Policy as Code for the Cloud Development Kit

Cloud Patrol let's you define common policies with remediation strategies for your AWS CDK stacks and enforce them across your CDK stacks / applications.

NB: This is an alpha release - Everything might change.

Use Cases

Make sure your Cloud resources are:

• Tagged properly
• Secure by default
• Following naming conventions
• Within your budget
• Not provisioned with hardcoded secrets
• Pretty much whatever you can think of :)

Geetting Started

yarn add cloudpatrol

Example

Given this example:

import * as cdk from '@aws-cdk/core';
import { ExampleStack } from '../lib/example-stack';
import { AwsCdkPatrol } from 'cloudpatrol/lib'
import { awsDefaults } from 'cloudpatrol/policies/aws/packs/good-defaults'

const app = new cdk.App();
const stack = new ExampleStack(app, 'ExampleStack');

const cloudPatrol = new AwsCdkPatrol(awsDefaults)
cloudPatrol.check(stack)

We can do the following:

Check the full example.

Reports

Currently, there are two reporting mechanisms:

AWS CDK inline report

As part of your normal CDK commands (e.g. cdk synth --app bin/example.js), will perform reporting on the Construct nodes itself and stop the synth process on errors.

Terminal Report

For CI / CD workflows and local testing, just execute your CDK app directly with node (e.g. node ./bin/example.js). This is great for dedicated validation of policies without the synthesized output.

Custom Reporting

Hasn't been implemented, yet. But it's on the agenda, and probably possible right now with a bit of effort.

Policies

Full Example

/**
 * This Policy ensures that a bucket is properly versioned
 *
 * @cloudformationResource AWS::S3::Bucket
 * @see https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-s3-bucket-versioningconfig.html
 */
export class BucketVersioningPolicy extends Policy implements PolicyInterface {  
  public policyName = 'Bucket Versioning'
  public description = 'This ensures that a bucket is properly versioned'
  public link = 'https//docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-s3-bucket-versioningconfig.html'
  public scope = s3.CfnBucket
  
  public validator(node: s3.CfnBucket, reporter: Reportable): void { 
    if (!node.versioningConfiguration || 
      (!cdk.Tokenization.isResolvable(node.versioningConfiguration) && node.versioningConfiguration.status !== 'Enabled')) {
      reporter.addWarning(node, this, 'Bucket versioning is not enabled');
    }
  }
}

Implemented Policies

• Ec2InstanceTypePolicy
• BucketVersioningPolicy
• BucketEncryptionPolicy
• ... create a Pull Request to add yours :)

Custom Policies

Policies have to follow this schema

class YourCustomPolicy extends Policy implements PolicyInterface {
  //...
}

Scope

There are two options to define the scope of a Policy:

Define an explicit scope:

class YourCustomPolicy extends Policy implements PolicyInterface {
  //...
  public scope = s3.CfnBucket
  //...
}

Overwrite isApplicable:

class YourCustomPolicy extends Policy implements PolicyInterface {
  //...
  public isApplicable(node: cdk.Resource): boolean {
    // your custom logic here
  }
  //...

Policy Validation Logic

class YourCustomPolicy extends Policy implements PolicyInterface {
  //...
  public validator(node: s3.CfnBucket, reporter: Reportable, context: PolicyContext): void { 
    // your custom logic here.
  }
  //...

Found issues can be reported via the reporter object. You can report multiple issues per Policy. There are three different issue severities:

• Info
• Warning
• Error

context is persistent across the entire Stack validation and can be passed in for dynamic information.

How does it work?

Cloud Patrol makes use of Aspects to visit all nodes in a given Construct (e.g. your stack). Aspects will be applied in the prepare stage, which will be called before synthesizing the stack. That's great if you're going to synthesize anyway. However, if you just wanna run the Cloud Patrol checks, we have to invoke the preparation by ourselves. Something along the lines of this:

  stack.node.applyAspect(this);
  cdk.ConstructNode.prepare(stack.node);

Roadmap

• [ ] Simplify Policy definition
• [ ] Drop dependency to aws-cdk/core where possible, extract the rest to dedicated package
• [ ] Implement remediation strategies
• [ ] Documentation
• [ ] Policy generator
• [ ] Modularize and detangle Reporter to allow multiple ways of reporting
• [ ] Github Actions for easy integration
• [ ] .cloudpatrol file?
• [ ] Provide more policies out of the box
• [ ] CLI which autodetects Stacks for inspection
• [ ] Integration tests against the last X releases of the AWS CDK
• [ ] Integrate supported languages of jsii
• [ ] Integrate in CDK based frameworks like cdk8s and terrastack