Calculate Session Identifier entropy with Claude Shannon formula.

calc_entropy.py

# calc_entropy.py
# Calculate Session Identifier entropy with Claude Shannon formula.
# https://github.com/4k1
import math
import sys
import time
import urllib.request

# Check params
if (len(sys.argv) != 3):
    print ('Usage: python3 %s url cookie' % sys.argv[0])
    quit()
p_url = sys.argv[1]
p_target = sys.argv[2]

# Initialize
charlist = []
maxlength = 0
def addcharlist(cl, v):
    ncl = list(set(cl + list(v)))
    return ncl

# SessionID collection
print ("[ ] Collecting " + p_target + "...")
for i in range(0, 10000):
    time.sleep(0.1)
    headers = { "User-Agent" :  "Mozilla/4.0 (compatible; MSIE 5.5; Windows NT)" } #
    req = urllib.request.Request(p_url, None, headers)
    response = urllib.request.urlopen(req)
    
    for h, v in response.headers.items():
        if h.lower() == "set-cookie":
            r = v.split(';')[0].strip()
            n = r.find('=')
            if p_target == r[:n]:
                charlist = addcharlist(charlist, r[n+1:])
                if len(r[n+1:]) > maxlength:
                    maxlength = len(r[n+1:])
                break
print ("[+] Collected.")

# Calculation
fb = len(charlist)
fl = maxlength
fbl = math.pow(fb, fl)
fH = math.log2(fbl)

# Report
print ("    Length   : " + str(fl))
print ("    Charlist : " + str(fb))
print ("    Strength : " + str(fH) + " bit(s).")
print ("[+] Ok.")
exit()