ima: add gid support

IMA currently supports the concept of rules based on uid where the rule
is based on the uid of the file owner or the uid of the user accessing
the file. Provide the ability to have similar rules based on gid.
Signed-off-by: Curtis Veit <veit@vpieng.com>
Co-developed-by: Alex Henrie <alexh@vpitech.com>
Signed-off-by: Alex Henrie <alexh@vpitech.com>
Reviewed-by: Petr Vorel <pvorel@suse.cz>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

Documentation/ABI/testing/ima_policy

@@ -22,8 +22,9 @@ Description:
 		  action: measure | dont_measure | appraise | dont_appraise |
 			  audit | hash | dont_hash
 		  condition:= base | lsm  [option]
-			base:	[[func=] [mask=] [fsmagic=] [fsuuid=] [uid=]
-				[euid=] [fowner=] [fsname=]]
+			base:	[[func=] [mask=] [fsmagic=] [fsuuid=] [fsname=]
+				[uid=] [euid=] [gid=] [egid=]
+				[fowner=] [fgroup=]]
 			lsm:	[[subj_user=] [subj_role=] [subj_type=]
 				 [obj_user=] [obj_role=] [obj_type=]]
 			option:	[[appraise_type=]] [template=] [permit_directio]
@@ -40,7 +41,10 @@ Description:
 			fsuuid:= file system UUID (e.g 8bcbe394-4f13-4144-be8e-5aa9ea2ce2f6)
 			uid:= decimal value
 			euid:= decimal value
+			gid:= decimal value
+			egid:= decimal value
 			fowner:= decimal value
+			fgroup:= decimal value
 		  lsm:  are LSM specific
 		  option:
 			appraise_type:= [imasig] [imasig|modsig]