phc-discussions - Re: [PHC] pre-hashed passwords?

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Date: Tue, 17 Mar 2015 12:15:48 -0500 (CDT)
From: Steve Thomas <steve@...tu.com>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] pre-hashed passwords?

> On March 17, 2015 at 8:08 AM Jean-Philippe Aumasson
> <jeanphilippe.aumasson@...il.com> wrote:
>
> (After reading this nice post about passwords including null bytes:
> http://blog.ircmaxell.com/2015/03/security-issue-combining-bcrypt-with.html)
>
> Has anyone already seen password hashes "pre-hashing" a password, to
> handle length limitations? Things like
>
> password_hash(hash('sha256', $password, true), PASSWORD_DEFAULT)
>
> password_hash(hash_hmac('sha256', $password, $key, true), PASSWORD_DEFAULT)
>

I suggested it back in mid 2012 but had "hash('sha256', $pw)" for PHP's crypt().
It was part of an encrypted bcrypt hash library I made. Luckily I went with hex
output. Probably because I knew about the problems with byte values >127 in some
versions of bcrypt. Also I apparently never updated it... I'll do it tomorrow.

P.S. PHP's crypt() also breaks with NUL characters.