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sd-boot: Remove unnecessary call to GetEventLog

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This PR reverts #4302 and part of #7568, as the call to GetEventLog
isn't necessary to get the logs from the OS runtime.

This has already been reverted in shim, see:
    fd7c3bd920

The reasoning for the change that added this is wrong, explained below:

> According to TCG EFI Protocol Specification for TPM 2.0 family,
> all events generated after the invocation of EFI_TCG2_GET_EVENT_LOG
> shall be stored in an instance of an EFI_CONFIGURATION_TABLE aka
> EFI TCG 2.0 final events table.

This is correct and a valid reading of the TCG spec.

> Hence, it is necessary to trigger the internal switch through calling
> get_event_log() in order to allow to retrieve the logs from OS runtime.

However, this reasoning is incorrect. The "EFI TCG 2.0 final events
table" exists to allow the OS Runtime to get TCG events created during
or after the call to ExitBootServices. If systemd-boot didn't call
trigger_tcg2_final_events_table(), the call to HashLogExtendEvent will
write the event to the normal events table (i.e. the same place the
PCR 0 - 7 related events are written). Then the OS can obtain these
systemd-boot events in the same way it obtains normal events, via a
call to GetEventLog().

Tested on amd64 w/ TPM2 using the newest Linux kernel patches that
get the TPM2 formatted log:
    https://www.lkml.org/lkml/2019/5/20/1590
I confirmed that this change still lets the OS runtime obtain the log
entries created by systemd-boot.

Signed-off-by: Joe Richey <joerichey@google.com>
This commit is contained in:
Joe Richey 2019-05-31 11:24:20 -07:00 committed by Zbigniew Jędrzejewski-Szmek
parent 741c73c076
commit f8e54bf319
1 changed files with 11 additions and 54 deletions
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65
src/boot/efi/measure.c
View file

@ -108,9 +108,6 @@ typedef UINT32 EFI_TCG2_EVENT_LOG_BITMAP;
typedef UINT32 EFI_TCG2_EVENT_LOG_FORMAT;
typedef UINT32 EFI_TCG2_EVENT_ALGORITHM_BITMAP;
#define EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2 0x00000001
#define EFI_TCG2_EVENT_LOG_FORMAT_TCG_2 0x00000002
typedef struct tdEFI_TCG2_BOOT_SERVICE_CAPABILITY {
UINT8 Size;
EFI_TCG2_VERSION StructureVersion;
@ -209,37 +206,11 @@ static EFI_STATUS tpm1_measure_to_pcr_and_event_log(const EFI_TCG *tcg, UINT32 p
return EFI_SUCCESS;
}
/*
* According to TCG EFI Protocol Specification for TPM 2.0 family,
* all events generated after the invocation of EFI_TCG2_GET_EVENT_LOG
* shall be stored in an instance of an EFI_CONFIGURATION_TABLE aka
* EFI TCG 2.0 final events table. Hence, it is necessary to trigger the
* internal switch through calling get_event_log() in order to allow
* to retrieve the logs from OS runtime.
*/
static EFI_STATUS trigger_tcg2_final_events_table(const EFI_TCG2 *tcg, EFI_TCG2_EVENT_LOG_FORMAT log_fmt)
{
EFI_PHYSICAL_ADDRESS loc;
EFI_PHYSICAL_ADDRESS last_loc;
BOOLEAN truncated;
return uefi_call_wrapper(tcg->GetEventLog, 5, (EFI_TCG2 *) tcg,
log_fmt, &loc, &last_loc, &truncated);
}
static EFI_STATUS tpm2_measure_to_pcr_and_event_log(const EFI_TCG2 *tcg, UINT32 pcrindex, const EFI_PHYSICAL_ADDRESS buffer,
UINT64 buffer_size, const CHAR16 *description, EFI_TCG2_EVENT_LOG_FORMAT log_fmt) {
UINT64 buffer_size, const CHAR16 *description) {
EFI_STATUS status;
EFI_TCG2_EVENT *tcg_event;
UINTN desc_len;
static BOOLEAN triggered = FALSE;
if (triggered == FALSE) {
status = trigger_tcg2_final_events_table(tcg, log_fmt);
if (EFI_ERROR(status))
return status;
triggered = TRUE;
}
desc_len = StrLen(description) * sizeof(CHAR16);
@ -295,31 +266,32 @@ static EFI_TCG * tcg1_interface_check(void) {
return tcg;
}
static EFI_TCG2 * tcg2_interface_check(EFI_TCG2_BOOT_SERVICE_CAPABILITY *caps) {
static EFI_TCG2 * tcg2_interface_check() {
EFI_GUID tpm2_guid = EFI_TCG2_PROTOCOL_GUID;
EFI_STATUS status;
EFI_TCG2 *tcg;
EFI_TCG2_BOOT_SERVICE_CAPABILITY capability;
status = LibLocateProtocol(&tpm2_guid, (void **) &tcg);
if (EFI_ERROR(status))
return NULL;
caps->Size = (UINT8) sizeof(EFI_TCG2_BOOT_SERVICE_CAPABILITY);
status = uefi_call_wrapper(tcg->GetCapability, 2, tcg, caps);
capability.Size = (UINT8) sizeof(EFI_TCG2_BOOT_SERVICE_CAPABILITY);
status = uefi_call_wrapper(tcg->GetCapability, 2, tcg, &capability);
if (EFI_ERROR(status))
return NULL;
if (caps->StructureVersion.Major == 1 &&
caps->StructureVersion.Minor == 0) {
if (capability.StructureVersion.Major == 1 &&
capability.StructureVersion.Minor == 0) {
TCG_BOOT_SERVICE_CAPABILITY *caps_1_0;
caps_1_0 = (TCG_BOOT_SERVICE_CAPABILITY *)caps;
caps_1_0 = (TCG_BOOT_SERVICE_CAPABILITY *)&capability;
if (caps_1_0->TPMPresentFlag)
return tcg;
}
if (!caps->TPMPresentFlag)
if (!capability.TPMPresentFlag)
return NULL;
return tcg;
@ -328,25 +300,10 @@ static EFI_TCG2 * tcg2_interface_check(EFI_TCG2_BOOT_SERVICE_CAPABILITY *caps) {
EFI_STATUS tpm_log_event(UINT32 pcrindex, const EFI_PHYSICAL_ADDRESS buffer, UINTN buffer_size, const CHAR16 *description) {
EFI_TCG *tpm1;
EFI_TCG2 *tpm2;
EFI_TCG2_BOOT_SERVICE_CAPABILITY caps;
tpm2 = tcg2_interface_check(&caps);
tpm2 = tcg2_interface_check();
if (tpm2) {
EFI_TCG2_EVENT_LOG_BITMAP supported_logs;
EFI_TCG2_EVENT_LOG_FORMAT log_fmt;
if (caps.StructureVersion.Major == 1 &&
caps.StructureVersion.Minor == 0)
supported_logs = ((TREE_BOOT_SERVICE_CAPABILITY *)&caps)->SupportedEventLogs;
else
supported_logs = caps.SupportedEventLogs;
if (supported_logs & EFI_TCG2_EVENT_LOG_FORMAT_TCG_2)
log_fmt = EFI_TCG2_EVENT_LOG_FORMAT_TCG_2;
else
log_fmt = EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2;
return tpm2_measure_to_pcr_and_event_log(tpm2, pcrindex, buffer, buffer_size, description, log_fmt);
return tpm2_measure_to_pcr_and_event_log(tpm2, pcrindex, buffer, buffer_size, description);
}
tpm1 = tcg1_interface_check();