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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2016 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"
"github.com/snapcore/snapd/interfaces"
"github.com/snapcore/snapd/interfaces/apparmor"
"github.com/snapcore/snapd/snap"
)
const boolFileSummary = `allows access to specific file with bool semantics`
const boolFileBaseDeclarationSlots = `
bool-file:
allow-installation:
slot-snap-type:
- core
- gadget
deny-auto-connection: true
`
// boolFileInterface is the type of all the bool-file interfaces.
type boolFileInterface struct{}
// String returns the same value as Name().
func (iface *boolFileInterface) String() string {
return iface.Name()
}
// Name returns the name of the bool-file interface.
func (iface *boolFileInterface) Name() string {
return "bool-file"
}
func (iface *boolFileInterface) StaticInfo() interfaces.StaticInfo {
return interfaces.StaticInfo{
Summary: boolFileSummary,
BaseDeclarationSlots: boolFileBaseDeclarationSlots,
}
}
var boolFileGPIOValuePattern = regexp.MustCompile(
"^/sys/class/gpio/gpio[0-9]+/value$")
var boolFileLedPattern = regexp.MustCompile(
"^/sys/devices/platform/leds/[^/]+/[^/]+/brightness$")
var boolFileAllowedPathPatterns = []*regexp.Regexp{
// The brightness of standard LED class device
regexp.MustCompile("^/sys/class/leds/[^/]+/brightness$"),
// The value of standard exported GPIO
boolFileGPIOValuePattern,
}
// BeforePrepareSlot checks and possibly modifies a slot.
// Valid "bool-file" slots must contain the attribute "path".
func (iface *boolFileInterface) BeforePrepareSlot(slot *snap.SlotInfo) error {
path, ok := slot.Attrs["path"].(string)
if !ok || path == "" {
return fmt.Errorf("bool-file must contain the 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)
for _, pattern := range boolFileAllowedPathPatterns {
if pattern.MatchString(path) {
return nil
}
}
return fmt.Errorf("bool-file can only point at LED brightness or GPIO value")
}
func (iface *boolFileInterface) AppArmorPermanentSlot(spec *apparmor.Specification, slot *snap.SlotInfo) error {
gpioSnippet := `
/sys/class/gpio/export rw,
/sys/class/gpio/unexport rw,
/sys/class/gpio/gpio[0-9]*/direction rw,
`
if iface.isGPIO(slot) {
spec.AddSnippet(gpioSnippet)
}
return nil
}
func (iface *boolFileInterface) AppArmorConnectedPlug(spec *apparmor.Specification, plug *interfaces.ConnectedPlug, slot *interfaces.ConnectedSlot) error {
// Allow write and lock on the file designated by the path.
// Dereference symbolic links to file path handed out to apparmor since
// sysfs is full of symlinks and apparmor requires uses real path for
// filtering.
path, err := iface.dereferencedPath(slot)
if err != nil {
return fmt.Errorf("cannot compute plug security snippet: %v", err)
}
spec.AddSnippet(fmt.Sprintf("%s rwk,", path))
// Provide read/write access to trigger, delay_on and delay_off kernel files
if boolFileLedPattern.MatchString(path) {
pathDir := filepath.Dir(path)
spec.AddSnippet(fmt.Sprintf("%s/trigger rw,", pathDir))
spec.AddSnippet(fmt.Sprintf("%s/delay_on rw,", pathDir))
spec.AddSnippet(fmt.Sprintf("%s/delay_off rw,", pathDir))
}
return nil
}
func (iface *boolFileInterface) dereferencedPath(slot *interfaces.ConnectedSlot) (string, error) {
var path string
if err := slot.Attr("path", &path); err == nil {
path, err = evalSymlinks(path)
if err != nil {
return "", err
}
return filepath.Clean(path), nil
}
panic("slot is not sanitized")
}
// isGPIO checks if a given bool-file slot refers to a GPIO pin.
func (iface *boolFileInterface) isGPIO(slot *snap.SlotInfo) bool {
var path string
if err := slot.Attr("path", &path); err == nil {
path = filepath.Clean(path)
return boolFileGPIOValuePattern.MatchString(path)
}
panic("slot is not sanitized")
}
// AutoConnect returns whether plug and slot should be implicitly
// auto-connected assuming they will be an unambiguous connection
// candidate and declaration-based checks allow.
//
// By default we allow what declarations allowed.
func (iface *boolFileInterface) AutoConnect(*snap.PlugInfo, *snap.SlotInfo) bool {
return true
}
func init() {
registerIface(&boolFileInterface{})
}
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