How do I make a cloudformation template for a cloudwatch event with a lambda function target?

Question

Instead of using the aws interface I want to write my cloudwatch event and function as a stack. However I am having trouble how to figure out the template of this cloudformation stack. The aws guides show examples but I haven't found anything that deals with the syntax of a cloudwatch event, any help? this is the event and lambda:

{
  "source": [
    "aws.s3"
  ],
  "detail-type": [
    "AWS API Call via CloudTrail"
  ],
  "detail": {
    "eventSource": [
      "s3.amazonaws.com"
    ],
    "eventName": [
      "CreateBucket"
    ]
  }
}

Lambda:

import boto3

s3 = boto3.client('s3')

def lambda_handler(event, context):
    # Get bucket name from the S3 event
    print(event)

    bucket_name = event['detail']['requestParameters']['bucketName']

    # Create a bucket policy
    bucket_policy =json.dumps({
        "Version": "2012-10-17",
        "Statement": [
            {
                "Sid": "MustBeEncryptedAtRest",
                "Effect": "Deny",
                "Principal": "*",
                "Action": "s3:PutObject",
                "Resource": [
                    "arn:aws:s3:::{}".format(bucket_name),
                    "arn:aws:s3:::{}/*".format(bucket_name)
                ],
                "Condition": {
                    "StringNotEquals": {
                        "s3:x-amz-server-side-encryption": [
                            "AES256",
                            "aws:kms"
                        ]
                    }
                }
            },
            {
                "Sid": "MustBeEncryptedInTransit",
                "Effect": "Deny",
                "Principal": "*",
                "Action": "s3:*",
                "Resource": [
                    "arn:aws:s3:::{}".format(bucket_name),
                    "arn:aws:s3:::{}/*".format(bucket_name)
                ],
                "Condition": {
                    "Bool": {
                        "aws:SecureTransport": "false"
                        }
                }
            } ] })


    # Set the new policy
    s3.put_bucket_policy(Bucket=bucket_name, Policy=bucket_policy)

Answer 1

Below is an example modified slightly from an example in the aws-events-rule CloudFormation documentation.

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Resources": {
        "LambdaFunction": .......
        "EventRule": {
            "Type": "AWS::Events::Rule",
            "Properties": {
                "Description": "EventRule",
                "EventPattern": {
                    "source": [
                        "aws.s3"
                    ],
                    "detail-type": [
                        "AWS API Call via CloudTrail"
                    ],
                    "detail": {
                        "eventSource": [
                            "s3.amazonaws.com"
                        ],
                        "eventName": [
                            "CreateBucket"
                        ]
                    }
                },
                "State": "ENABLED",
                "Targets": [{
                    "Arn": {
                        "Fn::GetAtt": ["LambdaFunction", "Arn"]
                    },
                    "Id": "TargetFunctionV1"
                }]
            }
        }
    }
}