ima: add support for different security.ima data types

IMA-appraisal currently verifies the integrity of a file based on a
known 'good' measurement value.  This patch reserves the first byte
of 'security.ima' as a place holder for the type of method used for
verifying file data integrity.

Changelog v1:
- Use the newly defined 'struct evm_ima_xattr_data'

Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@nokia.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index 41cce84..33d4685 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -147,8 +147,8 @@
 	if (!(iint->flags & IMA_COLLECTED)) {
 		u64 i_version = file->f_dentry->d_inode->i_version;
 
-		memset(iint->digest, 0, IMA_DIGEST_SIZE);
-		result = ima_calc_hash(file, iint->digest);
+		iint->ima_xattr.type = IMA_XATTR_DIGEST;
+		result = ima_calc_hash(file, iint->ima_xattr.digest);
 		if (!result) {
 			iint->version = i_version;
 			iint->flags |= IMA_COLLECTED;
@@ -196,7 +196,7 @@
 		return;
 	}
 	memset(&entry->template, 0, sizeof(entry->template));
-	memcpy(entry->template.digest, iint->digest, IMA_DIGEST_SIZE);
+	memcpy(entry->template.digest, iint->ima_xattr.digest, IMA_DIGEST_SIZE);
 	strcpy(entry->template.file_name,
 	       (strlen(filename) > IMA_EVENT_NAME_LEN_MAX) ?
 	       file->f_dentry->d_name.name : filename);