netdev - Re: [PATCH net-next] [RESEND] wireguard: disable in FIPS mode

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Message-ID: <20210409024143.GL2900@Leo-laptop-t470s>
Date:   Fri, 9 Apr 2021 10:41:43 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     Simo Sorce <simo@...hat.com>, Netdev <netdev@...r.kernel.org>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Ondrej Mosnacek <omosnace@...hat.com>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>
Subject: Re: [PATCH net-next] [RESEND] wireguard: disable in FIPS mode

On Thu, Apr 08, 2021 at 03:55:59PM -0600, Jason A. Donenfeld wrote:
> On Thu, Apr 8, 2021 at 7:55 AM Simo Sorce <simo@...hat.com> wrote:
> > > I'm not sure this makes so much sense to do _in wireguard_. If you
> > > feel like the FIPS-allergic part is actually blake, 25519, chacha, and
> > > poly1305, then wouldn't it make most sense to disable _those_ modules
> > > instead? And then the various things that rely on those (such as
> > > wireguard, but maybe there are other things too, like
> > > security/keys/big_key.c) would be naturally disabled transitively?
> >
> > The reason why it is better to disable the whole module is that it
> > provide much better feedback to users. Letting init go through and then
> > just fail operations once someone tries to use it is much harder to
> > deal with in terms of figuring out what went wrong.
> > Also wireguard seem to be poking directly into the algorithms
> > implementations and not use the crypto API, so disabling individual
> > algorithm via the regular fips_enabled mechanism at runtime doesn't
> > work.
> 
> What I'm suggesting _would_ work in basically the exact same way as
> this patch. Namely, something like:

Hi Jason,

I agree that the best way is to disable the crypto modules in FIPS mode.
But the code in lib/crypto looks not the same with crypto/. For modules
in crypto, there is an alg_test() to check if the crytpo is FIPS allowed
when do register.

- crypto_register_alg()
  - crypto_wait_for_test()
    - crypto_probing_notify(CRYPTO_MSG_ALG_REGISTER, larval->adult)
      - cryptomgr_schedule_test()
        - cryptomgr_test()
          - alg_test()

But in lib/crypto the code are more like a library. We can call it anytime
and there is no register. Maybe we should add a similar check in lib/crypto.
But I'm not familiar with crypto code... Not sure if anyone in linux-crypto@
would like help do that.

> 
> diff --git a/lib/crypto/curve25519.c b/lib/crypto/curve25519.c
> index 288a62cd29b2..b794f49c291a 100644
> --- a/lib/crypto/curve25519.c
> +++ b/lib/crypto/curve25519.c
> @@ -12,11 +12,15 @@
>  #include <crypto/curve25519.h>
>  #include <linux/module.h>
>  #include <linux/init.h>
> +#include <linux/fips.h>
> 
>  bool curve25519_selftest(void);
> 
>  static int __init mod_init(void)
>  {
> + if (!fips_enabled)
> + return -EOPNOTSUPP;

Question here, why it is !fips_enabled? Shouldn't we return error when
fips_enabled?

Thanks
Hangbin