test_unix_test.go

// Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || plan9
// +build aix darwin dragonfly freebsd linux netbsd openbsd plan9

package test

// functional test harness for unix.

import (
	"bytes"
	"crypto/rand"
	"encoding/base64"
	"fmt"
	"log"
	"net"
	"os"
	"os/exec"
	"os/user"
	"path/filepath"
	"testing"
	"text/template"

	"golang.org/x/crypto/ssh"
	"golang.org/x/crypto/ssh/testdata"
)

const (
	defaultSshdConfig = `
Protocol 2
Banner {{.Dir}}/banner
HostKey {{.Dir}}/id_rsa
HostKey {{.Dir}}/id_dsa
HostKey {{.Dir}}/id_ecdsa
HostCertificate {{.Dir}}/id_rsa-sha2-512-cert.pub
Pidfile {{.Dir}}/sshd.pid
#UsePrivilegeSeparation no
KeyRegenerationInterval 3600
ServerKeyBits 768
SyslogFacility AUTH
LogLevel DEBUG2
LoginGraceTime 120
PermitRootLogin no
StrictModes no
RSAAuthentication yes
PubkeyAuthentication yes
AuthorizedKeysFile	{{.Dir}}/authorized_keys
TrustedUserCAKeys {{.Dir}}/id_ecdsa.pub
IgnoreRhosts yes
RhostsRSAAuthentication no
HostbasedAuthentication no
PubkeyAcceptedKeyTypes=*
`
	multiAuthSshdConfigTail = `
UsePAM yes
PasswordAuthentication yes
ChallengeResponseAuthentication yes
AuthenticationMethods {{.AuthMethods}}
`
)

var configTmpl = map[string]*template.Template{
	"default":   template.Must(template.New("").Parse(defaultSshdConfig)),
	"MultiAuth": template.Must(template.New("").Parse(defaultSshdConfig + multiAuthSshdConfigTail))}

type server struct {
	t          *testing.T
	cleanup    func() // executed during Shutdown
	configfile string
	cmd        *exec.Cmd
	output     bytes.Buffer // holds stderr from sshd process

	testUser     string // test username for sshd
	testPasswd   string // test password for sshd
	sshdTestPwSo string // dynamic library to inject a custom password into sshd

	// Client half of the network connection.
	clientConn net.Conn
}

func username() string {
	var username string
	if user, err := user.Current(); err == nil {
		username = user.Username
	} else {
		// user.Current() currently requires cgo. If an error is
		// returned attempt to get the username from the environment.
		log.Printf("user.Current: %v; falling back on $USER", err)
		username = os.Getenv("USER")
	}
	if username == "" {
		panic("Unable to get username")
	}
	return username
}

type storedHostKey struct {
	// keys map from an algorithm string to binary key data.
	keys map[string][]byte

	// checkCount counts the Check calls. Used for testing
	// rekeying.
	checkCount int
}

func (k *storedHostKey) Add(key ssh.PublicKey) {
	if k.keys == nil {
		k.keys = map[string][]byte{}
	}
	k.keys[key.Type()] = key.Marshal()
}

func (k *storedHostKey) Check(addr string, remote net.Addr, key ssh.PublicKey) error {
	k.checkCount++
	algo := key.Type()

	if k.keys == nil || bytes.Compare(key.Marshal(), k.keys[algo]) != 0 {
		return fmt.Errorf("host key mismatch. Got %q, want %q", key, k.keys[algo])
	}
	return nil
}

func hostKeyDB() *storedHostKey {
	keyChecker := &storedHostKey{}
	keyChecker.Add(testPublicKeys["ecdsa"])
	keyChecker.Add(testPublicKeys["rsa"])
	keyChecker.Add(testPublicKeys["dsa"])
	return keyChecker
}

func clientConfig() *ssh.ClientConfig {
	config := &ssh.ClientConfig{
		User: username(),
		Auth: []ssh.AuthMethod{
			ssh.PublicKeys(testSigners["user"]),
		},
		HostKeyCallback: hostKeyDB().Check,
		HostKeyAlgorithms: []string{ // by default, don't allow certs as this affects the hostKeyDB checker
			ssh.KeyAlgoECDSA256, ssh.KeyAlgoECDSA384, ssh.KeyAlgoECDSA521,
			ssh.KeyAlgoRSA, ssh.KeyAlgoDSA,
			ssh.KeyAlgoED25519,
		},
	}
	return config
}

// unixConnection creates two halves of a connected net.UnixConn.  It
// is used for connecting the Go SSH client with sshd without opening
// ports.
func unixConnection() (*net.UnixConn, *net.UnixConn, error) {
	dir, err := os.MkdirTemp("", "unixConnection")
	if err != nil {
		return nil, nil, err
	}
	defer os.Remove(dir)

	addr := filepath.Join(dir, "ssh")
	listener, err := net.Listen("unix", addr)
	if err != nil {
		return nil, nil, err
	}
	defer listener.Close()
	c1, err := net.Dial("unix", addr)
	if err != nil {
		return nil, nil, err
	}

	c2, err := listener.Accept()
	if err != nil {
		c1.Close()
		return nil, nil, err
	}

	return c1.(*net.UnixConn), c2.(*net.UnixConn), nil
}

func (s *server) TryDial(config *ssh.ClientConfig) (*ssh.Client, error) {
	return s.TryDialWithAddr(config, "")
}

// addr is the user specified host:port. While we don't actually dial it,
// we need to know this for host key matching
func (s *server) TryDialWithAddr(config *ssh.ClientConfig, addr string) (*ssh.Client, error) {
	sshd, err := exec.LookPath("sshd")
	if err != nil {
		s.t.Skipf("skipping test: %v", err)
	}

	c1, c2, err := unixConnection()
	if err != nil {
		s.t.Fatalf("unixConnection: %v", err)
	}

	s.cmd = exec.Command(sshd, "-f", s.configfile, "-i", "-e")
	f, err := c2.File()
	if err != nil {
		s.t.Fatalf("UnixConn.File: %v", err)
	}
	defer f.Close()
	s.cmd.Stdin = f
	s.cmd.Stdout = f
	s.cmd.Stderr = &s.output

	if s.sshdTestPwSo != "" {
		if s.testUser == "" {
			s.t.Fatal("user missing from sshd_test_pw.so config")
		}
		if s.testPasswd == "" {
			s.t.Fatal("password missing from sshd_test_pw.so config")
		}
		s.cmd.Env = append(os.Environ(),
			fmt.Sprintf("LD_PRELOAD=%s", s.sshdTestPwSo),
			fmt.Sprintf("TEST_USER=%s", s.testUser),
			fmt.Sprintf("TEST_PASSWD=%s", s.testPasswd))
	}

	if err := s.cmd.Start(); err != nil {
		s.t.Fail()
		s.Shutdown()
		s.t.Fatalf("s.cmd.Start: %v", err)
	}
	s.clientConn = c1
	conn, chans, reqs, err := ssh.NewClientConn(c1, addr, config)
	if err != nil {
		return nil, err
	}
	return ssh.NewClient(conn, chans, reqs), nil
}

func (s *server) Dial(config *ssh.ClientConfig) *ssh.Client {
	conn, err := s.TryDial(config)
	if err != nil {
		s.t.Fail()
		s.Shutdown()
		s.t.Fatalf("ssh.Client: %v", err)
	}
	return conn
}

func (s *server) Shutdown() {
	if s.cmd != nil && s.cmd.Process != nil {
		// Don't check for errors; if it fails it's most
		// likely "os: process already finished", and we don't
		// care about that. Use os.Interrupt, so child
		// processes are killed too.
		s.cmd.Process.Signal(os.Interrupt)
		s.cmd.Wait()
	}
	if s.t.Failed() {
		// log any output from sshd process
		s.t.Logf("sshd: %s", s.output.String())
	}
	s.cleanup()
}

func writeFile(path string, contents []byte) {
	f, err := os.OpenFile(path, os.O_WRONLY|os.O_TRUNC|os.O_CREATE, 0600)
	if err != nil {
		panic(err)
	}
	defer f.Close()
	if _, err := f.Write(contents); err != nil {
		panic(err)
	}
}

// generate random password
func randomPassword() (string, error) {
	b := make([]byte, 12)
	_, err := rand.Read(b)
	if err != nil {
		return "", err
	}
	return base64.RawURLEncoding.EncodeToString(b), nil
}

// setTestPassword is used for setting user and password data for sshd_test_pw.so
// This function also checks that ./sshd_test_pw.so exists and if not calls s.t.Skip()
func (s *server) setTestPassword(user, passwd string) error {
	wd, _ := os.Getwd()
	wrapper := filepath.Join(wd, "sshd_test_pw.so")
	if _, err := os.Stat(wrapper); err != nil {
		s.t.Skip(fmt.Errorf("sshd_test_pw.so is not available"))
		return err
	}

	s.sshdTestPwSo = wrapper
	s.testUser = user
	s.testPasswd = passwd
	return nil
}

// newServer returns a new mock ssh server.
func newServer(t *testing.T) *server {
	return newServerForConfig(t, "default", map[string]string{})
}

// newServerForConfig returns a new mock ssh server.
func newServerForConfig(t *testing.T, config string, configVars map[string]string) *server {
	if testing.Short() {
		t.Skip("skipping test due to -short")
	}
	u, err := user.Current()
	if err != nil {
		t.Fatalf("user.Current: %v", err)
	}
	uname := u.Name
	if uname == "" {
		// Check the value of u.Username as u.Name
		// can be "" on some OSes like AIX.
		uname = u.Username
	}
	if uname == "root" {
		t.Skip("skipping test because current user is root")
	}
	dir, err := os.MkdirTemp("", "sshtest")
	if err != nil {
		t.Fatal(err)
	}
	f, err := os.Create(filepath.Join(dir, "sshd_config"))
	if err != nil {
		t.Fatal(err)
	}
	if _, ok := configTmpl[config]; ok == false {
		t.Fatal(fmt.Errorf("Invalid server config '%s'", config))
	}
	configVars["Dir"] = dir
	err = configTmpl[config].Execute(f, configVars)
	if err != nil {
		t.Fatal(err)
	}
	f.Close()

	writeFile(filepath.Join(dir, "banner"), []byte("Server Banner"))

	for k, v := range testdata.PEMBytes {
		filename := "id_" + k
		writeFile(filepath.Join(dir, filename), v)
		writeFile(filepath.Join(dir, filename+".pub"), ssh.MarshalAuthorizedKey(testPublicKeys[k]))
	}

	for k, v := range testdata.SSHCertificates {
		filename := "id_" + k + "-cert.pub"
		writeFile(filepath.Join(dir, filename), v)
	}

	var authkeys bytes.Buffer
	for k := range testdata.PEMBytes {
		authkeys.Write(ssh.MarshalAuthorizedKey(testPublicKeys[k]))
	}
	writeFile(filepath.Join(dir, "authorized_keys"), authkeys.Bytes())

	return &server{
		t:          t,
		configfile: f.Name(),
		cleanup: func() {
			if err := os.RemoveAll(dir); err != nil {
				t.Error(err)
			}
		},
	}
}

func newTempSocket(t *testing.T) (string, func()) {
	dir, err := os.MkdirTemp("", "socket")
	if err != nil {
		t.Fatal(err)
	}
	deferFunc := func() { os.RemoveAll(dir) }
	addr := filepath.Join(dir, "sock")
	return addr, deferFunc
}