src/net/smtp/smtp_test.go - go - Git at Google

 // Copyright 2010 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.

 package smtp

 import (
 	"bufio"
 	"bytes"
 	"crypto/tls"
 	"crypto/x509"
 	"io"
 	"net"
 	"net/textproto"
 	"strings"
 	"testing"
 	"time"
 )

 type authTest struct {
 	auth       Auth
 	challenges []string
 	name       string
 	responses  []string
 }

 var authTests = []authTest{
 	{PlainAuth("", "user", "pass", "testserver"), []string{}, "PLAIN", []string{"\x00user\x00pass"}},
 	{PlainAuth("foo", "bar", "baz", "testserver"), []string{}, "PLAIN", []string{"foo\x00bar\x00baz"}},
 	{CRAMMD5Auth("user", "pass"), []string{"<123456.1322876914@testserver>"}, "CRAM-MD5", []string{"", "user 287eb355114cf5c471c26a875f1ca4ae"}},
 }

 func TestAuth(t *testing.T) {
 testLoop:
 	for i, test := range authTests {
 		name, resp, err := test.auth.Start(&ServerInfo{"testserver", true, nil})
 		if name != test.name {
 			t.Errorf("#%d got name %s, expected %s", i, name, test.name)
 		}
 		if !bytes.Equal(resp, []byte(test.responses[0])) {
 			t.Errorf("#%d got response %s, expected %s", i, resp, test.responses[0])
 		}
 		if err != nil {
 			t.Errorf("#%d error: %s", i, err)
 		}
 		for j := range test.challenges {
 			challenge := []byte(test.challenges[j])
 			expected := []byte(test.responses[j+1])
 			resp, err := test.auth.Next(challenge, true)
 			if err != nil {
 				t.Errorf("#%d error: %s", i, err)
 				continue testLoop
 			}
 			if !bytes.Equal(resp, expected) {
 				t.Errorf("#%d got %s, expected %s", i, resp, expected)
 				continue testLoop
 			}
 		}
 	}
 }

 func TestAuthPlain(t *testing.T) {

 	tests := []struct {
 		authName string
 		server   *ServerInfo
 		err      string
 	}{
 		{
 			authName: "servername",
 			server:   &ServerInfo{Name: "servername", TLS: true},
 		},
 		{
 			// OK to use PlainAuth on localhost without TLS
 			authName: "localhost",
 			server:   &ServerInfo{Name: "localhost", TLS: false},
 		},
 		{
 			// NOT OK on non-localhost, even if server says PLAIN is OK.
 			// (We don't know that the server is the real server.)
 			authName: "servername",
 			server:   &ServerInfo{Name: "servername", Auth: []string{"PLAIN"}},
 			err:      "unencrypted connection",
 		},
 		{
 			authName: "servername",
 			server:   &ServerInfo{Name: "servername", Auth: []string{"CRAM-MD5"}},
 			err:      "unencrypted connection",
 		},
 		{
 			authName: "servername",
 			server:   &ServerInfo{Name: "attacker", TLS: true},
 			err:      "wrong host name",
 		},
 	}
 	for i, tt := range tests {
 		auth := PlainAuth("foo", "bar", "baz", tt.authName)
 		_, _, err := auth.Start(tt.server)
 		got := ""
 		if err != nil {
 			got = err.Error()
 		}
 		if got != tt.err {
 			t.Errorf("%d. got error = %q; want %q", i, got, tt.err)
 		}
 	}
 }

 // Issue 17794: don't send a trailing space on AUTH command when there's no password.
 func TestClientAuthTrimSpace(t *testing.T) {
 	server := "220 hello world\r\n" +
 		"200 some more"
 	var wrote bytes.Buffer
 	var fake faker
 	fake.ReadWriter = struct {
 		io.Reader
 		io.Writer
 	}{
 		strings.NewReader(server),
 		&wrote,
 	}
 	c, err := NewClient(fake, "fake.host")
 	if err != nil {
 		t.Fatalf("NewClient: %v", err)
 	}
 	c.tls = true
 	c.didHello = true
 	c.Auth(toServerEmptyAuth{})
 	c.Close()
 	if got, want := wrote.String(), "AUTH FOOAUTH\r\n*\r\nQUIT\r\n"; got != want {
 		t.Errorf("wrote %q; want %q", got, want)
 	}
 }

 // toServerEmptyAuth is an implementation of Auth that only implements
 // the Start method, and returns "FOOAUTH", nil, nil. Notably, it returns
 // zero bytes for "toServer" so we can test that we don't send spaces at
 // the end of the line. See TestClientAuthTrimSpace.
 type toServerEmptyAuth struct{}

 func (toServerEmptyAuth) Start(server *ServerInfo) (proto string, toServer []byte, err error) {
 	return "FOOAUTH", nil, nil
 }

 func (toServerEmptyAuth) Next(fromServer []byte, more bool) (toServer []byte, err error) {
 	panic("unexpected call")
 }

 type faker struct {
 	io.ReadWriter
 }

 func (f faker) Close() error                     { return nil }
 func (f faker) LocalAddr() net.Addr              { return nil }
 func (f faker) RemoteAddr() net.Addr             { return nil }
 func (f faker) SetDeadline(time.Time) error      { return nil }
 func (f faker) SetReadDeadline(time.Time) error  { return nil }
 func (f faker) SetWriteDeadline(time.Time) error { return nil }

 func TestBasic(t *testing.T) {
 	server := strings.Join(strings.Split(basicServer, "\n"), "\r\n")
 	client := strings.Join(strings.Split(basicClient, "\n"), "\r\n")

 	var cmdbuf bytes.Buffer
 	bcmdbuf := bufio.NewWriter(&cmdbuf)
 	var fake faker
 	fake.ReadWriter = bufio.NewReadWriter(bufio.NewReader(strings.NewReader(server)), bcmdbuf)
 	c := &Client{Text: textproto.NewConn(fake), localName: "localhost"}

 	if err := c.helo(); err != nil {
 		t.Fatalf("HELO failed: %s", err)
 	}
 	if err := c.ehlo(); err == nil {
 		t.Fatalf("Expected first EHLO to fail")
 	}
 	if err := c.ehlo(); err != nil {
 		t.Fatalf("Second EHLO failed: %s", err)
 	}

 	c.didHello = true
 	if ok, args := c.Extension("aUtH"); !ok || args != "LOGIN PLAIN" {
 		t.Fatalf("Expected AUTH supported")
 	}
 	if ok, _ := c.Extension("DSN"); ok {
 		t.Fatalf("Shouldn't support DSN")
 	}

 	if err := c.Mail("user@gmail.com"); err == nil {
 		t.Fatalf("MAIL should require authentication")
 	}

 	if err := c.Verify("user1@gmail.com"); err == nil {
 		t.Fatalf("First VRFY: expected no verification")
 	}
 	if err := c.Verify("user2@gmail.com"); err != nil {
 		t.Fatalf("Second VRFY: expected verification, got %s", err)
 	}

 	// fake TLS so authentication won't complain
 	c.tls = true
 	c.serverName = "smtp.google.com"
 	if err := c.Auth(PlainAuth("", "user", "pass", "smtp.google.com")); err != nil {
 		t.Fatalf("AUTH failed: %s", err)
 	}

 	if err := c.Mail("user@gmail.com"); err != nil {
 		t.Fatalf("MAIL failed: %s", err)
 	}
 	if err := c.Rcpt("golang-nuts@googlegroups.com"); err != nil {
 		t.Fatalf("RCPT failed: %s", err)
 	}
 	msg := `From: user@gmail.com
 To: golang-nuts@googlegroups.com
 Subject: Hooray for Go

 Line 1
 .Leading dot line .
 Goodbye.`
 	w, err := c.Data()
 	if err != nil {
 		t.Fatalf("DATA failed: %s", err)
 	}
 	if _, err := w.Write([]byte(msg)); err != nil {
 		t.Fatalf("Data write failed: %s", err)
 	}
 	if err := w.Close(); err != nil {
 		t.Fatalf("Bad data response: %s", err)
 	}

 	if err := c.Quit(); err != nil {
 		t.Fatalf("QUIT failed: %s", err)
 	}

 	bcmdbuf.Flush()
 	actualcmds := cmdbuf.String()
 	if client != actualcmds {
 		t.Fatalf("Got:\n%s\nExpected:\n%s", actualcmds, client)
 	}
 }

 var basicServer = `250 mx.google.com at your service
 502 Unrecognized command.
 250-mx.google.com at your service
 250-SIZE 35651584
 250-AUTH LOGIN PLAIN
 250 8BITMIME
 530 Authentication required
 252 Send some mail, I'll try my best
 250 User is valid
 235 Accepted
 250 Sender OK
 250 Receiver OK
 354 Go ahead
 250 Data OK
 221 OK
 `

 var basicClient = `HELO localhost
 EHLO localhost
 EHLO localhost
 MAIL FROM:<user@gmail.com> BODY=8BITMIME
 VRFY user1@gmail.com
 VRFY user2@gmail.com
 AUTH PLAIN AHVzZXIAcGFzcw==
 MAIL FROM:<user@gmail.com> BODY=8BITMIME
 RCPT TO:<golang-nuts@googlegroups.com>
 DATA
 From: user@gmail.com
 To: golang-nuts@googlegroups.com
 Subject: Hooray for Go

 Line 1
 ..Leading dot line .
 Goodbye.
 .
 QUIT
 `

 func TestNewClient(t *testing.T) {
 	server := strings.Join(strings.Split(newClientServer, "\n"), "\r\n")
 	client := strings.Join(strings.Split(newClientClient, "\n"), "\r\n")

 	var cmdbuf bytes.Buffer
 	bcmdbuf := bufio.NewWriter(&cmdbuf)
 	out := func() string {
 		bcmdbuf.Flush()
 		return cmdbuf.String()
 	}
 	var fake faker
 	fake.ReadWriter = bufio.NewReadWriter(bufio.NewReader(strings.NewReader(server)), bcmdbuf)
 	c, err := NewClient(fake, "fake.host")
 	if err != nil {
 		t.Fatalf("NewClient: %v\n(after %v)", err, out())
 	}
 	defer c.Close()
 	if ok, args := c.Extension("aUtH"); !ok || args != "LOGIN PLAIN" {
 		t.Fatalf("Expected AUTH supported")
 	}
 	if ok, _ := c.Extension("DSN"); ok {
 		t.Fatalf("Shouldn't support DSN")
 	}
 	if err := c.Quit(); err != nil {
 		t.Fatalf("QUIT failed: %s", err)
 	}

 	actualcmds := out()
 	if client != actualcmds {
 		t.Fatalf("Got:\n%s\nExpected:\n%s", actualcmds, client)
 	}
 }

 var newClientServer = `220 hello world
 250-mx.google.com at your service
 250-SIZE 35651584
 250-AUTH LOGIN PLAIN
 250 8BITMIME
 221 OK
 `

 var newClientClient = `EHLO localhost
 QUIT
 `

 func TestNewClient2(t *testing.T) {
 	server := strings.Join(strings.Split(newClient2Server, "\n"), "\r\n")
 	client := strings.Join(strings.Split(newClient2Client, "\n"), "\r\n")

 	var cmdbuf bytes.Buffer
 	bcmdbuf := bufio.NewWriter(&cmdbuf)
 	var fake faker
 	fake.ReadWriter = bufio.NewReadWriter(bufio.NewReader(strings.NewReader(server)), bcmdbuf)
 	c, err := NewClient(fake, "fake.host")
 	if err != nil {
 		t.Fatalf("NewClient: %v", err)
 	}
 	defer c.Close()
 	if ok, _ := c.Extension("DSN"); ok {
 		t.Fatalf("Shouldn't support DSN")
 	}
 	if err := c.Quit(); err != nil {
 		t.Fatalf("QUIT failed: %s", err)
 	}

 	bcmdbuf.Flush()
 	actualcmds := cmdbuf.String()
 	if client != actualcmds {
 		t.Fatalf("Got:\n%s\nExpected:\n%s", actualcmds, client)
 	}
 }

 var newClient2Server = `220 hello world
 502 EH?
 250-mx.google.com at your service
 250-SIZE 35651584
 250-AUTH LOGIN PLAIN
 250 8BITMIME
 221 OK
 `

 var newClient2Client = `EHLO localhost
 HELO localhost
 QUIT
 `

 func TestNewClientWithTLS(t *testing.T) {
 	cert, err := tls.X509KeyPair(localhostCert, localhostKey)
 	if err != nil {
 		t.Fatalf("loadcert: %v", err)
 	}

 	config := tls.Config{Certificates: []tls.Certificate{cert}}

 	ln, err := tls.Listen("tcp", "127.0.0.1:0", &config)
 	if err != nil {
 		ln, err = tls.Listen("tcp", "[::1]:0", &config)
 		if err != nil {
 			t.Fatalf("server: listen: %s", err)
 		}
 	}

 	go func() {
 		conn, err := ln.Accept()
 		if err != nil {
 			t.Fatalf("server: accept: %s", err)
 			return
 		}
 		defer conn.Close()

 		_, err = conn.Write([]byte("220 SIGNS\r\n"))
 		if err != nil {
 			t.Fatalf("server: write: %s", err)
 			return
 		}
 	}()

 	config.InsecureSkipVerify = true
 	conn, err := tls.Dial("tcp", ln.Addr().String(), &config)
 	if err != nil {
 		t.Fatalf("client: dial: %s", err)
 	}
 	defer conn.Close()

 	client, err := NewClient(conn, ln.Addr().String())
 	if err != nil {
 		t.Fatalf("smtp: newclient: %s", err)
 	}
 	if !client.tls {
 		t.Errorf("client.tls Got: %t Expected: %t", client.tls, true)
 	}
 }

 func TestHello(t *testing.T) {

 	if len(helloServer) != len(helloClient) {
 		t.Fatalf("Hello server and client size mismatch")
 	}

 	for i := 0; i < len(helloServer); i++ {
 		server := strings.Join(strings.Split(baseHelloServer+helloServer[i], "\n"), "\r\n")
 		client := strings.Join(strings.Split(baseHelloClient+helloClient[i], "\n"), "\r\n")
 		var cmdbuf bytes.Buffer
 		bcmdbuf := bufio.NewWriter(&cmdbuf)
 		var fake faker
 		fake.ReadWriter = bufio.NewReadWriter(bufio.NewReader(strings.NewReader(server)), bcmdbuf)
 		c, err := NewClient(fake, "fake.host")
 		if err != nil {
 			t.Fatalf("NewClient: %v", err)
 		}
 		defer c.Close()
 		c.localName = "customhost"
 		err = nil

 		switch i {
 		case 0:
 			err = c.Hello("customhost")
 		case 1:
 			err = c.StartTLS(nil)
 			if err.Error() == "502 Not implemented" {
 				err = nil
 			}
 		case 2:
 			err = c.Verify("test@example.com")
 		case 3:
 			c.tls = true
 			c.serverName = "smtp.google.com"
 			err = c.Auth(PlainAuth("", "user", "pass", "smtp.google.com"))
 		case 4:
 			err = c.Mail("test@example.com")
 		case 5:
 			ok, _ := c.Extension("feature")
 			if ok {
 				t.Errorf("Expected FEATURE not to be supported")
 			}
 		case 6:
 			err = c.Reset()
 		case 7:
 			err = c.Quit()
 		case 8:
 			err = c.Verify("test@example.com")
 			if err != nil {
 				err = c.Hello("customhost")
 				if err != nil {
 					t.Errorf("Want error, got none")
 				}
 			}
 		default:
 			t.Fatalf("Unhandled command")
 		}

 		if err != nil {
 			t.Errorf("Command %d failed: %v", i, err)
 		}

 		bcmdbuf.Flush()
 		actualcmds := cmdbuf.String()
 		if client != actualcmds {
 			t.Errorf("Got:\n%s\nExpected:\n%s", actualcmds, client)
 		}
 	}
 }

 var baseHelloServer = `220 hello world
 502 EH?
 250-mx.google.com at your service
 250 FEATURE
 `

 var helloServer = []string{
 	"",
 	"502 Not implemented\n",
 	"250 User is valid\n",
 	"235 Accepted\n",
 	"250 Sender ok\n",
 	"",
 	"250 Reset ok\n",
 	"221 Goodbye\n",
 	"250 Sender ok\n",
 }

 var baseHelloClient = `EHLO customhost
 HELO customhost
 `

 var helloClient = []string{
 	"",
 	"STARTTLS\n",
 	"VRFY test@example.com\n",
 	"AUTH PLAIN AHVzZXIAcGFzcw==\n",
 	"MAIL FROM:<test@example.com>\n",
 	"",
 	"RSET\n",
 	"QUIT\n",
 	"VRFY test@example.com\n",
 }

 func TestSendMail(t *testing.T) {
 	server := strings.Join(strings.Split(sendMailServer, "\n"), "\r\n")
 	client := strings.Join(strings.Split(sendMailClient, "\n"), "\r\n")
 	var cmdbuf bytes.Buffer
 	bcmdbuf := bufio.NewWriter(&cmdbuf)
 	l, err := net.Listen("tcp", "127.0.0.1:0")
 	if err != nil {
 		t.Fatalf("Unable to to create listener: %v", err)
 	}
 	defer l.Close()

 	// prevent data race on bcmdbuf
 	var done = make(chan struct{})
 	go func(data []string) {

 		defer close(done)

 		conn, err := l.Accept()
 		if err != nil {
 			t.Errorf("Accept error: %v", err)
 			return
 		}
 		defer conn.Close()

 		tc := textproto.NewConn(conn)
 		for i := 0; i < len(data) && data[i] != ""; i++ {
 			tc.PrintfLine(data[i])
 			for len(data[i]) >= 4 && data[i][3] == '-' {
 				i++
 				tc.PrintfLine(data[i])
 			}
 			if data[i] == "221 Goodbye" {
 				return
 			}
 			read := false
 			for !read || data[i] == "354 Go ahead" {
 				msg, err := tc.ReadLine()
 				bcmdbuf.Write([]byte(msg + "\r\n"))
 				read = true
 				if err != nil {
 					t.Errorf("Read error: %v", err)
 					return
 				}
 				if data[i] == "354 Go ahead" && msg == "." {
 					break
 				}
 			}
 		}
 	}(strings.Split(server, "\r\n"))

 	err = SendMail(l.Addr().String(), nil, "test@example.com", []string{"other@example.com"}, []byte(strings.Replace(`From: test@example.com
 To: other@example.com
 Subject: SendMail test

 SendMail is working for me.
 `, "\n", "\r\n", -1)))

 	if err != nil {
 		t.Errorf("%v", err)
 	}

 	<-done
 	bcmdbuf.Flush()
 	actualcmds := cmdbuf.String()
 	if client != actualcmds {
 		t.Errorf("Got:\n%s\nExpected:\n%s", actualcmds, client)
 	}
 }

 var sendMailServer = `220 hello world
 502 EH?
 250 mx.google.com at your service
 250 Sender ok
 250 Receiver ok
 354 Go ahead
 250 Data ok
 221 Goodbye
 `

 var sendMailClient = `EHLO localhost
 HELO localhost
 MAIL FROM:<test@example.com>
 RCPT TO:<other@example.com>
 DATA
 From: test@example.com
 To: other@example.com
 Subject: SendMail test

 SendMail is working for me.
 .
 QUIT
 `

 func TestAuthFailed(t *testing.T) {
 	server := strings.Join(strings.Split(authFailedServer, "\n"), "\r\n")
 	client := strings.Join(strings.Split(authFailedClient, "\n"), "\r\n")
 	var cmdbuf bytes.Buffer
 	bcmdbuf := bufio.NewWriter(&cmdbuf)
 	var fake faker
 	fake.ReadWriter = bufio.NewReadWriter(bufio.NewReader(strings.NewReader(server)), bcmdbuf)
 	c, err := NewClient(fake, "fake.host")
 	if err != nil {
 		t.Fatalf("NewClient: %v", err)
 	}
 	defer c.Close()

 	c.tls = true
 	c.serverName = "smtp.google.com"
 	err = c.Auth(PlainAuth("", "user", "pass", "smtp.google.com"))

 	if err == nil {
 		t.Error("Auth: expected error; got none")
 	} else if err.Error() != "535 Invalid credentials\nplease see www.example.com" {
 		t.Errorf("Auth: got error: %v, want: %s", err, "535 Invalid credentials\nplease see www.example.com")
 	}

 	bcmdbuf.Flush()
 	actualcmds := cmdbuf.String()
 	if client != actualcmds {
 		t.Errorf("Got:\n%s\nExpected:\n%s", actualcmds, client)
 	}
 }

 var authFailedServer = `220 hello world
 250-mx.google.com at your service
 250 AUTH LOGIN PLAIN
 535-Invalid credentials
 535 please see www.example.com
 221 Goodbye
 `

 var authFailedClient = `EHLO localhost
 AUTH PLAIN AHVzZXIAcGFzcw==
 *
 QUIT
 `

 func TestTLSClient(t *testing.T) {
 	ln := newLocalListener(t)
 	defer ln.Close()
 	errc := make(chan error)
 	go func() {
 		errc <- sendMail(ln.Addr().String())
 	}()
 	conn, err := ln.Accept()
 	if err != nil {
 		t.Fatalf("failed to accept connection: %v", err)
 	}
 	defer conn.Close()
 	if err := serverHandle(conn, t); err != nil {
 		t.Fatalf("failed to handle connection: %v", err)
 	}
 	if err := <-errc; err != nil {
 		t.Fatalf("client error: %v", err)
 	}
 }

 func TestTLSConnState(t *testing.T) {
 	ln := newLocalListener(t)
 	defer ln.Close()
 	clientDone := make(chan bool)
 	serverDone := make(chan bool)
 	go func() {
 		defer close(serverDone)
 		c, err := ln.Accept()
 		if err != nil {
 			t.Errorf("Server accept: %v", err)
 			return
 		}
 		defer c.Close()
 		if err := serverHandle(c, t); err != nil {
 			t.Errorf("server error: %v", err)
 		}
 	}()
 	go func() {
 		defer close(clientDone)
 		c, err := Dial(ln.Addr().String())
 		if err != nil {
 			t.Errorf("Client dial: %v", err)
 			return
 		}
 		defer c.Quit()
 		cfg := &tls.Config{ServerName: "example.com"}
 		testHookStartTLS(cfg) // set the RootCAs
 		if err := c.StartTLS(cfg); err != nil {
 			t.Errorf("StartTLS: %v", err)
 			return
 		}
 		cs, ok := c.TLSConnectionState()
 		if !ok {
 			t.Errorf("TLSConnectionState returned ok == false; want true")
 			return
 		}
 		if cs.Version == 0 || !cs.HandshakeComplete {
 			t.Errorf("ConnectionState = %#v; expect non-zero Version and HandshakeComplete", cs)
 		}
 	}()
 	<-clientDone
 	<-serverDone
 }

 func newLocalListener(t *testing.T) net.Listener {
 	ln, err := net.Listen("tcp", "127.0.0.1:0")
 	if err != nil {
 		ln, err = net.Listen("tcp6", "[::1]:0")
 	}
 	if err != nil {
 		t.Fatal(err)
 	}
 	return ln
 }

 type smtpSender struct {
 	w io.Writer
 }

 func (s smtpSender) send(f string) {
 	s.w.Write([]byte(f + "\r\n"))
 }

 // smtp server, finely tailored to deal with our own client only!
 func serverHandle(c net.Conn, t *testing.T) error {
 	send := smtpSender{c}.send
 	send("220 127.0.0.1 ESMTP service ready")
 	s := bufio.NewScanner(c)
 	for s.Scan() {
 		switch s.Text() {
 		case "EHLO localhost":
 			send("250-127.0.0.1 ESMTP offers a warm hug of welcome")
 			send("250-STARTTLS")
 			send("250 Ok")
 		case "STARTTLS":
 			send("220 Go ahead")
 			keypair, err := tls.X509KeyPair(localhostCert, localhostKey)
 			if err != nil {
 				return err
 			}
 			config := &tls.Config{Certificates: []tls.Certificate{keypair}}
 			c = tls.Server(c, config)
 			defer c.Close()
 			return serverHandleTLS(c, t)
 		default:
 			t.Fatalf("unrecognized command: %q", s.Text())
 		}
 	}
 	return s.Err()
 }

 func serverHandleTLS(c net.Conn, t *testing.T) error {
 	send := smtpSender{c}.send
 	s := bufio.NewScanner(c)
 	for s.Scan() {
 		switch s.Text() {
 		case "EHLO localhost":
 			send("250 Ok")
 		case "MAIL FROM:<joe1@example.com>":
 			send("250 Ok")
 		case "RCPT TO:<joe2@example.com>":
 			send("250 Ok")
 		case "DATA":
 			send("354 send the mail data, end with .")
 			send("250 Ok")
 		case "Subject: test":
 		case "":
 		case "howdy!":
 		case ".":
 		case "QUIT":
 			send("221 127.0.0.1 Service closing transmission channel")
 			return nil
 		default:
 			t.Fatalf("unrecognized command during TLS: %q", s.Text())
 		}
 	}
 	return s.Err()
 }

 func init() {
 	testRootCAs := x509.NewCertPool()
 	testRootCAs.AppendCertsFromPEM(localhostCert)
 	testHookStartTLS = func(config *tls.Config) {
 		config.RootCAs = testRootCAs
 	}
 }

 func sendMail(hostPort string) error {
 	host, _, err := net.SplitHostPort(hostPort)
 	if err != nil {
 		return err
 	}
 	auth := PlainAuth("", "", "", host)
 	from := "joe1@example.com"
 	to := []string{"joe2@example.com"}
 	return SendMail(hostPort, auth, from, to, []byte("Subject: test\n\nhowdy!"))
 }

 // (copied from net/http/httptest)
 // localhostCert is a PEM-encoded TLS cert with SAN IPs
 // "127.0.0.1" and "[::1]", expiring at the last second of 2049 (the end
 // of ASN.1 time).
 // generated from src/crypto/tls:
 // go run generate_cert.go  --rsa-bits 512 --host 127.0.0.1,::1,example.com --ca --start-date "Jan 1 00:00:00 1970" --duration=1000000h
 var localhostCert = []byte(`-----BEGIN CERTIFICATE-----
 MIIBjjCCATigAwIBAgIQMon9v0s3pDFXvAMnPgelpzANBgkqhkiG9w0BAQsFADAS
 MRAwDgYDVQQKEwdBY21lIENvMCAXDTcwMDEwMTAwMDAwMFoYDzIwODQwMTI5MTYw
 MDAwWjASMRAwDgYDVQQKEwdBY21lIENvMFwwDQYJKoZIhvcNAQEBBQADSwAwSAJB
 AM0u/mNXKkhAzNsFkwKZPSpC4lZZaePQ55IyaJv3ovMM2smvthnlqaUfVKVmz7FF
 wLP9csX6vGtvkZg1uWAtvfkCAwEAAaNoMGYwDgYDVR0PAQH/BAQDAgKkMBMGA1Ud
 JQQMMAoGCCsGAQUFBwMBMA8GA1UdEwEB/wQFMAMBAf8wLgYDVR0RBCcwJYILZXhh
 bXBsZS5jb22HBH8AAAGHEAAAAAAAAAAAAAAAAAAAAAEwDQYJKoZIhvcNAQELBQAD
 QQBOZsFVC7IwX+qibmSbt2IPHkUgXhfbq0a9MYhD6tHcj4gbDcTXh4kZCbgHCz22
 gfSj2/G2wxzopoISVDucuncj
 -----END CERTIFICATE-----`)

 // localhostKey is the private key for localhostCert.
 var localhostKey = []byte(`-----BEGIN RSA PRIVATE KEY-----
 MIIBOwIBAAJBAM0u/mNXKkhAzNsFkwKZPSpC4lZZaePQ55IyaJv3ovMM2smvthnl
 qaUfVKVmz7FFwLP9csX6vGtvkZg1uWAtvfkCAwEAAQJART2qkxODLUbQ2siSx7m2
 rmBLyR/7X+nLe8aPDrMOxj3heDNl4YlaAYLexbcY8d7VDfCRBKYoAOP0UCP1Vhuf
 UQIhAO6PEI55K3SpNIdc2k5f0xz+9rodJCYzu51EwWX7r8ufAiEA3C9EkLiU2NuK
 3L3DHCN5IlUSN1Nr/lw8NIt50Yorj2cCIQCDw1VbvCV6bDLtSSXzAA51B4ZzScE7
 sHtB5EYF9Dwm9QIhAJuCquuH4mDzVjUntXjXOQPdj7sRqVGCNWdrJwOukat7AiAy
 LXLEwb77DIPoI5ZuaXQC+MnyyJj1ExC9RFcGz+bexA==
 -----END RSA PRIVATE KEY-----`)
	// Copyright 2010 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.

	package smtp

	import (
	"bufio"
	"bytes"
	"crypto/tls"
	"crypto/x509"
	"io"
	"net"
	"net/textproto"
	"strings"
	"testing"
	"time"
	)

	type authTest struct {
	auth Auth
	challenges []string
	name string
	responses []string
	}

	var authTests = []authTest{
	{PlainAuth("", "user", "pass", "testserver"), []string{}, "PLAIN", []string{"\x00user\x00pass"}},
	{PlainAuth("foo", "bar", "baz", "testserver"), []string{}, "PLAIN", []string{"foo\x00bar\x00baz"}},
	{CRAMMD5Auth("user", "pass"), []string{"<123456.1322876914@testserver>"}, "CRAM-MD5", []string{"", "user 287eb355114cf5c471c26a875f1ca4ae"}},
	}

	func TestAuth(t *testing.T) {
	testLoop:
	for i, test := range authTests {
	name, resp, err := test.auth.Start(&ServerInfo{"testserver", true, nil})
	if name != test.name {
	t.Errorf("#%d got name %s, expected %s", i, name, test.name)
	}
	if !bytes.Equal(resp, []byte(test.responses[0])) {
	t.Errorf("#%d got response %s, expected %s", i, resp, test.responses[0])
	}
	if err != nil {
	t.Errorf("#%d error: %s", i, err)
	}
	for j := range test.challenges {
	challenge := []byte(test.challenges[j])
	expected := []byte(test.responses[j+1])
	resp, err := test.auth.Next(challenge, true)
	if err != nil {
	t.Errorf("#%d error: %s", i, err)
	continue testLoop
	}
	if !bytes.Equal(resp, expected) {
	t.Errorf("#%d got %s, expected %s", i, resp, expected)
	continue testLoop
	}
	}
	}
	}

	func TestAuthPlain(t *testing.T) {

	tests := []struct {
	authName string
	server *ServerInfo
	err string
	}{
	{
	authName: "servername",
	server: &ServerInfo{Name: "servername", TLS: true},
	},
	{
	// OK to use PlainAuth on localhost without TLS
	authName: "localhost",
	server: &ServerInfo{Name: "localhost", TLS: false},
	},
	{
	// NOT OK on non-localhost, even if server says PLAIN is OK.
	// (We don't know that the server is the real server.)
	authName: "servername",
	server: &ServerInfo{Name: "servername", Auth: []string{"PLAIN"}},
	err: "unencrypted connection",
	},
	{
	authName: "servername",
	server: &ServerInfo{Name: "servername", Auth: []string{"CRAM-MD5"}},
	err: "unencrypted connection",
	},
	{
	authName: "servername",
	server: &ServerInfo{Name: "attacker", TLS: true},
	err: "wrong host name",
	},
	}
	for i, tt := range tests {
	auth := PlainAuth("foo", "bar", "baz", tt.authName)
	_, _, err := auth.Start(tt.server)
	got := ""
	if err != nil {
	got = err.Error()
	}
	if got != tt.err {
	t.Errorf("%d. got error = %q; want %q", i, got, tt.err)
	}
	}
	}

	// Issue 17794: don't send a trailing space on AUTH command when there's no password.
	func TestClientAuthTrimSpace(t *testing.T) {
	server := "220 hello world\r\n" +
	"200 some more"
	var wrote bytes.Buffer
	var fake faker
	fake.ReadWriter = struct {
	io.Reader
	io.Writer
	}{
	strings.NewReader(server),
	&wrote,
	}
	c, err := NewClient(fake, "fake.host")
	if err != nil {
	t.Fatalf("NewClient: %v", err)
	}
	c.tls = true
	c.didHello = true
	c.Auth(toServerEmptyAuth{})
	c.Close()
	if got, want := wrote.String(), "AUTH FOOAUTH\r\n*\r\nQUIT\r\n"; got != want {
	t.Errorf("wrote %q; want %q", got, want)
	}
	}

	// toServerEmptyAuth is an implementation of Auth that only implements
	// the Start method, and returns "FOOAUTH", nil, nil. Notably, it returns
	// zero bytes for "toServer" so we can test that we don't send spaces at
	// the end of the line. See TestClientAuthTrimSpace.
	type toServerEmptyAuth struct{}

	func (toServerEmptyAuth) Start(server *ServerInfo) (proto string, toServer []byte, err error) {
	return "FOOAUTH", nil, nil
	}

	func (toServerEmptyAuth) Next(fromServer []byte, more bool) (toServer []byte, err error) {
	panic("unexpected call")
	}

	type faker struct {
	io.ReadWriter
	}

	func (f faker) Close() error { return nil }
	func (f faker) LocalAddr() net.Addr { return nil }
	func (f faker) RemoteAddr() net.Addr { return nil }
	func (f faker) SetDeadline(time.Time) error { return nil }
	func (f faker) SetReadDeadline(time.Time) error { return nil }
	func (f faker) SetWriteDeadline(time.Time) error { return nil }

	func TestBasic(t *testing.T) {
	server := strings.Join(strings.Split(basicServer, "\n"), "\r\n")
	client := strings.Join(strings.Split(basicClient, "\n"), "\r\n")

	var cmdbuf bytes.Buffer
	bcmdbuf := bufio.NewWriter(&cmdbuf)
	var fake faker
	fake.ReadWriter = bufio.NewReadWriter(bufio.NewReader(strings.NewReader(server)), bcmdbuf)
	c := &Client{Text: textproto.NewConn(fake), localName: "localhost"}

	if err := c.helo(); err != nil {
	t.Fatalf("HELO failed: %s", err)
	}
	if err := c.ehlo(); err == nil {
	t.Fatalf("Expected first EHLO to fail")
	}
	if err := c.ehlo(); err != nil {
	t.Fatalf("Second EHLO failed: %s", err)
	}

	c.didHello = true
	if ok, args := c.Extension("aUtH"); !ok \|\| args != "LOGIN PLAIN" {
	t.Fatalf("Expected AUTH supported")
	}
	if ok, _ := c.Extension("DSN"); ok {
	t.Fatalf("Shouldn't support DSN")
	}

	if err := c.Mail("user@gmail.com"); err == nil {
	t.Fatalf("MAIL should require authentication")
	}

	if err := c.Verify("user1@gmail.com"); err == nil {
	t.Fatalf("First VRFY: expected no verification")
	}
	if err := c.Verify("user2@gmail.com"); err != nil {
	t.Fatalf("Second VRFY: expected verification, got %s", err)
	}

	// fake TLS so authentication won't complain
	c.tls = true
	c.serverName = "smtp.google.com"
	if err := c.Auth(PlainAuth("", "user", "pass", "smtp.google.com")); err != nil {
	t.Fatalf("AUTH failed: %s", err)
	}

	if err := c.Mail("user@gmail.com"); err != nil {
	t.Fatalf("MAIL failed: %s", err)
	}
	if err := c.Rcpt("golang-nuts@googlegroups.com"); err != nil {
	t.Fatalf("RCPT failed: %s", err)
	}
	msg := `From: user@gmail.com
	To: golang-nuts@googlegroups.com
	Subject: Hooray for Go

	Line 1
	.Leading dot line .
	Goodbye.`
	w, err := c.Data()
	if err != nil {
	t.Fatalf("DATA failed: %s", err)
	}
	if _, err := w.Write([]byte(msg)); err != nil {
	t.Fatalf("Data write failed: %s", err)
	}
	if err := w.Close(); err != nil {
	t.Fatalf("Bad data response: %s", err)
	}

	if err := c.Quit(); err != nil {
	t.Fatalf("QUIT failed: %s", err)
	}

	bcmdbuf.Flush()
	actualcmds := cmdbuf.String()
	if client != actualcmds {
	t.Fatalf("Got:\n%s\nExpected:\n%s", actualcmds, client)
	}
	}

	var basicServer = `250 mx.google.com at your service
	502 Unrecognized command.
	250-mx.google.com at your service
	250-SIZE 35651584
	250-AUTH LOGIN PLAIN
	250 8BITMIME
	530 Authentication required
	252 Send some mail, I'll try my best
	250 User is valid
	235 Accepted
	250 Sender OK
	250 Receiver OK
	354 Go ahead
	250 Data OK
	221 OK
	`

	var basicClient = `HELO localhost
	EHLO localhost
	EHLO localhost
	MAIL FROM:<user@gmail.com> BODY=8BITMIME
	VRFY user1@gmail.com
	VRFY user2@gmail.com
	AUTH PLAIN AHVzZXIAcGFzcw==
	MAIL FROM:<user@gmail.com> BODY=8BITMIME
	RCPT TO:<golang-nuts@googlegroups.com>
	DATA
	From: user@gmail.com
	To: golang-nuts@googlegroups.com
	Subject: Hooray for Go

	Line 1
	..Leading dot line .
	Goodbye.
	.
	QUIT
	`

	func TestNewClient(t *testing.T) {
	server := strings.Join(strings.Split(newClientServer, "\n"), "\r\n")
	client := strings.Join(strings.Split(newClientClient, "\n"), "\r\n")

	var cmdbuf bytes.Buffer
	bcmdbuf := bufio.NewWriter(&cmdbuf)
	out := func() string {
	bcmdbuf.Flush()
	return cmdbuf.String()
	}
	var fake faker
	fake.ReadWriter = bufio.NewReadWriter(bufio.NewReader(strings.NewReader(server)), bcmdbuf)
	c, err := NewClient(fake, "fake.host")
	if err != nil {
	t.Fatalf("NewClient: %v\n(after %v)", err, out())
	}
	defer c.Close()
	if ok, args := c.Extension("aUtH"); !ok \|\| args != "LOGIN PLAIN" {
	t.Fatalf("Expected AUTH supported")
	}
	if ok, _ := c.Extension("DSN"); ok {
	t.Fatalf("Shouldn't support DSN")
	}
	if err := c.Quit(); err != nil {
	t.Fatalf("QUIT failed: %s", err)
	}

	actualcmds := out()
	if client != actualcmds {
	t.Fatalf("Got:\n%s\nExpected:\n%s", actualcmds, client)
	}
	}

	var newClientServer = `220 hello world
	250-mx.google.com at your service
	250-SIZE 35651584
	250-AUTH LOGIN PLAIN
	250 8BITMIME
	221 OK
	`

	var newClientClient = `EHLO localhost
	QUIT
	`

	func TestNewClient2(t *testing.T) {
	server := strings.Join(strings.Split(newClient2Server, "\n"), "\r\n")
	client := strings.Join(strings.Split(newClient2Client, "\n"), "\r\n")

	var cmdbuf bytes.Buffer
	bcmdbuf := bufio.NewWriter(&cmdbuf)
	var fake faker
	fake.ReadWriter = bufio.NewReadWriter(bufio.NewReader(strings.NewReader(server)), bcmdbuf)
	c, err := NewClient(fake, "fake.host")
	if err != nil {
	t.Fatalf("NewClient: %v", err)
	}
	defer c.Close()
	if ok, _ := c.Extension("DSN"); ok {
	t.Fatalf("Shouldn't support DSN")
	}
	if err := c.Quit(); err != nil {
	t.Fatalf("QUIT failed: %s", err)
	}

	bcmdbuf.Flush()
	actualcmds := cmdbuf.String()
	if client != actualcmds {
	t.Fatalf("Got:\n%s\nExpected:\n%s", actualcmds, client)
	}
	}

	var newClient2Server = `220 hello world
	502 EH?
	250-mx.google.com at your service
	250-SIZE 35651584
	250-AUTH LOGIN PLAIN
	250 8BITMIME
	221 OK
	`

	var newClient2Client = `EHLO localhost
	HELO localhost
	QUIT
	`

	func TestNewClientWithTLS(t *testing.T) {
	cert, err := tls.X509KeyPair(localhostCert, localhostKey)
	if err != nil {
	t.Fatalf("loadcert: %v", err)
	}

	config := tls.Config{Certificates: []tls.Certificate{cert}}

	ln, err := tls.Listen("tcp", "127.0.0.1:0", &config)
	if err != nil {
	ln, err = tls.Listen("tcp", "[::1]:0", &config)
	if err != nil {
	t.Fatalf("server: listen: %s", err)
	}
	}

	go func() {
	conn, err := ln.Accept()
	if err != nil {
	t.Fatalf("server: accept: %s", err)
	return
	}
	defer conn.Close()

	_, err = conn.Write([]byte("220 SIGNS\r\n"))
	if err != nil {
	t.Fatalf("server: write: %s", err)
	return
	}
	}()

	config.InsecureSkipVerify = true
	conn, err := tls.Dial("tcp", ln.Addr().String(), &config)
	if err != nil {
	t.Fatalf("client: dial: %s", err)
	}
	defer conn.Close()

	client, err := NewClient(conn, ln.Addr().String())
	if err != nil {
	t.Fatalf("smtp: newclient: %s", err)
	}
	if !client.tls {
	t.Errorf("client.tls Got: %t Expected: %t", client.tls, true)
	}
	}

	func TestHello(t *testing.T) {

	if len(helloServer) != len(helloClient) {
	t.Fatalf("Hello server and client size mismatch")
	}

	for i := 0; i < len(helloServer); i++ {
	server := strings.Join(strings.Split(baseHelloServer+helloServer[i], "\n"), "\r\n")
	client := strings.Join(strings.Split(baseHelloClient+helloClient[i], "\n"), "\r\n")
	var cmdbuf bytes.Buffer
	bcmdbuf := bufio.NewWriter(&cmdbuf)
	var fake faker
	fake.ReadWriter = bufio.NewReadWriter(bufio.NewReader(strings.NewReader(server)), bcmdbuf)
	c, err := NewClient(fake, "fake.host")
	if err != nil {
	t.Fatalf("NewClient: %v", err)
	}
	defer c.Close()
	c.localName = "customhost"
	err = nil

	switch i {
	case 0:
	err = c.Hello("customhost")
	case 1:
	err = c.StartTLS(nil)
	if err.Error() == "502 Not implemented" {
	err = nil
	}
	case 2:
	err = c.Verify("test@example.com")
	case 3:
	c.tls = true
	c.serverName = "smtp.google.com"
	err = c.Auth(PlainAuth("", "user", "pass", "smtp.google.com"))
	case 4:
	err = c.Mail("test@example.com")
	case 5:
	ok, _ := c.Extension("feature")
	if ok {
	t.Errorf("Expected FEATURE not to be supported")
	}
	case 6:
	err = c.Reset()
	case 7:
	err = c.Quit()
	case 8:
	err = c.Verify("test@example.com")
	if err != nil {
	err = c.Hello("customhost")
	if err != nil {
	t.Errorf("Want error, got none")
	}
	}
	default:
	t.Fatalf("Unhandled command")
	}

	if err != nil {
	t.Errorf("Command %d failed: %v", i, err)
	}

	bcmdbuf.Flush()
	actualcmds := cmdbuf.String()
	if client != actualcmds {
	t.Errorf("Got:\n%s\nExpected:\n%s", actualcmds, client)
	}
	}
	}

	var baseHelloServer = `220 hello world
	502 EH?
	250-mx.google.com at your service
	250 FEATURE
	`

	var helloServer = []string{
	"",
	"502 Not implemented\n",
	"250 User is valid\n",
	"235 Accepted\n",
	"250 Sender ok\n",
	"",
	"250 Reset ok\n",
	"221 Goodbye\n",
	"250 Sender ok\n",
	}

	var baseHelloClient = `EHLO customhost
	HELO customhost
	`

	var helloClient = []string{
	"",
	"STARTTLS\n",
	"VRFY test@example.com\n",
	"AUTH PLAIN AHVzZXIAcGFzcw==\n",
	"MAIL FROM:<test@example.com>\n",
	"",
	"RSET\n",
	"QUIT\n",
	"VRFY test@example.com\n",
	}

	func TestSendMail(t *testing.T) {
	server := strings.Join(strings.Split(sendMailServer, "\n"), "\r\n")
	client := strings.Join(strings.Split(sendMailClient, "\n"), "\r\n")
	var cmdbuf bytes.Buffer
	bcmdbuf := bufio.NewWriter(&cmdbuf)
	l, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
	t.Fatalf("Unable to to create listener: %v", err)
	}
	defer l.Close()

	// prevent data race on bcmdbuf
	var done = make(chan struct{})
	go func(data []string) {

	defer close(done)

	conn, err := l.Accept()
	if err != nil {
	t.Errorf("Accept error: %v", err)
	return
	}
	defer conn.Close()

	tc := textproto.NewConn(conn)
	for i := 0; i < len(data) && data[i] != ""; i++ {
	tc.PrintfLine(data[i])
	for len(data[i]) >= 4 && data[i][3] == '-' {
	i++
	tc.PrintfLine(data[i])
	}
	if data[i] == "221 Goodbye" {
	return
	}
	read := false
	for !read \|\| data[i] == "354 Go ahead" {
	msg, err := tc.ReadLine()
	bcmdbuf.Write([]byte(msg + "\r\n"))
	read = true
	if err != nil {
	t.Errorf("Read error: %v", err)
	return
	}
	if data[i] == "354 Go ahead" && msg == "." {
	break
	}
	}
	}
	}(strings.Split(server, "\r\n"))

	err = SendMail(l.Addr().String(), nil, "test@example.com", []string{"other@example.com"}, []byte(strings.Replace(`From: test@example.com
	To: other@example.com
	Subject: SendMail test

	SendMail is working for me.
	`, "\n", "\r\n", -1)))

	if err != nil {
	t.Errorf("%v", err)
	}

	<-done
	bcmdbuf.Flush()
	actualcmds := cmdbuf.String()
	if client != actualcmds {
	t.Errorf("Got:\n%s\nExpected:\n%s", actualcmds, client)
	}
	}

	var sendMailServer = `220 hello world
	502 EH?
	250 mx.google.com at your service
	250 Sender ok
	250 Receiver ok
	354 Go ahead
	250 Data ok
	221 Goodbye
	`

	var sendMailClient = `EHLO localhost
	HELO localhost
	MAIL FROM:<test@example.com>
	RCPT TO:<other@example.com>
	DATA
	From: test@example.com
	To: other@example.com
	Subject: SendMail test

	SendMail is working for me.
	.
	QUIT
	`

	func TestAuthFailed(t *testing.T) {
	server := strings.Join(strings.Split(authFailedServer, "\n"), "\r\n")
	client := strings.Join(strings.Split(authFailedClient, "\n"), "\r\n")
	var cmdbuf bytes.Buffer
	bcmdbuf := bufio.NewWriter(&cmdbuf)
	var fake faker
	fake.ReadWriter = bufio.NewReadWriter(bufio.NewReader(strings.NewReader(server)), bcmdbuf)
	c, err := NewClient(fake, "fake.host")
	if err != nil {
	t.Fatalf("NewClient: %v", err)
	}
	defer c.Close()

	c.tls = true
	c.serverName = "smtp.google.com"
	err = c.Auth(PlainAuth("", "user", "pass", "smtp.google.com"))

	if err == nil {
	t.Error("Auth: expected error; got none")
	} else if err.Error() != "535 Invalid credentials\nplease see www.example.com" {
	t.Errorf("Auth: got error: %v, want: %s", err, "535 Invalid credentials\nplease see www.example.com")
	}

	bcmdbuf.Flush()
	actualcmds := cmdbuf.String()
	if client != actualcmds {
	t.Errorf("Got:\n%s\nExpected:\n%s", actualcmds, client)
	}
	}

	var authFailedServer = `220 hello world
	250-mx.google.com at your service
	250 AUTH LOGIN PLAIN
	535-Invalid credentials
	535 please see www.example.com
	221 Goodbye
	`

	var authFailedClient = `EHLO localhost
	AUTH PLAIN AHVzZXIAcGFzcw==
	*
	QUIT
	`

	func TestTLSClient(t *testing.T) {
	ln := newLocalListener(t)
	defer ln.Close()
	errc := make(chan error)
	go func() {
	errc <- sendMail(ln.Addr().String())
	}()
	conn, err := ln.Accept()
	if err != nil {
	t.Fatalf("failed to accept connection: %v", err)
	}
	defer conn.Close()
	if err := serverHandle(conn, t); err != nil {
	t.Fatalf("failed to handle connection: %v", err)
	}
	if err := <-errc; err != nil {
	t.Fatalf("client error: %v", err)
	}
	}

	func TestTLSConnState(t *testing.T) {
	ln := newLocalListener(t)
	defer ln.Close()
	clientDone := make(chan bool)
	serverDone := make(chan bool)
	go func() {
	defer close(serverDone)
	c, err := ln.Accept()
	if err != nil {
	t.Errorf("Server accept: %v", err)
	return
	}
	defer c.Close()
	if err := serverHandle(c, t); err != nil {
	t.Errorf("server error: %v", err)
	}
	}()
	go func() {
	defer close(clientDone)
	c, err := Dial(ln.Addr().String())
	if err != nil {
	t.Errorf("Client dial: %v", err)
	return
	}
	defer c.Quit()
	cfg := &tls.Config{ServerName: "example.com"}
	testHookStartTLS(cfg) // set the RootCAs
	if err := c.StartTLS(cfg); err != nil {
	t.Errorf("StartTLS: %v", err)
	return
	}
	cs, ok := c.TLSConnectionState()
	if !ok {
	t.Errorf("TLSConnectionState returned ok == false; want true")
	return
	}
	if cs.Version == 0 \|\| !cs.HandshakeComplete {
	t.Errorf("ConnectionState = %#v; expect non-zero Version and HandshakeComplete", cs)
	}
	}()
	<-clientDone
	<-serverDone
	}

	func newLocalListener(t *testing.T) net.Listener {
	ln, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
	ln, err = net.Listen("tcp6", "[::1]:0")
	}
	if err != nil {
	t.Fatal(err)
	}
	return ln
	}

	type smtpSender struct {
	w io.Writer
	}

	func (s smtpSender) send(f string) {
	s.w.Write([]byte(f + "\r\n"))
	}

	// smtp server, finely tailored to deal with our own client only!
	func serverHandle(c net.Conn, t *testing.T) error {
	send := smtpSender{c}.send
	send("220 127.0.0.1 ESMTP service ready")
	s := bufio.NewScanner(c)
	for s.Scan() {
	switch s.Text() {
	case "EHLO localhost":
	send("250-127.0.0.1 ESMTP offers a warm hug of welcome")
	send("250-STARTTLS")
	send("250 Ok")
	case "STARTTLS":
	send("220 Go ahead")
	keypair, err := tls.X509KeyPair(localhostCert, localhostKey)
	if err != nil {
	return err
	}
	config := &tls.Config{Certificates: []tls.Certificate{keypair}}
	c = tls.Server(c, config)
	defer c.Close()
	return serverHandleTLS(c, t)
	default:
	t.Fatalf("unrecognized command: %q", s.Text())
	}
	}
	return s.Err()
	}

	func serverHandleTLS(c net.Conn, t *testing.T) error {
	send := smtpSender{c}.send
	s := bufio.NewScanner(c)
	for s.Scan() {
	switch s.Text() {
	case "EHLO localhost":
	send("250 Ok")
	case "MAIL FROM:<joe1@example.com>":
	send("250 Ok")
	case "RCPT TO:<joe2@example.com>":
	send("250 Ok")
	case "DATA":
	send("354 send the mail data, end with .")
	send("250 Ok")
	case "Subject: test":
	case "":
	case "howdy!":
	case ".":
	case "QUIT":
	send("221 127.0.0.1 Service closing transmission channel")
	return nil
	default:
	t.Fatalf("unrecognized command during TLS: %q", s.Text())
	}
	}
	return s.Err()
	}

	func init() {
	testRootCAs := x509.NewCertPool()
	testRootCAs.AppendCertsFromPEM(localhostCert)
	testHookStartTLS = func(config *tls.Config) {
	config.RootCAs = testRootCAs
	}
	}

	func sendMail(hostPort string) error {
	host, _, err := net.SplitHostPort(hostPort)
	if err != nil {
	return err
	}
	auth := PlainAuth("", "", "", host)
	from := "joe1@example.com"
	to := []string{"joe2@example.com"}
	return SendMail(hostPort, auth, from, to, []byte("Subject: test\n\nhowdy!"))
	}

	// (copied from net/http/httptest)
	// localhostCert is a PEM-encoded TLS cert with SAN IPs
	// "127.0.0.1" and "[::1]", expiring at the last second of 2049 (the end
	// of ASN.1 time).
	// generated from src/crypto/tls:
	// go run generate_cert.go --rsa-bits 512 --host 127.0.0.1,::1,example.com --ca --start-date "Jan 1 00:00:00 1970" --duration=1000000h
	var localhostCert = []byte(`-----BEGIN CERTIFICATE-----
	MIIBjjCCATigAwIBAgIQMon9v0s3pDFXvAMnPgelpzANBgkqhkiG9w0BAQsFADAS
	MRAwDgYDVQQKEwdBY21lIENvMCAXDTcwMDEwMTAwMDAwMFoYDzIwODQwMTI5MTYw
	MDAwWjASMRAwDgYDVQQKEwdBY21lIENvMFwwDQYJKoZIhvcNAQEBBQADSwAwSAJB
	AM0u/mNXKkhAzNsFkwKZPSpC4lZZaePQ55IyaJv3ovMM2smvthnlqaUfVKVmz7FF
	wLP9csX6vGtvkZg1uWAtvfkCAwEAAaNoMGYwDgYDVR0PAQH/BAQDAgKkMBMGA1Ud
	JQQMMAoGCCsGAQUFBwMBMA8GA1UdEwEB/wQFMAMBAf8wLgYDVR0RBCcwJYILZXhh
	bXBsZS5jb22HBH8AAAGHEAAAAAAAAAAAAAAAAAAAAAEwDQYJKoZIhvcNAQELBQAD
	QQBOZsFVC7IwX+qibmSbt2IPHkUgXhfbq0a9MYhD6tHcj4gbDcTXh4kZCbgHCz22
	gfSj2/G2wxzopoISVDucuncj
	-----END CERTIFICATE-----`)

	// localhostKey is the private key for localhostCert.
	var localhostKey = []byte(`-----BEGIN RSA PRIVATE KEY-----
	MIIBOwIBAAJBAM0u/mNXKkhAzNsFkwKZPSpC4lZZaePQ55IyaJv3ovMM2smvthnl
	qaUfVKVmz7FFwLP9csX6vGtvkZg1uWAtvfkCAwEAAQJART2qkxODLUbQ2siSx7m2
	rmBLyR/7X+nLe8aPDrMOxj3heDNl4YlaAYLexbcY8d7VDfCRBKYoAOP0UCP1Vhuf
	UQIhAO6PEI55K3SpNIdc2k5f0xz+9rodJCYzu51EwWX7r8ufAiEA3C9EkLiU2NuK
	3L3DHCN5IlUSN1Nr/lw8NIt50Yorj2cCIQCDw1VbvCV6bDLtSSXzAA51B4ZzScE7
	sHtB5EYF9Dwm9QIhAJuCquuH4mDzVjUntXjXOQPdj7sRqVGCNWdrJwOukat7AiAy
	LXLEwb77DIPoI5ZuaXQC+MnyyJj1ExC9RFcGz+bexA==
	-----END RSA PRIVATE KEY-----`)