15_ELF

import urllib2
import hashlib
def request(url,data,cookie):
    headers = {"Cookie": cookie}
    req = urllib2.Request(url, data, headers)
    response = urllib2.urlopen(req).read()
    return response

cookie = "XXX"
url = "http://ringzer0team.com/challenges/15"
res = request(url,"",cookie)
s1 = "----- BEGIN Elf Message -----<br />"
s2 = "<br />"
i1 = res.index(s1)+len(s1)
i2 = res.index(s2,i1)
data = res[i1+4:i2]
while "FLE" not in data:
    data = data.decode("base64")
data=data[::-1]
s1 = "31c0c7".decode("hex")
s2 = "66c745f4".decode("hex")
id = data.index(s1)
key = data[id+5:id+15].replace(s2,"")
url = "http://ringzer0team.com/challenges/15/"+key
res = request(url,"",cookie)
print res[res.index("FLAG-"):]