Platforms may have support to measure their initial firmware components and pass the event log to u-boot. The event log address can be passed in property tpm_event_log_addr and tpm_event_log_size of the tpm node. Platforms may choose their own specific mechanism to do so. A weak function is added to check if even log has been passed to u-boot from earlier firmware components. If available, the eventlog is parsed to check for its correctness and further event logs are appended to the passed log.
Signed-off-by: Ruchika Gupta ruchika.gupta@linaro.org --- v4: Add SCRTM version to log only if previous firmware doesn;t pass the eventlog
v3: Return as soon as you detect error
v2: Moved firmware eventlog code parsing to tcg2_get_fw_eventlog() lib/efi_loader/efi_tcg2.c | 334 ++++++++++++++++++++++++++++++++++++-- 1 file changed, 317 insertions(+), 17 deletions(-)
diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c index 8c1f22e337..1713cfff70 100644 --- a/lib/efi_loader/efi_tcg2.c +++ b/lib/efi_loader/efi_tcg2.c @@ -324,6 +324,45 @@ __weak efi_status_t platform_get_tpm2_device(struct udevice **dev) return EFI_NOT_FOUND; }
+/** + * platform_get_eventlog() - retrieve the eventlog address and size + * + * This function retrieves the eventlog address and size if the underlying + * firmware has done some measurements and passed them. + * + * This function may be overridden based on platform specific method of + * passing the eventlog address and size. + * + * @dev: udevice + * @addr: eventlog address + * @sz: eventlog size + * Return: status code + */ +__weak efi_status_t platform_get_eventlog(struct udevice *dev, u64 *addr, + u32 *sz) +{ + const u64 *basep; + const u32 *sizep; + + basep = dev_read_prop(dev, "tpm_event_log_addr", NULL); + if (!basep) + return EFI_NOT_FOUND; + + *addr = be64_to_cpup((__force __be64 *)basep); + + sizep = dev_read_prop(dev, "tpm_event_log_size", NULL); + if (!sizep) + return EFI_NOT_FOUND; + + *sz = be32_to_cpup((__force __be32 *)sizep); + if (*sz == 0) { + log_debug("event log empty\n"); + return EFI_NOT_FOUND; + } + + return EFI_SUCCESS; +} + /** * tpm2_get_max_command_size() - get the supported max command size * @@ -1181,6 +1220,250 @@ static const struct efi_tcg2_protocol efi_tcg2_protocol = { .get_result_of_set_active_pcr_banks = efi_tcg2_get_result_of_set_active_pcr_banks, };
+/** + * parse_event_log_header() - Parse and verify the event log header fields + * + * @buffer: Pointer to the event header + * @size: Size of the eventlog + * @pos: Position in buffer after event log header + * + * Return: status code + */ +efi_status_t parse_event_log_header(void *buffer, u32 size, u32 *pos) +{ + struct tcg_pcr_event *event_header = (struct tcg_pcr_event *)buffer; + int i = 0; + + if (size < sizeof(*event_header)) + return EFI_COMPROMISED_DATA; + + if (get_unaligned_le32(&event_header->pcr_index) != 0 || + get_unaligned_le32(&event_header->event_type) != EV_NO_ACTION) + return EFI_COMPROMISED_DATA; + + for (i = 0; i < sizeof(event_header->digest); i++) { + if (event_header->digest[i] != 0) + return EFI_COMPROMISED_DATA; + } + + *pos += sizeof(*event_header); + + return EFI_SUCCESS; +} + +/** + * parse_specid_event() - Parse and verify the specID Event in the eventlog + * + * @dev: udevice + * @buffer: Pointer to the start of the eventlog + * @log_size: Size of the eventlog + * @pos: Offset in the evenlog where specID event starts + * + * Return: status code + * @pos Offset in the eventlog where the specID event ends + * @digest_list: list of digests in the event + */ +efi_status_t parse_specid_event(struct udevice *dev, void *buffer, u32 log_size, + u32 *pos, + struct tpml_digest_values *digest_list) +{ + struct tcg_efi_spec_id_event *spec_event; + struct tcg_pcr_event *event_header = (struct tcg_pcr_event *)buffer; + size_t spec_event_size; + u32 active = 0, supported = 0, pcr_count = 0, alg_count = 0; + u32 spec_active = 0; + u16 hash_alg, hash_sz; + u8 vendor_sz; + int err, i; + + /* Check specID event data */ + spec_event = (struct tcg_efi_spec_id_event *)((uintptr_t)buffer + *pos); + /* Check for signature */ + if (memcmp(spec_event->signature, TCG_EFI_SPEC_ID_EVENT_SIGNATURE_03, + sizeof(TCG_EFI_SPEC_ID_EVENT_SIGNATURE_03))) { + log_err("specID Event: Signature mismatch\n"); + return EFI_COMPROMISED_DATA; + } + + if (spec_event->spec_version_minor != + TCG_EFI_SPEC_ID_EVENT_SPEC_VERSION_MINOR_TPM2 || + spec_event->spec_version_major != + TCG_EFI_SPEC_ID_EVENT_SPEC_VERSION_MAJOR_TPM2) + return EFI_COMPROMISED_DATA; + + if (spec_event->number_of_algorithms > MAX_HASH_COUNT || + spec_event->number_of_algorithms < 1) { + log_err("specID Event: Number of algorithms incorrect\n"); + return EFI_COMPROMISED_DATA; + } + + alg_count = spec_event->number_of_algorithms; + + err = tpm2_get_pcr_info(dev, &supported, &active, &pcr_count); + if (err) + return EFI_DEVICE_ERROR; + + digest_list->count = 0; + /* + * We may need to worry about the order of algs in this structure as + * subsequent entries in event should be in same order + */ + for (i = 0; i < alg_count; i++) { + hash_alg = + get_unaligned_le16(&spec_event->digest_sizes[i].algorithm_id); + hash_sz = + get_unaligned_le16(&spec_event->digest_sizes[i].digest_size); + + if (!(supported & alg_to_mask(hash_alg))) { + log_err("specID Event: Unsupported algorithm\n"); + return EFI_COMPROMISED_DATA; + } + digest_list->digests[digest_list->count++].hash_alg = hash_alg; + + spec_active |= alg_to_mask(hash_alg); + } + + /* TCG spec expects the event log to have hashes for all active PCR's */ + if (spec_active != active) { + /* + * Previous stage bootloader should know all the active PCR's + * and use them in the Eventlog. + */ + log_err("specID Event: All active hash alg not present\n"); + return EFI_COMPROMISED_DATA; + } + + /* + * the size of the spec event and placement of vendor_info_size + * depends on supported algoriths + */ + spec_event_size = + offsetof(struct tcg_efi_spec_id_event, digest_sizes) + + alg_count * sizeof(spec_event->digest_sizes[0]); + + vendor_sz = *(uint8_t *)((uintptr_t)buffer + *pos + spec_event_size); + + spec_event_size += sizeof(vendor_sz) + vendor_sz; + *pos += spec_event_size; + + if (get_unaligned_le32(&event_header->event_size) != spec_event_size) { + log_err("specID event: header event size mismatch\n"); + /* Right way to handle this can be to call SetActive PCR's */ + return EFI_COMPROMISED_DATA; + } + + return EFI_SUCCESS; +} + +efi_status_t tcg2_parse_event(struct udevice *dev, void *buffer, u32 log_size, + u32 *offset, struct tpml_digest_values *digest_list, + u32 *pcr) +{ + struct tcg_pcr_event2 *event = NULL; + u32 event_type, count, size, event_size; + size_t pos; + + if (*offset > log_size) + return EFI_COMPROMISED_DATA; + + event = (struct tcg_pcr_event2 *)((uintptr_t)buffer + *offset); + + *pcr = get_unaligned_le32(&event->pcr_index); + + event_size = tcg_event_final_size(digest_list); + + if (*offset + event_size > log_size) { + log_err("Event exceeds log size\n"); + return EFI_COMPROMISED_DATA; + } + + event_type = get_unaligned_le32(&event->event_type); + + /* get the count */ + count = get_unaligned_le32(&event->digests.count); + if (count != digest_list->count) + return EFI_COMPROMISED_DATA; + + pos = offsetof(struct tcg_pcr_event2, digests); + pos += offsetof(struct tpml_digest_values, digests); + + for (int i = 0; i < digest_list->count; i++) { + u16 alg; + u16 hash_alg = digest_list->digests[i].hash_alg; + u8 *digest = (u8 *)&digest_list->digests[i].digest; + + alg = get_unaligned_le16((void *)((uintptr_t)event + pos)); + + if (alg != hash_alg) + return EFI_COMPROMISED_DATA; + + pos += offsetof(struct tpmt_ha, digest); + memcpy(digest, (void *)((uintptr_t)event + pos), alg_to_len(hash_alg)); + pos += alg_to_len(hash_alg); + } + + size = get_unaligned_le32((void *)((uintptr_t)event + pos)); + event_size += size; + pos += sizeof(u32); /* tcg_pcr_event2 event_size*/ + pos += size; + + /* make sure the calculated buffer is what we checked against */ + if (pos != event_size) + return EFI_COMPROMISED_DATA; + + if (pos > log_size) + return EFI_COMPROMISED_DATA; + + *offset += pos; + + return EFI_SUCCESS; +} + +efi_status_t tcg2_get_fw_eventlog(struct udevice *dev, void *log_buffer, + size_t *log_sz) +{ + struct tpml_digest_values digest_list; + void *buffer; + efi_status_t ret; + u32 pcr, pos; + u64 base; + u32 sz; + + ret = platform_get_eventlog(dev, &base, &sz); + if (ret != EFI_SUCCESS) + return ret; + + if (sz > TPM2_EVENT_LOG_SIZE) + return EFI_VOLUME_FULL; + + buffer = (void *)base; + pos = 0; + /* Parse the eventlog to check for its validity */ + ret = parse_event_log_header(buffer, sz, &pos); + if (ret || pos > sz) + return EFI_COMPROMISED_DATA; + + ret = parse_specid_event(dev, buffer, sz, &pos, &digest_list); + if (ret || pos > sz) { + log_err("Error parsing SPEC ID Event\n"); + return EFI_COMPROMISED_DATA; + } + + while (pos < sz) { + ret = tcg2_parse_event(dev, buffer, sz, &pos, &digest_list, + &pcr); + if (ret) { + log_err("Error parsing event\n"); + return ret; + } + } + + memcpy(log_buffer, buffer, sz); + *log_sz = sz; + + return ret; +} + /** * create_specid_event() - Create the first event in the eventlog * @@ -1340,6 +1623,12 @@ static efi_status_t efi_init_event_log(void) * last log entry */ memset(event_log.buffer, 0xff, TPM2_EVENT_LOG_SIZE); + + /* + * The log header is defined to be in SHA1 event log entry format. + * Setup event header + */ + event_header = (struct tcg_pcr_event *)event_log.buffer; event_log.pos = 0; event_log.last_event_size = 0; event_log.get_event_called = false; @@ -1347,20 +1636,37 @@ static efi_status_t efi_init_event_log(void) event_log.truncated = false;
/* - * The log header is defined to be in SHA1 event log entry format. - * Setup event header + * Check if earlier firmware have passed any eventlog. Different + * platforms can use different ways to do so */ - event_header = (struct tcg_pcr_event *)event_log.buffer; - put_unaligned_le32(0, &event_header->pcr_index); - put_unaligned_le32(EV_NO_ACTION, &event_header->event_type); - memset(&event_header->digest, 0, sizeof(event_header->digest)); - ret = create_specid_event(dev, (void *)((uintptr_t)event_log.buffer + sizeof(*event_header)), - &spec_event_size); + ret = tcg2_get_fw_eventlog(dev, event_log.buffer, &event_log.pos); + /* + * If earlier firmware hasn't passed any eventlog, go ahead and + * create the eventlog header + */ + if (ret == EFI_NOT_FOUND) { + put_unaligned_le32(0, &event_header->pcr_index); + put_unaligned_le32(EV_NO_ACTION, &event_header->event_type); + memset(&event_header->digest, 0, sizeof(event_header->digest)); + ret = create_specid_event(dev, + (void *)((uintptr_t)event_log.buffer + + sizeof(*event_header)), + &spec_event_size); + if (ret != EFI_SUCCESS) + goto free_pool; + put_unaligned_le32(spec_event_size, &event_header->event_size); + event_log.pos = spec_event_size + sizeof(*event_header); + event_log.last_event_size = event_log.pos; + + /* + * Add SCRTM version to the log if previous firmmware + * doesn't pass an eventlog + */ + ret = efi_append_scrtm_version(dev); + } + if (ret != EFI_SUCCESS) goto free_pool; - put_unaligned_le32(spec_event_size, &event_header->event_size); - event_log.pos = spec_event_size + sizeof(*event_header); - event_log.last_event_size = event_log.pos;
ret = create_final_event(); if (ret != EFI_SUCCESS) @@ -1963,12 +2269,6 @@ efi_status_t efi_tcg2_register(void) if (ret != EFI_SUCCESS) goto fail;
- ret = efi_append_scrtm_version(dev); - if (ret != EFI_SUCCESS) { - tcg2_uninit(); - goto fail; - } - ret = efi_add_protocol(efi_root, &efi_guid_tcg2_protocol, (void *)&efi_tcg2_protocol); if (ret != EFI_SUCCESS) {