[Haskell-cafe] ANN: nonce package

[Felipe Lessa]

(Please forgive me if you received multiple copies of this e-mail.)

Hello,

The nonce package [1] contains functions to easily generate
cryptographic nonces for many situations. Some places where these
generated nonces can be used include:

- Password recovery e-mail tokens.

- XSRF protection tokens.

- Session IDs sent on cookies.

- Initialization vectors.

It uses an AES CPRNG periodically reseeded from /dev/urandom (or
equivalent). It has no frills, no knobs, so it's hard to misuse. It's
been available for an year but I just realized I've never properly
announced it.

Regrettably, I've seen many uses of the random package (System.Random)
when generating nonces. It's a bad choice: it is not a
cryptographically secure PRNG, contains low entropy (64-bit state), and
its default usage is seeded predictably (using a constant seed). Please
avoid using the random package for generating nonces at all costs. In
its stead, use the nonce package or something similar.

Cheers,

[1] http://hackage.haskell.org/package/nonce

--
Felipe.

[Tobias Dammers]

Looks useful; feature request: something like

nonce :: MonadIO => Int -> Generator

(plus -url and -T flavors, obviously). I believe allowing the programmer
to balance security vs. usability demands would be a good thing overall
and worth a knob.

-> m ByteString

> _______________________________________________
> Haskell mailing list
> Has...@haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell


--
Tobias Dammers - tdam...@gmail.com
_______________________________________________
Haskell-Cafe mailing list
Haskel...@haskell.org
http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe

[Geraldus]

Hi, Felipe! Thank you for sharing!

The one question I have is there some good way to generate unique nonces?

сб, 23 мая 2015 г. в 22:01, Tobias Dammers <tdam...@gmail.com>:

[Geraldus]

Also it is good to make a new generator in function which

produces a nonce? E.g.

generateNonce :: forall (m :: * -> *). (MonadIO m, Functor m) => m Text

generateNonce =

  do g <- new

     nonce128urlT g

вс, 7 июня 2015 г. в 13:26, Geraldus <hera...@gmail.com>:

[Felipe Lessa]

On 07-06-2015 06:44, Geraldus wrote:
> вс, 7 июня 2015 г. в 13:26, Geraldus <hera...@gmail.com

> <mailto:hera...@gmail.com>>:

>
> Hi, Felipe! Thank you for sharing!
>
> The one question I have is there some good way to generate unique
> nonces?

Nonces generated by the nonce package are always unique. If not,
there's a huge bug, or your /dev/urandom is broken.

> Also it is good to make a new generator in function which
> produces a nonce? E.g.
>
> generateNonce :: forall (m :: * -> *). (MonadIO m, Functor m) => m Text
> generateNonce =
> do g <- new
> nonce128urlT g

You will not shoot yourself in the foot security-wise. You are not able
to distinguish a sequence of nonces generated by

replicateM n (new >>= nonce128urlT)

vs

new >>= replicateM n . nonce128urlT

However, 'new' is a _very_ expensive function. Your generateNonce
function will have abysmal performance (and so will the first example
above). Please avoid creating many generators.

Cheers,

--
Felipe.