在Windows内核中，SSSDT（System Service Shadow Descriptor Table）是SSDT（System Service Descriptor Table）的一种变种，其主要用途是提供Windows系统对系统服务调用的阴影拷贝。SSSDT表存储了系统调用的函数地址，类似于SSDT表，但在某些情况下，Windows系统会使用SSSDT表来对系统服务进行引导和调用。
SSSDT表的存在是为了加强系统的安全性和稳定性。通过使用SSSDT表，操作系统可以在运行时检查系统服务的合法性，并确保其不被非法修改。这有助于防止恶意软件或恶意行为修改系统服务地址，提高系统的整体安全性。
在笔者上一篇文章《枚举完整SSDT地址表》实现了针对SSDT表的枚举功能，本章继续实现对SSSDT表的枚举，ShadowSSDT中文名影子系统服务描述表，SSSDT其主要的作用是管理系统中的图形化界面，其Win32子系统的内核实现是Win32k.sys驱动，属于GUI线程的一部分，其自身没有导出表，枚举SSSDT表其与SSDT原理基本一致。
如下是闭源ARK工具的枚举效果:
首先需要找到SSSDT表的位置，通过《Win10内核枚举SSDT表基址》文章中的分析可知，SSSDT就在SSDT的下面，只需要枚举4c8d1dde1e3a00特征即可，如果你找不到上一篇具体分析流程了，那么多半你是看到了转载文章。
先实现第一个功能，得到SSSDT表的基地址以及SSDT函数个数，完整代码如下所示。
#include <ntifs.h>
#pragma intrinsic(__readmsr)
typedef struct _SYSTEM_SERVICE_TABLE
{
PVOID ServiceTableBase;
PVOID ServiceCounterTableBase;
ULONGLONG NumberOfServices;
PVOID ParamTableBase;
} SYSTEM_SERVICE_TABLE, *PSYSTEM_SERVICE_TABLE;
PSYSTEM_SERVICE_TABLE KeServiceDescriptorTableShadow = 0;
ULONG64 ul64W32pServiceTable = 0;
// 获取 KeServiceDescriptorTableShadow 首地址
ULONGLONG GetKeServiceDescriptorTableShadow()
{
// 设置起始位置
PUCHAR StartSearchAddress = (PUCHAR)__readmsr(0xC0000082) - 0x1808FE;
// 设置结束位置
PUCHAR EndSearchAddress = StartSearchAddress 0x8192;
// DbgPrint("扫描起始地址: %p --> 扫描结束地址: %p n", StartSearchAddress, EndSearchAddress);
PUCHAR ByteCode = NULL;
UCHAR OpCodeA = 0, OpCodeB = 0, OpCodeC = 0;
ULONGLONG addr = 0;
ULONG templong = 0;
for (ByteCode = StartSearchAddress; ByteCode < EndSearchAddress; ByteCode )
{
// 使用MmIsAddressValid()函数检查地址是否有页面错误
if (MmIsAddressValid(ByteCode) && MmIsAddressValid(ByteCode 1) && MmIsAddressValid(ByteCode 2))
{
OpCodeA = *ByteCode;
OpCodeB = *(ByteCode 1);
OpCodeC = *(ByteCode 2);
// 对比特征值 寻找 nt!KeServiceDescriptorTable 函数地址
/*
lyshark kd> u KiSystemServiceRepeat
nt!KiSystemServiceRepeat:
fffff802`7c1d2b94 4c8d15e59c3b00 lea r10,[nt!KeServiceDescriptorTable (fffff802`7c58c880)]
fffff802`7c1d2b9b 4c8d1dde1e3a00 lea r11,[nt!KeServiceDescriptorTableShadow (fffff802`7c574a80)]
fffff802`7c1d2ba2 f7437880000000 test dword ptr [rbx 78h],80h
fffff802`7c1d2ba9 7413 je nt!KiSystemServiceRepeat 0x2a (fffff802`7c1d2bbe)
fffff802`7c1d2bab f7437800002000 test dword ptr [rbx 78h],200000h
fffff802`7c1d2bb2 7407 je nt!KiSystemServiceRepeat 0x27 (fffff802`7c1d2bbb)
fffff802`7c1d2bb4 4c8d1d051f3a00 lea r11,[nt!KeServiceDescriptorTableFilter (fffff802`7c574ac0)]
fffff802`7c1d2bbb 4d8bd3 mov r10,r11
*/
if (OpCodeA == 0x4c && OpCodeB == 0x8d && OpCodeC == 0x1d)
{
// 获取高位地址fffff802
memcpy(&templong, ByteCode 3, 4);
// 与低位64da4880地址相加得到完整地址
addr = (ULONGLONG)templong (ULONGLONG)ByteCode 7;
return addr;
}
}
}
return 0;
}
// 得到SSSDT个数
ULONGLONG GetSSSDTCount()
{
PSYSTEM_SERVICE_TABLE pWin32k;
ULONGLONG W32pServiceTable;
pWin32k = (PSYSTEM_SERVICE_TABLE)((ULONG64)KeServiceDescriptorTableShadow sizeof(SYSTEM_SERVICE_TABLE));
W32pServiceTable = (ULONGLONG)(pWin32k->ServiceTableBase);
// DbgPrint("Count => %d n", pWin32k->NumberOfServices);
return pWin32k->NumberOfServices;
}
VOID UnDriver(PDRIVER_OBJECT driver)
{
DbgPrint(("驱动程序卸载成功! n"));
}
NTSTATUS DriverEntry(PDRIVER_OBJECT DriverObject, PUNICODE_STRING RegistryPath)
{
DbgPrint("hello lyshark n");
KeServiceDescriptorTableShadow = (PSYSTEM_SERVICE_TABLE)GetKeServiceDescriptorTableShadow();
DbgPrint("[LyShark] SSSDT基地址 = 0x%p n", KeServiceDescriptorTableShadow);
ULONGLONG count = GetSSSDTCount();
DbgPrint("[LyShark] SSSDT个数 = %d n", count);
DriverObject->DriverUnload = UnDriver;
return STATUS_SUCCESS;
}这段代码运行后即可得到SSSDT表基地址，以及该表中函数个数。
在此基础之上增加枚举计算过程即可，完整源代码如下所示。
SSSDT 函数起始index是0x1000，但W32pServiceTable是从基址开始记录的，这个误差则需要(index-0x1000)来得到，至于 4则是下一个元素与上一个元素的偏移。
计算公式：
- W32pServiceTable 4 * (index-0x1000)
#include <ntifs.h>
#pragma intrinsic(__readmsr)
typedef struct _SYSTEM_SERVICE_TABLE
{
PVOID ServiceTableBase;
PVOID ServiceCounterTableBase;
ULONGLONG NumberOfServices;
PVOID ParamTableBase;
} SYSTEM_SERVICE_TABLE, *PSYSTEM_SERVICE_TABLE;
PSYSTEM_SERVICE_TABLE KeServiceDescriptorTableShadow = 0;
ULONG64 ul64W32pServiceTable = 0;
// 获取 KeServiceDescriptorTableShadow 首地址
ULONGLONG GetKeServiceDescriptorTableShadow()
{
// 设置起始位置
PUCHAR StartSearchAddress = (PUCHAR)__readmsr(0xC0000082) - 0x1808FE;
// 设置结束位置
PUCHAR EndSearchAddress = StartSearchAddress 0x8192;
// DbgPrint("扫描起始地址: %p --> 扫描结束地址: %p n", StartSearchAddress, EndSearchAddress);
PUCHAR ByteCode = NULL;
UCHAR OpCodeA = 0, OpCodeB = 0, OpCodeC = 0;
ULONGLONG addr = 0;
ULONG templong = 0;
for (ByteCode = StartSearchAddress; ByteCode < EndSearchAddress; ByteCode )
{
// 使用MmIsAddressValid()函数检查地址是否有页面错误
if (MmIsAddressValid(ByteCode) && MmIsAddressValid(ByteCode 1) && MmIsAddressValid(ByteCode 2))
{
OpCodeA = *ByteCode;
OpCodeB = *(ByteCode 1);
OpCodeC = *(ByteCode 2);
// 对比特征值 寻找 nt!KeServiceDescriptorTable 函数地址
/*
lyshark kd> u KiSystemServiceRepeat
nt!KiSystemServiceRepeat:
fffff802`7c1d2b94 4c8d15e59c3b00 lea r10,[nt!KeServiceDescriptorTable (fffff802`7c58c880)]
fffff802`7c1d2b9b 4c8d1dde1e3a00 lea r11,[nt!KeServiceDescriptorTableShadow (fffff802`7c574a80)]
fffff802`7c1d2ba2 f7437880000000 test dword ptr [rbx 78h],80h
fffff802`7c1d2ba9 7413 je nt!KiSystemServiceRepeat 0x2a (fffff802`7c1d2bbe)
fffff802`7c1d2bab f7437800002000 test dword ptr [rbx 78h],200000h
fffff802`7c1d2bb2 7407 je nt!KiSystemServiceRepeat 0x27 (fffff802`7c1d2bbb)
fffff802`7c1d2bb4 4c8d1d051f3a00 lea r11,[nt!KeServiceDescriptorTableFilter (fffff802`7c574ac0)]
fffff802`7c1d2bbb 4d8bd3 mov r10,r11
*/
if (OpCodeA == 0x4c && OpCodeB == 0x8d && OpCodeC == 0x1d)
{
// 获取高位地址fffff802
memcpy(&templong, ByteCode 3, 4);
// 与低位64da4880地址相加得到完整地址
addr = (ULONGLONG)templong (ULONGLONG)ByteCode 7;
return addr;
}
}
}
return 0;
}
// 得到SSSDT个数
ULONGLONG GetSSSDTCount()
{
PSYSTEM_SERVICE_TABLE pWin32k;
ULONGLONG W32pServiceTable;
pWin32k = (PSYSTEM_SERVICE_TABLE)((ULONG64)KeServiceDescriptorTableShadow sizeof(SYSTEM_SERVICE_TABLE));
W32pServiceTable = (ULONGLONG)(pWin32k->ServiceTableBase);
// DbgPrint("Count => %d n", pWin32k->NumberOfServices);
return pWin32k->NumberOfServices;
}
VOID UnDriver(PDRIVER_OBJECT driver)
{
DbgPrint(("驱动程序卸载成功! n"));
}
NTSTATUS DriverEntry(PDRIVER_OBJECT DriverObject, PUNICODE_STRING RegistryPath)
{
DbgPrint("hello lyshark n");
KeServiceDescriptorTableShadow = (PSYSTEM_SERVICE_TABLE)GetKeServiceDescriptorTableShadow();
DbgPrint("[LyShark] SSSDT基地址 = 0x%p n", KeServiceDescriptorTableShadow);
ULONGLONG count = GetSSSDTCount();
DbgPrint("[LyShark] SSSDT个数 = %d n", count);
// 循环枚举SSSDT
for (size_t Index = 0; Index < count; Index )
{
PSYSTEM_SERVICE_TABLE pWin32k;
ULONGLONG W32pServiceTable;
pWin32k = (PSYSTEM_SERVICE_TABLE)((ULONG64)KeServiceDescriptorTableShadow sizeof(SYSTEM_SERVICE_TABLE));
W32pServiceTable = (ULONGLONG)(pWin32k->ServiceTableBase);
// 获取SSSDT地址
//ln win32k!W32pServiceTable ((poi(win32k!W32pServiceTable 4*(1-1000))&0x00000000`ffffffff)>>4)-10000000
//u win32k!W32pServiceTable ((poi(win32k!W32pServiceTable 4*(Index-0x1000))&0x00000000`ffffffff)>>4)-0x10000000
//u poi(win32k!W32pServiceTable 4*(1-0x1000))
//u poi(win32k!W32pServiceTable 4*(1-0x1000))&0x00000000`ffffffff
//u (poi(win32k!W32pServiceTable 4*(1-0x1000))&0x00000000`ffffffff)>>4
//u win32k!W32pServiceTable ((poi(win32k!W32pServiceTable 4*(1-0x1000))&0x00000000`ffffffff)>>4)-0x10000000
ULONGLONG qword_temp = 0;
LONG dw = 0;
// SSSDT 下标从1000开始，而W32pServiceTable是从0开始
// 4 则是每次向下4字节就是下一个地址
qword_temp = W32pServiceTable 4 * (Index - 0x1000);
dw = *(PLONG)qword_temp;
// dw = qword_temp & 0x00000000ffffffff;
dw = dw >> 4;
qword_temp = W32pServiceTable (LONG64)dw;
DbgPrint("[LyShark] ID: %d | SSSDT: 0x%p n", Index, qword_temp);
}
DriverObject->DriverUnload = UnDriver;
return STATUS_SUCCESS;
}枚举效果如下图所示所示，注意这一步必须要在GUI线程中执行，否则会异常，建议将枚举过程写成DLL文件，注入到explorer.exe进程内执行；
