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https://github.com/aljazceru/python-teos.git
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126 lines
3.9 KiB
Python
126 lines
3.9 KiB
Python
import re
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from common.cryptographer import Cryptographer
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# TODO: UNITTEST
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class NotEnoughSlots(ValueError):
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"""Raise this when trying to subtract more slots than a user has available."""
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def __init__(self, user_pk, requested_slots):
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self.user_pk = user_pk
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self.requested_slots = requested_slots
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class IdentificationFailure(Exception):
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"""
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Raise this when a user can not be identified. Either the user public key cannot be recovered or the user is
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not found within the registered ones.
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"""
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pass
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class Gatekeeper:
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"""
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The Gatekeeper is in charge of managing the access to the tower. Only registered users are allowed to perform
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actions.
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Attributes:
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registered_users (:obj:`dict`): a map of user_pk:appointment_slots.
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"""
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def __init__(self, default_slots):
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self.default_slots = default_slots
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self.registered_users = {}
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@staticmethod
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def check_user_pk(user_pk):
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"""
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Checks if a given value is a 33-byte hex encoded string.
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Args:
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user_pk(:obj:`str`): the value to be checked.
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Returns:
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:obj:`bool`: Whether or not the value matches the format.
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"""
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return isinstance(user_pk, str) and re.match(r"^[0-9A-Fa-f]{66}$", user_pk) is not None
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def add_update_user(self, user_pk):
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"""
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Adds a new user or updates the subscription of an existing one, by adding additional slots.
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Args:
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user_pk(:obj:`str`): the public key that identifies the user (33-bytes hex str).
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Returns:
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:obj:`int`: the number of available slots in the user subscription.
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"""
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if not self.check_user_pk(user_pk):
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raise ValueError("provided public key does not match expected format (33-byte hex string)")
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if user_pk not in self.registered_users:
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self.registered_users[user_pk] = self.default_slots
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else:
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self.registered_users[user_pk] += self.default_slots
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return self.registered_users[user_pk]
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def identify_user(self, message, signature):
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"""
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Checks if the provided user signature comes from a registered user.
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Args:
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message (:obj:`bytes`): byte representation of the original message from where the signature was generated.
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signature (:obj:`str`): the user's signature (hex encoded).
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Returns:
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:obj:`str`: a compressed key recovered from the signature and matching a registered user.
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Raises:
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:obj:`<teos.gatekeeper.IdentificationFailure>`: if the user cannot be identified.
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"""
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if isinstance(message, bytes) and isinstance(signature, str):
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rpk = Cryptographer.recover_pk(message, signature)
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compressed_pk = Cryptographer.get_compressed_pk(rpk)
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if compressed_pk in self.registered_users:
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return compressed_pk
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else:
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raise IdentificationFailure("User not found.")
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else:
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raise IdentificationFailure("Wrong message or signature.")
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def fill_slots(self, user_pk, n):
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"""
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Fills a given number os slots of the user subscription.
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Args:
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user_pk(:obj:`str`): the public key that identifies the user (33-bytes hex str).
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n: the number of slots to fill.
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Raises:
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:obj:`<teos.gatekeeper.NotEnoughSlots>`: if the user subscription does not have enough slots.
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"""
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if n <= self.registered_users.get(user_pk):
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self.registered_users[user_pk] -= n
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else:
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raise NotEnoughSlots(user_pk, n)
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def free_slots(self, user_pk, n):
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"""
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Frees some slots of a user subscription.
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Args:
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user_pk(:obj:`str`): the public key that identifies the user (33-bytes hex str).
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n: the number of slots to free.
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"""
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self.registered_users[user_pk] += n
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