Re: Binary (un)safety of password_hash() used with PASSWORD_BCRYPT
> Le 22 avr. 2021 à 03:47, Sara Golemon <pollita@php.net> a écrit :
>
> I have this notion that we've discussed this before, I'm certain I knew
> that bcrypt wasn't binary safe, but someone reminded me that
> password_hash() could be called with null bytes in the password itself and
> that is just SCREAMING to have some safety-rails put on IMO.
>
> So I've thrown together https://github.com/php/php-src/pull/6897 to test
> that argon2 algos behave well (they do!), and modified the bcrypt algo to
> throw an exception if you try to hash a new password containing a null, but
> only warns if you've got a null when running password_verify(). My
> reasoning for the latter is because anyone trying to auth with a null
> character that succeeds does definitely know enough of the password to pass
> by simply not passing the null, so we shouldn't break existing users who
> already have hashes. This only aims to break users who would otherwise be
> able to include a null, because they would have a false sense of security
> having their password truncated and can remedy that in their password
> choosing.
>
> Since this does introduce a (small) break, I'm putting it to the list for
> opinions.
> If nobody objects, I'll merge this (8.1 only) at the end of the month.
>
> -Sara
Hi,
The intention is good, but the solution not so, especially for password_verify. You introduce a new,
subtle way for this function to behave unexpectedly; because currently, password_verify does not
currently trigger warning when given input of correct type. (Or if it does, it must be documented
and fixed, because it would be a bad thing.)
Also, the warning message you introduced contains “... this hash should be regenerated using
...”. There is already a dedicated function for conveying that information in a coder-friendly
way, namely password_needs_rehash(): let’s use that (it implies that the default
algorithm should be changed).
—Claude
Thread (15 messages)