audit: audit feature to only allow unsetting the loginuid

This is a new audit feature which only grants processes with CAP_AUDIT_CONTROL the ability to unset their loginuid. They cannot directly set it from a valid uid to another valid uid. The ability to unset the loginuid is nice because a priviledged task, like that of container creation, can unset the loginuid and then priv is not needed inside the container when a login daemon needs to set the loginuid.

Eric Paris committed 13 years ago

Commit d040e5a1 parent 81407c83 files · +7 −2Browse files

Unified · Split

3 files

include/uapi/linux/audit.h +2 −1
kernel/audit.c +2 −1
kernel/auditsc.c +3 −0

include/uapi/linux/audit.h+2−1

@@ -386,7 +386,8 @@ struct audit_features { · 385 unmodified lines
386	386	__u32 lock; /* which features to lock */
387	387	};
388	388
389		−#define AUDIT_LAST_FEATURE -1
	389	+#define AUDIT_FEATURE_ONLY_UNSET_LOGINUID 0
	390	+#define AUDIT_LAST_FEATURE AUDIT_FEATURE_ONLY_UNSET_LOGINUID
390	391
391	392	#define audit_feature_valid(x) ((x) >= 0 && (x) <= AUDIT_LAST_FEATURE)
392	393	#define AUDIT_FEATURE_TO_MASK(x) (1 << ((x) & 31)) /* mask for __u32 */

kernel/audit.c+2−1

@@ -144,7 +144,8 @@ static struct audit_features af = {.vers = AUDIT_FEATURE_VERSION, · 143 unmodified lines
144	144	.features = 0,
145	145	.lock = 0,};
146	146
147		−static char *audit_feature_names[0] = {
	147	+static char *audit_feature_names[1] = {
	148	+ "only_unset_loginuid",
148	149	};
149	150
150	151

kernel/auditsc.c+3−0

@@ -1974,6 +1974,9 @@ static int audit_set_loginuid_perm(kuid_t loginuid) · 1973 unmodified lines
1974	1974	/* it is set, you need permission */
1975	1975	if (!capable(CAP_AUDIT_CONTROL))
1976	1976	return -EPERM;
	1977	+ /* reject if this is not an unset and we don't allow that */
	1978	+ if (is_audit_feature_set(AUDIT_FEATURE_ONLY_UNSET_LOGINUID) && uid_valid(loginuid))
	1979	+ return -EPERM;
1977	1980	return 0;
1978	1981	}
1979	1982