feat: Implement disconnection from backing service(s) (#27)

Fixes #10

src/lib/KmsRsaPssProvider.ts

@@ -1,3 +1,5 @@
 import { RsaPssProvider } from 'webcrypto-core';
 
-export abstract class KmsRsaPssProvider extends RsaPssProvider {}
+export abstract class KmsRsaPssProvider extends RsaPssProvider {
+  public abstract close(): Promise<void>;
+}

src/lib/aws/AwsKmsRsaPssProvider.spec.ts

@@ -460,4 +460,16 @@ describe('AwsKmsRsaPssProvider', () => {
       );
     });
   });
+
+  describe('close', () => {
+    test('Client should be destroyed', async () => {
+      const client = new KMSClient({});
+      const mockDestroy = jest.spyOn(client, 'destroy').mockReturnValue(undefined);
+      const provider = new AwsKmsRsaPssProvider(client);
+
+      await provider.close();
+
+      expect(mockDestroy).toHaveBeenCalledWith();
+    });
+  });
 });

src/lib/aws/AwsKmsRsaPssProvider.ts

@@ -114,6 +114,10 @@ export class AwsKmsRsaPssProvider extends KmsRsaPssProvider {
     throw new KmsError('Signature verification is unsupported');
   }
 
+  async close(): Promise<void> {
+    this.client.destroy();
+  }
+
   private async retrievePublicKey(key: AwsKmsRsaPssPrivateKey): Promise<ArrayBuffer> {
     const command = new GetPublicKeyCommand({ KeyId: key.arn });
     const response = await this.client.send(command, REQUEST_OPTIONS);

src/lib/gcp/GcpKmsRsaPssProvider.spec.ts

@@ -770,3 +770,15 @@ describe('onVerify', () => {
     );
   });
 });
+
+describe('close', () => {
+  test('Client should be closed', async () => {
+    const client = new KeyManagementServiceClient();
+    const mockClose = jest.spyOn(client, 'close').mockResolvedValue(undefined);
+    const provider = new GcpKmsRsaPssProvider(client, KMS_CONFIG);
+
+    await provider.close();
+
+    expect(mockClose).toHaveBeenCalledWith();
+  });
+});

src/lib/gcp/GcpKmsRsaPssProvider.ts

@@ -120,6 +120,10 @@ export class GcpKmsRsaPssProvider extends KmsRsaPssProvider {
     throw new KmsError('Signature verification is unsupported');
   }
 
+  async close(): Promise<void> {
+    await this.client.close();
+  }
+
   private async getGCPProjectId(): Promise<string> {
     // GCP client library already caches the project id.
     return this.client.getProjectId();