fix(s3): grantDelete with KMS SSE (aws#7528)

Added empty array check for keyActions. This will make sure that `grantDelete` will not create malformed policy when used with `KMS` key.

Added a new integ test to check CloudFormation will not error out during the deployment.

Fixes aws#4380

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

@@ -627,7 +627,7 @@ abstract class BucketBase extends Resource implements IBucket {
       });
     }
 
-    if (this.encryptionKey) {
+    if (this.encryptionKey && keyActions && keyActions.length !== 0) {
       this.encryptionKey.grant(grantee, ...keyActions);
     }
 

packages/@aws-cdk/aws-s3/test/integ.bucket-grantdelete-kms.expected.json

@@ -0,0 +1,115 @@
+{
+  "Resources": {
+    "MyKey6AB29FA6": {
+      "Type": "AWS::KMS::Key",
+      "Properties": {
+        "KeyPolicy": {
+          "Statement": [
+            {
+              "Action": [
+                "kms:Create*",
+                "kms:Describe*",
+                "kms:Enable*",
+                "kms:List*",
+                "kms:Put*",
+                "kms:Update*",
+                "kms:Revoke*",
+                "kms:Disable*",
+                "kms:Get*",
+                "kms:Delete*",
+                "kms:ScheduleKeyDeletion",
+                "kms:CancelKeyDeletion",
+                "kms:GenerateDataKey",
+                "kms:TagResource",
+                "kms:UntagResource"
+              ],
+              "Effect": "Allow",
+              "Principal": {
+                "AWS": {
+                  "Fn::Join": [
+                    "",
+                    [
+                      "arn:",
+                      {
+                        "Ref": "AWS::Partition"
+                      },
+                      ":iam::",
+                      {
+                        "Ref": "AWS::AccountId"
+                      },
+                      ":root"
+                    ]
+                  ]
+                }
+              },
+              "Resource": "*"
+            }
+          ],
+          "Version": "2012-10-17"
+        }
+      },
+      "UpdateReplacePolicy": "Retain",
+      "DeletionPolicy": "Retain"
+    },
+    "Deleter1FEDC09A": {
+      "Type": "AWS::IAM::User"
+    },
+    "DeleterDefaultPolicyCD33B8A0": {
+      "Type": "AWS::IAM::Policy",
+      "Properties": {
+        "PolicyDocument": {
+          "Statement": [
+            {
+              "Action": "s3:DeleteObject*",
+              "Effect": "Allow",
+              "Resource": {
+                "Fn::Join": [
+                  "",
+                  [
+                    {
+                      "Fn::GetAtt": [
+                        "MyBucketF68F3FF0",
+                        "Arn"
+                      ]
+                    },
+                    "/*"
+                  ]
+                ]
+              }
+            }
+          ],
+          "Version": "2012-10-17"
+        },
+        "PolicyName": "DeleterDefaultPolicyCD33B8A0",
+        "Users": [
+          {
+            "Ref": "Deleter1FEDC09A"
+          }
+        ]
+      }
+    },
+    "MyBucketF68F3FF0": {
+      "Type": "AWS::S3::Bucket",
+      "Properties": {
+        "BucketEncryption": {
+          "ServerSideEncryptionConfiguration": [
+            {
+              "ServerSideEncryptionByDefault": {
+                "KMSMasterKeyID": {
+                  "Fn::GetAtt": [
+                    "MyKey6AB29FA6",
+                    "Arn"
+                  ]
+                },
+                "SSEAlgorithm": "aws:kms"
+              }
+            }
+          ]
+        },
+        "BucketName": "my-bucket-physical-name-grant-delete"
+      },
+      "UpdateReplacePolicy": "Retain",
+      "DeletionPolicy": "Retain"
+    }
+  }
+}

packages/@aws-cdk/aws-s3/test/integ.bucket-grantdelete-kms.ts

@@ -0,0 +1,22 @@
+#!/usr/bin/env node
+import * as iam from '@aws-cdk/aws-iam';
+import * as kms from '@aws-cdk/aws-kms';
+import * as cdk from '@aws-cdk/core';
+import * as s3 from '../lib';
+
+const app = new cdk.App();
+
+const stack = new cdk.Stack(app, 'aws-cdk-s3');
+
+const key = new kms.Key(stack, 'MyKey');
+const deleter = new iam.User(stack, 'Deleter');
+const bucket = new s3.Bucket(stack, 'MyBucket', {
+  bucketName: 'my-bucket-physical-name-grant-delete',
+  encryptionKey: key,
+  encryption: s3.BucketEncryption.KMS,
+});
+
+// when
+bucket.grantDelete(deleter);
+
+app.synth();

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

@@ -1053,6 +1053,50 @@ export = {
     test.done();
   },
 
+  'grantDelete, with a KMS Key'(test: Test) {
+    // given
+    const stack = new cdk.Stack();
+    const key = new kms.Key(stack, 'MyKey');
+    const deleter = new iam.User(stack, 'Deleter');
+    const bucket = new s3.Bucket(stack, 'MyBucket', {
+      bucketName: 'my-bucket-physical-name',
+      encryptionKey: key,
+      encryption: s3.BucketEncryption.KMS,
+    });
+
+    // when
+    bucket.grantDelete(deleter);
+
+    // then
+    expect(stack).to(haveResourceLike('AWS::IAM::Policy', {
+      'PolicyDocument': {
+        'Statement': [
+          {
+            'Action': 's3:DeleteObject*',
+            'Effect': 'Allow',
+            'Resource': {
+              'Fn::Join': [
+                '',
+                [
+                  {
+                    'Fn::GetAtt': [
+                      'MyBucketF68F3FF0',
+                      'Arn',
+                    ],
+                  },
+                  '/*',
+                ],
+              ],
+            },
+          },
+        ],
+        'Version': '2012-10-17',
+      },
+    }));
+
+    test.done();
+  },
+
   'cross-stack permissions': {
     'in the same account and region'(test: Test) {
       const app = new cdk.App();