Monkey patch Chef::REST::AuthCredentials to support keys directly

gistfile1.rb

#Chef::REST::AuthCredentials accepts only filenames by default
#this extends the Chef::REST::AuthCredentials so that the key can be provided directly
require 'chef/rest/auth_credentials'
class Chef
  class REST
    class AuthCredentials
      alias :original_load_signing_key :load_signing_key

      def load_signing_key
        if key_file.start_with?("-----BEGIN RSA PRIVATE KEY-----")
          @raw_key = key_file.strip
          begin
            @key = OpenSSL::PKey::RSA.new(@raw_key)
          rescue OpenSSL::PKey::RSAError
            msg = "The key is not a correctly formatted private key.\n"
            msg << "The key should begin with '-----BEGIN RSA PRIVATE KEY-----' and end with '-----END RSA PRIVATE KEY-----'"
            raise Chef::Exceptions::InvalidPrivateKey, msg
          end
        else
          original_load_signing_key
        end

      end
    end
  end
end