Another security question

Frank Millman frank at chagford.com
Fri Dec 23 08:52:41 EST 2016


"Chris Angelico"  wrote in message 
news:CAPTjJmpPPGM+_ut_AMTNb7vgo0vRgPtu6iAgYjqWVpXG5ypd_A at mail.gmail.com...
>
> On Fri, Dec 23, 2016 at 9:19 PM, Frank Millman <frank at chagford.com> wrote:
>
> > 3. Generate the password from the string supplied by the user as 
> > follows -
> >    from hashlib import blake2b
> >    password = blake2b('my_password'.encode('utf-8'), salt=salt).digest()
> >
> > The hashlib docs have the following warning -
> >
> > "Salted hashing (or just hashing) with BLAKE2 or any other 
> > general-purpose
> > cryptographic hash function, such as SHA-256, is not suitable for 
> > hashing
> > passwords. See BLAKE2 FAQ for more information."
> >
> > I propose to ignore this warning. I feel that, for my purposes, the 
> > above
> > procedure is adequate.
> >
> > Does all this sound reasonable?
>
> Check out some prior art. When I build a web app using Flask, I
> generally use Werkzeug's password management features:
>
> http://werkzeug.pocoo.org/docs/0.11/utils/#werkzeug.security.generate_password_hash
> http://werkzeug.pocoo.org/docs/0.11/utils/#werkzeug.security.check_password_hash
>
> As well as doing everything I said above about salting and hashing and
> having signatures, it pushes the responsibility onto someone else. You
> just give it a password and get back an ASCII string that you stash in
> the database. If there's a security flaw, Werkzeug can push a new
> version that fixes it - it's not your problem.
>
> At very least, be aware of what these kinds of libraries are doing.
> I'm not saying you should blindly trust them or automatically reach
> for a dependency, but they're worth looking at.
>

All excellent advice - thanks very much.

It seems that Werkzeug (which looks great, by the way) uses something called 
pbkdf2.

The new kid on the block seems to be Argon2. A python implementation called 
argon2_cffi has been released by Hynek Schlawack, who has written this 
article -
    https://hynek.me/articles/storing-passwords/

This is his preamble - "if you’re hashing your passwords with 
bcrypt/scrypt/PBKDF2 today, there’s nothing to worry about in the immediate 
future. This article is for you if you’re choosing a password hash today and 
want a future-proof solution."

I eventually got argon2_cffi installed, and it works very nicely, so I will 
run with that for now.

Thanks again

Frank





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