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

Vitaly Chikunov
2019-03-28T06:16:53Z

On Wed, Mar 27, 2019 at 04:21:07PM -0400, Mimi Zohar wrote:
> > > 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.

Ah. No, I did not implement RSA(Streebog) intentionally, since Streebog is
not in the list of permitted hashes for PKCS1. You may notice this by the
lack of appropriate rsa_asn1_template[] entry.

Thanks,

>
> Mimi
>
> >
> > 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;
> >