123 lines
6.9 KiB
Markdown
123 lines
6.9 KiB
Markdown
不清楚是不是兼容问题，这个crackme在winxp、win7都无法显示窗体
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1. 修bug
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排查了一下
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```assembly
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0040108B | 6A 00 | push 0 |
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0040108D | 6A 00 | push 0 |
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0040108F | 6A 00 | push 0 |
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00401091 | 68 1F304000 | push crackme1.40301F | 40301F:"MainWindow"
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00401096 | FF35 3C314000 | push dword ptr ds:[40313C] |
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0040109C | E8 1F020000 | call <JMP.&_CreateDialogParamA@20> |
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```
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这里call完之后返回值为null，错误`0x57F`
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尝试下修一下
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```assembly
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00401096 | FF35 3C314000 | push dword ptr ds:[40313C] | Patch
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00401096 | 6A 00 | push 0 |
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00401098 | 90 | nop |
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00401099 | 90 | nop |
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0040109A | 90 | nop |
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0040109B | 90 | nop |
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```
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2. name
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```assembly
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0040124B | 55 | push ebp |
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0040124C | 8BEC | mov ebp,esp |
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0040124E | 53 | push ebx |
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0040124F | 51 | push ecx | ecx:_lstrlenA@4+2F
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00401250 | 52 | push edx |
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00401251 | 57 | push edi |
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00401252 | 56 | push esi |
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00401253 | 55 | push ebp |
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00401254 | 33D2 | xor edx,edx |
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00401256 | 8B75 08 | mov esi,dword ptr ss:[ebp+8] |
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00401259 | 8B4D 0C | mov ecx,dword ptr ss:[ebp+C] | ecx:_lstrlenA@4+2F
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0040125C | 49 | dec ecx | ecx:_lstrlenA@4+2F
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0040125D | 0FBE06 | movsx eax,byte ptr ds:[esi] | 循环
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00401260 | 2B05 00304000 | sub eax,dword ptr ds:[403000] |
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00401266 | 0FBE5E 01 | movsx ebx,byte ptr ds:[esi+1] |
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0040126A | 2B1D 04304000 | sub ebx,dword ptr ds:[403004] |
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00401270 | 0FAFC3 | imul eax,ebx |
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00401273 | 03D0 | add edx,eax |
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00401275 | 46 | inc esi |
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00401276 | E2 E5 | loop crackme1_fix.40125D |
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00401278 | 8BC2 | mov eax,edx |
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0040127A | 5D | pop ebp |
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0040127B | 5E | pop esi |
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0040127C | 5F | pop edi |
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0040127D | 5A | pop edx |
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0040127E | 59 | pop ecx | ecx:_lstrlenA@4+2F
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0040127F | 5B | pop ebx |
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00401280 | C9 | leave |
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00401281 | C2 0800 | ret 8 |
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```
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```c#
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string name = "userinput";
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int ecx = name.Length - 1;
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int index = 0;
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int edx = 0;
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while (ecx > 0)
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{
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char c = (char)(name[index] - '*');
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char c2 = (char)(name[index + 1] - 'A');
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c = (char)(c * c2);
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edx += (int)c;
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index++;
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ecx--;
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}
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```
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Name（不能使用数字）会计算出一个edx值
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3. Serial
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```assembly
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00401284 | 55 | push ebp |
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00401285 | 8BEC | mov ebp,esp |
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00401287 | 53 | push ebx |
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00401288 | 51 | push ecx | ecx:_lstrlenA@4+2F
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00401289 | 52 | push edx |
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0040128A | 56 | push esi |
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0040128B | 57 | push edi |
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0040128C | 55 | push ebp |
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0040128D | 8B75 08 | mov esi,dword ptr ss:[ebp+8] |
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00401290 | 8B4D 0C | mov ecx,dword ptr ss:[ebp+C] | ecx:_lstrlenA@4+2F
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00401293 | 33D2 | xor edx,edx |
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00401295 | 0FB64431 FF | movzx eax,byte ptr ds:[ecx+esi-1] |
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0040129A | 83E8 30 | sub eax,30 |
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0040129D | 51 | push ecx | ecx:_lstrlenA@4+2F
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0040129E | 8BD9 | mov ebx,ecx | ecx:_lstrlenA@4+2F
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004012A0 | 2B4D 0C | sub ecx,dword ptr ss:[ebp+C] | ecx:_lstrlenA@4+2F
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004012A3 | F7D9 | neg ecx | ecx:_lstrlenA@4+2F
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004012A5 | 85C9 | test ecx,ecx | ecx:_lstrlenA@4+2F
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004012A7 | 74 05 | je crackme1_fix.4012AE |
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004012A9 | 6BC0 0A | imul eax,eax,A |
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004012AC | E2 FB | loop crackme1_fix.4012A9 |
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004012AE | 59 | pop ecx | ecx:_lstrlenA@4+2F
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004012AF | 03D0 | add edx,eax |
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004012B1 | E2 E2 | loop crackme1_fix.401295 |
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004012B3 | 8BC2 | mov eax,edx |
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004012B5 | 5D | pop ebp |
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004012B6 | 5F | pop edi |
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004012B7 | 5E | pop esi |
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004012B8 | 5A | pop edx |
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004012B9 | 59 | pop ecx | ecx:_lstrlenA@4+2F
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004012BA | 5B | pop ebx |
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004012BB | C9 | leave |
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004012BC | C2 0800 | ret 8 |
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```
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这里似乎只是将传入的serial字符串转成整形，后面比较用
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