Execute in chroot

2 files changed, 88 insertions, 0 deletions

diff --git a/app.go b/app.go
index 4ab6a3e7..9157b8f2 100644
--- a/app.go
+++ b/app.go
@@ -26,6 +26,7 @@ func (a *theApp) domain(host string) *domain {
 	return domain
 }
 
+
 func (a *theApp) ServeTLS(ch *tls.ClientHelloInfo) (*tls.Certificate, error) {
 	if ch.ServerName == "" {
 		return nil, nil
diff --git a/daemon.go b/daemon.go
index f47b9703..2f8aee9d 100644
--- a/daemon.go
+++ b/daemon.go
@@ -1,16 +1,20 @@
 package main
 
 import (
+	"crypto/rand"
 	"encoding/json"
+	"fmt"
 	"log"
 	"os"
 	"os/exec"
 	"os/signal"
 	"os/user"
+	"path/filepath"
 	"strconv"
 	"syscall"
 
 	"github.com/kardianos/osext"
+	"io"
 )
 
 const daemonRunProgram = "gitlab-pages-unprivileged"
@@ -105,6 +109,79 @@ func passSignals(cmd *exec.Cmd) {
 	}()
 }
 
+func copyFile(dest, src string, perm os.FileMode) (err error) {
+	srcFile, err := os.Open(src)
+	if err != nil {
+		return
+	}
+	defer srcFile.Close()
+
+	destFile, err := os.OpenFile(dest, os.O_RDWR|os.O_CREATE|os.O_EXCL, perm)
+	if err != nil {
+		return
+	}
+	defer destFile.Close()
+
+	_, err = io.Copy(destFile, srcFile)
+	return
+}
+
+func daemonCreateExecutable(name string, perm os.FileMode) (file *os.File, err error) {
+	// We assume that crypto random generates true random, non-colliding hash
+	b := make([]byte, 16)
+	_, err = rand.Read(b)
+	if err != nil {
+		return
+	}
+
+	path := fmt.Sprintf("%s.%x", name, b)
+	file, err = os.OpenFile(path, os.O_RDWR|os.O_CREATE|os.O_EXCL, perm)
+	if err != nil {
+		return
+	}
+	return
+}
+
+func daemonChroot(cmd *exec.Cmd) (path string, err error) {
+	wd, err := os.Getwd()
+	if err != nil {
+		return
+	}
+
+	// Generate temporary file
+	temporaryExecutable, err := daemonCreateExecutable(".daemon", 0755)
+	if err != nil {
+		return
+	}
+	defer temporaryExecutable.Close()
+	defer func() {
+		// Remove the temporary file in case of failure
+		if err != nil {
+			os.Remove(temporaryExecutable.Name())
+		}
+	}()
+
+	// Open current executable
+	executableFile, err := os.Open(cmd.Path)
+	if err != nil {
+		return
+	}
+	defer executableFile.Close()
+
+	// Copy the executable content
+	_, err = io.Copy(temporaryExecutable, executableFile)
+	if err != nil {
+		return
+	}
+
+	// Update command to use chroot
+	cmd.SysProcAttr.Chroot = wd
+	cmd.Path = "/" + temporaryExecutable.Name()
+	cmd.Dir = "/"
+	path = filepath.Join(wd, temporaryExecutable.Name())
+	return
+}
+
 func daemonize(config appConfig, cmdUser string) {
 	var err error
 	defer func() {
@@ -120,6 +197,13 @@ func daemonize(config appConfig, cmdUser string) {
 	}
 	defer killProcess(cmd)
 
+	// Run daemon in chroot environment
+	temporaryExecutable, err := daemonChroot(cmd)
+	if err != nil {
+		return
+	}
+	defer os.Remove(temporaryExecutable)
+
 	// Create a pipe to pass the configuration
 	configReader, configWriter, err := os.Pipe()
 	if err != nil {
@@ -144,6 +228,9 @@ func daemonize(config appConfig, cmdUser string) {
 	}
 	configWriter.Close()
 
+	// Remove executable
+	os.Remove(temporaryExecutable)
+
 	// Pass through signals
 	passSignals(cmd)