[PATCH 2/7] ima: use ima_parse_buf() to parse measurements headers

Roberto Sassu
2017-05-16T12:59:19Z

The binary_hdr_v1 and binary_data_v1 structures defined in
ima_restore_measurement_list() have been replaced with an array of four
ima_field_data structures where pcr, digest, template name and
template data lengths and pointers are stored.

The length of pcr and digest in the ima_field_data array and the bits
in the bitmap are set before ima_parse_buf() is called. The ENFORCE_FIELDS
bit is set for all entries except the last one (there is still data to
parse), and ENFORCE_BUFEND is set only for the last entry.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
security/integrity/ima/ima_template.c | 80 ++++++++++++-----------------------
1 file changed, 28 insertions(+), 52 deletions(-)

diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
index cebb37c..624e2a1 100644
--- a/security/integrity/ima/ima_template.c
+++ b/security/integrity/ima/ima_template.c
@@ -19,6 +19,9 @@
#include "ima.h"
#include "ima_template_lib.h"

+enum header_fields { HDR_PCR, HDR_DIGEST, HDR_TEMPLATE_NAME,
+ HDR_TEMPLATE_DATA, HDR__LAST };
+
static struct ima_template_desc builtin_templates[] = {
{.name = IMA_TEMPLATE_IMA_NAME, .fmt = IMA_TEMPLATE_IMA_FMT},
{.name = "ima-ng", .fmt = "d-ng|n-ng"},
@@ -337,27 +340,19 @@ static int ima_restore_template_data(struct ima_template_desc *template_desc,
/* Restore the serialized binary measurement list without extending PCRs. */
int ima_restore_measurement_list(loff_t size, void *buf)
{
- struct binary_hdr_v1 {
- u32 pcr;
- u8 digest[TPM_DIGEST_SIZE];
- u32 template_name_len;
- char template_name[0];
- } __packed;
char template_name[MAX_TEMPLATE_NAME_LEN];

- struct binary_data_v1 {
- u32 template_data_size;
- char template_data[0];
- } __packed;
-
struct ima_kexec_hdr *khdr = buf;
- struct binary_hdr_v1 *hdr_v1;
- struct binary_data_v1 *data_v1;
+ struct ima_field_data hdr[HDR__LAST] = {
+ [HDR_PCR] = {.len = sizeof(u32)},
+ [HDR_DIGEST] = {.len = TPM_DIGEST_SIZE},
+ };

void *bufp = buf + sizeof(*khdr);
void *bufendp;
struct ima_template_entry *entry;
struct ima_template_desc *template_desc;
+ DECLARE_BITMAP(hdr_mask, HDR__LAST);
unsigned long count = 0;
int ret = 0;

@@ -380,6 +375,10 @@ int ima_restore_measurement_list(loff_t size, void *buf)
return -EINVAL;
}

+ bitmap_zero(hdr_mask, HDR__LAST);
+ bitmap_set(hdr_mask, HDR_PCR, 1);
+ bitmap_set(hdr_mask, HDR_DIGEST, 1);
+
/*
* ima kexec buffer prefix: version, buffer size, count
* v1 format: pcr, digest, template-name-len, template-name,
@@ -387,31 +386,25 @@ int ima_restore_measurement_list(loff_t size, void *buf)
*/
bufendp = buf + khdr->buffer_size;
while ((bufp < bufendp) && (count++ < khdr->count)) {
- hdr_v1 = bufp;
- if (bufp > (bufendp - sizeof(*hdr_v1))) {
- pr_err("attempting to restore partial measurement\n");
- ret = -EINVAL;
- break;
- }
- bufp += sizeof(*hdr_v1);
+ int enforce_mask = ENFORCE_FIELDS;

- if (ima_canonical_fmt)
- hdr_v1->template_name_len =
- le32_to_cpu(hdr_v1->template_name_len);
+ enforce_mask |= (count == khdr->count) ? ENFORCE_BUFEND : 0;
+ ret = ima_parse_buf(bufp, bufendp, &bufp, HDR__LAST, hdr, NULL,
+ hdr_mask, enforce_mask, "entry header");
+ if (ret < 0)
+ break;

- if ((hdr_v1->template_name_len >= MAX_TEMPLATE_NAME_LEN) ||
- (bufp > (bufendp - hdr_v1->template_name_len))) {
+ if (hdr[HDR_TEMPLATE_NAME].len >= MAX_TEMPLATE_NAME_LEN) {
pr_err("attempting to restore a template name \
that is too long\n");
ret = -EINVAL;
break;
}
- data_v1 = bufp += (u_int8_t)hdr_v1->template_name_len;

/* template name is not null terminated */
- memcpy(template_name, hdr_v1->template_name,
- hdr_v1->template_name_len);
- template_name[hdr_v1->template_name_len] = 0;
+ memcpy(template_name, hdr[HDR_TEMPLATE_NAME].data,
+ hdr[HDR_TEMPLATE_NAME].len);
+ template_name[hdr[HDR_TEMPLATE_NAME].len] = 0;

if (strcmp(template_name, "ima") == 0) {
pr_err("attempting to restore an unsupported \
@@ -441,34 +434,17 @@ int ima_restore_measurement_list(loff_t size, void *buf)
break;
}

- if (bufp > (bufendp - sizeof(data_v1->template_data_size))) {
- pr_err("restoring the template data size failed\n");
- ret = -EINVAL;
- break;
- }
- bufp += (u_int8_t) sizeof(data_v1->template_data_size);
-
- if (ima_canonical_fmt)
- data_v1->template_data_size =
- le32_to_cpu(data_v1->template_data_size);
-
- if (bufp > (bufendp - data_v1->template_data_size)) {
- pr_err("restoring the template data failed\n");
- ret = -EINVAL;
- break;
- }
- bufp += data_v1->template_data_size;
-
ret = ima_restore_template_data(template_desc,
- data_v1->template_data,
- data_v1->template_data_size,
+ hdr[HDR_TEMPLATE_DATA].data,
+ hdr[HDR_TEMPLATE_DATA].len,
&entry);
if (ret < 0)
break;

- memcpy(entry->digest, hdr_v1->digest, TPM_DIGEST_SIZE);
- entry->pcr =
- !ima_canonical_fmt ? hdr_v1->pcr : le32_to_cpu(hdr_v1->pcr);
+ memcpy(entry->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);
if (ret < 0)
break;
--
2.9.3