Merge bradfitz's tcpproxy codebase with the software formerly known as tlsrouter.

Brad's code will be the place for future development, and the base for the binary
formerly known as tlsrouter. This merge is the first step towards converging the
codebases.

1 files changed, 76 insertions, 0 deletions

diff --git a/sni.go b/sni.go
new file mode 100644
index 0000000..e12c744
--- /dev/null
+++ b/sni.go
@@ -0,0 +1,76 @@
+// Copyright 2017 Google Inc.
+//
+// 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 tcpproxy
+
+import (
+	"bufio"
+	"bytes"
+	"crypto/tls"
+	"io"
+	"net"
+)
+
+// AddSNIRoute appends a route to the ipPort listener that says if the
+// incoming TLS SNI server name is sni, the connection is given to
+// dest. If it doesn't match, rule processing continues for any
+// additional routes on ipPort.
+//
+// The ipPort is any valid net.Listen TCP address.
+func (p *Proxy) AddSNIRoute(ipPort, sni string, dest Target) {
+	p.addRoute(ipPort, sniMatch(sni), dest)
+}
+
+type sniMatch string
+
+func (sni sniMatch) match(br *bufio.Reader) bool {
+	return clientHelloServerName(br) == string(sni)
+}
+
+// clientHelloServerName returns the SNI server name inside the TLS ClientHello,
+// without consuming any bytes from br.
+// On any error, the empty string is returned.
+func clientHelloServerName(br *bufio.Reader) (sni string) {
+	const recordHeaderLen = 5
+	hdr, err := br.Peek(recordHeaderLen)
+	if err != nil {
+		return ""
+	}
+	const recordTypeHandshake = 0x16
+	if hdr[0] != recordTypeHandshake {
+		return "" // Not TLS.
+	}
+	recLen := int(hdr[3])<<8 | int(hdr[4]) // ignoring version in hdr[1:3]
+	helloBytes, err := br.Peek(recordHeaderLen + recLen)
+	if err != nil {
+		return ""
+	}
+	tls.Server(sniSniffConn{r: bytes.NewReader(helloBytes)}, &tls.Config{
+		GetConfigForClient: func(hello *tls.ClientHelloInfo) (*tls.Config, error) {
+			sni = hello.ServerName
+			return nil, nil
+		},
+	}).Handshake()
+	return
+}
+
+// sniSniffConn is a net.Conn that reads from r, fails on Writes,
+// and crashes otherwise.
+type sniSniffConn struct {
+	r        io.Reader
+	net.Conn // nil; crash on any unexpected use
+}
+
+func (c sniSniffConn) Read(p []byte) (int, error) { return c.r.Read(p) }
+func (sniSniffConn) Write(p []byte) (int, error)  { return 0, io.EOF }