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Rack middleware for authentication using JSON Web Tokens
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This is pre-release software. It is pretty well tested but has not yet been used in production. Your feedback is requested.


Rack::JsonWebTokenAuth is a Rack middleware that makes it easy for your Rack based application (Sinatra, Rails) to authenticate clients that present a valid Authorization: Bearer token header with a JSON Web Token (JWT).

This middleware was inspired by the similar eigenbart/rack-jwt middleware but provides a leaner codebase that relies upon the excellent garyf/jwt_claims and garyf/json_web_token gems to provide all JWT token validation. This gem also makes extensive use of the contracts gem to enforce strict type checking on all inputs and outputs. It is designed to fail-fast on errors and reject invalid inputs before even trying to parse them using JWT.


Add this line to your application's Gemfile:

gem 'rack-json_web_token_auth'

And then execute:

$ bundle install

Or install it directly with:

$ gem install rack-json_web_token_auth


This Rack middleware is designed to allow adding a simple authentication layer, using JSON Web Tokens (JWT), to your Rack based applications. It's easy to configure with a simple Ruby DSL.

This middleware is not responsible for creating valid JWT tokens for you. It only receives and validates them. If the token provided is valid for a specific path the request will be allowed to continue as normal. If the token is invalid, or the path requested is not a configured path, a 401 Not Authorized HTTP response will be sent.

For token creation I recommend the garyf/json_web_token gem.

Creating a JWT

Here is an example of creating a JWT with a pretty full set of claims. You may not need all of these for your application.

require 'json_web_token'

key = '4a7b98c31c3b6918f916d809443c096d02bf686d6bead5baa4a162642cea98b3'

claims = {
  name: 'John Doe',
  iat: - 1,
  nbf: - 5,
  exp: + 10,
  aud: %w(api web),
  sub: 'my-user-id',
  jti: 'my-unique-token-id',
  iss: ''

# generate a signed token
jwt = JsonWebToken.sign(claims, key: key, alg: 'HS256')
#=> "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJuYW1lIjoiSm9obiBEb2UiLCJpYXQiOjE0NzY0MTUwMjUsIm5iZiI6MTQ3NjQxNTAyMSwiZXhwIjoxNDc2NDE1MDM2LCJhdWQiOlsiYXBpIiwid2ViIl0sInN1YiI6Im15LXVzZXItaWQiLCJqdGkiOiJteS11bmlxdWUtdG9rZW4taWQiLCJpc3MiOiJodHRwczovL215LmV4YW1wbGUuY29tLyJ9.-zu-FGfLmwLX69DC2UIsk-8oEGoRSkCOUqbJwcarSm4"

Submitting a JWT

Your client of choice needs to submit an Authorization Bearer request header.

How you do this is client specific and left as an exercise for the reader.

'Authorization' => "Bearer #{jwt}"

Server Config

This middleware should be inserted as early as possible into your middleware stack.

Configuring the Rack middleware to accept JWT tokens on your server is just a matter of adding the middleware and configuring which paths are to be considered public and unsecured (no JWT needed), and which require a valid token to continue. These are private secured paths.

For each secured resource you must also provide the JWT config needed to validate incoming tokens. The available claims are processed by the garyf/jwt_claims gem and more info about claims can be found in the README for that project. At a minimum a :key must be provided except if the none algorithm is being used (probably not recommended).

For secured resources you can optionally also pass in a :methods option, which specifies an array of HTTP methods that are allowed for the specified resource. One or more of [:any, :get, :head, :post, :put, :patch, :delete, :options] can be provided. If the :any option is desired it must be the only option provided.

Configuration directives are processed in the order that you provide and requests match against the first path match. For this reason you should probably put your unsecured resources first and order all resources from most specific to least specific. If multiple resources with the same path are configured, but with different options, only the first resource matched will be used to test the request, all others will be ignored.

The DSL was heavily inspired by the rack-cors gem.

require 'rack/json_web_token_auth'

# Sinatra style Rack middleware `use` syntax
use Rack::JsonWebTokenAuth do

  # You can define JWT options for all `secured` resources globally
  # or you can specify a hash like this inside each block. If you want to
  # get really granular this config can even be different per `secure` resource.
  jwt_opts = {
    key: '4a7b98c31c3b6918f916d809443c096d02bf686d6bead5baa4a162642cea98b3',
    alg: 'HS256',
    aud: 'api',
    sub: 'my-user-id',
    jti: 'my-unique-token-id',
    iss: '',
    leeway_seconds: 30

  # Resources defined in this block are whitelisted and
  # require no token for requests to the configured
  # resource path. You should probably define your unsecured
  # paths first. Resources in this block will raise an exception
  # if provided with the :jwt options hash.
  unsecured do
    resource '/users/registration'
    resource '/users/login'

  # Resources defined in this block require a valid JWT token
  # for access. Each resource takes a path and a Hash of options.
  # The only option supported at the moment is `jwt`. The `:jwt` Hash
  # key should be set to a Hash and only a `:key` must be defined
  # which is a random key of sufficient strength.
  # Additional JWT claims can also be provided in this hash as shown in
  # this example.
  # Resources defined in this block will raise an exception if they
  # are not provided with the `:jwt` options hash and a valid `:key`
  # (unless using the 'none' algorithm).
  secured do
    # a resource can start with a slash and match an exact path
    resource '/private', jwt: jwt_opts

    # or it can contain a wildcard '*'. The entire path
    # can even be specified with '*' if you wanted to
    # match all paths.
    resource '/private/*/wildcard', jwt: jwt_opts

    # Every resource can be configured with its own
    # JWT keys and all other valid JWT claim options.
    # For example you could require one token config for
    # login and registration, and on successful login mint
    # another flavor of token for all other app API access.
    resource '/another/path', jwt: {key: 'a long random key', alg: 'HS512'}

  # You can get very granular by specifying that a resource can only be accessed
  # when requested with certain HTTP methods. The default for any resource is
  # to allow HTTP `GET` requests only. You need to pass in a :methods array if
  # you want to expose additional methods.
  # The available choices are:
  #   [:any, :get, :head, :post, :put, :patch, :delete, :options]
  # If you try to specify :methods on an `unsecured` resource it will throw
  # an exception.
  secured do
    # GET only
    resource '/http_get_only', jwt: jwt_opts, methods: [:get]

    # GET or POST
    resource '/http_post_or_get', jwt: jwt_opts, methods: [:get, :post]

    # ANY HTTP method allowed
    resource '/http_any', jwt: jwt_opts, methods: [:any]

    # ANY HTTP method allowed (alternate)
    # This is the same as [:any]
    resource '/http_any_manual', jwt: jwt_opts, methods: [:get, :head, :post, :put, :patch, :delete, :options]

    # IGNORED! This resource path was already defined above!
    # Even though it has different methods allowed it will be ignored.
    resource '/http_post_or_get', jwt: jwt_opts, methods: [:post]

  # You can have more than one `unsecured` or `secured` block if you like.
  unsecured do
    # WARNING : this resource will never be used since it is masked
    # by another resource higher in the stack with the same '/private' path.
    resource '/private'

  # Requests to any resource path not explictly marked as 'secured' or
  # `unsecured` above will fail-safe and return a 401 status.
  # e.g. /path/to/somewhere/else


After checking out the repo, run bundle install to install dependencies. Then, run bundle exec rake to run the specs.

To install this gem onto your local machine, run bundle exec rake install.

Installation Security : Signed Ruby Gem

This gem is cryptographically signed. To be sure the gem you install hasn’t been tampered with you can install it using the following method:

Add my public key (if you haven’t already) as a trusted certificate

# Caveat: Gem certificates are trusted globally, such that adding a
# cert.pem for one gem automatically trusts all gems signed by that cert.
gem cert --add <(curl -Ls

To install, it is possible to specify either HighSecurity or MediumSecurity mode. Since this gem depends on one or more gems that are not cryptographically signed you will likely need to use MediumSecurity. You should receive a warning if any signed gem does not match its signature.

# All signed dependent gems must be verified.
gem install rack-json_web_token_auth -P MediumSecurity

You can learn more about security and signed Ruby Gems.

Installation Security : Signed Git Commits

Most, if not all, of the commits and tags to this repository are signed with my PGP/GPG code signing key. I have uploaded my code signing public keys to GitHub and you can now verify those signatures with the GitHub UI. See this list of commits and look for the Verified tag next to each commit. You can click on that tag for additional information.

You can also clone the repository and verify the signatures locally using your own GnuPG installation. You can find my certificates and read about how to conduct this verification at


Bug reports and pull requests are welcome on GitHub at This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.



(c) 2016 Glenn Rempe <> (


The gem is available as open source under the terms of the MIT License.


Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the LICENSE.txt file for the specific language governing permissions and limitations under the License.

Thank You!

Thanks to Gary Fleshman (@garyf) for his very well written implementation of JWT and for accepting my patches.

And of course thanks to Mr. Eigenbart (@eigenbart) for the inspiration.

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