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Homework answers / question archive / Design and implement a university computer server system, on which all students, teaching staff, and others have accounts
Design and implement a university computer server system, on which all students, teaching staff, and others have accounts. You will also implement an authentication and authorization subsystem. You can consider using the approach in the code provided to you in our textbook in the Case Study at the end of Chapter 4.
Your computer server system needs to define
Your system should allow users to login to the system to be able to execute any of the allowed functions.
You can "create your" own scenario based on, for example, a GNU/Linux system or another operating system.
The work required here is essentially about reworking the book example with relatively minor modifications/additions.
>>>>>>>>>>>>> Case Study at the end of Chapter 4.<<<<<<<<<<<<<<<<
auth_driver.py
import auth
# Set up a test user and permission
auth.authenticator.add_user("joe", "joepassword")
auth.authorizor.add_permission("test program")
auth.authorizor.add_permission("change program")
auth.authorizor.permit_user("test program", "joe")
class Editor:
def __init__(self):
self.username = None
self.menu_map = {
"login": self.login,
"test": self.test,
"change": self.change,
"quit": self.quit,
}
def login(self):
logged_in = False
while not logged_in:
username = input("username: ")
password = input("password: ")
try:
logged_in = auth.authenticator.login(username, password)
except auth.InvalidUsername:
print("Sorry, that username does not exist")
except auth.InvalidPassword:
print("Sorry, incorrect password")
else:
self.username = username
def is_permitted(self, permission):
try:
auth.authorizor.check_permission(permission, self.username)
except auth.NotLoggedInError as e:
print("{} is not logged in".format(e.username))
return False
except auth.NotPermittedError as e:
print("{} cannot {}".format(e.username, permission))
return False
else:
return True
def test(self):
if self.is_permitted("test program"):
print("Testing program now...")
def change(self):
if self.is_permitted("change program"):
print("Changing program now...")
def quit(self):
raise SystemExit()
def menu(self):
try:
answer = ""
while True:
print(
"""
Please enter a command:
tlogintLogin
ttesttTest the program
tchangetChange the program
tquittQuit
"""
)
answer = input("enter a command: ").lower()
try:
func = self.menu_map[answer]
except KeyError:
print("{} is not a valid option".format(answer))
else:
func()
finally:
print("Thank you for testing the auth module")
Editor().menu()
auth.py
??import hashlib
class AuthException(Exception):
def __init__(self, username, user=None):
super().__init__(username, user)
self.username = username
self.user = user
class UsernameAlreadyExists(AuthException):
pass
class PasswordTooShort(AuthException):
pass
class InvalidUsername(AuthException):
pass
class InvalidPassword(AuthException):
pass
class PermissionError(Exception):
pass
class NotLoggedInError(AuthException):
pass
class NotPermittedError(AuthException):
pass
class User:
def __init__(self, username, password):
""" Create a new user object. The password
will be encrypted before storing."""
self.username = username
self.password = self._encrypt_pw(password)
self.is_logged_in = False
def _encrypt_pw(self, password):
"""Encrypt the password with the username and return
the sha digest."""
hash_string = self.username + password
hash_string = hash_string.encode("utf8")
return hashlib.sha256(hash_string).hexdigest()
def check_password(self, password):
"""Return True if the password is valid for this
user, false otherwise."""
encrypted = self._encrypt_pw(password)
return encrypted == self.password
class Authenticator:
def __init__(self):
"""Construct an authenticator to manage
users logging in and out."""
self.users = {}
def add_user(self, username, password):
if username in self.users:
raise UsernameAlreadyExists(username)
if len(password) < 6:
raise PasswordTooShort(username)
self.users[username] = User(username, password)
def login(self, username, password):
try:
user = self.users[username]
except KeyError:
raise InvalidUsername(username)
if not user.check_password(password):
raise InvalidPassword(username, user)
user.is_logged_in = True
return True
def is_logged_in(self, username):
if username in self.users:
return self.users[username].is_logged_in
return False
class Authorizor:
def __init__(self, authenticator):
self.authenticator = authenticator
self.permissions = {}
def add_permission(self, perm_name):
"""Create a new permission that users
can be added to"""
try:
perm_set = self.permissions[perm_name]
except KeyError:
self.permissions[perm_name] = set()
else:
raise PermissionError("Permission Exists")
def permit_user(self, perm_name, username):
"""Grant the given permission to the user"""
try:
perm_set = self.permissions[perm_name]
except KeyError:
raise PermissionError("Permission does not exist")
else:
if username not in self.authenticator.users:
raise InvalidUsername(username)
perm_set.add(username)
def check_permission(self, perm_name, username):
if not self.authenticator.is_logged_in(username):
raise NotLoggedInError(username)
try:
perm_set = self.permissions[perm_name]
except KeyError:
raise PermissionError("Permission does not exist")
else:
if username not in perm_set:
raise NotPermittedError(username)
else:
return True
authenticator = Authenticator()
authorizor = Authorizor(authenticator)
