From d6fa15b7b66d679b7a6291aa6c85780a09cb1755 Mon Sep 17 00:00:00 2001
From: xengineering <me@xengineering.eu>
Date: Fri, 30 Jun 2023 12:28:48 +0200
Subject: Add detection for SASL mechanism

This is needed to respond with a SASL auth attempt.
---
 xmpp/stream_pair.go | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/xmpp/stream_pair.go b/xmpp/stream_pair.go
index 3e42cd1..b353947 100644
--- a/xmpp/stream_pair.go
+++ b/xmpp/stream_pair.go
@@ -91,6 +91,31 @@ func closeStream(s *session) {
 	}
 }
 
+func getCharData(t xml.Token) string {
+	switch c := t.(type) {
+	case xml.CharData:
+		return string(c)
+	default:
+		return ""
+	}
+}
+
 func streamFeaturesHandler(e []xml.Token) {
-	log.Println("Received stream features")
+	mechanism := xml.Name{`urn:ietf:params:xml:ns:xmpp-sasl`, `mechanism`}
+
+	for i, t := range e {
+		switch s := t.(type) {
+		case xml.StartElement:
+			if s.Name == mechanism {
+				if i+1 < len(e) {
+					if getCharData(e[i+1]) == `PLAIN` {
+						log.Println("Got offer for SASL PLAIN")
+						return
+					}
+				}
+			}
+		}
+	}
+
+	log.Println("No compatible SASL mechanism offered!")
 }
-- 
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