环境
Windows xp sp3
工具
exeinfope
ollydbg
查壳
无壳的MFC程序
测试
字符串搜索：
004014F5 |. E8 AA030000 call <jmp.&MFC42.#CWnd::GetWindowTextLengthA_>
004014FA |. 8945 EC mov [local.5],eax
004014FD |. 837D EC 05 cmp [local.5],0x5 ; Name要大于5，不然就显示错误
00401501 |. 7F 05 jg Xcosh_3.00401508
00401503 |. E9 BB000000 jmp cosh_3.004015C3
00401508 |> 8B4D E0 mov ecx,[local.8]
0040150B |. 83C1 60 add ecx,0x60
0040150E |. E8 91030000 call <jmp.&MFC42.#CWnd::GetWindowTextLengthA_>
00401513 |. 8945 E8 mov [local.6],eax
00401516 |. 837D E8 05 cmp [local.6],0x5
0040151A |. 7F 05 jg Xcosh_3.00401521 ; Serail也要大于5
0040151C |. E9 A2000000 jmp cosh_3.004015C3
00401521 |> 8B45 E0 mov eax,[local.8]
00401524 |. 05 E0000000 add eax,0xE0
00401529 |. 50 push eax
0040152A |. 8B4D E0 mov ecx,[local.8]
0040152D |. 81C1 A0000000 add ecx,0xA0
00401533 |. E8 66030000 call <jmp.&MFC42.#CWnd::GetWindowTextA_3874> ; 获取Name
00401538 |. 8B4D E0 mov ecx,[local.8]
0040153B |. 81C1 E4000000 add ecx,0xE4
00401541 |. 51 push ecx
00401542 |. 8B4D E0 mov ecx,[local.8]
00401545 |. 83C1 60 add ecx,0x60
00401548 |. E8 51030000 call <jmp.&MFC42.#CWnd::GetWindowTextA_3874> ; 获取Serial
0040154D |. 8B55 E0 mov edx,[local.8]
00401550 |. 81C2 E0000000 add edx,0xE0
00401556 |. 52 push edx
00401557 |. 8D4D E4 lea ecx,[local.7]
0040155A |. E8 39030000 call <jmp.&MFC42.#CString::operator=_858>
0040155F |. 8B45 E0 mov eax,[local.8]
00401562 |. 05 E4000000 add eax,0xE4
00401567 |. 50 push eax
00401568 |. 8D4D F0 lea ecx,[local.4]
0040156B |. E8 28030000 call <jmp.&MFC42.#CString::operator=_858>
00401570 |. 33C0 xor eax,eax
00401572 |. 33DB xor ebx,ebx
00401574 |. 33C9 xor ecx,ecx
00401576 |. B9 01000000 mov ecx,0x1
0040157B |. 33D2 xor edx,edx
0040157D |. 8B45 E4 mov eax,[local.7] ; name
00401580 |> 8A18 /mov bl,byte ptr ds:[eax]
00401582 |. 32D9 |xor bl,cl
00401584 |. 8818 |mov byte ptr ds:[eax],bl
00401586 |. 41 |inc ecx
00401587 |. 40 |inc eax
00401588 |. 8038 00 |cmp byte ptr ds:[eax],0x0
0040158B |.^ 75 F3 \jnz Xcosh_3.00401580
0040158D |. 33C0 xor eax,eax
0040158F |. 33DB xor ebx,ebx
00401591 |. 33C9 xor ecx,ecx
00401593 |. B9 0A000000 mov ecx,0xA
00401598 |. 33D2 xor edx,edx
0040159A |. 8B45 F0 mov eax,[local.4] ; serial
0040159D |> 8A18 /mov bl,byte ptr ds:[eax]
0040159F |. 32D9 |xor bl,cl
004015A1 |. 8818 |mov byte ptr ds:[eax],bl
004015A3 |. 41 |inc ecx
004015A4 |. 40 |inc eax
004015A5 |. 8038 00 |cmp byte ptr ds:[eax],0x0
004015A8 |.^ 75 F3 \jnz Xcosh_3.0040159D
004015AA |. 8B45 E4 mov eax,[local.7]
004015AD |. 8B55 F0 mov edx,[local.4] ; 比较计算后的Name和Serial是否相同
004015B0 |> 33C9 /xor ecx,ecx
004015B2 |. 8A18 |mov bl,byte ptr ds:[eax]
004015B4 |. 8A0A |mov cl,byte ptr ds:[edx]
004015B6 |. 3AD9 |cmp bl,cl
004015B8 |. 75 09 |jnz Xcosh_3.004015C3
004015BA |. 40 |inc eax
004015BB |. 42 |inc edx
004015BC |. 8038 00 |cmp byte ptr ds:[eax],0x0
004015BF |.^ 75 EF \jnz Xcosh_3.004015B0
004015C1 |. EB 16 jmp Xcosh_3.004015D9
004015C3 |> 6A 00 push 0x0
004015C5 |. 68 6C304000 push cosh_3.0040306C ; ASCII "ERROR"
004015CA |. 68 40304000 push cosh_3.00403040 ; ASCII "One of the Details you entered was wrong"
004015CF |. 8B4D E0 mov ecx,[local.8]
004015D2 |. E8 BB020000 call <jmp.&MFC42.#CWnd::MessageBoxA_4224>
004015D7 |. EB 14 jmp Xcosh_3.004015ED
004015D9 |> 6A 00 push 0x0
004015DB |. 68 34304000 push cosh_3.00403034 ; ASCII "YOU DID IT"
004015E0 |. 68 20304000 push cosh_3.00403020 ; ASCII "Well done,Cracker"前两个函数用来确定Name和Serial的长度要大于5，然后取得Name的每个字符，分别于字符的位置异或。
Serial也是取每个字符，分别与每个字符的位置加0x9异或，比较两个字符串的异或结果是否相同，相同就显示正确的消息框，否则显示错误的消息框。
可以简单写出注册机：
char Name[50];
scanf("%s",Name);
for(int i=0;i<strlen(Name);i++){
printf("%c",Name[i]^(1+i)^(10+i));
}
