--- a/include/grub/tpm.h +++ b/include/grub/tpm.h @@ -36,6 +36,12 @@ #define EV_IPL 0x0d +struct grub_tpm_digest { + const char * algorithm; + unsigned int size; + unsigned char value[1]; /* variable length */ +}; + grub_err_t grub_tpm_measure (unsigned char *buf, grub_size_t size, grub_uint8_t pcr, const char *description); int grub_tpm_present (void); @@ -45,5 +51,7 @@ { return grub_env_get_bool ("tpm_fail_fatal", false); } +struct grub_tpm_digest *grub_tpm_read_pcr (grub_uint8_t index, const char *algo); +void grub_tpm_digest_free (struct grub_tpm_digest *d); #endif --- a/grub-core/commands/efi/tpm.c +++ b/grub-core/commands/efi/tpm.c @@ -24,6 +24,7 @@ #include #include #include +#include #include #include #include @@ -186,6 +187,91 @@ return grub_efi_log_event_status (status); } +static void +grub_tpm2_select_pcr(TPML_PCR_SELECTION *o, unsigned int pcrIndex, unsigned int algo) +{ + TPMS_PCR_SELECTION *pcr; + + pcr = &o->pcrSelections[o->count++]; + pcr->hash = algo; + pcr->sizeOfSelect = 3; + pcr->pcrSelect[TPM2_PCR_TO_SELECT(pcrIndex)] |= TPM2_PCR_TO_BIT(pcrIndex); +} + +struct grub_tpm_hash_info { + const char *name; + grub_size_t size; + int id; +}; + +static const struct grub_tpm_hash_info * +grub_tpm2_get_digest_info (const char *algo) +{ + static struct grub_tpm_hash_info __hashes[] = { + { "sha256", 32, TPM_ALG_SHA256 }, /* first entry is the default */ + { "sha512", 64, TPM_ALG_SHA512 }, + { "sha1", 20, TPM_ALG_SHA1 }, + { NULL } + }; + struct grub_tpm_hash_info *h; + + if (algo == NULL) + return &__hashes[0]; + + for (h = __hashes; h->name; ++h) + if (!grub_strcmp(h->name, algo)) + return h; + + return NULL; +} + +static grub_err_t +grub_tpm2_read_pcr (grub_int8_t pcrIndex, const char *algo, struct grub_tpm_digest **ret) +{ + const struct grub_tpm_hash_info *info; + TPML_PCR_SELECTION inSelection, outSelection; + grub_uint32_t pcrUpdateCounter; + TPML_DIGEST digests = { 0 }; + TPM2B_DIGEST *d; + struct grub_tpm_digest *result; + int rc; + + info = grub_tpm2_get_digest_info (algo); + if (info == NULL) + return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("Unknown digest algorithm %s"), algo); + + grub_memset(&inSelection, 0, sizeof(inSelection)); + grub_memset(&outSelection, 0, sizeof(outSelection)); + grub_tpm2_select_pcr(&inSelection, pcrIndex, info->id); + + rc = TPM2_PCR_Read( + NULL, + &inSelection, + &pcrUpdateCounter, + &outSelection, + &digests, + NULL + ); + + if (rc != 0) + return grub_error (GRUB_ERR_BAD_DEVICE, "TPM2_PCR_Read failed, status=%d", rc); + + d = &digests.digests[0]; + + *ret = result = grub_malloc (sizeof (*result) + d->size); + grub_memcpy (result->value, d->buffer, d->size); + result->algorithm = info->name; + result->size = d->size; + + return GRUB_ERR_NONE; +} + +void +grub_tpm_digest_free (struct grub_tpm_digest *d) +{ + grub_free (d); +} + static grub_err_t grub_tpm2_log_event (grub_efi_handle_t tpm_handle, unsigned char *buf, grub_size_t size, grub_uint8_t pcr, @@ -323,3 +409,26 @@ return grub_tpm2_present (tpm); } } + +struct grub_tpm_digest * +grub_tpm_read_pcr (grub_uint8_t pcr, const char *algo) +{ + grub_efi_handle_t tpm_handle; + grub_efi_uint8_t protocol_version; + struct grub_tpm_digest *result = NULL; + + + if (!grub_tpm_handle_find (&tpm_handle, &protocol_version)) + return 0; + + if (protocol_version != 2) + { + grub_error (GRUB_ERR_BAD_DEVICE, N_("%s: TPM version %d not implemented"), __func__, protocol_version); + return NULL; + } + + if (grub_tpm2_read_pcr (pcr, algo, &result)) + return NULL; + + return result; +} --- a/include/grub/tpm2/tpm2.h +++ b/include/grub/tpm2/tpm2.h @@ -23,6 +23,10 @@ #include #include +/* Defined in: TCG TPM Specification, v1.59, Part 2, Section 10.6.1. */ +#define TPM2_PCR_TO_SELECT(x) ((x) / 8) +#define TPM2_PCR_TO_BIT(x) (1 << ((x) % 8)) + /* Well-Known Windows SRK handle */ #define TPM2_SRK_HANDLE 0x81000001