Unencrypted, plaintext JWTs in Ruby

plain_text_jwt.rb

require 'base64'
require 'json'

module PlainTextJWT
  HEADER = Base64.strict_encode64({typ: 'JWT', alg: 'none'}.to_json)
  HEADER_SIZE = HEADER.size

  module_function

  def encode payload
    "#{HEADER}.#{Base64.strict_encode64 JSON.unparse payload}."
  end

  def decode payload
    JSON.parse Base64.strict_decode64 payload[HEADER_SIZE.next..-2]
  end
end

PlainTextJWT.encode [42]
#=> "eyJ0eXAiOiJKV1QiLCJhbGciOiJub25lIn0=.WzQyXQ==."

PlainTextJWT.decode "eyJ0eXAiOiJKV1QiLCJhbGciOiJub25lIn0=.WzQyXQ==."
#=> [42]