[v2][PATCH 1/3] efi_loader: Add check for event log passed from firmware
Masahisa Kojima
masahisa.kojima at linaro.org
Wed Nov 24 08:38:24 CET 2021
Hi Ruchika, Ilias,
On Tue, 23 Nov 2021 at 20:53, Ruchika Gupta <ruchika.gupta at linaro.org> wrote:
>
> 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.
It implies that U-Boot is no longer s-crtm, so existing
efi_append_scrtm_version()
call shall be skipped in this case.
Thanks,
Masahisa Kojima
>
> Signed-off-by: Ruchika Gupta <ruchika.gupta at linaro.org>
> ---
> v2:
> Moved firmware eventlog code parsing to tcg2_get_fw_eventlog()
>
> lib/efi_loader/efi_tcg2.c | 322 ++++++++++++++++++++++++++++++++++++--
> 1 file changed, 308 insertions(+), 14 deletions(-)
>
> diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c
> index 8c1f22e337..c3ebdf92f5 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 +1220,249 @@ 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;
> + efi_status_t ret;
> + u32 pcr, pos;
> + u64 base;
> + u32 sz;
> +
> + ret = platform_get_eventlog(dev, &base, &sz);
> + if (ret == EFI_SUCCESS) {
> + void *buffer = (void *)base;
> +
> + if (sz > TPM2_EVENT_LOG_SIZE)
> + return EFI_VOLUME_FULL;
> +
> + 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 +1622,12 @@ 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;
> @@ -1347,22 +1635,28 @@ 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);
> - 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 = tcg2_get_fw_eventlog(dev, event_log.buffer, &event_log.pos);
> + 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;
> + }
> +
> + if (ret == EFI_SUCCESS)
> + ret = create_final_event();
>
> - ret = create_final_event();
> if (ret != EFI_SUCCESS)
> goto free_pool;
>
> --
> 2.25.1
>
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