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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 (
"fmt"
"regexp"
"github.com/snapcore/snapd/interfaces"
"github.com/snapcore/snapd/interfaces/seccomp"
"github.com/snapcore/snapd/snap"
)
const netlinkDriverSummary = `allows operating a kernel driver module exposing itself via a netlink protocol family`
const netlinkDriverBaseDeclarationSlots = `
netlink-driver:
allow-installation:
slot-snap-type:
- core
- gadget
deny-auto-connection: true
`
// netlinkDriverInterface type
type netlinkDriverInterface struct {
commonInterface
}
const netlinkDriverConnectedPlugApparmor = `
# allow accessing the Linux kernel custom netlink protocol
# this allows all netlink protocol communication - further
# confinement for particular families/protocols is
# implemented via seccomp filtering
network netlink,
# CAP_NET_ADMIN required per 'man 7 netlink'
capability net_admin,
`
// regex for family-name must match:
// - at least 2 characters long
// - must start with letter
// - must not end in a hyphen
// - can contain numbers, letters and hyphens for all character positions except
// as described above
var familyNameRegexp = regexp.MustCompile(`^[a-z]+[a-z0-9-]*[^\-]$`)
// BeforePrepareSlot checks the slot definition is valid
func (iface *netlinkDriverInterface) BeforePrepareSlot(slot *snap.SlotInfo) error {
// Must have a protocol number identified as family
number, ok := slot.Attrs["family"]
if !ok {
return fmt.Errorf("netlink-driver slot must have a family number attribute")
}
// Valid values of number
if _, ok := number.(int64); !ok {
return fmt.Errorf("netlink-driver slot family number attribute must be an int")
}
// must also have a family-name, used for identifying plug <-> slot
return validateFamilyNameAttr(slot, "slot")
}
func validateFamilyNameAttr(a interfaces.Attrer, side string) error {
name, ok := a.Lookup("family-name")
if !ok {
return fmt.Errorf("netlink-driver %s must have a family-name attribute", side)
}
nameStr, ok := name.(string)
if !ok {
return fmt.Errorf("netlink-driver %s family-name attribute must be a string", side)
}
// ensure it matches the regex
if !familyNameRegexp.MatchString(nameStr) {
return fmt.Errorf("netlink-driver %s family-name %q is invalid", side, nameStr)
}
// attribute is good
return nil
}
// BeforePreparePlug checks the plug definition is valid
func (iface *netlinkDriverInterface) BeforePreparePlug(plug *snap.PlugInfo) error {
return validateFamilyNameAttr(plug, "plug")
}
func (iface *netlinkDriverInterface) SecCompConnectedPlug(spec *seccomp.Specification, plug *interfaces.ConnectedPlug, slot *interfaces.ConnectedSlot) error {
var familyNum int64
if err := slot.Attr("family", &familyNum); err != nil {
return err
}
var familyName string
if err := slot.Attr("family-name", &familyName); err != nil {
return err
}
spec.AddSnippet(fmt.Sprintf(`# Description: Can access the Linux kernel custom netlink protocol
# for family %s
socket AF_NETLINK - %d
bind`, familyName, familyNum))
return nil
}
func (iface *netlinkDriverInterface) AutoConnect(plug *snap.PlugInfo, slot *snap.SlotInfo) bool {
// ensure that the family name on the plug side matches the family name
// on the slot side
var slotFamily, plugFamily string
if err := plug.Attr("family-name", &plugFamily); err != nil {
return false
}
if err := slot.Attr("family-name", &slotFamily); err != nil {
return false
}
return slotFamily == plugFamily
}
func init() {
registerIface(&netlinkDriverInterface{
commonInterface: commonInterface{
name: "netlink-driver",
summary: netlinkDriverSummary,
baseDeclarationSlots: netlinkDriverBaseDeclarationSlots,
connectedPlugAppArmor: netlinkDriverConnectedPlugApparmor,
},
})
}
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