linux-kernel - Re: [v2 PATCH] crypto: api - Disallow sha1 in FIPS-mode while allowing hmac(sha1)

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Date:   Wed, 26 Jan 2022 10:01:17 +0100
From:   Stephan Mueller <smueller@...onox.de>
To:     Nicolai Stange <nstange@...e.de>,
        Herbert Xu <herbert@...dor.apana.org.au>
Cc:     "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: [v2 PATCH] crypto: api - Disallow sha1 in FIPS-mode while allowing hmac(sha1)

Am Freitag, 14. Januar 2022, 11:55:26 CET schrieb Herbert Xu:

Hi Herbert,

> 
> > This looks all good to me, but as !->fips_allowed tests aren't skipped
> > over anymore now, it would perhaps make sense to make their failure
> > non-fatal in FIPS mode. Because in FIPS mode a failure could mean a
> > panic and some of the existing TVs might not pass because of e.g. some
> > key length checks or so active only for fips_enabled...
> 
> You mean a buggy non-FIPS algorithm that fails when tested in
> FIPS mode?  I guess we could skip the panic in that case if
> everyone is happy with that.  Stephan?

As we consider FIPS 140-3, we can allow a "degrated mode of operation". A 
degraded mode of operation disables only the algorithm that caused the 
failure. With a failing self test and not having a panic(), the offending 
algorithm implementation will not be available to the kernel crypto API and 
thus to a user.

In this case, we can replace the panic with a graceful error.

If that change is applied, I would like to mention to anybody that wants to 
backport the change: this change is not appropriate for FIPS 140-2.

Ciao
Stephan