linux-kernel - Re: [PATCH v8 10/10] integrity: support EC-RDSA signatures for asymmetric

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Date:   Wed, 27 Mar 2019 14:10:20 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Vitaly Chikunov <vt@...linux.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        David Howells <dhowells@...hat.com>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        linux-integrity@...r.kernel.org, keyrings@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 10/10] integrity: support EC-RDSA signatures for
 asymmetric_verify

On Tue, 2019-03-26 at 15:58 +0300, Vitaly Chikunov wrote:
> Allow to use EC-RDSA signatures for IMA by determining signature type by
> the hash algorithm name. This works good for EC-RDSA since Streebog and
> EC-RDSA should always be used together.
> 
> Cc: Mimi Zohar <zohar@...ux.ibm.com>
> Cc: Dmitry Kasatkin <dmitry.kasatkin@...il.com>
> Cc: linux-integrity@...r.kernel.org
> Signed-off-by: Vitaly Chikunov <vt@...linux.org>
> ---
>  security/integrity/digsig_asymmetric.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/security/integrity/digsig_asymmetric.c b/security/integrity/digsig_asymmetric.c
> index d775e03fbbcc..99080871eb9f 100644
> --- a/security/integrity/digsig_asymmetric.c
> +++ b/security/integrity/digsig_asymmetric.c
> @@ -104,9 +104,16 @@ int asymmetric_verify(struct key *keyring, const char *sig,
>  
>  	memset(&pks, 0, sizeof(pks));
>  
> -	pks.pkey_algo = "rsa";
>  	pks.hash_algo = hash_algo_name[hdr->hash_algo];
> -	pks.encoding = "pkcs1";
> +	if (hdr->hash_algo == HASH_ALGO_STREEBOG_256 ||
> +	    hdr->hash_algo == HASH_ALGO_STREEBOG_512) {
> +		/* EC-RDSA and Streebog should go together. */
> +		pks.pkey_algo = "ecrdsa";
> +		pks.encoding = "raw";

IMA signatures are stored as xattrs, making them persistent.  Support
for streebog was upstreamed in linux-5.0.  This change would break
existing systems using streebog.  As long as this is not yet a concern

Reviewed-by:  Mimi Zohar <zohar@...ux.ibm.com>

> +	} else {
> +		pks.pkey_algo = "rsa";
> +		pks.encoding = "pkcs1";
> +	}
>  	pks.digest = (u8 *)data;
>  	pks.digest_size = datalen;
>  	pks.s = hdr->sig;