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微软轻量级系统监控工具sysmon原理与实现(2)
2018-09-18 20:47:56

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

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;

1537273661_5ba0ef3d15daa.png!small然后从pRegistry注册表中去获取sysmon的策略规则

1537273679_5ba0ef4f48d13.png!small

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 = 0x7000007;   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 = 0x3000000;   QueryRegTable[3].Flags = 304;   QueryRegTable[3].Name =(PWSTR)&g_wOption;   QueryRegTable[3].DefaultType = 0x4000000;   QueryRegTable[4].Flags = 304;   QueryRegTable[4].Name =(PWSTR)&g_wHashingalgorithm;   QueryRegTable[4].DefaultType = 0x4000000;   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”

1537273707_5ba0ef6b1e738.png!small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。

1537273723_5ba0ef7bb31e3.png!small下面展示出部分规则的数组

1537273737_5ba0ef89a6def.png!small

上面的过程结束后就开始判断操作系统是否支持flt

1537273756_5ba0ef9ccfb28.png!small

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。

1537273784_5ba0efb85f136.png!small然后根据操作系统是否支持FltRegisterFilter(Driver, &g_Registration, &g_pFilter);

1537273797_5ba0efc5f03b0.png!small具体创建了哪些minifilter,接着看结构体

1537273811_5ba0efd3d1cee.png!small

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_CREATEIRP_MJ_CLEANUPIRP_MJ_SET_INFORMATIONIRP_MJ_CLOSEIRP_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);

1537273834_5ba0efea27450.png!small

1537273843_5ba0eff3598b2.png!small为了记录注册表sysmon还注册表注册表CmRegisterCallback(RegisterCallback, 0, &Cookie);回调,

1537273858_5ba0f002545aa.png!small

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 = 0x10100;

  g_CallbackRegistration.RegistrationContext =0;

  RtlInitUnicodeString(&g_CallbackRegistration.Altitude,L"1000");

  Status =g_ObRegisterCallbacks(&g_CallbackRegistration, &RegistrationHandle);

1537273875_5ba0f013e196b.png!small

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

1537273892_5ba0f0242f271.png!small至此sysmon的DriverEntry的初始化动作基本结束了。

二、IRP_MJ_DEVICE_CONTROL例程

Case 0x83400000:

打开驱动开启标志,并且获取且保存当前UI进程的句柄

1537273918_5ba0f03edab05.png!small1537273924_5ba0f04479633.png!small

Case  0x83400004

Ring3请求事件信息,并返回到ring3的缓冲区

1537273940_5ba0f0549713b.png!small

Case 0x83400008

加载策略规则

1537273955_5ba0f063760e1.png!small

Case 0x8340000C

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

1537273969_5ba0f071a979e.png!small1537273976_5ba0f07895880.png!small还会获取进程pImagePathName、pCommandLine、CurrentDirectory

1537273987_5ba0f083ca84a.png!small获取进程的CreateTime

1537273999_5ba0f08fd45b6.png!small该事件类型为4或者1

1537274011_5ba0f09b971da.png!small

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

1537274031_5ba0f0afb7199.png!small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。

1537274045_5ba0f0bd0334c.png!small1537274050_5ba0f0c2091c3.png!smallPreOperation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。

1537274063_5ba0f0cfe72bf.png!small

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

1537274082_5ba0f0e225aef.png!small1537274087_5ba0f0e702125.png!small1537274092_5ba0f0ec86889.png!small

五、进程操作过滤

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

1537274145_5ba0f121bf908.png!small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

1537274172_5ba0f13c574d9.png!small

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;

};

1537274198_5ba0f15681b1d.png!small

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

1537274218_5ba0f16a0be0d.png!small

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

1537274241_5ba0f18161a94.png!small

1537274254_5ba0f18eb0ef7.png!small1537274259_5ba0f1936a8f2.png!small1537274263_5ba0f197c8f74.png!small

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。


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