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Date:   Mon, 21 Feb 2022 15:19:49 +0100
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Subject: Re: [PATCH v4 13/15] crypto: dh - disallow plain "dh" usage in FIPS
 mode
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To:     Nicolai Stange <nstange@suse.de>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        "David S. Miller" <davem@davemloft.net>
Cc:     =?UTF-8?Q?Stephan_M=c3=bcller?= <smueller@chronox.de>,
        Torsten Duwe <duwe@suse.de>,
        David Howells <dhowells@redhat.com>,
        Jarkko Sakkinen <jarkko@kernel.org>,
        linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org,
        keyrings@vger.kernel.org
References: <20220221121101.1615-1-nstange@suse.de>
 <20220221121101.1615-14-nstange@suse.de>
From:   Hannes Reinecke <hare@suse.de>
In-Reply-To: <20220221121101.1615-14-nstange@suse.de>
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On 2/21/22 13:10, Nicolai Stange wrote:
> SP800-56Arev3, sec. 5.5.2 ("Assurance of Domain-Parameter Validity")
> asserts that an implementation needs to verify domain paramtere validity,
> which boils down to either
> - the domain parameters corresponding to some known safe-prime group
>    explicitly listed to be approved in the document or
> - for parameters conforming to a "FIPS 186-type parameter-size set",
>    that the implementation needs to perform an explicit domain parameter
>    verification, which would require access to the "seed" and "counter"
>    values used in their generation.
> 
> The latter is not easily feasible and moreover, SP800-56Arev3 states that
> safe-prime groups are preferred and that FIPS 186-type parameter sets
> should only be supported for backward compatibility, if it all.
> 
> Mark "dh" as not fips_allowed in testmgr. Note that the safe-prime
> ffdheXYZ(dh) wrappers are not affected by this change: as these enforce
> some approved safe-prime group each, their usage is still allowed in FIPS
> mode.
> 
> This change will effectively render the keyctl(KEYCTL_DH_COMPUTE) syscall
> unusable in FIPS mode, but it has been brought up that this might even be
> a good thing ([1]).
> 
> [1] https://lore.kernel.org/r/20211217055227.GA20698@gondor.apana.org.au
> 
> Signed-off-by: Nicolai Stange <nstange@suse.de>
> ---
>   crypto/testmgr.c | 1 -
>   1 file changed, 1 deletion(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		           Kernel Storage Architect
hare@suse.de			                  +49 911 74053 688
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg
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