On Wed, 2020-09-30 at 13:01 +0200, Harald Welte wrote:

Hi Richard,

I don't fully understand in which context you need / use those
SELinux GTP hooks,

As in the reply to Pablo, I did it for no particular reason other than
idle curiosity, and given the attempted move to Open 5G I thought
adding MAC support might be useful somewhere along the line.

however one comment from the point of view of somebody who is working
on GGSN/P-GW
software using the GTP kernel module:

On Wed, Sep 30, 2020 at 10:49:34AM +0100, Richard Haines wrote:

quoted

+selinux_gtp_dev_cmd()
+~~~~~~~~~~~~~~~~~~~~~
+Validate if the caller (current SID) and the GTP device SID have
the required
+permission to perform the operation. The GTP/SELinux permission
map is
+as follow::
+
+    GTP_CMD_NEWPDP = gtp { add }
+    GTP_CMD_DELPDP = gtp { del }
+    GTP_CMD_GETPDP = gtp { get }

Wouldn't it make sense to differentiate between:

a) add/del/get on the GTP netdev
b) add/del/get on the indivudual PDP wihin the GTP netdev

'a' is typically only created once at startup of a GGSN/P-GW
software, or is
done even at system stat-up time.

'b' is performed frequently during runtime as the GGSN/P-GW function
runs, as
subscribers attach to / detach from the cellular network.

By differentiating between those two, one could further constrain the
permissions
required at runtime.

Yes, at first I did separate them (add_dev, del_dev, add_pkt, del_pkt,
get_pkt), so if this patchset goes anywhere then I can change it no
problem. I guess the '*_pkt' permissions would cover PDP for 3G and PDR
& FAR for 5G ?.
I didn't implement 'get_dev' but thought it could be useful for
retrieving the security context of a device, but that requires passing
it back via netlink so thought I would leave it until later.