Configure WAF custom rules

This page provides examples of creating WAF custom rules in a zone or account using Terraform. The examples cover the following scenarios:

• Zone-level configurations:

  • Add a custom rule to a zone

• Account-level configurations:

  • Create and deploy a custom ruleset
  • Add a custom rule checking for exposed credentials

For more information on custom rules, refer to Custom rules in the Cloudflare WAF documentation.

​​ Before you start

​​ Obtain the necessary account or zone IDs

The Terraform configurations provided in this page need the zone ID (or account ID) of the zone/account where you will deploy rulesets.

• To retrieve the list of accounts you have access to, including their IDs, use the List accounts Open API docs link operation.
• To retrieve the list of zones you have access to, including their IDs, use the List zones Open API docs link operation.

​​ Import or delete existing rulesets

Terraform assumes that it has complete control over account and zone rulesets. If you already have rulesets configured in your account or zone, do one of the following:

• Import existing rulesets to Terraform using the cf-terraforming tool. Recent versions of the tool can generate resource definitions for existing rulesets and import their configuration to Terraform state.
• Start from scratch by deleting existing rulesets (account and zone rulesets with "kind": "root" and "kind": "zone", respectively) and then defining your rulesets configuration in Terraform.

​​ Zone-level configurations

​​ Add a custom rule to a zone

The following example configures a custom rule in the zone entry point ruleset for the http_request_firewall_custom phase for zone with ID <ZONE_ID>. The rule will block all traffic on non-standard HTTP(S) ports:

resource "cloudflare_ruleset" "zone_custom_firewall" {
  zone_id     = "<ZONE_ID>"
  name        = "Phase entry point ruleset for custom rules in my zone"
  description = ""
  kind        = "zone"
  phase       = "http_request_firewall_custom"

  rules {
    action = "block"
    expression = "(not cf.edge.server_port in {80 443})"
    description = "Block ports other than 80 and 443"
    enabled = true
  }
}

To create another custom rule, add a new rules object to the same cloudflare_ruleset resource.

​​ Account-level configurations

​​ Create and deploy a custom ruleset

The following example creates a custom ruleset in the account with ID <ACCOUNT_ID> containing a single custom rule. This custom ruleset is then deployed using a separate cloudflare_ruleset Terraform resource. If you do not deploy a custom ruleset, it will not execute.

The following configuration creates the custom ruleset with a single rule:

resource "cloudflare_ruleset" "account_firewall_custom_ruleset" {
  account_id  = "<ACCOUNT_ID>"
  name        = "Custom ruleset blocking traffic in non-standard HTTP(S) ports"
  description = ""
  kind        = "custom"
  phase       = "http_request_firewall_custom"

  rules {
    action = "block"
    expression = "(not cf.edge.server_port in {80 443})"
    description = "Block ports other than 80 and 443"
    enabled = true
  }
}

To create another custom rule in the custom ruleset, add a new rules object to the same cloudflare_ruleset resource.

The following configuration deploys the custom ruleset at the account level. It defines a dependency on the account_firewall_custom_ruleset resource and uses the ID of the created custom ruleset in action_parameters:

resource "cloudflare_ruleset" "account_firewall_custom_entrypoint" {
  account_id  = "<ACCOUNT_ID>"
  name        = "Account-level entry point ruleset for the http_request_firewall_custom phase deploying a custom ruleset"
  description = ""
  kind        = "root"
  phase       = "http_request_firewall_custom"

  depends_on = [cloudflare_ruleset.account_firewall_custom_ruleset]

  rules {
    action = "execute"
    action_parameters {
      id = cloudflare_ruleset.account_firewall_custom_ruleset.id
    }
    expression = "(cf.zone.name eq \"example.com\")"
    description = "Deploy custom ruleset for example.com"
    enabled = true
  }
}

For more information on configuring and deploying custom rulesets, refer to Work with custom rulesets in the Ruleset Engine documentation.

​​ Add a custom rule checking for exposed credentials

The following configuration creates a custom ruleset with a single rule that checks for exposed credentials.

resource "cloudflare_ruleset" "account_firewall_custom_ruleset_exposed_creds" {
  account_id  = "<ACCOUNT_ID>"
  name        = "Custom ruleset checking for exposed credentials"
  description = ""
  kind        = "custom"
  phase       = "http_request_firewall_custom"

  rules {
    action = "rewrite"
    action_parameters {
      headers {
        name = "Exposed-Credential-Check"
        operation = "set"
        value = "1"
      }
    }
    exposed_credential_check {
      username_expression = "url_decode(http.request.body.form[\"username\"][0])"
      password_expression = "url_decode(http.request.body.form[\"password\"][0])"
    }
    expression = "http.request.method == \"POST\" && http.request.uri == \"/login.php\""
    description = "Add header when there is a rule match and exposed credentials are detected"
    enabled = true
  }
}

To create another rule, add a new rules object to the same cloudflare_ruleset resource.

The following configuration deploys the custom ruleset. It defines a dependency on the account_firewall_custom_ruleset_exposed_creds resource and obtains the ID of the created custom ruleset:

resource "cloudflare_ruleset" "account_firewall_custom_entrypoint" {
  account_id  = "<ACCOUNT_ID>"
  name        = "Account-level entry point ruleset for the http_request_firewall_custom phase deploying a custom ruleset checking for exposed credentials"
  description = ""
  kind        = "root"
  phase       = "http_request_firewall_custom"

  depends_on = [cloudflare_ruleset.account_firewall_custom_ruleset_exposed_creds]

  rules {
    action = "execute"
    action_parameters {
      id = cloudflare_ruleset.account_firewall_custom_ruleset_exposed_creds.id
    }
    expression = "(cf.zone.name eq \"example.com\")"
    description = "Deploy custom ruleset for example.com"
    enabled = true
  }
}