Mossu

Mossu (aka MOSS Uploader) is a Ruby on Rails application that performs plagiarism checking on Javascript programs.

Introduction

Measure of Software Similarity (MOSS) is an automatic system for determining the similarity of software programs. It is a battle-tested plagiarism checking system used by many institutions. The MOSS system is proprietary (although there is a whitepaper on the core algorithm). Student submissions must be uploaded to the MOSS servers to be processed, after which a report in the form of a URL is provided.

As part of my Final Year Project, I was tasked to implement an automated plagiarism checking feature in Falcon, a system used to autograde Node.js web API submissions.

A concern that our project supervisor had was the potential violation of Instruction Manual 8 personal data protections related policies. Student submissions typically contain personal information (name, email, admin number) in the submission zip name and code (as comments).

To work around this, the Mossu system was built. It anonymizes student submissions before submitting them to MOSS.

Here is a high-level overview of how Mossu works and is intended to be used:

Features

• Anonymizes submissions before submitting to MOSS
• Downloads MOSS report for long-term storage
• Unanonymizes MOSS report
• Designed to allow multiple services to integrate

API Documentation

Refer to docs/api.md

Requirements

• Ruby 2.6.3
• Rails 6.0.3.4
• Node 10 (for bin/comment_stripper/)
• Bash (including zip, unzip, and wget)
• Perl (for bin/mossnet)
• Redis
• Postgres

Set up

Install ruby packages:

bundle install

Install bin/comment_stripper/ packages:

cd bin/comment_stripper/ && npm install && cd ../../

Register for MOSS and put the mossnet perl script containing your user id in bin/mossnet.

Set the appropriate Sidekiq username/password:

EDITOR="vim" rails credentials:edit

sidekiq_admin_user: <username>
sidekiq_admin_password: <password> 

Start the Rails server:

bundle exec rails s

Start the Sidekiq process:

bundle exec sidekiq

To start managed processes on production, run:

pm2 start ecosystem.config.js

FAQ

What exactly is being anonymized?

• Zip file name
• Extracted file names
• Javascript comments (with Babel)

Here is a diagram of the submission processing:

Why is this built as an API?

Mossu is hosted on a Singapore Polytechnic server, and the hope is that eventually services used to host student submissions other than Falcon (e.g. Mimosa) can integrate with it regardless of the language/OS those services are using.