Opening the Firewall up for Salt¶
The Salt master communicates with the minions using an AES-encrypted ZeroMQ connection. These communications are done over TCP ports 4505 and 4506, which need to be accessible on the master only. This document outlines suggested firewall rules for allowing these incoming connections to the master.
No firewall configuration needs to be done on Salt minions. These changes refer to the master only.
RHEL 6 / CentOS 6¶
The lokkit command packaged with some Linux distributions makes opening iptables firewall ports very simple via the command line. Just be careful to not lock out access to the server by neglecting to open the ssh port.
lokkit -p 22:tcp -p 4505:tcp -p 4506:tcp
The system-config-firewall-tui command provides a text-based interface to modifying the firewall.
Salt installs firewall rules in /etc/sysconfig/SuSEfirewall2.d/services/salt. Enable with:
SuSEfirewall2 open SuSEfirewall2 start
If you have an older package of Salt where the above configuration file is not included, the SuSEfirewall2 command makes opening iptables firewall ports very simple via the command line.
SuSEfirewall2 open EXT TCP 4505 SuSEfirewall2 open EXT TCP 4506
The firewall module in YaST2 provides a text-based interface to modifying the firewall.
Different Linux distributions store their iptables (also known as netfilter) rules in different places, which makes it difficult to standardize firewall documentation. Included are some of the more common locations, but your mileage may vary.
Fedora / RHEL / CentOS:
Follow these instructions: http://wiki.debian.org/iptables
Once you've found your firewall rules, you'll need to add the two lines below to allow traffic on tcp/4505 and tcp/4506:
-A INPUT -m state --state new -m tcp -p tcp --dport 4505 -j ACCEPT -A INPUT -m state --state new -m tcp -p tcp --dport 4506 -j ACCEPT
Salt installs firewall rules in /etc/ufw/applications.d/salt.ufw. Enable with:
ufw allow salt
The BSD-family of operating systems uses packet filter (pf). The following example describes the additions to pf.conf needed to access the Salt master.
pass in on $int_if proto tcp from any to $int_if port 4505 pass in on $int_if proto tcp from any to $int_if port 4506
Once these additions have been made to the pf.conf the rules will need to be reloaded. This can be done using the pfctl command.
pfctl -vf /etc/pf.conf
Whitelist communication to Master¶
There are situations where you want to selectively allow Minon traffic from specific hosts or networks into your Salt Master. The first scenario which comes to mind is to prevent unwanted traffic to your Master out of security concerns, but another scenario is to handle Minion upgrades when there are backwards incompatible changes between the installed Salt versions in your environment.
Here is an example Linux iptables ruleset to be set on the Master:
# Allow Minions from these networks -I INPUT -s 10.1.2.0/24 -p tcp -m multiport --dports 4505,4506 -j ACCEPT -I INPUT -s 10.1.3.0/24 -p tcp -m multiport --dports 4505,4506 -j ACCEPT # Allow Salt to communicate with Master on the loopback interface -A INPUT -i lo -p tcp -m multiport --dports 4505,4506 -j ACCEPT # Reject everything else -A INPUT -p tcp -m multiport --dports 4505,4506 -j REJECT
The important thing to note here is that the salt command needs to communicate with the listening network socket of salt-master on the loopback interface. Without this you will see no outgoing Salt traffic from the master, even for a simple salt '*' test.ping, because the salt client never reached the salt-master to tell it to carry out the execution.