完成一个 Python 程序，实现密码存储和验证，用于模拟身份验证服务器，以便破解数据库的对手无法获得用户的明文密码。实现基本的注册和登录功能。
测试样例如下：
input
R
timerring
i love cryptography
L
timerring
i love cryptography
L
timerring
i love cipher
L
Who
i love cryptography
Q
该系统的源码如下：
source code
from __future__ import annotations
from typing import Dict
import getpass
import hashlib
import os
database: Dict[str, UserPassword] = dict()
class UserPassword:
def __init__(self, in_username, in_password_hash, in_salt):
self.username: str = in_username
self.password_hash: bytes = in_password_hash
self.salt: bytes = in_salt
self.method: str = 'scrypt'
# define verify_password function
def verify_password(self, password: str) -> bool:
password_ver: bytes = password.encode("utf-8")
# use the same salt
salt_ver: bytes = self.salt
# set corresponding parameters
n: int = 4
r: int = 8
p: int = 16
password_hash_ver: bytes = hashlib.scrypt(password_ver, salt=salt_ver, n=n, r=r, p=p)
# verify the hash value of the password
if password_hash_ver == self.password_hash:
return True
else:
return False
def database_add_item(user: UserPassword) -> None:
if user.username in database:
raise Exception('User {} already exists.'.format(user.username))
database[user.username] = user
def login_user(username: str, password_plaintext: str) -> bool:
if username not in database:
raise Exception('User {} does not exist.'.format(username))
return database[username].verify_password(password_plaintext)
def register_user(username: str, password_plaintext: str) -> None:
password_bytes: bytes = password_plaintext.encode("utf-8")
# The os.urandom function is used to obtain random bytes of a specified length
# generate the salt bytes
salt_bytes: bytes = os.urandom(64)
# set corresponding parameters
n: int = 4
r: int = 8
p: int = 16
# Hash encryption
password_hash: bytes = hashlib.scrypt(password_bytes, salt=salt_bytes, n=n, r=r, p=p)
# construct instance object
User: UserPassword = UserPassword(username, password_hash, salt_bytes)
# Add to database
database_add_item(User)
if __name__ == '__main__':
while True:
try:
print('Usage:')
print('\tR - register a new user')
print('\tL - login with an existing user')
print('\tQ - exit')
print('')
command: str = input('Input command:')
if command == 'Q':
exit(0)
elif command == 'R' or command == 'L':
username: str = input('Input username:')
# password: str = getpass.getpass('Input password:') # will not work properly for PyCharm, IDLE, etc.
password: str = input('Input password:')
if command == 'R':
register_user(username, password)
print('User created successfully.')
elif command == 'L':
login_valid: bool = login_user(username, password)
if login_valid:
print('User logged in successfully.')
else:
print('Password verification failed. Can not logged in.')
else:
assert False
else:
raise Exception('Invalid command.')
except Exception as e:
print('Error: {}'.format(e))
output
Usage:
R - register a new user
L - login with an existing user
Q - exit
Input command:R
Input username:timerring
Input password:i love cryptography
User created successfully.
Usage:
R - register a new user
L - login with an existing user
Q - exit
Input command:L
Input username:timerring
Input password:i love cryptography
User logged in successfully.
Usage:
R - register a new user
L - login with an existing user
Q - exit
Input command:L
Input username:timerring
Input password:i love cipher
Password verification failed. Can not logged in.
Usage:
R - register a new user
L - login with an existing user
Q - exit
Input command:L
Input username:Who
Input password:i love cryptography
Error: User Who does not exist.
Usage:
R - register a new user
L - login with an existing user
Q - exit
Input command:Q
进程已结束，退出代码为 0
由输出可知，系统功能一切正常。
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