How can I password-protect my /sidekiq route (i.e. require authentication for the Sidekiq::Web tool)?

Put the following into your sidekiq initializer

require 'sidekiq'
require 'sidekiq/web'

Sidekiq::Web.use(Rack::Auth::Basic) do |user, password|
  # Protect against timing attacks:
  # - See https://codahale.com/a-lesson-in-timing-attacks/
  # - See https://thisdata.com/blog/timing-attacks-against-string-comparison/
  # - Use & (do not use &&) so that it doesn't short circuit.
  # - Use digests to stop length information leaking
  Rack::Utils.secure_compare(::Digest::SHA256.hexdigest(user), ::Digest::SHA256.hexdigest(ENV["SIDEKIQ_USER"])) &
  Rack::Utils.secure_compare(::Digest::SHA256.hexdigest(password), ::Digest::SHA256.hexdigest(ENV["SIDEKIQ_PASSWORD"]))
end

And in the routes file:

mount Sidekiq::Web => '/sidekiq'