About anti-SoftICE tricks

显示全部楼层 · 发表于 2008-9-28 16:34:50

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<TD><PRE>Method 01
=========

This method of detection of SoftICE (as well as the following one) is
used by the majority of packers/encryptors found on Internet.
It seeks the signature of BoundsChecker in SoftICE

mov    ebp, 04243484Bh       ; 'BCHK'
mov    ax, 04h
int    3
cmp    al,4
jnz    SoftICE_Detected

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Method 02
=========

Still a method very much used (perhaps the most frequent one).  It is used
to get SoftICE 'Back Door commands' which gives infos on Breakpoints,
or execute SoftICE commands...
It is also used to crash SoftICE and to force it to execute any commands
(HBOOT...) :-((

Here is a quick description:
-AX = 0910h (Display string in SIce windows)
-AX = 0911h (Execute SIce commands -command is displayed is ds:dx)
-AX = 0912h (Get breakpoint infos)
-AX = 0913h (Set Sice breakpoints)
-AX = 0914h (Remove SIce breakoints)

Each time you'll meet this trick, you'll see:
-SI = 4647h
-DI = 4A4Dh
Which are the 'magic values' used by SoftIce.
For more informations, see "Ralf Brown Interrupt list" chapter int 03h.

Here is one example from the file "Haspinst.exe" which is the dongle HASP
Envelope utility use to protect DOS applications:

4C19:0095 MOV AX,0911  ; execute command.
4C19:0098 MOV DX,[BX]  ; ds:dx point to the command (see below).
4C19:009A MOV SI,4647  ; 1st magic value.
4C19:009D MOV DI,4A4D  ; 2nd magic value.
4C19:00A0 INT 3       ; Int call.(if SIce is not loaded, jmp to 00AD*)
4C19:00A1 ADD BX,02 ; BX+2 to point to next command to execute
4C19:00A4 INC CX
4C19:00A5 CMP CX,06 ; Repeat 6 times  to execute
4C19:00A8 JB    0095    ; 6 different commands.
4C19:00AA JMP 0002    ; Bad_Guy jmp back.
4C19:00AD MOV BX,SP ; Good_Guy go ahead :)

The program will execute 6 different SIce commands located at ds:dx, which
are: LDT, IDT, GDT, TSS, RS, and ...HBOOT.

* the "jmp to 00ADh" is performed via an SEH if the debugger is not loaded.
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Method 03
=========

Less used method.  It seeks the ID of SoftICE VxD via the int 2Fh/1684h
(API Get entry point)


xor    di,di
mov    es,di
mov    ax, 1684h
mov    bx, 0202h    ; VxD ID of winice
int    2Fh
mov    ax, es       ; ES:DI -> VxD API entry point
add    ax, di
test ax,ax
jnz    SoftICE_Detected

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Method 04
=========

Method identical to the preceding one except that it seeks the ID of SoftICE
GFX VxD.

xor    di,di
mov    es,di
mov    ax, 1684h
mov    bx, 7a5Fh    ; VxD ID of SIWVID
int    2fh
mov    ax, es       ; ES:DI -> VxD API entry point
add    ax, di
test ax,ax
jnz    SoftICE_Detected

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Method 05
=========

Method seeking the 'magic number' 0F386h returned (in ax) by all system
debugger. It calls the int 41h, function 4Fh.
There are several alternatives.

The following one is the simplest:

mov    ax,4fh
int    41h
cmp    ax, 0F386
jz    SoftICE_detected

Next method as well as the following one are 2 examples from Stone's
"stn-wid.zip" (www.cracking.net):

mov    bx, cs
lea    dx, int41handler2
xchg dx, es:[41h*4]
xchg bx, es:[41h*4+2]
mov    ax,4fh
int    41h
xchg dx, es:[41h*4]
xchg bx, es:[41h*4+2]
cmp    ax, 0f386h
jz    SoftICE_detected

int41handler2 PROC
iret
int41handler2 ENDP

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Method 06
=========

2nd method similar to the preceding one but more difficult to detect:

int41handler PROC
mov    cl,al
iret
int41handler ENDP

xor    ax,ax
mov    es,ax
mov    bx, cs
lea    dx, int41handler
xchg dx, es:[41h*4]
xchg bx, es:[41h*4+2]
in    al, 40h
xor    cx,cx
int    41h
xchg dx, es:[41h*4]
xchg bx, es:[41h*4+2]
cmp    cl,al
jnz    SoftICE_detected

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Method 07
=========

Method of detection of the WinICE handler in the int68h (V86)

mov    ah,43h
int    68h
cmp    ax,0F386h
jz    SoftICE_Detected

=> it is not possible to set a BPINT 68 with softice but you can hook a 32Bit
app like this:

BPX exec_int if ax==68
(function called is located at byte ptr [ebp+1Dh] and client eip is
located at [ebp+48h] for 32Bit apps)
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Method 08
=========

It is not a method of detection of SoftICE but a possibility to crash the
system by intercepting int 01h and int 03h and redirecting them to another
routine.
It calls int 21h functions 25h and 35h (set/get int vector) and ds:dx points
to the new routine to execute (hangs computer...)

mov    ah, 25h
mov    al, Int_Number (01h or 03h)
mov    dx, offset New_Int_Routine
int    21h

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Method 09
=========

This method is closed to methods 03 and 04 (int 2Fh/1684h) but it is only
performed in ring0 (VxD or a ring3 app using the VxdCall).
The Get_DDB service is used to determine whether or not a VxD is installed
for the specified device and returns a Device Description Block (in ecx) for
that device if it is installed.

mov    eax, Device_ID ; 202h for SICE or 7a5Fh for SIWVID VxD ID
mov    edi, Device_Name ; only used if no VxD ID (useless in our case ;-)
VMMCall Get_DDB
mov    [DDB], ecx    ; ecx=DDB or 0 if the VxD is not installed

Note as well that you can easily detect this method with SoftICE:
bpx Get_DDB if ax==0202 || ax==7a5fh

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Method 10
=========

=>Disable or clear breakpoints before using this feature. DO NOT trace with
  SoftICE while the option is enable!!

This trick is very efficient:
by checking the Debug Registers, you can detect if SoftICE is loaded
(dr7=0x700 if you loaded the soft with SoftICE loader, 0x400 otherwise) or if
there are some memory breakpoints set (dr0 to dr3) simply by reading their
value (in ring0 only). Values can be manipulated and or changed as well
(clearing BPMs for instance)

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Method 11
=========

This method is most known as 'MeltICE' because it has been freely distributed
via www.winfiles.com. However it was first used by NuMega people to allow
Symbol Loader to check if SoftICE was active or not (the code is located
inside nmtrans.dll).

The way it works is very simple:
It tries to open SoftICE drivers handles (SICE, SIWVID for Win9x, NTICE for
WinNT) with the CreateFileA API.

Here is a sample (checking for 'SICE'):

BOOL IsSoftIce95Loaded()
{
HANDLE hFile;
hFile = CreateFile( "\\\\.\\SICE", GENERIC_READ | GENERIC_WRITE,
                  FILE_SHARE_READ | FILE_SHARE_WRITE,
                  NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
if( hFile != INVALID_HANDLE_VALUE )
{
   CloseHandle(hFile);
   return TRUE;
}
return FALSE;
}

Although this trick calls the CreateFileA function, don't even expect to be
able to intercept it by installing a IFS hook: it will not work, no way!
In fact, after the call to CreateFileA it will get through VWIN32 0x001F
service _VWIN32_ReleaseWin32Mutex (via Kernel32!ORD_0001/VxDCall function)
and then browse the DDB list until it find the VxD and its DDB_Control_Proc
field.
In fact, its purpose is not to load/unload VxDs but only to send a
W32_DEVICEIOCONTROL (0x23) control message (DIOC_OPEN and DIOC_CLOSEHANDLE)
to the VxD Control_Dispatch proc (how the hell a shareware soft could try
to load/unload a non-dynamically loadable driver such as SoftICE ;-).
If the VxD is loaded, it will always clear eax and the Carry flag to allow
its handle to be opened and then, will be detected.
You can check that simply by hooking Winice.exe control proc entry point
while running MeltICE.

  00401067:  push    00402025 ; \\.\SICE
  0040106C:  call    CreateFileA
  00401071:  cmp    eax,-001
  00401074:  je       00401091

There could be hundreds of BPX you could use to detect this trick.
-The most classical one is:
  BPX CreateFileA if *(esp->4+4)=='SICE' || *(esp->4+4)=='SIWV' ||
*(esp->4+4)=='NTIC'

-The most exotic ones (could be very slooooow :-(
BPINT 30 if eax==002A001F && (*edi=='SICE' || *edi=='SIWV')
   ;will break 3 times :-(

-or (a bit) faster:
BPINT 30 if (*edi=='SICE' || *edi=='SIWV')

BPX KERNEL32!ORD_0001 if *edi=='SICE' || *edi=='SIWV'
   ;will break 3 times :-(

-Much faster:
BPX VMM_GetDDBList if eax->3=='SICE' || eax->3=='SIWV'

Note also that some programs (like AZPR3.00) use de old 16-bit _lopen
function to do the same job:

push 00                      ; OF_READ
mov    eax,[00656634]          ; '\\.\SICE',0
push eax
call KERNEL32!_lopen
inc    eax
jnz    00650589                ; detected
push 00                      ; OF_READ
mov    eax,[00656638]          ; '\\.\SICE'
push eax
call KERNEL32!_lopen
inc    eax
jz    006505ae                ; not detected

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Method 12
=========

This trick is similar to int41h/4fh Debugger installation check (code 05
& 06) but very limited because it's only available for Win95/98 (not NT)
as it uses the VxDCall backdoor. This detection was found in Bleem Demo.

push  0000004fh       ; function 4fh
push  002a002ah       ; high word specifies which VxD (VWIN32)
                        ; low word specifies which service
                           (VWIN32_Int41Dispatch)
call  Kernel32!ORD_001  ; VxdCall
cmp ax, 0f386h       ; magic number returned by system debuggers
jz SoftICE_detected

Here again, several ways to detect it:

BPINT 41 if ax==4f

BPINT 30 if ax==0xF386 ; SoftICE must be loaded for this one

BPX Exec_PM_Int if eax==41 && edx->1c==4f && edx->10==002A002A

BPX Kernel32!ord_0001 if esp->4==002A002A && esp->8==4f ; slooooow!

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Method 13
=========

Not a real method of detection, but a good way to know if SoftICE is
installed on a computer and to locate its installation directory.
It is used by few softs which access the following registry keys (usually #2) :

-#1: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion
\Uninstall\SoftICE
-#2: HKEY_LOCAL_MACHINE\Software\NuMega\SoftICE
-#3: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion
\App Paths\Loader32.Exe

Note that some nasty apps could then erase all files from SoftICE directory
(I faced that once :-(

Useful breakpoint to detect it:

   BPX _regopenkey if *(esp->8+0x13)=='tICE' || *(esp->8+0x37)=='tICE'

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Method 14
=========

A call to VMM 'Test_Debug_Installed' service. As the name says, its purpose
is to determines whether a debugger is running on your system (ring0 only).

VMMCall Test_Debug_Installed
je    not_installed

This service just checks a flag.
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