os: add component for filtering USB devices report
The 'usb_report_filter' component takes the devices report from the USB driver and generates a new devices report after checking each entry against its device white-list. Before emitting the new report it changes the configuration of the USB driver to contain the required policy entries. See 'repos/os/src/app/usb_report_filter/README' for more details. Issue #1863.
This commit is contained in:
Josef Söntgen
Christian Helmuth
parent
716eab21e3
commit
e233fe0b71
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This directory contains a USB device report filter component. It filters the
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device report coming from the USB driver by checking each device reported
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against the given list of devices. Only approved devices are reported to a
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consumer of the report coming from the filter component.
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Configuration
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~~~~~~~~~~~~~
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A typical example configuration looks as follows:
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!<config>
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! <client label="component_xyz"/>
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! <device vendor_id="0x13fe" product_id="0x5200"/>
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! <device vendor_id="0x148f" product_id="0x2573"/>
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! <device vendor_id="0x04f9" product_id="0x0051"/>
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! <device vendor_id="0x1b1c" product_id="0x1a09"/>
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</config>
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The component that may use the devices is identified by the 'client' node.
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In addition to the 'vendor_id' and 'product_id' attribute a 'device' node
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can contain a 'bus' and 'dev' attribute. If these attributes are present they
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have a stronger significance than the 'vendor_id' and the 'product_id'.
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Whenever the 'usb_report_filter' component receives a new USB device report
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from the driver it will generate a new driver configuration that contains
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a policy entry for each matching device. After the driver's configuration has
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been updated, the filter component will generate a new USB device report that
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only contains the devices the component is allowed to access.
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Example
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~~~~~~~
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In the following example we will give a VirtualBox instance access to a
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Corsair Voyager USB stick:
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!<start name="usb_report_filter">
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![...]
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! <config>
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! <client label="vbox"
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! <device vendor_id="0x1b1c" product_id="0x1a09"/>
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! </config>
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!</start>
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!<start name="report_rom">
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! <resource name="RAM" quantum="1M"/>
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! <provides> <service name="Report"/> <service name="ROM"/> </provides>
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! <config>
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! <policy label="usb_report_filter -> devices" report="usb_drv -> devices"/>
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! <policy label="usb_report_filter -> usb_drv_config" report="usb_drv -> config"/>
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! <policy label="vbox -> usb_devices" report="usb_report_filter -> usb_devices"/>
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! </config>
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!</start>
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After the USB stick has been plugged in, the filter will generate the
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following USB driver configuration:
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!<start name="usb_drv">
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![...]
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! <config uhci="yes" ehci="yes" xhci="yes">
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! <hid/>
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! <raw>
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! <report devices="yes"/>
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! <policy label="vbox -> usb-1-3" vendor_id="0x1b1c" product_id="0x1a09" bus="0x0001" device="0x0003"/>
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! </raw>
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! </config>
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!</start>
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After the driver has reloaded its configuration it will send a config report
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that provokes the filter component to send the following USB device report to
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VirtualBox:
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!<devices>
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! <device label="usb-1-3" vendor_id="0x1b1c" product_id="0x1a09" bus="0x0001" device="0x0003"/>
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!</device>
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In return, VirtualBox will try to access the USB device. Since the configuration
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of the USB driver contains a matching policy entry the access attempt will
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succeed.
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/*
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* \brief Component that filters USB device reports
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* \author Josef Soentgen
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* \date 2016-01-13
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*/
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/*
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* Copyright (C) 2016 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU General Public License version 2.
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*/
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/* Genode includes */
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#include <base/allocator_avl.h>
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#include <os/attached_rom_dataspace.h>
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#include <os/config.h>
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#include <os/reporter.h>
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#include <os/server.h>
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#include <util/list.h>
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#include <util/string.h>
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#include <util/xml_generator.h>
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#include <util/xml_node.h>
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#include <file_system_session/connection.h>
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#include <file_system/util.h>
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namespace Usb_filter {
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using Genode::Xml_node;
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using Genode::Xml_generator;
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using Genode::Attached_rom_dataspace;
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using Genode::snprintf;
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struct Device_registry;
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struct Main;
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}
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static bool const verbose = false;
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static char const * const config_file = "usb_drv.config";
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class Usb_filter::Device_registry
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{
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private:
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Genode::Allocator &_alloc;
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Server::Entrypoint &_ep;
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Genode::Reporter _reporter { "usb_devices" };
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Attached_rom_dataspace _devices_rom { "devices" };
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Attached_rom_dataspace _usb_drv_config_rom { "usb_drv_config" };
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Genode::Allocator_avl _fs_packet_alloc { &_alloc };
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File_system::Connection _fs { _fs_packet_alloc, 128*1024, "usb_drv.config" };
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File_system::File_handle _file;
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struct Entry : public Genode::List<Entry>::Element
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{
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unsigned bus;
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unsigned dev;
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unsigned vendor;
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unsigned product;
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Entry(unsigned b, unsigned d, unsigned v, unsigned p)
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: bus(b), dev(d), vendor(v), product(p) { }
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};
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Genode::List<Entry> _list;
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enum { MAX_LABEL_LEN = 512 };
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typedef Genode::String<MAX_LABEL_LEN> Label;
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Label _client_label;
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template <typename FUNC>
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void _for_each_entry(FUNC const &func) const
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{
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Entry const *e = _list.first();
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Entry const *next = nullptr;
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for (; e; e = next) {
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/*
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* Obtain next element prior calling the functor because
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* the functor may remove the current element from the list.
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*/
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next = e->next();
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func(*e);
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}
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}
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static inline unsigned _get_value(Xml_node node, char const * const attr) {
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return node.attribute_value<unsigned long>(attr, 0); }
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static bool _config_has_device(Xml_node config, Entry const &entry)
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{
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bool result = false;
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config.for_each_sub_node("device", [&] (Xml_node usb_device) {
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result |= (_get_value(usb_device, "bus") == entry.bus &&
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_get_value(usb_device, "dev") == entry.dev);
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if (result) return;
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result |= (_get_value(usb_device, "vendor") == entry.vendor &&
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_get_value(usb_device, "product") == entry.product);
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});
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return result;
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}
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static bool _devices_matches(Xml_node &device, Entry const & entry)
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{
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unsigned const bus = _get_value(device, "bus");
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unsigned const dev = _get_value(device, "dev");
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unsigned const vendor = _get_value(device, "vendor_id");
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unsigned const product = _get_value(device, "product_id");
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return (bus == entry.bus && dev == entry.dev) ||
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(vendor == entry.vendor && product == entry.product);
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}
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static void _gen_policy_entry(Xml_generator &xml, Xml_node &node,
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Entry const &entry, char const *label)
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{
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xml.node("policy", [&] {
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char buf[MAX_LABEL_LEN + 16];
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unsigned const bus = _get_value(node, "bus");
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unsigned const dev = _get_value(node, "dev");
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snprintf(buf, sizeof(buf), "%s -> usb-%d-%d", label, bus, dev);
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xml.attribute("label", buf);
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snprintf(buf, sizeof(buf), "0x%4x", _get_value(node, "vendor_id"));
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xml.attribute("vendor_id", buf);
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snprintf(buf, sizeof(buf), "0x%4x", _get_value(node, "product_id"));
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xml.attribute("product_id", buf);
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snprintf(buf, sizeof(buf), "0x%4x", bus);
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xml.attribute("bus", buf);
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snprintf(buf, sizeof(buf), "0x%4x", dev);
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xml.attribute("dev", buf);
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});
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}
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void _write_usb_drv_config(Xml_node & usb_devices)
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{
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using namespace Genode;
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try {
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File_system::Dir_handle root_dir = _fs.dir("/", false);
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_file = _fs.file(root_dir, config_file, File_system::READ_WRITE, false);
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} catch (...) {
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PERR("Could not open '%s'", config_file);
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return;
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}
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char old_file[1024];
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size_t n = File_system::read(_fs, _file, old_file,
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sizeof(old_file));
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if (n == 0) {
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PERR("Could not read '%s'", config_file);
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return;
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}
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Xml_node drv_config(old_file, n);
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bool const uhci_enabled = drv_config.attribute_value<bool>("uhci", false);
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bool const ehci_enabled = drv_config.attribute_value<bool>("ehci", false);
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bool const xhci_enabled = drv_config.attribute_value<bool>("xhci", false);
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char new_file[1024];
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Genode::Xml_generator xml(new_file, sizeof(new_file), "config", [&] {
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if (uhci_enabled) xml.attribute("uhci", "yes");
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if (ehci_enabled) xml.attribute("ehci", "yes");
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if (xhci_enabled) xml.attribute("xhci", "yes");
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/* copy other nodes */
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drv_config.for_each_sub_node([&] (Xml_node &node) {
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if (!node.has_type("raw")) {
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xml.append(node.addr(), node.size());
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return;
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}
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});
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if (!drv_config.has_sub_node("raw"))
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PINF("enable raw support in usb_drv");
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xml.node("raw", [&] {
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xml.node("report", [&] {
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xml.attribute("devices", "yes");
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});
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char const * const label = _client_label.string();
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usb_devices.for_each_sub_node("device", [&] (Xml_node &node) {
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auto add_policy_entry = [&] (Entry const &entry) {
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if (!_devices_matches(node, entry)) return;
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_gen_policy_entry(xml, node, entry, label);
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};
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_for_each_entry(add_policy_entry);
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});
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});
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});
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new_file[xml.used()] = 0;
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if (verbose)
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PLOG("new usb_drv configuration:\n%s", new_file);
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n = File_system::write(_fs, _file, new_file, xml.used());
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if (n == 0)
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PERR("Could not write '%s'", config_file);
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_fs.close(_file);
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}
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Genode::Signal_rpc_member<Device_registry> _devices_dispatcher =
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{ _ep, *this, &Device_registry::_handle_devices };
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void _handle_devices(unsigned)
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{
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_devices_rom.update();
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if (!_devices_rom.is_valid()) return;
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if (verbose)
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PLOG("device report:\n%s", _devices_rom.local_addr<char>());
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Xml_node usb_devices(_devices_rom.local_addr<char>(), _devices_rom.size());
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_write_usb_drv_config(usb_devices);
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}
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bool _check_config(Xml_node &drv_config)
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{
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if (!drv_config.has_sub_node("raw")) {
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PERR("Could not access <raw> node");
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return false;
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}
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auto check_policy = [&] (Entry const &entry) {
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bool result = false;
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drv_config.sub_node("raw").for_each_sub_node("policy", [&] (Xml_node &node) {
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result |= (entry.bus == _get_value(node, "bus") &&
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entry.dev == _get_value(node, "dev"));
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if (result) return;
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result |= (entry.vendor == _get_value(node, "vendor_id") &&
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entry.product == _get_value(node, "product_id"));
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});
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if (verbose && !result)
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PWRN("No matching policy was created for device %d-%d (%x:%x)",
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entry.bus, entry.dev, entry.vendor, entry.product);
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};
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_for_each_entry(check_policy);
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return true;
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}
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static void _gen_device_entry(Xml_generator &xml, Xml_node &node,
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Entry const &entry)
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{
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xml.node("device", [&] {
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char buf[16];
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unsigned const bus = _get_value(node, "bus");
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unsigned const dev = _get_value(node, "dev");
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snprintf(buf, sizeof(buf), "usb-%d-%d", bus, dev);
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xml.attribute("label", buf);
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snprintf(buf, sizeof(buf), "0x%4x", _get_value(node, "vendor_id"));
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xml.attribute("vendor_id", buf);
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snprintf(buf, sizeof(buf), "0x%4x", _get_value(node, "product_id"));
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xml.attribute("product_id", buf);
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snprintf(buf, sizeof(buf), "0x%4x", bus);
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xml.attribute("bus", buf);
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snprintf(buf, sizeof(buf), "0x%4x", dev);
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xml.attribute("dev", buf);
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});
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}
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void _report_usb_devices()
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{
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using namespace Genode;
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/*
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* XXX it might happen that the device list has changed after we are
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* waiting for the usb_drv_config update
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*/
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Xml_node usb_devices(_devices_rom.local_addr<char>(), _devices_rom.size());
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Reporter::Xml_generator xml(_reporter, [&] () {
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usb_devices.for_each_sub_node("device", [&] (Xml_node &node) {
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auto check_entry = [&] (Entry const &entry) {
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if (!_devices_matches(node, entry)) return;
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_gen_device_entry(xml, node, entry);
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};
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_for_each_entry(check_entry);
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});
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});
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}
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Genode::Signal_rpc_member<Device_registry> _usb_drv_config_dispatcher =
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{ _ep, *this, &Device_registry::_handle_usb_drv_config };
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void _handle_usb_drv_config(unsigned)
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{
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_usb_drv_config_rom.update();
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if (!_usb_drv_config_rom.is_valid()) return;
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Xml_node config(_usb_drv_config_rom.local_addr<char>(),
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_usb_drv_config_rom.size());
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if (!_check_config(config)) return;
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/* report devices if the USB drivers has changed its policies */
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_report_usb_devices();
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}
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bool _entry_exists(unsigned bus, unsigned dev,
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unsigned vendor, unsigned product)
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{
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bool result = false;
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auto check_exists = [&] (Entry const &entry) {
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result |= (bus && dev) &&
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(entry.bus == bus && entry.dev == dev);
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result |= (vendor && product) &&
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(entry.vendor == vendor && entry.product == product);
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};
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_for_each_entry(check_exists);
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return result;
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}
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public:
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/**
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* Constructor
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*/
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Device_registry(Genode::Allocator &alloc,
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Server::Entrypoint &ep)
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: _alloc(alloc), _ep(ep)
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{
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_reporter.enabled(true);
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_devices_rom.sigh(_devices_dispatcher);
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_usb_drv_config_rom.sigh(_usb_drv_config_dispatcher);
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}
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/**
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* Update internal device registry
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*/
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void update_entries(Genode::Xml_node config)
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{
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auto remove_stale_entry = [&] (Entry const &entry) {
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if (_config_has_device(config, entry))
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return;
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_list.remove(const_cast<Entry *>(&entry));
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Genode::destroy(&_alloc, const_cast<Entry *>(&entry));
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};
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_for_each_entry(remove_stale_entry);
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auto add_new_entry = [&] (Xml_node const &node) {
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unsigned const bus = _get_value(node, "bus");
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unsigned const dev = _get_value(node, "dev");
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unsigned const vendor = _get_value(node, "vendor_id");
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unsigned const product = _get_value(node, "product_id");
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if (_entry_exists(bus, dev, vendor, product)) return;
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Entry *entry = new (&_alloc) Entry(bus, dev, vendor, product);
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_list.insert(entry);
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};
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config.for_each_sub_node("device", add_new_entry);
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try {
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config.sub_node("client").attribute("label").value(&_client_label);
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} catch (...) {
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PERR("Could not update client label");
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}
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}
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};
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struct Usb_filter::Main
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{
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Server::Entrypoint &ep;
|
||||
|
||||
Genode::Signal_rpc_member<Main> _config_dispatcher =
|
||||
{ ep, *this, &Main::_handle_config };
|
||||
|
||||
void _handle_config(unsigned)
|
||||
{
|
||||
Genode::config()->reload();
|
||||
device_registry.update_entries(Genode::config()->xml_node());
|
||||
}
|
||||
|
||||
Device_registry device_registry { *Genode::env()->heap(), ep };
|
||||
|
||||
Main(Server::Entrypoint &ep) : ep(ep)
|
||||
{
|
||||
Genode::config()->sigh(_config_dispatcher);
|
||||
|
||||
_handle_config(0);
|
||||
}
|
||||
};
|
||||
|
||||
|
||||
namespace Server {
|
||||
char const *name() { return "usb_report_filter_ep"; }
|
||||
size_t stack_size() { return 4*1024*sizeof(addr_t); }
|
||||
void construct(Entrypoint &ep) { static Usb_filter::Main main(ep); }
|
||||
}
|
||||
|
|
@ -0,0 +1,3 @@
|
|||
TARGET = usb_report_filter
|
||||
SRC_CC = main.cc
|
||||
LIBS = base config server
|
||||
Loading…
Reference in New Issue