linux-kernel - Re: [PATCH] crypto: api - Disallow sha1 in FIPS-mode while allowing hmac(sha1)

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Date:   Tue, 11 Jan 2022 08:50:18 +0100
From:   Nicolai Stange <nstange@...e.de>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     Stephan Mueller <smueller@...onox.de>,
        Nicolai Stange <nstange@...e.de>,
        "David S. Miller" <davem@...emloft.net>,
        Hannes Reinecke <hare@...e.de>, Torsten Duwe <duwe@...e.de>,
        Zaibo Xu <xuzaibo@...wei.com>,
        Giovanni Cabiddu <giovanni.cabiddu@...el.com>,
        David Howells <dhowells@...hat.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        qat-linux@...el.com, keyrings@...r.kernel.org, simo@...hat.com,
        Eric Biggers <ebiggers@...nel.org>, Petr Vorel <pvorel@...e.cz>
Subject: Re: [PATCH] crypto: api - Disallow sha1 in FIPS-mode while allowing hmac(sha1)

Hi Herbert,

Herbert Xu <herbert@...dor.apana.org.au> writes:

> On Fri, Jan 07, 2022 at 01:44:34PM +1100, Herbert Xu wrote:
>>
>> I'm already writing this up for sha1 anyway so let me polish it
>> off and I'll post it soon which you can then reuse it for dh.
>
> Here is something that seems to work for sha1/hmac.  Please let
> me know if you see any issues with this approach for dh.
>
> Thanks,
>
> ---8<---
> Currently we do not distinguish between algorithms that fail on
> the self-test vs. those which are disabled in FIPS mode (not allowed).
> Both are marked as having failed the self-test.
>
> As it has been requested that we need to disable sha1 in FIPS
> mode while still allowing hmac(sha1) this approach needs to change.
>
> This patch allows this scenario by adding a new flag FIPS_INTERNAL
> to indicate those algorithms that have passed the self-test and are
> not FIPS-allowed.  They can then be used for the self-testing of
> other algorithms or by those that are explicitly allowed to use them
> (currently just hmac).

I haven't tried, but wouldn't this allow the instantiation of e.g.
hmac(blake2s-256) in FIPS mode?

Thanks,

Nicolai

>
> Note that as a side-effect of this patch algorithms which are not
> FIPS-allowed will now return ENOENT instead of ELIBBAD.  Hopefully
> this is not an issue as some people were relying on this already.
>
> Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
>

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