FEATURE: Compute distance between logins to generate login alerts. (#6562)

app/models/user_auth_token.rb

@@ -30,23 +30,23 @@ class UserAuthToken < ActiveRecord::Base
     end
   end
 
-  # Returns the login location as it will be used by the the system to detect
-  # suspicious login.
-  #
-  # This should not be very specific because small variations in location
-  # (i.e. changes of network, small trips, etc) will be detected as suspicious
-  # logins.
-  #
-  # On the other hand, if this is too broad it will not report any suspicious
-  # logins at all.
-  #
-  # For example, let's choose the country as the only component in login
-  # locations. In general, this should be a pretty good choce with the
-  # exception that for users from huge countries it might not be specific
-  # enoguh. For US users where the real user and the malicious one could
-  # happen to live both in USA, this will not detect any suspicious activity.
+  RAD_PER_DEG = Math::PI / 180
+  EARTH_RADIUS_KM = 6371 # kilometers
+
   def self.login_location(ip)
-    DiscourseIpInfo.get(ip)[:country]
+    ipinfo = DiscourseIpInfo.get(ip)
+
+    ipinfo['latitude'] && ipinfo['longitude'] ? [ipinfo['latitude'], ipinfo['longitude']] : nil
+  end
+
+  def self.distance(loc1, loc2)
+    lat1_rad, lon1_rad = loc1[0] * RAD_PER_DEG, loc1[1] * RAD_PER_DEG
+    lat2_rad, lon2_rad = loc2[0] * RAD_PER_DEG, loc2[1] * RAD_PER_DEG
+
+    a = Math.sin((lat2_rad - lat1_rad) / 2)**2 + Math.cos(lat1_rad) * Math.cos(lat2_rad) * Math.sin((lon2_rad - lon1_rad) / 2)**2
+    c = 2 * Math::atan2(Math::sqrt(a), Math::sqrt(1 - a))
+
+    c * EARTH_RADIUS_KM
   end
 
   def self.is_suspicious(user_id, user_ip)
@@ -57,8 +57,13 @@ class UserAuthToken < ActiveRecord::Base
     ips.uniq!
     return false if ips.empty? # first login is never suspicious
 
-    user_location = login_location(user_ip)
-    ips.none? { |ip| user_location == login_location(ip) }
+    if user_location = login_location(user_ip)
+      ips.none? do |ip|
+        if location = login_location(ip)
+          distance(user_location, location) < SiteSetting.max_suspicious_distance_km
+        end
+      end
+    end
   end
 
   def self.generate!(user_id: , user_agent: nil, client_ip: nil, path: nil, staff: nil, impersonate: false)

config/site_settings.yml

@@ -381,6 +381,9 @@ login:
   verbose_auth_token_logging:
     hidden: true
     default: true
+  max_suspicious_distance_km:
+    hidden: true
+    default: 500
   sso_url:
     default: ''
     regex: '^https?:\/\/.+[^\/]$'

spec/jobs/suspicious_login_spec.rb

@@ -4,10 +4,25 @@ describe Jobs::SuspiciousLogin do
 
   let(:user) { Fabricate(:moderator) }
 
+  let(:zurich) { [47.3686498, 8.5391825] } # Zurich, Switzerland
+  let(:bern) { [46.947922, 7.444608] }  # Bern, Switzerland
+  let(:london) { [51.5073509, -0.1277583] } # London, United Kingdom
+
   before do
-    UserAuthToken.stubs(:login_location).with("1.1.1.1").returns("Location 1")
-    UserAuthToken.stubs(:login_location).with("1.1.1.2").returns("Location 1")
-    UserAuthToken.stubs(:login_location).with("1.1.2.1").returns("Location 2")
+    UserAuthToken.stubs(:login_location).with("1.1.1.1").returns(zurich)
+    UserAuthToken.stubs(:login_location).with("1.1.1.2").returns(bern)
+    UserAuthToken.stubs(:login_location).with("1.1.2.1").returns(london)
+  end
+
+  it "will correctly compute distance" do
+    def expect_distance(from, to, distance)
+      expect(UserAuthToken.distance(from, to).to_i).to eq(distance)
+      expect(UserAuthToken.distance(to, from).to_i).to eq(distance)
+    end
+
+    expect_distance(zurich, bern, 95)
+    expect_distance(zurich, london, 776)
+    expect_distance(bern, london, 747)
   end
 
   it "will not send an email on first login" do