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gojail.go
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gojail.go
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// SPDX-License-Identifier: BSD-2-Clause-FreeBSD
//
// Copyright (c) 2020 Florian Limberger <flo@purplekraken.com>
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
// OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
// OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
// SUCH DAMAGE.
package gojail // import "purplekraken.com/pkg/gojail"
import (
"fmt"
"net"
"os"
"strconv"
sys "syscall"
"golang.org/x/sys/unix"
"purplekraken.com/pkg/gojail/syscall"
)
const (
errmsglen = 1024
maxnamelen = 256 // MAXHOSTNAMELEN on FreeBSD, defined in include/sys/param.h
)
type Flags int
const (
CreateFlag Flags = syscall.JAIL_CREATE
UpdateFlag Flags = syscall.JAIL_UPDATE
AttachFlag Flags = syscall.JAIL_ATTACH
AllowDyingFlag Flags = syscall.JAIL_DYING
)
type ParamType int
const (
String ParamType = 0
Int ParamType = 1
Raw ParamType = 2
)
type JailParam interface {
Name() []byte
Data() []byte
Type() ParamType
}
type jailParam struct {
name []byte
data []byte
ptype ParamType
}
func (jp jailParam) Name() []byte {
return jp.name
}
func (jp jailParam) Data() []byte {
return jp.data
}
func (jp jailParam) Type() ParamType {
return jp.ptype
}
func NewStringParam(name, value string) (JailParam, error) {
nameb, err := unix.ByteSliceFromString(name)
if err != nil {
return nil, err
}
valueb, err := unix.ByteSliceFromString(value)
if err != nil {
return nil, err
}
return jailParam{
name: nameb,
data: valueb,
ptype: String,
}, nil
}
func NewIntParam(name string, value int) (JailParam, error) {
nameb, err := unix.ByteSliceFromString(name)
if err != nil {
return nil, err
}
buf := make([]byte, 4)
hostByteOrder.PutUint32(buf, uint32(value))
return jailParam{
name: nameb,
data: buf,
ptype: Int,
}, nil
}
// TODO: The IP must be added to some interface
// otherwise is just an IP :)
// inet 192.168.0.222 netmask 0xffffffff broadcast 192.168.0.222
func NewIPParam(value string) (JailParam, error) {
ip := net.ParseIP(value)
if ip == nil {
return nil, fmt.Errorf("Invalid IP address provided")
}
var nameb []byte
var buf []byte
if ip4 := ip.To4(); ip4 != nil {
nameb = byteSliceFromStringOrDie("ip4.addr")
buf = ip4
} else {
nameb = byteSliceFromStringOrDie("ip6.addr")
buf = ip
}
return jailParam{
name: nameb,
data: buf,
ptype: Raw,
}, nil
}
// Error message from the jail subsystem.
// Represents an error returned as the "errmsg" parameter from JailGet or JailSet.
type JailErr struct {
errmsg string
}
func (je *JailErr) Error() string {
return je.errmsg
}
// Error returned by GetId and GetName if the specified jail does not exist.
var NoJail error = &JailErr{errmsg: "No such jail"}
func makeJailErr(errmsg []byte) error {
return &JailErr{
errmsg: string(errmsg),
}
}
func byteSliceFromStringOrDie(s string) []byte {
b, err := unix.ByteSliceFromString(s)
if err != nil {
panic(err)
}
return b
}
func intToBytes(i int) []byte {
b := make([]byte, 4)
hostByteOrder.PutUint32(b, uint32(i))
return b
}
// Converts errno to an instance of os.SyscallError using errno if retval is
// not zero.
func asSyscallError(name string, err error) error {
if err != nil {
if errno, ok := err.(sys.Errno); ok {
err = os.NewSyscallError(name, errno)
}
}
return err
}
// Returns the JID of the jail identified by name, -1 if it doesn't exist.
func GetId(name string) (int, error) {
var iov [4][]byte
if jid, err := strconv.Atoi(name); err == nil {
if jid == 0 {
return jid, nil
}
iov[0] = byteSliceFromStringOrDie("jid")
iov[1] = intToBytes(jid)
} else {
iov[0] = byteSliceFromStringOrDie("name")
iov[1], err = unix.ByteSliceFromString(name)
if err != nil {
return -1, err
}
}
iov[2] = byteSliceFromStringOrDie("errmsg")
iov[3] = make([]byte, errmsglen)
jid, err := syscall.JailGet(iov[:], 0)
if err != nil {
// The jail does not exist, but that is not really an error.
// Checking the kind of error is tedious for the users, so
// differentiate here.
// Attention: jail_get(2) returns ENOENT on three occasions:
// 1. The jail referred to by a jid or name parameter does
// not exist.
// 2. The jail referred to by a jid is not accessible by the
// process, because the process is in a different jail.
// 3. The lastjid parameter is greater than the highest
// current jail ID.
// We don't care for the second case, because the situation
// is equivalent to the first case, for processes in a jail
// other jails do not exist, but we need to be careful with
// the third case.
// In this function, there is no "lastjid" parameter, so
// everything is fine, but this is not the general case.
if syserr, ok := err.(sys.Errno); ok && syserr == sys.ENOENT {
err = NoJail
} else {
err = asSyscallError("jail_get", err)
}
} else if jid == -1 && iov[3][0] != 0 {
err = makeJailErr(iov[3])
}
return jid, err
}
// Returns the name of the jail identified by jid.
func GetName(jid int) (string, error) {
var iov [6][]byte
iov[0] = byteSliceFromStringOrDie("jid")
iov[1] = intToBytes(jid)
iov[2] = byteSliceFromStringOrDie("name")
iov[3] = make([]byte, maxnamelen)
iov[4] = byteSliceFromStringOrDie("errmsg")
iov[5] = make([]byte, errmsglen)
jid, err := syscall.JailGet(iov[:], 0)
if err != nil {
if syserr, ok := err.(sys.Errno); ok && syserr == sys.ENOENT {
err = NoJail
} else {
err = asSyscallError("jail_get", err)
}
} else if jid == -1 && iov[5][0] != 00 {
err = makeJailErr(iov[5])
}
return string(iov[3]), err
}
// Attach the current process to the jail identified by jid.
// See jail_attach(2) for further information.
func Attach(jid int) error {
return asSyscallError("jail_attach", syscall.JailAttach(jid))
}
// Remove the jail idenified by jid.
// See jail_remove(2) for further information.
func Remove(jid int) error {
return asSyscallError("jail_remove", syscall.JailRemove(jid))
}
func paramsToBytes(ps []JailParam) [][]byte {
bs := make([][]byte, len(ps)*2)
for pi, p := range ps {
bi := pi * 2
bs[bi] = p.Name()
bs[bi+1] = p.Data()
}
return bs
}
func SetParams(params []JailParam, flags Flags) (int, error) {
p := paramsToBytes(params)
jid, err := syscall.JailSet(p, int(flags))
return jid, asSyscallError("jail_set", err)
}
func GetParams(params []JailParam, flags Flags) (int, error) {
p := paramsToBytes(params)
jid, err := syscall.JailGet(p, int(flags))
return jid, asSyscallError("jail_get", err)
}