Re: [PATCH v2 1/3] selftests: tpm2: Probe for available PCR bank

[Stefan Berger <stefanb@xxxxxxxxxxxxx>]

On 11/24/21 18:54, Jarkko Sakkinen wrote:
> On Wed, Nov 24, 2021 at 09:13:12AM -0500, Stefan Berger wrote:
> > Probe for an available PCR bank to accommodate devices that do not have a
> > SHA-1 PCR bank or whose SHA-1 bank is deactivated. Use the bank that can
> > be used in the TPM2 commands. Assert on the probing function to not
> > return None.
> What is *the bank* that can be used?

The bank can be either SHA-1 or SHA-256 at this point.

> In addition, I don't understand the last sentence.


If the probing function returns None the test fails due to an 
assertIsNotNone().

   stefan

> /Jarkko
>
>
> > Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
> > ---
> >   tools/testing/selftests/tpm2/tpm2_tests.py | 35 +++++++++++++++++-----
> >   1 file changed, 27 insertions(+), 8 deletions(-)
> >
> > diff --git a/tools/testing/selftests/tpm2/tpm2_tests.py b/tools/testing/selftests/tpm2/tpm2_tests.py
> > index 9d764306887b..6b88ff0e47b9 100644
> > --- a/tools/testing/selftests/tpm2/tpm2_tests.py
> > +++ b/tools/testing/selftests/tpm2/tpm2_tests.py
> > @@ -27,7 +27,23 @@ class SmokeTest(unittest.TestCase):
> >           result = self.client.unseal(self.root_key, blob, auth, None)
> >           self.assertEqual(data, result)
> >   
> > +    def determine_bank_alg(self):
> > +        # Probe for available PCR bank
> > +        for bank_alg in [tpm2.TPM2_ALG_SHA1, tpm2.TPM2_ALG_SHA256]:
> > +            try:
> > +                handle = self.client.start_auth_session(tpm2.TPM2_SE_TRIAL)
> > +                self.client.policy_pcr(handle, [17], bank_alg=bank_alg)
> > +                return bank_alg
> > +            except tpm2.UnknownPCRBankError:
> > +                pass
> > +            finally:
> > +                self.client.flush_context(handle)
> > +        return None
> > +
> >       def test_seal_with_policy(self):
> > +        bank_alg = self.determine_bank_alg()
> > +        self.assertIsNotNone(bank_alg)
> > +
> >           handle = self.client.start_auth_session(tpm2.TPM2_SE_TRIAL)
> >   
> >           data = ('X' * 64).encode()
> > @@ -35,7 +51,7 @@ class SmokeTest(unittest.TestCase):
> >           pcrs = [16]
> >   
> >           try:
> > -            self.client.policy_pcr(handle, pcrs)
> > +            self.client.policy_pcr(handle, pcrs, bank_alg=bank_alg)
> >               self.client.policy_password(handle)
> >   
> >               policy_dig = self.client.get_policy_digest(handle)
> > @@ -47,7 +63,7 @@ class SmokeTest(unittest.TestCase):
> >           handle = self.client.start_auth_session(tpm2.TPM2_SE_POLICY)
> >   
> >           try:
> > -            self.client.policy_pcr(handle, pcrs)
> > +            self.client.policy_pcr(handle, pcrs, bank_alg=bank_alg)
> >               self.client.policy_password(handle)
> >   
> >               result = self.client.unseal(self.root_key, blob, auth, handle)
> > @@ -72,6 +88,9 @@ class SmokeTest(unittest.TestCase):
> >           self.assertEqual(rc, tpm2.TPM2_RC_AUTH_FAIL)
> >   
> >       def test_unseal_with_wrong_policy(self):
> > +        bank_alg = self.determine_bank_alg()
> > +        self.assertIsNotNone(bank_alg)
> > +
> >           handle = self.client.start_auth_session(tpm2.TPM2_SE_TRIAL)
> >   
> >           data = ('X' * 64).encode()
> > @@ -79,7 +98,7 @@ class SmokeTest(unittest.TestCase):
> >           pcrs = [16]
> >   
> >           try:
> > -            self.client.policy_pcr(handle, pcrs)
> > +            self.client.policy_pcr(handle, pcrs, bank_alg=bank_alg)
> >               self.client.policy_password(handle)
> >   
> >               policy_dig = self.client.get_policy_digest(handle)
> > @@ -91,13 +110,13 @@ class SmokeTest(unittest.TestCase):
> >           # Extend first a PCR that is not part of the policy and try to unseal.
> >           # This should succeed.
> >   
> > -        ds = tpm2.get_digest_size(tpm2.TPM2_ALG_SHA1)
> > -        self.client.extend_pcr(1, ('X' * ds).encode())
> > +        ds = tpm2.get_digest_size(bank_alg)
> > +        self.client.extend_pcr(1, ('X' * ds).encode(), bank_alg=bank_alg)
> >   
> >           handle = self.client.start_auth_session(tpm2.TPM2_SE_POLICY)
> >   
> >           try:
> > -            self.client.policy_pcr(handle, pcrs)
> > +            self.client.policy_pcr(handle, pcrs, bank_alg=bank_alg)
> >               self.client.policy_password(handle)
> >   
> >               result = self.client.unseal(self.root_key, blob, auth, handle)
> > @@ -109,14 +128,14 @@ class SmokeTest(unittest.TestCase):
> >   
> >           # Then, extend a PCR that is part of the policy and try to unseal.
> >           # This should fail.
> > -        self.client.extend_pcr(16, ('X' * ds).encode())
> > +        self.client.extend_pcr(16, ('X' * ds).encode(), bank_alg=bank_alg)
> >   
> >           handle = self.client.start_auth_session(tpm2.TPM2_SE_POLICY)
> >   
> >           rc = 0
> >   
> >           try:
> > -            self.client.policy_pcr(handle, pcrs)
> > +            self.client.policy_pcr(handle, pcrs, bank_alg=bank_alg)
> >               self.client.policy_password(handle)
> >   
> >               result = self.client.unseal(self.root_key, blob, auth, handle)
> > --
> > 2.31.1