaults/main.yml
pf_filtering Stateful and stateless filtering for rule-based packet blocking or passing see defaults/main.yml

OS-Specific:

Variables Description Default
pf_conf path to main pf configuration file
  • Darwin: /etc/pf.prefix.conf
  • Others (BSD): /etc/pf.conf
pf_prefix just a prefix for customizing the configuration. Will be added to all the filenames, generated by this role "{{ ansible_user_id }}"

NOTE: that because of the default value for pf_prefix var the role requires Fact Gathering. If you override this variable with some static value, the Fact Gathering will not be necessary.

Dependencies

None

Example Playbook

- hosts: dev_clients_macos
  gather_facts: yes
  roles:
  - drew1kun.pf

Checking Results (OPTIONAL)

See if pf is Enabled:

sudo pfctl -s info | grep Status

No ALTQ support in kernel
ALTQ related functions disabled
Status: Enabled for 0 days 00:20:41           Debug: Urgent

Show the eto and other pf rules loaded:

sudo pfctl -s all

Show the launchd jobs loaded:

watch -n1 -d 'launchctl list | grep <pf_prefix>'

SSH Bruteforce Table

Start the ssh bruteforce attack from kali machine (192.168.68.113):

hydra

hydra -l root -P /usr/share/wordlists/fasttrack.txt 192.168.68.104 ssh

medusa

medusa -u root -P /usr/share/wordlists/fasttrack.txt -h 192.168.68.104 -M ssh

ncrack (most efficient):

ncrack -U users.txt -P /usr/share/wordlists/fasttrack.txt 192.168.68.104:22

At some point, you may to check to see if you have attackers in your attackers table. To do that, use this command:

watch -n1 -d 'sudo pfctl -a drew.sshd -t ssh_bruteforce -T show'

This command lists the IPs in the attackers table for the sshd anchor.

On MacOS result will look like this:

No ALTQ support in kernel
ALTQ related functions disabled
   192.168.68.113

See screenshot:

If you accidentally (or during testing) get a legitimate IP in the attackers table, you can remove it with this command (replace a.b.c.d with your IP):

sudo pfctl -a drew.sshd -t ssh_bruteforce -Tdelete a.b.c.d

You can also save the existing attackers table and reload it later. This can be useful for saving the table through a system restart. Use the following commands to save the table:

sudo pfctl -a drew.sshd -t ssh_bruteforce -Tshow > /etc/pf.attackers-table.txt

To load the table later, use this command:

sudo pfctl -a drew.sshd -t ssh_bruteforce -Tload -f /etc/pf.attackers-table.txt

License

MIT

Author Information

Andrew Shagayev | e-mail