ima: extend the measurement list to include the file signature

This patch defines a new template called 'ima-sig', which includes
the file signature in the template data, in addition to the file's
digest and pathname.

A template is composed of a set of fields.  Associated with each
field is an initialization and display function.  This patch defines
a new template field called 'sig', the initialization function
ima_eventsig_init(), and the display function ima_show_template_sig().

This patch modifies the .field_init() function definition to include
the 'security.ima' extended attribute and length.

Changelog:
- remove unused code (Dmitry Kasatkin)
- avoid calling ima_write_template_field_data() unnecesarily (Roberto Sassu)
- rename DATA_FMT_SIG to DATA_FMT_HEX
- cleanup ima_eventsig_init() based on Roberto's comments

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
Signed-off-by: Roberto Sassu <roberto.sassu@polito.it>
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 14d4cb5..149ee11 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -225,7 +225,8 @@
 		pathname = (const char *)file->f_dentry->d_name.name;
 
 	if (action & IMA_MEASURE)
-		ima_store_measurement(iint, file, pathname);
+		ima_store_measurement(iint, file, pathname,
+				      xattr_value, xattr_len);
 	if (action & IMA_APPRAISE_SUBMASK)
 		rc = ima_appraise_measurement(_func, iint, file, pathname,
 					      xattr_value, xattr_len);