aws API Gateway - {“message”:“Missing Authentication Token”}

Question

My lambda works locally and returns the JSON.
My API Gateway works locally, i.e. calls the lambda and returns the JSON.

However when I publish my API to my DEV stage and then try to use the invoke url - https://jbpqyp3142.execute-api.us-east-2.amazonaws.com/DEV I get

{"message":"Missing Authentication Token"}

Lambda:

require 'json'

def lambda_handler(event:, context:)
  if event['queryStringParameters'].nil?
    input = 1
  else
    if event['queryStringParameters']['in']
      input = event['queryStringParameters']['in'].to_i
    else
      input = 1
    end
  end
  triple = (input * 3).to_s
  { statusCode: 200, body: JSON.generate("Hello from Lambda! Result is " + input.to_s + " *3 = " + triple) }
end

API Gateway:

I tried to create an 'authorizer' but got the following error:

See Also: Missing Authentication Token while accessing API Gateway? — KyleMit

TheClassic TheClassic · Accepted Answer · 2019-11-09T17:40:02

You are making a request to the root url for your endpoint, which was the link amazon provided, however it will not work as you need to specify the resource you are requesting. You see this when you open up the stage and look for the URL inside it, i.e.

Add the path for the resource, e.g.

https://jbpqyp3142.execute-api.us-east-2.amazonaws.com/DEV/tripler

You shouldn't need an authorizer unless you want one for your use case. Read more about API Gateway access control: https://docs.aws.amazon.com/apigateway/latest/developerguide/apigateway-control-access-to-api.html

I thought your problem might be that you are not signing your requests using SigV4: https://docs.aws.amazon.com/apigateway/api-reference/signing-requests/

However, before writing this answer, I did a quick search to see if there was anything simpler I might be missing and there was. It seems that you are making a request to the root url for your endpoint, but not specifying the resource you are requesting. The top stack overflow result when searching for the error you are receiving explains the problem: https://stackoverflow.com/a/43285585/715780

aws API Gateway - {“message”:“Missing Authentication Token”}

3 Answers

You are making a request to the root url for your endpoint, which was the link amazon provided, however it will not work as you need to specify the resource you are requesting. You see this when you open up the stage and look for the URL inside it, i.e.