题目
给了一个exe文件，打开后如图
分析
真-逆向
- Kali中用file指令检查一下
PE32 executable (console) Intel 80386, for MS Windows
- 用ida打开并检索"flag"，发现
- 双击看到基本块的控制流程，直接F5
int sub_45E940()
{
signed int i; // [esp+D0h] [ebp-94h]
char v2; // [esp+DCh] [ebp-88h]
char v3; // [esp+DDh] [ebp-87h]
char v4; // [esp+DEh] [ebp-86h]
char v5; // [esp+DFh] [ebp-85h]
char v6; // [esp+E0h] [ebp-84h]
char v7; // [esp+E1h] [ebp-83h]
char v8; // [esp+E2h] [ebp-82h]
char v9; // [esp+E3h] [ebp-81h]
char v10; // [esp+E4h] [ebp-80h]
char v11; // [esp+E5h] [ebp-7Fh]
char v12; // [esp+E6h] [ebp-7Eh]
char v13; // [esp+E7h] [ebp-7Dh]
char v14; // [esp+E8h] [ebp-7Ch]
char v15; // [esp+E9h] [ebp-7Bh]
char v16; // [esp+EAh] [ebp-7Ah]
char v17; // [esp+EBh] [ebp-79h]
char v18; // [esp+ECh] [ebp-78h]
char v19; // [esp+EDh] [ebp-77h]
char v20; // [esp+EEh] [ebp-76h]
char v21; // [esp+EFh] [ebp-75h]
char v22; // [esp+F0h] [ebp-74h]
char v23; // [esp+F1h] [ebp-73h]
char v24; // [esp+F2h] [ebp-72h]
char v25; // [esp+F3h] [ebp-71h]
char v26; // [esp+F4h] [ebp-70h]
char v27; // [esp+F5h] [ebp-6Fh]
char v28; // [esp+F6h] [ebp-6Eh]
char v29; // [esp+F7h] [ebp-6Dh]
char v30; // [esp+F8h] [ebp-6Ch]
char v31; // [esp+F9h] [ebp-6Bh]
char v32; // [esp+FAh] [ebp-6Ah]
char v33; // [esp+FBh] [ebp-69h]
char v34; // [esp+FCh] [ebp-68h]
char v35; // [esp+FDh] [ebp-67h]
char v36; // [esp+FEh] [ebp-66h]
char v37; // [esp+FFh] [ebp-65h]
char v38; // [esp+100h] [ebp-64h]
char v39; // [esp+101h] [ebp-63h]
char v40; // [esp+102h] [ebp-62h]
char v41; // [esp+103h] [ebp-61h]
char v42; // [esp+104h] [ebp-60h]
char v43; // [esp+105h] [ebp-5Fh]
char v44; // [esp+106h] [ebp-5Eh]
char v45; // [esp+107h] [ebp-5Dh]
char v46; // [esp+108h] [ebp-5Ch]
char v47; // [esp+109h] [ebp-5Bh]
char v48; // [esp+10Ah] [ebp-5Ah]
char v49; // [esp+10Bh] [ebp-59h]
char v50; // [esp+10Ch] [ebp-58h]
char v51; // [esp+10Dh] [ebp-57h]
char v52; // [esp+10Eh] [ebp-56h]
char v53; // [esp+10Fh] [ebp-55h]
char v54; // [esp+110h] [ebp-54h]
char v55; // [esp+111h] [ebp-53h]
char v56; // [esp+112h] [ebp-52h]
char v57; // [esp+113h] [ebp-51h]
char v58; // [esp+114h] [ebp-50h]
char v59; // [esp+120h] [ebp-44h]
char v60; // [esp+121h] [ebp-43h]
char v61; // [esp+122h] [ebp-42h]
char v62; // [esp+123h] [ebp-41h]
char v63; // [esp+124h] [ebp-40h]
char v64; // [esp+125h] [ebp-3Fh]
char v65; // [esp+126h] [ebp-3Eh]
char v66; // [esp+127h] [ebp-3Dh]
char v67; // [esp+128h] [ebp-3Ch]
char v68; // [esp+129h] [ebp-3Bh]
char v69; // [esp+12Ah] [ebp-3Ah]
char v70; // [esp+12Bh] [ebp-39h]
char v71; // [esp+12Ch] [ebp-38h]
char v72; // [esp+12Dh] [ebp-37h]
char v73; // [esp+12Eh] [ebp-36h]
char v74; // [esp+12Fh] [ebp-35h]
char v75; // [esp+130h] [ebp-34h]
char v76; // [esp+131h] [ebp-33h]
char v77; // [esp+132h] [ebp-32h]
char v78; // [esp+133h] [ebp-31h]
char v79; // [esp+134h] [ebp-30h]
char v80; // [esp+135h] [ebp-2Fh]
char v81; // [esp+136h] [ebp-2Eh]
char v82; // [esp+137h] [ebp-2Dh]
char v83; // [esp+138h] [ebp-2Ch]
char v84; // [esp+139h] [ebp-2Bh]
char v85; // [esp+13Ah] [ebp-2Ah]
char v86; // [esp+13Bh] [ebp-29h]
char v87; // [esp+13Ch] [ebp-28h]
char v88; // [esp+13Dh] [ebp-27h]
char v89; // [esp+13Eh] [ebp-26h]
char v90; // [esp+13Fh] [ebp-25h]
char v91; // [esp+140h] [ebp-24h]
char v92; // [esp+141h] [ebp-23h]
char v93; // [esp+142h] [ebp-22h]
char v94; // [esp+143h] [ebp-21h]
char v95; // [esp+144h] [ebp-20h]
char v96; // [esp+145h] [ebp-1Fh]
char v97; // [esp+146h] [ebp-1Eh]
char v98; // [esp+147h] [ebp-1Dh]
char v99; // [esp+148h] [ebp-1Ch]
char v100; // [esp+149h] [ebp-1Bh]
char v101; // [esp+14Ah] [ebp-1Ah]
char v102; // [esp+14Bh] [ebp-19h]
char v103; // [esp+14Ch] [ebp-18h]
char v104; // [esp+14Dh] [ebp-17h]
char v105; // [esp+14Eh] [ebp-16h]
char v106; // [esp+14Fh] [ebp-15h]
char v107; // [esp+150h] [ebp-14h]
char v108; // [esp+151h] [ebp-13h]
char v109; // [esp+152h] [ebp-12h]
char v110; // [esp+153h] [ebp-11h]
char v111; // [esp+154h] [ebp-10h]
char v112; // [esp+155h] [ebp-Fh]
char v113; // [esp+156h] [ebp-Eh]
char v114; // [esp+157h] [ebp-Dh]
char v115; // [esp+158h] [ebp-Ch]
sub_45A7BE((int)"done!!! the flag is ");
v59 = 18;
v60 = 64;
v61 = 98;
v62 = 5;
v63 = 2;
v64 = 4;
v65 = 6;
v66 = 3;
v67 = 6;
v68 = 48;
v69 = 49;
v70 = 65;
v71 = 32;
v72 = 12;
v73 = 48;
v74 = 65;
v75 = 31;
v76 = 78;
v77 = 62;
v78 = 32;
v79 = 49;
v80 = 32;
v81 = 1;
v82 = 57;
v83 = 96;
v84 = 3;
v85 = 21;
v86 = 9;
v87 = 4;
v88 = 62;
v89 = 3;
v90 = 5;
v91 = 4;
v92 = 1;
v93 = 2;
v94 = 3;
v95 = 44;
v96 = 65;
v97 = 78;
v98 = 32;
v99 = 16;
v100 = 97;
v101 = 54;
v102 = 16;
v103 = 44;
v104 = 52;
v105 = 32;
v106 = 64;
v107 = 89;
v108 = 45;
v109 = 32;
v110 = 65;
v111 = 15;
v112 = 34;
v113 = 18;
v114 = 16;
v115 = 0;
v2 = 123;
v3 = 32;
v4 = 18;
v5 = 98;
v6 = 119;
v7 = 108;
v8 = 65;
v9 = 41;
v10 = 124;
v11 = 80;
v12 = 125;
v13 = 38;
v14 = 124;
v15 = 111;
v16 = 74;
v17 = 49;
v18 = 83;
v19 = 108;
v20 = 94;
v21 = 108;
v22 = 84;
v23 = 6;
v24 = 96;
v25 = 83;
v26 = 44;
v27 = 121;
v28 = 104;
v29 = 110;
v30 = 32;
v31 = 95;
v32 = 117;
v33 = 101;
v34 = 99;
v35 = 123;
v36 = 127;
v37 = 119;
v38 = 96;
v39 = 48;
v40 = 107;
v41 = 71;
v42 = 92;
v43 = 29;
v44 = 81;
v45 = 107;
v46 = 90;
v47 = 85;
v48 = 64;
v49 = 12;
v50 = 43;
v51 = 76;
v52 = 86;
v53 = 13;
v54 = 114;
v55 = 1;
v56 = 117;
v57 = 126;
v58 = 0;
for ( i = 0; i < 56; ++i )
{
*(&v2 + i) ^= *(&v59 + i);
*(&v2 + i) ^= 0x13u;
}
return sub_45A7BE((int)"%s
");
}
- 所以基本逻辑还是很简单的，关键就是那个for循环，进行两次异或后，直接将v2为起始的56个单位按字符输出即可。求解代码如下
v2 = 123
v3 = 32
v4 = 18
v5 = 98
v6 = 119
v7 = 108
v8 = 65
v9 = 41
v10 = 124
v11 = 80
v12 = 125
v13 = 38
v14 = 124
v15 = 111
v16 = 74
v17 = 49
v18 = 83
v19 = 108
v20 = 94
v21 = 108
v22 = 84
v23 = 6
v24 = 96
v25 = 83
v26 = 44
v27 = 121
v28 = 104
v29 = 110
v30 = 32
v31 = 95
v32 = 117
v33 = 101
v34 = 99
v35 = 123
v36 = 127
v37 = 119
v38 = 96
v39 = 48
v40 = 107
v41 = 71
v42 = 92
v43 = 29
v44 = 81
v45 = 107
v46 = 90
v47 = 85
v48 = 64
v49 = 12
v50 = 43
v51 = 76
v52 = 86
v53 = 13
v54 = 114
v55 = 1
v56 = 117
v57 = 126
v58 = 0
v59 = 18
v60 = 64
v61 = 98
v62 = 5
v63 = 2
v64 = 4
v65 = 6
v66 = 3
v67 = 6
v68 = 48
v69 = 49
v70 = 65
v71 = 32
v72 = 12
v73 = 48
v74 = 65
v75 = 31
v76 = 78
v77 = 62
v78 = 32
v79 = 49
v80 = 32
v81 = 1
v82 = 57
v83 = 96
v84 = 3
v85 = 21
v86 = 9
v87 = 4
v88 = 62
v89 = 3
v90 = 5
v91 = 4
v92 = 1
v93 = 2
v94 = 3
v95 = 44
v96 = 65
v97 = 78
v98 = 32
v99 = 16
v100 = 97
v101 = 54
v102 = 16
v103 = 44
v104 = 52
v105 = 32
v106 = 64
v107 = 89
v108 = 45
v109 = 32
v110 = 65
v111 = 15
v112 = 34
v113 = 18
v114 = 16
v115 = 0
v_2begin = []
v_59begin = []
for i in range(56):
v_2begin.append(eval("v"+str(2+i)))
v_59begin.append(eval("v"+str(59+i)))
v_2begin[i] ^= v_59begin[i]
v_2begin[i] ^= 0x13
print(v_2begin)
flag = ""
for i in v_2begin:
flag += chr(i)
print(flag)
游戏
实际上玩游戏直接输入12345678可以直接拿到flag
zsctf{T9is_tOpic_1s_v5ry_int7resting_b6t_others_are_n0t}