94 lines
3.5 KiB
Python
94 lines
3.5 KiB
Python
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from datetime import date
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from django.conf import settings
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from django.utils.crypto import constant_time_compare, salted_hmac
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from django.utils.http import base36_to_int, int_to_base36
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class PasswordResetTokenGenerator:
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"""
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Strategy object used to generate and check tokens for the password
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reset mechanism.
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"""
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key_salt = "django.contrib.auth.tokens.PasswordResetTokenGenerator"
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secret = settings.SECRET_KEY
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def make_token(self, user):
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"""
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Return a token that can be used once to do a password reset
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for the given user.
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"""
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return self._make_token_with_timestamp(user, self._num_days(self._today()))
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def check_token(self, user, token):
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"""
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Check that a password reset token is correct for a given user.
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"""
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if not (user and token):
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return False
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# Parse the token
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try:
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ts_b36, hash = token.split("-")
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except ValueError:
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return False
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try:
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ts = base36_to_int(ts_b36)
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except ValueError:
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return False
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# Check that the timestamp/uid has not been tampered with
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if not constant_time_compare(self._make_token_with_timestamp(user, ts), token):
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return False
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# Check the timestamp is within limit. Timestamps are rounded to
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# midnight (server time) providing a resolution of only 1 day. If a
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# link is generated 5 minutes before midnight and used 6 minutes later,
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# that counts as 1 day. Therefore, PASSWORD_RESET_TIMEOUT_DAYS = 1 means
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# "at least 1 day, could be up to 2."
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if (self._num_days(self._today()) - ts) > settings.PASSWORD_RESET_TIMEOUT_DAYS:
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return False
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return True
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def _make_token_with_timestamp(self, user, timestamp):
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# timestamp is number of days since 2001-1-1. Converted to
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# base 36, this gives us a 3 digit string until about 2121
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ts_b36 = int_to_base36(timestamp)
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hash = salted_hmac(
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self.key_salt,
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self._make_hash_value(user, timestamp),
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secret=self.secret,
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).hexdigest()[::2] # Limit to 20 characters to shorten the URL.
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return "%s-%s" % (ts_b36, hash)
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def _make_hash_value(self, user, timestamp):
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"""
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Hash the user's primary key and some user state that's sure to change
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after a password reset to produce a token that invalidated when it's
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used:
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1. The password field will change upon a password reset (even if the
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same password is chosen, due to password salting).
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2. The last_login field will usually be updated very shortly after
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a password reset.
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Failing those things, settings.PASSWORD_RESET_TIMEOUT_DAYS eventually
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invalidates the token.
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Running this data through salted_hmac() prevents password cracking
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attempts using the reset token, provided the secret isn't compromised.
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"""
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# Truncate microseconds so that tokens are consistent even if the
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# database doesn't support microseconds.
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login_timestamp = '' if user.last_login is None else user.last_login.replace(microsecond=0, tzinfo=None)
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return str(user.pk) + user.password + str(login_timestamp) + str(timestamp)
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def _num_days(self, dt):
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return (dt - date(2001, 1, 1)).days
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def _today(self):
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# Used for mocking in tests
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return date.today()
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default_token_generator = PasswordResetTokenGenerator()
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