custom authorizers in Amazon API Gateway 500 error

Question

I use Serverless-Authentication-boilerplate and want to map custom error response. But it always return 500 error.

authorize.js

// Authorize
function authorize(event, callback) {
  let providerConfig = config(event);
  try {
    let data = utils.readToken(event.authorizationToken, providerConfig.token_secret);
    console.log("Decrypted data: " + JSON.stringify(data));

    let methodArn = event.methodArn.replace(/(GET|POST|PUT|DELETE)/g, '*').replace(/mgnt.+/g, 'mgnt/*');

    console.log(`Change methodArn to: ${methodArn}`);

    // TODO: handle expiration time validation
    callback(null, utils.generatePolicy(
      data.id, // which is $context.authorizer.principalId
      'Allow',
      methodArn));
  } catch (err) {
    console.log(err);
    callback('401 Unauthenticated');
  }
}

s-function.json

responses:{ 
  "401 Unauthenticated.*": {
      "statusCode": "401"
  },
  "default": {
      "statusCode": "200",
      "responseModels": {
        "application/json;charset=UTF-8": "Empty"
      },
      "responseTemplates": {
        "application/json;charset=UTF-8": ""
      }
  }
}

Answer 1

After ask to Amazon Web Services.

Unfortunately the mapping of the Authorizer is not currently configurable and every returned error from a lambda function will map to a 500 status code in API gateway. Moreover, the mapping is performed on an exact string match of the output, so, in order to return the intended 401 Error to the client, you should execute a call to 'context.fail('Unauthorized');.

Finally, I change

callback('401 Unauthenticated');

to

context.fail('Unauthorized');

and work fine.

Sharing to whom may encounter this.