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 using fetch(), then check out aws4fetch – otherwise you can also bundle this library for use in older browsers.

The only AWS service I know of that doesn't support v4 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 https = require('https')
var aws4  = require('aws4')

// to illustrate usage, we'll create a utility function to request and pipe to stdout
function request(opts) { https.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":[]}
...
*/

// you can also specify extra headers to ignore during signing
request(aws4.sign({
  host: '07tjusf2h91cunochc.us-east-1.aoss.amazonaws.com',
  method: 'PUT',
  path: '/my-index',
  body: '{"mappings":{}}',
  headers: {
    'Content-Type': 'application/json',
    'X-Amz-Content-Sha256': 'UNSIGNED-PAYLOAD'
  },
  extraHeadersToIgnore: {
    'content-length': true
  }
}))

// and headers to include that would normally be ignored
request(aws4.sign({
  service: 'mycustomservice',
  path: '/whatever',
  headers: {
    'Range': 'bytes=200-1000, 2000-6576, 19000-'
  },
  extraHeadersToInclude: {
    'range': true
  }
}))


// The raw RequestSigner can be used to generate CodeCommit Git passwords
var signer = new aws4.RequestSigner({
  service: 'codecommit',
  host: 'git-codecommit.us-east-1.amazonaws.com',
  method: 'GIT',
  path: '/v1/repos/MyAwesomeRepo',
})
var password = signer.getDateTime() + 'Z' + signer.signature()

// see example.js for examples with other services

API

aws4.sign(requestOptions, [credentials])

Calculates and populates any necessary AWS headers and/or request options on requestOptions. 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)
• signQuery (to sign the query instead of adding an Authorization header, defaults to false)
• extraHeadersToIgnore (an object with lowercase header keys to ignore when signing, eg { 'content-length': true })
• extraHeadersToInclude (an object with lowercase header keys to include when signing, overriding any ignores)
• 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.