HTTPi with curb and SPNEGO, based on https://gist.github.com/pullmonkey/3179054

gistfile1.rb

require 'rubygems'
require 'httpi'
require 'curb'
require 'pp'
require 'json'
 
################################
# kinit user@REALM
# kinit -k -t /ticket/path
################################
 
HOST = 'localhost'
PORT = 443
PATH = 'resource.json'

HTTPI.adapter = :curb
req = HTTPI::Request.new
req.url = URI.escape("https://#{HOST}:#{PORT}/#{PATH}")
 
# use spnego
req.auth.gssnegotiate
 
resp = HTTPI.get(req){ |http| http.use_ssl }

if resp.code == 200
  STDERR.puts "Endpoint successfully queried, dumping JSON body:\n"
  pp JSON.parse(resp.body)
else
  STDERR.puts "Error :("
  STDERR.puts resp.inspect
end