How to do AWS Signature Version 4 from a local machine?

Question

I'm trying to test some Node.js code from my local machine for use in an AWS Lambda function. This involves signing a request with Signature Version 4.

I've signed in with my access key using AWS CLI but when I try to make a request using the following code I get this error at signer.addAuthorization . What step am I missing? It works fine from a Lambda function.

Code:

const AWS = require('aws-sdk');
const creds = new AWS.EnvironmentCredentials('AWS');
...
var signer = new AWS.Signers.V4(req, 'es');
signer.addAuthorization(creds, new Date());

Error:

TypeError [ERR_INVALID_ARG_TYPE]: The "key" argument must be one of type string, TypedArray, or DataView. Received type undefined
    at new Hmac

Answer 1

According to the documentation of EnvironmentCredentials ,

By default, this class will look for the matching environment variables prefixed by a given envPrefix

Therefore you need to set AWS_ACCESS_KEY_ID , AWS_SECRET_ACCESS_KEY and AWS_SESSION_TOKEN environment variables before invoking your code.

In AWS Lambda environment, these environment variables are already set, that's why it is working.