libselinux: normalize enforce values from the kernel

Normalize enforce values received from the kernel via
/sys/fs/selinux/enforce or netlink selinux notifications
to ensure that we always return a 0 or 1 to userspace code.
selinux_status_getenforce(), which reads the enforce value
via the SELinux kernel status page (/sys/fs/selinux/status)
already normalizes its result, so we do not need to update it.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>

libselinux/src/avc_internal.c

@@ -176,6 +176,7 @@ static int avc_netlink_process(void *buf)
 
 	case SELNL_MSG_SETENFORCE:{
 		struct selnl_msg_setenforce *msg = NLMSG_DATA(nlh);
+		msg->val = !!msg->val;
 		avc_log(SELINUX_INFO,
 			"%s:  received setenforce notice (enforcing=%d)\n",
 			avc_prefix, msg->val);

libselinux/src/getenforce.c

@@ -34,7 +34,7 @@ int security_getenforce(void)
 	if (sscanf(buf, "%d", &enforce) != 1)
 		return -1;
 
-	return enforce;
+	return !!enforce;
 }
 
 hidden_def(security_getenforce)