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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2015-2024 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 daemon
import (
"errors"
"fmt"
"net"
"regexp"
"strconv"
"strings"
"sync"
sys "syscall"
"github.com/snapcore/snapd/strutil"
)
var errNoID = errors.New("no pid/uid found")
const (
ucrednetNoProcess = int32(0)
ucrednetNobody = uint32((1 << 32) - 1)
)
var raddrRegexp = regexp.MustCompile(`^pid=(\d+);uid=(\d+);socket=([^;]*);(iface=([^;]*);)?$`)
var ucrednetGet = ucrednetGetImpl
var ucrednetGetWithInterfaces = ucrednetGetWithInterfacesImpl
func ucrednetGetImpl(remoteAddr string) (*ucrednet, error) {
uc, _, err := ucrednetGetWithInterfaces(remoteAddr)
return uc, err
}
func ucrednetGetWithInterfacesImpl(remoteAddr string) (ucred *ucrednet, ifaces []string, err error) {
// NOTE treat remoteAddr at one point included a user-controlled
// string. In case that happens again by accident, treat it as tainted,
// and be very suspicious of it.
u := &ucrednet{
Pid: ucrednetNoProcess,
Uid: ucrednetNobody,
}
subs := raddrRegexp.FindStringSubmatch(remoteAddr)
if subs != nil {
if v, err := strconv.ParseInt(subs[1], 10, 32); err == nil {
u.Pid = int32(v)
}
if v, err := strconv.ParseUint(subs[2], 10, 32); err == nil {
u.Uid = uint32(v)
}
// group: ([^;]*) - socket path following socket=
u.Socket = subs[3]
// group: (iface=([^;]*);)
if len(subs[4]) > 0 {
// group: ([^;]*) - actual interfaces joined together with & separator
ifaces = strings.Split(subs[5], "&")
}
}
if u.Pid == ucrednetNoProcess || u.Uid == ucrednetNobody {
return nil, nil, errNoID
}
return u, ifaces, nil
}
func ucrednetAttachInterface(remoteAddr, iface string) string {
inds := raddrRegexp.FindStringSubmatchIndex(remoteAddr)
if inds == nil {
// This should only occur if remoteAddr is invalid.
return fmt.Sprintf("%siface=%s;", remoteAddr, iface)
}
// start of string matching group "(iface=([^;]*);)"
ifaceSubStart := inds[8]
ifaceSubEnd := inds[9]
if ifaceSubStart == ifaceSubEnd {
// "(iface=([^;]*);)" not present.
return fmt.Sprintf("%siface=%s;", remoteAddr, iface)
}
// string matching group "([^;]*)" within "(iface=([^;]*);)"
ifacesStr := remoteAddr[inds[10]:inds[11]]
ifaces := strings.Split(ifacesStr, "&")
if strutil.ListContains(ifaces, iface) {
return remoteAddr
}
ifaces = append(ifaces, iface)
return fmt.Sprintf("%siface=%s;", remoteAddr[:ifaceSubStart], strings.Join(ifaces, "&"))
}
type ucrednet struct {
Pid int32
Uid uint32
Socket string
}
func (un *ucrednet) String() string {
if un == nil {
return "pid=;uid=;socket=;"
}
return fmt.Sprintf("pid=%d;uid=%d;socket=%s;", un.Pid, un.Uid, un.Socket)
}
type ucrednetAddr struct {
net.Addr
*ucrednet
}
func (wa *ucrednetAddr) String() string {
// NOTE we drop the original (user-supplied) net.Addr from the
// serialization entirely. We carry it this far so it helps debugging
// (via %#v logging), but from here on in it's not helpful.
return wa.ucrednet.String()
}
type ucrednetConn struct {
net.Conn
*ucrednet
}
func (wc *ucrednetConn) RemoteAddr() net.Addr {
return &ucrednetAddr{wc.Conn.RemoteAddr(), wc.ucrednet}
}
type ucrednetListener struct {
net.Listener
idempotClose sync.Once
closeErr error
}
var getUcred = sys.GetsockoptUcred
func (wl *ucrednetListener) Accept() (net.Conn, error) {
con, err := wl.Listener.Accept()
if err != nil {
return nil, err
}
var unet *ucrednet
if ucon, ok := con.(*net.UnixConn); ok {
syscallConn, err := ucon.SyscallConn()
if err != nil {
return nil, err
}
var ucred *sys.Ucred
scErr := syscallConn.Control(func(fd uintptr) {
ucred, err = getUcred(int(fd), sys.SOL_SOCKET, sys.SO_PEERCRED)
})
if scErr != nil {
return nil, scErr
}
if err != nil {
return nil, err
}
unet = &ucrednet{
Pid: ucred.Pid,
Uid: ucred.Uid,
Socket: ucon.LocalAddr().String(),
}
}
return &ucrednetConn{con, unet}, nil
}
func (wl *ucrednetListener) Close() error {
wl.idempotClose.Do(func() {
wl.closeErr = wl.Listener.Close()
})
return wl.closeErr
}
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