Introduce package xengineering.eu/limox/xmpp

The XMPP logic is now big enough to create a corresponding package for
it.

1 files changed, 188 insertions, 0 deletions

diff --git a/xmpp/xmpp.go b/xmpp/xmpp.go
new file mode 100644
index 0000000..64ca494
--- /dev/null
+++ b/xmpp/xmpp.go
@@ -0,0 +1,188 @@
+package xmpp
+
+import (
+	"crypto/tls"
+	"crypto/x509"
+	"encoding/xml"
+	"log"
+	"os"
+)
+
+type Event uint8
+
+const (
+	DisconnectEvent Event = iota
+	ConnectEvent
+	ShouldDisconnectEvent
+)
+
+func Run(rxChan chan Event, txChan chan any, jid string, pwd string) {
+	conn, err := setupConn(jid)
+	if err != nil {
+		log.Print(err)
+		return
+	}
+	defer conn.Close()
+
+	receiver := newXmppReceiver(conn)
+	go receiver.run()
+	defer receiver.stop()
+
+	enc := xml.NewEncoder(conn)
+	defer enc.Close()
+	dbg := xml.NewEncoder(os.Stdout)
+	defer dbg.Close()
+
+	end := sendStreamStart(enc, dbg, jid)
+	defer sendStreamEnd(enc, dbg, end)
+
+	txChan <- ConnectEvent
+	defer func() { txChan <- DisconnectEvent }()
+
+	for {
+		select {
+		case ev := <-rxChan:
+			switch ev {
+			case ShouldDisconnectEvent:
+				return
+			default:
+				log.Printf("Unknown Event '%d'!\n", ev)
+			}
+		case rx := <-receiver.data:
+			dbg.Indent("S: ", "    ")
+			dbg.EncodeToken(rx)
+			dbg.Flush()
+		}
+	}
+}
+
+type xmppReceiver struct {
+	terminator chan bool
+	data chan xml.Token
+	decoder *xml.Decoder
+}
+
+func newXmppReceiver(conn *tls.Conn) xmppReceiver {
+	return xmppReceiver{
+		make(chan bool),
+		make(chan xml.Token),
+		xml.NewDecoder(conn),
+	}
+}
+
+func (r *xmppReceiver) run() {
+	for {
+		select {
+		case <-r.terminator:
+			return
+		default:
+			t, err := r.decoder.Token()
+			if err != nil {
+				log.Print(err)
+			}
+			if t != nil {
+				c := xml.CopyToken(t)
+				r.data <- c
+			}
+		}
+	}
+}
+
+func (r *xmppReceiver) stop() {
+	r.terminator <- true
+}
+
+func setupConn(jid string) (*tls.Conn, error) {
+	domain := domainpart(jid)
+
+	roots, err := x509.SystemCertPool()
+	if err != nil {
+		return nil, err
+	}
+
+	return tls.Dial("tcp", domain+":"+"5223", &tls.Config{RootCAs: roots})
+}
+
+func sendStreamStart(enc *xml.Encoder, dbg *xml.Encoder, jid string) xml.EndElement {
+	start := xml.StartElement{
+		xml.Name{"jabber:client", "stream:stream"},
+		[]xml.Attr{
+			xml.Attr{xml.Name{"", "from"}, jid},
+			xml.Attr{xml.Name{"", "to"}, domainpart(jid)},
+			xml.Attr{xml.Name{"", "version"}, "1.0"},
+			xml.Attr{xml.Name{"", "xml:lang"}, "en"},
+			xml.Attr{xml.Name{"", "xmlns:stream"}, "http://etherx.jabber.org/streams"},
+		},
+	}
+
+	err := enc.EncodeToken(start)
+	if err != nil {
+		log.Println("Could not encode stream start to TCP channel!")
+	}
+
+	err = enc.Flush()
+	if err != nil {
+		log.Println("Could not flush TCP channel XML encoder!")
+	}
+
+	dbg.Indent("C: ", "    ")
+
+	err = dbg.EncodeToken(start)
+	if err != nil {
+		log.Println("Could not encode stream start to debug output!")
+	}
+
+	err = dbg.Flush()
+	if err != nil {
+		log.Println("Could not flush debug XML encoder!")
+	}
+
+	return start.End()
+}
+
+func sendStreamEnd(enc *xml.Encoder, dbg *xml.Encoder, end xml.EndElement) {
+
+	err := enc.EncodeToken(end)
+	if err != nil {
+		log.Println("Could not encode stream end to TCP channel!")
+	}
+
+	err = enc.Flush()
+	if err != nil {
+		log.Println("Could not flush TCP channel XML encoder!")
+	}
+
+	dbg.Indent("C: ", "    ")
+
+	err = dbg.EncodeToken(end)
+	if err != nil {
+		log.Println("Could not encode stream end to debug output!")
+	}
+
+	err = dbg.Flush()
+	if err != nil {
+		log.Println("Could not flush debug XML encoder!")
+	}
+}
+
+// domainpart extracts the domain name from a JID / XMPP address. See
+// https://datatracker.ietf.org/doc/html/rfc7622#section-3.2 for details.
+func domainpart(jid string) string {
+	list := []rune(jid)
+
+	for i, v := range list {
+		if v == '/' {
+			list = list[:i]
+			break
+		}
+	}
+
+	for i, v := range list {
+		if v == '@' {
+			list = list[i+1:]
+			break
+		}
+	}
+
+	return string(list)
+}