Configure Linux iptables Firewall for Self-Managed Deployments
On contemporary Linux systems, the iptables program provides
methods for managing the Linux Kernel's netfilter or network
packet filtering capabilities. These firewall rules make it possible
for administrators to control what hosts can connect to the system,
and limit risk exposure by limiting the hosts that can connect to a
system.
This document outlines basic firewall configurations for iptables
firewalls on Linux. Use these approaches as a starting point for your
larger networking organization. For a detailed overview of security
practices and risk management for MongoDB, see Security.
Overview
Rules in iptables configurations fall into chains, which describe
the process for filtering and processing specific streams of
traffic. Chains have an order, and packets must pass through earlier
rules in a chain to reach later rules. This document addresses only the
following two chains:
INPUT- Controls all incoming traffic.
OUTPUT- Controls all outgoing traffic.
Given the default ports of all
MongoDB processes, you must configure networking rules that permit only
required communication between your application and the appropriate
mongod and mongos instances.
Be aware that, by default, the default policy of iptables is to
allow all connections and traffic unless explicitly disabled. The
configuration changes outlined in this document will create rules that
explicitly allow traffic from specific addresses and on specific
ports, using a default policy that drops all traffic that is not
explicitly allowed. When you have properly configured your
iptables rules to allow only the traffic that you want to permit,
you can Change Default Policy to DROP.
Patterns
This section contains a number of patterns and examples for
configuring iptables for use with MongoDB deployments. If you have
configured different ports using the port configuration
setting, you will need to modify the rules accordingly.
Traffic to and from mongod Instances
This pattern is applicable to all mongod instances running
as standalone instances or as part of a replica set.
The goal of this pattern is to explicitly allow traffic to the
mongod instance from the application server. In the
following examples, replace <ip-address> with the IP address of
the application server:
iptables -A INPUT -s <ip-address> -p tcp --destination-port 27017 -m state --state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -d <ip-address> -p tcp --source-port 27017 -m state --state ESTABLISHED -j ACCEPT
The first rule allows all incoming traffic from <ip-address> on
port 27017, which allows the application server to connect to the
mongod instance. The second rule, allows outgoing traffic
from the mongod to reach the application server.
Note
Optional
If you have only one application server, you can replace
<ip-address> with either the IP address itself, such as:
198.51.100.55. You can also express this using CIDR notation as
198.51.100.55/32. If you want to permit a larger block of
possible IP addresses you can allow traffic from a /24 using
one of the following specifications for the <ip-address>, as
follows:
10.10.10.10/24 10.10.10.10/255.255.255.0
Traffic to and from mongos Instances
mongos instances provide query routing for sharded
clusters. Clients connect to mongos instances, which
behave from the client's perspective as mongod
instances. In turn, the mongos connects to all
mongod instances that are components of the sharded
cluster.
Use the same iptables command to allow traffic to and from these
instances as you would from the mongod instances that are
members of the replica set. Take the configuration outlined in the
Traffic to and from mongod Instances section as an example.
Traffic to and from a MongoDB Config Server
Config servers host the config database that stores metadata
for sharded clusters. Config servers listen for connections on port
27019. As a result, add the following iptables rules to the
config server to allow incoming and outgoing connection on port
27019, for connection to the other config servers.
iptables -A INPUT -s <ip-address> -p tcp --destination-port 27019 -m state --state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -d <ip-address> -p tcp --source-port 27019 -m state --state ESTABLISHED -j ACCEPT
Replace <ip-address> with the address or address space of all
the mongod that provide config servers.
Additionally, config servers need to allow incoming connections from
all of the mongos instances in the cluster and all
mongod instances in the cluster. Add rules that
resemble the following:
iptables -A INPUT -s <ip-address> -p tcp --destination-port 27019 -m state --state NEW,ESTABLISHED -j ACCEPT
Replace <ip-address> with the address of the
mongos instances and the shard mongod
instances.
Traffic to and from a MongoDB Shard Server
Shard servers default to port number
27018. You must configure the following iptables rules to allow
traffic to and from each shard:
iptables -A INPUT -s <ip-address> -p tcp --destination-port 27018 -m state --state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -d <ip-address> -p tcp --source-port 27018 -m state --state ESTABLISHED -j ACCEPT
Replace the <ip-address> specification with the IP address of all
mongod. This allows you to permit incoming and outgoing
traffic between all shards including constituent replica set members,
to:
Furthermore, shards need to be able make outgoing connections to:
all
mongodinstances in the config servers.
Create a rule that resembles the following, and replace the
<ip-address> with the address of the config servers and the
mongos instances:
iptables -A OUTPUT -d <ip-address> -p tcp --source-port 27018 -m state --state ESTABLISHED -j ACCEPT
| [1] | All shards in a cluster need to be able to communicate with all other shards to facilitate chunk and balancing operations. |
Provide Access For Monitoring Systems
The mongostat diagnostic tool, when running with the
--discover needs to be able to reach
all components of a cluster, including the config servers, the shard
servers, and the mongos instances.
Change Default Policy to DROP
The default policy for iptables chains is to allow all
traffic. After completing all iptables configuration changes, you
must change the default policy to DROP so that all traffic that
isn't explicitly allowed as above will not be able to reach components
of the MongoDB deployment. Issue the following commands to change this
policy:
iptables -P INPUT DROP iptables -P OUTPUT DROP
Manage and Maintain iptables Configuration
This section contains a number of basic operations for managing and
using iptables. There are various front end tools that automate
some aspects of iptables configuration, but at the core all
iptables front ends provide the same basic functionality:
Make all iptables Rules Persistent
By default all iptables rules are only stored in memory. When
your system restarts, your firewall rules will revert to their
defaults. When you have tested a rule set and have guaranteed that it
effectively controls traffic you can use the following operations to
you should make the rule set persistent.
On Red Hat Enterprise Linux, Fedora Linux, and related distributions you can issue the following command:
service iptables save
On Debian, Ubuntu, and related distributions, you can use the
following command to dump the iptables rules to the
/etc/iptables.conf file:
iptables-save > /etc/iptables.conf
Run the following operation to restore the network rules:
iptables-restore < /etc/iptables.conf
Place this command in your rc.local file, or in the
/etc/network/if-up.d/iptables file with other similar operations.
List all iptables Rules
To list all of currently applied iptables rules, use the following
operation at the system shell.
iptables -L
Flush all iptables Rules
If you make a configuration mistake when entering iptables rules
or simply need to revert to the default rule set, you can use the
following operation at the system shell to flush all rules:
iptables -F
If you've already made your iptables rules persistent, you will
need to repeat the appropriate procedure in the
Make all iptables Rules Persistent section.