.gitignore

@@ -1,3 +1 @@
-port80
-port80fg
-port80and443
+example/example

LICENSE

@@ -1,4 +1,4 @@
-Copyright (C) 2022 Marius Schellenberger
+Copyright (C) 2016 Marius Schellenberger
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without

README.md

@@ -1,5 +1,3 @@
 # godrop - drop privileges
 
-Godrop is a simple library to drop privileges on Linux and OpenBSD.
-
-See the examples directory on how to use the `Drop` and `MultiDrop` functions.
+Godrop is a simple library to drop privileges on linux maschines.

example/main.go

@@ -2,12 +2,11 @@ package main
 
 import (
 	"fmt"
-	"log"
 	"net"
 	"net/http"
 	"os"
 
-	"git.giftfish.de/ston1th/godrop/v2"
+	"git.giftfish.de/ston1th/godrop"
 )
 
 func main() {
@@ -17,16 +16,16 @@ func main() {
 	}
 	err := godrop.Drop(cfg, func() (net.Listener, error) { return net.Listen("tcp", ":80") })
 	if err != nil {
-		log.Fatal(err)
+		fmt.Println(err)
 	}
 
 	l, err := godrop.GetListener()
 	if err != nil {
-		log.Fatal("Failed to listen on FD 3:", err)
+		fmt.Println("Failed to listen on FD 3:", err)
+		os.Exit(1)
 	}
-	_, port, _ := net.SplitHostPort(l.Addr().String())
 
 	http.Serve(l, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		fmt.Fprintf(w, "port %s\npid %d\nuid %d\ngid %d", port, os.Getpid(), os.Getuid(), os.Getgid())
+		fmt.Fprintf(w, "pid %d\nuid %d\ngid %d", os.Getpid(), os.Getuid(), os.Getgid())
 	}))
 }

example/port80and443.go

@@ -1,54 +0,0 @@
-package main
-
-import (
-	"fmt"
-	"log"
-	"net"
-	"net/http"
-	"os"
-
-	"git.giftfish.de/ston1th/godrop/v2"
-)
-
-func main() {
-	cfg := godrop.Config{
-		User:       "nobody",
-		Group:      "nobody",
-		Foreground: true,
-	}
-	err := godrop.MultiDrop(cfg, func() ([]net.Listener, error) {
-		l1, err := net.Listen("tcp", ":80")
-		if err != nil {
-			return nil, err
-		}
-		l2, err := net.Listen("tcp", ":443")
-		return []net.Listener{l1, l2}, err
-	})
-	if err != nil {
-		log.Fatal(err)
-	}
-
-	l1, err := godrop.GetListener()
-	if err != nil {
-		log.Fatal("Failed to listen on FD 3:", err)
-	}
-	_, port1, _ := net.SplitHostPort(l1.Addr().String())
-
-	l2, err := godrop.GetListenerFd(4)
-	if err != nil {
-		log.Fatal("Failed to listen on FD 4:", err)
-	}
-	_, port2, _ := net.SplitHostPort(l2.Addr().String())
-
-	fmt.Printf("port1 %s\nport2 %s\npid %d\nuid %d\ngid %d\n", port1, port2, os.Getpid(), os.Getuid(), os.Getgid())
-
-	go func() {
-		http.Serve(l1, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-			fmt.Fprintf(w, "port %s\npid %d\nuid %d\ngid %d", port1, os.Getpid(), os.Getuid(), os.Getgid())
-		}))
-	}()
-
-	http.Serve(l2, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		fmt.Fprintf(w, "port %s\npid %d\nuid %d\ngid %d", port2, os.Getpid(), os.Getuid(), os.Getgid())
-	}))
-}

example/port80fg.go

@@ -1,35 +0,0 @@
-package main
-
-import (
-	"fmt"
-	"log"
-	"net"
-	"net/http"
-	"os"
-
-	"git.giftfish.de/ston1th/godrop/v2"
-)
-
-func main() {
-	cfg := godrop.Config{
-		User:       "nobody",
-		Group:      "nobody",
-		Foreground: true,
-	}
-	err := godrop.Drop(cfg, func() (net.Listener, error) { return net.Listen("tcp", ":80") })
-	if err != nil {
-		log.Fatal(err)
-	}
-
-	l, err := godrop.GetListener()
-	if err != nil {
-		log.Fatal("Failed to listen on FD 3:", err)
-	}
-	_, port, _ := net.SplitHostPort(l.Addr().String())
-
-	fmt.Printf("port %s\npid %d\nuid %d\ngid %d\n", port, os.Getpid(), os.Getuid(), os.Getgid())
-
-	http.Serve(l, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		fmt.Fprintf(w, "port %s\npid %d\nuid %d\ngid %d", port, os.Getpid(), os.Getuid(), os.Getgid())
-	}))
-}

go.mod

@@ -1,5 +0,0 @@
-module git.giftfish.de/ston1th/godrop/v2
-
-go 1.19
-
-require golang.org/x/sys v0.24.0

go.sum

@@ -1,2 +0,0 @@
-golang.org/x/sys v0.24.0 h1:Twjiwq9dn6R1fQcyiK+wQyHWfaz/BJB+YIpzU/Cv3Xg=
-golang.org/x/sys v0.24.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=

godrop.go

@@ -1,76 +1,129 @@
-// Copyright (C) 2022 Marius Schellenberger
-
-//go:build go1.11
-// +build go1.11
-
-// Package godrop provides a simple library to drop privileges on Linux and OpenBSD.
 package godrop
 
 import (
 	"errors"
-	"fmt"
+	"io/ioutil"
 	"net"
 	"os"
 	"os/exec"
-	"os/signal"
+	"regexp"
+	"strconv"
 	"syscall"
 )
 
-// Config represents the drop config
+func readFile(name, file string) (id int, err error) {
+	id = -1
+	if name == "" {
+		return
+	}
+	f, err := os.Open(file)
+	if err != nil {
+		return
+	}
+	b, err := ioutil.ReadAll(f)
+	if err != nil {
+		return
+	}
+	r := regexp.MustCompile(name + ":.*:(\\d+)")
+	m := r.FindAllStringSubmatch(string(b), 1)
+	if len(m) == 1 {
+		if len(m[0]) == 2 {
+			return strconv.Atoi(m[0][1])
+		}
+	}
+	return
+}
+
+// UID of user
+func UID(user string) (int, error) {
+	return readFile(user, "/etc/passwd")
+}
+
+// GID of group
+func GID(group string) (int, error) {
+	return readFile(group, "/etc/group")
+}
+
 type Config struct {
-	// User is the user to drop privileges to.
 	User   string
-	// Group is the group to drop privileges to.
 	Group  string
-	// Chroot is the directory to chroot into. Leave this emptry for no chroot.
-	// When compiling without cgo, make sure the chroot directory contains the /etc/passwd and /etc/group files.
 	Chroot string
-	// Set to true, to run the process in the foreground.
-	Foreground bool
 }
 
-// Drop will spawn a new process and hand over the listening socket file descriptor
+// Drop will spawn a new process, hand over the listening socket file descriptor and terminate itself after
 func Drop(c Config, f func() (net.Listener, error)) error {
-	return MultiDrop(c, func() ([]net.Listener, error) {
-		l, err := f()
-		return []net.Listener{l}, err
-	})
+	uid, err := UID(c.User)
+	if err != nil {
+		return err
+	}
+	gid, err := GID(c.Group)
+	if err != nil {
+		return err
+	}
+	switch os.Getuid() {
+	case 0:
+		ln, err := f()
+		if err != nil {
+			return err
 		}
 
-// MultiDrop will spawn a new process and hand over the all listening sockets
+		l, ok := ln.(*net.TCPListener)
+		if !ok {
+			return errors.New("godrop: interface conversion failed")
+		}
+		f, err := l.File()
+		if err != nil {
+			return err
+		}
+
+		cmd := exec.Command(os.Args[0], os.Args[1:]...)
+		cmd.ExtraFiles = []*os.File{f}
+		cmd.SysProcAttr = &syscall.SysProcAttr{
+			Chroot: c.Chroot,
+			Credential: &syscall.Credential{
+				Uid: uint32(uid),
+				Gid: uint32(gid),
+			},
+			Setsid: true,
+		}
+
+		if err := cmd.Start(); err != nil {
+			return err
+		}
+
+		cmd.Process.Release()
+		os.Exit(0)
+	case uid:
+		return nil
+	}
+	return errors.New("godrop: droping priviledges failed")
+}
+
+// MultiDrop will spawn a new process, hand over the all listening sockets and terminate itself after
 func MultiDrop(c Config, f func() ([]net.Listener, error)) error {
-	uid, err := userID(c.User)
+	uid, err := UID(c.User)
 	if err != nil {
-		return errors.New("godrop: " + err.Error())
+		return err
 	}
-	if uid == 0 {
-		return fmt.Errorf("godrop: you can't drop privileges to uid 0 (%s)", c.User)
-	}
-	gid, err := groupID(c.Group)
+	gid, err := GID(c.Group)
 	if err != nil {
-		return errors.New("godrop: " + err.Error())
+		return err
 	}
 	switch os.Getuid() {
 	case 0:
 		cmd := exec.Command(os.Args[0], os.Args[1:]...)
 		ln, err := f()
 		if err != nil {
-			return errors.New("godrop: " + err.Error())
+			return err
 		}
-		for i, v := range ln {
-			var f *os.File
-			switch l := v.(type) {
-			case *net.TCPListener:
-				f, err = l.File()
-				l.Close()
-			case *net.UnixListener:
-				f, err = l.File()
-				l.Close()
-			default:
-				return fmt.Errorf("godrop: index %d listener is not type of either *net.TCPListener or *net.UnixListener", i)
+		for _, v := range ln {
+			l, ok := v.(*net.TCPListener)
+			if !ok {
+				return errors.New("godrop: interface conversion failed")
 			}
+			f, err := l.File()
 			if err != nil {
-				return fmt.Errorf("godrop: index %d %s", i, err)
+				return err
 			}
 			cmd.ExtraFiles = append(cmd.ExtraFiles, f)
 		}
@@ -84,54 +137,24 @@ func MultiDrop(c Config, f func() ([]net.Listener, error)) error {
 			Setsid: true,
 		}
 
-		if c.Foreground {
-			cmd.Stdin = os.Stdin
-			cmd.Stdout = os.Stdout
-			cmd.Stderr = os.Stderr
-		}
-
 		if err := cmd.Start(); err != nil {
-			return errors.New("godrop: " + err.Error())
+			return err
 		}
 
-		if c.Foreground {
-			go func() {
-				term := make(chan os.Signal)
-				signal.Notify(term, syscall.SIGHUP, syscall.SIGINT, syscall.SIGTERM, syscall.SIGQUIT)
-				sigs := make(chan os.Signal)
-				signal.Notify(sigs, syscall.SIGSTOP, syscall.SIGCONT, syscall.SIGUSR1, syscall.SIGUSR2)
-				for {
-					select {
-					case sig := <-term:
-						cmd.Process.Signal(sig)
-						return
-					case sig := <-sigs:
-						cmd.Process.Signal(sig)
-					}
-				}
-			}()
-			_ = cmd.Wait()
-			os.Exit(int(cmd.ProcessState.Sys().(syscall.WaitStatus)))
-		}
 		cmd.Process.Release()
 		os.Exit(0)
 	case uid:
 		return nil
 	}
-	return errors.New("godrop: dropping priviledges failed")
+	return errors.New("godrop: droping priviledges failed")
 }
 
 // GetListener returns the listener socket of file descriptor 3
 func GetListener() (net.Listener, error) {
-	return GetListenerFd(3)
+	return net.FileListener(os.NewFile(3, "[socket]"))
 }
 
 // GetListenerFd returns the listener socket of the given file descriptor
 func GetListenerFd(fd int) (net.Listener, error) {
-	if fd < 3 {
-		return nil, errors.New("godrop: fd is less than 3")
-	}
-	f := os.NewFile(uintptr(fd), "")
-	defer f.Close()
-	return net.FileListener(f)
+	return net.FileListener(os.NewFile(uintptr(fd), "[socket]"))
 }

godrop_test.go

@@ -1,11 +1,9 @@
-// Copyright (C) 2022 Marius Schellenberger
-
 package godrop
 
 import "testing"
 
-func TestUserID(t *testing.T) {
-	uid, err := userID("root")
+func TestUID(t *testing.T) {
+	uid, err := UID("root")
 	if err != nil {
 		t.Error(err)
 	}
@@ -14,8 +12,8 @@ func TestUserID(t *testing.T) {
 	}
 }
 
-func TestGroupID(t *testing.T) {
-	gid, err := groupID("root")
+func TestGID(t *testing.T) {
+	gid, err := GID("root")
 	if err != nil {
 		t.Error(err)
 	}

lookup.go

@@ -1,35 +0,0 @@
-// Copyright (C) 2022 Marius Schellenberger
-
-//go:build go1.11
-// +build go1.11
-
-package godrop
-
-import (
-	"os/user"
-	"strconv"
-)
-
-func atoi(a string) (int, error) {
-	i, err := strconv.Atoi(a)
-	if err != nil {
-		return -1, err
-	}
-	return i, nil
-}
-
-func userID(username string) (int, error) {
-	u, err := user.Lookup(username)
-	if err != nil {
-		return -1, err
-	}
-	return atoi(u.Uid)
-}
-
-func groupID(name string) (int, error) {
-	g, err := user.LookupGroup(name)
-	if err != nil {
-		return -1, err
-	}
-	return atoi(g.Gid)
-}

pledge.go

@@ -1,15 +0,0 @@
-// Copyright (C) 2022 Marius Schellenberger
-
-//go:build !openbsd
-// +build !openbsd
-
-package godrop
-
-// Pledge is currently only supported on OpenBSD.
-func Pledge(promises, execpromises string) error { return nil }
-
-// PledgePromises is currently only supported on OpenBSD.
-func PledgePromises(promises string) error { return nil }
-
-// PledgeExecPromises is currently only supported on OpenBSD.
-func PledgeExecpromises(execpromises string) error { return nil }

pledge_openbsd.go

@@ -1,44 +0,0 @@
-// Copyright (C) 2022 Marius Schellenberger
-
-//go:build openbsd
-// +build openbsd
-
-package godrop
-
-import (
-	"errors"
-	"golang.org/x/sys/unix"
-)
-
-// Pledge is a wrapper for x/sys/unix Pledge.
-//
-// See https://go.googlesource.com/sys/+/master/unix/openbsd_pledge.go for usage.
-func Pledge(promises, execpromises string) (err error) {
-	err = unix.Pledge(promises, execpromises)
-	if err != nil {
-		err = errors.New("pledge: " + err.Error())
-	}
-	return
-}
-
-// PledgePromises is a wrapper for x/sys/unix PledgePromises.
-//
-// See https://go.googlesource.com/sys/+/master/unix/openbsd_pledge.go for usage.
-func PledgePromises(promises string) (err error) {
-	err = unix.PledgePromises(promises)
-	if err != nil {
-		err = errors.New("pledge: " + err.Error())
-	}
-	return
-}
-
-// PledgeExecpromises is a wrapper for x/sys/unix PledgeExecpromises.
-//
-// See https://go.googlesource.com/sys/+/master/unix/openbsd_pledge.go for usage.
-func PledgeExecpromises(execpromises string) (err error) {
-	err = unix.PledgeExecpromises(execpromises)
-	if err != nil {
-		err = errors.New("pledge: " + err.Error())
-	}
-	return
-}

unveil.go

@@ -1,12 +0,0 @@
-// Copyright (C) 2022 Marius Schellenberger
-
-//go:build !openbsd
-// +build !openbsd
-
-package godrop
-
-// Unveil is currently only supported on OpenBSD.
-func Unveil(path, flags string) error { return nil }
-
-// UnveilBlock is currently only supported on OpenBSD.
-func UnveilBlock() error { return nil }

unveil_openbsd.go

@@ -1,33 +0,0 @@
-// Copyright (C) 2022 Marius Schellenberger
-
-//go:build openbsd
-// +build openbsd
-
-package godrop
-
-import (
-	"errors"
-	"golang.org/x/sys/unix"
-)
-
-// Unveil is a wrapper for x/sys/unix Unveil.
-//
-// See https://go.googlesource.com/sys/+/master/unix/openbsd_unveil.go for usage.
-func Unveil(path, flags string) (err error) {
-	err = unix.Unveil(path, flags)
-	if err != nil {
-		err = errors.New("unveil: " + err.Error())
-	}
-	return
-}
-
-// UnveilBlock is a wrapper for x/sys/unix UnveilBlock.
-//
-// See https://go.googlesource.com/sys/+/master/unix/openbsd_unveil.go for usage.
-func UnveilBlock() (err error) {
-	err = unix.UnveilBlock()
-	if err != nil {
-		err = errors.New("unveil: " + err.Error())
-	}
-	return
-}