ima: Switch to dynamically allocated buffer for template digests

This patch dynamically allocates the array of tpm_digest structures in
ima_alloc_init_template() and ima_restore_template_data(). The size of the
array is equal to the number of PCR banks plus ima_extra_slots, to make
room for SHA1 and the IMA default hash algorithm, when PCR banks with those
algorithms are not allocated.

Calculating the SHA1 digest is mandatory, as SHA1 still remains the default
hash algorithm for the measurement list. When IMA will support the Crypto
Agile format, remaining digests will be also provided.

The position in the measurement entry array of the SHA1 digest is stored in
the ima_sha1_idx global variable and is determined at IMA initialization
time.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

1 files changed, 13 insertions, 2 deletions

diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
index 062d9ad49afb..de84252e65e9 100644
--- a/security/integrity/ima/ima_template.c
+++ b/security/integrity/ima/ima_template.c
@@ -301,6 +301,7 @@ static int ima_restore_template_data(struct ima_template_desc *template_desc,
 				     int template_data_size,
 				     struct ima_template_entry **entry)
 {
+	struct tpm_digest *digests;
 	int ret = 0;
 	int i;
 
@@ -309,11 +310,21 @@ static int ima_restore_template_data(struct ima_template_desc *template_desc,
 	if (!*entry)
 		return -ENOMEM;
 
+	digests = kcalloc(NR_BANKS(ima_tpm_chip) + ima_extra_slots,
+			  sizeof(*digests), GFP_NOFS);
+	if (!digests) {
+		kfree(*entry);
+		return -ENOMEM;
+	}
+
+	(*entry)->digests = digests;
+
 	ret = ima_parse_buf(template_data, template_data + template_data_size,
 			    NULL, template_desc->num_fields,
 			    (*entry)->template_data, NULL, NULL,
 			    ENFORCE_FIELDS | ENFORCE_BUFEND, "template data");
 	if (ret < 0) {
+		kfree((*entry)->digests);
 		kfree(*entry);
 		return ret;
 	}
@@ -445,8 +456,8 @@ int ima_restore_measurement_list(loff_t size, void *buf)
 		if (ret < 0)
 			break;
 
-		memcpy(entry->digest, hdr[HDR_DIGEST].data,
-		       hdr[HDR_DIGEST].len);
+		memcpy(entry->digests[ima_sha1_idx].digest,
+		       hdr[HDR_DIGEST].data, hdr[HDR_DIGEST].len);
 		entry->pcr = !ima_canonical_fmt ? *(hdr[HDR_PCR].data) :
 			     le32_to_cpu(*(hdr[HDR_PCR].data));
 		ret = ima_restore_measurement_entry(entry);