Description:

I thought I found a perfect match but she ended up being my regEx girlfriend.

nc misc.chal.csaw.io 8001

It wasn’t so hard, I asked google for the best way to generate matched string to a given pattern and wrote the following script. The only headache was when my generator used newlines (“\n”) so I removed them.

from pwn import *
import rstr
import exrex
from time import sleep
import re

# conect to server
r = remote('misc.chal.csaw.io', 8001)

# Print the question string
print r.recvline()

# Counter
i=1

while True:
	# Recieve the regex pattern
    reg = r.recvline()[:-1]
    print "%d -------\n"%i
    print reg
    print "-------\n"
    ans=rstr.xeger(reg).replace('\n','') # Remove newlines!
    # ans=exrex.getone(reg).replace('\n','')  # Another possible option
    r.sendline(ans)
    i+=1
	sleep(0.2)

And after 1000 tests we got the flag: flag{^regularly_express_yourself$}

Description:

#Hope #Change #Obama2008

nc misc.chal.csaw.io 8000

Let’s connect to the server and see what will happen:

[Megabeets] /tmp/CSAW/Coinslot# nc misc.chal.csaw.io 8000
$0.07
$10,000 bills: 0
$5,000 bills: 0
$1,000 bills: 0
$500 bills: 0
$100 bills: 0
...
...

So, the server is displaying a wanted amount of money and we need to calculate the number of bills and coins given the amount. All we need is writing a simple python script and a coffee break because it will take about 10 minutes for the flag to come up 🙁

from pwn import *

r = remote('misc.chal.csaw.io',8000)

# Create an array of dollars and coins values
money = [10000.0, 5000.0, 1000.0, 500.0, 100.0, 50.0, 20.0, 10.0, 5.0, 1.0, 0.5, 0.25, 0.1, 0.05, 0.01]
count = 0

while(True):
	count += 1
	amount = 0.0
	
	# Recieve the wanted amount of money
	amount = float(r.recvline()[1:])
	print "Wanted amount is " + str(amount)

	# Send the number of dollars and coins for each value
	for m in money:
		print r.recv()
		ans = int(amount/m)
		print "Sending %d" %ans
		r.sendline(str(ans))
		amount = round((amount - (ans*m)), 2)
		print "Left with " + str(amount)
	print "[+] Finished %d" %count
	print r.recvline()

The flag is: flag{started-from-the-bottom-now-my-whole-team-fucking-here}