Date: Fri, 8 Aug 2014 21:57:49 +0400 From: gremlin@...mlin.ru To: oss-security@...ts.openwall.com Subject: Re: BadUSB discussion On 08-Aug-2014 09:21:02 -0700, Greg KH wrote: >>> Oh, and if you want, you can disable all USB devices on your >>> Linux system by default, and only "authorize" them explicitly >>> if you programatically think they should be enabled. We have >>> had support in the kernel for that for years now, but very few >>> people actually use it. >> I've faced that only once, and my solution was straightforward: >> those two servers were running a kernel built with only basic >> USB HID support (keyboard+mouse, IIRC) and without module load >> support. That appeared to be quite enough. > That doesn't prevent any other USB HID device from being plugged > in and instantly working. Which again, you can prevent if you > want to, but no one seems to do that... Hmmm... To avoid possible confusion: that was CONFIG_USB_KBD - "USB HIDBP Keyboard (simple Boot) support", and CONFIG_USB_HID was turned off. >>> So the tools to do this are already there, why aren't you using >>> them? :) >> You could guess: sometimes I'm developing USB devices and have >> to test them. That formed a good habit of connecting my devices >> to a hub instead of directly to BB :-) > A USB hub doesn't do anything special except slow things down and > add complexity to the overall USB system, and does nothing for > "security" at all. Sometimes they may hang when plugged device misbehaviors. Pulling out the cable and then plugging it back resumes normal operation. With direct connection, I sometimes ended up with all USB devices being inaccessible. Now, I keep a mouse plugged into the hub to detect these situations. Look here, I had some experiments recently: Bus 002 Device 063: ID 05e3:0606 Genesys Logic, Inc. USB 2.0 Hub Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 002 Device 064: ID 046d:c016 Logitech, Inc. Optical Wheel Mouse Device IDs tell us the hub was reset several times :-) -- Alexey V. Vissarionov aka Gremlin from Kremlin <gremlin ПРИ gremlin ТЧК ru> GPG: 8832FE9FA791F7968AC96E4E909DAC45EF3B1FA8 @ hkp://keys.gnupg.net
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