[Rootkit] 修改 peb 隐藏 dll（断链）

PEB 中有一个成员 Ldr：

typedef struct _PEB
{
     UCHAR InheritedAddressSpace;
     UCHAR ReadImageFileExecOptions;
     UCHAR BeingDebugged;
     UCHAR BitField;
     ULONG ImageUsesLargePages: 1;
     ULONG IsProtectedProcess: 1;
     ULONG IsLegacyProcess: 1;
     ULONG IsImageDynamicallyRelocated: 1;
     ULONG SpareBits: 4;
     PVOID Mutant;
     PVOID ImageBaseAddress;
     PPEB_LDR_DATA Ldr;						// <----------
     PRTL_USER_PROCESS_PARAMETERS ProcessParameters;
     PVOID SubSystemData;
     PVOID ProcessHeap;
     PRTL_CRITICAL_SECTION FastPebLock;
     PVOID AtlThunkSListPtr;
     PVOID IFEOKey;
     ULONG CrossProcessFlags;
     ULONG ProcessInJob: 1;
     ULONG ProcessInitializing: 1;
     ULONG ReservedBits0: 30;
     union
     {
          PVOID KernelCallbackTable;
          PVOID UserSharedInfoPtr;
     };
     ULONG SystemReserved[1];
     ULONG SpareUlong;
     PPEB_FREE_BLOCK FreeList;
     ULONG TlsExpansionCounter;
     PVOID TlsBitmap;
     ULONG TlsBitmapBits[2];
     PVOID ReadOnlySharedMemoryBase;
     PVOID HotpatchInformation;
     VOID * * ReadOnlyStaticServerData;
     PVOID AnsiCodePageData;
     PVOID OemCodePageData;
     PVOID UnicodeCaseTableData;
     ULONG NumberOfProcessors;
     ULONG NtGlobalFlag;
     LARGE_INTEGER CriticalSectionTimeout;
     ULONG HeapSegmentReserve;
     ULONG HeapSegmentCommit;
     ULONG HeapDeCommitTotalFreeThreshold;
     ULONG HeapDeCommitFreeBlockThreshold;
     ULONG NumberOfHeaps;
     ULONG MaximumNumberOfHeaps;
     VOID * * ProcessHeaps;
     PVOID GdiSharedHandleTable;
     PVOID ProcessStarterHelper;
     ULONG GdiDCAttributeList;
     PRTL_CRITICAL_SECTION LoaderLock;
     ULONG OSMajorVersion;
     ULONG OSMinorVersion;
     WORD OSBuildNumber;
     WORD OSCSDVersion;
     ULONG OSPlatformId;
     ULONG ImageSubsystem;
     ULONG ImageSubsystemMajorVersion;
     ULONG ImageSubsystemMinorVersion;
     ULONG ImageProcessAffinityMask;
     ULONG GdiHandleBuffer[34];
     PVOID PostProcessInitRoutine;
     PVOID TlsExpansionBitmap;
     ULONG TlsExpansionBitmapBits[32];
     ULONG SessionId;
     ULARGE_INTEGER AppCompatFlags;
     ULARGE_INTEGER AppCompatFlagsUser;
     PVOID pShimData;
     PVOID AppCompatInfo;
     UNICODE_STRING CSDVersion;
     _ACTIVATION_CONTEXT_DATA * ActivationContextData;
     _ASSEMBLY_STORAGE_MAP * ProcessAssemblyStorageMap;
     _ACTIVATION_CONTEXT_DATA * SystemDefaultActivationContextData;
     _ASSEMBLY_STORAGE_MAP * SystemAssemblyStorageMap;
     ULONG MinimumStackCommit;
     _FLS_CALLBACK_INFO * FlsCallback;
     LIST_ENTRY FlsListHead;
     PVOID FlsBitmap;
     ULONG FlsBitmapBits[4];
     ULONG FlsHighIndex;
     PVOID WerRegistrationData;
     PVOID WerShipAssertPtr;
} PEB, *PPEB;

这个 Ldr 的数据类型是 _PEB_LDR_DATA：

typedef struct _PEB_LDR_DATA
{
　ULONG Length;
　BOOLEAN Initialized; 
　PVOID SsHandle; 
　LIST_ENTRY InLoadOrderModuleList;				// <---------
　LIST_ENTRY InMemoryOrderModuleList; 
　LIST_ENTRY InInitializationOrderModuleList;
} PEB_LDR_DATA,*PPEB_LDR_DATA;

InLoadOrderModuleList 成员保存了模块信息，而模块信息的结构为 _LDR_DATA_TABLE_ENTRY。

typedef struct _LDR_DATA_TABLE_ENTRY
{
LIST_ENTRY InLoadOrderLinks;
LIST_ENTRY InMemoryOrderLinks;
LIST_ENTRY InInitializationOrderLinks;
PVOID      DllBase;
PVOID      EntryPoint;
ULONG32    SizeOfImage;
UINT8      Unknow0[0x4];
UNICODE_STRING FullDllName;
UNICODE_STRING BaseDllName;
}LDR_DATA_TABLE_ENTRY, *PLDR_DATA_TABLE_ENTRY;

所以 ，我们获取到了这个结构.因为是链表.可以遍历链表. 根据DllBase判断 你的模块基址跟这个模块基址是否一样.如果一样那么我们就断开链表，从而实现 dll 的隐藏。

代码参考来自：https://cloud.tencent.com/developer/article/1432475

#include <stdio.h>
#include <Windows.h>
#include <stdlib.h>

DWORD g_isHide = 0;
typedef struct _UNICODE_STRING
{
    USHORT Length;
    USHORT MaximumLength;
    PWSTR  Buffer;
} UNICODE_STRING, *PUNICODE_STRING;

typedef struct _PEB_LDR_DATA {
    ULONG                   Length;
    BOOLEAN                 Initialized;
    PVOID                   SsHandle;
    LIST_ENTRY              InLoadOrderModuleList;
    LIST_ENTRY              InMemoryOrderModuleList;
    LIST_ENTRY              InInitializationOrderModuleList;
} PEB_LDR_DATA, *PPEB_LDR_DATA;

typedef struct _LDR_MODULE
{
    LIST_ENTRY          InLoadOrderModuleList;   //+0x00
    LIST_ENTRY          InMemoryOrderModuleList; //+0x08  
    LIST_ENTRY          InInitializationOrderModuleList; //+0x10
    void*               BaseAddress;  //+0x18
    void*               EntryPoint;   //+0x1c
    ULONG               SizeOfImage;
    UNICODE_STRING      FullDllName;
    UNICODE_STRING      BaseDllName;
    ULONG               Flags;
    SHORT               LoadCount;
    SHORT               TlsIndex;
    HANDLE              SectionHandle;
    ULONG               CheckSum;
    ULONG               TimeDateStamp;
} LDR_MODULE, *PLDR_MODULE;
void HideDll()　　　　　　　　　　　　　　　　　　　　　　　　　　//这个函数是主要的
{
    HMODULE hMod = ::GetModuleHandle("ntdll.dll");
    PLIST_ENTRY Head, Cur;
    PPEB_LDR_DATA ldr;
    PLDR_MODULE ldm;
    __asm
    {
        mov eax, fs:[0x30]　　　　　　　　　　　　　　　　　　//获取PEB结构
        mov ecx, [eax + 0x0c] //Ldr                     //获取_PEB_LDR_DATA结构
        mov ldr, ecx
    }
    Head = &(ldr->InLoadOrderModuleList);               //获取模块链表地址
    Cur = Head->Flink;                                  //获取指向的结点.
    do
    {
        ldm = CONTAINING_RECORD(Cur, LDR_MODULE, InLoadOrderModuleList); //获取 _LDR_DATA_TABLE_ENTRY结构体地址
        //printf("EntryPoint [0x%X]\n",ldm->BaseAddress);
        if (hMod == ldm->BaseAddress)                                    //判断要隐藏的DLL基址跟结构中的基址是否一样
        {
            g_isHide = 1;                                                //如果进入.则标志置为1,表示已经开始进行隐藏了.
            ldm->InLoadOrderModuleList.Blink->Flink =                    //双向链表. 断开链表
                ldm->InLoadOrderModuleList.Flink;
            ldm->InLoadOrderModuleList.Flink->Blink =
                ldm->InLoadOrderModuleList.Blink;
            ldm->InInitializationOrderModuleList.Blink->Flink =
                ldm->InInitializationOrderModuleList.Flink;
            ldm->InInitializationOrderModuleList.Flink->Blink =
                ldm->InInitializationOrderModuleList.Blink;
            ldm->InMemoryOrderModuleList.Blink->Flink =
                ldm->InMemoryOrderModuleList.Flink;
            ldm->InMemoryOrderModuleList.Flink->Blink =
                ldm->InMemoryOrderModuleList.Blink;
            break;
        }
        Cur = Cur->Flink;
    } while (Head != Cur);
}

int main()
{

    printf("按键开始隐藏\r\n");
    getchar();
    HideDll();

    if (g_isHide == 0)
    {
        printf("没有成功隐藏\r\n");
        system("pause");
        return 0;
    }

    printf("成功隐藏\r\n");
    system("pause");
    return 0;
}