Warn on suspicious login, after long period of inactivity

app/lib/ldap_authenticatable_tiny/strategy.rb

@@ -60,9 +60,9 @@ def authenticate_without_consistent_timing!
           ldap_login = PerDistrict.new.ldap_login_for_educator(educator)
           return fail!(:invalid) unless is_authorized_by_ldap?(ldap_login, password_text)
 
-          # Success, run password checks and store results encrypted and noised,
-          # ignoring any errors in the process.
+          # Success, run security checks
           store_password_check(password_text)
+          warn_if_suspicious(educator)
 
           # Return success
           return success!(educator)
@@ -106,6 +106,10 @@ def store_password_check(password_text)
         nil
       end
 
+      def warn_if_suspicious(educator)
+        LoginChecker.new(educator).warn_if_suspicious
+      end
+
       def logger
         Rails.logger
       end

app/lib/login_checker.rb

@@ -0,0 +1,29 @@
+# Check for suspicious bits about the login, for warning.
+class LoginChecker
+  def initialize(educator, options = {})
+    @educator = educator
+    @time_now = options.fetch(:time_now, Time.now)
+  end
+
+  def warn_if_suspicious
+    flags = infer_flags
+    warn_about(flags)
+    flags
+  end
+
+  private
+  def infer_flags
+    last_login_at = LoginActivity.last_login_at(@educator)
+
+    flags = []
+    flags << :first_login_month_after_creation if last_login_at.nil? && @educator.created_at < (@time_now - 30.days)
+    flags << :first_login_after_year if last_login_at.present? && last_login_at < (@time_now - 1.year)
+    flags.sort
+  end
+
+  def warn_about(flags)
+    if flags.size > 0
+      Rollbar.warn('LoginChecker#warn_if_suspicious', flags: flags)
+    end
+  end
+end

app/models/login_activity.rb

@@ -14,4 +14,13 @@ class LoginActivity < ApplicationRecord
   belongs_to :user,
              polymorphic: true,
              optional: true
+
+  # Return ActiveSupport::TimeWithZone or nil
+  def self.last_login_at(educator_id)
+    LoginActivity.where(user_id: educator_id)
+      .order(created_at: :desc)
+      .limit(1)
+      .first
+      .try(:created_at)
+  end
 end

spec/lib/login_checker_spec.rb

@@ -0,0 +1,26 @@
+require 'spec_helper'
+
+RSpec.describe LoginChecker do
+  let!(:pals) { TestPals.create! }
+
+  it '#warn_if_suspicious reports to Rollbar on :first_login_after_year' do
+    LoginActivity.create!({
+      user_id: pals.healey_vivian_teacher.id,
+      created_at: pals.time_now - 2.years
+    })
+
+    allow(Rollbar).to receive(:warn)
+    expect(Rollbar).to receive(:warn).once.with('LoginChecker#warn_if_suspicious', flags: [:first_login_after_year])
+    checker = LoginChecker.new(pals.healey_vivian_teacher, time_now: pals.time_now)
+    expect(checker.warn_if_suspicious).to eq [:first_login_after_year]
+  end
+
+  it '#warn_if_suspicious reports to Rollbar on :first_login_month_after_creation' do
+    pals.healey_vivian_teacher.update!(created_at: pals.time_now - 32.days)
+
+    allow(Rollbar).to receive(:warn)
+    expect(Rollbar).to receive(:warn).once.with('LoginChecker#warn_if_suspicious', flags: [:first_login_month_after_creation])
+    checker = LoginChecker.new(pals.healey_vivian_teacher, time_now: pals.time_now)
+    expect(checker.warn_if_suspicious).to eq [:first_login_month_after_creation]
+  end
+end