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Merge pull request #33461 from poettering/boot-measured-flag-rework

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stub: rework how we combine the "measured" flags in sd-stub
This commit is contained in:
Lennart Poettering 2024-06-25 09:48:38 +02:00 committed by GitHub
commit 953bddee2f
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GPG Key ID: B5690EEEBB952194
2 changed files with 43 additions and 28 deletions
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7
src/boot/efi/measure.c
View File

@ -240,7 +240,6 @@ EFI_STATUS tpm_log_ipl_event(uint32_t pcrindex, EFI_PHYSICAL_ADDRESS buffer, siz
return err;
err = tcg2_log_ipl_event(pcrindex, buffer, buffer_size, description, &tpm_ret_measured);
if (err == EFI_SUCCESS && ret_measured)
*ret_measured = tpm_ret_measured || cc_ret_measured;
@ -289,7 +288,6 @@ EFI_STATUS tpm_log_ipl_event_ascii(uint32_t pcrindex, EFI_PHYSICAL_ADDRESS buffe
}
EFI_STATUS tpm_log_load_options(const char16_t *load_options, bool *ret_measured) {
bool measured = false;
EFI_STATUS err;
/* Measures a load options string into the TPM2, i.e. the kernel command line */
@ -299,16 +297,13 @@ EFI_STATUS tpm_log_load_options(const char16_t *load_options, bool *ret_measured
POINTER_TO_PHYSICAL_ADDRESS(load_options),
strsize16(load_options),
load_options,
&measured);
ret_measured);
if (err != EFI_SUCCESS)
return log_error_status(
err,
"Unable to add load options (i.e. kernel command) line measurement to PCR %i: %m",
TPM2_PCR_KERNEL_CONFIG);
if (ret_measured)
*ret_measured = measured;
return EFI_SUCCESS;
}

64
src/boot/efi/stub.c
View File

@ -26,6 +26,25 @@ DECLARE_NOALLOC_SECTION(".sdmagic", "#### LoaderInfo: systemd-stub " GIT_VERSION
DECLARE_SBAT(SBAT_STUB_SECTION_TEXT);
static void combine_measured_flag(int *value, int measured) {
assert(value);
/* Combine the "measured" flag in a sensible way: if we haven't measured anything yet, the first
* write is taken as is. Later writes can only turn off the flag, never on again. Or in other words,
* we eventually want to return true iff we really measured *everything* there was to measure.
*
* Reminder how the "measured" flag actually works:
* > 0 → something was measured
* == 0 → there was something to measure but we didn't (because no TPM or so)
* < 0 → nothing has been submitted for measurement so far
*/
if (measured < 0)
return;
*value = *value < 0 ? measured : *value && measured;
}
/* Combine initrds by concatenation in memory */
static EFI_STATUS combine_initrds(
const void * const initrds[], const size_t initrd_sizes[], size_t n_initrds,
@ -286,7 +305,7 @@ static void dtb_install_addons(
size_t *dt_sizes,
char16_t **dt_filenames,
size_t n_dts,
bool *ret_parameters_measured) {
int *ret_parameters_measured) {
int parameters_measured = -1;
EFI_STATUS err;
@ -316,7 +335,7 @@ static void dtb_install_addons(
i,
TPM2_PCR_KERNEL_CONFIG);
parameters_measured = parameters_measured < 0 ? m : (parameters_measured && m);
combine_measured_flag(&parameters_measured, m);
}
}
@ -502,9 +521,9 @@ static EFI_STATUS run(EFI_HANDLE image) {
EFI_LOADED_IMAGE_PROTOCOL *loaded_image;
size_t addrs[_UNIFIED_SECTION_MAX] = {}, szs[_UNIFIED_SECTION_MAX] = {};
_cleanup_free_ char16_t *cmdline = NULL, *cmdline_addons_global = NULL, *cmdline_addons_uki = NULL;
int sections_measured = -1, parameters_measured = -1;
int sections_measured = -1, parameters_measured = -1, sysext_measured = -1, confext_measured = -1;
_cleanup_free_ char *uname = NULL;
bool sysext_measured = false, confext_measured = false, m;
bool m;
uint64_t loader_features = 0;
EFI_STATUS err;
@ -581,19 +600,18 @@ static EFI_STATUS run(EFI_HANDLE image) {
if (szs[section] == 0) /* not found */
continue;
m = false;
/* First measure the name of the section */
m = false;
(void) tpm_log_ipl_event_ascii(
TPM2_PCR_KERNEL_BOOT,
POINTER_TO_PHYSICAL_ADDRESS(unified_sections[section]),
strsize8(unified_sections[section]), /* including NUL byte */
unified_sections[section],
&m);
sections_measured = sections_measured < 0 ? m : (sections_measured && m);
combine_measured_flag(&sections_measured, m);
/* Then measure the data of the section */
m = false;
(void) tpm_log_ipl_event_ascii(
TPM2_PCR_KERNEL_BOOT,
POINTER_TO_PHYSICAL_ADDRESS(loaded_image->ImageBase) + addrs[section],
@ -601,7 +619,7 @@ static EFI_STATUS run(EFI_HANDLE image) {
unified_sections[section],
&m);
sections_measured = sections_measured < 0 ? m : (sections_measured && m);
combine_measured_flag(&sections_measured, m);
}
/* After we are done, set an EFI variable that tells userspace this was done successfully, and encode
@ -619,7 +637,7 @@ static EFI_STATUS run(EFI_HANDLE image) {
* any boot menu, let's measure things anyway. */
m = false;
(void) tpm_log_load_options(cmdline, &m);
parameters_measured = m;
combine_measured_flag(&parameters_measured, m);
} else if (szs[UNIFIED_SECTION_CMDLINE] > 0) {
cmdline = xstrn8_to_16(
(char *) loaded_image->ImageBase + addrs[UNIFIED_SECTION_CMDLINE],
@ -632,7 +650,7 @@ static EFI_STATUS run(EFI_HANDLE image) {
* so that the order is reversed from "most hardcoded" to "most dynamic". The global addons are
* loaded first, and the image-specific ones later, for the same reason. */
cmdline_append_and_measure_addons(cmdline_addons_global, cmdline_addons_uki, &cmdline, &m);
parameters_measured = parameters_measured < 0 ? m : (parameters_measured && m);
combine_measured_flag(&parameters_measured, m);
/* SMBIOS OEM Strings data is controlled by the host admin and not covered
* by the VM attestation, so MUST NOT be trusted when in a confidential VM */
@ -647,7 +665,7 @@ static EFI_STATUS run(EFI_HANDLE image) {
* measurements that are not under control of the machine owner. */
m = false;
(void) tpm_log_load_options(extra16, &m);
parameters_measured = parameters_measured < 0 ? m : (parameters_measured && m);
combine_measured_flag(&parameters_measured, m);
}
}
@ -665,7 +683,7 @@ static EFI_STATUS run(EFI_HANDLE image) {
&credential_initrd,
&credential_initrd_size,
&m) == EFI_SUCCESS)
parameters_measured = parameters_measured < 0 ? m : (parameters_measured && m);
combine_measured_flag(&parameters_measured, m);
if (pack_cpio(loaded_image,
u"\\loader\\credentials",
@ -679,7 +697,7 @@ static EFI_STATUS run(EFI_HANDLE image) {
&global_credential_initrd,
&global_credential_initrd_size,
&m) == EFI_SUCCESS)
parameters_measured = parameters_measured < 0 ? m : (parameters_measured && m);
combine_measured_flag(&parameters_measured, m);
if (pack_cpio(loaded_image,
/* dropin_dir= */ NULL,
@ -693,7 +711,7 @@ static EFI_STATUS run(EFI_HANDLE image) {
&sysext_initrd,
&sysext_initrd_size,
&m) == EFI_SUCCESS)
sysext_measured = m;
combine_measured_flag(&sysext_measured, m);
if (pack_cpio(loaded_image,
/* dropin_dir= */ NULL,
@ -707,7 +725,7 @@ static EFI_STATUS run(EFI_HANDLE image) {
&confext_initrd,
&confext_initrd_size,
&m) == EFI_SUCCESS)
confext_measured = m;
combine_measured_flag(&confext_measured, m);
dt_size = szs[UNIFIED_SECTION_DTB];
dt_base = dt_size != 0 ? POINTER_TO_PHYSICAL_ADDRESS(loaded_image->ImageBase) + addrs[UNIFIED_SECTION_DTB] : 0;
@ -720,26 +738,28 @@ static EFI_STATUS run(EFI_HANDLE image) {
log_error_status(err, "Error loading embedded devicetree: %m");
}
int dtb_measured;
dtb_install_addons(&dt_state,
dt_bases_addons_global,
dt_sizes_addons_global,
dt_filenames_addons_global,
n_dts_addons_global,
&m);
parameters_measured = parameters_measured < 0 ? m : (parameters_measured && m);
&dtb_measured);
combine_measured_flag(&parameters_measured, dtb_measured);
dtb_install_addons(&dt_state,
dt_bases_addons_uki,
dt_sizes_addons_uki,
dt_filenames_addons_uki,
n_dts_addons_uki,
&m);
parameters_measured = parameters_measured < 0 ? m : (parameters_measured && m);
&dtb_measured);
combine_measured_flag(&parameters_measured, dtb_measured);
if (parameters_measured > 0)
(void) efivar_set_uint_string(MAKE_GUID_PTR(LOADER), u"StubPcrKernelParameters", TPM2_PCR_KERNEL_CONFIG, 0);
if (sysext_measured)
if (sysext_measured > 0)
(void) efivar_set_uint_string(MAKE_GUID_PTR(LOADER), u"StubPcrInitRDSysExts", TPM2_PCR_SYSEXTS, 0);
if (confext_measured)
if (confext_measured > 0)
(void) efivar_set_uint_string(MAKE_GUID_PTR(LOADER), u"StubPcrInitRDConfExts", TPM2_PCR_KERNEL_CONFIG, 0);
/* If the PCR signature was embedded in the PE image, then let's wrap it in a cpio and also pass it