Implement User Avatar spoofing of XMPP users (#1090)

* Implement User Avatar spoofing of XMPP users

bridge/xmpp/handler.go

@@ -0,0 +1,34 @@
+package bxmpp
+
+import (
+	"github.com/42wim/matterbridge/bridge/config"
+	"github.com/42wim/matterbridge/bridge/helper"
+	"github.com/matterbridge/go-xmpp"
+)
+
+// handleDownloadAvatar downloads the avatar of userid from channel
+// sends a EVENT_AVATAR_DOWNLOAD message to the gateway if successful.
+// logs an error message if it fails
+func (b *Bxmpp) handleDownloadAvatar(avatar xmpp.AvatarData) {
+	rmsg := config.Message{
+		Username: "system",
+		Text:     "avatar",
+		Channel:  b.parseChannel(avatar.From),
+		Account:  b.Account,
+		UserID:   avatar.From,
+		Event:    config.EventAvatarDownload,
+		Extra:    make(map[string][]interface{}),
+	}
+	if _, ok := b.avatarMap[avatar.From]; !ok {
+		b.Log.Debugf("Avatar.From: %s", avatar.From)
+
+		err := helper.HandleDownloadSize(b.Log, &rmsg, avatar.From+".png", int64(len(avatar.Data)), b.General)
+		if err != nil {
+			b.Log.Error(err)
+			return
+		}
+		helper.HandleDownloadData(b.Log, &rmsg, avatar.From+".png", rmsg.Text, "", &avatar.Data, b.General)
+		b.Log.Debugf("Avatar download complete")
+		b.Remote <- rmsg
+	}
+}