feat(s3): add CORS Property to S3 Bucket (aws#2101)

Add CORS Property to S3 Bucket for configuring bucket cross-origin
access rules.

You can either specify the metrics as properties:

     new Bucket(stack, 'Bucket', {
       cors: [
         {
           allowedHeaders: [
             "*"
           ],
           allowedMethods: [
             "GET"
           ],
           allowedOrigins: [
             "*"
           ],
           exposedHeaders: [
             "Date"
           ],
           id: "myCORSRuleId1",
           maxAge: 3600
         }
       ]
     });

Or use the `addCors` function:

    const bucket = new Bucket(stack, 'Bucket');
    bucket.addCors({
      allowedMethods: ["GET", "HEAD"],
      allowedOrigins: ["https://example.com"]
    });

packages/@aws-cdk/aws-s3/lib/bucket.ts

@@ -632,6 +632,36 @@ export interface BucketMetrics {
   readonly tagFilters?: {[tag: string]: any};
 }
 
+/**
+ * Specifies a cross-origin access rule for an Amazon S3 bucket.
+ */
+export interface CorsRule {
+  /**
+   * A unique identifier for this rule.
+   */
+  readonly id?: string;
+  /**
+   * The time in seconds that your browser is to cache the preflight response for the specified resource.
+   */
+  readonly maxAge?: number;
+  /**
+   * Headers that are specified in the Access-Control-Request-Headers header.
+   */
+  readonly allowedHeaders?: string[];
+  /**
+   * An HTTP method that you allow the origin to execute.
+   */
+  readonly allowedMethods: Array<"GET"|"PUT"|"HEAD"|"POST"|"DELETE">;
+  /**
+   * One or more origins you want customers to be able to access the bucket from.
+   */
+  readonly allowedOrigins: string[];
+  /**
+   * One or more headers in the response that you want customers to be able to access from their applications.
+   */
+  readonly exposedHeaders?: string[];
+}
+
 export interface BucketProps {
   /**
    * The kind of server-side encryption to apply to this bucket.
@@ -725,6 +755,15 @@ export interface BucketProps {
    * @default - No metrics configuration.
    */
   readonly metrics?: BucketMetrics[];
+
+  /**
+   * The CORS configuration of this bucket.
+   *
+   * @see https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-s3-bucket-cors.html
+   *
+   * @default - No CORS configuration.
+   */
+  readonly cors?: CorsRule[];
 }
 
 /**
@@ -808,6 +847,7 @@ export class Bucket extends BucketBase {
   private readonly versioned?: boolean;
   private readonly notifications: BucketNotifications;
   private readonly metrics: BucketMetrics[] = [];
+  private readonly cors: CorsRule[] = [];
 
   constructor(scope: Construct, id: string, props: BucketProps = {}) {
     super(scope, id, {
@@ -826,7 +866,8 @@ export class Bucket extends BucketBase {
       lifecycleConfiguration: Lazy.anyValue({ produce: () => this.parseLifecycleConfiguration() }),
       websiteConfiguration: this.renderWebsiteConfiguration(props),
       publicAccessBlockConfiguration: props.blockPublicAccess,
-      metricsConfigurations: Lazy.anyValue({ produce: () => this.parseMetricConfiguration() })
+      metricsConfigurations: Lazy.anyValue({ produce: () => this.parseMetricConfiguration() }),
+      corsConfiguration: Lazy.anyValue({ produce: () => this.parseCorsConfiguration() })
     });
 
     applyRemovalPolicy(resource, props.removalPolicy !== undefined ? props.removalPolicy : RemovalPolicy.Orphan);
@@ -855,6 +896,8 @@ export class Bucket extends BucketBase {
 
     // Add all bucket metric configurations rules
     (props.metrics || []).forEach(this.addMetric.bind(this));
+    // Add all cors configuration rules
+    (props.cors || []).forEach(this.addCors.bind(this));
 
     // Add all lifecycle rules
     (props.lifecycleRules || []).forEach(this.addLifecycleRule.bind(this));
@@ -892,6 +935,15 @@ export class Bucket extends BucketBase {
     this.metrics.push(metric);
   }
 
+  /**
+   * Adds a cross-origin access configuration for objects in an Amazon S3 bucket
+   *
+   * @param rule The CORS configuration rule to add
+   */
+  public addCors(rule: CorsRule) {
+    this.cors.push(rule);
+  }
+
   /**
    * Adds a bucket notification event destination.
    * @param event The event to trigger the notification
@@ -1096,6 +1148,25 @@ export class Bucket extends BucketBase {
     }
   }
 
+  private parseCorsConfiguration(): CfnBucket.CorsConfigurationProperty | undefined {
+    if (!this.cors || this.cors.length === 0) {
+      return undefined;
+    }
+
+    return { corsRules: this.cors.map(parseCors) };
+
+    function parseCors(rule: CorsRule): CfnBucket.CorsRuleProperty {
+      return {
+        id: rule.id,
+        maxAge: rule.maxAge,
+        allowedHeaders: rule.allowedHeaders,
+        allowedMethods: rule.allowedMethods,
+        allowedOrigins: rule.allowedOrigins,
+        exposedHeaders: rule.exposedHeaders
+      };
+    }
+  }
+
   private parseTagFilters(tagFilters?: {[tag: string]: any}) {
     if (!tagFilters || tagFilters.length === 0) {
       return undefined;

packages/@aws-cdk/aws-s3/test/test.cors.ts

@@ -0,0 +1,121 @@
+import { expect, haveResource } from '@aws-cdk/assert';
+import { Stack } from '@aws-cdk/cdk';
+import { Test } from 'nodeunit';
+import { Bucket } from '../lib';
+
+export = {
+  'Can use addCors() to add a CORS configuration'(test: Test) {
+    // GIVEN
+    const stack = new Stack();
+
+    // WHEN
+    const bucket = new Bucket(stack, 'Bucket');
+    bucket.addCors({
+      allowedMethods: ["GET", "HEAD"],
+      allowedOrigins: ["https://example.com"]
+    });
+
+    // THEN
+    expect(stack).to(haveResource('AWS::S3::Bucket', {
+      CorsConfiguration: {
+        CorsRules: [{
+          AllowedMethods: ["GET", "HEAD"],
+          AllowedOrigins: ["https://example.com"]
+        }]
+      }
+    }));
+
+    test.done();
+  },
+
+  'Bucket with multiple cors configurations'(test: Test) {
+    // GIVEN
+    const stack = new Stack();
+
+    // WHEN
+    new Bucket(stack, 'Bucket', {
+      cors: [
+        {
+          allowedHeaders: [
+            "*"
+          ],
+          allowedMethods: [
+            "GET"
+          ],
+          allowedOrigins: [
+            "*"
+          ],
+          exposedHeaders: [
+            "Date"
+          ],
+          id: "myCORSRuleId1",
+          maxAge: 3600
+        },
+        {
+          allowedHeaders: [
+            "x-amz-*"
+          ],
+          allowedMethods: [
+            "DELETE"
+          ],
+          allowedOrigins: [
+            "http://www.example1.com",
+            "http://www.example2.com"
+          ],
+          exposedHeaders: [
+            "Connection",
+            "Server",
+            "Date"
+          ],
+          id: "myCORSRuleId2",
+          maxAge: 1800
+        }
+      ]
+    });
+
+    // THEN
+    expect(stack).to(haveResource('AWS::S3::Bucket', {
+      CorsConfiguration: {
+        CorsRules: [
+          {
+            AllowedHeaders: [
+              "*"
+            ],
+            AllowedMethods: [
+              "GET"
+            ],
+            AllowedOrigins: [
+              "*"
+            ],
+            ExposedHeaders: [
+              "Date"
+            ],
+            Id: "myCORSRuleId1",
+            MaxAge: 3600
+          },
+          {
+            AllowedHeaders: [
+              "x-amz-*"
+            ],
+            AllowedMethods: [
+              "DELETE"
+            ],
+            AllowedOrigins: [
+              "http://www.example1.com",
+              "http://www.example2.com"
+            ],
+            ExposedHeaders: [
+              "Connection",
+              "Server",
+              "Date"
+            ],
+            Id: "myCORSRuleId2",
+            MaxAge: 1800
+          }
+        ]
+      }
+    }));
+
+    test.done();
+  },
+};