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measure: strip tpm 1.x remnants and make GetActivePcrBanks() work (#39089)

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Let's never bother with old TPM 1.x structures, they are not mentioned
in the TCG for TPM2 spec at all. However, the spec does say we should
check the Size field of the relevant structs, before accessing them,
hence do that.

Use that to determine the version of the protocol, before accessing
GetActiveBanks().

Alternative to: #39034
Fixes: #38932
Follow-up to: 6eab4cd44c
This commit is contained in:
Yu Watanabe
2025-09-24 18:14:09 +09:00
committed by GitHub
parent 01598d644f b388fa20c7
commit a359d92547
2 changed files with 29 additions and 34 deletions
Download Patch File Download Diff File Expand all files Collapse all files

47
src/boot/measure.c
View File

@@ -150,48 +150,59 @@ static EFI_CC_MEASUREMENT_PROTOCOL *cc_interface_check(void) {
return cc;
}
static EFI_TCG2_PROTOCOL *tcg2_interface_check(void) {
EFI_TCG2_BOOT_SERVICE_CAPABILITY capability = {
.Size = sizeof(capability),
};
static EFI_TCG2_PROTOCOL* tcg2_interface_check(EFI_TCG2_VERSION *ret_version) {
EFI_STATUS err;
EFI_TCG2_PROTOCOL *tcg;
EFI_TCG2_PROTOCOL *tcg;
err = BS->LocateProtocol(MAKE_GUID_PTR(EFI_TCG2_PROTOCOL), NULL, (void **) &tcg);
if (err != EFI_SUCCESS)
return NULL;
EFI_TCG2_BOOT_SERVICE_CAPABILITY capability = {
.Size = sizeof(capability),
};
err = tcg->GetCapability(tcg, &capability);
if (err != EFI_SUCCESS)
return NULL;
if (capability.StructureVersion.Major == 1 &&
capability.StructureVersion.Minor == 0) {
EFI_TCG_BOOT_SERVICE_CAPABILITY *caps_1_0 =
(EFI_TCG_BOOT_SERVICE_CAPABILITY*) &capability;
if (caps_1_0->TPMPresentFlag)
return tcg;
}
assert(capability.Size >= endoffsetof_field(EFI_TCG2_BOOT_SERVICE_CAPABILITY, Size));
/* 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");
@@ -207,7 +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;
@@ -289,7 +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;

16
src/boot/proto/tcg.h
View File

@@ -10,27 +10,11 @@
#define EV_IPL 13
#define EV_EVENT_TAG UINT32_C(6)
typedef struct {
uint8_t Major;
uint8_t Minor;
uint8_t RevMajor;
uint8_t RevMinor;
} TCG_VERSION;
typedef struct {
uint8_t Major;
uint8_t Minor;
} EFI_TCG2_VERSION;
typedef struct {
uint8_t Size;
TCG_VERSION StructureVersion;
TCG_VERSION ProtocolSpecVersion;
uint8_t HashAlgorithmBitmap;
bool TPMPresentFlag;
bool TPMDeactivatedFlag;
} EFI_TCG_BOOT_SERVICE_CAPABILITY;
typedef struct {
uint8_t Size;
EFI_TCG2_VERSION StructureVersion;