FEATURE: optional default off global per ip rate limiter

config/discourse_defaults.conf

@@ -175,3 +175,8 @@ max_user_api_reqs_per_minute = 20
 max_user_api_reqs_per_day = 2880
 
 max_admin_api_reqs_per_key_per_minute = 60
+
+max_requests_per_ip_per_minute = 200
+max_requests_per_ip_per_10_seconds = 50
+# global rate limiter will simply warn if the limit is exceeded, can be warn, block or none
+max_requests_per_ip_mode = none

lib/middleware/request_tracker.rb

@@ -126,6 +126,13 @@ class Middleware::RequestTracker
   end
 
   def call(env)
+    result = nil
+
+    if rate_limit(env)
+      result = [429, {}, ["Slow down, too Many Requests from this IP Address"]]
+      return result
+    end
+
     env["discourse.request_tracker"] = self
     MethodProfiler.start if @@detailed_request_loggers
     result = @app.call(env)
@@ -135,6 +142,46 @@ class Middleware::RequestTracker
     log_request_info(env, result, info) unless env["discourse.request_tracker.skip"]
   end
 
+  def rate_limit(env)
+    if (
+      GlobalSetting.max_requests_per_ip_mode == "block" ||
+      GlobalSetting.max_requests_per_ip_mode == "warn"
+    )
+
+      ip = Rack::Request.new(env).ip
+
+      limiter10 = RateLimiter.new(
+        nil,
+        "global_ip_limit_10_#{ip}",
+        GlobalSetting.max_requests_per_ip_per_10_seconds,
+        10,
+        global: true
+      )
+
+      limiter60 = RateLimiter.new(
+        nil,
+        "global_ip_limit_60_#{ip}",
+        GlobalSetting.max_requests_per_ip_per_10_seconds,
+        10,
+        global: true
+      )
+
+      type = 10
+      begin
+        limiter10.performed!
+        type = 60
+        limiter60.performed!
+      rescue RateLimiter::LimitExceeded
+        if GlobalSetting.max_requests_per_ip_mode == "warn"
+          Rails.logger.warn("Global IP rate limit exceeded for #{ip} type: #{type}")
+          false
+        else
+          true
+        end
+      end
+    end
+  end
+
   def log_later(data, host)
     Scheduler::Defer.later("Track view", _db = nil) do
       self.class.log_request_on_site(data, host)

lib/rate_limiter.rb

@@ -28,6 +28,12 @@ class RateLimiter
     $redis.delete_prefixed(RateLimiter.key_prefix)
   end
 
+  def self.clear_all_global!
+    $redis.without_namespace.keys("GLOBAL::#{key_prefix}*").each do |k|
+      $redis.without_namespace.del k
+    end
+  end
+
   def build_key(type)
     "#{RateLimiter.key_prefix}:#{@user && @user.id}:#{type}"
   end
@@ -38,7 +44,7 @@ class RateLimiter
     @key = build_key(type)
     @max = max
     @secs = secs
-    @global = false
+    @global = global
   end
 
   def clear!

spec/components/middleware/request_tracker_spec.rb

@@ -68,6 +68,79 @@ describe Middleware::RequestTracker do
 
   end
 
+  context "rate limiting" do
+
+    class TestLogger
+      attr_accessor :warnings
+
+      def initialize
+        @warnings = 0
+      end
+
+      def warn(*args)
+        @warnings += 1
+      end
+    end
+
+    before do
+      RateLimiter.enable
+      RateLimiter.clear_all_global!
+
+      @old_logger = Rails.logger
+      Rails.logger = TestLogger.new
+    end
+
+    after do
+      RateLimiter.disable
+      Rails.logger = @old_logger
+    end
+
+    let :middleware do
+      app = lambda do |env|
+        [200, {}, ["OK"]]
+      end
+
+      Middleware::RequestTracker.new(app)
+    end
+
+    it "does nothing by default" do
+      global_setting :max_requests_per_ip_per_10_seconds, 1
+
+      status, _ = middleware.call(env)
+      status, _ = middleware.call(env)
+
+      expect(status).to eq(200)
+    end
+
+    it "does warn if rate limiter is enabled" do
+      global_setting :max_requests_per_ip_per_10_seconds, 1
+      global_setting :max_requests_per_ip_mode, 'warn'
+
+      status, _ = middleware.call(env)
+      status, _ = middleware.call(env)
+
+      expect(Rails.logger.warnings).to eq(1)
+      expect(status).to eq(200)
+    end
+
+    it "does block if rate limiter is enabled" do
+      global_setting :max_requests_per_ip_per_10_seconds, 1
+      global_setting :max_requests_per_ip_mode, 'block'
+
+      env1 = env("REMOTE_ADDR" => "1.1.1.1")
+      env2 = env("REMOTE_ADDR" => "1.1.1.2")
+
+      status, _ = middleware.call(env1)
+      status, _ = middleware.call(env1)
+
+      expect(status).to eq(429)
+
+      status, _ = middleware.call(env2)
+      expect(status).to eq(200)
+
+    end
+  end
+
   context "callbacks" do
     def app(result, sql_calls: 0, redis_calls: 0)
       lambda do |env|