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tpm2: add tpm2_pcr_read_missing_values()

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

Also publish tpm2_pcr_read() in header.
This commit is contained in:
Dan Streetman 2023-07-18 12:56:25 -04:00
parent 53b91e1981
commit b4a6fcd5c5
2 changed files with 70 additions and 2 deletions
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68
src/shared/tpm2-util.c
View file

@ -2251,7 +2251,7 @@ 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,
@ -2324,6 +2324,70 @@ 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,
@ -2385,7 +2449,7 @@ 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) {

4
src/shared/tpm2-util.h
View file

@ -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);