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.h b/security/integrity/ima/ima.h
index 72d013e..bf03c6a 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -59,7 +59,8 @@
 	const char field_id[IMA_TEMPLATE_FIELD_ID_MAX_LEN];
 	int (*field_init) (struct integrity_iint_cache *iint, struct file *file,
 			   const unsigned char *filename,
-			   struct ima_field_data *field_data);
+			   struct evm_ima_xattr_data *xattr_value,
+			   int xattr_len, struct ima_field_data *field_data);
 	void (*field_show) (struct seq_file *m, enum ima_show_type show,
 			    struct ima_field_data *field_data);
 };
@@ -134,12 +135,15 @@
 			    struct evm_ima_xattr_data **xattr_value,
 			    int *xattr_len);
 void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file,
-			   const unsigned char *filename);
+			   const unsigned char *filename,
+			   struct evm_ima_xattr_data *xattr_value,
+			   int xattr_len);
 void ima_audit_measurement(struct integrity_iint_cache *iint,
 			   const unsigned char *filename);
 int ima_alloc_init_template(struct integrity_iint_cache *iint,
 			    struct file *file, const unsigned char *filename,
-			    struct ima_template_entry **entry);
+			    struct evm_ima_xattr_data *xattr_value,
+			    int xattr_len, struct ima_template_entry **entry);
 int ima_store_template(struct ima_template_entry *entry, int violation,
 		       struct inode *inode, const unsigned char *filename);
 const char *ima_d_path(struct path *path, char **pathbuf);