szu

from base64 import b64encode
from random import choices

from Crypto.Cipher import AES
from more_itertools import first
from requests_html import HTMLSession

url_login = 'https://webvpn.ujs.edu.cn/https/77726476706e69737468656265737421e0f6528f69256243300d8db9d6562d/cas/login'

username = 'asdf'
pwd = '123456'

def pad(m):
    return m+chr(16-len(m)%16)*(16-len(m)%16)

def unpad(ct):
    return ct[:-ord(ct[-1])]

def rds(n):
    return ''.join(choices('ABCDEFGHJKMNPQRSTWXYZabcdefhijkmnprstwxyz2345678', k=n))

# getting initial variable
s = HTMLSession()
r = s.get(url_login)
html = r.html
salt = first(html.xpath('//input[@id="pwdDefaultEncryptSalt"]/@value'), None)
lt = first(html.xpath('//input[@name="lt"]/@value'), None)
dllt = first(html.xpath('//input[@name="dllt"]/@value'), None)
execution = first(html.xpath('//input[@name="execution"]/@value'), None)
rmShown = first(html.xpath('//input[@name="rmShown"]/@value'), None)

# encrypt password
key = salt.encode()
cipher = AES.new(key, AES.MODE_CBC, iv=rds(16).encode())
encrypted_pwd = b64encode(cipher.encrypt((pad(rds(64)+pwd)).encode()))


d = {
    'username': username,
    'password': encrypted_pwd,
    'lt': lt,
    'dllt': dllt,
    'execution': execution,
    '_eventId': 'submit',
    'rmShown': rmShown,
}

r = s.post(url_login, d)


if __name__ == '__main__':
    pass