Create the tun device after dropping root privileges.
Currently, clatd creates the clat4 interface as root using
root's dac_override abilities. Instead, change the drop_root code
to acquire membership in the AID_VPN group, and use that
membership to create the interface. This removes the need for
dac_override.
Change-Id: I1f824254f52a441f21c5b7963d9993be88cea2db
diff --git a/clatd.c b/clatd.c
index 6871129..1333e30 100644
--- a/clatd.c
+++ b/clatd.c
@@ -212,7 +212,7 @@
* drops root privs but keeps the needed capability
*/
void drop_root() {
- gid_t groups[] = { AID_INET };
+ gid_t groups[] = { AID_INET, AID_VPN };
if(setgroups(sizeof(groups)/sizeof(groups[0]), groups) < 0) {
logmsg(ANDROID_LOG_FATAL,"drop_root/setgroups failed: %s",strerror(errno));
exit(1);
@@ -486,18 +486,19 @@
net_id_str ? net_id_str : "(none)",
mark_str ? mark_str : "(none)");
- // open the tunnel device and our raw sockets before dropping privs
+ // open our raw sockets before dropping privs
+ open_sockets(&tunnel, mark);
+
+ // run under a regular user
+ drop_root();
+
+ // we can create tun devices as non-root because we're in the VPN group.
tunnel.fd4 = tun_open();
if(tunnel.fd4 < 0) {
logmsg(ANDROID_LOG_FATAL, "tun_open4 failed: %s", strerror(errno));
exit(1);
}
- open_sockets(&tunnel, mark);
-
- // run under a regular user
- drop_root();
-
// When run from netd, the environment variable ANDROID_DNS_MODE is set to
// "local", but that only works for the netd process itself.
unsetenv("ANDROID_DNS_MODE");