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Diffstat (limited to 'Documentation/usb/authorization.txt')
| -rw-r--r-- | Documentation/usb/authorization.txt | 75 |
1 files changed, 41 insertions, 34 deletions
diff --git a/Documentation/usb/authorization.txt b/Documentation/usb/authorization.txt index 9dd1dc7b1009..9e53909d04c2 100644 --- a/Documentation/usb/authorization.txt +++ b/Documentation/usb/authorization.txt @@ -1,7 +1,8 @@ - +============================================================== Authorizing (or not) your USB devices to connect to the system +============================================================== -(C) 2007 Inaky Perez-Gonzalez <inaky@linux.intel.com> Intel Corporation +Copyright (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 @@ -12,24 +13,25 @@ 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: +Usage +===== -Authorize a device to connect: +Authorize a device to connect:: -$ echo 1 > /sys/bus/usb/devices/DEVICE/authorized + $ echo 1 > /sys/bus/usb/devices/DEVICE/authorized -Deauthorize a device: +De-authorize a device:: -$ echo 0 > /sys/bus/usb/devices/DEVICE/authorized + $ echo 0 > /sys/bus/usb/devices/DEVICE/authorized Set new devices connected to hostX to be deauthorized by default (ie: -lock down): +lock down):: -$ echo 0 > /sys/bus/usb/devices/usbX/authorized_default + $ echo 0 > /sys/bus/usb/devices/usbX/authorized_default -Remove the lock down: +Remove the lock down:: -$ echo 1 > /sys/bus/usb/devices/usbX/authorized_default + $ 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 @@ -40,21 +42,21 @@ USB ports. 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): +USB port):: -boot up -rc.local -> + boot up + rc.local -> - for host in /sys/bus/usb/devices/usb* - do - echo 0 > $host/authorized_default - done + for host in /sys/bus/usb/devices/usb* + do + echo 0 > $host/authorized_default + done -Hookup an script to udev, for new USB devices +Hookup an script to udev, for new USB devices:: if device_is_my_type $DEV then @@ -67,10 +69,10 @@ checking if the class, type and protocol match something is the worse security verification you can make (or the best, for someone willing to break it). If you need something secure, use crypto and Certificate Authentication or stuff like that. Something simple for an storage key -could be: +could be:: -function device_is_my_type() -{ + function device_is_my_type() + { echo 1 > authorized # temporarily authorize it # FIXME: make sure none can mount it mount DEVICENODE /mntpoint @@ -83,7 +85,7 @@ function device_is_my_type() else echo 0 > authorized fi -} + } Of course, this is lame, you'd want to do a real certificate @@ -95,30 +97,35 @@ welcome. Interface authorization ----------------------- + There is a similar approach to allow or deny specific USB interfaces. That allows to block only a subset of an USB device. -Authorize an interface: -$ echo 1 > /sys/bus/usb/devices/INTERFACE/authorized +Authorize an interface:: -Deauthorize an interface: -$ echo 0 > /sys/bus/usb/devices/INTERFACE/authorized + $ 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 +Allow interfaces per default:: + + $ echo 1 > /sys/bus/usb/devices/usbX/interface_authorized_default + +Deny interfaces per default:: -Deny interfaces per default: -$ echo 0 > /sys/bus/usb/devices/usbX/interface_authorized_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 + 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. |