Rack JWT Decode

This is a Rack middleware that will look for a JSON Web Token (JWT) in the Authorization Bearer header and if it is present, decode it and add the values from the payload to the Rack env, with the Rack env key prefixed with "jwt.".

For example, say your application generated a JWT like this:

>> token = JWT.encode({ sub: 1234, iat: Time.now.utc.to_i }, ENV["APPLICATION_SECRET"])
=> "eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOjEyMzQsImlhdCI6MTU5ODg5ODc3Mn0.MOaM22JkvCi2Bg-vUXAPuYXA9NtsApGNDplRdYMYerw"

Now say that clients pass that token back in an HTTP Header like this:

curl -v -H 'Authorization: Bearer eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOjEyMzQsImlhdCI6MTU5ODg5ODc3Mn0.MOaM22JkvCi2Bg-vUXAPuYXA9NtsApGNDplRdYMYerw' 'http://localhost:9292'

This middleware would then result in the following additions to the Rack env:

env["jwt.sub"] # => 1234
env["jwt.iat"] # => 1598898472

Add this line to your application's Gemfile:

gem "rack-jwt-decode"

And then execute:

$ bundle install

Or install it yourself as:

$ gem install rack-jwt-decode

Configure your Rack application to use this middleware in your Rackup file like this:

use RackJWTDecode, ENV["APPLICATION_SECRET"]

The second argument is the secret key that you used to encode the JWT token.

Bug reports and pull requests are welcome on GitHub at https://github.com/pjb3/rack-jwt-decode.

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