feat(kinesisfirehose-alpha): enable server-side encryption for delivery stream by default

packages/@aws-cdk/aws-kinesisfirehose-alpha/README.md

@@ -135,7 +135,7 @@ before being written to the service's internal storage layer and decrypted after
 received from the internal storage layer. The service manages keys and cryptographic
 operations so that sources and destinations do not need to, as the data is encrypted and
 decrypted at the boundaries of the service (i.e., before the data is delivered to a
-destination). By default, delivery streams do not have SSE enabled.
+destination). By default, delivery streams have SSE enabled with an AWS-owned key.
 
 The Key Management Service keys (KMS keys) used for SSE can either be AWS-owned or
 customer-managed. AWS-owned KMS keys are created, owned and managed by AWS for use in
@@ -172,6 +172,24 @@ new firehose.DeliveryStream(this, 'Delivery Stream with Customer Managed and Pro
 See: [Data Protection](https://docs.aws.amazon.com/firehose/latest/dev/encryption.html)
 in the *Amazon Data Firehose Developer Guide*.
 
+### Restriction for Kinesis Data Stream as Source
+
+When using a Kinesis Data Stream as the source for a Delivery Stream, server-side encryption (SSE) must be explicitly disabled on the Delivery Stream. This is because the encryption should be specified on the source Kinesis Data Stream instead.
+
+```ts
+declare const kinesisStream: kinesis.Stream;
+declare const destination: firehose.IDestination;
+
+// SSE must be explicitly disabled when using a Kinesis Data Stream as source
+new firehose.DeliveryStream(this, 'Delivery Stream with Kinesis Source', {
+  source: new firehose.KinesisStreamSource(kinesisStream),
+  encryption: firehose.StreamEncryption.unencrypted(),
+  destination: destination,
+});
+```
+
+It's recommended to specify SSE on the source Kinesis Data Stream if encryption is required.
+
 ## Monitoring
 
 Amazon Data Firehose is integrated with CloudWatch, so you can monitor the performance of

packages/@aws-cdk/aws-kinesisfirehose-alpha/lib/delivery-stream.ts

@@ -215,7 +215,10 @@ export interface DeliveryStreamProps {
   /**
    * Indicates the type of customer master key (CMK) to use for server-side encryption, if any.
    *
-   * @default StreamEncryption.unencrypted()
+   * If the source is a Kinesis Data Stream, encryption must be set to `StreamEncryption.unencrypted()`.
+   * To enable server-side encryption when using a Kinesis Data Stream as the source, apply the encryption settings directly on the data stream itself.
+   *
+   * @default StreamEncryption.awsOwnedKey()
    */
   readonly encryption?: StreamEncryption;
 }
@@ -328,17 +331,20 @@ export class DeliveryStream extends DeliveryStreamBase {
       });
     }
 
+    const encryption = props.encryption ?? StreamEncryption.awsOwnedKey();
+    const encryptionKey = encryption.encryptionKey ?? (encryption.type === StreamEncryptionType.CUSTOMER_MANAGED ? new kms.Key(this, 'Key') : undefined);
+    const encryptionConfig = (encryptionKey || (encryption?.type === StreamEncryptionType.AWS_OWNED)) ? {
+      keyArn: encryptionKey?.keyArn,
+      keyType: encryptionKey ? 'CUSTOMER_MANAGED_CMK' : 'AWS_OWNED_CMK',
+    } : undefined;
+
     if (
       props.source &&
-        (props.encryption?.type === StreamEncryptionType.AWS_OWNED || props.encryption?.type === StreamEncryptionType.CUSTOMER_MANAGED)
+        (encryption.type === StreamEncryptionType.AWS_OWNED || encryption.type === StreamEncryptionType.CUSTOMER_MANAGED)
     ) {
       throw new Error('Requested server-side encryption but delivery stream source is a Kinesis data stream. Specify server-side encryption on the data stream instead.');
     }
-    const encryptionKey = props.encryption?.encryptionKey ?? (props.encryption?.type === StreamEncryptionType.CUSTOMER_MANAGED ? new kms.Key(this, 'Key') : undefined);
-    const encryptionConfig = (encryptionKey || (props.encryption?.type === StreamEncryptionType.AWS_OWNED)) ? {
-      keyArn: encryptionKey?.keyArn,
-      keyType: encryptionKey ? 'CUSTOMER_MANAGED_CMK' : 'AWS_OWNED_CMK',
-    } : undefined;
+
     /*
      * In order for the service role to have access to the encryption key before the delivery stream is created, the
      * CfnDeliveryStream below should have a dependency on the grant returned by the function call below:

packages/@aws-cdk/aws-kinesisfirehose-alpha/test/delivery-stream.test.ts

@@ -51,7 +51,10 @@ describe('delivery stream', () => {
     });
 
     Template.fromStack(stack).hasResourceProperties('AWS::KinesisFirehose::DeliveryStream', {
-      DeliveryStreamEncryptionConfigurationInput: Match.absent(),
+      DeliveryStreamEncryptionConfigurationInput: {
+        KeyARN: Match.absent(),
+        KeyType: 'AWS_OWNED_CMK',
+      },
       DeliveryStreamName: Match.absent(),
       DeliveryStreamType: 'DirectPut',
       KinesisStreamSourceConfiguration: Match.absent(),
@@ -135,6 +138,7 @@ describe('delivery stream', () => {
 
     new firehose.DeliveryStream(stack, 'Delivery Stream', {
       destination: mockS3Destination,
+      encryption: StreamEncryption.unencrypted(),
       source: new source.KinesisStreamSource(sourceStream),
     });
 
@@ -182,6 +186,7 @@ describe('delivery stream', () => {
     new firehose.DeliveryStream(stack, 'Delivery Stream', {
       destination: mockS3Destination,
       source: new source.KinesisStreamSource(sourceStream),
+      encryption: StreamEncryption.unencrypted(),
       role: deliveryStreamRole,
     });
 
@@ -298,6 +303,23 @@ describe('delivery stream', () => {
     });
   });
 
+  test('not setting encryption defaults to AWS-owned key and does not create key and creates configuration', () => {
+    new firehose.DeliveryStream(stack, 'Delivery Stream', {
+      destination: mockS3Destination,
+      role: deliveryStreamRole,
+    });
+
+    Template.fromStack(stack).resourceCountIs('AWS::KMS::Key', 0);
+    Template.fromStack(stack).resourceCountIs('AWS::IAM::Policy', 0);
+    Template.fromStack(stack).hasResourceProperties('AWS::KinesisFirehose::DeliveryStream', {
+      DeliveryStreamType: 'DirectPut',
+      DeliveryStreamEncryptionConfigurationInput: {
+        KeyARN: Match.absent(),
+        KeyType: 'AWS_OWNED_CMK',
+      },
+    });
+  });
+
   test('requesting no encryption creates no configuration', () => {
     new firehose.DeliveryStream(stack, 'Delivery Stream', {
       destination: mockS3Destination,
@@ -331,6 +353,10 @@ describe('delivery stream', () => {
       encryption: StreamEncryption.customerManagedKey(new kms.Key(stack, 'Key')),
       source: new source.KinesisStreamSource(sourceStream),
     })).toThrowError('Requested server-side encryption but delivery stream source is a Kinesis data stream. Specify server-side encryption on the data stream instead.');
+    expect(() => new firehose.DeliveryStream(stack, 'Delivery Stream 4', {
+      destination: mockS3Destination,
+      source: new source.KinesisStreamSource(sourceStream),
+    })).toThrowError('Requested server-side encryption but delivery stream source is a Kinesis data stream. Specify server-side encryption on the data stream instead.');
   });
 
   test('grant provides access to stream', () => {