Re: [PATCH v8 10/10] integrity: support EC-RDSA signatures for asymmetric_verify

Vitaly Chikunov
2019-03-27T20:14:48Z

On Wed, Mar 27, 2019 at 02:10:20PM -0400, Mimi Zohar wrote:
> 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@linux.ibm.com>
> > Cc: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>
> > Cc: linux-integrity@vger.kernel.org
> > Signed-off-by: Vitaly Chikunov <vt@altlinux.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

In what sense it would break systems?

Unless kernel crashes or signature is recognized as valid, I think, it should
not be called a break.

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

Thanks!

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