Messages in this thread | | | Date | Fri, 26 Nov 2021 22:43:42 -0500 | Subject | Re: [PATCH v3 1/3] selftests: tpm2: Probe for available PCR bank | From | Stefan Berger <> |
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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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