Output apikey value in cloud formation

I have a cloudformation template that outputs variables. One of the output variable is

 ApiGKeyId:
    Description: "Api Key Id"
    Value: !Ref ApplicationApiGatewayApiKey

This returns the Id of API gateway key and not the actual value. Is there a way to get the value?

Solution 1:

attribute "Value" is not supported according to below thread~
https://github.com/awslabs/serverless-application-model/issues/206

3rd party maintained available attributes at a glance here: https://theburningmonk.com/cloudformation-ref-and-getatt-cheatsheet/

After some research, I felt there is no other way to retrieve the ApiKey's value but using Custom Resource invoking an lambda function. Here is my sample code fyr.

#######################################################
##### Start of Custom functions #####
#######################################################
ValueFunc:
  Type: AWS::Lambda::Function
  Properties:
    Code:
      ZipFile: >
        var response = require('cfn-response');
        var AWS = require('aws-sdk');

        exports.handler = function(event, context) {
          var apiKeyID = event.ResourceProperties.ApiKeyID;
          var apigateway = new AWS.APIGateway();
          var params = {
            apiKey: apiKeyID,
            includeValue: true
          };

          apigateway.getApiKey(params, function(err, ApiKeyData) {
            if (err) {
              console.log(err, err.stack); // an error occurred
              var responseData = { "mykey" : "error reading ApiKey" };
              response.send(event, context, response.SUCCESS, responseData);
            } else {
              console.log(ApiKeyData.value);      // successful response
              var responseData = { "mykey" : ApiKeyData.value };
              response.send(event, context, response.SUCCESS, responseData);
            }
          });
        };
    Handler: index.handler
    Runtime: nodejs8.10
    Timeout: 30
    Role: !Sub "arn:aws:iam::${AWS::AccountId}:role/${LambdaExecutionRole}"
GetApiKeyValue:
  Type: Custom::LambdaCallout
  Properties:
    ServiceToken: !GetAtt ValueFunc.Arn
    ApiKeyID: !Ref ApiKey