fxa-auth-server/crypto/hkdf.js

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

var HKDF = require('hkdf')
var P = require('../promise')

const NAMESPACE = 'identity.mozilla.com/picl/v1/'

function KWE(name, email) {
  return Buffer(NAMESPACE + name + ':' + email)
}

function KW(name) {
  return Buffer(NAMESPACE + name)
}

function hkdf(km, info, salt, len) {
  var d = P.defer()
  var df = new HKDF('sha256', salt, km)
  df.derive(
    KW(info),
    len,
    function(key) {
      d.resolve(key)
    }
  )
  return d.promise
}

hkdf.KW = KW
hkdf.KWE = KWE

module.exports = hkdf