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

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Date:   Wed, 27 Mar 2019 16:21:07 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Vitaly Chikunov <vt@...linux.org>
Cc:     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

> > 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
> 
> In what sense it would break systems?

For example, if executable files are currently labeled with
rsa/streebog signatures, then enforcing file data integrity I assume
would break if the kernel uses ecrdsa/streebog.

Mimi

> 
> Unless kernel crashes or signature is recognized as valid, I think, it should
> not be called a break.
> 
> > Reviewed-by:  Mimi Zohar <zohar@...ux.ibm.com>
> 
> Thanks!
> 
> > 
> > > +	} else {
> > > +		pks.pkey_algo = "rsa";
> > > +		pks.encoding = "pkcs1";
> > > +	}
> > >  	pks.digest = (u8 *)data;
> > >  	pks.digest_size = datalen;
> > >  	pks.s = hdr->sig;
>