Adds a Rake task to generate the private key

README.md

@@ -41,14 +41,19 @@ $ rails db:migrate
 
 ### Private Key
 
-You will need to generate a unique private key per application.
+This gem signs the generated [JWT (JSON Web Tokens)](https://jwt.io/) using a
+private key that should exist at the path `lib/oidc_provider_key.pem` in your
+Rails application.
+
+You can pass its passphrase using the `OIDC_PROVIDER_KEY_PASSPHRASE` environment
+variable.
+
+This gem provide a convenient way of generating one if you need it by running :
 
 ```bash
-$ ssh-keygen
+$ rails oidc_provider:generate_key
 ```
 
-Due to Docker Composes' lack of support for multiline `.env` variables, put a passphrase on it. Then add the key to your application at `lib/oidc_provider_key.pem` and add the passphrase as an environment variables in your application: `ENV["OIDC_PROVIDER_KEY_PASSPHRASE"]`.
-
 # Testing
 
 Visit: https://demo.c2id.com/oidc-client/

app/models/oidc_provider/id_token.rb

@@ -1,5 +1,9 @@
+# frozen_string_literal: true
+
 module OIDCProvider
   class IdToken < ApplicationRecord
+    PASSPHRASE_ENV_VAR = 'OIDC_PROVIDER_KEY_PASSPHRASE'
+
     belongs_to :authorization
 
     attribute :expires_at, :datetime, default: -> { 1.hour.from_now }
@@ -24,8 +28,19 @@ def to_jwt
     private
 
     class << self
+      def config
+        {
+          issuer: OIDCProvider.issuer,
+          jwk_set: JSON::JWK::Set.new(public_jwk)
+        }
+      end
+
+      def oidc_provider_key_path
+        Rails.root.join("lib/oidc_provider_key.pem")
+      end
+
       def key_pair
-        @key_pair ||= OpenSSL::PKey::RSA.new(File.read(Rails.root.join("lib/oidc_provider_key.pem")), ENV["OIDC_PROVIDER_KEY_PASSPHRASE"])
+        @key_pair ||= OpenSSL::PKey::RSA.new(File.read(oidc_provider_key_path), ENV[PASSPHRASE_ENV_VAR])
       end
 
       def private_jwk
@@ -35,13 +50,6 @@ def private_jwk
       def public_jwk
         JSON::JWK.new key_pair.public_key
       end
-
-      def config
-        {
-          issuer: OIDCProvider.issuer,
-          jwk_set: JSON::JWK::Set.new(public_jwk)
-        }
-      end
     end
   end
 end

lib/oidc_provider.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "openid_connect"
 require "oidc_provider/engine"
 

lib/oidc_provider/engine.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rack/oauth2'
 
 module OIDCProvider

lib/tasks/oidc_provider.rake

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+namespace :oidc_provider do
+  desc 'Generate the lib/oidc_provider_key.pem key file'
+  task generate_key: :environment do
+    key_filepath = OIDCProvider::IdToken.oidc_provider_key_path
+
+    File.exist?(key_filepath) && raise("ERROR: A key file already exists at #{key_filepath}.")
+
+    passphrase_env_var = OIDCProvider::IdToken::PASSPHRASE_ENV_VAR
+
+    pass_phrase = ENV.fetch(passphrase_env_var, '')
+
+    if pass_phrase == ''
+      puts "\033[33mWARNING: You haven't defined a passphrase to be used to " \
+           'generate the new key which is concidered as insecured. You can ' \
+           "do it by setting the #{passphrase_env_var} environment variable " \
+           "and re-run this task.\033[0m"
+
+      raise
+    end
+
+    key_file_content = OpenSSL::PKey::RSA.new(2048).export(
+      OpenSSL::Cipher.new('AES-128-CBC'),
+      pass_phrase
+    )
+
+    File.write(key_filepath, key_file_content)
+    FileUtils.chmod(0_600, key_filepath)
+
+    puts "SUCCESS: A new key file has been created at #{key_filepath}."
+  end
+end