Firewall policy rule components

This page describes the components of firewall rules that you create in one of the following firewall policies that apply to a regular Virtual Private Cloud (VPC) network :

• Hierarchical firewall policies
• Global network firewall policies
• Regional network firewall policies

For details about firewall rules and Remote Direct Memory Access (RDMA) network profiles, see Cloud NGFW for RoCE VPC networks .

Each firewall policy rule applies to incoming (ingress) or outgoing (egress) connections, not both. When you create a firewall policy rule , you specify the components that define what the rule does. In addition to the direction, you can specify source, destination, and Layer 4 characteristics such as protocol and destination port (if the protocol uses ports).

Priority

The priority of a rule in a firewall policy is an integer from 0 to 2,147,483,547, inclusive. Lower integers indicate higher priorities. The priority of a rule in a firewall policy is similar to the priority of a VPC firewall rule , with the following differences:

• Each rule in a firewall policy must have a unique priority.
• The priority of a rule in a firewall policy serves as the rule's unique identifier. Rules in firewall policies don't use names for identification.
• The priority of a rule in a firewall policy defines the evaluation order within the firewall policy itself. VPC firewall rules and rules in hierarchical firewall policies, global network firewall policies, and regional network firewall policies are evaluated as described in Apply firewall policies and rules to a network .

Action on match

A rule in a firewall policy can have one of the following actions:

Action parameter	Description
allow	Allows packets for a new connection. Stops evaluating rules in the firewall policy that contains the matching rule. Doesn't evaluate any other firewall rules. Regardless of the direction of the rule, if the packet protocol and firewall policy type support connection tracking, an allow rule creates a firewall connection tracking table entry that permits both ingress and egress packets.
deny	Disallows packets for a new connection. Stops evaluating rules in the firewall policy that contains the matching rule. Doesn't evaluate any other firewall rules. Cloud NGFW always checks for a firewall connection tracking table entry before it evaluates firewall rules. Consequently, if an allow rule created a connection tracking table entry, that connection tracking table entry takes precedence.
apply_security_profile_group	Intercepts packets for a new connection, sending them to a firewall endpoint or intercept endpoint group . Stops evaluating rules in the firewall policy that contains the matching rule. Doesn't evaluate any other firewall rules. Regardless of the direction of the rule, if the packet protocol and firewall policy type support connection tracking, a rule with the apply_security_profile_group action creates a firewall connection tracking table entry so that both ingress and egress packets are intercepted by the firewall endpoint or intercept endpoint group. You can't create rules with the apply_security_profile_group action in regional network firewall policies. Regional system firewall policies don't support rules with this action.
goto_next	Stops evaluating other rules in the firewall policy, and evaluates rules in the next step of the firewall policy and rule evaluation order . The next step of the firewall policy and rule evaluation order might be evaluation of rules in another firewall policy or the implied firewall rules.

Enforcement

You can choose whether a firewall policy rule is enforced by setting its state to enabled or disabled. You set the enforcement state when you create a rule or when you update a rule.

If you don't set an enforcement state when you create a new firewall rule, the firewall rule is automatically enabled.

Protocols and ports

Similar to VPC firewall rules, you must specify one or more protocol and port constraints when you create a rule. When specifying TCP or UDP in a rule, you can specify the protocol, the protocol and a destination port, or the protocol and a destination port range; you cannot specify only a port or port range. Also, you can only specify destination ports. Rules based on source ports aren't supported.

You can use the following protocol names in firewall rules: tcp , udp , icmp (for IPv4 ICMP), esp , ah , sctp , and ipip . For all other protocols, use the IANA protocol numbers .

Many protocols use the same name and number in both IPv4 and IPv6, but some protocols, such as ICMP, don't. To specify IPv4 ICMP, use icmp or protocol number 1 . To specify IPv6 ICMP, use protocol number 58 .

Firewall rules don't support specifying ICMP types and codes, just the protocol.

The IPv6 Hop-by-Hop protocol isn't supported in firewall rules.

If you don't specify protocol and port parameters, the rule applies to all protocols and destination ports.

Logging

Logging for firewall policy rules works the same as for VPC VPC firewall rules logging except for the following:

• The reference field includes the firewall policy ID and a number indicating the level of the resource to which the policy is attached. For example, 0 means that the policy is applied to an organization, and 1 means that the policy is applied to a top-level folder under the organization.

• Logs for firewall policy rules include a target_resource field that identifies the VPC networks to which the rule applies.

• Logging can only be enabled for allow , deny , and apply_security_profile_group rules; logging cannot be enabled for goto_next rules.

• When you enable logging for a rule that uses the apply_security_profile_group action, Cloud NGFW generates a single log entry when it intercepts a traffic session and redirects the traffic to the firewall endpoint for deep packet inspection. This log entry confirms that the firewall rule matched the traffic and successfully redirected it to the firewall endpoint. For more information, see VPC firewall rules logging .

• The firewall endpoint performs deep packet inspection, such as intrusion detection and prevention service and URL filtering service, and generates its own set of logs. These logs provide detailed information about the connections within the intercepted session, listing any detected threats or URL filtering actions. These deep packet inspection logs can generate multiple log entries per session.

Target, source, destination

Target, source, and destination parameters work together to determine the scope of a firewall rule.

• Target parameters: identify the resources that the firewall rule applies to.

• Source and destination parameters: define the traffic criteria. You can specify both for ingress and egress rules. Valid options for source and destination parameters depend on the target parameters and the direction of the firewall rule.

Targets

The target type parameter and one or more target parameters define the targets of a firewall rule. These targets of a firewall rule are the resources that the firewall rule protects.

• If the target type is omitted or is set to INSTANCES , the firewall rule applies to the network interfaces of Compute Engine instances, including Google Kubernetes Engine nodes and App Engine flexible environment instances. Both ingress and egress rules are supported.

  To specify which VM network interfaces the firewall rule applies to, use target parameters:

  • If you omit all target parameters, the firewall rule applies to the broadest instance targets .

  • For target parameter and target parameter combination details, see Specific targets and Specific target combinations .

• If the target type is set to INTERNAL_MANAGED_LB ( Preview ), the firewall rule applies to the managed Envoy proxies used by internal Application Load Balancers and internal proxy Network Load Balancers. Only ingress rules are supported.

  • If you omit the target forwarding rules parameter, the firewall rule applies to the broadest load balancer targets .

  • To restrict the firewall rule to a single load balancer, use the target forwarding rules parameter. For more information, see Specific targets .

Broadest instance targets

The broadest instance targets depend on the firewall policy type:

• Broadest instance targets for a rule in a hierarchical firewall policy: all VM network interfaces in a subnet in any region of any VPC network that's located in a project under the Resource Manager node (folder or organization) associated with the hierarchical firewall policy.

• Broadest instance targets for a rule in a global network firewall policy: all VM network interfaces in a subnet in any region of the VPC network that's associated with the global network firewall policy.

• Broadest instance targets for a rule in regional network firewall policy: all VM network interfaces in a subnet within the region and VPC network that are associated with the regional network firewall policy.

Broadest load balancer targets

Regional network firewall policies are the only policies whose rules support load balancer targets. The broadest load balancer targets are the forwarding rules for internal Application Load Balancers and internal proxy Network Load Balancers in the policy's region and associated VPC network.

Specific targets

The following table lists the target parameters, the firewall policies that support rules with each parameter, and the supported rule target types. If you don't specify a target parameter, the rule uses either the broadest instance targets or broadest load balancer targets , based on the rule's target type. The checkmark indicates that the parameter is supported, and the symbol indicates that the parameter isn't supported.

Specific target combinations

Rules that support the target-resources parameter can combine it with another target parameter to create a target parameter combination. The following table lists supported target parameter combinations, the firewall policies that support rules with each parameter, and the supported rule target types. If you don't specify a target parameter, the rule uses either the broadest instance targets or broadest load balancer targets , based on the rule's target type.

The checkmark indicates that the parameter is supported, and the symbol indicates that the parameter isn't supported.

Target forwarding rules format

When a firewall rule's target type is set to INTERNAL_MANAGED_LB ( Preview ), the target forwarding rules parameter accepts values in the following formats:

• For regional internal Application Load Balancers and regional internal proxy Network Load Balancers:

  • https://compute.googleapis.com/compute/v1/projects/ PROJECT_ID /regions/ REGION /forwardingRules/ FORWARDING_RULE_NAME
  • projects/ PROJECT_ID /regions/ REGION /forwardingRules/ FORWARDING_RULE_NAME

• For cross-region internal Application Load Balancers and cross-region internal proxy Network Load Balancers:

  • https://compute.googleapis.com/compute/v1/projects/ PROJECT_ID /global/forwardingRules/ FORWARDING_RULE_NAME
  • projects/ PROJECT_ID /global/forwardingRules/ FORWARDING_RULE_NAME

Targets and IP addresses for ingress rules

When a firewall rule target type is either omitted or set to INSTANCES , the rule applies to packets that are routed to network interfaces of target VMs.

• If the ingress firewall rule includes a destination IP address range, the packet's destination must fit within one of the explicitly defined destination IP address ranges.

• If the ingress firewall rule does not include a destination IP address range, the packet's destination must match one of the following IP addresses of each target VM:

  • The primary internal IPv4 address assigned to the instance's NIC.

  • Any configured alias IP address ranges on the instance's NIC.

  • The external IPv4 address that's associated with the instance's NIC.

  • If IPv6 is configured on the subnet, any of the IPv6 addresses assigned to the NIC.

  • An internal or external IP address associated with a forwarding rule used for pass-through load balancing, where the instance is a backend for an internal passthrough Network Load Balancer or an external passthrough Network Load Balancer.

  • An internal or external IP address associated with a forwarding rule used for protocol forwarding, where the instance is referenced by a target instance.

  • An IP address within the destination range of a custom static route that uses the instance ( next-hop-instance or next-hop-address ) as a next hop VM.

  • An IP address within the destination range of a custom static route that uses an internal passthrough Network Load Balancer ( next-hop-ilb ) as a next hop if the VM is a backend for that load balancer.

When a firewall rule's target type is set to INTERNAL_MANAGED_LB ( Preview ), the rule filters packets routed to the managed Envoy proxies associated with internal Application Load Balancers and internal proxy Network Load Balancers. When using destination IP ranges in an ingress rule, make sure that the range includes the relevant load balancer forwarding rule IP address.

Targets and IP addresses for egress rules

When a firewall rule target type is either omitted or set to INSTANCES , the rule applies to packets that are emitted by network interfaces of target VMs.

• If the target VM has IP forwarding disabled (default), the VM can only emit packets with the following sources:

  • The primary internal IPv4 address of an instance's NIC.

  • Any configured alias IP address range on an instance's NIC.

  • If IPv6 is configured on the subnet, any of the IPv6 addresses assigned to the NIC.

  • An internal or external IP address associated with a forwarding rule, for pass-through load balancing or protocol forwarding. This is valid if the instance is a backend for an internal passthrough Network Load Balancer, an external passthrough Network Load Balancer, or is referenced by a target instance.

  If the egress firewall rule includes source IP address ranges, the target VMs are still limited to the source IP addresses mentioned previously, but a source parameter can be used to refine the sources. Use of a source parameter without enabling IP forwarding never expands the set of possible packet source addresses.

  If the egress firewall rule does not include a source IP address range, all the source IP addresses mentioned previously are permitted.

• If the target VM has IP forwarding enabled, the VM can emit packets with arbitrary source addresses. You can use the source parameter to more precisely define the set of allowed packet sources.

Sources

Source parameter values depend on the direction of the firewall rule.

Sources for ingress rules

This table lists the source parameters for ingress rules, the firewall policies that support each parameter, and the rule target types that are compatible with each parameter. You must specify at least one source parameter. The checkmark indicates that the parameter is supported, and the symbol indicates that the parameter isn't supported.

Hierarchical	Global network	Regional network	INSTANCES	INTERNAL_MANAGED_LB
Source IP address ranges A list consisting of IPv4 addresses in CIDR format or IPv6 addresses in CIDR format. The list is stored within the firewall policy rule itself.
Source address groups Reusable collections of IPv4 addresses in CIDR format or IPv6 addresses in CIDR format. The firewall rule references the collection. For more information, see Address groups for firewall policies .
Source domain names A list of one or more source domain names. For more information, including how domain names are converted to IP addresses, see FQDN objects .
Source secure tag values from a tag key with network purpose data A list of one or more tag values from a tag key whose purpose data specifies a single VPC network. For more information, see Secure tags for firewalls and How source secure tags imply packet sources .
Source secure tag values from a tag key with organization purpose data A list of one or more tag values from a tag key whose purpose data is organization=auto . For more information, see Secure tags for firewalls and How source secure tags imply packet sources .
Source geolocations A list of one or more source geographic locations specified as two-letter country or region codes. For more information, see Geolocation objects
Source Google Threat Intelligence lists A list of one or more predefined Google Threat Intelligence list names. For more information, see Google Threat Intelligence for firewall policy rules .
Source network context A constraint that defines a security boundary. Valid values depend on the target type of the rule. For more information, see Network contexts .

Ingress rule source combinations

In a single ingress rule, you can use two or more source parameters to produce a source combination. Cloud NGFW enforces the following constraints on source combinations of each ingress rule:

• Source IP address ranges must contain either IPv4 or IPv6 CIDRs, not a combination of both.
• A source address group that contains IPv4 CIDRs cannot be used with a source address group that contains IPv6 CIDRs.
• A source IP address range that contains IPv4 CIDRs cannot be used with a source address group that contains IPv6 CIDRs.
• A source IP address range that contains IPv6 CIDRs cannot be used with a source address group that contains IPv4 CIDRs.
• The internet network context cannot be used with the source secure tags.
• Non-internet context, VPC networks context, and inter-VPC context cannot be used with source Google Threat Intelligence lists or source geolocations.

Cloud NGFW applies the following logic to match the packets to an ingress rule that uses a source combination:

• If the source combination does not include a source network context, packets match the ingress rule if they match at least one source parameter in the source combination.

• If the source combination includes a source network context, packets match the ingress rule if they match the source network context and at least one of the other source parameters in the source combination.

How source secure tags imply packet sources

An ingress firewall rule can use source secure tag values when its target type is omitted or set to INSTANCES . Secure tag values identify network interfaces, not packet characteristics like IP addresses.

Packets sent from a network interface of a VM instance match an ingress rule that uses a source secure tag value according to the following rules:

• If the ingress rule is in a regional network policy, the VM instance must be located in a zone of the same region as the regional network firewall policy. Otherwise, the VM instance can be located in any zone.

• The VM instance must be associated with the same secure tag value that is used as a source secure tag in an ingress firewall rule.

• The secure tag value associated with the VM instance and used by the ingress firewall rule must come from a tag key whose purpose-data attribute identifies at least one VPC network that contains a network interface of the VM instance:

  • If the tag key's purpose data specifies a single VPC network, ingress firewall rules that use the source secure tag value apply to the network interfaces of the VM instance that are in that VPC network.

  • If the tag key's purpose data specifies the organization, ingress firewall rules that use the source secure tag value apply to the network interfaces of the VM instance that are in any VPC network of the organization.

• The identified VM network interface must meet one of the following criteria:

  • The VM network interface is in the same VPC network as the VPC network to which the firewall policy applies.
  • The VM network interface is in a VPC network that's connected, using VPC Network Peering, to the VPC network to which the firewall policy applies.

For more information about secure tags for firewalls, see Specifications .

Sources for egress rules

You can use the following sources for egress rules in both hierarchical firewall policies and network firewall policies:

• Default—implied by target: if you omit the source parameter from an egress rule, packet sources are defined implicitly as described in Targets and IP addresses for egress rules .

• Source IPv4 address ranges: a list of IPv4 addresses in CIDR format.

• Source IPv6 address ranges: a list of IPv6 addresses in CIDR format.

Follow these guidelines to add source IP address ranges for egress rules:

• If a VM interface has both internal and external IPv4 addresses assigned, only the internal IPv4 address is used during rule evaluation.

• If you have a source IP address range and destination parameters in the egress rule, then the destination parameters are resolved into the same IP version as the source IP version.

  For example, in an egress rule, you have an IPv4 address range in the source parameter and an FQDN object in the destination parameter. If the FQDN resolves into both IPv4 and IPv6 addresses, only the resolved IPv4 address is used during rule enforcement.

Destinations

Destination parameter values depend on the direction of the firewall rule.

Destinations for ingress rules

You can use the following destinations for ingress firewall rules in both hierarchical and network firewall policies:

• Default—implied by target: if you omit the destination parameter from an ingress rule, packet destinations are defined implicitly as described in Targets and IP addresses for ingress rules .

• Destination IPv4 address ranges: a list of IPv4 addresses in CIDR format.

• Destination IPv6 address ranges: a list of IPv6 addresses in CIDR format.

Follow these guidelines to add destination IP address ranges for ingress rules:

• If a VM interface has both internal and external IPv4 addresses assigned, only the internal IPv4 address is used during rule evaluation.

• If you have both source and destination parameters defined in an ingress rule, then the source parameters are resolved into the same IP version as the destination IP version. To learn more about how to define a source for ingress rules, see Sources for ingress rules in hierarchical firewall policies and Sources for ingress rules in network firewall policies .

  For example, in an ingress rule, you have an IPv6 address range in the destination parameter and a geolocation country code in the source parameter. During rule enforcement, only the mapped IPv6 address is used for the specified source country code.

Destinations for egress rules

This table lists the destination parameters for egress rules, the firewall policies that support each parameter, and the rule target types that are compatible with each parameter. You must specify at least one destination parameter. The checkmark indicates that the parameter is supported, and the symbol indicates that the parameter isn't supported.

Hierarchical	Global network	Regional network	INSTANCES	INTERNAL_MANAGED_LB
Destination IP address ranges A list consisting of IPv4 addresses in CIDR format or IPv6 addresses in CIDR format. The list is stored within the firewall policy rule itself.
Destination address groups Reusable collections of IPv4 addresses in CIDR format or IPv6 addresses in CIDR format. The firewall policy rule references the collection. For more information, see Address groups for firewall policies .
Destination domain names A list of one or more destination domain names. For more information, including how domain names are converted to IP addresses, see FQDN objects .
Destination geolocations A list of one or more source geographic locations specified as two-letter country or region codes. For more information, see Geolocation objects .
Destination Google Threat Intelligence lists A list of one or more predefined Google Threat Intelligence list names. For more information, see Google Threat Intelligence for firewall policy rules .
Destination network context A constraint that defines a security boundary.

Egress rule destination combinations

In a single egress rule, you can use two or more destination parameters to produce a destination combination. Cloud NGFW enforces the following constraints on destination combinations of each egress rule:

• Destination IP address ranges must contain either IPv4 or IPv6 CIDRs, not a combination of both.
• A destination address group that contains IPv4 CIDRs cannot be used with a destination address group that contains IPv6 CIDRs.
• A destination IP address range that contains IPv4 CIDRs cannot be used with a destination address group that contains IPv6 CIDRs.
• A destination IP address range that contains IPv6 CIDRs cannot be used with a destination address group that contains IPv4 CIDRs. 8 Destination Google Threat Intelligence lists or destination geolocations cannot be used with destination non-internet network context.

Cloud NGFW applies the following logic to match the packets to an egress rule that uses a destination combination:

• If the destination combination does not include a destination network context, packets match the egress rule if they match at least one destination parameter in the destination combination.

• If the destination combination includes a destination network context, packets match the egress rule if they match the destination network context and at least one of the other destination parameters in the destination combination.

What's next

• Google Threat Intelligence for firewall policy rules
• Fully qualified domain name objects overview
• Address groups for firewall policies