Fixed #29289 -- Clarified PasswordResetTokenGenerator comment regarding the data hashed to generate tokens.

Thanks Luke Plant for the draft text.
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Tim Graham 2018-04-06 11:05:51 -04:00 committed by GitHub
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commit 85d853b2d3
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1 changed files with 17 additions and 10 deletions

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@ -55,23 +55,30 @@ class PasswordResetTokenGenerator:
# 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
hash = salted_hmac(
self.key_salt,
self._make_hash_value(user, timestamp),
secret=self.secret,
).hexdigest()[::2]
).hexdigest()[::2] # Limit to 20 characters to shorten the URL.
return "%s-%s" % (ts_b36, hash)
def _make_hash_value(self, user, timestamp):
# Ensure results are consistent across DB backends
"""
Hash the user's primary key and some user state that's sure to change
after a password reset to produce a token that invalidated when it's
used:
1. The password field will change upon a password reset (even if the
same password is chosen, due to password salting).
2. The last_login field will usually be updated very shortly after
a password reset.
Failing those things, settings.PASSWORD_RESET_TIMEOUT_DAYS eventually
invalidates the token.
Running this data through salted_hmac() prevents password cracking
attempts using the reset token, provided the secret isn't compromised.
"""
# Truncate microseconds so that tokens are consistent even if the
# database doesn't support microseconds.
login_timestamp = '' if user.last_login is None else user.last_login.replace(microsecond=0, tzinfo=None)
return str(user.pk) + user.password + str(login_timestamp) + str(timestamp)