nojwt

README

NoJWT

This is for now a simple proof of concept not a full-blown library, although if you are ok with using HS256 and parsing your own payloads, it's totally functional.

The idea is that in JWT we can't ever trust the alg header, and the typ and cty are very seldom needed when you control when and how you would be getting JWTs. This makes the JWT header totally unnecessary, so we could do without it making our tokens smaller.

Aside from being "headerless JWTs", the payload can be any []byte blob, not necessarily JSON content, and we only base64-encode it once (to produce the final token), not before at signature creation. This saves a bit of creation and verification time, although it's probably negligible.

Installation

go get -u github.com/antoniomo/nojwt

Sample usage

package main

import (
	"fmt"

	"github.com/antoniomo/nojwt"
)

func main() {
	payload := []byte(`{"hello": "world!"}`)
	secret := []byte("my secret")

	token := nojwt.SignHS256(payload, secret)
	fmt.Println(token)

	payload2, ok := nojwt.VerifyHS256(token, secret)
	fmt.Println(string(payload2), ok)

	// Lets tamper it!
	tamperedToken := []byte(token)
	tamperedToken[42] = 'x'
	fmt.Println(string(tamperedToken))

	payload3, ok := nojwt.VerifyHS256(string(tamperedToken), secret)
	fmt.Println(string(payload3), ok)

	// There's also unsafe nowjt.Parse for when we don't care about the
	// signature, but it test that it's valid nojwt format
	payload4, ok := nojwt.Parse(string(tamperedToken))
	fmt.Println(string(payload4), ok)
}

The output of that should be:

eyJoZWxsbyI6ICJ3b3JsZCEifQ.g8o_EQ3pOt9qBQ-Yz8vK_rSoqWO47ds5hUsbPf9eObU
{"hello": "world!"} <nil>
eyJoZWxsbyI6ICJ3b3JsZCEifQ.g8o_EQ3pOt9qBQ-xz8vK_rSoqWO47ds5hUsbPf9eObU
{"hello": "world!"} invalid nojwt signature
{"hello": "world!"} <nil>

CLI

There's a very minimal CLI included. It doesn't check all use cases, but it's good for experimentation purposes.

Check the help:

$ ./nojwt -h
nojwt command line tool.

Commands:
	sign	Signs a payload with a secret, prints token
	verify	Verifies a token with a secret, prints payload and possible error
	parse	Parses a token, prints payload

Usage:
	nojwt <command> [options]

Use "nojwt <command> --help" for more information about a given command.

$./nojwt sign -h
Usage of sign:
  -p string
    	Payload
  -s string
    	Signature

$./nojwt verify -h
Usage of verify:
  -s string
    	Signature
  -t string
    	Token

$./nojwt parse -h
Usage of parse:
  -t string
    	Token

Documentation

Index

• Variables
• func Parse(token string) ([]byte, error)
• func SignHS256(payload, secret []byte) string
• func VerifyHS256(token string, secret []byte) ([]byte, error)

Variables

var (
	ErrInvalidFormat    = errors.New("invalid nojwt format")
	ErrInvalidSignature = errors.New("invalid nojwt signature")
)

Functions

func Parse

func Parse(token string) ([]byte, error)

Parse doesn't verify signature.

func SignHS256

func SignHS256(payload, secret []byte) string

SignHS256 ...

func VerifyHS256

func VerifyHS256(token string, secret []byte) ([]byte, error)

VerifyHS256 ...