1package mail
2
3import (
4	"bytes"
5	"errors"
6	"fmt"
7	"net/smtp"
8)
9
10// loginAuth is an smtp.Auth that implements the LOGIN authentication mechanism.
11type loginAuth struct {
12	username string
13	password string
14	host     string
15}
16
17func (a *loginAuth) Start(server *smtp.ServerInfo) (string, []byte, error) {
18	if !server.TLS {
19		advertised := false
20		for _, mechanism := range server.Auth {
21			if mechanism == "LOGIN" {
22				advertised = true
23				break
24			}
25		}
26		if !advertised {
27			return "", nil, errors.New("gomail: unencrypted connection")
28		}
29	}
30	if server.Name != a.host {
31		return "", nil, errors.New("gomail: wrong host name")
32	}
33	return "LOGIN", nil, nil
34}
35
36func (a *loginAuth) Next(fromServer []byte, more bool) ([]byte, error) {
37	if !more {
38		return nil, nil
39	}
40
41	switch {
42	case bytes.Equal(fromServer, []byte("Username:")):
43		return []byte(a.username), nil
44	case bytes.Equal(fromServer, []byte("Password:")):
45		return []byte(a.password), nil
46	default:
47		return nil, fmt.Errorf("gomail: unexpected server challenge: %s", fromServer)
48	}
49}
50