feat(waf): add basic WAF monitoring (#89)

Related #76 

---

_By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license_

README.md

@@ -90,6 +90,7 @@ You can also browse the documentation at https://constructs.dev/packages/cdk-mon
 | AWS SNS Topic (`.monitorSnsTopic()`) | Message count, size, failed notifications | Failed notifications | |
 | AWS SQS Queue (`.monitorSqsQueue()`, `.monitorSqsQueueWithDlq()`) | Message count, age, size | Message count, age, DLQ incoming messages | |
 | AWS Step Functions (`.monitorStepFunction()`, `.monitorStepFunctionActivity()`, `monitorStepFunctionLambdaIntegration()`, `.monitorStepFunctionServiceIntegration()`) | Execution count and breakdown per state | Duration, failed, failed rate, aborted, throttled, timed out executions | |
+| AWS Web Application Firewall (`.monitorWebApplicationFirewallAcl()`) | Allowed/blocked requests | | |
 | CloudWatch Logs (`.monitorLog()`) | Patterns present in the log group | | |
 | Custom metrics (`.monitorCustom()`) | Addition of custom metrics into the dashboard (each group is a widget) | | Supports anomaly detection |
 

lib/facade/MonitoringAspect.ts

@@ -22,6 +22,7 @@ import * as sns from "monocdk/aws-sns";
 import * as sqs from "monocdk/aws-sqs";
 import * as stepfunctions from "monocdk/aws-stepfunctions";
 import * as synthetics from "monocdk/aws-synthetics";
+import * as wafv2 from "monocdk/aws-wafv2";
 
 import { ElastiCacheClusterType } from "../monitoring";
 import { MonitoringAspectProps, MonitoringAspectType } from "./aspect-types";
@@ -64,6 +65,7 @@ export class MonitoringAspect implements IAspect {
     this.monitorSqs(node);
     this.monitorStepFunctions(node);
     this.monitorSyntheticsCanaries(node);
+    this.monitorWebApplicationFirewallV2Acls(node);
 
     if (!this.addedNodeIndependentMonitoringToScope) {
       this.addedNodeIndependentMonitoringToScope = true;
@@ -365,6 +367,18 @@ export class MonitoringAspect implements IAspect {
       });
     }
   }
+
+  private monitorWebApplicationFirewallV2Acls(node: IConstruct) {
+    const [isEnabled, props] = this.getMonitoringDetails(
+      this.props.webApplicationFirewallAclV2
+    );
+    if (isEnabled && node instanceof wafv2.CfnWebACL) {
+      this.monitoringFacade.monitorWebApplicationFirewallAclV2({
+        acl: node,
+        ...props,
+      });
+    }
+  }
 }
 
 export * from "./aspect-types";

lib/facade/MonitoringFacade.ts

@@ -103,6 +103,8 @@ import {
   getQueueProcessingFargateServiceMonitoring,
   SyntheticsCanaryMonitoringProps,
   SyntheticsCanaryMonitoring,
+  WafV2MonitoringProps,
+  WafV2Monitoring,
 } from "../monitoring";
 import { MonitoringAspect, MonitoringAspectProps } from "./MonitoringAspect";
 
@@ -613,6 +615,12 @@ export class MonitoringFacade extends MonitoringScope {
     return this;
   }
 
+  monitorWebApplicationFirewallAclV2(props: WafV2MonitoringProps) {
+    const segment = new WafV2Monitoring(this, props);
+    this.addSegment(segment, props);
+    return this;
+  }
+
   monitorBilling(props?: BillingMonitoringProps) {
     const segment = new BillingMonitoring(this, props ?? {});
     this.addSegment(segment, props);

lib/facade/aspect-types.ts

@@ -24,6 +24,7 @@ import {
   SqsQueueMonitoringOptions,
   StepFunctionMonitoringOptions,
   SyntheticsCanaryMonitoringOptions,
+  WafV2MonitoringOptions,
 } from "../monitoring";
 
 export interface MonitoringAspectType<T> {
@@ -66,4 +67,5 @@ export interface MonitoringAspectProps {
   readonly sqs?: MonitoringAspectType<SqsQueueMonitoringOptions>;
   readonly stepFunctions?: MonitoringAspectType<StepFunctionMonitoringOptions>;
   readonly syntheticsCanaries?: MonitoringAspectType<SyntheticsCanaryMonitoringOptions>;
+  readonly webApplicationFirewallAclV2?: MonitoringAspectType<WafV2MonitoringOptions>;
 }

lib/monitoring/aws-wafv2/WafV2MetricFactory.ts

@@ -0,0 +1,60 @@
+import { DimensionHash } from "monocdk/aws-cloudwatch";
+import { CfnWebACL } from "monocdk/aws-wafv2";
+import { MetricFactory, MetricStatistic } from "../../common";
+
+const MetricNamespace = "AWS/WAFV2";
+const AllRulesDimensionValue = "ALL";
+
+export interface WafV2MetricFactoryProps {
+  readonly region?: string;
+  readonly acl: CfnWebACL;
+}
+
+/**
+ * https://docs.aws.amazon.com/waf/latest/developerguide/monitoring-cloudwatch.html
+ */
+export class WafV2MetricFactory {
+  protected readonly metricFactory: MetricFactory;
+  protected readonly dimensions: DimensionHash;
+
+  constructor(metricFactory: MetricFactory, props: WafV2MetricFactoryProps) {
+    this.metricFactory = metricFactory;
+    this.dimensions = {
+      Rule: AllRulesDimensionValue,
+      WebACL: props.acl.name,
+    };
+  }
+
+  metricAllowedRequests() {
+    return this.metricFactory.createMetric(
+      "AllowedRequests",
+      MetricStatistic.SUM,
+      "Allowed",
+      this.dimensions,
+      undefined,
+      MetricNamespace
+    );
+  }
+
+  metricBlockedRequests() {
+    return this.metricFactory.createMetric(
+      "BlockedRequests",
+      MetricStatistic.SUM,
+      "Blocked",
+      this.dimensions,
+      undefined,
+      MetricNamespace
+    );
+  }
+
+  metricBlockedRequestsRate() {
+    return this.metricFactory.createMetricMath(
+      "100 * (blocked / (allowed + blocked))",
+      {
+        allowed: this.metricAllowedRequests(),
+        blocked: this.metricBlockedRequests(),
+      },
+      "Blocked (rate)"
+    );
+  }
+}

lib/monitoring/aws-wafv2/WafV2Monitoring.ts

@@ -0,0 +1,119 @@
+import { GraphWidget, IWidget } from "monocdk/aws-cloudwatch";
+import {
+  BaseMonitoringProps,
+  CountAxisFromZero,
+  DefaultGraphWidgetHeight,
+  DefaultSummaryWidgetHeight,
+  MetricWithAlarmSupport,
+  Monitoring,
+  MonitoringScope,
+  RateAxisFromZero,
+  ThirdWidth,
+} from "../../common";
+import {
+  MonitoringHeaderWidget,
+  MonitoringNamingStrategy,
+} from "../../dashboard";
+import {
+  WafV2MetricFactory,
+  WafV2MetricFactoryProps,
+} from "./WafV2MetricFactory";
+
+export interface WafV2MonitoringOptions extends BaseMonitoringProps {}
+
+export interface WafV2MonitoringProps
+  extends WafV2MetricFactoryProps,
+    WafV2MonitoringOptions {}
+
+/**
+ * Monitoring for AWS Web Application Firewall.
+ *
+ * @see https://docs.aws.amazon.com/waf/latest/developerguide/monitoring-cloudwatch.html
+ */
+export class WafV2Monitoring extends Monitoring {
+  protected readonly humanReadableName: string;
+
+  protected readonly allowedRequestsMetric: MetricWithAlarmSupport;
+  protected readonly blockedRequestsMetric: MetricWithAlarmSupport;
+  protected readonly blockedRequestsRateMetric: MetricWithAlarmSupport;
+
+  constructor(scope: MonitoringScope, props: WafV2MonitoringProps) {
+    super(scope, props);
+
+    const namingStrategy = new MonitoringNamingStrategy({
+      ...props,
+      namedConstruct: props.acl,
+    });
+    this.humanReadableName = namingStrategy.resolveHumanReadableName();
+
+    const metricFactory = new WafV2MetricFactory(
+      scope.createMetricFactory(),
+      props
+    );
+
+    this.allowedRequestsMetric = metricFactory.metricAllowedRequests();
+    this.blockedRequestsMetric = metricFactory.metricBlockedRequests();
+    this.blockedRequestsRateMetric = metricFactory.metricBlockedRequestsRate();
+  }
+
+  summaryWidgets(): IWidget[] {
+    return [
+      this.createTitleWidget(),
+      this.createAllowedRequestsWidget(ThirdWidth, DefaultSummaryWidgetHeight),
+      this.createBlockedRequestsWidget(ThirdWidth, DefaultSummaryWidgetHeight),
+      this.createBlockedRequestsRateWidget(
+        ThirdWidth,
+        DefaultSummaryWidgetHeight
+      ),
+    ];
+  }
+
+  widgets(): IWidget[] {
+    return [
+      this.createTitleWidget(),
+      this.createAllowedRequestsWidget(ThirdWidth, DefaultGraphWidgetHeight),
+      this.createBlockedRequestsWidget(ThirdWidth, DefaultSummaryWidgetHeight),
+      this.createBlockedRequestsRateWidget(
+        ThirdWidth,
+        DefaultSummaryWidgetHeight
+      ),
+    ];
+  }
+
+  protected createTitleWidget() {
+    return new MonitoringHeaderWidget({
+      family: "Web Application Firewall",
+      title: this.humanReadableName,
+    });
+  }
+
+  protected createAllowedRequestsWidget(width: number, height: number) {
+    return new GraphWidget({
+      width,
+      height,
+      title: "Allowed Requests",
+      left: [this.allowedRequestsMetric],
+      leftYAxis: CountAxisFromZero,
+    });
+  }
+
+  protected createBlockedRequestsWidget(width: number, height: number) {
+    return new GraphWidget({
+      width,
+      height,
+      title: "Blocked Requests",
+      left: [this.blockedRequestsMetric],
+      leftYAxis: CountAxisFromZero,
+    });
+  }
+
+  protected createBlockedRequestsRateWidget(width: number, height: number) {
+    return new GraphWidget({
+      width,
+      height,
+      title: "Blocked Requests (rate)",
+      left: [this.blockedRequestsRateMetric],
+      leftYAxis: RateAxisFromZero,
+    });
+  }
+}

lib/monitoring/aws-wafv2/index.ts

@@ -0,0 +1,2 @@
+export * from "./WafV2MetricFactory";
+export * from "./WafV2Monitoring";

lib/monitoring/index.ts

@@ -24,4 +24,5 @@ export * from "./aws-sns";
 export * from "./aws-sqs";
 export * from "./aws-step-functions";
 export * from "./aws-synthetics";
+export * from "./aws-wafv2";
 export * from "./custom";

test/facade/MonitoringAspect.test.ts

@@ -26,6 +26,7 @@ import * as sns from "monocdk/aws-sns";
 import * as sqs from "monocdk/aws-sqs";
 import * as stepfunctions from "monocdk/aws-stepfunctions";
 import * as synthetics from "monocdk/aws-synthetics";
+import { CfnWebACL } from "monocdk/aws-wafv2";
 
 import {
   DefaultDashboardFactory,
@@ -535,4 +536,26 @@ describe("MonitoringAspect", () => {
     // THEN
     expect(Template.fromStack(stack)).toMatchSnapshot();
   });
+
+  test("WAF v2", () => {
+    // GIVEN
+    const stack = new Stack();
+    const facade = createDummyMonitoringFacade(stack);
+
+    new CfnWebACL(stack, "DummyAcl", {
+      defaultAction: { allow: {} },
+      scope: "REGIONAL",
+      visibilityConfig: {
+        sampledRequestsEnabled: true,
+        cloudWatchMetricsEnabled: true,
+        metricName: "DummyMetricName",
+      },
+    });
+
+    // WHEN
+    facade.monitorScope(stack, defaultAspectProps);
+
+    // THEN
+    expect(Template.fromStack(stack)).toMatchSnapshot();
+  });
 });