systemd/SOURCES/0570-tpm2-add-tpm2_pcr_read_missing_values.patch

From 84ac655ce759bb906e9c428261c2a25b0f42241d Mon Sep 17 00:00:00 2001
From: Dan Streetman <ddstreet@ieee.org>
Date: Tue, 18 Jul 2023 12:56:25 -0400
Subject: [PATCH] tpm2: add tpm2_pcr_read_missing_values()

Add function to read all unset values in an array of Tpm2PCRValue entries.

Also publish tpm2_pcr_read() in header.

(cherry picked from commit b4a6fcd5c5cf95dde2d08769a86ff0d3f907b974)

Related: RHEL-16182
---
 src/shared/tpm2-util.c | 68 ++++++++++++++++++++++++++++++++++++++++--
 src/shared/tpm2-util.h |  4 +++
 2 files changed, 70 insertions(+), 2 deletions(-)

diff --git a/src/shared/tpm2-util.c b/src/shared/tpm2-util.c
index cd48988ab1..fadf3af9d6 100644
--- a/src/shared/tpm2-util.c
+++ b/src/shared/tpm2-util.c
@@ -2247,7 +2247,7 @@ int tpm2_create_loaded(
  * exactly what is in the provided selection, but the TPM may ignore some selected PCRs (for example, if an
  * unimplemented PCR index is requested), in which case those PCRs will be absent from the provided pcr
  * values. */
-static int tpm2_pcr_read(
+int tpm2_pcr_read(
                 Tpm2Context *c,
                 const TPML_PCR_SELECTION *pcr_selection,
                 Tpm2PCRValue **ret_pcr_values,
@@ -2320,6 +2320,70 @@ static int tpm2_pcr_read(
         return 0;
 }
 
+/* Read the PCR value for each TPM2PCRValue entry in the array that does not have a value set. If all entries
+ * have an unset hash (i.e. hash == 0), this first detects the "best" PCR bank to use; otherwise, all entries
+ * must have a valid hash set. All entries must have a valid index. If this cannot read a PCR value for all
+ * appropriate entries, this returns an error. This does not check the array for validity. */
+int tpm2_pcr_read_missing_values(Tpm2Context *c, Tpm2PCRValue *pcr_values, size_t n_pcr_values) {
+        TPMI_ALG_HASH pcr_bank = 0;
+        int r;
+
+        assert(c);
+        assert(pcr_values || n_pcr_values == 0);
+
+        if (n_pcr_values > 0) {
+                size_t hash_count;
+                r = tpm2_pcr_values_hash_count(pcr_values, n_pcr_values, &hash_count);
+                if (r < 0)
+                        return log_error_errno(r, "Could not get hash count from pcr values: %m");
+
+                if (hash_count == 1 && pcr_values[0].hash == 0) {
+                        uint32_t mask;
+                        r = tpm2_pcr_values_to_mask(pcr_values, n_pcr_values, 0, &mask);
+                        if (r < 0)
+                                return r;
+
+                        r = tpm2_get_best_pcr_bank(c, mask, &pcr_bank);
+                        if (r < 0)
+                                return r;
+                }
+        }
+
+        for (size_t i = 0; i < n_pcr_values; i++) {
+                Tpm2PCRValue *v = &pcr_values[i];
+
+                if (v->hash == 0)
+                        v->hash = pcr_bank;
+
+                if (v->value.size > 0)
+                        continue;
+
+                TPML_PCR_SELECTION selection;
+                r = tpm2_tpml_pcr_selection_from_pcr_values(v, 1, &selection, NULL, NULL);
+                if (r < 0)
+                        return r;
+
+                _cleanup_free_ Tpm2PCRValue *read_values = NULL;
+                size_t n_read_values;
+                r = tpm2_pcr_read(c, &selection, &read_values, &n_read_values);
+                if (r < 0)
+                        return r;
+
+                if (n_read_values == 0)
+                        return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
+                                               "Could not read PCR hash 0x%" PRIu16 " index %u",
+                                               v->hash, v->index);
+
+                assert(n_read_values == 1);
+                assert(read_values[0].hash == v->hash);
+                assert(read_values[0].index == v->index);
+
+                v->value = read_values[0].value;
+        }
+
+        return 0;
+}
+
 static int tpm2_pcr_mask_good(
                 Tpm2Context *c,
                 TPMI_ALG_HASH bank,
@@ -2381,7 +2445,7 @@ static int tpm2_bank_has24(const TPMS_PCR_SELECTION *selection) {
         return valid;
 }
 
-static int tpm2_get_best_pcr_bank(
+int tpm2_get_best_pcr_bank(
                 Tpm2Context *c,
                 uint32_t pcr_mask,
                 TPMI_ALG_HASH *ret) {
diff --git a/src/shared/tpm2-util.h b/src/shared/tpm2-util.h
index dc496a0135..2dffcf922d 100644
--- a/src/shared/tpm2-util.h
+++ b/src/shared/tpm2-util.h
@@ -99,6 +99,7 @@ bool tpm2_test_parms(Tpm2Context *c, TPMI_ALG_PUBLIC alg, const TPMU_PUBLIC_PARM
 
 int tpm2_get_good_pcr_banks(Tpm2Context *c, uint32_t pcr_mask, TPMI_ALG_HASH **ret_banks);
 int tpm2_get_good_pcr_banks_strv(Tpm2Context *c, uint32_t pcr_mask, char ***ret);
+int tpm2_get_best_pcr_bank(Tpm2Context *c, uint32_t pcr_mask, TPMI_ALG_HASH *ret);
 
 int tpm2_extend_bytes(Tpm2Context *c, char **banks, unsigned pcr_index, const void *data, size_t data_size, const void *secret, size_t secret_size);
 
@@ -145,6 +146,9 @@ void tpm2_log_debug_buffer(const void *buffer, size_t size, const char *msg);
 void tpm2_log_debug_digest(const TPM2B_DIGEST *digest, const char *msg);
 void tpm2_log_debug_name(const TPM2B_NAME *name, const char *msg);
 
+int tpm2_pcr_read(Tpm2Context *c, const TPML_PCR_SELECTION *pcr_selection, Tpm2PCRValue **ret_pcr_values, size_t *ret_n_pcr_values);
+int tpm2_pcr_read_missing_values(Tpm2Context *c, Tpm2PCRValue *pcr_values, size_t n_pcr_values);
+
 int tpm2_calculate_name(const TPMT_PUBLIC *public, TPM2B_NAME *ret_name);
 int tpm2_calculate_policy_auth_value(TPM2B_DIGEST *digest);
 int tpm2_calculate_policy_authorize(const TPM2B_PUBLIC *public, const TPM2B_DIGEST *policy_ref, TPM2B_DIGEST *digest);