added pledge and unveil support

godrop.go

@@ -2,10 +2,11 @@
 
 // +build go1.11
 
-// Package godrop provides a simple privileges dropping library
+// Package godrop provides a simple library to drop privileges on Linux and OpenBSD.
 package godrop
 
 import (
+	"errors"
 	"fmt"
 	"net"
 	"os"
@@ -14,10 +15,6 @@ import (
 	"syscall"
 )
 
-func errf(i interface{}) error {
-	return fmt.Errorf("godrop: %s", i)
-}
-
 // Config represents the drop config
 type Config struct {
 	// User is the user to drop privileges to.
@@ -43,21 +40,21 @@ func Drop(c Config, f func() (net.Listener, error)) error {
 func MultiDrop(c Config, f func() ([]net.Listener, error)) error {
 	uid, err := userID(c.User)
 	if err != nil {
-		return errf(err)
+		return errors.New("godrop: " + err.Error())
 	}
 	if uid == 0 {
-		return errf("unable to drop privileges to uid 0 (root)")
+		return fmt.Errorf("godrop: you can't drop privileges to uid 0 (%s)", c.User)
 	}
 	gid, err := groupID(c.Group)
 	if err != nil {
-		return errf(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 errf(err)
+			return errors.New("godrop: " + err.Error())
 		}
 		for i, v := range ln {
 			var f *os.File
@@ -69,10 +66,10 @@ func MultiDrop(c Config, f func() ([]net.Listener, error)) error {
 				f, err = l.File()
 				l.Close()
 			default:
-				return errf(fmt.Sprintf("index %d listener is not type of either *net.TCPListener or *net.UnixListener", i))
+				return fmt.Errorf("godrop: index %d listener is not type of either *net.TCPListener or *net.UnixListener", i)
 			}
 			if err != nil {
-				return errf(fmt.Sprintf("index %d %s", i, err))
+				return fmt.Errorf("godrop: index %d %s", i, err)
 			}
 			cmd.ExtraFiles = append(cmd.ExtraFiles, f)
 		}
@@ -93,7 +90,7 @@ func MultiDrop(c Config, f func() ([]net.Listener, error)) error {
 		}
 
 		if err := cmd.Start(); err != nil {
-			return errf(err)
+			return errors.New("godrop: " + err.Error())
 		}
 
 		if c.Foreground {
@@ -120,7 +117,7 @@ func MultiDrop(c Config, f func() ([]net.Listener, error)) error {
 	case uid:
 		return nil
 	}
-	return errf("dropping priviledges failed")
+	return errors.New("godrop: dropping priviledges failed")
 }
 
 // GetListener returns the listener socket of file descriptor 3
@@ -131,7 +128,7 @@ func GetListener() (net.Listener, error) {
 // GetListenerFd returns the listener socket of the given file descriptor
 func GetListenerFd(fd int) (net.Listener, error) {
 	if fd < 3 {
-		return nil, errf("fd is less than 3")
+		return nil, errors.New("godrop: fd is less than 3")
 	}
 	f := os.NewFile(uintptr(fd), "")
 	defer f.Close()