ston1th/godrop
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simplified library and added better examples and net.UnixListener support

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ston1th 2017-04-19 20:42:19 +02:00
commit 694ac1e8a9
7 changed files with 95 additions and 61 deletions
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3
.gitignore vendored
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@ -1 +1,2 @@
example/example
port80
port80and443

2
LICENSE
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@ -1,4 +1,4 @@
Copyright (C) 2016 Marius Schellenberger
Copyright (C) 2017 Marius Schellenberger
All rights reserved.
Redistribution and use in source and binary forms, with or without

2
README.md
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@ -1,3 +1,5 @@
# godrop - drop privileges
Godrop is a simple library to drop privileges on linux maschines.
See the examples directory on how to use the `Drop` and `MultiDrop` functions.

3
example/main.go → example/port80.go
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@ -24,8 +24,9 @@ func main() {
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, "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())
}))
}

52
example/port80and443.go Normal file
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@ -0,0 +1,52 @@
package main
import (
"fmt"
"net"
"net/http"
"os"
"git.giftfish.de/ston1th/godrop"
)
func main() {
cfg := godrop.Config{
User: "nobody",
Group: "nobody",
}
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 {
fmt.Println(err)
}
l1, err := godrop.GetListener()
if err != nil {
fmt.Println("Failed to listen on FD 3:", err)
os.Exit(1)
}
_, port1, _ := net.SplitHostPort(l1.Addr().String())
l2, err := godrop.GetListenerFd(4)
if err != nil {
fmt.Println("Failed to listen on FD 4:", err)
os.Exit(1)
}
_, port2, _ := net.SplitHostPort(l2.Addr().String())
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())
}))
}

92
godrop.go
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@ -1,7 +1,11 @@
// Copyright (C) 2017 Marius Schellenberger
// Package godrop provides a simple privileges dropping library
package godrop
import (
"errors"
"fmt"
"io/ioutil"
"net"
"os"
@ -11,6 +15,10 @@ import (
"syscall"
)
func errf(err error) error {
return fmt.Errorf("godrop: %s", err)
}
func readFile(name, file string) (id int, err error) {
id = -1
if name == "" {
@ -44,6 +52,7 @@ func GID(group string) (int, error) {
return readFile(group, "/etc/group")
}
// Config represents the drop config
type Config struct {
User string
Group string
@ -52,78 +61,43 @@ type Config struct {
// 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 {
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
func MultiDrop(c Config, f func() ([]net.Listener, error)) error {
uid, err := UID(c.User)
if err != nil {
return err
return errf(err)
}
gid, err := GID(c.Group)
if err != nil {
return err
return errf(err)
}
switch os.Getuid() {
case 0:
cmd := exec.Command(os.Args[0], os.Args[1:]...)
ln, err := f()
if err != nil {
return err
return errf(err)
}
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 errf(fmt.Errorf("index: %d listener is not type of either *net.TCPListener or *net.UnixListener", i))
}
f, err := l.File()
if err != nil {
return err
return errf(fmt.Errorf("index: %d %s", i, err))
}
cmd.ExtraFiles = append(cmd.ExtraFiles, f)
}
@ -138,7 +112,7 @@ func MultiDrop(c Config, f func() ([]net.Listener, error)) error {
}
if err := cmd.Start(); err != nil {
return err
return errf(err)
}
cmd.Process.Release()
@ -146,15 +120,17 @@ func MultiDrop(c Config, f func() ([]net.Listener, error)) error {
case uid:
return nil
}
return errors.New("godrop: droping priviledges failed")
return errf(errors.New("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]"))
f := os.NewFile(uintptr(fd), "")
defer f.Close()
return net.FileListener(f)
}

2
godrop_test.go
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@ -1,3 +1,5 @@
// Copyright (C) 2017 Marius Schellenberger
package godrop
import "testing"