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 = 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”
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 = 0x10100; 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 0x83400000:
打开驱动开启标志，并且获取且保存当前UI进程的句柄
Case 0x83400004：
Ring3请求事件信息，并返回到ring3的缓冲区
Case 0x83400008：
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。
来源：freebuf.com 2018-09-18 20:47:56 by: 浪子_三少
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