tpm: Don't create an EventLog if algorithms are misconfigured

We already check the active banks vs what U-Boot was compiled with when
trying to extend a PCR and we refuse to do so if the TPM active ones
don't match the ones U-Boot supports.

Do the same thing for the EventLog creation since extending will fail
anyway and print a message so the user can figure out the missing
algorithms.

Co-developed-by: Raymond Mao <raymond.mao@linaro.org>
Signed-off-by: Raymond Mao <raymond.mao@linaro.org>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

1 files changed, 26 insertions, 1 deletions

diff --git a/lib/tpm_tcg2.c b/lib/tpm_tcg2.c
index 99671804e3b..e77a9041299 100644
--- a/lib/tpm_tcg2.c
+++ b/lib/tpm_tcg2.c
@@ -567,11 +567,36 @@ int tcg2_log_prepare_buffer(struct udevice *dev, struct tcg2_event_log *elog,
 			    bool ignore_existing_log)
 {
 	struct tcg2_event_log log;
-	int rc;
+	int rc, i;
 
 	elog->log_position = 0;
 	elog->found = false;
 
+	/*
+	 * Make sure U-Boot is compiled with all the active PCRs
+	 * since we are about to create an EventLog and we won't
+	 * measure anything if the PCR banks don't match
+	 */
+	if (!tpm2_check_active_banks(dev)) {
+		log_err("Cannot create EventLog\n");
+		log_err("Mismatch between U-Boot and TPM hash algos\n");
+		log_info("TPM:\n");
+		tpm2_print_active_banks(dev);
+		log_info("U-Boot:\n");
+		for (i = 0; i < ARRAY_SIZE(hash_algo_list); i++) {
+			const struct digest_info *algo = &hash_algo_list[i];
+			const char *str;
+
+			if (!algo->supported)
+				continue;
+
+			str = tpm2_algorithm_name(algo->hash_alg);
+			if (str)
+				log_info("%s\n", str);
+		}
+		return -EINVAL;
+	}
+
 	rc = tcg2_platform_get_log(dev, (void **)&log.log, &log.log_size);
 	if (!rc) {
 		log.log_position = 0;