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|
package main
import (
"encoding/json"
"log"
"os"
"os/exec"
"os/signal"
"os/user"
"strconv"
"syscall"
"github.com/kardianos/osext"
)
const daemonRunProgram = "daemon-run"
func daemonMain() {
if os.Args[0] != daemonRunProgram {
return
}
log.Printf("Starting the daemon as unprivileged user (uid: %d, gid: %d)...", syscall.Getuid(), syscall.Getgid())
// read the configuration from the pipe "ExtraFiles"
var config appConfig
if err := json.NewDecoder(os.NewFile(3, "options")).Decode(&config); err != nil {
log.Fatalln(err)
}
runApp(config)
os.Exit(0)
}
func daemonReexec(cmdUser string, args ...string) (cmd *exec.Cmd, err error) {
path, err := osext.Executable()
if err != nil {
return
}
u, err := user.Lookup(cmdUser)
if err != nil {
return
}
uid, err := strconv.Atoi(u.Uid)
if err != nil {
return
}
gid, err := strconv.Atoi(u.Gid)
if err != nil {
return
}
cmd = &exec.Cmd{
Path: path,
Args: args,
Stdin: os.Stdin,
Stdout: os.Stdout,
Stderr: os.Stderr,
SysProcAttr: &syscall.SysProcAttr{
Credential: &syscall.Credential{
Uid: uint32(uid),
Gid: uint32(gid),
},
Setsid: true,
},
}
return
}
func daemonUpdateFd(cmd *exec.Cmd, fd *uintptr) {
if *fd == 0 {
return
}
file := os.NewFile(*fd, "[socket]")
// we add 3 since, we have a 3 predefined FDs
*fd = uintptr(3 + len(cmd.ExtraFiles))
cmd.ExtraFiles = append(cmd.ExtraFiles, file)
}
func killProcess(cmd *exec.Cmd) {
if cmd.Process != nil {
cmd.Process.Kill()
}
cmd.Wait()
for _, file := range cmd.ExtraFiles {
file.Close()
}
}
func passSignals(cmd *exec.Cmd) {
if cmd.Process == nil {
return
}
s := make(chan os.Signal)
signal.Notify(s, syscall.SIGTERM, os.Interrupt, os.Kill)
go func() {
for cmd.Process != nil {
cmd.Process.Signal(<-s)
}
}()
}
func daemonize(config appConfig, cmdUser string) {
var err error
defer func() {
if err != nil {
log.Fatalln(err)
}
}()
log.Printf("Running the daemon as unprivileged user: %v...", cmdUser)
cmd, err := daemonReexec(cmdUser, daemonRunProgram)
if err != nil {
return
}
defer killProcess(cmd)
// Create a pipe to pass the configuration
configReader, configWriter, err := os.Pipe()
if err != nil {
return
}
defer configWriter.Close()
cmd.ExtraFiles = append(cmd.ExtraFiles, configReader)
// Create a new file and store the FD
daemonUpdateFd(cmd, &config.ListenHTTP)
daemonUpdateFd(cmd, &config.ListenHTTPS)
daemonUpdateFd(cmd, &config.listenProxy)
// Start the process
if err = cmd.Start(); err != nil {
return
}
// Write the configuration
if err = json.NewEncoder(configWriter).Encode(config); err != nil {
return
}
configWriter.Close()
// Pass through signals
passSignals(cmd)
// Wait for process to exit
err = cmd.Wait()
}
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