One login auth

app/controllers/one_login_controller.rb

@@ -0,0 +1,85 @@
+class OneLoginController < ApplicationController
+  before_action :redirect_to_candidate_sign_in_unless_one_login_enabled
+
+  def callback
+    auth = request.env['omniauth.auth']
+    session[:one_login_id_token] = auth&.credentials&.id_token
+    candidate = OneLoginUser.authenticate_or_create_by(auth)
+
+    sign_in_candidate(candidate)
+
+    redirect_to candidate_interface_interstitial_path
+  rescue OneLoginUser::Error => e
+    session[:one_login_error] = e.message
+    redirect_to auth_one_login_sign_out_path
+  end
+
+  def bypass_callback
+    one_login_user_bypass = OneLoginUserBypass.new(
+      token: request.env['omniauth.auth']&.uid,
+    )
+    candidate = one_login_user_bypass.authenticate
+
+    if candidate.present?
+      sign_in_candidate(candidate)
+
+      redirect_to candidate_interface_interstitial_path
+    else
+      flash[:warning] = one_login_user_bypass.errors.full_messages.join('\n')
+      redirect_to candidate_interface_create_account_or_sign_in_path
+    end
+  end
+
+  def sign_out
+    id_token = session[:one_login_id_token]
+    one_login_error = session[:one_login_error]
+    reset_session
+
+    session[:one_login_error] = one_login_error
+    if OneLogin.bypass?
+      redirect_to candidate_interface_create_account_or_sign_in_path
+    else
+      # Go back to one login to sign out the user on their end as well
+      redirect_to logout_one_login(id_token), allow_other_host: true
+    end
+  end
+
+  def sign_out_complete
+    if session[:one_login_error].present?
+      Sentry.capture_message(session[:one_login_error], level: :error)
+      redirect_to internal_server_error_path
+    else
+      redirect_to candidate_interface_create_account_or_sign_in_path
+    end
+  end
+
+  def failure
+    session[:one_login_error] = "One login failure with #{params[:message]} " \
+                                "for one_login_id_token: #{session[:one_login_id_token]}"
+
+    redirect_to auth_one_login_sign_out_path
+  end
+
+private
+
+  def redirect_to_candidate_sign_in_unless_one_login_enabled
+    if FeatureFlag.inactive?(:one_login_candidate_sign_in)
+      redirect_to candidate_interface_create_account_or_sign_in_path
+    end
+  end
+
+  def sign_in_candidate(candidate)
+    sign_in(candidate, scope: :candidate)
+    candidate.update!(last_signed_in_at: Time.zone.now)
+  end
+
+  def logout_one_login(id_token_hint)
+    params = {
+      post_logout_redirect_uri: URI(auth_one_login_sign_out_complete_url),
+      id_token_hint:,
+    }
+    URI.parse("#{ENV['GOVUK_ONE_LOGIN_ISSUER_URL']}logout").tap do |uri|
+      uri.query = URI.encode_www_form(params)
+    end.to_s
+  end
+end

app/models/one_login_user.rb

@@ -0,0 +1,50 @@
+class OneLoginUser
+  class Error < StandardError; end
+  attr_reader :email_address, :token
+
+  def initialize(omniauth_object)
+    @email_address = omniauth_object.info.email
+    @token = omniauth_object.uid
+  end
+
+  def self.authenticate_or_create_by(omniauth_auth)
+    new(omniauth_auth).authenticate_or_create_by
+  end
+
+  def authenticate_or_create_by
+    one_login_auth = OneLoginAuth.find_by(token:)
+    existing_candidate = Candidate.find_by(email_address:)
+
+    return candidate_with_one_login(one_login_auth) if one_login_auth
+    return existing_candidate_without_one_login(existing_candidate) if existing_candidate
+
+    create_candidate!
+  end
+
+private
+
+  def candidate_with_one_login(one_login_auth)
+    one_login_auth.update!(email_address:)
+    one_login_auth.candidate
+  end
+
+  def existing_candidate_without_one_login(existing_candidate)
+    if existing_candidate.one_login_auth.present? && existing_candidate.one_login_auth.token != token
+      raise(
+        Error,
+        "Candidate #{existing_candidate.id} has a different one login " \
+        "token than the user trying to login. Token used to auth #{token}",
+      )
+    end
+
+    existing_candidate.create_one_login_auth!(token:, email_address:)
+    existing_candidate
+  end
+
+  def create_candidate!
+    candidate = Candidate.create!(email_address:)
+    candidate.create_one_login_auth!(token:, email_address:)
+
+    candidate
+  end
+end

app/models/one_login_user_bypass.rb

@@ -0,0 +1,29 @@
+class OneLoginUserBypass
+  include ActiveModel::Model
+
+  validates :token, presence: true
+  validate :token_format
+
+  attr_accessor :token
+
+  def authenticate
+    return unless valid?
+
+    bypass_one_login = OneLoginAuth.find_by(token: 'dev-candidate')
+
+    if bypass_one_login && bypass_one_login.token == token
+      bypass_one_login.candidate
+    else
+      errors.add(:base, "There is no candidate with #{token} uid")
+      nil
+    end
+  end
+
+private
+
+  def token_format
+    return if token.nil?
+
+    errors.add(:token, :invalid) if token.match?(URI::MailTo::EMAIL_REGEXP)
+  end
+end

app/views/candidate_interface/start_page/create_account_or_sign_in.html.erb

@@ -4,31 +4,39 @@
 
 <div class="govuk-grid-row">
   <div class="govuk-grid-column-two-thirds">
-    <%= form_with(
-      model: @create_account_or_sign_in_form,
-      url: candidate_interface_create_account_or_sign_in_path(providerCode: params[:providerCode], courseCode: params[:courseCode]),
-      method: :post,
-    ) do |f| %>
-      <%= f.govuk_error_summary %>
+    <h1 class="govuk-heading-xl">
+      <%= t('page_titles.create_account_or_sign_in') %>
+    </h1>
 
-      <h1 class="govuk-heading-xl">
-        <%= t('page_titles.create_account_or_sign_in') %>
-      </h1>
+    <% if FeatureFlag.active?(:one_login_candidate_sign_in) %>
+      <p class="govuk-body">
+        <%= t('govuk.one_login_account_guidance') %>
+      </p>
 
-      <%= f.govuk_radio_buttons_fieldset :existing_account, legend: { text: 'Do you already have an account?' } do %>
-        <%= f.govuk_radio_button :existing_account, true, label: { text: 'Yes, sign in' }, link_errors: true do %>
-          <%= f.govuk_email_field :email, label: { text: 'Email address', size: 's' }, hint: { text: 'Enter the email address you used to register, and we will send you a link to sign in.' }, width: 'two-thirds', autocomplete: 'email', spellcheck: false %>
+      <%= govuk_button_to(t('continue'), OneLogin.bypass? ? '/auth/one-login-developer' : '/auth/one_login') %>
+    <% else %>
+     <%= form_with(
+        model: @create_account_or_sign_in_form,
+        url: candidate_interface_create_account_or_sign_in_path(providerCode: params[:providerCode], courseCode: params[:courseCode]),
+        method: :post,
+      ) do |f| %>
+        <%= f.govuk_error_summary %>
+
+        <%= f.govuk_radio_buttons_fieldset :existing_account, legend: { text: 'Do you already have an account?' } do %>
+          <%= f.govuk_radio_button :existing_account, true, label: { text: 'Yes, sign in' }, link_errors: true do %>
+            <%= f.govuk_email_field :email, label: { text: 'Email address', size: 's' }, hint: { text: 'Enter the email address you used to register, and we will send you a link to sign in.' }, width: 'two-thirds', autocomplete: 'email', spellcheck: false %>
+          <% end %>
+          <%= f.govuk_radio_button :existing_account, false, label: { text: 'No, I need to create an account' } %>
         <% end %>
-        <%= f.govuk_radio_button :existing_account, false, label: { text: 'No, I need to create an account' } %>
+        <%= f.govuk_submit t('continue') %>
       <% end %>
-      <%= f.govuk_submit t('continue') %>
-    <% end %>
 
-    <p class="govuk-body">
-      You can usually start applying for teacher training in October, the
-      year before your course starts. Courses can fill up quickly, so apply
-      as soon as you can.
-      <%= govuk_link_to 'Read how the application process works', candidate_interface_guidance_path %></a>.
-    </p>
+      <p class="govuk-body">
+        You can usually start applying for teacher training in October, the
+        year before your course starts. Courses can fill up quickly, so apply
+        as soon as you can.
+        <%= govuk_link_to 'Read how the application process works', candidate_interface_guidance_path %>.
+      </p>
+    <% end %>
   </div>
 </div>

app/views/layouts/_header.html.erb

@@ -7,9 +7,10 @@
             )) %>
   <%= render PhaseBannerComponent.new(no_border: current_candidate.present?) %>
   <% if current_candidate %>
+    <% sign_out_path = FeatureFlag.active?(:one_login_candidate_sign_in) ? auth_one_login_sign_out_path : candidate_interface_sign_out_path %>
     <%= render(PrimaryNavigationComponent.new(
                 items: NavigationItems.candidate_primary_navigation(current_candidate:, current_controller: controller),
-                items_right: [NavigationItems::NavigationItem.new('Sign out', candidate_interface_sign_out_path)],
+                items_right: [NavigationItems::NavigationItem.new('Sign out', sign_out_path)],
               )) %>
   <% end %>
 <% when 'support_interface' %>

config/application.rb

@@ -40,7 +40,7 @@ class Application < Rails::Application
     # Please, add to the `ignore` list any other `lib` subdirectories that do
     # not contain `.rb` files, or that should not be reloaded or eager loaded.
     # Common ones are `templates`, `generators`, or `middleware`, for example.
-    config.autoload_lib(ignore: %w[assets tasks generators rubocop])
+    config.autoload_lib(ignore: %w[assets tasks generators rubocop omniauth])
 
     # Configuration for the application, engines, and railties goes here.
     #

config/initializers/omniauth.rb

@@ -1,4 +1,6 @@
 OmniAuth.config.logger = Rails.logger
+require 'omniauth/strategies/one_login_developer'
+require 'omniauth/one_login_setup'
 
 dfe_sign_in_identifier = ENV['DFE_SIGN_IN_CLIENT_ID']
 dfe_sign_in_secret = ENV['DFE_SIGN_IN_SECRET']
@@ -32,6 +34,12 @@ def self.bypass?
   end
 end
 
+module ::OneLogin
+  def self.bypass?
+    HostingEnvironment.review? || HostingEnvironment.loadtest? || Rails.env.development?
+  end
+end
+
 if DfESignIn.bypass?
   Rails.application.config.middleware.use OmniAuth::Builder do
     provider :developer,
@@ -41,3 +49,17 @@ def self.bypass?
 else
   Rails.application.config.middleware.use OmniAuth::Strategies::OpenIDConnect, options
 end
+
+if OneLogin.bypass?
+  Rails.application.config.middleware.use OmniAuth::Builder do
+    provider :one_login_developer,
+             request_path: '/auth/one-login-developer',
+             callback_path: '/auth/one-login-developer/callback',
+             fields: %i[uid],
+             uid_field: :uid
+  end
+else
+  Rails.application.config.middleware.use OmniAuth::Builder do |builder|
+    OneLoginSetup.configure(builder)
+  end
+end

config/locales/en.yml

@@ -24,6 +24,7 @@ en:
   national_careers_service:
     find_a_course_url: https://nationalcareers.service.gov.uk/find-a-course/search
   govuk:
+    one_login_account_guidance: You need a GOV.UK One Login to sign in to this service. You can create one if you do not already have one.
     url: https://www.gov.uk
     terms_conditions_url: https://www.gov.uk/help/terms-conditions
     safeguarding: https://www.gov.uk/tell-employer-or-college-about-criminal-record

config/routes.rb

@@ -23,6 +23,12 @@
   get '/auth/developer/callback' => 'dfe_sign_in#bypass_callback'
   get '/auth/dfe/sign-out' => 'dfe_sign_in#redirect_after_dsi_signout'
 
+  get '/auth/one-login/callback', to: 'one_login#callback'
+  get '/auth/one-login-developer/callback' => 'one_login#bypass_callback'
+  get '/auth/one-login/sign-out', to: 'one_login#sign_out'
+  get '/auth/one-login/sign-out-complete', to: 'one_login#sign_out_complete'
+  get '/auth/failure', to: 'one_login#failure'
+
   direct :find do
     if HostingEnvironment.sandbox_mode?
       I18n.t('find_teacher_training.sandbox_url')
@@ -56,6 +62,6 @@
     get '/404', to: 'errors#not_found'
     get '/406', to: 'errors#not_acceptable'
     get '/422', to: 'errors#unprocessable_entity'
-    get '/500', to: 'errors#internal_server_error'
+    get '/500', to: 'errors#internal_server_error', as: :internal_server_error
   end
 end

lib/omniauth/one_login_setup.rb

@@ -0,0 +1,41 @@
+module OneLoginSetup
+  class OmniAuth::Strategies::GovukOneLogin < OmniAuth::Strategies::OpenIDConnect; end
+
+  def self.configure(builder)
+    client_id = ENV.fetch('GOVUK_ONE_LOGIN_CLIENT_ID', '')
+    one_login_issuer_uri = URI(ENV.fetch('GOVUK_ONE_LOGIN_ISSUER_URL', ''))
+    private_key_pem = ENV.fetch('GOVUK_ONE_LOGIN_PRIVATE_KEY', '')
+    application_url = HostingEnvironment.application_url
+
+    begin
+      private_key_pem = private_key_pem.gsub('\n', "\n")
+      private_key = OpenSSL::PKey::RSA.new(private_key_pem)
+    rescue OpenSSL::PKey::RSAError => e
+      Rails.logger.warn "GOVUK ONE LOGIN PRIVATE error, is the key present? #{e.message}"
+    end
+
+    builder.provider :govuk_one_login,
+                     name: :one_login,
+                     allow_authorize_params: %i[session_id],
+                     callback_path: '/auth/one-login/callback',
+                     discovery: true,
+                     issuer: one_login_issuer_uri.to_s,
+                     path_prefix: '/auth',
+                     post_logout_redirect_uri: "#{application_url}/auth/one-login/sign-out-complete",
+                     response_type: :code,
+                     scope: %w[email openid],
+                     client_auth_method: :jwt_bearer,
+                     client_options: {
+                       authorization_endpoint: '/oauth2/authorize',
+                       end_session_endpoint: '/oauth2/logout',
+                       token_endpoint: '/oauth2/token',
+                       userinfo_endpoint: '/oauth2/userinfo',
+                       host: one_login_issuer_uri.host,
+                       identifier: client_id,
+                       port: 443,
+                       redirect_uri: "#{application_url}/auth/one-login/callback",
+                       scheme: 'https',
+                       private_key: private_key,
+                     }
+  end
+end

lib/omniauth/strategies/one_login_developer.rb

@@ -0,0 +1,9 @@
+require 'omniauth'
+
+module OmniAuth
+  module Strategies
+    class OneLoginDeveloper < Developer
+      include OmniAuth::Strategy
+    end
+  end
+end

lib/tasks/local_dev.rake

@@ -14,6 +14,13 @@ task setup_local_dev_data: %i[environment copy_feature_flags_from_production syn
     first_name: 'Susan',
     last_name: 'Upport',
   )
+  candidate = Candidate.create!(
+    email_address: '[email protected]',
+  )
+  candidate.create_one_login_auth!(
+    token: 'dev-candidate',
+    email_address: candidate.email_address,
+  )
 
   puts 'Creating various provider users...'
   CreateExampleProviderUsersWithPermissions.call

spec/factories/one_login_auth.rb

@@ -0,0 +1,7 @@
+FactoryBot.define do
+  factory :one_login_auth do
+    candidate
+    token { SecureRandom.hex(10) }
+    email_address { "#{SecureRandom.hex(5)}@example.com" }
+  end
+end