feat(custom-resources): add custom environmentEncryption for Provider…

… lambda functions (#26236) The `providerFunctionEnvEncryption` property on the `Provider` class allows users to specify a custom KMS key that will be used to encrypt the environment variables of the generated lambda functions. Closes #26197. ---- *By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*
aws · Jul 12, 2023 · 546456a · 546456a
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diff --git a/packages/aws-cdk-lib/custom-resources/README.md b/packages/aws-cdk-lib/custom-resources/README.md
@@ -387,6 +387,27 @@ const myProvider = new cr.Provider(this, 'MyProvider', {
 
 ```
 
+### Customizing Provider Function environment encryption key
+
+Sometimes it may be useful to manually set a AWS KMS key for the Provider Function Lambda and therefore
+be able to view, manage and audit the key usage.
+
+```ts
+declare const onEvent: lambda.Function;
+declare const isComplete: lambda.Function;
+declare const myRole: iam.Role;
+
+const key = new kms.Key(this, 'MyKey');
+const myProvider = new cr.Provider(this, 'MyProvider', {
+  onEventHandler: onEvent,
+  isCompleteHandler: isComplete,
+  logRetention: logs.RetentionDays.ONE_DAY,
+  role: myRole,
+  providerFunctionEnvEncryption: key,   // Optional
+});
+
+```
+
 ## Custom Resources for AWS APIs
 
 Sometimes a single API call can fill the gap in the CloudFormation coverage. In

diff --git a/packages/aws-cdk-lib/custom-resources/lib/provider-framework/provider.ts b/packages/aws-cdk-lib/custom-resources/lib/provider-framework/provider.ts
@@ -6,6 +6,7 @@ import { WaiterStateMachine } from './waiter-state-machine';
 import { CustomResourceProviderConfig, ICustomResourceProvider } from '../../../aws-cloudformation';
 import * as ec2 from '../../../aws-ec2';
 import * as iam from '../../../aws-iam';
+import * as kms from '../../../aws-kms';
 import * as lambda from '../../../aws-lambda';
 import * as logs from '../../../aws-logs';
 import { Duration } from '../../../core';
@@ -118,6 +119,13 @@ export interface ProviderProps {
    * @default -  CloudFormation default name from unique physical ID
    */
   readonly providerFunctionName?: string;
+
+  /**
+   * AWS KMS key used to encrypt provider lambda's environment variables.
+   *
+   * @default -  AWS Lambda creates and uses an AWS managed customer master key (CMK)
+   */
+  readonly providerFunctionEnvEncryption?: kms.IKey;
 }
 
 /**
@@ -149,6 +157,7 @@ export class Provider extends Construct implements ICustomResourceProvider {
   private readonly vpcSubnets?: ec2.SubnetSelection;
   private readonly securityGroups?: ec2.ISecurityGroup[];
   private readonly role?: iam.IRole;
+  private readonly providerFunctionEnvEncryption?: kms.IKey;
 
   constructor(scope: Construct, id: string, props: ProviderProps) {
     super(scope, id);
@@ -167,6 +176,7 @@ export class Provider extends Construct implements ICustomResourceProvider {
     this.securityGroups = props.securityGroups;
 
     this.role = props.role;
+    this.providerFunctionEnvEncryption = props.providerFunctionEnvEncryption;
 
     const onEventFunction = this.createFunction(consts.FRAMEWORK_ON_EVENT_HANDLER_NAME, props.providerFunctionName);
 
@@ -216,6 +226,7 @@ export class Provider extends Construct implements ICustomResourceProvider {
       securityGroups: this.securityGroups,
       role: this.role,
       functionName: name,
+      environmentEncryption: this.providerFunctionEnvEncryption,
     });
 
     fn.addEnvironment(consts.USER_ON_EVENT_FUNCTION_ARN_ENV, this.onEventHandler.functionArn);

diff --git a/packages/aws-cdk-lib/custom-resources/test/provider-framework/provider.test.ts b/packages/aws-cdk-lib/custom-resources/test/provider-framework/provider.test.ts
@@ -2,6 +2,7 @@ import * as path from 'path';
 import { Template } from '../../../assertions';
 import * as ec2 from '../../../aws-ec2';
 import * as iam from '../../../aws-iam';
+import * as kms from '../../../aws-kms';
 import * as lambda from '../../../aws-lambda';
 import * as logs from '../../../aws-logs';
 import { Duration, Stack } from '../../../core';
@@ -419,3 +420,33 @@ describe('name', () => {
     });
   });
 });
+
+describe('environment encryption', () => {
+  it('uses custom KMS key for environment encryption when present', () => {
+    // GIVEN
+    const stack = new Stack();
+    const key: kms.IKey = new kms.Key(stack, 'EnvVarEncryptKey', {
+      description: 'sample key',
+    });
+
+    // WHEN
+    new cr.Provider(stack, 'MyProvider', {
+      onEventHandler: new lambda.Function(stack, 'MyHandler', {
+        code: lambda.Code.fromAsset(path.join(__dirname, './integration-test-fixtures/s3-file-handler')),
+        handler: 'index.onEvent',
+        runtime: lambda.Runtime.NODEJS_14_X,
+      }),
+      providerFunctionEnvEncryption: key,
+    });
+
+    // THEN
+    Template.fromStack(stack).hasResourceProperties('AWS::Lambda::Function', {
+      KmsKeyArn: {
+        'Fn::GetAtt': [
+          'EnvVarEncryptKey1A7CABDB',
+          'Arn',
+        ],
+      },
+    });
+  });
+});