拖进IDA（32）查看伪代码
输入flag后有一点不一样，要经过函数sub_4110BE处理，后经过for与str2比较
进入该函数查看
1 void *__cdecl sub_411AB0(char *a1, unsigned int a2, int *a3)
2 {
3 int v4; // STE0_4
4 int v5; // STE0_4
5 int v6; // STE0_4
6 int v7; // [esp+D4h] [ebp-38h]
7 signed int i; // [esp+E0h] [ebp-2Ch]
8 unsigned int v9; // [esp+ECh] [ebp-20h]
9 int v10; // [esp+ECh] [ebp-20h]
10 signed int v11; // [esp+ECh] [ebp-20h]
11 void *Dst; // [esp+F8h] [ebp-14h]
12 char *v13; // [esp+104h] [ebp-8h]
13
14 if ( !a1 || !a2 )
15 return 0;
16 v9 = a2 / 3;
17 if ( (signed int)(a2 / 3) % 3 )
18 ++v9;
19 v10 = 4 * v9;
20 *a3 = v10;
21 Dst = malloc(v10 + 1);
22 if ( !Dst )
23 return 0;
24 j_memset(Dst, 0, v10 + 1);
25 v13 = a1;
26 v11 = a2;
27 v7 = 0;
28 while ( v11 > 0 )
29 {
30 byte_41A144[2] = 0;
31 byte_41A144[1] = 0;
32 byte_41A144[0] = 0;
33 for ( i = 0; i < 3 && v11 >= 1; ++i )
34 {
35 byte_41A144[i] = *v13;
36 --v11;
37 ++v13;
38 }
39 if ( !i )
40 break;
41 switch ( i )
42 {
43 case 1:
44 *((_BYTE *)Dst + v7) = aAbcdefghijklmn[(signed int)(unsigned __int8)byte_41A144[0] >> 2];
45 v4 = v7 + 1;
46 *((_BYTE *)Dst + v4++) = aAbcdefghijklmn[((byte_41A144[1] & 0xF0) >> 4) | 16 * (byte_41A144[0] & 3)];
47 *((_BYTE *)Dst + v4++) = aAbcdefghijklmn[64];
48 *((_BYTE *)Dst + v4) = aAbcdefghijklmn[64];
49 v7 = v4 + 1;
50 break;
51 case 2:
52 *((_BYTE *)Dst + v7) = aAbcdefghijklmn[(signed int)(unsigned __int8)byte_41A144[0] >> 2];
53 v5 = v7 + 1;
54 *((_BYTE *)Dst + v5++) = aAbcdefghijklmn[((byte_41A144[1] & 0xF0) >> 4) | 16 * (byte_41A144[0] & 3)];
55 *((_BYTE *)Dst + v5++) = aAbcdefghijklmn[((byte_41A144[2] & 0xC0) >> 6) | 4 * (byte_41A144[1] & 0xF)];
56 *((_BYTE *)Dst + v5) = aAbcdefghijklmn[64];
57 v7 = v5 + 1;
58 break;
59 case 3:
60 *((_BYTE *)Dst + v7) = aAbcdefghijklmn[(signed int)(unsigned __int8)byte_41A144[0] >> 2];
61 v6 = v7 + 1;
62 *((_BYTE *)Dst + v6++) = aAbcdefghijklmn[((byte_41A144[1] & 0xF0) >> 4) | 16 * (byte_41A144[0] & 3)];
63 *((_BYTE *)Dst + v6++) = aAbcdefghijklmn[((byte_41A144[2] & 0xC0) >> 6) | 4 * (byte_41A144[1] & 0xF)];
64 *((_BYTE *)Dst + v6) = aAbcdefghijklmn[byte_41A144[2] & 0x3F];
65 v7 = v6 + 1;
66 break;
67 }
68 }
69 *((_BYTE *)Dst + v7) = 0;
70 return Dst;
71 }
发现奇怪的编码，进入查看
是base64编码
写脚本记得for-i后base64逆运算
1 import base64 2 s="e3nifIH9b_C@n@dH" 3 flag="" 4 for i in range(0,len(s)): 5 flag+=chr(ord(s[i])-i) 6 print(base64.b64decode(flag))