Accept inbound emails from a variety of ingresses

Gemfile

@@ -4,3 +4,5 @@ git_source(:github) { |repo_path| "https://github.com/#{repo_path}.git" }
 gemspec
 
 gem "rails", github: "rails/rails"
+
+gem "aws-sdk-sns"

Gemfile.lock

@@ -71,6 +71,17 @@ PATH
 GEM
   remote: https://rubygems.org/
   specs:
+    aws-eventstream (1.0.1)
+    aws-partitions (1.105.0)
+    aws-sdk-core (3.30.0)
+      aws-eventstream (~> 1.0)
+      aws-partitions (~> 1.0)
+      aws-sigv4 (~> 1.0)
+      jmespath (~> 1.0)
+    aws-sdk-sns (1.5.0)
+      aws-sdk-core (~> 3, >= 3.26.0)
+      aws-sigv4 (~> 1.0)
+    aws-sigv4 (1.0.3)
     builder (3.2.3)
     byebug (10.0.2)
     concurrent-ruby (1.0.5)
@@ -80,6 +91,7 @@ GEM
       activesupport (>= 4.2.0)
     i18n (1.1.0)
       concurrent-ruby (~> 1.0)
+    jmespath (1.4.0)
     loofah (2.2.2)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
@@ -125,6 +137,7 @@ PLATFORMS
 
 DEPENDENCIES
   actionmailbox!
+  aws-sdk-sns
   bundler (~> 1.15)
   byebug
   rails!

app/controllers/action_mailbox/base_controller.rb

@@ -0,0 +1,11 @@
+class ActionMailbox::BaseController < ActionController::Base
+  skip_forgery_protection
+
+  private
+    def authenticate
+      authenticate_or_request_with_http_basic("Action Mailbox") do |given_username, given_password|
+        ActiveSupport::SecurityUtils.secure_compare(given_username, username) &&
+          ActiveSupport::SecurityUtils.secure_compare(given_password, password)
+      end
+    end
+end

app/controllers/action_mailbox/inbound_emails_controller.rb

@@ -1,17 +0,0 @@
-# TODO: Add access protection using basic auth with verified tokens. Maybe coming from credentials by default?
-# TODO: Spam/malware catching?
-# TODO: Specific bounces for SMTP good citizenship: 200/404/400
-class ActionMailbox::InboundEmailsController < ActionController::Base
-  skip_forgery_protection
-  before_action :require_rfc822_message, only: :create
-
-  def create
-    ActionMailbox::InboundEmail.create_and_extract_message_id!(params[:message])
-    head :created
-  end
-
-  private
-    def require_rfc822_message
-      head :unsupported_media_type unless params.require(:message).content_type == 'message/rfc822'
-    end
-end

app/controllers/action_mailbox/ingresses/amazon/inbound_emails_controller.rb

@@ -0,0 +1,26 @@
+class ActionMailbox::Ingresses::Amazon::InboundEmailsController < ActionMailbox::BaseController
+  before_action :ensure_verified
+
+  # TODO: Lazy-load the AWS SDK
+  require "aws-sdk-sns/message_verifier"
+  cattr_accessor :verifier, default: Aws::SNS::MessageVerifier.new
+
+  def create
+    ActionMailbox::InboundEmail.create_and_extract_message_id! raw_email
+    head :no_content
+  end
+
+  private
+    def raw_email
+      StringIO.new params.require(:content)
+    end
+
+
+    def ensure_verified
+      head :unauthorized unless verified?
+    end
+
+    def verified?
+      verifier.authentic?(request.body)
+    end
+end

app/controllers/action_mailbox/ingresses/mailgun/inbound_emails_controller.rb

@@ -0,0 +1,61 @@
+class ActionMailbox::Ingresses::Mailgun::InboundEmailsController < ActionMailbox::BaseController
+  before_action :ensure_authenticated
+
+  def create
+    ActionMailbox::InboundEmail.create_and_extract_message_id! raw_email
+    head :ok
+  end
+
+  private
+    def raw_email
+      StringIO.new params.require("body-mime")
+    end
+
+
+    def ensure_authenticated
+      head :unauthorized unless authenticated?
+    end
+
+    def authenticated?
+      Authenticator.new(authentication_params).authenticated?
+    rescue ArgumentError
+      false
+    end
+
+    def authentication_params
+      params.permit(:timestamp, :token, :signature).to_h.symbolize_keys
+    end
+
+
+    class Authenticator
+      cattr_accessor :key
+
+      attr_reader :timestamp, :token, :signature
+
+      def initialize(timestamp:, token:, signature:)
+        @timestamp, @token, @signature = timestamp, token, signature
+      end
+
+      def authenticated?
+        signed? && recent?
+      end
+
+      private
+        def signed?
+          ActiveSupport::SecurityUtils.secure_compare signature, expected_signature
+        end
+
+        # Allow for 10 minutes of drift between Mailgun time and local server time.
+        def recent?
+          time >= 10.minutes.ago
+        end
+
+        def expected_signature
+          OpenSSL::HMAC.hexdigest OpenSSL::Digest::SHA256.new, key, "#{timestamp}#{token}"
+        end
+
+        def time
+          Time.at Integer(timestamp)
+        end
+    end
+end

app/controllers/action_mailbox/ingresses/postfix/inbound_emails_controller.rb

@@ -0,0 +1,11 @@
+class ActionMailbox::Ingresses::Postfix::InboundEmailsController < ActionMailbox::BaseController
+  cattr_accessor :username, default: "actionmailbox"
+  cattr_accessor :password
+
+  before_action :authenticate
+
+  def create
+    ActionMailbox::InboundEmail.create_and_extract_message_id! params.require(:message)
+    head :no_content
+  end
+end

app/controllers/action_mailbox/ingresses/sendgrid/inbound_emails_controller.rb

@@ -0,0 +1,16 @@
+class ActionMailbox::Ingresses::Sendgrid::InboundEmailsController < ActionMailbox::BaseController
+  cattr_accessor :username, default: "actionmailbox"
+  cattr_accessor :password
+
+  before_action :authenticate
+
+  def create
+    ActionMailbox::InboundEmail.create_and_extract_message_id! raw_email
+    head :no_content
+  end
+
+  private
+    def raw_email
+      StringIO.new params.require(:email)
+    end
+end

app/models/action_mailbox/inbound_email/message_id.rb

@@ -7,7 +7,14 @@ module ActionMailbox::InboundEmail::MessageId
 
   module ClassMethods
     def create_and_extract_message_id!(raw_email, **options)
-      create! raw_email: raw_email, message_id: extract_message_id(raw_email), **options
+      create! message_id: extract_message_id(raw_email), **options do |inbound_email|
+        case raw_email
+        when ActionDispatch::Http::UploadedFile
+          inbound_email.raw_email.attach raw_email
+        else
+          inbound_email.raw_email.attach io: raw_email.tap(&:rewind), filename: "message.eml", content_type: "message/rfc822"
+        end
+      end
     end
 
     private

config/routes.rb

@@ -1,7 +1,14 @@
 # frozen_string_literal: true
 
 Rails.application.routes.draw do
-  post "/rails/action_mailbox/inbound_emails" => "action_mailbox/inbound_emails#create", as: :rails_inbound_emails
+  scope "/rails/action_mailbox" do
+    post "/amazon/inbound_emails"   => "action_mailbox/ingresses/amazon/inbound_emails#create",   as: :rails_amazon_inbound_emails
+    post "/postfix/inbound_emails"  => "action_mailbox/ingresses/postfix/inbound_emails#create",  as: :rails_postfix_inbound_emails
+    post "/sendgrid/inbound_emails" => "action_mailbox/ingresses/sendgrid/inbound_emails#create", as: :rails_sendgrid_inbound_emails
+
+    # Mailgun requires that the webhook's URL end in 'mime' for it to receive the raw contents of emails.
+    post "/mailgun/inbound_emails/mime" => "action_mailbox/ingresses/mailgun/inbound_emails#create", as: :rails_mailgun_inbound_emails
+  end
 
   # TODO: Should these be mounted within the engine only?
   scope "rails/conductor/action_mailbox/", module: "rails/conductor/action_mailbox" do

test/controllers/ingresses/amazon/inbound_emails_controller_test.rb

@@ -0,0 +1,18 @@
+require "test_helper"
+
+ActionMailbox::Ingresses::Amazon::InboundEmailsController.verifier =
+  Module.new { def self.authentic?(message); true; end }
+
+class ActionMailbox::Ingresses::Amazon::InboundEmailsControllerTest < ActionDispatch::IntegrationTest
+  test "receiving an inbound email from Amazon" do
+    assert_difference -> { ActionMailbox::InboundEmail.count }, +1 do
+      post rails_amazon_inbound_emails_url, params: { content: file_fixture("../files/welcome.eml").read }, as: :json
+    end
+
+    assert_response :no_content
+
+    inbound_email = ActionMailbox::InboundEmail.last
+    assert_equal file_fixture("../files/welcome.eml").read, inbound_email.raw_email.download
+    assert_equal "0CB459E0-0336-41DA-BC88-E6E28C697DDB@37signals.com", inbound_email.message_id
+  end
+end

test/controllers/ingresses/mailgun/inbound_emails_controller_test.rb

@@ -0,0 +1,51 @@
+require "test_helper"
+
+ActionMailbox::Ingresses::Mailgun::InboundEmailsController::Authenticator.key = "tbsy84uSV1Kt3ZJZELY2TmShPRs91E3yL4tzf96297vBCkDWgL"
+
+class ActionMailbox::Ingresses::Mailgun::InboundEmailsControllerTest < ActionDispatch::IntegrationTest
+  test "receiving an inbound email from Mailgun" do
+    assert_difference -> { ActionMailbox::InboundEmail.count }, +1 do
+      travel_to "2018-10-09 15:15:00 EDT"
+      post rails_mailgun_inbound_emails_url, params: {
+        timestamp: 1539112500,
+        token: "7VwW7k6Ak7zcTwoSoNm7aTtbk1g67MKAnsYLfUB7PdszbgR5Xi",
+        signature: "ef24c5225322217bb065b80bb54eb4f9206d764e3e16abab07f0a64d1cf477cc",
+        "body-mime" => file_fixture("../files/welcome.eml").read
+      }
+    end
+
+    assert_response :ok
+
+    inbound_email = ActionMailbox::InboundEmail.last
+    assert_equal file_fixture("../files/welcome.eml").read, inbound_email.raw_email.download
+    assert_equal "0CB459E0-0336-41DA-BC88-E6E28C697DDB@37signals.com", inbound_email.message_id
+  end
+
+  test "rejecting a delayed inbound email from Mailgun" do
+    assert_no_difference -> { ActionMailbox::InboundEmail.count } do
+      travel_to "2018-10-09 15:26:00 EDT"
+      post rails_mailgun_inbound_emails_url, params: {
+        timestamp: 1539112500,
+        token: "7VwW7k6Ak7zcTwoSoNm7aTtbk1g67MKAnsYLfUB7PdszbgR5Xi",
+        signature: "ef24c5225322217bb065b80bb54eb4f9206d764e3e16abab07f0a64d1cf477cc",
+        "body-mime" => file_fixture("../files/welcome.eml").read
+      }
+    end
+
+    assert_response :unauthorized
+  end
+
+  test "rejecting a forged inbound email from Mailgun" do
+    assert_no_difference -> { ActionMailbox::InboundEmail.count } do
+      travel_to "2018-10-09 15:15:00 EDT"
+      post rails_mailgun_inbound_emails_url, params: {
+        timestamp: 1539112500,
+        token: "Zx8mJBiGmiiyyfWnho3zKyjCg2pxLARoCuBM7X9AKCioShGiMX",
+        signature: "ef24c5225322217bb065b80bb54eb4f9206d764e3e16abab07f0a64d1cf477cc",
+        "body-mime" => file_fixture("../files/welcome.eml").read
+      }
+    end
+
+    assert_response :unauthorized
+  end
+end

test/controllers/ingresses/postfix/inbound_emails_controller_test.rb

@@ -0,0 +1,33 @@
+require "test_helper"
+
+ActionMailbox::Ingresses::Postfix::InboundEmailsController.password = "tbsy84uSV1Kt3ZJZELY2TmShPRs91E3yL4tzf96297vBCkDWgL"
+
+class ActionMailbox::Ingresses::Postfix::InboundEmailsControllerTest < ActionDispatch::IntegrationTest
+  test "receiving an inbound email from Postfix" do
+    assert_difference -> { ActionMailbox::InboundEmail.count }, +1 do
+      post rails_postfix_inbound_emails_url, headers: { authorization: credentials },
+        params: { message: fixture_file_upload("files/welcome.eml", "message/rfc822") }
+    end
+
+    assert_response :no_content
+
+    inbound_email = ActionMailbox::InboundEmail.last
+    assert_equal file_fixture("../files/welcome.eml").read, inbound_email.raw_email.download
+    assert_equal "0CB459E0-0336-41DA-BC88-E6E28C697DDB@37signals.com", inbound_email.message_id
+  end
+
+  test "rejecting an unauthorized inbound email from Postfix" do
+    assert_no_difference -> { ActionMailbox::InboundEmail.count } do
+      post rails_postfix_inbound_emails_url, params: { message: fixture_file_upload("files/welcome.eml", "message/rfc822") }
+    end
+
+    assert_response :unauthorized
+  end
+
+  private
+    delegate :username, :password, to: ActionMailbox::Ingresses::Postfix::InboundEmailsController
+
+    def credentials
+      ActionController::HttpAuthentication::Basic.encode_credentials username, password
+    end
+end

test/controllers/ingresses/sendgrid/inbound_emails_controller_test.rb

@@ -0,0 +1,33 @@
+require "test_helper"
+
+ActionMailbox::Ingresses::Sendgrid::InboundEmailsController.password = "tbsy84uSV1Kt3ZJZELY2TmShPRs91E3yL4tzf96297vBCkDWgL"
+
+class ActionMailbox::Ingresses::Sendgrid::InboundEmailsControllerTest < ActionDispatch::IntegrationTest
+  test "receiving an inbound email from Sendgrid" do
+    assert_difference -> { ActionMailbox::InboundEmail.count }, +1 do
+      post rails_sendgrid_inbound_emails_url,
+        headers: { authorization: credentials }, params: { email: file_fixture("../files/welcome.eml").read }
+    end
+
+    assert_response :no_content
+
+    inbound_email = ActionMailbox::InboundEmail.last
+    assert_equal file_fixture("../files/welcome.eml").read, inbound_email.raw_email.download
+    assert_equal "0CB459E0-0336-41DA-BC88-E6E28C697DDB@37signals.com", inbound_email.message_id
+  end
+
+  test "rejecting an unauthorized inbound email from Sendgrid" do
+    assert_no_difference -> { ActionMailbox::InboundEmail.count } do
+      post rails_sendgrid_inbound_emails_url, params: { email: file_fixture("../files/welcome.eml").read }
+    end
+
+    assert_response :unauthorized
+  end
+
+  private
+    delegate :username, :password, to: ActionMailbox::Ingresses::Sendgrid::InboundEmailsController
+
+    def credentials
+      ActionController::HttpAuthentication::Basic.encode_credentials username, password
+    end
+end

test/unit/controller_test.rb

@@ -1,27 +0,0 @@
-require_relative '../test_helper'
-
-class ActionMailbox::InboundEmailsControllerTest < ActionDispatch::IntegrationTest
-  test "receiving a valid RFC 822 message" do
-    assert_difference -> { ActionMailbox::InboundEmail.count }, +1 do
-      post_inbound_email "welcome.eml"
-    end
-
-    assert_response :created
-
-    inbound_email = ActionMailbox::InboundEmail.last
-    assert_equal file_fixture('../files/welcome.eml').read, inbound_email.raw_email.download
-  end
-
-  test "rejecting a message of an unsupported type" do
-    assert_no_difference -> { ActionMailbox::InboundEmail.count } do
-      post rails_inbound_emails_url, params: { message: fixture_file_upload('files/text.txt', 'text/plain') }
-    end
-
-    assert_response :unsupported_media_type
-  end
-
-  private
-    def post_inbound_email(fixture_name)
-      post rails_inbound_emails_url, params: { message: fixture_file_upload("files/#{fixture_name}", 'message/rfc822') }
-    end
-end