[PATCH v8 1/3] efi_loader: Add check for event log passed from firmware

[PATCH v8 1/3] efi_loader: Add check for event log passed from firmware

[Ruchika Gupta]

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>
---
v8:
Addressed issues reported by cppcheck and warning on 32 bit builds

v7:
Addressed Heinrich's comments
Changed functions not exported out of this file as static.
Corrected function decsriptions and added few.
Added declaration of weak function in header file
Moved offset check to parse functions

v6: No change

v5:
Shift the efi_init_event_log() to a different location in the file.
This help fixes compilation issue introduced by calling efi_append_scrtm_version()
from it.

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()

 include/efi_loader.h      |   2 +
 lib/efi_loader/efi_tcg2.c | 469 ++++++++++++++++++++++++++++++++------
 2 files changed, 402 insertions(+), 69 deletions(-)

diff --git a/include/efi_loader.h b/include/efi_loader.h
index d52e399841..67c40ca57a 100644
--- a/include/efi_loader.h
+++ b/include/efi_loader.h
@@ -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 */
diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c
index 8c1f22e337..ce3e599c83 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 +1220,280 @@ 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) {
-- 
2.25.1

[PATCH v8 2/3] tpm: use more algorithms than sha256 on pcr_read

[Ruchika Gupta]

The current tpm2_pcr_read is hardcoded using SHA256. Make the
actual command to TPM configurable to use wider range of algorithms.
The current command line is kept as is i.e limited to SHA-256 only.

Signed-off-by: Ruchika Gupta <ruchika.gupta@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
---
v8: No change

v7: No change

v6: No change

v5: No change

v4: No change

v3: No change

v2:
Change algorithm from u32 to u16
Add parameter description in function declaration

 cmd/tpm-v2.c     |  3 ++-
 include/tpm-v2.h |  5 ++++-
 lib/tpm-v2.c     | 12 ++++++++----
 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/cmd/tpm-v2.c b/cmd/tpm-v2.c
index daae91100a..4ea5f9f094 100644
--- a/cmd/tpm-v2.c
+++ b/cmd/tpm-v2.c
@@ -151,7 +151,8 @@ static int do_tpm_pcr_read(struct cmd_tbl *cmdtp, int flag, int argc,
 
 	data = map_sysmem(simple_strtoul(argv[2], NULL, 0), 0);
 
-	rc = tpm2_pcr_read(dev, index, priv->pcr_select_min, data, &updates);
+	rc = tpm2_pcr_read(dev, index, priv->pcr_select_min, TPM2_ALG_SHA256,
+			   data, TPM2_DIGEST_LEN, &updates);
 	if (!rc) {
 		printf("PCR #%u content (%u known updates):\n", index, updates);
 		print_byte_string(data, TPM2_DIGEST_LEN);
diff --git a/include/tpm-v2.h b/include/tpm-v2.h
index ceff7d245e..4e9dd52cb6 100644
--- a/include/tpm-v2.h
+++ b/include/tpm-v2.h
@@ -512,13 +512,16 @@ u32 tpm2_nv_write_value(struct udevice *dev, u32 index, const void *data,
  * @dev		TPM device
  * @idx		Index of the PCR
  * @idx_min_sz	Minimum size in bytes of the pcrSelect array
+ * @algorithm	Algorithm used, defined in 'enum tpm2_algorithms'
  * @data	Output buffer for contents of the named PCR
+ * @digest_len  len of the data
  * @updates	Optional out parameter: number of updates for this PCR
  *
  * @return code of the operation
  */
 u32 tpm2_pcr_read(struct udevice *dev, u32 idx, unsigned int idx_min_sz,
-		  void *data, unsigned int *updates);
+		  u16 algorithm, void *data, u32 digest_len,
+		  unsigned int *updates);
 
 /**
  * Issue a TPM2_GetCapability command.  This implementation is limited
diff --git a/lib/tpm-v2.c b/lib/tpm-v2.c
index 2e7b27bd6b..1bf627853a 100644
--- a/lib/tpm-v2.c
+++ b/lib/tpm-v2.c
@@ -254,7 +254,8 @@ u32 tpm2_nv_write_value(struct udevice *dev, u32 index, const void *data,
 }
 
 u32 tpm2_pcr_read(struct udevice *dev, u32 idx, unsigned int idx_min_sz,
-		  void *data, unsigned int *updates)
+		  u16 algorithm, void *data, u32 digest_len,
+		  unsigned int *updates)
 {
 	u8 idx_array_sz = max(idx_min_sz, DIV_ROUND_UP(idx, 8));
 	u8 command_v2[COMMAND_BUFFER_SIZE] = {
@@ -264,7 +265,7 @@ u32 tpm2_pcr_read(struct udevice *dev, u32 idx, unsigned int idx_min_sz,
 
 		/* TPML_PCR_SELECTION */
 		tpm_u32(1),			/* Number of selections */
-		tpm_u16(TPM2_ALG_SHA256),	/* Algorithm of the hash */
+		tpm_u16(algorithm),		/* Algorithm of the hash */
 		idx_array_sz,			/* Array size for selection */
 		/* bitmap(idx)			   Selected PCR bitmap */
 	};
@@ -283,10 +284,13 @@ u32 tpm2_pcr_read(struct udevice *dev, u32 idx, unsigned int idx_min_sz,
 	if (ret)
 		return ret;
 
+	if (digest_len > response_len)
+		return TPM_LIB_ERROR;
+
 	if (unpack_byte_string(response, response_len, "ds",
 			       10, &counter,
-			       response_len - TPM2_DIGEST_LEN, data,
-			       TPM2_DIGEST_LEN))
+			       response_len - digest_len, data,
+			       digest_len))
 		return TPM_LIB_ERROR;
 
 	if (updates)
-- 
2.25.1

[PATCH v8 3/3] efi_loader: Extend PCR's for firmware measurements

[Ruchika Gupta]

Firmwares before U-Boot may be capable of doing tpm measurements
and passing them to U-Boot in the form of eventlog. However there
may be scenarios where the firmwares don't have TPM driver and
are not capable of extending the measurements in the PCRs.
Based on TCG spec, if previous firnware has extended PCR's, PCR0
would not be 0. So, read the PCR0 to determine if the PCR's need
to be extended as eventlog is parsed or not.

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>
---
v8:
Addressed issues reported by cppcheck

v7:
Addressed Heinrick's comments - Added missing parameter in function header

v6: Changed TPM2_DIGEST_LEN to TPM2_SHA512_DIGEST_SIZE

v5 : No change

v4 : No change

v3 : 
Rebase changes on top of changes made in first patch series

v2 : 
Removed check for PCR0 in eventlog

 lib/efi_loader/efi_tcg2.c | 76 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)

diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c
index ce3e599c83..7d0ee8e1f1 100644
--- a/lib/efi_loader/efi_tcg2.c
+++ b/lib/efi_loader/efi_tcg2.c
@@ -199,6 +199,44 @@ static efi_status_t tcg2_pcr_extend(struct udevice *dev, u32 pcr_index,
 	return EFI_SUCCESS;
 }
 
+/* tcg2_pcr_read - Read PCRs for a TPM2 device for a given tpml_digest_values
+ *
+ * @dev:		device
+ * @pcr_index:		PCR index
+ * @digest_list:	list of digest algorithms to extend
+ *
+ * @Return: status code
+ */
+static efi_status_t tcg2_pcr_read(struct udevice *dev, u32 pcr_index,
+				  struct tpml_digest_values *digest_list)
+{
+	struct tpm_chip_priv *priv;
+	unsigned int updates, pcr_select_min;
+	u32 rc;
+	size_t i;
+
+	priv = dev_get_uclass_priv(dev);
+	if (!priv)
+		return EFI_DEVICE_ERROR;
+
+	pcr_select_min = priv->pcr_select_min;
+
+	for (i = 0; i < digest_list->count; i++) {
+		u16 hash_alg = digest_list->digests[i].hash_alg;
+		u8 *digest = (u8 *)&digest_list->digests[i].digest;
+
+		rc = tpm2_pcr_read(dev, pcr_index, pcr_select_min,
+				   hash_alg, digest, alg_to_len(hash_alg),
+				   &updates);
+		if (rc) {
+			EFI_PRINT("Failed to read PCR\n");
+			return EFI_DEVICE_ERROR;
+		}
+	}
+
+	return EFI_SUCCESS;
+}
+
 /* put_event - Append an agile event to an eventlog
  *
  * @pcr_index:		PCR index
@@ -1458,6 +1496,8 @@ static efi_status_t tcg2_get_fw_eventlog(struct udevice *dev, void *log_buffer,
 	u32 pcr, pos;
 	u64 base;
 	u32 sz;
+	bool extend_pcr = false;
+	int i;
 
 	ret = platform_get_eventlog(dev, &base, &sz);
 	if (ret != EFI_SUCCESS)
@@ -1479,6 +1519,26 @@ static efi_status_t tcg2_get_fw_eventlog(struct udevice *dev, void *log_buffer,
 		return ret;
 	}
 
+	ret = tcg2_pcr_read(dev, 0, &digest_list);
+	if (ret) {
+		log_err("Error reading PCR 0\n");
+		return ret;
+	}
+
+	/*
+	 * If PCR0 is 0, previous firmware didn't have the capability
+	 * to extend the PCR. In this scenario, extend the PCR as
+	 * the eventlog is parsed.
+	 */
+	for (i = 0; i < digest_list.count; i++) {
+		u8 hash_buf[TPM2_SHA512_DIGEST_SIZE] =  { 0 };
+		u16 hash_alg = digest_list.digests[i].hash_alg;
+
+		if (!memcmp((u8 *)&digest_list.digests[i].digest, hash_buf,
+			    alg_to_len(hash_alg)))
+			extend_pcr = true;
+	}
+
 	while (pos < sz) {
 		ret = tcg2_parse_event(dev, buffer, sz, &pos, &digest_list,
 				       &pcr);
@@ -1486,6 +1546,22 @@ static efi_status_t tcg2_get_fw_eventlog(struct udevice *dev, void *log_buffer,
 			log_err("Error parsing event\n");
 			return ret;
 		}
+		if (extend_pcr) {
+			ret = tcg2_pcr_extend(dev, pcr, &digest_list);
+			if (ret != EFI_SUCCESS) {
+				log_err("Error in extending PCR\n");
+				return ret;
+			}
+
+			/* Clear the digest for next event */
+			for (i = 0; i < digest_list.count; i++) {
+				u16 hash_alg = digest_list.digests[i].hash_alg;
+				u8 *digest =
+				   (u8 *)&digest_list.digests[i].digest;
+
+				memset(digest, 0, alg_to_len(hash_alg));
+			}
+		}
 	}
 
 	memcpy(log_buffer, buffer, sz);
-- 
2.25.1