[refpolicy] labels on /dev/tty.*

Christopher J. PeBenito cpebenito at tresys.com
Thu Oct 23 12:14:56 UTC 2014


On 10/22/2014 12:09 PM, Jason Zaman wrote:
> Hi all,
> 
> I am confused about the labels on the tty dev nodes. I looked in refpol
> and the only fcontext is:
> 
> /dev/.*tty[^/]* -c gen_context(system_u:object_r:tty_device_t,s0)
> 
> The implications of this are that everything is labelled with
> tty_device_t but I am pretty sure this is wrong. I have seen several
> different types of nodes which I think should have separate labels.
> 
> Ones that I am aware of (please add more or correct my understanding if
> it is wrong)
> 
> /dev/tty0 -- The consoles (eg ctrl+alt+f1)
> /dev/ttyS -- A physical serial port
> /dev/ttyUSB0 -- A usb-to-serial port
> /dev/ttyACM0 -- I have seen this for both usb-to-serial on embedded
> microcontrollers as well as 3G modems and the like.
> /dev/usb/tty.* -- I have no idea what this is, its not on my system but
> it is labelled usbtty_device_t in refpol.
> 
> The label on tty0 seems correct, the label on ttyUSB0 and ttyACM0 should
> probably be usbtty_device_t. As for what the label should be on ttyS0, I
> am not sure.
> 
> Thoughts? I dont want to just send in a patch changing this before I
> understand *exactly* what these are used for in case they break
> something else.

It seems more likely that usbtty_device_t should be dropped.  I don't
see any reason for there to be a distinction based on the underlying
hardware.


-- 
Chris PeBenito
Tresys Technology, LLC
www.tresys.com | oss.tresys.com


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