2020祥云杯网络安全大赛 MISC Writeup

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签到

PS C:\Users\Administrator> php -r "var_dump(base64_decode('ZmxhZ3txcV9ncm91cF84MjY1NjYwNDB9'));"
string(24) "flag{qq_group_826566040}"

进制反转

题目描述：

电脑中到底使用的是什么进制呢？真是麻烦，有时候还是手机好用。结果用flag{
   }包住，并且全为大写

WinRAR打开显示文件头损坏，其次有加密，猜测RAR伪加密，使用010 Editor打开

文件结尾发现提示：flag is the song's name

接着找到第三块struct RarBlock block[0]下的struct FileHeadFlags HEAD_FLAGS

修改ubyte PASSWORD_ENCRYPTED的值为0

解压得到flag.wav，无法使用Audacity打开，就通过导入文件->导入->原始数据

听着很明显是歌声但是却是倒放，Ctrl+A全选，点击效果 > 反向(时间)，然后再效果 > 改变速率，调节到一个正常歌曲的播放速度，然后经过降噪，消除咔嚓声等一系列操作，最后听歌识别

先推个在线识别歌曲网站：https://www.acrcloud.com/identify-songs-music-recognition-online/

听歌识曲识别不出来，就听歌词找吧，也挺快的，考验听力水平
歌名：《Too Good At Goodbyes》

flag{
   TOOGOODATGOODBYES}

到点了

题目描述：

我那么多遗憾，那么多期盼，你知道吗（下雨熊猫头

1.docx打开，勾选隐藏文字

2.docx有加密，根据1.docx提供的提示，使用Accent OFFICE Password Recovery爆破密码

先尝试爆破8位纯数字，毕竟8位字母数字就太多了，还不知道分不分大小写

爆破过程就不看了，时间太长了，直接贴结果，密码为：20201024

解开2.docx，全选标红，发现有一串AB字符，很明显应该是培根密码

AABBAABBBAABBBAAAABBABBABABAAAAABBAAABBBBAABBBAABABABBAAABAAAABAABAABBABAAAAABAA

培根在线解码：https://tool.bugku.com/peigen/

GOODNIGHTSWEETIE
goodnightsweetie

binwalk分离3.docx，得到一个4.zip，里面有一张4.bmp

4.bmp

bmp隐写，有密码，试了不是LSB，尝试使用wbs43open

密码：goodnightsweetie

flag{
   2ec9405ac7bcfb16f5fd494bcf21337c}

xixixi

题目描述：

室友最近沉迷y神，又氪又肝，还ghs。为了他的身体着想，我把他的s图整没了。但我明明删了脚本啊，为什么还能被他发现......8说了，医院的空调真舒服~

new.vhd

可以使用DiskGenius或者Win7的磁盘管理进行挂载，建议使用DiskGenius挂载

DiskGenius->磁盘->打开虚拟磁盘文件

kejin.png

以及还有两个Py脚本

import struct

class FAT32Parser(object):
	def __init__(self, vhdFileName):
		with open(vhdFileName, 'rb') as f:
			self.diskData = f.read()
		self.DBR_off = self.GetDBRoff()
		self.newData = ''.join(self.diskData)

	def GetDBRoff(self):
		DPT_off = 0x1BE
		target = self.diskData[DPT_off+8:DPT_off+12]
		DBR_sector_off, = struct.unpack("<I", target)
		return DBR_sector_off * 512

	def GetFAT1off(self):
		target = self.diskData[self.DBR_off+0xE:self.DBR_off+0x10]
		FAT1_sector_off, = struct.unpack("<H", target)
		return self.DBR_off + FAT1_sector_off * 512

	def GetFATlength(self):
		target = self.diskData[self.DBR_off+0x24:self.DBR_off+0x28]
		FAT_sectors, = struct.unpack("<I", target)
		return FAT_sectors * 512

	def GetRootoff(self):
		FAT_length = self.GetFATlength()
		FAT2_off = self.GetFAT1off() + FAT_length
		return FAT2_off + FAT_length

	def Cluster2FAToff(self, cluster):
		FAT1_off = self.GetFAT1off()
		return FAT1_off + cluster * 4

	def Cluster2DataOff(self, cluster):
		rootDir_off = self.GetRootoff()
		return rootDir_off + (cluster - 2) * 512

import struct
from xixi import FAT32Parser
from xixixi import Padding, picDepartList

def EncodePieces():
	global clusterList
	res = []
	Range = len(picDepartList)    # 58
	# GetRandomClusterList(n) - Generate a random cluster list with length n
	clusterList = GetRandomClusterList(Range)

	for i in range(Range):
		if i != Range - 1:
			newCRC = struct.pack("<I", clusterList[i+1])
			plainData = picDepartList[i][:-4] + newCRC
		else:
			plainData = picDepartList[i]

		# Show the first piece to him, hhh
		if i == 0:
			newPiece = plainData
		else:
			newPiece = ''
			key = clusterList[i] & 0xFE
			for j in plainData:
				newPiece += chr(ord(j) ^ key)
		# Padding() -- Fill to an integral multiple of 512 with \xFF
		res.append(Padding(newPiece))
	return res

参考上面给出的脚本进行还原，还原脚本参考的是Timeline Sec团队的脚本

原文地址：https://mp.weixin.qq.com/s/CP3-W8VcLokQNYMSbXw9wg

# -*- coding: utf-8 -*-
# @Project: Hello Python!
# @File   : exp
# @Author : Tr0jAn <Tr0jAn@birkenwald.cn>
# @Date   : 2020-11-22
import struct
import binascii

class FAT32Parser(object):
  def __init__(self, vhdFileName):
    with open(vhdFileName, 'rb') as f:
      self.diskData = f.read()
    self.DBR_off = self.GetDBRoff()
    self.newData = ''.join(str(self.diskData))


  def GetDBRoff(self):
    DPT_off = 0x1BE
    target = self.diskData[DPT_off+8:DPT_off+12]
    DBR_sector_off, = struct.unpack("<I", target)
    return DBR_sector_off * 512


  def GetFAT1off(self):
    target = self.diskData[self.DBR_off+0xE:self.DBR_off+0x10]
    FAT1_sector_off, = struct.unpack("<H", target)
    return self.DBR_off + FAT1_sector_off * 512


  def GetFATlength(self):
    target = self.diskData[self.DBR_off+0x24:self.DBR_off+0x28]
    FAT_sectors, = struct.unpack("<I", target)
    return FAT_sectors * 512


  def GetRootoff(self):
    FAT_length = self.GetFATlength()
    FAT2_off = self.GetFAT1off() + FAT_length
    return FAT2_off + FAT_length


  def Cluster2FAToff(self, cluster):
    FAT1_off = self.GetFAT1off()
    return FAT1_off + cluster * 4


  def Cluster2DataOff(self, cluster):
    rootDir_off = self.GetRootoff()
    return rootDir_off + (cluster - 2) * 512

    
def read(n):
    global key
    binary = b''
    for i in vhd.read(n):
        binary += (i ^ (key & 0xFE)).to_bytes(length=1, byteorder='big', signed=False)
    return binary


FAT = FAT32Parser("new.vhd")
vhd = open("new.vhd", "rb")
vhd.seek(0x27bae00)  # 定位磁盘中图片位置
flag = open("flag.png", "wb")
flag.write(vhd.read(8))  # 写入png头
key = 0
while True:
    d = read(8)
    length, cType = struct.unpack(">I4s", d)
    print(length, cType)  # length为数据长度，cType为数据块类型
    data = read(length)
    CRC = struct.unpack(">I", read(4))[0]
    print(CRC)
    rCRC = binascii.crc32(cType + data) & 0xffffffff
    print(rCRC)
    rDATA = struct.pack(">I", length) + cType + data + struct.pack(">I", rCRC)
    flag.write(rDATA)
    if CRC != rCRC:  # CRC错误的IDAT数据块
        b_endian = struct.pack(">I", CRC)
        clusterList = struct.unpack("<I", b_endian)[0]
        print(clusterList)
        vhd.seek(FAT.Cluster2DataOff(clusterList))
        key = clusterList & 0xFE
    if cType == b"IEND":
        break

flag{
   0cfdd1ad80807da6c0413de606bb0ae4}

带音乐家

MIDI文件

Velato语言使用MIDI文件作为源代码，音乐的模式决定程序命令

官网下载编译器

http://velato.net/

Hello, World!

Doc1.rar注释有东西

摩斯，短的转为.，长的转为-

.- . ... -.- . -.-- ----. ..--- .---- ----. ..--- ...-- ..--- ...-- ..--- ..---

AESKEY9219232322

解压Doc1.rar，打开Doc1.docx(记得开启隐藏字符)

nvPrjrss1PyqAZB/14lkvJGTJ9l4rOfwJeqSqSHSqXU=

flag{
   mU51c_And_ch@ract0rs~}

Charles Sensor

等待大佬wp…orz

转载：https://blog.csdn.net/mochu7777777/article/details/109913252