How to create a private AWS Api Gateway using cloudformation?

Question

I am trying to create an AWS API Gateway of PRIVATE type,
This requires a resource policy, which I have as I'm able to create the gateway from the AWS Console,
I wanted to know how I could add the resource policy via the CF template -

Following is the swagger definition of the resource policy -

x-amazon-apigateway-policy:
  Version: "2012-10-17"
  Statement:
  - Effect: "Deny"
    Principal: "*"
    Action: "execute-api:Invoke"
    Resource: "arn:aws:execute-api:us-east-1:awsAccountId:xxxx/*/*/*"
    Condition:
      StringNotEquals:
        aws:sourceVpc: "vpc-xxxxx"
  - Effect: "Allow"
    Principal: "*"
    Action: "execute-api:Invoke"
    Resource: "arn:aws:execute-api:us-east-1:xxxx:xxxx/*/*/*"

How can I configure it in the CF template -

AWSTemplateFormatVersion: 2010-09-09
Transform: 'AWS::Serverless-2016-10-31'
Description: G2G Api Template Stack

Resources:
   g2gPrivate:
    Type: 'AWS::ApiGateway::RestApi'
    Properties:
      Name: 'private-gw'
      EndpointConfiguration:
        Types:
          - PRIVATE

Reference -
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-apigateway-restapi.html

https://medium.com/@cathmgarcia/conditional-resource-policy-on-aws-sam-with-inline-swagger-816ce946dbb

Answer 1

You need to supply the policy under a key (called Policy at the same level as Name.

https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-apigateway-restapi.html#cfn-apigateway-restapi-policy

This needs to be supplied in the JSON format.

Something like...

AWSTemplateFormatVersion: 2010-09-09
Transform: 'AWS::Serverless-2016-10-31'
Description: G2G Api Template Stack

Resources:
   g2gPrivate:
    Type: 'AWS::ApiGateway::RestApi'
    Properties:
      Name: 'private-gw'
      EndpointConfiguration:
        Types:
          - PRIVATE
      Policy: !Sub |
        {
          "Version": "2012-10-17",
          "Statement": [
            {
              "Effect": "Deny",
              "Principal": "*",
              "Action": "execute-api:Invoke",
              "Resource": "arn:aws:execute-api:us-east-1:${AWS::AccountId}:*/*/*/*",
              "Condition": {
                "StringNotEquals": {
                  "aws:sourceVpc": "vpc-xxxxx"
                }
              }
            },
            {
              "Effect": "Allow",
              "Principal": "*",
              "Action": "execute-api:Invoke",
              "Resource": "arn:aws:execute-api:us-east-1:${AWS::AccountId}:*/*/*/*"
            }
          ]
        }