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Reverse/clone/solve.md

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solved new crackme
2024-11-25 15:33:52 +08:00
算serial
先上一组可用密钥：
```
Name: chenx221
Serial: 6237A3FB
```
检查逻辑（c#实现）：
未给出的自定义函数见keygen源码
```c#
public static bool Check(string user, string serial)
{
if (!(CheckStrLen(serial, 8, 8) && CheckStrLen(user, 5, 0)))
return false;
uint eax, ebx, ecx;
ushort cx;
byte cl, ch, dl = 0, bl;
byte[] userBytes, serialBytes;
foreach (char c in user[4..])
{
dl += (byte)c;
}
ecx = (uint)(dl << 24) | (uint)(dl << 16) | (uint)(dl << 8) | dl;
userBytes = Encoding.ASCII.GetBytes(user[..4]);
eax = BitConverter.ToUInt32(userBytes, 0);
ecx ^= eax;
ecx = BSwap(ecx);
ecx += 0x3022006;
ecx = BSwap(ecx);
ecx -= 0xDEADC0DE;
ecx = BSwap(ecx);
cl = (byte)((ecx & 0xFF) + 1);
ecx = (ecx & 0xFFFFFF00) | cl;
ch = (byte)(((ecx >> 8) & 0xFF) + 1);
ecx = (ecx & 0xFFFF00FF) | ((uint)ch << 8);
ecx = BSwap(ecx);
cl = (byte)((ecx & 0xFF) - 1);
ecx = (ecx & 0xFFFFFF00) | cl;
ch = (byte)(((ecx >> 8) & 0xFF) - 1);
ecx = (ecx & 0xFFFF00FF) | ((uint)ch << 8);
ecx = BSwap(ecx);
ecx ^= 0xEDB88320;
ecx = BSwap(ecx);
ecx += 0xD76AA478;
ecx = BSwap(ecx);
ecx -= 0xB00BFACE;
ecx = BSwap(ecx);
ecx += 0xBADBEEF;
ecx = BSwap(ecx);
ecx++;
ecx = BSwap(ecx);
ecx--;
ecx = BSwap(ecx);
ecx += eax;
ecx = BSwap(ecx);
cx = (ushort)((ecx & 0xFFFF) + 1);
ecx = (ecx & 0xFFFF0000) | cx;
ecx = BSwap(ecx);
cx = (ushort)((ecx & 0xFFFF) + 1);
ecx = (ecx & 0xFFFF0000) | cx;
ecx = BSwap(ecx); //true serial result
serialBytes = ParseHstr(serial);
ebx = (uint)(serialBytes[0] * 0x10 + serialBytes[1]);
bl = (byte)(ebx & 0xFF);
bl = (byte)((bl ^ 0x12) + 0x34);
ebx = bl;
eax = ebx;
eax <<= 8;
ebx = (uint)(serialBytes[2] * 0x10 + serialBytes[3]);
bl = (byte)(ebx & 0xFF);
bl = (byte)((bl ^ 0x56) + 0x78);
ebx = bl;
eax += ebx;
eax <<= 8;
ebx = (uint)(serialBytes[4] * 0x10 + serialBytes[5]);
bl = (byte)(ebx & 0xFF);
bl = (byte)((bl ^ 0x90) + 0xAB);
ebx = bl;
eax += ebx;
eax <<= 8;
ebx = (uint)(serialBytes[6] * 0x10 + serialBytes[7]);
bl = (byte)(ebx & 0xFF);
bl = (byte)((bl ^ 0xCD) + 0xEF);
ebx = bl;
eax += ebx;
eax = BSwap(eax); //user input serial result
return eax == ecx; //ecx<->ebx(crackme)
}
```
反向计算（c#实现）：
```c#
public static void CalcSerial(string user)
{
...
... //这部分与Check相同，故省略
...
ecx = BSwap(ecx); //true serial result
eax = BSwap(ecx);
int[] key = [0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF];
int keyIndex = key.Length - 1;
byte[] byteArray = new byte[4];
for (int i = 3; i >= 0; i--)
{
byte temp = (byte)(eax & 0xFF);
temp = (byte)(temp - key[keyIndex--]);
temp = (byte)(temp ^ key[keyIndex--]);
byteArray[i] = temp;
eax >>= 8;
}
Console.WriteLine($"Serial: {BitConverter.ToString(byteArray).Replace("-", "")}");
}
```
细节：
```assembly
004011DB | 6A 19 | push 19 | event
004011DD | 68 9A304000 | push clone.40309A | 40309A:"123456" (serial)
004011E2 | 6A 66 | push 66 |
004011E4 | FF75 08 | push dword ptr ss:[ebp+8] |
004011E7 | E8 F4010000 | call <JMP.&GetDlgItemTextA> |
004011EC | 83F8 08 | cmp eax,8 | serial length == 8
004011EF | 0F85 A9010000 | jne <clone.Fail> |
004011F5 | 6A 1E | push 1E |
004011F7 | 68 7C304000 | push clone.40307C | 40307C:"chenx221" (user)
004011FC | 6A 65 | push 65 |
004011FE | FF75 08 | push dword ptr ss:[ebp+8] |
00401201 | E8 DA010000 | call <JMP.&GetDlgItemTextA> |
00401206 | 83F8 05 | cmp eax,5 | user length >=5
00401209 | 0F82 8F010000 | jb <clone.Fail> |
0040120F | 8D05 7C304000 | lea eax,dword ptr ds:[40307C] | user
00401215 | 8D48 04 | lea ecx,dword ptr ds:[eax+4] | user去前四位
00401218 | 33D2 | xor edx,edx |
0040121A | 0211 | add dl,byte ptr ds:[ecx] | 累加user去前四位后每位asc(注意:dl)
0040121C | 41 | inc ecx |
0040121D | 8039 00 | cmp byte ptr ds:[ecx],0 |
00401220 | 75 F8 | jne clone.40121A |
00401222 | 33C9 | xor ecx,ecx |
00401224 | 8ACA | mov cl,dl | 上一步的结果(ex:ab)
00401226 | 8AEA | mov ch,dl | 上一步的结果
00401228 | 0FC9 | bswap ecx | 1
0040122A | 8ACA | mov cl,dl |
0040122C | 8AEA | mov ch,dl | (ex: ecx=abababab)
0040122E | 8B00 | mov eax,dword ptr ds:[eax] | user
00401230 | 33C8 | xor ecx,eax | abababab ^ user前四位(小端序
00401232 | 0FC9 | bswap ecx | 2
00401234 | 81C1 06200203 | add ecx,3022006 |
0040123A | 0FC9 | bswap ecx | 3
0040123C | 81E9 DEC0ADDE | sub ecx,DEADC0DE |
00401242 | 0FC9 | bswap ecx | 4
00401244 | FEC1 | inc cl |
00401246 | FEC5 | inc ch |
00401248 | 0FC9 | bswap ecx | 5
0040124A | FEC9 | dec cl |
0040124C | FECD | dec ch |
0040124E | 0FC9 | bswap ecx | 6
00401250 | 81F1 2083B8ED | xor ecx,EDB88320 |
00401256 | 0FC9 | bswap ecx | ...
00401258 | 81C1 78A46AD7 | add ecx,D76AA478 |
0040125E | 0FC9 | bswap ecx |
00401260 | 81E9 CEFA0BB0 | sub ecx,B00BFACE |
00401266 | 0FC9 | bswap ecx |
00401268 | 81C1 EFBEAD0B | add ecx,BADBEEF |
0040126E | 0FC9 | bswap ecx |
00401270 | 41 | inc ecx |
00401271 | 0FC9 | bswap ecx |
00401273 | 49 | dec ecx |
00401274 | 0FC9 | bswap ecx |
00401276 | 03C8 | add ecx,eax | 还是user
00401278 | 0FC9 | bswap ecx |
0040127A | 66:41 | inc cx |
0040127C | 0FC9 | bswap ecx |
0040127E | 66:41 | inc cx |
00401280 | 0FC9 | bswap ecx |
00401282 | 890D C8304000 | mov dword ptr ds:[4030C8],ecx |
00401288 | 33C9 | xor ecx,ecx |
0040128A | 8D05 9A304000 | lea eax,dword ptr ds:[40309A] | serial
00401290 | 33DB | xor ebx,ebx | 十六进制字符转实际数值
00401292 | 8A18 | mov bl,byte ptr ds:[eax] |
00401294 | 80FB 00 | cmp bl,0 |
00401297 | 74 3A | je clone.4012D3 | serial读完了?
00401299 | 80FB 30 | cmp bl,30 | 30:'0'
0040129C | 0F82 FC000000 | jb <clone.Fail> |
004012A2 | 80FB 39 | cmp bl,39 | 39:'9'
004012A5 | 77 0D | ja clone.4012B4 |
004012A7 | 80EB 30 | sub bl,30 | 0~9数字处理部分(str2int)
004012AA | 8899 B8304000 | mov byte ptr ds:[ecx+4030B8], |
004012B0 | 40 | inc eax |
004012B1 | 41 | inc ecx |
004012B2 | EB DC | jmp clone.401290 |
004012B4 | 80FB 41 | cmp bl,41 | 41:'A'
004012B7 | 0F82 E1000000 | jb <clone.Fail> |
004012BD | 80FB 46 | cmp bl,46 | 46:'F'
004012C0 | 0F87 D8000000 | ja <clone.Fail> |
004012C6 | 80EB 37 | sub bl,37 | 只接受A~F
004012C9 | 8899 B8304000 | mov byte ptr ds:[ecx+4030B8], | A~F处理部分(str2int)
004012CF | 40 | inc eax |
004012D0 | 41 | inc ecx |
004012D1 | EB BD | jmp clone.401290 |
004012D3 | 33C0 | xor eax,eax |
004012D5 | 33DB | xor ebx,ebx |
004012D7 | 33C9 | xor ecx,ecx | 0
004012D9 | 33D2 | xor edx,edx |
004012DB | 0FB699 B8304000 | movzx ebx,byte ptr ds:[ecx+40 | 读取第一位
004012E2 | C1E3 04 | shl ebx,4 | <<4
004012E5 | 41 | inc ecx | 1
004012E6 | 0FB691 B8304000 | movzx edx,byte ptr ds:[ecx+40 |
004012ED | 03DA | add ebx,edx | +=第二位
004012EF | 80F3 12 | xor bl,12 |
004012F2 | 80C3 34 | add bl,34 |
004012F5 | 81E3 FF000000 | and ebx,FF |
004012FB | 41 | inc ecx | 2
004012FC | 03C3 | add eax,ebx |
004012FE | C1E0 08 | shl eax,8 |
00401301 | 0FB699 B8304000 | movzx ebx,byte ptr ds:[ecx+40 |
00401308 | C1E3 04 | shl ebx,4 |
0040130B | 41 | inc ecx | 3
0040130C | 0FB691 B8304000 | movzx edx,byte ptr ds:[ecx+40 |
00401313 | 03DA | add ebx,edx |
00401315 | 80F3 56 | xor bl,56 |
00401318 | 80C3 78 | add bl,78 |
0040131B | 81E3 FF000000 | and ebx,FF |
00401321 | 41 | inc ecx | 4
00401322 | 03C3 | add eax,ebx |
00401324 | C1E0 08 | shl eax,8 |
00401327 | 0FB699 B8304000 | movzx ebx,byte ptr ds:[ecx+40 |
0040132E | C1E3 04 | shl ebx,4 |
00401331 | 41 | inc ecx | 5
00401332 | 0FB691 B8304000 | movzx edx,byte ptr ds:[ecx+40 |
00401339 | 03DA | add ebx,edx |
0040133B | 80F3 90 | xor bl,90 |
0040133E | 80C3 AB | add bl,AB |
00401341 | 81E3 FF000000 | and ebx,FF |
00401347 | 41 | inc ecx | 6
00401348 | 03C3 | add eax,ebx |
0040134A | C1E0 08 | shl eax,8 |
0040134D | 0FB699 B8304000 | movzx ebx,byte ptr ds:[ecx+40 |
00401354 | C1E3 04 | shl ebx,4 |
00401357 | 41 | inc ecx | 7
00401358 | 0FB691 B8304000 | movzx edx,byte ptr ds:[ecx+40 |
0040135F | 03DA | add ebx,edx |
00401361 | 80F3 CD | xor bl,CD |
00401364 | 80C3 EF | add bl,EF |
00401367 | 81E3 FF000000 | and ebx,FF |
0040136D | 41 | inc ecx | 8
0040136E | 03C3 | add eax,ebx |
00401370 | 0FC8 | bswap eax |
00401372 | 8B1D C8304000 | mov ebx,dword ptr ds:[4030C8] |
00401378 | 3BD8 | cmp ebx,eax | eax是用户输入serial计算结果,ebx是正确的结果
0040137A | 75 22 | jne <clone.Fail> |
0040137C | 6A 40 | push 40 | Success
0040137E | 68 50304000 | push clone.403050 | 403050:"Bravo!"
00401383 | 68 19304000 | push clone.403019 | 403019:"Well done! Now make good tutorial :)"
00401388 | 6A 00 | push 0 |
0040138A | E8 75000000 | call clone.401404 |
0040138F | 68 3E304000 | push clone.40303E | 40303E:"clone - defeated!"
00401394 | FF75 08 | push dword ptr ss:[ebp+8] |
00401397 | E8 86000000 | call <JMP.&SetWindowTextA> |
0040139C | EB 00 | jmp <clone.Fail> |
0040139E | EB 15 | jmp clone.4013B5 |
```
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