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Design and implement a university computer server system, on which all students, teaching staff, and others have accounts

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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

• at least three types of users:
•  

1. Students
2. Teaching staff
3. Computer administrators

• privileges/permissions for a variety of tasks (For example, create/delete/move/rename files/directories/links, connect to internet, etc.)
• which type of users have which type of privileges/permissions.

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)