linux-kernel - Re: [PATCH 1/3] crypto: drbg - ignore jitterentropy errors if not in FIPS mode

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Message-ID: <2799389.mtFdQKXovp@tauon.chronox.de>
Date:   Tue, 30 Nov 2021 19:04:48 +0100
From:   Stephan Mueller <smueller@...onox.de>
To:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Nicolai Stange <nstange@...e.de>
Cc:     Torsten Duwe <duwe@...e.de>, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org, Nicolai Stange <nstange@...e.de>
Subject: Re: [PATCH 1/3] crypto: drbg - ignore jitterentropy errors if not in FIPS mode

Am Dienstag, 30. November 2021, 15:10:07 CET schrieb Nicolai Stange:

Hi Nicolai,

> A subsequent patch will make the jitterentropy RNG to unconditionally
> report health test errors back to callers, independent of whether
> fips_enabled is set or not. The DRBG needs access to a functional
> jitterentropy instance only in FIPS mode (because it's the only SP800-90B
> compliant entropy source as it currently stands). Thus, it is perfectly
> fine for the DRBGs to obtain entropy from the jitterentropy source only
> on a best effort basis if fips_enabled is off.
> 
> Make the DRBGs to ignore jitterentropy failures if fips_enabled is not set.
> 
> Signed-off-by: Nicolai Stange <nstange@...e.de>

Reviewed-by: Stephan Mueller <smueller@...onox.de>

Thanks
Stephan
> ---
>  crypto/drbg.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/crypto/drbg.c b/crypto/drbg.c
> index 5977a72afb03..177983b6ae38 100644
> --- a/crypto/drbg.c
> +++ b/crypto/drbg.c
> @@ -1193,11 +1193,14 @@ static int drbg_seed(struct drbg_state *drbg, struct
> drbg_string *pers, pr_devel("DRBG: (re)seeding with %u bytes of entropy\n",
>  				 entropylen);
>  		} else {
> -			/* Get seed from Jitter RNG */
> +			/*
> +			 * Get seed from Jitter RNG, failures are
> +			 * fatal only in FIPS mode.
> +			 */
>  			ret = crypto_rng_get_bytes(drbg->jent,
>  						   entropy + entropylen,
>  						   entropylen);
> -			if (ret) {
> +			if (fips_enabled && ret) {
>  				pr_devel("DRBG: jent failed with %d\n", ret);
> 
>  				/*


Ciao
Stephan