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Diffstat (limited to 'Documentation/usb/authorization.txt')
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diff --git a/Documentation/usb/authorization.txt b/Documentation/usb/authorization.txt deleted file mode 100644 index f901ec77439c..000000000000 --- a/Documentation/usb/authorization.txt +++ /dev/null @@ -1,123 +0,0 @@ - -Authorizing (or not) your USB devices to connect to the system - -(C) 2007 Inaky Perez-Gonzalez <inaky@linux.intel.com> Intel Corporation - -This feature allows you to control if a USB device can be used (or -not) in a system. This feature will allow you to implement a lock-down -of USB devices, fully controlled by user space. - -As of now, when a USB device is connected it is configured and -its interfaces are immediately made available to the users. With this -modification, only if root authorizes the device to be configured will -then it be possible to use it. - -Usage: - -Authorize a device to connect: - -$ echo 1 > /sys/bus/usb/devices/DEVICE/authorized - -Deauthorize a device: - -$ echo 0 > /sys/bus/usb/devices/DEVICE/authorized - -Set new devices connected to hostX to be deauthorized by default (ie: -lock down): - -$ echo 0 > /sys/bus/usb/devices/usbX/authorized_default - -Remove the lock down: - -$ echo 1 > /sys/bus/usb/devices/usbX/authorized_default - -By default, Wired USB devices are authorized by default to -connect. Wireless USB hosts deauthorize by default all new connected -devices (this is so because we need to do an authentication phase -before authorizing). - - -Example system lockdown (lame) ------------------------ - -Imagine you want to implement a lockdown so only devices of type XYZ -can be connected (for example, it is a kiosk machine with a visible -USB port): - -boot up -rc.local -> - - for host in /sys/bus/usb/devices/usb* - do - echo 0 > $host/authorized_default - done - -Hookup an script to udev, for new USB devices - - if device_is_my_type $DEV - then - echo 1 > $device_path/authorized - done - - -Now, device_is_my_type() is where the juice for a lockdown is. Just -checking if the class, type and protocol match something is the worse -security verification you can make (or the best, for someone willing -to break it). If you need something secure, use crypto and Certificate -Authentication or stuff like that. Something simple for an storage key -could be: - -function device_is_my_type() -{ - echo 1 > authorized # temporarily authorize it - # FIXME: make sure none can mount it - mount DEVICENODE /mntpoint - sum=$(md5sum /mntpoint/.signature) - if [ $sum = $(cat /etc/lockdown/keysum) ] - then - echo "We are good, connected" - umount /mntpoint - # Other stuff so others can use it - else - echo 0 > authorized - fi -} - - -Of course, this is lame, you'd want to do a real certificate -verification stuff with PKI, so you don't depend on a shared secret, -etc, but you get the idea. Anybody with access to a device gadget kit -can fake descriptors and device info. Don't trust that. You are -welcome. - - -Interface authorization ------------------------ -There is a similar approach to allow or deny specific USB interfaces. -That allows to block only a subset of an USB device. - -Authorize an interface: -$ echo 1 > /sys/bus/usb/devices/INTERFACE/authorized - -Deauthorize an interface: -$ echo 0 > /sys/bus/usb/devices/INTERFACE/authorized - -The default value for new interfaces -on a particular USB bus can be changed, too. - -Allow interfaces per default: -$ echo 1 > /sys/bus/usb/devices/usbX/interface_authorized_default - -Deny interfaces per default: -$ echo 0 > /sys/bus/usb/devices/usbX/interface_authorized_default - -Per default the interface_authorized_default bit is 1. -So all interfaces would authorized per default. - -Note: -If a deauthorized interface will be authorized so the driver probing must -be triggered manually by writing INTERFACE to /sys/bus/usb/drivers_probe - -For drivers that need multiple interfaces all needed interfaces should be -authorized first. After that the drivers should be probed. -This avoids side effects. |