From 7cffbc8ba8f72161aed46ef7822baedb86243dde Mon Sep 17 00:00:00 2001
From: Arpit Jalan <arpit@techapj.com>
Date: Wed, 5 Jul 2017 22:39:45 +0530
Subject: [PATCH] FEATURE: new site setting to limit message recipients

New site setting `max_allowed_message_recipients` to limit message
recipients

https://meta.discourse.org/t/one-of-my-users-just-group-messaged-100-other-user-with-a-spam-offer/65612/7?u=techapj
---
 config/locales/server.en.yml         |  3 ++
 config/site_settings.yml             |  3 ++
 lib/post_creator.rb                  |  6 ++++
 spec/components/post_creator_spec.rb | 53 ++++++++++++++++++++++++++++
 4 files changed, 65 insertions(+)

diff --git a/config/locales/server.en.yml b/config/locales/server.en.yml
index 395f78bbdf3..a3a2563be4d 100644
--- a/config/locales/server.en.yml
+++ b/config/locales/server.en.yml
@@ -213,6 +213,7 @@ en:
   user_is_suspended: "Suspended users are not allowed to post."
   topic_not_found: "Something has gone wrong. Perhaps this topic was closed or deleted while you were looking at it?"
   not_accepting_pms: "Sorry, %{username} is not accepting messages at the moment."
+  max_pm_recepients: "Sorry, you can send a message to maximum %{recipients_limit} recipients."
 
   just_posted_that: "is too similar to what you recently posted"
   invalid_characters: "contains invalid characters"
@@ -1498,6 +1499,8 @@ en:
 
     code_formatting_style: "Code button in composer will default to this code formatting style"
 
+    max_allowed_message_recipients: "Maximum recipients allowed in a message."
+
     default_email_digest_frequency: "How often users receive summary emails by default."
     default_include_tl0_in_digests: "Include posts from new users in summary emails by default. Users can change this in their preferences."
     default_email_private_messages: "Send an email when someone messages the user by default."
diff --git a/config/site_settings.yml b/config/site_settings.yml
index 06100c657a0..ab2db791ae9 100644
--- a/config/site_settings.yml
+++ b/config/site_settings.yml
@@ -600,6 +600,9 @@ posting:
     client: true
     default: ''
     type: list
+  max_allowed_message_recipients:
+    default: 30
+    min: 1
 
 email:
   email_time_window_mins:
diff --git a/lib/post_creator.rb b/lib/post_creator.rb
index 7f515a7ee45..405a7e0537a 100644
--- a/lib/post_creator.rb
+++ b/lib/post_creator.rb
@@ -92,6 +92,12 @@ class PostCreator
       return false
     end
 
+    # Make sure max_allowed_message_recipients setting is respected
+    if @opts[:target_usernames].present? && !skip_validations? && !@user.staff?
+      errors[:base] << I18n.t(:max_pm_recepients, recipients_limit: SiteSetting.max_allowed_message_recipients) if @opts[:target_usernames].split(',').length > SiteSetting.max_allowed_message_recipients
+      return false if errors[:base].present?
+    end
+
     # Make sure none of the users have muted the creator
     names = @opts[:target_usernames]
     if names.present? && !skip_validations? && !@user.staff?
diff --git a/spec/components/post_creator_spec.rb b/spec/components/post_creator_spec.rb
index 6ea5228e5f4..5e3441784f5 100644
--- a/spec/components/post_creator_spec.rb
+++ b/spec/components/post_creator_spec.rb
@@ -997,4 +997,57 @@ describe PostCreator do
       expect(pc.errors).to be_blank
     end
   end
+
+  context "private message recipients limit (max_allowed_message_recipients) reached" do
+    let(:target_user1) { Fabricate(:coding_horror) }
+    let(:target_user2) { Fabricate(:evil_trout) }
+    let(:target_user3) { Fabricate(:walter_white) }
+
+    before do
+      SiteSetting.max_allowed_message_recipients = 2
+    end
+
+    context "for normal user" do
+      it 'fails when sending message to multiple recipients' do
+        pc = PostCreator.new(
+          user,
+          title: 'this message is for multiple recipients!',
+          raw: "Lorem ipsum dolor sit amet, id elitr praesent mea, ut ius facilis fierent.",
+          archetype: Archetype.private_message,
+          target_usernames: [target_user1.username, target_user2.username, target_user3.username].join(',')
+        )
+        expect(pc).not_to be_valid
+        expect(pc.errors).to be_present
+      end
+
+      it 'succeeds when sending message to multiple recipients if skip_validations is true' do
+        pc = PostCreator.new(
+          user,
+          title: 'this message is for multiple recipients!',
+          raw: "Lorem ipsum dolor sit amet, id elitr praesent mea, ut ius facilis fierent.",
+          archetype: Archetype.private_message,
+          target_usernames: [target_user1.username, target_user2.username, target_user3.username].join(','),
+          skip_validations: true
+        )
+        expect(pc).to be_valid
+        expect(pc.errors).to be_blank
+      end
+    end
+
+    context "always succeeds if the user is staff" do
+      let(:staff_user) { Fabricate(:admin) }
+
+      it 'when sending message to multiple recipients' do
+        pc = PostCreator.new(
+          staff_user,
+          title: 'this message is for multiple recipients!',
+          raw: "Lorem ipsum dolor sit amet, id elitr praesent mea, ut ius facilis fierent.",
+          archetype: Archetype.private_message,
+          target_usernames: [target_user1.username, target_user2.username, target_user3.username].join(',')
+        )
+        expect(pc).to be_valid
+        expect(pc.errors).to be_blank
+      end
+    end
+  end
 end