ima: add audit log support for larger hashes

Different files might be signed based on different hash algorithms.
This patch prefixes the audit log measurement hash with the hash
algorithm.

Changelog:
- use generic HASH_ALGO defintions
- use ':' as delimiter between the hash algorithm and the digest
  (Roberto Sassu)
- always include the hash algorithm used when audit-logging a measurement
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: Roberto Sassu <roberto.sassu@polito.it>
Signed-off-by: Peter Moody <pmoody@google.com>

security/integrity/ima/ima_api.c

@@ -270,6 +270,8 @@ void ima_audit_measurement(struct integrity_iint_cache *iint,
 {
 	struct audit_buffer *ab;
 	char hash[(iint->ima_hash->length * 2) + 1];
+	const char *algo_name = hash_algo_name[iint->ima_hash->algo];
+	char algo_hash[sizeof(hash) + strlen(algo_name) + 2];
 	int i;
 
 	if (iint->flags & IMA_AUDITED)
@@ -287,7 +289,8 @@ void ima_audit_measurement(struct integrity_iint_cache *iint,
 	audit_log_format(ab, "file=");
 	audit_log_untrustedstring(ab, filename);
 	audit_log_format(ab, " hash=");
-	audit_log_untrustedstring(ab, hash);
+	snprintf(algo_hash, sizeof(algo_hash), "%s:%s", algo_name, hash);
+	audit_log_untrustedstring(ab, algo_hash);
 
 	audit_log_task_info(ab, current);
 	audit_log_end(ab);