[Linux-ima-user] [PATCH 1/2] ima: add support for new "euid" policy condition

[Mimi Z. <zo...@li...>]

The new "euid" policy condition measures files with the specified
effective uid (euid).  In addition, for CAP_SETUID files it measures
files with the specified uid or suid.

Signed-off-by: Mimi Zohar <zo...@li...>
---
 Documentation/ABI/testing/ima_policy |  3 ++-
 security/integrity/ima/ima_policy.c  | 21 +++++++++++++++++++--
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
index 8ae3f57..4a571fa 100644
--- a/Documentation/ABI/testing/ima_policy
+++ b/Documentation/ABI/testing/ima_policy
@@ -20,7 +20,7 @@ Description:
 		action: measure | dont_measure | appraise | dont_appraise | audit
 		condition:= base | lsm  [option]
 			base:	[[func=] [mask=] [fsmagic=] [fsuuid=] [uid=]
-				 [fowner]]
+				[euid=] [fowner=]]
 			lsm:	[[subj_user=] [subj_role=] [subj_type=]
 				 [obj_user=] [obj_role=] [obj_type=]]
 			option:	[[appraise_type=]] [permit_directio]
@@ -31,6 +31,7 @@ Description:
 			fsmagic:= hex value
 			fsuuid:= file system UUID (e.g 8bcbe394-4f13-4144-be8e-5aa9ea2ce2f6)
 			uid:= decimal value
+			euid:= decimal value
 			fowner:=decimal value
 		lsm:  	are LSM specific
 		option:	appraise_type:= [imasig]
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index b4f9021..fcefa5c 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -27,6 +27,7 @@
 #define IMA_UID		0x0008
 #define IMA_FOWNER	0x0010
 #define IMA_FSUUID	0x0020
+#define IMA_EUID	0x0080
 
 #define UNKNOWN		0
 #define MEASURE		0x0001	/* same as IMA_MEASURE */
@@ -193,6 +194,16 @@ static bool ima_match_rules(struct ima_rule_entry *rule,
 		return false;
 	if ((rule->flags & IMA_UID) && !uid_eq(rule->uid, cred->uid))
 		return false;
+	if (rule->flags & IMA_EUID) {
+		if (capable(CAP_SETUID)) {
+			if (!uid_eq(rule->uid, cred->euid)
+			    && !uid_eq(rule->uid, cred->suid)
+			    && !uid_eq(rule->uid, cred->uid))
+			return false;
+		} else if (!uid_eq(rule->uid, cred->euid))
+			return false;
+	}
+
 	if ((rule->flags & IMA_FOWNER) && !uid_eq(rule->fowner, inode->i_uid))
 		return false;
 	for (i = 0; i < MAX_LSM_RULES; i++) {
@@ -372,7 +383,8 @@ enum {
 	Opt_audit,
 	Opt_obj_user, Opt_obj_role, Opt_obj_type,
 	Opt_subj_user, Opt_subj_role, Opt_subj_type,
-	Opt_func, Opt_mask, Opt_fsmagic, Opt_uid, Opt_fowner,
+	Opt_func, Opt_mask, Opt_fsmagic,
+	Opt_uid, Opt_euid, Opt_fowner,
 	Opt_appraise_type, Opt_fsuuid, Opt_permit_directio
 };
 
@@ -393,6 +405,7 @@ static match_table_t policy_tokens = {
 	{Opt_fsmagic, "fsmagic=%s"},
 	{Opt_fsuuid, "fsuuid=%s"},
 	{Opt_uid, "uid=%s"},
+	{Opt_euid, "euid=%s"},
 	{Opt_fowner, "fowner=%s"},
 	{Opt_appraise_type, "appraise_type=%s"},
 	{Opt_permit_directio, "permit_directio"},
@@ -565,6 +578,9 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
 			break;
 		case Opt_uid:
 			ima_log_string(ab, "uid", args[0].from);
+		case Opt_euid:
+			if (token == Opt_euid)
+				ima_log_string(ab, "euid", args[0].from);
 
 			if (uid_valid(entry->uid)) {
 				result = -EINVAL;
@@ -577,7 +593,8 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
 				if (!uid_valid(entry->uid) || (((uid_t)lnum) != lnum))
 					result = -EINVAL;
 				else
-					entry->flags |= IMA_UID;
+					entry->flags |= (token == Opt_uid)
+					    ? IMA_UID : IMA_EUID;
 			}
 			break;
 		case Opt_fowner:
-- 
2.1.0