activeresource Gem for Ruby lib/active_resource/base.rb element_path Lack of Encoding

activeresource contains a lack of encoding flaw in the element_path function of
lib/active_resource/base.rb.

There is an issue with the way Active Resource encodes data before querying the back end server. This encoding mechanism can allow specially crafted requests to possibly access data that may not be expected.

Impacted code will look something like this:

require 'activeresource'

class Test < ActiveResource::Base
  self.site = 'http://127.0.0.1:3000'
end

Test.exists?(untrusted_user_input)

Where untrusted user input is passed to an Active Resource model. Specially crafted untrusted input can cause Active Resource to access data in an unexpected way and possibly leak information.

Workarounds

For those that can’t upgrade, the following monkey patch can be applied:

module ActiveResource
 class Base
   class << self
     def element_path(id, prefix_options = {}, query_options = nil)
       check_prefix_options(prefix_options)

       prefix_options, query_options = split_options(prefix_options) if query_options.nil?
       "#{prefix(prefix_options)}#{collection_name}/#{URI.encode_www_form_component(id.to_s)}#{format_extension}#{query_string(query_options)}"
     end
   end
 end
end