/
kernel_module_load.go
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/
kernel_module_load.go
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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2021 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 (
"errors"
"fmt"
"regexp"
"strings"
"github.com/snapcore/snapd/interfaces"
"github.com/snapcore/snapd/interfaces/kmod"
"github.com/snapcore/snapd/snap"
)
const kernelModuleLoadSummary = `allows constrained control over kernel module loading`
const kernelModuleLoadBaseDeclarationPlugs = `
kernel-module-load:
allow-installation: false
deny-auto-connection: true
`
const kernelModuleLoadBaseDeclarationSlots = `
kernel-module-load:
allow-installation:
slot-snap-type:
- core
deny-connection: true
`
var modulesAttrTypeError = errors.New(`kernel-module-load "modules" attribute must be a list of dictionaries`)
// kernelModuleLoadInterface allows creating transient and persistent modules
type kernelModuleLoadInterface struct {
commonInterface
}
type loadOption int
const (
loadNone loadOption = iota
loadDenied
loadOnBoot
loadDynamic
)
type ModuleInfo struct {
name string
load loadOption
options string
}
var kernelModuleNameRegexp = regexp.MustCompile(`^[-a-zA-Z0-9_]+$`)
var kernelModuleOptionsRegexp = regexp.MustCompile(`^([a-zA-Z][a-zA-Z0-9_]*(=[[:graph:]]+)? *)+$`)
func enumerateModules(plug interfaces.Attrer, handleModule func(moduleInfo *ModuleInfo) error) error {
var modules []map[string]interface{}
err := plug.Attr("modules", &modules)
if err != nil && !errors.Is(err, snap.AttributeNotFoundError{}) {
return modulesAttrTypeError
}
for _, module := range modules {
name, ok := module["name"].(string)
if !ok {
return errors.New(`kernel-module-load "name" must be a string`)
}
var load loadOption
if loadAttr, found := module["load"]; found {
loadString, ok := loadAttr.(string)
if !ok {
return errors.New(`kernel-module-load "load" must be a string`)
}
switch loadString {
case "denied":
load = loadDenied
case "on-boot":
load = loadOnBoot
case "dynamic":
load = loadDynamic
default:
return fmt.Errorf(`kernel-module-load "load" value is unrecognized: %q`, loadString)
}
}
var options string
if optionsAttr, found := module["options"]; found {
options, ok = optionsAttr.(string)
if !ok {
return errors.New(`kernel-module-load "options" must be a string`)
}
}
moduleInfo := &ModuleInfo{
name: name,
load: load,
options: options,
}
if err := handleModule(moduleInfo); err != nil {
return err
}
}
return nil
}
func validateNameAttr(name string) error {
if !kernelModuleNameRegexp.MatchString(name) {
return errors.New(`kernel-module-load "name" attribute is not a valid module name`)
}
return nil
}
func validateOptionsAttr(moduleInfo *ModuleInfo) error {
if moduleInfo.options == "" {
return nil
}
if moduleInfo.load == loadDenied {
return errors.New(`kernel-module-load "options" attribute incompatible with "load: denied"`)
}
dynamicLoadingWithAnyOptions := moduleInfo.load == loadDynamic && moduleInfo.options == "*"
if !dynamicLoadingWithAnyOptions && !kernelModuleOptionsRegexp.MatchString(moduleInfo.options) {
return fmt.Errorf(`kernel-module-load "options" attribute contains invalid characters: %q`, moduleInfo.options)
}
return nil
}
func validateModuleInfo(moduleInfo *ModuleInfo) error {
if err := validateNameAttr(moduleInfo.name); err != nil {
return err
}
if err := validateOptionsAttr(moduleInfo); err != nil {
return err
}
if moduleInfo.options == "" && moduleInfo.load == loadNone {
return errors.New(`kernel-module-load: must specify at least "load" or "options"`)
}
return nil
}
func (iface *kernelModuleLoadInterface) BeforeConnectPlug(plug *interfaces.ConnectedPlug) error {
numModulesEntries := 0
err := enumerateModules(plug, func(moduleInfo *ModuleInfo) error {
numModulesEntries++
return validateModuleInfo(moduleInfo)
})
if err != nil {
return err
}
if numModulesEntries == 0 {
return modulesAttrTypeError
}
return nil
}
func (iface *kernelModuleLoadInterface) KModConnectedPlug(spec *kmod.Specification, plug *interfaces.ConnectedPlug, slot *interfaces.ConnectedSlot) error {
snapInfo := plug.Snap()
commonDataDir := snapInfo.CommonDataDir()
err := enumerateModules(plug, func(moduleInfo *ModuleInfo) error {
var err error
switch moduleInfo.load {
case loadDenied:
err = spec.DisallowModule(moduleInfo.name)
case loadOnBoot:
err = spec.AddModule(moduleInfo.name)
if err != nil {
break
}
fallthrough
case loadNone, loadDynamic:
if len(moduleInfo.options) > 0 && moduleInfo.options != "*" {
// module options might include filesystem paths. Beside
// supporting hardcoded paths, it makes sense to support also
// paths to files provided by the snap; for this reason, we
// support expanding the $SNAP_COMMON variable here.
// We do not use os.Expand() because that supports both $ENV
// and ${ENV}, and we'd rather not alter the options which
// contain a "$" but are not meant to be expanded. Instead,
// just look for the "$SNAP_COMMON/" string and replace it; the
// extra "/" at the end ensures that the variable is
// terminated.
options := strings.ReplaceAll(moduleInfo.options, "$SNAP_COMMON/", commonDataDir+"/")
err = spec.SetModuleOptions(moduleInfo.name, options)
}
default:
// we can panic, this will be catched on validation
panic("Unsupported module load option")
}
return err
})
return err
}
func (iface *kernelModuleLoadInterface) AutoConnect(*snap.PlugInfo, *snap.SlotInfo) bool {
return true
}
func init() {
registerIface(&kernelModuleLoadInterface{
commonInterface: commonInterface{
name: "kernel-module-load",
summary: kernelModuleLoadSummary,
baseDeclarationPlugs: kernelModuleLoadBaseDeclarationPlugs,
baseDeclarationSlots: kernelModuleLoadBaseDeclarationSlots,
implicitOnCore: true,
implicitOnClassic: true,
},
})
}