package gomail import ( "bytes" "errors" "fmt" "net/smtp" ) // plainAuth is an smtp.Auth that implements the PLAIN authentication mechanism. // It fallbacks to the LOGIN mechanism if it is the only mechanism advertised // by the server. type plainAuth struct { username string password string host string login bool } func (a *plainAuth) Start(server *smtp.ServerInfo) (string, []byte, error) { if server.Name != a.host { return "", nil, errors.New("gomail: wrong host name") } var plain, login bool for _, a := range server.Auth { switch a { case "PLAIN": plain = true case "LOGIN": login = true } } if !server.TLS && !plain && !login { return "", nil, errors.New("gomail: unencrypted connection") } if !plain && login { a.login = true return "LOGIN", nil, nil } return "PLAIN", []byte("\x00" + a.username + "\x00" + a.password), nil } func (a *plainAuth) Next(fromServer []byte, more bool) ([]byte, error) { if !a.login { if more { return nil, errors.New("gomail: unexpected server challenge") } return nil, nil } if !more { return nil, nil } switch { case bytes.Equal(fromServer, []byte("Username:")): return []byte(a.username), nil case bytes.Equal(fromServer, []byte("Password:")): return []byte(a.password), nil default: return nil, fmt.Errorf("gomail: unexpected server challenge: %s", fromServer) } }