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

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Date:   Wed, 24 Nov 2021 19:15:10 -0500
From:   Stefan Berger <stefanb@...ux.ibm.com>
To:     Jarkko Sakkinen <jarkko@...nel.org>
Cc:     linux-integrity@...r.kernel.org, peterhuewe@....de,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        skhan@...uxfoundation.org
Subject: Re: [PATCH v2 1/3] selftests: tpm2: Probe for available PCR bank


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@...ux.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, 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
>>