解除某下载软件的注册限制
PEID查壳为NeoLite v2.0，这壳很简单，本文就不多说了，直接脱壳并修复。
脱壳后反汇编得到如下信息：
:0040F490 8BC3 mov eax, ebx
:0040F492 E879030000 call 0040F810 //看看下面提示语句就知道很经典的，让我们跟进这个Call
:0040F497 84C0 test al, al
:0040F499 7460 je 0040F4FB //跳则死
:0040F49B 6A00 push 00000000
* Possible StringData Ref from Data Obj ->"感谢您，您已经注册成功!
重新启动系统，注册将会"
->"生效!"
|
:0040F49D BA15E24E00 mov edx, 004EE215
:0040F4A2 66C746102C00 mov [esi+10], 002C
:0040F4A8 8D45E4 lea eax, dword ptr [ebp-1C]
:0040F4AB E864350C00 call 004D2A14
:0040F4B0 FF461C inc [esi+1C]
:0040F4B3 8B10 mov edx, dword ptr [eax]
:0040F4B5 52 push edx
:0040F4B6 6A02 push 00000002
:0040F4B8 6A00 push 00000000
:0040F4BA 8D4DBA lea ecx, dword ptr [ebp-46]
:0040F4BD 51 push ecx
:0040F4BE E885940B00 call 004C8948
:0040F4C3 83C40C add esp, 0000000C
:0040F4C6 8D45BA lea eax, dword ptr [ebp-46]
:0040F4C9 804DBA04 or byte ptr [ebp-46], 04
:0040F4CD 668B08 mov cx, word ptr [eax]
:0040F4D0 58 pop eax
:0040F4D1 B202 mov dl, 02
:0040F4D3 E8E8310700 call 004826C0
:0040F4D8 FF4E1C dec [esi+1C]
:0040F4DB 8D45E4 lea eax, dword ptr [ebp-1C]
:0040F4DE BA02000000 mov edx, 00000002
:0040F4E3 E8C8360C00 call 004D2BB0
:0040F4E8 C7833402000001000000 mov dword ptr [ebx+00000234], 00000001
:0040F4F2 8BC3 mov eax, ebx
:0040F4F4 E83BAB0600 call 0047A034
:0040F4F9 EB58 jmp 0040F553
* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:0040F499(C)
|
:0040F4FB 6A00 push 00000000
* Possible StringData Ref from Data Obj ->"注册码错误!请重新输入!"
|
:0040F4FD BA49E24E00 mov edx, 004EE249
:0040F502 66C746103800 mov [esi+10], 0038
-----------------来自 0040F492 E879030000 call 0040F810----
:0040F810 55 push ebp
:0040F811 8BEC mov ebp, esp
:0040F813 83C4A8 add esp, FFFFFFA8
:0040F816 53 push ebx
:0040F817 56 push esi
:0040F818 57 push edi
:0040F819 8BD8 mov ebx, eax
:0040F81B 8D75B8 lea esi, dword ptr [ebp-48]
:0040F81E B8B0E64E00 mov eax, 004EE6B0
:0040F823 E83C940B00 call 004C8C64
:0040F828 8BC3 mov eax, ebx
:0040F82A E8BD030000 call 0040FBEC
:0040F82F 66C746100800 mov [esi+10], 0008
:0040F835 33D2 xor edx, edx
:0040F837 33C9 xor ecx, ecx
:0040F839 8955FC mov dword ptr [ebp-04], edx
:0040F83C 33C0 xor eax, eax
:0040F83E FF461C inc [esi+1C]
:0040F841 8D933C030000 lea edx, dword ptr [ebx+0000033C]
:0040F847 66C746101400 mov [esi+10], 0014
:0040F84D 66C746102000 mov [esi+10], 0020
:0040F853 894DF8 mov dword ptr [ebp-08], ecx
:0040F856 FF461C inc [esi+1C]
:0040F859 66C746101400 mov [esi+10], 0014
:0040F85F 66C746102C00 mov [esi+10], 002C
.......省略基本无关初始化的语句，来到下面的计算注册码的核心代码：
* Possible StringData Ref from Data Obj ->"0x"
|
:0040F9C6 B8F2E24E00 mov eax, 004EE2F2
:0040F9CB E828350C00 call 004D2EF8
:0040F9D0 8D45E4 lea eax, dword ptr [ebp-1C]
:0040F9D3 8B00 mov eax, dword ptr [eax]
:0040F9D5 E89AD00A00 call 004BCA74
:0040F9DA 8945B0 mov dword ptr [ebp-50], eax
:0040F9DD 8955B4 mov dword ptr [ebp-4C], edx
:0040F9E0 FF4E1C dec [esi+1C]
:0040F9E3 8D45E4 lea eax, dword ptr [ebp-1C]
:0040F9E6 BA02000000 mov edx, 00000002
:0040F9EB E8C0310C00 call 004D2BB0
:0040F9F0 FF4E1C dec [esi+1C]
:0040F9F3 8D45E8 lea eax, dword ptr [ebp-18]
:0040F9F6 BA02000000 mov edx, 00000002
:0040F9FB E8B0310C00 call 004D2BB0
:0040FA00 66C746101400 mov [esi+10], 0014
:0040FA06 33DB xor ebx, ebx
:0040FA08 EB6E jmp 0040FA78
--------------- 以上作用主要是把机器码转为16进制数，即0x...... ----------------
* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:0040FAA4(C)
|
:0040FA0A 837DFC00 cmp dword ptr [ebp-04], 00000000 <---[ebp-04]保存的是我们填入的E-mail。判断是否为空
:0040FA0E 7408 je 0040FA18
:0040FA10 8B45FC mov eax, dword ptr [ebp-04] <---E-mail 地址
:0040FA13 8B50FC mov edx, dword ptr [eax-04] <---E-mail 字符位数
:0040FA16 EB02 jmp 0040FA1A
* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:0040FA0E(C)
|
:0040FA18 33D2 xor edx, edx
* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:0040FA16(U)
|
:0040FA1A 3BDA cmp ebx, edx <--- ebx初始值为0 ，并判断该计算E-mail字符位数是否大于已经循环的次数
:0040FA1C 7D3B jge 0040FA59 <--- 若大于已经循环的次数，则转到0040FA59进行处理
:0040FA1E 8D7B01 lea edi, dword ptr [ebx+01]
:0040FA21 57 push edi
:0040FA22 8D45FC lea eax, dword ptr [ebp-04]
:0040FA25 50 push eax
:0040FA26 E8652F0C00 call 004D2990
:0040FA2B 83C408 add esp, 00000008
:0040FA2E 8D45FC lea eax, dword ptr [ebp-04]
:0040FA31 E8D2320C00 call 004D2D08
:0040FA36 037DFC add edi, dword ptr [ebp-04]
:0040FA39 4F dec edi
:0040FA3A 0FBE07 movsx eax, byte ptr [edi]
:0040FA3D 99 cdq <-----CDQ指令以方便做64位运算
:0040FA3E 52 push edx
:0040FA3F 50 push eax
:0040FA40 8B45B0 mov eax, dword ptr [ebp-50] <---保存机器码后 8 位计算的累计结果
:0040FA43 8B55B4 mov edx, dword ptr [ebp-4C] <---保存机器码前 8 位计算的累计结果
:0040FA46 E8D1BE0B00 call 004CB91C
----------------------call 004CB91C---start--------------------------
|:0040F1DE , :0040FA46 , :0040FA66
|
:004CB91C 52 push edx
:004CB91D 50 push eax
:004CB91E 8B442410 mov eax, dword ptr [esp+10]
:004CB922 F72424 mul dword ptr [esp]
:004CB925 8BC8 mov ecx, eax
:004CB927 8B442404 mov eax, dword ptr [esp+04] <---[esp+04]： 原始机器码前 8 位
:004CB92B F764240C mul [esp+0C] <---[esp+0c]保存E-mail码地址的ASCII的值或00:A1
并与原始机器码前 8 位相乘，结果保存在EDX（符号）和EAX（数值）
:004CB92F 03C8 add ecx, eax <---ECX保存中间结果
:004CB931 8B0424 mov eax, dword ptr [esp] <---[Esp]： 原始机器码后 8 位
:004CB934 F764240C mul [esp+0C] <---[esp+0c]保存E-mail码地址的ASCII的值或00:A1
并与原始机器码后 8 位相乘，结果保存在EDX（符号）和EAX
:004CB938 03D1 add edx, ecx <---EDX为上步运算结果的符号位，并与ECX相加
:004CB93A 59 pop ecx
:004CB93B 59 pop ecx
:004CB93C C20800 ret 0008
----------------------call 004CB91C---End---------------------------
:0040FA4B 83C001 add eax, 00000001 <----后8位计算结果加1
:0040FA4E 83D200 adc edx, 00000000 <----前8位计算结果加0（多此一举？*^_^*）
:0040FA51 8945B0 mov dword ptr [ebp-50], eax <----保存前8位计算结果
:0040FA54 8955B4 mov dword ptr [ebp-4C], edx <----保存后8位计算结果
:0040FA57 EB1E jmp 0040FA77
* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:0040FA1C(C)
|
:0040FA59 6A00 push 00000000 <-----符号位
:0040FA5B 68A1000000 push 000000A1 <-----原始值
:0040FA60 8B45B0 mov eax, dword ptr [ebp-50]
:0040FA63 8B55B4 mov edx, dword ptr [ebp-4C]
:0040FA66 E8B1BE0B00 call 004CB91C <-----用00:A1代替原E-mail 地址的 ASCII码
依次与机器码前、后 8 位做相同运算
:0040FA6B 83C001 add eax, 00000001 -----
:0040FA6E 83D200 adc edx, 00000000 |---作用如前述。
:0040FA71 8945B0 mov dword ptr [ebp-50], eax |
:0040FA74 8955B4 mov dword ptr [ebp-4C], edx -----
* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:0040FA57(U)
|
:0040FA77 43 inc ebx <---计算标志，用于判断E-mail字符串运算是否结束。
若结束，则用A1代替E-mail字符串的ASC值进行运算
* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:0040FA08(U)
|
:0040FA78 837DFC00 cmp dword ptr [ebp-04], 00000000
:0040FA7C 7408 je 0040FA86
:0040FA7E 8B4DFC mov ecx, dword ptr [ebp-04] <---E-mail 地址
:0040FA81 8B41FC mov eax, dword ptr [ecx-04] <---E-mail 位数
:0040FA84 EB02 jmp 0040FA88
* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:0040FA7C(C)
|
:0040FA86 33C0 xor eax, eax
* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:0040FA84(U)
|
:0040FA88 8945AC mov dword ptr [ebp-54], eax
:0040FA8B C745A808000000 mov [ebp-58], 00000008
:0040FA92 8B55A8 mov edx, dword ptr [ebp-58]
:0040FA95 3B55AC cmp edx, dword ptr [ebp-54]
:0040FA98 7E05 jle 0040FA9F
:0040FA9A 8D4DA8 lea ecx, dword ptr [ebp-58]
:0040FA9D EB03 jmp 0040FAA2
* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:0040FA98(C)
|
:0040FA9F 8D4DAC lea ecx, dword ptr [ebp-54]
* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:0040FA9D(U)
|
:0040FAA2 3B19 cmp ebx, dword ptr [ecx] <---ecx=8
:0040FAA4 0F8C60FFFFFF jl 0040FA0A <---循环 8 次
:0040FAAA 66C746105000 mov [esi+10], 0050
:0040FAB0 FF75B4 push [ebp-4C] <----保存最终后 8 位结果
:0040FAB3 FF75B0 push [ebp-50] <----保存最终前 8 位结果
:0040FAB6 33D2 xor edx, edx
:0040FAB8 B808000000 mov eax, 00000008
:0040FABD 8955E0 mov dword ptr [ebp-20], edx
将前、后 8 位结果算出后的最终结果作为字符串简单相加即为注册码。
本软件的注册信息保存在注册表中，删除该键值就可以重新注册，也可以根据本文的算法写出内存注册机，这里就不写了。
