Merge pull request #1 from basecamp/ingresses

Accept inbound emails from a variety of ingresses

8 files changed, 214 insertions, 22 deletions

diff --git a/app/controllers/action_mailbox/base_controller.rb b/app/controllers/action_mailbox/base_controller.rb
new file mode 100644
index 0000000000..c234ecd250
--- /dev/null
+++ b/app/controllers/action_mailbox/base_controller.rb
@@ -0,0 +1,42 @@
+class ActionMailbox::BaseController < ActionController::Base
+  skip_forgery_protection
+
+  def self.prepare
+    # Override in concrete controllers to run code on load.
+  end
+
+  before_action :ensure_configured
+
+  private
+    def ensure_configured
+      unless ActionMailbox.ingress == ingress_name
+        head :not_found
+      end
+    end
+
+    def ingress_name
+      self.class.name[/^ActionMailbox::Ingresses::(.*?)::/, 1].underscore.to_sym
+    end
+
+
+    def authenticate_by_password
+      if password.present?
+        http_basic_authenticate_or_request_with username: "actionmailbox", password: password, realm: "Action Mailbox"
+      else
+        raise ArgumentError, "Missing required ingress credentials"
+      end
+    end
+
+    def password
+      Rails.application.credentials.dig(:action_mailbox, :ingress_password) || ENV["RAILS_INBOUND_EMAIL_PASSWORD"]
+    end
+
+
+    # TODO: Extract to ActionController::HttpAuthentication
+    def http_basic_authenticate_or_request_with(username:, password:, realm: nil)
+      authenticate_or_request_with_http_basic(realm || "Application") do |given_username, given_password|
+        ActiveSupport::SecurityUtils.secure_compare(given_username, username) &
+          ActiveSupport::SecurityUtils.secure_compare(given_password, password)
+      end
+    end
+end
diff --git a/app/controllers/action_mailbox/inbound_emails_controller.rb b/app/controllers/action_mailbox/inbound_emails_controller.rb
deleted file mode 100644
index ec9bd6f229..0000000000
--- a/app/controllers/action_mailbox/inbound_emails_controller.rb
+++ /dev/null
@@ -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
diff --git a/app/controllers/action_mailbox/ingresses/amazon/inbound_emails_controller.rb b/app/controllers/action_mailbox/ingresses/amazon/inbound_emails_controller.rb
new file mode 100644
index 0000000000..d3998be2d4
--- /dev/null
+++ b/app/controllers/action_mailbox/ingresses/amazon/inbound_emails_controller.rb
@@ -0,0 +1,21 @@
+class ActionMailbox::Ingresses::Amazon::InboundEmailsController < ActionMailbox::BaseController
+  before_action :authenticate
+
+  cattr_accessor :verifier
+
+  def self.prepare
+    self.verifier ||= begin
+      require "aws-sdk-sns/message_verifier"
+      Aws::SNS::MessageVerifier.new
+    end
+  end
+
+  def create
+    ActionMailbox::InboundEmail.create_and_extract_message_id! params.require(:content)
+  end
+
+  private
+    def authenticate
+      head :unauthorized unless verifier.authentic?(request.body)
+    end
+end
diff --git a/app/controllers/action_mailbox/ingresses/mailgun/inbound_emails_controller.rb b/app/controllers/action_mailbox/ingresses/mailgun/inbound_emails_controller.rb
new file mode 100644
index 0000000000..e878192603
--- /dev/null
+++ b/app/controllers/action_mailbox/ingresses/mailgun/inbound_emails_controller.rb
@@ -0,0 +1,58 @@
+class ActionMailbox::Ingresses::Mailgun::InboundEmailsController < ActionMailbox::BaseController
+  before_action :authenticate
+
+  def create
+    ActionMailbox::InboundEmail.create_and_extract_message_id! params.require("body-mime")
+  end
+
+  private
+    def authenticate
+      head :unauthorized unless authenticated?
+    end
+
+    def authenticated?
+      if key.present?
+        Authenticator.new(
+          key:       key,
+          timestamp: params.require(:timestamp),
+          token:     params.require(:token),
+          signature: params.require(:signature)
+        ).authenticated?
+      else
+        raise ArgumentError, <<~MESSAGE.squish
+          Missing required Mailgun API key. Set action_mailbox.mailgun_api_key in your application's
+          encrypted credentials or provide the MAILGUN_INGRESS_API_KEY environment variable.
+        MESSAGE
+      end
+    end
+
+    def key
+      Rails.application.credentials.dig(:action_mailbox, :mailgun_api_key) || ENV["MAILGUN_INGRESS_API_KEY"]
+    end
+
+    class Authenticator
+      attr_reader :key, :timestamp, :token, :signature
+
+      def initialize(key:, timestamp:, token:, signature:)
+        @key, @timestamp, @token, @signature = key, Integer(timestamp), token, signature
+      end
+
+      def authenticated?
+        signed? && recent?
+      end
+
+      private
+        def signed?
+          ActiveSupport::SecurityUtils.secure_compare signature, expected_signature
+        end
+
+        # Allow for 2 minutes of drift between Mailgun time and local server time.
+        def recent?
+          Time.at(timestamp) >= 2.minutes.ago
+        end
+
+        def expected_signature
+          OpenSSL::HMAC.hexdigest OpenSSL::Digest::SHA256.new, key, "#{timestamp}#{token}"
+        end
+    end
+end
diff --git a/app/controllers/action_mailbox/ingresses/mandrill/inbound_emails_controller.rb b/app/controllers/action_mailbox/ingresses/mandrill/inbound_emails_controller.rb
new file mode 100644
index 0000000000..b32b254076
--- /dev/null
+++ b/app/controllers/action_mailbox/ingresses/mandrill/inbound_emails_controller.rb
@@ -0,0 +1,65 @@
+class ActionMailbox::Ingresses::Mandrill::InboundEmailsController < ActionMailbox::BaseController
+  before_action :authenticate
+
+  def create
+    raw_emails.each { |raw_email| ActionMailbox::InboundEmail.create_and_extract_message_id! raw_email }
+    head :ok
+  rescue JSON::ParserError => error
+    logger.error error.message
+    head :unprocessable_entity
+  end
+
+  private
+    def raw_emails
+      events.select { |event| event["event"] == "inbound" }.collect { |event| event.dig("msg", "raw_msg") }
+    end
+
+    def events
+      JSON.parse params.require(:mandrill_events)
+    end
+
+
+    def authenticate
+      head :unauthorized unless authenticated?
+    end
+
+    def authenticated?
+      if key.present?
+        Authenticator.new(request, key).authenticated?
+      else
+        raise ArgumentError, <<~MESSAGE.squish
+          Missing required Mandrill API key. Set action_mailbox.mandrill_api_key in your application's
+          encrypted credentials or provide the MANDRILL_INGRESS_API_KEY environment variable.
+        MESSAGE
+      end
+    end
+
+    def key
+      Rails.application.credentials.dig(:action_mailbox, :mandrill_api_key) || ENV["MANDRILL_INGRESS_API_KEY"]
+    end
+
+    class Authenticator
+      attr_reader :request, :key
+
+      def initialize(request, key)
+        @request, @key = request, key
+      end
+
+      def authenticated?
+        ActiveSupport::SecurityUtils.secure_compare given_signature, expected_signature
+      end
+
+      private
+        def given_signature
+          request.headers["X-Mandrill-Signature"]
+        end
+
+        def expected_signature
+          Base64.strict_encode64 OpenSSL::HMAC.digest(OpenSSL::Digest::SHA1.new, key, message)
+        end
+
+        def message
+          request.url + request.POST.sort.flatten.join
+        end
+    end
+end
diff --git a/app/controllers/action_mailbox/ingresses/postfix/inbound_emails_controller.rb b/app/controllers/action_mailbox/ingresses/postfix/inbound_emails_controller.rb
new file mode 100644
index 0000000000..133accf651
--- /dev/null
+++ b/app/controllers/action_mailbox/ingresses/postfix/inbound_emails_controller.rb
@@ -0,0 +1,14 @@
+class ActionMailbox::Ingresses::Postfix::InboundEmailsController < ActionMailbox::BaseController
+  before_action :authenticate_by_password, :require_valid_rfc822_message
+
+  def create
+    ActionMailbox::InboundEmail.create_and_extract_message_id! request.body.read
+  end
+
+  private
+    def require_valid_rfc822_message
+      unless request.content_type == "message/rfc822"
+        head :unsupported_media_type
+      end
+    end
+end
diff --git a/app/controllers/action_mailbox/ingresses/sendgrid/inbound_emails_controller.rb b/app/controllers/action_mailbox/ingresses/sendgrid/inbound_emails_controller.rb
new file mode 100644
index 0000000000..b856eb5b94
--- /dev/null
+++ b/app/controllers/action_mailbox/ingresses/sendgrid/inbound_emails_controller.rb
@@ -0,0 +1,7 @@
+class ActionMailbox::Ingresses::Sendgrid::InboundEmailsController < ActionMailbox::BaseController
+  before_action :authenticate_by_password
+
+  def create
+    ActionMailbox::InboundEmail.create_and_extract_message_id! params.require(:email)
+  end
+end
diff --git a/app/models/action_mailbox/inbound_email/message_id.rb b/app/models/action_mailbox/inbound_email/message_id.rb
index a1ec5c0437..5cfcadaba1 100644
--- a/app/models/action_mailbox/inbound_email/message_id.rb
+++ b/app/models/action_mailbox/inbound_email/message_id.rb
@@ -6,14 +6,16 @@ module ActionMailbox::InboundEmail::MessageId
   end
 
   module ClassMethods
-    def create_and_extract_message_id!(raw_email, **options)
-      create! raw_email: raw_email, message_id: extract_message_id(raw_email), **options
+    def create_and_extract_message_id!(source, **options)
+      create! message_id: extract_message_id(source), **options do |inbound_email|
+        inbound_email.raw_email.attach io: StringIO.new(source), filename: "message.eml", content_type: "message/rfc822"
+      end
     end
 
     private
-      def extract_message_id(raw_email)
-        mail_from_source(raw_email.read).message_id
-      rescue
+      def extract_message_id(source)
+        mail_from_source(source).message_id
+      rescue => e
         # FIXME: Add logging with "Couldn't extract Message ID, so will generating a new random ID instead"
       end
   end