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Date:   Wed, 24 Jun 2020 18:33:45 -0300
From:   Bruno Meneguele <bmeneg@redhat.com>
To:     Stefan Berger <stefanb@linux.ibm.com>
Cc:     Maurizio Drocco <maurizio.drocco@ibm.com>, zohar@linux.ibm.com,
        Silviu.Vlasceanu@huawei.com, dmitry.kasatkin@gmail.com,
        jejb@linux.ibm.com, jmorris@namei.org,
        linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-security-module@vger.kernel.org, mdrocco@linux.vnet.ibm.com,
        roberto.sassu@huawei.com, serge@hallyn.com
Subject: Re: [PATCH v2] ima_evm_utils: extended calc_bootaggr to PCRs 8 - 9
Message-ID: <20200624213345.GB2639@glitch>
References: <1592856871.4987.21.camel@linux.ibm.com>
 <20200623180122.209-1-maurizio.drocco@ibm.com>
 <20200623181357.GC4983@glitch>
 <92a0d170-8157-476b-8083-ae567b11f364@linux.ibm.com>
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On Wed, Jun 24, 2020 at 05:17:52PM -0400, Stefan Berger wrote:
> On 6/23/20 2:13 PM, Bruno Meneguele wrote:
> > On Tue, Jun 23, 2020 at 02:01:22PM -0400, Maurizio Drocco wrote:
> > > From: Maurizio <maurizio.drocco@ibm.com>
> > >=20
> > > If PCRs 8 - 9 are set (i.e. not all-zeros), cal_bootaggr should inclu=
de
> > > them into the digest.
>=20
>=20
> Wouldn't you have to check for not all-zeros in your code?
>=20

boot_aggregate in kernel, after the following patch be applied:

https://lkml.org/lkml/2020/6/23/833

is calculated regardless PCR 8 & 9 being zero or not.
Thus evmctl is only reflecting the same behavior.

I think it would be worth changing the commit log here.

>=20
> =A0=A0 Stefan
>=20
>=20
> > >=20
> > > Signed-off-by: Maurizio Drocco <maurizio.drocco@ibm.com>
> > > ---
> > > Changelog:
> > > v2:
> > > - Always include PCRs 8 & 9 to non-sha1 hashes
> > > v1:
> > > - Include non-zero PCRs 8 & 9 to boot aggregates
> > >=20
> > >   src/evmctl.c | 15 +++++++++++++--
> > >   1 file changed, 13 insertions(+), 2 deletions(-)
> > >=20
> > > diff --git a/src/evmctl.c b/src/evmctl.c
> > > index 1d065ce..46b7092 100644
> > > --- a/src/evmctl.c
> > > +++ b/src/evmctl.c
> > > @@ -1930,6 +1930,16 @@ static void calc_bootaggr(struct tpm_bank_info=
 *bank)
> > >   =09=09}
> > >   =09}
> > > +=09if (strcmp(bank->algo_name, "sha1") !=3D 0) {
> > > +=09=09for (i =3D 8; i < 10; i++) {
> > > +=09=09=09err =3D EVP_DigestUpdate(pctx, bank->pcr[i], bank->digest_s=
ize);
> > > +=09=09=09if (!err) {
> > > +=09=09=09=09log_err("EVP_DigestUpdate() failed\n");
> > > +=09=09=09=09return;
> > > +=09=09=09}
> > > +=09=09}
> > > +=09}
> > > +
> > >   =09err =3D EVP_DigestFinal(pctx, bank->digest, &mdlen);
> > >   =09if (!err) {
> > >   =09=09log_err("EVP_DigestFinal() failed\n");
> > > @@ -1972,8 +1982,9 @@ static int append_bootaggr(char *bootaggr, stru=
ct tpm_bank_info *tpm_banks)
> > >   /*
> > >    * The IMA measurement list boot_aggregate is the link between the =
preboot
> > >    * event log and the IMA measurement list.  Read and calculate all =
the
> > > - * possible per TPM bank boot_aggregate digests based on the existin=
g
> > > - * PCRs 0 - 7 to validate against the IMA boot_aggregate record.
> > > + * possible per TPM bank boot_aggregate digests based on the existin=
g PCRs
> > > + * 0 - 9 to validate against the IMA boot_aggregate record. If the d=
igest
> > > + * algorithm is SHA1, only PCRs 0 - 7 are considered to avoid ambigu=
ity.
> > >    */
> > >   static int cmd_ima_bootaggr(struct command *cmd)
> > >   {
> > > --=20
> > > 2.17.1
> > >=20
> > Reviewed-by: Bruno Meneguele <bmeneg@redhat.com>
> >=20
>=20

--=20
bmeneg=20
PGP Key: http://bmeneg.com/pubkey.txt

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