feat: add syncthing for clone mode (#270)

* feat: add syncthing for clone mode

---------

Co-authored-by: wencaiwulue <895703375@qq.com>

vendor/github.com/go-ldap/ldap/v3/request.go

@@ -0,0 +1,110 @@
+package ldap
+
+import (
+	"errors"
+
+	ber "github.com/go-asn1-ber/asn1-ber"
+)
+
+var (
+	errRespChanClosed = errors.New("ldap: response channel closed")
+	errCouldNotRetMsg = errors.New("ldap: could not retrieve message")
+	// ErrNilConnection is returned if doRequest is called with a nil connection.
+	ErrNilConnection = errors.New("ldap: conn is nil, expected net.Conn")
+)
+
+type request interface {
+	appendTo(*ber.Packet) error
+}
+
+type requestFunc func(*ber.Packet) error
+
+func (f requestFunc) appendTo(p *ber.Packet) error {
+	return f(p)
+}
+
+func (l *Conn) doRequest(req request) (*messageContext, error) {
+	if l == nil || l.conn == nil {
+		return nil, ErrNilConnection
+	}
+
+	packet := ber.Encode(ber.ClassUniversal, ber.TypeConstructed, ber.TagSequence, nil, "LDAP Request")
+	packet.AppendChild(ber.NewInteger(ber.ClassUniversal, ber.TypePrimitive, ber.TagInteger, l.nextMessageID(), "MessageID"))
+	if err := req.appendTo(packet); err != nil {
+		return nil, err
+	}
+
+	if l.Debug {
+		l.Debug.PrintPacket(packet)
+	}
+
+	msgCtx, err := l.sendMessage(packet)
+	if err != nil {
+		return nil, err
+	}
+	l.Debug.Printf("%d: returning", msgCtx.id)
+	return msgCtx, nil
+}
+
+func (l *Conn) readPacket(msgCtx *messageContext) (*ber.Packet, error) {
+	l.Debug.Printf("%d: waiting for response", msgCtx.id)
+	packetResponse, ok := <-msgCtx.responses
+	if !ok {
+		return nil, NewError(ErrorNetwork, errRespChanClosed)
+	}
+	packet, err := packetResponse.ReadPacket()
+	l.Debug.Printf("%d: got response %p", msgCtx.id, packet)
+	if err != nil {
+		return nil, err
+	}
+
+	if packet == nil {
+		return nil, NewError(ErrorNetwork, errCouldNotRetMsg)
+	}
+
+	if l.Debug {
+		if err = addLDAPDescriptions(packet); err != nil {
+			return nil, err
+		}
+		l.Debug.PrintPacket(packet)
+	}
+	return packet, nil
+}
+
+func getReferral(err error, packet *ber.Packet) (referral string) {
+	if !IsErrorWithCode(err, LDAPResultReferral) {
+		return ""
+	}
+
+	if len(packet.Children) < 2 {
+		return ""
+	}
+
+	// The packet Tag itself (of child 2) is generally a ber.TagObjectDescriptor with referrals however OpenLDAP
+	// seemingly returns a ber.Tag.GeneralizedTime. Every currently tested LDAP server which returns referrals returns
+	// an ASN.1 BER packet with the Type of ber.TypeConstructed and Class of ber.ClassApplication however. Thus this
+	// check expressly checks these fields instead.
+	//
+	// Related Issues:
+	//   - https://github.com/authelia/authelia/issues/4199 (downstream)
+	if len(packet.Children[1].Children) == 0 || (packet.Children[1].TagType != ber.TypeConstructed || packet.Children[1].ClassType != ber.ClassApplication) {
+		return ""
+	}
+
+	var ok bool
+
+	for _, child := range packet.Children[1].Children {
+		// The referral URI itself should be contained within a child which has a Tag of ber.BitString or
+		// ber.TagPrintableString, and the Type of ber.TypeConstructed and the Class of ClassContext. As soon as any of
+		// these conditions is not true  we can skip this child.
+		if (child.Tag != ber.TagBitString && child.Tag != ber.TagPrintableString) || child.TagType != ber.TypeConstructed || child.ClassType != ber.ClassContext {
+			continue
+		}
+
+		if referral, ok = child.Children[0].Value.(string); ok {
+			return referral
+		}
+	}
+
+	return ""
+}