Working with stateless rule groups in AWS Network Firewall - AWS Network Firewall

Working with stateless rule groups in AWS Network Firewall

For stateless rule groups, the AWS Network Firewall stateless rules engine examines each packet in isolation. Network Firewall doesn't consider context such as traffic direction or other related packets.

Network Firewall supports standard network connection identifiers (source IP address, source port, destination IP address, destination port, and protocol) for network traffic inspection. When Network Firewall finds a match between a rule's inspection criteria and a packet, we say that the packet matches the rule and its rule group, and Network Firewall applies the rule's specified action to the packet.

You can add multiple stateless rules to your stateless rule group.

All rule groups have the common settings that are defined at Common rule group settings in AWS Network Firewall.

General settings

A stateless rule has the following general settings.

  • Priority – Number that indicates the processing order of the stateless rule within the rule group. This must be unique within the stateless rule group and it must be a positive integer. Network Firewall processes the rules starting from the lowest numbered priority setting. When you plan the rules in your rule group, provide priority settings with space in between, to leave yourself room to add rules later. For example, you might start by using priority settings that are multiples of 100.

  • Actions – Defines how Network Firewall handles a packet that matches the rule match settings. You assign one standard setting, from among pass, drop, and forward to stateful. You can optionally add a custom setting, for example, to send metrics for the rule match to Amazon CloudWatch metrics. For more information about actions, see Defining rule actions in AWS Network Firewall.

Match settings

A stateless rule has the following match settings. These specify what the Network Firewall stateless rules engine looks for in a packet. To be a match, a packet must satisfy all of the match settings in the rule.

  • Protocol – Valid settings include ALL and specific protocol settings, like UDP and TCP. You can choose more than one specific setting.

  • Source IP – Source IP addresses and ranges. If specified, a packet must come from a source address that's included in this list in order to match.

  • Source port range – Source ports and port ranges. If specified, a packet must have a source port that's included in this list in order to match.

  • Destination IP – Destination IP addresses and ranges. If specified, a packet must have a destination address that's included in this list in order to match.

  • Destination port range – Destination ports and port ranges. If specified, a packet must have a destination port that's included in this list in order to match.

  • Optional TCP flags – Optional, standard TCP flag settings, which indicate which flags to inspect and the values to inspect for. Each flag can be either enabled or disabled. You indicate the flags that you want to inspect in a masks setting, and then you indicate which of those flags must be enabled in the flags setting in order to match. The flags that you specify in the masks setting and don't specify in the flags setting must be unset in order to match.

Example

To create a very simple stateless rule group that passes all traffic from two CIDR blocks, you could provide the following stateless rule settings in a single rule:

  • Priority – 100

  • Action – PASS

  • Protocol – ALL

  • Source – 192.0.2.0/8, 198.51.100.0/16

To block all other traffic, you would set the firewall policy's stateless default actions to Drop. For more information, see Firewall policy settings in AWS Network Firewall.