CAS + SAML authentication feature (#6425)

* Cas authentication feature

* Config

* Remove class_eval + Omniauth initializer

* Codeclimate review

* Codeclimate review 2

* Codeclimate review 3

* Remove uid/email reconciliation

* SAML authentication

* Clean up code

* Improve login form

* Fix code style issues

* Add locales

3 files changed, 105 insertions, 0 deletions

diff --git a/app/models/concerns/omniauthable.rb b/app/models/concerns/omniauthable.rb
new file mode 100644
index 000000000..a3d55108d
--- /dev/null
+++ b/app/models/concerns/omniauthable.rb
@@ -0,0 +1,81 @@
+# frozen_string_literal: true
+
+module Omniauthable
+  extend ActiveSupport::Concern
+
+  TEMP_EMAIL_PREFIX = 'change@me'
+  TEMP_EMAIL_REGEX = /\Achange@me/
+
+  included do
+    def omniauth_providers
+      Devise.omniauth_configs.keys
+    end
+
+    def email_verified?
+      email && email !~ TEMP_EMAIL_REGEX
+    end
+  end
+
+  class_methods do
+    def find_for_oauth(auth, signed_in_resource = nil)
+      # EOLE-SSO Patch
+      auth.uid = (auth.uid[0][:uid] || auth.uid[0][:user]) if auth.uid.is_a? Hashie::Array
+      identity = Identity.find_for_oauth(auth)
+
+      # If a signed_in_resource is provided it always overrides the existing user
+      # to prevent the identity being locked with accidentally created accounts.
+      # Note that this may leave zombie accounts (with no associated identity) which
+      # can be cleaned up at a later date.
+      user = signed_in_resource ? signed_in_resource : identity.user
+      user = create_for_oauth(auth) if user.nil?
+
+      if identity.user.nil?
+        identity.user = user
+        identity.save!
+      end
+
+      user
+    end
+
+    def create_for_oauth(auth)
+      # Check if the user exists with provided email if the provider gives us a
+      # verified email.  If no verified email was provided or the user already
+      # exists, we assign a temporary email and ask the user to verify it on
+      # the next step via Auth::ConfirmationsController.finish_signup
+
+      user = User.new(user_params_from_auth(auth))
+      user.account.avatar_remote_url = auth.info.image if auth.info.image =~ /\A#{URI.regexp(%w(http https))}\z/
+      user.skip_confirmation!
+      user.save!
+      user
+    end
+
+    private
+
+    def user_params_from_auth(auth)
+      email_is_verified = auth.info.email && (auth.info.verified || auth.info.verified_email)
+      email             = auth.info.email if email_is_verified && !User.exists?(email: auth.info.email)
+
+      {
+        email: email ? email : "#{TEMP_EMAIL_PREFIX}-#{auth.uid}-#{auth.provider}.com",
+        password: Devise.friendly_token[0, 20],
+        account_attributes: {
+          username: ensure_unique_username(auth.uid),
+          display_name: [auth.info.first_name, auth.info.last_name].join(' '),
+        },
+      }
+    end
+
+    def ensure_unique_username(starting_username)
+      username = starting_username
+      i        = 0
+
+      while Account.exists?(username: username)
+        i       += 1
+        username = "#{starting_username}_#{i}"
+      end
+
+      username
+    end
+  end
+end
diff --git a/app/models/identity.rb b/app/models/identity.rb
new file mode 100644
index 000000000..a5e0c09ec
--- /dev/null
+++ b/app/models/identity.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+# == Schema Information
+#
+# Table name: identities
+#
+#  id         :integer          not null, primary key
+#  user_id    :integer
+#  provider   :string           default(""), not null
+#  uid        :string           default(""), not null
+#  created_at :datetime         not null
+#  updated_at :datetime         not null
+#
+
+class Identity < ApplicationRecord
+  belongs_to :user, dependent: :destroy
+  validates :uid, presence: true, uniqueness: { scope: :provider }
+  validates :provider, presence: true
+
+  def self.find_for_oauth(auth)
+    find_or_create_by(uid: auth.uid, provider: auth.provider)
+  end
+end
diff --git a/app/models/user.rb b/app/models/user.rb
index fa4ebfc71..fba478453 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -39,6 +39,7 @@
 
 class User < ApplicationRecord
   include Settings::Extend
+  include Omniauthable
 
   ACTIVE_DURATION = 14.days
 
@@ -52,6 +53,7 @@ class User < ApplicationRecord
          :confirmable
 
   devise :pam_authenticatable
+  devise :omniauthable
 
   belongs_to :account, inverse_of: :user
   belongs_to :invite, counter_cache: :uses, optional: true