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package main
import (
"encoding/json"
"os"
"os/exec"
"os/signal"
"path/filepath"
"strings"
"syscall"
"github.com/sirupsen/logrus"
"gitlab.com/gitlab-org/gitlab-pages/internal/config"
)
const (
daemonRunProgram = "gitlab-pages-unprivileged"
)
func daemonMain() {
if os.Args[0] != daemonRunProgram {
return
}
// Validate that a working directory is valid
// https://man7.org/linux/man-pages/man2/getcwd.2.html
wd, err := os.Getwd()
if err != nil {
fatal(err, "could not get current working directory")
} else if strings.HasPrefix(wd, "(unreachable)") {
fatal(os.ErrPermission, "could not get current working directory")
}
logrus.WithFields(logrus.Fields{
"uid": syscall.Getuid(),
"gid": syscall.Getgid(),
"wd": wd,
}).Info("starting the daemon as unprivileged user")
// read the configuration from the pipe "ExtraFiles"
var config config.Config
if err := json.NewDecoder(os.NewFile(3, "options")).Decode(&config); err != nil {
fatal(err, "could not decode app config")
}
runApp(&config)
os.Exit(0)
}
func daemonReexec(uid, gid uint, args ...string) (cmd *exec.Cmd, err error) {
path, err := os.Executable()
if err != nil {
return
}
cmd = &exec.Cmd{
Path: path,
Args: args,
Env: os.Environ(),
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) (childFd uintptr) {
file := os.NewFile(fd, "[socket]")
// we add 3 since, we have a 3 predefined FDs
childFd = uintptr(3 + len(cmd.ExtraFiles))
cmd.ExtraFiles = append(cmd.ExtraFiles, file)
return
}
func daemonUpdateFds(cmd *exec.Cmd, fds []uintptr) {
for idx, fd := range fds {
fds[idx] = daemonUpdateFd(cmd, fd)
}
}
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, 1)
signal.Notify(s, syscall.SIGTERM, os.Interrupt, os.Kill)
go func() {
for cmd.Process != nil {
cmd.Process.Signal(<-s)
}
}()
}
func daemonize(config *config.Config) error {
uid := config.Daemon.UID
gid := config.Daemon.GID
pagesRoot := config.General.RootDir
// Ensure pagesRoot is an absolute path. This will produce a different path
// if any component of pagesRoot is a symlink (not likely). For example,
// -pages-root=/some-path where ln -s /other-path /some-path
// pagesPath will become: /other-path and we will fail to serve files from /some-path.
// GitLab Rails also resolves the absolute path for `pages_path`
// https://gitlab.com/gitlab-org/gitlab/blob/981ad651d8bd3690e28583eec2363a79f775af89/config/initializers/1_settings.rb#L296
pagesRoot, err := filepath.Abs(pagesRoot)
if err != nil {
return err
}
logrus.WithFields(logrus.Fields{
"uid": uid,
"gid": gid,
"pages-root": pagesRoot,
}).Info("running the daemon as unprivileged user")
cmd, err := daemonReexec(uid, gid, daemonRunProgram)
if err != nil {
return err
}
defer killProcess(cmd)
// Create a pipe to pass the configuration
configReader, configWriter, err := os.Pipe()
if err != nil {
return err
}
defer configWriter.Close()
cmd.ExtraFiles = append(cmd.ExtraFiles, configReader)
updateFds(config, cmd)
// Start the process
if err := cmd.Start(); err != nil {
logrus.WithError(err).Error("start failed")
return err
}
// Write the configuration
if err := json.NewEncoder(configWriter).Encode(config); err != nil {
return err
}
configWriter.Close()
// Pass through signals
passSignals(cmd)
// Wait for process to exit
return cmd.Wait()
}
func updateFds(config *config.Config, cmd *exec.Cmd) {
for _, fds := range [][]uintptr{
config.Listeners.HTTP,
config.Listeners.HTTPS,
config.Listeners.Proxy,
config.Listeners.HTTPSProxyv2,
} {
daemonUpdateFds(cmd, fds)
}
for _, fdPtr := range []*uintptr{
&config.ListenMetrics,
} {
if *fdPtr != 0 {
*fdPtr = daemonUpdateFd(cmd, *fdPtr)
}
}
}
|
