feat(config): add custom policy rule constructs (aws#21794)

feat(config) aws#21441

I have created a `new config.CustomPolicy` so that this functionality is available in L2 Constructs.

The resources that can currently be created with `AWS::Config::ConfigRule` can be created with `config.CustomRule` and `config.ManagedRule` in the CDK. This is because the restrictions on the various properties are different.
CustomPolicy has different constraints compared to CustomRule as follows.

- There is a restriction on the format that can be selected in `SourceDetails`.
    - [docs](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-config-configrule-source.html)
- Properties that refer to Lambda are unnecessary.
- `CustomPolicyDetails` must be specified.
    - [docs](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-config-configrule-source-sourcedetails.html)

To avoid this limitation and complexity, `CustomPolicy` can be separated, making it more convenient for users. It also reduces the dependence on each rule type for updates during maintenance.



----

### All Submissions:

* [x] Have you followed the guidelines in our [Contributing guide?](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md)

### Adding new Unconventional Dependencies:

* [x] This PR adds new unconventional dependencies following the process described [here](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md/#adding-new-unconventional-dependencies)

### New Features

* [x] Have you added the new feature to an [integration test](https://github.com/aws/aws-cdk/blob/main/INTEGRATION_TESTS.md)?
	* [x] Did you use `yarn integ` to deploy the infrastructure and generate the snapshot (i.e. `yarn integ` without `--dry-run`)?

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk/aws-config/README.md

@@ -116,8 +116,60 @@ new config.CloudFormationStackNotificationCheck(this, 'NotificationCheck', {
 ### Custom rules
 
 You can develop custom rules and add them to AWS Config. You associate each custom rule with an
-AWS Lambda function, which contains the logic that evaluates whether your AWS resources comply
-with the rule.
+AWS Lambda function and Guard.
+
+#### Custom Lambda Rules
+
+Lambda function which contains the logic that evaluates whether your AWS resources comply with the rule.
+
+```ts
+// Lambda function containing logic that evaluates compliance with the rule.
+const evalComplianceFn = new lambda.Function(this, "CustomFunction", {
+  code: lambda.AssetCode.fromInline(
+    "exports.handler = (event) => console.log(event);"
+  ),
+  handler: "index.handler",
+  runtime: lambda.Runtime.NODEJS_14_X,
+});
+
+// A custom rule that runs on configuration changes of EC2 instances
+const customRule = new config.CustomRule(this, "Custom", {
+  configurationChanges: true,
+  lambdaFunction: evalComplianceFn,
+  ruleScope: config.RuleScope.fromResource(config.ResourceType.EC2_INSTANCE),
+});
+```
+
+#### Custom Policy Rules
+
+Guard which contains the logic that evaluates whether your AWS resources comply with the rule.
+
+```ts
+const samplePolicyText = `
+# This rule checks if point in time recovery (PITR) is enabled on active Amazon DynamoDB tables
+let status = ['ACTIVE']
+
+rule tableisactive when
+    resourceType == "AWS::DynamoDB::Table" {
+    configuration.tableStatus == %status
+}
+
+rule checkcompliance when
+    resourceType == "AWS::DynamoDB::Table"
+    tableisactive {
+        let pitr = supplementaryConfiguration.ContinuousBackupsDescription.pointInTimeRecoveryDescription.pointInTimeRecoveryStatus
+        %pitr == "ENABLED"
+}
+`;
+
+new config.CustomPolicy(stack, "Custom", {
+  policyText: samplePolicyText,
+  enableDebugLog: true,
+  ruleScope: config.RuleScope.fromResources([
+    config.ResourceType.DYNAMODB_TABLE,
+  ]),
+});
+```
 
 ### Triggers
 

packages/@aws-cdk/aws-config/lib/rule.ts

@@ -281,6 +281,63 @@ export class ManagedRule extends RuleNew {
   }
 }
 
+/**
+ * The source of the event, such as an AWS service,
+ * that triggers AWS Config to evaluate your AWS resources.
+ */
+enum EventSource {
+
+  /* from aws.config */
+  AWS_CONFIG = 'aws.config',
+
+}
+
+/**
+ * The type of notification that triggers AWS Config to run an evaluation for a rule.
+ */
+enum MessageType {
+
+  /**
+   * Triggers an evaluation when AWS Config delivers a configuration item as a result of a resource change.
+   */
+  CONFIGURATION_ITEM_CHANGE_NOTIFICATION = 'ConfigurationItemChangeNotification',
+
+  /**
+   * Triggers an evaluation when AWS Config delivers an oversized configuration item.
+   */
+  OVERSIZED_CONFIGURATION_ITEM_CHANGE_NOTIFICATION = 'OversizedConfigurationItemChangeNotification',
+
+  /**
+   * Triggers a periodic evaluation at the frequency specified for MaximumExecutionFrequency.
+   */
+  SCHEDULED_NOTIFICATION = 'ScheduledNotification',
+
+  /**
+   * Triggers a periodic evaluation when AWS Config delivers a configuration snapshot.
+   */
+  CONFIGURATION_SNAPSHOT_DELIVERY_COMPLETED = 'ConfigurationSnapshotDeliveryCompleted',
+}
+
+/**
+ * Construction properties for a CustomRule.
+ */
+interface SourceDetail {
+  /**
+   * The source of the event, such as an AWS service,
+   * that triggers AWS Config to evaluate your AWS resources.
+   *
+   */
+  readonly eventSource: EventSource;
+  /**
+   * The frequency at which you want AWS Config to run evaluations for a custom rule with a periodic trigger.
+   */
+  readonly maximumExecutionFrequency?: MaximumExecutionFrequency;
+  /**
+   * The type of notification that triggers AWS Config to run an evaluation for a rule.
+   */
+  readonly messageType: MessageType;
+}
+
 /**
  * Construction properties for a CustomRule.
  */
@@ -331,25 +388,24 @@ export class CustomRule extends RuleNew {
       throw new Error('At least one of `configurationChanges` or `periodic` must be set to true.');
     }
 
-    const sourceDetails: any[] = [];
+    const sourceDetails: SourceDetail[] = [];
     this.ruleScope = props.ruleScope;
-
     if (props.configurationChanges) {
       sourceDetails.push({
-        eventSource: 'aws.config',
-        messageType: 'ConfigurationItemChangeNotification',
+        eventSource: EventSource.AWS_CONFIG,
+        messageType: MessageType.CONFIGURATION_ITEM_CHANGE_NOTIFICATION,
       });
       sourceDetails.push({
-        eventSource: 'aws.config',
-        messageType: 'OversizedConfigurationItemChangeNotification',
+        eventSource: EventSource.AWS_CONFIG,
+        messageType: MessageType.OVERSIZED_CONFIGURATION_ITEM_CHANGE_NOTIFICATION,
       });
     }
 
     if (props.periodic) {
       sourceDetails.push({
-        eventSource: 'aws.config',
+        eventSource: EventSource.AWS_CONFIG,
         maximumExecutionFrequency: props.maximumExecutionFrequency,
-        messageType: 'ScheduledNotification',
+        messageType: MessageType.SCHEDULED_NOTIFICATION,
       });
     }
 
@@ -391,6 +447,88 @@ export class CustomRule extends RuleNew {
   }
 }
 
+/**
+ * Construction properties for a CustomPolicy.
+ */
+export interface CustomPolicyProps extends RuleProps {
+  /**
+   * The policy definition containing the logic for your AWS Config Custom Policy rule.
+   */
+  readonly policyText: string;
+
+  /**
+   * The boolean expression for enabling debug logging for your AWS Config Custom Policy rule.
+   *
+   * @default false
+   */
+  readonly enableDebugLog?: boolean;
+}
+
+/**
+ * A new custom policy.
+ *
+ * @resource AWS::Config::ConfigRule
+ */
+export class CustomPolicy extends RuleNew {
+  /** @attribute */
+  public readonly configRuleName: string;
+
+  /** @attribute */
+  public readonly configRuleArn: string;
+
+  /** @attribute */
+  public readonly configRuleId: string;
+
+  /** @attribute */
+  public readonly configRuleComplianceType: string;
+
+  constructor(scope: Construct, id: string, props: CustomPolicyProps) {
+    super(scope, id, {
+      physicalName: props.configRuleName,
+    });
+
+    if (!props.policyText || [...props.policyText].length === 0) {
+      throw new Error('Policy Text cannot be empty.');
+    }
+    if ( [...props.policyText].length > 10000 ) {
+      throw new Error('Policy Text is limited to 10,000 characters or less.');
+    }
+
+    const sourceDetails: SourceDetail[] = [];
+    this.ruleScope = props.ruleScope;
+
+    sourceDetails.push({
+      eventSource: EventSource.AWS_CONFIG,
+      messageType: MessageType.CONFIGURATION_ITEM_CHANGE_NOTIFICATION,
+    });
+    sourceDetails.push({
+      eventSource: EventSource.AWS_CONFIG,
+      messageType: MessageType.OVERSIZED_CONFIGURATION_ITEM_CHANGE_NOTIFICATION,
+    });
+    const rule = new CfnConfigRule(this, 'Resource', {
+      configRuleName: this.physicalName,
+      description: props.description,
+      inputParameters: props.inputParameters,
+      scope: Lazy.any({ produce: () => renderScope(this.ruleScope) }), // scope can use values such as stack id (see CloudFormationStackDriftDetectionCheck)
+      source: {
+        owner: 'CUSTOM_POLICY',
+        sourceDetails,
+        customPolicyDetails: {
+          enableDebugLogDelivery: props.enableDebugLog,
+          policyRuntime: 'guard-2.x.x',
+          policyText: props.policyText,
+        },
+      },
+    });
+
+    this.configRuleName = rule.ref;
+    this.configRuleArn = rule.attrArn;
+    this.configRuleId = rule.attrConfigRuleId;
+    this.configRuleComplianceType = rule.attrComplianceType;
+    this.isCustomWithChanges = true;
+  }
+}
+
 /**
  * Managed rules that are supported by AWS Config.
  * @see https://docs.aws.amazon.com/config/latest/developerguide/managed-rules-by-aws-config.html

packages/@aws-cdk/aws-config/package.json

@@ -84,6 +84,7 @@
     "@aws-cdk/aws-events-targets": "0.0.0",
     "@aws-cdk/cdk-build-tools": "0.0.0",
     "@aws-cdk/integ-runner": "0.0.0",
+    "@aws-cdk/integ-tests": "0.0.0",
     "@aws-cdk/cfn2ts": "0.0.0",
     "@aws-cdk/pkglint": "0.0.0",
     "@types/jest": "^27.5.2",

packages/@aws-cdk/aws-config/test/custompolicy.integ.snapshot/aws-cdk-config-custompolicy.assets.json

@@ -0,0 +1,19 @@
+{
+  "version": "21.0.0",
+  "files": {
+    "51dce3b1479f4a685a2f5a815b141fdf3e07e49181ce9da06750e820f5b92859": {
+      "source": {
+        "path": "aws-cdk-config-custompolicy.template.json",
+        "packaging": "file"
+      },
+      "destinations": {
+        "current_account-current_region": {
+          "bucketName": "cdk-hnb659fds-assets-${AWS::AccountId}-${AWS::Region}",
+          "objectKey": "51dce3b1479f4a685a2f5a815b141fdf3e07e49181ce9da06750e820f5b92859.json",
+          "assumeRoleArn": "arn:${AWS::Partition}:iam::${AWS::AccountId}:role/cdk-hnb659fds-file-publishing-role-${AWS::AccountId}-${AWS::Region}"
+        }
+      }
+    }
+  },
+  "dockerImages": {}
+}

packages/@aws-cdk/aws-config/test/custompolicy.integ.snapshot/aws-cdk-config-custompolicy.template.json

@@ -0,0 +1,100 @@
+{
+ "Resources": {
+  "Custom8166710A": {
+   "Type": "AWS::Config::ConfigRule",
+   "Properties": {
+    "Source": {
+     "CustomPolicyDetails": {
+      "EnableDebugLogDelivery": true,
+      "PolicyRuntime": "guard-2.x.x",
+      "PolicyText": "\n# This rule checks if point in time recovery (PITR) is enabled on active Amazon DynamoDB tables\nlet status = ['ACTIVE']\n\nrule tableisactive when\n    resourceType == \"AWS::DynamoDB::Table\" {\n    configuration.tableStatus == %status\n}\n\nrule checkcompliance when\n    resourceType == \"AWS::DynamoDB::Table\"\n    tableisactive {\n        let pitr = supplementaryConfiguration.ContinuousBackupsDescription.pointInTimeRecoveryDescription.pointInTimeRecoveryStatus\n        %pitr == \"ENABLED\"\n}\n"
+     },
+     "Owner": "CUSTOM_POLICY",
+     "SourceDetails": [
+      {
+       "EventSource": "aws.config",
+       "MessageType": "ConfigurationItemChangeNotification"
+      },
+      {
+       "EventSource": "aws.config",
+       "MessageType": "OversizedConfigurationItemChangeNotification"
+      }
+     ]
+    },
+    "Scope": {
+     "ComplianceResourceTypes": [
+      "AWS::DynamoDB::Table"
+     ]
+    }
+   }
+  },
+  "sampleuser2D3A0B43": {
+   "Type": "AWS::IAM::User"
+  },
+  "Customlazy5E6C8AE4": {
+   "Type": "AWS::Config::ConfigRule",
+   "Properties": {
+    "Source": {
+     "CustomPolicyDetails": {
+      "EnableDebugLogDelivery": true,
+      "PolicyRuntime": "guard-2.x.x",
+      "PolicyText": "lazy-create-test"
+     },
+     "Owner": "CUSTOM_POLICY",
+     "SourceDetails": [
+      {
+       "EventSource": "aws.config",
+       "MessageType": "ConfigurationItemChangeNotification"
+      },
+      {
+       "EventSource": "aws.config",
+       "MessageType": "OversizedConfigurationItemChangeNotification"
+      }
+     ]
+    },
+    "Scope": {
+     "ComplianceResourceId": {
+      "Ref": "sampleuser2D3A0B43"
+     },
+     "ComplianceResourceTypes": [
+      "AWS::IAM::User"
+     ]
+    }
+   }
+  }
+ },
+ "Parameters": {
+  "BootstrapVersion": {
+   "Type": "AWS::SSM::Parameter::Value<String>",
+   "Default": "/cdk-bootstrap/hnb659fds/version",
+   "Description": "Version of the CDK Bootstrap resources in this environment, automatically retrieved from SSM Parameter Store. [cdk:skip]"
+  }
+ },
+ "Rules": {
+  "CheckBootstrapVersion": {
+   "Assertions": [
+    {
+     "Assert": {
+      "Fn::Not": [
+       {
+        "Fn::Contains": [
+         [
+          "1",
+          "2",
+          "3",
+          "4",
+          "5"
+         ],
+         {
+          "Ref": "BootstrapVersion"
+         }
+        ]
+       }
+      ]
+     },
+     "AssertDescription": "CDK bootstrap stack version 6 required. Please run 'cdk bootstrap' with a recent version of the CDK CLI."
+    }
+   ]
+  }
+ }
+}