"You need to give a SHA parameter" error when serving Dragonfly images through Cloudfront

Question

I've successfully installed and uploaded images in my Rails app using the dragonfly gem. Loading images works fine if I load it directly through the app. However, if I load the images through Cloudfront, I get an error page that says "You need to give a SHA parameter" which is strange because the SHA is included in the URL already:

For context here's my dragonfly settings:

# config/initializers/dragonfly.rb

require 'dragonfly'

# Configure
Dragonfly.app.configure do
  plugin :imagemagick

  secret "randomsecret"

  url_format "/media/:job/:name"

  datastore :file,
    root_path: Rails.root.join('public/system/dragonfly', Rails.env),
    server_root: Rails.root.join('public')
end

# Logger
Dragonfly.logger = Rails.logger

# Mount as middleware
Rails.application.middleware.use Dragonfly::Middleware

# Add model functionality
if defined?(ActiveRecord::Base)
  ActiveRecord::Base.extend Dragonfly::Model
  ActiveRecord::Base.extend Dragonfly::Model::Validations
end

I've already read the CDN section in the documentation of dragonfly, but it didn't fix the problem. The only difference it made is that it included the url_host when calling image.url instead of just the relative path that it normally returns.

Answer 1

By default, CloudFront does not forward query strings to the origin. Have you verified that you have query string forwarding enabled?