新手脱壳系列教程——CI Crypt V0.1 手动脱壳,Crypt,脱壳技术 2008年06月23日 星期一 下午 06:33 【作者声明】：只是感兴趣，没有其他目的。失误之处敬请诸位大侠赐教 【调试环境】：WinXP、OllyDbg、PEiD、LordPE、ImportREC _____________________________________________________________ 【脱壳过程】： CI Crypt是个不常见的壳，脱壳比压缩壳稍微复杂点，建议学习过UPX/AsPacK手动脱壳的朋友再来练习这个 脱壳的方法有很多，也可以使用ESP定律。大家先跟随练习，掌握后再去寻找自己的脱壳方法 _____________________________________________________________ 一.EP 用LordPE察看目标文件的PE信息: ImageBase=00570000 SizeOfImage=00075000 设置OllyDbg忽略所有异常选项，用IsDebugPresent插件Hide，清除以前的所有断点 CODE //进入OllyDbg后暂停在这 00571746 F5 cmc 00571747 79 01 jns short 0057174A 00571749 F8 clc 0057174A F5 cmc 0057174B F9 stc 0057174C 60 pushad 0057174D C0C1 70 rol cl,70 00571750 E9 1B000000 jmp 00571770 _______________________________________________________ 二.数据恢复 BP VirtualAlloc Shift F9，中断后取消断点，Alt F9返回 CODE 0013FD6C 005713CC /CALL to VirtualAlloc from UnPackMe.005713CA 0013FD70 00400000 |Address = 00400000 0013FD74 0006B000 |Size = 6B000 (438272.) 0013FD78 00003000 |AllocationType = MEM_COMMIT|MEM_RESERVE 0013FD7C 00000040 \Protect = PAGE_EXECUTE_READWRITE 我们看到申请的内存地址是00400000 一般EXE文件的基址大多是00400000，而CI Crypt加壳后这个文件基址是ImageBase=00570000 原来CI Crypt加壳后改了基址，运行时要把代码还原的。 多看代码，最好能看明白壳的流程，这样看的多了就能学习到很多知识了。 CODE 005713C0 51 push ecx 005713C1 6A 40 push 40 005713C3 68 00300000 push 3000 005713C8 51 push ecx 005713C9 50 push eax 005713CA FFD3 call near ebx; kernel32.VirtualAlloc 005713CC 59 pop ecx //返回这里 005713CD 85C0 test eax,eax 005713CF 75 13 jnz short 005713E4 005713D1 6A 40 push 40 005713D3 68 00100000 push 1000 005713D8 51 push ecx 005713D9 50 push eax 005713DA FFD3 call near ebx 005713DC 85C0 test eax,eax 005713DE 0F84 4D020000 je 00571631 005713E4 8945 F4 mov dword ptr ss:[ebp-C],eax 005713E7 89C7 mov edi,eax 005713E9 8B75 08 mov esi,dword ptr ss:[ebp 8] 005713EC 56 push esi 005713ED 89F1 mov ecx,esi 005713EF 034E 3C add ecx,dword ptr ds:[esi 3C] 005713F2 8B49 54 mov ecx,dword ptr ds:[ecx 54] 005713F5 F3:A4 rep movs byte ptr es:[edi],byte ptr ds:[esi] //ecx=00000400 (decimal 1024.) //ds:[esi]=[00571B79]=4D ('M') //es:[edi]=[00400000]=00 //开始把PE头数据复制回00400000 005713F7 5E pop esi 005713F8 0376 3C add esi,dword ptr ds:[esi 3C] 005713FB 81C6 F8000000 add esi,0F8 00571401 8B45 08 mov eax,dword ptr ss:[ebp 8] 00571404 0340 3C add eax,dword ptr ds:[eax 3C] 00571407 0FB640 06 movzx eax,byte ptr ds:[eax 6] 0057140B 8D7D C8 lea edi,dword ptr ss:[ebp-38] 0057140E 57 push edi 0057140F 6A 0A push 0A 00571411 59 pop ecx 00571412 F3:A5 rep movs dword ptr es:[edi],dword ptr ds:[esi] //[esi]处是加壳前文件的区段信息 00571414 5F pop edi 00571415 8B57 14 mov edx,dword ptr ds:[edi 14] 00571418 85D2 test edx,edx 0057141A 74 14 je short 00571430 0057141C 56 push esi 0057141D 8B75 08 mov esi,dword ptr ss:[ebp 8] 00571420 01D6 add esi,edx 00571422 8B4F 10 mov ecx,dword ptr ds:[edi 10] 00571425 8B57 0C mov edx,dword ptr ds:[edi C] 00571428 8B7D F4 mov edi,dword ptr ss:[ebp-C] 0057142B 01D7 add edi,edx 0057142D F3:A4 rep movs byte ptr es:[edi],byte ptr ds:[esi] //ecx=00049200 (decimal 299520.) //ds:[esi]=[00571F79]=56 ('V') //es:[edi]=[00401000]=00 //复制回各区段数据 0057142F 5E pop esi 00571430 48 dec eax //原始 NumberOfSections 00571431 75 D8 jnz short 0057140B //依次复制回所有的区段数据 00571433 8B55 F4 mov edx,dword ptr ss:[ebp-C] 00571436 2B55 FC sub edx,dword ptr ss:[ebp-4] 00571439 74 5C je short 00571497 //判断是否需要重定位处理，DLL使用 0057143B 8B45 F4 mov eax,dword ptr ss:[ebp-C] 0057143E 89C3 mov ebx,eax 00571440 035B 3C add ebx,dword ptr ds:[ebx 3C] 00571443 8B9B A0000000 mov ebx,dword ptr ds:[ebx A0] 00571449 85DB test ebx,ebx 0057144B 74 4A je short 00571497 0057144D 01C3 add ebx,eax 0057144F 8B43 04 mov eax,dword ptr ds:[ebx 4] 00571452 85C0 test eax,eax 00571454 74 41 je short 00571497 00571456 8D48 F8 lea ecx,dword ptr ds:[eax-8] 00571459 D1E9 shr ecx,1 0057145B 8D7B 08 lea edi,dword ptr ds:[ebx 8] 0057145E 0FB707 movzx eax,word ptr ds:[edi] 00571461 52 push edx 00571462 89C2 mov edx,eax 00571464 C1E8 0C shr eax,0C 00571467 8B75 F4 mov esi,dword ptr ss:[ebp-C] 0057146A 66:81E2 FF0F and dx,0FFF 0057146F 0333 add esi,dword ptr ds:[ebx] 00571471 01D6 add esi,edx 00571473 5A pop edx 00571474 48 dec eax 00571475 75 07 jnz short 0057147E 00571477 89D0 mov eax,edx 00571479 C1E8 10 shr eax,10 0057147C EB 06 jmp short 00571484 0057147E 48 dec eax 0057147F 75 08 jnz short 00571489 00571481 0FB7C2 movzx eax,dx 00571484 66:0106 add word ptr ds:[esi],ax 00571487 EB 05 jmp short 0057148E 00571489 48 dec eax 0057148A 75 02 jnz short 0057148E 0057148C 0116 add dword ptr ds:[esi],edx 0057148E 47 inc edi 0057148F 47 inc edi 00571490 E2 CC loopd short 0057145E 00571492 035B 04 add ebx,dword ptr ds:[ebx 4] 00571495 EB B8 jmp short 0057144F _____________________________________________________________ 三.修改PEB中信息 新手可以跳开这个部分，直接看第四部分的Dump PEB (Process Environment Block)——进程环境块，存放进程信息。 PEB 008 处是ImageBaseAddress CODE 00571497 8B4D F4 mov ecx,dword ptr ss:[ebp-C] //ECX=[ebp-C]=00400000 新基址 0057149A 8B55 B0 mov edx,dword ptr ss:[ebp-50] 0057149D 0155 B4 add dword ptr ss:[ebp-4C],edx 005714A0 64:8B05 30000000 mov eax,dword ptr fs:[30] //获得PEB首地址 005714A7 837D BC 00 cmp dword ptr ss:[ebp-44],0 005714AB 75 03 jnz short 005714B0 005714AD 8948 08 mov dword ptr ds:[eax 8],ecx //写入00400000新基址 005714B0 8B40 0C mov eax,dword ptr ds:[eax C] 005714B3 8B40 0C mov eax,dword ptr ds:[eax C] 005714B6 89C6 mov esi,eax 005714B8 8B50 18 mov edx,dword ptr ds:[eax 18] 005714BB 3B55 B0 cmp edx,dword ptr ss:[ebp-50] 005714BE 75 27 jnz short 005714E7 005714C0 8B50 1C mov edx,dword ptr ds:[eax 1C] 005714C3 3B55 B4 cmp edx,dword ptr ss:[ebp-4C] 005714C6 75 1F jnz short 005714E7 005714C8 8B50 20 mov edx,dword ptr ds:[eax 20] 005714CB 3B55 B8 cmp edx,dword ptr ss:[ebp-48] 005714CE 75 17 jnz short 005714E7 005714D0 8948 18 mov dword ptr ds:[eax 18],ecx 005714D3 038D 30FEFFFF add ecx,dword ptr ss:[ebp-1D0] 005714D9 8948 1C mov dword ptr ds:[eax 1C],ecx //写入新的EP 005714DC 8B8D 58FEFFFF mov ecx,dword ptr ss:[ebp-1A8] 005714E2 8948 20 mov dword ptr ds:[eax 20],ecx //写入新的SizeOfImage 005714E5 EB 08 jmp short 005714EF 005714E7 3930 cmp dword ptr ds:[eax],esi 005714E9 74 04 je short 005714EF 005714EB 8B00 mov eax,dword ptr ds:[eax] 005714ED EB C9 jmp short 005714B8 _____________________________________________________________ 四.Dump 从上面走到这里就可以dump了 现在壳还没有把输入表填充系统函数地址，而所有数据都已还原，正是dump的最佳时机 由于壳把数据恢复到新的基址，因此LordPE需要设置一下，这样才可以完美的抓取进程 Options->Task Viewer->去掉 Full dump:Paste header from disk 选项，也就是不使用物理文件的PE头 看看保存的dump.exe，基本就是加壳前的原始文件了。到这里CI Crypt脱壳就完成了 下面在继续看看壳的流程吧 CODE 005714EF 8B9D 88FEFFFF mov ebx,dword ptr ss:[ebp-178] //[ebp-178]是输入表RVA 005714F5 85DB test ebx,ebx 005714F7 74 6C je short 00571565 005714F9 8B75 F4 mov esi,dword ptr ss:[ebp-C] 005714FC 01F3 add ebx,esi 005714FE 8B43 0C mov eax,dword ptr ds:[ebx C] 00571501 85C0 test eax,eax 00571503 74 60 je short 00571565 00571505 8B4B 10 mov ecx,dword ptr ds:[ebx 10] 00571508 01F1 add ecx,esi 0057150A 894D C4 mov dword ptr ss:[ebp-3C],ecx 0057150D 8B0B mov ecx,dword ptr ds:[ebx] 0057150F 85C9 test ecx,ecx 00571511 75 03 jnz short 00571516 00571513 8B4B 10 mov ecx,dword ptr ds:[ebx 10] 00571516 01F1 add ecx,esi 00571518 894D C0 mov dword ptr ss:[ebp-40],ecx 0057151B 01F0 add eax,esi 0057151D 50 push eax 0057151E 8B45 10 mov eax,dword ptr ss:[ebp 10] 00571521 FF10 call near dword ptr ds:[eax]; kernel32.LoadLibraryA 00571523 85C0 test eax,eax 00571525 0F84 06010000 je 00571631 0057152B 89C7 mov edi,eax 0057152D 8B4D C0 mov ecx,dword ptr ss:[ebp-40] 00571530 8B11 mov edx,dword ptr ds:[ecx] 00571532 85D2 test edx,edx 00571534 74 2A je short 00571560 00571536 F7C2 00000080 test edx,80000000 0057153C 74 08 je short 00571546 0057153E 81E2 FFFFFF7F and edx,7FFFFFFF 00571544 EB 04 jmp short 0057154A 00571546 01F2 add edx,esi 00571548 42 inc edx 00571549 42 inc edx 0057154A 52 push edx 0057154B 57 push edi 0057154C 8B45 0C mov eax,dword ptr ss:[ebp C] 0057154F FF10 call near dword ptr ds:[eax]; kernel32.GetProcAddress 00571551 8B4D C4 mov ecx,dword ptr ss:[ebp-3C] 00571554 8901 mov dword ptr ds:[ecx],eax //填充函数系统地址 00571556 8345 C4 04 add dword ptr ss:[ebp-3C],4 0057155A 8345 C0 04 add dword ptr ss:[ebp-40],4 0057155E EB CD jmp short 0057152D 00571560 83C3 14 add ebx,14 00571563 EB 99 jmp short 005714FE //循环处理输入表 _____________________________________________________________ 五.OEP CODE 0057161F 3B5D 90 cmp ebx,dword ptr ss:[ebp-70] 00571622 0F85 4DFFFFFF jnz 00571575 00571628 8B85 30FEFFFF mov eax,dword ptr ss:[ebp-1D0] //[ebp-1D0]=000271B0 OEP RVA 0057162E 0345 F4 add eax,dword ptr ss:[ebp-C] //EAX=000271B0 00400000=004271B0 00571631 8B4D F4 mov ecx,dword ptr ss:[ebp-C] 00571634 5E pop esi 00571635 5F pop edi 00571636 5B pop ebx 00571637 C9 leave 00571638 C2 0C00 retn 0C //返回00571217 00571217 5F pop edi 00571218 5E pop esi 00571219 5D pop ebp 0057121A 83C4 04 add esp,4 0057121D 5B pop ebx 0057121E 5A pop edx 0057121F 83C4 08 add esp,8 00571222 894C24 04 mov dword ptr ss:[esp 4],ecx 00571226 FFE0 jmp near eax //飞向光明之巅 CODE 004271B0 55 push ebp //OEP 004271B1 8BEC mov ebp,esp 004271B3 6A FF push -1 004271B5 68 600E4500 push 00450E60 004271BA 68 C8924200 push 004292C8 004271BF 64:A1 00000000 mov eax,dword ptr fs:[0] 004271C5 50 push eax 004271C6 64:8925 00000000 mov dword ptr fs:[0],esp 004271CD 83C4 A8 add esp,-58 004271D0 53 push ebx 004271D1 56 push esi 004271D2 57 push edi 004271D3 8965 E8 mov dword ptr ss:[ebp-18],esp 004271D6 FF15 DC0A4600 call near dword ptr ds:[460ADC]; kernel32.GetVersion _____________________________________________________________ 六.简化脱壳流程 OllyDBG载入CI Crypt V0.1加壳文件暂停在EP BP VirtualAlloc Shift F9，中断后取消断点，Alt F9返回 Ctrl F向下搜索命令： mov ebx,dword ptr ss:[ebp-178] 找到在005714EF处后F4过去，或者设断后Shift F9中断 此时就可以使用LordPE抓取进程了，注意LordPE的Task Viewer选项设置 在这里脱壳可以说是完美脱壳，dump的文件基本就是加壳前的原始文件了 Game Over |
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