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boot: check protocol version before assuming GetActiveBanks() exists

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Alternative to: #39034
Fixes: #38932
Follow-up to: 6eab4cd44c
This commit is contained in:
Lennart Poettering
2025-09-23 13:42:02 +02:00
parent 496489c2a7
commit b388fa20c7
1 changed files with 22 additions and 8 deletions
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30
src/boot/measure.c
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@@ -150,7 +150,7 @@ static EFI_CC_MEASUREMENT_PROTOCOL *cc_interface_check(void) {
return cc;
}
static EFI_TCG2_PROTOCOL *tcg2_interface_check(void) {
static EFI_TCG2_PROTOCOL* tcg2_interface_check(EFI_TCG2_VERSION *ret_version) {
EFI_STATUS err;
EFI_TCG2_PROTOCOL *tcg;
@@ -167,28 +167,42 @@ static EFI_TCG2_PROTOCOL *tcg2_interface_check(void) {
assert(capability.Size >= endoffsetof_field(EFI_TCG2_BOOT_SERVICE_CAPABILITY, Size));
if (capability.Size < endoffsetof_field(EFI_TCG2_BOOT_SERVICE_CAPABILITY, TPMPresentFlag))
/* This is a paranoia check, given these fields existed from day one of the spec. But the spec also
* suggests checking the structure size before accessing any fields, hence let's do so, for extra
* paranoia. */
if (capability.Size < CONST_MAX(endoffsetof_field(EFI_TCG2_BOOT_SERVICE_CAPABILITY, TPMPresentFlag),
endoffsetof_field(EFI_TCG2_BOOT_SERVICE_CAPABILITY, ProtocolVersion)))
return NULL;
if (!capability.TPMPresentFlag)
return NULL;
if (ret_version)
*ret_version = capability.ProtocolVersion;
return tcg;
}
bool tpm_present(void) {
return tcg2_interface_check();
return tcg2_interface_check(/* ret_version= */ NULL);
}
uint32_t tpm_get_active_pcr_banks(void) {
uint32_t active_pcr_banks = 0;
EFI_TCG2_PROTOCOL *tpm2;
EFI_STATUS err;
tpm2 = tcg2_interface_check();
EFI_TCG2_PROTOCOL *tpm2;
EFI_TCG2_VERSION version;
tpm2 = tcg2_interface_check(&version);
if (!tpm2)
return 0;
/* GetActivePcrBanks() was added only in version 1.1 of the spec */
if (version.Major < 1 || (version.Major == 1 && version.Minor < 1)) {
log_debug("TCG protocol too old for GetActivePcrBanks(), claiming no active banks.");
return 0;
}
uint32_t active_pcr_banks = 0;
err = tpm2->GetActivePcrBanks(tpm2, &active_pcr_banks);
if (err != EFI_SUCCESS) {
log_warning_status(err, "Failed to get TPM2 active PCR banks, assuming none: %m");
@@ -204,7 +218,7 @@ static EFI_STATUS tcg2_log_ipl_event(uint32_t pcrindex, EFI_PHYSICAL_ADDRESS buf
assert(ret_measured);
tpm2 = tcg2_interface_check();
tpm2 = tcg2_interface_check(/* ret_version= */ NULL);
if (!tpm2) {
*ret_measured = false;
return EFI_SUCCESS;
@@ -286,7 +300,7 @@ EFI_STATUS tpm_log_tagged_event(
/* If EFI_SUCCESS is returned, will initialize ret_measured to true if we actually measured
* something, or false if measurement was turned off. */
tpm2 = tcg2_interface_check();
tpm2 = tcg2_interface_check(/* ret_version= */ NULL);
if (!tpm2 || pcrindex == UINT32_MAX) { /* PCR disabled? */
if (ret_measured)
*ret_measured = false;