[ACTF新生赛2020]rome
无壳, 直接拖进IDA32
y键把v2改成char[49], n键重命名为iuput
int func()
{int result; // eaxint v1[4]; // [esp+14h] [ebp-44h]char input[49]; // [esp+24h] [ebp-34h] BYREFstrcpy(&input[23], "Qsw3sj_lz4_Ujw@l");printf("Please input:");scanf("%s", input);result = (unsigned __int8)input[0];if ( input[0] == 65 ){result = (unsigned __int8)input[1];if ( input[1] == 67 ){result = (unsigned __int8)input[2];if ( input[2] == 84 ){result = (unsigned __int8)input[3];if ( input[3] == 70 ){result = (unsigned __int8)input[4];if ( input[4] == 123 ){result = (unsigned __int8)input[21];if ( input[21] == 125 ){v1[0] = *(_DWORD *)&input[5];v1[1] = *(_DWORD *)&input[9];v1[2] = *(_DWORD *)&input[13];v1[3] = *(_DWORD *)&input[17];*(_DWORD *)&input[40] = 0;while ( *(int *)&input[40] <= 15 ){if ( *((char *)v1 + *(_DWORD *)&input[40]) > 64 && *((char *)v1 + *(_DWORD *)&input[40]) <= 90 )*((_BYTE *)v1 + *(_DWORD *)&input[40]) = (*((char *)v1 + *(_DWORD *)&input[40]) - 51) % 26 + 65;if ( *((char *)v1 + *(_DWORD *)&input[40]) > 96 && *((char *)v1 + *(_DWORD *)&input[40]) <= 122 )*((_BYTE *)v1 + *(_DWORD *)&input[40]) = (*((char *)v1 + *(_DWORD *)&input[40]) - 79) % 26 + 97;++*(_DWORD *)&input[40];}*(_DWORD *)&input[40] = 0;while ( *(int *)&input[40] <= 15 ){result = (unsigned __int8)input[*(_DWORD *)&input[40] + 23];if ( *((_BYTE *)v1 + *(_DWORD *)&input[40]) != (_BYTE)result )return result;++*(_DWORD *)&input[40];}return printf("You are correct!");}}}}}}return result;
}
0-4位是'ACTF{'最后1位是'}'直接爆破5-20位
s = 'Qsw3sj_lz4_Ujw@l'
print(len(s))
brutestr = ''def transchar(num):if num > ord('@') and num <= ord('Z'):return (num - ord('3')) % 26 + ord('A')if num > ord('`') and num <= ord('z'):return (num - ord('O')) % 26 + ord('a')return numfor i in range(16):for n in range(128):if transchar(n) == ord(s[i]):print(i, n)brutestr += chr(n)breakflag = 'ACTF{' + brutestr + '}'
print(len(flag), flag)
[FlareOn4]login
html写的flag checker
<!DOCTYPE Html />
<html><head><title>FLARE On 2017</title></head><body><input type="text" name="flag" id="flag" value="Enter the flag" /><input type="button" id="prompt" value="Click to check the flag" /><script type="text/javascript">document.getElementById("prompt").onclick = function () {var flag = document.getElementById("flag").value;var rotFlag = flag.replace(/[a-zA-Z]/g, function(c){return String.fromCharCode((c <= "Z" ? 90 : 122) >= (c = c.charCodeAt(0) + 13) ? c : c - 26);});if ("PyvragFvqrYbtvafNerRnfl@syner-ba.pbz" == rotFlag) {alert("Correct flag!");} else {alert("Incorrect flag, rot again");}}</script></body>
</html>
看到rotFlag那行, 可以猜测是rot13加密, 因为对每个字母字符做+13处理
最后要等于PyvragFvqrYbtvafNerRnfl@syner-ba.pbz, 直接解密得到flag
在线网址https://rot13.com/
[2019红帽杯]easyRE
无壳, 直接分析, string定位到关键字符串
__int64 sub_4009C6()
{__int64 result; // raxint i; // [rsp+Ch] [rbp-114h]__int64 v2; // [rsp+10h] [rbp-110h]__int64 v3; // [rsp+18h] [rbp-108h]__int64 v4; // [rsp+20h] [rbp-100h]__int64 v5; // [rsp+28h] [rbp-F8h]__int64 v6; // [rsp+30h] [rbp-F0h]__int64 v7; // [rsp+38h] [rbp-E8h]__int64 v8; // [rsp+40h] [rbp-E0h]__int64 v9; // [rsp+48h] [rbp-D8h]__int64 v10; // [rsp+50h] [rbp-D0h]__int64 v11; // [rsp+58h] [rbp-C8h]char v12[13]; // [rsp+60h] [rbp-C0h] BYREFchar v13[4]; // [rsp+6Dh] [rbp-B3h] BYREFchar v14[19]; // [rsp+71h] [rbp-AFh] BYREFchar v15[32]; // [rsp+90h] [rbp-90h] BYREFint v16; // [rsp+B0h] [rbp-70h]char v17; // [rsp+B4h] [rbp-6Ch]char v18[72]; // [rsp+C0h] [rbp-60h] BYREFunsigned __int64 v19; // [rsp+108h] [rbp-18h]v19 = __readfsqword(0x28u);qmemcpy(v12, "Iodl>Qnb(ocy", 12);v12[12] = 127;qmemcpy(v13, "y.i", 3);v13[3] = 127;qmemcpy(v14, "d`3w}wek9{iy=~yL@EC", sizeof(v14));memset(v15, 0, sizeof(v15));v16 = 0;v17 = 0;sub_4406E0(0LL, v15, 37LL);v17 = 0;if ( sub_424BA0(v15) == 36 ){for ( i = 0; i < (unsigned __int64)sub_424BA0(v15); ++i ){if ( (unsigned __int8)(v15[i] ^ i) != v12[i] ){result = 4294967294LL;goto LABEL_13;}}sub_410CC0("continue!");memset(v18, 0, 0x40uLL);v18[64] = 0;sub_4406E0(0LL, v18, 64LL);v18[39] = 0;if ( sub_424BA0(v18) == 39 ){v2 = sub_400E44(v18);v3 = sub_400E44(v2);v4 = sub_400E44(v3);v5 = sub_400E44(v4);v6 = sub_400E44(v5);v7 = sub_400E44(v6);v8 = sub_400E44(v7);v9 = sub_400E44(v8);v10 = sub_400E44(v9);v11 = sub_400E44(v10);if ( !(unsigned int)sub_400360(v11, off_6CC090) ){sub_410CC0("You found me!!!");sub_410CC0("bye bye~");}result = 0LL;}else{result = 4294967293LL;}}else{result = 0xFFFFFFFFLL;}
LABEL_13:if ( __readfsqword(0x28u) != v19 )sub_444020();return result;
}
盲猜base64, 提取数据
from idaapi import *bytes_addr = 0x00000000004A23A8
bytes_size = 0x00000000004A2690 - 0x00000000004A23A8
data = get_bytes(bytes_addr,bytes_size)
print(data)
连续base64解码10次得到一个地址https://bbs.pediy.com/thread-254172-3.htm
进去之后看评论区, 得到flag (= =
非预期解属于是, 正解是定位到下面的一串字符串的交叉引用函数sub_400D35
unsigned __int64 sub_400D35()
{unsigned __int64 result; // raxunsigned int v1; // [rsp+Ch] [rbp-24h]int i; // [rsp+10h] [rbp-20h]int j; // [rsp+14h] [rbp-1Ch]unsigned int v4; // [rsp+24h] [rbp-Ch]unsigned __int64 v5; // [rsp+28h] [rbp-8h]v5 = __readfsqword(0x28u);v1 = sub_43FD20(0LL) - qword_6CEE38;for ( i = 0; i <= 1233; ++i ){sub_40F790(v1);sub_40FE60();sub_40FE60();v1 = sub_40FE60() ^ 0x98765432;}v4 = v1;if ( ((unsigned __int8)v1 ^ byte_6CC0A0[0]) == 102 && (HIBYTE(v4) ^ (unsigned __int8)byte_6CC0A3) == 103 ){for ( j = 0; j <= 24; ++j )sub_410E90((unsigned __int8)(byte_6CC0A0[j] ^ *((_BYTE *)&v4 + j % 4)));}result = __readfsqword(0x28u) ^ v5;if ( result )sub_444020();return result;
}
就是异或处理, 查看byte_6CC0A0的数据, 就是刚刚base 字符串幌子的下面的一串数据
就是用flag作为已知明文求出密钥, 然后用密钥与输入进行异或得到的值, 与这arr一串数据比较
from idaapi import *addr = 0x00000000006CC0A0
sizes = 0x00000000006CC0C0 - 0x00000000006CC0A0
data = get_bytes(addr, sizes)
print(data)arr = []
for i in data:arr.append(i)
print(arr)
解密
#include<iostream>
#include<stdlib.h>
#include<string>
using namespace std;int main() {int arr[] = {64, 53, 32, 86, 93, 24, 34, 69, 23, 47, 36, 110, 98, 60, 39, 84, 72, 108, 36, 110, 114, 60, 50, 69, 91};string str0 = "flag";int key[5] = {0};cout << sizeof(arr) / sizeof(arr[0]) << endl;for (int i = 0; i < 4; ++i) {key[i] = str0[i] ^ arr[i];}for (int i = 0; i < sizeof(arr) / sizeof(arr[0]); ++i) {cout << char(arr[i] ^ key[i % 4]);}cout << endl;
}
[GUET-CTF2019]re
upx脱壳, 拖入IDA
_BOOL8 __fastcall sub_4009AE(char *a1)
{if ( 1629056 * *a1 != 166163712 )return 0LL;if ( 6771600 * a1[1] != 731332800 )return 0LL;if ( 3682944 * a1[2] != 357245568 )return 0LL;if ( 10431000 * a1[3] != 1074393000 )return 0LL;if ( 3977328 * a1[4] != 489211344 )return 0LL;if ( 5138336 * a1[5] != 518971936 )return 0LL;if ( 7532250 * a1[7] != 406741500 )return 0LL;if ( 5551632 * a1[8] != 294236496 )return 0LL;if ( 3409728 * a1[9] != 177305856 )return 0LL;if ( 13013670 * a1[10] != 650683500 )return 0LL;if ( 6088797 * a1[11] != 298351053 )return 0LL;if ( 7884663 * a1[12] != 386348487 )return 0LL;if ( 8944053 * a1[13] != 438258597 )return 0LL;if ( 5198490 * a1[14] != 249527520 )return 0LL;if ( 4544518 * a1[15] != 445362764 )return 0LL;if ( 3645600 * a1[17] != 174988800 )return 0LL;if ( 10115280 * a1[16] != 981182160 )return 0LL;if ( 9667504 * a1[18] != 493042704 )return 0LL;if ( 5364450 * a1[19] != 257493600 )return 0LL;if ( 13464540 * a1[20] != 767478780 )return 0LL;if ( 5488432 * a1[21] != 312840624 )return 0LL;if ( 14479500 * a1[22] != 1404511500 )return 0LL;if ( 6451830 * a1[23] != 316139670 )return 0LL;if ( 6252576 * a1[24] != 619005024 )return 0LL;if ( 7763364 * a1[25] != 372641472 )return 0LL;if ( 7327320 * a1[26] != 373693320 )return 0LL;if ( 8741520 * a1[27] != 498266640 )return 0LL;if ( 8871876 * a1[28] != 452465676 )return 0LL;if ( 4086720 * a1[29] != 208422720 )return 0LL;if ( 9374400 * a1[30] == 515592000 )return 5759124 * a1[31] == 719890500;return 0LL;
}
直接解就行
a1 = chr(166163712 // 1629056)
a2 = chr(731332800 // 6771600)
a3 = chr(357245568 // 3682944)
a4 = chr(1074393000 // 10431000)
a5 = chr(489211344 // 3977328)
a6 = chr(518971936 // 5138336)
a8 = chr(406741500 // 7532250)
a9 = chr(294236496 // 5551632)
a10 = chr(177305856 // 3409728)
a11 = chr(650683500 // 13013670)
a12 = chr(298351053 // 6088797)
a13 = chr(386348487 // 7884663)
a14 = chr(438258597 // 8944053)
a15 = chr(249527520 // 5198490)
a16 = chr(445362764 // 4544518)
a17 = chr(981182160 // 10115280)
a18 = chr(174988800 // 3645600)
a19 = chr(493042704 // 9667504)
a20 = chr(257493600 // 5364450)
a21 = chr(767478780 // 13464540)
a22 = chr(312840624 // 5488432)
a23 = chr(1404511500 // 14479500)
a24 = chr(316139670 // 6451830)
a25 = chr(619005024 // 6252576)
a26 = chr(372641472 // 7763364)
a27 = chr(373693320 // 7327320)
a28 = chr(498266640 // 8741520)
a29 = chr(452465676 // 8871876)
a30 = chr(208422720 // 4086720)
a31 = chr(515592000 // 9374400)
a32 = chr(719890500 // 5759124)print (a1,a2,a3,a4,a5,a6,a8,a9,a10,a11,a12,a13,a14,a15,a16,a17,a18,a19,a20,a21,a22,a23,a24,a25,a26,a27,a28,a29,a30,a31,a32)
最后差个a7, 爆破服务器得到1
[WUSTCTF2020]level1
无壳直接分析
int __cdecl main(int argc, const char **argv, const char **envp)
{int i; // [rsp+4h] [rbp-2Ch]FILE *stream; // [rsp+8h] [rbp-28h]char ptr[24]; // [rsp+10h] [rbp-20h] BYREFunsigned __int64 v7; // [rsp+28h] [rbp-8h]v7 = __readfsqword(0x28u);stream = fopen("flag", "r");fread(ptr, 1uLL, 0x14uLL, stream);fclose(stream);for ( i = 1; i <= 19; ++i ){if ( (i & 1) != 0 )printf("%ld\n", (unsigned int)(ptr[i] << i));elseprintf("%ld\n", (unsigned int)(i * ptr[i]));}return 0;
}
i = 1 ~ 19, 奇数时左移i位, 偶数时乘上i; 结合output.txt
198
232
816
200
1536
300
6144
984
51200
570
92160
1200
565248
756
1474560
800
6291456
1782
65536000
写逆
#include<stdlib.h>int main () {long long arr[] = {198, 232, 816, 200, 1536, 300,6144, 984, 51200, 570, 92160,1200, 565248, 756, 1474560,800, 6291456, 1782, 65536000};for (int i = 1; i <= 19; ++i) {if ( (i & 1) != 0 )printf("%c", (arr[i - 1] >> i));elseprintf("%c", (arr[i - 1] / i));}
}
[SUCTF2019]SignIn
直接逆
__int64 __fastcall main(int a1, char **a2, char **a3)
{char v4[16]; // [rsp+0h] [rbp-4A0h] BYREFchar v5[16]; // [rsp+10h] [rbp-490h] BYREFchar v6[16]; // [rsp+20h] [rbp-480h] BYREFchar v7[16]; // [rsp+30h] [rbp-470h] BYREFchar v8[112]; // [rsp+40h] [rbp-460h] BYREFchar v9[1000]; // [rsp+B0h] [rbp-3F0h] BYREFunsigned __int64 v10; // [rsp+498h] [rbp-8h]v10 = __readfsqword(0x28u);puts("[sign in]");printf("[input your flag]: ");__isoc99_scanf("%99s", v8);sub_96A(v8, v9);__gmpz_init_set_str(v7, "ad939ff59f6e70bcbfad406f2494993757eee98b91bc244184a377520d06fc35", 16LL);__gmpz_init_set_str(v6, v9, 16LL);__gmpz_init_set_str(v4, "103461035900816914121390101299049044413950405173712170434161686539878160984549", 10LL);__gmpz_init_set_str(v5, "65537", 10LL);__gmpz_powm(v6, v6, v5, v4);if ( (unsigned int)__gmpz_cmp(v6, v7) )puts("GG!");elseputs("TTTTTTTTTTql!");return 0LL;
}
输入的数经过sub_96A, 执行 x 65537 % 103461035900816914121390101299049044413950405173712170434161686539878160984549 x^{65537} \% 103461035900816914121390101299049044413950405173712170434161686539878160984549 x65537%103461035900816914121390101299049044413950405173712170434161686539878160984549运算后与ad939ff59f6e70bcbfad406f2494993757eee98b91bc244184a377520d06fc35比较
归约到RSA大数分解问题
M = ?
E = 65537
C = ad939ff59f6e70bcbfad406f2494993757eee98b91bc244184a377520d06fc35
N = 103461035900816914121390101299049044413950405173712170434161686539878160984549
分解N得到
P = 282164587459512124844245113950593348271
Q = 366669102002966856876605669837014229419
可以写解密脚本
import gmpy2
import binasciin = 103461035900816914121390101299049044413950405173712170434161686539878160984549
e = 65537
p = 282164587459512124844245113950593348271
q = 366669102002966856876605669837014229419
c = 0xad939ff59f6e70bcbfad406f2494993757eee98b91bc244184a377520d06fc35d = gmpy2.invert(e,(p-1)*(q-1))
m = gmpy2.powmod(c,d,n)
print(binascii.unhexlify(hex(m)[2:]).decode(encoding="utf-8"))
[MRCTF2020]Transform
int __cdecl main(int argc, const char **argv, const char **envp)
{char Str[104]; // [rsp+20h] [rbp-70h] BYREFint j; // [rsp+88h] [rbp-8h]int i; // [rsp+8Ch] [rbp-4h]sub_402230(argc, argv, envp);sub_40E640("Give me your code:\n");sub_40E5F0("%s", Str);if ( strlen(Str) != 33 ) // 32 bytes length{sub_40E640("Wrong!\n");system("pause");exit(0);}for ( i = 0; i <= 32; ++i ){byte_414040[i] = Str[dword_40F040[i]];byte_414040[i] ^= LOBYTE(dword_40F040[i]); // byte_414040[i] = Str[dword_40F040[i]] ^ dword_40F040[i]}for ( j = 0; j <= 32; ++j ){if ( byte_40F0E0[j] != byte_414040[j] ){sub_40E640("Wrong!\n");system("pause");exit(0);}}sub_40E640("Right!Good Job!\n");sub_40E640("Here is your flag: %s\n", Str);system("pause");return 0;
}
rev
#include <stdio.h>
#include <string.h>
#include <stdlib.h>unsigned char indexs[] =
{9, 0, 0, 0, 10, 0, 0, 0, 15, 0, 0, 0, 23, 0, 0, 0, 7, 0, 0, 0, 24, 0, 0, 0, 12, 0, 0, 0, 6, 0, 0, 0, 1, 0, 0, 0, 16, 0, 0, 0, 3, 0, 0, 0, 17, 0, 0, 0, 32, 0, 0, 0, 29, 0, 0, 0, 11, 0, 0, 0, 30, 0, 0, 0, 27, 0, 0, 0, 22, 0, 0, 0, 4, 0, 0, 0, 13, 0, 0, 0, 19, 0, 0, 0, 20, 0, 0, 0, 21, 0, 0, 0, 2, 0, 0, 0, 25, 0, 0, 0, 5, 0, 0, 0, 31, 0, 0, 0, 8, 0, 0, 0, 18, 0, 0, 0, 26, 0, 0, 0, 28, 0, 0, 0, 14, 0, 0, 0, 0, 0
};unsigned char testvalues[] =
{103, 121, 123, 127, 117, 43, 60, 82, 83, 121, 87, 94, 93, 66, 123, 45, 42, 102, 66, 126, 76, 87, 121, 65, 107, 126, 101, 60, 92, 69, 111, 98, 77, 0, 0, 0, 0, 0, 0, 0
};int main(int argc, char **argv)
{char flag[33] = "\x00";int i = 0;for (i = 0; i < 32; ++i) {int pos = indexs[i*4];// printf("%d\n", indexs[i*4]);flag[pos] = indexs[i*4] ^ testvalues[i]; // printf("%d %c\n", flag[pos], flag[pos]); }printf("flag: %s\n", flag + 1);
}
[WUSTCTF2020]level2
脱壳，拉进IDA, shift + f12
完事
[ACTF新生赛2020]usualCrypt
int __cdecl main(int argc, const char **argv, const char **envp)
{int v3; // esiint v5[3]; // [esp+8h] [ebp-74h] BYREF__int16 v6; // [esp+14h] [ebp-68h]char v7; // [esp+16h] [ebp-66h]char v8[100]; // [esp+18h] [ebp-64h] BYREFsub_403CF8(&unk_40E140);scanf("%s", v8);memset(v5, 0, sizeof(v5));v6 = 0;v7 = 0;sub_401080(v8, strlen(v8), v5);v3 = 0;while ( *((_BYTE *)v5 + v3) == byte_40E0E4[v3] ){if ( ++v3 > strlen((const char *)v5) )goto LABEL_6;}sub_403CF8(aError);
LABEL_6:if ( v3 - 1 == strlen(byte_40E0E4) )return sub_403CF8(aAreYouHappyYes);elsereturn sub_403CF8(aAreYouHappyNo);
}int __cdecl sub_401080(int a1, int a2, int a3)
{int v3; // ediint v4; // esiint v5; // edxint v6; // eaxint v7; // ecxint v8; // esiint v9; // esiint v10; // esiint v11; // esi_BYTE *v12; // ecxint v13; // esiint v15; // [esp+18h] [ebp+8h]v3 = 0;v4 = 0;sub_401000();v5 = a2 % 3;v6 = a1;v7 = a2 - a2 % 3;v15 = a2 % 3;if ( v7 > 0 ){do{LOBYTE(v5) = *(_BYTE *)(a1 + v3);v3 += 3;v8 = v4 + 1;*(_BYTE *)(v8 + a3 - 1) = byte_40E0A0[(v5 >> 2) & 0x3F];*(_BYTE *)(++v8 + a3 - 1) = byte_40E0A0[16 * (*(_BYTE *)(a1 + v3 - 3) & 3)+ (((int)*(unsigned __int8 *)(a1 + v3 - 2) >> 4) & 0xF)];*(_BYTE *)(++v8 + a3 - 1) = byte_40E0A0[4 * (*(_BYTE *)(a1 + v3 - 2) & 0xF)+ (((int)*(unsigned __int8 *)(a1 + v3 - 1) >> 6) & 3)];v5 = *(_BYTE *)(a1 + v3 - 1) & 0x3F;v4 = v8 + 1;*(_BYTE *)(v4 + a3 - 1) = byte_40E0A0[v5];}while ( v3 < v7 );v5 = v15;}if ( v5 == 1 ){LOBYTE(v7) = *(_BYTE *)(v3 + a1);v9 = v4 + 1;*(_BYTE *)(v9 + a3 - 1) = byte_40E0A0[(v7 >> 2) & 0x3F];v10 = v9 + 1;*(_BYTE *)(v10 + a3 - 1) = byte_40E0A0[16 * (*(_BYTE *)(v3 + a1) & 3)];*(_BYTE *)(v10 + a3) = 61;
LABEL_8:v13 = v10 + 1;*(_BYTE *)(v13 + a3) = 61;v4 = v13 + 1;goto LABEL_9;}if ( v5 == 2 ){v11 = v4 + 1;*(_BYTE *)(v11 + a3 - 1) = byte_40E0A0[((int)*(unsigned __int8 *)(v3 + a1) >> 2) & 0x3F];v12 = (_BYTE *)(v3 + a1 + 1);LOBYTE(v6) = *v12;v10 = v11 + 1;*(_BYTE *)(v10 + a3 - 1) = byte_40E0A0[16 * (*(_BYTE *)(v3 + a1) & 3) + ((v6 >> 4) & 0xF)];*(_BYTE *)(v10 + a3) = byte_40E0A0[4 * (*v12 & 0xF)];goto LABEL_8;}
LABEL_9:*(_BYTE *)(v4 + a3) = 0;return sub_401030(a3);
}
经过sub_401080处理后, 与硬编码数据比较
int sub_401000()
{int result; // eaxchar v1; // clfor ( result = 6; result < 15; ++result ){v1 = byte_40E0AA[result];byte_40E0AA[result] = byte_40E0A0[result];byte_40E0A0[result] = v1;}return result;
}
会进行base64变表, 然后base64编码, 再转换大小写
int __cdecl sub_401030(const char *a1)
{__int64 v1; // raxchar v2; // alv1 = 0i64;if ( strlen(a1) ){do{v2 = a1[HIDWORD(v1)];if ( v2 < 97 || v2 > 122 ){if ( v2 < 65 || v2 > 90 )goto LABEL_9;LOBYTE(v1) = v2 + 32;}else{LOBYTE(v1) = v2 - 32;}a1[HIDWORD(v1)] = v1;
LABEL_9:LODWORD(v1) = 0;++HIDWORD(v1);}while ( HIDWORD(v1) < strlen(a1) );}return v1;
}
REV
import base64
import stringchangelist = list('ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/')
origintable = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
testValue = 'zMXHz3TIgnxLxJhFAdtZn2fFk3lYCrtPC2l9'for i in range(6, 15):changelist[i], changelist[i+10] = changelist[i+10], changelist[i]changetable = ''.join(changelist)
testValue = testValue.swapcase()
flag = base64.b64decode(testValue.translate(str.maketrans(changetable, origintable)))
print(flag)
Youngter-drive
如果运行时报错缺少dll, 或者0xc000007b错误, 去dll修复 / 检查system的dll文件版本(32bits / 64bits)解决
注意看文档, 32bit dll放在syswow64, 64bit dll放在system32, 不要想当然乱放
参考:
https://blog.csdn.net/VeryDelicious/article/details/119278996
https://blog.csdn.net/qq_16645423/article/details/83743220
https://www.dll-files.com/download/d57e2eda325bac8081fd054209d736ae/msvcr100d.dll.html?c=OWhmSFQ4MDZnTnpQQjE0Y2MyUHBqZz09
脱壳, 拖进IDA32
int __cdecl main_0(int argc, const char **argv, const char **envp)
{void *v3; // ecxHANDLE Thread; // [esp+D0h] [ebp-14h]HANDLE hObject; // [esp+DCh] [ebp-8h]j_Inputs(v3);::hObject = CreateMutexW(0, 0, 0);j_strcpy(Destination, Source);hObject = CreateThread(0, 0, StartAddress, 0, 0, 0);Thread = CreateThread(0, 0, sub_41119F, 0, 0, 0);CloseHandle(hObject);CloseHandle(Thread);while ( cnt != -1 );j_testfunc();CloseHandle(::hObject);return 0;
}int sub_411880()
{int i; // [esp+D0h] [ebp-8h]for ( i = 0; i < 29; ++i ){if ( Source[i] != off_418004[i] )exit(0);}return printf("\nflag{%s}\n\n", Destination);
}// positive sp value has been detected, the output may be wrong!
char *__cdecl sub_411940(int a1, int a2)
{char *result; // eaxchar v3; // [esp+D3h] [ebp-5h]v3 = *(_BYTE *)(a2 + a1);if ( (v3 < 'a' || v3 > 122) && (v3 < 65 || v3 > 90) )// check upper & lower charsexit(0);if ( v3 < 97 || v3 > 122 ) // not lower chars{result = off_418000[0];*(_BYTE *)(a2 + a1) = off_418000[0][*(char *)(a2 + a1) - 38];}else // lower chars{result = off_418000[0];*(_BYTE *)(a2 + a1) = off_418000[0][*(char *)(a2 + a1) - 96];}return result;
}
根据大小写字母相对QWERTYUIOPASDFGHJKLZXCVBNMqwertyuiopasdfghjklzxcvbnm的位置进行置换, 输入串长度为30(坑点, 最后比较的串只有29长, 最后一位理论上是随意输入都可以通过, 不过BUU这里是E, 只能说程序写的有问题)
同时注意该程序是多线程编程, 两个线程一个有process函数, 一个没有, 单纯是cnt--, 所以是奇数序数处理, 偶数维持不变
REV
#include <stdlib.h>
#include <iostream>
#include <stdio.h>
#include <string>
using namespace std;void revfunc(string source, int cnt, const string changetable, char *flag) {char v3 = source[cnt];if ( (v3 < 97 || v3 > 122) && (v3 < 65 || v3 > 90) ) {// check upper & lower charscout << v3 << endl;cout << "invalid char" << endl;exit(0);}cout << v3 << changetable.find(v3) << endl;if ( v3 < 97 || v3 > 122 ) { // not lower charsflag[cnt] = changetable.find(v3) + 96;}else { // lower charsflag[cnt] = changetable.find(v3) + 38;}
}int main() {string testValues = "TOiZiZtOrYaToUwPnToBsOaOapsySE"; // 29 length but 30 actuallystring changetable = "QWERTYUIOPASDFGHJKLZXCVBNMqwertyuiopasdfghjklzxcvbnm";char flag[31] = "TOiZiZtOrYaToUwPnToBsOaOapsySE"; // last char is E on BUUCTF = =cout << testValues.size() << endl;for (int i = 28; i >= 0; --i)if (i % 2 == 1)revfunc(testValues, i, changetable, flag); cout << sizeof(flag) << ' ' << flag << endl;
}
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