chef.rb

require 'base64'
require 'time'
require 'digest/sha1'
require 'openssl'
require 'net/https'
require 'json'

class Chef

  attr_accessor :http, :path
  attr_accessor :client_name, :key_file

  def initialize(opts={})
    server            = opts[:server]
    port              = opts.fetch(:port, 443)

    # They way you had it before would mean that setting it to false
    # would actually set it to true. something = false || true. See what I
    # mean?
    use_ssl           = opts.fetch(:use_ssl, true)
    ssl_insecure      = opts[:ssl_insecure] ? OpenSSL::SSL::VERIFY_NONE :  OpenSSL::SSL::VERIFY_PEER
    @client_name      = opts[:client_name]
    @key_file         = opts[:key_file]

    @http             = Net::HTTP.new(server, port)
    @http.use_ssl     = use_ssl
    @http.verify_mode = ssl_insecure
  end

  def headers
    body      = ""
    timestamp = Time.now.utc.iso8601
    key       = OpenSSL::PKey::RSA.new(File.read(key_file))
    canonical = "Method:GET\nHashed Path:#{encode(path)}\nX-Ops-Content-Hash:#{encode(body)}\nX-Ops-Timestamp:#{timestamp}\nX-Ops-UserId:#{client_name}"

    header_hash = {
      'Accept'             => 'application/json',
      'X-Ops-Sign'         => 'version=1.0',
      'X-Ops-Userid'       => client_name,
      'X-Ops-Timestamp'    => timestamp,
      'X-Ops-Content-Hash' => encode(body)
    }

    signature = Base64.encode64(key.private_encrypt(canonical))
    signature_lines = signature.split(/\n/)
    signature_lines.each_index do |idx|
      key = "X-Ops-Authorization-#{idx + 1}"
      header_hash[key] = signature_lines[idx]
    end

    header_hash
  end

  def encode(string)
    ::Base64.encode64(Digest::SHA1.digest(string)).chomp
  end

  def get_request(req_path)
    @path = req_path

    begin
      request  = Net::HTTP::Get.new(path, headers)
      response = http.request(request)

      JSON.parse(response.body).keys
    rescue OpenSSL::SSL::SSLError => e
      raise "SSL error: #{e.message}."
    end

  end

end



chef = Chef.new(
  :server       => 'chef.server.com',
  :client_name  => 'client-name',
  :key_file     => '/path/to/your/client-name.pem',
  :ssl_insecure => true
)

print chef.get_request('/environments/_default/nodes')

Simple Ruby class for manually querying the Chef REST API (using Net::HTTP instead of Chef's REST resources)