英语会话精灵20.sn

假设：
用户编号：222961388
注册码：654321

一、先脱壳，查找出错信息。
* referenced by a (u)nconditional or (c)onditional jump at address:
|:0047a05c(c)
|
:0047a19f 6830000400              push 00040030
:0047a1a4 b908a24700              mov ecx, 0047a208

* possible stringdata ref from code obj ->"注册码无效！"
                                 |
:0047a1a9 ba6ca24700              mov edx, 0047a26c
:0047a1ae a1e8794b00              mov eax, dword ptr [004b79e8]
:0047a1b3 8b00                    mov eax, dword ptr [eax]
:0047a1b5 e8a22afdff              call 0044cc5c
:0047a1ba 8b86e8020000            mov eax, dword ptr [esi+000002e8]
:0047a1c0 8b10                    mov edx, dword ptr [eax]
:0047a1c2 ff92cc000000            call dword ptr [edx+000000cc]

向上看：
0047a053 8b55f8                  mov edx, dword ptr [ebp-08]＝＝＞在这下断
:0047a056 58                      pop eax
:0047a057 e8489ef8ff              call 00403ea4
:0047a05c 0f853d010000            jne 0047a19f=========>
:0047a062 6840000400              push 00040040
:0047a067 b908a24700              mov ecx, 0047a208

* possible stringdata ref from code obj ->"注册成功！请保留好您的注册码，谢谢！"
                                 |

二、用ollydbg载入，动态分析。
0047a002  |.  8b1d 28784b00 mov ebx,dword ptr ds:[4b7828]            ;  unpacked.004b8930
0047a008  |.  33c0          xor eax,eax
0047a00a  |.  55            push ebp
0047a00b  |.  68 fba14700   push unpacked.0047a1fb
0047a010  |.  64:ff30       push dword ptr fs:[eax]
0047a013  |.  64:8920       mov dword ptr fs:[eax],esp
0047a016  |.  6a 00         push 0
0047a018  |.  6a 1b         push 1b
0047a01a  |.  e8 a9fdffff   call unpacked.00479dc8                   ;  用户编号十六进制值入eax,此eax=0d4a1eec
0047a01f  |.  2d 1f17f601   sub eax,1f6171f                          ;  eax减1f6171f，eax=b5407cd
0047a024  |.  83da 00       sbb edx,0
0047a027  |.  e8 44c5f8ff   call unpacked.00406570                   ;  b5407cd值乘以1b，此eax=131dcd29f
0047a02c  |.  52            push edx                                 ; /arg2
0047a02d  |.  50            push eax                                 ; |arg1
0047a02e  |.  8d45 fc       lea eax,dword ptr ss:[ebp-4]             ; |
0047a031  |.  e8 6ae9f8ff   call unpacked.004089a0                   ; \把串31dcd29f转换为十进制，即为5131522719
0047a036  |.  8b45 fc       mov eax,dword ptr ss:[ebp-4]
0047a039  |.  50            push eax
0047a03a  |.  8d55 f4       lea edx,dword ptr ss:[ebp-c]
0047a03d  |.  8b86 e8020000 mov eax,dword ptr ds:[esi+2e8]
0047a043  |.  e8 444afbff   call unpacked.0042ea8c                   ;  取输入注册码
0047a048  |.  8b45 f4       mov eax,dword ptr ss:[ebp-c]
0047a04b  |.  8d55 f8       lea edx,dword ptr ss:[ebp-8]
0047a04e  |.  e8 9de7f8ff   call unpacked.004087f0
0047a053  |.  8b55 f8       mov edx,dword ptr ss:[ebp-8]             ;  输入注册码，此为edx=654321
0047a056  |.  58            pop eax                                  ;  真码入eax
0047a057  |.  e8 489ef8ff   call unpacked.00403ea4                   ;  关键比较unpa
0047a05c  |.  0f85 3d010000 jnz unpacked.0047a19f                    ;  不等就跳npac
0047a062  |.  68 40000400   push 40040

总结：

1、用户编号转为十六进制：222961388－＞d4a1eec
2、十六进制值减1f6171f：d4a1eec-1f6171f=b5407cd
3、第二步的值乘1b:b5407cd＊1b=131dcd29f
4、第三步的值转为十进制就是注册码：131dcd29f－＞5131522719


所以我的注册码如下：
　　 用户编号：222961388
　　 注册码：5131522719