微软轻量级系统监控工具sysmon内核实现原理

上文讲解了sysmon的ring3部分实现原理，本文则开始讲解ring0部分。Sysmon的ring0是一个minifilter类型的驱动，内部实现了进程信息、文件访问信息以及注册表访问信息的记录，下面开始具体讲解它的实现流程。 

一、          驱动DriverEntry的初始化 

从DriverEntry(PDRIVER_OBJECTDriverObject, UNICODE_STRING *pRegistry)的pRegistry中截取末尾名称去获取并计算出设备名和DosDevices的名字。 

 

pDriverName= pRegistry->Buffer;
  Len = pRegistry->Length >> 1;
  pFirstName = &pDriverName[Len];
  if ( pFirstName == pDriverName )
  {
LABEL_8:
    if ( *pFirstName != ‘\\’ )
      goto LABEL_10;
  }
  else
  {
    while ( *pFirstName != ‘\\’ )
    {
      –pFirstName;
      if ( pFirstName == pDriverName )
        goto LABEL_8;
    }
  }
  ++pFirstName;

 

然后从pRegistry注册表中去获取sysmon的策略规则

使用RtlQueryRegistryValues函数，填入5个RTL_QUERY_REGISTRY_TABLE结构体

 

RTL_QUERY_REGISTRY_TABLE QueryRegTable[5];

RtlInitUnicodeString(&g_ProcessAccessNamesRule,0);

  memset(QueryRegTable, 0, 560u);

  QueryRegTable[0].Flags = 1;

  QueryRegTable[0].Name =L”Parameters”;
  QueryRegTable[3].EntryContext =&OptionRulesv18;
  QueryRegTable[4].EntryContext =&hash_alogrithms;
  QueryRegTable[1].Flags = 304;
  QueryRegTable[1].Name =g_Name_ProcessAccessNames;
  QueryRegTable[1].EntryContext =&g_ProcessAccessNamesRule;
  QueryRegTable[1].DefaultType = 0×7000007;
  QueryRegTable[1].DefaultData =&unk_10015C34;
  QueryRegTable[1].DefaultLength = 4;
  QueryRegTable[2].Flags = 304;
  QueryRegTable[2].Name = L”ProcessAccessMasks”;
  QueryRegTable[2].EntryContext =&g_ProcessAccessMasksRule;
  QueryRegTable[2].DefaultType = 0×3000000;
  QueryRegTable[3].Flags = 304;
  QueryRegTable[3].Name =(PWSTR)&g_wOption;
  QueryRegTable[3].DefaultType = 0×4000000;
  QueryRegTable[4].Flags = 304;
  QueryRegTable[4].Name =(PWSTR)&g_wHashingalgorithm;
  QueryRegTable[4].DefaultType = 0×4000000;
  RtlQueryRegistryValues(0,g_SysmonRegisterPath.Buffer, QueryRegTable, 0, 0);
  if ( !g_ProcessAccessNamesRule.Buffer
    || g_ProcessAccessNamesRule.Length <= 2u
    || g_ProcessAccessNamesRule.MaximumLength<= 4u )
  {
   RtlFreeUnicodeString(&g_ProcessAccessNamesRule);
   RtlInitUnicodeString(&g_ProcessAccessNamesRule, 0);
  }

  g_OptionRules =(OptionRulesv18 >> 1) & 1; 

 

对应的注册表键分别是L”Parameters”、L”ProcessAccessNames”、L”ProcessAccessMasks” 、L” Option”、L” Hashingalgorithm”

然后再次获取L”Parameters”项下面的对应的L”Rules”的KeyValues信息，这里是驱动设置的规则。

下面展示出部分规则的数组

上面的过程结束后就开始判断操作系统是否支持flt

如果支持只实现IRP_MJ_CREATE、IRP_MJ_CLOSE 、IRP_MJ_DEVICE_CONTROL三个例程，后续会注册miniFlt过滤，如果不支持Flt就使用老的模式Sfilter的模式

 

DriverObject->MajorFunction[IRP_MJ_DEVICE_CONTROL]= (PDRIVER_DISPATCH)SysmonDispatchIrp;
  DriverObject->MajorFunction[IRP_MJ_CLOSE]= (PDRIVER_DISPATCH)SysmonDispatchIrp;
  DriverObject->MajorFunction[IRP_MJ_CREATE]= (PDRIVER_DISPATCH)SysmonDispatchIrp;
  if ( IsOpenPipeConnect &&!IsSupportFlt )

  {

   DriverObject->MajorFunction[IRP_MJ_CREATE] =(PDRIVER_DISPATCH)SysmonDispatchIrp;
    DriverObject->MajorFunction[1] =(PDRIVER_DISPATCH)SysmonDispatchIrp;
   DriverObject->MajorFunction[IRP_MJ_CLOSE] =(PDRIVER_DISPATCH)SysmonDispatchIrp;
    DriverObject->MajorFunction[IRP_MJ_READ]= (PDRIVER_DISPATCH)SysmonDispatchIrp;
    DriverObject->MajorFunction[IRP_MJ_WRITE]= (PDRIVER_DISPATCH)SysmonDispatchIrp;
   DriverObject->MajorFunction[IRP_MJ_QUERY_INFORMATION] =(PDRIVER_DISPATCH)SysmonDispatchIrp;
   DriverObject->MajorFunction[IRP_MJ_SET_INFORMATION] =(PDRIVER_DISPATCH)SysmonDispatchIrp;
   DriverObject->MajorFunction[IRP_MJ_QUERY_EA] =(PDRIVER_DISPATCH)SysmonDispatchIrp;
   DriverObject->MajorFunction[IRP_MJ_SET_EA] =(PDRIVER_DISPATCH)SysmonDispatchIrp;
   DriverObject->MajorFunction[IRP_MJ_FLUSH_BUFFERS] =(PDRIVER_DISPATCH)SysmonDispatchIrp;
   DriverObject->MajorFunction[IRP_MJ_QUERY_VOLUME_INFORMATION] =(PDRIVER_DISPATCH)SysmonDispatchIrp;
   DriverObject->MajorFunction[IRP_MJ_SET_VOLUME_INFORMATION] =(PDRIVER_DISPATCH)SysmonDispatchIrp;
    DriverObject->MajorFunction[IRP_MJ_DIRECTORY_CONTROL]= (PDRIVER_DISPATCH)SysmonDispatchIrp;
   DriverObject->MajorFunction[IRP_MJ_FILE_SYSTEM_CONTROL] =(PDRIVER_DISPATCH)SysmonDispatchIrp;
   DriverObject->MajorFunction[IRP_MJ_DEVICE_CONTROL] =(PDRIVER_DISPATCH)SysmonDispatchIrp;
    DriverObject->MajorFunction[IRP_MJ_INTERNAL_DEVICE_CONTROL]= (PDRIVER_DISPATCH)SysmonDispatchIrp;
   DriverObject->MajorFunction[IRP_MJ_SHUTDOWN] =(PDRIVER_DISPATCH)SysmonDispatchIrp;
   DriverObject->MajorFunction[IRP_MJ_LOCK_CONTROL] = (PDRIVER_DISPATCH)SysmonDispatchIrp;
   DriverObject->MajorFunction[IRP_MJ_CLEANUP] =(PDRIVER_DISPATCH)SysmonDispatchIrp;
   DriverObject->MajorFunction[IRP_MJ_CREATE_MAILSLOT] =(PDRIVER_DISPATCH)SysmonDispatchIrp;
   DriverObject->MajorFunction[IRP_MJ_QUERY_SECURITY] =(PDRIVER_DISPATCH)SysmonDispatchIrp;
   DriverObject->MajorFunction[IRP_MJ_SET_SECURITY] =(PDRIVER_DISPATCH)SysmonDispatchIrp;
   DriverObject->MajorFunction[IRP_MJ_POWER] =(PDRIVER_DISPATCH)SysmonDispatchIrp;
    DriverObject->MajorFunction[IRP_MJ_SYSTEM_CONTROL]= (PDRIVER_DISPATCH)SysmonDispatchIrp;

   DriverObject->MajorFunction[IRP_MJ_DEVICE_CHANGE] =(PDRIVER_DISPATCH)SysmonDispatchIrp;
   DriverObject->MajorFunction[IRP_MJ_QUERY_QUOTA] =(PDRIVER_DISPATCH)SysmonDispatchIrp;
    DriverObject->MajorFunction[IRP_MJ_SET_QUOTA]= (PDRIVER_DISPATCH)SysmonDispatchIrp;

  } 

 

然后就是常规过程，IoCreateDevice、IoCreateSymbolicLink。

然后根据操作系统是否支持FltRegisterFilter(Driver, &g_Registration, &g_pFilter);

具体创建了哪些minifilter，接着看结构体

 

OperationRegistrationdd IRP_MJ_CREATE  ; DATA XREF:.data:10015014↓o

.rdata:10013454                 dd 0

.rdata:10013458                 dd offset PreOperation

.rdata:1001345C                 dd offset PostOperation

.rdata:10013460                 dd 0

.rdata:10013464                 dd IRP_MJ_CLEANUP

.rdata:10013468                 dd 0

.rdata:1001346C                 dd offset PreOperation

.rdata:10013470                 dd offset PostOperation

.rdata:10013474                 dd 0

.rdata:10013478                 dd IRP_MJ_SET_INFORMATION

.rdata:1001347C                 dd 0

.rdata:10013480                 dd offset PreOperation

.rdata:10013484                 dd offset PostOperation

.rdata:10013488                 dd 0

.rdata:1001348C                 dd IRP_MJ_CLOSE

.rdata:10013490                 dd 0

.rdata:10013494                 dd offset PreOperation

.rdata:10013498                 dd offset PostOperation

.rdata:1001349C                 dd 0

.rdata:100134A0                 dd IRP_MJ_CREATE_NAMED_PIPE

.rdata:100134A4                 dd 0

.rdata:100134A8                 dd offset PreOperation

.rdata:100134AC                 dd offset PostOperation

.rdata:100134B0                 dd 0

.rdata:100134B4                 dd IRP_MJ_OPERATION_END

.rdata:100134B8                 dd 0

.rdata:100134BC                 dd 0

.rdata:100134C0                 dd 0

.rdata:100134C4                 dd 0

 

从上可以看到minifilter过滤了IRP_MJ_CREATE、IRP_MJ_CLEANUP、IRP_MJ_SET_INFORMATION、IRP_MJ_CLOSE、IRP_MJ_CREATE_NAMED_PIPE 

文件系统相关的注册完毕，然后就是设置一些进程、线程相关的回调函数例程

 

PsSetLoadImageNotifyRoutine(SysmonLoadImageNotifyRoutine);
PsSetCreateThreadNotifyRoutine(PsCreateThreadNotifyRoutine);
PsSetCreateProcessNotifyRoutine(PsCreateProcessNotifyRoutine, 0);

 

为了记录注册表sysmon还注册表注册表CmRegisterCallback(RegisterCallback, 0, &Cookie);回调，

为了记录进程open对象的事件注册了ob事件 

 

g_bIsRegisterCallback= 1;

  g_OperationRegistration.ObjectType =(POBJECT_TYPE *)PsProcessType;

  g_OperationRegistration.Operations = 1;

  g_OperationRegistration.PreOperation =PreProcessOperation;

  g_OperationRegistration.PostOperation =PostProcessOperation;

  g_CallbackRegistration.OperationRegistration= &g_OperationRegistration;

  *(_DWORD*)&g_CallbackRegistration.Version = 0×10100;

  g_CallbackRegistration.RegistrationContext =0;

  RtlInitUnicodeString(&g_CallbackRegistration.Altitude,L”1000″);

  Status =g_ObRegisterCallbacks(&g_CallbackRegistration, &RegistrationHandle);

 

为了获取管道的事件，它挂接了设备L\\Device\\NamedPipe，创建了L\\Device\\SysmonPipeFilter的过滤设备

至此sysmon的DriverEntry的初始化动作基本结束了。

二、          IRP_MJ_DEVICE_CONTROL例程 

Case 0×83400000:

打开驱动开启标志，并且获取且保存当前UI进程的句柄

Case  0×83400004：

Ring3请求事件信息，并返回到ring3的缓冲区

Case 0×83400008：

加载策略规则

Case 0x8340000C：

获取传入进程的相关信息（包括TokenUser、pTokenStatics、TokenGroup、TokenSeesion）

还会获取进程pImagePathName、pCommandLine、CurrentDirectory

获取进程的CreateTime

该事件类型为4或者1

三、文件信息的记录

Minifilter的PreOperation(PFLT_CALLBACK_DATA pData, PFLT_RELATED_OBJECTSFltObjects, PVOID *CompletionContext)例程为主要的判断逻辑例程，先判断当前FileObject的路径是否为管道路径，管道事件直接记录上报事件

特别判断下IRP_MJ_SET_INFORMATION、IRP_MJ_CLEANUP,并且分别上报_，注意在判断IRP_MJ_SET_INFORMATION的时候只记录了RequestorMode是1即USER_MODE，并且是设置FileBasicInformation的请求。

PreOperation处理完毕，则PostOperation(PFLT_CALLBACK_DATA pData, PFLT_RELATED_OBJECTSpFltFileObj, PVOID CompletionContext, int Flags)对前者处理的上下文CompletionContext进行记录日志或者释放的处理，以IRP_MJ_SET_INFORMATION为例，PostOPerate则对PreOperate的CompletionContext的数据进行上报。

四、注册表信息的记录

Sysmon初始化的时候注册了一个注册表过滤，CmRegisterCallback(RegisterCallback, 0, &Cookie);回调函数是NTSTATUS__stdcall RegisterCallback(PVOID CallbackContext, PVOID Argument1, PVOIDArgument2)，参数Argument1是过滤的注册表操作类型，sysmon过滤了0（RegNtDeleteKey   /  RegNtPreDeleteKey） 、4( RegNtRenameKey\RegNtPreRenameKey)、11（RegNtPostCreateKey）、15（RegNtPostDeleteKey）、16（RegNtPostSetValueKey）、17（RegNtPostDeleteValueKey）、19（RegNtPostRenameKey）27（RegNtPostCreateKeyEx）的注册表操作

五、进程操作过滤

Sysmon注册了进程操作过滤，g_ObRegisterCallbacks(&g_CallbackRegistration, &RegistrationHandle);，

他只记录操作类型为OB_OPERATION_HANDLE_CREATE，并且只记录A进程操作B进程，A和B不是同一个进程，注意RtlWalkFrameChain这个函数是获取当前操作线程的线程栈，KeQuerySystemTime(&pOpenInfo.CreateTime);是获取当前系统时间，并且会把这些信息上报。

六、其他重点技术细节

1.     进程模块的枚举

ZwQueryInformationProcess(ProcessHandle, ProcessBasicInformation,&ProcessInformation, 0x18u, 0)获取ProcessInformation的信息，从PebBaseAddress= ProcessInformation.PebBaseAddress;取得进程PEB的地址，在PEB结构中得到LDR的地址，LDR是进程加载模块的结构体，

 

struct _PEB

{

UCHAR InheritedAddressSpace;

UCHAR ReadImageFileExecOptions;

UCHAR BeingDebugged;

UCHAR BitField;

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;

unsigned __int32 ProcessInJob : 1;

unsigned __int32 ProcessInitializing : 1;

unsigned __int32 ReservedBits0 : 30;

union

{

PVOID KernelCallbackTable;

PVOID UserSharedInfoPtr;

};

ULONG SystemReserved[1];

。。。。。。

} 

 

PPEB_LDR_DATA Ldr;这个就是加载模块的结构，有三种加载表内存加载表，加载顺序表，初始化加载表从中可以枚举出模块信息。

 

struct _PEB_LDR_DATA

{

ULONG Length;

UCHAR Initialized;

PVOID SsHandle;

LIST_ENTRY InLoadOrderModuleList;

LIST_ENTRY InMemoryOrderModuleList;

LIST_ENTRY InInitializationOrderModuleList;

};

 

2.     进程参数的获取

大致可以看到如下，首先要KeStackAttachProcess进程的空间，然后获取PEB地址，从PEB中的到ProcessParameters的结构

ProcessParameters结构如下：

 

struct _RTL_USER_PROCESS_PARAMETERS

{

ULONG MaximumLength;

ULONG Length;

ULONG Flags;

ULONG DebugFlags;

PVOID ConsoleHandle;

ULONG ConsoleFlags;

PVOID StandardInput;

PVOID StandardOutput;

PVOID StandardError;

CURDIR CurrentDirectory;

UNICODE_STRING DllPath;

UNICODE_STRINGImagePathName;

UNICODE_STRING CommandLine;

PVOID Environment;

ULONG StartingX;

ULONG StartingY;

ULONG CountX;

ULONG CountY;

ULONG CountCharsX;

ULONG CountCharsY;

ULONG FillAttribute;

ULONG WindowFlags;

ULONG ShowWindowFlags;

UNICODE_STRING WindowTitle;

UNICODE_STRING DesktopInfo;

UNICODE_STRING ShellInfo;

UNICODE_STRING RuntimeData;

RTL_DRIVE_LETTER_CURDIRCurrentDirectores[32];

ULONG EnvironmentSize;

}; 

 

可以看到该结构中进程参数相关的各种信息。 

3.     进程Token相关信息的获取

都是通过ZwQueryInformationToken函数去获取，只是是使用不同的ClassInformation类去获取，定义如下

 

typedef enum _TOKEN_INFORMATION_CLASS {

  TokenUser                             ,

  TokenGroups                           ,

  TokenPrivileges                       ,

  TokenOwner                            ,

  TokenPrimaryGroup                     ,

  TokenDefaultDacl                      ,

  TokenSource                           ,

  TokenType                             ,

  TokenImpersonationLevel               ,

  TokenStatistics                       ,

  TokenRestrictedSids                   ,

  TokenSessionId                        ,

  TokenGroupsAndPrivileges              ,

  TokenSessionReference                 ,

  TokenSandBoxInert                     ,

  TokenAuditPolicy                      ,

  TokenOrigin                           ,

  TokenElevationType                    ,

  TokenLinkedToken                      ,

  TokenElevation                        ,

  TokenHasRestrictions                  ,

  TokenAccessInformation                ,

  TokenVirtualizationAllowed            ,

  TokenVirtualizationEnabled            ,

  TokenIntegrityLevel                   ,

  TokenUIAccess                         ,

  TokenMandatoryPolicy                  ,

  TokenLogonSid                         ,

  TokenIsAppContainer                   ,

  TokenCapabilities                     ,

  TokenAppContainerSid                  ,

  TokenAppContainerNumber               ,

  TokenUserClaimAttributes              ,

  TokenDeviceClaimAttributes            ,

 TokenRestrictedUserClaimAttributes   ,

 TokenRestrictedDeviceClaimAttributes ,

  TokenDeviceGroups                     ,

  TokenRestrictedDeviceGroups           ,

  TokenSecurityAttributes               ,

  TokenIsRestricted                     ,

  TokenProcessTrustLevel                ,

  TokenPrivateNameSpace                 ,

  TokenSingletonAttributes              ,

  TokenBnoIsolation                     ,

  TokenChildProcessFlags                ,

  MaxTokenInfoClass

} TOKEN_INFORMATION_CLASS, *PTOKEN_INFORMATION_CLASS;

 

需要获取那个就可以选择那一个。

 

本文大致讲解完毕，内部还有很多很有意思的技术细节由于篇幅原因，读者可以自己深入挖掘，在做一个产品的时候，我们可以分析他人的产品，不仅可以了解他人的产品的长处和不足，同时也可以补充自己产品的不足的之处，一个好的产品就是在不断的琢磨研究与推翻，更重要的是细节的体现才能做好产品。