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bwt

Travis AppVeyor

Better Web Token

Powered by Curve25519, ChaCha20 derivatives, and Poly1305

⚠️ Not yet formally reviewed :construction:

Features

What a BWT Looks Like

QldUAAAAAWygrOCJAAABbKCs4iz5wub7BvcERzge0rd2++YzNTY2MDYzNzc5OTgx.5eHsXu2v5IUnE+DS1TVaStc=.Scb9ifOg3cEcy582KKfg7Q==

Usage

import * as bwt from "https://denopkg.com/chiefbiiko/bwt/mod.ts";

const alice = { ...bwt.generateKeyPair(), stringify: null };
const bob = { ...bwt.generateKeyPair(), parse: null };

alice.stringify = bwt.createStringify(alice.secretKey, {
  kid: bob.kid,
  publicKey: bob.publicKey
});

bob.parse = bwt.createParse(bob.secretKey, {
  kid: alice.kid,
  publicKey: alice.publicKey
});

const iat = Date.now();
const exp = iat + 1000;

const token = alice.stringify(
  { typ: bwt.Typ.BWTv0, kid: alice.kid, iat, exp },
  { info: "jwt sucks" }
);

console.log("alice seals and gets this token to bob:", token);

const contents = bob.parse(token);

console.log("bob opens it...:", JSON.stringify(contents));

API

Basics

Besides a few constants and interfaces, the module’s main exports are two factory functions, createStringify and createParse, that each create corresponding marshalling functions, stringify and parse.

As BWT uses assymetric keys the module also exports a key generation function: generateKeyPair. Make sure to store your private keys somewhere safe.

In case of exceptions, fx input validation or MAC verification errors, marshalling ops return null rather than throwing errors (to avoid leaking sensitive information). generateKeyPair, createStringify, and createParse will throw on invalid inputs though.

Find basic interfaces and constants below.

/** Supported BWT versions. */
export const SUPPORTED_VERSIONS: Set<number> = new Set<number>([0]);

/** Maximum allowed number of characters of a token. */
export const MAX_TOKEN_CHARS: number = 4096;

/** Byte length of a Curve25519 secret key. */
export const SECRET_KEY_BYTES: number = 32;

/** Byte length of a Curve25519 public key. */
export const PUBLIC_KEY_BYTES: number = 32;

/** Byte length of a BWT kid. */
export const KID_BYTES: number = 16;

/** Typ enum indicating a BWT version @ the Header.typ field. */
export const enum Typ {
  BWTv0
}

/**
 * BWT header object.
 *
 * typ must be a supported BWT version, currently that is Typ.BWTv0 only.
 * iat and exp denote the issued-at and expiry ms timestamps of a token.
 * kid is the public key identifier of the issuing party.
 */
export interface Header {
  typ: Typ;
  iat: number;
  exp: number;
  kid: Uint8Array;
}

/** BWT body object. */
export interface Body {
  [key: string]: unknown;
}

/** BWT contents. */
export interface Contents {
  header: Header;
  body: Body;
}

/** BWT stringify function. */
export interface Stringify {
  (header: Header, body: Body): string;
}

/** BWT parse function. */
export interface Parse {
  (token: string): Contents;
}

/**
 * BWT keypair object including a key identifier for the public key.
 *
 * secretKey is the 32-byte secret key.
 * publicKey is the 32-byte public key.
 * kid is a 16-byte key identifier for the public key.
 */
export interface KeyPair {
  secretKey: Uint8Array;
  publicKey: Uint8Array;
  kid: Uint8Array;
}

/**
 * BWT public key of a peer.
 *
 * publicKey is the 32-byte public key.
 * kid is a 16-byte key identifer for the public key.
 * name can be an arbitrarily encoded string.
 */
export interface PeerPublicKey {
  publicKey: Uint8Array;
  kid: Uint8Array;
  name?: string;
}

Core Callables

generateKeyPair(): KeyPair

Generates a new keypair.

createStringify(ownSecretKey: Uint8Array, peerPublicKey: PeerPublicKey): Stringify

Creates a stringify function.

ownSecretKey is the secret key of the keypair of the issuing party.

peerPublicKey must be the peer public key object of the party that the to-be-generated tokens are meant for.

createStringify mutates, zeroes the secret key buffer after computing the shared secret with the indicated peer in order to protect against attacks targeting strayman memory. Just be aware that createStringify clears ownSecretKey.

createParse(ownSecretKey: Uint8Array, ...peerPublicKeys: PeerPublicKey[]): Parse

Creates a parse function.

ownSecretKey is the secret key of the keypair of the party that is going to parse and verify tokens. peerPublicKeys must be a non-empty list of peer public key objects to be used for verification of incoming tokens.

createParse mutates, zeroes the secret key buffer after computing the shared secret with the indicated peer in order to protect against attacks targeting strayman memory. Just be aware that createParse clears ownSecretKey.

stringify(header: Header, body: Body): string

Stringifies a token.

header must contain four props:

  • typ set to one of the Typ enum variants, currently that is Typ.BWTv0 only

  • iat a millisecond timestamp indicating the current time

  • exp a millisecond timestamp indicating the expiry of the token

  • kid a binary of 16 bytes, the public key identifier of the issuing party

exp must be greater than iat.

body must be an object. Apart from that it can contain any type of fields. Nonetheless, make sure not to bloat the body as stringify will return null if a generated token exceeds 4KiB.

In case of invalid inputs or any other exceptions stringify returns null, otherwise a BWT token.

parse(token: string): Contents

Parses a token.

In case of invalid inputs, exceptions, corrupt or forged tokens parse returns null, otherwise a BWT header and body.

Besides format and cryptographic validation parse verifies that the iat and exp header claims are unsigned integers, iat <= Date.now() < exp, and that the total token size does not exceed 4KiB.

Dear Reviewers

Quick setup:

  1. Install deno:

    curl -fsSL https://deno.land/x/install/install.sh | sh

  2. Get this repo:

    git clone https://github.com/chiefbiiko/bwt && cd ./bwt && mkdir ./cache

  3. Cache all dependencies and run tests:

    DENO_DIR=./cache $HOME/.deno/bin/deno run --reload ./test.ts

Find all non-dev dependencies in the following two directories:

./cache/deps/https/raw.githubusercontent.com/chiefbiiko/:

curve25519, chacha20, hchacha20, poly1305, chacha20-poly1305, xchacha20-poly1305, std-encoding

./cache/deps/https/deno.land/x/:

base64

Please open an issue for your review findings. Looking forward to your feedback!

Thank you for reviewing!

License

MIT