Cognito User Pool Authorizer defined in openapi without hardcoded values

Question

I have a API Gateway Rest Api resource defined with this template:

AWSTemplateFormatVersion: '2010-09-09'
Description: "Api gateway"
Resources:
  ApiGateway:
    Type: "AWS::ApiGateway::RestApi"
    Properties:
      BodyS3Location: "./openapi-spec.yaml"

And the contents of openapi-spec.yaml (based on this example) being:

openapi: "3.0.2"
info:
  title: SampleApi
paths:
  /test:
    get:
      summary: Test
      responses:
        "200":
          description: Ok
      security:
        - UserPool: [ ]
      x-amazon-apigateway-integration:
        # ....

components:
  securitySchemes:
    UserPool:
      type: apiKey
      name: Authorization
      in: header
      x-amazon-apigateway-authtype: cognito_user_pools
      x-amazon-apigateway-authorizer:
        type: cognito_user_pools
        providerARNs:
          ### THIS VALUE ###
          - "arn:aws:cognito-idp:eu-west-1:123456789012:userpool/eu-west-1_abcd12345"

I'd like to be able to deploy this template in multiple environments/account and having this hardcoded providerARN is limiting that. So my questions are:

How can values for the providerARNs field be passed in dynamically?

If that can't be done, then are there any workarounds to this so that I don't have to hardcode the providerArns here?

Note: Already tried to use stage variables and they don't seem to work here.

Answer 1

Aswering this question even though it's late cause I struggled myself a lot to find an answer for this problem. I was able to do this by using the Stage Variables feature of api gateway. Your Authorizer declaration in open api spec file would look like this.

Your api gateway declaration will have to declare this stage variable like this in temaplate.yaml

I'm declaring this as parameter in template.yaml file :

Now don't get confused if you see this in your API Gateway->Authorizer:

This is exactly what it should look like. This will actually use the stage variable which is here in your stages->{stage_name}->stage variables:

Answer 2

If you don't have an existing Cognito user pool then you would have to define one using AWS::Cognito::UserPool in CloudFormation, then you can simply reference the arn of this user pool using !GetAtt.

But if you have an existing Cognito user pool then you can also import it to a stack using CloudFormation following these steps.

Here's an example:

template.yaml

Resources:
  ApiGateway:
    Type: "AWS::ApiGateway::RestApi"
    Properties:
      BodyS3Location: "./openapi-spec.yaml"

  CognitoUserPool:
    Type: AWS::Cognito::UserPool
    Properties:
      # ....

openapi-spec.yaml

openapi: "3.0.2"
# ....
components:
  securitySchemes:
    UserPool:
      type: apiKey
      name: Authorization
      in: header
      x-amazon-apigateway-authtype: cognito_user_pools
      x-amazon-apigateway-authorizer:
        type: cognito_user_pools
        providerARNs:
          - !GetAtt CognitoUserPool.Arn