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package main
import (
"encoding/json"
"os"
"os/exec"
"os/signal"
"syscall"
"github.com/kardianos/osext"
log "github.com/sirupsen/logrus"
"gitlab.com/gitlab-org/gitlab-pages/internal/jail"
)
const (
daemonRunProgram = "gitlab-pages-unprivileged"
pagesRootInChroot = "/pages"
)
func daemonMain() {
if os.Args[0] != daemonRunProgram {
return
}
log.WithFields(log.Fields{
"uid": syscall.Getuid(),
"gid": syscall.Getgid(),
}).Info("starting the daemon as unprivileged user")
// read the configuration from the pipe "ExtraFiles"
var config appConfig
if err := json.NewDecoder(os.NewFile(3, "options")).Decode(&config); err != nil {
fatal(err)
}
runApp(config)
os.Exit(0)
}
func daemonReexec(uid, gid uint, args ...string) (cmd *exec.Cmd, err error) {
path, err := osext.Executable()
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) (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)
signal.Notify(s, syscall.SIGTERM, os.Interrupt, os.Kill)
go func() {
for cmd.Process != nil {
cmd.Process.Signal(<-s)
}
}()
}
func daemonChroot(cmd *exec.Cmd) (*jail.Jail, error) {
cage := jail.TimestampedJail("gitlab-pages", 0755)
wd, err := os.Getwd()
if err != nil {
return nil, err
}
// Add gitlab-pages inside the jail
err = cage.CopyTo("/gitlab-pages", cmd.Path)
if err != nil {
return nil, err
}
// Add /etc/resolv.conf inside the jail
cage.MkDir("/etc", 0755)
err = cage.Copy("/etc/resolv.conf")
if err != nil {
return nil, err
}
// Copy SSL_CERT_FILE inside the jail
sslCertFile := os.Getenv("SSL_CERT_FILE")
if sslCertFile != "" {
cage.MkDir("/etc/ssl", 0755)
err = cage.CopyTo("/etc/ssl/ca-bundle.pem", sslCertFile)
if err != nil {
return nil, err
}
cmd.Env = append(os.Environ(), "SSL_CERT_FILE=/etc/ssl/ca-bundle.pem")
} else {
log.Print("Missing SSL_CERT_FILE environment variable. HTTPS requests will fail")
}
// Bind mount shared folder
cage.MkDir(pagesRootInChroot, 0755)
cage.Bind(pagesRootInChroot, wd)
// Update command to use chroot
cmd.SysProcAttr.Chroot = cage.Path()
cmd.Path = "/gitlab-pages"
cmd.Dir = pagesRootInChroot
err = cage.Build()
if err != nil {
return nil, err
}
return cage, nil
}
func daemonize(config appConfig, uid, gid uint) {
var err error
defer func() {
if err != nil {
fatal(err)
}
}()
log.WithFields(log.Fields{
"uid": uid,
"gid": gid,
}).Info("running the daemon as unprivileged user")
cmd, err := daemonReexec(uid, gid, daemonRunProgram)
if err != nil {
return
}
defer killProcess(cmd)
// Run daemon in chroot environment
chroot, err := daemonChroot(cmd)
if err != nil {
log.WithError(err).Print("chroot failed")
return
}
defer chroot.Dispose()
// 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 for each listener
daemonUpdateFds(cmd, config.ListenHTTP)
daemonUpdateFds(cmd, config.ListenHTTPS)
daemonUpdateFds(cmd, config.ListenProxy)
if config.ListenMetrics != 0 {
config.ListenMetrics = daemonUpdateFd(cmd, config.ListenMetrics)
}
// Start the process
if err = cmd.Start(); err != nil {
log.WithError(err).Error("start failed")
return
}
//detach binded mountpoints
if err = chroot.LazyUnbind(); err != nil {
log.WithError(err).Print("chroot lazy umount failed")
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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