Whats a magic packet (wake on lan) (in terms of routability, and security)

qwijibow · 01-19-2005, 09:17 AM

ooookay....
i have a VNF3-250 motherboard with an onboard realtech network card.

Info gathered from PCI interface

Code:

0000:02:07.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL-8029(AS)

info gathered from Driver

Code:

eth0: RealTek RTL8139 at 0xffffff0000118000, 00:50:70:f5:31:24, IRQ 19
eth0:  Identified 8139 chip type 'RTL-8100B/8139D'
eth0: link up, 100Mbps, full-duplex, lpa 0x45E1

I cant find a Wake On Lan socket, to plug the onboard ethernet to the motherboard, and there is no mention
of this procedure in my instruction manual, so i assume that the connection is hard wired on the motherboard. (safe asumtion ?)
(it can be enabled / disabled inthe BIOS)

Even when the computer is powerd off, the Router Link light stays lit, so the network card is remaining on
when the pc if off, (as it should be)

Ive turned On the "Wake on magic packet" on the network card with "ethtool"

And ive downloaded a program to generate a magic packet.

So... the magic question...
the magic packet sends a message telling the computer to power on... okay..

but what IS it ?
ICMP / TCP / UDG / UGMP / Raw IP frame ?

what protocol ?

and will i be able to set my router to forward this packet from the internet oto my machine ?
(my router supports UDP / TCP port forwarding, and DMZ)

am i correct in thinking that if the magic packet is not a standard TCP / UDP packet, it will still get forwarded through DMZ if i set my machine as the DMZ taret ?

ALSO... my network card does not support passwords on the magic packet... how secure is this ?
are there many "magic packets" being flung arount the internet ?

i sometimes get port scanned... do virii / script kiddies often send magic packets to random machines ?

thanKs.

dtimms · 01-28-2005, 07:52 PM

see:
http://gsd.di.uminho.pt/jpo/software...i-howto-2.html

the magic is that no matter where it appears, it should still activate WOL, ie it is protocol-less. It seems various tools authors encapsulate it in any easy method, eg udp+port no. though this appears to be necessary only to get it through standard IP protocols.

For your card then: if it received:
\xFF\xFF\xFF\xFF\xFF\xFF
\x00\x50\x70\xf5\x31\x24\x00\x50\x70\xf5\x31\x24
\x00\x50\x70\xf5\x31\x24\x00\x50\x70\xf5\x31\x24
\x00\x50\x70\xf5\x31\x24\x00\x50\x70\xf5\x31\x24
\x00\x50\x70\xf5\x31\x24\x00\x50\x70\xf5\x31\x24
\x00\x50\x70\xf5\x31\x24\x00\x50\x70\xf5\x31\x24
\x00\x50\x70\xf5\x31\x24\x00\x50\x70\xf5\x31\x24
\x00\x50\x70\xf5\x31\x24\x00\x50\x70\xf5\x31\x24
\x00\x50\x70\xf5\x31\x24\x00\x50\x70\xf5\x31\x24
then it should turn on.

However, on the internet, only IP is transferred. Also, TCP is no good because it requires setting up a connection (including response from the receiver - wake on lan is one way) before sending the payload. So UDP seems like the answer, as long as you pass it through your firewall.

An attacker would need to know your MAC address to be successful, and which port you decided to use. Probably be wise to limit incoming WOLs to IP address you xpect to be at.