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efi_loader: Add check for event log passed from firmware

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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>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Tested-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
This commit is contained in:
Ruchika Gupta 2021-11-29 13:09:44 +05:30 committed by Heinrich Schuchardt
parent 3b7bf8a9e4
commit 34287efdaf
2 changed files with 402 additions and 69 deletions
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2
include/efi_loader.h
View file

@ -988,4 +988,6 @@ efi_status_t efi_esrt_register(void);
*/
efi_status_t efi_esrt_populate(void);
efi_status_t efi_load_capsule_drivers(void);
efi_status_t platform_get_eventlog(struct udevice *dev, u64 *addr, u32 *sz);
#endif /* _EFI_LOADER_H */

469
lib/efi_loader/efi_tcg2.c
View file

@ -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 +1220,280 @@ 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 start of the eventlog
* @size: Size of the eventlog
* @pos: Return offset of the next event in buffer right
* after the event header i.e specID
*
* Return: status code
*/
static 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])
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: [in] Offset of specID event in the eventlog buffer
* [out] Return offset of the next event in the buffer
* after the specID
* @digest_list: list of digests in the event
*
* Return: status code
* @pos Offset in the eventlog where the specID event ends
* @digest_list: list of digests in the event
*/
static 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;
u8 vendor_sz;
int err, i;
if (*pos >= log_size || (*pos + sizeof(*spec_event)) > log_size)
return EFI_COMPROMISED_DATA;
/* 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 have to take care that the sequence of algorithms that we record
* in digest_list matches the sequence in eventlog.
*/
for (i = 0; i < alg_count; i++) {
hash_alg =
get_unaligned_le16(&spec_event->digest_sizes[i].algorithm_id);
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 specification 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]);
if (*pos + spec_event_size >= log_size)
return EFI_COMPROMISED_DATA;
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;
}
/**
* tcg2_parse_event() - Parse the event in the eventlog
*
* @dev: udevice
* @buffer: Pointer to the start of the eventlog
* @log_size: Size of the eventlog
* @offset: [in] Offset of the event in the eventlog buffer
* [out] Return offset of the next event in the buffer
* @digest_list: list of digests in the event
* @pcr Index of the PCR in the event
*
* Return: status code
*/
static 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 count, size, event_size;
size_t pos;
event_size = tcg_event_final_size(digest_list);
if (*offset >= log_size || *offset + event_size > log_size) {
log_err("Event exceeds log size\n");
return EFI_COMPROMISED_DATA;
}
event = (struct tcg_pcr_event2 *)((uintptr_t)buffer + *offset);
*pcr = get_unaligned_le32(&event->pcr_index);
/* 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;
}
/**
* tcg2_get_fw_eventlog() - Get the eventlog address and size
*
* If the previous firmware has passed some eventlog, this function get it's
* location and check for it's validity.
*
* @dev: udevice
* @log_buffer: eventlog address
* @log_sz: eventlog size
*
* Return: status code
*/
static 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 *)(uintptr_t)base;
pos = 0;
/* Parse the eventlog to check for its validity */
ret = parse_event_log_header(buffer, sz, &pos);
if (ret)
return ret;
ret = parse_specid_event(dev, buffer, sz, &pos, &digest_list);
if (ret) {
log_err("Error parsing SPEC ID Event\n");
return ret;
}
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
*
@ -1312,69 +1625,6 @@ out:
return ret;
}
/**
* efi_init_event_log() - initialize an eventlog
*/
static efi_status_t efi_init_event_log(void)
{
/*
* vendor_info_size is currently set to 0, we need to change the length
* and allocate the flexible array member if this changes
*/
struct tcg_pcr_event *event_header = NULL;
struct udevice *dev;
size_t spec_event_size;
efi_status_t ret;
ret = platform_get_tpm2_device(&dev);
if (ret != EFI_SUCCESS)
goto out;
ret = efi_allocate_pool(EFI_BOOT_SERVICES_DATA, TPM2_EVENT_LOG_SIZE,
(void **)&event_log.buffer);
if (ret != EFI_SUCCESS)
goto out;
/*
* initialize log area as 0xff so the OS can easily figure out the
* last log entry
*/
memset(event_log.buffer, 0xff, TPM2_EVENT_LOG_SIZE);
event_log.pos = 0;
event_log.last_event_size = 0;
event_log.get_event_called = false;
event_log.ebs_called = false;
event_log.truncated = false;
/*
* 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;
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 = create_final_event();
if (ret != EFI_SUCCESS)
goto free_pool;
out:
return ret;
free_pool:
efi_free_pool(event_log.buffer);
event_log.buffer = NULL;
return ret;
}
/**
* tcg2_measure_event() - common function to add event log and extend PCR
*
@ -1427,6 +1677,93 @@ static efi_status_t efi_append_scrtm_version(struct udevice *dev)
return ret;
}
/**
* efi_init_event_log() - initialize an eventlog
*
* Return: status code
*/
static efi_status_t efi_init_event_log(void)
{
/*
* vendor_info_size is currently set to 0, we need to change the length
* and allocate the flexible array member if this changes
*/
struct tcg_pcr_event *event_header = NULL;
struct udevice *dev;
size_t spec_event_size;
efi_status_t ret;
ret = platform_get_tpm2_device(&dev);
if (ret != EFI_SUCCESS)
return ret;
ret = efi_allocate_pool(EFI_BOOT_SERVICES_DATA, TPM2_EVENT_LOG_SIZE,
(void **)&event_log.buffer);
if (ret != EFI_SUCCESS)
return ret;
/*
* initialize log area as 0xff so the OS can easily figure out the
* 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;
event_log.ebs_called = false;
event_log.truncated = false;
/*
* Check if earlier firmware have passed any eventlog. Different
* platforms can use different ways to do so.
*/
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;
ret = create_final_event();
if (ret != EFI_SUCCESS)
goto free_pool;
return ret;
free_pool:
efi_free_pool(event_log.buffer);
event_log.buffer = NULL;
return ret;
}
/**
* tcg2_measure_variable() - add variable event log and extend PCR
*
@ -1963,12 +2300,6 @@ 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) {