How to filter parts of your path (not parameters) on logging?

Question

In my routes I have a route similar to GET 'check/:secret.

When I send a request to that route in the logs I see:

Started GET "/check/the-secret-here" for ::1 at 2021-01-14 16:38:01 -0600
...

I want to filter/redact the secret so it looks like:

Started GET "/check/[FILTERED]" for ::1 at 2021-01-14 16:38:01 -0600
...

I'm using Rails 5.1, I've added config.filter_parameters += %i[secret] which does filter the value but only on POST Params.

Reggy

Answer 1

What you're describing isn't a parameter but part of the url.
If you're disclosuring your secret as part of a url that could be shared anywhere, probably that won't be something so secret as you're expecting, so maybe is a good idea to change that action to a POST request?
Anyway, if there's any strong reason to keep it in that way, the only thing I can see is monkey-patching your rails instance, specifically ActionDispatch::Http::FilterParameters. So, add in your config/initializers folder:

module ActionDispatch
  module Http
    module FilterParameters
      def filtered_path
        # Keep an eye here adding a really good filtering regex, or potentially
        # you'll filter more than you were expecting
        secret_path = path.gsub(/\/the-secret-here\//, "\/[FILTERED]\/")
        @filtered_path ||= query_string.empty? ? secret_path : "#{secret_path}?#{filtered_query_string}"
      end
    end
  end
end

Chromonema

Dude you are a genius. Thanks! – Reggy