[PATCH for 5.0.x & 4.y] tests: tpm: Skip over pcrUpdateCounter byte in result comparison

[Stefan Berger <stefanb@linux.vnet.ibm.com>]

The TPM 2 code in libtpms was fixed to handle the PCR 'TCB group' according
to the PCClient profile. The change of the PCRs belonging to the 'TCB group'
now affects the pcrUpdateCounter in the TPM2_PCRRead() responses where its
value is now different (typically lower by '1') than what it was before. To
not fail the tests, we skip the comparison of the 14th byte, which
represents the pcrUpdateCounter.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-id: 20200707201625.4177419-3-stefanb@linux.vnet.ibm.com
---
 tests/qtest/tpm-util.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tests/qtest/tpm-util.c b/tests/qtest/tpm-util.c
index 34efae8f18..58a9593745 100644
--- a/tests/qtest/tpm-util.c
+++ b/tests/qtest/tpm-util.c
@@ -139,7 +139,11 @@ void tpm_util_pcrread(QTestState *s, tx_func *tx,
 
     tx(s, tpm_pcrread, sizeof(tpm_pcrread), buffer, sizeof(buffer));
 
-    g_assert_cmpmem(buffer, exp_resp_size, exp_resp, exp_resp_size);
+    /* skip pcrUpdateCounter (14th byte) in comparison */
+    g_assert(exp_resp_size >= 15);
+    g_assert_cmpmem(buffer, 13, exp_resp, 13);
+    g_assert_cmpmem(&buffer[14], exp_resp_size - 14,
+                    &exp_resp[14], exp_resp_size - 14);
 }
 
 bool tpm_util_swtpm_has_tpm2(void)
-- 
2.24.1