use latest sys

.gitignore

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

LICENSE

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

README.md

@@ -1,3 +1,5 @@
 # godrop - drop privileges
 
-Godrop is a simple library to drop privileges on linux maschines.
+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.

example/port80.go

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

example/port80and443.go

@@ -0,0 +1,54 @@
+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

@@ -0,0 +1,35 @@
+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

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

go.sum

@@ -0,0 +1,2 @@
+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

@@ -1,129 +1,76 @@
+// 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"
-	"io/ioutil"
+	"fmt"
 	"net"
 	"os"
 	"os/exec"
-	"regexp"
-	"strconv"
+	"os/signal"
 	"syscall"
 )
 
-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")
-}
-
+// Config represents the drop config
 type Config struct {
-	User   string
-	Group  string
+	// 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, hand over the listening socket file descriptor and terminate itself after
+// Drop will spawn a new process and hand over the listening socket file descriptor
 func Drop(c Config, f func() (net.Listener, error)) error {
-	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
-		}
-
-		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")
+	return MultiDrop(c, func() ([]net.Listener, error) {
+		l, err := f()
+		return []net.Listener{l}, err
+	})
 }
 
-// MultiDrop will spawn a new process, hand over the all listening sockets and terminate itself after
+// MultiDrop will spawn a new process and hand over the all listening sockets
 func MultiDrop(c Config, f func() ([]net.Listener, error)) error {
-	uid, err := UID(c.User)
+	uid, err := userID(c.User)
 	if err != nil {
-		return err
+		return errors.New("godrop: " + err.Error())
 	}
-	gid, err := GID(c.Group)
+	if uid == 0 {
+		return fmt.Errorf("godrop: you can't drop privileges to uid 0 (%s)", c.User)
+	}
+	gid, err := groupID(c.Group)
 	if err != nil {
-		return err
+		return errors.New("godrop: " + err.Error())
 	}
 	switch os.Getuid() {
 	case 0:
 		cmd := exec.Command(os.Args[0], os.Args[1:]...)
 		ln, err := f()
 		if err != nil {
-			return err
+			return errors.New("godrop: " + err.Error())
 		}
-		for _, v := range ln {
-			l, ok := v.(*net.TCPListener)
-			if !ok {
-				return errors.New("godrop: interface conversion failed")
+		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)
 			}
-			f, err := l.File()
 			if err != nil {
-				return err
+				return fmt.Errorf("godrop: index %d %s", i, err)
 			}
 			cmd.ExtraFiles = append(cmd.ExtraFiles, f)
 		}
@@ -137,24 +84,54 @@ func MultiDrop(c Config, f func() ([]net.Listener, error)) error {
 			Setsid: true,
 		}
 
-		if err := cmd.Start(); err != nil {
-			return err
+		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())
+		}
+
+		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: droping priviledges failed")
+	return errors.New("godrop: dropping priviledges failed")
 }
 
 // GetListener returns the listener socket of file descriptor 3
 func GetListener() (net.Listener, error) {
-	return net.FileListener(os.NewFile(3, "[socket]"))
+	return GetListenerFd(3)
 }
 
 // GetListenerFd returns the listener socket of the given file descriptor
 func GetListenerFd(fd int) (net.Listener, error) {
-	return net.FileListener(os.NewFile(uintptr(fd), "[socket]"))
+	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)
 }

lookup.go

@@ -0,0 +1,35 @@
+// 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)
+}

lookup_test.go

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

pledge.go

@@ -0,0 +1,15 @@
+// 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

@@ -0,0 +1,44 @@
+// 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

@@ -0,0 +1,12 @@
+// 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

@@ -0,0 +1,33 @@
+// 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
+}