Add optional Clerk OIDC login

Adds omniauth_openid_connect with Clerk as the IdP, gated on
CLERK_DISCOVERY_URL / CLERK_CLIENT_ID / CLERK_CLIENT_SECRET. When unset,
behaves identically to upstream. Password login + 2FA preserved as
fallback.

Access gate (v1): email-domain allowlist via CLERK_ALLOWED_EMAIL_DOMAINS.
First-time login auto-creates the User on the singleton Account with
role=admin. Drops into the empty _omniauthable.html.erb partial DocuSeal
already reserved in the login view.

Gemfile

@@ -26,6 +26,8 @@ gem 'jwt', require: false
 gem 'lograge'
 gem 'numo-narray-alt', require: false
 gem 'oj'
+gem 'omniauth_openid_connect'
+gem 'omniauth-rails_csrf_protection'
 gem 'onnxruntime', require: false
 gem 'pagy'
 gem 'pg', require: false

app/controllers/users/omniauth_callbacks_controller.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+module Users
+  class OmniauthCallbacksController < Devise::OmniauthCallbacksController
+    skip_before_action :verify_authenticity_token, only: [:clerk_oidc]
+
+    def clerk_oidc
+      user = User.from_clerk_oidc(request.env['omniauth.auth'])
+
+      if user&.persisted?
+        sign_in_and_redirect(user, event: :authentication)
+        set_flash_message(:notice, :success, kind: 'Clerk') if is_navigational_format?
+      else
+        flash[:alert] = I18n.t('clerk_oidc_login_not_allowed',
+                               default: 'Sign-in not permitted for this account.')
+        redirect_to new_user_session_path
+      end
+    end
+
+    def failure
+      flash[:alert] = I18n.t('clerk_oidc_login_failed', default: 'Clerk sign-in failed. Please try again.')
+      redirect_to new_user_session_path
+    end
+  end
+end

app/models/user.rb

@@ -69,7 +69,12 @@ class User < ApplicationRecord
   has_many :encrypted_configs, dependent: :destroy, class_name: 'EncryptedUserConfig'
   has_many :email_messages, dependent: :destroy, foreign_key: :author_id, inverse_of: :author
 
-  devise :two_factor_authenticatable, :recoverable, :rememberable, :validatable, :trackable, :lockable
+  if Docuseal.clerk_oidc_enabled?
+    devise :two_factor_authenticatable, :recoverable, :rememberable, :validatable, :trackable, :lockable,
+           :omniauthable, omniauth_providers: [:clerk_oidc]
+  else
+    devise :two_factor_authenticatable, :recoverable, :rememberable, :validatable, :trackable, :lockable
+  end
 
   attribute :role, :string, default: ADMIN_ROLE
   attribute :uuid, :string, default: -> { SecureRandom.uuid }
@@ -121,4 +126,27 @@ class User < ApplicationRecord
       email
     end
   end
+
+  def self.from_clerk_oidc(auth)
+    email = auth.info.email.to_s.downcase
+    return nil if email.blank?
+    return nil unless Docuseal.clerk_email_allowed?(email)
+
+    account = Account.first
+    return nil if account.blank?
+
+    user = active.find_by(email:)
+    return user if user
+
+    first, *rest = auth.info.name.to_s.split(' ', 2)
+
+    create!(
+      account:,
+      email:,
+      first_name: auth.info.first_name.presence || first,
+      last_name: auth.info.last_name.presence || rest.join(' '),
+      role: ADMIN_ROLE,
+      password: Devise.friendly_token(40)
+    )
+  end
 end

app/views/devise/sessions/_omniauthable.html.erb

@@ -0,0 +1,8 @@
+<% if Docuseal.clerk_oidc_enabled? %>
+  <div class="divider text-base-content/40 text-sm my-6"><%= t(:or, default: 'or') %></div>
+  <%= button_to user_clerk_oidc_omniauth_authorize_path,
+                data: { turbo: false },
+                class: 'base-button base-button-outline w-full flex items-center justify-center gap-2' do %>
+    <span><%= t(:sign_in_with_clerk, default: 'Sign in with Clerk') %></span>
+  <% end %>
+<% end %>

config/initializers/devise.rb

@@ -334,6 +334,22 @@ Devise.setup do |config|
   # changed. Defaults to true, so a user is signed in automatically after changing a password.
   # config.sign_in_after_change_password = true
 
+  if Docuseal.clerk_oidc_enabled?
+    config.omniauth_path_prefix = '/users/auth'
+    config.omniauth :openid_connect, {
+      name: :clerk_oidc,
+      issuer: Docuseal::CLERK_DISCOVERY_URL.sub(%r{/\.well-known/openid-configuration\z}, ''),
+      discovery: true,
+      scope: %i[openid email profile],
+      response_type: :code,
+      client_options: {
+        identifier: Docuseal::CLERK_CLIENT_ID,
+        secret: Docuseal::CLERK_CLIENT_SECRET,
+        redirect_uri: "#{Docuseal::DEFAULT_APP_URL.sub(%r{/\z}, '')}/users/auth/clerk_oidc/callback"
+      }
+    }
+  end
+
   ActiveSupport.run_load_hooks(:devise_config, config)
 end
 # rubocop:enable Metrics/BlockLength

config/routes.rb

@@ -14,8 +14,14 @@ Rails.application.routes.draw do
   get 'up' => 'rails/health#show'
   get 'manifest' => 'pwa#manifest'
 
-  devise_for :users, path: '/', only: %i[sessions passwords],
-                     controllers: { sessions: 'sessions', passwords: 'passwords' }
+  if Docuseal.clerk_oidc_enabled?
+    devise_for :users, path: '/', only: %i[sessions passwords omniauth_callbacks],
+                       controllers: { sessions: 'sessions', passwords: 'passwords',
+                                      omniauth_callbacks: 'users/omniauth_callbacks' }
+  else
+    devise_for :users, path: '/', only: %i[sessions passwords],
+                       controllers: { sessions: 'sessions', passwords: 'passwords' }
+  end
 
   devise_scope :user do
     resource :invitation, only: %i[update] do

lib/docuseal.rb

@@ -37,6 +37,13 @@ module Docuseal
 
   CERTS = JSON.parse(ENV.fetch('CERTS', '{}'))
   TIMESERVER_URL = ENV.fetch('TIMESERVER_URL', nil)
+
+  CLERK_DISCOVERY_URL = ENV.fetch('CLERK_DISCOVERY_URL', nil)
+  CLERK_CLIENT_ID = ENV.fetch('CLERK_CLIENT_ID', nil)
+  CLERK_CLIENT_SECRET = ENV.fetch('CLERK_CLIENT_SECRET', nil)
+  CLERK_ALLOWED_EMAIL_DOMAINS = ENV.fetch('CLERK_ALLOWED_EMAIL_DOMAINS', '')
+                                   .split(',').map { |d| d.strip.downcase }.compact_blank.freeze
+
   VERSION_FILE_PATH = Rails.root.join('.version')
   VERSION_FILE2_PATH = Rails.public_path.join('version')
 
@@ -60,6 +67,17 @@ module Docuseal
     ENV['MULTITENANT'] == 'true'
   end
 
+  def clerk_oidc_enabled?
+    CLERK_DISCOVERY_URL.present? && CLERK_CLIENT_ID.present? && CLERK_CLIENT_SECRET.present?
+  end
+
+  def clerk_email_allowed?(email)
+    return true if CLERK_ALLOWED_EMAIL_DOMAINS.empty?
+
+    domain = email.to_s.split('@').last.to_s.downcase
+    CLERK_ALLOWED_EMAIL_DOMAINS.include?(domain)
+  end
+
   def advanced_formats?
     multitenant?
   end