Re: Can I bind USB/other interface/device number (e.g. cdceX) to particular MAC, USB serial number or the like?

Hi,

What I meant was, it's fairly easy for interface numbers (e.g. NIC A as
CDCE0 and NIC B as CDCE1) to become exchanged.

With lots of unluck, there could be mechanical stress on USB ports so
that they would rearrange spontaneously so NIC B would become CDCE0 and
NIC A would become CDCE1.

Or more probable, an ignorant user would intentionally replug his
devices but the change of order of interfaces would be unintentional to
him, and then when he ifconfig/dhclient:s his interfaces, very bad
things could happen.

This is not a big deal, but it does add one more thing to think about,
and in extreme corner cases it could be a security problem - God forbid
you'd have a public network on CDCE0 and a private network on CDCE1 and
then a little mistake causes everyone's medical records etc. to be
leaked on the Internet.


The same would apply to USB serial ports (UART:s) and probably some
other hardware -

I was talking to someone who was worried that it (unintended device
ordering) could happen even to PCI devices though I guess that's
overkill.

His solution is to enforce device names by using different hardware,
though that kind of illustrates the problem rather than resolve it,
doesn't it.


OpenBSD leaves IP configuration as manual work to the user so OpenBSD
itself won't mess it up for you, so this is not a per-se OpenBSD
problem.

But maybe OpenBSD could help people do it right. Interface number
hard-binding to a particular device descriptor (MAC/USB serial etc.)
would solve it.

Interface name aliasing would work too (hardbound to descriptor).


Anyhow I just wanted to bring up the potential problem.

(Also Peter - this is not specifically a PF problem, however, how would
you use egress as part of the solution?)

Thanks,
Tinker

On 2017-05-30 07:04, Peter Hessler wrote:
> On 2017 May 29 (Mon) at 02:13:57 +0000 (+0000), Tinker wrote:
> :Hi misc@,
> :
> :For pluggable devices such as USB NIC:s, is there any way to make
> OpenBSD
> :bind a particular device based on its MAC or USB serial number or the
> like
> :variable, to a particular interface or device filename?
> :
> :E.g. MAC X is prebooked as cdce0, and MAC Y as cdce1 , and external
> USB
> :harddrive with serial number Z as /dev/sd0 and the one with serial
> number A
> :as /dev/sd1 (and plugging in other devices would automatically).
> :
> :(For storage devices there's the DUID-based mounting already though,
> so I
> :guess those are a non-issue.)
> :
> :Some things in the OS are specified per interface/device name, e.g. PF
> rules
> :(e.g. "pass in proto tcp from any to cdce0 port 123 rdr-to cdce1 ..",
> "match
> :out on cdce0 from 192.168.0.0/16 to any nat-to cdce0"), so having the
> :interface numbers garbled on replug may be an unnecessary reason to
> reboot?
> :
> :Would be happy to learn any best practice here, thanks,
> :Tinker
> :
>
> match out on egress from 192.168.0.0/16 to any nat-to (egress)
> ^^^^^^ ^^^^^^^^
>
> the interface group "egress" is added to the interface a default route
> uses. Wrapping that with (), will ensure that interface is updated
> when
> the default routes uses a different interface.