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      1 // Copyright 2015 The Go Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style
      3 // license that can be found in the LICENSE file.
      4 
      5 // +build linux
      6 
      7 package syscall_test
      8 
      9 import (
     10 	"io/ioutil"
     11 	"os"
     12 	"os/exec"
     13 	"regexp"
     14 	"strconv"
     15 	"strings"
     16 	"syscall"
     17 	"testing"
     18 )
     19 
     20 func whoamiCmd(t *testing.T, uid, gid int, setgroups bool) *exec.Cmd {
     21 	if _, err := os.Stat("/proc/self/ns/user"); err != nil {
     22 		if os.IsNotExist(err) {
     23 			t.Skip("kernel doesn't support user namespaces")
     24 		}
     25 		t.Fatalf("Failed to stat /proc/self/ns/user: %v", err)
     26 	}
     27 	cmd := exec.Command("whoami")
     28 	cmd.SysProcAttr = &syscall.SysProcAttr{
     29 		Cloneflags: syscall.CLONE_NEWUSER,
     30 		UidMappings: []syscall.SysProcIDMap{
     31 			{ContainerID: 0, HostID: uid, Size: 1},
     32 		},
     33 		GidMappings: []syscall.SysProcIDMap{
     34 			{ContainerID: 0, HostID: gid, Size: 1},
     35 		},
     36 		GidMappingsEnableSetgroups: setgroups,
     37 	}
     38 	return cmd
     39 }
     40 
     41 func testNEWUSERRemap(t *testing.T, uid, gid int, setgroups bool) {
     42 	cmd := whoamiCmd(t, uid, gid, setgroups)
     43 	out, err := cmd.CombinedOutput()
     44 	if err != nil {
     45 		// On some systems, there is a sysctl setting.
     46 		if os.IsPermission(err) && os.Getuid() != 0 {
     47 			data, errRead := ioutil.ReadFile("/proc/sys/kernel/unprivileged_userns_clone")
     48 			if errRead == nil && data[0] == '0' {
     49 				t.Skip("kernel prohibits user namespace in unprivileged process")
     50 			}
     51 		}
     52 
     53 		t.Fatalf("Cmd failed with err %v, output: %s", err, out)
     54 	}
     55 	sout := strings.TrimSpace(string(out))
     56 	want := "root"
     57 	if sout != want {
     58 		t.Fatalf("whoami = %q; want %q", out, want)
     59 	}
     60 }
     61 
     62 func TestCloneNEWUSERAndRemapRootDisableSetgroups(t *testing.T) {
     63 	if os.Getuid() != 0 {
     64 		t.Skip("skipping root only test")
     65 	}
     66 	testNEWUSERRemap(t, 0, 0, false)
     67 }
     68 
     69 func TestCloneNEWUSERAndRemapRootEnableSetgroups(t *testing.T) {
     70 	if os.Getuid() != 0 {
     71 		t.Skip("skipping root only test")
     72 	}
     73 	testNEWUSERRemap(t, 0, 0, false)
     74 }
     75 
     76 // kernelVersion returns the major and minor versions of the Linux
     77 // kernel version.  It calls t.Skip if it can't figure it out.
     78 func kernelVersion(t *testing.T) (int, int) {
     79 	bytes, err := ioutil.ReadFile("/proc/version")
     80 	if err != nil {
     81 		t.Skipf("can't get kernel version: %v", err)
     82 	}
     83 	matches := regexp.MustCompile("([0-9]+).([0-9]+)").FindSubmatch(bytes)
     84 	if len(matches) < 3 {
     85 		t.Skipf("can't get kernel version from %s", bytes)
     86 	}
     87 	major, _ := strconv.Atoi(string(matches[1]))
     88 	minor, _ := strconv.Atoi(string(matches[2]))
     89 	return major, minor
     90 }
     91 
     92 func TestCloneNEWUSERAndRemapNoRootDisableSetgroups(t *testing.T) {
     93 	if os.Getuid() == 0 {
     94 		t.Skip("skipping unprivileged user only test")
     95 	}
     96 	testNEWUSERRemap(t, os.Getuid(), os.Getgid(), false)
     97 }
     98 
     99 func TestCloneNEWUSERAndRemapNoRootSetgroupsEnableSetgroups(t *testing.T) {
    100 	if os.Getuid() == 0 {
    101 		t.Skip("skipping unprivileged user only test")
    102 	}
    103 	cmd := whoamiCmd(t, os.Getuid(), os.Getgid(), true)
    104 	err := cmd.Run()
    105 	if err == nil {
    106 		t.Skip("probably old kernel without security fix")
    107 	}
    108 	if !os.IsPermission(err) {
    109 		t.Fatalf("Unprivileged gid_map rewriting with GidMappingsEnableSetgroups must fail")
    110 	}
    111 }
    112