this one gets monkeypatched into a library. I called mine cookbooks/libsonian/libraries/signed_url.rb & chef.rb

chef.rb

class Chef
  class Provider
    class RemoteS3File < Chef::Provider::RemoteFile
      def load_current_resource
        super
        %w{bucket object_name aws_access_key_id aws_secret_access_key}.map do |attribute|
          Chef::Application.fatal! "remote_s3_file: required attr: #{attribute} is nil", -92 if
            @new_resource.send(attribute.to_sym).nil?
        end

        @new_resource.source( LibSonian.signed_url(@new_resource.bucket,
                                                   @new_resource.object_name,
                                                   @new_resource.aws_access_key_id,
                                                   @new_resource.aws_secret_access_key)
                              )
      end
    end
  end

  class Resource
    class RemoteS3File < Chef::Resource::RemoteFile
      def provider
        Chef::Provider::RemoteS3File
      end

      def initialize(name, run_context=nil)
        super
        @resource_name = :remote_s3_file
        @cookbook = nil
        Chef::Log.info "remote_s3_file: initializing #{name}"
      end

      def bucket(args=nil)
        set_or_return(
                      :bucket,
                      args,
                      :kind_of => String
                      )
      end

      def object_name(args=nil)
        set_or_return(
                      :object_name,
                      args,
                      :kind_of => String
                      )
      end

      def aws_access_key_id(args=nil)
        set_or_return(
                      :aws_access_key_id,
                      args,
                      :kind_of => String
                      )
      end

      def aws_secret_access_key(args=nil)
        set_or_return(
                      :aws_secret_access_key,
                      args,
                      :kind_of => String
                      )
      end
    end
  end
end

Chef::Platform.platforms[:default].merge! :remote_s3_file => Chef::Provider::RemoteS3File

example.rb

include_recipe "aws"
include_recipe "libsonian" # you'll need both of these as deps

aws = data_bag_item("aws", "some credz for s3 yo")

remote_s3_file "/usr/src/remote_s3_file.tbz" do
  bucket "foo"
  object_name "bar/baz/bong.tbz"
  aws_access_key_id aws["aws_access_key_id"]
  aws_secret_access_key aws["aws_secret_access_key"]
  mode "00644"
end

signed_url.rb

module LibSonian
  def self.signed_url(bucket,
                      object_name,
                      aws_access_key_id,
                      aws_secret_access_key)
    begin
      Gem.clear_paths
      require 'fog'
    rescue LoadError
      Chef::Log.warn("Missing gem 'fog'")
    end

    @@s3 ||= ::Fog::AWS::Storage.new(:aws_access_key_id => aws_access_key_id,
                                     :aws_secret_access_key => aws_secret_access_key)
    url = @@s3.directories.get(bucket).files.get_url(object_name, Time.now + (60 * 10))
    Chef::Log.info "signed_url[#{bucket}/#{object_name}]: generated signed 10 minute S3 url #{url}"
    url
  end
end

I needed this exact functionality. I created an actual cookbook that installs fog and it's dependencies. I've only tested it on Ubuntu 10.0.4

http://cookbooks.opscode.com/cookbooks/awsclient

dope

Thanks for posting this man. I would have been lost without it!