appdomain: relax netlink_socket neverallow rule

Relax the neverallow netlink restrictions for app domains.
In particular, some non-AOSP app domains may use netlink sockets
to communicate with a kernel driver.

Continue to neverallow generic netlink sockets for untrusted_app.
The intention here is that only app domains which explicitly need
this functionality should be able to request it.

This change does not add or remove any SELinux rules. Rather, it
just changes SELinux compile time assertions, as well as allowing
this behavior in CTS.

Modify other neverallow rules to use "domain" instead of "self".
Apps shouldn't be able to handle netlink sockets, even those
created in other SELinux domains.

(cherry picked from commit d31936f8)

Bug: 19198997
Change-Id: Icfed1ee66f082df1117b090341f62981f01bc849

app.te

@@ -229,8 +229,7 @@ neverallow appdomain tee_device:chr_file { read write };
 
 # Privileged netlink socket interfaces.
 neverallow appdomain
-    self:{
-        netlink_socket
+    domain:{
         netlink_firewall_socket
         netlink_tcpdiag_socket
         netlink_nflog_socket
@@ -243,7 +242,7 @@ neverallow appdomain
 # These messages are broadcast messages from the kernel to userspace.
 # Do not allow the writing of netlink messages, which has been a source
 # of rooting vulns in the past.
-neverallow appdomain self:netlink_kobject_uevent_socket { write append };
+neverallow appdomain domain:netlink_kobject_uevent_socket { write append };
 
 # Sockets under /dev/socket that are not specifically typed.
 neverallow appdomain socket_device:sock_file write;

untrusted_app.te

@@ -76,7 +76,10 @@ allow untrusted_app cache_file:file create_file_perms;
 ###
 
 # Receive or send uevent messages.
-neverallow untrusted_app self:netlink_kobject_uevent_socket *;
+neverallow untrusted_app domain:netlink_kobject_uevent_socket *;
+
+# Receive or send generic netlink messages
+neverallow untrusted_app domain:netlink_socket *;
 
 # Too much leaky information in debugfs. It's a security
 # best practice to ensure these files aren't readable.