l4xmpp: Add support for matching XMPP connections, match TLS-ALPN (#33)

* Add generic ALPN matcher

* Add XMPP matcher

* Add XMPP matcher to imports.go

* Apply gofmt and remove superfluous line

imports.go

@@ -24,4 +24,5 @@ import (
 	_ "github.com/mholt/caddy-l4/modules/l4tee"
 	_ "github.com/mholt/caddy-l4/modules/l4throttle"
 	_ "github.com/mholt/caddy-l4/modules/l4tls"
+	_ "github.com/mholt/caddy-l4/modules/l4xmpp"
 )

modules/l4tls/alpn_matcher.go

@@ -0,0 +1,53 @@
+// Copyright 2020 Matthew Holt
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package l4tls
+
+import (
+	"crypto/tls"
+
+	"github.com/caddyserver/caddy/v2"
+	"github.com/caddyserver/caddy/v2/modules/caddytls"
+)
+
+func init() {
+	caddy.RegisterModule(MatchALPN{})
+}
+
+type MatchALPN []string
+
+// CaddyModule returns the Caddy module information.
+func (MatchALPN) CaddyModule() caddy.ModuleInfo {
+	return caddy.ModuleInfo{
+		ID:  "tls.handshake_match.alpn",
+		New: func() caddy.Module { return new(MatchALPN) },
+	}
+}
+
+func (m MatchALPN) Match(hello *tls.ClientHelloInfo) bool {
+	clientProtocols := hello.SupportedProtos
+	for _, alpn := range m {
+		for _, clientProtocol := range clientProtocols {
+			if alpn == string(clientProtocol) {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+// Interface guards
+var (
+	_ caddytls.ConnectionMatcher = (*MatchALPN)(nil)
+)

modules/l4xmpp/matcher.go

@@ -0,0 +1,54 @@
+// Copyright 2020 Matthew Holt
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package l4xmpp
+
+import (
+	"io"
+	"strings"
+
+	"github.com/caddyserver/caddy/v2"
+	"github.com/mholt/caddy-l4/layer4"
+)
+
+func init() {
+	caddy.RegisterModule(MatchXMPP{})
+}
+
+// MatchXMPP is able to match XMPP connections.
+type MatchXMPP struct{}
+
+// CaddyModule returns the Caddy module information.
+func (MatchXMPP) CaddyModule() caddy.ModuleInfo {
+	return caddy.ModuleInfo{
+		ID:  "layer4.matchers.xmpp",
+		New: func() caddy.Module { return new(MatchXMPP) },
+	}
+}
+
+// Match returns true if the connection looks like XMPP.
+func (m MatchXMPP) Match(cx *layer4.Connection) (bool, error) {
+	p := make([]byte, minXmppLength)
+	n, err := io.ReadFull(cx, p)
+	if err != nil || n < minXmppLength { // needs at least 50 (fix for adium/pidgin)
+		return false, nil
+	}
+	return strings.Contains(string(p), xmppWord), nil
+}
+
+var xmppWord = "jabber"
+var minXmppLength = 50
+
+// Interface guard
+var _ layer4.ConnMatcher = (*MatchXMPP)(nil)