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serial_port.go
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serial_port.go
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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2016-2017 Canonical Ltd
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package builtin
import (
"fmt"
"path/filepath"
"regexp"
"strconv"
"strings"
"github.com/snapcore/snapd/interfaces"
"github.com/snapcore/snapd/interfaces/apparmor"
"github.com/snapcore/snapd/interfaces/hotplug"
"github.com/snapcore/snapd/interfaces/udev"
"github.com/snapcore/snapd/snap"
)
const serialPortSummary = `allows accessing a specific serial port`
const serialPortBaseDeclarationSlots = `
serial-port:
allow-installation:
slot-snap-type:
- core
- gadget
deny-auto-connection: true
`
// serialPortInterface is the type for serial port interfaces.
type serialPortInterface struct{}
// Name of the serial-port interface.
func (iface *serialPortInterface) Name() string {
return "serial-port"
}
func (iface *serialPortInterface) StaticInfo() interfaces.StaticInfo {
return interfaces.StaticInfo{
Summary: serialPortSummary,
BaseDeclarationSlots: serialPortBaseDeclarationSlots,
}
}
func (iface *serialPortInterface) String() string {
return iface.Name()
}
// Pattern to match allowed serial device nodes, path attributes will be
// compared to this for validity when not using udev identification
// Known device node patterns we need to support
// - ttyUSBX (UART over USB devices)
// - ttyACMX (ACM modem devices )
// - ttyXRUSBx (Exar Corp. USB UART devices)
// - ttySX (UART serial ports)
// - ttyOX (UART serial ports on ARM)
// - ttymxcX (serial ports on i.mx6UL)
// - ttySCX (NXP SC16IS7xx serial devices)
// - ttyMSMX (Qualcomm msm7x serial devices)
// - ttyHSX (Qualcomm GENI based QTI serial cores)
var serialDeviceNodePattern = regexp.MustCompile("^/dev/tty(mxc|USB|ACM|AMA|XRUSB|S|O|SC|MSM|HS)[0-9]+$")
// Pattern that is considered valid for the udev symlink to the serial device,
// path attributes will be compared to this for validity when usb vid and pid
// are also specified
var serialUDevSymlinkPattern = regexp.MustCompile("^/dev/serial-port-[a-z0-9]+$")
// BeforePrepareSlot checks validity of the defined slot
func (iface *serialPortInterface) BeforePrepareSlot(slot *snap.SlotInfo) error {
// Check slot has a path attribute identify serial device
path, ok := slot.Attrs["path"].(string)
if !ok || path == "" {
return fmt.Errorf("serial-port slot must have a path attribute")
}
// XXX: this interface feeds the cleaned path into the regex and is
// left unchanged here for historical reasons. New interfaces (eg,
// like raw-volume) should instead use verifySlotPathAttribute() which
// performs additional verification.
path = filepath.Clean(path)
if iface.hasUsbAttrs(slot) {
// Must be path attribute where symlink will be placed and usb vendor and product identifiers
// Check the path attribute is in the allowable pattern
if !serialUDevSymlinkPattern.MatchString(path) {
return fmt.Errorf("serial-port path attribute specifies invalid symlink location")
}
usbVendor, vOk := slot.Attrs["usb-vendor"].(int64)
if !vOk {
return fmt.Errorf("serial-port slot failed to find usb-vendor attribute")
}
if (usbVendor < 0x1) || (usbVendor > 0xFFFF) {
return fmt.Errorf("serial-port usb-vendor attribute not valid: %d", usbVendor)
}
usbProduct, pOk := slot.Attrs["usb-product"].(int64)
if !pOk {
return fmt.Errorf("serial-port slot failed to find usb-product attribute")
}
if (usbProduct < 0x0) || (usbProduct > 0xFFFF) {
return fmt.Errorf("serial-port usb-product attribute not valid: %d", usbProduct)
}
usbInterfaceNumber, ok := slot.Attrs["usb-interface-number"].(int64)
if ok && (usbInterfaceNumber < 0 || usbInterfaceNumber >= UsbMaxInterfaces) {
return fmt.Errorf("serial-port usb-interface-number attribute cannot be negative or larger than %d", UsbMaxInterfaces-1)
}
} else {
// Just a path attribute - must be a valid usb device node
// Check the path attribute is in the allowable pattern
if !serialDeviceNodePattern.MatchString(path) {
return fmt.Errorf("serial-port path attribute must be a valid device node")
}
}
return nil
}
func (iface *serialPortInterface) UDevPermanentSlot(spec *udev.Specification, slot *snap.SlotInfo) error {
var usbVendor, usbProduct, usbInterfaceNumber int64
var path string
if err := slot.Attr("usb-vendor", &usbVendor); err != nil {
return nil
}
if err := slot.Attr("usb-product", &usbProduct); err != nil {
return nil
}
if err := slot.Attr("path", &path); err != nil || path == "" {
return nil
}
if err := slot.Attr("usb-interface-number", &usbInterfaceNumber); err == nil {
spec.AddSnippet(fmt.Sprintf(`# serial-port
IMPORT{builtin}="usb_id"
SUBSYSTEM=="tty", SUBSYSTEMS=="usb", ATTRS{idVendor}=="%04x", ATTRS{idProduct}=="%04x", ENV{ID_USB_INTERFACE_NUM}=="%02x", SYMLINK+="%s"`, usbVendor, usbProduct, usbInterfaceNumber, strings.TrimPrefix(path, "/dev/")))
} else {
spec.AddSnippet(fmt.Sprintf(`# serial-port
IMPORT{builtin}="usb_id"
SUBSYSTEM=="tty", SUBSYSTEMS=="usb", ATTRS{idVendor}=="%04x", ATTRS{idProduct}=="%04x", SYMLINK+="%s"`, usbVendor, usbProduct, strings.TrimPrefix(path, "/dev/")))
}
return nil
}
func (iface *serialPortInterface) AppArmorConnectedPlug(spec *apparmor.Specification, plug *interfaces.ConnectedPlug, slot *interfaces.ConnectedSlot) error {
if iface.hasUsbAttrs(slot) {
// This apparmor rule is an approximation of serialDeviceNodePattern
// (AARE is different than regex, so we must approximate).
// UDev tagging and device cgroups will restrict down to the specific device
spec.AddSnippet("/dev/tty[A-Z]*[0-9] rwk,")
return nil
}
// Path to fixed device node
var path string
if err := slot.Attr("path", &path); err != nil {
return nil
}
cleanedPath := filepath.Clean(path)
spec.AddSnippet(fmt.Sprintf("%s rwk,", cleanedPath))
return nil
}
func (iface *serialPortInterface) UDevConnectedPlug(spec *udev.Specification, plug *interfaces.ConnectedPlug, slot *interfaces.ConnectedSlot) error {
// For connected plugs, we use vendor and product ids if available,
// otherwise add the kernel device
hasOnlyPath := !iface.hasUsbAttrs(slot)
var usbVendor, usbProduct int64
var path string
if err := slot.Attr("usb-vendor", &usbVendor); err != nil && !hasOnlyPath {
return nil
}
if err := slot.Attr("usb-product", &usbProduct); err != nil && !hasOnlyPath {
return nil
}
if err := slot.Attr("path", &path); err != nil && hasOnlyPath {
return nil
}
if hasOnlyPath {
spec.TagDevice(fmt.Sprintf(`SUBSYSTEM=="tty", KERNEL=="%s"`, strings.TrimPrefix(path, "/dev/")))
} else {
var usbInterfaceNumber int64
if err := slot.Attr("usb-interface-number", &usbInterfaceNumber); err == nil {
spec.TagDevice(fmt.Sprintf(`IMPORT{builtin}="usb_id"
SUBSYSTEM=="tty", SUBSYSTEMS=="usb", ATTRS{idVendor}=="%04x", ATTRS{idProduct}=="%04x", ENV{ID_USB_INTERFACE_NUM}=="%02x"`, usbVendor, usbProduct, usbInterfaceNumber))
} else {
spec.TagDevice(fmt.Sprintf(`IMPORT{builtin}="usb_id"
SUBSYSTEM=="tty", SUBSYSTEMS=="usb", ATTRS{idVendor}=="%04x", ATTRS{idProduct}=="%04x"`, usbVendor, usbProduct))
}
}
return nil
}
func (iface *serialPortInterface) AutoConnect(*snap.PlugInfo, *snap.SlotInfo) bool {
// allow what declarations allowed
return true
}
func (iface *serialPortInterface) HotplugDeviceDetected(di *hotplug.HotplugDeviceInfo) (*hotplug.ProposedSlot, error) {
bus, _ := di.Attribute("ID_BUS")
if di.Subsystem() != "tty" || bus != "usb" || !serialDeviceNodePattern.MatchString(di.DeviceName()) {
return nil, nil
}
slot := hotplug.ProposedSlot{
Attrs: map[string]interface{}{
"path": di.DeviceName(),
},
}
if vendor, ok := di.Attribute("ID_VENDOR_ID"); ok {
slot.Attrs["usb-vendor"] = vendor
}
if product, ok := di.Attribute("ID_MODEL_ID"); ok {
slot.Attrs["usb-product"] = product
}
return &slot, nil
}
func slotDeviceAttrEqual(di *hotplug.HotplugDeviceInfo, devinfoAttribute string, slotAttributeValue int64) bool {
var attr string
var ok bool
if attr, ok = di.Attribute(devinfoAttribute); !ok {
return false
}
val, err := strconv.ParseInt(attr, 16, 64)
return err == nil && val == slotAttributeValue
}
func (iface *serialPortInterface) HandledByGadget(di *hotplug.HotplugDeviceInfo, slot *snap.SlotInfo) bool {
// if the slot has vendor, product and interface number set, check if they match
var usbVendor, usbProduct, usbInterfaceNumber int64
if err := slot.Attr("usb-vendor", &usbVendor); err == nil {
if !slotDeviceAttrEqual(di, "ID_VENDOR_ID", usbVendor) {
return false
}
if err := slot.Attr("usb-product", &usbProduct); err != nil {
return false
}
if !slotDeviceAttrEqual(di, "ID_MODEL_ID", usbProduct) {
return false
}
if err := slot.Attr("usb-interface-number", &usbInterfaceNumber); err == nil {
if !slotDeviceAttrEqual(di, "ID_USB_INTERFACE_NUM", usbInterfaceNumber) {
return false
}
}
return true
}
var path string
if err := slot.Attr("path", &path); err != nil {
return false
}
return di.DeviceName() == path
}
func (iface *serialPortInterface) hasUsbAttrs(attrs interfaces.Attrer) bool {
var v int64
if err := attrs.Attr("usb-vendor", &v); err == nil {
return true
}
if err := attrs.Attr("usb-product", &v); err == nil {
return true
}
if err := attrs.Attr("usb-interface-number", &v); err == nil {
return true
}
return false
}
func init() {
registerIface(&serialPortInterface{})
}