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fernet

Fernet.js

Javascript implementation of Fernet symmetric encryption.

Fernet is an opinionated way of using AES and HMAC authentication that makes shared-secret symmetric encryption simpler for communicating applications.

Fernet.js uses browserify to provide a library that works in both node and the browser.

Instead of using TypedArrays I use Hex Strings and CryptoJS's Hex.parse to build up CryptoJs.lib.WordArray objects.

WARNING

It's generally never considered safe to encrypt data in the browser.

However, you can use this library to encrypt/decrypt data server-side and decrypt data on a client.

That being said, the only randomness used by this library without your control is a call to crypto.randomBytes to generate IVs. This function defaults to OpenSSL server-side and browserify's random number generator implementation client-side. The browserify implementation only uses real browser crypto or throws an error. (IE: no calls to Math.random())

If you're planning on generating the secrets in the browser do yourself a favor and get an audit.

Use

node.js

var fernet = require('./fernet');

browser

<script src="fernetBrowser.js"></script>

Fernet

fernet.setSecret(string)

Sets the secret at the top level for all further Tokens made from this instance of Fernet.

fernet.ttl = seconds

Sets the ttl at the top level for all further Tokens made from this instance of Fernet.

Secret

Generating a secret

Generating appropriate secrets is beyond the scope of `Fernet`, but you should
generate it using `/dev/random` in a *nix. To generate a base64-encoded 256 bit
(32 byte) random sequence, try:

dd if=/dev/urandom bs=32 count=1 2>/dev/null | openssl base64

new fernet.Secret(string)

  var secret = new fernet.Secret("cw_0x689RpI-jtRR7oE8h_eQsKImvJapLeSbXpwF4e4=");
  /*
    {
      signingKeyHex: '730ff4c7af3d46923e8ed451ee813c87',
      signingKey: [CryptoJS.lib.WordArray],
      encryptionKeyHex: 'f790b0a226bc96a92de49b5e9c05e1ee',
      encryptionKey: [CryptoJS.lib.WordArray]
    }
  */

Token

new fernet.Token(options)

Options:

  • secret: a fernet.Secret object
  • token: a Fernet-encoded String
  • ttl: seconds of ttl

For testing:

  • time: Date object
  • iv: Array of Integers

Token.prototype.encode

//Have to include time and iv to make it deterministic. 
//Normally time would default to (new Date()) and iv to something random. 
var token = new fernet.Token({
  secret: secret,
  time: Date.parse(1),
  iv: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
})
token.encode("Message")
/*
'gAAAAABSO_yhAAECAwQFBgcICQoLDA0OD1PGoFV6wgWZG6AOBfQqevwJT2qKtCZ0EjKy1_TvyxTseR_3ebIF6Ph-xa2QT_tEvg=='
*/

Token.prototype.decode

Include tt

var token = new fernet.Token({
  secret: secret,
  token: 'gAAAAABSO_yhAAECAwQFBgcICQoLDA0OD1PGoFV6wgWZG6AOBfQqevwJT2qKtCZ0EjKy1_TvyxTseR_3ebIF6Ph-xa2QT_tEvg==',
  ttl: 0
})
token.decode();
 
/*
"Message"
*/

Test

> npm test

Compiles new fernetBrowser.js via browserify, tests node lib with mocha, then opens test.html via open.