tailscale/safesocket/unixsocket.go

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// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build !windows && !js
// +build !windows,!js
package safesocket
import (
"errors"
"fmt"
"io"
"log"
"net"
"os"
"os/exec"
"path/filepath"
"runtime"
"strconv"
)
// TODO(apenwarr): handle magic cookie auth
func connect(s *ConnectionStrategy) (net.Conn, error) {
if runtime.GOOS == "js" {
return nil, errors.New("safesocket.Connect not yet implemented on js/wasm")
}
if runtime.GOOS == "darwin" && s.fallback && s.path == "" && s.port == 0 {
return connectMacOSAppSandbox()
}
pipe, err := net.Dial("unix", s.path)
if err != nil {
if runtime.GOOS == "darwin" && s.fallback {
extConn, extErr := connectMacOSAppSandbox()
if extErr != nil {
return nil, fmt.Errorf("safesocket: failed to connect to %v: %v; failed to connect to Tailscale IPNExtension: %v", s.path, err, extErr)
}
return extConn, nil
}
return nil, err
}
return pipe, nil
}
// TODO(apenwarr): handle magic cookie auth
func listen(path string, port uint16) (ln net.Listener, _ uint16, err error) {
// Unix sockets hang around in the filesystem even after nobody
// is listening on them. (Which is really unfortunate but long-
// entrenched semantics.) Try connecting first; if it works, then
// the socket is still live, so let's not replace it. If it doesn't
// work, then replace it.
//
// Note that there's a race condition between these two steps. A
// "proper" daemon usually uses a dance involving pidfiles to first
// ensure that no other instances of itself are running, but that's
// beyond the scope of our simple socket library.
c, err := net.Dial("unix", path)
if err == nil {
c.Close()
if tailscaledRunningUnderLaunchd() {
return nil, 0, fmt.Errorf("%v: address already in use; tailscaled already running under launchd (to stop, run: $ sudo launchctl stop com.tailscale.tailscaled)", path)
}
return nil, 0, fmt.Errorf("%v: address already in use", path)
}
_ = os.Remove(path)
perm := socketPermissionsForOS()
sockDir := filepath.Dir(path)
if _, err := os.Stat(sockDir); os.IsNotExist(err) {
os.MkdirAll(sockDir, 0755) // best effort
// If we're on a platform where we want the socket
// world-readable, open up the permissions on the
// just-created directory too, in case a umask ate
// it. This primarily affects running tailscaled by
// hand as root in a shell, as there is no umask when
// running under systemd.
if perm == 0666 {
if fi, err := os.Stat(sockDir); err == nil && fi.Mode()&0077 == 0 {
if err := os.Chmod(sockDir, 0755); err != nil {
log.Print(err)
}
}
}
}
pipe, err := net.Listen("unix", path)
if err != nil {
return nil, 0, err
}
os.Chmod(path, perm)
return pipe, 0, err
}
func tailscaledRunningUnderLaunchd() bool {
if runtime.GOOS != "darwin" {
return false
}
plist, err := exec.Command("launchctl", "list", "com.tailscale.tailscaled").Output()
_ = plist // parse it? https://github.com/DHowett/go-plist if we need something.
running := err == nil
return running
}
// socketPermissionsForOS returns the permissions to use for the
// tailscaled.sock.
func socketPermissionsForOS() os.FileMode {
if PlatformUsesPeerCreds() {
return 0666
}
// Otherwise, root only.
return 0600
}
// connectMacOSAppSandbox connects to the Tailscale Network Extension (macOS App
// Store build) or App Extension (macsys standalone build), where the CLI itself
// is either running within the macOS App Sandbox or built separately (e.g.
// homebrew or go install). This little dance to connect a regular user binary
// to the sandboxed network extension is:
//
// * the sandboxed IPNExtension picks a random localhost:0 TCP port
// to listen on
// * it also picks a random hex string that acts as an auth token
// * the CLI looks on disk for that TCP port + auth token (see localTCPPortAndTokenDarwin)
// * we send it upon TCP connect to prove to the Tailscale daemon that
// we're a suitably privileged user to have access the files on disk
// which the Network/App Extension wrote.
func connectMacOSAppSandbox() (net.Conn, error) {
port, token, err := LocalTCPPortAndToken()
if err != nil {
return nil, fmt.Errorf("failed to find local Tailscale daemon: %w", err)
}
return connectMacTCP(port, token)
}
// connectMacTCP creates an authenticated net.Conn to the local macOS Tailscale
// daemon for used by the "IPN" JSON message bus protocol (Tailscale's original
// local non-HTTP IPC protocol).
func connectMacTCP(port int, token string) (net.Conn, error) {
c, err := net.Dial("tcp", "localhost:"+strconv.Itoa(port))
if err != nil {
return nil, fmt.Errorf("error dialing IPNExtension: %w", err)
}
if _, err := io.WriteString(c, token+"\n"); err != nil {
return nil, fmt.Errorf("error writing auth token: %w", err)
}
buf := make([]byte, 5)
const authOK = "#IPN\n"
if _, err := io.ReadFull(c, buf); err != nil {
return nil, fmt.Errorf("error reading from IPNExtension post-auth: %w", err)
}
if string(buf) != authOK {
return nil, fmt.Errorf("invalid response reading from IPNExtension post-auth")
}
return c, nil
}