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from datetime import date
from django.conf import settings
from django.utils.http import int_to_base36, base36_to_int
from django.utils.crypto import constant_time_compare, salted_hmac
from django.utils import six
class PasswordResetTokenGenerator(object):
"""
Strategy object used to generate and check tokens for the password
reset mechanism.
"""
def make_token(self, user):
"""
Returns a token that can be used once to do a password reset
for the given user.
"""
return self._make_token_with_timestamp(user, self._num_days(self._today()))
def check_token(self, user, token):
"""
Check that a password reset token is correct for a given user.
"""
# Parse the token
try:
ts_b36, hash = token.split("-")
except ValueError:
return False
try:
ts = base36_to_int(ts_b36)
except ValueError:
return False
# Check that the timestamp/uid has not been tampered with
if not constant_time_compare(self._make_token_with_timestamp(user, ts), token):
return False
# Check the timestamp is within limit
if (self._num_days(self._today()) - ts) > settings.PASSWORD_RESET_TIMEOUT_DAYS:
return False
return True
def _make_token_with_timestamp(self, user, timestamp):
# timestamp is number of days since 2001-1-1. Converted to
# base 36, this gives us a 3 digit string until about 2121
ts_b36 = int_to_base36(timestamp)
# By hashing on the internal state of the user and using state
# that is sure to change (the password salt will change as soon as
# the password is set, at least for current Django auth, and
# last_login will also change), we produce a hash that will be
# invalid as soon as it is used.
# We limit the hash to 20 chars to keep URL short
key_salt = "django.contrib.auth.tokens.PasswordResetTokenGenerator"
# Ensure results are consistent across DB backends
login_timestamp = user.last_login.replace(microsecond=0, tzinfo=None)
value = (six.text_type(user.pk) + user.password +
six.text_type(login_timestamp) + six.text_type(timestamp))
hash = salted_hmac(key_salt, value).hexdigest()[::2]
return "%s-%s" % (ts_b36, hash)
def _num_days(self, dt):
return (dt - date(2001, 1, 1)).days
def _today(self):
# Used for mocking in tests
return date.today()
default_token_generator = PasswordResetTokenGenerator()
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