[RFC,2/8] ima-evm-utils: increase the size of "zero" and "fox" variables

Commit Message

Mimi Zohar Feb. 21, 2020, 6:38 p.m. UTC

Opening a file for write when it is already opened for read, results in
a time of measure, time of use (ToMToU) error.  Similarly, when opening
a file for read, when it is already opened for write, results in a file
measurement error.  These violations are flagged by including 0x00's as
the template digest in the measurement list, but extending the TPM with
0xFF's.

In preparation of extending the TPM banks with bank specific digest
values, increase the "zero" and "fox" variable sizes.

Signed-off-by: Mimi Zohar <[e-mail]>
---
 src/evmctl.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

Patch

diff --git a/src/evmctl.c b/src/evmctl.c
index 704615694cec..9c8544a95b6a 100644
--- a/src/evmctl.c
+++ b/src/evmctl.c
@@ -1477,8 +1477,8 @@  struct template_entry {
 	int template_buf_len;
 };
 
-static uint8_t zero[SHA_DIGEST_LENGTH];
-static uint8_t fox[SHA_DIGEST_LENGTH];
+static uint8_t zero[MAX_DIGEST_SIZE];
+static uint8_t fox[MAX_DIGEST_SIZE];
 
 int validate = 1;
 
@@ -1499,7 +1499,7 @@  static int ima_verify_template_hash(struct template_entry *entry)
 {
 	uint8_t digest[SHA_DIGEST_LENGTH];
 
-	if (!memcmp(zero, entry->header.digest, sizeof(zero)))
+	if (!memcmp(zero, entry->header.digest, sizeof(digest)))
 		return 0;
 
 	SHA1(entry->template, entry->template_len, digest);
@@ -1658,8 +1658,8 @@  static int ima_measurement(const char *file)
 	int i;
 
 	errno = 0;
-	memset(zero, 0, SHA_DIGEST_LENGTH);
-	memset(fox, 0xff, SHA_DIGEST_LENGTH);
+	memset(zero, 0, MAX_DIGEST_SIZE);
+	memset(fox, 0xff, MAX_DIGEST_SIZE);
 
 	log_debug("Initial PCR value: ");
 	log_debug_dump(pcr, sizeof(pcr));