windows deep internals

пятница, 8 января 2016 г.

CFG with LLVM

On holydays I read book "LLVM Cookbook" (not very good - lots of meaningless copy-pasted code blocks are annoying) and played a bit with fresh llvm-3.7.1 (was released 5 january)

So I decided to check whether it is possible to implement MS CFG in llvm. I have two news - good and bad, as usually

Good: yes, you can easy add instrumentation in llvm - just add some plugin for IR derived from FunctionPass and add call to your guard_check_icall before each VTBL call (or even on any ptr call). I think it will take one day for any CS-student

Bad: you need integration with MS linker and it seems that support of CFG in COFF files is totally undocumented. LLVM itself cannot make load_config and even more - their definition of coff_load_configuration in include\llvm\Object\COFF.h has no fields for CFG (like GuardCFCheckFunctionPointer and GuardCFFunctionTable)

суббота, 5 декабря 2015 г.

WNF identifiers

I have made a mistake in my previous article about WNF. It seems that WNF idenificators are not standard IID but pair of DWORDs, so struct my_wnf_item actually looks like:

// struct can be ripped from ntdll!RtlpCreateWnfNameSubscription
struct wnf_name
{
/*  0x0 */  DWORD tag; // 0x980912 under x64, 0x700912 under x86
/*  0x4 */  DWORD unk4;
/*  0x8 */  DWORD unk8;
/*  0xC */  DWORD unkC;
/* 0x10 */  DWORD id1;
/* 0x14 */  DWORD id2;
};

struct my_wnf_item
{
  LIST_ENTRY List; // linked list of my_wnf_item
  wnf_name *wnfId;
  PBYTE notify;
};

Sample from windows 10 build 10586:

CheckProcess PID 420 (csrss.exe):
PEB.NtGlobalFlag: 0
PEB.Ldr: 00007FF946ED5200
PEB.GdiSharedHandleTable: 000001EFD8BC0000
WnfRoot: 000001EFD8A05BF0
 Wnf[0] at 000001EFD8A08238: id1 A3BC4035 id2 96003D (WNF_PNPA_PORTS_CHANGED_SESSION) - 00007FF943335410 (C:\Windows\system32\winsrv.DLL)
 Wnf[1] at 000001EFD8A080C8: id1 A3BC3875 id2 96003D (WNF_PNPA_PORTS_CHANGED) - 00007FF943335410 (C:\Windows\system32\winsrv.DLL)
 Wnf[2] at 000001EFD8A07F58: id1 A3BC3035 id2 96003D (WNF_PNPA_HARDWAREPROFILES_CHANGED_SESSION) - 00007FF943335410 (C:\Windows\system32\winsrv.DLL)
 Wnf[3] at 000001EFD8A07DE8: id1 A3BC2875 id2 96003D (WNF_PNPA_HARDWAREPROFILES_CHANGED) - 00007FF943335410 (C:\Windows\system32\winsrv.DLL)
 Wnf[4] at 000001EFD8A07C78: id1 A3BC2035 id2 96003D (WNF_PNPA_VOLUMES_CHANGED_SESSION) - 00007FF943335410 (C:\Windows\system32\winsrv.DLL)
 Wnf[5] at 000001EFD8A07B08: id1 A3BC1875 id2 96003D (WNF_PNPA_VOLUMES_CHANGED) - 00007FF943335410 (C:\Windows\system32\winsrv.DLL)
 Wnf[6] at 000001EFD8A04EF8: id1 A3BC1035 id2 96003D (WNF_PNPA_DEVNODES_CHANGED_SESSION) - 00007FF943335410 (C:\Windows\system32\winsrv.DLL)
 Wnf[7] at 000001EFD8A05058: id1 A3BC0875 id2 96003D (WNF_PNPA_DEVNODES_CHANGED) - 00007FF943335410 (C:\Windows\system32\winsrv.DLL)

List of some WNF identifiers (sure is not completed):

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