help about a python script?

Question

hi,
could you someone explain this script, line by line?
thanks..

#! /usr/bin/env python3

__author__ = 'Felis-Sapiens'

from sys import argv

def gen_key(mac):
charset = '02345679abcdefghijkmnpqrstuvwxyzACDEFGHJKLMNPQRSTUVWXYZ'
tmp_key = ''
xored_mac = bytearray(mac)
for i in range(6, 0, -1):
for j in range(i):
if i != 6:
xored_mac[j] ^= mac[i]
tmp_key += charset[xored_mac[j] % 55]

key = ''
used = [0]*20
j = 7
for i in range(8):
key += tmp_key[j]
used[j] = 1
cnt = 0
for _ in range(20):
j = (j + 1) % 20
cnt += used[j] == 0
if cnt == 8:
break

return key

def main():
if len(argv) < 2:
print('Usage:', __file__, 'MAC')
return

mac = argv[1].replace(':', '').replace('-', '').replace(' ', '')
try:
mac = bytes.fromhex(mac)
except:
print('ERROR: Invalid MAC ', argv[1])
return

if len(mac) != 6:
print('ERROR: Invalid MAC ', argv[1])
return

print(gen_key(mac))

if __name__ == '__main__':
main()

Answer 1

it's a long script to go through line by line in a reply, there is a lot to explain.
where did you get it?
the script basically takes a MAC address and generates a key.
I ve seen something similar long time ago, some router manufacturers set the default password of their router web interface , ssh... based on the MAC address of their network interface.
could you specify what part of the code you didn't understand?

Answer 2

yes, this is mac to pass script.
this part :

tmp_key = ''
xored_mac = bytearray(mac)
for i in range(6, 0, -1):
for j in range(i):
if i != 6:
xored_mac[j] ^= mac[i]
tmp_key += charset[xored_mac[j] % 55]

key = ''
used = [0]*20
j = 7
for i in range(8):
key += tmp_key[j]
used[j] = 1
cnt = 0
for _ in range(20):
j = (j + 1) % 20
cnt += used[j] == 0
if cnt == 8:
break

if you can explain with a sample, will be good.

Mac:98DED0261826
Pass: wkH532Ns
152 222 208 38 24 38 HEX

98DED0261825
zpH930Nv

thanks...

.