CLDC-1015: limit password reset (#356)

* Add a failing test (for a wrong reason)

* Is that correct?

* Add rack attack config for reset password

* Add support to read redis configuration

* Add PaaS configuration for redis

* Add too many requests page

* Redirect to the too many requests error page

* update manifest

Co-authored-by: Stéphane Meny <smeny@users.noreply.github.com>

Gemfile

@@ -50,6 +50,8 @@ gem "paper_trail"
 # Store active record objects in version whodunnits
 gem "paper_trail-globalid"
 # Receive exceptions and configure alerts
+gem "rack-attack"
+gem "redis"
 gem "sentry-rails"
 gem "sentry-ruby"
 

Gemfile.lock

@@ -290,6 +290,8 @@ GEM
       nio4r (~> 2.0)
     racc (1.6.0)
     rack (2.2.3)
+    rack-attack (6.6.0)
+      rack (>= 1.0, < 3)
     rack-mini-profiler (2.3.4)
       rack (>= 1.2.0)
     rack-proxy (0.7.2)
@@ -332,6 +334,7 @@ GEM
     rb-fsevent (0.11.1)
     rb-inotify (0.10.1)
       ffi (~> 1.0)
+    redis (4.6.0)
     regexp_parser (2.2.1)
     request_store (1.5.1)
       rack (>= 1.4)
@@ -490,8 +493,10 @@ DEPENDENCIES
   postcodes_io
   pry-byebug
   puma (~> 5.0)
+  rack-attack
   rack-mini-profiler (~> 2.0)
   rails (~> 7.0.1)
+  redis
   roo
   rspec-rails
   rubocop-govuk

app/controllers/errors_controller.rb

@@ -22,4 +22,11 @@ class ErrorsController < ApplicationController
       format.json { render json: { error: "Unprocessable entity" }, status: :unprocessable_entity }
     end
   end
+
+  def too_many_requests
+    respond_to do |format|
+      format.html { render status: :too_many_requests }
+      format.json { render json: { error: "Too many requests" }, status: :too_many_requests }
+    end
+  end
 end

app/services/paas_configuration_service.rb

@@ -1,10 +1,11 @@
 class PaasConfigurationService
-  attr_reader :s3_buckets
+  attr_reader :s3_buckets, :redis_uris
 
   def initialize(logger = Rails.logger)
     @logger = logger
     @paas_config = read_pass_config
     @s3_buckets = read_s3_buckets
+    @redis_uris = read_redis_uris
   end
 
   def config_present?
@@ -15,6 +16,10 @@ class PaasConfigurationService
     config_present? && @paas_config.key?(:"aws-s3-bucket")
   end
 
+  def redis_config_present?
+    config_present? && @paas_config.key?(:redis)
+  end
+
 private
 
   def read_pass_config
@@ -42,4 +47,16 @@ private
     end
     s3_buckets
   end
+
+  def read_redis_uris
+    return {} unless redis_config_present?
+
+    redis_uris = {}
+    @paas_config[:redis].each do |redis_config|
+      if redis_config.key?(:instance_name)
+        redis_uris[redis_config[:instance_name].to_sym] = redis_config.dig(:credentials, :uri)
+      end
+    end
+    redis_uris
+  end
 end

app/views/errors/too_many_requests.erb

@@ -0,0 +1,8 @@
+<% content_for :title, "Sorry, you have sent too many requests to our service" %>
+
+<div class="govuk-grid-row">
+  <div class="govuk-grid-column-two-thirds">
+    <h1 class="govuk-heading-l"><%= content_for(:title) %></h1>
+    <p class="govuk-body">Try again in a minute.</p>
+  </div>
+</div>

config/initializers/rack_attack.rb

@@ -0,0 +1,20 @@
+if Rails.env.development? || Rails.env.test?
+  Rack::Attack.cache.store = ActiveSupport::Cache::MemoryStore.new
+  Rack::Attack.enabled = false
+else
+  redis_url = PaasConfigurationService.new.redis_uris[:"dluhc-core-#{Redis.env}-redis-rate-limit"]
+  Rack::Attack.cache.store = ActiveSupport::Cache::RedisCacheStore.new(url: redis_url)
+end
+
+Rack::Attack.throttle("password reset requests", limit: 5, period: 60.seconds) do |request|
+  if request.params["user"].present? && request.path == "/users/password" && request.post?
+    request.params["user"]["email"].to_s.downcase.gsub(/\s+/, "")
+  end
+end
+
+Rack::Attack.throttled_responder = lambda do |_env|
+  headers = {
+    "Location" => "/429",
+  }
+  [301, headers, []]
+end

config/routes.rb

@@ -71,6 +71,7 @@ Rails.application.routes.draw do
 
   scope via: :all do
     match "/404", to: "errors#not_found"
+    match "/429", to: "errors#too_many_requests", status: 429
     match "/422", to: "errors#unprocessable_entity"
     match "/500", to: "errors#internal_server_error"
   end

manifest.yml

@@ -17,6 +17,7 @@ applications:
       RAILS_ENV: staging
     services:
       - dluhc-core-staging-postgres
+      - dluhc-core-staging-redis-rate-limit
 
   - name: dluhc-core-production
     <<: *defaults
@@ -30,3 +31,4 @@ applications:
     host: submit-social-housing-lettings-sales-data
     services:
       - dluhc-core-production-postgres
+      - dluhc-core-production-redis-rate-limit

spec/requests/rack_attack_spec.rb

@@ -0,0 +1,64 @@
+require "rails_helper"
+require_relative "../support/devise"
+require "rack/attack"
+
+describe "Rack::Attack" do
+  let(:limit) { 5 }
+  let(:under_limit) { limit / 2 }
+  let(:over_limit) { limit + 1 }
+
+  let(:page) { Capybara::Node::Simple.new(response.body) }
+  let(:notify_client) { instance_double(Notifications::Client) }
+  let(:devise_notify_mailer) { DeviseNotifyMailer.new }
+
+  let(:params) { { user: { email: } } }
+  let(:user) { FactoryBot.create(:user) }
+  let(:email) { user.email }
+
+  before do
+    Rack::Attack.enabled = true
+    allow(DeviseNotifyMailer).to receive(:new).and_return(devise_notify_mailer)
+    allow(devise_notify_mailer).to receive(:notify_client).and_return(notify_client)
+    allow(notify_client).to receive(:send_email).and_return(true)
+  end
+
+  after do
+    Rack::Attack.enabled = false
+    Rack::Attack.reset!
+  end
+
+  context "when a password reset is requested" do
+    context "when the number of requests is under the throttle limit" do
+      it "does not throttle" do
+        under_limit.times do
+          post "/users/password", params: params
+          follow_redirect!
+        end
+        last_response = response
+        expect(last_response.status).to eq(200)
+      end
+    end
+
+    context "when the number of requests is at the throttle limit" do
+      it "does not throttle" do
+        limit.times do
+          post "/users/password", params: params
+          follow_redirect!
+        end
+        last_response = response
+        expect(last_response.status).to eq(200)
+      end
+    end
+
+    context "when the number of requests is over the throttle limit" do
+      it "throttles" do
+        over_limit.times do
+          post "/users/password", params: params
+          follow_redirect!
+        end
+        last_response = response
+        expect(last_response.status).to eq(429)
+      end
+    end
+  end
+end

spec/services/paas_configuration_service_spec.rb

@@ -20,12 +20,15 @@ RSpec.describe PaasConfigurationService do
       expect(config_service.s3_buckets).to be_a(Hash)
       expect(config_service.s3_buckets).to be_empty
     end
+
+    it "does not retrieve any redis configuration" do
+      expect(config_service.redis_uris).to be_a(Hash)
+      expect(config_service.redis_uris).to be_empty
+    end
   end
 
   context "when configuration is present but invalid" do
-    let(:vcap_services) do
-      { "aws-s3-bucket": [{ instance_name: "bucket_1" }, { instance_name: "bucket_2" }] }
-    end
+    let(:vcap_services) { "random text" }
 
     before do
       allow(ENV).to receive(:[]).with("VCAP_SERVICES").and_return(vcap_services)
@@ -85,4 +88,52 @@ RSpec.describe PaasConfigurationService do
       expect(config_service.s3_buckets).to be_empty
     end
   end
+
+  context "when the paas configuration is present with redis configurations" do
+    let(:vcap_services) do
+      <<-JSON
+        {"redis": [{"instance_name": "redis_1", "credentials": {"uri": "redis_uri" }}]}
+      JSON
+    end
+
+    before do
+      allow(ENV).to receive(:[]).with("VCAP_SERVICES").and_return(vcap_services)
+    end
+
+    it "returns the configuration as present" do
+      expect(config_service.config_present?).to be(true)
+    end
+
+    it "returns the redis configuration as present" do
+      expect(config_service.redis_config_present?).to be(true)
+    end
+
+    it "does retrieve the redis configurations" do
+      redis_uris = config_service.redis_uris
+
+      expect(redis_uris).not_to be_empty
+      expect(redis_uris.count).to be(1)
+      expect(redis_uris).to have_key(:redis_1)
+      expect(redis_uris[:redis_1]).to eq("redis_uri")
+    end
+  end
+
+  context "when the paas configuration is present without redis configuration" do
+    before do
+      allow(ENV).to receive(:[]).with("VCAP_SERVICES").and_return("{}")
+    end
+
+    it "returns the configuration as present" do
+      expect(config_service.config_present?).to be(true)
+    end
+
+    it "returns the redis configuration as not present" do
+      expect(config_service.redis_config_present?).to be(false)
+    end
+
+    it "does not retrieve any redis uris from configuration" do
+      expect(config_service.redis_uris).to be_a(Hash)
+      expect(config_service.redis_uris).to be_empty
+    end
+  end
 end