Add secure mode

config/config.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"net"
 	"strconv"
+	"strings"
 
 	"github.com/juju/errors"
 )
@@ -90,6 +91,9 @@ func NewConfig(debug, verbose bool, // nolint: gocyclo
 	publicIPv6 net.IP, publicIPv6Port uint16,
 	statsIP net.IP, statsPort uint16,
 	secret, adtag string) (*Config, error) {
+	if strings.HasPrefix(secret, "dd") {
+		secret = secret[2:]
+	}
 	if len(secret) != 32 {
 		return nil, errors.New("Telegram demands secret of length 32")
 	}

mtproto/connection_options.go

@@ -39,6 +39,7 @@ const (
 	ConnectionTypeUnknown ConnectionType = iota
 	ConnectionTypeAbridged
 	ConnectionTypeIntermediate
+	ConnectionTypeSecure
 )
 
 // ConnectionProtocol* define which connection protocols to use.
@@ -53,6 +54,7 @@ const (
 var (
 	ConnectionTagAbridged     = []byte{0xef, 0xef, 0xef, 0xef}
 	ConnectionTagIntermediate = []byte{0xee, 0xee, 0xee, 0xee}
+	ConnectionTagSecure       = []byte{0xdd, 0xdd, 0xdd, 0xdd}
 )
 
 // Tag maps connection type to the corresponding handshake tag.
@@ -62,6 +64,8 @@ func (t ConnectionType) Tag() ([]byte, error) {
 		return ConnectionTagAbridged, nil
 	case ConnectionTypeIntermediate:
 		return ConnectionTagIntermediate, nil
+	case ConnectionTypeSecure:
+		return ConnectionTagSecure, nil
 	default:
 		return nil, errors.Errorf("Unknown connection type %d", t)
 	}
@@ -75,6 +79,9 @@ func ConnectionTagFromHandshake(magic []byte) (ConnectionType, error) {
 	if bytes.Equal(magic, ConnectionTagAbridged) {
 		return ConnectionTypeAbridged, nil
 	}
+	if bytes.Equal(magic, ConnectionTagSecure) {
+		return ConnectionTypeSecure, nil
+	}
 
 	return ConnectionTypeUnknown, errors.New("Unknown handshake protocol")
 }