aws-device-gateway-signed-url

Utility function that produces a signed websocket URL for AWS IOT Device Gateway, allowing browsers to connect directly to AWS IOT data pipelines.

The code is mostly extracted from the AWS IOT websocket MQTT Sample, and packaged as a NPM library for convenient use.

Here is a list of changes from the original code:
* removed UI dependencies so it can easily be used with a different UI,
* extended the signature function to support session tokens, for easy Cognito support

The original code copyright is by Amazon.com, Inc. or its affiliates.

Signature structure

See the IOT Protocols Guide and Signature V4 Signing Process for more information on the structure of the signed URL.

Usage

``js
var signUrl = require('aws-device-gateway-signed-url');
signedUrl = signUrl (params);
`

params is a key-value hash containing the following keys:

* regionName: AWS region, for example, us-east-1
* endpoint: AWS device gateway endpoint URL. (see _Retrieving your endpoint URL_ below)
* secretKey: AWS access Secret key
* accessKey: AWS access key ID
* sessionToken: _optional_ an AWS Session Token (from STS, Cognito, or assumed role)
* expires: _optional_ seconds until the signed url expires. default is 86400, 1 day

Retrieving your endpoint URL

Each AWS account has an associated IOT device gateway endpoint. Use the following AWS CLI command to discover your endpoint URL

`bash
aws iot describe-endpoint --query endpointAddress --output text
``