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tpm2-util: add helper that checks for the various facets of TPM2 support

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So far we were a bit sloppy regarding checks for TPM2 support. Let's
make things more precise and introduce a single helper that checks for
three axis of TPM2 support: whether we have a loaded kernel driver,
whether the firmware used it, and whether we ourselves are compiled for
it.

This only adds the helper. Follow-up patches will use it at various
places.
This commit is contained in:
Lennart Poettering 2022-04-19 14:42:27 +02:00
parent 47a9f91760
commit ba57855628
2 changed files with 33 additions and 0 deletions
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23
src/shared/tpm2-util.c
View File

@ -1,7 +1,9 @@
/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include "efi-api.h"
#include "extract-word.h"
#include "parse-util.h"
#include "stat-util.h"
#include "tpm2-util.h"
#if HAVE_TPM2
@ -1453,3 +1455,24 @@ int tpm2_primary_alg_from_string(const char *alg) {
return TPM2_ALG_RSA;
return -EINVAL;
}
Tpm2Support tpm2_support(void) {
Tpm2Support support = TPM2_SUPPORT_NONE;
int r;
r = dir_is_empty("/sys/class/tpmrm");
if (r < 0) {
if (r != -ENOENT)
log_debug_errno(r, "Unable to test whether /sys/class/tpmrm/ exists and is populated, assuming it is not: %m");
} else if (r == 0) /* populated! */
support |= TPM2_SUPPORT_DRIVER;
if (efi_has_tpm2())
support |= TPM2_SUPPORT_FIRMWARE;
#if HAVE_TPM2
support |= TPM2_SUPPORT_SYSTEM;
#endif
return support;
}

10
src/shared/tpm2-util.h
View File

@ -89,3 +89,13 @@ typedef struct {
uint32_t search_pcr_mask;
const char *device;
} systemd_tpm2_plugin_params;
typedef enum Tpm2Support {
TPM2_SUPPORT_NONE = 0, /* no support */
TPM2_SUPPORT_FIRMWARE = 1 << 0, /* firmware reports TPM2 was used */
TPM2_SUPPORT_DRIVER = 1 << 1, /* the kernel has a driver loaded for it */
TPM2_SUPPORT_SYSTEM = 1 << 2, /* we support it ourselves */
TPM2_SUPPORT_FULL = TPM2_SUPPORT_FIRMWARE|TPM2_SUPPORT_DRIVER|TPM2_SUPPORT_SYSTEM,
} Tpm2Support;
Tpm2Support tpm2_support(void);