JWT Auth + Refresh Tokens in Rails

README.md

JWT Auth + Refresh Tokens in Rails

This is just some code I recently used in my development application in order to add token-based authentication for my api-only rails app. The api-client was to be consumed by a mobile application, so I needed an authentication solution that would keep the user logged in indefinetly and the only way to do this was either using refresh tokens or sliding sessions.

I also needed a way to both blacklist and whitelist tokens based on a unique identifier (jti)

Before trying it out DIY, I considered using:

• devise-jwt which unfortunately does not support refresh tokens
• devise_token_auth I ran into issues when it came to the changing headers on request on mobile, disabling this meant users would have to sign in periodically
• doorkeeper This was pretty close to what I needed, however, it was quite complicated and I considered it wasn't worth the extra effort of implmeneting OAuth2 (for now)
• api_guard This was great, almost everything I needed but it didn't play too nicely with GraphQL and I needed to implement token whitelisting also.

So, since I couldn't find any widely-used gem to meet my needs; I decided to just go DIY, and the end result works pretty well. And overview of how things works is so:

• You call on the Jwt::Issuer module to create an access_token and refresh_token pair.
• You call on the Jwt::Authenticator module to authenticate the access_token get the current_user and the decoeded_token
• You call on the Jwt::Revoker module to revoke (blacklist/remove whitelist) a token
• You call on the Jwt::Refresher module to refresh an access_token based on a refresh_token

There are more modules, but you can preview them for yourself.

There are some prequistes you need in order to use this code:

1. You need to create a blacklisted tokens table like so: rails g model BlacklistedToken jti:string:uniq:index user:belongs_to exp:datetime

2. If you want to use whitelisting to, create a tokens table like so: rails g model WhitelistedToken jti:string:uniq:index user:belongs_to exp:datetime

3. Create a refresh tokens table like & model so: rails g model RefreshToken crypted_token:string:uniq user:belongs_to

class RefreshToken < ApplicationRecord
  belongs_to :user
  before_create :set_crypted_token

  attr_accessor :token

  def self.find_by_token(token)
    crypted_token = Digest::SHA256.hexdigest token
    RefreshToken.find_by(crypted_token: crypted_token)
  end

  private

  def set_crypted_token
    self.token = SecureRandom.hex
    self.crypted_token = Digest::SHA256.hexdigest(token)
  end
end

4. Update the user model to include the associations

  has_many :refresh_tokens, dependent: :delete_all
  has_many :whitelisted_tokens, dependent: :delete_all
  has_many :blacklisted_tokens, dependent: :delete_all

Then you are pretty much ready to go!

In the future, I might make this into a gem or add redis support or similar.

I hope this gist helps someone!

application_controller.rb

class ApplicationControler < ActionController::Base
  before_action :authenticate
  
  private
  
  def authenticate
    current_user, decoded_token = Jwt::Authenticator.call(
       headers: request.headers,
       access_token: params[:access_token] # authenticate from header OR params
     )

     @current_user = current_user
     @decoded_token = decoded_token
  end
end

authenticator.rb

module Jwt
  module Authenticator
    module_function

    def call(headers:, access_token:)
      token = access_token || Jwt::Authenticator.authenticate_header(
        headers
      )
      raise Errors::Jwt::MissingToken unless token.present?

      decoded_token = Jwt::Decoder.decode!(token)
      user = Jwt::Authenticator.authenticate_user_from_token(decoded_token)
      raise Errors::Unauthorized unless user.present?

      [user, decoded_token]
    end

    def authenticate_header(headers)
      headers['Authorization']&.split('Bearer ')&.last
    end

    def authenticate_user_from_token(decoded_token)
      raise Errors::Jwt::InvalidToken unless decoded_token[:jti].present? && decoded_token[:user_id].present?

      user = User.find(decoded_token.fetch(:user_id))
      blacklisted = Jwt::Blacklister.blacklisted?(jti: decoded_token[:jti])
      whitelisted = Jwt::Whitelister.whitelisted?(jti: decoded_token[:jti])
      valid_issued_at = Jwt::Authenticator.valid_issued_at?(user, decoded_token)

      return user if !blacklisted && whitelisted && valid_issued_at
    end

    def valid_issued_at?(user, decoded_token)
      !user.token_issued_at || decoded_token[:iat] >= user.token_issued_at.to_i
    end

    module Helpers
      extend ActiveSupport::Concern

      def logout!(user:, decoded_token:)
        Jwt::Revoker.revoke(
          decoded_token: decoded_token,
          user: user
        )
      end
    end
  end
end

blacklister.rb

module Jwt
  module Blacklister
    module_function

    def blacklist!(jti:, exp:, user:)
      user.blacklisted_tokens.create!(
        jti: jti,
        exp: Time.at(exp)
      )
    end

    def blacklisted?(jti:)
      BlacklistedToken.exists?(jti: jti)
    end
  end
end

decoder.rb

module Jwt
  module Decoder
    module_function

    def decode!(access_token, verify: true)
      decoded = JWT.decode(access_token, Jwt::Secret.secret, verify, verify_iat: true)[0]
      raise Errors::Jwt::InvalidToken unless decoded.present?

      decoded.symbolize_keys
    end

    def decode(access_token, verify: true)
      decode!(access_token, verify: verify)
    rescue StandardError
      nil
    end
  end
end

encoder.rb

module Jwt
  module Encoder
    module_function

    def call(user)
      jti = SecureRandom.hex
      exp = Jwt::Encoder.token_expiry
      access_token = JWT.encode(
        {
          user_id: user.id,
          jti: jti,
          iat: Jwt::Encoder.token_issued_at.to_i,
          exp: exp
        },
        Jwt::Secret.secret
      )

      [access_token, jti, exp]
    end

    def token_expiry
      (Jwt::Encoder.token_issued_at + Jwt::Expiry.expiry).to_i
    end

    def token_issued_at
      Time.now
    end
  end
end

expiry.rb

module Jwt
  module Expiry
    module_function

    def expiry
      2.hours
    end
  end
end

issuer.rb

module Jwt
  module Issuer
    module_function

    def call(user)
      access_token, jti, exp = Jwt::Encoder.call(user)
      refresh_token = user.refresh_tokens.create!
      Jwt::Whitelister.whitelist!(
        jti: jti,
        exp: exp,
        user: user
      )

      [access_token, refresh_token]
    end
  end
end

refresher.rb

module Jwt
  module Refresher
    module_function

    def refresh!(refresh_token:, decoded_token:, user:)
      raise Errors::Jwt::MissingToken, token: 'refresh' unless refresh_token.present? || decoded_token.nil?

      existing_refresh_token = user.refresh_tokens.find_by_token(
        refresh_token
      )
      raise Errors::Jwt::InvalidToken, token: 'refresh' unless existing_refresh_token.present?

      jti = decoded_token.fetch(:jti)

      new_access_token, new_refresh_token = Jwt::Issuer.call(user)
      existing_refresh_token.destroy!

      Jwt::Blacklister.blacklist!(jti: jti, exp: decoded_token.fetch(:exp), user: user)
      Jwt::Whitelister.remove_whitelist!(jti: jti)

      [new_access_token, new_refresh_token]
    end
  end
end

revoker.rb

module Jwt
  module Revoker
    module_function

    def revoke(decoded_token:, user:)
      jti = decoded_token.fetch(:jti)
      exp = decoded_token.fetch(:exp)

      Jwt::Whitelister.remove_whitelist!(jti: jti)
      Jwt::Blacklister.blacklist!(
        jti: jti,
        exp: exp,
        user: user
      )
    rescue StandardError
      raise Errors::Jwt::InvalidToken
    end
  end
end

secret.rb

module Jwt
  module Secret
    module_function

    def secret
      Rails.application.secrets.secret_key_base
    end
  end
end

whitelisted.rb

module Jwt
  module Whitelister
    module_function

    def whitelist!(jti:, exp:, user:)
      user.whitelisted_tokens.create!(
        jti: jti,
        exp: Time.at(exp)
      )
    end

    def remove_whitelist!(jti:)
      whitelist = WhitelistedToken.find_by(
        jti: jti
      )
      whitelist.destroy if whitelist.present?
    end

    def whitelisted?(jti:)
      WhitelistedToken.exists?(jti: jti)
    end
  end
end

Thanks for amazing work.
I'm getting #<NameError: uninitialized constant Jwt::Authenticator::Errors, how should I define these classes?

Thanks for amazing work.
I'm getting #<NameError: uninitialized constant Jwt::Authenticator::Errors, how should I define these classes?

Hi! So I actually created a superclass of StandardError to handle application-level errors (NotFoundError, ValidationError) etc, inside my lib/errors folder.

So unless you create something similar– you will get that error.
What you can do instead is just raise a StandardError instead of Errors::*, and pass a custom message.
Or you can do what I did– use this tutorial for guidance https://www.honeybadger.io/blog/ruby-custom-exceptions/

Hi @jesster2k10, thanks for sharing!
Can you please specify the license of this piece of code? I would like to partially copy-paste it, but not sure if I legally can do it. This can be helpful: https://choosealicense.com/

Hi @jesster2k10, thanks for sharing!
Can you please specify the license of this piece of code? I would like to partially copy-paste it, but not sure if I legally can do it. This can be helpful: https://choosealicense.com/

Hey! You're free to do as you please. The license would fall under MIT. Go for it!

Hey there @jesster2k10, great work! It looks like a really readable, testable piece of code :D
I have one question: do you blacklist access_token intentionally? From my perspective, it seems incorrect to store JWT access_token in the database and on each authentication query on DB (checking if the token is blacklisted or not). It seems to me like we are losing the biggest advantage of JWT itself. Could you elaborate a bit on the idea of blacklisting refresh_token (ofc with keeping TTL of access token relatively short)? It would prevent future refreshing tokens, ofc downside is that previous access_token can be still used for couple minutes.

Hey Thanks for your comment! The blacklisting is definitely not necessary, or even the whitelisting–especially if you make your tokens extremely short lived (say 45 minutes) It's really just for an optional extra layer of security. Of course it has its own drawbacks. Maintaining a blacklist and a whitelist in the database would definitely slow things down, but guarantee that no one can use a token that has been "flagged" (either at log out, or manually) You could set up the blacklist/whitelist to use Redis rather than ActiveRecord if your concern is speed. One advantage to maintaining a whitelist/blacklist is you can invalidate all of the user's sessions easily, by just blacklisting all the tokens that belong to them or removing them from the whitelist. But if your sessions are extremely short lived, this might not make much sense. It's really a decision that's up to you, you may want to just maintain a blacklist (which I wouldn't recommend personally) or use a whitelist (much better in my opinion) or a combination of both (like I did in the example) or none and just reduce the TTL for the session

…

On Sat, May 1, 2021 at 1:22 PM oadamczyk ***@***.***> wrote: ***@***.**** commented on this gist. ------------------------------ Hey there @jesster2k10 <https://github.com/jesster2k10>, great work! It looks like a really readable, testable piece of code :D I have one question: do you blacklist *access_token* intentionally? From my perspective, it seems incorrect to store JWT access_token in the database and on each authentication query on DB (checking if the token is blacklisted or not). It seems to me like we are losing the biggest advantage of JWT itself. Could you elaborate a bit on the idea of blacklisting *refresh_token* (ofc with keeping TTL of access token relatively short)? It would prevent future refreshing tokens, ofc downside is that previous access_token can be still used for couple minutes. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <https://gist.github.com/e626ee61d678350a21a9d3e81da2493e#gistcomment-3727946>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABRHYDSL3AU2WOWAM533SLLTLPW6ZANCNFSM4ULSJRDA> .

Totally right, seems like it depends on the use case - as it always is ^^ Thanks for the answer and keep up the good work!

Bless your soul my friend. Exactly what I need for my project.

hi @jesster2k10, would you be able to provide the relevant portions of the user model as well?
like this :token_issued_at field?
Is it simply overwritten everytime a new RefreshToken is created?

+1

+1

Hey @jesster2k10! thank you so much for this! I have an ignorant question though. When checking the code, I've seen that the Issuer model creates a refresh token which (among other keys) saves the 'crypted_token' information. However, the 'token' information, which is the original hash key of crypted_token is not stored. Thus, when I sent the first information to the client I sent the refresh token without the original token information. This results in an invalid token key as the method find_by_token of the refreshed model uses the original token, hash it and compare it to the crypto token.

I dunno If I'm missing something here. Please let me know your thoughts.

+1 The refresh_token needs an expiry imo, otherwise it can be abused.

@jesster2k10 works good, can we expect a gem for this? Would be a nice open source project maybe other could contribute to

@jesster2k10 I have also deployed successfully but it not have refresh token https://github.com/markcror/sample_app/blob/master/app/controllers/api/api_controller.rb, this is frontend nextjs for it https://github.com/markcror/sample_app_nextjs, and reference on nodejs https://github.com/markcror/sample_app_nodejs, Looking forward to your complete solution, do you think it's possible

https://github.com/nickeryno/rails-boilerplate recently after the support from my colleague i got the implementation with refresh token it can work hope to get your and everyone's contribution

https://github.com/maearon/maearon a e-commerce platform api for ruby on rails

I appreciate the content! very helpful!

This is such a hidden gem, thanks for this

I kept the devise-jwt gem and updated the user model, and created a refresh_tokens controller.
This gave me good guidance though. See my solution here.
https://gist.github.com/jwaiswa7/2b58535c33fe15bed3e025708ca1e56c

@jesster2k10

class Api::V1::AuthController < Api::V1::ApplicationController
  skip_before_action :authenticate_request, only: [:refresh_access_token]

  def refresh_access_token
    user = User.find_by(id: params[:id])
    refresh_token = user.refresh_tokens.last
    access_token = Jwt::Authenticator.authenticate_header(
      request.headers
    )

    begin
      # The `verify: false` option is used to skip the verification of the token's signature.
      # This is not good since if someone has an expired token, they can refresh it without verifying the signature.
      # The thing is that the access token is expired at this point and the code expects it to be expired here. The
      # issue is that JWT throws a JWT::ExpiredSignature error and haults the entire operation if `verify: true`.
      # I still think that I need to revisit this area of the code to see if there is a way to hand this solution.
      decoded_access_token = Jwt::Decoder.decode!(access_token, verify: false)

      new_access_token = Jwt::Refresher.refresh!(
        refresh_token: refresh_token,
        decoded_token: decoded_access_token,
        user: user,
      )

      render json: { access_token: new_access_token }, status: :ok
    rescue JWT::DecodeError => e
      render json: { error: "Invalid token: #{e.message}" }, status: :unauthorized
    rescue StandardError => e
      render json: { error: e.message }, status: :unauthorized
    end
  end
end

Thanks for this gist! I am using it for nextjs/rails app.

One area that stumped me was refreshing the access token using the Refresher module. Above, I kept running into JWT::SignatureExpired error whenever I tried decoding an expired access token. The only way to refresh the token was to set verify to false while decoding it, otherwise the error wouldn't let me continue.

Did you face this issue? If so, did you come up with a solution?