From 0227596f90aca99b1d291a7c6104bdcd5ef0895b Mon Sep 17 00:00:00 2001
From: Wichert Akkerman <wichert@wiggy.net>
Date: Fri, 1 Nov 2019 21:57:38 +0100
Subject: [PATCH] Increase size of XML decoder internal buffers

Since a transport (and a streamlogger) does not implement io.ByteReader
xml.Decoder wraps it using `bufio.NewReader(transport)` so it can easily read
bytes one at a time. This has the unfortuante effect of resulting in a panic if
we try to parse a stanza that is larger than the default buffer size of 4096
bytes.

To fix this we wrap the transport using `bufio.NewReaderSize()` with a much
larger buffer size.
---
 websocket_transport.go | 3 ++-
 xmpp_transport.go      | 5 +++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/websocket_transport.go b/websocket_transport.go
index bf43611..d7b62c4 100644
--- a/websocket_transport.go
+++ b/websocket_transport.go
@@ -1,6 +1,7 @@
 package xmpp
 
 import (
+	"bufio"
 	"context"
 	"encoding/xml"
 	"errors"
@@ -57,7 +58,7 @@ func (t *WebsocketTransport) Connect() (string, error) {
 	t.wsConn = wsConn
 	t.startReader()
 
-	t.decoder = xml.NewDecoder(t)
+	t.decoder = xml.NewDecoder(bufio.NewReaderSize(t, maxPacketSize))
 	t.decoder.CharsetReader = t.Config.CharsetReader
 
 	return t.StartStream()
diff --git a/xmpp_transport.go b/xmpp_transport.go
index a1a11be..a67d5bc 100644
--- a/xmpp_transport.go
+++ b/xmpp_transport.go
@@ -1,6 +1,7 @@
 package xmpp
 
 import (
+	"bufio"
 	"crypto/tls"
 	"encoding/xml"
 	"errors"
@@ -37,7 +38,7 @@ func (t *XMPPTransport) Connect() (string, error) {
 	}
 
 	t.readWriter = newStreamLogger(t.conn, t.logFile)
-	t.decoder = xml.NewDecoder(t.readWriter)
+	t.decoder = xml.NewDecoder(bufio.NewReaderSize(t.readWriter, maxPacketSize))
 	t.decoder.CharsetReader = t.Config.CharsetReader
 	return t.StartStream()
 }
@@ -90,7 +91,7 @@ func (t *XMPPTransport) StartTLS() error {
 
 	t.conn = tlsConn
 	t.readWriter = newStreamLogger(tlsConn, t.logFile)
-	t.decoder = xml.NewDecoder(t.readWriter)
+	t.decoder = xml.NewDecoder(bufio.NewReaderSize(t.readWriter, maxPacketSize))
 	t.decoder.CharsetReader = t.Config.CharsetReader
 
 	if !t.TLSConfig.InsecureSkipVerify {