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Google Cloud VPC Firewall

This module allows creation and management of different types of firewall rules for a single VPC network:

  • custom rules via the egress_rules and ingress_rules variables
  • optional predefined rules that simplify prototyping via the default_rules_config variable

The predefined rules are enabled by default and set to the ranges of the GCP health checkers for HTTP/HTTPS, and the IAP forwarders for SSH. See the relevant section below on how to configure or disable them.

Examples

Minimal open firewall

This is often useful for prototyping or testing infrastructure, allowing open ingress from the private range, enabling SSH to private addresses from IAP, and HTTP/HTTPS from the health checkers.

module "firewall" {
  source     = "./fabric/modules/net-vpc-firewall"
  project_id = "my-project"
  network    = "my-network"
  default_rules_config = {
    admin_ranges = ["10.0.0.0/8"]
  }
}
# tftest modules=1 resources=4

Custom rules

This is an example of how to define custom rules, with a sample rule allowing open ingress for the NTP protocol to instances with the ntp-svc tag.

Some implicit defaults are used in the rules variable types and can be controlled by explicitly setting specific attributes:

  • action is controlled via the deny attribute which defaults to true for egress and false for ingress
  • priority defaults to 1000
  • destination ranges (for egress) and source ranges (for ingress) default to ["0.0.0.0/0"] if not explicitly set or set to null, to disable the behaviour set ranges to the empty list ([])
  • rules default to all protocols if not set
module "firewall" {
  source     = "./fabric/modules/net-vpc-firewall"
  project_id = "my-project"
  network    = "my-network"
  default_rules_config = {
    admin_ranges = ["10.0.0.0/8"]
  }
  egress_rules = {
    # implicit deny action
    allow-egress-rfc1918 = {
      deny        = false
      description = "Allow egress to RFC 1918 ranges."
      destination_ranges = [
        "10.0.0.0/8", "172.16.0.0/12", "192.168.0.0/16"
      ]
    }
    allow-egress-tag = {
      deny        = false
      description = "Allow egress from a specific tag to 0/0."
      targets     = ["target-tag"]
    }
    deny-egress-all = {
      description = "Block egress."
    }
  }
  ingress_rules = {
    # implicit allow action
    allow-ingress-ntp = {
      description = "Allow NTP service based on tag."
      targets     = ["ntp-svc"]
      rules       = [{ protocol = "udp", ports = [123] }]
    }
    allow-ingress-tag = {
      description   = "Allow ingress from a specific tag."
      source_ranges = []
      sources       = ["client-tag"]
      targets       = ["target-tag"]
    }
  }
}
# tftest modules=1 resources=9

Controlling or turning off default rules

Predefined rules can be controlled or turned off via the default_rules_config variable.

Overriding default tags and ranges

Each protocol rule has a default set of tags and ranges:

  • the health check range and the http-server/https-server tag for HTTP/HTTPS, matching tags set via GCP console flags on GCE instances
  • the IAP forwarders range and ssh tag for SSH

Default tags and ranges can be overridden for each protocol, like shown here for SSH:

module "firewall" {
  source     = "./fabric/modules/net-vpc-firewall"
  project_id = "my-project"
  network    = "my-network"
  default_rules_config = {
    ssh_ranges = ["10.0.0.0/8"]
    ssh_tags   = ["ssh-default"]
  }
}
# tftest modules=1 resources=3

Disabling predefined rules

Default rules can be disabled individually by specifying an empty set of ranges:

module "firewall" {
  source     = "./fabric/modules/net-vpc-firewall"
  project_id = "my-project"
  network    = "my-network"
  default_rules_config = {
    ssh_ranges = []
  }
}
# tftest modules=1 resources=2

Or the entire set of rules can be disabled via the disabled attribute:

module "firewall" {
  source     = "./fabric/modules/net-vpc-firewall"
  project_id = "my-project"
  network    = "my-network"
  default_rules_config = {
    disabled = true
  }
}
# tftest modules=0 resources=0

Rules Factory

The module includes a rules factory (see Resource Factories) for the massive creation of rules leveraging YaML configuration files. Each configuration file can optionally contain more than one rule which a structure that reflects the custom_rules variable.

module "firewall" {
  source     = "./fabric/modules/net-vpc-firewall"
  project_id = "my-project"
  network    = "my-network"
  factories_config = {
    rules_folder  = "configs/firewall/rules"
    cidr_tpl_file = "configs/firewall/cidrs.yaml"
  }
  default_rules_config = { disabled = true }
}
# tftest modules=1 resources=3 files=lbs,cidrs
# tftest-file id=lbs path=configs/firewall/rules/load_balancers.yaml
ingress:
  allow-healthchecks:
    description: Allow ingress from healthchecks.
    source_ranges:
      - healthchecks
    targets: ["lb-backends"]
    rules:
      - protocol: tcp
        ports:
          - 80
          - 443
  allow-service-1-to-service-2:
    description: Allow ingress from service-1 SA
    targets: ["service-2"]
    use_service_accounts: true
    sources:
      - [email protected]
    rules:
      - protocol: tcp
        ports:
          - 80
          - 443
egress:
  block-telnet:
    description: block outbound telnet
    deny: true
    rules:
      - protocol: tcp
        ports:
          - 23
# tftest-file id=cidrs path=configs/firewall/cidrs.yaml
healthchecks:
  - 35.191.0.0/16
  - 130.211.0.0/22
  - 209.85.152.0/22
  - 209.85.204.0/22

Variables

name description type required default
network Name of the network this set of firewall rules applies to. string ✓
project_id Project id of the project that holds the network. string ✓
default_rules_config Optionally created convenience rules. Set the 'disabled' attribute to true, or individual rule attributes to empty lists to disable. object({…}) {}
egress_rules List of egress rule definitions, default to deny action. Null destination ranges will be replaced with 0/0. map(object({…})) {}
factories_config Paths to data files and folders that enable factory functionality. object({…}) null
ingress_rules List of ingress rule definitions, default to allow action. Null source ranges will be replaced with 0/0. map(object({…})) {}
named_ranges Define mapping of names to ranges that can be used in custom rules. map(list(string)) {…}

Outputs

name description sensitive
default_rules Default rule resources.
rules Custom rule resources.