cdk-nag

Check CDK applications or CloudFormation templates for best practices using a combination of available rule packs. Inspired by cfn_nag.

Check out this blog post for a guided overview!

Available Rules and Packs

See RULES for more information on all the available packs.

RULES also includes a collection of additional rules that are not currently included in any of the pre-built NagPacks, but are still available for inclusion in custom NagPacks.

Read the NagPack developer docs if you are interested in creating your own pack.

Usage

For a full list of options See NagPackProps in the API.md

Including in an application

import { App, Aspects } from 'aws-cdk-lib';
import { CdkTestStack } from '../lib/cdk-test-stack';
import { AwsSolutionsChecks } from 'cdk-nag';

const app = new App();
new CdkTestStack(app, 'CdkNagDemo');
// Simple rule informational messages
Aspects.of(app).add(new AwsSolutionsChecks());
// Additional explanations on the purpose of triggered rules
// Aspects.of(stack).add(new AwsSolutionsChecks({ verbose: true }));

Suppressing a Rule

Example 1) Default Construct

import { SecurityGroup, Vpc, Peer, Port } from 'aws-cdk-lib/aws-ec2';
import { Stack, StackProps } from 'aws-cdk-lib';
import { Construct } from 'constructs';
import { NagSuppressions } from 'cdk-nag';

export class CdkTestStack extends Stack {
  constructor(scope: Construct, id: string, props?: StackProps) {
    super(scope, id, props);
    const test = new SecurityGroup(this, 'test', {
      vpc: new Vpc(this, 'vpc'),
    });
    test.addIngressRule(Peer.anyIpv4(), Port.allTraffic());
    NagSuppressions.addResourceSuppressions(test, [
      { id: 'AwsSolutions-EC23', reason: 'lorem ipsum' },
    ]);
  }
}

Example 2) On Multiple Constructs

import { SecurityGroup, Vpc, Peer, Port } from 'aws-cdk-lib/aws-ec2';
import { Stack, StackProps } from 'aws-cdk-lib';
import { Construct } from 'constructs';
import { NagSuppressions } from 'cdk-nag';

export class CdkTestStack extends Stack {
  constructor(scope: Construct, id: string, props?: StackProps) {
    super(scope, id, props);
    const vpc = new Vpc(this, 'vpc');
    const test1 = new SecurityGroup(this, 'test', { vpc });
    test1.addIngressRule(Peer.anyIpv4(), Port.allTraffic());
    const test2 = new SecurityGroup(this, 'test', { vpc });
    test2.addIngressRule(Peer.anyIpv4(), Port.allTraffic());
    NagSuppressions.addResourceSuppressions(
      [test1, test2],
      [{ id: 'AwsSolutions-EC23', reason: 'lorem ipsum' }]
    );
  }
}

Example 3) Child Constructs

import { User, PolicyStatement } from 'aws-cdk-lib/aws-iam';
import { Stack, StackProps } from 'aws-cdk-lib';
import { Construct } from 'constructs';
import { NagSuppressions } from 'cdk-nag';

export class CdkTestStack extends Stack {
  constructor(scope: Construct, id: string, props?: StackProps) {
    super(scope, id, props);
    const user = new User(this, 'rUser');
    user.addToPolicy(
      new PolicyStatement({
        actions: ['s3:PutObject'],
        resources: ['arn:aws:s3:::bucket_name/*'],
      })
    );
    // Enable adding suppressions to child constructs
    NagSuppressions.addResourceSuppressions(
      user,
      [
        {
          id: 'AwsSolutions-IAM5',
          reason: 'lorem ipsum',
          appliesTo: ['Resource::arn:aws:s3:::bucket_name/*'], // optional
        },
      ],
      true
    );
  }
}

Example 4) Stack Level

import { App, Aspects } from 'aws-cdk-lib';
import { CdkTestStack } from '../lib/cdk-test-stack';
import { AwsSolutionsChecks, NagSuppressions } from 'cdk-nag';

const app = new App();
const stack = new CdkTestStack(app, 'CdkNagDemo');
Aspects.of(app).add(new AwsSolutionsChecks());
NagSuppressions.addStackSuppressions(stack, [
  { id: 'AwsSolutions-EC23', reason: 'lorem ipsum' },
]);

Example 5) Construct path

If you received the following error on synth/deploy

[Error at /StackName/Custom::CDKBucketDeployment8675309/ServiceRole/Resource] AwsSolutions-IAM4: The IAM user, role, or group uses AWS managed policies

import { Bucket } from 'aws-cdk-lib/aws-s3';
import { BucketDeployment } from 'aws-cdk-lib/aws-s3-deployment';
import { Stack, StackProps } from 'aws-cdk-lib';
import { Construct } from 'constructs';
import { NagSuppressions } from 'cdk-nag';

export class CdkTestStack extends Stack {
  constructor(scope: Construct, id: string, props?: StackProps) {
    super(scope, id, props);
    new BucketDeployment(this, 'rDeployment', {
      sources: [],
      destinationBucket: Bucket.fromBucketName(this, 'rBucket', 'foo'),
    });
    NagSuppressions.addResourceSuppressionsByPath(
      this,
      '/StackName/Custom::CDKBucketDeployment8675309/ServiceRole/Resource',
      [{ id: 'AwsSolutions-IAM4', reason: 'at least 10 characters' }]
    );
  }
}

Example 6) Granular Suppressions of findings

Certain rules support granular suppressions of findings. If you received the following errors on synth/deploy

[Error at /StackName/rFirstUser/DefaultPolicy/Resource] AwsSolutions-IAM5[Action::s3:*]: The IAM entity contains wildcard permissions and does not have a cdk-nag rule suppression with evidence for those permission.
[Error at /StackName/rFirstUser/DefaultPolicy/Resource] AwsSolutions-IAM5[Resource::*]: The IAM entity contains wildcard permissions and does not have a cdk-nag rule suppression with evidence for those permission.
[Error at /StackName/rSecondUser/DefaultPolicy/Resource] AwsSolutions-IAM5[Action::s3:*]: The IAM entity contains wildcard permissions and does not have a cdk-nag rule suppression with evidence for those permission.
[Error at /StackName/rSecondUser/DefaultPolicy/Resource] AwsSolutions-IAM5[Resource::*]: The IAM entity contains wildcard permissions and does not have a cdk-nag rule suppression with evidence for those permission.

By applying the following suppressions

import { User } from 'aws-cdk-lib/aws-iam';
import { Stack, StackProps } from 'aws-cdk-lib';
import { Construct } from 'constructs';
import { NagSuppressions } from 'cdk-nag';

export class CdkTestStack extends Stack {
  constructor(scope: Construct, id: string, props?: StackProps) {
    super(scope, id, props);
    const firstUser = new User(this, 'rFirstUser');
    firstUser.addToPolicy(
      new PolicyStatement({
        actions: ['s3:*'],
        resources: ['*'],
      })
    );
    const secondUser = new User(this, 'rSecondUser');
    secondUser.addToPolicy(
      new PolicyStatement({
        actions: ['s3:*'],
        resources: ['*'],
      })
    );
    const thirdUser = new User(this, 'rSecondUser');
    thirdUser.addToPolicy(
      new PolicyStatement({
        actions: ['sqs:CreateQueue'],
        resources: [`arn:aws:sqs:${this.region}:${this.account}:*`],
      })
    );
    NagSuppressions.addResourceSuppressions(
      firstUser,
      [
        {
          id: 'AwsSolutions-IAM5',
          reason:
            "Only suppress AwsSolutions-IAM5 's3:*' finding on First User.",
          appliesTo: ['Action::s3:*'],
        },
      ],
      true
    );
    NagSuppressions.addResourceSuppressions(
      secondUser,
      [
        {
          id: 'AwsSolutions-IAM5',
          reason: 'Suppress all AwsSolutions-IAM5 findings on Second User.',
        },
      ],
      true
    );
    NagSuppressions.addResourceSuppressions(
      thirdUser,
      [
        {
          id: 'AwsSolutions-IAM5',
          reason: 'Suppress AwsSolutions-IAM5 on the SQS resource.',
          appliesTo: [
            {
              regex: '/^Resource::arn:aws:sqs:(.*):\\*$/g',
            },
          ],
        },
      ],
      true
    );
  }
}

You would see the following error on synth/deploy

[Error at /StackName/rFirstUser/DefaultPolicy/Resource] AwsSolutions-IAM5[Resource::*]: The IAM entity contains wildcard permissions and does not have a cdk-nag rule suppression with evidence for those permission.

Suppressing `aws-cdk-lib/pipelines` Violations

The aws-cdk-lib/pipelines.CodePipeline construct and its child constructs are not guaranteed to be "Visited" by Aspects, as they are not added during the "Construction" phase of the cdk lifecycle. Because of this behavior, you may experience problems such as rule violations not appearing or the inability to suppress violations on these constructs.

You can remediate these rule violation and suppression problems by forcing the pipeline construct creation forward by calling .buildPipeline() on your CodePipeline object. Otherwise you may see errors such as:

Error: Suppression path "/this/construct/path" did not match any resource. This can occur when a resource does not exist or if a suppression is applied before a resource is created.

See this issue for more information.

Example) Supressing Violations in Pipelines

example-app.ts

import { App, Aspects } from 'aws-cdk-lib';
import { AwsSolutionsChecks } from 'cdk-nag';
import { ExamplePipeline } from '../lib/example-pipeline';

const app = new App();
new ExamplePipeline(app, 'example-cdk-pipeline');
Aspects.of(app).add(new AwsSolutionsChecks({ verbose: true }));
app.synth();

example-pipeline.ts

import { Stack, StackProps } from 'aws-cdk-lib';
import { Repository } from 'aws-cdk-lib/aws-codecommit';
import { CodePipeline, CodePipelineSource, ShellStep } from 'aws-cdk-lib/pipelines';
import { NagSuppressions } from 'cdk-nag';
import { Construct } from 'constructs';

export class ExamplePipeline extends Stack {
constructor(scope: Construct, id: string, props?: StackProps) {
  super(scope, id, props);

  const exampleSynth = new ShellStep('ExampleSynth', {
    commands: ['yarn build --frozen-lockfile'],
    input: CodePipelineSource.codeCommit(new Repository(this, 'ExampleRepo', { repositoryName: 'ExampleRepo' }), 'main'),
  });

  const ExamplePipeline = new CodePipeline(this, 'ExamplePipeline', {
    synth: exampleSynth,
  });

  // Force the pipeline construct creation forward before applying suppressions.
  // @See https://github.com/aws/aws-cdk/issues/18440
  ExamplePipeline.buildPipeline();

  // The path suppression will error if you comment out "ExamplePipeline.buildPipeline();""
  NagSuppressions.addResourceSuppressionsByPath(this, '/example-cdk-pipeline/ExamplePipeline/Pipeline/ArtifactsBucket/Resource', [
    {
      id: 'AwsSolutions-S1',
      reason: 'Because I said so',
    },
  ]);
}
}

Rules and Property Overrides

In some cases L2 Constructs do not have a native option to remediate an issue and must be fixed via Raw Overrides. Since raw overrides take place after template synthesis these fixes are not caught by cdk-nag. In this case you should remediate the issue and suppress the issue like in the following example.

Example) Property Overrides

import {
  Instance,
  InstanceType,
  InstanceClass,
  MachineImage,
  Vpc,
  CfnInstance,
} from 'aws-cdk-lib/aws-ec2';
import { Stack, StackProps } from 'aws-cdk-lib';
import { Construct } from 'constructs';
import { NagSuppressions } from 'cdk-nag';

export class CdkTestStack extends Stack {
  constructor(scope: Construct, id: string, props?: StackProps) {
    super(scope, id, props);
    const instance = new Instance(this, 'rInstance', {
      vpc: new Vpc(this, 'rVpc'),
      instanceType: new InstanceType(InstanceClass.T3),
      machineImage: MachineImage.latestAmazonLinux(),
    });
    const cfnIns = instance.node.defaultChild as CfnInstance;
    cfnIns.addPropertyOverride('DisableApiTermination', true);
    NagSuppressions.addResourceSuppressions(instance, [
      {
        id: 'AwsSolutions-EC29',
        reason: 'Remediated through property override.',
      },
    ]);
  }
}

Using on CloudFormation templates

You can use cdk-nag on existing CloudFormation templates by using the cloudformation-include module.

Example 1) CloudFormation template with suppression

Sample CloudFormation template with suppression

{
  "Resources": {
    "rBucket": {
      "Type": "AWS::S3::Bucket",
      "Properties": {
        "BucketName": "some-bucket-name"
      },
      "Metadata": {
        "cdk_nag": {
          "rules_to_suppress": [
            {
              "id": "AwsSolutions-S1",
              "reason": "at least 10 characters"
            }
          ]
        }
      }
    }
  }
}

Sample App

import { App, Aspects } from 'aws-cdk-lib';
import { CdkTestStack } from '../lib/cdk-test-stack';
import { AwsSolutionsChecks } from 'cdk-nag';

const app = new App();
new CdkTestStack(app, 'CdkNagDemo');
Aspects.of(app).add(new AwsSolutionsChecks());

Sample Stack with imported template

import { CfnInclude } from 'aws-cdk-lib/cloudformation-include';
import { NagSuppressions } from 'cdk-nag';
import { Stack, StackProps } from 'aws-cdk-lib';
import { Construct } from 'constructs';

export class CdkTestStack extends Stack {
  constructor(scope: Construct, id: string, props?: StackProps) {
    super(scope, id, props);
    new CfnInclude(this, 'Template', {
      templateFile: 'my-template.json',
    });
    // Add any additional suppressions
    NagSuppressions.addResourceSuppressionsByPath(
      this,
      '/CdkNagDemo/Template/rBucket',
      [
        {
          id: 'AwsSolutions-S2',
          reason: 'at least 10 characters',
        },
      ]
    );
  }
}

Example 2) CloudFormation template with granular suppressions

Sample CloudFormation template with suppression

{
  "Resources": {
    "myPolicy": {
      "Type": "AWS::IAM::Policy",
      "Properties": {
        "PolicyDocument": {
          "Statement": [
            {
              "Action": [
                "kms:Decrypt",
                "kms:DescribeKey",
                "kms:Encrypt",
                "kms:ReEncrypt*",
                "kms:GenerateDataKey*"
              ],
              "Effect": "Allow",
              "Resource": ["some-key-arn"]
            }
          ],
          "Version": "2012-10-17"
        }
      },
      "Metadata": {
        "cdk_nag": {
          "rules_to_suppress": [
            {
              "id": "AwsSolutions-IAM5",
              "reason": "Allow key data access",
              "applies_to": [
                "Action::kms:ReEncrypt*",
                "Action::kms:GenerateDataKey*"
              ]
            }
          ]
        }
      }
    }
  }
}

Sample App

import { App, Aspects } from 'aws-cdk-lib';
import { CdkTestStack } from '../lib/cdk-test-stack';
import { AwsSolutionsChecks } from 'cdk-nag';

const app = new App();
new CdkTestStack(app, 'CdkNagDemo');
Aspects.of(app).add(new AwsSolutionsChecks());

Sample Stack with imported template

import { CfnInclude } from 'aws-cdk-lib/cloudformation-include';
import { NagSuppressions } from 'cdk-nag';
import { Stack, StackProps } from 'aws-cdk-lib';
import { Construct } from 'constructs';

export class CdkTestStack extends Stack {
  constructor(scope: Construct, id: string, props?: StackProps) {
    super(scope, id, props);
    new CfnInclude(this, 'Template', {
      templateFile: 'my-template.json',
    });
    // Add any additional suppressions
    NagSuppressions.addResourceSuppressionsByPath(
      this,
      '/CdkNagDemo/Template/myPolicy',
      [
        {
          id: 'AwsSolutions-IAM5',
          reason: 'Allow key data access',
          appliesTo: ['Action::kms:ReEncrypt*', 'Action::kms:GenerateDataKey*'],
        },
      ]
    );
  }
}

Contributing

See CONTRIBUTING for more information.

License

This project is licensed under the Apache-2.0 License.

Name		Name	Last commit message	Last commit date
Latest commit History 623 Commits
.github		.github
.projen		.projen
docs		docs
src		src
test		test
.eslintrc.json		.eslintrc.json
.gitattributes		.gitattributes
.gitignore		.gitignore
.mergify.yml		.mergify.yml
.npmignore		.npmignore
.pre-commit-config.yaml		.pre-commit-config.yaml
.projenrc.js		.projenrc.js
API.md		API.md
CODE_OF_CONDUCT.md		CODE_OF_CONDUCT.md
CONTRIBUTING.md		CONTRIBUTING.md
LICENSE		LICENSE
NOTICE		NOTICE
README.md		README.md
RULES.md		RULES.md
cdk_nag.gif		cdk_nag.gif
package.json		package.json
tsconfig.dev.json		tsconfig.dev.json
yarn.lock		yarn.lock

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cdk-nag

Available Rules and Packs

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cdk-nag

Available Rules and Packs

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Using on CloudFormation templates

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