boot: add new pcrphase tool to measure barrier strings into PCR 11
This commit is contained in:
Lennart Poettering
@@ -0,0 +1,262 @@
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/* SPDX-License-Identifier: LGPL-2.1-or-later */
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#include <getopt.h>
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#include <sd-messages.h>
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#include "efivars.h"
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#include "main-func.h"
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#include "openssl-util.h"
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#include "parse-util.h"
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#include "pretty-print.h"
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#include "tpm-pcr.h"
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#include "tpm2-util.h"
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static char *arg_tpm2_device = NULL;
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static char **arg_banks = NULL;
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STATIC_DESTRUCTOR_REGISTER(arg_banks, strv_freep);
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STATIC_DESTRUCTOR_REGISTER(arg_tpm2_device, freep);
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static int help(int argc, char *argv[], void *userdata) {
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_cleanup_free_ char *link = NULL;
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int r;
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r = terminal_urlify_man("systemd-pcrphase", "1", &link);
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if (r < 0)
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return log_oom();
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printf("%1$s [OPTIONS...] COMMAND ...\n"
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"\n%5$sMeasure boot phase into TPM2 PCR 11.%6$s\n"
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"\n%3$sOptions:%4$s\n"
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" -h --help Show this help\n"
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" --version Print version\n"
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" --bank=DIGEST Select TPM bank (SHA1, SHA256)\n"
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" --tpm2-device=PATH Use specified TPM2 device\n"
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"\nSee the %2$s for details.\n",
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program_invocation_short_name,
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link,
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ansi_underline(),
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ansi_normal(),
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ansi_highlight(),
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ansi_normal());
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return 0;
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}
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static int parse_argv(int argc, char *argv[]) {
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enum {
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ARG_VERSION = 0x100,
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ARG_BANK,
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ARG_TPM2_DEVICE,
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};
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static const struct option options[] = {
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{ "help", no_argument, NULL, 'h' },
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{ "version", no_argument, NULL, ARG_VERSION },
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{ "bank", required_argument, NULL, ARG_BANK },
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{ "tpm2-device", required_argument, NULL, ARG_TPM2_DEVICE },
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{}
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};
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int c;
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assert(argc >= 0);
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assert(argv);
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while ((c = getopt_long(argc, argv, "h", options, NULL)) >= 0)
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switch (c) {
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case 'h':
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help(0, NULL, NULL);
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return 0;
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case ARG_VERSION:
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return version();
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case ARG_BANK: {
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const EVP_MD *implementation;
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implementation = EVP_get_digestbyname(optarg);
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if (!implementation)
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return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Unknown bank '%s', refusing.", optarg);
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if (strv_extend(&arg_banks, EVP_MD_name(implementation)) < 0)
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return log_oom();
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break;
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}
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case ARG_TPM2_DEVICE: {
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_cleanup_free_ char *device = NULL;
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if (streq(optarg, "list"))
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return tpm2_list_devices();
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if (!streq(optarg, "auto")) {
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device = strdup(optarg);
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if (!device)
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return log_oom();
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}
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free_and_replace(arg_tpm2_device, device);
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break;
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}
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case '?':
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return -EINVAL;
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default:
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assert_not_reached();
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}
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return 1;
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}
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static int determine_banks(struct tpm2_context *c) {
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_cleanup_free_ TPMI_ALG_HASH *algs = NULL;
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int n_algs, r;
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assert(c);
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if (!strv_isempty(arg_banks)) /* Explicitly configured? Then use that */
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return 0;
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n_algs = tpm2_get_good_pcr_banks(c->esys_context, UINT32_C(1) << TPM_PCR_INDEX_KERNEL_IMAGE, &algs);
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if (n_algs <= 0)
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return n_algs;
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for (int i = 0; i < n_algs; i++) {
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const EVP_MD *implementation;
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const char *salg;
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salg = tpm2_pcr_bank_to_string(algs[i]);
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if (!salg)
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return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE), "TPM2 operates with unknown PCR algorithm, can't measure.");
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implementation = EVP_get_digestbyname(salg);
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if (!implementation)
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return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE), "TPM2 operates with unsupported PCR algorithm, can't measure.");
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r = strv_extend(&arg_banks, EVP_MD_name(implementation));
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if (r < 0)
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return log_oom();
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}
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return 0;
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}
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static int run(int argc, char *argv[]) {
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_cleanup_(tpm2_context_destroy) struct tpm2_context c = {};
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_cleanup_free_ char *joined = NULL, *pcr_string = NULL;
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const char *word;
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unsigned pcr_nr;
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size_t length;
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TSS2_RC rc;
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int r;
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log_setup();
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r = parse_argv(argc, argv);
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if (r <= 0)
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return r;
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if (optind+1 != argc)
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return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Expected a single argument.");
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word = argv[optind];
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/* Refuse to measure an empty word. We want to be able to write the series of measured words
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* separated by colons, where multiple separating colons are collapsed. Thus it makes sense to
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* disallow an empty word to avoid ambiguities. */
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if (isempty(word))
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return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "String to measure cannot be empty, refusing.");
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length = strlen(word);
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/* Skip logic if sd-stub is not used, after all PCR 11 might have a very different purpose then. */
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r = efi_get_variable_string(EFI_LOADER_VARIABLE(StubPcrKernelImage), &pcr_string);
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if (r == -ENOENT) {
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log_info("Kernel stub did not measure kernel image into PCR %u, skipping measurement.", TPM_PCR_INDEX_KERNEL_IMAGE);
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return EXIT_SUCCESS;
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}
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if (r < 0)
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return log_error_errno(r, "Failed to read StubPcrKernelImage EFI variable: %m");
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/* Let's validate that the stub announced PCR 11 as we expected. */
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r = safe_atou(pcr_string, &pcr_nr);
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if (r < 0)
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return log_error_errno(r, "Failed to parse StubPcrKernelImage EFI variable: %s", pcr_string);
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if (pcr_nr != TPM_PCR_INDEX_KERNEL_IMAGE)
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return log_error_errno(SYNTHETIC_ERRNO(EREMOTE), "Kernel stub measured kernel image into PCR %u, which is different than expected %u.", pcr_nr, TPM_PCR_INDEX_KERNEL_IMAGE);
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r = dlopen_tpm2();
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if (r < 0)
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return log_error_errno(r, "Failed to load TPM2 libraries: %m");
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r = tpm2_context_init(arg_tpm2_device, &c);
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if (r < 0)
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return r;
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r = determine_banks(&c);
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if (r < 0)
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return r;
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if (strv_isempty(arg_banks)) /* Still none? */
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return log_error_errno(SYNTHETIC_ERRNO(ENOENT), "Found a TPM2 without enabled PCR banks. Can't operate.");
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TPML_DIGEST_VALUES values = {};
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STRV_FOREACH(bank, arg_banks) {
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const EVP_MD *implementation;
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int id;
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assert_se(implementation = EVP_get_digestbyname(*bank));
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if (values.count >= ELEMENTSOF(values.digests))
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return log_error_errno(SYNTHETIC_ERRNO(E2BIG), "Too many banks selected.");
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if ((size_t) EVP_MD_size(implementation) > sizeof(values.digests[values.count].digest))
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return log_error_errno(SYNTHETIC_ERRNO(E2BIG), "Hash result too large for TPM2.");
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id = tpm2_pcr_bank_from_string(EVP_MD_name(implementation));
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if (id < 0)
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return log_error_errno(id, "Can't map hash name to TPM2.");
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values.digests[values.count].hashAlg = id;
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if (EVP_Digest(word, length, (unsigned char*) &values.digests[values.count].digest, NULL, implementation, NULL) != 1)
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return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE), "Failed to hash word.");
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values.count++;
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}
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joined = strv_join(arg_banks, ", ");
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if (!joined)
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return log_oom();
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log_debug("Measuring '%s' into PCR index %u, banks %s.", word, TPM_PCR_INDEX_KERNEL_IMAGE, joined);
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rc = sym_Esys_PCR_Extend(
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c.esys_context,
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ESYS_TR_PCR0 + TPM_PCR_INDEX_KERNEL_IMAGE, /* → PCR 11 */
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ESYS_TR_PASSWORD,
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ESYS_TR_NONE,
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ESYS_TR_NONE,
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&values);
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if (rc != TSS2_RC_SUCCESS)
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return log_error_errno(
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SYNTHETIC_ERRNO(ENOTRECOVERABLE),
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"Failed to measure '%s': %s",
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word,
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sym_Tss2_RC_Decode(rc));
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log_struct(LOG_INFO,
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"MESSAGE_ID=" SD_MESSAGE_TPM_PCR_EXTEND_STR,
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LOG_MESSAGE("Successfully extended PCR index %u with '%s' (banks %s).", TPM_PCR_INDEX_KERNEL_IMAGE, word, joined),
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"MEASURING=%s", word,
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"PCR=%u", TPM_PCR_INDEX_KERNEL_IMAGE,
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"BANKS=%s", joined);
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return EXIT_SUCCESS;
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}
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DEFINE_MAIN_FUNCTION(run);
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