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aws4


A small utility to sign vanilla Node.js http(s) request options using Amazon's
AWS Signature Version 4.

If you want to sign and send AWS requests in a modern browser, or an environment like Cloudflare Workers, then check out aws4fetch – otherwise you can also bundle this library for use in older browsers.

The only AWS service that doesn't support v4 as of 2020-05-22 is
SimpleDB
(it only supports AWS Signature Version 2).

It also provides defaults for a number of core AWS headers and
request parameters, making it very easy to query AWS services, or
build out a fully-featured AWS library.


Example

var http = require('https')
var aws4  = require('aws4')

// to illustrate usage, we'll create a utility function to request and pipe to stdout
function request(opts) { http.request(opts, function(res) { res.pipe(process.stdout) }).end(opts.body || '') }

// aws4 will sign an options object as you'd pass to http.request, with an AWS service and region
var opts = { host: 'my-bucket.s3.us-west-1.amazonaws.com', path: '/my-object', service: 's3', region: 'us-west-1' }

// aws4.sign() will sign and modify these options, ready to pass to http.request
aws4.sign(opts, { accessKeyId: '', secretAccessKey: '' })

// or it can get credentials from process.env.AWS_ACCESS_KEY_ID, etc
aws4.sign(opts)

// for most AWS services, aws4 can figure out the service and region if you pass a host
opts = { host: 'my-bucket.s3.us-west-1.amazonaws.com', path: '/my-object' }

// usually it will add/modify request headers, but you can also sign the query:
opts = { host: 'my-bucket.s3.amazonaws.com', path: '/?X-Amz-Expires=12345', signQuery: true }

// and for services with simple hosts, aws4 can infer the host from service and region:
opts = { service: 'sqs', region: 'us-east-1', path: '/?Action=ListQueues' }

// and if you're using us-east-1, it's the default:
opts = { service: 'sqs', path: '/?Action=ListQueues' }

aws4.sign(opts)
console.log(opts)
/*
{
  host: 'sqs.us-east-1.amazonaws.com',
  path: '/?Action=ListQueues',
  headers: {
    Host: 'sqs.us-east-1.amazonaws.com',
    'X-Amz-Date': '20121226T061030Z',
    Authorization: 'AWS4-HMAC-SHA256 Credential=ABCDEF/20121226/us-east-1/sqs/aws4_request, ...'
  }
}
*/

// we can now use this to query AWS
request(opts)
/*
<?xml version="1.0"?>
<ListQueuesResponse xmlns="https://queue.amazonaws.com/doc/2012-11-05/">
...
*/

// aws4 can infer the HTTP method if a body is passed in
// method will be POST and Content-Type: 'application/x-www-form-urlencoded; charset=utf-8'
request(aws4.sign({ service: 'iam', body: 'Action=ListGroups&Version=2010-05-08' }))
/*
<ListGroupsResponse xmlns="https://iam.amazonaws.com/doc/2010-05-08/">
...
*/

// you can specify any custom option or header as per usual
request(aws4.sign({
  service: 'dynamodb',
  region: 'ap-southeast-2',
  method: 'POST',
  path: '/',
  headers: {
    'Content-Type': 'application/x-amz-json-1.0',
    'X-Amz-Target': 'DynamoDB_20120810.ListTables'
  },
  body: '{}'
}))
/*
{"TableNames":[]}
...
*/

// see example.js for examples with other services


API


aws4.sign(requestOptions, [credentials])

This calculates and populates the Authorization header of
requestOptions, and any other necessary AWS headers and/or request
options. Returns requestOptions as a convenience for chaining.

requestOptions is an object holding the same options that the node.js
http.request
function takes.

The following properties of requestOptions are used in the signing or
populated if they don't already exist:


hostname or host (will try to be determined from service and region if not given)

method (will use 'GET' if not given or 'POST' if there is a body)

path (will use '/' if not given)

body (will use '' if not given)

service (will try to be calculated from hostname or host if not given)

region (will try to be calculated from hostname or host or use 'us-east-1' if not given)

headers['Host'] (will use hostname or host or be calculated if not given)

headers['Content-Type'] (will use 'application/x-www-form-urlencoded; charset=utf-8'
if not given and there is a body)

headers['Date'] (used to calculate the signature date if given, otherwise new Date is used)


Your AWS credentials (which can be found in your
AWS console)
can be specified in one of two ways:


As the second argument, like this:


aws4.sign(requestOptions, {
  secretAccessKey: "<your-secret-access-key>",
  accessKeyId: "<your-access-key-id>",
  sessionToken: "<your-session-token>"
})


From process.env, such as this:


export AWS_ACCESS_KEY_ID="<your-access-key-id>"
export AWS_SECRET_ACCESS_KEY="<your-secret-access-key>"
export AWS_SESSION_TOKEN="<your-session-token>"


(will also use AWS_ACCESS_KEY and AWS_SECRET_KEY if available)

The sessionToken property and AWS_SESSION_TOKEN environment variable are optional for signing
with IAM STS temporary credentials.


Installation

With npm do:

npm install aws4


Can also be used in the browser.


Thanks

Thanks to @jed for his
dynamo-client lib where I first
committed and subsequently extracted this code.

Also thanks to the
official node.js AWS SDK for giving
me a start on implementing the v4 signature.