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 <20200813160811.3568494-1-lenaptr@google.com> <20200813193239.GA2470@sol.localdomain>
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From:   Elena Petrova <lenaptr@google.com>
Date:   Tue, 8 Sep 2020 18:18:41 +0100
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Subject: Re: [PATCH v5] crypto: af_alg - add extra parameters for DRBG interface
To:     Eric Biggers <ebiggers@kernel.org>
Cc:     "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@vger.kernel.org>,
        =?UTF-8?Q?Stephan_M=C3=BCller?= <smueller@chronox.de>,
        Ard Biesheuvel <ardb@kernel.org>,
        Jeffrey Vander Stoep <jeffv@google.com>
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On Thu, 13 Aug 2020 at 20:32, Eric Biggers <ebiggers@kernel.org> wrote:

> >  Depending on the RNG type, the RNG must be seeded. The seed is provided
> >  using the setsockopt interface to set the key. For example, the
> >  ansi_cprng requires a seed. The DRBGs do not require a seed, but may be
> > -seeded.
> > +seeded. The seed is also known as a *Personalization String* in DRBG800-90A
> > +standard.
>
> Isn't the standard called "NIST SP 800-90A"?
> "DRBG800-90A" doesn't return many hits on Google.

Fixed, thanks!

> > +For the purpose of CAVP testing, the concatenation of *Entropy* and *Nonce*
> > +can be provided to the RNG via ALG_SET_DRBG_ENTROPY setsockopt interface. This
> > +requires a kernel built with CONFIG_CRYPTO_USER_API_CAVP_DRBG, and
> > +CAP_SYS_ADMIN permission.
> > +
> > +*Additional Data* can be provided using the send()/sendmsg() system calls.
>
> This doesn't make it clear whether the support for "Additional Data" is
> dependent on CONFIG_CRYPTO_USER_API_CAVP_DRBG or not.

Fixed.

> > +config CRYPTO_USER_API_CAVP_DRBG
> > +     tristate "Enable CAVP testing of DRBG"
> > +     depends on CRYPTO_USER_API_RNG && CRYPTO_DRBG
> > +     help
> > +       This option enables extra API for CAVP testing via the user-space
> > +       interface: resetting of DRBG entropy, and providing Additional Data.
> > +       This should only be enabled for CAVP testing. You should say
> > +       no unless you know what this is.
>
> Using "tristate" here is incorrect because this option is not a module itself.
> It's an option *for* a module.  So it needs to be "bool" instead.

Done.

> Also, since this is an option to refine CRYPTO_USER_API_RNG, how about renaming
> it to "CRYPTO_USER_API_RNG_CAVP", and moving it to just below the definition of
> "CRYPTO_USER_API_RNG" so that they show up adjacent to each other?

Sounds good, done.

> > +static int rng_test_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
> > +                         int flags)
> > +{
> > +     struct sock *sk = sock->sk;
> > +     struct alg_sock *ask = alg_sk(sk);
> > +     struct rng_ctx *ctx = ask->private;
> > +     int err;
> > +
> > +     lock_sock(sock->sk);
> > +     err = _rng_recvmsg(ctx->drng, msg, len, ctx->addtl, ctx->addtl_len);
> > +     rng_reset_addtl(ctx);
> > +     release_sock(sock->sk);
> > +
> > +     return err ? err : len;
>
> Shouldn't this just return the value that _rng_recvmsg() returned?
>
> Also 'err' is conventionally just for 0 or -errno codes.  Use 'ret' if the
> variable can also hold a length.

Done.