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boot: measure loader.conf in PCR5

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Results in:

- EventNum: 26
  PCRIndex: 5
  EventType: EV_EVENT_TAG
  DigestCount: 4
  Digests:
  - AlgorithmId: sha1
    Digest: 155fb999ca61ba8c7b1f1d87cee821f772ef084a
  - AlgorithmId: sha256
    Digest: 4c26adf231603613afc00bb3d5cad046aec6a525ca01262417c7085caab452b5
  - AlgorithmId: sha384
    Digest: 3e0758cb6605ac274e55d747bf29ee3474fc4413cd5e7a451d1375219cd7f08a30fc915a8df7131657ca78b82b9ccec8
  - AlgorithmId: sha512
    Digest: e32d905b9092c543802f386db9a397d9b6593bdb8360fb747a6d23e491a09595fec8699184cc790d0873a3d52ed16d045538f0c73ece48278fae0fb6ed9b4ed6
  EventSize: 32
  Event: 2a58bcf5180000006c006f0061006400650072002e0063006f006e0066000000
This commit is contained in:
Luca Boccassi 2023-10-06 23:41:10 +01:00
parent 3e6f010e03
commit 12de4ed1ca
2 changed files with 29 additions and 5 deletions
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15
docs/TPM2_PCR_MEASUREMENTS.md
View file

@ -16,8 +16,8 @@ measurements listed below are (by default) only done if a system is booted with
to systemd's UEFI-mode measurements, and if the latter are not done the former
aren't made either.
systemd will measure to PCRs 11 (`kernel-boot`), 12 (`kernel-config`), 13
(`sysexts`), 15 (`system-identity`).
systemd will measure to PCRs 5 (`boot-loader-config`), 11 (`kernel-boot`),
12 (`kernel-config`), 13 (`sysexts`), 15 (`system-identity`).
Currently, four components will issue TPM2 PCR measurements:
@ -31,6 +31,17 @@ maintained in `/run/log/systemd/tpm2-measure.log`.
## PCR Measurements Made by `systemd-boot` (UEFI)
### PCS 5, `EV_EVENT_TAG`, "loader.conf"
The content of `systemd-boot`'s configuration file, `loader/loader.conf`, is
measured as a tagged event.
→ **Event Tag** `0xf5bc582a`
→ **Description** in the event log record is the file name, `loader.conf`.
→ **Measured hash** covers the content of `loader.conf` as it is read from the ESP.
### PCR 12, `EV_IPL`, "Kernel Command Line"
If the kernel command line was specified explicitly (by the user or in a Boot

19
src/boot/efi/boot.c
View file

@ -21,6 +21,7 @@
#include "secure-boot.h"
#include "shim.h"
#include "ticks.h"
#include "tpm2-pcr.h"
#include "util.h"
#include "version.h"
#include "vmm.h"
@ -38,6 +39,8 @@ DECLARE_NOALLOC_SECTION(
DECLARE_SBAT(SBAT_BOOT_SECTION_TEXT);
#define LOADER_CONF_CONTENT_EVENT_TAG_ID UINT32_C(0xf5bc582a)
typedef enum LoaderType {
LOADER_UNDEFINED,
LOADER_AUTO,
@ -1621,7 +1624,7 @@ static EFI_STATUS efivar_get_timeout(const char16_t *var, uint32_t *ret_value) {
static void config_load_defaults(Config *config, EFI_FILE *root_dir) {
_cleanup_free_ char *content = NULL;
size_t value = 0; /* avoid false maybe-uninitialized warning */
size_t content_size, value = 0; /* avoid false maybe-uninitialized warning */
EFI_STATUS err;
assert(root_dir);
@ -1638,9 +1641,19 @@ static void config_load_defaults(Config *config, EFI_FILE *root_dir) {
.timeout_sec_efivar = TIMEOUT_UNSET,
};
err = file_read(root_dir, u"\\loader\\loader.conf", 0, 0, &content, NULL);
if (err == EFI_SUCCESS)
err = file_read(root_dir, u"\\loader\\loader.conf", 0, 0, &content, &content_size);
if (err == EFI_SUCCESS) {
config_defaults_load_from_file(config, content);
err = tpm_log_tagged_event(
TPM2_PCR_BOOT_LOADER_CONFIG,
POINTER_TO_PHYSICAL_ADDRESS(content),
content_size,
LOADER_CONF_CONTENT_EVENT_TAG_ID,
u"loader.conf",
/* ret_measured= */ NULL);
if (err != EFI_SUCCESS)
log_error_status(err, "Error measuring loader.conf into TPM: %m");
}
err = efivar_get_timeout(u"LoaderConfigTimeout", &config->timeout_sec_efivar);
if (err == EFI_SUCCESS)