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    SubjectRe: [PATCH v3 1/3] selftests: tpm2: Probe for available PCR bank
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    On 11/26/21 19:29, Jarkko Sakkinen wrote:
    > On Wed, 2021-11-24 at 19:38 -0500, Stefan Berger wrote:
    >> From: Stefan Berger <stefanb@linux.ibm.com>
    >>
    >> Probe for an available PCR bank to accommodate devices that do not have a
    > What does "probing for an vailable PCR bank" even mean?

    Checking ? Testing ? What's the difference to those words?


    >
    >> SHA-1 PCR bank or whose SHA-1 bank is deactivated. Use the bank that can
    >> be used for the TPM2 commands, such as the SHA-256 bank.
    > This is incorrect, as the patch does not have code to query
    > available hash algorithms.

    I am not sure I understand. The new function determines which PCR banks
    (SHA-1 or SHA-256) the subsequent tests can use. It tries to execute the
    policy_pcr command with the given hash bank algorithm (SHA-256 or SHA-1)
    and if it returns an UnknowPcrBankError it tries the next one in the
    list. It doesn't need to query available hash algorithms. A TPM 2 may
    support SHA 256 and yet its SHA 256 bank may be deactivate.

    > What the code does, and only does that, is to use SHA-256 as
    > a fallback when SHA-1 is not enabled.
    >
    > /Jarkko
    >
    >
    >> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
    >> ---
    >>  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, p"Use SHA-256 as a fallback crs)
    >> +            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)

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