Lemmy v4.4

标题：我的第一篇破文,献给看学学院的!^_^高手免进! (10千字)
作者：bbbsl
时间：2002-6-20 15:56:04
链接：http://bbs.pediy.com

Lemmy v4.4 注册码分析

作者：bbbsl

软件介绍：这是一款在windows下模拟unix|linux下vi的一个工具，我们系没有用unix|linux做实验的条件，所以让我们
用这玩意体验一下，超级恶心！！！没发现用它有什么有意义的地方，但居然还有时间限制，所以，就拿它做个crackme吧！

平台：   windows 2000 advanced server

所用工具：softice for nt 4.05,calc(window自带计算器）

//运行lemmyreg后下断点bpx getwindowtexta后，按F10一直走到这一段代码（当然，前提是你得先输入了你的ID和SN^_^)：

:0040178F 8B17 mov edx, dword ptr [edi]
:00401791 50 push eax           //你输入的假注册码
:00401792 52 push edx           //你的ID
:00401793 8D4E68 lea ecx, dword ptr [esi+68]   //我一直不明白这个数是怎么来的，程序中用它加14得到一个地址，用这个地址的数做运算,高手给指点指点吧
:00401796 E865020000 call 00401A00           //关键！！！
:0040179B 85C0 test eax, eax           //正确否？
:0040179D 7457 je 004017F6           //正确则跳过！
:0040179F 6A00 push 00000000
:004017A1 6A30 push 00000030

* Possible StringData Ref from Data Obj ->"Check the values supplied"
|
:004017A3 68B0E04200 push 0042E0B0
:004017A8 E8FFD60100 call 0041EEAC

//下面是401A00的代码：

:00401A00 53 push ebx
:00401A01 55 push ebp
:00401A02 56 push esi
:00401A03 57 push edi
:00401A04 8BF9 mov edi, ecx
:00401A06 6A08 push 00000008
:00401A08 83CDFF or ebp, FFFFFFFF
:00401A0B E816650100 call 00417F26
:00401A10 8B74241C mov esi, dword ptr [esp+1C]
:00401A14 83C404 add esp, 00000004
:00401A17 8BD8 mov ebx, eax
:00401A19 33D2 xor edx, edx

* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:00401A71(C)
|
:00401A1B 0FBE06 movsx eax, byte ptr [esi]       //esi中是你是输入的假注册码
:00401A1E 0FBE4E01 movsx ecx, byte ptr [esi+01]       //两位两位处理
:00401A22 83F830 cmp eax, 00000030           //是数字否？
:00401A25 7C0A jl 00401A31               //如果小于‘0’则非数字..
:00401A27 83F839 cmp eax, 00000039
:00401A2A 7F05 jg 00401A31               //如果大于‘9’则非数字..
:00401A2C 83E830 sub eax, 00000030           //转成16进制中相应数字
:00401A2F EB11 jmp 00401A42               //下一位判断

* Referenced by a (U)nconditional or (C)onditional Jump at Addresses:
|:00401A25(C), :00401A2A(C)
|
:00401A31 83F841 cmp eax, 00000041           //不是数字，那是不是大写字母A-F中的一个呢？
:00401A34 7C0A jl 00401A40               //小则清eax
:00401A36 83F846 cmp eax, 00000046           //大也清eax
:00401A39 7F05 jg 00401A40
:00401A3B 83E837 sub eax, 00000037           //如果是则转成16进制中相应字符
:00401A3E EB02 jmp 00401A42

* Referenced by a (U)nconditional or (C)onditional Jump at Addresses:
|:00401A34(C), :00401A39(C)
|
:00401A40 33C0 xor eax, eax

* Referenced by a (U)nconditional or (C)onditional Jump at Addresses:
|:00401A2F(U), :00401A3E(U)
|
:00401A42 83F930 cmp ecx, 00000030           //第二位判断，以下均同第一位
:00401A45 7C0A jl 00401A51
:00401A47 83F939 cmp ecx, 00000039
:00401A4A 7F05 jg 00401A51
:00401A4C 83E930 sub ecx, 00000030
:00401A4F EB11 jmp 00401A62

* Referenced by a (U)nconditional or (C)onditional Jump at Addresses:
|:00401A45(C), :00401A4A(C)
|
:00401A51 83F941 cmp ecx, 00000041
:00401A54 7C0A jl 00401A60
:00401A56 83F946 cmp ecx, 00000046
:00401A59 7F05 jg 00401A60
:00401A5B 83E937 sub ecx, 00000037
:00401A5E EB02 jmp 00401A62

* Referenced by a (U)nconditional or (C)onditional Jump at Addresses:
|:00401A54(C), :00401A59(C)
|
:00401A60 33C9 xor ecx, ecx

* Referenced by a (U)nconditional or (C)onditional Jump at Addresses:
|:00401A4F(U), :00401A5E(U)
|
:00401A62 C0E004 shl al, 04               //合并刚刚处理过的两位假注册码
:00401A65 02C1 add al, cl               //即你输入的东西，假设为‘77’则变为16进制数77放入al中
:00401A67 83C602 add esi, 00000002
:00401A6A 880413 mov byte ptr [ebx+edx], al       //存入ebx所指向空间中
:00401A6D 42 inc edx               //edx为计数器
:00401A6E 83FA08 cmp edx, 00000008           //循环是否结束
:00401A71 7CA8 jl 00401A1B               //不结束继续。。
:00401A73 53 push ebx               //保存转换过的东东所在地
:00401A74 8BCF mov ecx, edi               //就是刚才那个数
:00401A76 E8E5F5FFFF call 00401060               //进一步处理，关键！！！
:00401A7B 8B542414 mov edx, dword ptr [esp+14]
:00401A7F 83C9FF or ecx, FFFFFFFF           //再往下是判断你的ID和用注册码算出来的ID是否一致的一个CALL
:00401A82 8BFA mov edi, edx
:00401A84 33C0 xor eax, eax
:00401A86 F2 repnz
:00401A87 AE scasb
:00401A88 F7D1 not ecx
:00401A8A 49 dec ecx
:00401A8B 83F908 cmp ecx, 00000008           //判断名字的位数是否大于8
:00401A8E 7607 jbe 00401A97               //是就继续不是截断
:00401A90 B908000000 mov ecx, 00000008
:00401A95 EB0C jmp 00401AA3

* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:00401A8E(C)
|
:00401A97 8BFA mov edi, edx
:00401A99 83C9FF or ecx, FFFFFFFF
:00401A9C 33C0 xor eax, eax
:00401A9E F2 repnz
:00401A9F AE scasb
:00401AA0 F7D1 not ecx
:00401AA2 49 dec ecx

* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:00401A95(U)
|
:00401AA3 85C9 test ecx, ecx               //位数是否为零
:00401AA5 7E11 jle 00401AB8
:00401AA7 51 push ecx               //这是位数
:00401AA8 53 push ebx               //这是用注册码推出来的ID
:00401AA9 52 push edx               //这是你输入的ID
:00401AAA E8515F0000 call 00407A00               //是否相同？
:00401AAF 83C40C add esp, 0000000C
:00401AB2 85C0 test eax, eax
:00401AB4 7502 jne 00401AB8               //如相同清ebp不然则相反，从而导致最后返回的eax值不同
:00401AB6 33ED xor ebp, ebp

* Referenced by a (U)nconditional or (C)onditional Jump at Addresses:
|:00401AA5(C), :00401AB4(C)
|
:00401AB8 53 push ebx
:00401AB9 E8A4640100 call 00417F62
:00401ABE 83C404 add esp, 00000004
:00401AC1 8BC5 mov eax, ebp               //eax<==ebp
:00401AC3 5F pop edi
:00401AC4 5E pop esi
:00401AC5 5D pop ebp
:00401AC6 5B pop ebx
:00401AC7 C20800 ret 0008

//下面是注册码的判断过程：

:00401060 83EC08 sub esp, 00000008
:00401063 8B54240C mov edx, dword ptr [esp+0C]
:00401067 53 push ebx
:00401068 56 push esi
:00401069 57 push edi
:0040106A 8A4204 mov al, byte ptr [edx+04]           //edx中是刚才处理过的假注册码
:0040106D 8BF9 mov edi, ecx                   //同样两位两位处理
:0040106F 8A4A02 mov cl, byte ptr [edx+02]
:00401072 8844240C mov byte ptr [esp+0C], al           //第五位放入第0位
:00401076 8A4207 mov al, byte ptr [edx+07]
:00401079 884C240D mov byte ptr [esp+0D], cl           //第三位放入第1位
:0040107D 8A0A mov cl, byte ptr [edx]
:0040107F 8844240E mov byte ptr [esp+0E], al           //第八位放入第2位
:00401083 8A4206 mov al, byte ptr [edx+06]
:00401086 884C240F mov byte ptr [esp+0F], cl           //第零位放入第3位
:0040108A 8A4A03 mov cl, byte ptr [edx+03]
:0040108D 88442410 mov byte ptr [esp+10], al           //第七位放入第4位
:00401091 8A4205 mov al, byte ptr [edx+05]
:00401094 884C2411 mov byte ptr [esp+11], cl           //第四位放入第5位
:00401098 8A4A01 mov cl, byte ptr [edx+01]
:0040109B 88442412 mov byte ptr [esp+12], al           //第六位放入第6位
:0040109F 8D74240C lea esi, dword ptr [esp+0C]           //传地址给esi
:004010A3 33C0 xor eax, eax
:004010A5 884C2413 mov byte ptr [esp+13], cl           //第二位放入第7位
:004010A9 2BF2 sub esi, edx                   //用edx作计数器

* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:004010BB(C)
|
:004010AB 8A4C3814 mov cl, byte ptr [eax+edi+14]           //开始将换过位的假注册码和edi+14中的数逐个异或
:004010AF 8A1C16 mov bl, byte ptr [esi+edx]           //edi+14中的数为312ACF04C76BF4DA
:004010B2 32CB xor cl, bl
:004010B4 40 inc eax
:004010B5 880A mov byte ptr [edx], cl           //异或出来的东东保存
:004010B7 42 inc edx
:004010B8 83F808 cmp eax, 00000008               //是否已结束
:004010BB 7CEE jl 004010AB                   //否则继续
:004010BD 5F pop edi
:004010BE 5E pop esi
:004010BF 5B pop ebx
:004010C0 83C408 add esp, 00000008
:004010C3 C20400 ret 0004

分析：
  其实已经很明显了，这是一个用注册码推ID的软件。它将我们输入的注册码转成16进制数的形式，然后进行换位，这一步得到的东东再和
16进制数31 2A CF 04 C7 6B F4 DA逐位异或，然后这个东东和你的ID比较，相同说明是正确的，否则就让你检查。
我们可以用计算器来推一个你自己的注册码，例如:我的ID为bbbsl,16进制为62 62 62 73 6c,假设注册码为数组a[8],则经它折腾之后实际上数组变为b[8]={
a[5],a[3],a[8],a[0],a[7],a[4],a[6],a[2]},若要让推出来的ID前五位同bbbsl相同，就必须是数组b前五位和31 2a cf 04 c7相异或后得到的东东==62 62 62
73 6c,so拿起计算器算算吧，62^31=53,62^2a=48,62^cf=AD,73^04=77,6c^c7=AB,即a[5]=53,a[3]=48,a[8]=AD,a[0]=77,a[7]=AB,其余各位随意，所以我的注册码为
id: bbbsl
sn: 770048005300ABAD