【脱壳目标】:影音嗅探专家 V2005.22
【下载页面】:http://www1.skycn.com/soft/20858.html
【加壳方式】:Armadillo 3.00a - 3.61 -> Silicon Realms Toolworks
【任 务】:此软件是免费软件，目的在于学习脱壳
【工 具】:Olydbg1.1、LORDPE、ImportREC1.6F
【操作平台】:Microsoft Windows XP Professional+sp2
【作 者】:wer412
【详细过程】:参考了前人的脱壳文章，说说自己的理解
一、避开函数加密
(一)设置Ollydbg，忽略所有异常
0045C000 > 60 PUSHAD *载入后停留在这*
0045C001 E8 00000000 CALL msniffer.0045C006
0045C006 5D POP EBP
0045C007 50 PUSH EAX
0045C008 51 PUSH ECX
0045C009 EB 0F JMP SHORT msniffer.0045C01A
(二)下断点HE GetModuleHandleA，F9运行。两次Shift+F9通过异常后，Ctrl+F9返回直到如下形式
00AF4E83 8B0D 00B8B100 MOV ECX,DWORD PTR DS:[B1B800]
00AF4E89 89040E MOV DWORD PTR DS:[ESI+ECX],EAX
00AF4E8C A1 00B8B100 MOV EAX,DWORD PTR DS:[B1B800]
00AF4E91 393C06 CMP DWORD PTR DS:[ESI+EAX],EDI
00AF4E94 75 16 JNZ SHORT 00AF4EAC
00AF4E96 8D85 B4FEFFFF LEA EAX,DWORD PTR SS:[EBP-14C]
00AF4E9C 50 PUSH EAX
00AF4E9D FF15 C030B100 CALL DWORD PTR DS:[B130C0] ; kernel32.LoadLibraryA
00AF4EA3 8B0D 00B8B100 MOV ECX,DWORD PTR DS:[B1B800]
00AF4EA9 89040E MOV DWORD PTR DS:[ESI+ECX],EAX
00AF4EAC A1 00B8B100 MOV EAX,DWORD PTR DS:[B1B800]
00AF4EB1 393C06 CMP DWORD PTR DS:[ESI+EAX],EDI
00AF4EB4 0F84 AD000000 JE 00AF4F67 *改为JMP，避开函数加密*
00AF4EBA 33C9 XOR ECX,ECX
00AF4EBC 8B03 MOV EAX,DWORD PTR DS:[EBX]
00AF4EBE 3938 CMP DWORD PTR DS:[EAX],EDI
00AF4EC0 74 06 JE SHORT 00AF4EC8
00AF4EC2 41 INC ECX
00AF4EC3 83C0 0C ADD EAX,0C
00AF4EC6 ^EB F6 JMP SHORT 00AF4EBE
二、寻找OEP
(三)取消断点，下BP GetCurrentThreadId断点，F9运行。Ctrl+F9和F9配合直到返回程序空间，向下寻找CALL EDI下断点
00B0A0AF A3 90F8B100 MOV DWORD PTR DS:[B1F890],EAX
00B0A0B4 E8 F4B0FEFF CALL 00AF51AD
00B0A0B9 6A 00 PUSH 0
00B0A0BB E8 5B03FFFF CALL 00AFA41B
00B0A0C0 59 POP ECX
00B0A0C1 E8 8D63FFFF CALL 00B00453
00B0A0C6 8BF8 MOV EDI,EAX
00B0A0C8 A1 80F8B100 MOV EAX,DWORD PTR DS:[B1F880]
00B0A0CD 8B48 74 MOV ECX,DWORD PTR DS:[EAX+74]
00B0A0D0 3348 5C XOR ECX,DWORD PTR DS:[EAX+5C]
00B0A0D3 3308 XOR ECX,DWORD PTR DS:[EAX]
00B0A0D5 03F9 ADD EDI,ECX
00B0A0D7 8B0E MOV ECX,DWORD PTR DS:[ESI]
00B0A0D9 85C9 TEST ECX,ECX
00B0A0DB 75 2E JNZ SHORT 00B0A10B
00B0A0DD 8B78 5C MOV EDI,DWORD PTR DS:[EAX+5C]
00B0A0E0 E8 6E63FFFF CALL 00B00453
00B0A0E5 8B0D 80F8B100 MOV ECX,DWORD PTR DS:[B1F880] ; msniffer.0046C258
00B0A0EB FF76 14 PUSH DWORD PTR DS:[ESI+14]
00B0A0EE 8B51 74 MOV EDX,DWORD PTR DS:[ECX+74]
00B0A0F1 FF76 10 PUSH DWORD PTR DS:[ESI+10]
00B0A0F4 33D7 XOR EDX,EDI
00B0A0F6 3311 XOR EDX,DWORD PTR DS:[ECX]
00B0A0F8 FF76 0C PUSH DWORD PTR DS:[ESI+C]
00B0A0FB 03C2 ADD EAX,EDX
00B0A0FD 8B51 78 MOV EDX,DWORD PTR DS:[ECX+78]
00B0A100 3351 14 XOR EDX,DWORD PTR DS:[ECX+14]
00B0A103 33D7 XOR EDX,EDI
00B0A105 2BC2 SUB EAX,EDX
00B0A107 FFD0 CALL EAX
00B0A109 EB 25 JMP SHORT 00B0A130
00B0A10B 83F9 01 CMP ECX,1
00B0A10E 75 22 JNZ SHORT 00B0A132
00B0A110 FF76 04 PUSH DWORD PTR DS:[ESI+4]
00B0A113 FF76 08 PUSH DWORD PTR DS:[ESI+8]
00B0A116 6A 00 PUSH 0
00B0A118 E8 3663FFFF CALL 00B00453
00B0A11D 50 PUSH EAX
00B0A11E A1 80F8B100 MOV EAX,DWORD PTR DS:[B1F880]
00B0A123 8B48 78 MOV ECX,DWORD PTR DS:[EAX+78]
00B0A126 3348 5C XOR ECX,DWORD PTR DS:[EAX+5C]
00B0A129 3348 14 XOR ECX,DWORD PTR DS:[EAX+14]
00B0A12C 2BF9 SUB EDI,ECX
00B0A12E FFD7 CALL EDI *取消以前断点。F2下断点于此，F9运行断下后F7进入程序OEP了*
00B0A130 8BD8 MOV EBX,EAX
00B0A132 5F POP EDI
00B0A133 8BC3 MOV EAX,EBX
00B0A135 5E POP ESI
00B0A136 5B POP EBX
00B0A137 C3 RETN
F7进入后
00423D7E 55 PUSH EBP *程序入口，OEP=423D70-400000=23D7E*
00423D7F 8BEC MOV EBP,ESP
00423D81 6A FF PUSH -1
00423D83 68 48C14200 PUSH msniffer.0042C148
00423D88 68 E83E4200 PUSH msniffer.00423EE8 ; JMP to msvcrt._except_handler3
00423D8D 64:A1 00000000 MOV EAX,DWORD PTR FS:[0]
00423D93 50 PUSH EAX
00423D94 64:8925 00000000 MOV DWORD PTR FS:[0],ESP
00423D9B 83EC 68 SUB ESP,68
00423D9E 53 PUSH EBX
00423D9F 56 PUSH ESI
00423DA0 57 PUSH EDI
00423DA1 8965 E8 MOV DWORD PTR SS:[EBP-18],ESP
00423DA4 33DB XOR EBX,EBX
00423DA6 895D FC MOV DWORD PTR SS:[EBP-4],EBX
三、程序的抓取及修复
(四)使用LOADPE抓取。运行ImportREC，选择程序进程，填入OEP=23D7E，点击右键选择“Advanced Commands”-->“Get Api Calls ”-->选择“Get' Call[X]' ... ”-->“Show Invalid”剪掉两个无效函数，修复即可。