Ignore incoming emails with X-Autoreply

Some messages may not contains the RFC-compliant Auto-Submitted
header, instead they may use X-Autoreply header for automated replies
(e.g. out of office emails).

changelogs/unreleased/ignore-autreply.yml

+---
+title: Ignore incoming emails with X-Autoreply header.
+merge_request: 18118
+author:
+type: fixed

lib/gitlab/email/receiver.rb

@@ -32,7 +32,7 @@ module Gitlab
 
         mail = build_mail
 
-        ignore_auto_submitted!(mail)
+        ignore_auto_reply!(mail)
 
         mail_key = extract_mail_key(mail)
         handler = Handler.for(mail, mail_key)
@@ -96,14 +96,25 @@ module Gitlab
         end
       end
 
-      def ignore_auto_submitted!(mail)
+      def ignore_auto_reply!(mail)
+        if auto_submitted?(mail) || auto_replied?(mail)
+          raise AutoGeneratedEmailError
+        end
+      end
+
+      def auto_submitted?(mail)
         # Mail::Header#[] is case-insensitive
         auto_submitted = mail.header['Auto-Submitted']&.value
 
         # Mail::Field#value would strip leading and trailing whitespace
-        raise AutoGeneratedEmailError if
-          # See also https://tools.ietf.org/html/rfc3834
-          auto_submitted && auto_submitted != 'no'
+        # See also https://tools.ietf.org/html/rfc3834
+        auto_submitted && auto_submitted != 'no'
+      end
+
+      def auto_replied?(mail)
+        autoreply = mail.header['X-Autoreply']&.value
+
+        autoreply && autoreply == 'yes'
       end
     end
   end

spec/fixtures/emails/auto_reply.eml

@@ -12,7 +12,7 @@ Mime-Version: 1.0
 Content-Type: text/plain;
  charset=ISO-8859-1
 Content-Transfer-Encoding: 7bit
-Auto-Submitted: auto-generated
+X-Autoreply: yes
 X-Sieve: CMU Sieve 2.2
 X-Received: by 10.0.0.1 with SMTP id n7mr11234144ipb.85.1371157428600; Thu,
  13 Jun 2013 14:03:48 -0700 (PDT)

spec/fixtures/emails/auto_submitted.eml

+Return-Path: <jake@adventuretime.ooo>
+Received: from iceking.adventuretime.ooo ([unix socket]) by iceking (Cyrus v2.2.13-Debian-2.2.13-19+squeeze3) with LMTPA; Thu, 13 Jun 2013 17:03:50 -0400
+Received: from mail-ie0-x234.google.com (mail-ie0-x234.google.com [IPv6:2607:f8b0:4001:c03::234]) by iceking.adventuretime.ooo (8.14.3/8.14.3/Debian-9.4) with ESMTP id r5DL3nFJ016967 (version=TLSv1/SSLv3 cipher=RC4-SHA bits=128 verify=NOT) for <reply+59d8df8370b7e95c5a49fbf86aeb2c93@discourse.example.com>; Thu, 13 Jun 2013 17:03:50 -0400
+Received: by mail-ie0-f180.google.com with SMTP id f4so21977375iea.25 for <reply+59d8df8370b7e95c5a49fbf86aeb2c93@discourse.example.com>; Thu, 13 Jun 2013 14:03:48 -0700
+Received: by 10.0.0.1 with HTTP; Thu, 13 Jun 2013 14:03:48 -0700
+Date: Thu, 13 Jun 2013 17:03:48 -0400
+From: Jake the Dog <jake@adventuretime.ooo>
+To: reply+636ca428858779856c226bb145ef4fad@appmail.adventuretime.ooo
+Message-ID: <CADkmRc+rNGAGGbV2iE5p918UVy4UyJqVcXRO2=otppgzduJSg@mail.gmail.com>
+Subject: re: [Discourse Meta] eviltrout posted in 'Adventure Time Sux'
+Mime-Version: 1.0
+Content-Type: text/plain;
+ charset=ISO-8859-1
+Content-Transfer-Encoding: 7bit
+Auto-Submitted: auto-generated
+X-Sieve: CMU Sieve 2.2
+X-Received: by 10.0.0.1 with SMTP id n7mr11234144ipb.85.1371157428600; Thu,
+ 13 Jun 2013 14:03:48 -0700 (PDT)
+X-Scanned-By: MIMEDefang 2.69 on IPv6:2001:470:1d:165::1
+
+Test reply to Discourse email digest

spec/lib/gitlab/email/receiver_spec.rb

@@ -40,7 +40,15 @@ describe Gitlab::Email::Receiver do
     end
   end
 
-  context "when the email was auto generated" do
+  context "when the email was auto generated with Auto-Submitted header" do
+    let(:email_raw) { fixture_file("emails/auto_submitted.eml") }
+
+    it "raises an AutoGeneratedEmailError" do
+      expect { receiver.execute }.to raise_error(Gitlab::Email::AutoGeneratedEmailError)
+    end
+  end
+
+  context "when the email was auto generated with X-Autoreply header" do
     let(:email_raw) { fixture_file("emails/auto_reply.eml") }
 
     it "raises an AutoGeneratedEmailError" do