buuctf SimpleRev

 1 unsigned __int64 Decry()
 2 {
 3   char v1; // [rsp+Fh] [rbp-51h]
 4   int v2; // [rsp+10h] [rbp-50h]
 5   int v3; // [rsp+14h] [rbp-4Ch]
 6   int i; // [rsp+18h] [rbp-48h]
 7   int v5; // [rsp+1Ch] [rbp-44h]
 8   char src[8]; // [rsp+20h] [rbp-40h]
 9   __int64 v7; // [rsp+28h] [rbp-38h]
10   int v8; // [rsp+30h] [rbp-30h]
11   __int64 v9; // [rsp+40h] [rbp-20h]
12   __int64 v10; // [rsp+48h] [rbp-18h]
13   int v11; // [rsp+50h] [rbp-10h]
14   unsigned __int64 v12; // [rsp+58h] [rbp-8h]
15 
16   v12 = __readfsqword(0x28u);
17   *(_QWORD *)src = 357761762382LL;
18   v7 = 0LL;
19   v8 = 0;
20   v9 = 512969957736LL;
21   v10 = 0LL;
22   v11 = 0;
23   text = (char *)join(key3, &v9);
24   strcpy(key, key1);
25   strcat(key, src);
26   v2 = 0;
27   v3 = 0;
28   getchar();
29   v5 = strlen(key);
30   for ( i = 0; i < v5; ++i )
31   {
32     if ( key[v3 % v5] > 64 && key[v3 % v5] <= 90 )
33       key[i] = key[v3 % v5] + 32;
34     ++v3;
35   }
36   printf("Please input your flag:", src);
37   while ( 1 )
38   {
39     v1 = getchar();
40     if ( v1 == 10 )
41       break;
42     if ( v1 == 32 )
43     {
44       ++v2;
45     }
46     else
47     {
48       if ( v1 <= 96 || v1 > 122 )
49       {
50         if ( v1 > 64 && v1 <= 90 )
51           str2[v2] = (v1 - 39 - key[v3++ % v5] + 97) % 26 + 97;
52       }
53       else
54       {
55         str2[v2] = (v1 - 39 - key[v3++ % v5] + 97) % 26 + 97;
56       }
57       if ( !(v3 % v5) )
58         putchar(32);
59       ++v2;
60     }
61   }
62   if ( !strcmp(text, str2) )
63     puts("Congratulation!\n");
64   else
65     puts("Try again!\n");
66   return __readfsqword(0x28u) ^ v12;
67 }

1 v1 = getchar();
2     if ( v1 == ‘\n‘ )
3       break;
4     if ( v1 == ‘ ‘ )
5     {
6       ++v2;
7     }