I added a section to this executable
external link to download the executable it is winmine from windows xp
using cff explorer
the only modification done to the executable is adding a section i have not editied the executable manually or otherwise cff explorer successfully adds the section
but if i execute the resulting executable
I get an error :
"Error starting the application (0xc000007b) ..."
i would like to understand why the modified application is crashing
blabb's answer may be right as far as it relates to what's wrong in the edited binary, but the suggestion to use a kernel debugger to find the problematic stack is way off course.
For this demonstration I use Windows XP rather than 7 like you. The effects are pretty much the same except that the NTSTATUS on XP is 0xC0000135 rather than 0xC000007B.
We open WinDbg and execute the binary:
Microsoft (R) Windows Debugger Version 6.12.0002.633 X86 Copyright (c) Microsoft Corporation. All rights reserved. CommandLine: "C:\Documents and Settings\Administrator\My Documents\Downloads\Winmine - XP - копия.exe" Symbol search path is: *** Invalid *** **************************************************************************** * Symbol loading may be unreliable without a symbol search path. * * Use .symfix to have the debugger choose a symbol path. * * After setting your symbol path, use .reload to refresh symbol locations. * **************************************************************************** Executable search path is: ModLoad: 01000000 01021000 winmine.exe ModLoad: 7c900000 7c9b2000 ntdll.dll ModLoad: 7c800000 7c8f6000 C:\WINDOWS\system32\kernel32.dll A message box pops up:
We don't dismiss the message box. Instead we break in WinDbg:
Break-in sent, waiting 30 seconds... WARNING: Break-in timed out, suspending. This is usually caused by another thread holding the loader lock (b58.e64): Wake debugger - code 80000007 (first chance) eax=c0000135 ebx=00000000 ecx=00000a2b edx=00090608 esi=7ffdfc00 edi=c0000135 eip=7c90e514 esp=0006f6f0 ebp=0006f7d4 iopl=0 nv up ei pl nz na po cy cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000203 *** ERROR: Symbol file could not be found. Defaulted to export symbols for ntdll.dll - ntdll!KiFastSystemCallRet: 7c90e514 c3 ret Yes, it actually takes these 30 seconds.
Let's look at the stack:
0:000> ~* k . 0 Id: b58.e64 Suspend: 1 Teb: 7ffdf000 Unfrozen ChildEBP RetAddr WARNING: Stack unwind information not available. Following frames may be wrong. 0006f7d4 7c91c880 ntdll!KiFastSystemCallRet 0006fa34 7c9246f2 ntdll!LdrDisableThreadCalloutsForDll+0xce 0006fa78 7c92469b ntdll!sprintf+0x13e 0006fa98 7c9247d5 ntdll!sprintf+0xe7 0006fb14 7c920244 ntdll!sprintf+0x221 0006fc94 7c91fad7 ntdll!RtlInitMemoryStream+0x2e8 0006fd1c 7c90e457 ntdll!RtlLookupElementGenericTable+0x80 00000000 00000000 ntdll!KiUserApcDispatcher+0x7 1 Id: b58.324 Suspend: 1 Teb: 7ffde000 Unfrozen ChildEBP RetAddr WARNING: Stack unwind information not available. Following frames may be wrong. 0028fc98 7c901046 ntdll!KiFastSystemCallRet 0028fd18 7c90e457 ntdll!RtlEnterCriticalSection+0x46 00000000 00000000 ntdll!KiUserApcDispatcher+0x7 The second thread is probably used to communicate with CSRSS to display the message or something like that and it's not really interesting. The first thread is what's important, and its symbols are all messed up.
Let's fix that:
0:000> lm start end module name 01000000 01021000 winmine (deferred) 7c800000 7c8f6000 kernel32 (deferred) 7c900000 7c9b2000 ntdll (export symbols) C:\WINDOWS\system32\ntdll.dll 0:000> .symfix+ 0:000> .reload /f Reloading current modules ... 0:000> lm start end module name 01000000 01021000 winmine (pdb symbols) C:\Documents and Settings\Administrator\Desktop\debugger_x86\sym\winmine.pdb\3B7D84751\winmine.pdb 7c800000 7c8f6000 kernel32 (pdb symbols) C:\Documents and Settings\Administrator\Desktop\debugger_x86\sym\kernel32.pdb\A02FC3EC19B4474FB75641AF4C5B031C2\kernel32.pdb 7c900000 7c9b2000 ntdll (pdb symbols) C:\Documents and Settings\Administrator\Desktop\debugger_x86\sym\ntdll.pdb\CEFC0863B1F84130A11E0F54180CD21A2\ntdll.pdb 0:000> k ChildEBP RetAddr 0006f6ec 7c90d9ca ntdll!KiFastSystemCallRet 0006f6f0 7c9423a9 ntdll!NtRaiseHardError+0xc 0006f7d4 7c91c880 ntdll!LdrpMapDll+0x1b8 0006fa34 7c9246f2 ntdll!LdrpLoadImportModule+0x174 0006fa78 7c92469b ntdll!LdrpHandleOneNewFormatImportDescriptor+0x53 0006fa98 7c9247d5 ntdll!LdrpHandleNewFormatImportDescriptors+0x20 0006fb14 7c920244 ntdll!LdrpWalkImportDescriptor+0x19e 0006fc94 7c91fad7 ntdll!LdrpInitializeProcess+0xe1c 0006fd1c 7c90e457 ntdll!_LdrpInitialize+0x183 00000000 00000000 ntdll!KiUserApcDispatcher+0x7 You get pretty much the same stack blabb got, without any kernel debugging. Amazing, even if I say so myself.
By the way, the second thread's stack is still uninteresting:
0:000> ~1 k ChildEBP RetAddr 0028fc0c 7c90df5a ntdll!KiFastSystemCallRet 0028fc10 7c919b23 ntdll!NtWaitForSingleObject+0xc 0028fc98 7c901046 ntdll!RtlpWaitForCriticalSection+0x132 0028fca0 7c924d2d ntdll!RtlEnterCriticalSection+0x46 0028fd18 7c90e457 ntdll!_LdrpInitialize+0xf0 00000000 00000000 ntdll!KiUserApcDispatcher+0x7 We can look at the parameters to these functions and see the problem in the bound import table:
0:000> kb ChildEBP RetAddr Args to Child 0006f6ec 7c90d9ca 7c9423a9 c0000135 00000002 ntdll!KiFastSystemCallRet 0006f6f0 7c9423a9 c0000135 00000002 00000003 ntdll!NtRaiseHardError+0xc 0006f7d4 7c91c880 00020498 7ffdfc00 00000000 ntdll!LdrpMapDll+0x1b8 0006fa34 7c9246f2 00020498 010002ab 01000000 ntdll!LdrpLoadImportModule+0x174 0006fa78 7c92469b 7ffd6000 00020498 00191ee0 ntdll!LdrpHandleOneNewFormatImportDescriptor+0x53 0006fa98 7c9247d5 7ffd6000 00020498 00191ee0 ntdll!LdrpHandleNewFormatImportDescriptors+0x20 0006fb14 7c920244 00020498 00191ee0 7ffdf000 ntdll!LdrpWalkImportDescriptor+0x19e 0006fc94 7c91fad7 0006fd30 7c900000 0006fce0 ntdll!LdrpInitializeProcess+0xe1c 0006fd1c 7c90e457 0006fd30 7c900000 00000000 ntdll!_LdrpInitialize+0x183 00000000 00000000 00000000 00000000 00000000 ntdll!KiUserApcDispatcher+0x7 0:000> du 7ffdfc00 7ffdfc00 "NEL32.dll" 0:000> db 010002ab 010002ab 4e 45 4c 33 32 2e 64 6c-6c 00 47 44 49 33 32 2e NEL32.dll.GDI32. 010002bb 64 6c 6c 00 55 53 45 52-33 32 2e 64 6c 6c 00 53 dll.USER32.dll.S 010002cb 48 45 4c 4c 33 32 2e 64-6c 6c 00 57 49 4e 4d 4d HELL32.dll.WINMM 010002db 2e 64 6c 6c 00 43 4f 4d-43 54 4c 33 32 2e 64 6c .dll.COMCTL32.dl 010002eb 6c 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 l............... 010002fb 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................ 0100030b 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................ 0100031b 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................ If you want to trace through the loading process rather than only see the stack after the fail you can do that too with the user mode debugger.
Let's dismiss the message box, and tell WinDbg to break at process creation instead of at the so-called initial breakpoint which happens only after the static imports have been resolved:
0:000> sxe cpr 0:000> .restart CommandLine: "C:\Documents and Settings\Administrator\My Documents\Downloads\Winmine - XP - копия.exe" Symbol search path is: srv* Executable search path is: eax=01003e21 ebx=7ffd4000 ecx=7c910060 edx=7c90e920 esi=0078c60c edi=00ecf554 eip=7c810735 esp=0006fffc ebp=7c91005d iopl=0 nv up ei pl nz na po nc cs=001b ss=0023 ds=0023 es=0023 fs=0038 gs=0000 efl=00000200 7c810735 ?? ??? 0:000> lm start end module name 01000000 01021000 winmine (deferred) 0:000> k ChildEBP RetAddr WARNING: Frame IP not in any known module. Following frames may be wrong. 0006fff8 00000000 0x7c810735 OMG what is this?! Only winmine loaded? But we know the ntdll is mapped into every Win32 process right from the start.
Well, ntdll is actually mapped, but the debugger still didn't get a debug event about it. That's how early we're in the process initialization process.
We can wait for this event by using sxe ld ntdll (or sxe ld), or we can force WinDbg to be made aware ntdll. Then we can put breakpoints on ntdll!LdrpHandleOneNewFormatImportDescriptor etc.:
0:000> sxe ld ntdll 0:000> g ModLoad: 7c900000 7c9b2000 ntdll.dll eax=01003e21 ebx=7ffd4000 ecx=7c910060 edx=7c90e920 esi=0078c60c edi=00ecf554 eip=7c810735 esp=0006fffc ebp=7c91005d iopl=0 nv up ei pl nz na po nc cs=001b ss=0023 ds=0023 es=0023 fs=0038 gs=0000 efl=00000200 7c810735 ?? ??? 0:000> lm start end module name 01000000 01021000 winmine (deferred) 7c900000 7c9b2000 ntdll (deferred) 0:000> .symfix+ 0:000> .reload /f Reloading current modules .. 0:000> bu ntdll!LdrpHandleOneNewFormatImportDescriptor 0:000> bl 0 e 7c9246ad 0001 (0001) 0:**** ntdll!LdrpHandleOneNewFormatImportDescriptor 0:000> g Breakpoint 0 hit eax=0006faac ebx=7ffd4000 ecx=000000b4 edx=0000415c esi=01000248 edi=00000001 eip=7c9246ad esp=0006fa7c ebp=0006fa98 iopl=0 nv up ei pl nz na pe nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000206 ntdll!LdrpHandleOneNewFormatImportDescriptor: 7c9246ad 8bff mov edi,edi There's absolutely no need for kernel debugging here.
Everything we need is available from user mode.
your exe is having bound import table address at 0x248 (at the end of last section ) and cff explorer is overwriting those entries (BOUND IMPORT From kernel32.dll with timestamp
5.1.2600.0 3B7DFE0E (18th August 2001) 926,720 Windows XP that is why it is crashing
dumpbin /headers Winmine_test.exe | grep -i bound 248 [ A8] RVA [size] of Bound Import Directory original exe the bound import modname is @ offset 0x48 from start which is msvcrt.dll
C:\wdscr\cfftest>xxd -s 0x248 -g4 -l 0xa8 "W 0000248: 0efe7d3b 48000000 0efe7d3b 53000000 0000258: 0efe7d3b 60000000 0efe7d3b 6d000000 0000268: 0efe7d3b 77000000 0ffe7d3b 82000000 0000278: 13fe7d3b 8e000000 32fe7d3b 98000000 0000288: 00000000 00000000 6d737663 72742e64 but in cff explorer edited exe the bound import table is corrupted
xxd -s 0x248 -g 4 -l 0xa8 Winmine_test.exe 0000248: 2e746573 **74000000** 00100000 00000200 .test........... 0000258: 00100000 00d40100 00000000 00000000 ................ 0000268: 00000000 200000e0 0ffe7d3b 82000000 .... .....};.... 0000278: 13fe7d3b 8e000000 32fe7d3b 98000000 ..};....2.};.... 0000288: 00000000 00000000 6d737663 72742e64 ........msvcrt.d 0000298: 6c6c0041 44564150 4933322e 646c6c00 ll.ADVAPI32.dll. 00002a8: 4b45524e 454c3332 2e646c6c 00474449 KERNEL32.dll.GDI 00002b8: 33322e64 6c6c0055 53455233 322e646c 32.dll.USER32.dl 00002c8: 6c005348 454c4c33 322e646c 6c005749 l.SHELL32.dll.WI 00002d8: 4e4d4d2e 646c6c00 434f4d43 544c3332 NMM.dll.COMCTL32 00002e8: 2e646c6c 00000000 .dll.... the bound import table module name is given as offset so the first offset is 0x74
0000248: 2e746573 74000000 so 248+74 = 0x2bc
and the loader is trying to load thus ll.dll and failing
6c6c0055 53455233 322e646c 32.d**ll.**USER32.dl
you cant trap this with a user mode debugger because the initialisation code is run before debugger gets a chance to attach
if you are running this exe in a vm connected to a kernel debugger you can watch the bound import failing if you set a break on
ntdll!LdrpHandleOneNewFormatImportDescriptor also you can enable gflag +sls (show loader snaps ) in the context to get the loader snap spewing out that winmine is bound to ll.dll and then trying to walk the imports in the non existant dll
kd> r eax=0006fa6c ebx=7ffdd000 ecx=000000b4 edx=0000415c esi=00191ec0 edi=010002bc eip=7c91d025 esp=0006fa38 ebp=0006fa78 iopl=0 nv up ei pl zr na pe nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000246 ntdll!LdrpLoadImportModule: 001b:7c91d025 8bff mov edi,edi kd> kb # ChildEBP RetAddr Args to Child 00 0006fa34 7c91e4cb 00020498 010002bc 01000000 ntdll!LdrpLoadImportModule 01 0006fa78 7c91e474 7ffdd000 00020498 00191ec0 ntdll!LdrpHandleOneNewFormatImportDescriptor+0x53 02 0006fa98 7c91e5ae 7ffdd000 00020498 00191ec0 ntdll!LdrpHandleNewFormatImportDescriptors+0x20 03 0006fb14 7c921e25 00020498 00191ec0 7ffdf000 ntdll!LdrpWalkImportDescriptor+0x19e 04 0006fc94 7c92108f 0006fd30 7c900000 0006fce0 ntdll!LdrpInitializeProcess+0xe02 05 0006fd1c 7c90e437 0006fd30 7c900000 00000000 ntdll!_LdrpInitialize+0x183 06 00000000 00000000 00000000 00000000 00000000 ntdll!KiUserApcDispatcher+0x7 kd> .fnent . Debugger function entry 039b6c60 for: (7c91d025) ntdll!LdrpLoadImportModule | (7c91d1a1) ntdll!LdrpInitSecurityCookie Exact matches: ntdll!LdrpLoadImportModule (<no parameter info>) OffStart: 0001d025 ProcSize: 0x23a Prologue: 0x29 Params: 0n5 (0x14 bytes) Locals: 0n141 (0x234 bytes) Non-FPO kd> dd esp l6 0006fa38 7c91e4cb 00020498 010002bc 01000000 0006fa48 0006fa6c 0006fa77 kd> db 20498 00020498 43 00 3a 00 5c 00 44 00-6f 00 63 00 75 00 6d 00 C.:.\.D.o.c.u.m. 000204a8 65 00 6e 00 74 00 73 00-20 00 61 00 6e 00 64 00 e.n.t.s. .a.n.d. 000204b8 20 00 53 00 65 00 74 00-74 00 69 00 6e 00 67 00 .S.e.t.t.i.n.g. 000204c8 73 00 5c 00 61 00 64 00-6d 00 69 00 6e 00 5c 00 s.\.a.d.m.i.n.\. 000204d8 44 00 65 00 73 00 6b 00-74 00 6f 00 70 00 5c 00 D.e.s.k.t.o.p.\. 000204e8 63 00 66 00 66 00 74 00-65 00 73 00 74 00 3b 00 c.f.f.t.e.s.t.;. 000204f8 43 00 3a 00 5c 00 57 00-49 00 4e 00 44 00 4f 00 C.:.\.W.I.N.D.O. 00020508 57 00 53 00 5c 00 73 00-79 00 73 00 74 00 65 00 W.S.\.s.y.s.t.e. kd> db 10002bc 010002bc 6c 6c 00 55 53 45 52 33-32 2e 64 6c 6c 00 53 48 ll.USER32.dll.SH 010002cc 45 4c 4c 33 32 2e 64 6c-6c 00 57 49 4e 4d 4d 2e ELL32.dll.WINMM. 010002dc 64 6c 6c 00 43 4f 4d 43-54 4c 33 32 2e 64 6c 6c dll.COMCTL32.dll 010002ec 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................ 010002fc 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................ 0100030c 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................ 0100031c 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................ 0100032c 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................ kd> db 10002bc-74 01000248 2e 74 65 73 74 00 00 00-00 10 00 00 00 00 02 00 .test........... 01000258 00 10 00 00 00 d4 01 00-00 00 00 00 00 00 00 00 ................ 01000268 00 00 00 00 20 00 00 e0-0f fe 7d 3b 82 00 00 00 .... .....};.... 01000278 13 fe 7d 3b 8e 00 00 00-32 fe 7d 3b 98 00 00 00 ..};....2.};.... 01000288 00 00 00 00 00 00 00 00-6d 73 76 63 72 74 2e 64 ........msvcrt.d 01000298 6c 6c 00 41 44 56 41 50-49 33 32 2e 64 6c 6c 00 ll.ADVAPI32.dll. 010002a8 4b 45 52 4e 45 4c 33 32-2e 64 6c 6c 00 47 44 49 KERNEL32.dll.GDI 010002b8 33 32 2e 64 6c 6c 00 55-53 45 52 33 32 2e 64 6c 32.dll.USER32.dl