Fix authentication failures after going halfway through a sign-in attempt (#16607)

* Add tests

* Add security-related tests

My first (unpublished) attempt at fixing the issues introduced (extremely
hard-to-exploit) security vulnerabilities, addressing them in a test.

* Fix authentication failures after going halfway through a sign-in attempt

* Refactor `authenticate_with_sign_in_token` and `authenticate_with_two_factor` to make the two authentication steps more obvious

app/controllers/auth/sessions_controller.rb

@@ -58,16 +58,20 @@ class Auth::SessionsController < Devise::SessionsController
   protected
 
   def find_user
-    if session[:attempt_user_id]
+    if user_params[:email].present?
+      find_user_from_params
+    elsif session[:attempt_user_id]
       User.find_by(id: session[:attempt_user_id])
-    else
-      user   = User.authenticate_with_ldap(user_params) if Devise.ldap_authentication
-      user ||= User.authenticate_with_pam(user_params) if Devise.pam_authentication
-      user ||= User.find_for_authentication(email: user_params[:email])
-      user
     end
   end
 
+  def find_user_from_params
+    user   = User.authenticate_with_ldap(user_params) if Devise.ldap_authentication
+    user ||= User.authenticate_with_pam(user_params) if Devise.pam_authentication
+    user ||= User.find_for_authentication(email: user_params[:email])
+    user
+  end
+
   def user_params
     params.require(:user).permit(:email, :password, :otp_attempt, :sign_in_token_attempt, credential: {})
   end

app/controllers/concerns/sign_in_token_authentication_concern.rb

@@ -16,14 +16,18 @@ module SignInTokenAuthenticationConcern
   end
 
   def authenticate_with_sign_in_token
-    user = self.resource = find_user
+    if user_params[:email].present?
+      user = self.resource = find_user_from_params
+      prompt_for_sign_in_token(user) if user&.external_or_valid_password?(user_params[:password])
+    elsif session[:attempt_user_id]
+      user = self.resource = User.find_by(id: session[:attempt_user_id])
+      return if user.nil?
 
-    if user.present? && session[:attempt_user_id].present? && session[:attempt_user_updated_at] != user.updated_at.to_s
-      restart_session
-    elsif user_params.key?(:sign_in_token_attempt) && session[:attempt_user_id]
-      authenticate_with_sign_in_token_attempt(user)
-    elsif user.present? && user.external_or_valid_password?(user_params[:password])
-      prompt_for_sign_in_token(user)
+      if session[:attempt_user_updated_at] != user.updated_at.to_s
+        restart_session
+      elsif user_params.key?(:sign_in_token_attempt)
+        authenticate_with_sign_in_token_attempt(user)
+      end
     end
   end
 

app/controllers/concerns/two_factor_authentication_concern.rb

@@ -35,16 +35,20 @@ module TwoFactorAuthenticationConcern
   end
 
   def authenticate_with_two_factor
-    user = self.resource = find_user
+    if user_params[:email].present?
+      user = self.resource = find_user_from_params
+      prompt_for_two_factor(user) if user&.external_or_valid_password?(user_params[:password])
+    elsif session[:attempt_user_id]
+      user = self.resource = User.find_by(id: session[:attempt_user_id])
+      return if user.nil?
 
-    if user.present? && session[:attempt_user_id].present? && session[:attempt_user_updated_at] != user.updated_at.to_s
-      restart_session
-    elsif user.webauthn_enabled? && user_params.key?(:credential) && session[:attempt_user_id]
-      authenticate_with_two_factor_via_webauthn(user)
-    elsif user_params.key?(:otp_attempt) && session[:attempt_user_id]
-      authenticate_with_two_factor_via_otp(user)
-    elsif user.present? && user.external_or_valid_password?(user_params[:password])
-      prompt_for_two_factor(user)
+      if session[:attempt_user_updated_at] != user.updated_at.to_s
+        restart_session
+      elsif user.webauthn_enabled? && user_params.key?(:credential)
+        authenticate_with_two_factor_via_webauthn(user)
+      elsif user_params.key?(:otp_attempt)
+        authenticate_with_two_factor_via_otp(user)
+      end
     end
   end