понедельник, 17 августа 2020 г.

etw part 4: _TlgProvider_t in kernel

let's continue to dissect ETW (parts 1,2 & 3)
Basically structure _TlgProvider_t in kernel almost the same as in user mode but field RegHandle points to ETW_REG_ENTRY. You can easily find them using simple search for known guids - I made PoC for arm64 (and for ndis.sys too)

kernel contains following tlg providers:
  • Microsoft.Windows.TlgAggregateInternal, GUID 703FCC13-B66F-5868-DDD9-E2DB7F381FFB
  • KernelExecutive, GUID 8944A53C-A561-4E53-A0C6-D565414745FC
  • Microsoft.Windows.Kernel.BootEnvironment, GUID 23B76A75-CE4F-56EF-F903-C3A2D6AE3F6B
  • MSTelCov, GUID 1DD9B8C9-E078-4075-B9DE-4E5125071A18
  • KernelProcess, GUID 2839FF94-8F12-4E1B-82E3-AF7AF77A450F
  • KernelGeneral, GUID 7614521C-4D0B-4341-BFC9-873082C0F1D3
  • Microsoft-Windows-Kernel-Vm, GUID B7FBD4E0-FA8F-4C58-B0FB-3CC227B86ED6. Located in section ALMOSTRO
  • Microsoft.Windows.Kernel.Security, GUID 09A69A38-2680-4BFA-AD01-792AD63A4FF2
  • Microsoft.Windows.Security.Capabilities, GUID 27A8FDF4-9B77-575B-BE3B-E7163EF159BB
  • Microsoft.Windows.Kernel.ProcessSubsystem, GUID C59673D8-B796-58DF-FBF8-A70BAD656DCA
  • Microsoft.Windows.Kernel.Ttm, GUID 5E753E4D-2B0D-4451-B8F9-0F1253CA0B44. Located in section PAGEDATA
  • Microsoft.Windows.Kernel.Power.PowerTransitions, GUID 050BF899-DA06-4852-A63A-81E6B9A1C74F
  • Microsoft.Windows.Kernel.Power.DirectedDrips, GUID 0D2ED727-38A0-4B2B-9F7E-EC79B5EC4AA5. Located in section PAGEDATA
  • Microsoft.Windows.Kernel.Power, GUID 63BCA7A1-77EC-4EA7-95D0-98D3F0C0EBF7
  • Microsoft.Windows.Kernel.Power.DiagFxAccounting, GUID 57D04B7B-550A-49A2-ABCC-A7FA15598A30
  • Microsoft.Windows.Kernel.ObjectManager, GUID F39412D1-C9FD-5E79-8A82-9C9CBD8CA809
  • Microsoft-Windows-Kernel-Mm, GUID 7E9E8B9C-406C-5D73-E566-0F50EA3ADE3E
  • Microsoft.Windows.Kernel.Kernel, GUID 061C37C3-1363-5C1B-B8ED-F3D8F74633CE
  • Microsoft.Windows.Kernel.PnP, GUID 6C0EBBBB-C292-457D-9675-DFCC1C0D58B0
  • Microsoft.Windows.Kernel.DeviceConfig, GUID C8BDE9FF-F31F-59DC-6C27-CA37C516ADA5
  • Microsoft.Windows.Kernel.SysEnv, GUID A9FDF37B-D72D-4051-A3CD-D422103CE079
  • Microsoft.Windows.Kernel.LiveDump, GUID A4D16FC5-D1CF-4D72-A055-25F3EB02A70E
  • Microsoft.Windows.Kernel.Dump, GUID A51EE86B-8EA5-454C-9A7D-37B6655A535D
  • IumTelemetryProvider, GUID 73A33AB2-1966-4999-8ADD-868C41415269
  • Microsoft.Windows.Containers.RegistryVirtualization, GUID 252D9ECC-1C9F-4917-8760-F872A83BF018
  • Microsoft.Windows.Kernel.FeatureConfigurationManager, GUID F7E83426-2B81-58F9-C5D4-F2DB6D0AD473
  • Microsoft.Windows.Kernel.Registry, GUID E9EAF418-0C07-464C-AD14-A7F353349A00
  • Microsoft.Windows.FileSystem.Cache, GUID 74093E1D-DBE3-4019-B97D-54EDCB02CFED
  • Microsoft.Windows.Kernel.HAL, GUID 0F51C5A7-0E76-47A5-BEDE-7CF62C5822F6

So what bad guys can do knowing addresses of this _TlgProvider_t?

вторник, 28 июля 2020 г.

etw tracing handles in kernel

let's continue to dissect ETW (part 1 & 2). This time consider how tracing is implemented in the kernel itself. I made PoC to find all tracing handles in arm64 kernel and now give short explanation of what each of them is used for

EtwpEventTracingProvRegHandle

GUID B675EC37-BDB6-4648-BC92-F3FDC74D3CA2 (EventTracingProvGuid). Used in lots of internal etw related functions like EtwpTraceStackWalk, EtwpWriteUserEvent, EtwpFailLogging, NtTraceEvent, WmiTraceMessage, EtwWriteEx, EtwWrite etc

EtwKernelProvRegHandle

GUID A68CA8B7-004F-D7B6-A698-07E2DE0F1F5D (KernelProvGuid). Used for kernel tracing in functions like SeLogAccessFailure, CmpReorganizeHive, SepSetTokenUserAndGroups, EtwTraceSystemTimeChange, EtwTraceTimeZoneInformationRefresh etc

EtwpPsProvRegHandle

GUID 22FB2CD6-0E7B-422B-A0C7-2FAD1FD0E716 (PsProvGuid). Used for tracing processes subsystem activity in functions like PsImpersonateContainerOfThread, PspRevertContainerImpersonation, PspSetJobIoRateControl, PspSetJobIoAttribution, EtwTraceFreezeThawProcess etc

EtwpNetProvRegHandle

GUID 7DD42A49-5329-4832-8DFD-43D979153A88 (NetProvGuid). Used only in function EtwpTraceNetwork which assigning as callback in WmiSetNetworkNotify

пятница, 24 июля 2020 г.

_TlgProvider_t

let's continue to dissect ETW and consider one of the many usermode tracing structures - _TlgProvider_t. It is even officially documented in platform sdk in header TraceLoggingProvider.h (sample of using):
struct _TlgProvider_t
{
    UINT32 LevelPlus1;
    UINT16 const UNALIGNED* ProviderMetadataPtr; // Points to the RemainingSize member of provider metadata.
    ULONGLONG KeywordAny;
    ULONGLONG KeywordAll;
    REGHANDLE RegHandle;
    TLG_PENABLECALLBACK EnableCallback;
    PVOID CallbackContext;
};


purpose of the fields is pretty obvious except RegHandle - it's not real HANDLE but some structure with address to ETW_REGISTRATION_ENTRY.

How we can find it? Field ProviderMetadataPtr is pointer to _TlgProviderMetadata_t:
struct _TlgProviderMetadata_t
{
    UINT8 Type; // = _TlgBlobProvider3
    GUID ProviderId;
#define _TLG_PROVIDER_METADATA_PREAMBLE 16 // = sizeof(ProviderId)
    UINT16 RemainingSize; // = sizeof(RemainingSize + ProviderName)
    /*
    char ProviderName[sizeof("providerName")]; // UTF-8 nul-terminated provider name
    for each additional chunk of metadata {
        UINT16 ChunkSize;
        UINT8 ChunkType;
        UINT8 ChunkData[ChunkSize - 3];
    }
    */
};

actually it points to _TlgProviderMetadata_t.RemainingSize. Algo is simple - if you know provider GUID you can locate _TlgProviderMetadata_t.ProviderId by signature (usually located in .text or .rdata sections) and then find in .data section _TlgProvider_t whose ProviderMetadataPtr points to _TlgProviderMetadata_t.RemainingSize. I made simple PoC for arm64

How we can abuse it? Let`s see how this structures used for example in combase.dll:

суббота, 11 июля 2020 г.

what`s wrong with Etw

Disclaimer: as I am aware that the given code examples can be dangerous for Etw-based EDR products - all code was made for least popular version of windows - for arm64

Let's assume that we have some application that wants to hide its activity from trace logs - not necessary evil or malicious, for example just to hide used algos or bit paranoid like crypto-wallet. Lets see how can it achieve this (I have no desire to consider trivial cases like removing records from eventlog)

Semiofficial ways

  1. Sure all you readed about COMPlus_ETWEnabled but there is also promising COMPlus_ETWFlags 
  2. You can switch off etw tracing for services.exe with registry key TracingDisabled in Software\Microsoft\Windows NT\CurrentVersion\Tracing\SCM\Regular
  3. And the same for rpcrt4.dll with registry key ExtErrorInformation in HKLM\Software\Policies\Microsoft\Windows NT\Rpc
Actually there are virtually countless ways to do it. And many perhaps not documented bcs was written in Ms by some poor intern who was kicked out in the cold after another review 10+ years ago. I struggled with temptation to make clickbait caption like "99% of windows dlls can disable etw logs" but it`s close to the truth

Patching

вторник, 30 июня 2020 г.

search references in arm64 code

Let's assume that you want to find address of non-exported CrashdmpCallTable in kernel. Usual old school way is to find unicode string "\SystemRoot\System32\Drivers\crashdmp.sys" and then to find reference to in .text section - if you are lucky enough this will be somewhere in middle of function IopLoadCrashdumpDriver. But on arm64 loading of address splitted in pair of instructions and even worse - values depends from address of instruction. Let`s see how it looks:

.text:00000001401AF700 6A 01 00 90     ADRP  X10, #aSystemrootSy_0@PAGE ; "\\SystemRoot\\System32\\Drivers\\crashd"...
.text:00000001401AF704 48 C1 09 91     ADD   X8, X10, #aSystemrootSy_0@PAGEOFF ; "\\SystemRoot\\System32\\Drivers\\crashd"...


Output from cmdline disasm for each of opcodes:
armpatched.exe 6A010090
Disassembled: adrp x10, 2c000

        This instruction is AD_INSTR_ADRP and is part of group AD_G_DataProcessingImmediate
        This instruction has 4 decode fields (from left to right):
                0x1, 0, 0xb, 0xa
        This instruction has 2 operands (from left to right):
                This operand is of type AD_OP_REG
                        Register: x10 size 40
                This operand is of type AD_OP_IMM
                        Immediate type: AD_IMM_ULONG
                        Value: 0x2c000

and
armpatched.exe 48C10991
Disassembled: add x8, x10, #0x270

        This instruction is AD_INSTR_ADD and is part of group AD_G_DataProcessingImmediate
        This instruction has 7 decode fields (from left to right):
                0x1, 0, 0, 0, 0x270, 0xa, 0x8
        This instruction has 3 operands (from left to right):
                This operand is of type AD_OP_REG
                        Register: x8 size 40
                This operand is of type AD_OP_REG
                        Register: x10 size 40
                This operand is of type AD_OP_IMM
                        Immediate type: AD_IMM_ULONG
                        Value: 0x270


What are the options?

пятница, 19 июня 2020 г.

sve/sve2 instructions for arm64

Today I finished adding of sve/sve2 instructions to my pet-project armpatched
I used as reference ISA_A64_xml_futureA-2019-09_OPT.pdf
Sure code is full of bugs, incomplete and has terrible style - all what you can expect from 7KLOC on plain C
Known problems:
  • since my main goal was code analysis disasm strings looks not very good - for example I totally emit register size suffixes (although size storing in op_reg.sz)
  • I don`t know for what used "fields" so they filled in voluntary random order
Zx registers marked as floating point with op_reg.fp == 2 and Px registers with op_reg.fp == 3
Code was tested on all possible instructions and looks like it does not crash. Bcs it seems that some instructions use floating point you must use KeSaveFloatingPointState/KeRestoreFloatingPointState in case of kernel mode