Add handling for message reply via email

If the reply_email_domain configuration is set the messages plugin will
use unique Reply-To addresses for every email. They contain enough
information to reconstruct the message context and a hash to avoid
user forgery and spam.
A mail transfer agent must be configured to call the new rake task
foodsoft:parse_reply_email for incoming mails. The rake task requires
the receipt of the mail in the RECIPIENT variable and the raw message
via standard input. An example invocation would look like:
rake foodsoft:parse_reply_email RECIPIENT=f.1.1.HASH < test.eml

Gemfile.lock

@@ -15,7 +15,9 @@ PATH
   remote: plugins/messages
   specs:
     foodsoft_messages (0.0.1)
+      base32
       deface (~> 1.0.0)
+      mail
       rails
 
 PATH
@@ -71,6 +73,7 @@ GEM
     addressable (2.4.0)
     arel (6.0.3)
     attribute_normalizer (1.2.0)
+    base32 (0.3.2)
     better_errors (2.1.1)
       coderay (>= 1.0.0)
       erubis (>= 2.6.6)
@@ -534,3 +537,6 @@ DEPENDENCIES
   uglifier (>= 1.0.3)
   web-console (~> 2.0)
   whenever
+
+BUNDLED WITH
+   1.10.6

config/app_config.yml.SAMPLE

@@ -116,6 +116,9 @@ default: &defaults
   # email address to be used as sender
   email_sender: foodsoft@foodcoop.test
 
+  # domain to be used for reply emails
+  #reply_email_domain: reply.foodcoop.test
+
   # If your foodcoop uses a mailing list instead of internal messaging system
   #mailing_list: list@example.org
   #mailing_list_subscribe: list-subscribe@example.org

db/migrate/20160226000000_add_email_to_message.foodsoft_messages_engine.rb

@@ -0,0 +1,7 @@
+# This migration comes from foodsoft_messages_engine (originally 20160226000000)
+class AddEmailToMessage < ActiveRecord::Migration
+  def change
+    add_column :messages, :salt, :string
+    add_column :messages, :received_email, :binary, :limit => 1.megabyte
+  end
+end

db/schema.rb

@@ -188,6 +188,8 @@ ActiveRecord::Schema.define(version: 20160217194036) do
     t.datetime "created_at"
     t.integer  "reply_to",       limit: 4
     t.integer  "group_id",       limit: 4
+    t.string   "salt"
+    t.binary   "received_email"
   end
 
   create_table "order_articles", force: :cascade do |t|

lib/foodsoft_config.rb

@@ -80,6 +80,10 @@ class FoodsoftConfig
       setup_database
     end
 
+    def select_multifoodcoop(foodcoop)
+      select_foodcoop foodcoop if config[:multi_coop_install]
+    end
+
     # Return configuration value for the currently selected foodcoop.
     #
     # First tries to read configuration from the database (cached),
@@ -134,15 +138,20 @@ class FoodsoftConfig
       keys.map(&:to_s).uniq
     end
 
+    # @return [Array<String>] Valid names of foodcoops.
+    def foodcoops
+      if config[:multi_coop_install]
+        APP_CONFIG.keys.reject { |coop| coop =~ /^(default|development|test|production)$/ }
+      else
+        config[:default_scope]
+      end
+    end
+
     # Loop through each foodcoop and executes the given block after setup config and database
     def each_coop
-      if config[:multi_coop_install]
-        APP_CONFIG.keys.reject { |coop| coop =~ /^(default|development|test|production)$/ }.each do |coop|
-          select_foodcoop coop
-          yield coop
-        end
-      else
-        yield config[:default_scope]
+      foodcoops.each do |coop|
+        select_multifoodcoop coop
+        yield coop
       end
     end
 

plugins/messages/README.md

@@ -14,5 +14,9 @@ gem 'foodsoft_messages', path: 'lib/foodsoft_messages'
 This plugin introduces the foodcoop config option `use_messages`, which can be
 set to `false` to disable messages. May be useful in multicoop deployments.
 
+To allow members to respond to messages via email, see the config option
+`reply_email_domain` and the rake task `foodsoft:parse_reply_email`. We need to
+add some documentation on setting it up, though.
+
 This plugin is part of the foodsoft package and uses the GPL-3 license (see
 foodsoft's LICENSE for the full license text).

plugins/messages/app/mailers/messages_mailer.rb

@@ -4,9 +4,17 @@ class MessagesMailer < Mailer
     set_foodcoop_scope
     @message = message
 
+    reply_email_domain = FoodsoftConfig[:reply_email_domain]
+    if reply_email_domain
+      hash = message.mail_hash_for_user recipient
+      reply_to = "Foodsoft <#{FoodsoftConfig.scope}.#{message.id}.#{recipient.id}.#{hash}@#{reply_email_domain}>"
+    else
+      reply_to = "#{show_user(message.sender)} <#{message.sender.email}>"
+    end
+
     mail subject: "[#{FoodsoftConfig[:name]}] " + message.subject,
          to: recipient.email,
          from: "#{show_user(message.sender)} via Foodsoft <#{FoodsoftConfig[:email_sender]}>",
-         reply_to: "#{show_user(message.sender)} <#{message.sender.email}>"
+         reply_to: reply_to
   end
 end

plugins/messages/app/models/message.rb

@@ -1,3 +1,5 @@
+require "base32"
+
 class Message < ActiveRecord::Base
   belongs_to :sender, :class_name => "User", :foreign_key => "sender_id"
   belongs_to :group, :class_name => "Group", :foreign_key => "group_id"
@@ -23,6 +25,7 @@ class Message < ActiveRecord::Base
   validates_length_of :subject, :in => 1..255
   validates_inclusion_of :email_state, :in => EMAIL_STATE.values
 
+  before_create :create_salt
   before_validation :clean_up_recipient_ids, :on => :create
 
   def self.deliver(message_id)
@@ -61,6 +64,16 @@ class Message < ActiveRecord::Base
     add_recipients([user])
   end
 
+  def mail_hash_for_user(user)
+    digest = Digest::SHA1.new
+    digest.update self.id.to_s
+    digest.update ":"
+    digest.update salt
+    digest.update ":"
+    digest.update user.id.to_s
+    Base32.encode digest.digest
+  end
+
   # Returns true if this message is a system message, i.e. was sent automatically by Foodsoft itself.
   def system_message?
     self.sender_id.nil?
@@ -94,6 +107,10 @@ class Message < ActiveRecord::Base
   def is_readable_for?(user)
     !private || sender == user || recipients_ids.include?(user.id)
   end
+
+  private
+
+  def create_salt
+    self.salt = [Array.new(6){rand(256).chr}.join].pack("m").chomp
+  end
 end
-
-

plugins/messages/db/migrate/20160226000000_add_email_to_message.rb

@@ -0,0 +1,6 @@
+class AddEmailToMessage < ActiveRecord::Migration
+  def change
+    add_column :messages, :salt, :string
+    add_column :messages, :received_email, :binary, :limit => 1.megabyte
+  end
+end

plugins/messages/foodsoft_messages.gemspec

@@ -17,7 +17,9 @@ Gem::Specification.new do |s|
   s.test_files = Dir["test/**/*"]
 
   s.add_dependency "rails"
+  s.add_dependency "base32"
   s.add_dependency "deface", "~> 1.0.0"
+  s.add_dependency "mail"
 
   s.add_development_dependency "sqlite3"
 end

plugins/messages/lib/tasks/foodsoft.rake

@@ -0,0 +1,60 @@
+require "mail"
+
+namespace :foodsoft do
+  desc "Parse incoming email on stdin (options: RECIPIENT=f.1.2.a1b2c3d3e5)"
+  task :parse_reply_email => :environment do
+    m = /(?<foodcoop>[^@]*)\.(?<message_id>\d+)\.(?<user_id>\d+)\.(?<hash>\w+)(@(?<hostname>.*))?/.match(ENV['RECIPIENT'])
+
+    raise "RECIPIENT is missing or has an invalid format" if m.nil?
+    raise "Foodcoop '#{m[:foodcoop]}' could not be found" unless FoodsoftConfig.foodcoops.include? m[:foodcoop]
+
+    FoodsoftConfig.select_multifoodcoop m[:foodcoop]
+    original_message = Message.find_by_id(m[:message_id])
+    user = User.find_by_id(m[:user_id])
+
+    raise "Message could not be found" if original_message.nil?
+    raise "User could not be found" if user.nil?
+
+    hash = original_message.mail_hash_for_user user
+    raise "Hash does not match expectations" unless hash.casecmp(m[:hash]) == 0
+
+    received_email = STDIN.read
+    mail = Mail.new received_email
+
+    mail_part = nil
+    if mail.multipart?
+      for part in mail.parts
+        mail_part = part if MIME::Type.simplified(part.content_type) == "text/plain"
+      end
+    else
+      mail_part = mail
+    end
+
+    body = mail_part.body.decoded
+    unless mail_part.content_type_parameters.nil?
+      body = body.force_encoding mail_part.content_type_parameters[:charset]
+    end
+
+    message = user.send_messages.new body: body,
+      group: original_message.group,
+      private: original_message.private,
+      received_email: received_email,
+      subject: mail.subject
+    if original_message.reply_to
+      message.reply_to_message = original_message.reply_to_message
+    else
+      message.reply_to_message = original_message
+    end
+    message.add_recipients original_message.recipients
+    message.add_recipients [original_message.sender]
+
+    message.save!
+    Resque.enqueue(MessageNotifier, FoodsoftConfig.scope, "message_deliver", message.id)
+    rake_say "Handled reply email from #{user.display}."
+  end
+end
+
+# Helper
+def rake_say(message)
+  puts message unless Rake.application.options.silent
+end