Automating IP blocking with Cloudflare security rulesets

Question

Pulumi · Accepted Answer

To automate IP blocking with Cloudflare, Pulumi provides a set of resources that enable the management of various security rules, including IP access rules and firewall rules which can be used to configure security settings and block or challenge traffic based on IP addresses or other criteria.

Below, I will present a Pulumi program in TypeScript that demonstrates how to create a Cloudflare firewall rule to block requests from a specific IP address. This is done using the `cloudflare.FirewallRule` resource, which allows you to define granular controls over how traffic is handled by Cloudflare's network.

In this example, we will add a firewall rule to block IP `198.51.100.4` (this is a sample IP - in a real-world scenario you will replace it with the IP you want to block). You will need to know your zone ID for the domain you are managing in Cloudflare.

Before jumping into the code, here's an overview of why we use `cloudflare.FirewallRule`:

- **cloudflare.FirewallRule**: This resource allows you to create and manage individual firewall rules that determine what action to take when traffic matches the rule. You can specify various kinds of traffic filtering criteria such as IP addresses, IP ranges, countries, or even more complex expressions.

Here's the program:

```typescript
import * as pulumi from '@pulumi/pulumi';
import * as cloudflare from '@pulumi/cloudflare';

// This is your Cloudflare zone ID where the rules will be applied
const zoneId = 'your-zone-id';

// Create a filter for the IP address to be blocked
const ipFilter = new cloudflare.Filter("ipFilter", {
    zoneId: zoneId,
    expression: "(ip.src eq 198.51.100.4)", // IP to block
    paused: false, // The filter is active
    description: "Filter to block a specific IP address", // A meaningful description
});

// Create a firewall rule using the filter above to block the IP
const blockIpRule = new cloudflare.FirewallRule("blockIpRule", {
    action: "block", // The action to take when the rule matches - block the request
    priority: 1, // Priority of the firewall rule (lower numbers have higher priority)
    zoneId: zoneId,
    filterId: ipFilter.id, // Reference to the filter created above
    description: "A rule to block a specific IP address", // A meaningful description
});

// The output showing the rule ID which you can use to manage the rule on Cloudflare dashboard
export const firewallRuleId = blockIpRule.id;
```

In this program, we perform the following:

1. Import the necessary Pulumi libraries for Cloudflare.
2. Define our Cloudflare zone ID, where the firewall rules will be applied.
3. Create a `cloudflare.Filter` resource with an expression that matches the specific IP address we wish to block.
4. Create a `cloudflare.FirewallRule` resource that uses the IP filter and specifies the action as "block" so that any requests from this IP are blocked.
5. Export the ID of the firewall rule for further reference.

To run this program, you will first need to have Pulumi installed and configured with your Cloudflare credentials. Then, replace `'your-zone-id'` with your actual zone ID. Make sure you have the `'@pulumi/cloudflare'` package installed in your Node.js project by running `npm install @pulumi/cloudflare`.

Note that in a real deployment, you will need to take care to keep sensitive information like your Cloudflare zone ID and any IP addresses you're blocking secure, and only share this information with trusted parties responsible for managing your infrastructure.

Remember to replace `'198.51.100.4'` with the IP address you intend to block. The priority can be adjusted based on other existing rules in your Cloudflare configuration, where a lower number indicates a higher precedence.

After you write the code, compile it with `tsc` to generate the JavaScript code which Pulumi uses to deploy your infrastructure. Then run `pulumi up` to preview and apply your infrastructure changes. If it's your first time using Pulumi, you may need to run `pulumi login` and `pulumi new` first to create a new Pulumi project.